Abstract: An inductive proximity sensor and a method of proximity sensing are described that permit targets of interest to be detected despite the presence of external magnetic fields due to AC or DC sources, such as resistive welding machines. The sensor has a pair of matched coils positioned adjacent to one another along a common central axis. The coils are coupled in series with oscillator and detecting circuitry, that also serves to drive a switching device. The coils are wound for current flow in opposite directions and produce oscillating electro-magnetic fields for detecting the targets in response to signals from the oscillator and detecting circuitry. Currents in the coils induced by strong external magnetic fields produces an additional components of the coil field which essentially cancel one another. The sensing field of the coil assembly may be shaped and directed by cooperation of the fields of the two coils and by appropriate shielding around one or both coils.

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 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 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 biasing assembly for a switching device is formed in a modular enclosure that may be mounted on either left or right sides of the switching device. The biasing assembly interfaces with the switching device to rapidly move the switching device between first and second stable positions, such as corresponding to open and closed contact orientations. The biasing assembly includes a hub and link plate coupled to a spring assembly. A spring in the spring assembly is precharged by initial movement of an actuating handle. Once a predetermined intermediate position is reached, a double roller arrangement is displaced along a support surface to rapidly toggle the spring assembly, link plate and hub to a second position. The enclosure includes abutment surfaces for stopping and holding the link plate in stable positions. The rolling contact afforded by the spring assembly rollers permits extremely rapid displacement and rolling friction during displacement of the assembly.

Abstract: A communication-efficient change log historian allows workstations having images of a shared memory to remain correlated to the shared memory. The system comprises one or more workstations connected to a microprocessor-based device which includes a memory device. The memory device includes the shared memory, and also stores a memory change list and a memory change index. The memory change list forms a list of changes which have been made to the information stored in the shared memory area, and the change index is indicative of the location of the most recent entry to the memory change list. The workstations maintain an image of the shared memory area, and store workstation change indexes which are indicative of the most recent entry to the memory change list which has also been implemented to respective images of the shared memory area in the workstations.

Abstract: An editor apparatus and method for programming industrial controllers in relay ladder language, the apparatus or method used to provide RLL logic to control machine tool movements in a desired sequence. The apparatus includes a display for creating a bar chart image that represents all functions in a cycle and graphically illustrates all function contingencies. The apparatus gleans function, cycle and contingency information from the image and, based on the information, creates modules that include logic required to make each function contingent upon illustrated conditions. A compiler then compiles the modules to provide an RLL program section to control the cycle.

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 data control system having a host microprocessor, a data receiving device and a DMA controller. The DMA controller being used to control the fragmentation and recombination of a buffer memory area. The data being processed in data packets and using DMA buffer chaining.

Abstract: A system for scheduling periodic events having varying rates. The system uses a linked list type data structure and an array to schedule the plurality of events having varying rates. In a preferred embodiment of the invention, data items are scheduled for transfer during a plurality of data transfer intervals. The linked list type data structure is traversed for each data transfer interval to collect the data items requiring transfer.

Abstract: A contactor includes an upper housing (1) for contact parts and a lower bobbin (5) that bears a coil and can be placed therein in an initial position or in a position displaced by 180 degrees. The coil terminals (6, 7) lie next to each other on one side of the bobbin (5). Before the assembly of the bobbin (5) in the housing (1, 4), at least two male parts (2, 3) comprising terminal pins, and at least one female part (8, 9) comprising a hole that is intended to receive one of the male parts (2 or 3), are molded on at the areas that will subsequently border each other. In order to arrange the coil terminals (6, 7) on one side of the contactor, the male part (2 or 3) that does not act in conjunction with a female part (8, 9) in this position must be broken off prior to assembly. In order to arrange the coil terminals (6, 7) on the other side of the contactor that is turned away by 180 degrees, the other male part (2 or 3) must be broken off.

Abstract: A multilayer circuit board system or laminated circuit board system for use in a motor controller includes a motherboard, at least one power substrate circuit board, and a capacitor circuit board. The mother board includes mounting areas for receiving the power substrate board and capacitor circuit board at a 90.degree. angle. The capacitor circuit board, power substrate circuit board, and mother circuit board can be interconnected without the use of external connectors or wires. A fan can be disposed at a front edge of the power substrate circuit boards to provide air flow across their planar surfaces.

Abstract: An auxiliary switch arrangement is located inside a housing (1) and is equipped with at least two fixed contact pieces (2, 3, 4), with one connecting contact bridge (9, 10) which can be uncoupled in pairs from the contact bridge. The contact bridge (9, 10) is formed onto one end of a U-shaped curved leaf spring strip (11), transverse to the longitudinal direction of the leaf spring strip (11). The other, free end (12) of the leaf spring strip (11), is fastened inside the housing (1). The leaf spring strip (11) is pre-tensioned by the amount of contact pressure in the contact-making position of the contact bridge (9, 10). A slide (14) equipped with linear cams (15, 18, 19, 20, 21), which moves in a guide inside of the housing (1), lifts the movable contact pieces (17) off the fixed contact pieces (2, 3, 4) in the switched-off position. The slide (14) is actuated through an extension (16) by a switching device.

Abstract: A method for generating electrical frequencies of a alternating current motor is disclosed wherein a torque current command signal, a d-axis voltage command signal and a d-axis voltage feedback signal are combined to generate the stator electrical frequency in the synchronous reference frame. The method also provides an estimate of the rotor electrical frequency as well as of the motor speed. The frequency generator is preferably incorporated in a variable frequency motor controller for driving a motor at desired speeds independent of changing load conditions. The generator permits the controller to maintain field oriented control without the need for speed sensing and feedback.

Abstract: A motion controller generates commands to control electric motors of a multi-axis industrial machine in accordance with calculated positions set forth in a path planning table. In a method of generating the path planning table, a series of coordinates are entered into a system that correspond to positions of the machine along a complete cycle of a desired path. The coordinates are proportionally spaced based on distance, maximum speed and maximum acceleration factors. A path planning table is generated by determining the calculated positions based on a predetermined resolution using an S-curve mathematical equation that includes an alpha variable corresponding to an acceleration to jerk ratio. The value of the alpha variable is adjustable by the user during a testing procedure to allow for an optimal setting thereof.

Abstract: A method and apparatus for compensating for deviations in the alternating voltage produced by a PWM inverter. The necessary sequence in which inverter components must be triggered results in voltage error pulses that accumulate over time and result in deviations from ideal voltage at motor terminals. By allowing the error pulses to continue and adjusting the trigger times to compensate for the error pulses, the effect of the error pulses is negated and the voltage deviations are eliminated.

Abstract: An auxiliary switch provides an output or feedback signal indicative of the position or logical state of a contactor, disconnect or other principal device to which it is coupled. The switch is formed as a modular unit which can be fixed directly to the principal device, and is actuated by movement of elements within the principal device. An optical switch set within the auxiliary switch includes an emitter and detector pair aligned in mutually facing relation. An actuator is movable with the principal device and supports an optical shield. The actuator displaces the shield between a position clear of the optical path and a position interposed between the emitter and detector to change the state of the auxiliary switch. A power supply circuit may be housed within the switch for supplying power to the optical switch and to output circuitry. The device is particularly tolerant to contamination and can reliably output low level logic signals indicative of the state of the principal device.

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: A communication system for power monitors and the like includes a plurality of communication nodes connected in series. A technique is provided for automatically detecting the status of the system, including the need to configure the communication nodes or identify the presence and location of a fault. Further, configuration of the nodes is automatically performed as required, and the location of faults is visually represented to assist an operator.