Vehicle Control Device Reducing Longitudinal Vibration During Stop
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Solution Overview
Problem
Regenerative braking in electric vehicles can cause vibration in the longitudinal direction of the vehicle body when decelerating to a stop, especially when the regenerative braking force is set high.
Innovation Solution
A control device for vehicles that includes a speed parameter detecting means, an accelerator operation amount detecting means, a disturbance torque estimating means, and a friction-braking-amount adjusting means to generate friction braking force, adjusting the friction braking amount based on the disturbance torque when the accelerator operation amount is low and the vehicle is approaching a stop, thereby reducing longitudinal vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If regenerative braking force is increased to improve deceleration performance, then deceleration efficiency is improved, but longitudinal vibration of vehicle body occurs during stopping
Solution Approach 1:
The braking force is segmented into two independent components: regenerative braking force (applied to the drive wheels through the motor) and friction braking force (applied to the non-drive wheels through the brake device). This segmentation allows each braking system to operate independently, enabling the friction brake to counteract vibrations caused by the regenerative brake without affecting the overall deceleration efficiency.
Solution Approach 2:
The friction brake acts as an intermediary device that indirectly suppresses longitudinal vibrations by applying braking force to the non-drive wheels. This intermediary approach allows vibration suppression without directly interfering with the regenerative braking system's deceleration function, maintaining deceleration efficiency while reducing harmful vibrations.
2Object-affected harmful factors
If friction braking amount is increased to suppress vibration, then vibration suppression is improved, but braking control complexity increases
Solution Approach 1:
Different braking forces are applied to different wheels based on their specific roles. The drive wheels receive regenerative braking force for deceleration, while the non-drive wheels receive friction braking force specifically for vibration suppression. This local differentiation of braking quality simplifies control by assigning specific functions to specific wheels rather than uniformly controlling all brakes.
Solution Approach 2:
The friction braking system automatically adjusts its braking force based on detected longitudinal vibrations, suppressing vibrations without requiring complex external control intervention. The system serves itself by using the vibration detection signal to directly modulate the friction braking amount, reducing control complexity.
3Use of energy by moving object
If regenerative braking force is set high to improve energy recovery, then energy efficiency is improved, but vehicle stopping smoothness deteriorates
Solution Approach 1:
The braking system is segmented into regenerative braking (for energy recovery) and friction braking (for smoothness control). This allows the regenerative brake to operate at high force for maximum energy recovery while the friction brake simultaneously operates to maintain stopping smoothness by counteracting vibrations, resolving the contradiction between energy efficiency and stopping smoothness.
Solution Approach 2:
The braking system uses a composite approach combining two different braking mechanisms (regenerative and friction braking) working together. The regenerative brake provides energy recovery while the friction brake provides smoothness, creating a composite braking system that achieves both energy efficiency and stopping smoothness simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The control device effectively reduces longitudinal vibrations during vehicle deceleration and stop, ensuring smooth deceleration and maintaining the vehicle's stop state without the need for driver input on brake pedals, even on varying road gradients.
Implementation Method 1
a regenerative brake control device for electric vehicles provided with setting means capable of any given setting of a regenerative braking force of a motor and regenerates the motor by the regenerative braking force set by the setting means
Implementation Method 2
a friction brake device that generates a friction braking force to decelerate the vehicle
Data Source
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AI summary
The device that generates the friction braking force to decelerate the vehicle estimates the disturbance torque acting on the vehicle. When the accelerator operation amount is equal to or less than the predetermined value and the vehicle is just before the stop of the vehicle, the control device for vehicle causes the friction braking amount to converge to the friction braking amount to the value decided on the basis of the disturbance torque estimated value Td in conjunction with the reduction in the motor rotation speed (speed parameter) proportionate to the traveling speed of the vehicle.