Correct Answer - Option 2 : Static velocity error coefficient
Explanation:
Type
It is defined as the number of poles at the origin in the open-loop transfer function.
Error: It is the deviation of output from the input.
- If the actual output of an open-loop system during the steady-state deviates from the reference input then the system is said to have a steady-state error.
- It is the index of accuracy of the control system.
- It is also called a ‘static error’.
Steady-state error is defined as:
\({e_{ss}} = \mathop {\lim }\limits_{t \to \infty } e\left( t \right) = \mathop {\lim }\limits_{s \to 0} sE\left( s \right)\)
Error constant and ess
The below table gives all information about the ess and error constant.
|
Type of input
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Input: r(t)
|
ess
|
Error constant
|
|
Step
|
A.u(t)
|
\(\frac{A}{{1 + {k_p}}}\)
|
Position error constant
\({k_p} = \mathop {\lim }\limits_{s \to 0} G\left( s \right)\)
|
|
Ramp
|
A.t.u(t)
|
\(\frac{A}{{{k_v}}}\)
|
Velocity error constant
\({k_v} = \mathop {\lim }\limits_{s \to 0} sG\left( s \right)\)
|
|
Parabolic
|
A.u(t).t2/2
|
\(\frac{A}{{{k_a}}}\)
|
Acceleration error constant
\({k_a} = \mathop {\lim }\limits_{s \to 0} {s^2}G\left( s \right)\)
|
Hence Static velocity error coefficient is associated with the Unit Ramp function.
