User's Manual

PMAC VME Hardware Reference Manual
32 PMAC Basic Specifications
Performance Specifications
Servo Cycle Time
Minimum of 55 microseconds per axis controlled (110 usec for two axes; 440
usec for eight axes) for 20 MHz CPU; proportionally less with faster CPUs.
Actual time can be set with hardware jumpers.
Servo Algorithm
Standard
PID with velocity and acceleration feedforward plus 2nd-order notch filter; all gains
with 24-bit resolution. Auto-tunable through PMAC Executive program. Capability
to accept custom servo algorithms written in DSP56000 assembly language.
Optional (OPT 6)
Advanced 7th-order pole-placement algorithm; 35 terms Auto-tunable through Servo
Evaluation Package software for IBM-PC and compatibles.
Phasing Update Time
Minimum of 27 microseconds (1 axis); Minimum of 110 microseconds (8 axes) for
20 MHz CPU; proportionally less with faster CPUs.
Actual time can be set with hardware jumpers.
Phasing Algorithm
Suitable for permanent magnet brushless motors, AC induction motors, switched
reluctance servo motors, micro-stepped stepping motors.
2, 3, or 4-phase motors, Y-wound, delta-wound, or electrically independent phases.
Capability to accept custom phase algorithms written in DSP56000 assembly
language.
Block Execution Rate
Up to 200 to 800 blocks (moves) per second (dependent on number of axes, servo
cycle time, CPU speed, and program complexity) for 20 MHz CPU; proportionally
greater with faster CPUs. Higher rates possible with careful optimization.
Velocity Range
Commanded Velocity
0, +/-0.0001 to 256M (268,435,456) counts/second
Measured Velocity
Dependent on type of feedback used.
Quadrature Feedback:
0 to 19,660, 800-encoder counts/second (edge rate) (slight hardware
modification required on PMAC PC to exceed 9,830,400 encoder
counts/second).
0 to 30,000,000 encoder counts per second with externally provided encoder
sample clock.
Parallel Feedback:
For N-bit feedback word, 2^(N-1)-1 counts/servo cycle
Velocity Accuracy
Long-term
0.005% absolute accuracy with standard crystal; 0.001% absolute accuracy with
optional crystal (OPT 8)
Short-term
System-dependent; typically 0.2% to 1.0%
Position Range
+/-128 trillion counts maximum (no sub-count interpolation, minimum position scale
factor)
+/-32 billion counts typical (sub-count interpolation, default position scale factor)
Position Accuracy
+/- 1 count; Sub-count interpolation possible with automatic 1/T decoding of
incremental encoder signal, or with parallel input lines from A/D converter
processing analog signal from which quadrature is derived.
Position Capture
Accuracy
+/- 1 count at any speed
Position Compare
Accuracy
(Signal output on reaching preset position)
+/- 1 count at any speed
Up to 1000 Hz repetition rate
Synchronization
Axes in the same coordinate system on one PMAC are perfectly synchronized (to the
servo cycle); Axes in different coordinate systems on one PMAC can be
synchronized to within +/-2 msec; Coordinate systems on separate PMACs sharing
same SYNC signal can be synchronized to +/-1 servo cycle.