Description

This virtual downloadable product comprises a Python framework with an executable example application. The framework can be used for modeling pallet warehouses and pallet stacks operated by a single forklift or storage handling machine in a single storage aisle with any amount of interchanges (inlets, outlets, and bi-directional interchanges). The project is developed in Python, using SimPy (a free and simple simulation engine in Python), and supports parametrization of relevant model settings. This downloadable virtual product furthermore also supports tracking of relevant KPIs. You can use the downloaded framework to model, dimension, and analyze your own pallet stack or pallet warehouse (automated or manually). Below video demonstrates the configurable model parameters that are supported by the framework and exemplary simulation model implementation. The video furthermore also shows some of the statistics that are tracked by the framework.

In detail, this virtual downloadable product contains the following files:

• requirements.txt – lists the required Python module dependencies for pip install (pip install -r “requirements.txt”)
• main.py – executable Python script that contains an exemplary simulation model, implemented by applying the framework provided through the other modules
• config.py – allows you to adjust relevant parameters such as the amount, type and position of interchanges, the dimension of the pallet storage rack, forklift kinematics, etc.
• equipment.py – provides a class for modeling a forklift
• jobdata.py – provides a class for modeling forklift jobs
• layoutdata.py – provides classes for modeling a storage aisle, and storage aisle interchanges

Configurable parametrization

The following parameters can be set and adjusted through the configuration file (config.py):

• forklift speed in x and z direction
• forklift acceleration in x and z direction
• interchange handling times for pallet pick and pallet placement
• compartment load handling time
• additional delay times per complete forklift move
• mean dispatch time, i.e. the average time between assigning a job to an interchange and the job actually being executable (e.g. a pallet putaway might be assigned to an inlet, but the pallet might only arrive at the inlet 40 to 60 seconds after the assignment, i.e. 50 seconds on average
• number of pallet storage columns
• number of tiers in the pallet storage rack (=1 if ground based pallet storage, greater than 1 if a pallet rack is used and if that rack has more than 1 tier)
• width of a column
• height of a compartment (tier height)
• positions per interchange, x-axis and z-axis positions in separate lists
• types per interchange (options are “inlet”, “outlet”, or “both”)
• maximum search radius when searching a pallet storage compartment
• maximum search radius when selecting a random pallet for retrieval to a defined interchange
• target throughput rates
• simulation run length, in seconds

Default assumptions made by this downloadable simulation project

By default, this downloadable simulation project makes the following assumptions:

• Random compartment selection
• Defined speed and acceleration for forklift / handling machine, for x and y axis
• Defined handling time, for load handling at compartment and at inlet/outlet (= interchange)
• Only one forklift or handling machine in the aisle
• Every compartment has the same height and width
• There is only one storage zone, i.e. any pallet can be stored anywhere in the aisle, in any of the compartments
• For inlets and bi-directional interchanges (allowing both putaways and retrievals), all non-reserved interchanges have the same probability of being assigned to a putaway job
• Likewise, for outlets and bi-directional interchanges, all non-reserved interchanges have the same probability of being assigned to a retrieval job