Dynamics and Aerial Attitude Control for Rapid Emergency Deployment of the Four-Wheel Independent Drive and Steering (4WIDS) Agile Ground Robot AGRO

Contributing USMA Research Unit(s)

Army Cyber Institute, Civil and Mechanical Engineering, Electrical Engineering and Computer Science, Robotics Research Center

Publication Date

Fall 10-25-2020

Publication Title

IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

Document Type

Conference Proceeding


In this work we present a Four-Wheeled Independent Drive and Steering (4WIDS) robot named AGRO and a method of controlling its orientation while airborne using wheel reaction torques. This is the first documented use of independently steerable wheels to both drive on the ground and achieve aerial attitude control when thrown. Inspired by a cat's self-righting reflex, this capability was developed to allow emergency response personnel to rapidly deploy AGRO by throwing it over walls and fences or through windows without the risk of it landing upside down. It also allows AGRO to drive off of obstacles and ensure it lands on all four wheels. We have demonstrated a successful thrown deployment of AGRO.

A novel parametrization and singularity analysis of 4WIDS kinematics reveals independent yaw authority with simultaneous adjustment of the ratio between roll and pitch authority. Simple PD controllers allow for stabilization of roll, pitch, and yaw. These controllers were tested in a simulation using derived dynamic equations of motion, then implemented on the AGRO Mk I prototype. An experiment comparing a controlled and non-controlled fall was conducted in which AGRO was dropped from a height 0.85 m with an initial roll and pitch angle of 16 degrees and -23 degrees respectively. With the controller enabled, AGRO can use the reaction torque from its wheels to stabilize its orientation within 402 milliseconds.

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