Motion Control
Linear Position v3
Description

Linear Position v3

Provides the actual, current position with floating point accuracy and flexibility. A preset facility and clamps are provided.

Counts that cause the position to exceed the clamps are discarded. Counts in the opposite direction are counted. The clamps are designed to support special applications;

Hard-stop, break-away clutch motors. Counts past the stop position are ignored. Any count in the opposite direction is assumed to be movement off the stop.

Rotary operator setpoint dial with no stops. Turning the dial past the setpoint clamp has no effect. Any rotation in the opposite direction has immediate effect.

The count input is freely connectable from any single Encoder or FI function block Count output in any smarty on the local network.

With Pulses/Rev and floating-point Scaler parameters, the output can be scaled as desired, e.g. meters or millimeters.

The Set Zero input predominates over Hold and Preset. Preset predominates over Hold

The Output is zero when Set Zero is Active

Asserting the Preset Enable input causes the output to be set to the preset value.

Hold input causes the output to hold at its current value and discard any ongoing counts. The output increments from the current value when made Inactive.

Transitions of Set Zero, Preset, or Hold should not be commanded while the count is actively incrementing. Transitions that occur while the count is actively changing will be associated with an uncertainty equal to the revs per second times the timebase setpoint of the containing device.

Example of position uncertainty from dynamic transitions -

The Linear Position function block is located in a speedy with the default timebase, 5ms.

The count is from an encoder spinning at 1800RPM.

Preset is asserted momentarily by passing a prox switch.

1800RPM / 60s x 0.005s = 0.15 rev uncertainty with transitions at full speed.

Eliminate dynamic position uncertainty with other motion control function blocks having high-speed event input capability; Registration, Event Measurer, Event Timer.

The function block Status is Fault and the function block output is zero if the count input is not updated for a period longer than approximately twenty times the timebase, i.e. 100ms, by default.

Design a complete motion control solution with three function blocks. The following pictures show examples of Linear Position v3 function block in three different systems. The first allows an index command to choose any position along evenly divided intervals. The second allows up to 100 positions to be pre-defined and selected via an index. The third system accepts explicit position commands.

Availability
  • Available only in the dw2xx-v2 series products
  • Requires library: Precision Motion (option -39)
  • Firmware versions 0x2111 and later
savvy-SFD Graphic linPos3
Graphic with Parameters linPos3

Parameters

Count Input, Read-only, Placeholder (special (count & timestamp))

Count

The count input is freely connectable from any single Encoder or FI function block Count output in any smarty on the local network.

Hold Input, Read-write, Boolean (signed 16-bit integer)

Hold

Hold input causes the count to hold at its current value and ignore any ongoing counts. The count resumes from the current value when made Inactive.

Typically, transitions of Hold should not occur while the count is actively incrementing. Transitions of Hold while the count is actively changing will be associated with an uncertainty equal to the counts per second times the timebase setpoint of the containing device.

Example

The Linear Position v2 function block is located in a speedy with the default timebase, 5ms.

The count is from an encoder spinning at 1800RPM.

1800RPM / 60s x 0.005s = 0.15 rev uncertainty with transitions at full speed.

Other motion control function blocks with high-speed event input capability that may be useful; Registration, Event Measurer, Event Timer.


0 = Inactive
1 = Hold
Pulses/Rev Input, Read-write, Analog (signed 16-bit integer)
1 ppr to 30000 ppr
Set Zero Input, Read-write, Boolean (signed 16-bit integer)

Set Zero

The Set Zero input predominates. The Output is zero when Active and the count continues from zero when Inactive.

Typically, transitions of Set Zero should not be commanded while the count is actively incrementing. Transitions that occur while the count is actively changing will be associated with an uncertainty equal to the revs per second times the timebase setpoint of the containing device.

Example of position uncertainty from dynamic transitions -

The Linear Position function block is located in a speedy with the default timebase, 5ms.

The count is from an encoder spinning at 1800RPM.

Set Zero is asserted momentarily by passing a prox switch.

1800RPM / 60s x 0.005s = 0.15 rev uncertainty with transitions at full speed.

Other motion control function blocks with high-speed event input capability that may be useful; Registration, Event Measurer, Event Timer.


0 = Inactive
1 = Set
Status Internal Parameter, Read-only, Boolean (signed 16-bit integer)

Status

The function block Status is Fault and the function block output is zero if the count input is not updated for a period longer than approximately twenty times the timebase, i.e. 100ms, by default.

0 = OK
1 = Fault
Output Output, Read-only, Analog (32-bit IEEE-754 floating point value)
-340E36 to 340E36

Output

The current, floating-point position.

Scaler Input, Read-write, Analog (32-bit IEEE-754 floating point value)
-340E36 per rev to 340E36 per rev
Lower Clamp Input, Read-write, Analog (32-bit IEEE-754 floating point value)
-340E36 to 340E36
Upper Clamp Input, Read-write, Analog (32-bit IEEE-754 floating point value)
-340E36 to 340E36
Preset Value Input, Read-write, Analog (32-bit IEEE-754 floating point value)
-340E36 to 340E36
Preset Enable Input, Read-write, Boolean (signed 16-bit integer)
0 = Inactive
1 = Preset