Power Tool Motor Flux-Angle 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 have limited speed regulation capabilities.
Innovation Solution
A power tool system that includes a motor capable of generating reluctance torque, a power supply device, a driver circuit, and a controller. The controller dynamically adjusts the current applied to the stator based on the motor's current, rotational speed, or rotor position to maintain an included angle between stator and rotor flux linkages within the range of 90° to 135°, allowing for efficient speed regulation and torque control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If square wave control 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 fixed six-state square wave to dynamically adjustable current with continuously variable torque angle (90°-135°), enabling efficient control without mechanical structures
Solution Approach 2:
The patent makes the torque angle dynamic and continuously adjustable between 90° and 135° based on load conditions, replacing the static six-state square wave control, thereby improving motor efficiency across different operating points
2Device complexity
If square wave control with six discrete vector torques is used, then the control is simple, but locked rotor appears frequently under heavy load
Solution Approach 1:
The patent changes the torque angle parameter to a continuous variable range (90°-135°) instead of fixed six discrete states, providing smooth torque delivery that prevents locked rotor under heavy load while maintaining control simplicity
Solution Approach 2:
The patent dynamically adjusts the torque angle within 90°-135° range according to load conditions, enabling the motor to adapt to heavy load situations and avoid locked rotor, while the control structure remains relatively simple
3Speed
If mechanical gear structure is used for speed regulation, then the speed regulation is achieved, but the weight of the whole machine increases
Solution Approach 1:
The patent replaces the mechanical gear structure with an electrical control system that adjusts the torque angle between 90° and 135° to achieve speed regulation, eliminating the need for mechanical gears and reducing overall machine weight
Solution Approach 2:
The patent uses electrical parameter adjustment (torque angle control) instead of mechanical gear changes to achieve speed regulation, providing a lighter and more efficient solution
4Speed
If mechanical gear structure is used for speed regulation, then the speed can be regulated, but the speed regulation range is greatly limited by the motor
Solution Approach 1:
The patent replaces the mechanical gear structure with an electrical control system that adjusts the torque angle between 90° and 135° to achieve speed regulation, eliminating the need for mechanical gears and reducing overall machine weight
Solution Approach 2:
The patent dynamically adjusts the torque angle within 90°-135° range according to load conditions, enabling the motor to adapt to heavy load situations and avoid locked rotor, while the control structure remains relatively simple
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
The proposed solution enhances the motor's efficiency and output performance by allowing continuous adjustment of the stator current to optimize the included angle between flux linkages, thereby improving speed regulation and reducing energy consumption.
Implementation Method 1
The motor includes a stator and a rotor, and the motor is configured to generate a reluctance torque
Implementation Method 2
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
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°.