Trailer Backup Assist Rate-Limited Brake Torque Control
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Solution Overview
Problem
Reversing a vehicle while towing a trailer can be challenging, especially for infrequent drivers, as existing systems struggle to reliably prevent the trailer from converging towards a jackknife angle, requiring advanced control systems to manage vehicle speed and steering.
Innovation Solution
A trailer backup assist system that includes a speed detector, brake system, and control system to determine a threshold speed, applying a rate-limited brake torque demand based on the error between the threshold and actual vehicle speed, while also outputting steering commands to control the trailer's reversing path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the vehicle speed is strictly limited to prevent jackknife conditions, then the reliability of trailer backup control is improved, but the ease of operation deteriorates due to abrupt brake applications
Solution Approach 1:
The patent applies rate-limiting to the brake torque demand before it is executed, effectively cushioning the abrupt control actions. The rate-limit operator constrains the rate of change of brake torque to a maximum value, preventing sudden harsh braking while still achieving speed control. This resolves the contradiction by maintaining reliability through speed control while improving ease of operation through smooth brake application.
Solution Approach 2:
The patent transitions from static speed limiting to dynamic rate-limited control. Instead of simply applying brakes when speed exceeds a threshold, the system dynamically adjusts the brake torque demand based on the rate of change, creating a more adaptive and comfortable control response that maintains reliability while improving operability.
2Device complexity
If a simple speed threshold control is used, then the device complexity is reduced, but the reliability of preventing jackknife conditions deteriorates
Solution Approach 1:
The patent implements feedback control by continuously monitoring vehicle speed, calculating speed error relative to a threshold, and adjusting brake torque demand based on this error. The rate-limit operator also provides feedback by constraining the rate of change of torque demand. This feedback mechanism enhances reliability compared to simple threshold control while maintaining manageable system complexity.
Data Source
AI summary
A vehicle includes a speed detector detecting a vehicle speed, a brake system and a control system implementing a control mode including determining a threshold speed. The control system further derives an initial brake torque demand proportional to an error between the threshold speed and a vehicle speed exceeding the threshold speed and outputs to the brake system a rate-limited brake torque demand by applying a rate-limit operator based on the error to the initial brake torque demand.