Design Approach For Online Measuring The Distance Of The Gap Between The Contactors Of Electric Relay Switch

Electric relay is a versatile control device for automatic circuit. Embodying the function of circuit adjustment, circuit protection and circuit transformation, it is widely used in the devices of household appliances, industry-control circuit, mechatronics, remote control and telemetry and astronomical projects. The assembly of the two contact points of relay requires high accuracy, the deficiency of which could account for the error of the whole machine. Because of this, during production, detections with high targets would be strictly conducted to the assembly accuracy of the relay contact point. And hereby the distance of the gap between two contact points is an important item included. Currently domestic methods are mainly limited to the usage of microscopic measurements tool to sample and test the relay in each batch, thus evaluating the quality. Such methods not only have the flaw of low efficiency, large intensity of labor and subjective influence, but also fail to do quality inspection to individual product. These problems are all barriers for modernizing the assembly line of the relay production.Based on technology of machine vision measurement and digital image processing, this paper designs an automated visual inspecting system for online measuring contact gap of electric relay. This system, taking CCD, optical lens and dual-channel high-speed image acquisition card as core elements, builds a visual image processing system, blends the functions of controlling, measuring and processing and can be applied to automatic measurement of distance of the gap between the relay contact points. LED red light source is applied as lighting system to keep the light emission of metal contact points from influencing the imaging quality. For improving the accuracy of the detecting system and meeting the request of real-time detection, two CCDs grab images under the dual-line parallel operation mode. In addition, during the process, the pre-stored standard model image, rotationally invariant matching algorithm and pyramid layered technology are together employed to rapidly spot and pinpoint the detecting subjects. Once the matching process succeeds, the system would immediately locate the edge detecting area of relay contact points according to the location relation of packages inside the relay switch. Then in smaller detecting area, with the coarse-to-fine edge detection algorithm, the system can find the edges of two contact points and calculate the gap between two relay contact points. Finally, through data communication network, the system would transport the information and results of the detected products to database of backstage for preservation and regulation.Based on above research, this paper use VC++6.0and Opencv function library to develop software and realize various algorithm mentioned above; and after conducting experiments in lab, the outcome of the study is utilized in the relay production lines of Xiamen Hongfa Electric Power Controls Co.,Ltd. It has been tested online that the time needed to detect individual relay is less than0.1s with an0.01mm minimum accuracy, which can satisfy the online real-time detection.