A magnetic disk drive requires a motor to position a read/write head over tracks of data on a spinning disk, as shown in Figure E4.4. The motor and head may be represented by the transfer function

where Ñ‚ = 0.001 second. The controller takes the difference of the actual and desired positions and generates an error. This error is multiplied by an amplifier K.
(a) What is the steady-state position error for a step change in the desired input?
(b) Calculate the required K in order to yield a steady-state error of 0.1 mm for a ramp input of 10 cm/s.

Transcribed Image Text:

G(s) = s(Ts +1). Desired position Controller Sensor signal Magnetie disk Read/write Motor inpu head Motor FIGURE E4.4 Disk drive control