Sensorless Motor Controller for Electric Power Steering
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Solution Overview
Problem
Current sensorless driving systems for brushless motors are not adequately adapted for applications like electric power steering systems, lacking a established control technique for such use cases.
Innovation Solution
A motor controller employing a virtual axis electric current value in a γδ coordinate system, with an addition angle computed based on torque or motor response, allowing torque generation without a rotation angle sensor, and including a limiting unit to prevent excessive addition angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resolver is used as a rotation angle sensor, then the motor control precision is improved, but the cost, wiring complexity, and installation space increase
Solution Approach 1:
The patent extracts and eliminates the rotation angle sensor (resolver) from the motor control system. Instead of using a physical sensor to detect rotor position, the invention computes the rotor position indirectly through sensorless control methods that analyze motor phase currents and voltages, thereby removing the complex wiring and installation requirements while maintaining control precision
Solution Approach 2:
The patent replaces the mechanical/physical resolution sensor system with an computational/electrical sensorless control system. By substituting physical measurement with mathematical computation based on electrical parameters, the system achieves the same control function without mechanical sensors, reducing wiring complexity and installation space
2Device complexity
If a sensorless driving system is used, then the cost and device complexity are reduced, but the control precision and reliability deteriorate
Solution Approach 1:
The patent implements feedback mechanisms in the sensorless control system by continuously monitoring motor phase currents and voltages, computing rotor position estimates, and using this information to adjust control commands. This closed-loop feedback approach maintains precision without requiring physical sensors, resolving the contradiction between simplified hardware and control accuracy
Solution Approach 2:
The patent changes the control parameters and computational methods used in sensorless control to improve precision. By optimizing current injection patterns, frequency selection, and computation algorithms for rotor position estimation, the system achieves high precision measurements without physical sensors, balancing simplicity and accuracy
3Adaptability or versatility
If existing sensorless control methods are applied to electric power steering systems, then the system adaptability is improved, but the control performance deteriorates due to lack of established techniques
Solution Approach 1:
The patent develops a universal sensorless control methodology that can be applied across different motor types and applications, including electric power steering systems. By creating a general-purpose control framework with adjustable parameters, the invention achieves both broad adaptability and reliable performance in specific applications like electric power steering
Solution Approach 2:
The patent implements dynamic adaptation in the sensorless control system by adjusting control parameters based on operating conditions. The system dynamically modifies current injection frequencies, amplitude ratios, and computation algorithms according to motor speed and load conditions, ensuring reliable performance across varying operating scenarios in electric power steering applications
Data Source
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AI summary
A motor controller (5) controls a motor (3) including a rotor (50) and a stator (55) opposed to the rotor (50). The motor controller (5) includes an electric current driving unit (31-36, 31A, 45) which drives the motor (3) with an axis electric current value (Iγ*) defined in a rotating coordinate system defined with respect to a control angle (θC) that is a rotation angle for control, a control angle computing unit (26) which computes a current value of the control angle (θC) by adding an addition angle (a) to a previous value of the control angle (θC) in each predetermined computing cycle, and an addition angle computing unit (23, 40, 47, 49) which computes the addition angle (a) according to a torque to be generated by the motor (3) or a response of the motor (3) to the axis electric current value (Iγ*).