Fractional Order Fault Tolerant Control - A Survey

In this paper, a comprehensive review of recent advances and trends regarding Fractional Order Fault Tolerant Control (FOFTC) design is presented. This novel robust control approach has been emerging in the last decade and is still gathering great research efforts mainly because of its promising results and outcomes. The purpose of this study is to provide a useful overview for researchers interested in developing this interesting solution for plants that are subject to faults and disturbances with an obligation for a maintained performance level. Throughout the paper, the various works related to FOFTC in literature are categorized first by considering their research objective between fault detection with diagnosis and fault tolerance with accommodation, and second by considering the nature of the studied plants depending on whether they are modelized by integer order or fractional order models. One of the main drawbacks of these approaches lies in the increase in complexity associated with introducing the fractional operators, their approximation and especially during the stability analysis. A discussion on the main disadvantages and challenges that face this novel fractional order robust control research field is given in conjunction with motivations for its future development. This study provides a simulation example for the application of a FOFTC against actuator faults in a Boeing 747 civil transport aircraft is provided to illustrate the efficiency of such robust control strategies

Real time implementation of socially acceptable collision avoidance of a low speed autonomous shuttle using the elastic band method

This paper presents the real time implementation of socially acceptable collision avoidance using the elastic band method for low speed autonomous shuttles operating in high pedestrian density environments. The modeling and validation of the research autonomous vehicle used in the experimental implementation is presented first, followed by the details of the Hardware-In-the-Loop connected and autonomous vehicle simulator used. The socially acceptable collision avoidance algorithm is formulated using the elastic band method as an online, local path modification algorithm. Parameter space based robust feedback plus feedforward steering controller design is used. Model-in-the-loop, Hardware-In-the-Loop and road testing in a proving ground are used to demonstrate the effectiveness of the real time implementation of the elastic band based socially acceptable collision avoidance method of this paper

Trends in vehicle motion control for automated driving on public roads

In this paper, we describe how vehicle systems and the vehicle motion control are affected by automated driving on public roads. We describe the redundancy needed for a road vehicle to meet certain safety goals. The concept of system safety as well as system solutions to fault tolerant actuation of steering and braking and the associated fault tolerant power supply is described. Notably restriction of the operational domain in case of reduced capability of the driving automation system is discussed. Further we consider path tracking, state estimation of vehicle motion control required for automated driving as well as an example of a minimum risk manoeuver and redundant steering by means of differential braking. The steering by differential braking could offer heterogeneous or dissimilar redundancy that complements the redundancy of described fault tolerant steering systems for driving automation equipped vehicles. Finally, the important topic of verification of driving automation systems is addressed

Actuators for Intelligent Electric Vehicles

This book details the advanced actuators for IEVs and the control algorithm design. In the actuator design, the configuration four-wheel independent drive/steering electric vehicles is reviewed. An in-wheel two-speed AMT with selectable one-way clutch is designed for IEV. Considering uncertainties, the optimization design for the planetary gear train of IEV is conducted. An electric power steering system is designed for IEV. In addition, advanced control algorithms are proposed in favour of active safety improvement. A supervision mechanism is applied to the segment drift control of autonomous driving. Double super-resolution network is used to design the intelligent driving algorithm. Torque distribution control technology and four-wheel steering technology are utilized for path tracking and adaptive cruise control. To advance the control accuracy, advanced estimation algorithms are studied in this book. The tyre-road peak friction coefficient under full slip rate range is identified based on the normalized tyre model. The pressure of the electro-hydraulic brake system is estimated based on signal fusion. Besides, a multi-semantic driver behaviour recognition model of autonomous vehicles is designed using confidence fusion mechanism. Moreover, a mono-vision based lateral localization system of low-cost autonomous vehicles is proposed with deep learning curb detection. To sum up, the discussed advanced actuators, control and estimation algorithms are beneficial to the active safety improvement of IEVs

Investigation on maneuverability improvement of a four-wheel drive and rear-wheel steering system : numerical simulation analysis

X-by-wire technology is an advancement in the automotive industry and is recognized by many countries in recent years. It includes drive-by-wire (DBW) and steer-by-wire (SBW). DBW is available in two-wheel drive (2WD) and four-wheel drive (4WD) forms. 4WD has two forms: centralized motor drive and distributed motor drive. A centralized motor drive is to use the motor to replace the engine to provide power for the vehicle. The distributed motor drive is mainly based on the in-wheel motor, and the wheel is driven by the in-wheel motor to provide power for the vehicle. SBW has two forms: two-wheel steering (2WS) and four-wheel steering (4WS). It not only dramatically reduces the operating burden of the driver but also solves the problem that ordinary vehicles cannot perform 4WS. Usually, the lower maneuverability is easy to show on 2WS vehicles during vehicle turning. No matter when driving a vehicle on a narrow city road or parking, it is required to turn the steering wheel several times when the vehicle needs to steer. Moreover, the vehicle can be prone to understeer (US) or oversteer (OS) phenomena that occur when steering. The main purpose of this research is to simulate the steering performance of the vehicle by constructing a model of modern conventional vehicles and to solve the problems that may occur during vehicle cornering by applying an active 4WS control system to control the yaw rate. In this research, experiments of 2WS cornering at several constant speeds and steer angles were conducted using an actual experimental vehicle. A simulation model of the test car was constructed in MATLAB Simulink using nonlinear vehicle dynamics equations with the specification of the vehicle as the parameters. A PID control system was used in this simulation to control the rear-wheel steering angle in order to achieve 4WS. By comparing the simulation and the experimental result, it can be concluded that the nonlinear vehicle dynamics equation can be used to do the simulation of the vehicle motion. After verifying the vehicle dynamics equation, in order to verify whether the time of rotating the steering wheel will affect the motion of the vehicle, this study simulated two different times to complete the rotation of the wheel which is 2 seconds and 25 seconds with the front steering angle is 10 degrees. The results show that no matter whether the time of steering wheel rotation is fast or slow, it does not affect the speed of the vehicle's US and OS phenomenon. By simulating the cornering situation of the vehicle speeds from 10km/h to 80 km/h in the 10km/h increment. It is concluded that the vehicle will occur US phenomenon when the vehicle turning speed is lower around 20km/h; when the vehicle corners with a speed higher than 50km/h, the vehicle will have an OS phenomenon happen. After applying the 4WS system, the OS and US problems are solved efficiently. Although the vehicle is turning at a speed of 80km/h, steady-state cornering (SSC) can still be achieved. After applying the PID control system, most of the cornering can be controlled. except when the wheels rotate to 10° in only two seconds and the vehicle speed is greater than 60km/h which is the vehicle is out of control in a very short time, the PID control system cannot make the rear wheels have an appropriate steering angle to make the vehicle have an SSC. In short, this study solved almost all US and OS phenomena that can occur in 2WS vehicles by applying the 4WS system

Steering angle sensorless control for four-wheel steering vehicle via sliding mode control method

This paper presents a new sensorless control method for four-wheel steering vehicles. Compared to the existing sensor-based control, this approach improved dynamic stability, manoeuvrability, and robustness in case of malfunction of the front steering angle sensor. It also provided a software redundancy and backup solution, as well as improved fault tolerance. The strategy of the sensorless control is based on the sliding mode method to estimate the replacement of the front steering input from the errors between the vehicle’s measured and desired values of the vehicle’s sideslip angle and yaw rate. The simulation results demonstrate that the observer effectively estimated the front-wheel steering angle at both low and high speeds scenarios in the cornering and lane change manoeuvres. Furthermore, the sensorless control approach can achieve equivalent control performances to the sensor-based controller including a small and stable yaw rate response and zero sideslip angle. The results of the study offer a potential solution for improving manoeuvrability, stability, and sensor fault tolerance of four-wheel steering vehicles

Fault tolerant control for nonlinear aircraft based on feedback linearization

The thesis concerns the fault tolerant flight control (FTFC) problem for nonlinear aircraft by making use of analytical redundancy. Considering initially fault-free flight, the feedback linearization theory plays an important role to provide a baseline control approach for de-coupling and stabilizing a non-linear statically unstable aircraft system. Then several reconfigurable control strategies are studied to provide further robust control performance:- A neural network (NN)-based adaption mechanism is used to develop reconfigurable FTFC performance through the combination of a concurrent updated learninglaw. - The combined feedback linearization and NN adaptor FTFC system is further improved through the use of a sliding mode control (SMC) strategy to enhance the convergence of the NN learning adaptor. - An approach to simultaneous estimation of both state and fault signals is incorporated within an active FTFC system.The faults acting independently on the three primary actuators of the nonlinear aircraft are compensated in the control system.The theoretical ideas developed in the thesis have been applied to the nonlinear Machan Unmanned Aerial Vehicle (UAV) system. The simulation results obtained from a tracking control system demonstrate the improved fault tolerant performance for all the presented control schemes, validated under various faults and disturbance scenarios.A Boeing 747 nonlinear benchmark model, developed within the framework of the GARTEUR FM-AG 16 project “fault tolerant flight control systems”,is used for the purpose of further simulation study and testing of the FTFC scheme developed by making the combined use of concurrent learning NN and SMC theory. The simulation results under the given fault scenario show a promising reconfiguration performance

A Flexible Hierarchical Model-Based Control Methodology for Vehicle Active Safety Systems.

To improve the stability and safety performance of active safety systems, vehicle control systems are increasingly incorporating sophisticated chassis actuator control functions. Thus vehicle control systems require efficient control algorithms to reduce the amount of duplicate hardware or adopt various actuator combinations in response to diverse customer demands and various hardware combinations from different suppliers. One of the main challenges for efficient controller design is how to create a flexible modular design which can respond to different reference vehicle behaviors and provide optimal actuator apportionment, while avoiding functional conflicts between chassis sub-systems. The proposed control methodology offers a total vehicle motion control solution for an active safety system by addressing the issue of flexible modular design in integrated vehicle control systems. In this thesis, modularity is realized by a model-based hierarchical control structure consisting of three layers: an upper layer for reference vehicle motions, an intermediate layer for actuator apportionment, and a lower layer for stand-alone actuator control. The reference vehicle motions can be determined by any type of reference model for vehicle stability control or collision avoidance control. The actuator apportionment uses Model Predictive Control (MPC) to provide flexibility by balancing tire forces to track target reference vehicle motions while simultaneously considering constrained conditions, such as actuator limits or available actuator combinations. Moreover, the MPC is designed to be feasible in real-time using a linear time-varying MPC approach which avoids the complexity of full nonlinear MPC and addresses the vehicle nonlinearity. The effectiveness of the proposed control structure is investigated for vehicle stability control in terms of handling stability and handling responsiveness. The handing stability and responsiveness of the control structure appear to be robust with respect to various uncertain environments including model-plant mismatch and diverse driving conditions. It is then applied to collision avoidance systems by adapting the reference vehicle motions at the upper level of the controller. Collision avoidance is found to be nearly as effective as that of the combination of an optimizing driver supported by the MPC-based stability controller; this suggests that the MPC approach could be used in future high performance collision avoidance systems.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57610/2/sehyun_1.pd

Direct thrust force control of primary permanent magnet linear motor based on improved extended state observer and model-free adaptive predictive control

A model-free adaptive predictive control algorithm based on an improved extended state observer (IESO) is proposed to solve the problem that the primary permanent magnet linear motor is susceptible to time-varying parameters and unknown disturbances. Firstly, a model-free adaptive control algorithm based on compact format is designed to achieve high control precision of the system and reduce thrust fluctuation, only through the input/output data of the system. Because the traditional model-free adaptive control is too sensitive to the internal parameters of the controller, a combination of model-free adaptive control and predictive control is further developed. By predicting the data for a future time in advance, the sensitivity to the internal parameters of the controller is reduced and the control performance is further improved. Since the load change and other nonlinear disturbances in practical applications have a great impact on the control effect of the system, an improved extended state observer is further used to compensate for the impact of nonlinear disturbances on the control system. In addition, the stability of the closed-loop system is analyzed. Comparable simulation results clearly demonstrate the good tracking performance and strong robustness of the proposed control