Ok so update. I have now got the system successfully modeled. and the response matches the physical devicemThe model is shown below:
YOu may notice it is slightly different to what you suggested but, I think that is probably because of misunderstandings, due to my trying to explain the system...
the desired height comes from a modified hertzian contact theory essentially the person pressed down on a force sensor and this is converted into the desired height, this happens before the controller so it shouldn't make too much difference to the system.
essentially yes... there is obviously the controller code, I'm using labview running on FPGA. so the code works by reading the current voltage from the laser, and converts it to a distance that distance is then set to the PID function which compares the desired height with the feedback from the...
The transfer function for the PID is the standard equation which is:
K_p + \frac{K_i}{s}+K_ds
where
kp is 0.898
ki is 0.00024
kd is 0.129
as for the transfer function for the laser I'm not sure what you mean? if you mean the relationship between voltage and distance, then it is a linear...
Talking things through with a collegue, I thought that maybe the solution it to use a feedforward system.
So I would have the original plant equation of \frac{X(s)}{V(s)} =\frac{K_b}{ RmS^2 +K_b K_ES}
and then a feedforward system using gravity which would be \frac{A(s)}{V(s)}...
I have both Matlab and Labview, both of which I'm confident using to run simulations.
The issue that I'm having it trying to obtain the transfer function for the overall system, the closest I have for the plant equation is what I showed you in an earlier post, which is in the time domain...
Firstly thanks for spending the time to help me out it is much appreciated!
I think the best thing to do is explain the entire set up of the system
So feedback wise I am using a laser displacement sensor that records the height of the voice coil motor. this is fed into a PID controller (I...
There is a negative acceleration when there is no current, it is essentially just free falling. The limiting factor is the table.
To keep it at a fixed height I have to apply a voltage.
but how can I get from the form of
X(s) = \frac{bV(s) - g/s}{s(s+a)}
to the transfer function G(s) where
G(s)=X(s)/V(s)=\frac{a_0}{a_1S^3+a_2S^2+a_3S+a_4}
I can't just divide by V(s) as it isn't in all the terms in the numerator.
There's another force? I thought gravity was the restoring force. Is this right or is there another force I've not realized? Assuming it is gravity do I want to go along the lines of:
s=ut+\frac{1}{2}at^2
or in terms of x
x(t) = \dot{x(t-1)}t+\frac{1}{2}\ddot{x}t^2
rearranging to get
g=...
The plant equation of the voice coil motor should take voltage as an input and give my a displacement as an output, the displacement modelling the deflection of a material with the youngs modules that is being simulated.
where did I have "BLi = mg = m d2x(t)/dt2" I came up with BLi - mg = m...
so do you mean take the equation in the form
\ddot{x} = \frac{BL\frac{v-K_E\dot{x}}{r}-mg}{m}
rearrange to get
\ddot{x} = \frac{K_bv}{mr}-\frac{K_E\dot{x}}{mr}-g
and then transform that?
Don't I still get the same issue that the gravity term will mess up any rearrangement?