电路各章习题及答案(5)

from the magnitude relationship:

2. Several studies have proposed an extravehicular robot that could move about a NASA space station and perform physical tasks at various worksites. The arm is controlled by a unity feedback control with

Draw the Bode diagram for K=100, and determine the frequency when 20log|G| is 0dB.

Low frequency: -90°

High frequency: -270°

Determine the frequency when20log|G| is 0dB:

3. A feedback system has a loop transfer function

(a) Determine the corner frequencies (break frequencies) for the Bode plot.

(b) Determine the slope of the asymptotic plot at very low frequencies and at high frequencies.

(c) Sketch the Bode magnitude plot.

(a) the corner frequencies:

(b) the slope of the asymptotic plot at very low frequencies is 0dB/dec

the slope of the asymptotic plot at high frequencies is -20dB/de

(c) the Bode magnitude plot

the phase: 180°~ -90°

4. A control system for controlling the pressure in a closed chamber is shown in FigP8.4.

The transfer function for the measuring element is

and the transfer function for the valve is

The controller transfer function is

Obtain the frequency response characteristics for the loop transfer function

the transfer function:

the corner frequencies:

K=1

the phase: -90°~-360°

5. The robot industry in the United States is growing at a rate of 30% a year. A typical industrial robot has six axes or degrees of freedom. A position control system for a force-sensing joint has a transfer function

where H(s)=1 and K=10. Sketch the Bode diagram of this system.

the phase: 0°~-360°

6. The asymptotic log-magnitude curves for two transfer function are given in FigP8.6. Sketch the corresponding asymptotic phase shift curves for each system. Determine the transfer function for each system. Assume that the systems have minimum phase transfer functions.

from the low frequency asymptotic, we have

where W=1 , K=3.98

The transfer function:

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