Woo-Keun Yoon

Analytical Inverse Kinematic Computation for 7-DOF Redundant Manipulators With Joint Limits and Its Application to Redundancy Resolution

This paper proposes an analytical methodology of inverse kinematic computation for 7 DOF redundant manipulators with joint limits. Specifically, the paper focuses on how to obtain all feasible inverse kinematic solutions in the global configuration space where joint movable ranges are limited. First, a closed-form inverse kinematic solution is derived based on a parameterization method. Second, how the joint limits affect the feasibility of the inverse solution is investigated to develop an analytical method for computing feasible solutions under the joint limits. Third, how to apply the method to the redundancy resolution problem is discussed and analytical methods to avoid joint limits are developed in the position domain. Lastly, the validity of the methods is verified by kinematic simulations.

Stiffness Analysis and Design of a Compact Modified Delta Parallel Mechanism

In our previous work, we developed a compact 6-DOF haptic interface as a master device which achieved an effective manual teleoperation. The haptic interface contains a modified Delta parallel-link positioning mechanism. Parallel mechanisms are usually characterized by a high stiffness, which, however, is reduced by elastic deformations of both parts and bearings. Therefore, to design such a parallel mechanism, we should analyze its structural stiffness, including elastic deformations of both parts and bearings. Then we propose a simple method to analyze structural stiffness in a parallel mechanism using bearings. Our method is based on standard concepts such as static elastic deformations. However, the important aspect of our method is the manner in which we combine these concepts and how we obtain the value of the elasticity coefficient of a rotation axis in a bearing. Finally, we design a modified Delta mechanism, with a well-balanced stiffness, based on our method of stiffness analysis.

Motion Control System that Realizes Physical Interaction between Robot's Hands and Environment during Walk

This paper addresses a whole-body motion control system that realizes desired absolute hand position trajectory which can be given online during continuous walk. External force that is exerted to the hand can also be managed by the system. The system is based on a short cycle dynamically stable walking pattern generation system, which generates and updates a motion pattern at every 20 [ms]. Short cycle generation realizes quick response to the change of commanded hand position. It also enables the system to reflect force sensor information to the dynamics model which is used for dynamically stable pattern generation with small latency. The robot can maintain dynamic balance even when measurable force is exerted to its hands by using this characteristic. We also implemented impedance control of the hand position in order to realize stable contact when the hands touch surrounding objects. We implemented the system on a full size humanoid, HRP-2. Basic experiments and an experiment of pushing a table show the performance of the system.

Design of a Compact 6-DOF Haptic Device to Use Parallel Mechanisms

We present design of a compact haptic device in which parallel mechanisms are utilized. The design realizes a large workspace of orientational motion in a compact volume of the device. The device is a parallel-serial mechanism consisting of a modified DELTA mechanism for translational motion and a spatial five-bar gimbal mechanism for orientational motion. We derive an analytical model of stiffness for the modified DELTA mechanism which we utilize for the design of a stiff platform for translational motion. The model shows that the compliance matrix is a function of kinematic parameters as well as elastic parameters of each mechanical element. Configuration dependency of the compliance matrix is therefore an important point to be noticed.

Development of evaluation indexes for assistive robots based on ICF

With the aging population trends in developed countries, there is an increased expectation of the application of assistive robots. A variety of robots have been developed to address this challenge. Although there are many technical problems to be solved, the lack of objective evaluation indexes for evaluating the benefit to the users is one of the important problems to be addressed before the commercialization of the assistive robots can be realized. The ICF (International Classification of Functioning, Disability and Health) is a classification of the health components of functioning and disability, and is being utilized in medical, healthcare, and welfare fields. The ICF has a basic framework to evaluate healthcare and welfare equipment, including robots, and it will be the basis of the evaluation indexes for assistive robots. In this paper, we present the development of evaluation indexes, and provide the results of preliminary experiments which were conducted using iARM and RAPUDA robots performing a certain lifting task. The experiments illustrate the issues involved in the development of ICF-based indexes for assitive robots.

User evaluation to apply the robotic arm RAPUDA for an upper-limb disabilities Patient's Daily Life

To help the patients who have disabilities for their upper limbs because of muscle dystrophy or cervical spine injuries, we have developed robot arm RAPUDA which can support their daily life action. We have evaluated the user operation of the RAPUDA with the Pegboard. Now we evaluate the RAPUDA with usual objects in the environment where the real users spend their daily life. From the previous human ergonomics experiments and interview with the examinees, the desired action and objects are obtained. For example, scratching and wiping their faces. We make preliminary experiments for these tasks and consider as training tasks to introduce the robot arm to the daily life and some muscle dystrophy patients try the RAPUDA in the hospital.

Experimental Validation of Task Skill Transfer Approach Using a Humanoid Robot

This paper demonstrates the validity of a task skill transfer approach using a humanoid robot. The task skill transfer approach is a methodology for transferring human skills to robot programs in an abstracted level to achieve various practical tasks in real environments regardless of robot hardware difference. First, the outline of the approach is presented. Second, how to acquire task skills is described. Finally, a task skill, which has been created with an industrial manipulator, is implemented to a humanoid robot to experimentally validate the reusability of the skill across the robot platforms.

Model‐based robot teleoperation with haptic interface

An experimental teleoperation system for space robotics has been developed. The purpose of using this system is the development of space robot teleoperation technologies which can replace the skills of an astronaut. Communication time delay is one of the biggest problems encountered by teleoperation of a space robot from the ground. To solve the time delay, we proposed a mixed force and motion command‐based space robot teleoperation system that is a model‐based teleoperation. Moreover, we have also developed a compact six‐DOF haptic interface as a master device. The effectiveness of our model‐based teleoperation technologies was verified by carrying out some tasks in a real space robotic system: the Engineering Test Satellite VII (ETS‐VII).

User evaluation of service robotic arms based on ICF through interviews with people with upper-limb disability

The iArm is a service robot arm to help people with upper-limb disability in their daily lives. The iArm has been produced for about 10 years in the Netherlands. The National Institute of Advanced Industrial Science and Technology has developed RAPUDA (Robotic Arm for Persons with Upper-limb DisAbility). The effectiveness of the RAPUDA was evaluated by conducting ergonomics experiments. We analyze the effectiveness of the robot arm in daily life through interviews with iArm users living in the Netherlands and with the participants in the human ergonomics experiments of RAPUDA. Effectiveness will be evaluated by the ICF (International Classification of Functioning, Disability and Health).

Shared autonomy architecture for skill execution manipulator

In this paper, we report a shared autonomy architecture for skill execution manipulator. A skill transfer method has been proposed in our previous research. Many skills for a plant maintenance also have been developed. Our goal is that an autonomous robot implemented the skills executes maintenance tasks in the plant. When the robot fails the task execution, the robot should recognize all conditions and recover by itself. However, in current technology, the robot to recover from all failed conditions could not be developed. Then, an idea of shared autonomy architecture for our research area is introduced. In this idea, when the robot fails to perform the task and can not recover from failed conditions, an operator intervenes to control the manipulator. The operator moves the manipulator to a convenient condition in a bilateral teleoperation. After the operators motion, the robot re-executes the target task. To demonstrate our proposed architecture, we choose a nut attachment task.