Elmo HARmonica, HARSFEN0602 software manual 140, Example

HARSFEN0602ElmoHARmonicaSoftwareManual PRELIMINARYDRAFT

4000

Counts/sec

2000

0

-2000		Time (sec)
0	0.1	0.2		0.3	0.4
100
0	Position reference
-100	Position Target
-200	Counts	Time (sec)
0	0.05	0.1	0.15	0.2	0.25

140

12.1.6PVT: Position-Velocity-Time interpolated motion

12.1.6.1What 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 3rd order interpolation between the position-speed data provided by the user.