Design

Home Stroke Current Rehabilitators Design Clinical Results References

ARMin

 

Mechanics

- ARMin I

For the mechanical structure of the ARMin robot, a semi-exoskeleton solution was selected. The first prototype of ARMin (ARMin I) was built with four active DoF (three for shoulder and one for elbow actuation). The range of motion (RoM) of the robot corresponds to the natural RoM of a healthy person for all axes except for shoulder flexion/extension. However, since most of the activities of daily living (ADLs) are exercised within the reachable RoM, this is considered to be an acceptable drawback. [14, 15]

Figure 1: Mechanical structure, sensors and motors of ARMin I

Mechanical structure, sensors and motors of ARMin I

- ARMin II

The kinematic structure with four active DoF enables positioning of the hand in the workspace of the human arm. However, in order to achieve functional upper limb rehabilitation, the hand orientation needs to be considered as well to allow grasping and manipulation of objects. In order to allow efficient ADL training, the ARMin robot was therefore extended by two additional active DoF (ARMin II). The two DoF allow forearm pronation/supination, as well as wrist flexion/extension. Fingers are not obstructed by the mechanics of the forearm exoskeleton. Consequently, either voluntary finger activity or use of functional electrical stimulation for grasping is possible. Furthermore, mechanical extensions could be attached. In addition to the two active DoF, two passive DoF were added to accommodate the exoskeleton to different forearm and hand lengths

Forearm Actuation

Forearm exoskeleton with two active and two passive degrees of freedom

ARMin II with a healty test person

ARMin II with a healthy test person

Training Scenarios

Figure 5: Game training scenarios

Game training scenarios

First Scenario : The therapist holds the subject's arm and performs a movement adapted to the individual impairment. The trajectory of this movement is recorded by the robot. Afterward, the robot repeats it, moving the affected limb for 20 minutes. In this part of the training, the subject is instructed to behave passive.

Second Scenario : The subject has to move the red ball on the yellow path and catch the black and yellow colored balls. The walls of the labyrinth (white quadrates) provide resistance, thus guiding the subject on the right way.

Third Scenario : The third scenario serves to train an activity of daily living. The screen displays a virtual table and a cupboard with a plate, cutlery, and a cup. The subject's task is to set the table. The trajectory of the movement can be determined by the subject. However, if he moves to far away from the intended destination, he is leaded back by the robot.

Training scenario Table Setting

Training scenario Table Setting

Back Next