Our goal for this project was to design a product that would improve the quality of life of our client James, who was diagnosed with Ehlers-Danlos Syndrome. In our initial meeting with him he presented a variety of potential problems for us to tackle. The problem we decided to create a solution for was reducing the discomfort caused by trying to grab small pieces and reach across the table when James plays board games with his son. The final prototype was a table mounted, linearly actuating arm with a gripper on the end. The base and arm components were constructed out of wood, while 3D printed parts were used for the handle, two-axis joint, linear actuation mechanism, and gripper. The two arm is controlled by four capacitive touch sensors mounted on an ergonomic handle with the functions: open gripper, close gripper, extend arm, and retract arm. The capacitive touch sensors interact with the stepper motors that open and close the gripper and extend the arm through an Arduino running a simple C++ program. The Arduino (Nicknamed JOHN for James’s Other HaNd). Detects a reading from one of the 4 capacitive touch sensors on the handle and then, depending on the actions, it tells one of the servos to rotate clockwise or counter clockwise which results in the gripper opening or closing, or the arm extending and retracting. The prototype offers many benefits to James. First, the device has a low impact on the body as it is self-supporting, so it does not put any weight on his weaker joints such as the shoulders. The arm is mounted so that it is balanced when it is half extended, making it easy to lift at both zero and full extension. The use of capacitive buttons to control the movement also reduces stress on the finger joints, as no pressure is required to activate them. Another benefit of the prototype is that it allows the user to be in complete control of their play. This ensures that James is fully involved with the game, instead of needing help from the other players.
Given more time and money, we would make improvements on the functionality and refinement of the device. The main issue with our final prototype was the inconsistency of the linear actuation. The friction between the inner and outer pieces of the arm was too large for the stepper motor to overcome at times, causing the motor to stall often. To improve on this, we would construct both arm pieces from a low friction material, such as ultra-high-molecular-weight polyethylene which has a coefficient of friction of 0.08 [vv1]. In addition, we would also use a larger sized stepper motor as it would be able to apply a larger force. Both improvements should allow for reliable actuation. Secondly, we would refine the overall construction of our model. Such refinements include the addition of a flush mounted USB port, sanding, routing, and painting of the outer arm piece, and tidier wiring.