Week 9

 Continuation of Design Details

This week primarily continued our focus of a more in-depth redesign of each module so that we can more efficiently build the initial prototype once parts are available.

Motor Backdrivability and Tracking (Elijah)

• Once deciding that the ClearPath-SC line was the most probable motor for our application, we needed to make sure that specific functions were possible.
• This first of these functions was backdrivability, which seems to be most probable through the motor's torque limits, which are programmable in both directions. A excerpt from the user manual detailing this can be seen below:

• The excerpt shows ClearPath's native motor control program, ClearView. When doing further research if it is possible to adjust these limits through the C++ API, it does seem possible through the sFnd::ILimits::TrqGlobal attribute.

• It is important to note that the documentation says the torque limit is not typically changed during an application, but this infers that it has the ability to do so.
• In terms of position tracking, the motors seem capable and would be the most probable way to define courses in our final application. Functions like the following would be the key to bridging the gap between final handle position and motor angle/position.

Linkage Arm Shaft Calculations and Design (Sean)

•  Another continued module of interest this week were the linkage arms and their interactions, specifically the mathematics behind them to ensure future success.
• Calculations began with the weight of the tubes used, as seen below:

• Time was also dedicated toward laying out the views of the linkages to gain the best understanding of their interactions.

• Then free body diagrams were developed with accompanying force calculations.

• Finally, various things like bending and stress analyses were conducted, along with a summary of the details used throughout the calculations.

Device Dimensions and Motor Mounting (Gavin)

• This week we had obtained updated dimensions for the overall robot due to involving new assumptions (such as the motor mount not obstructing the linkage arms if they bend back past the 180 degree line). 
• These updated linkage lengths were calculated using the Matlab program developed over the past few weeks, but a now more finalized version involving our new information.

• This allowed us to shorten the handle arm from 23 inches to 17, and change the geometry to a more force efficient diamond shape instead of a paw.
• In addition to linkage dimensions, with the probable motors more defined, the mounting system has begun to take shape to house the two motors, which are considerably heavy (25 pounds each).

• Multiple designs have been discussed modeled, with more finalized models looking like the one below where the motors are on an independent stand rather than connected to the table seating the user.

• More details on the mounting module such as interaction with a table, height of operation, and reduction of moments will be solidified once out available parts due to budget are in place. 

Handle Design and Connection (Nathan)

• Also continuing this week is the design of the user's handle, especially the rotation model that allows the user to select between a range of angles for the most comfortable experience.

• The handle is also planned to contain a forearm rest so that the user does not have to exert constant effort to keep their hand up in the air.
• Unfortunately this week, Nathan is out due to Covid, thus more work on the different handle designs and connections are planned for the near future.

Overall Team Meeting and Preparation

•  As this week was more segmented between team members working on their own modules, the important concept of keeping on the same page was stressed to avoid cases such as the linkage calculations using previous length specs. 
• Our weekly meeting primarily revolved around stating all of our known and proposed information so that each person on the team can design with the same content available.

• An important note from the meeting was the establishment of a goal for this semester, in which we aim for a prototype utilizing 

1. a single mounted motor
2. 4 link system
3. single handle type
4. basic course correction mode (or suggested by Dr. Kim, a mode in which the robot moves by itself).

• This would allow us to pinpoint areas to focus on in the next semester to deliver the best product possible.
• It is also expected that this first prototype not contain all the final product materials, as the manufacturing time correlated with some finalized modules could be too long for our current semester schedule.