Abstract
Guidance performances of an agricultural robot were evaluated when the robot traveled along cornrows and performed the row to row turning maneuver in cornfield with variable angle of view (AOV) camera arrangement. The arrangement with one low-cost camera has flexible AOV by controlling Servo motors motions as human vision. In this work, a forward far AOV was used to segment clearly and quickly cornrows due to more crop information and strong contrast between cornrows and soil, and a forward near AOV with less crop information was chosen once the number of crops pixels reduced due to the spacing headland. And a lateral near AOV was adopted to guide the robot by acquiring the crop image near the end of cornrows, due to a blind spot area in front of the robot for the near AOV arrangement. Then the headland turning was performed. During headland turning, the robot obtained the cornrows information using a lateral far AOV arrangement. After the headland turning, the robot traveled in the next cornrow with the AOV same to the first far AOV camera arrangement. Guidance information was detected with an image-processing algorithm employing mathematically morphological operations, and fuzzy logic control was applied to guide the robot according to guidance information. Tests showed that the robot traveled successfully and performed the headland turning in corn field with three replications. Test data from GPS were processed and showed stable guidance behavior with a maximum guidance error 22.58 mm and good headland turning operation. The low-cost variable AOV camera arrangement has a promising field application for autonomous agricultural vehicles. Key words: Machine vision, agricultural robot, row guidance, headland turning.
Highlights
Driving along the crop row and turning at the headland are the main maneuvers for autonomous agricultural vehicles
The row guidance performances for each test were evaluated according to the maximum error, average error, RMS
Variable angle of view (AOV) machine vision based guidance systems were applied to guide a robot along cornrows and implement headland turning operation
Summary
Driving along the crop row and turning at the headland (headland turning) are the main maneuvers for autonomous agricultural vehicles. For the former, there are many researches based on all kinds of sensors, visual navigation has been a research hotspot due to its low cost and good navigation performance (Reid et al, 2000; Mousazadeh, 2013). The same method was applied for autonomous agricultural robots (Bakker et al., 2008). –a fixed forward angle of view (AOV) of camera. The camera with a fixed AOV at a specific height that produces only a fixed vision scene cannot obtain the different scenes and more information with flexible vision angles as human vision by looking up, looking straight ahead, looking down and turning
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