Experimental Evaluation of Aerial Attitude Control Unit with Reaction Wheels for Hopping Robots

Abstract

This paper proposes an aerial attitude control system of a practical hopping robot in consideration of acceleration disturbance in taking-off and landing. The proposed system uses reaction wheels to control the attitude, and as a first step of development, a one-degree-of-freedom attitude control unit with no hopping mechanism to stabilize the pitch angle has been prototyped for experimental evaluation. In designing the attitude controller, according to the experimental results that quantitatively evaluate the impact of the acceleration disturbance on attitude estimation by using complementary filters, the filter bandwidth is set to be 0.5 Hz. Since the acceleration of gravity used for static attitude angle calculation cannot be observed in free fall, a dynamic attitude angle obtained from gyro sensor information is temporarily fed back for the flight duration of about 0.5 seconds. An experiment, where the robot is horizontally catapulted in the air upward in the direction of 30 degrees, has been conducted, and the results showed that the proposed attitude controller can keep the robot orientation almost all horizontal during the flight. The reaction wheels can be used as tires when the robot runs on the grounds. Thus, another experiment, where the robot runs using reaction wheels and then falls down from the edge of a table, has been conducted. The experimental results showed that by appropriately switching modes from the running velocity control to the aerial attitude control, the robot falls horizontally from the running condition. The future work will be to develop a hopping mechanism and to integrate it to the attitude control unit to realize a practical hopping robot.