Data processing: generic control systems or specific application – Generic control system – apparatus or process – Having preparation of program
Reexamination Certificate
1999-09-30
2002-08-27
Gordon, Paul P. (Department: 2121)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Having preparation of program
C700S018000, C700S083000, C700S180000, C700S181000, C318S568100, C345S960000
Reexamination Certificate
active
06442442
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to programming interfaces for industrial control systems. In a particularly preferred embodiment, this invention relates to a programming interface for an industrial control system in which the control system comprises multiple motion control axes, and in which the programming interface graphically provides the user with data flow information pertaining to the physical relationship between the various motion control axes.
2. Description of Related Art
Industrial control systems are used in a wide variety of operations such as manufacturing, processing, packaging and so on. Typically, an industrial control system comprises one or more industrial controllers, such as programmable controllers, which control a plurality of output devices based on input status information from a plurality of input devices.
In a multi-axis industrial control system, the industrial control system also comprises multiple motion control axes. Each motion control axis comprises a motion control system that may include for example a motion controller, a servo drive and an electric motor. Like the other output devices, the various motors of the motion control axes are controlled based on input status information from the plurality of input devices. The motion control axes are controlled in coordinated fashion such that various activities occur in synchronism as required by the controlled process.
Each motion controller is connected to a respective one of the servo drives that is in turn connected to a respective one of the motors. In combination, the motion controller and the servo drive implement a position feedback control loop, a velocity feedback control loop that is nested within the position feedback control loop, and a torque/current control loop that is nested with the velocity feedback control loop. (Because torque and current are proportional, the same loop can be viewed as either a torque control loop or a current control loop.) In combination, the motion controller and the servo drive are capable of accepting a position command and in response generating current to drive the motor and thereby to control the motor to obtain the commanded position. Motion controllers may for example be provided in the form of modules for a programmable controller system or as PC-based expansion cards or stand-alone units that communicate with the programmable controller system via a network communication link. Servo drives are usually provided as stand-alone units or are integrated with stand-alone motion controllers.
Industrial control systems typically operate based on execution of a user program that is tailored to the industrial control system and its intended use. The user program may be executed in the processor module of the industrial controller, or distributed computing techniques may be utilized such that the user program (which may comprise multiple subprograms) is executed both at the processor module and at the motion controllers. In an industrial control system with multiple industrial controllers, the user program may also be executed at the other industrial controllers and any additional motion controllers associated with the other industrial controllers.
Conventionally, industrial control systems have been programmed using sequential programming languages, such as ladder logic languages. Typically, with a windows-based sequential programming interface, the user program is graphically displayed in the form of a series of commands that are executed sequentially. For example, during programming, the user may drag and drop a timer icon and a move icon into the user program. When the user clicks on the timer icon, a dialog box appears that allows the user to program the timer for a specified period of time. Likewise, when the user clicks on the move icon, a dialog box appears that allows the user to program the parameters of the move, such as the final position, the maximum velocity, and so on. The user may then connect timer icon and the move icon with a connection line to indicate that, after the timer icon is executed, the move icon should be executed. Thus, the way in which the program is organized on the screen is indicative of the sequence of events that is programmed to occur.
When a move or other motion command is executed, the position control loop is provided with incremental reference position information to control the motor to obtain the commanded position. In practice, the position reference values may be provided every few milliseconds or so in the form of delta position information (change in position since the last update time) rather than absolute position information. The position control loop then compares the actual position of the motor (obtained from a feedback sensor) with a given position reference, and operates to cause the motor to “chase after” the position references until the final position is reached.
In addition to move commands, other types of commands are also available to users in multi-axis situations. For example, it is known to implement gear relationships and position cams in a sequential programming language environment. For example, a gear icon may be provided (or a pair of icons for starting and stopping) that allows a user to program a gear ratio between two motion control axes. When the user clicks on the gear icon, a dialog box appears that allows the user to program the parameters of the two-axis relationship. Typically, one motion control axis will be designated as the master axis, another motion control axis will be designated as the slave axis, and a gear relationship will be specified between the two axes. Additional slave axes may also be specified. Then, in operation, when the start-gear icon is encountered, the two motion control systems for the two motors will operate to electronically maintain the specified ratio between the two motion axes.
This arrangement has worked well in situations where the number of motion control axes is relatively small. When there are only a few motion control axes in the motion control system, it is not particularly difficult for the user to maintain an understanding of the relationships between the various motion control axes.
However, as industrial control systems have become more complex, this arrangement has been found to be unsatisfactory. In some systems, it is possible to have thirty-two or sixty-four motion control axes in a single industrial control system. In such situations, it is difficult for the user to maintain an understanding of the relationships between the various motion control axes due to the large number of axes in the industrial control system. The relationship between various motion control axes is not readily ascertainable with existing programming interfaces. For example, the gearing relationship between two axes is normally not displayed to the user unless the user clicks on the gear icon to bring up the dialog box that provides additional information. As the number of motion control axes increases, it becomes increasingly cumbersome to have to click on each individual icon to obtain additional information regarding the relationship of the various motion control axes. There is no way to simultaneously display information pertaining to the physical relationship between the various motion control axes in a single, coherent manner.
Additionally, a further complication arises where multiple industrial controllers are used in the motion control system and each industrial controller is individually programmed. For example, if multiple programmable logic controllers are used, and each programmable controller has its own user program with each user program controlling only a subset of the various motion control axes, then the physical interrelationship is not ascertainable from any given one of the user programs, regardless of how the information is displayed to the user.
Finally, this arrangement provides only limited flexibility and does not easily allow for complex relationships between motion control axes. In conventio
Gerasimow Alexander M.
Gordon Paul P.
Luettgen David G.
Rockwell Automation Technologies Inc.
Walbrun William R.
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