We developed an assistance apparatus for upper limbs for patients who can control their finger but they cannot lift up their arms themselves, for example myopathy and hemiplegic patients. The mechanism of assistance is utilized the differential gears to lose the weight and volume of the mechanical arm. That enabled us to configure three motors to drive two DOFs (Degrees of freedom) for the shoulder and one DOF for the elbow around the root of the mechanical arm. This arm has two support trays, for wrist and upper arm. Furthermore, to realize other ADL (activities of daily living) motions (for instance, eating, writing, putting on makeup, wiping his/her face, and so on) them selves, we proposed to control the device using the targeted posture map for the mechanical arm. To be able to choose the appropriate input for each patient, various input interfaces, for example, joy-stick, push buttons, sensor glove using bending sensors, and so on, are equipped.
In general, even though a human behaves an atonic motion, the maximum voluntary contraction (%MVC) outputs at least from 5 to 10%. The usage of this apparatus is to move the user’s upper limbs with dependence completely, and the purpose of this apparatus is to decrease the value of %MVC up to approximately 10%. Therefore, in this paper, the muscles of the user were evaluated with the ratio of %MVC. To confirm the effectiveness of assistance ability, we measured muscle activity while using the device, and compared the %MVC data between using the device or not. As a result, the activity decreased up to 80%, and the effectiveness of this device could be confirmed.
Finally, to expand the usage of this apparatus to encompass Neuro-Rehabilitation as well, we measured cerebral activity while using the device for rehabilitation with a near-infrared spectroscopy (NIRS). Then we compared the data from using the device or not, and input motion from a third person. By using this device, the cerebral activity decreased especially when the target motion was complex. However, when the subject input the motion themselves, the cerebral activity increased more than when the data is input by a third person, especially, when the target motion was complex. Therefore, for use in Neuro-Rehabilitation, we found it is important the subject input the target motion him/herself.