Electric Vehicle Torque Control for Slip Recovery
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Solution Overview
Problem
Existing electric vehicle systems fail to promptly recover grip force when wheel slipping occurs, as mere reduction in assist ratio is insufficient to address the issue effectively.
Innovation Solution
Incorporating a slip detection unit that calculates and alternately fluctuates torque command values between a first and a second value when slipping is detected, intermittently imparting driving force to recover grip force, with the second value potentially being zero to ensure static friction is achieved, and utilizing a comparison of wheel rotation speeds to detect slipping states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the assist ratio is merely reduced when wheel slip is detected, then the control system is simple to operate, but the grip force of the wheel cannot be promptly recovered
Solution Approach 1:
The patent applies periodic action by making the torque command value fluctuate alternately between a first value (not more than the normal torque command value) and a second value (smaller than the first value) when wheel slip is detected. This periodic fluctuation creates intermittent driving force application, allowing the wheel to repeatedly recover grip force during the fluctuation cycles, thereby promptly eliminating the slipping state while maintaining operational simplicity.
2Stability of the object's composition
If the torque command value is kept constant during normal operation, then the driving force is stable, but the wheel cannot quickly recover from slipping state
Solution Approach 1:
The patent switches from constant torque command to periodic fluctuation of the torque command value when slip is detected. The torque command value alternates between the first value and the second value, creating intermittent driving force that allows the wheel to repeatedly attempt grip recovery. This periodic action enables quick transition from slipping to gripping state while the average driving force remains stable.
Solution Approach 2:
The patent changes the parameter of torque command value from a constant state to a fluctuating state with two distinct levels (first value and second value). This parameter change enables the system to dynamically adjust the driving force characteristics - using higher torque (first value) to attempt grip recovery and lower torque (second value) to allow grip recovery, thereby achieving both stability and speed in grip force recovery.
3Reliability
If the second torque command value is set to zero to ensure static friction, then grip force recovery is maximized, but the driving force interruption is more noticeable
Solution Approach 1:
The patent allows the second value of the torque command value to be zero or a small positive value. When set to zero, this ensures maximum grip force recovery effectiveness by completely eliminating driving force during the recovery phase, allowing static friction to fully engage. The parameter change between first value (normal or reduced torque) and second value (zero or minimal torque) creates a clear distinction between driving and recovery states, maximizing reliability of grip recovery.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for rapid recovery of grip force before the rider senses slipping, ensuring stable driving force and improved riding experience by transitioning to an intermittent driving state quickly and reliably.
Implementation Method 1
a slipping state of the first wheel that is driven by the first electric motor is detected by the slip detection unit
Data Source
AI summary
A vehicle includes a wheel, an electric motor that drives the wheel, a drive torque operator that is operated by an operator, a slip detection unit that detects a slipping state of the wheel, a torque command value calculation unit that calculates a torque command value for the electric motor, and a motor drive unit that drives the electric motor according to a calculated torque command value. When the slip detection unit has not detected a slipping state of the wheel, the torque command value calculation unit calculates a torque command value for the electric motor according to an input to the drive torque operator. When the slip detection unit has detected a slipping state of the wheel, the torque command value calculation unit calculates a torque command value that repeatedly fluctuates alternately between a first value not more than a torque command value at the time when wheel slip has been detected and a second value smaller than the first value.