Motor Speed Control via Back-EMF Sampling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional motor control systems fail to accurately match the actual running speed with the set speed, leading to errors and potential motor burning issues, as they do not effectively monitor and adjust the motor speed in real-time.
Innovation Solution
A control system comprising a central processing module and a drive control module that samples the voltage of a phase coil with no applied voltage, converts it into a digital signal, and determines if the average value falls within predetermined thresholds to ensure the motor speed matches the preset speed, sending a control signal accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the motor operates based on set speed without real-time monitoring, then the control system is simple, but the actual running speed does not match the set speed causing large errors and potential motor burning
Solution Approach 1:
The patent implements feedback by sampling the back electromotive force (EMF) voltage of the motor during the period when no voltage is applied to any phase coil. The control system processes this sampled voltage to calculate actual running speed and compares it with the set speed, then sends control signals to adjust the motor speed accordingly. This closed-loop feedback mechanism ensures accurate speed matching while preventing motor burning.
Solution Approach 2:
The patent uses the back EMF voltage as an intermediary to indirectly measure the motor speed. Instead of directly measuring speed, the system samples the voltage generated by the motor's rotation during the off-period of phase coils, processes this voltage signal through the control system, and derives speed information from it. This intermediary approach enables accurate speed measurement without direct mechanical sensors.
2Reliability
If voltage is continuously applied to monitor motor speed, then real-time speed control is achieved, but energy consumption increases and motor burning risk increases
Solution Approach 1:
The patent employs periodic action by sampling the back EMF voltage only during specific time windows when no voltage is applied to any phase coil. The control system periodically activates the sampling function during these off-periods, processes the voltage signal to determine actual speed, and sends control signals accordingly. This periodic sampling approach enables reliable motor protection and speed control while minimizing energy consumption, as the sampling occurs only during natural off-periods without extending the motor's active operation time.
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 enables real-time monitoring and accurate control of motor speed, preventing errors and motor burning by determining if the actual speed aligns with the set speed within specified thresholds, thereby improving control accuracy.
Implementation Method 1
sampling a voltage of a phase coil of the motor, to which no voltage is applied, during a period in which no voltage is applied to any phase coil of the motor
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A control method and a control system (2), by which a motor (31) can be controlled. The control system (2) comprises a central processing module (22) and a drive control module (23). In a period in which a voltage is not applied to any phase coil of the motor (31), the drive control module (23) collects voltages of the coil to which the voltage is not applied, and converts the voltages of the coil into digital signals. The central processing module (22) reads the digital signals and determines whether the running speed of the motor (31) is consistent with a preset speed depending on whether an average value of the digital signals falls within a preset threshold range, which helps to improve the control precision.