Independent Wheel Torque Control Using Momentum Error Separation
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Solution Overview
Problem
Existing motion control systems for vehicles with independently driven left and right wheels struggle to accurately correct torque differences caused by motor differences, which can lead to instability and reduced control accuracy, especially when external influences like road gradients are involved.
Innovation Solution
A motion control device that calculates wheel torque values based on the difference between reference and actual vehicle states, extracts momentum errors caused by motor torque differences, and adjusts wheel torque commands to account for external influences such as road gradients, enhancing control accuracy by correcting torque differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If torque command values are provided to two traveling motors based on steering torque information, then the vehicle can be controlled to travel straight, but a difference in actual driving forces between left and right wheels occurs due to motor manufacturing variations and assembly accuracy
Solution Approach 1:
The patent implements feedback by detecting the actual driving forces of left and right driving wheels using wheel speed sensors and motor current detectors, comparing these actual values with target driving forces, and generating correction amounts to compensate for torque differences. This closed-loop feedback mechanism continuously adjusts the torque commands to maintain accurate driving force control despite motor manufacturing variations.
Solution Approach 2:
The patent changes the torque command parameters dynamically by calculating correction amounts based on detected wheel speeds and motor currents. The system adjusts the torque commands for left and right motors individually, modifying the parameters to compensate for manufacturing differences and assembly inaccuracies, thereby achieving precise driving force control.
2Measurement precision
If the driving force difference between left and right wheels is corrected based on torque command adjustments, then the control accuracy of driving forces is improved, but it becomes difficult to distinguish whether the cause of torque difference is motor-related or external factors such as road gradient
Solution Approach 1:
The patent segments the torque difference correction into distinct components: one addressing motor manufacturing variations and assembly accuracy, and another addressing external factors like road gradients. By separately calculating correction amounts for each cause based on detected wheel speed differences and motor current variations, the system avoids the complexity of trying to identify and correct all causes simultaneously while maintaining high control accuracy.
3Device complexity
If the same torque command values are given to both motors from steering torque information, then the control system remains simple, but the actual driving forces differ due to motor manufacturing system variations and assembly accuracy
Solution Approach 1:
The patent implements self-service by enabling the control system to automatically detect and compensate for its own torque differences without requiring complex external calibration or manual adjustment. The system uses its own sensors to detect wheel speed differences and motor current variations, calculates correction amounts, and adjusts torque commands autonomously, maintaining reliability while keeping the control system relatively simple.
Data Source
AI summary
A motion control device independently drives left and right wheels by calculating a wheel torque value from a difference between a reference vehicle state quantity or an operation instruction of a higher driving device and an actual vehicle state quantity regarding a motion and a posture of the vehicle, and controlling a plurality of motors based on the wheel torque value. The motion control device calculates a momentum error from a difference between a reference momentum based on wheel speed and a tire steering angle and an actual momentum based on the the motion and the posture of the vehicle, extracts a momentum error, calculates a wheel torque correction amount based on the extracted momentum error caused by the torque difference of the motor, adds the wheel torque correction amount to the wheel torque value, and outputs a wheel torque command to the plurality of motors.