Sensorless Motor Control for Air Compressor Startup
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Solution Overview
Problem
Conventional sensorless control methods for air compressors in fuel cell systems face challenges in initial motor position estimation and control responsiveness due to the lack of back electromotive force at startup, leading to inefficient open-loop control and reduced driving characteristics.
Innovation Solution
A method involving a controller that performs speed control to determine the motor stopped state, aligns the rotor position using d-axis current, and sets this position as the initial position for sensorless control, eliminating the need for open-loop control and improving responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensorless control methods are used for initial motor startup, then the control system is simpler, but the initial position estimation is inaccurate and control responsiveness is poor
Solution Approach 1:
The patent applies preliminary action by performing rotor position alignment using d-axis current before normal sensorless control begins. The controller aligns the rotor to a predetermined position (e.g., 0 electrical radians) by applying d-axis current during the stopping phase, so that when the motor restarts, the rotor is already at a known position. This preliminary positioning action eliminates the need for complex open-loop control and improves initial position estimation accuracy without requiring additional sensors.
2Speed
If open-loop control is used for initial motor driving, then the system is simpler to implement, but the control responsiveness and driving characteristics are reduced
Solution Approach 1:
The patent replaces the mechanical/open-loop control approach with an electromagnetic field-based sensorless control method. Instead of using open-loop control that does not require position feedback, the system uses d-axis current to create a magnetic field that aligns the rotor to a predetermined position. This substitution of electromagnetic field control for mechanical/open-loop control achieves faster responsiveness while maintaining sensorless operation.
3Measurement precision
If the motor is stopped using conventional speed control, then the stopping process is straightforward, but the rotor position is not accurately determined for subsequent startup
Solution Approach 1:
The patent applies continuity of useful action by making the rotor position alignment process part of the normal stopping procedure. Instead of treating position alignment as a separate time-consuming step, the system continuously applies d-axis current during the stopping phase to maintain rotor alignment. This allows the rotor to be stopped at a predetermined position without requiring additional time or separate alignment operations, thus eliminating time loss while achieving accurate position determination.
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
This approach enhances the initial speed control responsiveness of the air compressor, improving air supply and fuel cell stack output responsiveness, and vehicle acceleration performance while ensuring stable motor drive efficiency and fuel efficiency.
Implementation Method 1
performing a motor position control to align the rotor position to a predetermined position when the motor stopped state is determined by the controller
Data Source
AI summary
A method of controlling a sensorless motor of an air compressor is provided to overcome the known problems of sensorless control methods and to improve control responsiveness. In various aspects of the present invention, a method of controlling a sensorless motor of an air compressor includes: performing a speed control for stopping a motor by a controller; determining a motor stopped state from an estimated motor speed while the speed control is performed by the controller; determining a rotor position estimated as a fixed position when the motor stopped state is determined by the controller; performing motor position control for moving the rotor position to the fixed position when the motor stopped state is determined; and starting sensorless control for driving the motor by setting the fixed position to an initial position when requesting a motor driving while the rotor position is maintained at the fixed position.