Sensorless PMSM Start Control for Hand-Held Tool Breakaway Torque
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Solution Overview
Problem
Existing methods for operating permanent magnet synchronous motors in hand-held processing devices face challenges in sensorless determination of rotor position and direction, leading to inefficient starting and potential torque limitations.
Innovation Solution
A method for sensorless determination of rotor position and direction in a permanent magnet synchronous motor, enabling continuous rotation in a direction that maximizes achievable torque beyond the breakaway torque limit, without the need for magnetic sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensors are used to determine rotor position and control torque, then reliability of starting and continuous rotation is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the sensor component from the system. Instead of using sensors to detect rotor position, the control device determines position sensorlessly by evaluating current values and frequencies during motor operation. This removal of the sensor simplifies the device structure while maintaining reliable starting and continuous rotation through intelligent control algorithms.
Solution Approach 2:
The patent replaces the mechanical/sensor-based position detection system with an electrical/control-based system. The control device uses electrical current measurements and frequency analysis to infer rotor position, substituting physical sensors with electronic measurement and calculation methods. This substitution reduces device complexity while achieving the same functional goal of reliable motor control.
2Manufacturing precision
If sensors are installed for sensorless control, then manufacturing precision of control is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent removes sensors from the motor assembly, making the manufacturing process simpler and more cost-effective. The control precision is maintained through software-based position determination that calculates rotor position from current measurements, eliminating the need for precise sensor installation and calibration during manufacturing.
Solution Approach 2:
The control system performs self-position determination without external sensors. The control device automatically calculates rotor position by evaluating current values and frequencies generated during motor operation, enabling the system to self-regulate without requiring additional manufacturing steps for sensor integration.
3Force
If breakaway torque limit is increased, then starting capability is improved, but use of energy increases
Solution Approach 1:
The patent implements dynamic control of the motor during starting and continuous rotation. The control device continuously adjusts control parameters based on real-time current measurements and calculated rotor position, optimizing the torque output to match actual load requirements. This dynamic adjustment allows the motor to generate high breakaway torque when needed while reducing energy consumption during steady-state operation.
Solution Approach 2:
The control system changes operational parameters (current amplitude, frequency, phase) based on the determined rotor position and operational state. By dynamically adjusting these parameters, the motor can achieve high breakaway torque for starting while maintaining efficient energy usage during continuous rotation, avoiding constant high-energy operation.
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
Enables reliable, cost-effective, and efficient starting of the synchronous motor from any position, with uniform wear distribution and improved torque generation.
Implementation Method 1
sensorless determination of a position variable representative of a position of a rotor of the synchronous motor
Implementation Method 2
an amount of achievable torque generateable by the synchronous motor when it is controlled to rotate
Data Source
Figure 1a~1c
Figure 2
Figure 3~4
AI summary
The invention relates to a method for operating a permanent magnet synchronous motor (2) of a hand-held processing device (1), wherein the method comprises the steps: a) sensorless determination of a position parameter (POG) representative of a position (PO) of a rotor (4) of the synchronous motor (2) in a standstill, b) determination of a direction parameter (RIG) for continuous rotation of the rotor (4) from standstill in a direction (RI) as a function of the determined position parameter (POG) such that an amount (BDM) of an achievable torque (DM) achievable by the synchronous motor (2) when sensorlessly driven to rotate in the direction (RI) is greater than an amount (BLM) of a breakaway torque limit (LM) of the processing device (1), and c) sensorless driving of the synchronous motor (2) as a function of the determined direction parameter (RIG) to rotate in the direction (RI).