• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1476-1481
• /
• 2003

Kinematic calibration enhances absolute accuracy by compensating for the fabrication tolerances and installation errors. Effectiveness of calibration procedures depends greatly on the measurements performed. This paper investigates identifiable parameters and optimum postures for four different calibration procedures - measuring postures completely with inverse kinematic residuals, measuring postures completely with forward kinematics residuals, measuring only the three position components, and restraining the mobility of the end-effector using a constraint link. The study is performed for a six degree-of-freedom fully parallel HexaSlide type parallel manipulator, HSM. Results verify that all parameters are identifiable with complete posture measurements. For the case of position measurements, one and for the case of constraint link, three parameters were found non-identifiable. Selecting postures for measurement is also an important issue for efficient calibration procedure. Typically, the condition number of the identification Jacobian is minimized to find optimum postures. Optimal postures showed the same trend of orienting themselves on the boundaries of the search space.

• Journal of Biosystems Engineering
• /
• v.30 no.3 s.110
• /
• pp.179-184
• /
• 2005

The purpose of this study was the development of teat-cup attachment module for robot milking system. The teat-cups attachment module was controlled on the two dimensional space independently, Each teat cup of an end effector was independently controlled via two axis control based on the position information data obtained from the image processing system. This system was developed install of all 4 teat cups at the same time after adjusting positions of each teat sequentially. The individual motion system was operated using two servo motors for the high speed of teat position adjustment. The errors fur the individual motion system of teat cups were maximum 1.0mm, minimum 0.0mm, and average 0.6mm. The operating time for adjusting the teat cups position required about 1.0 second. It is envisaged that teat cups attachment module can be applicate to milking robot being developed in consideration of the experiment results for the teat cups operation accuracy and the actuation speed of servo motors.

• Journal of the Korean Society for Precision Engineering
• /
• v.34 no.2
• /
• pp.115-123
• /
• 2017

This paper presents the design and the control performance of a novel dynamic compliant-arm support with parallel elastic actuators that was developed to assist with the daily living activities of those whose arms are compromised by muscular disease or the aging process. The parallel elastic-arm support consists of a compliant mechanism with combined passive and active components for human interaction and to reach the user's desired positions. The achievement of these tasks requires impedance control, which can change the virtual stiffness, damping coefficients, and equilibrium points of the system; however, the desired-position tracking by the impedance control is limited when the end-effector weight varies according to the equipping of diverse objects. A prompt algorithm regarding weight calibration and friction compensation is adopted to overcome this problem. A result comparison shows that, by accurately assessing the desired workspace, the proposed algorithm is more effective for the accomplishment of the desired activities.

• Journal of the Korean Society of Physical Medicine
• /
• v.15 no.4
• /
• pp.101-109
• /
• 2020

PURPOSE: This study investigates the therapeutic effect of a prototype of a hand rehabilitation device based on magnetic forces. METHODS: Using an electromagnet and permanent magnets, we developed an end effector type device that induces various movements of the finger in accordance with the magnetic field direction. A total of 26 subacute stroke patients were enrolled and assigned to two groups in this randomized controlled trial. The intervention group received 30 minutes hand rehabilitation therapy per day for 4 weeks, using the device developed by us. Conventional physical therapies were conducted equally twice a day, 30 minutes per session, during the same period in both groups. RESULTS: After 4 weeks, rate of the Wolf Motor Function Test as a primary outcome measure showed significant improvement in the intervention group as compared to control group(p = .036). Scores of the Manual Function Test and Fugl-Meyer Assessment of upper limb were also significantly increased in the intervention group as compared to control group(p = .038 and p = .042, respectively). Moreover, the Korean version of Modified Barthel Index tended to improve after subjecting to physical therapy in both groups. CONCLUSION: Our results indicate that the novel hand rehabilitation device developed using a magnetic force, improves the hand motor functions and activities of daily life in subacute stroke patients.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.5
• /
• pp.599-605
• /
• 2011

A 3-D rehabilitation robot system is developed. The robot system is for the rehabilitation of upper extremities, especially the shoulder and elbow joints, and has 3-D workspace for occupational therapy to recover physical functions in activities of daily living(ADL). The rehabilitation robot system has 1 DOF in horizontal rotational motion and 2 DOF in vertical rotational motion, where all actuators are set on the ground. Parallelogram linkage mechanisms lower the equivalent inertia of the control elements as well as control forces. Also the mechanisms have high mechanical rigidity for the end effector and the handle. In this paper, a hybrid position/force controller is used for controlling positions and forces simultaneously The controller is tuned according to the robot posture. The active motion modes for rehabilitation program consist of active-resisted motion mode and active-free motion mode. The results of the experiments show that the proposed motion modes provide the intended forces effectively.

• The Journal of Korea Robotics Society
• /
• v.11 no.4
• /
• pp.248-255
• /
• 2016

Machining error makes the uncertainty of dimensional accuracy of the kinematic structure of a parallel robot system, which makes the uncertainty of kinematic accuracy of the end-effector of the parallel robot system. In this paper, the tendency of trajectory tracking error caused by the tolerance of design parameters of the parallel robot is analyzed. For this purpose, all the position errors are analyzed as the manipulator is moved on the target trajectory. X, Y, Z components of the trajectory errors are analyzed respectively, as well as resultant errors, which give the designer of the manipulator the intuitive and deep understanding on the effects of each design parameter to the trajectory tracking errors caused by the uncertainty of dimensional accuracy. The research results shows which design parameters are critically sensitive to the trajectory tracking error and the tendency of the trajectory tracking error caused by them.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.8
• /
• pp.4769-4775
• /
• 2014

This paper discusses the dynamics stress of each boom, which occurs as a result of the conflicts on a multi-joint boom at the end effector and structure. In this process, CATIA was applied to create 3D modeling, ADAMS and ANSYS were then performed using mesh analysis by obtaining the stress data to create a MNF(Modal Neutral File) of multi-joint boom. Two types of MNF models were analyzed using ADAMS FFT(Fast Fourier Transform) performing to check the validity of each model. In this process, the models were verified by ADAMS, which performs the dynamic characteristics of conflict. The ADAMS Durability was used to analyze the maximum stress between the multi-joint boom and structure.

• Special Issue of the Society of Naval Architects of Korea
• /
• 2005.06a
• /
• pp.171-176
• /
• 2005

This paper presents a novel Intelligent-Welding-Carriage (IWC) for automation of curved block in shipbuilding. The curved block is usually used in both front and back side of the ship. In curved block root gap is big, 1-7 (mm) and inclination, 0-30 (deg). Since available conventional carriage type is limited to use below root gap of 3 (mm), only manual welding is employed in curved block. To adopt an IWC in curved block, it requires control of the welding conditions, i.e., voltage. current, weaving speed, dwell time and travel speed, with respect to root gap and inclination to achieve good welding qualify. In this paper, an IWC is developed for automization of welding operation to accommodate gap and inclination. Kinematics model and dynamics using Lagrangian formulation of the manipulator is introduced. IWC utilizes a database to perform accurate welding. The database is programmed based on numerous experimental test results with respect to gap, inclination, material, travel speed, weaving condition, voltage, and current. Finally, experimental result using PID control is addressed for verifying the trajectory tracking accuracy of end-effector.

• Journal of Institute of Control, Robotics and Systems
• /
• v.6 no.9
• /
• pp.796-802
• /
• 2000

A master-slave system for teleoperation is usually used to control the robor's motion on remote place such as abyss, outer space etc.. When the slave robot is a humanoid one, it can make a better performance if the configuration of the master arm is similar to that of the slave arm and of the human. The master arm proposed in this paper has a type to be put on the human arm, that is, the exoskeleton type, and has a combination of serial joint and parallel mechanism imitating the human's arm structure of muscles and bones, so called hybrid mechanism so that it can follow arm's movement effectively. But it is easy to solve the forward kinematis of the parallel structure because relating equations are implicit functions. In order to solve that, the virtual joint angle corresponding to human arm's joint is introduced and a sequential computation step is employed in calculating virtual joint angles and the posture of the end effector. Also validity is checked up through computational simulation.

• Proceedings of the KIEE Conference
• /
• 1998.07g
• /
• pp.2360-2362
• /
• 1998

This paper presents a new collison-free trajectory problem for SCARA robot manipulator. we use artificial potential field for collison detection and avoidance. The potential function is typically defined as the sum of attractive potential pulling the robot toward the goal configuration and a repulsive potential pushing the robot away from the obstacles. In here, end-effector of manipulator is represented as a particle in configuration space and moving obstacles is simply represented, too. we consider not fixed obstacle but moving obstacle in random. So, we propose new distance function of artificial potential field with moving obstacle for SCARA robot. At every sampling time, the artificial potential field is update and the force driving manipulator is derived from the gradient vector of artificial potential field. To real-time path planning, we apply very simple modeling to obstacle. Some simulation results show the effectiveness of the proposed approach.