Stepper Motor Load Angle Detection via Back EMF
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Solution Overview
Problem
Stepper motors typically consume excessive power due to high motor current reserves, leading to unnecessary energy losses, as they are often controlled independently of the actual motor load without sensing the load angle, resulting in inefficient torque application.
Innovation Solution
A method and circuit arrangement that determine the momentary mechanical load and load angle of a stepper motor without sensors, using back EMF and chopper control to regulate the motor current, ensuring only the necessary current is supplied based on the actual load, thereby minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If stepper motors are controlled with high motor current reserves to ensure sufficient torque, then the torque reserve is improved, but the power consumption increases significantly
Solution Approach 1:
The patent implements dynamic current adjustment by continuously monitoring the load angle and adapting the motor current in real-time. The current is increased only when the load angle indicates actual load increase, and reduced when the load angle decreases, replacing static high-current operation with dynamic adaptive current control.
Solution Approach 2:
The patent uses the load angle as a feedback parameter to regulate motor current. By measuring the load angle and using it to control the current magnitude, the system creates a closed-loop control that automatically adjusts power consumption based on actual torque requirements, eliminating the need for constant high current reserves.
2Use of energy by moving object
If rotary sensors are used to detect rotor position for optimizing current, then the power consumption can be reduced, but the device complexity and cost increase
Solution Approach 1:
The patent uses the back EMF voltage as an intermediary parameter to indirectly obtain load angle information without direct position sensing. The back EMF, which is naturally generated during motor operation, serves as a mediator that provides load angle data through voltage measurement and evaluation, avoiding the need for additional sensors.
Solution Approach 2:
The patent exploits the back EMF voltage that is naturally generated by the motor during normal operation to obtain load angle information. Instead of requiring external sensing systems, the motor's own electrical characteristics are utilized for control purposes, making the system self-sufficient and eliminating additional hardware requirements.
3Loss of energy
If the motor current is reduced to match actual load, then the power loss is decreased, but the torque capability may become insufficient
Solution Approach 1:
The patent implements dynamic current adjustment by continuously monitoring the load angle and adapting the motor current in real-time. The current is increased only when the load angle indicates actual load increase, and reduced when the load angle decreases, replacing static high-current operation with dynamic adaptive current control.
Solution Approach 2:
The patent uses the load angle as a feedback parameter to regulate motor current. By measuring the load angle and using it to control the current magnitude, the system creates a closed-loop control that automatically adjusts power consumption based on actual torque requirements, eliminating the need for constant high current reserves.
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 reduces power consumption by adjusting the motor current in real-time according to the load angle, minimizing energy losses while maintaining sufficient torque, without requiring additional mechanical components or changes to the motor design.
Implementation Method 1
durations tON and tFD are then present at the output of the chopper control unit, during which the ON and FD phases are activated. The load angle of the motor can be determined from these two durations
Data Source
Figure 1(A)~1(C)
Figure 2
Figure 3
AI summary
The invention relates to a method and a circuit arrangement which enable a mechanical load applied to the motor shaft of a stepper motor (M) or a load angle of said stepper motor to be detected in a sensorless manner. The invention also relates to a method and circuit arrangement which enable the motor current(s) of a stepper motor to be controlled in accordance with the load value such that the load angle is as high as possible without risking step losses, in order to maintain the current consumption of the motor as low as possible. This is achieved according to the invention, essentially by evaluating the temporal duration of the ON- and the FD-phases during the chopper control of the motor.