Require assistance in Modelling a Vacuum Pump

Hello all

I am experienced in Simulink however I am new to Simscape (just finished the Simscape Onramp)

I need to simulate a diaphragm vacuum pump run by a BLDC motor to maintain a certain negative pressure

I think I can manage running the BLDC side of it but I am clueless in how to approach the problem of modelling a vaccum

Any and all assistance would be welcome

Thank you

[Yifeng Tang]

Do you have access to Simscape Fluids? You may start with a Positive-Displacment Compressor (G) block. My understanding is that a diaphragm pump/compressor tries to move a certain volume of gas with every movement/rotation, which is similar to what the compressor block above does.

Depending on what type of information you have, you may choose either "Volumetric displacement " or "Nominal mass flow rate and shaft speed" to specify the performance.

If you have more information on this pump, feel free to share and I can try to provide further suggestions.

Answer 1

[Umar]

Hi @Anirudh,

Following your comment, I've compiled a comprehensive blueprint for simulating a diaphragm vacuum pump driven by a BLDC motor in Simulink/Simscape Fluids, with a focus on maintaining a target negative pressure. This guide is tailored for someone experienced in Simulink but new to Simscape.

1. Motor Subsystem (BLDC Motor)

Block: Permanent Magnet Synchronous Machine (Simscape Electrical) This block models a three-phase permanent magnet synchronous machine, suitable for simulating BLDC motors. ([MathWorks][1])

Inputs: Voltage source controlled by a PID controller

Outputs: Shaft torque drives the pump

Optional: Include electrical dynamics (resistance, inductance) and mechanical dynamics (rotor inertia, damping)

2. Pump Subsystem (Diaphragm Pump)

Block: Positive-Displacement Compressor (2P) (Simscape Fluids) This block represents a positive-displacement compressor, such as a reciprocating piston, rotary screw, rotary vane, or scroll, in a two-phase fluid network. ([MathWorks][2])

Inputs: Mechanical shaft from the BLDC motor

Configuration: Specify volumetric displacement per stroke; optional efficiency table

Optional: Time-based pulsation source to mimic diaphragm motion

3. Vacuum Chamber (Negative Pressure)

Block: Gas Volume (Simscape Fluids)

This block models mass and energy storage in a gas network, representing the vacuum space. ([MathWorks][3])

Connections: Inlet from pump; optional outlet to simulate leakage

Sensor: Pressure Sensor measures chamber pressure

4. Check Valves

Block: Check Valve (2P) (Simscape Fluids) This block models a directional control check valve in a two-phase fluid network, ensuring correct flow direction and preventing backflow. ([MathWorks][4])

Placement: Pump inlet and outlet

5. Feedback Control Loop (Maintaining Negative Pressure)

Sensor: Pressure Sensor measures chamber pressure

Controller: PID Controller adjusts motor voltage/current to maintain target negative pressure

The PID Controller block implements a PID controller, outputting a weighted sum of input, integral, and derivative signals. ([MathWorks][5])

Notes: Carefully tune the PID to avoid overshoot or oscillations; a low-pass filter can smooth pulsatile pressure

6. Optional Enhancements

Leakage modeling: Use orifice/small flow resistance to simulate air loss

Transient analysis: Capture startup behavior, pressure overshoot, motor ramp-up

Data logging: Use Scope or To Workspace blocks to observe pressure, flow, motor speed, and torque

 *7. Simulation Workflow*

1. Initialize motor, pump, and chamber parameters 2. Connect all subsystems as described 3. Run simulation and monitor chamber pressure 4. Adjust PID and pump parameters to reach target negative pressure 5. Validate against experimental or expected performance

This blueprint integrates the BLDC motor, diaphragm pump, vacuum chamber, and control loop, while explicitly addressing how to model the vacuum and maintain a set negative pressure.

Please see attached.

References

[1]: https://www.mathworks.com/help/sps/powersys/ref/permanentmagnetsynchronousmachine.html "Permanent Magnet Synchronous Machine"

[2]: https://www.mathworks.com/help/hydro/ref/positivedisplacementcompressor2p.html "Positive-Displacement Compressor (2P)"

[3]: https://www.mathworks.com/help/simscape/ref/constantvolumechamberg.html "Constant Volume Chamber (G)"

[4]: https://www.mathworks.com/help/hydro/ref/ "Check Valve (2P) - Check valve in a two-phase fluid network"

[5]: https://www.mathworks.com/help/simulink/slref/pidcontroller.html “Continuous-time or discrete-time PID controller - Simulink"

[Anirudh]

Hey Umar Thank you very much this is exactly what I was looking for

You have put a lot of effort into your reply I want you to know that I really apprecitate it