SKEW_CTRL
Gantry / bridge skew control: trims the two runway drives to keep the crane square, with a trip and a supervised square-up.
When to use it
Use SKEW_CTRL when a wide crane or gantry is driven by an independent drive at each end of the bridge, each runway has position feedback, and the crane must be kept square to stop it crabbing and binding on the rails.
Interface
The published port signature. This is the whole of what the block exposes to your program — the implementation body is not shown here and ships with the download.
Inputs
| Port | Type | Unit |
|---|---|---|
| ENABLE | BOOL | — |
| SPD_REF | REAL | m/s |
| POS_L | REAL | m |
| POS_R | REAL | m |
| POS_OK | BOOL | — |
| SKEW_LIM | REAL | m |
| SKEW_WARN | REAL | m |
| SKEW_OK | REAL | m |
| KP | REAL | (m/s)/m |
| TI | REAL | s |
| TRIM_LIM | REAL | m/s |
| TRIM_FRAC | REAL | - |
| V_MAX | REAL | m/s |
| A_MAX | REAL | m/s2 |
| SKEW_DLY | TIME | — |
| SQUARE_TMO | TIME | — |
| SQUARE_SPD | REAL | m/s |
| ACK | BOOL | — |
Outputs
| Port | Type | Unit |
|---|---|---|
| DRIVE_L | REAL | m/s |
| DRIVE_R | REAL | m/s |
| SKEW | REAL | m |
| TRIM | REAL | m/s |
| SKEW_HIGH | BOOL | — |
| SQUARING | BOOL | — |
| ALM_SKEW_TRIP | BOOL | — |
| ALM_SQUARE_TMO | BOOL | — |
| ALM_POS_FAULT | BOOL | — |
| ALM_CFG_ERR | BOOL | — |
IEC 61499 event interface
EI INIT, REQ·EO INITO, CNF
Supervised control write
SKEW_CTRL commands a real actuator. It is written to sit underneath your own interlock, permissive and protection logic — not to replace it. Commission it as you would any control block you wrote yourself.
Validation evidence
- Tests
- 13
- Simulated scans
- 352
- Simulator
- v0.1.0
Complete IEC 61131-3 implementation with a published test suite that runs on the vplant simulator. The counts above are that suite, executed on this build.
- Conforms to IEC 61131-3
- Conforms to IEC 61499
Download SKEW_CTRL — free
Create a free Ri Tech account to download the block. You get the Structured Text body, the Rockwell Add-On Instruction (.L5X), the Schneider Control Expert DFB (.XDB), PLCopen XML, the IEC 61499 function block type (.fbt) and the datasheet.
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