Parking Brake Current Derivative Application Point Detection
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Solution Overview
Problem
Existing parking brake systems face challenges in accurately setting the brake-application force and clearance due to indirect measurement methods and errors in position determination, leading to reliability issues and potential overheating during vehicle operation.
Innovation Solution
A method involving the control unit determining the application point by forming the first derivative of the electric current taken up by the direct current motor during brake application, allowing for precise setting of brake-application force and clearance by considering hydraulic admission pressure and using a retightening function to adjust for deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If indirect measurement methods are used to determine brake-application force, then cost is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces direct mechanical force measurement with an electrical measurement system. The control unit determines the application point by forming the first derivative of the electric current taken up by the direct current motor during brake application. This substitutes a complex mechanical force sensor with an electrical current-based detection method, achieving both cost reduction and improved measurement precision through derivative calculation.
2Device complexity
If position determination is carried out by means of a motor model with unknown constants and approximations, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces the motor model-based position determination with a direct electrical derivative method. Instead of using a motor model with unknown constants and approximations, the control unit directly calculates the first derivative of the electric current to determine the application point. This eliminates model-based errors and integration errors while maintaining relatively simple device architecture.
Solution Approach 2:
The patent implements a feedback mechanism where the control unit continuously monitors the electric current derivative and uses this information to accurately determine the application point. This real-time feedback from the electrical system provides precise position information without requiring complex mechanical sensors or imprecise motor models.
3Ease of operation
If the application point is generally overshot during brake application and release, then reliability is reduced, but ease of operation is improved
Solution Approach 1:
The patent uses feedback from the electric current derivative to precisely identify the application point. By monitoring when the first derivative of the current becomes greater than zero, the control unit can accurately determine the moment of application point contact. This feedback mechanism prevents overshooting while maintaining simple operation, as the system automatically detects and responds to the application point condition.
Solution Approach 2:
The patent applies partial action by controlling the motor to stop precisely at the application point rather than overshooting to a predetermined position. The control unit monitors the current derivative and terminates the braking action exactly when the application point is reached, avoiding the excessive action that causes overshooting and subsequent reliability issues.
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 enhances the accuracy and reliability of brake force and clearance settings, preventing overheating and ensuring consistent brake performance across various conditions.
Implementation Method 1
an actuator (5) which is driven by a direct current motor (28) which can be operated in two directions
Implementation Method 2
which moves, via a self-locking gear mechanism of the actuator, at least one brake shoe for applying or releasing the parking brake
Implementation Method 3
the brake piston applies the friction lining against a rotary element, which can be connected in a rotationally fixed fashion to the wheel
Data Source
AI summary
A parking brake having an actuator, wherein the actuator is driven by a direct current motor which can be operated in two directions. The actuator moves, via a self-locking gear mechanism of the actuator, at least one brake shoe for applying or releasing the parking brake in the direction of a rotary element or away therefrom. A control unit for performing open-loop or closed-loop control of the movement of the direct current motor is also provided. The parking brake is designed such that, when the parking brake is applied or released, an application point of the brake shoes against the rotary element is generally overshot. In order to increase the accuracy and reliability of the setting of the brake-application force when the parking brake is applied or of the brake-application clearance when the parking brake is released, the control unit determines the application point by forming the first derivative over time of the electric current taken up by the direct current motor during the application of the brake. A corresponding method for operating such a parking brake is also described.