CANopen Programmer's Manual - Maccon.de

9: Cyclic Synchronous Modes CANopen Programmer’s Manual
PVT Profile Moves Using the Copley Controls Alternative Objects
As mentioned earlier, Copley Controls CANopen amplifiers provide an alternate set of objects for
more efficient execution of PVT moves and linear interpolation moves with variable time.
The basic method for sending PVT profile data over the CANopen network is:
1 Configure a transmit PDO to send out the Trajectory Buffer Status object (index 0x2012, p.
216). The preferred transmit type for this PDO is 255 (event driven). This causes the PDO to
be transmitted every time a segment is read from the buffer, or on error.
2 Configure a receive PDO to receive the PVT buffer data via the IP move segment command
(index 0x2010, p. 214).
3 Use either PDO or SDO transfers to fill the PVT buffer with the first N points of the profile
(where N is the size of the PVT buffer).
4 If using synchronization, start synchronization before starting motion.
5 Start the move by causing a 0-to-1 transition of bit 4 of the Control Word object (index 0x6040,
p. 58).
6 Each time a new Trajectory Buffer Status object (index 0x2012, p. 216) is received, first check
for error bits. If no errors have occurred, then one or more additional segments of PVT data
should be transmitted (until the trajectory has finished).
If the Trajectory Buffer Status object indicates that an error has occurred, then the reaction of
the controller will depend on the type of error:
Underflow errors indicate that the master controller is not able to keep up with the trajectory
information. When an amplifier detects a buffer underflow condition while executing an
interpolated profile, it will immediately abort the profile. In this case, using longer times
between segments is advisable.
Overflow errors indicate an error in the CANopen master software.
Segment sequencing errors suggest either an error in the CANopen master software or a lost
message, possibly due to noise on the bus. Since the next segment identifier value is passed
with the PVT status object, it should be possible to resend the missing segments starting with
the next expected segment. Note that the sequencing error code must be cleared with the
appropriate IP move segment command Buffer Command Mode message (p. 214) before any
new segments of PVT data are accepted.
7 End the move by setting the PVT segment time to zero. See IP move segment command
object (index 0x2010, p. 214), and Format of Data Bytes in PVT Segment Mode, p. 215.
212 Copley Controls