Regenerative Braking Torque Smoothing During Vehicle Mode Switching
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Solution Overview
Problem
Existing vehicle travel control systems face issues where regenerative braking force unexpectedly changes when switching from a first regenerative control mode to a second mode, leading to a discrepancy between the expected and actual braking force experienced by the driver.
Innovation Solution
A vehicle travel control device that calculates and limits the change rate of motor torque during mode switching, using accelerator opening degree and vehicle speed to maintain consistent regenerative braking force by integrating an accelerator required torque calculation unit, selection unit, and mode switching change rate limiting unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the control mode is switched from the first regenerative control mode to the second regenerative control mode, then the vehicle can perform gradual deceleration by regenerative braking force, but the regenerative braking force becomes smaller than before switching, causing the braking force expected by the driver to not be obtained
Solution Approach 1:
The mode switching change rate limiting unit performs preliminary action by calculating the current regenerative braking force before mode switching and setting a change rate limit. This preliminary calculation and limit setting ensures that when switching from the first regenerative control mode to the second regenerative control mode, the regenerative braking force does not drop below the pre-calculated level, maintaining the driver's expected braking force while enabling gradual deceleration control.
2Adaptability or versatility
If the regenerative braking force is increased in the first regenerative control mode according to shift position, then the braking force can be adjusted to driver needs, but when switching to the second regenerative control mode, the braking force becomes smaller than expected
Solution Approach 1:
The mode switching change rate limiting unit implements feedback by continuously monitoring the regenerative braking force before mode switching, calculating the appropriate change rate limit based on current vehicle conditions (vehicle speed, accelerator opening degree), and adjusting the braking force during mode transition to maintain consistency with driver expectations. This feedback mechanism ensures reliability of braking force throughout the mode switching process.
3Speed
If the accelerator required torque changes significantly by switching control modes, then the vehicle response changes, but the sudden torque change causes discomfort to the driver
Solution Approach 1:
The mode switching change rate limiting unit applies dynamics by making the torque change rate adaptive rather than fixed. It dynamically adjusts the change rate limit based on real-time vehicle conditions including vehicle speed and accelerator opening degree. This dynamic adjustment allows the system to maintain fast vehicle response when conditions permit while preventing sudden torque changes that would cause driver discomfort, thus resolving the contradiction between response speed and comfort.
Data Source
AI summary
A vehicle travel control device calculates torques required for a motor in a first regenerative control mode and a second regenerative control mode based on an accelerator opening degree and a vehicle speed, selects torque required for the motor suitable for the first regenerative control mode or the second regenerative control mode from among the calculated torques required for the motor, and limits a change rate of the torque required for the motor when the selected torque required for the motor changes beyond a predetermined change rate by switching from the first regenerative control mode to the second regenerative control mode.