The Application of Distance-Measuring by Ultrasonic Based on CPLD in the Field of Agriculture Robot

In order to further improve the accuracy of the distance measurement of agricultural robots and realize the precise delivery of crop feeds, thereby increasing the yield of crops, this paper proposed a ultrasonic distance measurement system for agricultural robots based on Complex Programmable Logic Device (CPLD). The system mainly included two parts: hardware and software. The hardware part mainly included CPLD control part, ultrasonic sensor and temperature sensor. The software part mainly included the identification and counting of ultrasonic signals, data processing and temperature compensation. The system performed accurate ultrasonic ranging based on the current temperature and ultrasonic echo measurement. In order to improve the degree of humanization of the system, the system used a high-brightness digital tube to display the measured data in real time. The part of hardware had been analyzed and designed, and the same time the part of software had been designed by the language of VHDL and simulated by wave in QUARTUSII platform. Finally the design was downloaded to a CPLD chip named EPM1270T144C5. The system was tested by measuring the distance of block range from 50mm to 5500mm in the temperature of 28°C. After actual system testing, we found that the precision of test could be controlled less than 0.1 mm as a result of temperature compensating and high-speed characteristic of CPLD.