Dual-Motor Vehicle Torque Sequencing for Low-Friction Starts
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Solution Overview
Problem
Vehicles equipped with multiple traveling motors experience unstable behavior due to excessive wheel slip when starting on low-friction road surfaces, such as snowy or icy roads, as the motor torques rise quickly, leading to increased slip and instability.
Innovation Solution
A vehicle control apparatus that includes a control system with processors and memory to estimate friction coefficients between wheels and the road surface, adjusting the power running torque of each motor based on delay times and smoothing factors set according to the friction coefficients, ensuring that the torque increase of one motor follows after the other if the friction coefficients differ significantly, thereby suppressing wheel slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power running torque of multiple traveling motors is increased quickly during vehicle start, then the vehicle can achieve faster acceleration and better starting performance, but excessive wheel slip occurs on low-friction road surfaces leading to unstable vehicle behavior
Solution Approach 1:
The control system performs preliminary estimation of road surface friction coefficients before vehicle start, and pre-determines the torque increase control strategy based on the estimated friction level. This preliminary assessment allows the system to prepare appropriate torque increase rates and delay times in advance, preventing excessive wheel slip from the outset while maintaining good starting performance on higher-friction surfaces
Solution Approach 2:
The control system dynamically adjusts the torque increase rate and delay time for each traveling motor based on real-time friction coefficient estimates. When low friction is detected, the system reduces the torque increase rate and extends delay times; when friction is sufficient, it allows faster torque increases. This dynamic adaptation resolves the contradiction by optimizing torque delivery according to actual road conditions
2Stability of the object's composition
If the power running torque of all traveling motors is increased simultaneously, then the vehicle can achieve balanced power distribution, but wheel slip cannot be suppressed on low-friction surfaces with significant friction differences between wheels
Solution Approach 1:
The control system applies different torque increase strategies to different traveling motors based on local friction conditions. Each motor's torque increase rate and delay time are individually adjusted according to the friction coefficient estimated for its specific wheel contact patch. This localized control allows the system to suppress wheel slip on low-friction surfaces while maintaining optimal power distribution across all motors
Solution Approach 2:
The control system performs preliminary estimation of friction coefficients for each wheel before initiating torque increase, and pre-determines the sequence and rate of torque application for each motor. This preliminary assessment enables the system to establish an optimized torque delivery sequence that prevents wheel slip while achieving balanced power distribution
Data Source
AI summary
A vehicle control apparatus to be applied to a vehicle includes a first traveling motor, a second traveling motor, and a control system. The control system estimates a first friction coefficient between a first wheel and a road surface and a second friction coefficient between a second wheel and a road surface. When the vehicle starts in a situation in which any of the first and second friction coefficients is less than a first threshold and a difference between the first and second friction coefficients is greater than a second threshold, the control system increases a power running torque of the first traveling motor after elapse of a first delay time after increasing a power running torque of the second traveling motor, if the first friction coefficient is smaller than the second friction coefficient. The first delay time is set on the basis of the first friction coefficient.