CVT Control System Zeroed-Out Wheel Slip Calculation
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Solution Overview
Problem
Existing CVT control systems inaccurately measure wheel slip due to vehicle turning, leading to unnecessary clamping pressure adjustments and potential damage, as they fail to differentiate between slip caused by turning and slip caused by road disturbances or low friction.
Innovation Solution
A method and system that calculate a zeroed-out wheel slip by subtracting theoretical wheel speed differences due to turning from actual wheel speed differences, allowing for accurate determination of actual wheel slip and appropriate clamping pressure adjustments based on predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CVT control system applies additional clamping pressure when detecting wheel slip, then the continuous member is prevented from slipping and torque capacity is maintained, but unnecessary clamping pressure is applied during turning maneuvers causing potential damage and reduced reliability
Solution Approach 1:
The control system introduces an intermediary calculation step that computes expected wheel speed differences during turning based on vehicle dynamics models. This intermediary value acts as a reference to distinguish between normal turning-induced speed differences and abnormal slip conditions, enabling the system to avoid unnecessary clamping pressure during turning while maintaining protection during actual slip events.
Solution Approach 2:
The system implements feedback by continuously monitoring actual wheel speeds, comparing them against expected speeds during turning maneuvers, and using this comparison to modulate clamping pressure decisions. The feedback loop enables the system to adapt clamping pressure in real-time based on whether detected wheel speed differences are due to normal turning or abnormal slip conditions.
2Measurement precision
If the CVT control system uses a lower wheel slip threshold to detect actual slip, then more accurate slip detection is achieved, but false detection during turning increases leading to unnecessary clamping pressure adjustments
Solution Approach 1:
The control system applies local quality by implementing different detection thresholds and evaluation criteria for different operating conditions. During turning maneuvers, the system uses elevated thresholds and compares actual speeds against turning-specific expected speeds, while during straight-line operation, it uses lower thresholds for sensitive slip detection. This localized adaptation of detection parameters eliminates false positives during turning while maintaining high sensitivity during normal operation.
Data Source
AI summary
A continuously variable transmission (CVT), a transmission control system, and a method is provided. The control system is configured to determine a measured wheel speed of two driven wheels and a first driving wheel, calculate a first driving wheel expected speed based on the driven wheel measured speeds, a track width, and a wheel base, and calculate an actual wheel speed difference between the first driving wheel measured speed and the additional wheel measured speed. The additional wheel can be either of the driven wheels or a second driving wheel. The control system is also configured to calculate a theoretical wheel speed difference between the first driving wheel expected speed and the additional wheel measured speed, calculate a zeroed-out wheel slip based on the difference between the actual wheel speed difference and the theoretical wheel speed difference, and determine whether the zeroed-out wheel slip exceeds a predetermined threshold.