DEVELOPMENT OF WEARABLE MASTER-SLAVE TRAINING DEVICE FOR UPPER LIMB CONSTRUCTED WITH PNEUMATIC ARTIFICIAL MUSCLES

Transcription

1 DEVELOPMENT OF WEARABLE MASTER-SLAVE TRAINING DEVICE FOR UPPER LIMB CONSTRUCTED WITH PNEUMATIC ARTIFICIAL MUSCLES Daisuke SASAKI*, Toshiro NORITSUGU* and Masahiro TAKAIWA* * Graduate School of Natural Science of Technology Okayama University Tsushimanaka, Kita-ku, Okayama, Japan ( daisuke@sys.okayama-u.ac.jp) ABSTRACT The purpose of this study is to develop a wearable master-slave upper limb training device, which can be used to a passive training for a trainee who can not move by themselves. Developed device has 7 D.O.F by using three kinds of pneumatic artificial muscles, which are chosen as suitable actuators to move each human joint. In this paper, cooperated movements are experimented to verify a capability of slave device. It is confirmed from the result that a subject who uses the slave device can follow the trainer movement. Therefore, this device may be expected to be able to train all upper limb joints independently or cooperatively. KEY WORDS Pneumatic, Artificial muscle, Soft mechanism, Wearable robot INTRODUCTION Many kinds of power assist device have been developed to assist a hard work, rehabilitate a human body in recent years [1]-[5]. These devices are driven with various actuators such as a electric motor, a hydraulic cylinder and so on. Above all, a pneumatic artificial rubber muscle is effective to drive these devices[4][5]. Since these devices used by a human is required a safety and a light weight. This actuator has a mechanical flexibility according to the air compressibility, a rubber material, and has a high power weight ratio. Therefore, this rubber muscle can realize a flexible and a light weight device with a simple mechanism. The purpose of this study is to develop a wearable master-slave upper limb training device for a trainer and a trainee. By realizing the wearable master-slave device, the trainer may be able to train the trainee easily since the trainer just moves the trainer s upper limb. A final goal of this study is shown in Fig.1. The trainer and the trainee use the devices, and the trainer moves the upper limb. By looking the trainee's condition and moving the Fig.1 Image of final goal

2 trainer s upper limb, the trainer teaches the trainee an upper limb trajectory. The trainer can train the trainee only by moving the trainer's body. Developed device has 7 D.O.F by using three kinds of pneumatic artificial muscles, which are chosen as suitable actuators to move each human joint. Therefore, this device can apply torques to each human upper limb joint independently. In addition the trainer can train easily without a complicated calculation since the trainer who uses the wearable master device only move a trainer s body intuitively. In this paper, the structure of developed device is discussed, and then the cooperated movement is experimented. It will be confirmed through the above experiment that the slave subject who uses the slave device can follow the master subject s movement cooperatively by applying the torques to each joint independently. MOVEMENT OF DEVELOPED DEVICE movement are shown in Fig.4, 5. (a)extension (b) Flexion Fig.3 Movement of elbow device Fig.2 shows an overview the developed master and slave devices. This device has 3 D.O.F at a shoulder and 1 D.O.F at an elbow, respectively. The same orthosis of the slave device in which the artificial muscle is not installed is used for a master device. Developed device has 7 D.O.F, which is the same as the human upper limb. Therefore, this device can move the subject as shown in Fig.3, 4. The each elbow movement is shown in Fig.3. Similarly, the shoulder and wrist (a)flexion/extension (a) Master device (b) Abduction/Adduction (b) Slave device Fig.2 Overview of developed device (c) Internal rotation/external rotation Fig.4 Movement of shoulder device

3 the shoulder joint via a nylon band in the slide rail as shown in Fig.8. (a) Palmar flexion/dorsal flexion (a-1) Initial state (a-2) Pressurized state (b) Ulnar flexion/radial flexion (a) Pneumatic muscle for extension (b-1) Initial state (c) Pronation/Supination Fig.5 Movement of wrist device STRUCUTURE OF DEVELOPED DEVICE Fig.6 shows the structure of the slave shoulder and elbow device. Layer type pneumatic muscles as shown in Fig.7 are put on a back side through a slide rail. Layer type pneumatic muscle expands to the height direction when the compressed air is supplied into this muscle. This expansion force is converted to the shoulder flexion/extension torque by the slide rail and (b-2) Pressurized state (b) Pneumatic muscle for flexion Fig.7 Overview of layer type pneumatic muscle (a) Side view (b) Rear view Fig.6 Structure of shoulder device (a) Extension (a) Flexion Fig.8 Principle of operation about shoulder flexion/extension

4 McKibben type pneumatic rubber muscles are used for generating an abduction/adduction torque. The contraction force from this muscle is also converted to the abduction/adduction torque by the shoulder joint. A shoulder internal/external rotation and an elbow flexion/extension torques are generated by extension type pneumatic rubber muscles as shown in Fig.9. This artificial muscle is installed to the orthosis with this muscle extended from the initial length. The restoring force of the rubber increases by extending to the length direction. Conversely, the restoring force decreases by pressurizing, since this muscle extends to the length direction when the compressed air is supplied. This restoring force is used to generate the above torques in this device. Two rubber muscles are installed on a slide rail alternately as shown in Fig.10. This slide rail is connected with the shoulder abduction/adduction device in which McKibben type pneumatic rubber muscles are installed as shown in Fig.7. Initially, both rubber muscles are supplied a balance pressures. In the case of external rotation, the rubber muscle for external rotation shown as red line in Fig.11 is decreased from the balance pressure, and the rubber muscle for internal rotation shown as blue line is increased. The human can be done the external rotation by the restoring force from the rubber muscle for external rotation. In the case of internal rotation, the human can be also done the internal rotation by the same principle. The wrist pronation/supination device shown in Fig.5 (c) in the following description has the almost same structure and principle of operation. Fig.12 shows the principle of operation about elbow device. The extension type pneumatic rubber muscles are put on the device so that both muscles are antagonized. When the rubber muscles for flexion and (a) Initial state (b) Pressurized state Fig.9 Overview of extension type Fig.11 Principle of operation about shoulder internal/external rotation device Fig.10 Structure of shoulder internal/external rotation device Fig.12 Principle of operation about elbow device

5 extension shown as blue and red lines are decreased and increased from the balance pressure, this device can flex a subject elbow. Conversely, when the rubber muscles for flexion and extension are increased and decreased from the balance pressure, a subject elbow is extended. Fig.13 shows the structure of the wrist device. In the wrist device, all movements are also driven with the extension type pneumatic rubber muscles. The pronation/supination device has the almost same structure of shoulder internal/external rotation device as the above description. The principle of operation about the palmar/dorsal and ulnar/radial flexion devices also is the almost same one about the elbow device. use muscular strength. In this experiment, the devices are controlled based on the unirateral master-slave control system. The each slave joint angle is controlled with the angle control system to follow the master joint angles, which are the reference angles in the slave angle control system. The inner pressure of the antagonized artificial muscle is calculated by the PI controller in the angle control system. Table 1 shows the main system parameters to show the each angle. Fig.15 show the experimental results and the definition of each angle. The master subject draw the circle three times. In flexion / extension and internal / external rotation shown in Fig15 (a), (c), the slave angles are saturated. This device has been designed as compactly as possible. Therefore, the generated torque from rubber muscle may be smaller than the required one to move the human body. It is the future work to cope with both the compactness and the increase in the generated torque. However, another slave angles can follow the master angles. It is another future work to improve the angle response against the master movement. CONCLUSION (a) Rear view (b) Side view Fig.13 Structure of wrist device COOPERATED MOVEMENT USING DEVELOPED DEVICE In this section, the cooperated movement using the master and slave devices is experimented. The master and slave subjects use each device as shown in Fig.14. The master subject moves the hand at 10s in period by using all upper limb joints to draw a circle, which is about 300[mm] in diameter. The slave subject does not The purpose of this study is to develop a wearable master-slave upper limb training device for a trainer and a trainee. In this paper, the structure of developed device has been discussed, and then the cooperated movement has been described. Table 1 Main system parameters Parameter Explanation about parameter Unit θ s θ sh1 θ sh2 θ sh3 Joint angle at slave device Part Shoulder Movement Flexion/Extension Abduction/Adduction Internal rotation /External rotation θ el Elbow Flexion/Extension rad θ wr1 θ wr2 Wrist Palmar flexion /Dorsal flexion Ulnar flexion /Radial flexion Fig.14 Image of experiment θ wr3 Pronation/Supination θ m Joint angle at master device rad

6 (a) θ sh1 (b) θ sh2 (c) θ sh3 (d) θ el (e) θ wr1 (f) θ wr2 (g) θ wr3 Fig.15 Experimental results and definition of each angle about cooperated movement In flexion / extension and internal / external rotation, the generated torque from rubber muscle may be smaller than the required one to move the human body. It is the future work to cope with both the compactness and the increase in the generated torque. However, another slave angles can follow the master angles. It is another future work to improve the angle response against the master movement. REFERENCES 1. A.Chu, H.Kazerooni, A.Zoss, On the Biomimetic Design of the Berkeley Lower Extremity Exoskeleton(BLEEX), Proc. of the 2005 IEEE International Conference on Robotics and Automation, pp , Y.Mori, K.Takayama, T.Zengo, T.Nakamura, Development of Straight Style Transfer Equipment for Lower Limbs Disabled: Verification of Basic Motion, Journal of Robotics and Mechatronics, Vol.16, No.5, pp , J. Nikitczuk, B. Weinberg, C. Mavroidis, Rehabilitative Knee Orthosis Driven by Electro-Rheological Fluid Based Actuators, Proc. of the 2005 IEEE International Conference on Robotics and Automation, pp , D.Sasaki, T.Noritsugu, Development of Wearable Master-Slave Training Device Constructed with Pneumatic Rubber Muscles, Proc. of the 18th IEEE International Symposium on Robot and Human Interactive Communication RO-MAN2009, pp.91-96, H.Kobayashi, T.Siiba, Y.Ishida, Realization of All 7 Motions for the Upper Limb by a Muscle Suit, Journal of Robotics and Mechatronics, Vol.16, No.5, pp , 2004.