Kinco FD5 AC series servo driver user manual Chatper 7 Performance regulation
103
Position loop tuning steps:
Step 1：Kpp adjustment
Increasing the Kpp can increase the position loop bandwidth to reduce the positioning time and the following error, but if the
setting is too large, it will cause noise or even oscillation, and it must be set according to the load conditions. Kpp = 103 * position
loop bandwidth。The bandwidth of the position loop cannot exceed the bandwidth of velocity loop. It is recommended that the
setting value of the position loop bandwidth be less than one quarter of the bandwidth of the velocity loop.
Step 2：Kvff adjustment
Increasing the Kvff can reduce the position following error and improve the dynamic response characteristics of the entire system,
but it may lead greater overshoot during acceleration and deceleration. When the position command signal is not smooth, reducing
the Kvff can reduce the motor oscillation. When the feedforward is set to 0, if only the Kvp is used to position the servo, the in-
position time will be longer.
Kvff function can be regarded as the upper controller, such as PLC, has the opportunity to directly control the velocity in position
operating mode. In fact, the function will consume part of the speed loop responsiveness, so the setting value needs to match the
position loop and velocity loop bandwidth.
The elastic factor of the flexible load, such as pulley, will cause the speed feedforward command loaded to the speed loop to be
unsmooth and cause the load to oscillate. In this type of load, the position loop speed feedforward can be appropriately reduced. In
a rigid load, if adjusting the Kpp cannot eliminate the vibration generated by the motor during acceleration and deceleration, you
can also try to gradually decrease the default 100% feedforward.
Figure 7-6 Speed step curve after Kvff adjustment
Step 3：Kaff adjustment
Users are not advised to adjust this parameter. When the practical application requires very high position loop response, the
acceleration feedforward can be adjusted to improve the response performance.
The acceleration feedforward function can be seen as the upper controller has the opportunity to directly control the torque in the
position operating mode. This function actually consumes some of the current loop responsiveness, so if the settings do not match
the Kvp and velocity loop bandwidth, overshoot and oscillation will occur.
Also, the velocity feed forward to the velocity loop may not be smooth and has some noise signal inside, so a large velocity feed
forward value will also amplify the noise.
Kaff can be calculated by following function:
ACC_％= 6746518 / K_Acc_FF / Easy_Kload * 100
ACC_% This means what percentage will be used for acceleration feedforward.
K_Acc_FF Kaff(60FB.03), calculates the final internal factor of the feedforward.
Easy_Kload Inertia Coefficient in Easy Mode (3040.07) Load coefficient calculated from auto-tuning or direct user input inertia
ratio.
Note
The smaller the value of the K_Acc_FF parameter, the greater the position loop acceleration
feedforward.
Step 4：Smooth filter adjustment
The smoothing filter is a moving average filter. It filters the velocity commands from the velocity generator to make the velocity
and position commands smoother. Using this filtering causes velocity and position commands to be delayed in the drive. So for
some applications, like CNC, it is better not to use this filter, but to do the smoothing in the CNC.
Smoothing filters reduce machine influence by smoothing commands. Smoothing Filter (60FB.05) defines the time constant of
this filter in ms. Under normal circumstances, if the machine system vibrates when starting and stopping, it is recommended to
increase the smoothing filter setting.
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