Yoichiro Nakamura

Development of prosthetic arm with pneumatic prosthetic hand and tendon-driven wrist

Recently, various prosthetic arms have been developed, but few are both attractive and functional. Considering human coexistence, prosthetic arms must be both safe and flexible. In this research, we developed a novel prosthetic arm with a five-fingered prosthetic hand using our original pneumatic actuators and a slender tendon-driven wrist using a wire drive and two small motors. Because the prosthetic hand’s driving source is comprised of small pneumatic actuators, the prosthetic hand is safe when it makes contact with people; it can also operate flexibly. In addition, the arm has a tendon-driven wrist to expand its motion space and to perform many operations. First, we explain the pneumatic hand’s drive mechanism and its tendon-driven wrist. Next, we identify the characteristics of the hand and the wrist and construct a control system for this arm and verify its control performance.

Spring-damper model and articulation control of pneumatic artificial muscle actuators

Recently, research and development in robotics have focused on robots performing tasks traditionally done by people. Therefore, it is necessary for robots to have the same flexibility as people. Additionally, such robots need to incorporate high-level safety features so as not to incur injury on others. We present artificial muscle-type pneumatic actuators as the driving source of a robot hand that is both safe and flexible. Development of robot hands using pneumatic actuators has already taken place. However, when a pneumatic actuator is used, a large compressor is needed. Therefore, the driving system also needs to be large. This is a major problem. Therefore, we developed low-pressure, low-volume pneumatic actuators for driving a robot hand that works flexibly and safely among people and a five-fingered robot hand with these pneumatic actuators installed. To accurately control the five-fingered robot hand, an accurate model with a pneumatic actuator is needed. We constructed such a model by using a spring element, which expresses the generative force of pneumatic pressure, and a damper element, which expresses the hysteresis characteristics. We then made a 1-link arm that has one degree of freedom using the pneumatic actuators and constructed a 1-link armmodel. We also constructed a spring-damper element model of the pneumatic actuators and a proportional-integral-derivative (PID) controller system. The gains of the system were determined with a simulation that uses our 1-link arm model. The step response of the joint angle was examined with these determined gains.

Development & Control of Master-Slave Robot Hand Driven by Pneumatic Actuator

We present an artificial muscle-type pneumatic actuator as the driving source of a robot hand that is both safe and flexible. Some development of robot hands using pneumatic actuators has already taken place. However, in using a pneumatic actuator, a big compressor is needed. So the driving system also needs to be big, and enlargement of the driving system is a major problem.

Feed Forward Control for Pneumatic Forearm Prosthesis, Manipulator

In order to reach a better productivity in numerous fields, robots have been wildly used for automatic tasks. The main issue of a robot is his lack of adaptability, which is one of the most important ability of human beings. The best tool for adaptability is the human hand. Using pneumatic actuators to drive a robot forearm grants the possibility to move light articles with accuracy and without harming it. It is then necessary to develop accurate model of the different types of actuators. As every human muscle are simulated by those actuators, the size of these must vary and so their properties as well. These artificial muscle-type pneumatic actuators are composed of a rubber balloon, a net, a feeding channel and finally two anchors at both end of the net. Starting with the simplest linear model, we increased the complexity of the model to finally obtain a powerful control of the plastic muscle. To obtain the data we needed for the model, we used a test bench for pneumatic actuators and adjust it to fit the new size of the current actuator. The main difficulty to control the actuator is to find a way to overcome its hysteresis cycle. Then once the model is ready we need to use it to control the different part of the pneumatic forearm. The previous wrist and hand control is enhanced by feed forward control and can perform motion with a great accuracy. The hand can therefore be used without any electronic devices on it and remains lighter and safer. Previous starting dead-zone has been understood and avoided.Copyright

Correction of image coordinate using landmark for setting error

In recently years, the production method has changed from the diversification of a sense of values from mass production to diverse-types-and-small-quantity production on the production site. Therefore, a productive system that can correspond to changes in the environment is required. In a productive system that performs handling tasks, we use a hand-eye system with a camera and a manipulator and perform hand-eye calibration from two dimension images obtained by camera to the manipulator coordinates a three dimension system of in the hand-eye system. However, the camera and the manipulator positions in the previous system changed, and great error from the position, which performed the calibration, was caused even when the error was minute. Therefore, in this hand-eye system, changing this production system is difficult or re-calibration is needed. The projection matrix must be calculated so that the image coordinates obtained with the camera and the manipulator coordinates of three dimensions correspond again in the re-calibration. However, calculating the projection matrix requires great care. We propose a technique that simply calculates the manipulator coordinates of three dimensions from image coordinates without calculating the projection matrix again by correcting the image coordinates. Our experiment results show that the image coordinates can be corrected without calculating the projection matrix again using a landmark. In addition, a three-dimensional position was corrected simply, and we were able to handle the object.