SAIWENNA / CONTROL ENGINEERING
Shade Position Feedback vs Estimated Position: An Acceptance Matrix
A screen displaying “50%” may be showing a requested target, a controller estimate or a value reported by a device. Those meanings are not interchangeable. Before approving a shading interface, give every displayed point a source, a meaning and a freshness rule.
Four statements that a position display can make
| Displayed information | Evidence it provides | What remains unproven |
|---|---|---|
| Requested target | The controller has a desired position in its command record | Delivery, accepted execution and actual movement |
| Command acknowledgement | The documented protocol response was received | Completion of travel unless the protocol explicitly defines it that way |
| Calculated or estimated position | A model has updated a value using its stated inputs, such as elapsed drive time | The real position when actual motion differs from the model assumptions |
| Device-reported position or status | The identified device returned a defined value at a recorded time | Its sensing basis, accuracy, physical meaning and freshness beyond that report |
Even the last row needs interpretation. A motor-side position value is not automatically an independent measurement of the fabric edge. Ask what the source measures or calculates, how it is referenced to limits, and what happens after interruption or external movement.
Scenario: the screen says 50%, but the buyer needs a verified position
Imagine an office specification requesting a “50% shade position” after a scene runs. This is an illustrative acceptance scenario. First decide what the percentage refers to: normalized motor travel, fabric coverage, a controller convention or another documented quantity. Do not assume 50% means half the glazing area is shaded.
Next, separate the target and the report in the interface schedule. A display can retain the requested target while another field reports the latest device state. If there is no supported report, label the value as an estimate or target. Do not present an unavailable observation as a confirmed position merely because the command was sent successfully.
Finally, agree on the freshness behavior. Record when a new report is expected, how its age is displayed, and what the interface shows when it becomes stale or unknown. The appropriate update interval depends on the selected equipment and project; no universal polling rate is provided here.
A point definition the integrator can implement
- Point identity
- Opening ______ Device/model ______ Controller/gateway ______ Firmware ______
- Meaning
- Target / acknowledgement / estimate / device report ______ Units and direction ______
- Evidence
- Protocol object or message ______ Manual revision/page ______ Sensing or calculation basis ______
- Freshness
- Report trigger ______ Timestamp source ______ Agreed stale-data rule ______
- Unknown state
- Display behavior ______ Alarm or operator action, if specified ______
- Acceptance
- Expected result ______ Observed result ______ Tolerance and method ______ Reviewer ______
Test the interpretation, not just the button
- With the qualified integrator, identify one representative approved configuration and its current limits and direction.
- Record a commanded move and the separate acknowledgement, position or status reports actually supported.
- Compare the displayed result with the agreed physical observation method. Preserve the source of each value.
- Include an approved interruption-and-recovery case if the project requires it. Do not deliberately obstruct a moving shade or defeat a protective function.
- Record any state that the system cannot distinguish. Resolve that limitation before claiming the requested acceptance result.
Keep this record with the BMS responsibility schedule and site acceptance record. Group commands and travel speed are separate issues, explained in the speed guide.
Prepare a feedback requirement for review Include the exact equipment and the decision the position value must support. Gateway availability, compatibility and supply responsibility remain configuration-specific.
Sources and scope
- Somfy SDN Integration Guide, DOC155888/003, July 2023, pp.7 and 26–27
- Theben JU 1 / JU 1 RF / JU 1 S RF KNX manual, 2021-10-14, pp.21 and 39
- Point matrix and scenario: original specification-review method
Reviewed 20 October 2026. Named manufacturer examples retain their own applicability. Supply scope and project acceptance require the selected equipment and responsible review.