Electric Parking Brake Torque Calculation
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Solution Overview
Problem
Existing electric parking brake systems often operate with excessive braking force, leading to reduced durability and inadequate calculation of necessary braking force for stopping a vehicle, especially on inclined surfaces.
Innovation Solution
An electric parking brake system that includes a drive controller calculating necessary braking force based on parking torque, vehicle mass, and inclination angle, using an electric motor to generate appropriate braking torque and control the parking brake actuator to maintain the vehicle stopped with the correct braking force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric parking brake operates with excessive braking force to ensure stopping on inclined surfaces, then the stopping reliability is improved, but the durability of brake components deteriorates
Solution Approach 1:
The system dynamically adjusts the braking force parameter based on detected road inclination angle and vehicle mass. By calculating the necessary braking force as a function of these parameters (F = m·g·sin(θ)), the system applies only the required braking force rather than excessive force, thereby improving component durability while maintaining stopping reliability on inclined surfaces.
2Loss of time
If the braking force is calculated based on service brake pressure sensor information, then the calculation speed is improved, but the accuracy of necessary braking force determination deteriorates
Solution Approach 1:
The system introduces an inclination angle sensor as an intermediary measurement device to directly measure the road slope angle. This enables accurate calculation of the component of gravitational force acting on the vehicle (m·g·sin(θ)), providing precise determination of necessary braking force without relying on indirect inference from service brake pressure, thus improving both accuracy and calculation speed.
3Reliability
If the parking brake actuator is controlled to generate higher braking force to account for unknown vehicle mass, then the stopping reliability on inclined surfaces is improved, but the energy consumption and component load increase
Solution Approach 1:
The system enables the vehicle to self-characterize its mass by measuring the braking force required to maintain constant speed on inclined surfaces during normal operation. This self-measured mass information is stored and reused for parking brake control, eliminating the need to assume conservative high mass values. Consequently, the parking brake actuator consumes only the necessary energy while maintaining stopping 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
The system ensures the generation of necessary and appropriate braking force, enhancing durability by preventing excessive load on components and effectively stopping the vehicle on various road conditions, including inclined surfaces.
Implementation Method 1
a wheel (20) driven by an electric motor (26)
Implementation Method 2
A rotation of the worm 130SS causes a pivotal movement of the worm wheel 130SL, which generates a tractive force of the parking wire 100W
Implementation Method 3
a parking brake (22) maintaining the wheel (20) stopped
Data Source
AI summary
An electric parking brake system includes a wheel driven by an electric motor to move a vehicle, a parking brake maintaining the wheel stopped, a parking brake actuator operating the parking brake, and a drive controller controlling the parking brake actuator. The drive controller controls the electric motor to maintain the wheel of the vehicle stopped while the vehicle is parked, and calculates a parking torque based on a control amount of the electric motor that maintains the wheel stopped. The drive controller calculates a necessary braking force for the parking brake to maintain the wheel stopped based on the calculated parking torque, and controls the parking brake actuator so that the necessary braking force is generated.