P16061: e-NABLE Hand Test Rig

Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

During this phase, our team planned on prototyping different sections of our final assembly to test feasibility and mitigate risks. The goal was to ensure we have finalized all of our subsystems and ordered the components of each.

We prototyped mounting our clamp to the base and outputting values from the strain gauge. We are continuing to prototype our electronics.

We also attended the Effective Access Technology Conference and represented the MAGIC ACT e-NABLE Lab at RIT and discussed our project with the public.

Subsystem Design Selection

Link to previous Powerpoint

Subsystem Products Chosen Last Phase

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public/Detailed Design Documents/Preliminary/StrainGauge.jpg

public/Detailed Design Documents/Preliminary/Arduino.jpg

public/Detailed Design Documents/Preliminary/MotorShield.jpg

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public/Detailed Design Documents/Preliminary/StrainShield.jpg

Rather than use a single Op-amp, we opted to buy a load cell amplifier shield.

After further analysis, it was discovered that "GoBetwino", the other primary option for exporting data from Arduino to Excel, is also a computer program separate from Arduino. PLX-DAQ was chosen since it was designed specifically to interface between the two. This will allow for the user to display data in the numerous methods Excel has to offer. Additionally, a member of our team has previous experience with PLX-DAQ.

Prototyping, Engineering Analysis, Simulation

Clamp Mounting Prototyping

To make the design modular, the clamp was designed to attach to a piece of wood with a threaded rod (picture of prototype is using much shorter rods than the final apparatus). The design was tested and it was decided that the clamp would need a second rod to make sure the clamp stayed upright. It was proved that the method by which we want to mount the clamp is feasible. The secondary guide rail is necessary to keep the clamp in the desired orientation. The adjustment rod is needed to adjust the clamp's horizontal position in relation to the pivot point.

The following pictures illustrate how we plan to attach the clamp to the base of the tester. Further prototyping will be done to verify that this is the right option for our project.

Clamp Attachment
public/Detailed Design Documents/Preliminary/ClampMount1.jpg public/Detailed Design Documents/Preliminary/ClampMount2.jpg public/Detailed Design Documents/Preliminary/ClampMount3.jpg public/Detailed Design Documents/Preliminary/ClampMount4.jpg

In conclusion, mounting the clamp using the method above is feasible, and easy to attach to the base. Furthermore, the design allows the clamp to be moved to adjust to different sized hands.

After obtaining some hands outside of the MAGIC ACT e-NABLE Lab at RIT for testing purposes, we noticed that the design of the Raptor Reloaded is more curved than the original Raptor. This difference meant that the clamp we had purchased no longer gripped the hand prosthetic as effectively. The hard plastic surface (shown below) makes it difficult to grip a curved surface.

Plastic surface that does not effectively grip curved surfaces.

Plastic surface that does not effectively grip curved surfaces.

Raptor Raptor Reloaded

Our team decided that the best solution was to add our own softer padding that can conform to the hand. We were able to find foam with adhesive on one side. The picture below shows a test run with the padding. By sticking the foam to the clamp, it was able to grip the hand well enough that the hand no longer slipped while the gauntlet was moved.

Clamp with Foam

Clamp with Foam

When layered, the foam is sufficient to improve the grip of the clamp to fit different hand designs. For the final design, a thicker foam would be optimal.

Strain Gauge Prototyping

Our team experimented with the Strain Gauge by connecting its shield onto the Arduino and the gauge. With code provided by Robotshop in a link below, it successfully output readings. However, due to the strain gauge not being calibrated yet the readings didn't communicate the weight values we expected. We attempted to send the strain gauge data to Excel through the PLX-DAQ program, but were unsuccessful for the moment. During the next design phase we plan to contact someone more familiar with the program to discern what we need to fix.

Robotshop Load Cell-Arduino Interface Code

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Test Plans

Tests are organized by equipment necessary to do the test, engineering requirements to be satisfied, and the individual tests for a subsystem with both the procedure and recorded data outcomes.

Link to document here

Apparatus Test


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Cost and Weight Test

This test will be performed by referencing the Bill of Materials and by weighing the apparatus once it is completely assembled.

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Gauge R&R Test

  1. Three team members will set up the test, and perform it with five different hands (for 15 data points)
  2. Collect data from each trial
  3. Input data into software and analyzed for variability
  4. Determine the variability between both different users and equipment

public/Detailed Design Documents/Test/Gauge.PNG

Motor Test


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Duration Test

Start the test and measure how long it takes the fingers of the prosthetic hand to reach 45 degrees from their starting position.

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Torque Test

Attach a bar to the stepper motor, add weights to the end of that bar, and record whether the motor can lift those weights through a full 180° rotation.

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Angle Accuracy Test

Mount protractor to base, with 0° being our neutral position. Input a given number of steps for the stepper motor to move through, and record the angle once it is finished moving.

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Strain Gauge Test


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Max Force and Accuracy Test

Attach load cell to one of the dowel halves and hang the assembly horizontally. Hang different weights off of the load cell and record its readings.

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Design Review Materials

Plans for next phase

Remainder of MSD I

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