Pneumatically Driven Prehension Orthosis with Force Control Function

Abstract

A prehension orthosis with a pneumatic actuator has been developed to compensate for the disability of cervical cord injury patients and support their daily activities. One major feature of this orthosis is that the user can continually pinch or hold a target object using a finely adjusted finger force. The movement and force applied to the fingers can be controlled by continuous instructional signals fromthe user through the activity of a command muscle, which is selected from among the muscles without functional impairment in the user’s body. The level of muscle activity can be obtained by using an original sensor that detects the hardness of the target muscle through contact with the skin. The level of muscle activity can be estimated by the hardness information of the muscle. This sensor is easily fixed to a user’s body by using an elastic belt and even works over clothing. Therefore, the user can wear the system very easily. This feature allows the system to be very user friendly. Users can handle fragile objects such as an egg or sculpted-glass by using this prehension orthosis because of its finger force control function. Excellent dexterity in the finger force control has been demonstrated through evaluation tests conducted with various subjects, including a spinal cord injury patient.