Every modern AS/RS stacker crane works inside a hard envelope: 1,000–1,300 kg per load for standard air-cargo or pallet units, up to 40 m vertical reach, and telescopic forks extending 1,500 mm with a 2.5 m/s horizontal travel ceiling [S3][S4]. That envelope is only safe if the load profile is validated at the induction conveyor before the crane is called, not after.
A load profile check gate is the WCS-side decision point that compares an inbound unit's measured weight, footprint, CoG offset, and declared load-handling-device class against the bay and crane it is being routed to, blocking the pick command when any parameter falls outside tolerance. It sits between conveyor scanning and the WMS-to-WCS dispatch message, and it is the cheapest place in the flow to reject a bad load.
Why the check gate exists between scanning and induction
Stacker cranes are mast or column systems running floor or rack-top rails with grippers, telescopic forks, or specialty load-handling devices, not a free-moving hoist [S1][S2]. That structural geometry means side-load and CoG errors propagate into mast deflection, rail-wheel wear, and sway on extraction; Konecranes' automated stacking cranes counter this with built-in Active Load Control to eliminate sway at landing, which only works when the declared mass matches reality [S7].
Heavy-load stacker cranes rated above 1,000 kg are explicitly described as relying on advanced sensors and software for accurate placement at high speed, and they are routinely specified for cold storage, automotive, and metal-handling duty where a mis-declared coil or engine block has no soft-fail mode [S3]. The check gate is the upstream sensor-and-software layer that keeps the crane's own positioning logic honest.
Parameters the gate must validate
The minimum parameter set, drawn from the OEM selection criteria for stacker cranes, breaks into four groups. First, load characteristics: unit mass, footprint, height, and CoG offset relative to the pallet centroid [S2]. Second, bay compatibility: rack opening width, clear height, and the aisle width, which must match the crane's travel envelope and rail tolerance.
Third, load-handling-device match: telescopic forks versus pallet shuttle versus on-board conveyor, and the extension stroke required, with 1,500 mm telescopic extension and two-tine configuration being a common reference pattern [S4]. Fourth, kinematic envelope: driving speed up to 2.5 m/s, driving acceleration 0.3 m/s², and lifting speed up to 0.5 m/s are the published limits that bound acceleration-induced sway and must be respected in the dispatch logic [S4]. Optional on-board weighing on the lifting platform is explicitly offered as the canonical way to close the mass loop [S4].
Comparison: check-gate options by integration point
Three implementation options dominate, and they trade cost against how late a bad load is caught. Option A, upstream vision-and-scale tunnel at the induction conveyor, catches mass, footprint, and label mismatch before the WMS commit, with the lowest aisle impact but the highest civil cost. Option B, on-board scale on the lifting platform, catches mass at the storage location after the crane has already cycled, trading one wasted cycle for zero added floor footprint and is the option Lödige packages as standard for air-cargo stacker cranes [S4].
Option C, WCS-only logical gate using pre-declared load data, costs almost nothing but trusts the upstream label and is the weakest of the three against barcode/RFID error. On throughput, A and C add under one second of latency at the conveyor handoff, B adds a full extraction-storage-return cycle per rejected unit but leaves the dispatch path clean. For AS/RS builds handling 1,300 kg-class pallet loads at 30 m/min lift and 150 m/min travel, B is the common retrofit, A is the common greenfield choice, and C is rarely used alone [S4].
Where the gate earns its keep: use cases
Air-cargo consignment storage is the cleanest case: in-house pallets up to 1,300 kg are scanned, weighed, and routed into multi-level racking by a stacker crane, and a missed CoG on a 1,500 mm-extended fork is a structural event, not a software fault [S4]. The same logic applies to metal-coil and industrial-die storage, where Demag's stacker-crane reference architecture places the crane directly on a transfer-car handoff and assumes the die or coil has already been dimensionally verified before dispatch [S1].
Heavy-load pallet stacks above 1,000 kg in manufacturing and cold-storage AS/RS, where cranes access heights up to 40 m, are the second case: at that lift height a single rejected cycle costs minutes of recovery and re-queue, which is why the on-board scale and the upstream check are typically deployed together [S3]. Automotive die retrieval and molten-mass pour lines are the third case, where a mis-declared load can damage the mast column itself rather than just the load, so a hard reject at the gate is preferred over a soft warning [S1][S5].
Limitations and failure modes
The check gate is only as good as the WMS-master data feeding it. Indef's reference workflow shows barcode or RFID identification at induction, with the crane moving to a designated slot only after the WMS commits, which means a mislabeled but in-tolerance load will still be accepted if the master data is wrong [S3][S5]. A second failure mode is dimension drift: pallets that meet mass but sit at the edge of the rack opening tolerance pass the logical gate and bind on telescopic-fork extension, which is why rail-tolerance and aisle-width engineering are coupled problems rather than independent ones.
A third is the dynamic envelope: with driving acceleration and lifting speed bounded by the OEM's published limits, a load that is in spec at rest can still swing outside the clear profile under extraction, and the gate cannot see that [S4]. This is exactly the regime Active Load Control is designed to suppress on container-handling ASCs, but the WCS-level check gate has no sway data and must rely on conservative static envelopes [S7]. Cold-storage builds add a fourth: ice accretion on the load footprint skews the dimension reading and can pass a pallet that physically binds, so cold-rated heavy-load stacker crane builds need the dimension check re-validated at temperature [S3].
Sourcing and standards posture
OEM-published spec sheets from Demag, AFE, Lödige, Indef, and Konecranes converge on the same check parameters: mass, footprint, CoG, load-handling-device class, and kinematic envelope [S1][S2][S4][S5][S7]. Inform's heavy-load reference adds vertical reach up to 40 m and regenerative braking as standard efficiency features, both of which interact with the dispatch profile because regenerative braking only recovers energy on a correctly-declared load [S3].
No single ISO or EN standard governs the WCS-level check gate as a discrete function; the gate composes rack-clause tolerances, fork-stroke data, and crane envelope data from the OEM manuals into a WCS rule set. The practical engineering move is to derive the rejection thresholds from the crane OEM's own capacity plate and the rack supplier's opening tolerance, then version-control that rule set against any AS/RS system layout change.
The next trackable signal is the WCS-side audit log of rejected inductions per shift: a healthy gate produces a steady, low-rate stream of CoG and mass rejects tied to specific SKUs or suppliers, and a sudden drop is itself a sensor-health alarm. A second signal is the on-board scale cross-check against the gate's declared mass, which should agree within the OEM-stated weighing tolerance on every cycle, with divergence flagged before the next shift's dispatch window opens.