At the INTRALOG pilot location in Velp all movements should be automated. Rotra forecasts 400 vehicle movements a day in Velp. The question remains how the heterogeneous fleet of Rotra can be automated. In our definition of cargo we assumed that cargo can be decoupled from the transporting entity. This gives bounds to which vehicles can be automated. As this thesis focuses on AGVs transporting cargo, only semi-trailers are marked as cargo for the pilot study, which is 79% of the current fleet of Rotra (2- and 3-axle semi-trailers and Huckepacks). The number of axles has consequences for the vehicle controller, but as this is static information the system can easily share this information with the vehicle controller to correctly maneuver the trailer.
Incorporating container movements of the container terminal are to be researched in further work. Another important design question is how manual and automated driving can co-exist at the cross-dock. For small loads or high-priority cargo it may not be beneficial to let the AGV do all the work, but let the truck driver maneuver and dock the semi-trailer himself. Whether or not this is beneficial depends on the (un)loading time, waiting time, driving regulations (maximum driving time) and the planning of the driver. Some threshold has to be designed to decide whether or not cargo is marked for AGV handling or manual handling. Also box trucks are handled manually and thus pose safety challenges. We propose a clear physical boundary between the AGV
maneuvering space and all other manual operations at the cross-dock.
4.5 System design
This paragraph describes the design of the physical entities required within the system. We first denote some issues arising from practice in Section 4.5.1. The vehicles which serve as AGVs are described in Section 4.5.2. In Section 4.5.3 we briefly introduce the need for a proper IT system.
4.5.1 Functional requirements
Currently there are still many manual operations required for the handling of the semi-trailers at Rotra. To make the transition from manual to fully autonomous, there are some challenges to tackle. From the analysis of the current practices at Rotra (see Section 4.3) we conclude that the following three functional requirements are absolutely necessary:
Automatic coupling between AGV and semi-trailers
Although the fifth wheel and the kingpin are international standards on trucks and semi- trailers, there are still some manual tasks required when coupling. For example, the electrical and pneumatic lines have to be coupled to the semi-trailer when the kingpin is locked in the fifth wheel. This requires a driver who leaves the cabin of the vehicle to
attach these lines. To develop a fully autonomous system this coupling needs to be done automatically. At the time of writing there exists no such system. The complexity of an automatic coupling device is the heterogeneous fleet of semi-trailers where the connectors are all positioned at different locations. Furthermore, the semi-trailers shall not be equipped with extra hardware from a costs perspective as raised by Rotra.
Dock design
An important part of the process of docking semi-trailers is the dock itself. It provides the dimensions and tolerances for the AGV to dock the semi-trailer. Also, currently the doors of the semi-trailer are opened by the truck driver. As we do not allow personnel in our automatic system, the doors of the semi-trailers need to be opened from the inside of the distribution center. There are already market-ready solutions for this, but we have to design (in cooperation with a dock door supplier) a dock door where not only semi- trailers but also containers can be docked automatically and the doors can be opened from the inside. Another potential aspect of the dock door in the automation process is the communication between the dock and the AGV to let the AGV know when the semi- trailer is properly docked using some kind of sensor technology.
Wireless charging
We deploy electrical AGVs and thus they have to be charged at some point in time. When the AGVs are charging there are not available to the system, so the charging strategy can have serious impact on the performance of the system. Furthermore, as we do not allow personnel in the system, the charging also has to be done autonomously and most likely also wirelessly.
All these functional requirements have to be researched in order to build the business case for an autonomous system. One can imagine that LSPs do not make large investments into an automatic handling system, when there is still personnel required to (de)couple the semi-trailers or to plug in a charging cable. At the time of writing the above topics are recognized by the consortium partners of INTRALOG and are in an early stage of development by several bachelor students of the UT and HAN.
4.5.2 Vehicles
Automated Guided Vehicles (AGVs) transport the cargo (i.e., semi-trailers) on the terminal between loading docks and parking areas. These AGVs are based on the yard tractors (YTs) made by Terberg Benschop. Currently there are no automated YTs available, but within INTRALOG some parties research the transition from manual to automatic YTs. The prototype has yet to be built, but most likely an electric driven AGV will be used for pilot testing. Figure 4-4 shows a manual YT which will be the basis for the AGV.
Based on data retrieved from meetings with Terberg Benschop, the following specifications can be used as input for the simulation study (see Chapter 6).
General specifications
Maximum forward speed (loaded/unloaded): 10 m/s
Maximum rearward speed (unloaded): 7 m/s
Maximum rearward speed (loaded): 2 m/s*
Acceleration (loaded): 1,8 m/s2
Number of wheels: 6 (2 front, 2x2 back)
Number of steered axles: 1
Maximum capacity: 1 semi-trailer
Maximum lifting capacity: 36 metric tons Electric AGV specifications
Average battery life: 4 hours (113 kWh) or 6 hours (169 kWh)
Average consumption container handling: 22 kWh
Average consumption logistic operations: 15 kWh
Recharging time: Battery life divided by 2 (2 or 3 hours)
Battery leveling required: after 140 operating hours
Battery leveling time: 6 hours
Acceleration (unloaded): 2,5 m/s2
* although the maximum loaded rearward speed is theoretically 7 m/s, from a safety and stability point-of-view this speed is capped at 2 m/s.
4.5.3 Operating and information system
When the MAS has been fully designed and the work of the other work packages within INTRALOG is mature enough, we can start with a pilot test. Although this thesis does not focus on IT infrastructure, we would like to point out that the transition from conceptual/simulation to real-world pilot testing may be challenging. In order for the entire system to function properly many different hardware platforms and pieces of software have to be integrated such that they can communicate with each other. For example, the MAS requires information from higher level planning software (e.g. a TMS) and also sends information the controller of the AGV. This vehicle controller on his turn needs hardware and software for vehicle positioning and orientation. Although we recognize the importance of the IT system, we leave this to further research.
4.6 Summary
As stated in this chapter, the pilot location will feature a multimodal cross-dock with 150 loading docks, a container terminal and approximately 100 parking slots for trucks and semi-trailers. A concept drawing of a multimodal cross-dock is shown in Figure 4-5.
To summarize the most important properties of the pilot location and assumptions:
15.000 m2 cross-dock (300x50x10 m);
150 loading docks;
100 parking slots;
The cargo consists only of standard-size semi-trailers (2- and 3-axle);
Integration of container movements of the container terminal at the pilot location is subject to further research;
All cargo is (un)loaded from the rear;
Forecasted vehicle movements: 400/day;
A clear physical boundary between AGVs and manual operations is necessary;
No humans should be involved in the handling process;
The AGVs are based on yard tractors made by Terberg Benschop;
We assume that the doors of the semi-trailers can be opened from the inside of the cross-dock;
We assume that the yard tractors can autonomously (de)couple semi-trailers and are charged wirelessly and autonomously.