Yuping He

A design methodology for mechatronic vehicles: application of multidisciplinary optimization, multibody dynamics and genetic algorithms

A design methodology for mechatronic vehicles is presented. With multidisciplinary optimization (MDO) methods, strongly coupled mechanical, control and other subsystems are integrated as a synergistic vehicle system. With genetic algorithms (GAs) at the system level, the mechanical, control and other relevant parameters can be optimized simultaneously. To demonstrate the feasibility and efficacy of the proposed design methodology for mechatronic vehicles, it is used to resolve the conflicting requirements for ride comfort, suspension working spaces and unsprung mass dynamic loads in the optimization of half-vehicle models with active suspensions. Both deterministic and random road excitations, both rigid and flexible vehicle bodies and both perfect measurement of full state variables and estimated limited state variables are considered. Numerical results show that the optimized vehicle systems based on the methodology have better overall performance than those using the linear quadratic Gaussian (LQG) controller. It is shown that the methodology is suitable for complex design optimization problems where: (1) there is interaction between different disciplines or subsystems; (2) there are multiple design criteria; (3) there are multiple local optima; (4) there is no need for sensitivity analysis for the optimizer at the system level; and (5) there are multiple design variables.

Optimization of curving performance of rail vehicles

The curving performance of a transit rail vehicle model with 21 degrees of freedom is optimized using a combination of multibody dynamics and a genetic algorithm (GA). The design optimization is to search for optimal design variables so that the noise or wear, arising from misalignment of the wheelsets with the track, is reduced to a minimum level during curve negotiations with flange contact forces guiding the rail vehicle. The objective function is a weighted combination of angle of attack on wheelsets and ratios of lateral to vertical forces on wheels. Using the combination of the GA and a multibody dynamics modelling program, A’GEM, the generation of governing equations of motion for complex nonlinear dynamic rail vehicle models and the search for global optimal design variables can be carried out automatically. To demonstrate the feasibility and efficacy of the proposed approach of using the combination of multibody dynamics and GAs, the numerical simulation results of the optimization are offered, the selected objective function is justified, and the sensitivity analysis of different design parameters and different design parameter sets on curving performance is performed. Numerical results show that compared with suspension and inertial parameter sets, the geometric parameter set has the most significant effect on curving performance.

A closed-loop dynamic simulation-based design method for articulated heavy vehicles with active trailer steering systems

This paper presents a closed-loop dynamic simulation-based design method for articulated heavy vehicles (AHVs) with active trailer steering (ATS) systems. AHVs have poor manoeuvrability at low speeds and exhibit low lateral stability at high speeds. From the design point of view, there exists a trade-off relationship between AHVs’ manoeuvrability and stability. For example, fewer articulation points and longer wheelbases will improve high-speed lateral stability, but they will degrade low-speed manoeuvrability. To tackle this conflicting design problem, a systematic method is proposed for the design of AHVs with ATS systems. In order to evaluate vehicle performance measures under a well-defined testing manoeuvre, a driver model is introduced and it ‘drivers’ the vehicle model to follow a prescribed route at a given speed. Considering the interactions between the mechanical trailer and the ATS system, the proposed design method simultaneously optimises the active design variables of the controllers and passive design variables of the trailer in a single design loop (SDL). Through the design optimisation of an ATS system for an AHV with a truck and a drawbar trailer combination, this SDL method is compared against a published two design loop method. The benchmark investigation shows that the former can determine better trade-off design solutions than those derived by the latter. This SDL method provides an effective approach to automatically implement the design synthesis of AHVs with ATS systems.

An Integrated Design Method for Articulated Heavy Vehicles with Active Trailer Steering Systems

This paper presents an integrated design method for active trailer steering (ATS) systems of articulated heavy vehicles (AHVs). Of all contradictory design goals of AHVs, two of them, i.e. path-following at low speeds and lateral stability at high speeds, may be the most fundamental and important, which have been bothering vehicle designers and researchers. To tackle this problem, a new design synthesis approach is proposed: with design optimization techniques, the active design variables of ATS systems and passive design variables of trailers can be optimized simultaneously; the ATS controller derived from this approach has two operational modes, one for improving lateral stability at high speeds and the other for enhancing path-following at low speeds. To demonstrate the effectiveness of the proposed approach, it is applied to the design of an ATS system for an AHV with a tractor and a full trailer. Simulation results illustrate that compared with the baseline vehicle, the one derived from the design synthesis approach decreases low-speed off-tracking by 35.2% and reduces high-speed rearward amplification ratio by 30.0%. The proposed approach may be used for identifying desired design variables and predicting performance envelopes in the early design stages of AHVs with ATS systems.

Design of an active trailer-steering system for multi-trailer articulated heavy vehicles using real-time simulations

This paper presents the design for an active trailer-steering system of multi-trailer articulated heavy vehicles using driver-software-in-the-loop real-time simulations. A linear yaw-plane multi-trailer articulated heavy-vehicle model is generated to derive an optimal active trailer-steering controller. Then, the controller is reconstructed in LabVIEW and integrated with a vehicle model for a tractor– double-trailer combination developed in TruckSim. The driver-software-in-the-loop real-time simulations are conducted on a vehicle simulator. The driver-software-in-the-loop real-time simulations indicate that the active trailer-steering controller can effectively improve the low-speed manoeuvrability and high-speed stability of the multi-trailer articulated heavy vehicle when testing using a low-speed 360° roundabout path-following manoeuvre and a high-speed single-lane-change manoeuvre respectively. The investigation based on the driver-software-in-the-loop real-time simulations paves the way to future development of electronic control units for the active trailer-steering system using driver-hardware-in-the-loop real-time simulations.

Application of optimisation algorithms and multibody dynamics to ground vehicle suspension design

A systematic method is proposed for automating the design synthesis of ground vehicle suspensions. This method combines optimisation algorithms and numerical multibody dynamics software and considers ISO 2631 standard requirements on ride quality. The proposed method is tested and evaluated by optimising three ground vehicle models. It is recommended that stochastic global search algorithms be used with numerical multibody dynamics software in the initial design optimisation, whereas gradient-based algorithms should be used in the fine stage of fine-tuning the parameters. Results show that compared with suspension stiffness and damping coefficients or inertial property parameters, geometric parameters have a more significant effect on the ride quality.

A Comparative Study of Active Control Strategies for Improving Lateral Stability of Car-Trailer Systems

This paper examines the performance of different active control strategies for improving lateral stability of car-trailer systems using numerical simulations. For car-trailer systems, three typical unstable motion modes, including trailer swing, jack-knifing and roll-over, have been identified. These unstable motion modes represent potentially hazardous situations. The effects of passive mechanical vehicle parameters on the stability of car-trailer systems have been well addressed. For a given car-trailer system, some of these passive parameters, e.g., the center of gravity of the trailer, are greatly varied under different operating conditions. Thus, lateral stability cannot be guaranteed by selecting a specific passive parameter set. To address this problem, various active control techniques have been proposed to improve handling and stability of car-trailer systems. Feasible control methods involve active trailer steering control (ATSC) and active trailer braking (ATB). Recently, a variable geometry approach (VGA) has been investigated. The essence of this method is to actively control the lateral displacement of the car-trailer hitch in order to improve high-speed stability of the vehicle system. To derive the three controllers, their respective yaw plane models are introduced. The simulation results based on each control method are examined and compared against each other. Through the benchmark comparisons, the features of different control strategies are identified and their applicability discussed.

A comparative study of multi-trailer articulated heavy-vehicle models

This paper provides valuable guidelines on the selection of dynamic vehicle models for control algorithm development, design optimization and linear stability analysis for multi-trailer articulated heavy vehicles with active safety systems. The validation of yaw-plane and yaw–roll models of a tractor–two-semitrailer combination using the TruckSim software package is presented in this paper. A linear four-degree-of-freedom yaw-plane model and a linear seven-degree-of-freedom yaw–roll model of the vehicle were generated, compared and evaluated. The linear models of the multi-trailer articulated heavy vehicle yield numerical simulation results which are validated by comparing with those obtained from the corresponding non-linear TruckSim model. This paper also includes eigenvalue and frequency-response analysis of the linear models to estimate the unstable motion modes and to predict the unique dynamic features of the multi-trailer articulated heavy vehicle in the frequency domain. A benchmark investigation of the models was performed to examine the fidelity, the complexity and the applicability of the linear models.

An Automated Design Method for Active Trailer Steering Systems of Articulated Heavy Vehicles

An important design decision for active trailer steering (ATS) systems for articulated heavy vehicles (AHVs) is the trade-off between maneuverability and lateral stability. This paper presents an automated design method for this trade-off. The proposed method has the following features: (1) a design framework for bilevel optimization of ATS systems is formulated; (2) design variables of ATS controllers and trailers are optimized simultaneously; (3) two controllers are designed for the ATS system for improving stability and enhancing maneuverability, respectively; and (4) a driver model is introduced in the virtual vehicle simulation for closed-loop testing maneuvers. The design framework allows automation of vehicle modeling, controller construction, performance evaluation, and design variable selection, and all required design processes are implemented in a single loop. The proposed method is compared to a previously published two-loop design method, showing that the new approach can effectively identify desired variables and predict performance envelopes.

A parallel design optimisation method for articulated heavy vehicles with active safety systems

This paper presents a parallel design optimisation method for Articulated Heavy Vehicles (AHVs) with Active Safety Systems (ASSs). In previous studies, a Genetic Algorithm (GA) has been applied to the design synthesis of AHVs and the objective function evaluations are computationally expensive. From a design point of view, the most challenging task is to deal with the trade-off relationship between unstable motion modes at high speeds and manoeuvrability at low speeds. To tackle the problem, a parallel computation technique with a master-slave system is proposed for the design of AVHs with ASSs. Active Trailer Steering (ATS), Differential Braking (DB) and Anti-Roll (AR) sub-systems are combined in an integrated ASS. Considering the interaction between the mechanical trailer and ASS, the proposed design method simultaneously optimises the active design variables of the controllers and passive design variables of the trailers in a single design loop using the masterslave computing system. The proposed method provides an effective approach to the design synthesis of AHVs with ASSs using a parallel computation technique.