The Fastory Production System

The Fastory line consists of 12 robotic cells connected by a circular conveyor line.

Each cell contains a conveyor consisting of five zones and a robot. The robot can perform assembly operations on any pallet that enters a certain conveyor zone inside the cell, which is called the robot processing location. In the test implementation, the assembly operations are in fact draw operations, in which the robot draws a mobile phone component onto the paper carried by the pallet. Thus, the papers represents the products being assembled. Figure 5.4 illustrates the layout of the simulated production line.

One of the robots, robot 1, is unable to perform assembly operations but can instead replace the paper carried by a pallet. To replace the paper, it first elevates

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(a) The Socrades demonstration line consists of three portions sequentially connected.

(b) A 2D overhead illustration of the upper and lower conveyor lines.

Figure 5.3: The demonstration line includes 29 conveyor segments, of which five are work-station processing locations.

the paper currently on the pallet and places it on the tray reserved for final products.

Then, the robot removes a paper from the tray reserved for blank papers and places it onto the pallet.

Each cell includes a dedicated controller device for both the robot and the con-veyor device. Each controller hosts a web service representing the controlled device.

The service interfaces provide operations through which the devices can be con-trolled. While the interfaces for the robot and conveyor devices are significantly different, the interfaces of different conveyor and robot instances are identical be-tween the 12 robotic cells. Only the set of operations in the robot 1 interface is somewhat different from the other robots. When the experiments described in this

5. Application Experiments 87

(a) The robotic cells form a circle. (b) Each robotic cell provides two web services.

Figure 5.4: The Fastory line consists of 12 robotic cells.

chapter were carried out, the conveyor cell 7 provided a direct route from cell 6 to cell 8. In particular, the cell included no functional robots but only a conveyor belt connecting the two adjacent cells.

The five conveyor zones in each robotic cell form two lanes. One of the lanes is traversed by pallets processed at the cell, whereas the other one is traversed by pallets bypassing the robot. Figure 5.5 illustrates the structure of the individual robotic cells in terms of the conveyor zones. Cell 1 differs from the other cells in that zone 4 is absent, and zone 2 is the robot processing location instead of zone 3.

The conveyor service interface includes the Transfer operation, which transports a pallet from one conveyor zone to an adjacent zone. In addition, the Transfer-Out operation makes it possible to transport pallets between adjacent robotic cells.

Table 5.1 summarizes the operations supported by the conveyor service.

The final zone, zone 5, of each conveyor includes no pallet stopper. Hence, when a conveyor transports a pallet from zone 3 or zone 4 to zone 5, the pallet stops at zone 1 of the next conveyor on the line. However, one end of the pallet will still reside on the former conveyor. Therefore, before requesting the latter conveyor to move a pallet from zone 1 to zone 2 or zone 4, it is necessary to request the former conveyor to start running by invoking its TransferOut operation. The conveyor motor will remain active for a fixed time interval, and the service will send an EquipmentChangeState notification both at the beginning and end of the interval.

The robot serviceDraw operation performs an assembly operation specified by the input parameter on the pallet currently at the robot processing location. However, for robot 1, theDraw operation is substituted by theReplacePaper operation, which replaces the assembly on the pallet with a new one and places the old one on the

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Figure 5.5: Each robotic cell contains five conveyor zones.

Figure 5.6: The Fastory robot service alternates between three states.

tray reserved for ready products. A robot can perform an operation only when a pallet occupies the robot processing location. In addition, each robot service sends the EquipmentChangeState notification whenever its internal state changes. For example, a notification is sent whenever the robot finishes an assembly operation.

Table 5.2 summarizes the operations supported by the robot service.

The robot service is normally in one of three states: ‘idle with no pallet’, ‘idle with a pallet’, or ‘performing an operation’. The three states are represented by the constant string values ‘READY-IDLE-STARVED’, ‘READY-IDLE-BLOCKED’ and

‘READY-PROCESSING-EXECUTING’. The state diagram in Figure 5.6 illustrates the transitions between the states. In the figure, the WSDL operations that trigger the transitions are indicated by the labels attached to the transition arcs. Although the Transfer operation actually belongs to the conveyor service, it may still cause state changes in the robot service by transporting a pallet either into or out of the robot processing zone.

The web services constituting the Fastory line have been implemented both on

5. Application Experiments 89 Table 5.1: The conveyor service provides three invokable operations and two event notifi-cations.

Operation Name Type Description

Transfer Request-response Transfers a pallet between adjacent zones.

TransferOut Request-response Transports a pallet to the next cell.

GetState Request-response Lists the pallets occupying the zones.

TransferResultEvt Notification Indicates that a pallet has been suc-cessfully transferred between zones as a result of the Transfer opera-tion.

PalletInEvt Notification Indicates that a pallet has arrived to zone 1 from the preceding cell.

EquipmentChangeState Notification Indicates that the conveyor has started or stopped unloading a pal-let.

Table 5.2: The robot service provides two invokable operations and one event notification.

Operation Name Type Description

Draw Request-response Performs the requested assembly operation.

ReplacePaper One-way Replaces the paper carried by a pal-let.

EquipmentChangeState Notification Indicates changes in the robot sta-tus.

S1000 controllers connected to actual devices and on Java applications simulating the devices. Application experiments involving the Fastory line are described in Sections 5.5, 5.6 and 5.7.