Reluctance Torque Power Tool Control for Locked Rotor Prevention
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Solution Overview
Problem
Existing power tools using square wave control for brushless direct current motors suffer from low efficiency and frequent locked rotor issues, especially under heavy loads, and limited speed regulation, which is further exacerbated by the need for mechanical gear structures that increase weight and complexity.
Innovation Solution
A power tool design that includes a motor capable of generating reluctance torque, with a controller dynamically adjusting the current applied to the stator to vary the included angle between stator and rotor flux linkages from 90° to 135°, allowing for improved torque and speed regulation through advanced control modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If square wave control mode is used to drive the brushless motor, then the control is easy to achieve, but the motor efficiency and whole machine efficiency are low
Solution Approach 1:
The patent changes the control parameter from square wave to sinusoidal wave, and dynamically adjusts the current amplitude and phase angle according to motor speed and load conditions. This parameter optimization resolves the contradiction by achieving both ease of control through standardized algorithms and improved motor efficiency through optimized current waveforms and dynamic adjustment strategies.
2Device complexity
If square wave control mode is used, then the control structure is simple, but locked rotor appears frequently under heavy load
Solution Approach 1:
The patent implements dynamic current adjustment where the controller continuously monitors motor speed and load conditions, then dynamically modifies the stator current amplitude and phase angle. This dynamic control prevents locked rotor under heavy load by adapting the magnetic field strength and orientation in real-time, while maintaining relatively simple control structure through standardized feedback loops.
3Adaptability or versatility
If mechanical gear structure is added for speed regulation, then the speed regulation range can be extended, but the weight of the whole machine increases
Solution Approach 1:
The patent replaces the mechanical gear structure with an electrical control system that achieves speed regulation through dynamic adjustment of stator current parameters. The controller modifies current amplitude and phase angle to vary motor torque and speed characteristics, eliminating the need for mechanical gears and reducing overall machine weight while maintaining extended speed regulation capability.
4Adaptability or versatility
If mechanical gear structure is added for speed regulation, then different gear ratios can be configured, but the device complexity increases
Solution Approach 1:
The patent substitutes the complex mechanical gear system with a simplified electrical control approach. The controller achieves multiple speed regulation levels by dynamically adjusting current parameters rather than through physical gear changes, thereby reducing device complexity while preserving speed regulation versatility.
5Productivity
If the motor operates at high speed under light load, then the productivity is improved, but the speed is difficult to be further improved in square wave control mode
Solution Approach 1:
The patent optimizes current parameters including amplitude and phase angle according to operating conditions. Under light load, the controller adjusts parameters to enable higher speeds beyond the limitations of square wave control, thereby improving both maximum speed capability and productivity without fundamental design changes.
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 solution enhances motor efficiency, increases output torque, and extends the constant-speed range, reducing the need for mechanical gear structures and improving overall power tool performance and endurance.
Implementation Method 1
a stator winding of the brushless motor can generate a magnetic field. A controller is configured to output a corresponding drive signal to the driver circuit according to a rotational position of a rotor so as to make the driver circuit switch the driving state. Therefore, a state of a voltage applied to the winding of the brushless motor is changed, and an alternating magnetic field is generated to drive the rotor to rotate
Implementation Method 2
The motor includes a stator and a rotor, and the motor is configured to generate a reluctance torque
Data Source
AI summary
A power tool includes a motor, a power supply device, a driver circuit, a parameter acquisition module, and a controller. The motor includes a stator and a rotor. The motor is configured to generate a reluctance torque. The driver circuit is electrically connected to the motor to drive the motor. The parameter acquisition module is configured to acquire a current of the motor, a rotational speed of the motor, and a position of the rotor. The controller is configured to: according to at least one of the current of the motor, the rotational speed of the motor, or the position of the rotor, dynamically adjust a current applied to the stator so that an included angle between a stator flux linkage of the motor and a rotor flux linkage of the motor ranges from 90° to 135°.