Heavy-Duty Vehicle Actuator Control for Unknown Tyre Slip Conditions
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Solution Overview
Problem
The interface between central and local controllers in heavy-duty vehicles is limited in bandwidth and latency, hindering efficient vehicle motion management, especially in unpredictable road conditions where the relationship between wheel slip and tyre force is unknown.
Innovation Solution
A control unit estimates applied torque and correlates it with wheel speed to maintain target wheel speed, executing a back-off procedure if an increase in wheel speed leads to a decrease in estimated torque, without relying on inverse tyre models or accurate vehicle speed data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If wheel slip-based control is used to improve responsiveness, then the control bandwidth is increased, but the system requires accurate knowledge of the relationship between wheel slip and tyre force which is unavailable in unknown road conditions
Solution Approach 1:
The control system performs self-characterization by autonomously exploring the tyre's force-slip relationship through controlled wheel speed variations. The system injects excitation signals (speed variations) and measures the resulting torque responses to build its own tyre model, eliminating the need for external or pre-stored tyre data.
Solution Approach 2:
The system performs preliminary exploration of the tyre characteristics before actual control is needed. By characterizing the tyre force-w slip relationship in advance through controlled experiments, the system prepares the necessary information for subsequent high-performance control without requiring real-time external data.
2Measurement precision
If inverse tyre model based control is used to achieve precise force control, then the control accuracy is improved, but the system complexity increases and requires accurate vehicle speed data which may not be available
Solution Approach 1:
The control system creates and uses its own simplified tyre model through self-characterization, eliminating the need for complex pre-programmed inverse tyre models. The system performs its own system identification by measuring torque responses to controlled wheel speed variations and uses this empirical data for control.
Solution Approach 2:
The patent replaces complex mechanical modelling (inverse tyre models requiring vehicle speed data) with a simplified empirical approach based on direct torque measurement and controlled wheel speed variation. This substitution eliminates the need for complex mathematical models while achieving comparable or superior control performance.
3Device complexity
If the interface between central and local controllers uses torque-based requests, then the control architecture is simple, but the bandwidth is limited and latency is high which hampers responsiveness to abrupt changes
Solution Approach 1:
The local controller performs self-characterization of the tyre and autonomous exploration of the force-slip relationship, eliminating the need for complex central coordination. This distributed intelligence approach maintains architectural simplicity while dramatically increasing bandwidth by enabling the local controller to respond independently and immediately to changing conditions.
Data Source
AI summary
A control unit for controlling at least one torque generating MSD on a heavy-duty vehicle. The control unit receives a motion request indicative of a desired positive longitudinal tire force to be generated by the torque generating MSD, obtains an estimated applied torque indicative of a current torque generated by the torque generating MSD, determines a target wheel speed based on the motion request and on the estimated applied torque, and configures the torque generating MSD to maintain the target wheel speed. The control unit is arranged to decrease the target wheel speed in case an increase in configured wheel speed results in a decrease in the estimated applied torque.