Configuring the main parameter - Selecting the reference velocity

Dead time compensation

The dead time compensation can be adjusted on the Time Compensation tab of Axis1_ENC.
It should theoretically be 3 cycles of the NC cycle time, although in practice 4 cycles are preferable.
Therefore, the settings of the parameters Time Compensation Mode Encoder should be ‚ON (with velocity)‘ and Encoder Delay in Cycles ‘4’.

Scaling factor

The scaling factor can be changed by selecting "Axis 1_Enc" and tab "Parameter" in the NC (see "Setting the Scaling Factor"). The value can be calculated with the formulas specified below.

Adaptation of the scaling factor The feedback system is directly related to the scaling factor of the TwinCAT NC, so that the scaling factor always has to be adjusted when the feedback system is changed.

Calculation of the scaling factor

with encoder, 4-fold evaluation:

SF = distance per revolution / (increments x 4) = 360° / (1024 x 4) = 0.087890625 ° / INC

without encoder:

SF = distance per revolution / (full steps x microsteps) = 360° / (200 x 64) = 0.028125 ° / INC

Position lag monitoring

The position lag monitoring function checks whether the current position lag of an axis has exceeded the limit value. The position lag is the difference between the set value (control value) and the actual value reported back. If the terminal parameters are set inadequately, the position lag monitoring function may report an error when the axis is moved. During commissioning it may therefore be advisable to increase the limits of the Position lag monitoring slightly.

K_v factors

In the NC two proportional factors K_v can be set under "Axis 1_Ctrl " in tab "Parameter". First select the position controller Type with two P constants (with K_a) under the “NC Controller” tab. The two P constants are for the Standstill range and for the Moving range (see Fig. "Setting the proportional factor K_v"). The factors can be used to set the start-up torque and the braking torque to a different value than the drive torque. The threshold value can be set directly below (Position control: Velocity threshold V dyn) between 0.0 (0 %) and 1.0 (100 %). Fig. "Velocity ramp with K factor limit values" shows speed ramp with thresholds of 30 %. The K_v factor for Standstill (t₁ and t₃) can be different than the Kv factor for Moving (t₂). In this case the same factor was used, since for stepper motors this function is less crucial than for DC motors.

Dead band for position errors

Microstepping can be used to target 200 * 64 = 12800 positions. Since the encoder can only scan 1024 * 4 = 4096 positions, positions between two encoder scan points may not be picked up correctly, in which case the terminal will control around this position The dead band for position errors is a tolerance range within which the position is regarded as reached (Fig. "Dead band for position errors").

Setting the acceleration time

In order to pass through any resonances that may occur as quickly as possible, the ramps for the acceleration time and the deceleration time should be as steep as possible.