METHOD AND DEVICE FOR MEASURING THE DEFORMATION OF A ROTATING SHAFT

Abstract: When measuring deformation of a rotation shaft calibration means like a bridge of strain gauges is used for calibrating the measured deformation value. In order to compensate not only proportional errors but also other errors the measuring signals as well as the calibration signals are transferred through the same transferring means from the rotating shaft onto the signal presentation device.

Description: Method and device for measuring the deformation of a rotating shaft. The invention relates to a method of measuring the deformation of a rotating shaft in which calibration means are used for calibrating the measured deformation value. Such a method is known from U.S. patent 3,134,279, in which the calibration means are formed by a resistor of known value connected parallel to a strain gauge. These calibration means are temperature sensitive and by this circuitry only the proportionality error of the measuring system is detected. The invention has for its object to obviate said disadvantage. This is achieved by a method as defined in Claim 1. When calibration and zero calibration means pick up signals by means of calibration and zero calibration bridges arranged on an annular metal carrier connected with the shaft and having the same temperature as the measuring bridge, the measuring value originating from the measuring bridge is compensated for temperature, whilst a calibration signal of the same order of magnitude as the measuring signal is OMPI obtained. Moreover, by the zero calibration signal picked up by means of a zero calibration bridge a satisfactory inter¬ polation of the proportionality error between zero calibration and calibration value is possible. Finally, owing to the accurate zero calibration value it is possible to measure a propulsion value in the direction of length, which differs only little fron the zero calibration value and which is a measure for the propulsion of, for example, a vessel. The propulsion (propelling pressure) is a very interesting datum for a ship for setting optimum operational conditions of a vessel. The number of revolutions and/or the blade of adjustable propellers can be set in dependence on the measured propelling pressure for different navigation conditions. A further developed method and the device provided by the invention are described in the subclaims. The invention will be described more fully herein¬ after with reference to a drawing. The drawing shows schematically in Figs. 1 and 4 each a rotating shaft provided with schematically shown, different devices embodying the invention, Fig. 2 a graph of the deformation measured by the device of Figs. 1 and 4, Figs. 3 and 5 a block diagram of the device of Figs. 1 and 4 respectively, Fig. 6 a perspective view of the device of Fig. 4. The rotating shaft 1 is provided with pick-up means 3 formed by a measuring bridge of strain gauges known per se. Furthermore, calibration means are rigidly connected with the shaft 1 so that they rotate together with the shaft 1, said calibration means 7 consisting of a carrying ring 8 having zero calibration means 9 not affected by the deformation of the shaft 1 and proportionality calibration means 10 con- sisting each of a bridge of strain gauges arranged at such a place in the carrying ring 8 that they have the same temperature as the shaft 1. Finally a first alternating switch 4, amplifying means 20, modulation means 5, trans¬ mitting means 6, an oscillator 21 and a secondary feed O cirσuit 24 for the electric feed are rigidly connected with the shaft 1 so that they rotate together with the shaft 1. There are statically aranged receiving means 11, demodulation means 12, a second alternating switch 13, .a synchronous oscillator 22, a primary feeding circuit 23, calculating means 16 and display means 18. The alternating switches 4 and 13 are synchronously adjustable between a measuring position a, a zero calibration position b, a measuring position £ and a proportionality calibration position d by means of any known circuit arrangement. This circuit arrangement may comprise a connection 19 of constant voltage Sd exceeding any measuring signal whatsoever. This voltage source 19 is connected to a contact point d of the alternating switch 4. The alternating switch 4 continuously switches in order of succession along the contact points 1, b, c, d, a etc. under the control of a master synchronous oscillator 21. Since the slave synchronous oscillator 22 perceives the high Sd signal, it follows by connecting on the contacts d, a, b, c. Then the slave synchronous oscillator 22 has again to perceive the high Dd signal in order to again carry out a through-connection d, a, b,c. Switch.4 changes each time over from the position 2 to contact point a_ when it perceives a high signal S (see Fig. 3), since switch 13 is controlled by synchronous oscillator 22, which is synchronized with oscillator 21 by the signal S s « In the zero calibration position b of the alternating switching means 4, 13 the zero signal is applied from the zero calibration means 9 to the amplifying means 20, which apply an amplified signal to modulation means 5. The amplified and modulated signal is transmitted by the transmitting means' 6, received by the receiving means 11, demodulated by demodulation means 12 and applied, in the zero calibration position b of the alternation switch 13, to the zero calibration signal input 14. The zero calibration signal applied to the calculating means 16 is stored in the memory of the calculating means 16. When at a different instant, by means of the oscillators 21, 22 the alternating switches 4 and 13 have changed over to their proportionality calibration position £, OMPI the proportionality signal of the proportionality calibration means 10 is applied through the same assembly of amplifiying means 20, modulation means 5, demodulation means 12, the transmitting means 6 via the receiving means 11 and the two alternating switches 4 and 13 " in processed condition to the proportionality signal input 15 of the calculating means 16, which temporarily store it in a memory concerned. At a different instant, after a change-over of alternating switches 4 and 13 into a measuring position a_, a measuring signal is applied through the same assembly of amplifying means 20, modulation means 5 and demodulation means 12 via the transmitting means 6 and receiving means 11 and the two alternating switches 4 and 13 in amplified condition to the measuring signal with the most recent zero processing error and the most recent proportionality processing " error. The calculation programmed in the calculating means 16 will be explained hereinafter with reference to Fig. 2. In Fig. 2 is plotted the instantaneous processing behaviour of .the assembly 20, 5, 12. Pick-up signals associated with the proportionality calibration value V c an< ^ the zero calibration value Vfc arrive at the calculating means 16 as processed signals having the signal magnitude S c and Sfc respectively. From the diagram of Fig. 2 it is apparent that the deformation V a occurring at a given instant with respect to the output deformation V - which will usually be equal to zero and is, therefore, termed the zero calibration value - can be calculated by the formula: This value calculated in the calculating means 16 is applied to the display means 18, for example, an indicating an/or recording device, as well as to a control device 40 which controls automatically a fuel supply mechanism 44 of a motor 41 driving the shaft 1. With the aid of the device 52 of Fig. 4 it is possible, for example, to measure the axial compression of a shaft 1 caused by the propulsion of a ship. The numerals of C PI Fig. 4 equal to those of Fig. 1 designate the same functiona means. As shown in Fig. 4, there is added a bridge of hook strain gauges 30 formed by two hook strain gauges 26, 27 arranged on both sides of the shaft and two unloaded, corresponding hook strain gauges 28, 29 arranged όh the carrying ring 8. The bridge 30 of hook strain gauges may be connected to contact e_ of the alternating switch 4. The slave synchronous oscillator 22 is synchronized, for example, by means of the proportionality calibration signal S G (Fig. 5). By means of the calibration and zero calibration 10, 9 it is possible to accurately distinguish a propulsion signal S- corresponding to a compression of the shaft 1 from the zero calibration signal Sb« In Fig. 4 the control device 40 controls particularly in dependence on the torque signal S a the fuel supply mechanism 44 and controls particularly in dependence on the propulsion signal S p a propeller blade adjusting mechanism 43 for adjusting the propeller blade angle of the propeller 42 driven by the shaft 1. Said control device 40 comprises a computer for calculating and setting the required fuel amount per unit of time and the required propeller angle for the most efficient operation of the ship. Fig. 6 shows that the aerial of the transmitting means 6 is located substantially in the middle of the annular carrier 8 and opposite the aerial of the fixed pick-up means 11 arranged on an arm 33 in a casing 32. On both sides of the aerials of the transmitting and receiving means 6 and 11 respectively are arranged the secondary and primary feed windings 24 and 23 respectively for the electric feed of the means arranged on the carrying ring 8. It is noted that the bridges of strain gauges 30 are fed by alternating voltage in order to avoid thermo-couple effects. For an accurate transmission a frequency-modulated signal is used for transmitting/receiving. On the carrying rings 8 is arranged a ring 31 ther¬ mally well coupled with the shaft 1, on which ring 31 are arranged the unloaded strain gauges 28, 29 as well as the bridges 9, 10. An annular cavity 34 is provided in the carrier for accommodating the electric and electronic "SURE OMPI amplifying, modulation and transmitting means 20, 5 and 6 respectively as well as the alternating switch 4 and the oscillator 21. l&fRE OMH

Claims: C A I M S 1. A method of measuring the deformation of a rotating shaft (1) in which a measuring signal relating to the deformation is picked up by rotating pick-up means (3), the picked-up signal is modulated by rotating amplifying means to a signal transmissible without wires, the modulated signal is transmitted by rotating transmitting means (6), the transmitted signal is received by static receiving means (11), the received signal is demodulated by demodulation means (12), the demodulated signal is displayed and in which periodically, each time, a calibration signal from the rotating calibration means (7) having a calibration value is passed through the same amplifying means (20), the same modulation means (5) and the same demodulation means (12) and applied to calculating means (16) for assessing a processing error of the amplified, modulated and demodulated calibration signal with respect to the known calibration value stored in the calculation means (16) and in that the measuring signal received at a different instant through the same amplifying means (20), the same modulation means (5) and the same OMPI demodulation means (12) is corrected for the processing error, in that the calibration means comprise a-bridge of .a resistor provided with calibrated values and in that periodically, each time, a zero calibration signal picked up from rotating zero and calibration means (9, 10) designed in the form of measuring ridges relating to a known zero value is passed through the same amplifying means (20), the same modulation means (5) and the same demodulation means (12) and applied to calculating means (16) for assessing a zero processing error of the amplified, modulated and demodulated zero calibration signal with respect to the known zero value stored in the calculating means and in that the measuring signal with the processing error received at a different instant through the same amplifying means (20), the same modulation means (5) and the same demodulation means (12) is corrected. 2. A method as claimed in Claim 1, characterized in that the calibration means comprise a bridge of strain gauges (3) independent of the deformation of the shaft (1). - 3.-A method as claimed in Claim 1 or 2, characterized in that a proporionality error of the amplifying means (2), the modulation means (5) and the demodulation means (12) is calculated on the basis of a proportionality calibration sig¬ nal applied to the calculating means (16), a zero calibration signal applied to the calculating means (16), the correspon¬ ding known proportionality calibration value and the corre¬ sponding known zero calibration value and in that the measuring signal passed through the same amplifying means (20), the same modulation means (5) and the same demodulation means (12) is corrected with respect to the proportionality error. 4. A method as claimed in Claim 1, 2 or 3, characterized in that a propulsion measuring signal is picked up by means of rotating propulsion means (30). 5. A device (2) for measuring the deformation of a rotating shaft (1) comprising - rotating pick-up means (3) picking up a measuring signal relating to the deformation, - rotating amplifying means (2) amplifying the received measuring signal, - rotating modulation means (5) modulating the - received signal into a signal transmissible without wires, - rotating transmitting means (6) transmitting the modulated signal, - static receiving means (11) receiving the transmitted signal, - static demodulation means (12) demodulating the received signal, and - display means (18) displaying the demodulated signal, characterized by at least one measuring bridge comprising rotating calibration means (7) having a known calibration value, calculating means (16) for assessing the processing error of the processing calibration signal applied thereto with respect to the known calibration value stored therein, said calculating means (16) being designed for correcting a processed pick-up signal applied thereto and by alternating switching means (4, 13) adjustable between a calibration position and a measuring position for passing the measuring signal and the calibration signal into the measuring position and the calibration position respectively from the pick-up means (3) and the calibration means (7) through the same assembly of amplifying means (20), modulaton means (5) and demodulation means (12) and through the calculation means (16). 6. A device (2) as claimed in Claim 5, characterized by calibration means having a zero value. 7. A device (2) as claimed in Claim 5 or 6, characterized by two sets of calibration means (9, 10) having a known difference between their calibration values and by calculating means (16) for assessing the proportionality error of the assembly of the amplifying means (10), the modulation means (5) and demodulation means (12) and for compensating for the proportionality error in calculating the measuring value associated with the measuring signal processed by said assembly. 8. A device (2) as claimed in Claim 5, 6 or 7, characterized in that the switching means (4, 13) comprise a CMPI first adjustable alternating switch (4) arranged on the rotating- shaft (1) connected in its measuring position, its zero calibration position and its proportionality calibrating position to pick-up means (3), zero calibration means (9) and proportionality calibration means (10) respectively and a statically arranged, adjustable second alternating switch (13) switchably coupled with, the first alternating switch (4) connected in its measuring position (c) to the measuring signal input, the zero signal input (14) and the proportionality signal input (15) respectively of the calculating means (16) . 9. A device (2) as claimed in anyone of Claims 5 to 8, characterized by propulsion measuring means picking up a propulsion measuring signal. 10. A device (2) as claimed in Claim 9, characterized in that the propulsion measuring means comprise a bridge (30) of hook strain gauges (26, 27) , in which two hook strain guages (26, 27) not connected in series in the bridge (30) are arranged on both sides of the rotating shaft (1).

Inventors: UITERMARKT ROMBARTUS WILLEM PI, UITERMARKT, ROMBARTUS, WILLEM, PIETER
Applicants: TECHNO DIAGNOSIS BV, TECHNO-DIAGNOSIS B. V.
Application year: 1984
Main classification: G01B7
IPC codes: G01B7, G01L1, G01L3