Root Locus in Control Systems and Bode plot
- 1. 1 IC 8451&CONTROL SYSTEMS Department of Electrical and Electronics Engineering Approved by AICTE | Affiliated to Anna University | Accredited by NAAC | Accredited NBA | Recognized by UGC under 2(f) and 12(B) Chennai Main Road, Kumbakonam- 612 501. ARASU ENGINEERING COLLEGE
- 2. 2 ARASU ENGINEERING COLLEGE IC 8451&CONTROL SYSTEMS LAGLEAD COMPENSATOR A compensator having the characteristics of lag-lead network is called lag-lead compensator. In a lag-lead network when sinusoidal signal is applied, both phase lag and phase lead occurs in the output, but in different frequency regions. Phase lag occurs in the low frequency region and phase lead occurs in the high frequency region (i.e) the phase angle varies from lag to lead as the frequency is increased from zero to infinity. A lead compensator basically increases bandwidth and speeds up the response and decreases the maximum overshoot in the step response. Lag compensation increases the low frequency gain and thus improves the steady state accuracy of the system, but reduces the
- 3. 3 ARASU ENGINEERING COLLEGE IC 8451&CONTROL SYSTEMS If improvements in both transient and steady state response are desired, then both a lead compensator and lag compensator may be used simultaneously, rather than introducing both a lead and lag compensator as separate elements. However it is economical to use a single lag-lead compensator. A lag-lead compensation combines the advantages of lag and lead compensations. Lag-lead compensator possess two poles and two zeros and so such a compensation increases the order of the system by two, unless cancellation of poles and zeros occurs in the compensated system.
- 5. 5 ARASU ENGINEERING COLLEGE IC 8451&CONTROL SYSTEMS • REALISATION OF LAG LEAD COMPENSATOR USING ELECTRICAL NETWORK
- 6. 6 ARASU ENGINEERING COLLEGE IC 8451&CONTROL SYSTEMS Bode plot of lag lead compensator
- 7. 7 ARASU ENGINEERING COLLEGE IC 8451&CONTROL SYSTEMS PROCEDURE FOR DESIGN OF LAG-LEAD COMPENSATOR USING BODE PLOT The lag-lead compensator is employed only when a large error constant and a large bandwidth are required. First design a lag section and then take α = 1/β and design a lead section. The step by step procedure for the design of lag-lead compensator is given below. Step- 1: Determine the open loop gain K of the uncompensated system to satisfy the specified error requirement. Step-2: Draw the bode plot of uncompensated system. Step-3. From the bode plot determine the gain margin of the uncompensated system.