International Journal of Vehicle Design (8 papers in press)
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.
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.