Our first idea was to use springs. The user has to pull or press the spring in order to exercise his or her hand. A motor can be used in combination to initialize the springs and to provide extra tension. Hence the motor can also be used to create the concept of different "levels". These levels mean there will be different gradations at which it will be harder to complete a full cycle. A cycle would mean pulling or pushing the spring the whole way.
Animating the process will be done using an attached screen. The basic ideas are to make a progress bar, and display the current level/difficulty, and a score.
As an added bonus, the plan was to integrate our rehabilitation tool with a joystick for increased interactivity. A "pinch" would in that case stand for a click, so that the robot could be used in combination with a computer.
The first idea to track the position of the hand during a cycle would be to use a linear potentiometer. However, linear potentiometers have a couple of disadvantages:
Therefore we opted for Hall effect sensors, which have several advantages: