A Low Cost Wrist Robot for Quantitative Upper Limb Assessment and Personalised Unilateral Stroke RehabilitationFollow project
A prototype rehabilitative wrist robot was manufactured and its precision and general design efficacy were evaluated using various experimental methods.
The design incorporates force-sensitive resistors for objective assessment of the user's functional wrist movement. A schematic of the force-sensitive resistor, or FSRs, wiring to the Arduino UNO can be seen below.
The FSRs are wired to the Arduino's analog inputs for recording and analysis of the force sensitive resistor readings. The force-sensitive resistors are integrated with the handle of the rehabilitative wrist robot. To assess whether this design concept was effective at objectively measuring force an experiment was undertaken. Force was applied to the handle in four directions and the resulting measurements from the Arduino UNO were recorded. The following graph shows the results of the force experiment.
Events 1-4 indicate the application of external forces in different directions to the device's handle. The response of the four sensors demonstrates the workable concept of using force-sensitive resistors for the assessment of the user's functional wrist movement.
The precision of the device was measured using potentiometers. The experimental setup can be seen in the setup below wherein potentiometers are placed at each rotational centre so the device's location can be measured, as seen in photos a-d below.
The device was moved to eight different goal positions. This was repeated three times for each goal position. Potentiometer measurements were logged throughout the movement to the goal position and averages of its final position were taken. The results from the experiments are shown in the graphs below wherein RUD.x and F/E.x are readings from the RUD and F/E joints, where x=1,2,3 depending on the experiment.
The standard deviation of the results from the experiments shows the device has a minimum precision of 1.6 degrees and a maximum precision of 0.12 degrees. This demonstrates the device's usability for the rehabilitation of patients as it can be safely used by patients.
Manufacture of a prototype of the device allowed for full design validation and the results facilitate design improvements including improvement of force-sensitive resistor resolution and improvement of accuracy through minor design changes.