Robocodo

Therapists often spend hours working with a patient to loosen the elbow joint manually (through humeroulnar distraction) after surgery to help the elbow recover flexion and extension mobility. There is a need for a device that can do this automatically so that the therapist can be free to work on other parts of the rehabilitation process to decrease rehabilitation time and maximize recovery.

Problem Definition
Problem Statement The Tecnalia Reasearch & Innovation in Donostia-San Sebasián, Spain has a prototype that weighs more then they expected. They are asked us to make a device that would create a humeroulnar distraction on the elbow. The device has to be less then 1 Kilogram (Kg) and apply 100 Newton (N) linear force 35-40 Newton meter (Nm) torsional force.



Design Goals and Deliverables  Document which solutions to pursue and which one didn’t work, and explain why it didn’t so they won’t waste there time repeating the same mistakes as us.    The gadget should be; confortable, wearable, weight < 1Kg, and have a safety release 	mechanism.  Specifications  Mobility: Keep arm rigid and allow for adjustment of different angles of pronosupination. The device should allow for a linear motion, which will apply a force just distal to the elbow, as well as a rotational motion, which will apply a torque to the forearm. Once an angle is chosen, the device should hold the arm rigidly in this position. Misalignment or rotation of the elbow during use could cause injury. The primary opposition to holding the arm rigidly is skin slippage. The motion of the skin allows the underlying bone structure to become misaligned even though the arm is being held tightly.  Strength/Motion: The device should be able to provide a linear force of 100 N and a torsional force of 35–40 Nm. The motion, which the device must recreate, is as follows:  1. A force of up to 100 N is placed just distally to the elbow. This is done to release the ulna from the humerus.  2. After the ulna is released a torque of 35-40 Nm is applied to rotate the forearm.  3. In some cases it is necessary to bring the elbow to its full extension and oscillate back and forth.

 Weight: Mass should not exceed 1 Kg at the forearm The device should ideally be as light as possible. The goal is to maximize patient comfort. To accomplish this, an effort should be made to keep the majority of the weight of the device proximal to the shoulder or back. If the weight must be placed distally on the arm, it should not exceed 1kg.  Safety: Easy to activate quick release There is always the possibility that a mechanical device can act in an unexpected way or a patient to react poorly to the procedure. For this reason, the device should have some sort of quick release mechanism, which will immediately release all pressure on the arm. The release mechanism should be easy to activate by both the therapist and the patient.  Feedback: Position feedback for FES In order for the FES system to activate at the right time, the mechanical system must be able to provide some sort of feedback which describes its current position.

<h5 style="text-indent: 20px"> Power: Grid Power Using Medical Grade Power Supply Although the final device is intended to be powered by a lightweight and compact battery pack, it is sufficient for this project to power the device using power supply running off of mains power. If possible, the power supply should be medical grade. All of the wiring should be kept neat and should in no way inhibit the movement of the device or increase risk to the user.

Project Learning
Thermoplastics research

<p style="text-indent: 50px"> Use: for attaching device to forearm and hand to minimize skin slippage during use. <p style="text-indent: 50px"> Low temperature thermoplastics: can be molded directly onto forearm and hand <p style="text-indent: 50px"> Rigidity: of thermoplastic will be adequate to fix forearm in place <p style="text-indent: 50px"> Memory:  of thermoplastic enables us to reheat and remold our design if it does not mold correctly the first time <p style="text-indent: 50px"> Specific Thermoplastics:  Rolyan Aquaplast, Omega Max Smooth, Rolyan Orthoplast <p style="text-indent: 50px"> Cost:  $40-80 per 1/8”x18”x24” sheet

Micro-Controler <p style="text-indent: 50px"> Adafruit Metro Mini will be used because it is light wieght and also fast enough with this project with 16MHz. <p style="text-indent: 50px"> Bluetooth module HC 05 will connect to the Adafruit Metro Mini and to the computer wirelessly

Example
Motor/Linear Actuators Looked into several linear actuators but found that servos that weight under 100g cannot product more than 200N of force, actuators that can produce over 200N of force jump up to a 800 to 1000 gram range. For this project it is more ideal to use several 100g actuators than it would be to compromise our weight goal of under 1kg by using the more powerful actuator.

<h5 style="text-indent: 20px">140 mm Stroke 44 lb Thrust Light Duty Linear Servo <p style="text-indent: 50px"> This servo is extremely light and also provides sufficient force for the distraction motion. <p style="text-indent: 50px"> It does not provide enough force to achieve the desired 40N/m of torsion on the forearm <p style="text-indent: 50px"> These motors are small enough that we could run several in parallel to increase the force and achieve 40N/m <p style="text-indent: 50px"> The motor moves at too slow of a speed to achieve the desired 30 to 90 degrees/sec extension of the arm while maintaining 40N/m, but with correct gear ratios we believe we can complete the extension going at 18 to 36 degrees/sec