Differential Clutch Torque Control for Steering-Adaptive Traction
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Solution Overview
Problem
Existing traction control systems for machines with differentially driven wheels do not adequately account for natural wheel speed differences during steering or turning, leading to suboptimal traction and reduced turning capability.
Innovation Solution
A system that senses wheel speeds and machine orientation to produce corner speed estimates, ideal and practical target speed signals, and converts these into clutch control signals to optimize torque distribution across wheels, using differential clutches to manage wheel spin and slip effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional traction control systems activate corrective controls when wheel speed threshold is exceeded, then wheel spin and slip are reduced, but natural wheel speed differences during steering are incorrectly treated as slip, reducing turning capability
Solution Approach 1:
The system dynamically adjusts the threshold for activating traction control based on steering angle. When steering angle exceeds a predetermined threshold, the system recognizes that wheel speed differences are due to turning rather than slip, and accordingly adjusts or disables the corrective control activation. This dynamic adaptation allows the system to maintain accurate traction control during straight driving while preserving natural wheel speed differences during steering maneuvers.
2Reliability
If differential clutch is engaged to reduce wheel spin, then torque control is improved, but turning capability is reduced
Solution Approach 1:
The differential clutch engagement is dynamically controlled based on steering angle detection. When the steering angle exceeds a predetermined threshold, the system reduces or disables differential clutch engagement to allow natural wheel speed differences during turning. When steering angle is within normal range, the clutch engages to provide torque control during acceleration. This dynamic control resolves the contradiction by adapting clutch behavior to operating conditions.
Solution Approach 2:
The system applies different control strategies to different operational contexts by monitoring steering angle. For straight-line or minor steering operations, aggressive torque control via differential clutch is applied. For significant steering maneuvers, the control strategy shifts to permit wheel speed differences. This local differentiation of control quality based on steering conditions resolves the contradiction between torque control and turning capability.
3Device complexity
If state machine based control strategies are used with predetermined thresholds, then wheel spin detection is simplified, but control dynamics change appreciably for different operating speeds
Solution Approach 1:
The system enhances the state machine approach by adding dynamic threshold adjustment based on steering angle and operating conditions. Rather than using fixed predetermined thresholds that cause abrupt state transitions at different speeds, the system dynamically adapts thresholds to account for steering maneuvers and varying operating speeds. This maintains the simplicity of state machine logic while improving adaptability across different operating conditions.
Solution Approach 2:
The system changes the parameters used for wheel spin detection based on operating conditions, particularly steering angle and wheel speed. By adjusting detection thresholds and parameters dynamically rather than using fixed values, the system maintains consistent performance across different operating speeds while preserving the relatively simple state machine control architecture.
Data Source
AI summary
An electronic traction optimization system includes a control unit adapted to produce a corner speed estimate signal for each wheel of a machine, produce an ideal target speed signal for each wheel having a value at least partially responsive to the corner speed estimate signals, produces a practical target speed signal for each wheel, generates an actual target speed signal having a value responsive to a comparison of the ideal target speed signal and the practical target speed signal for each wheel. The control unit compares each actual target speed signal to an associated wheel speed signal to obtain a wheel speed error signal for each wheel and converts each wheel speed error signal to a clutch control signal, wherein each differential clutch actuator is responsive to an associated clutch control signal.