3D Material Library

Automated Stereoscopic Warehouse System Design Proposal

 

I. Project Overview

This solution aims to design and build an intelligent automated warehouse system that integrates mechanical automation, electrical control, and information management. Centered around a stacker crane as the core execution unit, the system incorporates conveyor lines, racking, automatic identification, and inventory‑management software to achieve end‑to‑end automated operations—covering inbound receiving, storage, outbound picking, and information management. The方案 adheres to the design principles of “efficiency, stability, intelligence, and safety” and is tailored to meet the warehousing requirements for packaging materials used in nuclear power applications.

II. Mechanical Structure Design

2.1 Automated Storage and Retrieval System

• Structural configuration: A heavy-duty, bull‑leg‑type steel rack system is employed, with cold‑rolled thin‑walled steel members joined by high‑strength bolts. The uprights and beams form a rigid frame, ensuring both load‑carrying capacity and seismic performance.
• The overall dimensions of the automated storage system are: 25 m (length) × 3.9 m (width) × 7.6 m (height), with a fully enclosed design.
• Environmental Control: Humidity inside the warehouse must be continuously maintained below 60% to ensure the moisture‑resistance of packaging materials.
• Storage Location Layout: A matrix layout organized by “aisle + tier‑column” is adopted, with multi‑tier, multi‑column storage locations arranged on both sides of each aisle.
• Large‑storage pallet net dimensions: 2300 mm × 1000 mm × 1000 mm (designed to accommodate stacked foam strips, arranged in 9 columns × 2 rows × 3 tiers). Small‑storage pallet net dimensions: 2300 mm × 1000 mm × 850 mm (arranged in 9 columns × 2 rows × 3 tiers).
• Safety Protection: Anti-collision guardrails are installed at both ends of the racking, with limit stops on each level and a fall‑prevention mesh laid on the top level to prevent goods from sliding off or the stacker crane from overrunning its designated area.

 

2.2 Stacker Crane System

This solution employs a double‑column, single‑deep‑aisle stacker crane. Its structural composition comprises a metal frame, a traveling mechanism (horizontal drive), a lifting mechanism (vertical drive), a load platform, a three‑way fork extension mechanism, a set of guide wheels, and safety protection devices, all integrated into a single unit. It is divided into three motion units:

• Traveling mechanism: Moves horizontally along the ground track, driving the entire machine to operate.
• Lifting mechanism: drives the cargo platform to move vertically along the upright columns, enabling loading and unloading at different floor heights.
• Fork mechanism: three-stage telescopic forks, enabling the retrieval and placement of pallets on and from racking.

Stacker performance parameters:

Parameter	Parameter value	Explanation
Rated load capacity	600 kg	Adapted to the rated load of the storage location
Walking speed range	0-60 m/min	Variable-frequency speed control with positioning, supporting customizable acceleration and deceleration profiles.
Increase the speed range	0-15 m/min
Fork extension speed	0~20m/min
Positioning accuracy	Travel ±5 mm Increase by ±1 mm Fork ±2mm
Maximum lifting height	9m
Adaptable to aisle width	1560mm	Compatible with single-deep rack configurations

 

• Operating mode: Bidirectional operation within the tunnel, enabling coordinated motion along the X (horizontal), Y (vertical), and Z (telescopic) axes.

 

2.3 Positioning and Safety Detection Scheme

It employs a dual-redundant positioning design to eliminate cumulative errors and ensure long-term operational accuracy.

• Localization: Real-time position feedback from a laser rangefinder, combined with side‑wall barcode strips for absolute position correction—e.g., one correction point every 200 mm—completely eliminating encoder cumulative error.
• Enhanced positioning: cargo platform encoder feedback combined with photoelectric switches at each level for position correction, ensuring precise layer alignment.
• Fork positioning: encoder-based position detection combined with a limit photoelectric switch, providing dual verification of the pick-and-place position.
• Multi-layered security protection:

1. Tunnel entrance: Safety light curtain + access control interlock; any unauthorized entry immediately triggers an emergency stop.

2. At both ends of the stacker: laser anti-collision sensors, mechanical hard limit switches at the extreme positions, and hydraulic buffers—providing triple-layered collision protection.

3. Overload Protection: The lifting mechanism is equipped with a gravity sensor; in the event of overload, operation will stop immediately.

4. Power‑off protection: Equipped with a power‑off braking device, ensuring the cargo platform does not descend when power is lost.

2.4 Drive and Communication

• Travel Drive: Siemens variable-frequency drive with a variable-frequency motor, ensuring fast, stable operation and precise positioning.
• Drive upgrade: Inovance servo drive paired with a servo motor, delivering fast positioning response.
• Communication method: The stacker’s onboard distributed I/O communicates with the master PLC via a PROFINET bus, utilizing a conductor rail for power supply and wireless PROFINET communication. Compared to cable‑drag systems, this approach offers higher reliability and lower maintenance costs.

 

2.5 Conveying System

• Inbound and outbound conveyor lines: composed of conveyors, equipped with photoelectric sensors and barcode scanners to enable automated loading and information collection.
• Buffering and Guiding: Equipped with buffer roller conveyors and non-metallic guiding devices to ensure smooth material transport and prevent deviation.

2.6 Auxiliary Structures

• Power Supply System: A safe sliding contact system is employed to ensure the continuous operation of the stacker crane.
• Protection and Maintenance: Key transmission components are equipped with protective guards and foreign-object collection bins, while the equipment is enclosed by safety fences, fitted with emergency stop buttons, and illuminated by warning lights.

III. Electrical System Design

The Siemens S7‑1500 PLC is the mainstream core controller for modern automated storage and retrieval system (AS/RS) stacker cranes. Leveraging its robust multi‑axis motion control capabilities, native PROFINET communication advantages, and the seamless integrated development environment of TIA Portal, it perfectly meets the stacker crane’s requirements for high‑precision positioning, coordinated multi‑axis operation, and exceptional reliability, serving as a pivotal link: interfacing upward with WCS/WMS to receive operational commands and controlling all hardware components downward to ensure stable, reliable crane operation.

System Overall Architecture

The standard architecture adopts a three-tier layered design:

• Upper layer: WCS warehouse control system + HMI local touch screen, responsible for issuing operation commands, visually displaying equipment status, and providing a local operator interface.
• Control Layer: The S7-1500 PLC serves as the core, responsible for logic processing, motion control, safety protection, and system-wide data exchange.
• Field equipment layer: includes drive units (servo drives/inverters), sensing units (encoders, photoelectric switches, laser distance sensors, safety devices), and actuators (travel motors, lift motors, and fork‑extension mechanisms).

3.1 Control System Architecture Design and Selection

• Main Controller: A Siemens S7-1500 series PLC is employed as the system’s core, enabling logic control, task scheduling, and equipment coordination.
• Drive System:

3.1.1 Travel and Lifting: The Inovance SV660N servo system is employed, operating in speed/position mode to achieve high-precision motion control.

3.1.2 Fork Extension: Utilizes a variable-frequency motor for control, with high- and low-speed limit switches regulating speed and positioning to ensure precise alignment and smooth extension/retraction.

3.1.3 Position Feedback: The laser distance sensor communicates with the PLC via the Profinet fieldbus, enabling fully closed-loop control.

Control System Architecture

 

Network topology diagram

 

Main Electrical Control System Configuration List

Name	Specifications	Quantity	Brand
PLC	S7-1500	1	Siemens
Touch screen	12 inches	1	Siemens or Weintek
Travel drive	G120 drive	1	Siemens
Enhanced Drive	SV660N	2	Huichuan
Fork drive	G120 drive	1	Siemens
Laser rangefinding	DL100, DT500	1	SICK or Leuze
Safety relay		1	Sick or PILZ
Visual Inspection System	3D Dimensional and Appearance Inspection	1	Customization
Barcode reader	One-dimensional barcode or QR code	2	Hikvision or Cognex
Wireless gateway		1	TPllink
Encoder		1	P+F

 

3.2 Human-Computer Interaction System

The human-machine interface primarily implements the following functions:

• On-site operation: Configure the touch screen (HMI), supporting manual/automatic mode switching, parameter setting, status monitoring, and fault alarm display.
• Remote Monitoring: Supports communication with the host computer system, enabling remote start/stop operations, task assignment, and data visualization.

 

3.3 Communications

3.3.1 PLC–Stacker Communication

• Core Architecture: The system employs an architecture comprising “lane‑mounted fixed base station bridges, stacker‑mounted wireless clients, and ring‑topology industrial switches.” The stacker’s onboard PLC connects directly to the onboard client via Ethernet, while all base station bridges are aggregated through the ring switch and then integrated into the local area network hosting the master PLC, enabling end-to-end data exchange along the path from the WCS/WMS to the master PLC and on to the stacker’s onboard PLC.
• Standard deployment guidelines: At the top of each aisle, the overhead beams are positioned to avoid obstruction by rack‑mounted metal components. Two industrial wireless bridges are deployed, operating on the 5.2 GHz and 5.8 GHz dual‑band frequencies, with a spacing of 50–70 meters between them, ensuring that the stacker crane maintains a signal strength of at least −60 dBm at any point along its entire travel range. A dual‑band redundant client is installed inside the stacker crane’s control cabinet, enabling simultaneous reception of signals from both frequency bands and automatic, seamless handover in the event of signal degradation, thereby preventing any communication interruptions.
• Protocol Adaptation: Built on Ethernet pass‑through at the underlying layer, it natively supports mainstream industrial protocols such as PROFINET, Modbus TCP, and S7 TCP, seamlessly integrating with Siemens S7‑1200/1500 series master PLCs. Data transmission latency typically ranges from 10 to 30 ms, fully meeting the real-time control requirements of stacker cranes.

 

3.3.2 PLC–WCS Communication

Communication between the PLC control system and the WCS serves as a bridge connecting field devices with the upper-level management system, responsible for translating business instructions into device actions and feeding back device status to the management system.

• Network Architecture: Typically employs standard Industrial Ethernet, with the physical layer utilizing shielded twisted pair or fiber optics to ensure robust EMI immunity and stable long-distance transmission in industrial environments.

• Communication Protocol:
• Data exchange content:

Through this hierarchical, reliable communication architecture, the automated storage and retrieval system achieves seamless integration from management commands to physical execution, ensuring the efficient and intelligent operation of the entire warehouse system.

 

Visual Inspection System

 

Detection and Safety Systems

• Sensor network: includes photoelectric switches (for detecting the presence of goods), proximity switches (for limit detection), load cells (for overload protection), emergency stop buttons, and more.
• Appearance Inspection System: A vision-based inspection system that performs dimensional measurements of pallets and detects surface defects.
• Communication Network: An industrial Ethernet (Profinet) is deployed to build the device-layer network, ensuring real-time data transmission.

 

IV. Software Function Overview

4.1 PLC System Functions

As the “brain” of an automated high‑bay warehouse, the PLC coordinates the operations of various devices—such as stacker cranes, conveyor line isolation gates, and fire‑protection interlocks—ensuring smooth and safe material handling. The system typically employs a modular programming approach, breaking down complex control logic into independent function blocks (FBs/FCs) to facilitate development, debugging, and maintenance.

4.1.1 PLC Control Process

(1) High-precision multi-axis coordinated motion control

The stacker crane’s horizontal travel (X-axis), vertical lifting (Y-axis), and fork extension/retraction (Z-axis) are all centrally managed by the S7-1500’s native motion control functions:

• Supports absolute positioning (implemented via the MC_MoveAbsolute motion object), enabling S‑curve acceleration and deceleration, smooth adjustment of acceleration, significant reduction of mechanical shock, and prevention of cargo sway. Positioning accuracy can be consistently maintained within ±15 mm, meeting the operational requirements of narrow‑aisle automated storage systems.
• Supports multi-axis parallel operations, enabling simultaneous travel and lifting motions to shorten individual cycle times and enhance the overall throughput efficiency of the automated storage system.
• Supports multi-source positioning correction: integrates encoder position feedback with barcode/RFID-based address calibration, completely eliminating the cumulative error inherent in encoders alone and ensuring stable positioning accuracy even during long-term operation.

(2) Full-process automated operation control

• Automatically receives inbound/outbound, relocation, and inventory‑counting instructions issued by the WCS, and seamlessly executes the entire operational workflow:

• Supports one‑click switching among multiple operating modes: Automatic mode (for normal production), Manual mode (for debugging and maintenance, with independent control of each axis), Zeroing mode (for home‑position calibration upon startup), and Maintenance mode (which deactivates power to ensure safe servicing).
• Supports job priority management, allows the insertion of urgent orders, prioritizes high-priority jobs, and adapts to flexible production scheduling requirements.

(3) Stable and reliable data interaction capabilities

• It interfaces with WCS/WMS via PROFINET, providing real-time feedback on stacker crane location, operation progress, equipment status, and fault information. It features built-in heartbeat monitoring, network‑disconnection reconnection, and command‑retransmission mechanisms to prevent operational interruptions caused by network fluctuations.
• Via PROFINET, it interfaces with servo drives and inverters to read motor operating parameters—including current, temperature, and actual position—in real time, enabling comprehensive data acquisition and providing the data foundation for predictive maintenance of the equipment.
• Native support for HMI integration enables visual display of all device statuses and parameters, and also allows online modification of motion parameters and positioning deviation thresholds, making commissioning exceptionally convenient.

(4) Advanced condition monitoring and fault diagnosis

• Full‑state real‑time data acquisition: continuously tracks the stacker crane’s position, cargo status, and motor operating parameters; automatically accumulates equipment runtime and triggers scheduled maintenance reminders upon expiration.
• Standardized fault management: Each fault type is assigned a unique error code, with a complete fault history automatically recorded; the HMI directly displays the fault location and cause, often accompanied by preliminary troubleshooting recommendations, significantly reducing downtime.
• Leveraging the S7-1500’s built-in integrated web server, you can remotely access the PLC via a browser to view runtime data and diagnose faults online, enabling preliminary troubleshooting without needing to be on-site.

 

4.1.2 PLC Core Functional Modules

The S7-1500 is developed using TIA Portal and adheres to a modular, structured programming approach, facilitating subsequent maintenance and functional expansion.

1. Priority‑based architecture design: In the main loop, safety monitoring is assigned the highest priority. Whenever safety conditions are not met, all motion‑control logic is immediately halted, and no subsequent operations are executed, thereby ensuring safety‑first operation at the design level.
2. Independent Functional Block Decomposition: Divide the program into multiple loosely coupled, independent functional blocks; a typical decomposition is as follows:

State‑machine‑driven operation workflow: A state machine is used to manage the operational process, breaking down stacker operations into distinct states such as standby, travel, lifting, picking, placing, and returning. The state‑transition logic is straightforward and easy to understand, minimizing complexity and facilitating debugging and troubleshooting.

(1) Stacker Crane Control Module

● Function Description: This is the core control component of the automated storage and retrieval system, responsible for the stacker crane’s precise three-dimensional positioning (along the X, Y, and Z axes) within the aisles, as well as the operation of its forks.

● Key technical points: Motion control logic—based on tasks issued by the WCS, it computes the optimal path and coordinates the coordinated movements of horizontal travel, vertical lifting, and fork extension/retraction. Positioning typically employs dual verification, combining absolute encoders with laser ranging or address‑tagging methods.

● Speed Control: Implements multi‑stage speed control (high‑speed operation, medium‑speed deceleration, and low‑speed positioning) to ensure precise stopping accuracy.

● Task Queue Management: Manages the stacker crane’s task list, supporting task priority adjustment and emergency‑stop recovery.

(2) Code Reading and Inspection Module

● Function Description: Responsible for automatically identifying cargo information at the handover points (inbound/outbound gates).

● Key technical point: Barcode/QR code recognition: An industrial barcode reader scans the barcode on pallets or material bins and uploads the data to the host system (WMS/WCS) for verification.

● Dimensional Inspection: Optical sensors or 3D vision systems are used to measure the length, width, and height of goods and detect over‑dimensional shipments, preventing out‑of‑spec items from entering the automated storage system and causing equipment damage.

(3) WCS Communication Module

● Function Description: Acts as a bridge between the PLC and the Warehouse Control System (WCS), enabling data exchange.

● Key technical points: Task reception and feedback: Receive inbound and outbound instructions issued by the WCS (including source and destination addresses, etc.) and report task execution status in real time (start, completion, failure).

● Device Status Reporting: Periodically or upon change, reports the device’s operating status (running, standby, fault), its current location, and any alarm information to the WCS.

● Inventory Synchronization: Works in conjunction with the WCS to reconcile and update both physical and virtual inventory levels.

(4) Isolation Door and Peripheral Device Control Module

● Function Description: Controls the automated storage and retrieval system (AS/RS) aisle isolation doors, the roller conveyors at the inbound and outbound docks, photoelectric sensors, and other auxiliary equipment.

● Key technical points: Interlock control: Ensures that the access gate cannot be opened when the stacker crane is not in a safe position (to prevent unauthorized personnel from entering). Inbound and outbound handling process: Controls the start-up and shutdown of the conveyor system, coordinating with the stacker crane to facilitate cargo transfer.

(5) Security Control Module

● Functional Description: This is the system’s lifeline, ensuring the safety of personnel and equipment.

● Key technical point: Emergency stop circuit: A hardwired connection to the emergency stop button ensures that pressing the emergency stop directly cuts off power to the drive.

● Limit Protection: Dual protection—soft limits (programmable) and hard limits (physical switches)—prevents the stacker crane from overtraveling to the top or bottom.

● Rope‑slack/Overload Detection: Monitors wire‑rope tension or motor current to prevent rope breakage or mechanical overload.

● Personnel intrusion detection: Uses light curtains or door lock switches to detect the presence of personnel or foreign objects in the passage.

(6) Fire Alarm Interlock Module

● Function Description: Integrates with the building’s fire protection system to execute safety protocols in emergency situations such as fires.

● Key technical point: Fire signal reception: Receives dry-contact signals or communication signals from the fire alarm control panel.

● Emergency Shutdown and Evacuation: Upon receiving a fire alarm signal, immediately shut down all non-fire‑fighting equipment and command the stacker crane to ascend to the top floor to clear the sprinkler heads, or retract it to the maintenance position.

● Smoke exhaust/fire damper control: In accordance with fire safety requirements, the system interlocks to close fire-rated rolling shutters and start smoke exhaust fans.

(7) Fault Diagnosis and Logging Module

● Function Description: Records the system’s operational history, facilitating post-event traceability and fault analysis.

● Key technical point: Alarm logging—records the time, code, and description of each alarm event.

● Operation Log: Records critical operations (such as manual interventions and reset procedures).

(8) System Operation Logic

Power-up initialization, self‑diagnosis (safety circuit and communication status), waiting for WCS commands or local operation, executing inbound and outbound storage processes (including barcode reading, handling, and storage/retrieval), status feedback, and exception handling (alarm/shutdown).

(9) Stacker Crane Control Program

● PLC logic control: Enables automatic control of travel, lifting, fork extension, positioning, and safety interlocks.

● Path Optimization Algorithm: Automatically plans the shortest path based on task priority and the current location.

● Fault Diagnosis: Monitors equipment status in real time; automatically shuts down and logs fault codes upon detecting abnormalities, with support for remote diagnostics.

(10) System Integration and Interfaces

● Integration with ERP/MES: Data exchange is enabled via Web Service or OPC UA interfaces.

● Barcode/RFID Identification: Automatically captures item information upon receipt, ensuring reconciliation between records and physical inventory.

 

4.2 Human-Machine Interface Functions

It is divided into the following six major modules.

(1) Main Monitoring Interface

Functionality	Feature Overview
1 Automated Warehouse Visual Overview	Use an overhead simulation map with color coding to display the status of all storage locations, clearly distinguishing between vacant, occupied, in‑process, and faulty locations.
2. Display of the Stacker Crane’s Core Status	Real-time display of the stacker crane’s travel/lifting axis position, current task number, operation status, and positioning deviation.
3 System Connection Status Display	Displays the PLC operating status, WCS/WMS communication status, and the connection status of peripherals such as laser rangefinders and barcode readers.
4 Quick Access Area	Provides common quick-access functions such as emergency stop reset, mode switching, and rapid navigation to the alarm page.

(2) Operation Control Module

Functionality	Feature Overview
1 Automated Task Management	Displays the queue of pending and in-progress tasks, supporting task start, pause, cancel, and skip operations, as well as one-click triggering of the stacker crane to return to its home position.
2 Manual Debugging Control (requires engineer permissions)	Supports independent jog/ inching control for the stacker’s travel, lifting, and fork mechanisms, meeting equipment commissioning requirements.
3 Abnormal Operation Intervention	Supports single-step inbound and outbound testing, temporary fine-tuning of positioning parameters, and adaptation to manual inventory counts and exception-handling scenarios.

(3) Storage Location and Inventory Management Module

Functionality	Feature Overview
1 Multi-condition query for storage locations	Supports filtering and querying the target storage location by storage location number, pallet barcode, or cargo batch.
2 Warehouse Location Details Display	Displays the current status of a single storage location, along with details such as pallet information, cargo name, batch number, and inbound date.
3 Manual Adjustment of Abnormal Storage Locations	Supports manually locking faulty storage locations, releasing abnormally occupied storage locations, and modifying storage location binding information.
4 Inventory Statistics	Statistically analyze the total number of storage locations across the entire warehouse, the ratio of used to available spaces, and inventory levels by product category.

(4) Parameter Setting Module

Functionality	Feature Overview
1 Process Parameter Configuration Calibration	Supports setting segment‑based speed‑control thresholds and positioning tolerances for the stacker, and enables laser‑range zero‑point calibration and cargo‑location address offset correction.
2 View and Configure Communication Parameters	Supports viewing/modifying the PLC and WCS server IP addresses, as well as the communication timeout threshold, and viewing the status of peripheral connections.
3 System Parameter Maintenance	Supports adjusting screen brightness, enabling or disabling the alarm buzzer, and calibrating the system time; also supports exporting parameter configuration backups to a USB flash drive.
4 Hierarchical Permission Control	It is divided into three levels of access—operator, engineer, and administrator—with only authorized personnel permitted to modify core parameters, thereby preventing accidental misoperations.

(5) Fault Alarm and Diagnostic Module

Functionality	Feature Overview
1 Current Alarm Display	Sort all unresolved alarms in reverse chronological order, displaying the Chinese fault description and occurrence time directly, without parsing error codes.
2 Export of Historical Alarm Queries	Supports filtering and querying historical alarms by time range and fault type, with the option to export alarm records to a USB drive.
3 Fault-Assisted Diagnosis	Displays PLC I/O status, inverter current and fault codes, and the connection status of core peripherals, helping to quickly pinpoint issues.
4 Troubleshooting Guide	Built-in preliminary troubleshooting guides for common issues—simply click on an alert to view them, lowering the barrier to operations and maintenance.

(6) Data Statistics and Traceability Module

Functionality	Feature Overview
1 Equipment Operation Statistics	Statistics on the stacker crane’s cumulative operating hours, today’s/monthly workload, average operation time, and cumulative downtime due to failures.
2 Key Parameter Trend Display	Displays historical trends of key parameters such as laser positioning deviation, inverter load, and motor temperature, enabling proactive identification of potential equipment issues.
3 Job Record Traceability Query	Supports filtering and querying inbound and outbound history records by time period, pallet barcode, and storage location number.
4 Exporting Work Reports	Supports exporting job records as Excel‑formatted reports to meet production process traceability requirements.

 

 

4.3 Warehouse Management System (WMS)

WMS primarily comprises the following functions:

• Inbound Management: Supports various inbound types, including procurement and production. The system automatically assigns the optimal storage location based on item attributes (category, batch, weight) and generates an inbound task order.
• Outbound Management: Receives outbound instructions, generates picking tasks according to the first-in-first-out (FIFO) principle or a specified batch strategy, and optimizes picking routes.
• Inventory Management:
• Real-time monitoring: dynamically displays inventory quantities, locations, and statuses, with support for inventory threshold alerts and slow-moving‑item warnings.
• Inventory counting functionality: Supports periodic and dynamic inventory counts, with the system automatically generating inventory reports.
• Report Analysis: Generates inbound and outbound inventory reports, inventory turnover ratios, equipment utilization rates, and more, with data export capabilities.

The WMS (Warehouse Management System) dedicated to automated storage and retrieval systems serves as the core business management hub, responsible for inventory planning and operational decision-making. It interfaces with the WCS (Warehouse Control System) and higher-level ERP/MES systems, enabling end-to-end automated operations. The core modules and corresponding functions of a standard WMS for automated storage and retrieval systems are as follows:

• Basic Information Configuration Module: This module serves as the foundation for the entire system, responsible for configuring all static master data. It defines the warehouse’s physical layout by delineating functional areas such as aisles, storage zones, inbound/outbound areas, maintenance zones, and non-conforming‑goods areas.
• Storage location lifecycle management: Each storage location is assigned a unique identifier (e.g., A‑Aisle‑01‑Row‑03‑Level‑05), and its attributes—such as load capacity, dimensions, compatible pallet type, and status (available/frozen/disabled)—are maintained. This forms the core of precise address‑based operations in automated storage and retrieval systems.
• Basic Information Management: Manage materials such as SKUs, suppliers, customers, packaging unit conversions, and user roles and permissions; configure system parameters including inbound and outbound rules and picking strategies.
• Inbound Operations Management Module: Manages the end-to-end process from goods receipt to warehouse storage and final shelving, seamlessly integrating with automated operations in automated storage and retrieval systems. It supports scheduled inbound shipments, pre-receipt of goods via ASN (Advanced Shipping Notice), and proactive slot allocation to prevent operational bottlenecks.
• Scan the QR code to quickly verify incoming shipment information and record quality inspection results; nonconforming items are automatically flagged and isolated.
• Automatically recommends the optimal storage location based on predefined strategies: supports rules such as placing heavy items in lower zones, light items in upper zones, consolidating storage for the same SKU or batch, and assigning locations near entry/exit points, thereby maximizing space utilization and operational efficiency.
• Once the storage location assignment is complete, an inbound instruction is automatically generated and sent to the WCS. Upon completion of the operation, inventory levels and storage location statuses are updated in real time, and an inbound document is created.
• Outbound Operations Management Module: Integrates with production and sales orders to manage the end-to-end process, from issuing picking instructions to confirming outbound shipment. It receives outbound orders from higher-level systems (ERP/MES) and automatically consolidates tasks within the same aisle to optimize operational efficiency.
• Automatically select target storage locations according to predefined strategies: supports multiple put-away and picking strategies, including first-in-first-out (FIFO), first-expiry-first-out, fixed batch priority, and minimizing stacker travel distance.
• A outbound instruction is generated and sent to the WCS. Upon completion of the operation, inventory is automatically deducted, storage location statuses are updated, and outbound completion information is reported back to the upper-level system. Barcode verification during outbound processing is supported to prevent mis‑shipping.
• Inventory Fine-Grained Management Module: Enables comprehensive, dynamic management of in-stock goods across all dimensions.
• Real-time display of warehouse-wide inventory and the status of each storage location, with multi-dimensional inventory queries supported by SKU, batch, location, and supplier.
• Batch and Expiry Date Management: End-to-end tracking of product batch numbers, expiration dates, and serial numbers, ensuring compliance with production traceability and quality control requirements.
• Inventory Alerts: Supports alerts for safety stock upper and lower limits as well as overdue inventory, prompting management to take timely action.
• Automated inventory counting: The system can automatically issue inventory‑counting instructions to the WCS, dispatching stacker cranes to traverse all storage locations, automatically reconcile physical stock with system‑recorded inventory, and generate an inventory‑discrepancy report—eliminating the need for manual aisle inspections and significantly boosting counting efficiency.
• Supports warehouse relocation and adjustment: Enables you to reallocate inventory based on stock turnover, optimizing your warehouse layout.
• WCS Integration and Operation Monitoring Module: This is the core module that distinguishes a automated storage and retrieval system (AS/RS) WMS from a conventional flat‑warehouse WMS, serving as the bridge between the business layer and the equipment layer. It translates business commands—such as inbound/outbound operations and inventory counts—generated by the WMS into device‑control instructions that the WCS can interpret, and then dispatches these instructions to the scheduling system.
• Receive real-time feedback from the WCS on equipment status, job progress, and completion results, and synchronize system data accordingly.
• Visualized monitoring of the operational status of all warehouse equipment: displays stacker crane locations, task progress, and fault alarm information, while supporting manual intervention for handling abnormal operations.
• Auxiliary Operations Management Module: Meets the specialized operational requirements of automated storage and retrieval systems.
• Empty pallet management: Supports automatic return of empty pallets to the warehouse and on-demand outbound scheduling, optimizing the utilization rate of empty pallets.
• Exception Handling: For abnormal situations such as equipment jams, misaligned goods, and barcode recognition failures, manual intervention is supported to adjust storage locations and inventory statuses.
• Replenishment Management: For automated storage and retrieval systems operating under the “storage + piece-picking” model, the system can automatically trigger replenishment from the AS/RS to the picking area based on inventory levels in the picking zone.
• End-to-End Traceability and Quality Management Module: Designed to meet the compliance requirements of manufacturing enterprises, this module records a complete operational log for each pallet and each shipment—from receipt and storage through to dispatch—capturing details such as the operator, timestamp, equipment used, and origin/destination information. In the event of quality issues, it enables rapid traceability and pinpointing of the root cause.
• Supports non-conforming‑product freeze management, locking problematic items at their designated storage locations, prohibiting outbound shipments, and coordinating unified handling.
• Reporting and Data Analytics Module: Provides data-driven support for warehouse operations optimization. Automatically generates multi-dimensional operational reports, including inbound/outbound inventory statistics, inventory ledgers, inventory turnover ratio reports, equipment utilization efficiency reports, and inventory accuracy reports, with Excel export functionality.
• Conduct multi-dimensional analysis of warehouse operations data to help managers identify bottlenecks, optimize storage location allocation strategies, and enhance overall operational efficiency.
• External System Integration Module: Seamlessly Connects End-to-End Enterprise Data:
• Provides standardized interfaces to enable integration with enterprise-level systems such as ERP (for order and financial reconciliation), MES (for automated outbound of production raw materials and inbound of finished goods), stacker crane scheduling systems, and conveyor control systems, while supporting mainstream communication protocols including OPC UA, WebService, and HTTP.
• Achieve two-way data synchronization, eliminating the need for manual re-entry and seamlessly integrating end-to-end data across production, warehousing, and logistics.
• System Maintenance Module: Ensures stable system operation; supports user role and permission configuration, assigning distinct operational privileges to different roles (Administrator, Operator, Maintenance Technician).
• Full‑scale operation logging ensures that all actions are traceable.
• Supports automatic data backup, customizable label templates (including printing pallet barcodes and location labels), and online adjustment of system parameters.

The large on-site display shows the operational status and storage location information.

 

Core display content on site:

• 3D Digital Twin View: A three-dimensional visualized map that dynamically maps the physical locations of automated storage aisles, racking, and stacker cranes in real time. It provides a live display of storage location statuses—available, occupied, locked, or out of service—using color coding (e.g., green for available, red for full, and yellow for locked).
• Key Operational Metrics: Real-time, rolling display of today’s total inbound volume, total outbound volume, current inventory levels, inventory turnover rate, and overall equipment effectiveness.
• Equipment Health Monitoring: Centrally displays the operating status of stacker cranes, conveyor lines, and shuttle cars (running, standby, fault, maintenance). When integrated with environmental sensors, it can also show on the same screen environmental data such as warehouse temperature and humidity, as well as smoke detector status.
• Anomaly and Alarm Center: Highlights and proactively pushes system alarm notifications—such as motor overload, communication failure, or cargo over‑dimension—and displays the handling progress, helping management make swift decisions.

 

 

 

4.4 Warehouse Control System (WCS)

The WCS (Warehouse Control System) serves as the real-time scheduling and control hub that bridges the gap between the upper-level WMS/ERP/MES systems and the lower-level automated equipment. It is responsible for command forwarding, equipment dispatching, and status monitoring, ensuring the orderly operation of end-to-end automated processes. The core modules of a standard automated storage and retrieval system (AS/RS) WCS and their corresponding functions are as follows:

• Interface Communication Module: This is the foundational module that enables data exchange across the entire WCS system, with the following core functions:
• Task Management and Scheduling Module: This is the core decision-making module of the WCS, with the following key functions:
• Dedicated control module for underlying equipment: Implements hardware‑specific control logic tailored to different automated storage and retrieval systems; core functions:
• Positioning Accuracy Correction Module: A proprietary module designed to ensure the long-term operational accuracy of automated storage and retrieval systems. Core functions:
• Real-time Visualization and Monitoring Module: Provides operators with comprehensive situational awareness; core functions:
• Security Protection and Exception Handling Module: Ensures the safety of personnel and equipment and enhances system robustness; Core functions:
• Debugging and Equipment Maintenance Module: Meets the needs of equipment installation, maintenance, and parameter adjustment; core functions:
• Alarm Log and Operations Analytics Module: Supports fault troubleshooting and predictive maintenance; Core functions:
• System Basic Management Module: Ensures the secure and stable operation of the system; Core Functions:

Data Security: Supports automatic system data backups to prevent data loss.

 

V. Multi-Layered Security Protection Mechanism

Safety is a core requirement of stacker crane control systems. Stackers based on the S7-1500 typically incorporate multiple layers of protection:

1. Emergency Stop and Hard Safety Protection: The emergency stop button is wired in series with normally closed contacts, ensuring that activation of the emergency stop immediately cuts power and shuts down the machine under all operating conditions. Safety light curtains and safety door switches at tunnel entrances are connected to the safety circuit; upon detecting unauthorized personnel entering the area, the system triggers an immediate shutdown, meeting the requirements of SIL2/PLe safety integrity levels.
2. Dual‑stage limit protection: Both the traveling and lifting axes are equipped with software limits and mechanical hard stops; any overtravel immediately triggers an emergency stop, providing double protection to prevent the stacker crane from derailing or colliding with the racking.
3. Logical interlock protection: Implements multi‑action interlocks—e.g., prohibiting travel and lifting operations when the forks are not fully retracted to prevent fork‑shelf collisions; and preventing operation initiation when the load platform is overloaded, thereby mitigating operator error at the logical level.
4. Exception‑tolerant handling: Each motion is equipped with timeout monitoring and sensor‑signal conflict detection; upon fault activation, the system automatically locks itself and requires manual troubleshooting and reset before restarting. Once the fault is resolved, the system supports resuming from the interruption point, eliminating the need to return to the home position and re‑initiate the entire task, thereby improving efficiency.

 

VI. Description of the Operational Process

Inbound Process

• Goods onboarding: The goods are placed on the inbound conveyor line, triggering the photoelectric sensor, and the barcode scanner automatically reads the information.
• Information Validation and Task Generation: The WMS validates the information, automatically generates put‑away tasks, and assigns target storage locations.
• Conveyance to the aisle entrance: The conveyor line transports the goods to the designated aisle entrance and, upon arrival, sends a “ready” signal.
• Palletizer order picking: Upon receiving the instruction, the stacker travels to the aisle entrance, raises or lowers its load platform to the designated height, extends the forks to retrieve the pallet, and uses laser positioning to ensure precise alignment.
• Storing at the designated location: The stacker crane moves to the target storage location, scans the barcode to verify that the current location number matches, deposits the goods using its forks, and upon confirming proper placement, retracts and returns to standby.
• System Update: The WMS updates inventory status in real time and marks the storage location as “occupied.”

Outbound Process

• Task Assignment: The WMS receives the outbound instruction, generates an outbound task, and determines the target storage location.
• Palletizer retrieval: The palletizer travels to the target storage location, scans the location code for verification, and confirms accuracy. It then extends its forks to pick up the item and retracts them after confirming everything is correct.
• Delivery to the outbound port: The stacker crane transports the goods to the aisle’s outbound port and places them on the outbound conveyor line.
• Conveyor Sorting: The conveyor line transports goods to the sorting area or the shipping dock, where they are scanned to confirm outbound shipment.
• Inventory Update: The system automatically reduces the inventory quantity and marks the storage location as “Available.”

Exception Handling

• Equipment malfunction: If the stacker crane triggers an alarm, the system automatically suspends the task, and the HMI displays the fault code, with manual intervention supported.
• Goods exception: If scanning fails or the dimensions do not match, the system prompts manual intervention and logs the exception.

 

VII. Visual Inspection System

This system is deployed at critical nodes along the inbound conveyor line of an automated high‑bay warehouse, aiming to replace traditional manual inspection with machine‑vision technology. Its primary function is to perform non‑contact, all‑around scanning of inbound pallets and their contents, enabling real‑time measurement of the pallet’s overall dimensions (length, width, and height) and assessment of its external integrity. This ensures that only compliant pallets enter the storage area, thereby preventing safety incidents such as stacker‑crane jams or cargo drops caused by oversized pallets or damaged pallets.

7.1 System Architecture and Hardware Layout

The system employs a combined architecture of gantry frame, 3D vision, and 2D imaging, ensuring comprehensive inspection and high precision.

• 3D Profile Measurement Unit (Core)
• Equipment selection: Employ high-precision 3D profile measurement sensors or depth cameras (e.g., those based on structured light or time-of-flight principles).
• Installation Location: Mounted at the center of the gantry beam directly above the conveyor line, with the camera pointing vertically downward.
• Function: Acquires point cloud data of pallets and goods for precise calculation of length, width, height, and volume.
• 2D Appearance Inspection Unit (Auxiliary)
• Equipment selection: high-resolution industrial area-scan camera, equipped with a high-brightness linear light source.
• Installation Location: Mounted on both sides and above the conveyor line to provide multi‑angle coverage.
• Function: Captures high-resolution images of the pallet’s bottom and sides to assess structural integrity, such as chipped corners or broken boards.
• Trigger and Auxiliary Devices
• Photoelectric sensor: Installed at the entrance of the inspection area to trigger the camera to capture an image.
• Audio-visual alarm: Used to provide on-site, intuitive indication of test results (green light for pass, red light for alarm).

7.2 Core Detection Functions

• Overall Dimension Inspection
• Length and width detection: Automatically measures the length and width of the pallet’s bottom surface to determine compliance with standard dimensions (e.g., 1200 mm × 1000 mm). The allowable tolerance can be set (not less than ±10 mm).
• Height Detection: Measures the total height of the “pallet + goods” to prevent over-height loads from entering the aisle and colliding with rack beams.
• Over‑dimension detection: Checks whether the cargo extends beyond the pallet edges (over‑width/over‑length) to prevent interference during conveying or stacking.
• Appearance and Integrity Inspection
• Pallet Damage Detection: Identifies physical damage to wooden or plastic pallets, such as chipped corners, fractures, and blocked holes.
• Foreign-object detection: Checks whether non‑cargo debris is present on the pallet, or whether the cargo stack is severely tilted or collapsed.

7.3 Workflow and Logic

• In-position trigger: As the pallet enters the inspection zone via the conveyor, the entry‑side photoelectric sensor is blocked, and the system issues a camera‑capture command.
• Image Acquisition: A 3D sensor and a 2D camera simultaneously capture data, generating a point cloud and a high-definition planar image.
• Algorithmic Processing: Visual processing software performs real-time analysis of the data.
• Size Comparison: Compare the measured data with predefined standard parameters, such as the dimensions of a national‑standard pallet.
• Appearance assessment: Using image segmentation and feature extraction algorithms, the system determines whether the pallet structure is intact.
• Result output:
• Pass: The PLC receives the “OK” signal, the conveyor continues to operate, and the item is released for storage.
• Non-conforming: The PLC receives an “NG” signal, the conveyor stops or diverts to the anomaly‑handling area, the audible and visual alarm flashes, and the host computer displays the specific fault cause (e.g., “height out of tolerance” or “tray with a missing corner”).

7.4 Key Technical Indicators

• Measurement accuracy: Dimensional measurement accuracy can reach ±5 mm to ±10 mm.
• Detection speed: Supports dynamic detection and accommodates conveyor line speeds of 0–60 m/min.
• Response time: The processing time for a single detection is less than 1 second, meeting the requirements of high-frequency data ingestion.
• Compatibility: The software supports switching among multiple tray specifications, allowing it to adapt to different business scenarios without requiring hardware changes.

VIII. System Advantages and Guarantees

• Efficiency: Automated operations replace manual handling, boosting inbound and outbound efficiency by more than 80%.
• Precision: Dual closed-loop control with laser and encoder ensures high positioning accuracy, resulting in a product damage rate of less than 0.1%.
• Safety: Equipped with multiple safety protection mechanisms and compliant with standards such as GB/T 28576-2012 “Safety of Industrial Trucks.”
• Maintainability: Supports remote monitoring and fault diagnosis, with a scheduled maintenance regime ensuring long-term stable operation.
• Scalability: Modular design supports the addition of new aisles, stacker cranes, or system functionality in the future.

 

9. Delivery and Acceptance

9.1 List of Deliverables

Prior to project acceptance, Party B shall deliver to Party A the following complete documentation and physical assets, ensuring the system’s maintainability and the integrity of its assets.

Hardware and Physical Delivery

• Core equipment: automated storage and retrieval system (AS/RS) racking system (including uprights, beams, tie rods, etc.), stacker cranes or mini-load systems, and inbound/outbound conveyor lines (roller, chain, or belt types).
• Electrical and Control Systems: Main control cabinet (PLC), operator panel (HMI), handheld terminal (if applicable), field sensors, and cable trays.
• Spare Parts: A list of consumable components and physical samples (such as belts, photoelectric switches, fuses, lubricants, etc.) will be provided, typically covering 1%–2% of the equipment’s total price in spare parts.

Software and License Delivery

• Control System: PLC source code and the compiled executable file, as well as the HMI screen program.
• Management software: WMS (Warehouse Management System) or WCS (Warehouse Control System) installation packages and database scripts.
• Licensing: Software dongles, databases, and genuine operating system licenses.

Document Delivery

• Technical drawings: electrical schematic diagrams, pneumatic circuit diagrams, equipment layout plans, and foundation construction drawings.
• Operation Manuals: Equipment Operation Manual, Software User Manual, and Daily Maintenance and Servicing Manual.
• Test Reports: Factory Acceptance Test Report, On-site Commissioning Test Report.

9.2 Acceptance Criteria and Procedures

The acceptance process is divided into three phases—pre‑acceptance, on‑site commissioning and acceptance, and final acceptance—to ensure that all system performance indicators meet the requirements of the technical agreement.

Pre-acceptance

• Location: Party B’s factory or assembly workshop.
• Content: Conduct no-load operational tests on core equipment such as stacker cranes and conveyor lines, verifying mechanical assembly accuracy, electrical wiring compliance, and basic software functionality.
• Standard: The equipment exhibits no mechanical interference, the electrical circuits are intact, and the software communicates normally.

On-site commissioning and acceptance

• Location: Party A’s project site.
• Content: Single-unit commissioning and integrated system commissioning following equipment installation and positioning.
• Key test items:
• Dimensional verification: The rack’s verticality and the stacker crane track’s levelness comply with national standards.
• Functional verification: Inbound, outbound, and transfer processes operate smoothly, and the barcode reading/detection system achieves the required recognition rate (e.g., ≥99.9%).
• Safety Testing: The emergency stop button, limit switches, collision‑avoidance devices, and fire‑alarm interlock functions are all operational.

Final Acceptance

• Trial Operation: The system shall undergo continuous trial operation in Party A’s actual business environment, typically for 72 hours or one week.
• Performance Evaluation:
• Inbound and outbound handling capacity: Actual throughput meets the design specifications (e.g., inbound processing ≥ 10 pallets per hour).
• Failure Rate: During the trial operation period, no major shutdowns occurred, and the mean time between failures met the specified requirements.
• Signed and confirmed: Upon successful completion of the trial run, both parties shall sign the “Project Final Acceptance Report,” thereby officially entering the warranty period.

9.3 Training and After-Sales Service

• Personnel Training: Party B shall provide Party A with on-site training lasting no less than two days, covering equipment operation, troubleshooting of common malfunctions, software backend management, and routine maintenance.
• Warranty Service:
• Warranty Period: A 12-month free warranty shall be provided, commencing from the date of signature upon final acceptance.
• Response Time: We will respond within 2 hours of receiving a fault report and arrive on-site within 24–48 hours (depending on the distance).
• Regular Inspections: During the warranty period, on-site inspection services will be provided once every quarter or every six months.
  This plan covers the entire closed-loop process, from hardware delivery to after-sales training. Do you think the current acceptance criteria—such as the trial‑run duration and fault‑rate requirements—are aligned with your project’s actual conditions?
  If you need adjustments for a specific scenario, I can help you:

1. Add specific performance evaluation metrics (e.g., concrete values for inbound and outbound efficiency).
2. Supplement the provisions on liability for breach of contract or handling of delayed delivery.
3. Streamline it into a single acceptance confirmation form for quick on-site signing.