Hybrid Vehicle Engine Stability Control During Low-Friction Braking
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Solution Overview
Problem
Hybrid electric vehicles face challenges in maintaining engine stability during hard braking maneuvers on low-friction surfaces, where drive wheels can lock up and the engine drive shaft may spin reverse, complicating the unlocking process by active ABS controllers.
Innovation Solution
A control system for a hybrid electric vehicle that detects hard braking maneuvers on low-friction surfaces and injects feed-forward torque from traction motors into the driveline in the direction of engine torque to prevent reverse spinning of the drive shaft, using a distributed control system communicating with the engine and traction motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ABS controller commands high frequency brake pressure pulsations to unlock drive wheels, then the drive wheels can be unlocked, but the engine drive shaft may spin in reverse during the maneuver
Solution Approach 1:
The control system applies preliminary counteracting torque to the engine drive shaft before reverse spinning can occur during ABS activation. By detecting ABS activation signals and immediately applying opposing torque through the traction motor or engine control, the system prevents the drive shaft from rotating in reverse, thereby maintaining engine stability while allowing the ABS unlocking function to operate effectively
Solution Approach 2:
The control system introduces an intermediary torque application mechanism between the engine and the drive shaft. This intermediary control layer monitors ABS activation and inserts compensating torque commands to prevent reverse rotation, acting as a mediator that resolves the conflict between ABS wheel unlocking and engine drive shaft stability
2Ease of operation
If the engine drive shaft spins in reverse during hard braking, then the ABS controller can unlock drive wheels, but engine stability is compromised
Solution Approach 1:
The control system implements feedback by continuously monitoring engine rotational speed and direction, as well as ABS activation status. When reverse rotation is detected or anticipated during ABS operation, the system responds by applying corrective torque through the traction motor or engine management, creating a closed-loop control that maintains engine stability while permitting wheel unlocking
Solution Approach 2:
The control system takes preliminary action by preparing counter-torque commands in advance when ABS activation is detected. Rather than waiting for reverse rotation to occur, the system proactively applies stabilizing torque to prevent the condition from developing, ensuring both wheel unlocking capability and engine stability are maintained
Data Source
AI summary
A method for controlling a hybrid electric vehicle having a control system, a traction motor, and an engine includes generating an activation signal during a predetermined vehicle maneuver. The predetermined vehicle maneuver is a threshold hard braking maneuver on a surface having a low coefficient of friction. The method also includes processing the activation signal using the control system, and using the traction motor to command an injection or a passing of a feed-forward torque to the driveline of the vehicle. The feed-forward torque is in the same direction as the engine torque, and prevents a drive shaft of the engine from spinning in reverse during the maneuver. The method may include generating the activation signal in response to detecting an active state of the ABS controller. A hybrid electric vehicle includes an engine, a traction motor, and a control system configured to execute the above method.