Navigation of autonomous tractor for orchards and plantations using a laser range finder: Automatic control of trailer position with tractor
The autonomous control of a tractor trailer system in orchards and plantations has frequently been observed for the transportation, loading and unloading of products between plants and trees. The objective of this research was to develop a control algorithm for a single sensor tractor trailer navigation system for navigating within a row plantation and travelling between plots. A control scheme for stopping the tractor trailer for various in field tasks, such as product loading/unloading using a laser range finder (LRF) is presented. The LRF was used to navigate a full size autonomous agricultural tractor equipped with a two wheeled trailer. For ease of operation in narrow rows, a sliding hitch bar (SHB) was developed to control the trailer by adjusting the position of the hitch point between the tractor and trailer. Compared to the tractor trailer system driven by human, the control system could navigate the tractor trailer with the RMS differences of 0.275 m (SD: 0.009 m) 0.373 m (SD: 0.030 m) and 0.518 m (SD: 0.022 m) for wide curve tight curve and U turn experimental paths, respectively. The SHB unit also supported the navigation system with wider turn for the trailer than conventional single hitch point about 0.383 m (7.66% of the 5 m path width, SD: 0.028 m) 0.762 m (15.23% of 5 m path width, SD: 0.010 m) and 1.094 m (21.88% of 5 m path width, SD: 0.037 m) for wide curve tight curve and U turn experimental paths, respectively. The control system also stopped the tractor trailer at the specified landmarks. The results show that the navigation of the tractor trailer was demonstrated with satisfactory accuracy and that the trailer position was controlled by the SHB with a wider turn in the experimental paths. Therefore, this laser based landmark navigation system, and the SHB unit, can be adopted for different applications of autonomous tractor trailer systems with controlled trailer positioning.