Specifications

11– 2
11.SELECTION
11-1 Specification symbol list
Ta : Acceleration torque [N • m]
Tb : Deceleration torque [N • m]
TMa : Servo motor torque necessary for [N • m]
acceleration
TMb : Servo motor torque necessary for [N • m]
deceleration
TLH : Torque applied during servo motor stop [N • m]
TL : Load torque converted into equivalent [N • m]
value on servo motor shaft
TLM : Load torque converted into [N • m]
equivalent value on servo
motor shaft during stop
TU : Unbalance torque [N • m]
TF : Load friction torque [N • m]
TLO : Load torque on load shaft [N • m]
Trms :Continuous effective load torque [N • m]
converted into equivalent value
on servo motor shaft
JL : Load inertia moment converted [kg • cm
2
]
into equivalent value on servo
motor shaft
JLO : Load inertia moment on load shaft [kg • cm
2
]
JM : Servo motor's rotor inertia moment [kg • cm
2
]
N : Servo motor speed [r/min]
NO : Servo motor speed during fast feed [r/min]
NLO : Load shaft speed during fast feed [r/min]
V : Moving part speed [mm/min]
VO : Moving part speed during fast feed [mm/min]
PB : Ball screw lead [mm]
Z1 : Number of gear teeth on servo motor shaft
Z2 : Number of gear teeth on load gear
n : Gear ratio
Speed reduced when n>1,
Speed increased when n<1
η : Drive system efficiency
g : Gravitational acceleration (9.8[m/s
2
])
The following symbols are required for selecting the proper servo:
µ : Friction coefficient
π : Circle ratio (3.14)
Pt : Number of feedback pulses in [pulse/rev]
position control mode
f : Input pulse frequency in position [pps]
control mode
fo : Input pulse frequency during fast [pps]
feed in position control mode
Tpsa : Acceleration time constant of [s]
frequency command in
position control mode
Tpsb : Deceleration time constant of [s]
pulse frequency command in
position control mode
Kp : Position control gain 1 [rad/s]
Tp : Position control time constant (Tp=1/Kp) [s]
Kv : Speed control gain [rad/s]
Tv : Speed control time constant (Tv=1/Kv) [s]
∆R : Feed per feedback pulse in
position control mode [mm/pulse]
∆Ro : Feed per command pulse in position [mm/pulse]
control mode
R : Feed [mm]
P : Number of input command pulses in [pulse]
position control mode
ts : Settling time in position control mode [s]
to : Positioning time [s]
tc : Time at constant speed of servo [s]
motor in 1 cycle
tR : Stopping time in 1 cycle [s]
∆ε : Positioning accuracy [mm]
ε : Number of droop pulses [pulse]
∆θ : Load shaft rotation angle per pulse in position
control mode [degree/pulse]
e : Euler constant = 2.718278
∆S : Feed per servo motor revolution [mm/rev]
Z 2
Z 1
n =