Technical Manual for EA350 Analog Pulse Type Servo Driver V101 9.3 Settings of fully closed loop With fully closed-loop not enabled, set the gain parameter of the servo driver first to make sure the servo runs properly without any overshooting or over-tuning and stops without any abnormal noise. Upon meeting these conditions, set the parameters of fully closed loop in the steps described below: 1. Determine running direction of the external encoder The counting direction of the external encoder and the servo motor encoder must conform to the setting of PC-01. An error will lead to positive feedback and cause galloping.
Enter the JOG mode for the driver, and perform jogging upon setting a low speed for P8-00. Observe the display of pulse feedback of the motor encoder and the external encoder. If they share the same variation trend (increasing or decreasing concurrently), set the use method as 0 for the external encoder; otherwise set it as 1. 2. Determine the resolution of the external encoder (pulse count of the external encoder corresponding to each turn of the motor) This parameter indicates the count of pulses (upon quadruplicated frequency) returned by the external encoder for each turn completed by the motor, in PUL (Pulses/turn).
Assume there is a screw drive, the transmission ratio of the reducer is 1: 1, the screw lead is 10 mm, and the resolution of the external encoder is 0.005 mm/pulse. When the servo motor completes a turn, the nut will travel for 10 mm in linear distance, and the external encoder will return (10ч0.005) = 2,000 pulses, that is, the external encoder returns 2,000 pulses for every turn completed by the motor. Therefore, this parameter should be set to 2,000. 3. Alarm detection setting Settings of alarm detection (threshold of excessive deviation in fully closed-loop, and elimination setting of fully closed-loop position deviation).
a) Setting of threshold for excessive motor-load position deviation (detection value for excessive motor-load deviation) This sets the allowable difference in the counts of feedback pulses between the motor encoder and and the external encoder, expressed in external encoder unit. For example: If you set the alarm threshold as 1,000 for excessive motor-load position deviation, the alarm excessive motor-load position deviation will be raised when the absolute difference in feedback pulse count between the motor encoder and the external encoder exceeds 1,000. If this setting is 0, the servo drive will not perform alarm detection for excessive motor-load position deviation.
Instead, it will keep eliminating the motor-load position deviation. b) Setting of clearing excessive motor-load position deviation Sets after how many turns of the motor will the motor-load position deviation be cleared once during running of the driver. 9.4 Enable fully closed-loop feature With the abovementioned fully closed-loop parameters correctly set and confirmed, enable the fully closed-loop feature. To do this, set PC-00 as 1 and select the external encoder as the encoder feedback source. The setting can be performed only in S-OFF state. You can switch the source of encoder feedback through the DI terminal defined as FCL function.
If the DI terminal defined as the FCL function is valid, the external encoder will be used, and the fully closed-loop feature will be enabled. If the DI terminal defined as the FCL function is invalid, the motor encoder will be used, and the fully closed-loop feature will be disabled. Switching states of the FCL terminal is valid only in S-OFF state. That is, the servo can only detect the state of the FCL terminal before enabling. After enabling, swiching of FCL terminal will not take effect. Caution ☞ Please refer to the explanations on fully closed-loop parameter in 8.17.
237 Parameter description of function code Unit Default Ways of taking Function Code Name of function code setting effect PC-01 Selection of external encoder direction 0: standard direction 1:
reverse - 0 With immediate effect Name of function code Parameter description of function code Unit Default Ways of Function Code setting taking effect PC-02 Pulse count of external encoder feedback per motor revolution 0~1073741824 PUL 10000 Power-on again Parameter description of function code Unit Default setting Ways of taking Function Code Name of function code effect PC-04 Alarm threshold for excessive motor-load position deviation 0~1073741824 PUL 10000 With immediate effect Parameter description of function code Unit Default Ways of taking Function Code Name of function code setting effect PC-06 Setting of clearing excessive motor-load position deviation 0~100 Rev 0 With immediate effect Name of function code Parameter description of function code Unit Default Ways of taking Function Code setting effect PC-00 Encoder feedback selection 0:
Use motor encoder 1: Use external encoder - 0 With immediate effect