KR900008857B1 - Automatic calibration of sensor circuits in gear shapers - Google Patents

Abstract

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Description

Method and apparatus for automatic correction of detector circuit of gear shaper

1 is a block diagram schematically illustrating a control system constructed in accordance with a preferred embodiment of the present invention.

2 to 5 are flowcharts showing the operation in the preferred embodiment.

* Explanation of symbols for main parts of the drawings

10: automatic correction system 10: load side

22: cutter spindle 24: supply side

40: reference source 70 and 74: analog-to-digital converter

72: central processing unit

FIELD OF THE INVENTION The present invention relates primarily to automatic calibration circuits and, more particularly, to a method and apparatus for automatically calibrating the output of multiple pressure transducers used in hydrodynamic gear shaping machines.

Hydraulic transducers are used in hydrodynamic gear shapers as shown in US Pat. Nos. 4,125,056, 4,136,302 and 4,254,690. Each of these patents has been assigned to the assignee of the present invention and incorporated herein by reference. These pressure transducers generate analog electrical signals proportional to the associated hydraulic pressure level. Whether the hydrodynamic gear shaper works properly depends on whether the transducers work properly and whether the load and supply pressures are measured accurately.

Since pressure transducers used in prior art hydrodynamic gear sharing machines tend to drift after repeated operation, the electrical output of the detectors and their associated circuit components is also the result of an amplifier gain or voltage offset (transsecting) conversion. It has been found to drift.

These deviations are obviously detrimental to the proper operation of the machine and also require recalibration or replacement of the components that are causing the error. In addition, if the signals indicate that more power is actually required for the proper performance of the gear shaper, the detector output will be incorrect, resulting in inefficient operation.

It is therefore an object of the present invention to eliminate the drawbacks associated with these prior art pressure transducers by providing automatic correction means for compensating for detected errors.

Another object of the present invention is to produce such automatic correction means for periodically compensating for detected errors.

Another object of the present invention is to eliminate the need to accurately adjust the initial values of the various component parts associated with the converter circuit.

These and other objects of the present invention are achieved by an apparatus for calibrating a calibrated detector output to generate an analog electrical output signal representing a selected sensing parameter which is a preferred embodiment of the present invention. A signal adjusting circuit connected to adjust the output signal, a reference signal device for generating first and second reference signals, and one of the output signals or one of the first and second reference signals to a signal adjusting circuit. A multiplexer device interposed between the sensor and the signal conditioning circuit for selectively sending, the sensor and the signal conditioning to provide the calibrated sensor output signal and an analog-to-digital converter connected to the output of the sensor and the signal conditioning circuit. Periodically determine the selected characteristics of the circuit, A digital control device connected to the analog-to-digital converter, the multiplexer, and the reference signal device 40 to use the properties, wherein the predetermined characteristics include the signal using the first and second reference signals as input. Actual gain and output offset of the adjustment circuit, and the output offset of the sensors.

The present invention will now be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, there is shown a schematic block diagram of a control system constructed in accordance with the principles of the present invention to calibrate a pressure transducer of a hydrodynamic gear shaper, such as that shown in US Pat. No. 4,136,302. In addition, the supply and load pressure transducers indicated in the patent are also used in the present invention.

The automatic calibration system 10 is designed to operate on and calibrate the load pressure detector TD1, the redundant load pressure detector TD2 and the supply pressure detector TD3. The load pressure detector TD1 constitutes a primary load sensing device for controlling the hydrodynamic gear shaper.

An extra load pressure sensor TD2 is provided for back up. These two load pressure sensors detect the load hydraulic pressure on the load side 20 of the piston of the cutter spindle 22. One advantage of keeping this load pressure detector redundant is that a well-behaved detector circuit does not adversely affect gear shaper operation because any well-behaved device has been pre-calibrated in the event of any one detector or circuit failure. The characteristics of each detector and circuits are determined so that they can be combined. The supply pressure detector TD3 senses the water pressure supplied to the supply side 24 of the cutter spindle 22. These sensors generate signals that are ultimately used by the center processing unit (CPU) to control the operation of the gear shaper.

Each pressure sensor TD1, TD2 and TD3 provides an analog electrical output signal corresponding to the sensed pressure to each multiplexer MUX1, MUX2 and MUX3. In addition, each multiplexer receives the reference voltage pressure from the primary load pressure detector TD1 as well as the reference source 40. All multiplexers supply the same pressures and can be replaced with a control system as needed to compare the operation of a series of circuit elements with the operation of other series of circuit elements.

The output of each multiplexer MUX1, MUX2 and MUX3 is provided to respective amplifiers AMP1, AMP2 and AMP3 which are operatively connected to respective peak detectors PD1, PD2 and PD3. Each peak detector receives and maintains the maximum output of the amplifier associated therewith that occurs during a predetermined sample period (e.g., one cutting cycle). The outputs of the respective pressure detectors as well as the outputs of the peak detectors are provided to a number of ports of the analog-to-digital converter 70 (differential input, unipolar) operatively connected to the central processing unit 72. . As shown, the system 10 has three channels for passing a converter signal to the CPU. To simplify the description of the flow chart described below, a number of components are identified by this channel number. Peak detectors are shown in FIG. 1 because these peak detectors are used by the control system of the hydrodynamic gear shaper to control the operation of the gear shaper. These detectors are not necessary for the good operation of the present invention. However, it should be understood that the three channels may include any type of signal conditioning circuit to pass the converter signals to the CPU.

The reference voltage source 40 provides on the line 41 any one of two reference voltages V ₁ or V ₂ at a predetermined time under the control of the CPU 72. A second analog-to-digital converter 74 (single ended input, bipolar) is provided to receive a reference voltage along line 42 and to receive the output of amplifier AMP3 along line 78. Two different transducers are used to obtain a better resolution, since the pressures of the transducer 70 are only positive and the inputs of the transducer 74 are negative. The output of the converter 74 is also provided to the CPU 72. The output of this CPU is provided to a gear shaper control interface (not shown) to control the operation of the hydrodynamic gear shaper.

Operation of the calibration system 10 may be performed in hardware or software. The calibration system 10 of the preferred embodiment uses a computer program implemented in accordance with the program steps shown in the flow charts of FIGS. 2-5 to calibrate the pressure sensor outputs. Therefore, the operation of the present invention will be described with reference to this flowchart.

Some of the program steps included in FIGS. 2-5 are included in the start up diagnostics of the computer numerically cntrolled (CNC) gear shaper and are executed each time the quay shaper is started. Other program steps may be executed periodically at predetermined intervals during the gear shaper operation. For example, large gears require long manufacturing times, which are more prone to pressure variations or circuit errors. In the case of such large gears, it may be desirable to calibrate the detector periodically during manufacture.

The first step is to supply power to various nare systems without powering the gear shaper or hydraulic part. Therefore, the water pressure is initially zero. This initial pressure determines two partial subroutins, firstly, the output offset and gain error of the amplifier AMP3, and secondly the actual gain and offset of each amplifier and its associated peak detector circuit. It is used to determine the detector offset by using a subroutine.

Subroutine for determining the output offset and gain error of the amplifier (AMP3) proceeds by applying danjye 102 a known multiplexer (MUX3), the input reference voltage (V _1), which as shown in the second diagram. This reference voltage V1 is also provided to the CPU 72 via the line 41 and the converter 74 and stored in a memory address as shown by step 104. The resulting output of amplifier AMP3 is then read from line 78 and stored in memory as shown in step 106. Then, the pseudo-acid series of steps 107, 108 and 109 use the second input reference voltage V ₂ to determine the amplifier response at the second input reference voltage. Is stored in the memory results in the step (104, 106, 108 and 109) are calculating the actual gain, such as by subtracting the output of the amplifier at ₁ V / (V ₂ -V1) from the amplifier output at the V ₂ For use in step 110. Then, the amplifier offset is determined in step 112 as obtained by subtracting the product of the actual gain in the V ₂ at the amplifier output at V _2. These calculated values are used in other parts of the program as described below.

The calibration system 10 is part of a computer control system for hydrodynamic gear shapers and therefore works with input-output devices such as cathode ray tubes. The control program described in FIGS. 2 to 5 has several steps for promptly displaying a message on the CRT for the gear shaper operator.

For example, steps 114 and 115 of FIG. 2 determine whether the gain or offset of amplifier AMP3 is within some predetermined limit. If the backside or offset of amplifier AMP3 is within some predetermined threshold, the program branches to steps 116 and 117 to display the appropriate message to the operator so that the operator adjusts the backside or offset potentiometer.

If the gain and offset of amplifier AMP3 are not within some predetermined limit, the program continues to step 118 to determine the detector offset value using the circuit characteristics of amplifier AMP3 now known.

After the gain and offset characteristics of the amplifier AMP3 have been determined, the CPU 72 replaces the reference voltages V ₁ and V ₂ from the reference voltage source 400 with the outputs of the detectors TD1, TD2 and TD3. Which in turn is sequentially switched through the multiplexer MUX3 and amplifier AMP3. Corresponding outputs of the amplifier AMP3 are read and stored by the CPU 72, and the offset values of the plurality of detectors TD1, TD2 and TD3 as shown by steps 118 to 123 are represented by Offset- (sensor 0 signal-amplifier output offset) / amplifier gain. As shown by steps 124, 125, and 126, each of these detector offset values is compared with predetermined tolerance limits, and steps 127, 128, and 118 for proper zeroing where appropriate indication messages are needed. 129) to the operator.

Exceeding the predetermined offset limits, program steps 127, 128, and 129 set corresponding error flags to stop the running cycle. The system 10 performs automatic calibration of the detector outputs only within predetermined limits. If these limits are exceeded and, for safety reasons, other than normal drift or circuit error occurs, the gear shaper will stop until the operator manually corrects.

The program also uses the subroutine shown in FIG. 3 to determine the actual gain of each amplifier and corresponding peak detector circuit. This is carried out as shown by the program steps 202-210 in a similar manner to the program steps 102-110 described above in connection with FIG.

Here, the difference between FIG. 2 and FIG. 3 is that the amplifier outputs mentioned in FIG. 3 are determined as the digital outputs of each channel through the respective peak detectors PD1, PD2 and PD3 and the analog-to-digital converter 70. It is. In fact, the memory addresses of the data determined in FIG. 3 are different from those in FIG. 2, and the data shown in FIG. 3 is prepared in advance. Each amplified value is then compared with the tolerance limits selected in steps 212-214, where appropriate messages are displayed and error flags are set if necessary in steps 215, 216, and 217.

Next, the output offset for each of the amplifiers AMP1, AMP2 and AMP3 and the corresponding peak detector circuits is determined by the program steps shown in FIG. Steps 302-304 determine the output offset for the detection circuits associated with the detectors TD1, TD2 and TD3, respectively. This offset value is determined similarly to step 112 of FIG. For example, the difference between step 112 and step 304 is that the amplifier output used in step 304 is the output of the entire circuit through the peak detector PD3 (as in step 112). Is not the only output. Each output offset is then compared in step 305, 306 and 307 with a predetermined tolerance threshold, where appropriate indication messages are provided in steps 308, 309 and 310 and error flags set if necessary. .

As such, the actual gains and offsets at the outputs of the detectors and amplifier circuits have been determined and each signal by the same magnitude as the errors generated by the circuit in order to reach the true and correct values of the hydraulic pressure. Appropriate correction factors can be derived to adjust. This correction is ideally carried out periodically during the operation of the gear shaper, for example once every stone period.

The corrected sensor signal is calculated by the CPU 72 according to the following formula, i.e., corrected sensor signal = [sensor signal ± (sensor offset x real gain) ± output offset] x [necessary gain / actual gain]. The required gain is a theoretical gain due to the specific circuit components used. In a preferred embodiment, this gain is two. The calculation of this corrected detector signal for each of the three detectors is done in steps 402-407 of FIG. The corrected signals are the signals that are output to the gear shaper interface to control various functions described in the above-mentioned patents.

As described above, the correction system 10 not only provides error determination and automatic correction to maintain accurate and true signals for efficient and reliable gear shaper operation, but also precisely adjusts all the circuit elements described above initially. Eliminate the need

The automatic calibration system 10 can be applied to computer controlled manufacturing equipment where accurate sensor signals are needed in real time for control purposes.

It is also possible for those skilled in the art to modify the invention or to improve preferred embodiments of the invention without departing from the spirit and scope of the invention.

Claims (7)

An apparatus for generating a calibrated detector output to generate a calibrated detector output to generate an analog electrical output signal indicative of a selected sense parameter, the apparatus comprising: a signal conditioning circuit, first and second reference connected to adjust the output signal; A reference signal device 40 for generating a signal, interposed between the sensor and the signal conditioning circuit to selectively send the output signal or one of the first and second reference signals to the signal conditioning circuit. A digital device connected to the analog-to-digital converter 70, the multiplexer and the reference signal device 40 to periodically determine predetermined characteristics of the multiplexer device, the detector and the signal conditioning circuit and to use the predetermined characteristics. A counting device 72, wherein the predetermined characteristics are adapted to receive the first and second reference signals. The actual force gain and offset of the output signal conditioning circuit using a, and the automatic correction device characterized in that it comprises an output offset of the detector. The sensor of claim 1, wherein the corrected signal is determined by the equation Sc = [So ± (Sf · G) ± Of] (TG / G), where Sc is the calibrated detector output and So is the actual detector. Output, Sf is the detector offset determined when the input is zero, G is the actual gain of the signal conditioning circuit, Of is the output offset of the signal conditioning circuit, and TG is the theoretical gain of the signal conditioning circuit. Automatic correction device. 2. A sensor according to claim 1, characterized in that the sensor is connected to generate a signal indicative of the water pressure used in the gear production machine, and the corrected sensor output is used to control the selected operation of the gear production machine. Automatic calibration device. 2. A second detector connected to said transducer 70 for sensing a predetermined sensing parameter, a second signal conditioning circuit connected to said transducer 70 for adjusting the output of said second detector, A second multiplexer connected to the reference signal device interposed between the second sensor and the second signal conditioning circuit for selectively sending an output signal or one of the first and second reference signals to a second signal conditioning circuit; Further comprising a device, wherein the digital control device 72 is connected to the second detector and the second pulse multiplexer to periodically determine predetermined characteristics of the second detector and the signal conditioning circuit, Only by inspecting the detectors or their associated elements to periodically check each of the detectors and their associated elements to determine operation. The transducer output 70, the second multiplexer and the reference signal device so that the correction of the gear shaper can be continued without interruption in the event of a failure of the sensor or related elements by replacing them with other sensors and related elements. And the control device (70) is connected to (40). An apparatus for generating a calibrated detector output to generate an analog electrical output signal indicative of a selected sensing parameter, the apparatus for calibrating the output of the detector, comprising: a signal conditioning circuit, first and second reference connected to calibrate the output signal; A reference signal device 40 for generating a signal, interposed between the sensor and the signal conditioning circuit to selectively send the output signal or one of the first and second reference signals to the signal conditioning circuit. To periodically determine predetermined characteristics of the detector and the signal conditioning circuit to provide a multiplexer device, an analog-to-digital converter 70 connected to the output of the detector and the signal conditioning circuit, and the corrected detector output signal. The selected characteristics are also used to generate a calibrated detector output signal. Digital control device 72 connected to the analog-to-digital converter 70, the multiplexer and the reference signal device 40, wherein the predetermined characteristics are input to the first and second reference signals. The actual gain and output offset of the signal conditioning circuit used, and the output offset of the detectors, the corrected signal being determined by the equation Sc = [So ± (Sf · G) ± Of] (TG / G), Where Sc is the calibrated detector output, So is the actual detector output when the input is zero, Sf is the detector offset determined when the input is zero, G is the actual gain of the signal conditioning circuit, Of is the An offset based on offset, and TG is a theoretical gain of the signal adjustment circuit. 10. A method according to claim 9, wherein the detector is connected to generate a signal indicative of the revenue used in the gear production machine, wherein the corrected sensor output is used to control the selected operation of the gear production machine. Automatic calibration device. 10. A second detector, coupled to the transducer 70, for sensing a predetermined sense parameter, and a second signal conditioning circuit coupled to the transducer 70 for adjusting the output of the second detector. A second connected to said reference signal device interposed between said second sensor and said second signal conditioning circuit for selectively sending an output signal or one of said first and second reference signals to a second signal conditioning circuit; Further comprising a multiplexer device, wherein the digital control device 72 is connected to the second detector and the second multiplexer to periodically determine predetermined characteristics of the second detector and the signal conditioning circuit, and satisfactory operation. The detectors or their associated elements also unsatisfactorily determined to periodically inspect each of the detectors and their associated elements to determine The transducer output 70, the second multiplexer and the reference signal device so that gear shaper correction is continued without interruption in the event of failure of the sensor or related elements by replacing them with satisfactory detectors and related elements. And the control device (70) is connected to (40).

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