Feedback and Stability

Job carried out in: 14th May possibly, 2010

Report submitted upon: 07th Summer, 2010

Teachers of Engineering and Physical Sciences (FEPS)

Division of Physical, Medical and Jetstream Engineering (MMA)


The experiment aimed to demonstrate the huge benefits of using closed-loop control and to illustrate the stability ramifications of a reviews path. A familiarisation method and 3 experimental methods were completed in order to gratify these aims. Positive and negative volt quality signals were consecutively fed into the device and motor motion was observed to occur in clockwise and anti-clockwise directions respectively. Readings were then taken at several brake positions for a great open-loop and closed-loop build, and ideal graphs were plotted because speed against armature current. The areas under each curve were determined using numerical methods as ~56 and ~48 products respectively. The voltage gain was worked out as ~10 and the end result voltage was ~1. one particular V in magnitude. In the matter of negative feedback, the output base came to relax in conjunction with the insight shaft placement with delay and oscillations proportional to input, whereas it tended to walk away from the needed value regarding positive opinions. The introduction of a capacitor triggered sustained amplitude following a minimal disturbance, therefore clearly illustrating the concept of balance in control systems. The concepts of polarity, gain and phase perimeter were each investigated as a means to determine stability attributes of control systems.

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В§в„–1 Advantages

1 . 1

Control Systems


A control system is a single system, or a group of devices to manage, command, direct and/or control the conduct of various other devices or systems. Control systems stick to simple twoorder classification, numerous variations and combinations. They may be:

i) common sense or sequential control

ii) feedback or linear control

Control theory is a pluridisciplinary branch that deals with the behaviour of dynamic devices. When more than one output factors of a system need to comply with certain desired output ideals (or reference) over time, a controller manipulates the inputs to a system to obtain the desired effect on the outcome of the program. (i)

1 ) 2

The Open-loop Control System

A great open-loop system (Figure 1) consists of a control and the flower, along with a few control factors and in some cases, a great amplifier. A great open-loop control, also called a nonfeedback controller, is a kind of controller which in turn computes its input in a system only using the current state and its model of the system.

A characteristic in the open-loop controller is that that use responses to determine if perhaps its outcome has obtained the desired objective of the input. This means that the program does not take notice of the output of the processes that it can be controlling. Consequently, a true open-loop system are unable to engage in equipment learning and in addition cannot accurate any errors that it could make. It also might not exactly compensate for disruptions in the program. (ii)

1 ) 3

The Closed-loop Control System

The closed-loop program (Figure 2) is essentially an open-loop system closed using a sensing factor with its very own inherent transfer function, and a comparator. Information in the output is basically fed backside (or given forward) and compared with the desired output, and an error signal is generated. The problem is then provided into the program to correct the output to meet the standards and specifications set by designer. (ii)

1 . 4

The Long term Magnet DC Motor

The PMDC motor unit is a synchronous electric motor with a content spinning rotor and coils transferring the magnets at the same level as the direct current,...

References: i) Kuo, B. C. (1991). Automated Control Systems (6e). Nj-new jersey: Prentice Corridor.

ii) Thompson, S. (1989). Control Devices: Engineering and Design (1e). New York: David

Wiley and Sons.

iii) Topic no . 578321, Encyclopædia Britannica (2010).

iv) Dorf, R.; Bishop, R. (2008). Modern Control Systems (11e). New Jersey: Prentice Hall.

v) Horowitz, G.; Hill, T. (1989). The ability of Electronics (2e). Cambridge: C. U. S.

vi) Lekakou, C. (2010). Engineering Trials. University of Surrey.

vii) EE8223 (2001). Analogue IC Design. Powerful Comp. Lab. Mississippi State.


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