EPS Motor Control ASIC with Hardware Safety and Fast Diagnostics
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Solution Overview
Problem
Current motor electric control units for electromechanical power steering mechanisms have limited scalability and safety integrity, requiring frequent software validation and constraining power module diagnostics, leading to increased complexity and cost.
Innovation Solution
A motor electric control unit with an ASIC design that implements safety and platform features in hardware, including a gate driver unit, sensor interface, motor control block, and safety envelope block, allowing for quick diagnostics and reduced testing efforts, and enabling use without an external MCU for non-safety critical functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motor control is implemented in software on a safety-qualified microcontroller, then safety integrity level can be achieved, but device complexity and resource consumption increase
Solution Approach 1:
The control unit is divided into two independent channels, each capable of autonomous operation. The first channel handles non-safety-critical functions while the second channel handles safety-critical functions, allowing each to be optimized independently for its specific requirements.
Solution Approach 2:
The patent replaces software-based safety monitoring with hardware-based safety monitoring in the second channel. This hardware implementation provides intrinsic safety without requiring extensive software validation, thereby reducing overall system complexity while maintaining high safety integrity.
2Reliability
If complete motor control with safety diagnostics is implemented in software, then safety requirements are met, but testing and validation efforts increase at each software release
Solution Approach 1:
Safety-critical functions are implemented in hardware rather than software. This hardware implementation provides inherent safety without requiring repeated software validation and testing at each release, significantly reducing time loss while maintaining safety requirements.
3Adaptability or versatility
If software-based motor control is used, then flexibility is achieved, but power module diagnostics speed is insufficient
Solution Approach 1:
Power module diagnostics are implemented in hardware to achieve the required speed, while other control functions remain in software for flexibility. This hybrid approach allows fast diagnostics without sacrificing overall system adaptability.
4Reliability
If two MCUs are required for fail-safe operation, then safety integrity is improved, but device complexity and cost increase
Solution Approach 1:
The control unit is segmented into two independent channels with different functional assignments. The first channel handles non-safety-critical functions and the second channel handles safety-critical functions, providing fail-safe operation without requiring two complete MCUs.
Solution Approach 2:
Both channels can operate autonomously and can take over each other's functions if needed, providing universal functionality that reduces the need for separate dedicated hardware for each safety function.
Data Source
AI summary
A motor electric control unit (ECU) for an electromechanical power steering mechanism, which controls current through an electric assist motor in response to sensed vehicle signals, wherein the ECU comprises an application specific integrated circuit (ASIC) design, that implements safety and platform features in hardware.