A, A(s)

actuator transfer function

A, A(s)

even part of (s)

A(j) =
Re (j)

A_{o}

maximum available feedback

A

value of A at s =

B, B(s)

feedback path transfer function

B, B(s)

odd part of (s)

B(j) =
Im (j)

B_{n}

nonminimal phase lag

C, C(s)

compensator transfer function

F = T + 1

return difference

F, or, also, 20 logF

feedback

M = T/F

tracking system transmission coefficient

N_{A}

noise at the actuator input

P, P(s)

plant transfer function

R, R(s)

prefilter transfer function

S

sensitivity

T

return ratio, or loop transmission coefficient (T = CAPB)

f

frequency in Hz

f_{b}

frequency at which loop gain is 0 dB

f_{c}

lowest frequency at which loop gain is x dB

f_{d}

highest frequency at which loop gain is x dB

f_{g}

lowest frequency at which loop gain is x_{1} dB

f_{h}

highest frequency at which loop gain is x_{1} dB

f_{p}, f_{z}

frequencies of a pole, of a zero

k

motor constant

k

coefficient

n

slope coefficient of an asymptotic Bode diagram

s = + j

operational variable

t

time

t_{d}, t_{r}, t_{s}

delay, rise, and settling times

u, u(t)

signal at system's input, command

x

lower amplitude stability margin in dB

x_{1}

upper amplitude stability margin in dB

y, or y

phase stability margin

,
(s),
(j)

transfer function


angle of rotation


torque

= 1/(2Q)

damping coefficient


frequency, rad/sec
