Stepping Motor Control Device Back-EMF Torque Suppression
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Solution Overview
Problem
Existing control devices for stepping motors experience significant torque diminution at high rotation speeds due to back electromotive force, with existing solutions providing limited improvement or failing to effectively suppress this effect.
Innovation Solution
A control device that computes and boosts the voltage of drive signals for a stepping motor based on its output state, target and detected rotation speeds, and a dynamic model prediction, using a booster circuit to increase the motor power supply voltage in a stepwise fashion with multiple voltage levels, and executes moderate field current control to mitigate the influence of back electromotive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation speed of the stepping motor is increased, then the productivity is improved, but the torque significantly diminishes due to back electromotive force
Solution Approach 1:
The patent changes the voltage parameter dynamically based on rotation speed. A voltage command generation unit generates a voltage command value that increases with rotation speed, and a voltage adjustment unit adjusts the actual voltage applied to the motor based on this command. This parameter change allows the motor to overcome back electromotive force at high speeds while maintaining adequate torque, resolving the contradiction between high rotation speed and torque maintenance.
2Force
If moderate field current control is applied to alleviate back electromotive force influence, then the torque diminution is partially improved, but the improvement is limited
Solution Approach 1:
The patent implements feedback control by detecting the actual voltage applied to the motor and comparing it with the voltage command value. A voltage adjustment unit continuously adjusts the voltage based on this feedback to ensure it matches the commanded voltage. This feedback mechanism enhances torque control effectiveness while managing complexity through systematic control architecture.
Solution Approach 2:
The patent transitions from static voltage control to dynamic voltage control. The voltage command generation unit dynamically generates voltage commands based on rotation speed, and the voltage adjustment unit dynamically adjusts the applied voltage in real-time. This dynamic approach significantly improves torque maintenance at high speeds compared to static moderate field current control methods.
3Device complexity
If PWM voltage control with constant duty ratio is used above a given rotation speed, then the control is simplified, but the back electromotive force influence cannot be suppressed in high rotation speed
Solution Approach 1:
The patent replaces the static constant duty ratio PWM control with dynamic voltage control. The voltage command generation unit generates voltage commands that increase with rotation speed, and the voltage adjustment unit dynamically adjusts the duty ratio accordingly. This dynamic approach maintains simplicity while effectively suppressing back electromotive force influence in high rotation speed ranges.
Solution Approach 2:
The patent changes the voltage parameter dynamically based on rotation speed. Instead of maintaining a constant duty ratio, the system adjusts the voltage command value and actual voltage based on the motor's rotation speed, enabling effective torque maintenance at high speeds while keeping the control structure 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
This approach efficiently enhances torque in high rotation speed ranges by dynamically adjusting the motor power supply voltage and current, effectively suppressing the impact of back electromotive force and maintaining performance without excessive power consumption.
Implementation Method 1
tremendous back electromotive force causes the torque of stepping motors to significantly diminish in a high rotation speed range
Data Source
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AI summary
A control device (20) comprises a position command creation part (211) creating a target rotation angle value of a stepping motor (32), a position controller (213) calculating the rotation speed of the stepping motor (32) based on the deviation between the target rotation angle value and detected value, a boost command processing part (218) calculating the boosted voltage according to the calculated rotation speed, a booster circuit (22) boosting the motor power supply voltage, and a PWM inverter (25) creating pulse signals supplied to the stepping motor (32).