Electric Vehicle Slip Control via Differential Braking
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Solution Overview
Problem
In electric vehicles with a single motor controlling both drive wheels, differences in slip ratios between the wheels lead to unnecessary yaw moments due to unequal braking forces, compromising vehicle stability.
Innovation Solution
A control device that includes a motor connected to drive wheels via a differential gear and a mechanical braking system, where the motor torque is reduced and additional braking force is applied to the wheel with higher speed when the slip ratio exceeds a threshold, ensuring both wheels converge to target slip ratios, thereby stabilizing vehicle behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single motor controls both drive wheels via differential gear, then device complexity is reduced, but when slip ratios differ between wheels, unnecessary yaw moments are produced due to unequal braking forces, worsening vehicle stability
Solution Approach 1:
The braking system is segmented into two independent control paths: motor braking torque control and mechanical brake control. The mechanical brake can independently control each wheel's braking force, allowing differential braking between left and right wheels to correct yaw moments while maintaining overall system simplicity.
Solution Approach 2:
The control system applies local quality by enabling independent braking force control for each wheel through the mechanical brake system. When one wheel has a higher slip ratio than the other, the system applies different braking forces to each wheel locally, correcting the yaw moment while maintaining simplicity in the overall motor control architecture.
2Reliability
If motor torque is reduced to control slip ratio, then braking force is controlled, but when wheel speeds differ, unequal braking forces create yaw moments, worsening vehicle behavior stability
Solution Approach 1:
The mechanical brake acts as an intermediary device between the motor braking system and the wheels. When slip ratio control creates unequal braking forces, the mechanical brake compensates by applying additional braking force to the specific wheel needing correction, thereby eliminating yaw moments and stabilizing vehicle behavior.
Solution Approach 2:
The control system dynamically changes the braking force parameter by coordinating motor torque reduction with selective mechanical brake application. When wheel speed differences are detected, the system adjusts the mechanical brake force on individual wheels to maintain equal effective braking forces, preventing yaw moments while preserving slip control reliability.
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
This solution effectively reduces the difference in braking forces between wheels, preventing unintended yaw moments and ensuring stable vehicle behavior by adjusting motor torque and applying differential braking forces based on wheel speed.
Implementation Method 1
a motor 1 connected to drive wheels FR, FL of the vehicle via a differential gear 3 and a drive shaft 4 and configured to generate a braking or driving torque for the drive wheels
Implementation Method 2
a mechanical braking device capable of independently generating a braking force for each of the drive wheels
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Provided is a control device for an electric vehicle capable of stabilizing vehicle behavior when performing slip control of drive wheels. The control device for an electric vehicle according to the present invention is a control device for an electric vehicle to be used in an electric vehicle, the electric vehicle including: a motor which is connected to the drive wheels of the electric vehicle via a differential gear and a drive shaft, and which is configured to generate a braking or driving torque for each of the drive wheels; and a mechanical braking device capable of independently generating a braking force for each of the drive wheels. In this control device for an electric vehicle, when a slip ratio of each of the drive wheels is detected as being a predetermined slip ratio or more, a torque absolute value of the motor is reduced so that the slip ratio of each of the drive wheels is a target motor slip ratio, and a larger braking force is applied by the mechanical braking device to, of a right drive wheel and a left drive wheel, the drive wheel having a higher wheel speed than the drive wheel having a lower wheel speed.