Motor Controller Operating Modes for Brake Actuator Fault Tolerance
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Solution Overview
Problem
Electromechanical brake systems face challenges in maintaining operation and safety when there are faults in the control of electric motors, leading to potential complete failure or the need for mechanical fallback, which can compromise vehicle safety.
Innovation Solution
Defining additional operating modes for the electric motor controller that allow continued operation with limited access to state variables, reconstructing current measurements, and switching to voltage-commutated modes to maintain functionality and reduce the need for mechanical fallback, ensuring safety and consistent power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor controller operates in unrestricted mode with full access to state variables, then the control precision and braking performance are optimized, but the system becomes vulnerable to complete failure when faults occur in current measurement or state variable access
Solution Approach 1:
The control system dynamically adapts its operating mode based on the availability of state variables. When current measurement is functional, the system operates in unrestricted mode with full PWM control. When current measurement fails, it automatically transitions to restricted operating modes with voltage commutation, maintaining functionality despite the fault condition.
Solution Approach 2:
The system changes its control parameters and operating characteristics based on fault conditions. In normal operation, it uses pulse width modulation with full access to current state variables. In fault conditions, it switches to voltage commutation with limited state variable access, effectively changing the control parameters to match the available information.
2Reliability
If the system switches to mechanical fallback level in the event of faults, then safety is maintained, but the braking performance and system functionality are significantly compromised
Solution Approach 1:
The system prepares multiple operating modes in advance, including restricted modes that can be activated when faults occur. These pre-prepared fallback modes allow the system to maintain electromagnetic braking functionality even when current measurement fails, avoiding the need to switch to mechanical fallback and thus preserving braking performance while maintaining safety.
3Reliability
If the system operates with limited access to state variables, then the system can continue operation during faults, but the control precision and ability to detect fault currents are reduced
Solution Approach 1:
The system uses voltage commutation as an intermediary control method when direct current measurement is unavailable. Instead of directly measuring current to control the motor, it commutes based on voltage and position information, using the back-EMF and position sensors as intermediaries to maintain control without requiring direct current measurement.
4Reliability
If multiple operating modes are defined for different fault conditions, then the system can maintain functionality with limited state variables, but the control electronics and decision logic become more complex
Solution Approach 1:
The control system is segmented into distinct operating modes (unrestricted mode and multiple restricted modes). Each mode has specific activation conditions and control characteristics. This segmentation allows the system to handle different fault conditions independently, maintaining fault tolerance while organizing the control logic in a manageable structure.
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 reliability and safety of electromechanical brake systems by maintaining control and reducing the reliance on mechanical fallbacks, ensuring consistent braking performance and protecting the vehicle electrical system from faults.
Implementation Method 1
an electromechanical actuator of an electromechanical brake system (EMB) in a motor vehicle, comprising an electronic motor controller working in an unrestricted operating mode (normal operation) for a field-commutated electric motor controlled with pulse width modulation
Data Source
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AI summary
The invention relates to a method for improving the availability of an electromechanical actuator of an electromechanical or electrohydraulic brake system in a motor vehicle, comprising a motor controller for an electric motor, said motor controller operating in a non-restricted operating mode. Additional operating modes for the motor controller are defined in addition to the non-restricted operating mode, said additional operating modes operating with restricted access to state variables of the electric motor and the electronic control system of the electric motor, and a change of the control process and/or a deactivation of individual functions of the motor controller are carried out in said additional operating modes dependent on the restricted access. The invention further relates to an electronic device for use with an electromechanical or electrohydraulic brake system. The electronic device comprises multiple modules for controlling an electric motor, wherein a module for ascertaining (2) the target current is provided, said module being electrically connected to a field-oriented current regulator (3) and obtaining calculated target current values via said connection using different state variables and/or estimated variables as well as stored parameters.