Actuator Fault-Tolerant Vehicle Motion Control: A Survey

Abstract

The advent of automated vehicles operating at SAE levels 4 and 5 poses high fault tolerance demands for all functions contributing to the driving task. At the actuator level, fault-tolerant vehicle motion control, which exploits functional redundancies among the actuators, is one means to achieve the required degree of fault tolerance. Therefore, we give a comprehensive overview of the state of the art in actuator fault-tolerant vehicle motion control with a focus on drive, brake, and steering degradations, as well as tire blowouts. This review shows that actuator fault-tolerant vehicle motion is a widely studied field; yet, the presented approaches differ with respect to many aspects. To provide a starting point for future research, we survey the employed actuator topologies, the tolerated degradations, the presented control approaches, as well as the experiments conducted for validation. Overall, and despite the large number of different approaches, the covered literature reveals the potential of increasing fault tolerance by fault-tolerant vehicle motion control. Thus, besides developing novel approaches or demonstrating real-time applicability, future research should aim at investigating limitations and enabling comparison of fault-tolerant motion control approaches in order to allow for a thorough safety argumentation.

Toward Fault-Tolerant Vehicle Motion Control for Over-Actuated Automated Vehicles: A Non-Linear Model Predictive Approach

“…In this section, we concentrate on publications in the field of fault-tolerant vehicle motion control that are related to the present work, either by using the same actuator topology or by using model predictive control (MPC) as control scheme. Still, the general statements made in this section hold true for a wider body of literature as the comprehensive overview in [6] reveals. We briefly highlight the employed control techniques and structures, the ranges of tolerated degradation and failure types, as well as the corresponding control targets.…”

“…However, there is no publication available that covers the entire range of the categories listed above. This fact also applies to the body of literature in the field of fault-tolerant vehicle motion control that has been reviewed in [6].…”

“…Fault-tolerant vehicle motion control is a widely investigated field. However, the published approaches differ quite significantly with respect to the considered actuator topology, the employed control techniques, the regarded degradation and failure types, and the control targets [6].…”

“…First, to our best knowledge, the work of Liu et al is the sole contribution that investigates the handling of tire blowouts using the over-actuated actuator topology that is in the focus of the present work. At the same time, it is the only other work known to us that features fault tolerance against failed actuators and tire blowouts in a single control approach [6]. Finally, the approach of Liu et al [7] aims at tracking a temporal sequence of reference poses, which has only been investigated in the field of fault-tolerant vehicle motion control in our previous work in [3].…”

“…Different failure and degradation categories can be formed in order to determine the range of fault tolerance provided by different control approaches. The categories that describe non-nominal behavior according to [6] yield, on the one hand, five failure categories, which are F1: zero wheel torque, F2: unintended wheel torque, F3: locked or spinning wheel, F4: unintended steering angle, and F5: zero steering torque. Failure F5 is referred to as ''complete steering failure'' by some scholars [39].…”