Stepping Motor Control Device for Noise Reduction
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Solution Overview
Problem
Stepping motors generate abnormal noise during the transition from a two-phase excitation state to a one-phase excitation state during normal driving, due to sudden rotor movement after the hold period.
Innovation Solution
A control device and method that gradually increase and then decrease the excitation current in both phases of a stepping motor during the hold period, ensuring the current in one phase reaches zero by the end, and initiates one-phase excitation with the same polarity as at the hold period's end, to minimize sudden rotor movement and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the excitation current is suddenly applied to the coils during rotor locking operation, then the rotor can be quickly attracted to the initial position, but vibration sound and impact sound are generated
Solution Approach 1:
The patent applies preliminary action by gradually increasing the excitation current from a low level before the hold period to the target holding current during the hold period. This gradual increase prepares the rotor for positioning without sudden current changes, thereby suppressing vibration and impact sounds while still achieving quick positioning during the subsequent normal driving phase.
2Stability of the object's composition
If the two-phase excitation state is used during the hold period, then the rotor can be stably positioned at the initial position, but abnormal noise is generated when transitioning to the one-phase excitation state during normal driving
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the excitation current waveform during the transition from hold period to normal driving. Specifically, it sets the excitation current in the first phase to be continuous between the hold period and normal driving, while gradually changing the current in the second phase. This dynamic adjustment eliminates sudden rotor movements and abnormal noise during the transition.
3Object-generated harmful factors
If the excitation current is gradually increased during the hold period, then vibration sound and impact sound are suppressed, but the rotor moves slowly to the initial position
Solution Approach 1:
The patent applies segmentation by dividing the driving process into two distinct phases: hold period and normal driving phase. During the hold period, the excitation current is gradually increased to suppress noise. During normal driving, a different current waveform is applied to achieve faster rotor movement. This segmentation allows the system to optimize for noise suppression during positioning while maintaining speed during operation.
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 effectively suppresses abnormal noise and vibration by ensuring a smooth transition from the hold to the driving phase, reducing sound pressure levels and preventing sudden rotor rotation.
Implementation Method 1
A stepping motor magnetizes a stator by causing an excitation current to flow in multiple coils to drive a rotor to rotate in steps
Implementation Method 2
a holding current for attracting the rotor positioned at an arbitrary position to a position (initial position) facing the stator is caused to flow in the coils
Data Source
AI summary
A control device for a stepping motor gradually increases an absolute value of the excitation current in phase A from when the start until the end of the hold period such that the amount of change in the excitation current per unit time is smaller than or equal to a first predetermined value. From the start of the hold period until a predetermined time elapses, an absolute value of the excitation current in phase B gradually increases such that the amount of change in the excitation current per unit time is smaller than or equal to the first predetermined value. By the end of the hold period after the predetermined time has elapsed, the excitation current in phase B reaches zero. When the hold period ends, one-phase excitation operation starts and the excitation current flows in phase A first with the same polarity as at the end of the hold period.