Hoyul Lee

Stackable 4-BAR Manipulators for Single Port Access Surgery

This paper proposes a new robotic manipulator using stack able 4-BAR mechanisms for single port access (SPA) surgery where the operation is performed by inserting multiple manipulators through one small body cavity. The proposed manipulator has the advantage that all actuators are able to be separated from the driving mechanism. In other words, it is possible to separate the electrical actuators from the mechanical linkage/joint components in the manipulators. Thus, the robotic manipulators, including the working joints and linkages, can be fabricated using selective materials that are light-weight and slim so that the multiple manipulators can be inserted through one small cavity. Moreover, since the suggested manipulator makes use of an individual 4-BAR mechanism to drive each independent joint, it is structurally strong. Using the kinematic model, we conduct a kinematic synthesis (design methodology) because the operating range of each working joint is usually limited by the design parameters of 4-BAR. Finally, we show that the stackable 4-BAR manipulator is a good alternative for SPA surgery through numerical simulations and implementation of the proposed manipulator.

A New Actuator System Using Dual-Motors and a Planetary Gear

This paper proposes a new actuator system for mobile robot applications. Since the actuator system to be proposed consists of dual-motors and a planetary gear, it is referred to as the dual-motor system using a planetary gear (DuPG) in this paper. The suggested DuPG improves the speed-torque performance by combining two motors with one planetary gear, in which one motor is for high speed and the other for high torque. In other words, it is able to realize a high speed at low torque, and high torque at low speed, as an automatic transmission operates in an automobile. The proposed actuator system is able to extend the speed/torque operation region. Finally, several experimental results are suggested to show a few advantages such as the extended speed/torque operation region and the enhanced energy efficiency.

A realistic joint limit algorithm for kinematically redundant manipulators

There have been many researches on the joint limit algorithm exploiting kinematic redundancy in kinematically redundant manipulators. Existing joint limit algorithms tend to minimize the distance between the current joint angle and the middle angle of the given joint range. However, strictly speaking, these algorithms control the joint angle to come close to the middle angle, but sometimes this algorithm does not fully utilize the entire motion range of joints and consumes relatively large energy. Therefore, this paper proposes a new joint limit algorithm that not only prevents the joint limit violation, but also utilizes the wide motion range of joints. Two exemplary manipulator models having kinematic redundancy are employed to show the feasibility of the proposed algorithm.

Stackable manipulator for mobile manipulation robot

This paper proposes a new manipulator concept applied to a mobile robot manipulation system for reducing robot size and weight or increasing its work capacities such as a payload, operating radius, and operating speed. In detail, we propose a new robotic manipulator that uses stackable 4-BAR mechanisms for mobile manipulation robot. The proposed mechanism provides a clear advantage in which all the actuators can be separated from the working joints. Thus, the mechanism is able to select the Center of Mass (CoM) and the Zero-Moment Point (ZMP) in arbitrary points without any support from ZMP controller or ZMP compensation method. To confirm efficiency of the new manipulator, this paper addresses a design method using the simplified beam theory, based on the well-known Finite Element Method (FEM) for structural stiffness analysis of linkages. The reason behind this is that the CoM and ZMP are dependent on the weight of the motors and the linkages. Ultimately, we show the efficiency of the proposed stackable manipulator through simulations and experiments.

Stackable 4-BAR mechanisms and their robotic applications

This paper proposes a new planar robotic manipulator using stackable 4-BAR mechanisms for various applications such as a manipulator of surgical robot and a manipulator of field robot. The proposed manipulator has an advantage that all driving actuators can be separated from the mechanical mechanism, in other words, we are able to separate all electrical components such as electrical actuators and wirings from mechanical linkage/joint components in the robotic manipulator. Thus the robotic manipulator including working joints and linkages can be manufactured using one or a few material(s) with light-weight and slim-size. Also, the proposed mechanism does not require the actuators to attach directly to driving joints and it can be independently controlled. In addition, we suggest the kinematic analysis of the proposed manipulator composed of input mechanisms, multiple 4-BAR mechanisms and output mechanisms. Finally, a variety of simulation results and a prototype are suggested to show the effectiveness of the stackable 4-BAR mechanisms.

New actuator system using movable pulley for bio-mimetic system and wearable robot applications

This paper proposes a new actuator system using a movable pulley for a bio-mimetic system and wearable robot applications, which is able to store energy in advance and to release it in such a way to satisfy desired speed and force control performances, simultaneously. Since new actuator system consists of two motors (dual-motors), a movable pulley, and series spring connection for high speed/force operation characteristics, it is referred to as Dual-motor system using a Movable Pulley with a Series Elastic Actuator (DuMP-SEA) in this paper. Also, the proposed actuator system not only combines individual speed/force operation region of each motor, but also extends the combined operation region by using the energy stored in advance. Finally, we suggest the extended operation region (high speed and high force characteristics) obtained by using the DuMP-SEA through simulations and experiments.

Planar Manipulator using Stackable 4-BAR Mechanisms

This paper proposes a new planar robotic manipulator using stackable 4-BAR mechanisms for various applications. The proposed manipulator has an advantage that we can separate the driving actuators from a robotic manipulator. By separating actuators from the manipulator, we are able to separate the electrical component such as electrical wiring from the mechanical linkage/joint components in the robotic manipulator. Also, we suggest the kinematic analysis of the proposed manipulator which is composed of input mechanisms, multiple 4-BAR mechanisms and output mechanisms. Finally, we suggest numerical simulations to show the effectiveness of the proposed manipulator.