Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
The expectation for the Preliminary Detailed Design Phase is to complete theoretical analysis to ensure that the ventricle design is feasible. As well as to conduct Simulink simulations to analyze the ideal outcomes of the created system. Advanced Prototyping will also be done in this phase. The mold for the ventricle will be in construction. Cost analysis for the ventricle housing will be done to select the desired material. Originally the LabVIEW program was expected to be generated during this phase. However, time was re-prioritized towards the theoretical analysis. The currently expected outputs for the LabVIEW program for this phase is a detailed diagram for the design of the code.
Action Items from System Level Design
- Decide if the ventricle pump should continue as an option.
- Identify all material in the circulatory system that needs to be replaced.
- Identify the desired tubing
- Generate preliminary LabVIEW program: The LabVIEW program was generated. More emphasis was placed on theoretical analysis during this phase.
- Create and assemble the ventricle prototype: The mold has been created and the detailed design drawings have been created.
- Test the pump against the Engineering Requirements: The pump can not be tested until the prototype is complete.
Updated Design Concept
The vacuum and the air pressure is controlled by the solenoid. The air release is added for safety.
Analysis, Simulations, and Prototyping
- Ventricle fully inflates and deflates during each cycle
- Flow of air is along a streamline
- Fluid has constant density
- Friction is negligible
- Pressure for exit and entrance valves are 80mmHg and 10mmHg respectively.
- Pressure in chamber equals pressure of water
The process of the theoretical analysis was done in four steps.
1. Air Entering Chamber
2. Water Exiting Ventricle
3. Air Exiting Chamber
4. Water Entering Ventricle
The air entering the chamber was calculated using the Bernoulli equation. The velocity of air was found and then the flow rate was calculated using the known inlet diameter for the laboratory air line. Finally time was found using the flow rate and the volume the air will displace. Using this calculated information it was determined that the pressure from the shop air would be sufficient to open the exit valve.
To open the exit valve the pressure in the chamber must be higher than the pressure on the other side of the valve, 80 mmHg. The charts below show the velocity of air entering the camber and the time it takes for the pressure to change in the chamber. The horizontal line is the pressure required to open the valve.
Next it was determined that the increasing pressure would be sufficient to eject the needed stroke volume for the system. The range for stroke volume is determined by physiological conditions, 60 ml to 100 ml. Calculations for water leaving the chamber were done for minimum, maximum, and average stroke volumes. This is a value that can be regulated in the LabVIEW program to ensure accuracy. The end result shows that the amount of volume needed to be ejected from the ventricle is plausible.
Then the time for the air to exit the chamber causing a pressure differential to open the entrance valve was calculated. The pressure needed to open the entrance valve is 10mmHg. This calculation was done for all three volumes in using the Bernoulli equation. The horizontal line shows the pressure needed to open the entrance valve and begin allowing water to flow in.
Finally, the ability for the pressure differential to allow the needed amount of water to enter the ventricle was analyzed. The horizontal line shows the maximum fill volume. The flowing charts show the ventricle is capable of preforming each of the four tasks. A secondary analysis needs to be done for the force applied to the ventricle and the material properties to determine if the vacuum will cause the material to stretch.
SimulationTo better understand the effects that changes in compliance and preload have on the system, a computational model was created using MATLAB Simulink. Using the hydraulic analysis package, a representative model of the circulatory system was created. The Simulink system accounts for all dimensions and losses from tubing, valves, and tanks using real given values. Inputs include the changes to compliance and preload, and the pumping action of the heart, simulated as a sinusoidal wave with a peak value of 5lpm. Results from our simulations acknowledge a decrease in the pulsatility of the wave form as the compliance is increased. Introduction of compliance limits large drops in flow, more accurately modeling a philological waveform
- Input: Sine wave (A=2.5 G=2.5)
- flow of 0-5 LMP pulsatility
- Compliance: triggered at t=15s
- High compliance: xfinal=2cm
- Low compliance: xfinal=.3cm
- Preload: Remained constant
The creation of the ventricle prototype continued during this phase. The Pneumatic Cap Ring and the Hydraulic Ring can be used for both the ventricle design and the adaptation of the previous design. The mold for the silicone ventricle was printed during this phase.
With the ventricle designed in inventor, we were able to use the built in simulation to show ventricle compression with basic silicone material properties.
Bill of Material (BOM)
Diagrams and Flowcharts
Controller Diagram and Design
- Compact design for use in water-tight enclosure
- Removes the need for AC-DC transformer ($65)
- Cleaner, more visible wiring for easy diagnostics
- Din-rail construction allows for easy replication and repair
LabVIEW Flow Chart
Updated SME Meeting Information=
Design Review MaterialsPowerPoint for Design Review
Plans for next phase
Team Action Items
- Generate LabVIEW Program
- Force Analysis on Ventricle
- Build Ventricle Prototype
- Generate Detailed Test Plans
- Generate Detailed MSD2 Plans