Vehicle Control Allocation for Path Tracking During EPS Failure
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Solution Overview
Problem
When the electric power steering (EPS) system becomes non-functional due to issues like excessive heat, water infiltration, or electronic malfunctions, it is challenging for vehicles to maintain the planned path of travel, especially in semi-autonomous and autonomous vehicles.
Innovation Solution
A control allocation system that utilizes redundant actuation systems, such as active rear steering and combined torque vectoring and differential braking, to determine corrective constraints and control actions in real-time, distributing these actions to guide the vehicle along the planned path by solving a constrained optimization problem based on tracking errors and vehicle dynamics states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the EPS system is used for steering control, then steering assistance is provided, but the system becomes non-functional due to heat, water infiltration, or electronic malfunctions
Solution Approach 1:
The control allocation system is designed with redundant actuation systems and fault detection capabilities before the EPS system fails. When a fault is detected, the system automatically transitions to using alternative actuators (rear wheel steering, torque vectoring, differential braking) to maintain path tracking, thus cushioning against the harmful effects of EPS failure
Solution Approach 2:
The control allocation system acts as an intermediary layer between the path planning algorithm and the actuation systems. It monitors the functional status of the EPS system and dynamically reallocates control commands to alternative actuators when the EPS system becomes non-functional, mediating the transition without requiring direct driver intervention
2Reliability
If redundant actuation systems are implemented for path tracking when EPS fails, then path tracking capability is maintained, but device complexity increases
Solution Approach 1:
The control allocation system is designed to universally manage multiple actuation systems (EPS, rear wheel steering, torque vectoring, differential braking) through a single unified control framework. This multi-functional approach allows the same control allocation architecture to handle both normal EPS operation and fault条件下的 alternative actuation, reducing the need for separate control systems for different failure modes
Solution Approach 2:
The control allocation system dynamically adjusts the distribution of control commands based on the real-time functional status of available actuators. The actuator Boolean matrix and corrective constraints are dynamically updated to reflect which actuators are operational, allowing the system to adapt its control strategy without requiring complex manual reconfiguration
Data Source
AI summary
A control allocation system for a vehicle includes an electric power steering (EPS) system, one or more redundant actuation systems for controlling a plurality of wheels of the vehicle, and one or more controllers in electronic communication with the EPS system and the one or more redundant actuation systems. The one or more controllers execute instructions to determine tracking errors and vehicle dynamics states based on a plurality of local path planning references and receive a fault signal indicating the EPS system is non-functional. In response to receiving the fault signal, the one or more controllers determine a plurality of corrective constraints in real-time. The one or more controllers solve a real-time constrained optimization problem for each sampling interval of the control allocation system to determine a plurality of control actions based on the plurality of corrective constraints and the tracking errors.