CONTROL OF THE PENDULUM

Determination of Feedback Control Parameters

Two computer programs were written to aid in the selection of feedback control values. The first program, ACKERMAN, calculates the control vector K given the desired pole positions using Ackerman's formula. The second program, PENDULUM, does the reverse; it calculates the pole positions given a control vector K.

Control of the Pendulum

Various values of the control vector K were obtained using program ACKERMAN. The final control vector used was X = 3.5, xdot

= 7.0,

= 25.0,

= 3.0 Using these values the poles were calculated to be at 0.752 plusormi

0.382j, 0.929, 0.982

Using these values the pendulum remained upright with the cart slowly oscillating back and forth covering a distance of about 25 cm. The cart was run for a period of 2 minutes and showed no signs of instability.

Analysis of the Results

In a final effort to justify the endless hours spent in deriving a theoretical analysis of the pendulum system, it is gratifying to be able to sit back and say IT WORKS!

(If you've been paying attention you may have noticed that two of the poles were at 0.929 and 0.982, which is pretty close to being unstable. The reason is I initially made a mistake calculating the control values because I used the full length of the rod for

when

was originally defined as 1/2 the length of the rod. Recalculating using the correct value for

gave the true poles.)

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