Auxiliary Braking Coordination for EV Transmission Downshift Shock
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Solution Overview
Problem
Large electric vehicles equipped with transmissions experience shift shock and braking slip during regenerative braking, as existing technologies fail to properly control regenerative braking torque without using a retarder, leading to excessive reduction in regenerative braking and inability to maintain constant deceleration.
Innovation Solution
An apparatus and method that include an auxiliary braking signal unit, vehicle control unit, motor control unit, transmission control unit, and braking control unit, which estimate the vehicle's weight and adjust regenerative braking torque and braking pressure to minimize shift shock and braking slip by downshifting the transmission, allowing for controlled deceleration without a retarder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If regenerative braking torque is reduced to alleviate shift shock during transmission downshift, then shift shock is reduced, but braking slip occurs and deceleration becomes unstable
Solution Approach 1:
The patent introduces a brake system as an intermediary device to compensate for the reduction in regenerative braking torque during transmission downshift. When downshift is detected, the control unit activates the brake to provide additional braking force, thereby maintaining stable deceleration and preventing braking slip while allowing regenerative braking torque to be reduced to minimize shift shock.
Solution Approach 2:
The patent dynamically changes the braking force parameters by coordinating regenerative braking and friction braking based on transmission state. During normal operation, regenerative braking provides primary deceleration. During downshift events, the system adjusts the ratio of regenerative to friction braking, increasing friction brake engagement to maintain total braking force while reducing regenerative component to prevent shift shock.
2Object-affected harmful factors
If regenerative braking torque is excessively reduced during change in speed, then shift shock is minimized, but regenerative braking is temporarily released and deceleration is insufficient
Solution Approach 1:
The patent merges regenerative braking and friction braking systems into a coordinated unified braking system. The control unit manages both braking sources simultaneously, allowing them to complement each other. During downshift, regenerative braking is reduced to minimize shift shock while friction braking is increased to compensate, maintaining total braking force throughout the transmission change.
3Object-affected harmful factors
If a retarder is used to control regenerative braking during change in speed, then shift shock can be controlled, but device complexity increases
Solution Approach 1:
The patent enables the existing brake system to serve the dual function of both primary braking and regenerative braking assistance during transmission downshift. Instead of adding a dedicated retarder system, the control unit makes the existing friction brake system self-sufficient to handle the compensation task, thereby controlling shift shock without increasing device complexity.
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 solution optimally controls regenerative braking during speed changes, preventing shift shock and braking slip, and maintains constant deceleration in large electric vehicles equipped with transmissions, adhering to regulatory standards for auxiliary braking.
Implementation Method 1
a motor control unit (30) receiving a command for auxiliary braking from the vehicle control unit (20) and decelerating the vehicle by regenerative braking of a driving motor (1)
Implementation Method 2
a braking control unit (50) connected to a brake (5) through a fluid pressure line, and controlling the brake (5) so that the brake applies braking pressure to the wheel (4)
Data Source
AI summary
An apparatus for controlling a change in speed of a vehicle, includes: an auxiliary braking signal unit receiving an auxiliary braking related signal from a driver; a vehicle control unit receiving the auxiliary braking related signal from the auxiliary braking signal unit while controlling the vehicle; a motor control unit receiving a command for auxiliary braking from the vehicle control unit and decelerating the vehicle by regenerative braking of a driving motor; a transmission control unit controlling a transmission during deceleration of the vehicle and transmitting information of whether a change in speed is performed to the vehicle control unit; and a braking control unit connected to a brake through a fluid pressure line, and controlling the brake so that the brake applies braking pressure to a wheel by an amount of reduction in regenerative braking torque when the transmission is downshifted.