Electric Parking Brake Actuator Current Monitoring
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Solution Overview
Problem
Existing electric motor-actuated wheel brake systems face challenges with inconsistent application force due to cooling, stick-slip effects, and the need for extensive sensor monitoring, leading to unreliable current detection and increased electrical and mechanical stress during de-energized parking.
Innovation Solution
An electronically controlled parking brake actuation method that continuously monitors power requirements, performs standstill checks using vehicle sensor data, and triggers secondary or tertiary tensioning processes to ensure secure parking without force or distance measurement sensors, reducing electrical and mechanical stress while maintaining safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous monitoring and multiple tensioning processes are implemented, then parking reliability is improved, but electrical energy consumption increases
Solution Approach 1:
The control unit performs a preliminary primary tensioning process that tensions the cable to approximately 60% of minimum required cable tension before the vehicle is parked. This preliminary action ensures the brake is pre-positioned close to the desired state, reducing the need for extensive post-parking corrections and energy consumption during the overrun time.
Solution Approach 2:
The system uses the vehicle's existing sensor data (wheel speed, inclination, etc.) and control algorithms to automatically monitor and self-correct parking brake status during the overrun time. This self-service approach eliminates the need for external monitoring systems and minimizes energy consumption by only activating additional tensioning processes when actually needed based on real-time conditions.
2Measurement precision
If force or displacement measuring sensors are used for comprehensive monitoring, then monitoring precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses current consumption of the electric actuator as an intermediary parameter to indirectly measure cable tension and brake application force. Instead of directly measuring force with complex sensors, the system monitors the electrical current drawn by the actuator, which correlates with the mechanical load and tension state, providing sufficient monitoring precision without additional force sensors.
Solution Approach 2:
The system replaces mechanical force and displacement measuring sensors with an electrical monitoring approach. By measuring electrical parameters (current, voltage, power consumption) of the actuator, the system obtains information about the mechanical state of the brake system, thereby substituting complex mechanical measurement systems with simpler electrical sensing.
3Reliability
If minimum cable tension is maintained throughout the process, then parking safety is improved, but mechanical stress on components increases
Solution Approach 1:
The control unit performs a preliminary primary tensioning process that tensions the cable to approximately 60% of minimum required cable tension before the vehicle is parked. This preliminary action reduces the mechanical stress that would otherwise need to be applied and maintained throughout the entire parking process, while still achieving safe parking through subsequent monitoring and selective correction.
Solution Approach 2:
Instead of applying 100% of the minimum required cable tension continuously, the system applies a partial tension (approximately 60%) during the primary tensioning process and relies on monitoring and selective secondary tensioning to achieve and maintain the required safety level. This partial action approach reduces overall mechanical stress on components while maintaining parking safety.
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 method enables reliable and cost-effective de-energized parking with reduced electrical and mechanical stress, rapid error detection and correction, and the use of standardized components, allowing for smaller actuator dimensions and reduced hardware risk.
Implementation Method 1
An electrically actuated wheel brake actuator (3) with a pre-tensioned spring element (22) and a Duo-Servo type drum brake system
Implementation Method 2
a pre-tensioned spring element (22) and a Duo-Servo type drum brake system
Implementation Method 3
a Duo-Servo type drum brake system
Data Source
Figure 1
Figure 2
AI summary
In order to actuate electric parking brake systems in a controlled manner without using any force sensor or displacement sensor, a control unit always initiates a primary brake application process while monitoring the current, and secondary or tertiary brake application processes using a greater brake application force are carried out by the control unit exclusively in an automatic manner when a standstill monitoring device detects an unwanted vehicle movement during an interval in which no current is supplied.