Smooth Human-Robot Shared Control for Autonomous Orchard Monitoring with UGVs (I)

Abstract

Precision agriculture offers the opportunity to auto- mate routine or difficult tasks in orchards and vineyards, such as spraying or inspection, with Unmanned Ground Vehicles (UGV). In this context, human operators should be kept in the closed-loop control of the robot for safety and reliability. This work is motivated by the challenges of deploying effectively human-robot shared control in the field. First, an asymptotically stable controller must keep the robot on the desired trajectory between rows of trees, whose distance is on the order of the robot’s width. Second, the robot must efficiently avoid static and moving obstacles (e.g. a rock or a human) in its path. Third, the control inputs must not exceed the actuator limits, which can degrade the trajectory tracking performance, cause instability, or damage critical hardware. Finally, in real-life scenarios, user intervention is sometimes required to manage unpredictable situations. To overcome these challenges, we propose and deploy a shared controller that smoothly blends automatic trajectory tracking, collision avoidance, and human commands. At the same time, it guarantees the system is stable and control actions are within the actuator limits at all times. We extensively tested our approach in simulation and field experiments in an apple orchard.