The difference between a lag compensator and lead compensator is that the lead compensator modify the transient response of the system while the lag compensator modifies the steady state.
A Compensator Gc is of the form K*A(S+1/T)/(S+1/(AT))
the S=-1/T is the additional zero and S= -1/(AT) is the additional pole. For a lead compensator, A is between 0 and 1 while for the lag compensator A is bigger than 1 which allows of an appreciable change in gain, hence a change in steady state response.
A lead-lag compensator is a component in a control system that improves an undesirable frequency response in a feedback and control system. It is a fundamental building block in classicalcontrol theory. Contents [hide]
Given the control plant, desired specifications can be achieved using compensators. I, D, PI, PD, and PID, are optimizing controllers which are used to improve system parameters (such as reducing steady state error, reducing resonant peak, improving system response by reducing rise time). All these operations can be done by compensators as well. TheoryBoth lead compensators and lag compensators introduce a pole-zero pair into the open loop transfer function. The transfer function can be written in the Laplace domain as
where X is the input to the compensator, Y is the output, s is the complex Laplace transform variable, z is the zero frequency and p is the pole frequency. The pole and zero are both typically negative. In a lead compensator, the pole is left of the zero in the complex plane, , while in a lag compensator .
A lead-lag compensator consists of a lead compensator cascaded with a lag compensator. The overall transfer function can be written as
Typically , where z1 and p1 are the zero and pole of the lead compensator and z2 and p2 are the zero and pole of the lag compensator. The lead compensator provides phase lead at high frequencies. This shifts the poles to the left, which enhances the responsiveness and stability of the system. The lag compensator provides phase lag at low frequencies which reduces the steady state error.
The precise locations of the poles and zeros depend on both the desired characteristics of the closed loop response and the characteristics of the system being controlled. However, the pole and zero of the lag compensator should be close together so as not to cause the poles to shift right, which could cause instability or slow convergence. Since their purpose is to affect the low frequency behaviour, they should be near the origin.
temperature swing
In a flow of matter, such as in a rocket, velocity lag is the speed difference between the flowing gas particles and solid/liquid particles. Any amount of velocity lag slows down the overall force and speed of the matter flow.
no time lag.................
thermal lag
It means that an effect occurs some time after the cause.
A lead-lag compensator is a type of controller. It is used to control the frequency response of a system. The lead part helps speed of response while the lag part helps accuracy. Basically its a lot of Bode Plot work. Good results in this frequency domain usually corresponds to good results in the time domain as long as you follow the translation guidelines (I don't remember them off the top of my head but you can find them in any controls textbook).
Inside lag is the time to implement (pass) a policy, while outside lag is the time it needs to take effect.
0.5 lead PF or Power Factor means that the signal is ahead of the input voltage by a factor of 90 degrees. The lagging PF means it falls behind the input signal. In sinusoidal signals 0.5 lead or lag will be the same.
temperature swing
A lead or lag applies to a signal due to active components to make it lead or lag the original signal
lead
A lead indicator of revenue, a lag indicator of R&D expenditure.
the difference between the arrival of the p-wave and s-wave
the difference between the arrival of the p-wave and s-wave
Such indicators are found within scorecards where lead are short-term which affect lag long-term Example: training is lead indicator and service excellence resulted from good training is a lag indicator Best of luck
lead
In a flow of matter, such as in a rocket, velocity lag is the speed difference between the flowing gas particles and solid/liquid particles. Any amount of velocity lag slows down the overall force and speed of the matter flow.