How to completely eliminate the outer diameter measurement error caused by the jitter error?
In modern industrial production, wire and bar processing, such as cable , wire, steel wire, bare copper wire, steel rolling, fiber, rubber, small drill bit, filament production and processing are often encountered. These wires and bars are often processed on automated production lines. The processing speed is fast and the production efficiency is high. The improvement of the processing level is often closely related to the continuous improvement of measurement technology. It can be said that the product quality is largely It is determined by the accuracy of the monitoring instrument . With traditional contact measurement, the measurement accuracy is low due to the contact force, and dynamic measurement cannot be realized, and online measurement cannot be realized.
The development of modern industry requires high-precision, non-contact on-line rapid measurement of wire diameter, and requires feedback control signals to control production to automate the production process. For example, in the production of micro-drills, the diameter of micro-drills It is an important indicator that must be detected in time. It directly affects the quality of the product. Because of its high production efficiency and fast processing speed, it is necessary to quickly and accurately detect the diameter of the micro drill bit and give alarm signals and control signals. The diameter measurement proposes the following requirements:
1, high precision
2, high speed
3, non-contact
4, real-time feedback control
Obviously, the traditional method of diameter measurement is far from meeting the requirements of modern industrial production.
The CCD image sensor has the characteristics of high sensitivity, compact structure, accurate pixel position, self-scanning, etc. Therefore, many instruments that measure the outer diameter by optical methods use the CCD device as a photoelectric receiver. There are many methods for measuring the diameter, and each has its own strength. Among them, the projection imaging method using CCD as the photoelectric receiver is a relatively mature method for detecting cylindrical parts. The CCD photoelectric caliper is the video signal of the CCD device. After the binarization process is performed by the circuit, it is sent to the computer, and then the width of the signal is binarized by the standard clock pulse. According to the relationship between each pulse and the CCD pixel, the pulse number is multiplied by the pulse equivalent to obtain the measured value. The size of the size.
In order to accurately measure the diameter of the workpiece, the width signal of the workpiece must be accurately extracted. Therefore, the key problem of the caliper is to obtain the shadow signal of the workpiece, which first requires the workpiece to form a clear optical image on the photoelectric sensor through the optical system. The photoelectric sensor converts the optical signal into an electrical signal corresponding to the shadow of the workpiece without distortion, and obtains an accurate workpiece width signal through circuit processing.
When the caliper is used to measure the workpiece, the position of the workpiece will change slightly due to the dynamic measurement. When the axial position of the workpiece along the optical axis direction and the vertical position perpendicular to the optical axis direction change, it will cause certain The measurement error, therefore, we have taken some measures to reduce or even eliminate the jitter error.
After many experiments, we found that there are two main reasons for the jitter error: First, the imaging of the CCD chip has a ghost phenomenon when the object is shaken, resulting in a decrease in the signal voltage difference and an increase in the width of the output of the CCD chip; Acquisition and communication transmissions are not synchronized, and signals at different times combine to cause data confusion.
After finding the reason, the blue Peng measurement and control technicians worked hard for half a year, and adopted the imported LED light source with brightness above 50000mcd and introduced electronic shutter technology to shorten the exposure time of the probe to 100 microseconds. Eliminates the ghost phenomenon when the measured object shakes. At the same time, multiple synchronization technologies such as light source-signal acquisition unit pulse synchronization, multi-channel acquisition synchronization, signal acquisition-communication transmission synchronization are adopted in the circuit system. It is the first in the industry to solve the problem of jitter error and completely eliminate the jitter error.
The photoelectric caliper has been applied to various wire diameter size detection applications, and it is a high-precision online automatic inspection. It can also control the wire diameter size through the PID adjustment system. For the modernization of the commonly used but practical outer diameter caliper.
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