May 12, 2025

Use of Simulation from Design through Operations Support

System simulation consists of computer programs used to model the operation of a system. Generally, the simulation models the physical and logic operation of the system. Elements modeled can include automated equipment(AMRs, AS/RS cranes, shuttles, pallet shuttle system, conveyors, robotics), manual operations(walking, picking, packing), manually controlled equipment(fork trucks, pallet jacks), and related process elements. Data files are then used to provide demand or initial conditions(receipts, orders, and inventory levels), operating parameters(speeds, accelerations/decelerations, positioning times, walking times, processing times), and certain operating rules(receiving windows, shipping windows and cutoffs, wave plans and durations). Depending on the requirements, demand in a simulation can be created statistically using a variation of a peak rate or by using actual receipts and actual orders. The statistical model is simpler and faster to generate but might lack the variability of the actual operation.

Simulation is most useful with systems that involve a variety of flows through common resources, dynamic systems for which timing of various resources impact overall operation, and systems with high variability in demand. Examples of systems recently simulated by Invar Systems Includes:

Tote AMR solutions for carton buffering and for goods to person picking.
Pallet AMR solutions for dynamic picking.
Pallet AS/RS system servicing case pick operation, rail dock, and truck dock and using discrete cart based front end for overall movements.
Dynamic picking system for e-commerce fulfillment.

A computer generated image of a computer generated image

Picking, palletizing, and loading system for reverse stop loading of route truck in beverage operation.
System to automatically palletize product from production with wide range of product and high variability of flow by product.

Invar Systems uses simulation in various ways through the life of a system.

Proof of Concept- Simulation for proof of concept models a potential solution using either statistical inputs or actual data. Care is taken to capture resource performance and to incorporate appropriate system logic. The output is a measurement of time to complete work or equipment utilization.

System Requirements Definition- Certain systems require simulation to determine the peak requirements. This is the case when considering complex or overlapping flows or shared resources. The output is equipment or subsystem performance requirements needed to achieve a result. An example would be the number of moves to support a dynamic picking solution or the rate required on a sorter to support a waving strategy.

Evaluation of Detail Design Elements- As project implementation progresses, simulation is used to test detailed software logic, equipment parameters, and control logic. For software logic, this can include order processing, waving, order release, putaway strategies, picking strategies, replenishment, order consolidation, priorities, and outbound. For equipment parameters, this can include speeds, accel/decel, number of units or carriers or vehicles, command release and arbitration logic, etc. For control logic, it can include sortation, accumulation, sensor locations, merge logic, etc. In all cases, it can also include anomaly conditions and recovery strategies including equipment down, scanner read rate, load failures, jams and related stoppages, trucks arriving late, trucks arriving early, emergency orders, etc. In addition to addressing these detailed elements, simulation allows for sensitivity analysis to determine which elements have minimal impact and which elements have significant impact.

Continuous Improvement/Evaluation of Business Changes- With the time from early design through implementation potentially being long and the goal of a system operating efficiently for an extended period of time(years), it is likely that the operating environment and business requirements will change numerous times. In fact, It is common for the requirements to change before the system is even operational and then to continue to change over the life of the operating system. Simulation provides a tool to evaluate operational and business changes to either help anticipate the impact of upcoming changes and consider alternatives or to help recognize what happened(unfortunately after the fact).

In summary, Invar Systems uses system simulations through the life of a system. It is a valuable tool for systems requirements definition, proof of concept, detailed design, and continuous improvements, and evaluation of business changes.