Sensorless Motor Controller Using Phase Difference Modulation
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Solution Overview
Problem
Conventional motor driving methods using Hall sensors are prone to accuracy reduction due to environmental interference and increase system volume and cost, while sensorless methods generate noise and require complex computing circuits to estimate back electromotive force.
Innovation Solution
A motor controller with a simple computing circuit that includes a switch circuit, current detecting unit, waveform processing unit, and phase difference processing unit, which stabilizes the motor by modulating the difference between current and voltage phases without detecting phase switching time points, using a phase lock loop or proportional-integral-derivative controllers to adjust the electric period of the voltage signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall sensor is used for switching phases, then phase switching accuracy is improved, but system volume and cost increase
Solution Approach 1:
The patent extracts and eliminates the Hall sensor from the motor control system, replacing it with a sensorless control method that uses the motor's own back electromotive force (EMF) signals for phase detection, thereby reducing system volume and cost while maintaining control functionality
Solution Approach 2:
The motor controller uses the motor's own back EMF signals to detect phase information and determine commutation timing, allowing the system to self-diagnose and self-control without external sensors, thus achieving sensorless operation
2Device complexity
If sensorless driving method is used to avoid Hall sensor, then system volume and cost are reduced, but noise is generated due to discontinuity of output voltage
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the back EMF signals from each phase, uses them to detect zero-crossing points for commutation timing, and adjusts the switching signals accordingly to maintain continuous and smooth voltage output, thereby reducing noise
Solution Approach 2:
The controller dynamically adjusts the switching timing based on real-time detection of back EMF zero-crossing points, ensuring that phase switching occurs at optimal moments to maintain continuous current flow and minimize voltage discontinuities that cause noise
3Measurement precision
If back electromotive force is estimated using V=I×Rm+L×di/dt+BEMF, then BEMF detection accuracy is improved, but computing circuit complexity increases
Solution Approach 1:
The patent replaces the complex computational approach (solving the differential equation V=I×Rm+L×di/dt+BEMF) with a direct electrical measurement method that utilizes the natural back EMF signals present in the motor phases, eliminating the need for complex computing circuits while maintaining detection accuracy
Solution Approach 2:
The system utilizes the motor's own back EMF signals that are naturally present during operation to directly detect phase information and commutation timing, eliminating the need for external excitation signals or complex computation circuits
Data Source
AI summary
A motor controller comprises a switch circuit and a control unit. The switch circuit is coupled to a motor for driving the motor. The control unit is configured to generate a control signal to control the switch circuit. The motor controller is configured to generate a current signal and a voltage signal. When a current phase of the current signal is at a predetermined crossing phase, the motor controller calculates a difference value between the current phase of the current signal and a voltage phase of the voltage signal, where the motor controller is configured to control the difference value. The motor controller may stabilize the motor and avoid noise by modulating the difference value. The motor controller may modulate the difference value, such that the difference value is equal to a predetermined phase difference.