Vehicle Control Apparatus Friction Braking Transition
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Solution Overview
Problem
In deceleration traveling, the transition from regenerative braking to friction braking in vehicles results in reduced control accuracy, leading to shocks due to the lower control accuracy of friction braking compared to regenerative braking.
Innovation Solution
A vehicle control apparatus that includes an electric motor, a brake mechanism, and a control system, which increases the friction braking force while reducing the regenerative braking force in low vehicle speed ranges by correcting correlation data between control instruction values and friction braking forces, using a change rate of vehicle acceleration as a trigger to enhance control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If regenerative braking is used in low vehicle speed range, then energy efficiency is improved, but control accuracy deteriorates and shocks occur during transition to friction braking
Solution Approach 1:
The system performs preliminary correction of correlation data between brake fluid pressure and friction braking force before the transition occurs. By detecting when regenerative braking force becomes insufficient and friction braking force needs to increase, the system proactively corrects the correlation data to ensure accurate friction braking control from the start of the transition, preventing shocks and maintaining control accuracy.
Solution Approach 2:
The system uses feedback from the vehicle acceleration change rate to detect transition conditions and trigger correlation data correction. By continuously monitoring the acceleration change rate and comparing it against thresholds, the system receives feedback about the braking state and automatically initiates correction when transition conditions are met, ensuring timely adjustment of control parameters.
2Force
If friction braking force is increased while regenerative braking force is reduced, then deceleration control is maintained, but control accuracy decreases leading to shocks
Solution Approach 1:
The system corrects the correlation data between brake fluid pressure and friction braking force in advance, before the friction braking force needs to fully take over. This preliminary correction ensures that when the transition occurs and friction braking force increases, the control accuracy is already optimized, preventing shocks during the force transition.
Solution Approach 2:
The system dynamically changes the correlation data parameters based on detected transition conditions. By adjusting the correlation data between brake fluid pressure and friction braking force according to the vehicle acceleration change rate, the system adapts the control parameters to match the transition state, maintaining accuracy during the force shift from regenerative to friction braking.
3Measurement precision
If correlation data is corrected using vehicle acceleration change rate as trigger, then control accuracy is improved, but system complexity increases
Solution Approach 1:
The system uses the vehicle acceleration change rate as a feedback signal to trigger correlation data correction. This feedback mechanism allows the system to automatically detect transition conditions and initiate correction only when needed, improving control accuracy without requiring continuous complex processing. The acceleration change rate serves as a simple yet effective trigger condition.
Solution Approach 2:
The system changes the correlation data parameters based on the detected acceleration change rate threshold. By using a threshold-based parameter change approach, the system maintains simplicity while achieving improved control accuracy. The correction is triggered when the acceleration change rate exceeds a predetermined threshold, providing a straightforward method to adapt control parameters to transition conditions.
Data Source
AI summary
A vehicle control apparatus to be applied to a vehicle includes an electric motor, a brake mechanism, and a control system. The control system increases a friction braking force of the brake mechanism while reducing a regenerative braking force of the electric motor, in deceleration traveling performed in a low vehicle speed range where a vehicle speed of the vehicle is less than a first threshold in a state in which an accelerator operation and a brake operation performed by a driver who drives the vehicle are canceled. The control system corrects correlation data between a control instruction value indicated to the brake mechanism and the friction braking force generated by the control instruction value, by using, as a trigger, a situation in which a change rate of a vehicle acceleration of the vehicle exceeds a second threshold in the deceleration traveling in the low vehicle speed range.