User Manual - JVL Industri Elektronik A/S

2.4 Adjustment of BIAS
The Controller includes a parameter denoted BIAS. This parameter can be used in applications
where the motor is subjected to a static load, e.g. a lifting mechanism.
The BIAS function enables a compensation to be made for the static load, regardless of
whether the load is pushing or pulling on the motor. This BIAS adjustment is normally
advantageous since the load on the PID filter is uniform regardless of the direction of motor
rotation and ultimately enables easier adjustment of the complete system and a faster
response time.
Illustration of lifting mechanism:
Motor
Static load
Drive
Kg
TT0040GB
90 Degrees
Adjustment of the BIAS is made during system installation as follows:
1. Start Motoware and the Controller. Open the “On line editor”.
2. Check that there is contact with the Controller by keying ? (enter).
3. Ensure that the motor is loaded with the required load for the system.
4. Set the Controller to Mode 2 by keying MO=2 (enter).
5. Disable the PID filter by keying KP=0 (enter) KI=0 (enter) and KD=0 (enter).
Note however that current to the motor will be disconnected and the motor will therefore
release its load.
6. Adjust the BIAS to an appropriate value so that the motor is able to hold the load relatively
stable. Begin by setting the BIAS to 100 by keying BIAS=100 (enter). Increase
the BIAS in increments of 100 or less until the load is balanced.
Note that the Controller may produce an error condition during this adjustment if the
motor’s positioning error exceeds the preset value determined by the PE parameter.
If necessary, adjust PE to 0 during adjustment of BIAS so that the Controller ignores
positioning error. If the load is in opposition to the positive direction of rotation, the
BIAS must be set in a negative range, e.g. BIAS= -100 (enter). Note that if the BIAS
value is set too high, the motor will begin to run.
7. Finally, the filter parameters (KP, KI, KD) are reset to the values used before adjusting
the BIAS and the BIAS value is stored in the Controller’s non-volatile memory
by sending the command MS (enter). The filter constants may require re-adjustment
after setting the BIAS. See Adjustment of Servo Regulation, page 16
Desired velocity
KVFF
Desired position
+
KP
KI
+ +
+
+ +
To motor commutation
KD
TT0041GB
BIAS
Actual position
JVL Industri Elektronik A/S - User Manual - AC servocontroller AMC10/11/12 17