DEVELOPMENT OF ELECTRONIC CONTROL UNIT FOR THE ELECTRIC ROBOT VEHICLE IN AN ORCHARD APPLICATION

摘要

The objective of the research was to develop a hardware called electronic control unit (ECU) which is the most important for the development of electric utility robot vehicle. The goal of developing an electronic robot vehicle is to use in an orchard application. The research used Gator Electric Utility Vehicle as a platform manufactured by Deere and Company. The vehicle electric motor is powered by 48-VDC (Volt direct-current) with 8 batteries (6-Volt each battery). The ECU will be used as a vehicle controller to control different functions of the electronic robot vehicle. The controller can control steering, vehicle movement (forward, backward, and neutral), vehicle speed, and emergency stop (manual and remote control switch). In order to develop a controller for any robot vehicle, an appropriate consideration of controller specifications is necessary. The vehicle controller used PIC18F458 as its microchip device which has a program memory of 32 kbytes, data memory of 1536 bytes in SRAM (static random access memory) and 256 bytes in EEPROM (electrically erasable programmable read-only memory) with 33 pins of I/O and 8 channels of A/D in 10 bits.To control the vehicle movement (forward, backward, and neutral) and emergency stop, relays (5-Volt) were included to the vehicle ECU to command the vehilce by switching on and off the vehicle electric motor. To control the vehicle steering system and speed, a CAN (control-area-network) controller interface was included in the vehicle ECU to send and receive command data from the vehicle computer. And to obtain a feedback signal from the sensors attached to the vehilce, A/D (analog to digital) converter was included to the vehicle ECU. The vehilce controller was tested and evaluated by running the vehilce autonomously and sends commands from the vehilce computer to the controller. The vehilce ECU could control accurately the vehicle steering, movement, speed and emergency stop.