The system design and evaluation of a microprocessor controlled dispenser using a radar ground-speed sensor

This experimental research focused on the design of a new approach to control seed dispensers and to analyze the performance characteristics of a Doppler radar ground speed sensor for a microprocessor control dispenser. The research focused on comparing the effectiveness of using a radar unit with a fifth-wheel encoder for measuring ground speed when both were connected to a microprocessor controlled seed dispenser. The system designed for this study consisted of hardware and a computer program in 6502 assembly language. The hardware for this study consisted of a monitor device, microprocessor control unit, stepper motor, fifth-wheel encoder, Doppler radar and the device for the planting of seeds. the software was designed by the researcher during an internship at Rawson Control Systems Corporation. Laboratory tests and field tests were used in the study to test the Doppler radar and microprocessor control unit. Laboratory tests were conducted to determine the accuracy of the microprocessor based speedometer, seed spacing control and the output waveforms from the Doppler radar and the fifth-wheel encoder under controlled conditions. The laboratory provided an environment for controlling the variables of this research. Field tests were conducted to test the accuracy and variability of the seed spacing control under actual conditions. The resultanat data were analyzed using the t test, F test and one-way ANOVA. The most important findings were: 1. There was a significant difference between the mean indicated ground speeds of the Doppler radar and the fifth-wheel encoder controlled dispensing devices (calculated by the microcomputer in M. P. H.) when an input signal was varied from 1 Hz to 574 Hz to the control box. The Doppler radar was more sensitive to frequency changes than the fifth-wheel encoder. 2. Under the laboratory tests, without considering the slippage of the wheel, there was no significant difference between using the fifth-wheel encoder and the Doppler radar as sensors in dispensing seed at a uniform spacing. 3. In the field tests, a significant difference was found between using the Doppler radar sensor and a fifth-wheel encoder with regard to dispensed seeds at a uniform spacing, due to possible wheel slippage. The Doppler radar controlled unit dispensed seeds at a more uniform spacing than the fifth-wheel encoder control unit. 4. There was a significant difference between using the the Doppler radar sensor and a fifth-wheel encoder with regard to variability of output sigals from the sensors. The Doppler radar provided a less variable output signal than the fifth-wheel encoder. 5. During the field test, the researcher observed that one problem of using the Doppler radar unit was the slight vibration of the Doppler radar caused by the engine of the tractor. This caused some erroneous input signals to the microprocessor control unit because the monitor displayed a fractional part of a ground speed (MPH) while the tractor was stationary. The results obtained from the data analyses show that using the Doppler radar unit as a sensor in the field tests will provide a more uniform spacing control. In general, the Doppler radar controlled unit was considered to be more accurate than the fifth-wheel encoder control unit