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ARS Home » Research » Publications at this Location » Publication #93886
Title: AUTOMATIC GUIDANCE OF AGRICULTURAL VEHICLES AT HIGH FIELD SPEEDS

Author
item STOMBAUGH, TIMOTHY - OHIO STATE UNIV
item BENSON, ERIC - UNIV OF ILLINOIS
item HUMMEL, JOHN

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: 8/18/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: The trend in agricultural field production is toward bigger and faster machines, allowing operators to finish field operations faster, ultimately covering more field area. Typical field operations can be very monotonous and repetitive, while a higher skill level is required to operate the larger equipment at higher speeds. Automated guidance systems attempt to relieve the operator from many of the equipment guidance tasks, which could reduce the monotony and potentially, improve the placement of agricultural inputs. More precise guidance can improve swath placement, reducing overlap that can lead to adverse environmental impact. This study implemented an automatic guidance system on an agricultural tractor, and we studied the dynamics of the system at travel speeds up to 15 mph. A classical model-based guidance controller provided adequate performance, and the Global Positioning system should be able to provide adequate performance under similar conditions. These results will be useful to scientists involved in conducting similar research, and in improving precision and efficiency in the operation of agricultural equipment.

Technical Abstract: An automatic steering controller was installed on an agricultural vehicle. The primary posture sensor was a kinematic differential GPS. Open loop and closed loop frequency response tests were conducted to evaluate the steering controller dynamics. A double integrator transfer function adequately related vehicle lateral deviation to steering angle within the frequency range of 0.04 Hz to 0.5 Hz. Forward placement of the posture sensor was critical to reducing the phase lag, allowing the use of a simplified guidance controller design. Dead band characteristics of the steering control valve were shown to be critical to guidance system performance. The relatively slow update rate (5 Hz) of the GPS sensor resulted in natural filtering, allowing the use of a relatively unorthodox second-order derivative guidance controller.