Tire Size Calibration for Multi-Motor Torque Control
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Solution Overview
Problem
Work machines with independently controlled tires face instability and torque misalignment due to inaccurate wheel speed feedback caused by varying tire sizes, leading to motors fighting against each other, as they rely on assumed tire sizes that do not account for actual differences in tire radii or inflation pressures.
Innovation Solution
A system that calculates the actual tire sizes or relationships among tires by driving one motor at a calibration speed while others are inactive, using rotational velocity to determine accurate tire sizes, which are then used to generate precise torque commands for each motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a different motor is mounted to drive each tire and torque control is used to achieve common speed, then independent tire speed control is improved, but motor instability and torque misalignment occur due to inaccurate wheel speed feedback from varying tire sizes
Solution Approach 1:
The system changes the parameter of tire size information from assumed/fixed values to actual measured values. By detecting rotational velocity and calculating actual tire sizes, the control system uses accurate parameters to generate torque commands, resolving the instability caused by parameter inaccuracy.
Solution Approach 2:
The system introduces feedback by detecting the rotational velocity of each wheel and using this information to calculate actual tire sizes. This feedback loop allows the torque control system to continuously adjust torque commands based on real tire conditions, preventing motor instability.
2Device complexity
If assumed tire sizes are used for torque control calculations, then device complexity is reduced, but measurement precision of wheel speed feedback deteriorates due to not accounting for actual tire size variations
Solution Approach 1:
The system performs self-calibration by using the motors themselves to detect rotational velocity and calculate tire sizes. The work machine performs its own measurement during operation, eliminating the need for external measurement devices while maintaining high precision.
Solution Approach 2:
The system replaces physical tire size measurement devices with a computational approach. By using rotational velocity detection and mathematical calculation, the system substitutes mechanical measurement with electronic sensing and processing, maintaining precision while reducing device complexity.
3Ease of operation
If tire size variations due to wear, age, brand, or inflation pressure are not accounted for, then ease of operation is improved through simplified control assumptions, but traction performance deteriorates due to torque misalignment
Solution Approach 1:
The system transitions from static assumed tire size values to dynamic actual tire size measurements. By continuously detecting rotational velocity and calculating current tire sizes, the system adapts to changing tire conditions (wear, inflation, temperature), maintaining optimal traction performance throughout operation.
Data Source
AI summary
A work machine has a plurality of motors. Each motor drives a subset of a plurality of wheels/tires on the work machine. A motor control system controls one of the motors to drive the corresponding wheel/tire at a calibration speed and detects the rotational velocity of each of the other wheels/tires. A tire size indicator is generated which indicates a tire size relationship among the plurality of different tires. The tire size indicator is stored or output for use by a traction control system. The traction control system uses the tire size indicator for the different tires to generate torque command signals to the plurality of different motors.