Off-Road Speed Control System for Torque Overshoot
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Solution Overview
Problem
Existing vehicle speed control systems are not well-suited for off-road use, as they can cause vehicle lurching due to torque overshoot when transitioning from high-drag to low-drag terrain, leading to passenger discomfort and difficulty in maintaining vehicle composure on varying terrains.
Innovation Solution
An off-road speed control system that identifies patterns in vehicle drag and predicts potential speed overshoot or undershoot events, automatically applying opposing torque to the wheels through braking or gear changes to maintain the set speed and ensure vehicle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a powertrain controller provides sufficient torque to overcome high drag obstacle in off-road conditions, then vehicle progress is maintained, but torque overshoot occurs when drag reduces causing vehicle lurching and passenger discomfort
Solution Approach 1:
The system performs preliminary action by detecting changes in drag conditions and preemptively adjusting torque delivery before speed overshoot occurs. The controller monitors wheel speed, vehicle acceleration, and drag conditions to anticipate torque overshoot events and applies retarding torque in advance to prevent lurching while maintaining progress.
Solution Approach 2:
The system implements feedback by continuously monitoring wheel speed, vehicle acceleration, and drag conditions to detect torque overshoot events. The controller uses this feedback to dynamically adjust torque delivery, applying retarding torque when overshoot is detected and maintaining optimal torque during normal operation, thereby eliminating lurching while preserving vehicle progress.
2Reliability
If known cruise control systems cancel upon wheel slip detection, then traction control can operate, but vehicle progress cannot be maintained in off-road conditions where wheel slip is common
Solution Approach 1:
The system merges speed control and traction control functions into a unified off-road progress control system. The controller coordinates torque delivery with traction control operations, maintaining speed control authority during wheel slip events rather than canceling. This integration allows the system to maintain vehicle progress while accommodating necessary traction control interventions.
Solution Approach 2:
The system applies dynamics by making the speed control system adaptive to off-road conditions. The controller dynamically adjusts its behavior based on detected conditions, allowing temporary speed deviations during wheel slip while maintaining overall progress. The system transitions from rigid on-road cruise control to flexible off-road progress control that accommodates varying terrain conditions.
Data Source
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Figure 2
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AI summary
A method for operating an off-road speed control system of a vehicle is provided. The method comprises identifying a pattern or change in at least one component of vehicle drag. The method further comprises monitoring vehicle speed to predict where a change in the at least one component of vehicle drag may result in a speed overshoot event or a speed undershoot event. The method still further comprises, in response to the predicted speed overshoot event or speed undershoot event, automatically commanding the application of an appropriate opposing torque to one or more wheels of the vehicle to counteract the predicted speed overshoot or undershoot. An off-road speed control system for a vehicle comprising an electronic control unit (ECU) configured to perform the above-described methodology is also provided.