Electric Parking Brake Cable Tension Control
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Solution Overview
Problem
Electric parking brake systems often experience insufficient braking torque due to cable slack, leading to increased power consumption and reduced motor lifespan, especially when the vehicle is on a slope or when torque changes occur.
Innovation Solution
The system employs a slack-based tension control unit that adjusts cable tension to a target value combining moving force-based tension and slack compensation, minimizing cable slack and reducing unnecessary power consumption by determining the slack compensation amount based on torque changes and friction member pushing force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the cable tension is controlled to the moving force-based target tension when the drum brake is applied, then the power consumption is reduced, but the braking torque becomes insufficient when torque changes occur
Solution Approach 1:
The system performs preliminary action by detecting torque changes (through wheel acceleration/deceleration detection) and proactively increasing cable tension before braking torque insufficiency occurs. This prevents the harmful effect of insufficient braking torque while avoiding continuous excessive tension, thus reducing overall power consumption compared to maintaining constant high tension.
Solution Approach 2:
The system implements feedback control by continuously monitoring wheel acceleration and deceleration to detect torque changes, then adjusting cable tension accordingly. This feedback mechanism ensures braking torque sufficiency is maintained dynamically while optimizing power consumption by applying additional tension only when necessary.
2Reliability
If additional pulling control is executed frequently to compensate for cable slack, then the braking torque sufficiency is improved, but the motor lifespan is reduced
Solution Approach 1:
The system performs preliminary action by detecting torque changes early through wheel acceleration/deceleration monitoring and proactively adjusting cable tension before significant slack develops. This reduces the frequency and magnitude of additional pulling operations, thereby extending motor lifespan while maintaining braking torque sufficiency.
3Reliability
If the cable tension is controlled to an excess value to prevent braking torque insufficiency, then the braking torque sufficiency is improved, but the power consumption increases
Solution Approach 1:
The system applies dynamics by transitioning from static constant tension control to dynamic tension adjustment based on real-time torque change detection. The cable tension is adjusted actively only when torque changes are detected, and maintained at baseline levels otherwise, optimizing the balance between braking torque sufficiency and power consumption.
Solution Approach 2:
The system implements parameter changes by dynamically adjusting cable tension based on detected torque changes. Instead of maintaining constant excess tension, the system modifies the tension parameter adaptively - increasing it only when torque changes indicate potential insufficiency, and maintaining it at lower levels when not needed, thus reducing overall power consumption.
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 effectively maintains adequate braking torque, reduces the frequency and duration of additional pulling control, and extends motor lifespan by optimizing cable tension management.
Implementation Method 1
an electric motor; a motion conversion mechanism that converts the rotation of a rotating shaft of the electric motor into the linear motion
Implementation Method 2
a motion conversion mechanism that converts the rotation of a rotating shaft of the electric motor into the linear motion of an output member
Implementation Method 3
a drum brake that includes a drum which rotates together with a wheel of a vehicle and of which the inner peripheral face is used as a friction face, a shoe which is fitted to a backing plate that is a non-rotating body so as to be movable relative to the backing plate, and which has a friction member on the outer peripheral face
Data Source
AI summary
In an electric parking brake system, the moving force-based target tension is set based on the inclination angle of a vehicle and the shift position, and the slack compensation amount is determined based on the inclination angle of the vehicle and the shift position. The control target tension is set to a smaller value from among the slack-based target tension, which is the sum of the moving force-based target tension and the slack compensation amount, and the maximum value of the output power that can be produced by an electric motor. The electric motor is controlled such that the tension of the cable matches the control target tension (the slack-based target tension, in most cases).