Electric Power Steering Control Apparatus Phase Current Stabilization
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Solution Overview
Problem
Existing electric power steering systems face challenges in maintaining stable motor control and reducing torque ripple due to parameter changes in polyphase motors, especially when the neutral point potential is unstable, leading to increased costs and processing loads.
Innovation Solution
A control apparatus for electric power steering systems that uses (n−1) current detecting means and current control means for each phase, along with counter electromotive voltage calculation and compensation, to independently control each phase and stabilize the neutral point potential without requiring specific sensors, thereby reducing torque ripple and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional motor control methods are used with polyphase motors, then the control system can operate, but the neutral point potential becomes unstable and torque ripple increases
Solution Approach 1:
The patent divides the motor control into independent phase control units, where each phase has its own current control means that operates autonomously. This segmentation allows each phase to be controlled independently, preventing the neutral point potential instability that occurs in conventional unified control methods, thereby reducing torque ripple while maintaining control stability.
Solution Approach 2:
The patent implements different control strategies for different phases of the polyphase motor. Each phase has localized current detection and control means that adapt to the specific characteristics of that phase. This local quality approach ensures that each phase contributes to stable neutral point potential while minimizing individual phase variations that cause torque ripple.
2Object-generated harmful factors
If independent phase control is implemented, then torque ripple is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the detection and control functions into integrated current control means for each phase. By combining multiple functions (current detection, neutral point potential monitoring, and phase control) into unified control units, the system achieves independent phase control without proportionally increasing overall device complexity. The control means for each phase shares common computational resources and control architecture.
3Reliability
If neutral point potential stabilization is achieved through conventional methods, then control stability improves, but specific sensors and increased processing load are required
Solution Approach 1:
The patent enables the motor control system to self-monitor and self-regulate the neutral point potential through the current control means that inherently detect phase currents. The system uses the existing current detection infrastructure to calculate and stabilize neutral point potential without requiring additional dedicated sensors. This self-service approach maintains control stability while avoiding increased device complexity from extra sensing components.
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
The solution enables robust and stable motor control with reduced torque ripple and noise, improving the handling feel and reducing the computational burden on the control system.
Implementation Method 1
a counter electromotive voltage calculating means 10-3 for calculating a counter electromotive voltage generated in the polyphase motor 108
Data Source
AI summary
The invention relates to a control apparatus of an electric power steering apparatus structured such as to apply a steering assist force generated by a n-phase motor to a steering system of a vehicle, the control apparatus is provided with at least (n−1) numbers of current detecting means for detecting a current Im in each of phases of the motor, a current command value calculating means for outputting a current command value Imref in each of the phases, and n numbers of current control means, and the control apparatus executes a current control of each of the phases by the current control means having the current command value Imref in each of the phases and the current Im in each of the phases as an input.