This week we continued to work on the accelerometers, but found out it was a lot more complicated and had more issues than expected. We initially tried to use a door hinge mechanism to test the angle, but it varied as we moved it around. This was likely due to the fact that the acceleration of the accelerometers around by any movement could change the acceleration reading on the accelerometer. Thus there was an addition of error in the angle. After talking with Dr Klaesner about our problems, we realized that accelerometers would be a challenge to work with, as there were additional technical issues such as finding the constants to integrate from acceleration all the way to position, and dealing with complicated matrix math. Dr Klaesner suggested we use a potentiometer, which would be easier according to him. Chris and Galen are beginning to design a rotational potentiometer to test the angle. Galen will begin working on the CAD drawing in order to make the two rods that will attach the potentiometer at two different points. Chris will begin the coding process. On February 21, we talked with Dr. Yin about the change from accelerometer to potentiometer. He was okay with the change, but expressed concerns regarding stability as the potentiometer might move. The stability will likely decrease with the addition of the glove.
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This week we continued to work on the project attempting to determine what the issue with the accelerometer was. We also started to write our Verification and Validation report by outlining points for discussion. Galen helped to create a figure illustrating the specification regarding the feedback based on the angular displacement using Matlab and Adobe Illustrator. Olivia helped to work on the timeline and listing the design specifications. Chris worked to get the prototype started by debugging the accelerometer and potentially use Professor Widder’s accelerometers for our initial design. We discovered that the accelerometers we purchased use the SDA and SCL pins on the Arduino, meaning each Arduino can only support one accelerometer since each only has one of each of those types of pins. Chris then attempted to use two of Professor Widder’s accelerometers that use typical analog pins and was able to measure the angle between the two accelerometers with fair accuracy using only the z acceleration for both, but they must both be in the x-y plane for this approach to work. Next, Olivia will try finding the angle between the two accelerometers using all three axis and eliminating the same-plane limitation of a one axis approach. To read all three axis, however, three pins must be used for each Arduino with there only being six analog pins total. We may have to look into interfacing several Arduinos at once in order to use the appropriate number of accelerometers at once. We haven’t scheduled it yet, but we will reach out to Professor Klaesner for feedback on our progress and concerns about the accelerometer accuracy.
At the end of last week, two sensors arrived in the mail, and we were able to begin our first prototyping iteration. We soldered pins into the first pair of accelerometers that we will use for this first prototype. After downloading the test code for our chosen accelerometers, however, we found that they did not work. We suspected there were issues with the soldering, but we weren’t able to find a solution by the end of our team meeting on Friday. We had planned to correct this on Monday of this week.
Yet this week we were not able to go into Widder’s lab on Monday because of a biomechanics lab using the laboratory space. We plan to ask Professor Widder about whether the orientation of the pins is affecting the device. We plan to meet on Friday again to work and diagnose the problems from last week. We as a team also need to determine more times when we can meet during the week to move the building phase along faster. Moving forward, we will try to work more individually and divide up tasks in getting our first prototype running. We will also look to meet again with Dr. Carter to confirm our new specifications and metrics, but hopefully with at least a basic prototype in hand. On Friday of the last week we met with our client to update him on our status at the end of the first semester. Following Professor Yin’s advice we confirmed with our client what information exactly the client wants to deliver to the patients. Rather than having a binary feedback response based on whether or not the patient meets the feedback threshold, the client wants the feedback to increase linearly as the patient’s movements increase towards threshold. We will proceed with this in mind as we move to prototyping.This week, we met on Sunday to discuss what our plan for designing our first prototype will be. This first concept is to look to test the minimal design needs. We will utilize two accelerometers to obtain one joint angle and determine how effective this system is. We plan to get 3-axis Adafruit accelerometers from Amazon.
After meeting with Dr. Yin and our client last week, we updated our specs on Tuesday. Our specs are more quantitative, and we have a clearer understanding of how we can test whether our prototype has met the design needs in preparation for the Validation and Verification report. This Friday, we will begin our first building phase in Professor Widder’s lab. We plan to use wires and Arduino that Professor Widder has in the lab and the accelerometers should have arrived by then. Olivia who ordered the accelerometers will submit a reimbursement form to Professor Klaesner by the end of the week. |
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April 2018
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