External Wrench Estimation for Multilink Aerial Robot by Center of Mass Estimator Based on Distributed IMU System

External wrench estimation is very helpful for aerial exploration and manipulation tasks. During the exploration, there might be unseen obstacles to cause dangerous collisions. The estimation of the external force and torque is also beneficial in aerial manipulation tasks. In this paper, we present a framework of estimating the external wrench for the aerial multilink robot based on the onboard inertial measurement unit (IMU) sensors, joints state and robot dynamic models. Compared to the conventional multirotor robot, the center of mass (CoM) is always changing when the robot transforms. The sensor could not be attached to CoM to observe the acceleration data. Consequently, we present a novel method by applying a distributed IMU system to estimate the CoM linear and angular accelerations for the external wrench estimation. With the help of the robot model, the position of the contact point could be estimated, which is useful in exploring tasks to safely interact with the physical world. We design the contact-aided navigation strategy and computationally efficient motion primitives library to help our robot react to the unexpected collision. We experimentally validate our framework with a two-dimensional multilink aerial robot to show the results of external wrench estimator and its further applications
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Experiment video: https://youtu.be/R-WDReLnWWI