602 低圧駆動型空気圧アクチュエータの開発と応用

Recently, research and development has focused on robots that work in place of people. It is necessary for robots to perform the same flexible motions as people. Additionally, such robots need to incorporate high-level safety features in order not to injure people. For creation of such robots, we need to develop a robot hand that functions like a human hand. At the same time, this type of robot hand can be used as an artificial hand. Here, we present artificial muscle-type pneumatic actuators 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, until now, when a pneumatic actuator is used, a big compressor is needed. Therefore, the driving system also needs to be big, and enlargement of the driving system is a major problem. Consequently, in this research, we develop a low-pressure, low-volume pneumatic actuator for driving a robot hand that works flexibly and safely on the assumption that it will be in contact with people. We develop a five-fingered robot hand with pneumatic actuators. Next, we make a 1-link arm that has one degree of freedom using a pneumatic actuator, and models of the actuator and 1-link arm are constructed. A control PID control system is constructed, and the gains of the PID control system are determined by the simulation that uses the model of the 1-link arm. The step response of the joint angle is examined with the determined gains, and control performance of the PID control system is verified.

Since robotic arms operating close to people are becoming increasingly common, there is a need to better understand how they can be made safe when unintended contact occurs, while still providing the required performance. Several actuators and methods for improving robot safety are studied and compared in this paper. A robotic arm moving its end effector horizontally and colliding with a person’s head is simulated. The use of a conventional electric actuator (CEA), series elastic actuator (SEA), pneumatic actuator (PA) and hybrid pneumatic electric actuator (HPEA) with model-based controllers are studied. The addition of a compliant covering to the arm and the use of collision detection and reaction strategies are also studied. The simulations include sensor noise and modeling error to improve their realism. A systematic method for tuning the controllers fairly is proposed. The motion control performance and safety of the robot are quantified using root mean square error (RMSE) between the desired and actual joint angle trajectories and maximum impact force (MIF), respectively. The results show that the RMSE values are similar when the CEA, SEA, and HPEA drive the robot’s first joint. Regarding safety, using the PA or HPEA with a compliant covering can reduce the MIF below the safety limit established by the International Organization for Standardization (ISO). To satisfy this ISO safety limit with the CEA and SEA, a collision detection and reaction strategy must be used in addition to the compliant covering. The influences of the compliant covering’s stiffness and the detection delay are also studied.

In this paper, an interactive robotic anthropomorphic hand system is presented, which was developed as an important tool for the educational outreach activities. The robotic anthropomorphic hand incorporates 15 degrees of freedom, providing sufficient mobility in the demonstration of various postures. To increase the attractiveness of the robotic hand, pneumatic muscle actuators are used to drive the robotic hand motion through artificial tendons. The interaction of the robotic hand with a human is enabled with a control device, which allows the human operator to control the hand motion in a natural way. The robotic hand system has been successfully demonstrated in a recent engineering education outreach event, in which over 100 children at all ages operated the robotic hand through the control device.

Previous works about robotic arm for the automatic harvesting of an agricultural crop of quality small plants (red radicchio), were mainly concerned about the study of the control system for pneumatic actuators moving the robotic arm. The choice of pneumatic actuators was due to their physical favourable characteristics for positioning applications. The main problem of this choice was linked to non-linear behaviour of pneumatic systems. This non-linearity makes accurate position control of a pneumatic actuator difficult to achieve. A recent trend developed the use of inexpensive on/off solenoid valves to control pneumatic actuator systems. Furthermore, the use of pulse width modulated signals (PWM) across the power devices reduces control problems such as dead band and stiction. The results ensure the possibility of following a desired trajectory using potentiometer feedback and a PI controller with parameters tuned in an iterative way. This paper shows experimental results carried out considering a vision feedback obtained with a cheap cam mounted on the top of end-effector. This vision feedback is processed in order to localise the plant position along the movement plane of the robotic arm end-effector. A kinematical model of the robotic arm defines each actuator trajectory to lead end-effector to grasp the plant in the taking plane according to the vision feedback. All the control and localisation system was realised using a single commercial PC.

Research and development in the robotics of rehab and power assistance have recently focused on pneumatically driven robots. This is because of their low cost, light weight, and a simple design. We are able to build safe and flexible drives. We took particular note of a Mckibben pneumatic actuator as a drive mechanism for pneumatically driven robots. We developed a low-pressure, low-volume pneumatic actuator in previous studies. However, the generative force of these actuators is small, when you use a equipment like that used for rehab assistance. We originally developed membrane pneumatic actuators to solve this problem. A five-fingered robot hand was developed, that imitated a human's right hand with membrane pneumatic actuators. First, we present the characteristics of a pneumatic actuator from our experiment. Then, we constructed a model using results from another experiment in a one-link arm with membrane pneumatic actuators. Next, a PI-D control system was constructed, and its gains were determined by simulation. Then, we tried to control the pressing force of a one-link arm with the controllers we constructed. As a result, we could control the pressing force with the constructed PI-D controllers.

In this paper, we propose a novel pneumatic-electric hybrid drive robot hand for both powerful grasping and dexterous manipulation. The concept is to use both pneumatic actuators to exert a large grasping force and electric motors to precisely control fingers. However, this concept has been difficult to apply to a robot hand that needs to be lightweight and compact because pneumatic actuators are generally too large for the stroke requirement. We solved this problem by using lightweight pneumatic artificial muscles (PAMs) and a passive clutch mechanism that shuts off the drive of the PAMs to the fingers when the hand did not grasp, which reduces the stroke requirement of the PAM. We developed a 3-degrees-of-freedom (DoFs) and 3-fingered robot hand that was 220 × 220 × 160 mm and 1.45 kg. It achieved a grasping force of 110 N and speed of 1300 mm/s at its fingertips. We also attempted manipulation with the three fingers driven independently by electric motors. As an example, the hand achieved peg-in-hole operation by hand manipulation, with a tolerance of a few tens of micrometers. The hand can potentially perform hybrid control, where the PAMs are used to generate force while the electric motors are used for fine adjustment. Finally, we demonstrated heavy rail installation in which the robot hand brought an 8.5-kg rail with power grasping, adjusted its position using the hand with a hybrid control, and inserted screws with hand manipulation.

After introductory considerations on the main functional and design differences between anthropomorphic hands conceived as robotic end effectors or as prostheses, this chapter presents two topics related to advances in robotic hand design that seem transferable to prosthetic hands, in order to increase their functional capability yet coping with specific constraints like simplicity, lightweight, cost effectiveness, robustness, etc. The development of a bio-inspired robotic hand, called UB Hand IV, based on an endoskeletal articulated structure, actuated by tendons and covered by a soft dermal-epidermal layer is briefly illustrated, in order to show the potential of its design solutions to be transferred into prosthetic hands. The first part of the chapter presents alternative design approaches for articulated joints and finger structures based on purposely designed compliant hinges. The basic problem of compliant hinges adoption in robotic structures, that is the limitation of secondary compliance effects, is analyzed and considerations about comparative metrics are proposed. Two hinge morphologies which show promising features are critically compared and pros and cons the production of fully integral fingers with compliant joints are discussed. The second part reports on the development of thin soft covers for robotic (and prosthetic) hands capable of strictly mimicking the actual compliance of human finger pulps. A design method, called by the authors Differentiated Layer Design (DLD), is reviewed and its potential for application on both robotic and prosthetic devices is underlined. Conclusions summarize the main aspects that encourage the transfer of the described results from the world of robots to that of human portable devices.

This paper proposes a novel continuum robot arm based on the pneumatic muscle actuator (PMA). The simple design of the extensor and the contractor PMAs are used to implement the extension and the contraction sections respectively. Five actuators are used in each section to achieve an elongation and bending for the top section and a contraction and bending for the bottom section. Then, four self-bending contraction actuators (SBCA) are used instead of the five contractions PMA to enhance the bending performances. The performances of the proposed soft robot arm showed the advantages of using a biological inspiration robot arm for the unique features in comparison to its weight and cost.

Recently, research has focused on pneumatic robot. Here, we present artificial muscle-type pneumatic actuators as the driving source of a robot hand that is both safe and flexible. We develop a five-fingered robot hand with pneumatic actuators of low-pressure and low-volume. To control this hand in high accuracy, we construct the spring-damper model of the pneumatic actuator. We produce a I-link arm. We construct the model of 1-link arm that considers moment of inertia and the viscous friction coefficient. We construct a control system for 1-link arm. In addition, the effectiveness of the constructed model is verified by the experiment.

An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a jet flow (ECF jet) when subjected to high DC voltage. It is known that a strong ECF jet is generated under nonuniform electric field, for example, the field with a pair of needle and ring electrodes. We developed in our previous study a novel five-fingered flexible robot hand using the ECF. In this study, in order to improve the ECF hand we pay our attention to the flexion of palm because human hand can grasp an object with the flexion of palm. First, we propose a concept of five fingered robot hand which has balloon actuators driven by ECF jet to produce the flexion of palm. The actuator is mainly composed of silicone rubber membrane and a rubber base with a slit, so that when the actuator is pressurized the slit is opened, resulting in making the palm of the robot hand actuate. When the actuator is pressurized with 20 kPa the rubber slit is opened with approximately 60 deg. Finally we investigate the characteristics of the actuator and introduce it into the ECF robot hand.

We have presented the newly developed anthropomorphic robot hand named the KH Hand type S and its master slave system using the bilateral controller. The use of an elastic body has improved the robot hand in terms of weight, the backlash of the transmission, and friction between the gears. We have demonstrated the expression of the Japanese finger alphabet. We have also shown an experiment of a peg-in-hole task controlled by the bilateral controller. These results indicate that the KH Hand type S has a higher potential than previous robot hands in performing not only hand shape display tasks but also in grasping and manipulating objects in a manner like that of the human hand. In our future work, we are planning to study dexterous grasping and manipulation by the robot.

Recently, research and development in robotics of rehabilitation and power assist have focused on pneumatically driven robots, because of their low cost, light weight, and simple systems. Because there is a failure characteristic in the pneumatic actuators, it is possible to build a safe and flexible drive. As drive mechanism of pneumatically driven robots, we take particular note of Mckibben-type pneumatic actuator. We developed a low-pressure, low-volume pneumatic actuator in previous studies. However, generative force of this pneumatic actuator is small, if you use equipment such as rehabilitation assistance. To solve this problem, we develop originally membrane-type pneumatic actuators. We reveal the characteristics of a pneumatic actuator from experiment. We construct a model of the relationship between pressure and force on the results.

Drawing on the driving mechanism of biological muscles and combining the nonlinear hyperelastic characteristics of silicone rubber, a multi-degree-of-freedom pneumatic soft bionic actuator is designed, which can be used as the executing mechanism for soft robots and robotic arms. Using response surface analysis and numerical simulation algorithms, the optimal combination of structural dimensions parameters is determined with the maximum bending and torsion angles output by the actuator as the optimization objectives. Based on the idea of flexible mechanism Piecewise Constant Curvature (PCC) modeling, the kinematics equation of the actuator is derived. Analyze the equivalent motion structure of the actuator and establish a dynamic model of the actuator based on the Lagrange method. The physical model of the actuator is manufactured using rapid prototyping technology. Finally, experimental testing and analysis are conducted on the physical model to obtain the motion and dynamic characteristics curves and empirical formulas of the actuator, which are compared with theoretical and simulation results to verify that the pneumatic soft bionic actuator is feasible and effective. The above research methods, processes, and results can provide reference and inspiration for the research and implementation of pneumatic and hydraulic soft robots and gripping actuators for soft robotic arms.

Based on aging Japanese society, there has been a strong desire for development of rehabilitation devices that patients can use at home. The purpose of this study is to develop a home-based compact, lightweight, flexible, and safe rehabilitation device. In this study, a flexible robot arm for wrist rehabilitation that can be used, while patients hold the top of the robot arm, is proposed and tested. The proposed robot arm consists of three extension type flexible pneumatic actuators (EFPAs) restrained by 22 PET sheets. To achieve suitable bending stiffness of the robot arm, three EFPAs are restrained so as to form a tetrahedral shape. The robot arm can bend toward each radial direction. In this paper, the construction and operational principles of the tested robot arm are described. Additionally, the analytical model of the robot arm for attitude control is also described. In addition, the tracking control using the robot arm for the desired orbit is performed. As a result, the tested robot arm can trace the desired orbit based on the model. It is confirmed that the robot arm has the possibility for application as a wrist rehabilitation device for patients.

A bionic robotic hand can perform many movements similar to a human hand. However, there is still a significant gap in manipulation between robot and human hands. It is necessary to understand the finger kinematics and motion patterns of human hands to improve the performance of robotic hands. This study aimed to comprehensively investigate normal hand motion patterns by evaluating the kinematics of hand grip and release in healthy individuals. The data corresponding to rapid grip and release were collected from the dominant hands of 22 healthy people by sensory glove. The kinematics of 14 finger joints were analyzed, including the dynamic range of motion (ROM), peak velocity, joint sequence and finger sequence. The results show that the proximal interphalangeal (PIP) joint had a larger dynamic ROM than metacarpophalangeal (MCP) and distal interphalangeal (DIP) joints. Additionally, the PIP joint had the highest peak velocity, both in flexion and extension. For joint sequence, the PIP joint moved prior to the DIP or MCP joints during flexion, while extension started in DIP or MCP joints, followed by the PIP joint. Regarding the finger sequence, the thumb started to move before the four fingers, and stopped moving after the fingers during both grip and release. This study explored the normal motion patterns in hand grip and release, which provided a kinematic reference for the design of robotic hands and thus contributes to its development.