Power Tool Motor Control With Flux Angle Adjustment
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Solution Overview
Problem
Existing power tools using square wave control for brushless DC motors suffer from low efficiency and limited speed regulation, often resulting in locked rotors and requiring mechanical structures for speed adjustment, which increase weight and reduce usability.
Innovation Solution
A power tool with a controller that dynamically adjusts the included angle between stator and rotor flux linkages from 90° to 135°, using a driver circuit to optimize motor performance by controlling the current applied to the stator based on motor current, rotational speed, and rotor position.
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 fixed six-state square wave to dynamically adjustable current states by controlling switching elements, enabling continuous torque vector adjustment and improving motor efficiency while maintaining control feasibility
Solution Approach 2:
The patent transitions from static six discrete torque vectors to dynamic continuous torque vector control by adjusting current states in real-time based on rotor position and load conditions, eliminating locked rotor and improving efficiency
2Device complexity
If square wave control mode is used, then the control structure is simple, but the motor speed is difficult to improve beyond a certain speed
Solution Approach 1:
The patent changes the control approach from fixed six-state switching to dynamic current state adjustment with multiple intermediate states, enabling continuous torque control and extended speed range without increasing mechanical complexity
3Speed
If mechanical gear structure is used for speed regulation, then the speed regulation can be achieved, but the weight of the whole machine increases
Solution Approach 1:
The patent replaces mechanical gear structures with electronic control systems that adjust motor torque and speed through current control, eliminating the need for mechanical speed regulation components and reducing overall machine weight
4Device complexity
If six discrete torque vectors are used in square wave control, then the control is simple, but the locked rotor appears frequently under heavy load
Solution Approach 1:
The patent transitions from static six discrete torque vectors to dynamic continuous torque vector control, adjusting torque magnitude and direction in real-time to prevent locked rotor under heavy load while maintaining control simplicity
Solution Approach 2:
The patent uses rotor position feedback to dynamically adjust current states and torque vectors, ensuring optimal torque delivery under varying load conditions and preventing locked rotor through continuous adaptation
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
Enhances motor efficiency and output performance by maintaining a maximum electromagnetic torque, allowing for broader speed regulation without mechanical structures, thus improving usability and reducing weight.
Implementation Method 1
a stator winding of the brushless motor can generate a magnetic field... an alternating magnetic field is generated to drive the rotor to rotate
Implementation Method 2
the motor is configured to generate a reluctance torque... an included angle between a stator flux linkage of the motor and a rotor flux linkage of the motor
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°.