Department of Mechanical EngineeringIn the 21st century, the frequency of natural disaster has greatly increased. It is difficult for human to directly reach the disaster areas. A tele-operation system has been developed to perform tasks instead of human workers. For efficient control of the tele-operation system, a haptic interface is necessary. There are largely two types of interfaces for haptic feedback to the user: exoskeleton type interfaces and end-effector type interfaces (E-E interface). The exoskeleton type interfaces have several limitations including issues related to the transmission of the reaction force to the user and misalignment. The drawbacks of the researched E-E interface include restricted coverage of the entire range of arm movement of the user and unevenness of the maximum output range. For interface structure design, there are several conditions must be considered. In this thesis, 3 DOF kinematic structure design for a wearable haptic interface is proposed for intuitive control and improvement of task performance of a teleoperated robot. The user???s range of motion required to manipulate a tele-operated robot was assumed, and bent links of the interface were designed to avoid collision with the user. Simulations were conducted to verify that the proposed interface design covered the user???s range of motion. Based on this approach, a structure that satisfies approximately 95% of the range of motion was identified. Then a prototype was fabricated and evaluated while it was moved within the proposed range of motion.
To lower the inertia of the interface actuation mechanism, a cable-driven actuation mechanism (CDAM) was utilized. The adopted CDAM uses series elastic actuator (SEA) and linear spring. The linear spring maintains minimum required pretension of the cable. A typical CDAM uses a sheath for routing a cable. However, the sheath routing method makes a high and non-linear friction between cable and sheath. To avoid this problem, in this research, the cable was routed from actuator to distal joint using a pulley structure without sheath. For the driving method, a proportional-integral-differential (PID) controller was adopted and for tuning the PID gain, a Ziegler???Nichols tuning method was used. In addition, integral anti-windup was used to prevent the error accumulation of the PID controller. To transmit the intended force to the user, a total of three types of residual forces (friction, gravity, and tension) were compensated.
To determine whether the intended force was transmitted to the user, a virtual wall experiment was performed. To confirm the transmitted force, a force/torque sensor (F/T sensor) was attached to the handle of the interface. A peg-in-hole experiment was performed to verify if the efficiency of the tele-operation tasks improved when force feedback was provided to the user. The result revealed a reduction of the work time by approximately 32% and a reduction of impulse by approximately 70%.clos
