Hybrid Vehicle Torque Arbitration Preventing Reverse Propulsion
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Solution Overview
Problem
Conventional powertrains cannot prevent propulsion in a direction opposite of the intended motion in hybrid or fuel cell vehicles, as electric motors can provide torque in both directions, potentially causing unintended backward motion.
Innovation Solution
An electronic control module (ECM) determines the operator's desired axle torque and arbitrates it against other torque requests, applying a predetermined minimum axle torque to prevent reverse propulsion by increasing positive torque as vehicle speed decreases and limiting negative torque to prevent excessive deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electric motors are used in hybrid or fuel cell vehicles, then the vehicle can provide torque in both directions for enhanced mobility, but the vehicle may unintentionally propel in the direction opposite of intended motion
Solution Approach 1:
The control system applies preliminary anti-action by detecting when negative axle torque requests exceed the predetermined minimum threshold and actively counteracting them by limiting the torque to the threshold value. This prevents the harmful effect of unintended reverse propulsion before it can occur, while still allowing legitimate bidirectional torque operation within safe limits.
2Speed
If negative axle torque is applied to decelerate the vehicle at low speeds, then vehicle deceleration is achieved, but the vehicle may propel backward when speed approaches zero
Solution Approach 1:
The system dynamically changes the parameter of minimum axle torque threshold based on vehicle speed. As vehicle speed approaches zero, the predetermined minimum axle torque threshold increases (becomes less negative), automatically adjusting the torque limit to prevent backward propulsion at very low speeds while maintaining effective deceleration capability at higher speeds.
3Reliability
If torque intervention requests from vehicle systems are allowed to override operator torque requests, then vehicle safety and control functions are improved, but operator control over vehicle motion may be compromised
Solution Approach 1:
The predetermined minimum axle torque threshold acts as an intermediary between operator torque requests and actual torque application. Torque intervention requests from vehicle systems can override operator requests, but only within the bounds of the predetermined threshold, which prevents excessive negative torque that would cause unintended reverse motion. This mediator preserves operator intent while ensuring safety.
Data Source
AI summary
A method of controlling torque on a vehicle wheel axle includes comparing a torque intervention request to a predetermined minimum axle torque for a current vehicle speed and a current direction of motion of the vehicle. The predetermined minimum axle torque decreases as vehicle speed in an operator-selected direction of motion increases. An arbitrated axle torque is calculated based on an operator-requested torque, the current vehicle speed, the current direction of motion, and the greater of the torque intervention request and the predetermined minimum torque. Axle torque is applied to the vehicle's wheel axle based at least partially on the arbitrated axle torque.