Installation manual

Danaher Motion Kollmorgen System Operation
SERVOSTAR
®
S and SERVOSTAR
®
CD Series 67
Analog Input (ANIN)
The position, velocity, or torque loop can receive its command from an analog
voltage source and is selectable through the OPMODE variable. The analog
input to the SERVOSTAR is differential. This means that the signals received at
the two inputs are subtracted from each other to create a ‘difference’, which is
then used to command the rest of the system. This type of input has a high
degree of noise immunity and, in many cases, will allow for ground isolation
between systems. This analog input also has a low pass filter (ANLPFHZ) to
prevent high frequency noise from entering the system.
The input voltage from the differential receiver is applied to a precise 14-bit
Analog-to-Digital (A/D) conversion system. The A/D conversion system is read
by the microprocessor every 500µS for the position loop modes, every 250 µS
for the velocity loop mode, and every 62.5 µ
S for the torque (current) loop mode
of operation. Encoder-based units come with the additional benefit of a Dual
Gain (ANDG) input. When enabled, the system uses two 14-bit A/D inputs to
read the user-supplied analog signal. One input is a direct reading of the ± 10V
signal, while the other incorporates a 2x gain term. When the input voltage is
less than 4 V, the 2x channel is used to determine the input voltage, which
extends the resolution to a 15-bit equivalent. Above 4 V, the system uses the
straight 14-bit conversion. Special software algorithms are used to minimize
cross-over distortion and add 0.25 V of hysterisis.
Analog systems often require scaling and offset bias. The SERVOSTAR adds
an analog offset (ANOFF) variable to this reading, performs an analog deadband
(ANDB) adjustment, and scales it through the either the position loop input
scaling (GEARI, GEARO), velocity loop input scaling (VSCALE), or torque
loop input scaling (ISCALE) before passing the data to the selected control loop.
The analog input (ANIN) variable indicates the analog reading after the offset
(ANOFF) and the deadband (ANDB) adjustments but before the loop scaling.
The ANIN variable range is ± 22500 counts (or mV).
The SERVOSTAR also offers an automatic analog input zeroing function.
Invoking the ANZERO command while the drive is enabled or disabled samples
motor velocity over a 32 ms period and updates ANOFF accordingly to the
analog input offset. This command also incorporates an internal offset
mechanism that has finer resolution than ANOFF is capable of providing.