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HARSFEN0602
12 The position reference generator
The position reference signal is generated by the following components:
Software command generator
Auxiliary command generator
Stop manager.
This section describes the components of the position reference generator in detail.
12.1 The software reference generator
The Harmonica supports five modes of software references.
The reference modes are:
Idle – The motor just stands at place. This is the default mode after setting motor on,
and after an interpolated motion is complete.
PTP – Point to Point: The user specifies the position in which the motor is to stand,
and the limits subject to which the trajectory to the target is to be designed. The
Harmonica designs automatically a minimum-time trajectory and executes it.
Jogging: The user specifies the speed in which the motor should steadily move, and
the acceleration limits towards that speed. The Harmonica designs automatically a
minimum-time trajectory and executes it.
PT – Position/Time: The user specifies a set of point to be visited with fixed time
differences. The Harmonica interpolates a 3
rd
order polynomial between the user's
points. The speeds at the user points are selected to form a smooth motion
trajectory. Using the PT, complex motions are easily designed. PT data may be
transferred to the amplifier on-line using an efficient CAN PDO protocol, so that
infinite PT motions are possible.
PVT – Position/Velocity/Time: The user specifies a set of motion points. Each point
includes a position, and the speed and the time at which the position is to be visited.
The user points are interpolated using third order polynomials. The PVT mode
allows absolute time specification, thus several amplifiers may compose a fully
synchronized motion using the PVT mode. PVT data may be transferred to the
amplifier on-line using an efficient CAN PDO protocol, so that infinite PVT
motions are possible.
In order to initiate a software motion, you must initialize its parameters and issue a mode
command. The next BG (software, hardware, or timed) will start the motion.
The mode command are listed in the following table:
Command Mode
ST Idle. ST stops any motion.
PA PTP. PA=n specifies a PTP motion, to the absolute position n counts
JV Jogging. JV=n specifies a Jog motion, with the speed n counts/sec
PT PT. PT=n specifies a PT motion, beginning from the n’th item in the PT
data table
PV PVT. PV=n specifies a PVT motion, beginning from the n’th item in the
PVT data tables
Table 12-1: Software motion mode commands
12.1.1 Switching Between Motion Modes
Stopping by the ST command is available anytime. The amplifier will decelerate the
position reference until a complete stop.
PTP and jog motions can be commanded to anywhere, any time. The Amplifier will
calculate the path to be followed so that the desired speed or position is reached, subject to
the acceleration limits. PTP and jog motions can even be initiated while PT or PVT motion