Stepping Motor Driver Circuit Back-EMF Load Angle Control
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Solution Overview
Problem
Stepping motors often experience 'step-out' due to sudden load changes or speed variations, leading to inefficiencies and increased costs when trying to prevent this with motor driving circuits that apply margins or use sensors.
Innovation Solution
A driving circuit that includes a logic circuit, back electromotive force detector, and load angle estimation unit to control electric power supplied to the stepping motor, adjusting the load angle to a target value and preventing step-out while maintaining high efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a margin is applied to the assumed maximum load to prevent step-out, then reliability is improved, but energy consumption increases due to large power loss
Solution Approach 1:
The patent applies dynamics by making the driving voltage variable rather than constant. The logic circuit dynamically adjusts the driving voltage applied to the coil based on the detected back electromotive force, allowing the motor to operate at optimal power levels under different load conditions while preventing step-out when needed.
Solution Approach 2:
The patent implements feedback by detecting the back electromotive force generated by the motor and using this information to adjust the driving voltage. The logic circuit continuously monitors the back EMF and modifies the driving voltage accordingly, creating a closed-loop control system that prevents step-out while minimizing power loss.
2Reliability
If a sensor is used to detect the position of the rotor to prevent step-out, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies self-service by using the motor's own back electromotive force as the detection signal. Instead of requiring external sensors to detect rotor position, the system utilizes the electrical characteristic (back EMF) naturally generated by the motor itself, eliminating the need for additional sensing components.
Solution Approach 2:
The patent replaces the mechanical sensor-based detection system with an electrical detection method. By substituting physical sensors with electrical measurement of back EMF, the system achieves rotor position detection without mechanical contact or additional sensing components, reducing complexity and cost.
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 effectively drives stepping motors with high efficiency while suppressing step-out, reducing power loss and component costs by dynamically adjusting power supply based on detected back electromotive force and load angle.
Implementation Method 1
a back electromotive force detector that detects a back electromotive force across the coil
Data Source
AI summary
A logic circuit controls a bridge circuit connected to a coil of a stepping motor in synchronization with an input pulse, so as to control electric power supplied to the coil of the stepping motor. A back electromotive force detector detects the back electromotive force VBEMF across the coil L. A load angle estimation unit estimates the load angle φ based on the back electromotive force detected in the detection period set in the high-impedance period set for the coil L. A logic circuit is configured to adjust electric power supplied to the coil such that the estimated load angle φ approaches a predetermined target angle φREF.