Text: For the temperature control system of Problem 7.5-3 and Fig.P7.5-3, let K=1.
a. Determine the stability of the system.
b. Plot the Bode diagram and the Nyquist diagram.
c. If the system is stable, determine the gain and phase margins. If the system is unstable, find the value of K that gives a phase margin of 45.
d. From the Nyquist diagram, determine the value of K > 0 for which the system is marginally stable.
e. Find the frequency w at which the marginally stable system will oscillate.
7.5-3. Consider the temperature control system of Fig.P7.5-3. This system is described in Problem 1.6-1. For this problem, ignore the disturbance input, let T=0.6 s, and let the digital controller be a variable gain K such that D=K. Hence m(KT=KeKT, where et is the input to the sampler. It was shown in Problem 6.2-4 that
1 - Ts
2 s + 0.5
1.037
z - 0.7408
a. Write the closed-loop system characteristic equation.
b. Use the Routh-Hurwitz criterion to determine the range of K for stability.
c. Check the results of part (b) using the Jury test.
d. Let T=0.06s. Find the range of K for which the system is stable.
Chamber
Disturbance R(s)
2.5 s + 0.5
Controller
R(s)
D(z)
1 - e-Ts
M(s) Volts
2
C(s)
s + 0.5
Volts
Sensor
FIGURE P7.5-3 Chamber temperature control system
0.0