Aim\ To control travelling crane automatically going to and fro precisely between two fixed positions for loading and unloading goods. Methods\ Using infrared photoelectric couple to detect a shade block to obtain the positioning signal. To advance the performance of the detector
with singlechip processor as controller and using software filter technology. Results\ Through practical application
the positioning error of the device is less than 2 cm. The device has a good antinoise ability. Conclusion\ Using noncontact photoelectric sensor