Until recently, there were two options for networking your assembly equipment and providing cell controller functionality: 1) low-level, stand-alone control over a group (or cell) of equipment; or 2) interfacing the equipment with one or more factory host systems. Both options result in inflexible, high-cost networks. The KNetTM Assembly Equipment Network, a unique de-centralized system of networked servers, overcomes these disadvantages.

Figure 1. Single-node stand-alone Node Controller can manage a local cluster of equipment.

The KNet Assembly Equipment Network is based on a peer-to-peer concept that allows incremental expansion of the Computer Integrated Manufacturing system (CIM), factory-wide access to cell controller functions, redundancy of critical data, and distribution of processing load.

You can configure and reconfigure the resulting network to provide virtual cells of control and information anywhere they are needed. These cells can function independently, in support of client applications or in collaboration with more traditional host computing systems.

The Concept

You can begin by installing a single stand-alone Node Controller to manage a local cluster of equipment as shown in Figure 1.

You subsequently can network single-node controllers and reassign or add units of assembly equipment, regardless of physical location, as shown in Figure 2.

Previously, the information available at a cell controller would be restricted to the equipment controlled directly by that controller's hardware. A higher-level host would then be required to collect data across individual cell controllers as shown in Figure 3.

Kulicke & Soffa has eliminated this requirement. Application software at any location can create a virtual cell controller by subscribing to the resources managed by Node Controllers distributed throughout the network. The result is a true peer-to-peer architecture that you can configure and reconfigure, factory- or world-wide.

Figure 2. Interconnected Knet Node Controllers provide peer-to-peer architecture for factory or world-wide control.

Typical Hardware Connections

The layout of the cell controller network (Figure 2) is straightforward. Assembly equipment with SECS-I capability is linked through serial lines to terminal servers. The terminal servers are tied into the Ethernet Local Area Network (LAN) of the facility.

If the assembly equipment supports SEMI High Speed Message Services (HSMS), the terminal servers are bypassed and the equipment is linked directly to the LAN. Each unit of assembly equipment is assigned to a primary Node Controller through a configuration table in any networked controller.

The Node Controllers are specially configured servers running under a WindowsNT¨ operating system. Custom-developed software is installed in each controller to provide a user interface, or client application layer, and an equipment management, or server layer.

The equipment management layer includes a mailboxing message hub that handles requests. The system maintains data tables in a real-time database with subscription mechanisms and copies the information to a persistent database or filing system as shown in Figure 4.

For the maximum level of data accessibility, you can connect this Node Controller network to an existing company network or intranet as shown in Figure 2. (An optional network bridge is recommended to ensure the network segments used by the servers are not adversely impacted by network traffic from outside the assembly area.)

Figure 3. Interconnected cell controllers can be linked to your company network for maximum data accessibility.

De-centralized System Mechanisms

K&S addressed a number of difficult technical issues to make the de-centralized cell controller network robust and responsive.

One system requirement was that no server be relied upon as the central source of shared information and configuration data. The system needed to propagate copies of communal data and distribute local data to interested clients as needed. To meet this requirement, K&S utilized the Hume Integration Services DMH message hub and real-time subscription database and developed a system of I/O agents.

Real-Time Subscription Database

The real-time database hub maintains a system of structured tables, via System Query Language (SQL) commands from the applications.

Two classes of data tables are used. Definition tables are read-only and are included in the software distribution. Status tables are built during program execution from the definition tables and are updated in real time with values from the equipment.

Subscriptions from Node Controller applications to the status tables allow changes to be acted upon and/or displayed in an event-driven manner rather than through polling by the application.

Each Virtual Equipment Module (VEM) owns and updates status tables in the data hub. EventStatus, AlarmStatus, and VariableStatus tables contain the most recently read values from the equipment. There is a separate instance of each of these tables for each unit of equipment. This enables management of different types of equipment with differing capabilities.

Reports are defined as lists of status variables and equipment constants. These are stored in ReportDef tables as single instances per equipment type per server and are linked to events on a per unit of equipment basis in ReportLnk tables.

Distributed Agents

In a peer-to-peer network, there is not a central repository for common files. The map of the system configuration is shared by propagating copies to all servers and clients listed in the map whenever a change is made. Through a group of assigned agents, the KNet system synchronizes this activity to ensure that each user always has the most recent version of the system map.

Figure 4 shows the major software components of the cell connectivity design. The agents manage connectivity between applications by handling all addressing between entities through lookups in a resident entity table. All node agents in the cell network need access to the communal information resident at a particular server node, but the controlling server node agent has exclusive write access to the information. Intervention by the owning server node agent is required to prevent unauthorized simultaneous write access by the other node or client agents.

Figure 4. Client and node agents handle connectivity details.

Server node information changes are distributed to node agents or client I/O agents in the cell network through subscription notification.

Communal information is automatically transferred between server nodes by the node agents as specific changes occur to the information at each individual server node.

The cell connectivity package executes a complimentary process. All monitor clients are notified of cell network changes through subscription notification. All owner clients make changes to the state of the cell network through node agents.

Conclusion

The KNet Assembly Equipment Network is a significant improvement over inflexible, cumbersome, and expensive CIM systems.

Monitoring and management of equipment can be handled across the factory floor or around the world by a network of inexpensive Node Controllers that you can incrementally expand to meet your needs. Most important, the system supplies most WindowsTM or Windows NT based applications with the data you specify, tied to events you specify.