Work/PID LOX Ball Valve
Replacing a bang-bang solenoid with a valve a controller can actually steer.
Jake's PID-driven ball valve for Columbia Space Initiative, cut open along the flow line. A brushless servo turns the ball through a splined coupler; an outer PID loop on tank pressure commands the ball angle and an inner loop drives the servo to it (the cascaded control he planned), holding the LOX tank at 450 psi against a 4.5 ksi supply.
Overview
A solenoid valve is open or shut. To throttle liquid oxygen into the combustion chamber the team needed a valve whose flow tracks a command, so a PID loop can hold the tank where it should be.
Tools
- Python
- PID
- BLDC
- CAD
- simulation
- When
- Sep 2024 to now
- Where
- Columbia Space Initiative · Propulsion Fluids
- Role
- Propulsion Fluids Member
valve.
A ball valve on a brushless motor, steered by PID.
Finalized a PID operated ball valve, driven by a brushless motor, to control LOX flow in place of the solenoid valve.
Ran simulations to check the valve against 4.5 ksi upstream while maintaining the LOX tank's 450 psi internal pressure.
control.
Linear flow keeps one set of gains good across the whole stroke.
Modified the valve so flow is as linear as possible in angle, which keeps the PID's gains valid across the whole stroke.
Planned cascaded control: a secondary loop nested inside the primary PID.
analysis.
The numbers behind the fit and the flow.
Wrote the Python analysis of LOX flow nonlinearities, turbulence and thermal contraction, including the interference-fit contact pressure for the insert.
