Warehouse ASRS — Automated Storage and Retrieval System

Project Overview

Motionwell Automation deployed an Automated Storage and Retrieval System (ASRS) integrated with SIASUN AGV fleet for a logistics operator in Singapore. The project optimized warehouse storage density and picking efficiency, replacing manual forklift operations with automated material handling.

As the authorized SIASUN AGV distributor for Southeast Asia since 2017, Motionwell brings deep expertise in AGV fleet deployment, traffic management, and integration with warehouse management systems.

System Components

ASRS Racking and Retrieval

The ASRS installation uses double-deep selective racking reaching 12 meters in height with 8 storage levels, increasing cubic storage utilization by over 60% compared to the previous conventional racking layout:

• Stacker crane with telescopic fork for double-deep pallet access, rated for 1,500kg per pallet position
• Multi-deep storage configurations for high-volume SKUs with FIFO (first-in-first-out) lane management
• RFID-tagged locations using UHF passive tags at every storage cell for real-time inventory tracking
• Siemens S7-1500 PLC controlling crane sequencing, with Profinet communication to the fleet management server

SIASUN AGV Fleet

Motionwell deployed a fleet of 8 SIASUN AGF-L15 laser-guided AGVs, each rated for 1,500kg payload capacity. The AGVs replaced manual forklift operations on all transport routes between the ASRS, receiving docks, and shipping staging areas:

• Laser-guided navigation (LiDAR SLAM) with RFID floor tags at decision points for position verification
• Magnetic tape guidance along primary travel lanes with laser-based free navigation in open zones
• SIASUN RoboRoute traffic management system coordinating multi-vehicle routing, deadlock avoidance, and intersection priority scheduling
• 4 opportunity-charging stations positioned along travel routes, enabling continuous 24/7 operation without dedicated charging downtime
• Fleet scalable to 20+ vehicles on the same traffic management server without software license changes

Integration Architecture

The system integrates with the customer’s existing SAP EWM warehouse management system via standard RFC/BAPI interfaces:

• WMS interface for inbound/outbound work order management and task prioritization
• RFID-based inventory verification at every handoff point (dock, ASRS entry, staging)
• Web-based fleet management dashboard with real-time AGV position, battery status, and task queue monitoring
• Exception handling workflows with automatic rerouting and manual override via handheld terminals

Technical Details

AGV Chain Conveyor Modules

Each AGV in the fleet is equipped with a chain conveyor module mounted on its top platform, enabling automated pallet loading and unloading without forklifts or manual intervention. The AGV chain conveyor interfaces with stationary chain conveyors at the ASRS entry/exit points, receiving docks, and shipping staging areas.

The pallet transfer sequence operates as follows:

1. The AGV navigates to the target station and aligns with the stationary chain conveyor using its onboard sensors
2. The AGV’s chain conveyor and the stationary conveyor activate simultaneously at matched speed
3. The pallet transfers laterally from one conveyor to the other under chain drive power
4. Photoelectric sensors at both ends of the conveyor confirm pallet presence and transfer completion
5. The AGV’s chain conveyor stops, and the AGV proceeds to its next mission

This conveyor-to-conveyor handoff eliminates the need for the AGV to carry fork tines or lifting mechanisms, reducing vehicle complexity, weight, and maintenance requirements. The chain conveyor rated capacity matches the ASRS stacker crane at 1,500kg per pallet.

RFID Floor-Embedded Navigation Tags

The AGV navigation system uses RFID tags embedded in the warehouse floor at decision points throughout the travel network. Each RFID tag contains a unique position ID that the AGV reads via an undercarriage-mounted UHF RFID reader as it passes overhead.

The RFID tags serve as absolute position references that correct accumulated dead-reckoning error from the AGV’s wheel encoders and LiDAR SLAM system. At each RFID tag location, the AGV recalibrates its internal position estimate to the known tag coordinates stored in the fleet management server’s map database.

Tags are installed at:

• Every intersection and branch point in the travel network
• Docking positions at the ASRS entry/exit conveyors
• Charging station approach points
• Receiving and shipping dock positions

The floor-embedded installation (tags are grouted into shallow recesses cut into the concrete floor) protects the tags from forklift traffic and cleaning equipment, providing maintenance-free operation over the system lifetime.

Fleet Management Software

The SIASUN RoboRoute fleet management server coordinates all AGV routing and pallet assignment across the fleet. The software manages:

• Mission dispatching: Incoming transport requests from the WMS are queued and assigned to the nearest available AGV based on current position, battery level, and estimated travel time
• Traffic management: The server maintains a real-time map of all vehicle positions and planned routes. When two vehicles would converge at an intersection, the server assigns priority based on payload urgency and assigns hold/proceed commands to prevent deadlocks
• Route optimization: Travel routes are dynamically calculated to minimize total fleet travel distance. The server considers current traffic density, blocked lanes (maintenance zones), and one-way restrictions when computing routes
• Pallet tracking: Every pallet is tracked from pickup to delivery, with the fleet management server updating the WMS inventory database at each handoff point. This provides end-to-end material traceability without manual scanning

The fleet management dashboard displays real-time AGV positions, battery status, active missions, queue depth, and throughput metrics on a web-based interface accessible from any workstation on the facility network.

Automatic Contact-Based Charging

The AGV fleet uses automatic contact-based charging to maintain continuous operation. Four opportunity-charging stations are positioned along high-traffic travel routes. When an AGV’s battery level drops below a configurable threshold (typically 30% state of charge), the fleet management server automatically routes the vehicle to the nearest available charging station during a natural gap between transport missions.

The charging sequence:

1. The AGV navigates to the charging station and aligns with the charging contacts using its precision docking routine
2. Spring-loaded contact plates on the AGV make electrical connection with the station’s charging pads
3. The charger delivers high-current DC charging (typically 30-50A) to rapidly boost the battery level
4. When the battery reaches the target threshold (typically 80%) or a high-priority mission is assigned, the AGV disconnects and resumes transport operations

The opportunity-charging model means no AGV is ever taken out of service for dedicated charging periods. Combined with the fleet management server’s intelligent scheduling, this enables true 24/7 uninterrupted operation – the fleet continuously self-manages its energy state while maintaining transport throughput.

Battery health monitoring data (charge cycles, cell voltage balance, temperature history) is logged by the fleet management server and used to schedule preventive battery maintenance before degradation affects operational availability.

Related

This project demonstrates Motionwell’s robotics integration and custom machine design expertise for the warehouse & intralogistics industry.