International Journal of Vehicle Design (12 papers in press)
Investigation of the energy recuperation potential of the damper system for a compact class passenger car
by Christian Riese, Oliver Stump, Frank Gauterin
Abstract: In this paper, an investigation of the potential of harvesting the energy dissipated by shock absorbers is presented, with a special focus on compact-class passenger cars, representative of electric vehicles (EVs). The calculations include the pitch movement due to the acceleration of the vehicle. The road roughnesses are modelled according to DIN ISO 8608. The vehicle model considered is a half-car model. The tyre model considers the damping and the absorption behaviour via an integrative filter. A large number of driving cycles are studied by using their predefined velocity profiles, including the NEDC, the FTP75, and different city cycles such as the NYC-cycle and the Tokyo City cycle. The road roughnesses are projected onto the driving cycle profiles. The simulation results show the potential for energy-harvesting systems for different road roughnesses and driving cycles. Parameter studies are conducted to study the influence of different factors on the harvestable energy.
Keywords: energy harvesting; damper; road roughness; driving cycles; vehicle modelling; passenger cars.
Linear time-varying model based model predictive control for lateral path tracking
by Sara Mata, Asier Zubizarreta, Ione Nieva, Itziar Cabanes, Charles Pinto
Abstract: This paper presents a path following application for vehicles based on a model predictive control approach with a linear time-varying model. The control system is designed to guarantee proper path tracking under certain comfort standards and for a wide range of velocities and traces. Therefore, not only lateral error is considered, but also orientation error to the target trajectory. Additionally, strict constraints are considered in the control signal, in its variation and in the lateral path following error. Stability of the proposed controller is guaranteed using terminal cost and constraint approaches.
Keywords: MPC; model predictive control; LTV model; linear time-varying model; lateral dynamics; path following; active safety.
Reinvention of the EUSAMA diagnostic methodology
by Milan Klapka, Ivan Mazůrek, Michal Kubík, Ondrej Macháček
Abstract: The authors use the mathematical model of the vehicle suspension to simulate the diagnostic procedure of the EUSAMA methodology. Simulations on a large dataset of vehicle chassis are calculated to identify the causes of false-negative evaluation of car condition often found in cars that are in good technical shape. It is proved that the most important cause of the methodology failure is the concurrence of thecurrent trend to use stiff car tyres and a high excitation stroke of currently used test rigs. Such high amplitudes of excitation do not correspond to the excitation from modern roads. Next, the authors verify the effects of non-linear characteristics of the damper and tyre stiffness on the results obtained by simulation diagnostic tests. The present paper introduces the adjustments of the EUSAMA methodology which should eliminate a growing set of tests with contradictory diagnosis results. These adjustments involve either the additional correction of measured data or the adjustment of the test rig design with the aim to reduce the excitation stroke. The proposed adjustments can be easily applied to most EUSAMA test rigs already available.
Keywords: Car suspension; diagnostics; EUSAMA methodology; shock absorber; simulation.
Vehicle handling control of an electric vehicle using active torque distribution and rear wheel steering
by Husain Kanchwala, Annika Stensson Trigell
Abstract: There are two main objectives of this work. The first is to develop a detailed yet computationally inexpensive mathematical model of an electric vehicle that gives quick and fairly accurate results to the user. The second is to use that model to integrate a controller that makes the vehicle follow desired dynamic characteristics. In the first part, the equations of motion for the vehicle are presented. Complex suspension kinematics and compliance characteristics have been obtained from the half-car suspension models developed in Adams Carr. Suspension and tyre nonlinear characteristics, vehicle roll-pitch interactions and variations of roll and pitch centres with respect to wheel travel are considered. In the second part, a controller is developed as a combination of force allocation control and active rear wheel steering control. Reference trajectories of vehicle velocity, path geometry and vehicle slip angle are given as inputs to the controller. The controller transforms these user inputs and generates wheel torques and steering commands. It computes the desired global vehicle forces and yaw moment and allocates them to the local wheel forces. The longitudinal wheel forces are generated by in-hub wheel motors while the lateral wheel forces are generated by front wheel steering commands from the driver and rear wheel steering commands from the controller. The investigated control allocation strategy is based on a constrained nonlinear minimisation algorithm. A desired value of yaw rate is maintained by generating a restoring yaw moment from the unequal torque distribution between left and right wheels. The vehicle side slip is substantially reduced by a combined feed-forward and feedback type active rear wheel steering controller. Finally, simulation results illustrate the suitability of the controller.
Keywords: vehicle dynamics; four wheel drive; rear wheel steering; force allocation; direct yaw control.
Controls development for motor-assisted engine starting in a full hybrid electric vehicle with an integrated starter generator
by Zhenzhen Lei, Yonggang Liu
Abstract: This paper focuses on the control strategy and the related experiments for a motor-assisted engine starting in a full hybrid electric vehicle (FHEV) with an Integrated Starter Generator (ISG). The characteristics of the FHEV driving system are analysed based on the dynamic model of the hybrid powertrain system. The control strategy for the motor-assisted engine starting during transition from the electric driving mode to the engine driving mode is proposed. The coordinated torque control of motor and wet multi-plate clutch is aimed at reducing torque fluctuation of the powertrain system. A simulation model of the hybrid powertrain system is established based on the Matlab/Simulink software platform. The results show that the proposed control strategy satisfies the engine starting requirement in terms of transient response and smoothness. Furthermore, both a bench test system and a prototype vehicle have been developed based on the D2P (from Development to Production) rapid prototype developing system. The test data from both the test bench and the prototype vehicle are agree well with the simulation data, and the effectiveness of the engine starting control strategy is validated by the comparison between simulation results and the test data.
Keywords: full hybrid electric vehicle; mode transition; engine starting; torque compensation; control strategy; experiment.
Modelling and dynamic analysis of vehicles based on discrete constraints
by Ke Shao, Kang Huang, Songlin Duan, Shengchao Zhen
Abstract: In this paper, a novel approach to modelling and dynamic analysis of a full vehicle is proposed based on Udwadia-Kalaba theory. Because the vehicle is hierarchically modelled by using this approach, this approach is easily processed when handling the modelling of a many-degrees-of-freedom vehicle. Also, the analytical dynamic model based on this approach is free of calculation of the Lagrangian multiplier as used in the Lagrangian equation. To verify this approach, a 15 DOF vehicle is modelled by using Udwadia-Kalaba theory. Four tyres displacement is exerted and the vertical dynamic behaviour of each subsystem is simulated and analysed in MATLAB. By solving the Udwadia-Kalaba equation, the response of each subsystem is acquired. The simulation result is well coincident with that of the Lagrangian model, which supports the proposed approach.
Keywords: full vehicle; dynamic behaviour; mechanics analysis; Udwadia-Kalaba theory; subsystem.
Coordinated fault-tolerant control of over-actuated electric vehicles based on optimal tyre force distribution
by Yugong Luo, Kun Cao, Laiqing Xie, Keqiang Li
Abstract: Actuator faults of the driving/steering/suspension subsystems may lead to instability in over-actuated electric vehicles. Though many fault-tolerant control methods that rely on partial subsystems exist, a novel coordinated fault-tolerant control (CFTC) method based on optimal longitudinal/lateral/vertical tyre force distribution is proposed. First, the coordination principles of all the actuator subsystems are explained using vehicle dynamics control equations. Then, an optimal longitudinal/lateral/vertical tyre force distribution method is established. Results of simulations and HIL experiments show that the CFTC method successfully coordinates all the subsystems to compensate actuator faults and effectively improves vehicle stability and safety.
Keywords: over-actuated electric vehicles; coordinated fault-tolerant control; longitudinal/lateral/vertical tyre forces; vehicle safety; vehicle stability.
Influence of automobile seat form and comfort rating on willingness to pay
by Namwoo Kang, Alex Burnap, K. Han Kim, Matthew P. Reed, Panos Y. Papalambros
Abstract: Increasingly competitive global markets combined with the commoditisation of the automobiles have driven customers to consider more nuanced factors during the automobile purchase decision. One such factor is the drivers seat; specifically, its perception of comfort and aesthetic form. As a result, much research has been recently conducted into seat comfort and the influence of the visual appearance of the seat on the perception of comfort. However, the cost of the seat remains an important contributor to overall vehicle cost, and the visual appearance of a seat may influence a customers willingness to pay. We conducted an experiment measuring this tradeoff using hierarchical Bayesian conjoint analysis, a marketing method that elicits customer preferences and willingness to pay at the individual customer level. Utility models are statistically inferred for three brand segmentations using a dataset obtained through an online interactive web application. Results indicate that in a heterogeneous market in which individual customers have different utility functions, willingness to pay is affected by seat form and comfort rating, with particularly significant tradeoffs for the luxury automotive brand segment.
Keywords: aesthetic seat form; seat comfort; willingness to pay.
Parametric analysis of the stability of a bicycle taking into account geometrical, mass and compliance properties
by Alberto Doria, Valerio Favaron, Luca Taraborrelli
Abstract: Some studies of bicycle stability have applied the Whipple Carvallo Bicycle Model (WCBM), which describes the roll and steer behaviour of a bicycle, allowing analysis of its characteristics of stability and in particular self-stability. One of the limitations of this model is that all structural elements are assumed to be rigid bodies. In this paper, the WCBM is extended to include the effect of front assembly lateral compliance, and analysis focuses on study of the open loop stability of a benchmark bicycle. Experimental tests to identify fork and wheel properties are presented and discussed. Stability analysis is carried out by a MATLAB numerical code, and specific stability indexes are calculated from plots of eigenvalues against speed. In order to rank the influence of design parameters on stability, numerical calculations are carried out in a full factorial experiment with two levels of eight design parameters. The results show that introducing front assembly compliance generates a wobble mode, but this has little effect on the range of self-stability. The forward displacement of the centre of mass of the rear frame and the increment in trail lead to large increments in the self-stability range, whereas increments in front wheel radius and wheelbase cause reduced stability.
Keywords: bicycle; stability; weave; capsize; front fork; wheel.
Optimisation design of a steering system based on E-HAM algorithm
by Guan Zhou, Wanzhong Zhao, Libin Duan, Chunyan Wang, Guoping Chen
Abstract: The steering system is one of the most important subsystems in the car. Owing to the limitation of production cost, the idle shake problem is very common among the minivans. To improve the performance of the steering system efficiently while keeping the production cost not increased, an enhanced hybrid and adaptive meta-model based global optimisation (E-HAM) is applied in this work to optimise the structures. Based on the HAM algorithm, the new important region update method (IRU) and different sampling size strategies are integrated in the E-HAM. The resulting precision, convergence rate and search efficiency are improved remarkably. The minivan steering system is then optimised by other six optimisation algorithms to perform the comparisons. FEM analysis and experiments are also conducted to verify the effectiveness of the optimisation. The results show that the structures are optimised successfully by the E-HAM optimisation method and the idle shake problem is well solved. The research in this work also serves a good example for other structure optimisation problems.
Keywords: steering system; meta-modelling; global optimisation; important region update method; mode analysis.
A novel approach for efficient fatigue-based shape optimisation of large scale finite element analysis models
by Umud Esat Ozturk
Abstract: This paper presents a novel approach for efficient fatigue-based shape optimisation of large scale finite element analysis models using the engine block connection to the engine mount bracket as an example. Forces at this joint depend highly on the vehicle and engine dynamics. Stiffness and damping properties of the vehicle suspension and engine mount components have major impact on the joint loads. It is not practical to perform a shape optimisation study for such problems using standard analysis and optimisation procedures owing to the complexity of the multi-body dynamics and finite element analysis models needed. In this study, the global finite element model, including the components significant to the joint forces, was first validated by the vehicle durability test measurements. Then, the developed procedure was successfully employed to calculate the boundary conditions using nonlinear finite element analysis and to perform the fatigue-based shape optimisation using the pre-defined shapes as design variables. The modelling and computational efforts of the proposed method are within the practical limits of the product development process. The developed methodology can also be applied to other vehicle components where shape optimisation study is not feasible owing to the complexity of the interacting sub-systems.
Keywords: finite element analysis; fatigue analysis; submodel; shape optimisation; engine mount connection.
Experimental analysis of liquid movements in automotive fuel tanks
by Assunta Andreozzi, Luigi Di Matteo, Francesco Fortunato
Abstract: A complex activity is taking place to enhance the design and validation of automotive fuel tanks. It includes track tests, new bench tests and fluid-dynamic simulations. The target is to prevent issues with vapour pressure build-up and fuel spill to the vapour canister, operating as early as possible in the design process. A new test bench has been developed by Moog Inc. based on Fiat Chrysler Automobiles (FCA) specification and experience, which allows to simulate vehicle accelerations using a combination of tank motion and tilt on all axes. Accelerometric measurements have been conducted. A comparison between results obtained by means of the 8-DOF innovative test bench and the ones obtained by means of a simpler 6-DOF bench has been carried out. Moreover, the experimental results are compared with the ones obtained when the fuel tank is mounted on a vehicle running on a test track.
Keywords: fluid dynamics; automotive fuel tank; slosh; vibration control; experimental analysis.