In this paper, a dual-mode twisting actuation mechanism with an active clutch is newly presented for a high performance tendon-driven robot (e.g., robot hand). This mechanism is a kind of mechanical automatic power transmission mechanism which provides fast motion and large contraction force by two geared motors. One of the motors is adopted for main actuation and the other is utilized for active clutch. The active clutch consisting of low-power DC motor and gear set allows easy control of the dual-mode twisting actuation and simplifies relaxation process of twisted strings which was a critical problem by a passive brake in previous research [17]. Kinematics of the proposed mechanism is represented and its simulation is performed to verify the performance numerically. By using BLDC & DC motor with 8 W & 0.3 W power, we developed a prototype of the dual-mode twisting actuation with the weight of 45.7 g and the size of 71 mm × 21.5 × 15 mm. Despite of simple structure, the proposed mechanism shows that operation mode-change can be easily managed and the relaxation time was much more reduced than that of the passive brake version.

In this paper, a novel three-DOF ankle mechanism is introduced. A lower-limb exoskeleton is developed by our research group to strengthen wearer's muscle power in military missions. Owing to the tough operational condition, each module of the exoskeleton should be carefully designed for safety and to reduce the sense of fatigue of the wearer. To this end, it is desirable for the ankle module to be lightweight and compact and to have a remote center of rotation which is closely located to the rotation center of the wearer's ankle. In order to satisfy these design considerations, the proposed ankle mechanism consists of the parallel connection of a spherical five-bar linkage and an RSU (revolute-spherical-universal)- serial chain. The spherical five-bar linkage realizes two-DOF ankle rotations of inversion/eversion and internal/external rotation, and the RSU-serial chain controls the ankle dorsiflexion/plantar flexion. The forward and inverse kinematics are derived, and instantaneous kinematics as well as force relations are analyzed by deriving the screw-based Jacobian and the reciprocal Jacobian. Finally, based on the gait data obtained from a normal subject with 4km/h of walking speed and 45kg of backpack load, the initial version of it is designed as a fully passive-type mechanism with a torsional spring. It is shown from a simulation that 42% reduction of the wearer's ankle peak torque is expected by using the proposed ankle exoskeleton.

In this paper, the anthropomorphic robot hand is newly proposed by adopting dual-mode twisting actuation and EM joint locking mechanism. The proposed robot hand consists of five finger modules. Each finger has four links and three joints, and Joint 2 and 3 are coupled by the four-bar linkage mechanism. The dual-mode twisting actuation allows that the robot finger can move fast (up to 356.7 deg/sec) in Mode I and generate a large grasping force(up to 36.5 N) in Mode II. In addition, the workspace of the robot finger module is enlarged by EM joint locking mechanism depending on the locking states. In order to verify the effectiveness of the mechanisms adopted in the robot hand, we theoretically and numerically analyze the performances of the robot finger module such as bending speed, fingertip force, and workspace. Finally, through the developed robot hand, we perform the grasping test for various objects and the grasping performance is experimentally demonstrated.

In this paper, a pneumatic power generator based on the chemical reaction is newly proposed by using a small piston pump for the injection of the fuel. Based on the understanding of chemical reaction property, the piston pump is designed by crank-slider mechanism. The piston pump allows compact size and light weight of the entire power generation system compared to the conventional approaches using blow-down tank. In order to verify the effectiveness of the proposed power generation system, we theoretically and experimentally analyze the performance of the system. In addition, we realize the power generator and applies it to an underactuated robot finger for the feasibility test.

A dual-mode robot finger is proposed to achieve a high-speed motion and large grasping force with a single motor. The robot finger has two actuator modes, which consist of the speed mode and the force mode. Based on the geometric analysis of each mode, the main design parameters of the proposed robot finger are derived, and their effectiveness is verified by simulations. In addition, using experiments with a prototype of a robot finger, the validity of the proposed approach is demonstrated.

In this paper, a distributed-actuation method has been newly proposed based on a simple sliding-actuation mechanism for a finger-type manipulator design. Based on the spatially distributed force on the proposed sliding-actuation mechanism, it has been shown that the distributed actuation provides additional design freedom to optimize the manipulator performance. To verify the effectiveness of the proposed method, we developed a finger-type manipulator, which consists of four links with three joints, and performed experiments. The experimental results show that the fingertip force of the developed manipulator can be effectively increased and easily managed by the distributed-actuation method.

The authors propose an optimal force distribution method, called weak point force minimization, which minimizes linear, one-norm, or infinite-norm objective functions. A weak point is a generalized one which can be any point in multiple robots as well as a joint and/or an end-effector. To solve the weak point force minimization, the weak point forces are converted to the contact forces of end-effectors so as to reduce the computational burden. Then, the contact forces are obtained by using linear programming. The proposed method is applicable to diverse areas such as a long object, weakly connected assembly parts long links and weak joints in cooperating multiple robots. The method is also applicable to the multilegged vehicle and the multifingered hand.>