Automatic AGV Battery Recharge via FlexSim Simulation

Automatic AGV Battery Recharge

Why switch to an Automatic AGV Battery Recharging System

Usually, you charge AGVs using rechargeable batteries. However, recharging batteries, when done manually is certainly a source of disruption and inefficiency w.r.t AGVs.

The disadvantages of a manually recharging system are:

  • Requires an operator periodically checking the battery level in each vehicle. This affects the efficiency of the operation.
  • When the charge is low, the operator removes the battery and charges it.
    As this method involves manual labour, it is highly prone to errors.

This is where using an Automatic AGV Battery Recharging system helps. This system takes care of the above disadvantages. How? Well,

  1. The AGVs have battery monitors. So, when the battery is low, the AGV returns to the Recharging Station for charging.
  2. This thereby eliminates any manual involvement and thus, eliminates errors as well. Furthermore, the efficiency increases as there is no periodic checking of the battery’s charge.

Steps to create an Automatic AGV recharging model in FlexSim

Now that you know why you require an Automatic AGV Recharging System, you should know how to create your own Automatic AGV Recharging Model in FlexSim.

Given below is an example of an Automatic AGV Battery Recharging model. This model has been built on the basis of a real-time scenario wherein the AGV senses its battery level and automatically travels to the Charging station.

The location of the Recharging station is either pre-programmed into the AGV or, a remote computer in response to a request from the AGV provides the nearest charging location.

The model has

  • One each of Source, Sink and AGV
  • An AGV network- Allows the AGV to move in a preferred path.
  • 4 ControlPoints (North, South, East, and West).
  • 1 Charging station (ControlPoint1) near the ControlPoint West.
  • 1 parking station (ControlPoint2) near the ControlPoint West.
  • 2 pickup locations (ControlPoints3 and 4) near the ControlPoint South.
  • 2 drop-off locations (ControlPoints5, and 6) near the ControlPoint North.

AGV Automatic Battery Recharge model

The four ControlPoints

Any ControlPoint can check the battery level. Now, before assigning a task, the ControlPoint which the AGV is at checks the battery level of the AGV.
If it is sufficient, it carries out the task which has been assigned to it.

If it is not sufficient, it goes to the Charging Station.

The four ControlPoints North, South, East, and West define the next tasks for the AGV as well.

ControlPoint West is the starting point for the AGV. Now, when the AGV is at this point if the

  • Battery level is low, the AGV is sent to Charging Station, even if there are items ready for pickup.
  • AGV has sufficient battery, but, there are no items ready for pickup it will be sent to the parking station and wait until there is a new item ready for pick-up.
  • AGV has sufficient battery, and there are items ready for pickup, it is instructed to go to South ControlPoint.

The ControlPoint South provides the following instructions.

  • When empty, the AGV, on instructions, goes to the pickup location and picks up the item
  • If loaded, as per instructions, the AGV goes to the ControlPoint East.

When the AGV reaches the ControlPoint East, it is directed to reach the ControlPoint North.
ControlPoint North provides the following instructions:

  • If Empty, as per instructions, the AGV goes to ControlPoint West.
  • If Loaded, as per instructions, the AGV goes to the drop-off location for unloading.

Steps to build your Automatic Recharge Model

  1. Utilizing the Resource library, create Source and Sink.
  2. From Task Executers library create an AGV and elevator.
  3. Create a path for the AGV and obtain the ControlPoint for location reference from the AGV library. Also, you can create a ‘Straight’ or ‘Curved’ path, as well as ‘Join Paths’ from the AGV library.
  4. Connect the Source and Sink using ‘A‘ connection.
  5. Now, connect the AGV to ControlPoint West using ‘A‘ connection. Furthermore, when prompted whether it would be used as a ‘Location’ or ‘Traveler AGV’ choose ‘Traveler AGV‘.
  6. Create ‘A‘ connection from Source to ControlPoint South and when prompted whether it would be used a ‘Location’ or ‘Traveler AGV’ choose ‘Location‘. This indicates the AGV that this is a Pick-Up Location.
  7. Create ‘A‘ connection from ControlPoint South to ControlPoint3 and ControlPoint4 and choose ‘Pick-Up Location’. This will act as Pick-Up Location for the AGV.
  8. Create ‘A‘ connection from Sink to ControlPoint North and choose ‘Location‘ this indicates the AGV that this is a Drop-Off Location.
  9. Similarly, connect ControlPoint North to ControlPoint5 and ControlPoint6 and choose ‘Drop-Off Location’ this will act as Drop-Off locations for the AGV.
  10. Connect ControlPoint West to ControlPoint1  using another ‘A’ connection and choose ‘Parking Point‘. This will act Parking Location for the AGV.
  11. Finally, connect ControlPoint West to ControlPoint2 and choose ‘Charging Station‘. This will act as Charging Station for the AGV.

Steps to define the Battery Threshold level

  1. Open the AGV template from FlexSim process flow. Attach the AGV from the 3D-model to process flow so that the AGV function will be control by the process flow. This can be done by clicking plus symbol under Attach Object in process flow template and choose the AGV.
  2. Set ‘Battery Recharge Threshold‘ value to 30 (or any desired value) under Process flow variables. This value is the minimum battery level for an AGV. When the battery reaches the set threshold value the AGV should return to the Charging station.
  3. Set ‘Battery Resume Threshold‘ value to 90 (or any desired value) under Process flow variables. This value is the maximum battery level for an AGV. When the battery reaches this value the AGV will stop charging and return to the working state.
  4. Set the AGV battery configuration as below. The ‘Battery Cap’ is the total capacity of the AGV’s battery, ‘Idle Use’ is the battery consumed while the AGV is idle, and ‘Recharge’ is the recharging rate.
  5. Run the model and the AGV will travel between Pick-Up and Drop-Off point and if required it will move to the Charging Station and it will rest at parking location if there is no task allocated.

Conclusion

Similar to the above models, real-time AGVs, modelling of their routes, charging durations, idle use and other factors using FlexSim Simulation. This is doable either using the 3D Simulation Model or Process Flow Simulation option. Furthermore, any complex rules, such as traffic rules, shift timings, speed and many other factors are alterable as well.

A Simulation engineer will be able to model the resources, processes and rules in order to replicate the real-time scenario and then an optimum AGV recharging solutions can arrive.

Using the FlexSim simulation software and model, you can identify and analyze the following metrics.

  • Running time for an AGV with different battery capacity.
  • Time taken for the AGV’s charging with the given battery capacity. (including Queue, wait times etc).
  • The time spent on charging in each shift.
  • The Number of Charging stations that are required to reduce non-productive, idle times while charging.

For more samples of Supply chain simulation modelling, check out our simulation services page – http://www.bestirtech.com/services/flexsim

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