Abstract: Automated grinding is performed using a tracking means having a sufficient field of view to locate edges to be processed and using a high resolution profiler in order to provide grinding information for calculation of the amount of material which should be removed from the workpiece. Those sections of the workpiece not requiring additional grinding may be traversed at a high speed in order to improve productivity. A process control computer receives grinding information from the tracking means and high resolution profiler and uses it to control a manipulator to adjust the travel speed of the grinder, force with which a grinder is applied, position of the grinder, and/or speed of rotation of the grinder in order to remove the correct amount of material from a workpiece. The technique is especially advantageous in removing excess material, burrs, nicks, chips and other minor irregularities in workpieces. A second profiler may be used to check that the grinder has properly ground portions of the workpiece.
Abstract: Composites such as graphite reinforced PMR-15 resin are cured in a heated press by following a temperature schedule and changing from low to high pressure after the start of resin cross linking. A pressure control and method to time application of high pressure uses temperature and dielectric sensor outputs and a semi-empirical model of the resin electrical conductivity. The model estimates the future variation of resin conductivity and determines time-to-go to a maximum in electrical conductivity. A signal to apply high pressure is generated when the estimated time to maximum conductivity falls below a threshold. On-line fitting of the model to sensor data as it is gathered provides a mechanism for adapting the control to the peculiarities of a given batch of resins and a particular cure schedule.
Abstract: An acoustic tool break detector monitors vibration caused by a cutting process and has an analog amplifier to condition the signal, then searches for a rapid sustained change in signal level indicative of a cutting tool break. An automatic gain control circuit dynamically controls the gain of the analog amplifier and adjusts the output cutting noise signal to a desired average level during an active cut while allowing use of such a break algorithm. The time rate at which the AGC changes gain is constant and independent of gain; it is set such that a gain change of 2:1, for instance, takes longer than the confirmation period for a tool break. The analog amplifier has a variable attenuator whose gain is set by the outputs of an up/down counter; these outputs are fed back to a variable clock whose rate is dependent on gain at any instant. The clock outputs drive the counter until the analog cutting noise signal is within a preselected window.
Abstract: In a single point machining operation, such as metal cutting on a lathe, the precession angle of lobes on a rotating workpiece is determined by measuring the frequency and changing phase of the cutting vibrations, and the stability of the machining operation is monitored by comparing the lobe precession angle to a predetermined range of values within which regenerative chatter may occur. Stability of the machining operation is maintained and productivity is optimized by controlling the crossfeed to maintain the lobe precession angle close to but outside of the predetermined range of values.
Abstract: A dark field ultrasonic transducer is constructed with an outer annular spherical or conical transducer element and an inner spherical element. The outer annular element is excited and insonifies a small portion of a part surface near a discontinuity or crack with longitudinal waves or with surface waves. The inner dark field element is not focused to be sensitive to either reflected sound or waves reradiated from the surface waves, but detects sound scattered from surface discontinuities such as a crack edge. When surface waves strike a crack edge and restrike it after reflection from the bottom of the crack, two pulses are received and the time delay between them is a measure of crack depth. The crack shape and crack depth profile are determined as the part is scanned.
Abstract: Changes in the ultrasonic properties of fiber-reinforced plastics during the curing process are monitored by a marginal oscillator to determine the degree of cure. The plastic sample and transmitting and receiving transducers serve as a narrowband acoustic resonator and are placed in the feedback loop of a variable gain amplifier; using gain control the system is allowed to marginally oscillate. The resonant frequency of the sample and amplifier gain are related to the velocity and attenuation of sound in the plastic and are determined by measuring the received signal frequency and amplifier gain control voltage. The system has frequency locking means to track changes in resonant frequency during the cure cycle.
Abstract: A cutting tool is monitored on-line by measuring the heat generation rate at the cutting edge and relating this to the condition of the cutting edge. A flow of fluid coolant contacts the back surface of the cutting tool and the coolant temperature rise is measured during the machining process. The temperature difference and its rate of rise or fall is a direct indication of the heat generation rate and is related to tool conditions such as excessive and rapid wear and breakage. In the case of inserts, coolant channels are formed in the reusable seat, and tool holder channels provide for flow of coolant to the seat.
August 4, 1986
Date of Patent:
July 12, 1988
General Electric Company
Bahram Keramati, Minyoung Lee, William R. Reed, Jr.
Abstract: An ionization chamber X-ray detector which minimizes the effects of leakage X-rays in systems where a collimator is employed to define resolution. The active collection volume of each detector element is reduced to the actual volume occupied by the negative ion cloud resulting from an incident X-ray beam for optimum response to desired radiation while minimizing response to leakage radiation by a combination of reducing the width of the collector electrodes with wider spaces in between the collector electrodes, and providing metallized guard electrodes between the collector electrodes. The guard electrodes serve to collect electrons freed by ionization between the collector electrodes resulting from "noise" X-rays, preventing these particular electrons from building up a space charge, or from reaching the actual collector electrodes. In addition, electric field distortions are minimized, with a consequent avoidance of adverse effects on detector response characteristics.
Abstract: A frame synchronization method and apparatus wherein each computer system of a multiply redundant processing system periodically executes a frame synchronization procedure in which it sequentially assumes a plurality of different operating states during which it pauses in the execution of a task it was performing and readies itself for synchronization, determines which other computer systems are ready for synchronization, synchronizes itself with one or more of the systems, and then determines which of the other systems has also synchronized itself. At a predetermined frame interval, the procedure is repeated and the computer systems resynchronize themselves with one another. The invention is impervious to stuck-at type faults, and may be embodied either totally or partially in software within each computer system, or in a separate hardware device.
Abstract: The quality of a percussion weld is sensed by measuring and analyzing certain features of the weld current signature. Instantaneous current is measured by a Hall sensor and permits isolation of the welder from the monitoring system. Weld quality is strongly correlated to the time to vaporize the nib separating the parts, and the dwell time to forge the parts together after nib explosion. A weld is assumed defective if nib time is too short or dwell time is too long. These quality parameters may be supplemented by weld and forge timing, line voltage, and acoustic information; a weld is rejected if any of these are outside of acceptance limits. Experiments on the percussion welding of silver-cadmium oxide to brass show that cadmium-oxide is decomposed and expelled by the forge pressure and the joint is a silver to brass weld.
Abstract: Feed process control is accomplished using an optical profiler to determine the height, width, and cross sectional area of a bead produced by a bead producing tool. Feedback control of the height, width, and/or area is obtained by modifying various parameters of the bead producing tool. If the bead producing tool is a welding torch, the parameters may include the weld torch voltage, weld torch current, wire feed rate, and the speed of travel of the torch across the workpiece or workpieces. If the bead producing tool is a sealant or glue gun, the parameters may include the pressure of the sealant or the glue supplied to the sealant or the glue gun, the size of an adjustable nozzle orifice of the sealant or the glue gun, and the speed of travel of the sealant or the glue gun along the surface of the workpiece.
Abstract: The penetration in an arc welding process is measured in real time by monitoring the natural frequency of oscillation of the weld pool. Spatial oscillations are induced in the weld pool by modulating either the shielding gas or the welding current at a plurality of different frequencies, and the light reflected from the pool at a non-specular angle is sensed and processed to determine the natural frequency of oscillation. Both pulse and swept frequency modulations are employed for excitation of the weld pool.
November 24, 1986
Date of Patent:
December 8, 1987
General Electric Company
Robert D. Lillquist, Allen W. Case, Jr.
Abstract: In some machining conditions the background noise in an acoustic cutting tool break detection system is a low mean level with fairly dense high amplitude noise spikes. A common tool break vibration signature is the sudden appearance of a dense spiky noise. Digital signal pattern recognition logic uses an up/down counter to reject the noise on the basis of its lower spike density while alarming on such a tool break signature. Preprocessed vibration signal samples are tested against a detection threshold and an alarm generated if those whose amplitude is above the threshold amplitude exceeds those below by a preset count.
May 5, 1986
Date of Patent:
November 17, 1987
General Electric Company
Charles E. Thomas, William S. Yerazunis
Abstract: Vibrations at the cutting tool-workpiece interface are sensed and the accelerometer output is preprocessed to yield a cutting noise vibration signal. Digital analysis of the sampled signal is performed to detect a gradual cutting noise signal level decrease tool break signature, either continuously decreasing or decreasing in a series of small abrupt steps. A tool break alarm is generated, without false alarming on metal-to-air tool path transitions, as the mean cutting noise signal level falls below an upper check limit and, after a preset time has elapsed, crosses a lower check limit.
Abstract: A Machine Tool Monitor detects the sudden increase in vibration signal level when a slowly advancing cutting tool first touches the workpiece. The delay to a tool touch decision is reduced while still avoiding false alarms on high amplitude single-peaked and multi-peaked noise spikes. Samples of the preprocessed analog vibration signal that are above a low threshold level are analyzed by digital tool touch detection logic. The signal slope polarity is determined by comparison of a new sample to the tracking mean, or by sample-to-sample amplitude comparisons, and presented to an up/down counter. A tool touch alarm is generated when the positive slope counts exceed the negative slope counts by a preset number slightly greater than occur in a time period from the start of a noise spike until its peak amplitude is passed.
Abstract: An optical technique for determining remotely movement of a movable point such as a point on a robotic end effector moving in three-dimensional space, based on observation of moving fringe patterns. In a preferred embodiment, at least one moving interference fringe pattern is projected from at least one spaced pair of coherent point light sources, having different frequencies, and a photodetector responsive to illumination at the movable point is employed to count fringes as they cross the movable point. The difference frequency between the light sources causes the fringes to move at a known rate to provide sense-of-direction information in that this results in the detector output having a frequency component which reflects point motion. Full three-dimensional location is obtained by observing three independent fringe patterns in three independent directions. Such a set of patterns can be produced by as few as three point sources operating at three different frequencies.
Abstract: An imaging radiometer for high temperature measurements has a sensor head comprised of a solid-state video camera operated in fixed gain mode, preferably one with a charge injection device detector, an infrared filter, and a lens system to image a radiating object on the detector array. Spectral response of the system is limited to 700 to 1100 nanometers or a smaller portion of this near-infrared band. The video signal output of the sensor is processed and object temperature is displayed on a television monitor; alternatively the video signal is presented to a digital frame grabber and converted to a temperature map.
Abstract: A non-contact sensor system measures distance from a reference plane to many remote points on the surface of an object. The set of points at which range is measured lie along a straight line (N points) or are distributed over a rectangular plane (M.times.N points). The system is comprised of a pattern generator to produce a 1.times.N array of time/space coded light rays, optionally a means such as a rotating mirror to sweep the coded light rays orthogonally by steps, a linear array camera to image subsets of the light rays incident on the object surface, and a high speed range processor to determine depth by analyzing one-dimensional scan signals. The range camera output is a one-dimensional profile or a two-dimensional area range map, typically for inspection and robotic vision applications.
Abstract: A three-dimensional range camera, which produces a range map of the distances from a reference to each of M.times.N points in a scene, is modified to generate registered luminance and range images. The same sensor detects range and luminance variations. A planar pattern projector generates sequential presentations of time/space coded light rays which are projected onto the object. A linear array camera images the points of light on the object surface, and a processor analyzes one-dimensional scan signals to determine range. To detect luminance there is an additional presentation, either constant illumination or no artificial illumination, and the other scan signal yields luminance along the same strip of the scene.
Abstract: A self-checking detector for detecting faults in a multiple redundant clock system includes a majority voter circuit for receiving the clock signals from the redundant clock circuits and for providing a voted output, a comparison circuit for comparing each of the clock signals with the voted output, and failure signal producing circuits responsive to the outputs from the comparison circuit for producing a first failure signal upon a clock failure being detected and for producing a second failure signal upon a failure of the majority voter being detected. The detector further includes power-up reset circuitry for inhibiting its operation during a power-up interval, and a reset circuit enabling either automatic or manual reset of the detector for verification of the detected fault.