Are we cooking…? Or are we fried…? (Something actually got fried, read more to find out…)
30th June – 6th July
30th June:
We started the week off being productive in the lab! Quite a lot was accomplished today as we successfully 3D printed two bracket holders for our linear actuators and drilled holes (view video V4 here) into our aluminium plates which were then mounted onto the actuators. We also made progress on our airbags for the pillow’s upper head support which we tested using air pumps. We ended our day with some soldering work and settled on a block diagram to simplify our pillow’s system for future discussions.
Our Secretary Manatee is back from Laos and becoming a master-driller!
1st July:
Last week, Yaoxiang recommended us to include limit switches into our design. By positioning them beneath the support bars, a click will indicate that the lowest possible position has been reached, and the stepper motors will halt its rotation to stop the support bars in place, which will be useful in our program later on. Our team had initially intended to mount the switch on existing components in the build (i.e. the brackets of the linear actuators), but quickly realised that the movement of the actuators will inevitably be inhibited. To counter this, we designed a holder to lift the limit switch to the ideal height without any obstructions to the moving parts, while ensuring that the set-up can be fixed onto the base plate. After some testing and revisions made, we were satisfied with the snug fit and functionality of the final design (view video V5 here)!
Some light soldering was done to prepare additional film sensors to be used as spares for experimentation. More drilling work was also done on the aluminium strips to refine the dimensions of the holes. The team also continued with experimentations on the air bag system. However, due to shipping delays, we were still unable to construct the two-way air pump system. We remain hopeful that the connectors we require will arrive before the end of the week.
To end our day’s work, our resident engineers worked on finalising the working principle for the pillow. We considered different approaches to calibrate the film sensors. After some intense discussion, we arrived at three possible approaches explained below:
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- Equalise pressure distribution across each support strips.
- Determine ideal pressure range from datasets (the time has come to recruit more test subjects ^‿^).
- Manual calibration completed by user to personalise supine and lateral settings.
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We will dedicate the following weeks to determine which approach is most suited to our design’s function.
Custom 3D prints and honing our soldering skills
2nd July:
To commence our day of work, we continued printing the remaining limit switch holders and actuator brackets. Meanwhile, the team experimented with different methods of attaching sensors to the air pillow. We first placed the sensor on a base plate, with the air pillow above the sensor. However, with this configuration, the sensors were not able to detect any input. Next, we positioned the sensor on the air pillow itself, followed by a layer of foam covering the sensor. With this set-up, the sensors successfully picked up pressure readings. Furthermore, the foam was able to provide additional support for the user (especially when the pillow is slightly deflated). With this observation, we decided to proceed in that direction for our air pillow system.
Next, with the arrival of the Y-connector, we started on working on the two-way air flow system for the air pillow. We began by testing the speed of the air pumps for inflating and deflating to gauge the duration required to increase or decrease the pillow by a certain height. However, we faced some difficulty in accurately determining the height of the pillow due to its flexibility. Additionally, while the pillow could inflate easily, we found deflating it much more difficult. After some investigation, we realised that air was being sucked from the atmosphere via the inflation pump instead of drawing air from the pillow directly (because of the Y-connector’s open airway). With a new problem in sight, we headed back to research and found that a solenoid air valve could be used to segment the air flow depending on which pump was activated, potentially solving our problem. Hence, we decided to purchase it and we are hoping to receive it soon!
A sneak peak into what our final product might look like!
3rd July:
We have reached the last leg of 3D printing! Today, we printed our last few sets of linear actuator brackets before we assemble it to the wooden base and the linear actuators, which we are unfortunately still waiting on them to arrive. We are praying hard that they arrive next Monday so that we can assemble the prototype and work on calibrating it as soon as we can.
Unfortunately we faced a challenge right before we ended for the day. Our prototype did not work when we tried to turn it on! To make things worse, Communicating Manatee’s laptop also almost got fried with his USB port currently unusable (we are so immensely sorry for this our dear Communicating Manatee, we hope Captain Manatee will get a new laptop for you soon). As we are unsure where the problem lies, some troubleshooting is necessary. Seems like our dearest Manatees will have to work extra hard next week!
Communicating Manatee is very sad at the loss of one of his USB ports 🙁