Integrated control system for industrial automation applications

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FIELD OF THE INVENTION

The present invention relates generally to a system for generating, editing, executing, monitoring and debugging an application program which provides integrated control of sequential and continuous machine processes.

More particularly, the present invention relates to a system for generating, editing, executing, monitoring and debugging an application program which provides simultaneous control of all the logic, motion and process control components of an industrial automation application.

The present invention finds advantageous application to an automated transfer line and will be described with particular reference thereto, it being appreciated that the present invention has broader applications and may be used with other industrial automation applications, including material handling, metal forming, and robotics.

BACKGROUND OF THE INVENTION

A typical automated transfer line, as shown in FIG. 1, consists of a number of work stations where the work piece undergoes various operations, for example metal cutting and forming, in a specific, predetermined order. The flow of the work piece, such as an automotive engine block, from the point of entry into the line, its guidance and navigation through the work stations, and its final exit from the line after successful completion of all automated operations, must be controlled with high order of accuracy to result in the proper synchronization and coordination of the automated transfer line.

It is critical that the operation of the automated transfer line be error free and reliable as the smallest inaccuracy in any part of the control system, such as the communication link between various controls at each work station, can have disastrous results. It is also extremely important that the application program for the automated transfer line be relatively straightforward and reliable for both setup and integration, as well as continuous operation and troubleshooting by the factory floor personnel.

Today, automated transfer line applications generally require logic control (e.g., control of IF . . . THEN conditional actions) and motion control (e.g., control of a servo) and at times process control (e.g., control of the electrical current flow to a welder). It should be noted that motion control can be regarded as a specialized type of process control. Application engineers choose several industrial controllers, each specializing in one of the control technologies (i.e., logic, motion and process control), and each with its own specialized hardware and software implementations. The application engineers then program each of these individual devices, typically using different programming languages and development environments, to control a specific subset of the total industrial automation application. Additional hardware and software interconnections and communications must be added to get the individual devices to work together in a coordinated and synchronized manner. The difficulty and cost of programming, integrating, operating and supporting such a complex system is substantial. Key disadvantages of existing automated transfer line control arrangements include the following:

1. Hardware duplication; each controller usually has its own chassis, computer, I/O and power supply.

2. Multiple operator interfaces and program development support systems; this makes the system more difficult to program, debug and operate resulting in increased system support cost.

3. Error prone inter-connecting logic; the control device interconnections require extra integration time and often represent a major source of the system problems thereby reducing the overall reliability of the total system.

4. Sub-optimized usage of controller performance; generally, one or more of the controllers has much more performance than is required for its assigned portion of the application, and since there is no ability to share workload among different controllers, this excess performance is wasted while the total system cost is increased.

In the typical automated transfer line application shown in FIG. 1, control units 2, 4, 6, 8 and 10 require logic, motion, and/or process control. Accordingly, each of these control units requires multiple industrial controllers. In general, one controller for each control technology will be required at each control unit. The typical implementation process for one of these control units is shown in FIG. 2. The system Integrator or the original equipment manufacturer (OEM) carries the overall responsibility for implementing process plan 20 for an individual control unit. Process plan 20 is developed by a process engineer and the implementation of that plan requires the following tasks to be completed:

A. Separating process plan 20 into individual logic control program steps 22, motion control program steps 24 and process control program steps 26.

B. Selecting, purchasing and integrating individual logic controller(s) 28, motion controller(s) 30 and process controller(s) 32, each having its own hardware, operating system and program development environment.

C. Generating separate programs for each individual controller. In this respect, logic control program steps 22 are typically programmed in graphical ladder language (e.g., Relay Ladder Logic Network); the motion control program steps 24 are typically programmed in RS-274D or a proprietary motion language; and the process control program steps 26 are typically specified in Function Block Networks.

D. Adding inter-controller synchronization interconnections and program logic.

E. Debugging this complex architecture. It is noted that the integrated view of the entire system control, specified via these separate programs, is extremely difficult to observe as the interdependence, coordination and synchronization between the various control components is buried deep within the inter-control communication links and the program for each of the controls. Also, the man-machine interfaces 34a, 34b, and 34c are of a general purpose nature which makes the operation of the entire system very difficult for the factory floor personnel.

F. Documenting, maintaining and supporting the integrated system.

While logic, motion and process control have both sequential and continuous functions, a programmer is concerned primarily with sequential functions with respect to motion control, continuous functions with respect to logic control, and both sequential and continuous functions with respect to process control. Sequential functions are actions which are sequential in nature, while continuous functions are actions which are continuous in nature. Both types of functions will be described in greater detail below.

It has been standard practice to program "sequential" motion control functions using RS-274D or a proprietary motion control language on a computerized numerical control (CNC) or some other type of motion controller, to program "continuous" logic control functions using ladder logic and function blocks on a programmable logic controller (PLC), to program "sequential" process control functions using standard Sequential Function Charts, flow charts, or batch recipes, and to program "continuous" process control functions using Function Block Networks.

Each of these controllers and programs serve a specific need in a portion of the application program and present their own specialized programming environment and unique window into the application domain. Unfortunately, none of these programming techniques can adequately address the entire application requirements alone. When used together, these diverse programming techniques implemented on separate controllers are inefficient, do not integrate or interconnect well, are difficult to operate and troubleshoot, and can be prohibitively expensive. A new, simpler, more integrated solution is needed that does not deviate too far from the methods already used to program and troubleshoot on the factory floor to minimize training time.

Many industrial automation applications require the integration of sequential and continuous programs into a single application program, which controls the sequential and continuous machine processes of an industrial automation application.

Sequential programs are used to control the major sequencing of an application program. Accordingly, sequential program steps are executed only once, one step after the other, like a procedure, waiting for the previous step to complete before the next step is executed. Continuous programs are used to monitor and control environmental conditions either during the entire application program or during specific portions of the application program. Accordingly, continuous programs are scanned repeatedly and executed whenever the qualifying conditions are appropriate.

As noted above, sequential functions are actions which are sequential in nature, and accordingly are most easily and intuitively programmed using sequential programs. Likewise, continuous functions are actions which are continuous in nature, and accordingly are most easily and intuitively programmed using continuous programs.

Examples of sequential functions include:

1. machine operation or sequencing, for example: (a) turn the machine on and wait for all functions to report ready, (b) position the workpiece to be processed, (c) begin processing and wait for the