Stepping Motor Control via Back-EMF Feedback
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Solution Overview
Problem
The existing 1-2 phase excitation method for two-phase stepping motors has low tolerance to load changes, leading to decreased torque and increased likelihood of step-out when the load increases, as the excitation phases are switched before the rotor reaches the appropriate position.
Innovation Solution
A motor drive control device that alternately repeats one-phase and two-phase excitation based on back electromotive force detection, dynamically adjusting the periods of each excitation phase to adapt to load changes by determining the one-phase excitation period based on the back electromotive force generated in the unexcited coil and setting the two-phase excitation period based on the previous one-phase excitation period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed uniform periods are used for one-phase and two-phase excitation in the 1-2 phase excitation method, then the control structure is simple, but the tolerance to load changes is low and step-out easily occurs
Solution Approach 1:
The patent applies dynamics by making the excitation periods variable rather than fixed. The control device dynamically adjusts the period of one-phase excitation and two-phase excitation based on detected rotor position and load conditions, allowing the system to adapt to changing loads and prevent step-out while maintaining reliable operation.
Solution Approach 2:
The patent implements feedback by detecting the rotor position through back electromotive force (EMF) sensing and using this information to adjust the excitation periods. The control device continuously monitors the rotor state and modifies the timing of phase excitations accordingly, creating a closed-loop control system that improves tolerance to load changes.
2Loss of time
If the excitation phase is switched early to maintain fixed timing, then the control timing is precise, but the rotor cannot reach the appropriate position and torque decreases
Solution Approach 1:
The patent makes the excitation timing dynamic by adjusting the period based on actual rotor position feedback. Instead of using fixed uniform periods, the control device varies the duration of one-phase and two-phase excitation to ensure the rotor reaches the optimal position for torque generation, preventing torque loss while maintaining precise control timing.
Solution Approach 2:
The patent uses rotor position feedback from back EMF detection to determine the appropriate excitation timing. The control device measures the actual rotor state and adjusts the excitation phase switching timing accordingly, ensuring that excitation occurs at the optimal moment for maximum torque while maintaining precise timing control.
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 increases the tolerance of the two-phase stepping motor to load changes, reducing the likelihood of step-out and maintaining torque by dynamically adjusting the excitation periods in response to changing loads.
Implementation Method 1
the controller determines, based on a back electromotive force generated in the coil that was not excited during the one-phase excitation, a period of performing the one-phase excitation
Data Source
AI summary
A motor drive control device has a controller and a driver. The controller generates a control signal for controlling driving of a two-phase stepping motor so as to alternately repeat one-phase excitation in which a coil of one phase in coils of two phases of the two-phase stepping motor is excited and two-phase excitation in which the coils of two phases in the coils of the two phases are excited. The driver drives the coils of the two phases, based on the control signal. The controller determines, based on a back electromotive force generated in the coil that was not excited during the one-phase excitation, a period of performing the one-phase excitation, and determines, based on the period of the one-phase excitation performed before the two-phase excitation, a period of performing the two-phase excitation.