自动控制原理 Assignment 17
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1. A block diagram of a positive feedback system is shown below:
Sketch the root loci when K* varies from 0 to +∞.
2. The open-loop transfer function of a servo control system is 1()()(51)
G s H s s s =+, To improve the system’s performance, proportional controller K , PD controller K (0.8s+1) and feedback controller are used and are shown in the following block diagrams (a), (b) and (c), respectively. Sketch, for the three cases, the corresponding root loci when K varies from 0 to +∞.
（a ）
(b)
(c)
3. The open-loop transfer function of a unity-feedback system is
*2(3)()(2)(1050K s G s s s s s +=+++)
, Sketch root loci when K* varies from 0 to +∞.
4. The open-loop transfer function of a unity feedback is
*2(1)()(0.5)(1050)
K s G s s s s s +=+++ Sketch the root loci when K* varies from 0 to +∞.
5. The open-loop transfer function of a unity feedback is
*2
(10)()(1)(4)K s G s s s s +=++ Sketch the root loci when K* varies from 0 to +∞.
6. The open-loop transfer function of a control system is
*2(1)()(2)(4K s G s s s s +=++)
Sketch, for negative feedback and positive feedback cases, the root loci when K* varies from 0 to +∞ .
7. A block diagram of control system is shown below:
Sketch the root loci when K* varies from 0 to +∞ and determine the range of K for which the system is stable.