Digitax ST User Guide
87
Issue: 5
9.19 Interpolated position mode
Interpolated position mode operates in servo mode. Table 9-74 lists the
objects that are supported:
Table 9-74 Supported Interpolated position mode objects
When using one of the DSP-402 positioning modes, Distributed Clocks
must be enabled. Failure to do so may result in the EtherCAT interface
going into the SAFE-OPERATIONAL state (Pr
17.04
= 4).
9.19.1 0x60C0 Interpolation_sub-mode_select
Table 9-75 0x60C0 Interpolation_sub-mode_select
9.19.2 0x60C1 Interpolation_data_record
This object is used to specify the target position. Linear interpolation is
used to generate position demand values every 250 µs. The position is
specified in user-defined position units. The value is written into sub-
index 1.
Table 9-76 0x60C1 Interpolation_data_record
9.19.3 0x60C2 Interpolation_time_period
Table 9-77 Interpolation_time_period
The implementation of interpolated position mode allows synchronous
operation only, where a fixed, common interpolation interval is defined.
The time specified must always be an integer multiple of the control loop
cycle time. The time period index has a minimum value of -6 (i.e. the
smallest time unit will be microseconds), see Table 9-78 for more
information.
Table 9-78 Interpolation time period units
The time period is checked to ensure that it is an integer multiple of the
control loop cycle time. Only linear interpolation is currently supported,
this type inserts a delay of one interpolation time period.
The input buffer has a maximum size of 1 data record, and a data record
contains one position in profile-defined units. The buffer is a FIFO buffer.
On each interpolator time period, a value is read from this buffer. The
correct number of data points for a specific interpolation mode are stored
internally. When a new position command is loaded in, the oldest
position command in the data set is discarded.
Index
Name
0x60C0
interpolation_submode_select
0x60C1
interpolation_data_record
0x60C2
interpolation_time_period
0x60C0
Interpolation_sub-mode_select
Access: RW
Range: 0
Size: Signed 16 Unit: N/A
Default:
0 (Linear interpolation)
Description:
Specifies the interpolation type. At present the only
supported Interpolation Sub-Mode is ‘Linear
Interpolation’.
0x60C1
Interpolation_data_record
Sub-index 0
Access: RO
Range: N/A
Size:
Unsigned 8
Unit: N/A
Default: 1
Description: This object is used to specify the target position.
Sub-index 1
Access: RW
Range: 0 to
0xFFFFFFFF
Size:
Unsigned 32
Unit: N/A
Default: N/A
Description: The set-point.
NOTE
0x60C2
Interpolation_time_period
Sub-index 0
Access: RO
Range: N/A
Size:
Unsigned 8
Unit: N/A
Default: 2
Description: The number of the last sub-index in this object.
Sub-index 1
Access: RW
Range: 0 to 255
Size:
Unsigned 8
Unit:
(sub-index 2)
Default:
250 (units are dependant on the value in sub-index 2)
Description:
The number of time units between interpolator re-starts. A
time unit is defined by sub-index 2. The interpolator time
period value is checked to ensure that it is valid. Valid
values are 250 µs, 500 µs or any multiple of 1 ms. An
attempt to write other values results in an SDO Abort
code.
Sub-index 2
Access: RW
Range: -6 to 0
Size: Signed 8
Unit: N/A
Default:
-6 (a time unit of 1 µs)
Description:
This specifies the time unit for the interpolation time
period. Sub-index 2 specifies the unit exponent. The time
unit, therefore, is 10 (sub-index 2). The range of values
allows for the shortest time unit to be 1 µs, and the longest
to be 1 s.
Value in 0x60C2, sub-index 2
Description
0
1 second
-1
0.1 of a second
-2
0.01 of a second
-3
0.001 of a second
-4
0.0001 of a second
-5
0.00001 of a second
-6
0.000001 of a second
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