Network Hardware User Manual

HARSFEN0602
0 0.1 0.2 0.3 0.4
-2000
0
2000
4000
0 0.05 0.1 0.15 0.2 0.25
-200
-100
0
100
Time (sec)
Time (sec)
Position reference
Position Target
Counts/sec
Counts
12.1.6 PVT: Position-Velocity-Time interpolated motion
12.1.6.1 What is PVT?
PVT stands for Position Velocity Time.
In a PVT motion, the user provides the desired position and speed at certain time instances. Between the
times specified by the user, the motion controller interpolates to obtain smooth motion.
The position and speed specifications are absolute. The time specification is relative.
A PVT motion can be referred to absolute time by requiring the PVT motion to start at a specified start time.
Use the BT (Begin on Time) command to start a PVT motion exactly at a given time, with microsecond
resolution.
The ability to refer PVT motions to absolute time makes them ideal for multiply axis tightly synchronized
motions.
For an explanation how to synchronize the absolute time counters of several amplifiers to the precision of
few microseconds, refer the CAN manual.
Example
Suppose we want the system to be at the position of 1000 and the speed of 100000 count/sec at a given time,
and to be at the position of 1620 and the speed of 110000 count/sec, 6 msec later.
Then the first point is specified by
Position = 1000,
Speed = 100000,
Time = (Not relevant to the described motion, but to the previous motion segment)
The second point is specified by
Position = 1620,
Speed = 110000,
Time = 6msec
The time is defined with msec units, not in amplifier sampling times. The Amplifier interpolates the motion
specification to calculate the desired position and speed at the sampling instances, when it needs the
information.
PVT implements a 3
rd
order interpolation between the position-speed data provided by the user.