Elmo HARmonica, HARSFEN0602 150, Programming Sequence for The Auto Increment PVT Mode

HARSFEN0602ElmoHARmonicaSoftwareManual PRELIMINARYDRAFT

12.1.6.5.2 Programming Sequence for The Auto Increment PVT Mode

PVT motion must start with initial programming of the PVT arrays. Set

MP[1] = First valid line in the PVT table MP[2] = Last valid array in the PVT table MP[3] = 1 for cyclical mode.

MP[4] = Not relevant for PVT (PT only)

MP[5] = Number of left programmed motion rows to issue a “PVT queue low” Emergency object. Set to zero if no “PVT queue low” warning is desired.

MP[6]=the write pointer. This is the next position in the PVT table to be written by the CANopen object 0x2001.

Set the QP[N], QV[N], and QT[N] array elements for at least the first used two rows of the PVT table. This is since PVT requires at least two time points to interpolate the motion trajectory.

Set (if not already set) UM=4 or UM=5, and MO=1

Set PV=N, assuming QP[N] ,QV[N] ,QT[N] and QP[N+1] ,QV[N+1] ,QT[N+1] are all programmed to valid values.

Start the motion by a BG.

Use the CAN PVT/Auto increment command for the rest of the PVT motion.

Keep informed how the PVT motion advances, either by receiving the read and the write PVT table pointers continuously, mapped to a synchronous PDO, or by using the queue low emergency signal to signal the need for more data. The queue low emergency message includes the present location of the read pointer and the write pointer.

It is safe to send more PVT data PDOs until the write pointer is one location before the read-pointer specified by the queue low emergency message. The host is well aware to the location of the write pointer, since it can count its own messages. A data message may be, however, rejected since the queue is full, or since a message is lost. In that case, the Amplifier will issue an emergency object to the host. After receiving the emergency object the true location of the write pointer may be unclear. The host may then set MP[6] to the possibly rejected table row and continue the writing from there.

Do not set MP[5] (Number of rows left for queue low emergency) too high. For example, consider a slow- responding host managing a 64 rows long PVT queue in the Amplifier. Suppose that the PVT row times are 10 msec each, and that MP[5]=55. The host gets a queue low emergency object telling that there are 64-55+1

=8 free to program rows in the PVT table. Suppose that the host takes 50msec to respond, and 5 msec to program each row. Thus, the 8 rows have been programmed in 90 msec. In the meantime, 9 additional PVT table rows have been executed, and there are only 54 valid rows in the PVT table. As 54 is lower than MP[5], there will be no more queue-low emergency messages until the PVT table is exhausted, and the PVT mode is terminated. This situation may be remedied if the host asks the Amplifier for PV (location of read pointer) after the PVT table writes are complete. If PV<MP[5], the programming process took too much time, and the writing must be continued.

Accurate timing with respect to the host is the essence of multiple-axis synchronized motion. Accurate timing may be achieved by using the CAN SYNC signal, and the CAN synchronized BG service, as described in the CAN Manual.

12.1.6.6The Parameters of The PVT Motion Mode

The following parameters apply to PVT motion

What	How	Comment
Unit Mode (UM)	Unit modes 3, 4 and 5 select
	the position modes.

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