• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.27-34
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• 2016

This paper describes the development of a rehabilitation robot that can provide wrist bending exercise to a severe stroke patient staying in a bed ward or at home. The developed rehabilitation robot has a three-axis force sensor which detects three directional force Fx, Fy, and Fz. The sensor measures a bending force (Fz) exerted on the wrist and the signal force (Fx and Fy) which can be used for the safety purpose. The robot was designed for severe stroke patients in bed, and the robot program was developed to perform a wrist bending rehabilitation exercise. In our tests including a nine-day experimental exercise, the developed force sensor-based robot operated effectively and safely.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.1
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• pp.137-145
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• 1992

Considering the singularity of robot, singularity avoidance control of robot is very important. Because it is very difficult structurally to exclude the wrist singularity. Then new control policy is needed to overcome wrist singularity. In this paper, the singularity states of robot wrist was analyzed and control algorithms for 3 and 4 axes robot wrist were proposed. Application results of the proposed control algorithms to the path including singularity showed us their usefulness and validity.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.953-959
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• 2021

In this paper, the numerical inverse kinematics analysis is presented for a collaborative robot with an offset wrist. Robot manipulators with offset wrist are widely used in industrial applications, due to many advantages over those with wrist center and those with three parallel axes such as simple mechanical design, light weight, and so on. There may not exist a closed-form solution for a robot manipulator with offset wrist. A simple numerical method is applied to solve the inverse kinematics with offset wrist. Singularity is analyzed using Jacobian matrix and the numerical inverse kinematics algorithm is implemented on the real-time controller.

• International Journal of Control, Automation, and Systems
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• v.5 no.4
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• pp.419-428
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• 2007

This paper describes the development of a six-axis force/moment sensor with rectangular taper beams for an intelligent robot's wrist and ankle. In order to accurately push and pull an object with an intelligent robot's hand, and in order to safely walk with an intelligent robot's foot, the robot's wrist and ankle should measure three forces Fx, Fy, and Fz, and three moments Mx, My, and Mz simultaneously from the mounted six-axis force/moment sensor to the intelligent robot's wrist and ankle. Unfortunately, the developed six-axis force/moment sensor utilized in other industrial fields is not proper for an intelligent robot's wrist and ankle in the size and the rated output of the six-axis force/moment sensor. In this paper, the structure of a six-axis force/moment sensor with rectangular taper beams was newly modeled for an intelligent robot's wrist and ankle, and the sensing elements were designed by using the derived equations, following which the six-axis force/moment sensor was fabricated by attaching strain-gages on the sensing elements. Moreover, the characteristic test of the developed sensor was carried out by using the six-component force/moment sensor testing machine. The rated outputs from the derived equations agree well with those from the experiments. The interference error of the sensor is less than 2.87%.

• Proceedings of the IEEK Conference
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• summer
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• pp.263-268
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• 2004

The inverse kinematics problem is to find a set of joint variable values that will place the end effector of a robot manipulator into a given pose. Pieper has shown that a sufficient condition for a manipulator to have a closed form solution is that three adjacent joint axes intersects, hence the six axes robot with spherical wrist allows closed form solution. But many industrial robots have a non-spherical wrist to provide a stronger wrist configuration so that they can handle heavy payloads. Also, the use of a non-spherical wrist can result in a cheap and simple wrist arrangement than when all three axes intersect at a common point. In these cases, closed form solutions cannot be found. Therefore numerical technique must be used to solve the inverse kinematics equations. This paper proposes a new algorithm that can be used for finding inverse kinematics solution of the six axes robot with non-spherical wrist. Computer simulations are provided to prove the usefulness of our method.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.138-143
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• 1989

In considering the singularities of robot, singularity avoidance control of robot wrist is very important. Because it is more difficult structurally to exclude the wrist singularity than the arm singularity. Since control policies with Jacobian may bring about mathematical singularities, control policies with Euler parameters that never cause mathematical singularities are necessary. In this research, singular status of robot wrist was analyzed and control algorithms for 3 and 4 axes robot wrist were proposed. Application results of the proposed control algorithms to the path including singularity showed us usefulness and validity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.243-246
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• 2004

The dynamic characteristic of a wrist power transmission examine closely with mass property, to present the model which induce the vibration is ultimately the purpose. A robot wrist power transmission for analysis model got the mass property through the approach to be the experimental. A bearing equivalent stiffness which supports the axis and a gear contact equivalent stiffness are determined by the simplicity analysis model compared the result of the experiment. We calculate the vibration tendency of the robot wrist power transmission by an analysis tool which is called the RecurDyn. We compared it with a signal analysis experiment's which a robot operation happens which is based on the ambient noise.

• Journal of Sensor Science and Technology
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• v.22 no.2
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• pp.118-123
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• 2013

Most serious stroke patients have the paralysis of their wrists, and can't use of their hands freely. But their wrists can be recovered by rehabilitation exercise. Recently, professional rehabilitation therapeutists exercise the wrists of stroke patients in hospital. But the wrists of stroke patients have not rehabilitated, because the therapeutists are much less than stroke patients in number. Therefore, the wrist bending-exercise rehabilitation robot that can measure the bending force of the patients' wrists is developed. In this paper, the three-axis force sensor was designed for the wrist bending-exercise rehabilitation robot. As a test results, the interference error of the three-axis force sensor was less than 0.85%. It is thought that the sensor can be used to measure the wrist bending force of the patient.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.109-115
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• 2019

In arc-welding applying to the present automobile part manufacturing process, a wrist-hollow type arc welding robot can shorten the welding cycle time, because feedability of a welding wire is not affected by a robot posture and thus facilitates high-quality arc welding, based on stable feeding with no entanglement. In this paper, we will propose the optimization of wrist design for a wrist-hollow type 6-Axis articulated robot. Specifically, we will perform the investigation on the optimized design of inner diameter of hollow arms (Axis 4 and Axis 6) and width of the upper arm by using the simulation of robot motion characteristics, using a Genetic Algorithm (i.e., GA). Our simulations are based on $SolidWorks^{(R)}$ for robot modeling, $MATLAB^{(R)}$ for GA optimization, and $RecurDyn^{(R)}$ for analyzing dynamic characteristics of a robot. Especially $RecurDyn^{(R)}$ is incorporated in the GA module of $MATLAB^{(R)}$ for the optimization process. The results of the simulations will be verified by using $RecurDyn^{(R)}$ to show that the driving torque of each axis of the writs-hollow 6-axis robot with the optimized wrist design should be smaller than the rated output torque of each joint servomotor. Our paper will be a guide for improving the wrist-hollow design by optimizing the wrist shape at a detail design stage when the driving torque of each joint for the wrist-hollow 6-axis robot (to being developed) is not matched with the servomotor specifications.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.11
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• pp.1011-1016
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• 2013

Patients have the paralysis of their wrists, and can't use of their wrists freely. But their wrists can be recovered by wrist-bending rehabilitation exercise. Professional rehabilitation therapeutists exercise the wrists of patients in hospital. But the wrists of patients have not exercised enough for the rehabilitation, because the therapeutists are much less than patients in number. Therefore, the wrist rehabilitation robot should be developed, and it have to measure the applied force to the patients' wrists for their safety. In this paper, the four-axis force/moment sensor was designed for the wrist rehabilitation robot. As a test results, the interference error of the four-axis force/moment sensor was less than 0.91%. It is thought that the sensor can be used to measure the applied force to the patients' wrists.