Holistic simulation for integrated vehicle design

A holistic vehicle simulation capability is necessary for front-loading component, subsystem, and controller design, for the early detection of component and subsystem design flaws, as well as for the model-based calibration of powertrain control modules. The current document explores the concept of holistic vehicle simulation by means of reviewing the current trends automotive system design and available solutions in terms of model interfaces and neutral modelling environments. The review is followed by the presentation of a Simulink-based Multi- disciplinary Modelling Environment (MME) developed by the authors to accommodate simulation work across the vehicle development cycle

Co-Simulation Methods for Holistic Vehicle Design: A Comparison

Vehicle development involves the design and integration of subsystems of different domains to meet performance, efficiency, and emissions targets set during the initial developmental stages. Before a physical prototype of a vehicle or vehicle powertrain is tested, engineers build and test virtual prototypes of the design(s) on multiple stages throughout the development cycle. In addition, controllers and physical prototypes of subsystems are tested under simulated signals before a physical prototype of the vehicle is available. Different departments within an automotive company tend to use different modelling and simulation tools specific to the needs of their specific engineering discipline. While this makes sense considering the development of the said system, subsystem, or component, modern holistic vehicle engineering requires the constituent parts to operate in synergy with one-another in order to ensure vehicle-level optimal performance. Due to the above, integrated simulation of the models developed in different environments is necessary. While a large volume of existing co-simulation related publications aimed towards engineering software developers, user-oriented publications on the characteristics of integration methods are very limited. This paper reviews the current trends in model integration methods applied within the automotive industry. The reviewed model integration methods are evaluated and compared with respect to an array of criteria such as required workflow, software requirements, numerical results, and simulation speed by means of setting up and carrying out simulations on a set of different model integration case studies. The results of this evaluation constitute a comparative analysis of the suitability of each integration method for different automotive design applications. This comparison is aimed towards the end-users of simulation tools, who in the process of setting up a holistic high-level vehicle model, may have to select the most suitable among an array of available model integration techniques, given the application and the set of selection criteria

Investigation on Semi-active Suspension System for Multi-axle Armoured Vehicle using Co-simulation

The objective of the study is to evaluate the performance of various semi-active suspension control strategies for 8x8 multi-axle armoured vehicles in terms of comparative analysis of ride quality and mobility parameters during negotiation of typical military obstacles. Since the cost, complexity and time precludes realisation of actual system, co-simulation technique has been effectively implemented for this investigation. Co-simulation combines advanced virtual prototyping and control technology which offers a novel approach to investigate the dynamics of such complex system. The simulations for the integrated control system along with multi body model of the vehicle are carried out for the control strategies, viz. continuous sky hook control, cascade loop control and cascade loop with ride control and compared with passive suspension system. The vehicle with 8x8 configuration is run on the real world obstacle profiles, viz. step, trench, trapezoidal bump and corrugated road and the effect of control strategies on ride comfort, wheel displacement and ground reaction is presented. It is observed that cascade loop with ride control in semi-active mode offers better vehicle ride comfort while crossing the said obstacles. The improved performance parameters are achieved through stabilisation of heave, pitch and roll motions of the vehicle through outer loop and isolation of vehicle level uneven disturbances through the fuzzy logic controller employed in inner loop

Development of an Electronic Stability Control for Improved Vehicle Handling using Co-Simulation

The research project focuses on integrating the algorithms of recent automotive Electronic Stability Control (ESC) technologies into a commercial multi-body dynamics (MBD) software for full vehicle simulations. Among various control strategies for ESC, the sliding mode control (SMC) method is proposed to develop these algorithms, as it is proven to be excellent at overcoming the effect of uncertainties and disturbances. The ESC model integrates active front steering (AFS) system and direct yaw moment control (DYC) system, using differential braking system, therefore the type of the ESC model is called as integrated vehicle dynamic control (IVDC) system. The IVDC virtual model will be designed using a specialized control system software, called Simulink. The controller model will be used to perform full vehicle simulations, such as sine with dwell (SwD) and double lane change (DLC) tests on Simulink to observe its functionality in stabilizing vehicles. The virtual nonlinear full vehicle model in CarSim will be equipped with the IVDC virtual model to ensure that the proposed IVDC virtual model passes the regulations that describes the ESC homologation process for North America and European countries, each defined by National Highway Traffic Safety Administration (NHTSA) and United Nations (UN). The proposed research project will enable automotive engineers and researchers to perform full vehicle virtual simulations with ESC capabilities

Modelling and Co-simulation of hybrid vehicles: A thermal management perspective

Thermal management plays a vital role in the modern vehicle design and delivery. It enables the thermal analysis and optimisation of energy distribution to improve performance, increase efficiency and reduce emissions. Due to the complexity of the overall vehicle system, it is necessary to use a combination of simulation tools. Therefore, the co-simulation is at the centre of the design and analysis of electric, hybrid vehicles. For a holistic vehicle simulation to be realized, the simulation environment must support many physical domains. In this paper, a wide variety of system designs for modelling vehicle thermal performance are reviewed, providing an overview of necessary considerations for developing a cost-effective tool to evaluate fuel consumption and emissions across dynamic drive-cycles and under a range of weather conditions. The virtual models reviewed in this paper provide tools for component-level, system-level and control design, analysis, and optimisation. This paper concerns the latest techniques for an overall vehicle model development and software integration of multi-domain subsystems from a thermal management view and discusses the challenges presented for future studies

Study on the control algorithm for lower limb exoskeleton based on ADAMS/Simulink co-simulation

A sliding mode control algorithm based on proportional switching function was developed to make the lower limb exoskeleton more fit the human walking gait trajectory. It could improve the comfort of the exoskeleton wearer and enhance the reliability of the system. The three-dimensional mechanical model of the exoskeleton built using software SolidWorks was introduced to ADAMS and then the model parameters were set. The model was combined with the software MATLAB so that the human-machine cooperation control algorithm for lower limb exoskeleton based on ADAMS and Simulink co-simulation was developed. The simulation result was compared with the desired trajectory and the trajectory under PID control. The research discovered that the ability of trajectory tracking under the sliding mode control was much better than that under PID control. It provided an important theoretical basis for the research on human-machine cooperation control algorithm

A simple and low cost anti-lock braking system control method using in-wheel force sensor and wheel angular speed sensor

The ABS (Anti-lock Braking System) is an active safety system that is designed for emergency braking situations. In an emergency braking scenario, the ABS instructs the disk-pad braking force to achieve the maximum available tyre-road braking force without locking the wheels. The maximum available tyre-road braking force helps to achieve the optimal braking distance, while the rotating wheels allow the vehicle to retain directional control capability, which allows the driver to avoid dangerous obstacles during an emergency braking scenario. This research has delivered a new and novel approach to ABS design, which could be developed at a low cost in a way which will benefit specialist and niche vehicle manufacturers alike. The proposed ABS control method combines the control logic from both theory-based ABS and commercialised ABS. Therefore, it is more practical compared to the theory-based ABS and less complex compared to a commercialised ABS. The control method only has two control phases with simple decrease, hold, and increase control actions. The proposed ABS control method uses representable tyre-road braking force data from an in-wheel-hub force measurement sensor as well as wheel angular acceleration data from a wheel angular speed sensor as control references. It uses the detected peak tyre-road braking force and its relative predefined drop percentage as control activation and control phase alternation triggers. It uses wheel angular acceleration to identify the control phase and implement the correct control actions. Zero wheel angular acceleration is used to trigger the hold control action in the first control phase, while wheel angular acceleration is used as an aid to increase the accuracy of the in-wheel-hub force sensor. An ADAMS full vehicle model based on a Subaru Impreza and a Simulink ABS control logic model have been used to establish a co-simulation environment to test the performance of the proposed ABS control method using high, low friction and split-mu road surfaces. The co-simulation results demonstrate that the proposed novel ABS control method satisfies the ABS control target, and its control results are similar to commercialised ABS

An investigation into the roll control of vehicles with hydraulically interconnected suspensions

University of Technology Sydney. Faculty of Engineering and Information Technology.This thesis presents the investigation into a roll-plane hydraulically interconnected suspension (HIS), which is safety-oriented and designed for the vehicle with a high centre of gravity (CG) and a low rollover threshold. As a potential replacement of anti-roll bars, the HIS possesses the ability to resist the roll motion of the vehicle body during cornering or sharp turning by improving the vehicle roll stiffness. The previous research has concluded that the HIS is superior to the anti-roll bars in terms of the anti-roll performance, but its road holding performance has not been thoroughly studied. In this research, the modelling, modal analysis and simulations are conducted to compare the road holding ability of the HIS and anti-roll bars. A multi-function HIS test rig is developed and mounted on a typical Sports Utility Vehicle (SUV). The related experiments are implemented on a four-post test rig. Both the simulation and experiment results confirmed that the HIS is better than anti-roll bars from the perspective of the road holding performance. To overcome the drawback of the HIS that it is unable to handle the large roll motion and the vehicle roll caused by uneven roads, the HIS is then developed to be actively controlled by a control unit. Only one servo valve is included in the control unit of the active HIS so that the system’s cost and energy consumption are much lower in comparison with the conventional active suspensions with four independent motor-actuators. An output feedback H∞ controller is developed based on an empirically estimated active HIS model at a half-car level. The active HIS controlled by the designed H∞ controller is experimentally validated on the test rig with considerable roll angle reductions. For further verifying the controllability of the active HIS and also comparing the effect of different categories of control methods on the active HIS, other three representative control algorithms are also applied to the active HIS equipped vehicle. They are the classic control methods: proportional-integral-derivative (PID) control, the optimal control algorithm: linear-quadratic regulator (LQR) control and the intelligent control algorithm: fuzzy logic control. The obtained fuzzy, fuzzy-PID and LQR controllers are implemented in simulations. The experiments of the fuzzy and fuzzy-PID controllers are also conducted. The fuzzy-PID controller presents the most promising and stable control performance among these three controllers. After that, an attempt is made to improve the control performance of the model-based controllers to enhance the roll resistance ability of the active HIS further. A nine-degrees-of-freedom (nine-DOF) model that can capture the physical characteristics of the active HIS more accurately is developed. The new system model that addresses the relation between the flow change and pressure variation of the hydraulic system, and the viscous resistance of the fluid is also included. Then an H∞ controller and an LQR controller are designed based on the new model and validated in simulations. The experiment of the H∞ controller is also performed on the test rig and the H∞ controller derived from the new model is compared with the H∞ controller derived from the old model. The results show that the H∞ controller based on the new model improves the control performance slightly. Lastly, an effort is made to reduce the effects of the time delay caused by the fluid system by considering the system time delay when developing the controller. Delay-independent and delay-dependent H∞ state feedback controllers are designed and applied to the half car model. The simulation validations of the obtained controllers are carried out in MATLAB. It is found that the developed delay-dependent H∞ controller can provide stable and acceptably good control performance even with system time delay

Investigation of integrated control of articulated heavy vehicle using scaled multi-body dynamic model

Heavy vehicle handling control systems have proven to be an efficient way of reducing road accidents and improving road traffic safety. Testing these control systems on heavy vehicles can be expensive and unsafe. Meanwhile, the scaled model has proven a secure and inexpensive way of designing and deploying vehicle dynamics control. However, the scaled model's mathematical modelling has been mainly limited to the bicycle model, reducing the scope of exploring the handling dynamics. This study presents an innovative way of modelling a scaled tractor semi-trailer using multi-body dynamics software and testing control systems through co-simulation to help develop new control systems safely and inexpensively for improving road traffic safety. In this research, modelling the scaled model of an articulated vehicle was simulated on MSC ADAMS/View, which extends the mathematical model to 168 degrees of freedom. A 1/14 physical model was used to validate the simulation model and co-simulation has been established between MSC ADAMS/View and MATLAB to investigate the control of a scaled model built on MSC ADAMS/View with a developed control system built on MATLAB/Simulink. The scaled model is a 1/14 Scania R620 articulated lorry manufactured by TAMIYA. Different parameters of the scaled model have been measured and used as inputs to the simulation model. MSC ADAMS/View was used to model the vehicle and to capture its response. The results were validated through physical tests, so a microcontroller was added to the physical model with different accelerometers to control and record the vehicle's motion instead of the existing radio control. Co-simulation has been implemented using two different control schemes, which have been built and compared against each other. The first control scheme is the electronic stability control system only. The second one is an integrated control system which combines the active front steering with the electronic stability control scheme. The main target of the developed control systems is to stabilise the vehicle through manoeuvres using the Fuzzy logic methodology. The study's main findings are that the experimental results show reasonable similarity to the simulation results, although there are minor differences. The physical validation of the simulation model indicates that it is possible to model a scaled model using multi-body dynamics software with specific considerations. Also, the results give a good understanding of the performance of heavy vehicles. Finally, using the co-simulation implemented using two different control schemes proves that the control can be developed using the scaled model. The proposed control method has been shown to be useful in developing the stability of the vehicle. It enhances the yaw rate for both tractor-trailer by around 25% and the lateral acceleration by around 20% at manoeuvres. Also, the control can be tuned easily using MATLAB. Meanwhile, the electronic stability control scheme gives better performance than the combined active front steering and electronic stability control scheme

Integration of Active Chassis Control Systems for Improved Vehicle Handling Performance

This thesis investigates the principle of integration of vehicle dynamics control systems by proposing a novel control architecture to integrate the brake-based electronic stability control (ESC), active front steering (AFS), normal suspension force control (NFC) and variable torque distribution (VTD). A nonlinear 14 degree of freedom passive vehicle dynamics model was developed in Matlab/Simulink and validated against commercially available vehicle dynamics software CarSim. Dynamics of the four active vehicle control systems were developed. Fuzzy logic and PID control strategies were employed considering their robustness and effectiveness in controlling nonlinear systems. Effectiveness of active systems in extending the vehicle operating range against the passive ones was investigated. From the research, it was observed that AFS is effective in improving the stability at lower lateral acceleration (latac) region with less interference to the longitudinal vehicle dynamics. But its ability diminishes at higher latac regions due to tyre lateral force saturation. Both ESC and VTD are found to be effective in stabilising the vehicle over the entire operating region. But the intrusive nature of ESC promotes VTD as a preferred stability control mechanism at the medium latac range. But ESC stands out in improving stability at limits where safety is of paramount importance. NFC is observed to improve the ability to generate the tyre forces across the entire operating range. Based on this analysis, a novel rule based integrated chassis control (ICC) strategy is proposed. It uses a latac based stability criterion to assign the authority to control the stability and ensures the smooth transition of the control authority amongst the three systems, AFS, VTD and ESC respectively. The ICC also optimises the utilisation of NFC to improve the vehicle handling performance further, across the entire operating regions. The results of the simulation are found to prove that the integrated control strategy improves vehicle stability across the entire vehicle operating region