Hiroki Tomori

The position and vibration control of the artificial muscle manipulator by variable viscosity coefficient using MR brake

In this study, an artificial rubber muscle was selected as an actuator because it is safe to be used as a muscle manipulator that comes into contact with the human body. However, this actuator vibrates and can cause delayed responses because of the air pressure that is applied to the manipulation. We built a magnetorheological (MR) brake that uses MR fluid with a fast response into the joint to control the vibration. In this study, we focus on the variable damping of the MR brake. By variable damping of the MR brake, we could apply the brake torque depending on the rotational speed of the arm in response to the artificial muscle manipulator. Moreover, we could control the viscosity coefficient of the manipulator depending on its angle and calculate the optimum brake torque as an indicator. As a result, we found that the manipulators lifting operation was more stable without any sudden movement. We evaluated various aspects of the manipulator control to determine the best indicator of the viscosity coefficient, and studied the position control of an artificial muscle manipulator using these methods.

Variable impedance control with an artificial muscle manipulator using instantaneous force and MR brake

Highly rigid actuators such as geared motors or hydraulic actuators are widely used in industrial robots. To obtain high-speed motion, it is necessary to increase the actuator output as the robot weight increases. In contrast, humans perform motions using instantaneous force, such as jumping or throwing, via variable stiffness characteristics. We have developed a one-degree-of-freedom manipulator with a variable rheological joint using a straight-fiber-type artificial muscle and a magnetorheological (MR) brake. With the generation of instantaneous force, the dead and rise times decreased compared to the conventional method. After the generation of an arbitrary instantaneous force, we were able to control the robots arm position by applying an equilibrium force on the joint. Furthermore, we were able to control the vibrations of the arm by controlling the MR brake using an evaluation function.

Derivation of nonlinear dynamic model of novel pneumatic artificial muscle manipulator with a magnetorheological brake

An artificial rubber muscle was used as an actuator in the present study because it was safe for the muscle manipulator to come into contact with the human body. However, this actuator vibrates and can cause late responses because of the air pressure that is applied to the manipulation. We have built a magnetorheological (MR) brake that uses MR fluid with fast response into the joint to control the vibration. In this paper, we have described the manipulators dynamic characteristics by construction of a model for improvement of the control performance of the MR brake. Furthermore, a simulation was performed using the model and efficient braking by the MR brake was achieved.

POSITION AND VIBRATION CONTROL OF VARIABLE RHEOLOGICAL JOINTS USING ARTIFICIAL MUSCLES AND MAGNETO-RHEOLOGICAL BRAKE

In recent times, the chances of robot–human contact have increased; hence, safety is necessitated with regard to such contact. Thus, manipulators using a pneumatic rubber artificial muscle, which is lightweight and flexible, are studied. However, this artificial muscle manipulator has faults such as slow response and limited instantaneous power due to operation by air pressure. Because of these faults, uncontrollable vibrations can occur, leading to instability in the arm when an object is held and lifted. In this study, an artificial muscle manipulator with one DOF and a variable rheological joint mechanism using MR fluid is developed. Vibration control of the arm using MR fluid is realized when an object is held and lifted, confirming the reduction in vibration due to the MR effect.

Development of 1-DOF manipulator with variable rheological joint for instantaneous force

Highly rigid actuators such as a geared motor or hydraulic actuator are widely used in industrial robots. To obtain high-speed motion, actuators need to increase the actuator output. However, to increase high-rigidity actuators output, it is necessary to make actuators larger. In contrast, humans perform motions with instantaneous force such as jumping or throwing by using muscles. These instantaneous forces are realized by accumulating potential energy to the muscles and the muscles releasing the energy in a short time. Therefore, in this study a 1-DOF manipulator with variable rheological joint for instantaneous force using an artificial muscle and a magnetorheological (MR) brake was developed. In this paper, the method of generating instantaneous force for this manipulator was proposed. Further, the experiment of the proposed method was also conducted. As a result, generating instantaneous force by proposed method was realized.

Construction of a nonlinear dynamic characteristic model of pneumatic artificial rubber muscle manipulator using the magnetorheological (MR) brake

An artificial rubber muscle as an actuator was paid attention in this study because the manipulator was found to be safe to human when it comes in contact with human. However, this actuator vibrates easily with a late response because of the applied air pressure. Then, the magnetorheological brake that uses the magnetorheological fluid with an early response is built into the joint and controls the vibration. In this article, we have grasped the dynamic characteristics of a manipulator by the construction of a model for improvement in the control performance of the magnetorheological brake. Furthermore, the simulation was performed using the model, and efficient braking of the magnetorheological brake was examined.

Vibration control of an artificial muscle manipulator with a magnetorheological fluid brake

Recently, proposed applications of robots require them to contact human safely. Therefore, we focus on pneumatic rubber artificial muscle. This actuator is flexible, light, and has high-power density. However, because the artificial muscle is flexible, it vibrates when there is a high load. Therefore, we paid attention to the magnetorheological (MR) fluid. We propose a control method of the MR brake considering energy of the manipulator system. By this control method, MR brake dissipates energy leading to vibration of the manipulator. In this paper, we calculated the energy and controlled the MR brake. And, we deliberated the proposal method by simulation using the dynamic model of the manipulator, and experiment.

NONLINEAR DYNAMIC CHARACTERISTIC MODEL OF ARTIFICIAL RUBBER MUSCLE MANIPULATOR USING MR BRAKE

An artificial rubber muscle was paid to attention as an actuator in the present study because human was safe for the manipulator to have come in contact with human. However, this actuator occurs easily the vibration, and is late the response because of applying the air pressure. Then, the MR brake that uses the MR fluid with an early response is built into the joint, and controls the vibration. In this paper, we have grasped a manipulators dynamic characteristics by construction of a model for improvement in the control performance of MR brake. Furthermore, the simulation was performed using the model and efficient breaking of MR brake was examined.

Development and control of 1-DOF manipulator using electrostrictive rubber actuator

Recently, flexible and light actuators that mimic muscle fibers have been actively researched. Here, we focused on an electroactive polymer (EAP) dielectric elastomer. To construct the actuator, the dielectric elastomer is rolled into a tube, and extended by applying a voltage across its electrodes. In this paper, we experimentally obtained a static characteristic model of the electrostrictive rubber actuator, and proposed a control method. We then incorporated the actuator into a 1-DOF manipulator, and constructed a controller from a mechanical equilibrium model of this manipulator. Finally, the constructed controller was tested in a series of experiments. The angle of the arm fell below the desired angle because of friction in the joint and the spring characteristics of actuators. However, we confirmed that the controller reduced the influence of the load by torque feedback. We also investigated the influence of joint stiffness.

Motion control of instantaneous force for an artificial muscle manipulator with variable rheological joint

Highly rigid actuators such as a geared motor or hydraulic actuator are widely used in industrial robots. To obtain high-speed motion, it is necessary to increase the actuator output as the robot weight increases. In contrast, humans perform motions with instantaneous force-as in a jump or throw-via variable rheological characteristics. We developed a one-degree-of-freedom manipulator with a variable rheological joint using a straight-fiber-type artificial muscle and a magnetorheological (MR) brake. Then, we created a nonlinear dynamic characteristics model of this manipulator and proposed a method for generating instantaneous force. Furthermore, we validated the proposed method by experiment and simulation. The model reproduced the manipulator system characteristics, and the dead and rise times decreased compared with the conventional method. Furthermore, we controlled the manipulator arm motion by controlling the MR brake both experimentally and via simulation. The results were quite satisfactory.