Sewing Machine Dynamic Sampling for Stitch Pitch Control
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Solution Overview
Problem
Existing sewing machines face challenges in maintaining accurate detection of workpiece movement, particularly at varying speeds, due to noise interference and reduced detection accuracy when the workpiece is fed slowly, as the control device accesses optical sensors at a constant sampling period.
Innovation Solution
The sewing machine adjusts the sampling period based on the workpiece's movement speed, lengthening the period for slower movements to increase signal reception and improve accuracy, and shortening it for faster movements to maintain followability and reduce noise influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the control device accesses the optical sensor at a constant sampling period, then the control structure is simple and response time is predictable, but the detection accuracy deteriorates when the workpiece is fed slowly due to reduced pulse count and increased noise influence
Solution Approach 1:
The patent applies dynamics by making the sampling period variable rather than fixed. The control device dynamically adjusts the sampling period based on the detected workpiece movement speed - using longer periods for slow movement and shorter periods for fast movement. This dynamic adaptation resolves the contradiction by optimizing detection accuracy for each operating condition without requiring a completely complex adaptive control system.
Solution Approach 2:
The patent changes the temporal parameter (sampling period) of the control system based on operating conditions. By varying the sampling period according to workpiece movement speed, the system improves detection accuracy during slow feeding while maintaining reasonable response during fast feeding, thus resolving the contradiction between measurement precision and device complexity.
2Reliability
If the control device uses a constant sampling period for sensor access, then the control logic is simple, but the noise influence increases when few pulses are received during slow workpiece feeding
Solution Approach 1:
The system dynamically adjusts the sampling period based on detected movement speed. During slow workpiece feeding, the extended sampling period accumulates more pulse signals, improving signal-to-noise ratio and detection reliability. During fast feeding, the shorter period maintains timely response while still capturing sufficient pulses, thus improving reliability across varying speeds and reducing noise impact.
Solution Approach 2:
The control device uses feedback from the optical sensor to detect workpiece movement speed and adjusts the sampling period accordingly. This feedback mechanism allows the system to adapt to varying operating conditions, improving detection reliability by using appropriate sampling periods that minimize noise influence while maintaining accurate speed-dependent control.
3Measurement precision
If the sampling period is lengthened to improve detection accuracy at low speeds, then the noise influence is reduced, but the response time increases and followability deteriorates at high speeds
Solution Approach 1:
The patent implements dynamic sampling period adjustment that adapts to workpiece movement speed. At low speeds, the system uses longer sampling periods to accumulate sufficient pulse signals for accurate detection. At high speeds, it automatically switches to shorter sampling periods to maintain fast response and followability. This dynamic adaptation resolves the contradiction by optimizing the sampling period for each speed regime.
Solution Approach 2:
The system changes the sampling period parameter based on detected movement speed. By adjusting this temporal parameter dynamically, the system achieves high detection accuracy at low speeds while maintaining fast response capability at high speeds, thus resolving the contradiction between measurement precision and response speed.
4Loss of time
If the control device receives a small number of pulses during slow workpiece feeding, then the sampling period can be kept short, but the detection accuracy deteriorates due to increased noise influence
Solution Approach 1:
The control device dynamically extends the sampling period when slow workpiece feeding is detected, allowing more pulses to be accumulated during the extended sampling window. This dynamic adjustment ensures sufficient signal accumulation for accurate detection without unnecessarily extending sampling time during fast feeding, thus resolving the contradiction between sampling time and detection accuracy.
Solution Approach 2:
The system changes the sampling period parameter based on the detected workpiece feeding speed. During slow feeding, the extended sampling period compensates for the reduced pulse rate, ensuring adequate signal accumulation for accurate movement detection. This parameter adaptation resolves the contradiction by optimizing the balance between sampling time and detection accuracy according to operating conditions.
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 enhances detection accuracy at low speeds by increasing signal counts and reduces noise impact, while maintaining high followability and response at higher speeds by adjusting the sampling period dynamically.
Implementation Method 1
a detection portion that detects a movement amount of a workpiece
Data Source
AI summary
A sewing machine including a detection portion that detects a movement amount of a workpiece, a sewing machine motor that serves as a driving source for vertical movement of a needle bar, and a control device that controls the sewing machine motor based on the detection result by the detection portion and performs control to maintain a constant stitch pitch. The control device lengthens a period for obtaining an output of the detection portion when the movement amount of the workpiece per unit time based on the detection result by the detection portion is decreased, and shortens the period for obtaining the output of the detection portion when the movement amount of the workpiece per unit time based on the detection result by the detection portion is increased.