Equilibrium Control of Robot Arm Tip Mounted on a Transfer Coaxial Two-Wheel Robot

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Toshiharu Yasui
Minoru Sasaki
Kojiro Matsushita
Joseph Muguro
Waweru Njeri
Titus Mulembo


Coaxial Two-wheel Robot, Equilibrium control, LQ, LQI Control


Japan has continued to experience population decline which adversely affect working-age group (15-64 years). As a remedy to this social issue, advancements in robotics and human-machine cooperation is proposed to make up for the declining labor force. To this end, design of robots which can work in constrained (indoor) workspace is desirable. A coaxial two-wheeled robot with an appended robot arm aimed at transporting objects is proposed in this paper. The robot is designed with center of gravity below the axle to make it statically stable at rest. It is combined with a robot arm with two links, two degrees of freedom. The goal is to maintain equilibrium of the arm tip during motion with the robot-arm is inclined at 0-, 3-, and 120-degree. In this study, simulations to combine a stable coaxial two-wheel robot with the robot arm is performed to confirm the effectiveness of the designed LQ, and LQI controller. From the results, all the controllers are able to maintain the robot-arm tip at 0-degrees. For 120-degrees, LQI performs better than LQ controller in stabilizing the rotation speed of the wheels by 1.7 seconds. In the future, the proposed controller model will be incorporated in the actual robot to confirm the performance for object transportation.


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