Abstract: The present invention provides a spring integrally formed in a face plate of a housing for use with printed circuit board mounted operators having a central portion and J-shaped extensions. Stresses incurred when the central portion of the spring is pressed are distributed along the length of the extensions thus reducing maximum stress concentration in the spring. Additionally, material surrounding the spring is only minimally deflected when a spring is deflected, adjacent operators are not inadvertently actuated.

Abstract: A reflex I/O card for an industrial controller receives enabling inputs from the executed control program and triggering inputs from an industrial process to provide outputs at a fixed delay in time or portion of a machine cycle after the inputs through dedicated hardware thus avoiding transmission delays and processing delays associated with the communication of information to a central processor and the execution of the control program.

Abstract: Low voltage logic circuitry is used to permit an entire subsystem of an industrial controller to be placed within a hazardous environment to receive a high speed serial link and undertake the control of multiple control points without expensive and awkward long cable runs and electrically isolating circuits for each cable run. Energy and bandwidth limiting on the high speed link allows power levels commensurate with high data rates yet intrinsic safety of the media allowing it to freely pass in and out of the hazardous area. A mixture of intrinsically safe and non-intrinsically safe equipment on the same logical rack is allowed through a bus isolator providing isolated data communication in backplane fashion between modules while wholly isolating power transmission along the backplane.

Abstract: An integrated RISC and relay ladder logic processor uses shared registers, program counter, bus lines, and processing circuitry to eliminate delays associated with transfer of control in co-processor type architecture. The RISC instructions do not significantly interfere with the specialized hardware needed for rapid relay logic execution, the latter which may be further improved through the use of a pipeline well suited for relay ladder logic which creates few pipeline hazards. Two levels of condition codes are used for the arithmetic and logic instructions to permit nested arithmetic operations without interference with those instructions visible to the user. Hybrid instructions are provided to synchronize the relay ladder instructions with the arithmetic instructions, thus truly integrating the two instruction sets.

Abstract: A multi-tasking operating system for real-time control of industrial processes integrates ladder type programs and state-type programs by viewing each as a series of instructions with an implicit pointer list pointing to the next instruction. A fixed number of instructions of each program task are executed after which the effective pointer to the next instruction is stored toward the next time that task is invoked. Multiple tasks that need to be coordinated can be linked with subtasks that can be guaranteed complete execution by allocating sufficient instructions to those subtasks.

Abstract: A circuit card of an industrial controller may be removed or inserted under power without loss of memory or disturbance to the power supplies of other modules through the use of a power failure signal derived from shortened pins on the connector between the card and the industrial controller. The power failure signal activates a timer delaying connection of the board components to power until the physical connection between the card and the industrial controller has stabilized. At this time current drain is ramped up by a controlling series FET. Upon removal of the card, the power failure signal causes outputs of an on-board microprocessor to be pulled to particular states necessary to prevent disturbance of a battery backed-up RAM and to eliminate current flow through protection diodes on other memory type devices attached to the microprocessor.

Abstract: A redundant industrial controller system has a primary controller backed up by a secondary controller and recovers from a power loss by analyzing the state memories of the controllers to reach a determination of which controller would best be suited to assume primary control status without resorting to arbitrary tie-breaking procedures or race conditions. The rules and their inputs are applied by both controllers which independently make the determination as to which controller should be the primary controller.

Abstract: On-line upgrading of a primary industrial controller is provided through the use of a secondary industrial controller that may assume control of the process controlled by the primary industrial controller. A switch-over of control is orchestrated by a system back-up module that may detect removal of the functional components of the primary industrial controller to initiate the switch-over. Determination of removal of functional modules may be provided by a periodic polling of the functional components on the interconnecting communication link. The system back-up module designates one of the functional modules to poll the system back-up module so that complete coverage of removable components may be had.

Abstract: Inter-operability of products connected together to form an industrial control system is determined by defining each product as a set of services describing points of interface between the products and by determining complementary services necessary for inter-operability from a table listing complementary services. A new product may be evaluated for inter-operability by comparing its services to services of products with which inter-operability is desired. In one mode of operation after definition of the products in which inter-operability is desired, a necessary list of services is compiled from a database and translated by a relationship map to complementary services which define a virtual product having the desired inter-operability. Inter-operability of an entire control system may be thus modeled prior to construction.

Abstract: An industrial controller provides a primary controller and a redundant secondary controller and allows switchover between the controllers in the event of a failure in the primary controller. The process of qualification of the secondary controller in which its programming is made to match the primary controller may be inhibited to permit the secondary controller to maintain a clean version of an upgraded program executing on the primary controller. The clean program may be reverted to in the event an upgrading of the program in the primary controller is unsuccessful. Switchover is permitted even though the qualification of the secondary controller is not enabled.

Abstract: A redundant controller employs connection-based messaging to ensure reliability and determinacy in communications. The need to close connections and reopen connections with a backup module when control switches from a primary controller to a secondary controller is eliminated by keeping the secondary controller updated as to the connections that have been opened and having the secondary controller assume the connection identification numbers of the primary controller upon switch-over.

Abstract: A method and system for diagnosing the behavior of a machine which performs a discrete event process. A diagnostic engine observes occurrences of discrete events to detect timing patterns. A statistical analysis is performed on repetitions of the timing patterns, thus providing the basis for defining diagnostic rules. The rules are updated in real time and are subject to a rule competition procedure in which only the most precise and efficient rules are selected. Further occurrences of discrete events are evaluated relative to the diagnostic rules to identify and predict malfunctions of the machine.

Abstract: A method of reconstructing a control program from portions of that program contained in distributed processor modules of a distributed control system links each portion of the program with a source identifier. When the portions are collected, they are sorted by source identifier and merged to reveal the original control program as may be required for editing or the like.

Abstract: A pass-through table is developed to work in conjunction with an I/O table of a centralized industrial controller to permit a centralized controller to work seamlessly with a highly distributed control system. The pass-through table indicates data used in common between the centralized controller and the distributed controller and monitors a link connecting the distributed controller for changes in variables on the pass-through table to write those changes to the I/O table of the centralized controller. Conversely, changes in the I/O table of the centralized controller are detected and transmitted out to the common link to the distributed controller.

Abstract: A simple modification to a proportional integral controller allows for non-linear control strategies while maintaining the simplicity of set up and tuning of the loop through modifying the proportional and/or integral gains K.sub.p, K.sub.j by a linear or parabolic function of the feedback error signal. Provision is made for symmetrical or asymmetrical gain modification functions.

Abstract: An industrial control system employs a primary and secondary controller each having a processor and an I/O data table. Updating of the secondary processor's I/O data table is accomplished synchronously with execution of the program in the primary processor at a particular point in the program. A tracking of changes in the I/O data table of the primary processor is used to transmit only changes in the I/O table to the secondary processor thereby avoiding undue interruption of the executing program while preserving synchronicity.

Abstract: A memory system uses standard memory devices not normally supporting parity bits. Parity bits for multiple memory devices are stored in a dedicated parity device shared among multiple memory devices. Inadvertent erasure of the parity information, when writing to a single memory device, is prevented by a prereading of the parity device prior to a writing to the single memory device. Special circuitry stores the preread parity information and merges it back with the calculated parity bit for the written data to preserve complete parity information.

Abstract: An industrial control system employs a primary and secondary controller each having a processor and at least one I/O data table. Updating of the secondary processor's I/O data table is performed prior to the same data being transmitted to the controlled process. This eliminates possible retrogressive control at the time of switch-over of control from the primary industrial controller to the secondary industrial controller. Additional I/O data tables may be provided in each of the primary and secondary industrial controllers. In the case of the secondary industrial controller, this duplicate I/O data table temporarily holds data until the transmission is complete preventing the partial update of the working I/O data table of the secondary industrial controller. The duplicate I/O data table in the primary industrial controller allows simultaneous outputting of the I/O data transmitted to the controlled process without corruption while the user program of the primary industrial controller resumes execution.

Abstract: An inductive element in the form of a shorting turn is added to the rotor of a permanent magnet synchronous motor. Changes in inductive coupling between the rotor and a stationary coil as the rotor rotates permits inductive measurements to be used to deduce rotor position information such as position velocity and acceleration.

Abstract: A method of partitioning a control program among many spatially separated computing devices places most of the program instructions in computing devices supporting outputs to the controlled processor equipment. Inputs then simply report their data to the output computing devices rather than having that data processed by a path of computing devices communicating with each other such as may cause the evaluation of the outputs to be delayed by multiple transmissions on the common link.