Container Handling Vehicle Scheduling for Shared Port Queue Reduction
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Solution Overview
Problem
Existing automated storage and retrieval systems face inefficiencies due to container handling vehicles waiting in queue at the same port, leading to suboptimal utilization of operational capacity.
Innovation Solution
A method and control system that assigns tasks to container handling vehicles with deadlines and calculates end times, applies bonus/penalty points, and reassigns tasks to optimize arrival times, ensuring vehicles arrive just before others finish interacting with the port, thereby minimizing waiting time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple container handling vehicles are assigned to interact with the same port, then the port's transfer capacity is improved, but the vehicles experience queue waiting time that reduces operational capacity utilization
Solution Approach 1:
The control system performs preliminary calculation of end times for tasks without deadlines, and proactively ranks tasks before execution. By pre-calculating arrival times at ports and ranking tasks in advance, the system optimizes vehicle schedules to minimize queue waiting time before vehicles actually arrive at ports, thereby maintaining high port transfer capacity while reducing operational capacity loss.
Solution Approach 2:
The system dynamically adjusts task execution sequences based on real-time conditions. Tasks are ranked dynamically considering current vehicle positions, estimated arrival times, and deadline requirements. This dynamic optimization allows the system to adapt to changing conditions and minimize queue waiting time while maintaining efficient port transfer operations.
2Ease of operation
If vehicles are scheduled to arrive at the port early, then they can be ready for immediate transfer, but their operational capacity is not optimally utilized due to idle waiting
Solution Approach 1:
The control system continuously monitors vehicle positions, task completion status, and port interaction times. Based on this feedback, it dynamically recalculates end times for ongoing tasks and adjusts task rankings to optimize arrival timing. This feedback mechanism ensures vehicles arrive at ports just in time for transfer operations, minimizing both idle waiting time and operational capacity loss.
Solution Approach 2:
The system changes the timing parameters of task execution dynamically. By calculating end times based on current vehicle positions and adjusting task schedules, the system optimizes arrival times at ports. This parameter optimization allows vehicles to maintain high operational capacity utilization while being ready for immediate transfer when they arrive at ports.
3Productivity
If tasks without deadlines are prioritized, then vehicle utilization is improved, but tasks with deadlines may not be completed on time
Solution Approach 1:
The control system performs preliminary assessment of whether vehicles can complete deadline-critical tasks after finishing tasks without deadlines. By pre-calculating end times and checking deadline feasibility before task execution, the system ensures that prioritizing tasks without deadlines does not compromise deadline completion reliability.
Solution Approach 2:
The system continuously monitors task progress and deadline adherence. Based on feedback from ongoing operations, it dynamically adjusts task rankings to ensure deadline-critical tasks are completed on time while maintaining high vehicle utilization. This feedback mechanism balances productivity and reliability by adapting task priorities to actual system state.
Data Source
AI summary
An automatic storage and retrieval system includes a framework structure defining a storage grid for storing storage containers in storage columns. The storage containers are handled by the container handling vehicles running on top of the storage grid. A port is used for transferring storage containers to and from the storage and retrieval system. A method for utilizing operational capacity of container handling vehicles when assigned tasks of delivering or retrieving identified storage containers at the same port of the automatic storage and retrieval system includes the following steps performed by a control system communicating with a vehicle controller in each container handling vehicle: assigning tasks without deadlines and with deadlines for the container handling vehicles to arrive at the port; calculating end times and end positions of the container handling vehicles when the assigned tasks without a deadline complete; checking if container handling vehicles can meet a deadline after first completing a task without a deadline; ranking the tasks assigned to the container handling vehicles, where tasks that can meet the deadline, after first finishing a task without a deadline, are ranked first, and further according to arrival times of the container handling vehicles at the port; and executing tasks by communicating instructions to the container handling vehicles according to the ranking of tasks.