Electric Machine Mode Switching for Wheel Slip Control
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Solution Overview
Problem
Existing vehicle systems face inefficiencies in wheel slip control, particularly when using spark retard to reduce engine torque, which can lead to reduced powertrain efficiency and delayed response to wheel slip conditions.
Innovation Solution
Switching the operating mode of an electric machine from torque control to speed control when wheel slip is detected, allowing for more precise and responsive wheel slip management without significantly reducing driveline efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spark retard is used to control engine torque to limit wheel slip, then wheel slip control is achieved, but powertrain efficiency is reduced significantly
Solution Approach 1:
The system dynamically switches between torque control mode and speed control mode based on wheel slip conditions. During normal operation, the electric machine operates in torque control mode to meet driver demand. When wheel slip is detected, the system transitions to speed control mode to directly limit wheel speed, thereby controlling wheel slip without relying on spark retard which reduces powertrain efficiency.
Solution Approach 2:
The patent replaces the combustion-based torque control mechanism (spark retard) with an electric machine-based speed control mechanism. The electric machine can rapidly adjust its output torque to control wheel speed directly, eliminating the need for spark retard and its associated efficiency penalties while providing faster and more precise wheel slip control.
2Speed
If spark timing adjustments are used to control engine torque, then response to wheel slip is faster than air flow adjustments, but response speed is still insufficient to limit and control wheel slip as quickly as desired
Solution Approach 1:
The system replaces the combustion-based spark timing adjustment mechanism with an electric machine control mechanism. The electric machine can respond to wheel slip conditions almost instantaneously by adjusting its electromagnetic torque output, providing significantly faster response times compared to spark timing adjustments while ensuring effective wheel slip control.
Solution Approach 2:
The control system dynamically transitions from torque control to speed control mode when wheel slip is detected. This dynamic switching enables the system to prioritize rapid wheel speed limitation over torque delivery, achieving the fastest possible response to wheel slip conditions through direct speed control of the electric machine.
3Power
If torque control mode is used for the electric machine, then driver torque demand is met, but wheel slip control is less precise and slower to respond
Solution Approach 1:
The system implements dynamic mode switching between torque control and speed control based on real-time wheel slip detection. During normal conditions, torque control mode maintains power delivery to meet driver demand. When wheel slip is detected, the system transitions to speed control mode, dynamically adjusting the electric machine's operating characteristics to prioritize wheel speed limitation over torque delivery, thereby achieving precise and rapid wheel slip control.
Data Source
AI summary
Methods and system are described for controlling wheel slip of a four wheel drive vehicle. The methods and system may be applied to an electric vehicle or a hybrid vehicle. The method and system provide for operating vehicle propulsion sources in speed and torque control modes to manage wheel slip.