Stepper Motor Pulse Control Using Back-EMF for Stable Rotation
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Solution Overview
Problem
Step motor drive devices are prone to abnormal operation, such as temporary rotation cessation or reverse rotation, due to external disturbances like changes in battery voltage.
Innovation Solution
A step motor drive device with a rotor magnetized into two or more poles, a stator, and a coil, utilizing a drive circuit that outputs intermittent partial signals, a detecting circuit for electromagnetic induced current, and a control unit that adjusts signal intervals and intensities based on detected currents to ensure stable rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single pulse or multiple pulses of certain polarity are output to drive the step motor, then the motor can be properly driven according to the situation, but abnormal operation occurs when disturbance such as large change in battery voltage is applied, causing rotation to stop or rotate in opposite direction
Solution Approach 1:
The patent employs feedback control by measuring the electromagnetic induced current generated in the coil after drive signals are output. The control device adjusts the drive pattern based on the measured current, creating a closed-loop system that compensates for disturbances such as battery voltage changes, thereby preventing abnormal operations like rotation cessation or reverse rotation.
Solution Approach 2:
The patent dynamically changes drive parameters including pulse width, pulse interval, and current threshold values based on the measured electromagnetic induced current. By adjusting these parameters in response to real-time feedback, the system maintains reliable rotation performance under varying operating conditions and external disturbances.
2Use of energy by moving object
If partial pulses are output and next partial pulse is repeated when electromagnetic induced current is smaller than predetermined value, then power consumption is reduced, but rotation stability deteriorates when disturbance is applied
Solution Approach 1:
The patent dynamically adjusts the drive strategy based on real-time current measurements. Instead of using fixed partial pulses, the system modifies pulse width, pulse interval, and other drive parameters adaptively. This dynamic approach allows the motor to operate efficiently under normal conditions while maintaining rotation stability when disturbances occur, resolving the trade-off between power consumption and reliability.
3Power
If coil is short-circuited when current value above upper limit is detected and re-excited when lower limit is reached, then current control is achieved, but complex control logic is required to determine step completion and prevent abnormal operation
Solution Approach 1:
The patent simplifies control logic by focusing on dynamic parameter adjustment rather than complex state machine control. The system measures electromagnetic induced current and adjusts pulse width, pulse interval, and threshold values based on current trends. This approach achieves effective current control while avoiding the complexity of determining step completion through multiple conditions and states.
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 enables stable rotation of the step motor even under external disturbances by accurately determining rotor phase and adjusting drive signals, preventing abnormal operations.
Implementation Method 1
a coil that generates a magnetic force to the stator
Implementation Method 2
a detecting circuit that detects an electromagnetic induced current that is generated in the coil
Data Source
AI summary
A step motor drive device includes a step motor including a rotor, stators, and a coil, a drive circuit that outputs a drive signal including a plurality of partial signals that are output intermittently, a detecting circuit that detects an electromagnetic induced current that is generated in the coil after the partial signals are output, and a control unit that controls the drive circuit. The drive circuit outputs one of the partial signals included in the drive signal to the coil, and, in response to a change in an electromagnetic induced current generated in the coil after the partial signal is output, outputs a next partial signal to the coil. The control unit determines a control method of the step motor based on an interval of the plurality of partial signals, and controls the drive circuit based on the determined control method.