An intelligent wheelchair for adaptation to unknown and/or unstructured environment is developed in this paper. In the motion control under open environment, it is necessary for a robot to adapt to interference from other systems and unknown environment. Since both of the human force and the external force from the environment are applied to a robot as a disturbance, it is difficult for a robot to decompose them into each mode. In order to solve the above problem, a novel force sensing method named “Environment Quarrier” is proposed in this paper. Two same types of robots are required and they are controlled in the same position, velocity and acceleration by bilateral control. One robot is in contact motion and the other is unconstrained. The gravity and the friction effects are identified by the disturbance observer. The purity of external force is obtained by subtracting the disturbance torque in the unconstrained robot from the constrained one. The proposed method is applied for a power-assist wheelchair. An operationality of a human and adaptability to the environment are improved. Sensorless force control based on the environment quarrier is one of the fundamental techniques for evolution of human-cooperative robots. The experimental results show viability of the proposed method.
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