BECKHOFF DK9222-0909-0012 - Manual

I/O
Bus Terminal
Application Note DK9222-0909-0012
Keywords
Encoder simulation
Pulse Train
Stepper motor
Pulse direction signal
Fieldbus substitute
Servo controller
Servo drive
Frequency converter
KL2521
Pulse Train Output Terminal KL2521
This Application Example describes the control and positioning of drives through pulse patterns (pulse
train), which is common practice in Asia and the USA. In servo or stepper motors this technique is used for
realising simple positioning tasks. The pulses can be generated in the PLC or an associated I/O module, e.g.
Bus Terminal KL2521. It modulates a binary signal with a specified frequency that can be used directly for
control purposes.
The idea is that with the new KL2521 Pulse Train output terminal, Beckhoff are using simple pulses sent to stepper motors
and servo drives to implement digital technology for precise positioning tasks. To do this, the electronic Bus Terminal converts
a binary signal to a frequency, feeding this, electrically isolated from the terminal bus, to the positioning drive. The frequency
is preset by a 24 bit value from the automation unit. The advantage over conventional technology, such as an analog ± 10 V
interface, is that the Bus Terminal‘s high output frequency of 500 kHz allows the operation of the fastest servo drives currently
available. In contrast to analog technology, the set value signal is communicated without any offset drift. The 24 bit resolution
guarantees a high precision, in steps of 10 mHz. This means that set values can be specified in fine, almost continuous, steps.
In practice, the desired maximum output frequency is entered into a register, and then the frequency output can be used much
like a ± 10 V output by using 16 bits of the process image.
New Automation Technology Beckhoff 1
For application notes see disclaimer on the last page