EPS Motor Control Using Shared Voltage Reference to Cut Vibration
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Solution Overview
Problem
Existing motor control systems for electric power steering devices experience vibration and noise due to differences in motor control amounts caused by varying power supply voltages, leading to an unpleasant driving experience.
Innovation Solution
A motor control device with dual control units for first and second motor windings, each including a power supply voltage selection unit that selects the lower of two input voltages and a d-axis target current computation unit using the selected voltage to standardize the d-axis target current, thereby minimizing differences in motor control amounts between systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each control unit independently computes motor control amount using its own power supply voltage, then the control system operates independently and reliably, but the motor control amount differs between systems causing vibration and noise
Solution Approach 1:
The patent applies equipotentiality by making both control units operate at the same power supply voltage level. The first control unit uses its own power supply voltage, while the second control unit uses the power supply voltage from the first control unit, ensuring both systems compute motor control amounts under identical voltage conditions. This eliminates the potential difference between systems that causes vibration and noise, while maintaining independent operational reliability.
Solution Approach 2:
The patent uses the power supply voltage from the first control unit as an intermediary for the second control unit. Instead of the second control unit directly using its own potentially different power supply voltage, it uses the first control unit's power supply voltage as a reference, mediating the voltage difference that would otherwise cause control amount discrepancies and resulting motor vibration.
2Adaptability or versatility
If different power supply voltages are used in different control units, then each unit operates with its own voltage level, but this causes differences in motor control amounts between systems
Solution Approach 1:
The patent applies universality by making the power supply voltage from the first control unit serve multiple functions: it powers the first control unit directly and also serves as the reference voltage for the second control unit. This multi-functional use of the same voltage level ensures consistent motor control amounts across both systems while maintaining flexible power supply configuration.
Data Source
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AI summary
A motor control device that enables a reduction of an unpleasant sensation caused by vibration or noise occurring in a motor is obtained. A motor control device (100) including a first control unit (1a) that drives a first motor winding (3a) and a second control unit (1b) that drives a second motor winding (3a) is such that the first control unit (1a) selects the lower of values of an own power supply voltage (VBa) and a power supply voltage (VBb) of the second control unit (1b) and outputs a post-selection power supply voltage (VBmin), and computes a target d-axis current (Id*), a target q-axis voltage (Vq*), and a target d-axis voltage (Vd*) using the post-selection power supply voltage (VBmin).