Demands for human-robot collaboration in production line has increased and the problem of safety in robot becomes more and more important. This paper presents a manipulator with counterbalancing mechanism to secure safety of a human worker in human-robot collaboration environment by reducing a needed power to drive a manipulator. A counterbalancing torque to cancel out a gravitational torque was generated by a restoring force of spring. Also a control algorithm to minimize the effect of spring on tracking performance was proposed. Experimental results were suggested to verify the performance of the proposed method.

This paper presents a new antagonistic tendon-driven joint (TDJ) which has an advantage of enhanced stiffness characteristics. Detailed mathematical analyses on the stiffness of typical TDJs are worked out to compare the stiffness among them. Prototypes of the proposed TDJ design are introduced in the form of packaged modular structure that merges two TDJs generating a combined roll-pitch motion or similar ones. Numerical examples are given to confirm the superior stiffness of the proposed TDJ design.

Current virtual keyboards are known to be slower and less convenient than physical QWERTY keyboards because they simply imitate the traditional QWERTY keyboards on touchscreens. In order to improve virtual keyboards, we consider two reasonable assumptions based on the observation of skilled typists. First, the keys are already assigned to each finger for typing. Based on this assumption, we suggest restricting each finger to entering pre-allocated keys only. Second, non-touching fingers move in correlation with the touching finger because of the intrinsic structure of human hands. To verify of our assumptions, we conducted two experiments with skilled typists. In the first experiment, we statistically verified the second assumption. We then suggest a novel virtual keyboard using our observations. In the second experiment, we show that our suggested keyboard outperforms existing virtual keyboards.

In this paper, we propose an in-hand motion planning algorithm for 3D objects under rolling contacts. By assuming the in-hand motion is quasi-static, we apply the concept of independent contact region (ICR) to determine stable boundaries of finger contact points during the in-hand motion. A specified level of grasp quality margin representing the ability to bear external load is guaranteed. The overall scheme contains two motion planning phases: one is the motion planning with fingers simultaneously rolling over the object surface, and the other is the planning associated with switching fingers of contact and non-contact. Simulation/experimental results are provided to show the feasibility of the proposed algorithm.

In this paper, a consistent kinematic modeling method for mobile manipulators is proposed. We transform the mobile manipulators into conventional manipulators via appropriate change of kinematic structure. Consequently, analyses of kinematics for mobile manipulators can be conveniently carried out with the transformed manipulators. Cases of differential-drive and car-like types of mobile platforms are formulated, but theoretically not limited to these.

In this paper, we present a practically useful and intuitive grasp quality measure that takes into account the shapes of object geometries and the torque limits of finger actuators. The proposed grasp quality measure is defined by the distance between the convex hulls of the absolute grasp wrench space (a-GWS) and the object wrench space (OWS), where a-GWS and OWS are, respectively, created by the active wrenches from the robot fingers with limited torque bounds and the uniform distribution of unitary normal disturbances on the surface of a polyhedral object. The computational algorithm for the grasp quality measure also yields the information of which spots of the object are fatal under the disturbance, which makes the algorithm practically useful. We demonstrate the validity of the proposed measure through numerical examples.

This paper addresses a new control strategy for synchronizing two or more distributed and interconnected dynamic systems having communication time delays. The proposed strategy that uses the Smith predictor principle and delay information not only achieves synchronization but also preserves the natural local dynamics of each subsystem without being affected by the feedback nature of control. The proposed synchronization scheme is generalized to cases that deal with an arbitrary number of heterogeneous interconnected systems through dynamic scaling of input under a ring-type network configuration. In addition, possibility of applying the proposed scheme to nonlinear systems is discussed. Simulation and experimental tests are conducted to validate theoretical results.

This paper proposes a generalized version of control strategy that enables state synchronization among distributed subsystems without altering the natural dynamics that each separate system is supposed to show. To handle the general case of N-subsystem with heterogeneous dynamics, a method of dynamic scaling and ring type network topology are proposed. The associated stability bound is analyzed. We performed several experiments to show the validity of stability analysis and dynamic scaling

This paper proposes a motion duplication control scheme, which not only synchronizes motions between two distributed separate dynamic systems but also perfectly preserves prescribed dynamics. The proposed scheme sophisticatedly utilizes two-way Smith predictor to meet the simultaneous purposes. Closed loop behavior is mathematically investigated, and stability via natural damping and robustness are analyzed over the system, by examining the characteristic equation with delay components. Ways to compute robust stability margins are presented under the uncertainties in plant dynamics and amount of delay. Numerical simulations are presented to verify the theoretical results proposed in this paper

A straightforward inverse kinematic algorithm for multilink flexible robots is proposed to improve the control performance. The inclusion of a dynamic constraint maximizes the performance of feedback controllers in high-speed applications. To obtain a numerically feasible solution, the singular perturbation approach is employed, which decomposes the inverse kinematics into an averaged part (slow part) and a parasitic part (fast part). The solution of the averaged part is considered the desired inverse kinematics, while the parasitic part is intentionally removed. The parameter expansion is carried out to obtain the solution sequentially. The implicit expansion method, which is a refined version of the expansion method, reduces computing time considerably. The formula in discrete time offers efficiency in computer applications. In addition, a requirement on differentiability of the desired task trajectory is derived.

This paper deals with the sequential inverse kinematics for the high speed tracking of flexible robots. As a continuation of the implicit expansion method in, the explicit version of the sequential inverse kinematics is presented which is easier to be understood conceptually. The accuracy and stability of the two algorithms are compared and proved. Numerical study verifies the validity of the theoretical results.

This paper proposes a PID-type composite controller for controlling flexible arms modeled by the singular perturbation approach, and investigates a tuning method based on the proposed controller structure. For the slow sub-controller, a PD plus disturbance observer is used, which eventually takes on PID form, and for the fast sub-controller, modal feedback PID control is utilized. The effects of design parameters of the controller on the closed loop response are investigated. Through simulation and experiments, the adequacy and performance of the proposed method are verified.

This paper proposes an improved differential inverse kinematics algorithm which works good for high speed motion control. The dynamic constraint as well as the kinematic constraint is utilized for the inverse kinematics. The singular perturbation method helps to reduce inverse kinematics to be solvable. The numerical and experimental results show the performance of the proposed method clearly.

A simple direct parameter update rule is presented to suppress the vibration more quickly by considering the dynamics of the flexible subsystem. Different from most of adaptive control schemes in multilink flexible robots, which are a model independent approach, the proposed adaptive control utilizes model parameters and updates them. Usually, the precise modeling of multi-link flexible robot is hard to obtain and even if we can get it, it is difficult to use in the online control tasks. For these reasons, a simplified model is used to describe the robot dynamics. The modelling errors and other structured uncertainty are considered as parameter perturbation. We verify the effectiveness of the proposed algorithm through experiments.

Focuses on the design of rigid part motion control and the selection of bandwidth of the rigid subsystem. Based on the passivity approach and disturbance observer, we investigate the relationship between macro joint tracking performance and vibration suppression capability using the joint motion bandwidth parameter. For the flexibility isolated system, the independent sub-controllers for the rigid and flexible part are proposed just like the singular perturbation approach. The validity of the proposed method is verified by experiments.