Recent content by khedira

  1. K

    MATLAB nyquist plot help needed

    Hi MATLABdude, That is the problem. I have tried that before but it generates the following error: "??? Cell contents reference from a non-cell array object." Do you have any resolution to the above error?
  2. K

    MATLAB nyquist plot help needed

    i understand that the "nyquist" command in matlab requires one to key in the transfer function.. however, i am stuck here as i am unable to form a transfer function from the following numerator and denominator: num = s-3/2-1/2*(-24*s+1)^(1/2) den = 1.25*s^2 +3.75*s + 2.5 i know that...
  3. K

    Engineering DC Motor

    Homework Statement A separately excited DC motor with 220V, 970rpm, 100A and Ra=0.05ohms. It is braked by plugging from an initial speed of 1000rpm. I need to calculate i)the resistance to be placed in the armature circuit to limit braking current to twice the full load value, ii)the...
  4. K

    Impulse Response Function

    Oh so sorry, i thought what i have given is the general representation of a state space equation, where x is the state variable, u is the input and y is the output. and yes, "x(dot)" is the derivative of x with respect to t but y is just y.
  5. K

    Impulse Response Function

    Hi, given the state equations of a system, x(dot) = Ax + Bu y = Cx is the impulse response function of this system C(e^(At))B? If not, how can i identify the impulse response from a given state equations? Please advise. Thank you.
  6. K

    Matlab Plot Help Needed

    yes, you are right, i declared a range for t and it's working. Thank you.
  7. K

    Matlab Plot Help Needed

    i need to convert my transfer function to t-domain format and then plot the graph of the equivalent t-domain equation. i am using the ilaplace function to convert the s-domain transfer function to the t-domain equation. my code is >> f = (s + 3.1)/(s^2 +3.1*s + 2.23) f =...
  8. K

    Combine two different size matrix in state equations

    Hi lanedance, Thank you for your reply. I confused myself and is able to get the answer already. The problem was that i have this A1 2x2 matrix, e.g. [1 2; 3 4] and i have another A2 1x1 matrix [5]. I wish to add them together, i.e. A = A1 + A2. At first i thought that the size different...
  9. K

    Combine two different size matrix in state equations

    i have two sets of state equations: 1) x(dot) = (2x2)x + (2x1)u y = (1x2)x 2) x(dot) = (0)x + (1x1)u y = (1x1)x given the above, since A, B and C are of different sizes, how can i add the A from 1) and 2) to get a combined A? Is that possible? Please advise. Thank you.
  10. K

    Transfer Function

    Hi rock.freak667, sorry i don't get you. do you mean shift the disturbance D(s) to the left of G1(s) as in in the block diagram? or do you mean the equation Y(s) - G2(s)D(s) = U(s)G1(s)G2(s)? please advise. thank you.
  11. K

    Transfer Function

    U(s) is my input, Y(s) is the output. I have two plants, G1(s) and G2(s). Between these two plants, i have a disturbance input, D(s). Am i right to say Y(s) = U(s)G1(s)G2(s) + G2(s)D(s)? If that is the case, how can i get the overall transfer function Y(s)/U(s)? Please advise. Thank you.
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