Trajectory generation for road vehicle obstacle avoidance using convex optimization

This paper presents a method for trajectory generation using convex optimization to find a feasible, obstacle-free path for a road vehicle. Consideration of vehicle rotation is shown to be necessary if the trajectory is to avoid obstacles specified in a fixed Earth axis system. The paper establishes that, despite the presence of significant non-linearities, it is possible to articulate the obstacle avoidance problem in a tractable convex form using multiple optimization passes. Finally, it is shown by simulation that an optimal trajectory that accounts for the vehicle’s changing velocity throughout the manoeuvre is superior to a previous analytical method that assumes constant speed

Advanced electric vehicle components for long-distance daily trips

This paper introduces a holistic engineering approach for the design of an electric sport utility vehicle focused on the reliable capability of long-distance daily trips. This approach is targeting integration of advanced powertrain and chassis components to achieve energy-efficient driving dynamics through manifold contribution of their improved functions. The powertrain layout of the electric vehicle under discussion is designed for an e-traction axle system including in-wheel motors and the dual inverter. The main elements of the chassis layout are the electro-magnetic suspension and the hybrid brake-by-wire system with electro-hydraulic actuators on the front axle and the electro-mechanical actuators on the rear axle. All the listed powertrain and chassis components are united under an integrated vehicle dynamics and energy management control strategy that is also outlined in the paper. The study is illustrated with the experimental results confirming the achieved high performance on the electric vehicle systems level

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

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

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

DESIGN OF A SEMI-ACTIVE STEERING SYSTEM FOR A PASSENGER CAR

This thesis presents research into an improved active steering system technology for a passenger car road vehicle, based on the concept of steer-by-wire (SBW) but possessing additional safety features and advanced control algorithms to enable active steering intervention. An innovative active steering system has been developed as 'Semi-Active Steering' (SAS) in which the rigid steering shaft is replaced with a low stiffness resilient shaft (LSRS). This allows active steer to be performed by producing more or less steer angle to the front steered road wheels relative to the steering wheel input angle. The system could switch to either being 'active' or 'conventional' depending on the running conditions of the vehicle; e.g. during normal driving conditions, the steering system behaves similarly to a power-assisted steering system, but under extreme conditions the control system may intervene in the vehicle driving control. The driver control input at the steering wheel is transmitted to the steered wheels via a controlled steering motor and in the event of motor failure, the LSRS provides a basic steering function. During operation of the SAS, a reaction motor applies counter torque to the steering wheel which simulates the steering 'feel' experienced in a conventional steering system and also applies equal and opposite counter torque to eliminate disturbance force from being felt at the steering wheel during active control operation. The thesis starts with the development of a mathematical model for a cornering road vehicle fitted with hydraulic power-assisted steering, in order to understand the relationships between steering characteristics such as steering feel, steering wheel torque and power boost characteristic. The mathematical model is then used to predict the behaviour of a vehicle fitted with the LSRS to represent the SAS system in the event of system failure. The theoretical minimum range of stiffness values of the flexible shaft to maintain safe driving was predicted. Experiments on a real vehicle fitted with an LSRS steering shaft simulator have been conducted in order to validate the mathematical model. It was found that a vehicle fitted with a suitable range of steering shaft stiffness was stable and safe to be driven. The mathematical model was also used to predict vehicle characteristics under different driving conditions which were impossible to conduct safely as experiments. Novel control algorithms for the SAS system were developed to include two main criteria, viz. power-assistance and active steer. An ideal power boost characteristic curve for a hydraulic power-assisted steering was selected and modified and a control strategy similar to Steer-by-Wire (SBW) was implemented on the SAS system. A full-vehicle computer model of a selected passenger car was generated using ADAMS/car software in order to demonstrate the implementation of the proposed SAS system. The power-assistance characteristics were optimized and parameters were determined by using an iteration technique inside the ADAMS/car software. An example of an open-loop control system was selected to demonstrate how the vehicle could display either under-steer or over-steer depending on the vehicle motion. The simulation results showed that a vehicle fitted with the SAS system could have a much better performance in terms of safety and vehicle control as compared to a conventional vehicle. The characteristics of the SAS system met all the requirements of a robust steering system. It is concluded that the SAS has advantages which could lead to its being safely fitted to passenger cars in the future. Keywords: steer-by-wire, active steering, innovative, power-assisted steering, steering control, flexible shaft, steering intervention, system failure, safety features

High-speed civil transport flight- and propulsion-control technological issues

Technology advances required in the flight and propulsion control system disciplines to develop a high speed civil transport (HSCT) are identified. The mission and requirements of the transport and major flight and propulsion control technology issues are discussed. Each issue is ranked and, for each issue, a plan for technology readiness is given. Certain features are unique and dominate control system design. These features include the high temperature environment, large flexible aircraft, control-configured empennage, minimizing control margins, and high availability and excellent maintainability. The failure to resolve most high-priority issues can prevent the transport from achieving its goals. The flow-time for hardware may require stimulus, since market forces may be insufficient to ensure timely production. Flight and propulsion control technology will contribute to takeoff gross weight reduction. Similar technology advances are necessary also to ensure flight safety for the transport. The certification basis of the HSCT must be negotiated between airplane manufacturers and government regulators. Efficient, quality design of the transport will require an integrated set of design tools that support the entire engineering design team