Electric Parking Brake Motor Current Control
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Solution Overview
Problem
In electric parking brakes, determining the optimal timing to interrupt the current flowing to the motor is challenging, as it requires a sufficient braking force without complicating the system configuration, and existing methods using sensors or current changing rates are inefficient due to variability in motor states and friction forces.
Innovation Solution
A control device that determines a cut-off current value based on a predetermined rule correlating it with the increasing rate of the motor current, allowing the motor to be stopped when the current reaches this value, thus ensuring a suitable braking force is generated without complicating the system configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current flowing to the motor is interrupted at an early timing, then the mechanism of the electric parking brake does not malfunction, but a sufficient braking force cannot be generated
Solution Approach 1:
The control device monitors the motor current in real-time and uses the changing rate of current as feedback to determine the optimal timing for interrupting the current. By continuously measuring how the current changes during motor operation, the system can identify the precise moment when the friction member achieves sufficient contact force with the disc or drum, ensuring both reliable operation and adequate braking force.
2Force
If the current flowing to the motor is interrupted at a late timing, then a sufficient braking force is generated, but the mechanism of the electric parking brake may malfunction
Solution Approach 1:
The control device monitors the motor current in real-time and uses the changing rate of current as feedback to determine the optimal timing for interrupting the current. By continuously measuring how the current changes during motor operation, the system can identify the precise moment when the friction member achieves sufficient contact force with the disc or drum, ensuring both reliable operation and adequate braking force.
3Measurement precision
If sensors for measuring load are added to determine the timing for interrupting the current, then the timing can be determined accurately, but the configuration and control of the system becomes complicated
Solution Approach 1:
The system uses the motor's own current characteristics to determine the optimal interrupt timing. The control device measures the motor current that is already flowing during normal operation and uses its changing rate as the basis for timing determination. This self-service approach eliminates the need for additional load measurement sensors while maintaining accurate timing control.
Solution Approach 2:
The motor current serves as an intermediary parameter that indirectly reflects the contact force between the friction member and the disc or drum. Instead of directly measuring the load or contact force with additional sensors, the system uses the easily measurable motor current as a mediator to infer the appropriate interrupt timing.
4Device complexity
If the timing for interrupting the current is determined based on the changing rate of the motor current, then the system configuration remains simple, but it is impossible to determine whether a required braking force is obtained
Solution Approach 1:
The control device monitors the motor current in real-time and uses the changing rate of current as feedback to determine the optimal timing for interrupting the current. By continuously measuring how the current changes during motor operation, the system can identify the precise moment when the friction member achieves sufficient contact force with the disc or drum, ensuring both reliable operation and adequate braking force.
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 approach allows for the timely interruption of the motor current, ensuring a consistent braking force is applied, reducing system complexity and improving the robustness of the electric parking brake mechanism.
Implementation Method 1
a motor for driving a friction member
Implementation Method 2
a friction force between the friction member and the disc or the drum becomes small
Data Source
AI summary
A control device for an electric parking brake controls a motor for driving a friction member of the electric parking brake. The control device includes a processing unit which starts the motor in order to drive the friction member to a direction for placing the electric parking brake in a locked state; measures a current value of the motor in an operating state thereof; determines a cut-off current value from the measured current value of the motor according to a predetermined rule defining a correlation between the cut-off current value of the motor, by which a braking force necessary for the electric parking brake in the locked state is generated, and an increasing rate of the current; and stops the motor when the current value of the motor reaches the determined cut-off current value.