Inertial Guidance System.wmv

this is the basic idea behind inertial guidance systems in inertial guidance systems you have a spinning wheel at least in the days that the guidance system had mechanical wheels you have a spinning wheel but that spinning wheel is mounted in such a way that you cannot put a torque on the axis of rotation of the spinning wheel that's the way it's mounted we call it three axial gimballed gyros so the moment that you put a torque on it the housings in this case the yellow and the black housing will start to rotate and you never managed to get that torque on the spinning wheel you never get it on on this axis and therefore if now you put it on your boat or you put it in a plane missile for that matter if you can never put a torque on the spinning wheel and if the angular momentum for spin is in this direction it will stay there forever and ever assuming that we have no frictional losses and then the plane turns the direction of the spin angular momentum will not change but what will happen of course is that this yellow frame will rotate or this black frame will rotate and in these bearings here our shaft encoders and they sense that a rotation that the outer housing makes in order to keep this thing pointing at the same direction and that signal is being fed back to the automatic pilot and that keeps the plane flying in the direction that you want to so you use as a reference all the time the spin angular momentum of your gyro which is now mounted in such a way that you cannot put a torque on it even when the plane changes direction and I want to show that to you Oh okay this is the direction of my spin angular momentum and I'm the airplane and I'm going to fly look at that spin angular momentum it has no respect for me it stays in the same direction no matter how I fly and the error signals that come from the bearings of the yellow housing and the black housing those arrow signals are fed back to the automatic pilot and so the plane will stay on course now what I can do for you to come to a final test on your thinking this wheel is suspended in such a way that there is no gravitational torque on it like there was here but I can put a torque on it by simply putting some weights on the axis and what do you think will happen now if I put some weight here on the axis so this is your really spinning but now I'm going to put a torque on it here it is spinning in this direction angular momentum is pointing straight at me away from you I'm going to put a torque on like this put it on the way there torque will be in this direction what will the spin angular momentum do torque is in this direction spin angular momentum is in this direction spin angular momentum will start to change the torque watch it there goes the spin angular momentum is changed chasing the torque you see exactly the same thing that I've shown you before and if I make the torque higher then the precession frequency will go up see it stops now immediately when I take it off put it back on again continues put more on it goes way faster what happens now if I put a weight on this side so I change the direction of the torque if I put it on this side torque is now in this direction spin angular momentum is in this direction it's going to reverse direction there we go and you see it does amazingly non-intuitive if you have problems with this you're not alone see you Wednesday you

Channel: ProfWaterLewin

Views: 324,813

Keywords: Inertial, Guidance, System

Id: ekzwbt3hu2k

Length: 5min 23sec (323 seconds)

Published: Sat Jan 14 2012