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

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

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

Effect of Adverse Weather Conditions on Vehicle Braking Distance of Highways

The effect of adverse weather conditions on the safety of vehicles moving on different types of roads and measuring its margin of safety have always been a major research issue of highways. Determining the exact value of friction coefficient between the wheels of the vehicle and the surface of the pavement (usually Asphalt Concrete) in different weather conditions is assumed as a major factor in design process. An appropriate method is analyzing the dynamic motion of the vehicle and its interactions with geometrical elements of road using dynamic simulation of vehicles. In this paper the effect of changes of friction coefficient caused by the weather conditions on the dynamic responses of three types of vehicles: including Sedan, Bus, and Truck based on the results of Adams/car Simulator are investigated. The studies conducted on this issue for different weather conditions suggest values ranging from 0.04 to 1.25. The results obtained from simulation based on Adams/car represent that the friction coefficient in values of 0.9, 0.8, 0.7, 0.6 do not effect on braking distance significantly and it is possible to attribute them all to dry weather condition. However, as it was anticipated the values of 0.5, 0.4, 0.28 and 0.18 have significant differences in braking distance. Hence, the values of 0.5, 0.4, 0.28 and 0.18 can be attributed to wet, rainy, snowy and icy conditions respectively

Function Analysis of Industrial Robot under Cubic Polynomial Interpolation in Animation Simulation Environment

In order to study the effect of cubic polynomial interpolation in the trajectory planning of polishing robot manipulator, firstly, the articular robot operating arm is taken as the research object, and the overall system of polishing robot operating arm with 7 degrees of freedom is constructed. Then through the transformation of space motion and pose coordinate system, Denavit-Hartenberg (D-H) Matrix is introduced to describe the coordinate direction and parameters of the adjacent connecting rod of the polishing robot, and the kinematic model of the robot is built, and the coordinate direction and parameters of its adjacent link are described. A multi-body Dynamic simulation software, Automatic Dynamic Analysis of Mechanical Systems (ADAMS), is used to analyze the kinematic simulation of the robot operating arm system. Finally, the trajectory of the robot manipulator is planned based on the cubic polynomial difference method, and the simulation is verified by Matrix Laboratory (MATLAB). Through calculation, it is found that the kinematic model of polishing robot operating arm constructed in this study is in line with the reality; ADAMS software is used to generate curves of the rotation angles of different joint axes and the displacement of end parts of the polishing robot operating arm changing with time. After obtaining relevant parameters, they are put into the kinematic equation constructed in this study, and the calculated position coordinates are consistent with the detection results; moreover, the polishing robot constructed in this study can realize the functions of deburring, polishing, trimming, and turning table. MATLAB software is used to generate the simulation of the movement trajectory of the polishing robot operating arm, which can show the change curve of angle and angular velocity. The difference between the angle at which the polishing robot reaches the polishing position, the change curve of angular velocity, and the time spent before and after the path optimization is compared. It is found that after path optimization based on cubic polynomial, the change curve of the polishing robot's angle and angular velocity is smoother, and the time is shortened by 17.21s. It indicates that the cubic polynomial interpolation method can realize the trajectory planning of the polishing robot operating arm, moreover, the optimized polishing robot has a continuous and smooth trajectory, which can improve the working efficiency of the robot

Development of a fuel-saving algorithm for a vehicle's driver assistant system

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2018.A fim de reduzir o consumo de combustível em sistemas de propulsão automotivos, a implementação de conjuntos motrizes híbridos, o downsizing de motores à combustão interna e a automatização do câmbio têm crescido no mercado de veículos de passeio. No entanto, as melhorias individuais em sistemas de um veículo não necessariamente aproximam a sua operação do ponto de ótima eficiência, e a adição de diferentes fontes de energia deve ser feita de forma metódica e estruturada, a fim de proporcionar ganhos consideráveis em consumo de combustível. Ademais, o comportamento do condutor e as trajetórias percorridas pelo veículo são características extremamente dependentes da região em análise, dificultando ainda mais o desenvolvimento de uma estratégia única de redução de consumo de combustível. Assim, a partir de um modelo de dinâmica longitudinal com três graus de liberdade para um veículo genérico, desenvolvido utilizando as equações de Euler-Lagrange do segundo tipo, essa dissertação tem como objetivo principal a proposta de um algoritmo para um assistente de direção automotivo, o qual promove a redução do consumo de combustível a partir do ajuste da relação de transmissão e abertura da válvula borboleta, em função da demanda de torque imposta pelo condutor, dinâmica do powertrain e características da fonte de potência. As características de desempenho do motor foram modeladas utilizando Redes Neurais Artificiais do tipo Feedforward Multi-Layer Perceptron, viabilizando a simulação de ciclos urbanos em tempo hábil e a inserção de propriedades relacionadas ao gradiente dos mapas estáticos no algoritmo do assistente de direção. O sistema foi implementado e simulado em Matlab , e seu desempenho avaliado através de um estudo de caso, utilizando modelos da literatura como referência.Abstract : The adoption of hybrid powertrain systems in passenger vehicles, as well as downsized engines and automatic transmissions, has been increasing in the last years as solutions to reduce the fuel consumption. However, the individual optimization of components or layout does not necessarily approximates the operation to conditions of maximum efficiency, and the addition of power sources should be done methodically, such that improvements of fuel efficiency can actually be achieved. Furthermore, the behavior of the driver and traffic conditions, factors which have major influence on the fuel consumption, vary with the geographic region, increasing the difficulty to develop a single solution to minimize the fuel consumption. Given such complex scenario, this dissertation proposes an algorithm for a Fuel-saving Driver Assistant System, which actuates on the throttle valve and gearbox, based on the demand of torque imposed by the driver, powertrain dynamics and characteristics of the power sources. In order to do so, a mathematical model of powertrain and longitudinal dynamics with 3 Degrees of Freedom was developed, which allows the simulation of urban traffic conditions. The performance of the engine was modeled using Artificial Neural Networks (ANN), which allies a flexible representation of the nonlinear characteristics of the power source, low computational costs and possibility to derive gradient information from the static maps, which is used by the Driver Assistant Algorithm. The system was implemented on Matlab and its performance compared to different models available in the literature

Model-free intelligent Control for anti-lock braking systems on rough terrain

Advances made in Advanced Driver Assistance Systems such as Antilock Braking Systems (ABS), have significantly improved the safety of road vehicles. ABS enhances the braking performance and steerability of a vehicle under severe braking conditions. However, ABS performance degrades on rough terrain. This is largely due to noisy measurements, the type of ABS control algorithm used, and the excitation of complex dynamics such as higher order tyre mode shapes that are neglected in the control strategy. This study proposes a model-free intelligent control technique with no modelling constraints that can overcome these un-modelled dynamics and parametric uncertainties. The Double Deep Q-learning Network algorithm with the Temporal Convolutional Network is presented as the intelligent control algorithm. The model is initially trained with a simplified single wheel model. The initial training data is transferred to and then enhanced by using a validated full-vehicle model including a physics-based tyre model, a 3D rough road profile with added stochasticity. The performance of the newly developed ABS controller is compared to a Bosch algorithm tuned for off-road use. Simulation results show a generalizable and robust control algorithm that can prevent wheel lockup over rough terrain without significantly deteriorating the vehicle’s stopping distance on smooth roadsDissertation (MEng (Mechanical Engineering))--University of Pretoria, 2022.Mechanical and Aeronautical EngineeringMEng (Mechanical Engineering)Unrestricte

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

Development of a vehicle dynamics controller for obstacle avoidance

As roads become busier and automotive technology improves, there is considerable potential for driver assistance systems to improve the safety of road users. Longitudinal collision warning and collision avoidance systems are starting to appear on production cars to assist drivers when required to stop in an emergency. Many luxury cars are also equipped with stability augmentation systems that prevent the car from spinning out of control during aggressive lateral manoeuvres. Combining these concepts, there is a natural progression to systems that could assist in aiding or performing lateral collision avoidance manoeuvres. A successful automatic lateral collision avoidance system would require convergent development of many fields of technology, from sensors and instrumentation to aid environmental awareness through to improvements in driver vehicle interfaces so that a degree of control can be smoothly and safely transferred between the driver and vehicle computer. A fundamental requirement of any collision avoidance system is determination of a feasible path that avoids obstacles and a means of causing the vehicle to follow that trajectory. This research focuses on feasible trajectory generation and development of an automatic obstacle avoidance controller that integrates steering and braking action. A controller is developed to cause a specially modified car (a Mercedes `S' class with steer-by-wire and brake-by-wire capability) to perform an ISO 3888-2 emergency obstacle avoidance manoeuvre. A nonlinear two-track vehicle model is developed and used to derive optimal controller parameters using a series of simulations. Feedforward and feedback control is used to track a feasible reference trajectory. The feedforward control loops use inverse models of the vehicle dynamics. The feedback control loops are implemented as linear proportional controllers with a force allocation matrix used to apportion braking effort between redundant actuators. Two trajectory generation routines are developed: a geometric method, for steering a vehicle at its physical limits; and an optimal method, which integrates steering and braking action to make full use of available traction. The optimal trajectory is obtained using a multi-stage convex optimisation procedure. The overall controller performance is validated by simulation using a complex proprietary model of the vehicle that is reported to have been validated and calibrated against experimental data over several years of use in an industrial environment