- #1
e-dard
- 14
- 0
Hi all,
this is my first post. Google has failed me, although i have learned a lot of physics in the meantime. I am not a physicist (am an evolutionary computation person). Anyway, i am building a physics simulator for an auv submersible and i wanted something cleared up :-)
http://www.edward-robinson.co.uk/mech.jpg"
the link above shows you a diagram of my auv, labelled are the two thruster, the centre of mass and the distance between the thrusters. I am having trouble understanding how to convert the thrusters into rotational motion (i.e. how much to rotate the vehicle (upon its centre) in each time slice (am using euler integration). the thrusters are always directed in the same place, and are parallel to each other.
is it this:?
drag:
for each side, where area = surface area of auv and v2 relates to the velocity for each thruster point vl and vr.
rotational acceleration for each thruster point:
where Tl and Tr are the thrusters on each side. d = distance between thrusters. Inertia is same for both sides?
then the velocities just equal:
where al and ar are the accelerations at each point.
For tangential velocityi just added these up since the force is in the same direction..
then to calculate rotational velocity i used the 2nd part of the diagram.
the ICR (instantaneous centre rotation) is the point that the craft would move around in a circle at that instant if no changes to forces exerted on the craft occurred. To get the radius of the circle the craft is moving around, and since the rotational velocity of a line is the same at any point on it:
Ok, i don't think this is quite right, but it looks ok on screen. I am expecting parts of it to be wrong, so i just wondered what they were. The original method i tried was less successful because i was getting conservation of angular momentum after i stopped applying any force which is not what i expect. See the next link for a picture. The craft accelerates for a bit and then twice as much thrust is applied to one side, sending it into a turn (yaw). The power is then cut to both sides when the trail goes red. On the left of the picture, using a different method, i was getting conservation of momentum---so when i cut the power to the craft it carried on moving into a circle. What i am getting now is like on the right, which i think is right. Its just i don't think i the equations are right.
thanks a lot for looking, wow long post!
edd
http://www.edward-robinson.co.uk/rot.jpg"
this is my first post. Google has failed me, although i have learned a lot of physics in the meantime. I am not a physicist (am an evolutionary computation person). Anyway, i am building a physics simulator for an auv submersible and i wanted something cleared up :-)
http://www.edward-robinson.co.uk/mech.jpg"
the link above shows you a diagram of my auv, labelled are the two thruster, the centre of mass and the distance between the thrusters. I am having trouble understanding how to convert the thrusters into rotational motion (i.e. how much to rotate the vehicle (upon its centre) in each time slice (am using euler integration). the thrusters are always directed in the same place, and are parallel to each other.
is it this:?
drag:
Code:
DRAG = 1/2 p v2 a dcoef
rotational acceleration for each thruster point:
Code:
F = ma --> Tao = I alpha --> alpha = ( Tl + left_DRAG) * (d/2) / I
F = ma --> Tao = I alpha --> alpha = ( Tr + right_DRAG) * (d/2) / I
then the velocities just equal:
Code:
vl = al * time_slice
vr = ar * time_slice
For tangential velocityi just added these up since the force is in the same direction..
Code:
VX = vl + vr
then to calculate rotational velocity i used the 2nd part of the diagram.
Code:
ICR = (d/2) * (( vr + vl) / (vr - vl))
Code:
omega = VX / r
Ok, i don't think this is quite right, but it looks ok on screen. I am expecting parts of it to be wrong, so i just wondered what they were. The original method i tried was less successful because i was getting conservation of angular momentum after i stopped applying any force which is not what i expect. See the next link for a picture. The craft accelerates for a bit and then twice as much thrust is applied to one side, sending it into a turn (yaw). The power is then cut to both sides when the trail goes red. On the left of the picture, using a different method, i was getting conservation of momentum---so when i cut the power to the craft it carried on moving into a circle. What i am getting now is like on the right, which i think is right. Its just i don't think i the equations are right.
thanks a lot for looking, wow long post!
edd
http://www.edward-robinson.co.uk/rot.jpg"
Last edited by a moderator: