Limits...
Design of a novel telerehabilitation system with a force-sensing mechanism.

Zhang S, Guo S, Gao B, Hirata H, Ishihara H - Sensors (Basel) (2015)

Bottom Line: Patients' safety is guaranteed by monitoring the motor's current from the exoskeleton device.To compensate for any possible time delay or data loss, a torque-limiter mechanism was also designed in the exoskeleton device for patients' safety.Finally, we successfully performed a system performance test for passive training with transmission control protocol/internet protocol communication.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan. s13d505@stmail.eng.kagawa-u.ac.jp.

ABSTRACT
Many stroke patients are expected to rehabilitate at home, which limits their access to proper rehabilitation equipment, treatment, or assessment by therapists. We have developed a novel telerehabilitation system that incorporates a human-upper-limb-like device and an exoskeleton device. The system is designed to provide the feeling of real therapist-patient contact via telerehabilitation. We applied the principle of a series elastic actuator to both the master and slave devices. On the master side, the therapist can operate the device in a rehabilitation center. When performing passive training, the master device can detect the therapist's motion while controlling the deflection of elastic elements to near-zero, and the patient can receive the motion via the exoskeleton device. When performing active training, the design of the force-sensing mechanism in the master device can detect the assisting force added by the therapist. The force-sensing mechanism also allows force detection with an angle sensor. Patients' safety is guaranteed by monitoring the motor's current from the exoskeleton device. To compensate for any possible time delay or data loss, a torque-limiter mechanism was also designed in the exoskeleton device for patients' safety. Finally, we successfully performed a system performance test for passive training with transmission control protocol/internet protocol communication.

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Prototype of the master device (i.e., a human-upper-limb-like device).
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sensors-15-11511-f004: Prototype of the master device (i.e., a human-upper-limb-like device).

Mentions: A prototype of the master device was designed as shown in Figure 4. As mentioned above, we selected a weight-to-torque ratio motor (ARM66AC-PS25; Oriental Motor, Tokyo, Japan) to provide sufficient force/torque performance. The maximum nominal output torque of the driving unit is limited to 16 N·m by the mechanical strength of the planetary gear. An unavoidable problem with large reduction ratio gearheads is non-backdrivability resulting from the high-reflected inertia and friction; i.e., the motor cannot be turned by an outside force acting on its output shaft. To obtain variable impedances or a compliant joint, elastic elements have to be added between the motor shaft and output of the device. This kind of mechanism is called an SEA, and it can provide many benefits in force control [23,24,25]. Specifically, SEAs realize high shock tolerance, low reflected inertia, high energy-storage capacity, and accurate/stable force control. The newly proposed design in the master device measures the elastic element deflection, and the deflection is relative to the sensed force. To magnify the deflection and measure it at the extreme part of the master device, a long steel bar is installed on the motor shaft parallel to the elastic element. This method can effectively decrease the signal-to-noise ratio, because the deflection of elastic elements is usually designed quite small to enlarge the force bandwidth.


Design of a novel telerehabilitation system with a force-sensing mechanism.

Zhang S, Guo S, Gao B, Hirata H, Ishihara H - Sensors (Basel) (2015)

Prototype of the master device (i.e., a human-upper-limb-like device).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481901&req=5

sensors-15-11511-f004: Prototype of the master device (i.e., a human-upper-limb-like device).
Mentions: A prototype of the master device was designed as shown in Figure 4. As mentioned above, we selected a weight-to-torque ratio motor (ARM66AC-PS25; Oriental Motor, Tokyo, Japan) to provide sufficient force/torque performance. The maximum nominal output torque of the driving unit is limited to 16 N·m by the mechanical strength of the planetary gear. An unavoidable problem with large reduction ratio gearheads is non-backdrivability resulting from the high-reflected inertia and friction; i.e., the motor cannot be turned by an outside force acting on its output shaft. To obtain variable impedances or a compliant joint, elastic elements have to be added between the motor shaft and output of the device. This kind of mechanism is called an SEA, and it can provide many benefits in force control [23,24,25]. Specifically, SEAs realize high shock tolerance, low reflected inertia, high energy-storage capacity, and accurate/stable force control. The newly proposed design in the master device measures the elastic element deflection, and the deflection is relative to the sensed force. To magnify the deflection and measure it at the extreme part of the master device, a long steel bar is installed on the motor shaft parallel to the elastic element. This method can effectively decrease the signal-to-noise ratio, because the deflection of elastic elements is usually designed quite small to enlarge the force bandwidth.

Bottom Line: Patients' safety is guaranteed by monitoring the motor's current from the exoskeleton device.To compensate for any possible time delay or data loss, a torque-limiter mechanism was also designed in the exoskeleton device for patients' safety.Finally, we successfully performed a system performance test for passive training with transmission control protocol/internet protocol communication.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan. s13d505@stmail.eng.kagawa-u.ac.jp.

ABSTRACT
Many stroke patients are expected to rehabilitate at home, which limits their access to proper rehabilitation equipment, treatment, or assessment by therapists. We have developed a novel telerehabilitation system that incorporates a human-upper-limb-like device and an exoskeleton device. The system is designed to provide the feeling of real therapist-patient contact via telerehabilitation. We applied the principle of a series elastic actuator to both the master and slave devices. On the master side, the therapist can operate the device in a rehabilitation center. When performing passive training, the master device can detect the therapist's motion while controlling the deflection of elastic elements to near-zero, and the patient can receive the motion via the exoskeleton device. When performing active training, the design of the force-sensing mechanism in the master device can detect the assisting force added by the therapist. The force-sensing mechanism also allows force detection with an angle sensor. Patients' safety is guaranteed by monitoring the motor's current from the exoskeleton device. To compensate for any possible time delay or data loss, a torque-limiter mechanism was also designed in the exoskeleton device for patients' safety. Finally, we successfully performed a system performance test for passive training with transmission control protocol/internet protocol communication.

Show MeSH
Related in: MedlinePlus