Robotic Irrigation Water Management: Estimating Soil Moisture Content by Feel and Appearance

In this paper we propose a robotic system for Irrigation Water Management in a structured robotic greenhouse environment. A commercially available robotic manipulator is equipped with an RGB-D camera and a soil moisture sensor. The two will be used to automate the procedure known as "feel and appearance method", which is a way of monitoring soil moisture to determine when to irrigate and how much water to apply. RGB-D camera is used to estimate the soil surface position in order to plan the soil sampling approach. A compliant force control framework is used to enable the robot to insert the soil moisture sensor in the sensitive plant root zone of the soil, without harming the plant. The adaptive force control framework relying on RGB-D information enables the robot to sample the soil without knowing the exact soil stiffness a priori.