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Design Requirements
Design Requirements
Figure 5: The list off all design requirements considered when competing the final design.
Final Design
Final Design
The Overall function of pump is to regulate the pressure inside the lower body suit.
1. PID controller takes in pressure and outputs a PWM wave to control the motor.
2. Air inlets allow for dissipation of heat generated by wearer.
3. Outputs values to an LCD screen for external monitoring.
Take a look at the final testing set up!
Figure 6a: The testing set up with pressure chamber attached to all necessary sensors along with the vacuum pack.
Figure 6b: A closer look at the pressure chamber with the computer directly obtaining all the necessary data from the sensors and Arduino.
Vacuum Wiring
Vacuum Wiring
The Makita XCV10 vacuum was rewired to be controllable by an Electronic Speed Controller (ESC) and an Arduino UNO. The ESC is connected to the brushless motor through its Hall Sensors and Phase A, B, and C wires and to the batteries. Most importantly connected to the PWM connection on the ESC is the Arduino, the brain of the system.
Figure 7a: The main vacuum wiring with appropriate labeling of each component necessary for reassembly.
Figure 7b: The final vacuum wiring complete with assembly of 3D prints.
How is the Arduino the brain of the system?
How is the Arduino the brain of the system?
DATA COLLECTION ON PRESSURE CHAMBER
After Vacuum wiring test can now be done on the constructed pressure chamber. The testing protocol is on display in Figure 5.
Figure 8: The testing procedure for collecting the data of the vacuum control on the pressure chamber.
Overall System Performance
Overall System Performance
Robustness
Capable of reaching pressure of -20 mmHg
50 second rise time
Zero steady error
> Key finding: Controller is able to quickly return back to steady state following changes in air flow
Resiliency
Opened 1 cm inlet at approximately 180 seconds
Closed 1 cm inlet at approximately 440 seconds
> Key finding: Controller is able to respond to varying levels of air flow
Figure 9a: Pressure Response of Chamber at 15 mmHg with no added air inlet.
Figure 9b: Pressure Response of Chamber at 10 mmHg with varying air intake at approximately 180 seconds and 440 seconds.
Pressure Feedback Loop Simulation
Pressure Feedback Loop Simulation
The controller values from the Matlab simulation were adapted into Arduino PID control code. With the controller values: Kp=0.5 V/mmHg, Ki=0.5 V/mmHg, Kd=0.025 V/mmHg the simulation predicted smaller voltage and a quicker response time than our experimental results.
Figure 10a: Pressure Response of Chamber at -10 mmHg with no air inlet.
Figure 10b: Simulation pressure response at -10 mmHg with no air inlet.
What Worked Well...
General response of the trends that we get from testing on the pressure chamber
Shows the rise time is unaffected by the target pressure difference
> Key finding: Somewhat indicative of the response at larger pressure differences like -20mmHg.
Areas of Improvement...
Longer rise time and maximum PWM values since our motor had to do a lot more work to create pressure differences than our simulation predicted
Incorporating air inlets
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