Proportional Control Offset Error
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Proportional Controller Example
posting ads with us Software Engineering Questions Tags Users Badges Unanswered Ask Question _ Software Engineering proportional controller steady state error Stack Exchange is a question and answer site for professionals, academics, and students working within the systems development life cycle who care about creating, delivering, proportional offset definition and maintaining software responsibly. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top Why does a proportional controller
Proportional Only Control Offset
have a steady state error? up vote 2 down vote favorite I've read about feedback loops, how much this steady state error is for a given gain and what to do to remove this steady state error (add integral and/or derivative gains to the controller), but I don't understand at all why this steady state error occurs in the first place. If I understand how a proportional control works correctly, the output is equal to the current output plus the error, multiplied
Integral Action In A Proportional Integral Controller
by the proportional gain (Kp). However, wouldn't the error slowly diminish over time as it is added (reaching 0 at infinite time), not have a steady state error? From my confusion, it seems I'm completely misunderstanding how it works - a proper explanation of how this steady state error eventuates would be fantastic. algorithms feedback share|improve this question asked Oct 19 '13 at 5:03 Qantas 94 Heavy 1581110 (so no- the output is not the current output plus the error multiplied by Kp, the output is the error multiplied by Kp, if you are adding then it's Ki...) –Guy Sirton Oct 19 '13 at 5:41 (this isn't really a programming question but while we're at it :-) you can get by with I as you describe but a PI controller is going to be a lot more responsive... –Guy Sirton Oct 19 '13 at 5:51 add a comment| 3 Answers 3 active oldest votes up vote 2 down vote accepted The controller you are describing where you keep adding the error times a constant to the current output value is an Integrator. You are clearly integrating the error. A proportional controller would be setting the output to P times the error. It also matters what the output controls, e.g. whether it's torque, or position, or velocity for a motor control system. (something proportional in velocity is integral in torque...) The reason for a steady state error with P only is
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Proportional Controller Pdf
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method, the control system acts in a way that the control effort is proportional to the error. You should not forget that phrase. The control effort is proportional to the error in a proportional control system, and that's what makes it a proportional control system. If it doesn't have that property, it isn't a proportional control systems. Here’s a block diagram of such a system. In this lesson we will examine how a proportional control system works. We assume that you understand where this block diagram comes from. Click here to review the material in the introductory lesson where a typical block diagram is developed. Here's what you need to get out of this lesson. Given a closed loop, proportional control system, Determine the SSE for the closed loop system for a given proportional gain. OR Determine the proportional gain to produce a specified SSE in the system Steady State Analysis To determine SSE, we will do a steady state analysis of a typical proportional control system. Let's look at the characteristics of a proportional control system. There is an input to the entire system. In the block diagram above, the input is U(s). There is an output, Y(s), and the output is measured with a sensor of some sort. In the block diagram above, the sensor has a transfer function H(s). Examples of sensors are: Pressure sensors for pressure and height of liquids, Thermocouples for temperature, Potentiometers for angular shaft position, and tachometers for shaft speed, etc. Continuing with our discussion of proportional control systems, the criticial properties of a proportional control system are how it computes the control effort. The block diagram below shows how the computation is performed. The measured output is subtracted from the input (the desired output) to form an error signal. A controller exerts a control effort on the system being controlled The control effort is proportional to the error giving this method its name of proportional control. We can do a steady state analysis of a proportional control system. Let’s assume that the steady state output is proportional to the control effort. Call the constant of proportionality DCGain. The output is then given by: Output = DC Gain x Control Effort and Control Effort = Kp * Error Here, Kp is the gain