Yaskawa Sigma-5 User Manual: Design and Maintenance - Rotary Motors - Manual (Page 145)

5 Adjustments
5.1.4 Safety Precautions on Adjustment of Servo Gains
5-8
5.1.4 Safety Precautions on Adjustment of Servo Gains
Yaskawa recommends that the following protective functions of the SERVOPACK are set to the correct set-
tings before starting to adjust the servo gains.
(1) Overtravel Function
Set the overtravel function. For details on how to set the overtravel function, refer to 4.2.3 Overtravel.
(2) Torque Limit
Calculate the torque required to operate the machine. Set the torque limits so that the output torque will not be
greater than required. Setting the torque limits can reduce the amount of shock applied to the machine in colli-
sions and other cases.
If the torque is set below the level of torque required to operate the machine, overshooting or vibration may
occur.
(3) Excessive Position Error Alarm Level
The excessive position error alarm is a protective function that will be enabled when the servo drive is used in
position control mode.
For the optimum setting, the servomotor will be stopped after the error occurs if the servomotor performs
unpredictably after receiving a reference.
The position error is the difference between the position reference and the actual position. The position error
can be calculated from the position loop gain (Pn102) and the motor speed with the following equation.
• Excessive Position Error Alarm Level (Pn520 [reference unit])
∗1. Refer to 4.2.4 Electronic Gear.
∗2. To check the setting for Pn102, set the parameter display to “Displays all parameters” (Pn00B.0 = 1).
Set the level to a value that satisfies these equations, and no alarm will be generated during normal operation.
The servomotor will be stopped, however, if the servomotor runs unpredictably after a reference is input. At
the end of the equation, a coefficient is shown as “ × (1.2 to 2). ” This coefficient is used to add a margin that
prevents a faulty alarm from occurring in actual operation of the servomotor.
If the servomotor’s maximum number of rotations is 6000 min -1 and Pn102 equals 40 with an encoder resolu-
tion of 20-bit (1048576), the setting of Pn520 is calculated as shown with the following equation.
If the acceleration/deceleration of the position reference exceeds the capacity of the servomotor, the servomo-
tor cannot perform at the requested speed, and the allowable level for position error will be increased as not to
satisfy these equations. If so, lower the level of the acceleration/deceleration for the position reference so that
the servomotor can perform at the requested speed or raise the allowable level of the position errors.
CAUTION
• If adjusting the servo gains, observe the following precautions.
• Do not touch the rotating section of the motor while the servomotor power is ON.
• Before starting the servomotor, make sure that the emergency-stop circuit works correctly.
• Make sure that a trial run has been performed without any trouble.
• Install a safety brake on the machine.
Position Error =
×
Motor Speed [min ] -1
60
Encoder Resolution* 1
Pn102 (1/s)* 2
Pn520
> ×
× (1.2 to 2) Max. Motor Speed [min ]
-1
60
Encoder Resolution* 1
Pn102 (1/s)* 2
Pn520 =
2621440 × 2
5242880 (The factor setting of Pn520)
× × 2
6000
60
1048576
40
=
=