International Journal of Vehicle Design (57 papers in press)

Regular Issues

• Steering energy optimisation strategy of steer-by-wire system with dual electric motors  
  by An Wang, Chunyan Wang, Wanzhong Zhao 
  Abstract: In order to improve the fault-tolerant ability of a steer-by-wire system, a dual-motor structure is introduced to improve the system reliability as well as the steering safety. However, the redundant motor will change steering energy consumption. Therefore, a dual-motor coupling steering (DMCS) strategy is proposed to minimise steering energy while maintaining steering stability. The proposed control strategy contains two layers, namely an upper stability controller and a lower energy optimisation controller. First of all, stability controller is designed to ensure the operational stability under external interference and model uncertainty. Then, the instantaneous overall efficiency is optimised based on the working point between main and auxiliary motors and the operating principles of energy optimisation controller in various modes are analysed. Last but not least, this paper formulates the optimal mode switch strategy and power split strategy on the premise of satisfying stability during steering process. Simulation results conducted by Matlab/Simulink demonstrate that the DMCS strategy can satisfy the stability demands at different steering conditions and realise the optimal allocation of energy between motors, thereby improving the efficiency of energy use.
  Keywords: steer-by-wire system; vehicle stability control; dual electric motors; efficiency optimisation; power split.
  
  
• Influence of capacity and energy density of lithium-ion battery on thermal reaction during high rate charging  
  by Xiaogang Wu, Haoqi Guo, Jiuyu Du 
  Abstract: Long range and fast charging are the future development trends in battery-operated electric vehicles. NCM ternary lithium-ion batteries have been widely used in electric vehicles owing to their high energy density and long cycle life. However, the resultant negative impacts of the increased energy density cannot be ignored, particularly the heat generation problem of the battery under the condition of high rate charging and the performance degradation and safety concerns caused by it. The optimal operating temperature of NCM series batteries ranges from 25
  Keywords: high energy density; lithium-ion battery; thermo-physical parameters; capacity and size; high rate charging; temperature rising; heat generation rate.
  
  
• Quantifying parameters of the seat-occupant interface during laboratory simulated low speed rear-impact collisions  
  by Jackie D. Zehr, Kayla M. Fewster, David C. Kingston, Chad E. Gooyers, Robert J. Parkinson, Jack P. Callaghan 
  Abstract: The influence of supplemental lumbar support on automobile seat surface pressures was measured during simulated rear impact collisions with human volunteers. Men and women (age = 25.4 +/- 3.4 years; BMI = 25.2(3.9); stature = 1.73 m (0.06)) experienced two low-velocity rear impact collisions. Simulated collisions with and without a lumbar support were conducted in random sequence. Using a pressure-sensing mat that contained 2288 ferroresistive sensors, seatback pressure was recorded at a frequency of 500 Hz. These data were used to compute the total seatback force, area of force concentration, and centre-of-force (CoF). Total seatback force was not significantly different from body mass for either men or women (c. 1.2 times body mass). Average contact area of the occupants back with the seatback (i.e., area of force concentration) was approximately 221.3 cm2 and 100.1 cm2 greater without supplemental lumbar support for men and women, respectively. With respect to the L4 spinal level, the CoF had a greater vertical distance without lumbar support and a greater horizontal distance with lumbar support. In conclusion, the lumbar support used in this study altered the location and distribution of seatback forces applied to the occupants back.
  Keywords: lumbar support; rear impact; accidents; low-back injuries; seatback pressure.
  
  
• Robust model referenced control for vehicle rollover prevention with time-varying speed  
  by Ke Shao, Jinchuan Zheng, Kang Huang, Mingming Qiu, Zhe Sun 
  Abstract: In this paper, an active steering control strategy is proposed to prevent rollover of a vehicle with a time-varying forward speed. The controller is designed with the aim of reducing the rollover index (RI) from an initial dangerous status to an absolutely safe status by active steering. The controller consists of two parts. The nominal control is firstly designed on the basis of the fundamental equation of constrained motion (FECM) of the vehicle, which will guarantee the nominal vehicle to track the desired states and thus rollover is prevented. To handle system uncertainties, compensatory sliding mode control (SMC) is proposed, by which the actual states are forced to track the desired ones. In the controller, the chattering problem can be alleviated by selecting a suitable performance function. To indicate the merits of the designed controller, simulation is conducted. Simulation results demonstrate that compared with conventional controllers, the proposed controller can prevent the vehicle from rollover with stronger robustness and without system chattering.
  Keywords: rollover prevention; active steering; time-varying speed; FECM; SMC; robustness.
  
  
• Model-based characterisation of vehicle occupants using a depth camera  
  by Byoung-keon Park, Jian Wan, Ksenia Kozak, Matthew Reed 
  Abstract: Owing to recent advances in sensing technologies, modern vehicle occupant classification systems enable personalised vehicle experiences and adaptive occupant crash protection. However, most systems are limited to occupant detection and simple classification, and thus, accurate estimation of body characteristics is needed to support more advanced occupant classification. This paper presents a model-based characterisation method for vehicle occupants using a 3D depth camera. This method automatically estimates standard anthropometric data of an occupant, such as stature and weight, along with the body shape by fitting a statistical body shape model to depth image data. The system is even robust to a wide range of clothing and is capable of generating accurate results. A variety of other algorithms were developed to improve the fitting result, including seat geometry detection and head location estimation. The new capability has a range of potential applications for improving occupant safety and providing an optimised interior configuration for the occupant.
  Keywords: occupant characterisation; occupant detection; occupant classification; time-of-flight camera; depth camera; statistical body shape model; SBSM; body shape estimation; anthropometry; model fitting.
  
  
• Refined modelling of thin-walled beam, plate and joint for automobile frame  
  by Jiantao Bai, Wenjie Zuo 
  Abstract: At the conceptual design stage, the simplified frame is extensively applied in the body-in-white (BIW) structure to rapidly calculate its performances. However, it is difficult to acquire an accurate simplified frame of the BIW structure for the calculation of the bending stiffness, torsional stiffness and frequencies. This paper proposes a simplified modelling method by using the thin-walled beams (TWBs) with complex sections, semi-rigid elements and cross beam structures to create the simplified frame. Compared with the traditional modelling method, the TWBs contain more types of the complex section, the semi-rigid elements can describe various deformations, and the plate structures are further considered. Firstly, the properties of the complex sections are summarised. Especially, the torsional moments of inertia of the multi-cell sections are derived. Secondly, the semi-rigid beam element is reduced to a super element, which is composed of one beam element and three translational and three rotational springs. Among them, the spring stiffness of the semi-rigid element is obtained by solving the detailed finite element model of the TWBs, which can be accurately and rapidly solved by using this method. Thirdly, the cross beam structure is introduced to replace the plate structure by the equivalence of the mass and central deflection for the first time. This method can further improve the accuracy of the simplified frame. Lastly, a numerical example demonstrates that the simplified frame can accelerate the conceptual design of the BIW structure.
  Keywords: conceptual design; frame structure; complex section; semi-rigid element; cross beam structure.
  
  
• Slime mould algorithm and kriging surrogate model-based approach for enhanced crashworthiness of electric vehicles  
  by Betül Sultan Yildiz 
  Abstract: Especially since the last decade, electric vehicles have been used frequently in most of the developed and developing countries. With the establishment and expansion of charging station infrastructures, fossil fuel vehicles will inevitably be replaced by electric vehicles in the next ten years. For this reason, electric vehicle components need to be developed very quickly. This paper concentrates on designing a new thin-walled energy absorber to be used in the design of electric vehicles. The material of the thin-walled energy absorber developed in this paper is cold-rolled advanced high-strength steel, which is Docol 1300. In this paper, a comparative study of the recent optimisation algorithms such as slime mould algorithm (SMA), salp swarm algorithm(SSA), and water cycle algorithm (WCA) are presented for optimum design of an automobile energy absorber. This research presents the first application of the slime mould algorithm to the optimum design of automobile components in the literature. The design problem aims to find optimum geometry while minimising mass and meeting energy absorption constraints. Function evaluations are carried out using finite element analysis and estimated by using the kriging surrogate model. The results show that both the SMA and Docol 1300 advanced high-strength material provide exceptional features for enhancing crashworthiness in electric vehicle design, simultaneously.
  Keywords: slime mould algorithm; water cycle algorithm; salp swarm algorithm; electric vehicles; energy absorber; optimum design; Docol 1300; advanced high-strength steel.
  
  
• Marine predators algorithm and multi-verse optimization algorithm for optimal battery case design of electric vehicles  
  by Betül Sultan Yildiz 
  Abstract: This article focuses on the optimum design of a battery case of an electric racing car. Two recently developed metaheuristics, which are marine predators algorithm (MPA) and the multi-verse optimisation algorithm (MVO), are used to create an optimal design where the mass is considered as an objective function, and the geometric dimensions of the component are considered to be the design variables. The kriging surrogate modelling is used to obtain the proxy model to increase the efficiency of the optimisation. The results show the robustness of the MPA in the optimum design of the electric car components. The MPA can be used in other product development processes.
  Keywords: marine predators algorithm; electric vehicles; battery case; shape design optimisation; multi-verse optimisation algorithm.
  
  
• Artificial road input data synthesis: a full vehicle model case study  
  by Adebola Ogunoiki, Oluremi Olatunbosun 
  Abstract: In order to reduce the time and cost of developing a vehicle, it is important that virtual durability testing is carried out. In this research project, the aim is to predict the road input for the virtual durability test simulation of a new vehicle variant by transforming the data from a predecessor model using the vehicle's configuration parameters to generate a new and representative road input. To achieve this, a full vehicle model of a sport utility vehicle (SUV) is developed and validated with test data collected on a proving ground; this model is used to generate data to train and validate a NARX-based artificial neural network tool which is then subsequently used to predict the road input to the new variant of the vehicle. The use of artificial neural networks in this project shows one of the many potentials of artificial intelligence in developing virtual capabilities within the automotive industry.
  Keywords: multi-body dynamics; artificial neural network; durability; computer aided engineering; CAE; road load data; RLD; full vehicle model; vehicle variant; QanTiM; SIMPACK; multi-body simulation; MBS.
  
  
• A novel design of a dry clutch pressure plate for weight reduction without compromising its thermo-mechanical performance  
  by Tolga Cakmak, Muhsin Kilic 
  Abstract: The main objective of this study is to conduct experimental research to investigate the effect of ventilation channels that have never been incorporated into the conventional automotive clutch pressure plate. The purpose is to reduce its weight without compromising its thermo-mechanical performance. Both convective and conductive heat transfers of the clutch pressure plate have been enhanced in order to meet thermo-mechanical performance requirements, by ventilation channels and by chemical composition adjustment, respectively. The novel design of ventilated
  Keywords: dry clutch; heat transfer enhancement; weight reduction.
  
  
• Steady-state modelling and analysis for a proportional electromagnet in a semi-active damper  
  by Xianju Yuan, Hongtao Ling, Tianyu Qiu, Jiwei Zhou, Tianyu Tian 
  Abstract: Achieving a modified method of reluctance, mathematical models are developed firstly. Then considering more details in materials, reference boundaries of currents and a method of mesh regulation, a finite element model is also established. Finally reflected through an instance, the maximum error within the effective range, less than 1 N, demonstrates improvements of accuracy of these mathematical models. Compared with results of experiments, the maximum error and fluctuations from the finite element method are evidently smaller than those of mathematical models. Therefore, such mathematical models and the finite element method would be helpful to obtain the steady-state force of complex electromagnets.
  Keywords: proportional electromagnet; steady-state analysis; mathematical model; finite element model.
  
  
• Development of a sorption thermal energy storage to support the thermal management of hybrid vehicles  
  by Georg Engel, Roland Kerschenbauer, Markus Hinteregger, Gregor Gregorcic, Anna Maria Fulterer, Waldemar Wagner, Wim Van Helden 
  Abstract: A sorption thermal energy storage is developed for the thermal management of hybrid vehicles. The thermal storage is charged using waste heat of the combustion engine, and discharged to provide heating and cooling for the battery and cabin, for example. A functional module of the storage system is assembled and assessed in experiment, where a cooling peak power of 2 kW and an average power of 1 kW are observed for 30 minutes. Assuming an optimised system design, this translates into key performance indicators of about 27 Wh/l and 55 W/l for cooling. Detailed system simulations show energy savings of 60% for cooling the battery during a worldwide harmonised light vehicles test cycle at elevated ambient temperature levels, saving 80 seconds for heating a chilled battery up to 20 deg. C and saving 26 seconds for preheating the combustion engine up to 80 deg. C.
  Keywords: thermal management; e-mobility; hybrid vehicles; thermal storage; closed adsorption; co-simulation.
  
  
• Implementation of a Design for Six Sigma methodology on the car bumper production process  
  by Ali Yurdun Orbak 
  Abstract: Competition increases daily in any market; therefore, continuous improvement of a product or service is an essential tool for survival and making an impact on the industry. Companies that have successfully implemented the Six Sigma method have gained the most from incorporating their Design for Six Sigma (DFSS) programs into their production processes. The primary purpose of DFSS is to design it right the first time to avoid negative experiences in the production flow. In this study, the parameters involved in the design of a selected passenger-vehicle bumper are optimised in the process of commissioning a new product using the DFSS method. The DFSS method is discussed on the first two steps of implementation of the define, measure, analyse, design, verify (DMADV) protocol. By additionally implementing the house of quality and failure mode and effects analysis approaches, a vehicle bumper that will meet the maximum level of customer requirements is produced.
  Keywords: Design for Six Sigma; house of quality; failure mode and effects analysis; bumper production process; experimental design.
  
  
• Research on an energy management strategy and energy optimisation of hydraulic hybrid power mining trucks  
  by Hongliang Li, Denglin Zhu, Lihua Shang, Ping Fan 
  Abstract: A design scheme of a parallel hydraulic hybrid mining truck (HHMT) is proposed, and its energy management and energy consumption optimisation are studied. A multi-disciplinary physical model is established, and a rule-based multi-mode conversion energy management strategy is formulated, combined with orthogonal experimental design (OED) to determine the optimal combination of parameters to minimise fuel consumption. Sequential quadratic programming (NLPQL) is also used to obtain the optimal solution on this basis. Through OED, the influence law of power system parameters and control parameters on the energy saving effect is obtained, and the influence of a parameter change under the best parameters on fuel consumption and energy storage (discharge), as well as the sensitivity of fuel consumption and energy storage(discharge),on driving conditions are quantitatively analysed. The effect of this energy management strategy is evaluated. Using the optimal parameters to simulate the HHMT on a joint simulation platform composed of Amesim and Stateflow, it is found that the actual vehicle speed can track the target vehicle speed very well. Compared with the original vehicle, the engine can work more often in the fuel economy zone, and fuel consumption is reduced by 11.39%, effectively reducing operating costs. The simulation results verify the correctness of the physical model and energy management strategy and prove the effectiveness of OED for fuel economy evaluation. This research may provide guidance and reference for HHMT research and development.
  Keywords: hydraulic hybrid mining truck; energy management strategy; energy consumption optimisation; orthogonal experimental design; fuel consumption.
  
  
• Linearisation modelling and active performance simulation of active engine mounts with an oscillating coil actuator for automotive powertrain  
  by Rang-Lin Fan, Jia-Ao Chen, Chu-Yuan Zhang, Zhen-Nan Fei, Pu Wang, Quan-Fa Wu 
  Abstract: Active engine mounts (AEMs) are key elements for improving automotive noise, vibration and harshness (NVH) performance. An accurate AEM model is crucial for its active control. This work focuses on the establishment and verification of a linear model for AEM with an oscillating coil actuator (OCA). Experiments and simulations of an actuator with an attached decoupling membrane and a conventional hydraulic engine mount (HEM) are employed to verify the fundamental linear models for an OCA and HEM. An integrated linear model for an AEM with an OCA is established and verified by experimental analysis of active characteristics. Based on the AEM linear model, three control algorithms, i.e., PID, fuzzy PID and FxLMS, are established to implement an active isolation performance simulation. The FxLMS is superior to the other two algorithms for an AEM considering the active performance for rotary machine.
  Keywords: active engine mount; active hydraulic mount; active control mount; active control; oscillating coil actuator; linearisation modelling; lumped parameter model; active characteristics; passive characteristics; powertrain mounting system; automotive; rotary machine; NVH performance.
  
  
• AUKF based unified estimation scheme for nonlinear vehicle dynamics  
  by Shouvik Chakraborty, Anindita Sengupta, Ashoke Sutradhar 
  Abstract: The paper presents an additive unscented Kalman filter (AUKF) based modular approach to estimate lateral vehicle dynamics and tyre forces. In this approach, a simplified single-track vehicular model and a dynamics-oriented tyre model are adopted to represent the vehicular motion. Subsequently, multiple observer modules for each dynamical state are designed and integrated into a Unified Estimation Scheme (UES-AUKF). Two additional non-modular observers using AUKF and EKF are designed for comparative analysis of estimation accuracy and computational efficiency of the designed scheme. The simplified model and the designed estimators are simulated using double lane change and sinusoidal manoeuvres for high and low surfaces, respectively, and the results are analysed. Thereby the scheme is further validated using real vehicle dataset for estimation accuracy. Simulation results for the simplified vehicle and the tyre model conform with the standard results with acceptable deviations. The proposed scheme exhibits improved accuracy with reduced computational time compared with the non-modular observers.
  Keywords: UKF; vehicle dynamics; yaw rate; slip angle; tyre force; modular estimation; tyre model; lateral dynamics estimation; Kalman filter; bicycle model.
  
  
• Development of a novel testing procedure and optimisation of a rubber spring using constrained simulated annealing algorithm for automobile clutch system  
  by Mehmet Onur Genç, Süleyman Konakçi, Necmettin Kaya, Samet Kartal, Ali Kamil Serbest 
  Abstract: Rubber compounds have widely used in many industry areas with many advantages, including in the automotive industry. However, the use of rubber-based springs within the clutch system of automobiles requires further investigation owing to the mechanical behaviour variations of rubber-based materials under dynamic conditions. In this study, a new methodology is proposed for the use of elastomer-based damper springs in automobile clutch systems. The design of the rubber damper spring and validation are comparatively investigated for an automobile clutch system, and a novel approach is developed. For this purpose, clutch usage on the automobile was simulated with a torsional fatigue test bench, which represents the loading and unloading case on damper springs at specific cycles and frequencies. NBR (nitrile rubber) was chosen as the sample rubber spring material, since it has representative material characteristics. As a result of the performed tests, a target stiffness value was obtained for the specified clutch requirements, and then a simulated annealing algorithm was coded in Python programming language and applied using specific design constraints from the response surface methodology.
  Keywords: rubber damper; hyper-viscoelastic modelling; simulated annealing; torsional fatigue; clutch disc; powertrain system; system optimisation.
  
  
• Local aerodynamic optimisation and drag reduction for a sedan at late stage styling  
  by Qi-Liang Wang, Ying-Chao Zhang, Xue-Dong Xue, Xin Chen 
  Abstract: An automatic optimisation process was devised based on a half-scale sedan to improve local aerodynamic shape and reduce wind resistance. Computational fluid dynamics simulations were used to verify grid independence. The appropriate designs of experiments algorithm, fitting model, and optimisation algorithm are selected depending on local shape complexity and its influence on drag coefficient, and important shapes are optimised for multivariable deformation. Vehicle drag coefficient was reduced by 1.23%, 1.85%, 3.09%, and 7.12% after optimising front and rear fenders, A-pillars, and trunk lid, respectively. Main effect analysis enabled the study of weight influence for each variable on drag. The interaction diagram shows mutual influence from reducing drag for each variable. Thus, reducing overall drag cannot simply superimpose local optimisation effects due to interactions between local flow fields.
  Keywords: sedan; drag reduction; automatic optimisation; DOE algorithm; fitting model; interaction diagram.
  
  
• Morphing applications in automobiles: a review  
  by Anumodh R, Balbir Singh, Mohammad Zuber 
  Abstract: Morphing structures are structures capable of altering their shape and size upon stimulus application. This field has been of interest to numerous researchers all over the world owing to its advantages over conventionally used materials. Most reported studies are limited to aerospace applications but studies for automotive applications are limited. This paper discusses the popularly used skin materials such as shape memory alloy, shape memory polymer, elastomers and other materials. Systems such as sensors and actuators that are needed for the working of morphing structures are also discussed. Applications of morphing in an automobile are discussed in brief. Some studies in the morphing of aerostructures can be incorporated into the automobile field, and hence some of the potential applications of morphing in automobiles are detailed.
  Keywords: morphing; shape memory alloy; shape memory polymer; actuators; smart materials.
  
  
• Design and fatigue analysis of an aluminium alloy aerodynamic wheel  
  by Róbert Huňady, Michal Fabian, Pavol Lengvarský, Albert Mareš, František Kupec 
  Abstract: The deployment of CAx systems has a great influence on the design of individual car components. One of the components that must meet not only aesthetic requirements but also strict safety criteria, guarantee mechanical integrity and have good aerodynamic properties, is a car wheel. Before production begins, wheels must undergo a series of numerical analyses as well as experimental tests. Based on these tests, design modifications are made so that the wheel meets the safety criteria in real operation. The aim of this paper is to present the wheel design process, including the simulation of the rotary bending test using FEM. The paper describes boundary conditions of the numerical model, the process of finite element mesh generation and the results of linear static analysis and fatigue analysis of an aerodynamic wheel.
  Keywords: aerodynamic wheel; CAD design; strength analysis; fatigue analysis; FEM.
  
  
• Design optimisation of a hybrid electric vehicle cooling system considering performance and packaging  
  by Kwang Jae Lee, Namwoo Kang, Michael Kokkolaras, Panos Y. Papalambros 
  Abstract: Optimal system design at the conceptual functional level, i.e., before the embodiment of the functions is determined in detail, focuses primarily on performance. Embodiment determines the geometry and position of subsystems and components, which must be packaged usually within strict spatial envelops to achieve compactness or other external requirements such as styling. Packaging objectives and constraints may therefore compete with performance ones, leading to redesign and costly delays if these conflicts are not addressed early in the design process. This paper presents a design optimization framework for coupled performance and packaging problems. Using the cooling system for a heavy duty tracked series hybrid electric vehicle as an example, we demonstrate the framework combining commercial CAD software with optimization tools and including pipe routing which is a basic requirement in many mechanical systems.
  Keywords: performance; packaging; pipe routing; system design optimisation.
  
  

Special Issue on: Multi-Objective Design and Structural Optimisation of Vehicle Components with Nature-Inspired Optimisation Algorithms

• A new hybrid salp swarm algorithm and radial basis function-based approach for robust design of vehicle control arm  
  by Betül Sultan Yildiz 
  Abstract: Considering the light-weight design expectations and government requirements in the automotive industry, both structural optimisation approaches and swarm intelligence methods have been receiving gigantic attention for their high accuracy and robustness. This paper presents the topology and shape optimisation of a vehicle control arm considering stress constraint conditions. The primary purpose of the design is to minimise weight while meeting the stress constraint conditions. There is a growing interest in designing light-weight and low-cost vehicles. In this research, a new hybrid salp swarm-Nelder-Mead (HSSA-NM) algorithm is developed and used to optimise a vehicle control arm. Both Latin hypercube sampling methodology and radial basis function surrogate modelling approach are used for obtaining equations of constraints and objectives used in the shape optimisation. Initially, the performance of the HSSA-NM is tested using a coil spring problem. Finally, the HSSA-NM is used for the optimum design of a vehicle control arm. As a result, a design problem is solved using the HSSA-NM. The optimal design meets all of the problem constraints and reduces the weight by about 2056 grams compared with that of the initial model. Thus, the proposed design method is an efficient method for shape optimisation design.
  Keywords: multiverse algorithm; vehicle design; control arm; shape optimisation.
  
  
• Integrated optimisation of two-speed powertrain parameters and shifting strategy for energy in electric vehicle  
  by Daoguang Zhu, Congbo Li, Lingling Li, Ying Tang 
  Abstract: In order to improve the economic performance and extend the range of electric vehicles (EV), an integrated optimisation method for the design and optimisation for powertrain parameters and shifting strategy are proposed. Firstly, the powertrain parameters are matched to ensure the dynamic performance of electric vehicles and the shifting strategy with comprehensive performance is designed based on the analysis of dynamic and economy performances. Secondly, a multi-objective integration model of powertrain parameter and shifting strategy optimisation is proposed to take the minimum energy consumption as the optimisation objective without sacrificing dynamic performance, which is solved by a multi-objective particle swarm optimisation algorithm. Finally, to verify the energy-saving performance of the proposed multi-objective integration problem, case studies have been conducted and a whole vehicle simulation model is proposed based on Matlab/Simulink platform. The simulation results show that the proposed method can effectively reduce the energy consumption and extend the range of electric vehicles under different driving cycle.
  Keywords: electric vehicle; powertrain parameter; shifting strategy; multi-objective integrated optimisation; particle swarm optimisation algorithm.
  
  

Special Issue on: Recent Advances in Motion Control for Unmanned Marine Vehicles

• Research on motion control of an autonomic launch and recovery device for unmanned surface vehicles  
  by Xiaomao Li, Xingang Jiang, Yang Yang, Yan Peng, Songyi Zhong, Huayan Pu, Shaorong Xie, Jun Luo 
  Abstract: In this study, a floating bracket device with visual inspection technology is developed for the autonomous launch and recovery of unmanned surface vehicles (USVs). To improve the success rate of docking between USVs and brackets in the recovery process, a reasonable controller is proposed to realise the position/posture regulation of the bracket. The state space equation is used to establish a system model, and the specific parameters are identified by using collected motion data. A sectional-type control framework is designed by model predictive control (MPC), which can satisfy the control requirements in different motion stages. The simulation results verify the accuracy of the identification model and the rationality of the MPC controller. The docking experiments demonstrated that the floating bracket with the proposed control system can be applied to launch and recovery missions of USVs.
  Keywords: launch and recovery; unmanned surface vehicles; motion control; model predictive control; parameter identification.
  
  
• Three-dimensional trajectory tracking control of underactuated autonomous underwater vehicles  
  by Zhenzhong Chu, Xuan Zhang, Daqi Zhu 
  Abstract: This study proposes a three-dimensional (3-D) trajectory-tracking control scheme for an underactuated autonomous underwater vehicle (AUV). Given the 3-D reference trajectory, the reference velocities, angles, angular velocities, forces, and torques were planned first. These reference variables were used to obtain the error dynamics. The backstepping technique was used to design the trajectory-tracking controller for tracking the AUVs reference trajectory. According to the Lyapunov stability theory, the trajectory-tracking system was stable and bounded, and the tracking errors converged close to a small neighbourhood of zero. Finally, the effectiveness of the developed control method was demonstrated using simulations.
  Keywords: autonomous underwater vehicle; three-dimensional control scheme; trajectory tracking; backstepping.
  DOI: 10.1504/IJVD.2020.10034236
   
  
• Network-based sampled-data control for unmanned marine vehicles with dynamic positioning system  
  by Minjie Zheng, Shenhua Yang, Lina Li 
  Abstract: This study investigates the network-based control problem for an unmanned marine vehicle (UMV) based on sampled data. Firstly, the network-based model for the UMV with dynamic positioning system (DPS) is established. Then sufficient conditions are provided to make the system asymptotically stable and satisfy H? performance. And the sampled-data controller is designed by analysing the stability conditions. Simulation result is shown that the sampled-data controller is effective to guarantee that the states of the UMV are stable under the external disturbance.
  Keywords: unmanned marine vehicle; dynamic positioning system; network-based control; sampled-data control.
  
  
• Trajectory tracking of underactuated unmanned surface vehicle with uncertain external disturbances and model parameters  
  by Jianjian Liu, Meijiao Zhao, Yan Peng, Dan Zhang, Shaorong Xie 
  Abstract: This paper investigates trajectory tracking control problem for an underactuated unmanned surface vehicle under external disturbance and model parameters uncertainty. Within the framework of backstepping control, a trajectory tracking control method based on constant bearing guidance is proposed, which can avoid the singularity that often appears in circular motion of the vehicles by redefining the differential of virtual heading angle. Moreover, disturbance observers are designed to estimate the equivalent disturbance, so that the vehicle can track the desired trajectory stably in the unknown ocean environment. Finally, owing to the limitation of the propellers mechanical performance, dynamic saturation of surge force and yaw moment is designed according to the upper and lower limits of two propellers' thrust to ensure the stable operation of the control system. Based on Lyapunov stability theory, the stability of the system is proved. And the numerical simulation results show the effectiveness of the presented control method.
  Keywords: underactuated unmanned surface vehicle; trajectory tracking; backstepping; disturbance observer; dynamic saturation.
  
  
• State observer-based adaptive fuzzy backstepping point stabilisation control of underactuated unmanned surface vehicles with input constraints  
  by Weixiang Zhou, Pingfang Zhou, Zheng Chen, Dengping Duan 
  Abstract: In this study, the point stabilisation control of an underactuated unmanned surface vehicle (USV) is addressed considering input constraints, missing velocity measurement and external disturbance. Different from other methods, in this proposed control framework, the point stabilisation is transformed into a straight line path-following problem. Then a state observer-based adaptive fuzzy backstepping controller is designed. The missing velocity variables are estimated by an extended state observer (ESO). An adaptive fuzzy algorithm is used to approximate the unknown nonlinear items in the dynamics model of the vehicle, and auxiliary items are introduced to deal with the actuator saturations. The system stability is proved by using Lyapunov theory, and the effectiveness of the proposed approach is demonstrated by the simulation results.
  Keywords: Point stabilization; Underactuated unmanned surface vehicle; State observer; Adaptive fuzzy method; Backstepping control; Input constraints.
  
  
• Formation control for underactuated unmanned surface vehicles based on consistency theory and leader-follower mode  
  by Limei Jiang, Rubo Zhang, Naifeng Wen, Guanqun Liu, Junwei Wu, Xingru Qu, Xiao Liang 
  Abstract: The formation involving multiple unmanned surface vehicles (USVs) is a new hotspot in research on USVs. Considering the formation control problem of underactuated USVs, a distributed formation control algorithm is proposed based on consistency theory and leaderfollower mode. The motion processes of the reference USV with respect to each USV are obtained with a consistency algorithm. By adjusting the control input, each USV converges to the reference vehicle. Thus, the expected formation of all USVs can be guaranteed if the trajectories of these two types of USV coincide. The entire formation uses distributed control, which has certain tolerance to special situations, such as communication delay and communication interruption. The effectiveness of the control strategy is verified through simulations.
  Keywords: unmanned surface vehicle; formation control; stability; backstepping.
  
  
• Investigating capacity degradation of LiFePO4 batteries for electric vehicles under different overcharge conditions  
  by Xiaogang Wu, Xu Han, Jiuyu Du 
  Abstract: When the state of charge (SOC) estimation by a battery management system (BMS) is inaccurate or the battery balance fails, the power battery in an electric vehicle may be overcharged, which results in a decline in the capacity and performance of the battery. In this paper, commercial large-format LiFePO4 batteries were used as overcharge targets and different overcharge paths and overcharge cut-off states of charge (SOCOC) were adopted to study the influence of different overcharge conditions on battery performance decay. The experimental results showed that different charge rates in the 0~80% SOC phase also had a certain degree of influence on the performance decay of the overcharged battery, but the SOCOC is the main reason for decline in battery performance. At the same time, battery performance after overcharge was not stable and a series of phenomena occurred when the battery was charged and discharged at a standard rate (1/3C). These phenomena included capacity recovery, synchronous recovery of the time of the constant voltage-charging segment, and charging capacity ratio of the constant voltage-charging segment. The battery discharge capacity overcharged to 110% and recovered from 59.7% to 68.4%. One battery which was overcharged to 105% recovered from 58.2% to 96.5% and the other battery recovered from 86% to 97.5%.
  Keywords: electric vehicle; battery; overcharge; capacity degradation; capacity recovery.
  
  
• High-gain-observer based adaptive output-feedback formation control for underactuated unmanned surface vessels with input saturation and uncertainties  
  by Meijiao Zhao, Huayan Pu, Yueying Wang, Jun Luo, Shaorong Xie, Yan Peng 
  Abstract: An adaptive output feedback formation control strategy based on a high gain observer has been developed to solve the problem of the control of underactuated surface vessels formation with uncertain dynamics, ocean environment disturbance and input saturation. In this strategy, a high gain observer that only depends on position information is used to estimate the unmeasurable velocity, and in order to solve the 'complex explosion' problem in the conventional backstepping control algorithm, a first-order low-pass filter is adopted to obtain the derivative of the virtual control signal. In addition, adaptive neural networks (NNs) and minimum learning parameters (MLP) algorithms are used to approximate environmental disturbances and uncertain dynamics, while reducing online update parameters. Stability analysis proved that all signals in closed-loop are uniformly ultimately bounded and the formation tracking errors are arbitrarily small. Simulation results demonstrate the effectiveness of the controller.
  Keywords: output feedback; adaptive; backstepping; neural networks; formation control; high gain observer; underactuated surface vessels; input saturation; uncertainty.
  
  
• Motion reliability evaluation of a six-axes robot based on non-probability interval theory  
  by Haimiao Wu, Guohua Cui, Peng Chen, Hongjuan Hou 
  Abstract: The error of position and posture of a robot end operator can affect the posture positioning accuracy. Therefore, an analysis study of motion reliability is important for ensuring the motion safety and normal operation of robots. Considering the effects of the link size deviations and joint clearance on the robot end operator, the error model of position and posture were analysed based on the non-probability interval theory. Then the time-varying motion reliability evaluation model of the robot was established using non-probability interval theory, and the motion reliability variation of the robot during trajectory points were obtained. The optimum design of the robot model was established by taking the deviations of the link size deviations and joint clearance as the optimisation variables, and reasonable ranges of link parameters were determined. The proposed analysis method lays a foundation for further upgrading the robot end operators position and posture accuracy.
  Keywords: robot; interval uncertainty theory; motion reliability; optimisation design.
  
  
• Finite-time tracking control of underactuated surface vehicle with tracking error constraints  
  by Huizi Chen, Dan Zhang, Meijiao Zhao, Shaorong Xie 
  Abstract: This paper studies the finite-time tracking control of an underactuated surface vehicle subject to lumped uncertainties, including actuator faults, external disturbances, and plant uncertainties. A tracking controller with error constraints is given to derive the prescribed tracking performance for vehicle. Subsequently, the adaptive neural network is adopted to estimate the lumped uncertainties. Meanwhile, an adaptive switching mechanism is devised to avoid chattering of state output and improve adaptation rate to compensate approximation error. Furthermore, the new performance function is introduced to obtain a clear indication of actual convergence time, and the non-logarithmic transformation function is constructed to solve the potential singularity problem in the logarithmic error mapping function. Some simulations are presented to prove the excellent tracking performance of the developed method.
  Keywords: underactuated surface vehicle; adaptive switching mechanism; actuator faults; tracking error constraints.
  
  
• Network-based global H pinning synchronisation for unmanned marine vehicles subject to disturbances  
  by Yanzhou Li, Yuanqing Wu, Shenghuang He 
  Abstract: The network-based global H pinning synchronisation of unmanned marine vehicles (UMVs) via sampled-data communications is investigated in this paper. {color{blue}By using Lyapunov stability theory, linear matrix inequality (LMI) technique and free-weighting matrix approach, some sufficient conditions are derived to ensure the global pinning synchronisation of UMVs. Furthermore, the maximum allowable sampling interval is estimated by a simple algorithm. Further study is then extended to address the global H pinning synchronisation problem of UMVs with external disturbances, showing that a better H performance can be guaranteed under some suitable conditions. Two numerical examples are presented to verify the validity and effectiveness of the obtained approaches.
  Keywords: unmanned marine vehicles; pinning synchronisation; sampled-data communications; performance index.
  
  
• 3D trajectory tracking control of an underactuated AUV based on adaptive neural network dynamic surface  
  by Xiao Liang, Zhao Zhang, Xingru Qu, Ye Li, Rubo Zhang 
  Abstract: This paper addresses the 3D trajectory tracking control of an underactuated autonomous underwater vehicle under uncertain model parameters and unknown external disturbances. An adaptive dynamic surface control scheme based on a neural network and filters is proposed. In the controller design, the first-order integral filters are employed to estimate the derivative of virtual control, which avoids repeated derivative of virtual control. To deal with the effect of the unknown disturbances and the uncertain model parameters, the unknown nonlinear functions are approximated using a neural network. All of the error signals in the close-loop system are uniformly ultimately bounded based on Lyapunov stability theory. Simulation studies and comparisons with dynamic surface control scheme are used to illustrate the effectiveness and superiority of the proposed control scheme.
  Keywords: underactuated AUV; trajectory tracking; dynamic surface control; adaptive neural network.
  
  

Special Issue on: Fault Diagnosis and Reliable Control for Vehicle Powertrain Systems

• Plug-in HEV energy management strategy based on SOC trajectory  
  by Jing Lian, Xinran Wang, Linhui Li, Yafu Zhou, Shuzhou Yu, Xiujie Liu 
  Abstract: This paper proposes a predictive control algorithm constrained by the State Of Charge (SOC) trajectory for the Plug-in Hybrid Electric Vehicle (PHEV) hybrid system. Firstly, the hybrid system energy consumption model is linearised in piecewise and the mixed logic dynamics (MLD) model of PHEV with the minimum equivalent fuel consumption as the optimal cost function is established. Secondly, Long Short-Term Memory (LSTM) network is used to forecast the vehicle speed through the historical vehicle speed data. Finally, the SOC trajectory curve is obtained as the constraint condition according to the change of vehicle speed. The optimal motor torque control sequence in the vehicle driving speed prediction horizon is calculated by the model predictive control strategy. The simulation results on different standard operating conditions show that the energy consumption of the PHEV is successfully reduced under the constraints of SOC trajectory.
  Keywords: PHEV; LSTM; MPC; SOC trajectory.
  
  
• An energy-efficient torque distribution strategy for in-wheel-motored electric vehicles based on model predictive control  
  by Bingtao Ren, Weiwen Deng, Hong Chen 
  Abstract: In order to improve the energy efficiency (EE) for in-wheel-motored electric vehicles (IWM EVs), an optimal torque distribution algorithm is investigated based on model predictive control (MPC). Firstly, an energy efficiency optimisation structure is developed by considering the energy efficiency characteristics of the motor and the energy loss of tyre slip. To achieve the driving requirements, an upper layer controller is designed to determine a desired motor torque, which takes into account the maximum capacity of the motor drive and regenerative braking. Then, a torque distribution algorithm in the lower layer applies MPC strategy to deal with this energy efficiency optimisation problem with system dynamic and torque saturation constraints. Then to obtain the optimal motor torques fast, an efficient solution approach is given by exploiting the particular structure of the problem and combining constraint conversion and numerical methods. Finally, simulation results in different driving cycles indicate that overall energy efficiency and computational efficiency of the vehicle can be improved. Also, the real-time control performance is guaranteed in the hardware-in-the-loop simulation.
  Keywords: optimal control; electric vehicle; model predictive control; energy distribution.
  
  
• Research on multi-mode regenerative braking energy recovery of electric vehicle with double rotor hub motor  
  by Liwei Zhang, Ren He 
  Abstract: In this study, a new type of double rotor hub motor is proposed. Then, its structure, the working principle and the regenerative braking energy recovery modes are described. In detail, three kinds of regenerative braking energy recovery mode, i.e. double motor regenerative braking mode, single inner motor regenerative braking mode and single outer motor regenerative braking mode, are introduced. The mathematical models of the single wheel dynamics model and the double rotor hub motor model are established. The three kinds of braking energy recovery mode are compared and the simulation results show that by using the sliding mode control strategy, on the condition that the maximum braking energy recovery of the motor is satisfied, the hydraulic braking torque can make corresponding response according to the change of the regenerative braking torque of the motor. At the same time, antilock braking of the wheel is achieved.
  Keywords: electric vehicle; double rotor hub motor; regenerative braking mode.
  
  
• Active steering PMSM speed control with wavelet neural network  
  by Mingzhu Xu, Zhaohan Huo, Shaohua Li, Li Jiang 
  Abstract: In view of the high requirements of active steering system on the noise, vibration and weight of the motor, this paper chooses the permanent magnet synchronous motor as the active power steering motor. A speed control strategy of this motor based on wavelet neural network PID is proposed. According to the change of system operation parameters, a three-layer feedforward artificial neural network is used to update the PID parameters online training based on gradient descent correction error method. Wavelet neural network and incremental PID are used to construct the speed loop controller. A control system based on DSP28335 is designed for experimental verification. The results show that the proposed control strategy has better static and dynamic performance, which can provide a new choice for small motor control of vehicles.
  Keywords: active steering motor; permanent magnet synchronous motor; wavelet neural network; incremental PID.
  
  
• Path tracking controller design for autonomous vehicle based on robust tube MPC  
  by Chuanyang Sun, Han Dong, Xin Zhang 
  Abstract: A robust tube MPC controller based on tube-division with a linear time-varying (LTV) model is proposed for autonomous vehicle path tracking. To reduce the conservativeness, a novel offline method is designed to calculate the tubes by dividing the original N-steps invariant sets into sequences of tighter candidate tubes. The propagation limits of the vehicle time-varying parameters within a prediction horizon are used in the division to ensure each candidate tube contains any state trajectory starting at its origin. A corresponding tube will be selected instead of being calculated online at each sampling instant in terms of vehicle states, which makes a more efficient online computation. The results of the simulation show the improved performance of the proposed robust tube MPC controller.
  Keywords: path tracking; robust tube MPC; autonomous vehicle; time-varying system; invariant sets.
  
  
• Heavy-duty vehicle longitudinal automation with hydraulic retarder via H infinity control and off-policy reinforcement learning  
  by Chaoxian Wu, Xuexun Guo, Bo Yang, Xiaofei Pei, Zhenfu Chen 
  Abstract: The longitudinal automation of a heavy-duty vehicle (HDV) is able to improve the safety, efficiency, and productivity of HDVs. However, the excessive use of the friction brake in a long downhill road to track the desired vehicle velocity in the deceleration process can overheat the brake pads, which can compromise the braking performance of the HDV and lead to dangerous situations. The hydraulic retarder is often employed to apply additional braking force to handle these situations in an HDV. However, according to the results of our experiments, the disturbance from the retarder oil temperature has a great impact on the retarder torque and strong nonlinearity, hence it is difficult to build its mathematical model and can severely compromise the retarder torque control accuracy and the speed tracking performance. In this paper, we propose a novel hierarchical HDV longitudinal control strategy with a hydraulic retarder to achieve the HDV downhill longitudinal automation in the deceleration process. The upper level controller generates the optimal desired retarder torque through the H infinity control and the off-policy reinforcement learning (RL), in which the H infinity control is able to attenuate those disturbances and the off-policy RL can solve the H infinity control with completely unknown system dynamics. Then, according to the optimal desired retarder torque, the lower level controller can calculate the desired control pressure for the retarder to control the HDV. The effectiveness of this HDV longitudinal control strategy is verified by simulations based on an experimentally verified retarder model. Compared to the sliding-mode-control based controller, the simulation result shows the proposed control strategy has better capability to attenuate the disturbances and guarantee the longitudinal speed tracking performance.
  Keywords: heavy-duty vehicle; longitudinal control; H infinity control; reinforcement learning; hydraulic retarder.
  
  
• Multi-step torque distribution for an over-actuated electric vehicle  
  by Houhua Jing, Zhiyuan Liu 
  Abstract: The over-actuated electric vehicle can flexibly adjust the torque of four wheels, to improve operational efficiency and vehicle motion performance. A multi-step torque distribution strategy is proposed, which can comprehensively consider the energy optimisation, vehicle stability and actuator dynamics, and realise the comprehensive control of longitudinal and lateral motion. It is composed of a static control allocation for energy optimisation, and a dynamic control allocation for manoeuvrability and stability enhancement based on model predictive control. It does not rely on complex online optimisation and is adaptive to highlight energy-saving, motion performance or stability under various scenarios. Finally, the controller is validated using a high-fidelity simulator called veDYNA.
  Keywords: over-actuated electric vehicle; wheel torque distribution; integrated motion control; energy efficiency optimisation; model predictive control.
  
  
• Design of nonlinear hierarchical controller for intake manifold pressure and boost pressure of turbocharged gasoline engine  
  by Hu Yunfeng, Wang Yaohan, Gong Xun, Gao Jinwu, Zhao Jinghua 
  Abstract: Precise tracking control of airpath systems, including intake manifold pressure and boost pressure, is key to ensuring the performance of turbocharged gasoline engines. Aiming at the above objective, we propose a nonlinear hierarchical controller to address the nonlinear and coupling characteristics of airpath systems in this paper. First, a control-oriented airpath model is obtained based on the working principle of a turbocharged gasoline engine. Second, the upper nonlinear controller is deduced in the framework of triple-step control method, whose asymptotic stability is guaranteed by linear system theory. Third, the lower controller performs a throttle-opening transformation, and a turbine speed tracking controller to achieve the value calculated by the upper controller. Specifically, the throttle-opening area is converted into a throttle-opening position by MAP (lookup tables), and a nonlinear observer-based turbine speed controller is obtained to address the unknown disturbance. Then, the actual input controls consisting of the throttle-opening position, and the wastegate opening position are obtained. Finally, the tracking performance and robustness of the proposed controller are verified by co-simulation using AMESim and Simulink.
  Keywords: turbocharged gasoline engine; hierarchical control; nonlinear control; asymptotic stability; intake manifold pressure; boost pressure.
  
  
• Temperature prediction and winding temperature measurement of a solenoid valve  
  by Yanyu Liu, Junqiang Xi, Fei Meng 
  Abstract: It is difficult to measure the temperature of solenoid valve windings in an automatic transmission with high precision. Distributed optical fibre sensing technology was used to measure the temperature of solenoid valve windings in this study. The finite element method was also used to establish an electromagnetic- thermal-mechanical coupling model describing the temperature of the solenoid valve. Bidirectional coupling between the electromagnetic field and temperature, and dynamic changes in material properties with temperature, are considered in the model presented here. The simulation presented here is a closer representation of an actual solenoid valve. The temperature distribution was calculated for each component during operation. The simulated winding temperature and that measured with the inverse resistance method in ideal conditions are compared with the fibre optic temperature measurements. The results illustrate the feasibility and accuracy of the method for measuring the temperature of small windings. Finally, the reproducibility of the temperature measurement method was evaluated.
  Keywords: solenoid valve; distributed optical fiber sensing technology; multi-physics coupling; winding temperature measurement.
  
  
• Investigation into transmission radiated noise during the acceleration of electric buses based on response surface methodology  
  by Yong Chen, Ningning Qiu, Libin Zang, Changyin Wei, Guangxin Li, Lin Li 
  Abstract: Without the masking effect of engine noise, the transmission noise of the electric bus becomes prominent, which affects the NVH (Noise, Vibration, and Harshness) of the whole vehicle state. In this study, noise sources of 4-speed automated mechanical transmission of a pure electric bus were identified and optimised. The vehicle noise test under the acceleration condition is carried out. The test results show that the third-gear acceleration noise is more prominent than the others. Subsequently, the radiation noise model of the transmission is established by using the BEM (Boundary Element Method) and revised by the noise test under the acceleration condition. The gear lead crown and involute modifications of the shifting gear pair of the third-gear were selected as design variables based on Response Surface Methodology (RSM). The relationships between the design variables and the objective function were established. Finally, RSM is applied to optimise the transmission radiation noise transmission. The gear lead crown and involute modifications of shifting gears of the third-gear were selected as 2
  Keywords: electric bus; the gearbox; the radiation noise; response surface method; order analysis; NVH; powertrain system; simulation.
  
  
• Real-time model predictive control for thermal management in an automotive ICE with an electrified cooling system  
  by Liang Lu, Yunfeng Hu, Xun Gong, Hong Chen 
  Abstract: The electrified cooling system of automotive internal combustion engine decouples the actuators from the engine, allowing for the advanced control methods to improve fuel economy. At present, almost all thermal management control strategies focus only on the cooling system itself, which considers only the influence of the thermal chain on the engine performance, while ignoring the electric chain and dynamic chain. This paper elevates the control strategy from the cooling system level to the power system level. First, based on the mechanism-electricity-heat integrated optimisation control, a minimum fuel consumption control strategy is proposed. Then an efficient solving method that combines Pontryagins minimum principle and bisection method is proposed, realising the online model predictive control (MPC). Simulation results show that the proposed control strategy reduces fuel consumption by around 1% at warm-up phase and by 2.96-5.61% at warmed phase compared with the traditional cooling system over worldwide light-duty test cycle. The proposed solving method improves computational efficiency by 65% and 96% compared with the normally used interior point and dynamic programming method. The MPC controller is also implemented on a hardware platform, which confirms the real-time feasibility and achieves nearly global optimal fuel economy.
  Keywords: thermal management; cooling system; internal combustion engine; model predictive control; Pontryagin's minimum principle.
  
  
• Analysis of a passive scissor-like structure isolator with quasi-zero stiffness for a seating system vibration-isolation application  
  by Linchuan Guo, Rang-lin Fan, Axconny Khiua, Xu Wang 
  Abstract: It is widely known that vibration is a mechanical motion phenomenon where a mass point oscillates around an equilibrium point. Vibrations are a source of discomfort and are extremely harmful to vehicle drivers and passengers. The motivations of this research are to develop an innovative vehicle seating suspension system to isolate vibrations transmitted to vehicle drivers and passengers and to improve ride comfort to ensure that their health is not negatively impacted and to improve the working efficiency of the driver. An innovative design of a passive multi-degree-of-freedom vibration isolator is presented in a truck seat suspension system where a Stewart platform configuration with a six-degree-of-freedom (6-DOF) isolation system is used rather than the traditional Stewart platform. A scissor-like structure (SLS) is used as one of the supporting legs to provide a nonlinear system with quasi-zero stiffness. Vibration is effectively attenuated without a loss of the systems load capacity. The effects of structural parameters in the proposed system are studied to determine how to adjust the parameters to achieve better vibration-isolation performance. The results reveal that a SLS supporting leg with a small assembly angle, more layers, a shorter link length and less spring stiffness has led to better vibration isolation and higher system stability than the conventional baseline supporting structure.
  Keywords: passive isolator; six degrees of freedom; vibration isolation; truck seats; seating suspension system; nonlinear stiffness; scissor-like structure; quasi-zero stiffness.
  
  
• Active synchronising control of dual-mode coupling transmission for electric vehicles  
  by Lipeng Zhang, Xiaobin Guo, Liuquan Yang, Yunao Peng, Bingnan Qi 
  Abstract: Since the drive motor is more precise than the internal combustion engine in speed and torque adjustment, the clutches could be removed from an automated manual transmission (AMT) developed for electric vehicles. However, the synchroniser is reserved to adjust the residual speed and angle difference between the target gear and the engagement sleeve, which can improve the reliability of the transmission by avoiding significant wear and tear. Since the rotation angle of the drive motor can be precisely controlled, it offers a possibility to remove synchronisers and only rely on the motor to achieve the speed and angle synchronisation. In this paper, an active synchronisation control tactic is devised for a novel two-speed AMT named dual-mode coupling transmission. A speed-current double-closed-loop controller for regulating the drive motors speed is constructed, and a sliding mode observer is developed for the estimation of the state feedback information. And an odd-even tooth strategy based on particle swarm optimisation is designed to reduce the angle difference. The gear shift of the actuator adopts simple PID control. The proposed control strategy is validated by a series of simulation comparison. Furthermore, the feasibility of replacing the synchronisers with engagement sleeves and only relying on the active synchronisation control of the motor is analysed. This study illustrates that the active synchronisation control can reduce the reliance on the synchroniser to a large degree, and ensure the shift quality while reducing synchroniser wear, but the shift impact is still large after canceling the synchroniser rings, so the engagement sleeve structure and actuator control strategy must be optimised before replacing the synchroniser.
  Keywords: electric vehicle; dual-mode coupling transmission; active synchronisation; shift control; odd-even tooth.
  
  

Special Issue on: Safety and Standards for Connected and Autonomous Vehicles

• Coordinated torque vectoring control and path-following of autonomous vehicles with sideslip angle estimation  
  by Lin Zhang, Wei Pan, Qin Li, Haobo Sun, Nian Wang 
  Abstract: This paper proposes a coordinated control strategy that considers torque vectoring control and path-following system for autonomous vehicles with four in-wheel motors, while a state observer is designed to obtain some core vehicle states. Firstly, a non-linear vehicle state observer based on the UniTire tyre model is proposed to estimate longitudinal and lateral speed. Then the sideslip angle and tyre slip ratio can be obtained. Secondly, a lateral and longitudinal path-following algorithm using the driver model based on optimal preview theory and PI (proportion integral) controller is established. For the vehicle safety control of autonomous driving, a layered control scheme is proposed, in which the upper layer employs an adaptive second-order sliding mode controller to get additional yaw moment. The lower layer adopts an optimal moment distribution strategy to calculate the output torque of each motor considering the additional yaw torque control error, tyre workload usage, and the driver's longitudinal demand torque. Finally, simulation test results prove that the proposed state observation and coordinated control algorithm is valid.
  Keywords: autonomous vehicles; torque vectoring control; path-following; sideslip angle estimation; in-wheel motors.
  
  
• Action intention recognition of cars and bicycles in intersections  
  by Cristofer Englund 
  Abstract: Action intention recognition is becoming increasingly important in the road vehicle automation domain. Autonomous vehicles must be aware of their surroundings if we are to build safe and efficient transport systems. This paper presents a method for predicting the action intentions of road users based on sensors in the road infrastructure. The scenarios used for demonstration are recorded on two different public road sections. The first scenario includes bicyclists and the second includes cars that are driving in a road approaching an intersection where they are either leaving or continuing straight. A 3D camera-based data acquisition system is used to collect trajectories of the road users that are used as input for models trained to predict the action intention of the road users. The proposed system enables future connected and automated vehicles to receive collision warnings from an infrastructure-based sensor system well in advance to enable better planning.
  Keywords: intention recognition; random forest; data mining; traffic behaviour modelling; variable selection.
  
  
• Driver distraction detection using machine learning algorithms: an experimental approach  
  by Zhaozhong Zhang, Efstathios Velenis, Abbas Fotouhi, Daniel Auger, Dongpu Cao 
  Abstract: Driver distraction is a leading cause of accidents that contributes to 25% of all road crashes. In order to reduce the risks posed by distraction, a warning must be given to the driver once distraction is detected. According to the literature, no rankings of relevant features have been presented. In this study, the most relevant features in detecting driver distraction are identified in a closed testing environment. The relevant features are found to be the mean values of speed and lane deviation, maximum values of eye gaze in y direction, and head movement in x direction. After the relevant features have been identified, pre-processed data with relevant features are fed into decision tree classifiers to discriminate the data into normal and distracted driving. The results show that a detection accuracy of 78.4% using decision tree can be achieved. By eliminating unhelpful features, the time required to process data is reduced by around 40% to make the proposed technique suitable for real-time application.
  Keywords: driver distraction; feature extraction; machine learning; decision tree.
  
  
• Fuel economy benefit analysis of pass-at-green V2I application on urban routes with STOP signs  
  by Ozgenur Kavas-Torris, Mustafa Ridvan Cantas, Sukru Yaren Gelbal, Bilin Aksun-Guvenc, Levent Guvenc 
  Abstract: Developments in Vehicle to Infrastructure (V2I) communication technology have enhanced the capabilities of connected and automated vehicles. In this paper, the fuel economy benefit of a V2I algorithm called Pass-at-Green (PaG) is analysed and compared with different speed profile characteristics. The first speed profile that is compared with the PaG Informed Speed Profile (ISP) is the Intelligent Driver Model (IDM), whose parameters were modified to model cautious, normal and aggressive speed profiles. The fuel-optimal speed profile that was calculated offline using Dynamic Programming (DP) was used for a benchmarking comparison with the PaG ISP. Manual Driving Speed Profile (MDSP) was also included in the analysis as the human driver. The state-of-the-art connected and autonomous driving Hardware-in-the-loop (HIL) setup enabled the use of Electronic Horizon (eHorizon), which provided localisation and detailed map information to the simulated test vehicle. An eHorizon Informed MDSP, where the eHorizon HIL system provided upcoming STOP sign location information, was also modelled to be compared with the PaG ISP. The results showed that having V2I capability in the longitudinal speed control of a vehicle has potential for substantial fuel consumption reduction while navigating through signalised and non-signalised intersections. It was also seen that having a longer V2I communication range improves the fuel economy benefit of the test vehicles.
  Keywords: automated vehicles; connected vehicles; V2I technology; HIL simulations; eHorizon; speed profile calculations; driver characteristics.
  
  
• Robust pedestrian detection for driver assistance systems using machine learning  
  by Sabrine Hamdi, Souhir Sghaier, Hassene Faiedh, Chokri Souani 
  Abstract: Pedestrian detection is a critical task for a variety of applications, particularly when used in driving assistance systems. Most pedestrian detection systems perform accurately for clearly visible images. However, at night, the accuracy of these systems is reduced and their performance is limited, owing to the lack of the highly discriminative information provided by the spectrum besides visible light. Therefore, it is important to fuse visible images with corresponding infrared images for the context enhancement of scenes in night vision. In this study, an approach for pedestrian detection is developed based on infrared and visible images of the same scene. This approach uses two basic modules: (1) region of interest (ROI) generation, where the ROI are generated; and (2) ROI classification, to verify the existence of pedestrians in the generated hypotheses. In the first module, an Otsu thresholding technique is applied to infrared images to detect hot spots mostly likely representing a pedestrian, after applying some morphological operations to enhance the original image and compensate for clothing-based distortions. After retaining the significant ROIs by performing a post-processing stage, the ROIs obtained in the infrared image are mapped into corresponding visible images. The second module uses a support vector machine as a classifier and multispectral aggregated channel features, together with a discrete cosine transform on the infrared channel. The proposed approach is implemented and tested on the publicly available 'KAIST' multispectral dataset to prove its efficiency.
  Keywords: pedestrian detection; day/night-time; Otsu thresholding; aggregated channel features; discrete cosine transform; support vector machines.
  
  
• Trajectory planning for autonomous vehicles based on improved Hybrid A*  
  by Chao Wang, Nan Xu, Yanjun Huang, Konghui Guo, Yang Liu, Qin Li 
  Abstract: Trajectory planning plays an important role in autonomous driving technology. This paper presents an improved Hybrid A* algorithm by considering vehicle dynamics in planning. First, a vehicle dynamic model with three degrees of freedom and a nonlinear UniTire tyre model is developed to describe the vehicle dynamics. Then, in order to generate curvature-continuous trajectory, the method of expanding nodes based on the rotation speed of steering wheel is introduced. Then, heuristic functions are designed for trajectory searching. In addition, the feasibility of the planning result is verified in the driver-vehicle-road closed loop system. Simulation results show the proposed trajectory planning method performs well under a variety of working conditions, and the planned trajectory is trackable even at extreme conditions, e.g. high speed and low-adhesion road surfaces. Specifically, on the icy road, the planned results are good and the maximum lateral tracking error of this trajectory is limited to 0.24 m. Therefore, the proposed planning method is effective and can be easily used for autonomous driving.
  Keywords: autonomous vehicles; trajectory planning; Hybrid A*; vehicle dynamics; emergency obstacle avoidance.
  
  
• Longitudinal motion control for vehicle platooning in mixed traffic based on virtual mass-spring-damper theory  
  by Luo Jiang, Jie Ji, Yue Ren, Hong Wang 
  Abstract: This paper proposes a novel control method based on the virtual mass-spring-damper (MSD) theory to improve the platoons system safety in mixed traffic flows consisting of connected and automated vehicles (CAVs) and human-driven vehicles (HDVs). To validate the proposed control method, two kinds of mixed platoons composed of five CAVs and one HDV are modelled and simulated by using CarSim and Matlab/Simulink. The simulation results demonstrate that when the HDV is at the head of the platoon, the maximum spacing error is 1.73 m; when the HDV is in the middle of the platoon, it increases to 3.59 m. Meanwhile, the inter-vehicle spacing errors do not increase as they propagate along the platoon. Therefore, by selecting the appropriate spring constant and damping coefficient of the virtual MSD system according to platoon form, the proposed control method can effectively ensure the stability and improve the safety of the mixed vehicular platoon.
  Keywords: vehicular platoons; mass-spring-damper system; mixed traffic; string stability; traffic safety.
  
  
• Multi-mode collision avoidance closed-loop control system  
  by Xuewu Ji, Cong Fei, Tao Xu, Xiangkun He 
  Abstract: Autonomous vehicles are a research area of active interest. A collision avoidance system (CAS) is one of the central concerns to provide security protection for autonomous vehicles. This paper proposes a multi-mode collision avoidance system (mCAS), which combines a trajectory prediction module, a risk assessment module and a motion planning module into the closed-loop system. At each step, the trajectory prediction module predicts the trajectories of an autonomous vehicle and surrounding vehicles. The risk assessment model calculates the collision probability and chooses a reasonable control mode. Then the motion planning module designs the desired deceleration profile based on it. The car takes the first step of the planned deceleration and repeats this cycle, achieving closed-loop control. The mCAS is tested in the closed-loop simulation setup and the results show that the proposed mCAS is of good effectiveness and feasibility, which can significantly reduce collision probability as well as false alarms.
  Keywords: autonomous vehicles; collision avoidance system; trajectory prediction; risk assessment.
  
  

Special Issue on: Revisiting Vehicle Dynamics and Control for Electrified and Autonomous Vehicles

• Optimised robust path-following control of autonomous vehicles with pole constraints  
  by Yixiao Liang, Yinong Li, Amir Khajepour, Ling Zheng 
  Abstract: This paper presents a robust output-feedback guaranteed-cost control strategy for the path-following control of autonomous vehicles. First, the model of vehicle dynamics and path-following is established, which takes the uncertainties of cornering stiffness into account. Then, to deal with such uncertainties and improve the transient performance, a robust guaranteed-cost controller is introduced with the regional pole constraint ability. Considering that it is expensive and difficult to measure the side slip angle accurately, the proposed controller uses an output-feedback scheme without side slip angle information. Moreover, the particle swarm optimisation algorithm is selected to optimise the performance index of the guaranteed-cost controller such that the priorities among different objectives can be decided reasonably. Simulation results demonstrate the effectiveness of the proposed controller and its advantages over previous studies in the presence of parameter uncertainties.
  Keywords: autonomous vehicle; path-following control; robust guaranteed-cost control; output-feedback control; particle swarm optimisation.