HK1058917B - A method of controlling an injection molding system - Google Patents

Description

Method for controlling injection molding system

The invention is a divisional application with the application number of 99119750.X, 9/29 in 1999, entitled "integrated control platform for injection molding system and method thereof".

Technical Field

The present invention relates generally to a method of controlling an injection molding system, and more particularly to a method of controlling an injection molding system having a plurality of injection molding devices for performing an injection molding process and providing feedback signals, and a human-machine interface having a display and at least one manual input device for inputting operator commands.

Background

Injection molding systems are widely used to produce inexpensive plastic articles such as plastic PET preforms that can be blown into various beverage containers common to everyday life. Such injection molding systems typically include a variety of analog and digital devices for performing injection molding operations. For example, extruder drivers, proportional flow control valves, electric drivers, heating and cooling elements, and other electro-hydraulic mechanical and electro-mechanical drivers, are simulation devices that perform injection molding functions in a well-known manner. Examples of the digital devices include proximity switches, clamping pressure limit transducer sensors, digital solenoid valves, and the like. Each of the above-described analog and digital devices must not only be controlled by appropriate analog and digital commands, but are often equipped with feedback sensors for outputting analog and/or digital feedback signals that effectively control the various devices to enable the system to be produced quickly and with high quality. For example, feedback signals may be used in closed loop control of real-time changes in the injection molding apparatus (e.g., temperature set points, injection pressure, etc.). In addition, the feedback signals are also used to display operational information (e.g., operating conditions, temperature, part count, etc.) to the operator on a human-machine interface or operator control panel.

In the prior art, it was necessary to use an Analog Signal Processor (ASP) to provide real-time control to various analog devices in an injection molding system. Similarly, a Programmable Logic Controller (PLC) must be provided to control the digital devices in the injection molding system. As an example of controlling an injection molding machine using both ASP and PLC, us patent No.5,062,052 (incorporated herein by reference) can be cited. Although the use of a general purpose computer is also referred to in the' 052 patent, its use is limited to the connection between the PLC and HMI. There is still a need to perform injection molding operations using PLCs and ASPs.

A limitation of existing injection control designs is that the injection molding apparatus cannot be reconfigured in real time. The configuration changes must be made by revising or reprogramming the ASP and PLC at the same time. This often requires that the entire system be powered down for reconfiguration when new technology needs to be introduced into the injection molding system. In addition, the operating status of each injection molding system can only be confirmed by its HMI. Furthermore, each injection molding machine manufacturer typically employs its own proprietary design in its PLC, which would limit the application of various new processing techniques to such machines due to compatibility issues and the like. In addition, ASP and PLC process control using a multi-layer structure will adversely affect the process and create process bottlenecks that will slow the response speed of the machine to achieve a corresponding state change.

Thus, there is a need for a new injection control design that provides true real-time control of the injection molding system, allows for rapid reconfiguration of the system equipment, facilitates the use of the latest commercially available software, and allows for the transfer of system status and control information outside the system, such as to the factory office or even to the company headquarters.

Disclosure of Invention

It is an object of the present invention to provide an injection molding control design that seamlessly integrates the highest state of the art hardware and software components into one controller. It is another object to provide a control design that provides true real-time control and network functionality. It is yet another object of the present invention to provide an open control design that can easily integrate other auxiliary equipment and extended machine functions. It is a further object to provide a smart diagnostic system for reducing system downtime and remote access capability for inputting or outputting knowledge and information from or into an external data source. It is still another object of the present invention to simultaneously provide an injection molding system control function, a human-machine interface function, a motion control function, a sequential logic function, a continuous process control function, and a network communication function by a single general-purpose computer.

Additional objects of the invention include: a standard application program interface is provided that supports external communications (such as e-mail, paging, etc. for monitoring, troubleshooting, and information exchange between systems and plant management), provides an expert system with embedded process knowledge to assist in system assembly and production processes, provides intelligent alarm management and system diagnostic functions, and provides a predefined template with embedded function options to assist users in assembly and operation of the injection molding system.

In accordance with the present invention, the above objects and other advantages are achieved by a method for controlling an injection molding system having (i) a plurality of injection molding devices for performing an injection molding process and providing feedback signals, and (ii) a human-machine interface having a display and at least one manual input device for inputting operator commands, comprising the steps of:

inputting the feedback signal and the signal from the operator input device into a single processor; and

utilizing the single processor to simultaneously control the plurality of injection molding devices and the human-machine interface display in real time.

As with the method described above, the single processor multitasks the feedback signal and the signal from the operator input device.

As with the method described above, the single processor has an open design capable of running commercially available software.

As with the method described above, the single processor utilizes a real-time extended kernel to perform multitasking.

In the method described above, the single processor controls the plurality of injection molding apparatuses and the input apparatus simultaneously without a programmable logic controller.

In the method described above, the single processor is located remotely from the injection molding machine.

As described above, the single processor communicates with the input device through a serial bus at gigabyte rate in a manner that multiplexes information.

In the method, the single processor communicates with the plurality of injection molding devices through a field bus having an error correction function.

In the method described above, the single processor performs closed-loop control of the injection molding apparatus.

The above objects and other advantages are also achieved in accordance with the present invention by an apparatus for controlling an injection molding system comprising a plurality of devices that generate a plurality of feedback signals. The device includes: (i) a human-machine interface preferably disposed adjacent to the injection molding system and having a display and at least one operator input device; and (ii) a general purpose computer coupled to the human-machine interface and the plurality of injection molding apparatuses, wherein the general purpose computer is configured to perform real-time closed-loop control of the injection molding apparatuses in response to a plurality of commands and feedback signals.

According to another aspect of the present invention, a single computer is used to control an injection molding system having a plurality of injection molding machines for performing an injection molding process and providing feedback signals, and a human-machine interface having a display and at least one manual input device for inputting operator commands. The computer includes: (i) a first input/output for receiving command signals from the human-machine interface manual input device(s) and providing display signals to the human-machine interface display, (ii) a second input/output for receiving feedback signals directly from the injection molding devices and providing real-time control signals thereto, and (iii) a CPU for generating real-time control signals based on the feedback signals and command signals, the CPU multitasking the command signals, display signals, feedback signals and control signals.

Another aspect of the invention features an injection molding system, comprising: (i) a plurality of injection molding devices receiving real-time control signals and outputting real-time feedback signals to perform an injection molding operation, (ii) a human-machine interface having a display and at least one operator input device, and (iii) a single processor receiving real-time feedback signals from the plurality of injection molding devices and command signals from the operator input device, the processor multitasking the received plurality of signals according to a plurality of predetermined injection molding control programs and display programs, and outputting real-time control signals to the plurality of injection molding devices and display signals to the human-machine interface display according to the plurality of predetermined injection molding control programs and display programs, and having installed therein an operating system capable of running commercial software.

In accordance with another aspect of the present invention, a method for controlling a plurality of injection molding apparatuses performing an injection molding process and providing feedback signals, and an injection molding machine having a human-machine interface with a display and at least one operator input device, comprises the steps of: (i) inputting the feedback signals and signals from the one or more operator input devices into a single processor, and (ii) controlling the injection molding apparatus and the control panel display in real time using the single processor.

Another aspect of the invention features at least one computer-readable storage medium storing computer-readable data for causing a general-purpose computer to control an injection molding system that includes a plurality of injection molding apparatuses for performing an injection molding process and generating a plurality of feedback signals, and a human-machine interface having a display and at least one operator input device. Such computer-readable storage media would cause a general-purpose computer to (i) receive feedback signals and other signals from one or more human-machine interface manual input devices, and (ii) execute a multitasking process to perform real-time control of the injection molding apparatus and the human-machine interface, the multitasking process executing human-machine interface functions having relatively low priority in the "background" and injection molding apparatus functions having relatively high priority in the "foreground".

Drawings

The invention is described with reference to the accompanying drawings, in which

FIG. 1 is a schematic block diagram of an injection molding system according to the present invention;

FIG. 2 is a schematic block diagram of a human-machine interface and a general-purpose computer according to the present invention;

FIG. 3 is a schematic diagram of a software control module according to the present invention;

fig. 4 is a schematic diagram of a control scheme according to the present invention.

Detailed Description

The advantages of the present invention will be described in detail below using a plastic injection molding system or injection molding machine as an example. However, the invention is not limited to this solution only, but can be applied to any type of injection moulding technology within the scope covered by the invention.

The control scheme according to the present invention provides both real-time control of the injection molding system and a real-time interface for operator control. The design also includes a Human Machine Interface (HMI) necessary for operating and monitoring the injection molding system, as well as an interface for information exchange with the factory and company headquarters. The integration of software and hardware has enabled a typical general purpose computer to become a system controller that not only controls machine functions and operator controls, but also has an open design that can be easily integrated into any other auxiliary equipment and exchange information with external systems and networks. In addition, the functionality of the general purpose computer is extended by additional hardware and software to provide deterministic real-time control of the injection molding system to achieve high performance and intelligent manufacturing cells.

Thus, the flexible, reconfigurable manufacturing system according to the present invention can easily adapt to new technologies and processes and transmit critical, real-time performance data outside of the human-machine interface at the production site, such as other departments of the plant and the corporate headquarters to provide real-time information to all departments of the unit. The use of commercially available general Purpose Computer (PC) technology enables the use of faster and better CPUs, more powerful operating systems, more types of peripherals, a wider range of communication and networking capabilities, and the ability to extend control of machines from a production site to a remote site.

Regarding injection molding system control design:

FIG. 1 is a schematic block diagram illustrating the general nature of an injection molding system control design according to the present invention. In FIG. 1, an injection molding system or machine 10 utilizes digital devices 12, 14, 16 and 18 and analog devices 20 and 22 to effect an injection molding process in a well known manner. Each of the digital and analog devices preferably includes an input for driver control and an output that provides a feedback signal to the closed loop control of the respective device. The digital devices 12, 14 and the analog devices 20, 22 preferably receive control signals from or output feedback signals to a fieldbus 24 (see below for details); and digital devices 16 and 18 receive control signals from, or output feedback signals to, digital bus 26 (described in more detail below). Of course, the fieldbus 24 and digital bus 26 may transmit all necessary control and feedback signals to control the injection molding process, depending on the particular injection molding system being controlled.

The operator utilizes a human-machine interface (or control panel or control station) 30 to input control data and view process feedback information. The HMI30 has a keyboard 32 and a pointing device (i.e., a position input device such as a mouse) 34 with which an operator can input data. Depending on the system being controlled, the operator may also use a system function keypad (which may include an LED display) device 36 to enter specific machine commands. The display 38 provides the operator with at least one viewing device for viewing the display of data based on the feedback signal and provides an interface for manual entry of data. The control panel 30 may also have a removable storage drive 40 (e.g., floppy drive) installed thereon to allow the operator to enter programmed control information, as well as new control programs, or may be used to download feedback data to the removable storage device. The control panel 30 also includes a multiplexer 42 (see below for details) for multiplexing various control and feedback data between the HMI30 and the general purpose computer 44.

The general purpose computer 44 is preferably a off-the-shelf personal computer having a CPU 46, ROM 48 and RAM 50. Preferably, the computer 44 includes a control panel interface 52 coupled to the multiplexer 42 of the HMI30 via a bi-directional serial bus link 54 (described in more detail below) having a transmission rate greater than 1 Gbit/s. Interface 52 preferably employs a Beckhoff industrial electronics CP-Link PC multiplexer. Although not shown, the general purpose computer 44 may also be equipped with peripheral devices such as a CRT, keyboard, disk drive, CD-ROM drive, mouse, touch screen, light pen, and the like.

Computer 44 also has a digital interface 56 coupled to digital bus 26 by connection 58. Likewise, the computer 44 also has an interface 60 coupled to the fieldbus 24 by a connection 62.

The computer 44 also includes a local area network interface 64 that may be coupled to a local area network (e.g., Ethernet; not shown) used within the plant. In addition, the computer 44 may also include a modem or other external interface 66 operable to connect the computer 44 to, for example, an Internet or intranet.

With the above-described configuration, the control scheme according to the present invention does not require the use of a PLC or ASP as is necessary in the prior art, but provides true real-time closed-loop control of the injection molding machines 12-22. In addition, the operator can control the injection molding process at the HMI30 through the computer 44. The computer 44 has a sufficiently fast processing speed and a sufficiently strong capacity for multitasking the injection molding function and the HMI function. For example, the computer 44 may process injection molding apparatus high priority closed loop control instructions in the foreground and lower priority HMI function instructions in the background. Thus, the computer 44 will take turns processing machine control functions and HMI functions.

With respect to general purpose computers:

as described above, a single general-purpose computer according to the present invention includes a hardware structure similar to that of a standard general-purpose commercial or industrial computer, and preferably operates in the context of a general-purpose operating system such as Window NT (Tm). The computer 44 is preferably a model C6150 industrial PC available from Beckhoff electronics. The PC is characterized by having a Pentium II microprocessor, a 2G sized (or higher capacity) hard drive, and a 64M RAM memory. The computer may also be equipped with a CD ROM drive, 1.44M and/or 1.20M disk drives, 4 serial interfaces, a printer interface, and multiple (e.g., 7) expansion card slots. The interfaces serving as local area network and/or internet/intranet connections are optimally installed in additional slots. The computer is capable of multitasking at least 3 functions simultaneously, namely control of the injection molding system, control of the HMI, and functions as a plant-wide web server.

To receive the analog feedback signal and provide the analog control signal via the fieldbus 24, the computer 44 performs a/D and D/a functions. Thus, the computer 44 digitally processes the control program, the HMI program, and the network program. By operating in a digital manner, the computer 44 is able to provide a better performing and more accurate solution than conventional analog circuits. The efficient computing power and substantially large working memory of the computer 44, coupled with the software real-time extension kernel (described below), may provide real-time performance for machine control, HMI and networking functions. Since the real-time extended kernel operates at a rate on the order of microseconds, the computer 44 may act as a multitasking scheduler for all computer functions. I.e. the computer 44 can control all injection moulding devices simultaneously using a multitasking process. Additionally, machine control functions may be multitasked with HMI functions and/or network functions. The system can realize the control update of the control loop of the injection molding device in microsecond order, so that the analog closed-loop controller for controlling the injection molding device in real time is not needed.

Thus, the computer 44 is capable of controlling the injection molding apparatus using a variety of predetermined equipment control programs (e.g., charge injection, mold clamping operations, etc.) and the HMI30 using a variety of predetermined HMI programs (e.g., display, keyboard, mouse, keypad, etc.). The computer 44 also communicates with other computing devices over a local area network (and/or the internet) using a variety of predetermined programs, such as an internet browser, a word processing program, spreadsheet processing, and the like. The computer 44 not only operates on a plurality of such control and network programs, it may also operate through multitasking according to predetermined priorities, such as in order of the critical injection molding device first bit, the feedback and status device second bit, the HMI device third bit, the network communication function last bit. In addition, the open design of computer 44 also allows a user to modify, upgrade, install or replace any of these predetermined control and network programs as needed.

The computer 44 not only eliminates the need for an ASP, it also replaces the PLC used in the prior art. The ability of the computer 44 to readily install new applications therein provides a way to map process input/output to images that can be displayed to the operator. The computer 44 additionally has input and output capabilities and a real-time kernel that are extensions of its general operating system and programming software while complying with international industry standards such as IEC 1131-3. Thus, the computer 44 replaces a commonly used PLC or dedicated controller for controlling the process of the various injection system devices to perform the desired injection functions. In addition to functioning as a master for controlling machine functions, computer 44 may also function as an information archive for bringing together (and subsequently communicating to the plant monitoring system) all machine device operational information and machine status.

Regarding the real-time extension kernel:

as described above, the computer 44 according to the present invention preferably runs a real-time extended kernel to an operating system such as Windows NT. This kernel allows faster multitasking of machine functions, HMI functions and network functions. There are many commercially available automation solution software packages on the market today, each of which provides real-time control of a general purpose computer. These real-time extended kernels allow independent processing, but can also take advantage of the ever increasing processing power of general purpose computers. The preferred embodiment employs the TwinCAT real-time kernel extension developed by Beckhoff industrial electronics. The TwinCAT kernel extension provides the basis for PLC and motion control solutions. The twinCAT kernel is a run time system (run time system) with program real-time execution, programming tools, analysis tools, and configuration management functions. All Windows programs (e.g., visualization tools and office software products) can interact with TwinCAT through a standard Microsoft interface to exchange data and control services. Thus, the real-time extended kernel according to the present invention allows multitasking and full integration into the operating system while still keeping all Windows NT operating system standard features unchanged, and it also enables sharing of CPU processing power between real-time control tasks and user NT operations and provides a software-only solution without the additional need for other hardware.

With respect to the human-machine interface:

the HMI (or control panel or control station) 30 is used to input control information for controlling the injection molding apparatuses 12-22 and receives feedback from a display, storage or transmission device. The HMI30 includes standard control equipment such as a keyboard 32, a pointing device (mouse) 34, a keypad 36, an active storage device 40, a display 38, and a multiplexer 42. The HMI30 preferably employs a Beckhoff CP7000 control panel on which are mounted special PLC keys, LED displays, touch screens, 15 inch TFT displays, PC keyboards, 3.5 inch floppy drives and CP-Link interfaces.

In the present invention, the integration of operator interface and machine control functions into a single general purpose computer eliminates the processing bottleneck typically created by the communication link between the HMI, PLC and ASP of the prior art, thereby allowing the communication efficiency between the HMI30 and the computer 44 to be greatly improved.

As shown in FIG. 2, the HMI30 is coupled to the computer 44 via a serial bus link 54 having a transmission rate greater than 1 Gbit/s. Because of the use of such a high rate of bi-directional multiplexed bus between the HMI30 and the computer 44, operator controls and display elements can be truly separated from the computer 44. In the preferred embodiment, the link 54 is selected to be 50 meters, although it could be slightly shorter, such as only 10 meters. By placing the HMI30 at a location remote from the computer 44, all vulnerable computer devices, such as hard disks, modems, CPUs, etc., can be protected from the high temperatures, vibrations, shocks, etc. that are typically encountered in an injection molding environment. With such a high speed link, the HMI30 can be mounted in an optimal position close to and spaced sufficiently from the computer 44 for ease of operation. For this reason, the number of electronic components in the HMI should be reduced as much as possible, while satisfying the requirements of being able to display data, input data, and more easily manually input commands through the keyboard 32, the pointing device 34, and the function aid keyboard 36.

In FIG. 2, the HMI display preferably employs a TFT display 382, although LEDs, LCDs, CRTs, or other types of display devices may also be employed. The HMI30 also includes one or more pointing devices 342, including a mouse, light pen, touch screen device, and the like. The keyboard 32 is preferably a standard PC keyboard, although a dedicated keyboard with dedicated function keys may also be used. The machine function buttons and LED display 36 are the same as commonly used in existing injection molding systems. The active storage device 40 is used to input control program or set point information, or to store feedback signals. The input and output devices are connected to the HMI multiplexer 42 for multiplexing the transmitted information via a serial bus link 54 with a transmission rate greater than 1 Gbit/s. The multiplexer 42 also controls a 5 volt power supply (not shown). Finally, the HMI30 may also include an emergency stop button or device 80 that may be used to stop operation of the injection molding apparatus in an emergency. The emergency stop button 80 is connected to a safety circuit 82 which is in turn connected to the computer 44 via an interface.

The link 54 may provide bi-directional communication between the HMI and the computer 44, thereby greatly simplifying system design and increasing system reliability. A bi-directional link 54 connects the HMI30 with the computer 44 for video control and data entry. The vast amount of HMI information is then processed by the computer 44 rather than the HMI 30. The communication rate between HMI30 and computer 44 is in the Gbit/s range, which enables computer 44 to respond in real time to changes in the status of machine devices 12-22 caused by the operator. The Link 54 may be implemented by a commercially available Link of the type such as PaneLink, and a product based on the international industry standard IEEE P139b or a CP-Link from Beckhoff industrial electronics. In a preferred embodiment, CP-Link from Beckhoff is used.

The HMI30 is therefore required to have only minimal processing capabilities, preferably only those functions required to display data, enter data, perform manual control functions via the function keys 36, and communicate with the operator via graphical, textual, and visual displays. Because the computer 44 may be placed in a controlled environment remote from the HMI30 to protect vulnerable computer devices, the operator control and display function devices may be closer to the injection molding system, thereby enabling the operator to more closely view machine functions.

The bi-directional link 54 may be formed from a two-wire coaxial cable, two single-wire coaxial cables, one or more fiber optic cables, or other communication equipment. Link 54 typically requires no additional power. The cable interface may be formed from a printed circuit board connected to a standard personal computer bus (e.g., an ISA or PCI bus), and thus may be used in any type of general purpose computer.

As shown in FIG. 2, computer 44 may include additional structures than those shown in FIG. 1. Specifically, the computer 44 also preferably includes an LCD graphics controller board 84 for controlling the display 382. The controller 84 preferably includes an LCD interface. The computer 44 also includes a keyboard interface 86 for the keyboard 32, and an active storage device controller 90 for controlling the active storage device 40. The serial interface 88 is used to control the serial communication port.

Signals from the LCD, keyboard, pointing device, communication port, and computer interface of the active storage device are converted by the PC interface link card 52 into high frequency serial signals that are then transmitted to the HMI30 via link 54. The serial signal is converted by the HMI multiplexer 42 into a signal originally produced by the computer interface and then transmitted to the devices for control and feedback. Thus, devices on the HMI30 can be controlled by the computer 44 over distances much longer than currently achievable. Since the link 54 preferably has at least two independent channels, there is one link channel in each direction of communication between the control panel 30 and the computer 44. As shown in fig. 1, the computer 44 also includes an interface 56 for direct connection (if necessary) to the digital devices 16 and 18 via the digital bus 26. Preferably, the interface 56 is a SERCOS (serial real-time communication System). Also, the open design of the computer 44 allows control of the injection molding devices 16 and 18 directly via the digital bus 26, or alternatively via the field bus 24.

With regard to the field bus:

in FIG. 1, a computer 44 is connected to the digital injection molding apparatuses 12, 14 and the analog injection molding apparatuses 20, 22 via a field bus 24. Preferably, the fieldbus 24 is a standard industrial fieldbus such as a CANopen bus, Lightbus, Interbus, Controlnet bus, profibus dp/FMS, or some equivalent type of bus. The preferred embodiment employs a Profibus DP that operates at a rate of 12 Mbit/s. As described above, the computer 44 may also use the digital bus 26 (preferably a SERCOS) to route the digital servo drives and other digital devices 16, 18.

Integration of the inputs from the injection molding devices, sensors, and control outputs for actuators and digital drives is accomplished through an open device network interface of the computer 44. The control platform of the computer 44 supports the field bus of all the major devices. The present invention replaces the multiple dedicated conductors used in the prior art with an industrial-grade fieldbus operating in a fault tolerant protocol having a high-speed multiplexed signal bus. Thereby avoiding the costly and poor reliability problems associated with dedicated wires. The interface protocol of the field bus is preferably implemented using a microcontroller. Such microcontrollers are able to handle harmful effects such as signal noise directly and are also able to make a feasibility check on the command. In addition, integrating the fieldbus interface with a dedicated controller may form a so-called "control island". The control island includes dedicated input/output and has localized processing capabilities to enable distributed control design that can bring the controller closer to the system being controlled by improving the signaling capabilities and responsiveness at the internet edge. This ability to localize the solution problem reduces the traffic burden on the network backbone (i.e., the CPU in the computer). Since the injection molding function can be distributed among a plurality of dedicated subsystems with well-defined boundaries and grouped control elements, the use of control islands to control the subsystems will greatly improve the degree of modularity of the control system and the performance of the system. The control island is connected to the system controller via a physical fieldbus connection. These connections provide logical connections, messages; the control islands are loosely coupled with the system controller so that the control system has scalability.

With regard to the control software:

FIG. 3 is a schematic diagram of a preferred control software module according to the present invention. Fig. 3 is shown in the form of a functional block diagram of a software control design for use with computer 44. In fig. 3, the control software 300 includes a software module 302 for sequence control, a software module 304 for data logging, and a software module 306 for alarm management (see below for details). Connected to the 3 software modules are an initialization and processing control module 308, an operational mode module 310, a synchronization and coordination control module 312 and an input signal processing module 314. The initialization and processing control module 308 sends control signals 316 to the injection molding system 10, and sensor signals 318 from the injection molding system 10 are provided to the input signal processing module 314. The module 314 also receives sensor signals from other software control modules (not shown).

Operator input 320 from HMI30 is provided to an operating mode module 310 that provides input to modules 302, 304, and 306. Other HMI interface signals 322 are provided to the synchronization and coordination control module 312, which is also coupled to the modules 302, 304, and 306. Such a software control design provides great flexibility in upgrading and/or modifying existing software.

Fig. 4 is a functional block diagram of a control scheme according to the present invention. In FIG. 4, an injection molding process 400 utilizes injection molding system 10 to perform an injection molding operation. The injection molding element 402 includes devices 12-22 driven by digital and analog outputs 404 received via the fieldbus 24. Feedback sensors 406 associated with the machine elements 402 provide digital and analog feedback signals over the fieldbus 24.

One or more position measurement devices 408 driven by servo motors 410 may provide a measure of the actual processing position. The input and output 414 are coupled to the position measurement device 408, and information thereof is transmitted over the digital bus 26 to a digital drive controller 412 that transmits signals to the computer 44 or receives signals from the computer 44.

Computer 44 transmits digital and analog signals over fieldbus 24 under the control of fieldbus master 420. Similarly, computer 44 transmits digital signals over digital bus 26 under the control of digital bus master 422. Signals to or from the HMI30 are communicated over a link 54 via an interface 52, such as a PC multiplexer. The computer 44 is installed with a software-based program for performing the following functions: input and output mappings 424; temperature control 426; a programmable logic control 428; hydro-mechanical motion control 430; electromechanical motion control 432; and process controls 434. In addition, the computer 44 may also have other functions based on software such as engineering and business software tools 436 and HMI application software 438.

The control software, control program, HMI program, and other software may be loaded into the computer 44 from a computer-readable storage medium such as a magnetic disk, CD ROM, magnetic tape, magneto-optical disk, or remotely over a LAN or internet connection.

The control design shown in fig. 4 integrates real-time commands, program control commands, and manual commands. Since it features a general-purpose computer with an open design, all of these commands can be easily modified and upgraded. The real-time kernel running in the common operating system provides real-time injection molding system control interleaved with program control and manual input in a multitasking process. The real-time kernel gives system control a higher priority and provides a window for handling general information.

This control design has multiple levels of processing under the control of the kernel's multitasking scheduler, with each level itself performing its particular function. Together with the emergency shutdown and sequential shutdown functions, real-time closed-loop system control and real-time high-speed switching in response to feedback signals from system components are performed with highest priority. The software provides the functionality of a programmable logic controller to control the system process. While the communication speed and processing power of the computer may actually allow the HMI functions to be performed in true real-time, the computer still performs the HMI functions in a background manner. A common database is shared between various machine control functions and HMI functions, thereby eliminating the multi-processor bottleneck problem of the prior art and increasing the throughput of information processing.

Such a general purpose computer can be connected to many types of peripherals such as CD ROMs and modems for intranet/internet or remote connections, and local area networks of the type such as ethernet for factory wide communication. Thus, a single computer can perform the closed loop control functions of the injection molding system by sending commands locally by installed system devices or remotely by communication to/from other sites, receiving input data from the HMI or from a networked customer, and controlling the display on the HMI.

Regarding the additional capabilities:

because of its processing power, such a general purpose computer may also provide other capabilities that may be used in an injection molding environment. For example, a general purpose computer may also intelligently filter information, provide an expert system for improving process settings and operations, and provide an alarm management system.

Smart filtering is a processing technique that selectively filters signals processed by a CPU that limits signals that are overloaded at high priority multitasking levels. This is the process of selecting a level of information for further processing of the data. The system may refuse to receive non-critical data as the network management level rises to enable the highest level network management console to concentrate on higher level processing such as trend analysis and capacity planning. Doing so will reduce the burden on the network and improve the communication throughput of the entire network. A general purpose computer of the present invention may include such intelligent filtering processing so that signals at a predetermined system level do not have to be transmitted over a network.

The high processing power of a single general purpose computer according to the present invention enables it to be used in an expert system for managing an injection molding system. Such expert systems may improve the performance of alarm management systems (described below) by diagnosing process interruptions, generating more accurate operator information, and assisting in performing corrective actions, such as reconfiguring the system wirelessly. The result is a more powerful alarm management system to assist operators in managing process interrupts safely, efficiently, and with minimal system downtime. Such an expert system can also improve process settings by providing recommended process parameters to the operator based on knowledge stored in computer memory that is specific to the system. Such a computer can also archive the material information of its associated mold or store this information on a remote storage unit via intranet/internet access.

Expert systems are applications of artificial intelligence that employ inference engines, fuzzy logic techniques, and/or other suitable methods to reason about events occurring in dynamic processes, such as those used in injection molding processes, in real time. The inference engine infers on the basis of specific predefined rules defined in a knowledge base derived from empirical data and operator input.

The use of a general-purpose computer in real time in an expert system according to the invention is possible in at least two ways, namely as an advisor system or as a monitoring system. In advisor-type applications, the expert system infers dynamic changes in the process data, makes decisions based on process events, and publishes conclusions and rationales to the operator. The expert system can thus provide timely and accurate recommendations for processing events and problems to be solved. In a monitoring type application, the expert system according to the invention proactively (pro-active) assists the operator in solving problems, optimizing the molding operation, or achieving other objectives defined in the knowledge base, such as predictive maintenance adjustments, by adjusting set points and changing the on or off state of discrete devices. It is the high processing power of the general-purpose computer according to the invention that makes it possible to implement an expert system in an injection molding environment.

Many injection molding systems have an alarm system that alerts an operator to a system malfunction and performs a set of system functions such as shutdown, operation deceleration, etc. A single general purpose computer according to the present invention has sufficient processing power to allow the computer to manage an intelligent alarm system, i.e., an alarm system capable of fault diagnosis reasoning about alarm conditions. This allows a computer or user to apply higher levels of logic to system functions so that the system is not simply turned off, thereby avoiding adverse effects on system performance and throughput due to a simple system turn off. That is, if the alarm analysis shows that only non-critical problems of the type such as a slight over-temperature have occurred, the computer can still continue to operate the injection molding system at a slower rate.

The intelligent alarm system can accurately capture the dynamic changes of the injection molding system under different alarm states. For example, system shut-down may be automatically controlled or production may be performed only at a slower rate; or the operator may be prompted to enter additional data to correct the condition in which the alarm was generated. In addition, if the computer also requires additional information regarding the alarm state, the operator can input the required data at the HMI according to the feedback information presented on the display. The operator may also consult an online manual (stored in computer memory) to provide corrective information for this alarm condition in a timely manner. Such alarm management information may be provided to the operator in text, graphics, audio, or even video.

The intelligent alarm management system according to the present invention can provide predetermined coping operations for any state such as alarm enable, alarm confirm, and alarm abort. These coping operations range from simple consultative text messages, to paging operators in the plant, or sending e-mail over a network to maintenance, plant monitoring personnel, or other engineering personnel.

Since the computer according to the invention can be equipped with a general-purpose operating system, real-time or stored feedback signals can be used in the most current application software, such as spreadsheet processing software or relational database management software. Thus, statistical process analysis and preventive or predictive maintenance functions may be implemented using the computer of the present invention, or another server coupled to the computer via a network. In addition, since the computer of the present invention preferably employs the open data communication standard commonly used in the computer industry, it will no longer require a dedicated driver that is currently used in the injection molding industry. Even though some manufacturers still require a dedicated driver for some type of injection molding apparatus, it can quickly download the required dedicated driver to computer 44 via the internet and modem 66.

Preferably, the computer according to the invention comprises a plurality of predetermined installation programs (wizards) for guiding the operator through the software installation operation in an understandable way. For example, to enter parameters required by a particular system, the operator may be presented with a series of predefined templates that allow the user to select among the data field options. Such wizards may be provided separately for each individual system or installation wizards may also be provided for the entire system together and upgrades may also be made via the internet or a local area network.

Thus, the single general purpose computer for the injection molding system described above eliminates the need for a programmable logic controller or analog signal processor, while also being able to multitask the injection molding functions and HMI functions and provide open type communication with a local area network and/or the Internet. The method is a powerful tool for improving the precision and the production efficiency of the injection molding system, and can improve the management approach and the control on the system operation.

Of course, other aspects of the present invention may be devised by those skilled in the art. For example, a general purpose computer of the present invention may control more than one injection molding system, or it may simultaneously control an injection molding system and one or more auxiliary machines such as conveyors, robots, or product handling equipment. Integrating the control of these machines into the single processor of the present invention allows for smooth shipping of products in the factory.

In addition, the HMI of each system need not be arranged in close proximity to one another. For example, the central console may be equipped with multiple control panels from multiple systems so that an operator may control multiple injection molding and auxiliary machines simultaneously. In this configuration, the general purpose computer may be located on a central console or may be located at a remote location. By further extending this configuration, it can be seen that the computer 44 (or even the HMI) can also be located in the factory's office to enable an administrator to immediately receive operational information and to quickly reconfigure the injection molding operation.

Claims (9)

1. A method of controlling an injection molding system having (i) a plurality of injection molding devices for performing an injection molding process and providing feedback signals, and (ii) a human-machine interface having a display and at least one manual input device for inputting operator commands, the method comprising the steps of:

inputting the feedback signal and the signal from the operator input device into a single processor; and

utilizing the single processor to simultaneously control the plurality of injection molding devices and the human-machine interface display in real time.

2. The method of claim 1, wherein the single processor multitasks the feedback signal and signals from an operator input device.

3. The method of claim 2, wherein the single processor has an open design capable of running commercially available software.

4. The method of claim 3, wherein the single processor utilizes a real-time extended kernel to perform multitasking.

5. The method of claim 1, wherein the single processor controls the plurality of injection molding devices and the input device simultaneously without a programmable logic controller.

6. The method of claim 1, wherein said single processor is located remotely from said injection molding machine.

7. The method of claim 6, wherein the single processor communicates with the input device over a serial bus at gigabyte rates in a manner that multiplexes information.

8. The method of claim 7, wherein the single processor communicates with the plurality of injection molding devices via a fieldbus having error correction capabilities.

9. The method of claim 1, wherein the single processor performs closed loop control of the injection molding apparatus.