Wheel Counter-Torque Sampling for Accurate Speed Over Ground
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Solution Overview
Problem
Existing methods for determining vehicle speed over ground in heavy-duty vehicles, particularly under challenging conditions, are unreliable and costly, and wheel-slip based control lacks accurate speed over ground measurements due to wheel slip errors.
Innovation Solution
A VMM system applies a transient counter-torque to wheels to un-slip them from their current slip state, allowing faster and more accurate wheel speed sampling for vehicle speed determination, using wheel speed sensors and IMUs to enhance estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wheel speed sensors are used to determine vehicle speed over ground during high wheel slip conditions, then the measurement process is simple and low-cost, but the measurement accuracy deteriorates due to wheel slip errors
Solution Approach 1:
The system applies a transient counter-torque to the wheel before sampling the wheel speed signal. This preliminary action reduces the wheel slip condition temporarily, allowing the wheel speed sensor to provide an accurate measurement of vehicle speed over ground. After the measurement is taken, the original torque is restored to maintain vehicle performance.
2Measurement precision
If GPS or camera systems are used to determine vehicle speed over ground, then measurement accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts and utilizes the existing wheel speed sensor already present in the vehicle for the purpose of determining vehicle speed over ground. By temporarily improving the measurement conditions through counter-torque application, the system makes the existing simple sensor effective, eliminating the need for complex GPS or camera systems.
3Measurement precision
If torque is reduced to minimize wheel slip for accurate speed measurement, then measurement accuracy is improved, but vehicle motion control performance deteriorates due to longer latency
Solution Approach 1:
The system applies torque reduction in periodic, transient pulses just before measurement sampling occurs. This periodic action temporarily minimizes wheel slip to obtain an accurate measurement, then restores full torque to maintain vehicle performance. The timing is synchronized to achieve measurements without prolonged loss of control authority.
Data Source
AI summary
A vehicle motion management, VMM, system for a heavy-duty vehicle has at least one wheel speed sensor to output a wheel speed signal indicative of a rotation speed of a wheel on the vehicle, and at least one torque-generating device to apply torque to the wheel. The VMM system comprises processing circuitry arranged to determine at least the direction of a current applied torque at the wheel, and in preparation for determining wheel speed by the wheel speed signal, to apply a transient amount of torque to the wheel by the torque-generating device during a limited time period in a direction opposite to the direction of the current applied torque at the wheel.