Research on human-guided active following mode with 3D spatial relative positioning for vehicles in hilly and mountainous orchards

Hilly mountainous orchards are an important agricultural scenario, which have narrow spaces that are only suitable for low-speed operations with small-size agricultural machinery. Manned agricultural machinery not only reduces the vehicle's carrying capacity but also affects the driver's safety due to the uneven terrain. To address these issues, a human-guided active following mode with 3D spatial relative positioning method was proposed in this study where human motion can be sensed by the vehicle that can actively move towards them. The complex 3D spatial relationship with relative distance, relative angle and vehicle attitude between the guiding-person and following-vehicle was calculated in the relative coordinate system by ultra-wideband positioning techniques. An active following controller is designed, which is simulated and field experimented on a six-wheel off-road chassis. The results indicate that larger desired distances lead to larger trajectory errors. In the space keeping field experiment, the root mean square error of relative distance and relative angle was 0.045 m and 2.591 degrees when the optimal desired distance was set to 1 m and the optimal desired angle was set to 0 degrees. The following-vehicle and guiding-person maintain synchronized motion, wherein the following-vehicle can accomplish acceleration, deceleration and braking based on the motion state of the guiding-person. This research has the potential to free farmers from operating vehicles and concentrate on other agricultural tasks.