Coaxial Electric Power Steering Control Unit with Redundant Inverters
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Solution Overview
Problem
Existing electric power steering devices with redundant systems are cumbersome and costly, making them difficult to mount in vehicles while ensuring reliable motor control during abnormalities.
Innovation Solution
An electric power steering device with two control units mounted coaxially with the motor output shaft, featuring independent inverter circuits and CPUs for redundant operation, allowing continued motor control during abnormalities and reducing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant system with two control units is configured to ensure reliable motor control during abnormalities, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges two control units into a single integrated control unit with dual inverter circuits and dual CPUs. This combining approach maintains the redundant system reliability while reducing device complexity and cost compared to having completely separate control units. The two inverter circuits (3a, 3b) and dual CPUs (10a, 10b) share common hardware resources such as the housing (51), control substrate (4c), and motor connection structure.
Solution Approach 2:
The control unit is designed with multi-functionality where a single control unit structure can perform both normal operation control and abnormal condition handling. The dual inverter circuits and dual CPUs within the same control unit can independently or cooperatively control the motor depending on system state, making the control unit universal for both normal and fault-tolerant operations.
2Volume of moving object
If two control units are mounted coaxially with the motor output shaft to reduce device size, then volume is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent implements a nested structure where the two inverter circuits and dual CPUs are arranged coaxially around the motor output shaft within a single control unit housing. The control substrate is positioned centrally with inverter circuits arranged around it, creating a compact nested layout that minimizes volume while maintaining manufacturability through standardized mounting patterns.
Solution Approach 2:
The control units are arranged asymmetrically around the motor output shaft rather than in a symmetric configuration. This asymmetric arrangement optimizes space utilization and simplifies the mounting structure by allowing components to be positioned according to their functional requirements rather than geometric symmetry, thereby reducing manufacturing complexity.
3Reliability
If independent inverter circuits are provided for each control unit to enable continued operation during abnormalities, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent segments the control system into two independent inverter circuits (3a, 3b) with separate CPUs (10a, 10b) within the same control unit. Each inverter circuit can independently control the motor phases, providing redundancy while maintaining manageable complexity through modular circuit design. The segmentation allows fault isolation where one inverter can fail without affecting the other.
Solution Approach 2:
Different parts of the control system have specialized functions with local quality optimization. Each inverter circuit is designed with specific local characteristics for independent operation, while sharing common resources. The dual inverter circuits have identical functional capabilities locally, but are integrated into a unified control architecture that manages overall system complexity.
Data Source
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AI summary
With an object of allowing steering wheel operation to be carried out easily at a normal time and when an abnormality occurs, the invention includes a motor 2 having two coil windings and a control unit 1 having two control systems that supply control signals individually to the coil windings of the motor 2, and when an abnormality occurs in a coil winding of the motor 2 or in one system of the control unit 1, a supply of current to the coil winding in which the abnormality has occurred is cut to zero, and the motor 2 is driven by a predetermined current necessary at a normal time being supplied to the other coil winding, while at a time of a normal drive, the current supply is shared between the two coil windings, whereby the motor 2 is driven.