Week 4

     At the end of last week, we had created decision matrices and had narrowed down our concept options. This week, we discussed the advantages of using either a spring system or elastic band system as the primary means of resistance with our project Tech Advisor (Dr. Gordon). This was also determined to be the critical module, because the failure of one of these mechanisms would render the entire device essentially useless.

     As neither one had a clear advantage over the other, it was decided that both would be tested in a shakedown test. We drafted plans to create a very simple two-board system that would represent the upper arm, forearm, and elbow joint. We are planning on attaching constant force springs and strings to the arm, and testing the moment generated using a force transducer. We will do the same thing with elastic bands, and then compare the two results. 

Critical module testing. This picture shows the two boards representing the arm and the spring system that would be used. 

This shows the test using elastic bands. 

Additionally, Isaac Need designed a spring casing in Solidworks which will be 3D printed. This will hold the constant force spring and keep it from moving. 

     The following shows some of our ideas from brainstorming modules. 

Module categories.

The items in red are examples of module brainstorming.

     We felt that we could not move forward with further detailed designs on specific modules until after we perform the shakedown tests and decide which method we will utilize (all of the modules depend on our method).

     We ordered parts for our shakedown tests, which should be arriving at the beginning of Week 5. We will then construct the test described above, and move forward with our designs.