Biological Systems Engineering, Department of


First Advisor

Dr. Santosh Pitla

Date of this Version

Winter 11-2016

Document Type



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agricultural and Biological Systems Engineering, Under the Supervision of Professor Santosh Pitla. Lincoln, Nebraska: November, 2016

Copyright (c) 2016 Jared Patrick Werner


Automation technology in agriculture is growing, making agricultural robotics viable. Innovative field usable multi-purpose robotic platforms are needed for the successful progression of agricultural robotics. Furthermore, the field of agricultural robotics would benefit from a robotic platform design allowing for variable height, thus accommodating navigation throughout various crop growth stages. A variable height machine, Flex-Ro was developed to accommodate this feature. Multiple sub-assemblies were designed and implemented for Flex-Ro. An electronic control unit (ECU) enabled engine was used to power Flex-Ro. An embedded application program was developed to control engine speed using proprietary Controller Area Network (CAN) messages in conjunction with J1939 standard messages. It was observed that the maximum standard deviation from the requested set speed was 8.423 rpm. A hydrostatic transmission system was designed and implemented on Flex-Ro. An embedded application program was developed for controlling the pumps and motors of the hydrostatic transmission utilizing proprietary CAN messages. Additionally, the embedded controller operated a Control Cut Off (CCO) that regulated flow to the spring applied motor brakes and the Electronic Displacement Control (EDC) which controls pump flow. Based on the motor speed data collected, it was observed that an increase in deviation occurred as the operational speed increased with a minimum standard deviation of 6.98 rpm at 50 RPM and a maximum standard deviation of 36.13 rpm at 156 RPM. The measured data should be used in developing further higher level control programs. A vertically adjustable frame was developed to allow Flex-Ro to enter crops at various growth stages. A steering system was developed and programmed to allow for steering control through the CAN bus again using proprietary CAN messages. Lastly, a remote control program was developed to allow messages to be created and wirelessly transmitted to Flex-Ro’s CAN bus for teleoperation. Sub-assemblies of Flex-Ro will be further developed for fully autonomous navigation, and performing various field operations.

Advisor: Santosh Pitla