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My control systems prof said every engineer has done an inverted pendulum problem in school and nobody in their career has ever been asked to balance an inverte
by bandrami 3y ago
My control systems prof said every engineer has done an inverted pendulum problem in school and nobody in their career has ever been asked to balance an inverted pendulum. So our final was a thermostat instead.
- nullc 3y ago> nobody in their career has ever been asked to balance an inverted pendulum Thats what all those self-balancing scooters are.
- e-_pusher 3y agoSome engineers do balance inverted pendulums in their careers! https://space.stackexchange.com/questions/15486/how-does-the-spacex-falcon-9-first-stage-straighten-for-landing https://space.stackexchange.com/questions/15486/how-does-the...
- goku12 3y agoAn unstable rocket (almost all of the big ones) is an inverted pendulum of sorts. The combined center of thrust and aerodynamic forces is usually below the C.G, and the rocket tends to tip over if not actively stabilized. To add a little, a slight margin of tipping is allowed, but the rocket tends to break up if the angle of attack crosses certain limit at high speeds.
- regularfry 3y agoLiquid fuel rockets complicate matters: think "inverted pendulum with a couple of stacked, full wine glasses that you absolutely must not spill balanced on top. Oh, and there's a gremlin drinking from them so both CG and total mass are constantly moving."
- thfuran 3y agoAlso, it's extremely windy.
- goku12 3y agoTrue. Liquids make control difficult. > full wine glasses that you absolutely must not spill balanced I'm not sure what you mean by spilling. The liquids are usually contained in fully closed tanks and cannot spill. The thrust usually keeps the liquid at the bottom around the engine intakes. However, liquid sloshing inside the tanks is a problem. Even with slosh dampers, sloshing liquid manages to create attitude disturbances that can cause control instability unless managed carefully.
- yetihehe 3y agoI think they also don't actually use wine, gremlins or any glass containers...
- TeMPOraL 3y agoMy inner child of Doc Brown and Wernher von Kerman says, it's time to develop non-newtonian fuel sponges, which would release fuel if squeezed gently and steadily, but behave like solid if things start shaking too much, preventing sloshing.
- yetihehe 3y agoOr maybe giant syringes? There can't be sloshing if there is no free space because top of cylinder just moves to adjust volume.
- tnecniv 3y agoClearly your professor hasn’t had to stand upright in his career or walk for that matter. The (spring loaded) inverted pendulum was one of the earliest analyzed models of legged locomotion.
- FirmwareBurner 3y agoYeah, his professor wasn't too bright if he said that. He probably never heard of Segway, One-Wheel, "hoverboards", or motorcycles with stability control.
- bandrami 3y agoNone of which existed in 1995
- FirmwareBurner 3y agoOk, then how about the gun barrel stabilizers on tanks and gunships which had PID controllers since WW2.
- bandrami 3y agoNow compare those to the number of thermostats built since that time
- jcarrano 3y agoHolding a fixed position on a double integrator system (like a hovering drone) in discrete time is a nice problem too.