Motor Torque Control for Uniform Braking Force
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Solution Overview
Problem
Vehicles with motor-driven sources, such as electric and hybrid vehicles, face challenges in maintaining uniform braking force due to unintended changes in frictional braking force during regenerative braking, leading to issues like vapor lock and fade, which affect braking performance and responsiveness.
Innovation Solution
A method that determines the relationship between vehicle wheel torque change and driving acceleration change, calculates a target acceleration based on the driver's braking request, and compensates for differences in real-time acceleration through motor torque control, increasing regenerative braking to maintain uniform braking force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hydraulic pressure control is used for frictional braking, then braking force can be applied, but responsiveness is low and precise control is difficult
Solution Approach 1:
The patent replaces hydraulic pressure control with motor torque control for braking. The motor control unit adjusts motor torque based on acceleration feedback to achieve precise and responsive braking force control, eliminating the responsiveness and precision limitations of hydraulic systems.
Solution Approach 2:
The patent implements a feedback control mechanism where the acceleration sensor detects real-time acceleration, compares it with target acceleration, and adjusts motor torque accordingly. This closed-loop feedback enables precise control of braking force, resolving the control precision issue of hydraulic systems.
2Reliability
If frictional braking is frequently used, then braking force can be maintained, but vapor lock and fade occur reducing braking effectiveness
Solution Approach 1:
The patent converts the harmful effect of frequent braking (heat generation leading to vapor lock and fade) into a benefit by using regenerative braking. The motor recovers kinetic energy during deceleration, converting mechanical energy to electrical energy stored in the battery, thereby reducing reliance on frictional braking and preventing overheating.
Solution Approach 2:
The patent changes the braking mechanism from friction-based to motor-based control. By adjusting motor torque parameters dynamically, the system achieves braking without the thermal limitations of friction materials, eliminating vapor lock and fade phenomena.
3Use of energy by moving object
If regenerative braking co-operative control is implemented, then energy recovery is achieved, but uniform braking force is difficult to maintain due to friction material characteristics
Solution Approach 1:
The patent uses acceleration feedback to maintain uniform total braking force during regenerative braking co-operative control. The control unit continuously monitors acceleration and adjusts motor torque to compensate for variations in frictional braking force, ensuring stable and uniform overall braking performance.
Solution Approach 2:
The patent dynamically adjusts motor torque parameters to compensate for friction material characteristic changes. By changing the motor torque parameter based on acceleration feedback, the system maintains uniform total braking force despite variations in frictional braking due to temperature effects.
Data Source
AI summary
A method of improving braking performance through motor torque control of a vehicle includes: determining a relation between a vehicle wheel torque change amount and a driving acceleration change amount prior to a start of braking of the vehicle; calculating a target acceleration that is changed according to a driver's braking request when a driver presses a brake pedal to start the braking of the vehicle; detecting a real acceleration of the vehicle in real-time; comparing the real acceleration with the target acceleration; and compensating for a difference between the real acceleration and the target acceleration by increasing a regenerative braking amount through motor torque control when the real acceleration differs from the target acceleration.