Compensation in control system lag lead compensation. We will see that from frequency response in this class. Relieving the drudgery of many routine repetitive manual operation, and more. A lag compensator provides phase lag negative phase in the frequency response of system. Find a downloadable version of this story in pdf format at the end of the story. Design lag, lead, lead lag compensators and verify experimental results using matlab. The phase margin of the system remains close to 900 as rl and cl vary over wide limits. These systems occur when an energy storage unit and an energy dissipator are combined. A firstorder phase lag compensator can be designed using the frequency response.
When graphically changing pole and zero locations for a lead or lag compensator, in the editor plot, you can drag the pole and. Chang 2004 used phase lag and phase lead compensators to. Compensator with filter for use with a three phase drive powering a one phase load. With single lag or lead compensation may not satisfied design specifications.
Modern control lec 04 analysis and design of control. Based on the usual electronic implementation of the compensator 3, the circuit for a lead or lag compensator is the series combination of two inverting operational ampli. Control systems objective questions and answers pdf free download,mcqs,lab viva,online quiz bits test electrical engineering interview questions. In this section we introduce their structures and indicate their main properties. The phaselag, phaselead, and phaselead keywords lag compensator. The original unstable closedloop system is now stable. Modern control lec 04 analysis and design of control systems using root locus slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Control system engineeringii 3 10 modulei 10 hours state variable analysis and design. Design of lead and lag compensators using frequency domain techniques tim davidson mcmaster university. Zeros of the transfer function dominate in phase lead compensation technique.
Lag compensators design using frequency response techniques ahmed abu. Introduction, concepts of state, sate variables and state model, state models for linear continuoustime systems, state variables and linear discretetime. The phase lag compensator does, however, reduce the. This handout addresses phase lead compensators and improved damping, specifically. In order to obtain the desired performance of the system, we use compensating networks. For a lag compensator, however, the zero is less than the pole zo compensator. The time constant \t\ of the lag compensator should not be unnecessarily large. A lag compensator is one which adds a pole the system and is used to improve the steady state response of the system. The procedure for designing the lag lead compensator is presented in section ii. The name phase lag system comes from the fact that a sinusoidal input causes a sinusoidal output, but with a phase lag. If we combine the two types, we can get a special lead lag compensator system. Lag compensators reduce the high frequency gain of the system. Use nyquists stability criterion on ls we might like to make sure that the closed loop remains stable even if there is an increase in the gain. A lag compensator in frequency response form is given by.
Compensator structure the basic phase lead or phase lag compensator consists of a gain, one real pole, and one real zero. The main difference is that the lag compensator adds negative phase to the. Loh, cai and tan 2004 studied the autotuning of phase lead lag compensators using the frequency response of the plant using relays with hysteresis 2. Designing lead and lag compensators simon fraser university. Specify the maximum amount of phase angle change and the frequency at which this change occurs. Pdf complex lead and lag compensators are new additions to the repertoire of compensator structures for loop shaping. The paper aims to describe short steps to design a phaselead compensator for the massspringdamper system to achieve the desired level of phase margin for. There are three types of compensators lag, lead and lag lead compensators. Analyze toque speed characteristics of dc and ac servomotors. Design of compensators for speed control of dc motor by.
Choose this frequency as the new gain crossover frequency. Lead and lag compensators lead compensator cs gs controller plant re im lag compensator re im why these are called lead and lag. It is a fundamental building block in classical control theory. Because the phase lag compensator adds a negative phase angle to a system, the phase lag is not a useful effect of the compensation and does not provide a direct means of improving the phase margin. The phase lag compensator looks similar to a phase lead compensator, except that a is now less than 1. Fall 2008 8 lead compensator positive angle contribution re test point im sp1z1. A lag compensator in frequency response form is given by the following. One example is the rc lowpass in chapter 2, and an additional example is the waterbath that is covered in detail in chapters 5 and 6 chapter 5 chapter 6. By adding equal numbers of poles and zeros, a phase lag controller provides an appreciable amount of relative stability to a system, yielding slow response time. The reader is referred to those notes for details on the individual design procedures. Lag or phaselag compensator using frequency response. The lag compensator is an electrical network which produces a sinusoidal output having the phase lag when a sinusoidal input is applied. Pandey published on 20180424 download full article with reference data and citations.
Us7602622b2 compensator with filter for use with a three. Pdf implementation and simulation of digital control. Frazzoli 151059100 control systems i hs 2015 solution exercise set 11 loop shaping noele norris, 9th december 2016 exercise 1 a nonminimum phase system to increase the rise time of the system, we need to increase the bandwidth of the system and. Placing the pole and zero further apart increases the amount of phase angle change. Consider of lead compensator having the following transfer function. Two common types of compensators are lead and lag compensators. A firstorder phase lag compensator also can be designed using a frequency response approach. Phase lag compensator design using bode plotsand phase lead compensator design using bode plots, theses notes will concentrate on the use of those two designs together. Finally, the result of phase lead and phase led compensator is presented by using matlabgui. The lag compensator is expressed in the same form as a lead compensator. This topic is important from the point of view of gate ee and gate ec. It is also useful for exams like ies, bsnl, barc, drdo etc. Design of phase lead and phase lag compensator for pitch.
If you continue browsing the site, you agree to the use of cookies on this website. Pdf lead and lag compensators with complex poles and zeros. A phase lag compensator increases the dc gain of the system with negligible phase contribution. Pdf design of a leadlag compensator for position loop control of.
Download fulltext pdf design of a lead lag compensator for position loop control of a gimballed payload conference paper pdf available april 2015 with 3,468 reads. The positive phase shift of the network then improves the phase margin of the system. Phase lead compensators are placed in cascade, in the forward path, and are used to manipulate the phase margin. Z p compensator the pole zero location of lead compensator in splane is given as transfer function of compensator can also be written as. For an unstable uncompensated system, lead compensation provides fast response but does not provide enough phase margin whereas lag compensation stabilize the system but does not provide enough bandwidth. In a phase lag controller, the pole of the controller is placed closer to the origin as. Type ii compensators are widely used in the control loops for power converters. Analyze the effect of p, pi, pd and pid controllers on a control system.
The compensator can be defined as a lag compensator if a p. Continuous and digital closed loop systems with compensators 4leadlag. Pdf design of leadlag compensators for robust control. To provide attenuation reduction in magnitude after z. In this article the lead and lag compensators will be briefly discussed. Lec41 compensator design using frequency response plots. Design of a lead lag compensator for position loop control of a gimballed payload. Phase lead compensators are used in feedback control, usually to improve gain margins and add additional damping to a system. Lag or phase lag compensator using frequency response.
The proposed phase lead and phase lag compensator design can be used for any system that the. Lag compensators summary of frequency response we have established that bode diagram comprises two plots gain in db, phase in degrees. Introduction the purpose of phase lag compensator design in the frequency domain generally is to satisfy speci. However, there are cases where the phase lag of a power converter can approach 180 degrees, while the maximal phase from a type ii compensator at any frequencies is at most zero degree. They are known as pd, pi, pid, phase lag, phase lead,and phase lag leadcontrollers.
Hence, the high frequency noise attenuation becomes better. Using the concept of virtual ground the op amp lag compensator can be designed and the circuit can be validated. This function provides an easy way to construct a phase lead compensator with specified centre frequency and lead. Lagcompensator the transfer function p z km p z the objective. The transfer function of the compensator takes the form of. Madan gopal, department of electrical engineering, iit delhi. Type iii compensator design for power converters power. Pdf design of a leadlag compensator for position loop. Design of lag compensator for process control using. Lag compensators reduce the gain crossover frequency of the system. Phase lead compensators shift bode phase plots of kghjw open loop transfer function upward in a desired frequency range.