Eliminate Steady State Error Proportional Controller
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Steady State Error Matlab
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Offset Error In Proportional Controller
ads with us Programmers Questions Tags Users Badges Unanswered Ask Question _ Programmers Stack Exchange is a how to reduce steady state error question and answer site for professional programmers interested in conceptual questions about software development. Join them; it only takes a minute: Sign up Here's pid controller pdf 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 have a steady state error? up vote 2 down vote favorite I've read about http://ctms.engin.umich.edu/CTMS/index.php?example=Introduction§ion=ControlPID 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 by the proportional gain (Kp). However, wouldn't the error slowly diminish over time http://programmers.stackexchange.com/questions/214912/why-does-a-proportional-controller-have-a-steady-state-error 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 that as your system approaches the set-point the error signal gets smalle
Control controlguru Like the P-Only controller, the Proportional-Integral (PI) algorithm computes and transmits a controller output (CO) signal every sample time, T, to the final http://controlguru.com/integral-action-and-pi-control/ control element (e.g., valve, variable speed pump). The computed CO from the PI algorithm is influenced by the controller tuning parameters and the controller error, e(t). PI controllers have two tuning parameters to adjust. While this makes them more challenging to tune than a P-Only controller, they are not as complex as the three parameter PID controller. Integral steady state action enables PI controllers to eliminate offset, a major weakness of a P-only controller. Thus, PI controllers provide a balance of complexity and capability that makes them by far the most widely used algorithm in process control applications. The PI Algorithm While different vendors cast what is essentially the same algorithm in different forms, here we explore what is steady state error variously described as the dependent, ideal, continuous, position form: Where: CO = controller output signal (the wire out) CObias = controller bias or null value; set by bumpless transfer as explained below e(t) = current controller error, defined as SP – PV SP = set point PV = measured process variable (the wire in) Kc = controller gain, a tuning parameter Ti = reset time, a tuning parameter The first two terms to the right of the equal sign are identical to the P-Only controller referenced at the top of this article. The integral mode of the controller is the last term of the equation. Its function is to integrate or continually sum the controller error, e(t), over time. Some things we should know about the reset time tuning parameter, Ti: ▪ It provides a separate weight to the integral term so the influence of integral action can be independently adjusted. ▪ It is in the denominator so smaller values provide a larger weight to (i.e. increase the influence of) the integral term. ▪
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