IPC (GROUP-5) SR. NO NAME EN. NO 1 SAVAN PADARIYA 130450105023 2 KEWAL PATEL 130450105031 3 MAULIK PATEL 130450105033 4 KEVAL JOSHI 140453105005

Introduction : what is transfer function ? A  transfer function  is a mathematical representation for fit or to describe inputs and outputs of black box models. Transfer functions are commonly used in the analysis of systems such as single-input single-output filters, typically within the fields of signal processing, communication theory, and control theory.

Single loop system The closed-loop transfer function is measured at the output. The output signal wave form can be calculated from the closed-loop transfer function and the input signal waveform. An example of a closed-loop transfer function is shown below: The summing node and the G(s) and H(s) blocks can all be combined into one block, which would have the following transfer function:

Above figure we may write :

Block diagram : multi loop system

Differences between Open-loop and Closed-loop control systems These two types of control system have contrast with each other. They have dissimilarities some of which are discussed below: Effect of output – An open loop control system acts completely on the basis of input and the output has no effect on the control action. – A closed loop control system considers the current output and alters it to the desired condition. The control action in these systems is based on the output.

Reaction to Internal and External Disturbances – An open loop control system works on fixed operation conditions and there are no disturbances. – A closed loop control system doesn’t encounter and react on external disturbances or internal variations. Stability – Open loop control systems are mostly stable. – In closed loop control systems stability is a major issue.

Effect on gain – There is no effect on gain. – There is no-linear change in system gain. Implementation – The structure of open loop control system is rather easy to construct. These systems can be easily implemented. – The working principle and structures of closed loop control systems are rather complex and they are often difficult to implement.

Cost – As an open loop control system is easy to implement, it needs lesser number of components to be constructed. Such systems need good calibration and lesser power rating. The overall cost of these systems is low. – As the principle is complex, a closed loop control system needs larger number of components than an open loop control systems. These systems comparatively need less calibration and higher power rating. The overall cost of these systems is higher.

Any drive motor is controlled by either an open loop or closed loop system.  It is important to decide which system you will need for your motor.  We are going to cover what a general control system looks like and open loop vs. closed loop control systems for drive motors to help you discover which is the better fit for your motor design.  Both systems have the same parts.  The first section of a system is the input.  An input can be potentiometer, analog or digital. Some examples of inputs are velocity, heat or position.

The next section of a motor control system is where the input becomes amplified.  Two major amplifiers are transfer functions and gains.  Transfer functions modify the input to the output format desired.  Gains are flat multipliers that increase or decrease the value of the input signal. After this happens the data leaves the system through the output.  Open and closed loop systems are different by how the input and outputs communicate through the process.  Let's compare the two systems.

Open Loop This control system is the simpler of the two.  In an open loop control system the input passes through amplifiers to produce the correct output and out of the system.  There is no feedback or adjustments made. The input needs to return to zero before the output can return to zero. Pros Easy to design Lower costs Quick to build Cons Harder to maintain desired speed Susceptible to external influences like temperature, load or air density

Closed Loop The closed loop control system self adjusts.  The input data doesn't only flow one way.  It can pass an amplifier and go back to the start to adjust the specific input whether it is velocity, heat, position, etc.   Pros Easier to achieve and maintain desired speed More intuitive controls Speed isn't susceptible to external influences Cons More engineering investment up front Specifically tuned for each motor or blower Most motors or blowers are built with closed loop control systems because it allows for more information to be used and a greater ability of the motor. 

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