Controls Homework Problem

This is rather fundamental.

It is the product of three terms. Sketch each individually.

1/S * 1/(s+2) * 1/(s+4)

==1/s * .5/(.5S +1) * .25/(.25S+1) or

==.125/s*1/(.5S+1)*1/(.25S+1) in standard form

So you start with a slope of -20 db/decade, gain of 20 log(.125) at 1 rad and 90 deg lag, then a lag at .25 rad and another lag at .5 rad total end phase shift will be 270 degrees.

Check it with some points, w=.1, .2, 1, 2, 10, 20, 100 rad/sec