Power Tool Motor Control With Overmodulated PWM
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Solution Overview
Problem
Conventional square wave modulation in power tools results in low output power, low motor efficiency, and poor energy utilization due to discrete and discontinuous torque vectors, limiting the performance of power tools.
Innovation Solution
Implementing a control system that utilizes a seven-segment or discontinuous PWM signal with overmodulation to adjust the phase currents and voltages of the motor, enhancing voltage utilization and maintaining a constant phase voltage for improved rotational speed and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional square wave modulation is used to control motor speed and torque, then the control implementation is simple, but the output power is low and motor efficiency is poor
Solution Approach 1:
The patent changes the modulation parameters from conventional square wave to seven-segment or discontinuous PWM signals with overmodulation. This parameter change enables continuous torque vectors instead of discrete ones, improving output power and motor efficiency while maintaining controllable implementation through updated control algorithms
2Device complexity
If conventional square wave modulation is used, then the control structure is simple, but energy utilization rate is low
Solution Approach 1:
The patent implements continuous torque vectors through seven-segment or discontinuous PWM modulation, ensuring continuous useful action in torque production. This eliminates the discontinuous nature of conventional square wave control, improving energy utilization rate by maintaining smooth torque delivery throughout the motor cycle
3Ease of operation
If conventional square wave modulation is used, then the control method is easy to implement, but torque vectors are discrete and discontinuous resulting in poor output performance
Solution Approach 1:
The patent transitions from static discrete torque vectors in conventional square wave control to dynamic continuous torque vectors through seven-segment or discontinuous PWM modulation. This dynamic approach allows real-time adjustment of torque magnitude and direction, improving output performance while maintaining ease of implementation through updated control algorithms
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 solution increases the output power and efficiency of power tools by optimizing torque and rotational speed, particularly in light to moderate load conditions, thereby improving their working efficiency and performance.
Implementation Method 1
Implementing a control system that utilizes a seven-segment or discontinuous PWM signal with overmodulation to adjust the phase currents and voltages of the motor
Implementation Method 2
a motor and a motor-control device
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Provided is a power tool. The power tool includes a motor, a speed regulation mechanism, a driver circuit, and a control module. The motor includes a stator winding and a rotor rotating around a stator. The speed regulation mechanism is at least used for setting a target rotational speed of the motor. The driver circuit is used for delivering electrical energy provided by a power supply device from a direct current bus to the motor, where the driver circuit includes multiple electronic switches connected between the power supply device and the motor. The control module is configured to calculate a voltage vector according to a measured rotational speed of the motor, a phase current of the stator winding, and the target rotational speed and overmodulate the voltage vector to output a pulse-width modulation (PWM) signal to the driver circuit. A per-unit value of an amplitude of the voltage vector ranges from 0 to 1.15. Through the preceding technical solutions, output power of the power tool can be increased