EV Motor Torque Limiting for Road-Adaptive Slip Control
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Solution Overview
Problem
Existing electric vehicle control methods face challenges in accurately calculating the friction coefficient of the road surface, making it difficult to achieve appropriate slip control, especially due to fluctuations in road conditions.
Innovation Solution
A control method for electric vehicles that estimates disturbance torque based on motor torque command values and angular velocity, sets limiting torque to prevent excessive slipping, and limits motor torque to maintain a predetermined slipping rate, thereby avoiding the need to calculate the friction coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the friction coefficient is calculated to control slip, then slip control can be achieved, but the control accuracy deteriorates due to large fluctuations in road surface conditions
Solution Approach 1:
The patent introduces disturbance torque as an intermediary parameter that indirectly reflects road surface conditions without requiring direct friction coefficient calculation. The disturbance torque estimator uses the relationship between motor torque command values and angular velocity to derive disturbance torque, which serves as a mediator to achieve slip control while avoiding the accuracy problems of direct friction coefficient measurement
Solution Approach 2:
The patent replaces the traditional friction coefficient-based control mechanism with a disturbance torque-based control mechanism. Instead of calculating friction coefficient from road surface conditions, the system substitutes this with estimating disturbance torque through the relationship between motor torque command and angular velocity, thereby eliminating the need for accurate friction coefficient calculation
2Reliability
If the motor torque is limited using disturbance torque estimation, then slip control is improved without friction coefficient calculation, but the control system complexity increases
Solution Approach 1:
The disturbance torque estimator performs multiple functions simultaneously: it estimates road surface conditions, provides feedback for torque limitation, and enables slip control without requiring separate sensors or complex algorithms. The same estimation mechanism serves both as a diagnostic tool and a control input, reducing overall system complexity despite the advanced control strategy
Solution Approach 2:
The system uses its own operational data (motor torque command values and angular velocity) to estimate disturbance torque and perform slip control. No external sensors, friction coefficient measurements, or additional input devices are required - the system serves itself by utilizing data already generated during normal operation, thereby avoiding the complexity of additional measurement systems
Data Source
AI summary
A control method of an electric vehicle using one or a plurality of motors as a traveling drive source, includes: a motor torque command value calculating step that calculates a motor torque command value; an angular velocity detecting step that detects an angular velocity correlating with a rotation speed of a drive shaft which transmits a drive force of the motor to a drive wheel; a disturbance torque estimating step that estimates a disturbance torque acting on the motor based on the motor torque command value and the angular velocity; a limiting torque setting step that sets a limiting torque corresponding to the disturbance torque in a manner that a slipping rate of the drive wheel does not exceed a first predetermined value; and a motor torque limiting step that limits the motor torque command value using the limiting torque.