Predicted Wheel Speed Traction Control for Electric Vehicles
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Solution Overview
Problem
Current traction control systems for electric vehicles do not effectively utilize the rapid torque response of electric motors due to outdated wheel speed information updates, leading to delayed system responses and an unnatural driving experience.
Innovation Solution
A traction control system that monitors multiple wheel speed sensors, determines synchronized wheel speeds, and uses a high-frequency motor speed update to minimize delays, allowing for real-time torque adjustments through a proportional or non-linear controller, ensuring natural and responsive control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel speed information is updated at low frequency (based on ABS controller capabilities), then the system can rely on existing sensor infrastructure, but the system response delay increases and cannot take advantage of electric motor's fast torque response capability
Solution Approach 1:
The patent applies preliminary action by using predicted wheel speed values (calculated from previous measurements and motor torque) to generate torque commands before actual wheel speed measurements are available. This allows the control system to act proactively based on predicted states rather than waiting for delayed sensor updates, thereby reducing control delay while maintaining reliability of the control decisions.
2Ease of operation
If a PI controller or controller with memory is used to send torque to the axle with most traction, then torque distribution can be controlled, but system delay increases making the control feel less natural and more intrusive
Solution Approach 1:
The patent extracts the memory function from the controller itself and places it in the wheel speed sensor system. By using predicted wheel speed values that inherently contain information about recent wheel behavior and traction conditions, the system eliminates the need for separate PI controllers or memory elements, thereby removing the associated delays and achieving more natural-feeling control while maintaining effective torque distribution.
3Productivity
If electric motor's rapid torque response capability is utilized, then traction control performance is improved, but requires wheel speed information updated at high frequency which is not available from existing ABS sensors
Solution Approach 1:
The patent introduces predicted wheel speed values as an intermediary between the low-frequency ABS wheel speed sensors and the high-frequency motor torque control. These predicted values, calculated from previous measurements and current motor torque, serve as a mediator that provides high-frequency information to the torque controller without requiring actual high-frequency sensor updates, thereby enabling effective traction control despite information loss in the sensor update rate.
Data Source
AI summary
A traction control system is provided that is applicable to both two wheel drive and four wheel drive electric vehicles, and which is capable of handling both low frequency and high frequency control duties. The system uses proportional gains in order to minimize controller delays and insure a natural feeling traction control system.