Ultra-sonic distance sensor and monitoring of surface profile utilizing ultra-sonic distance sensor

Abstract: An ultra-sonic distance sensor generates ultra-sonic waves and transmit same toward a target surface, the distance to which is to be measured, through a predetermined path. The sensor is also provided with a reference surface which reflects ultra-sonic waves, which reference surface is disposed within the aforementioned predetermined path of the ultra-sonic waves. A receiver associated with an enabling means receives the ultra-sonic waves reflected by the reference surface or by the target surface, selectively. Arithmetic operations based on the elapsed time between transmission of the ultra-sonic waves and reception of the ultra-sonic waves from the reference surface derive the transmission velocity of the ultra-sonic wave based on the known distance to the reference surface. On the basis of the derived transmission velocity and the elapsed time measured with respect to the ultra-sonic waves reflected by the target surface, the distance to the target surface is derived. The aforementioned ultra-sonic sensor is used to monitor the external shape of an object. In order to monitor the external shape of the object, a system is composed of a plurality of the ultra-sonic sensors. The sensors comprises a primary sensor or sensors directed toward the external surface of the object and an auxiliary sensor or sensors directed to a reference line.

Description: BACKGROUND OF THE INVENTION The present invention relates generally to a system using ultra-sonic distance sensors suitable for monitoring the profile of a roller in a rolling mill. The invention makes use of distance sensors transmitting ultra-sonic waves towards a roller, receiving reflected ultra-sonic waves and deriving the distance to the roller based on an elapsed time between transmission of the ultra-sonic waves and reception thereof, for monitoring or scanning the surface profile of the roller thus detecting the external shape of the roller. In the steel industry and especially in rolling steel, ultra-sonic distance sensors have been used for precise distance measurement or surface monitoring. In the known art, for instance in JP-A-57-168108, the ultra-sonic waves are transmitted through a water jets to a target surface to measure the distance by measuring the elapsed time between transmission and reception of the reflected ultra-sonic waves. However, during transmission, the water temperature has a large enough effort to cause errors in the measured distance to the target surface due to deviation of the transmission time. In order to eliminate the influence of the water temperature, it is necessary to correct the measured elapsed time or derived distance. This water temperature-dependent correction of the measured value was proposed in "Materials Evaluation" Vol. 35, No. 2, published in 1977, on pages 45 to 50. In the proposed system, an auxiliary sensor monitors the elapsed time to reception of an ultra-sonic waves reflected by a reference surface which is located at a known distance from the auxiliary sensor. Based on the elapsed time measured by the auxiliary sensor, the transmission velocity of ultra-sonic waves through the water is derived. The elapsed time measurement then utilizes the transmission velocity of the ultra-sonic wave derived with respect to the reference surface. This proposed system helps to improve the accuracy of the resultant measured distance. However, the prior proposed system set forth above requires primary and auxiliary sensors for water temperature dependent correction, which increases the overall cost. Also, since the points of measurement of the primary and auxiliary sensors are separate, their water temperatures will tend to differ. so that the correction value will not necessarily be accurate. As is well known, the variation of transmission velocity of the ultra-sonic waves relative to the water temperature is about 1.6 x 10⁻³/°C. This means that when a temperature difference of 0.1°C exists between the measurement points and the distance to be measured is about 30 mm., the error of the distance measurement will be about 5 µm. This error is unacceptably large for precise measurement of the distance. Furthermore, the aforementioned known system utilizes a ramp wave and samples the ramp wave voltage upon reception of the reflected ultra-sonic waves to measure the elapsed time. Accuracy of this system is limited to the linearity of the ramp wave and thus is rather low, at an error of about 0.1%. This means when the distance being measured is 30 mm., the error will be about 30 µm. The error due to the temperature difference between the two measuring points will be superimposed on the fundamental error set forth above. The foregoing conventional system is not able to satisfy the requirements for accuracy of products such as rollers in rolling mills. SUMMARY OF THE INVENTION The invention provides for a roller profile monitoring system as disclosed in claim 1. Additional features of this system are disclosed in claims 2 to 5. The invention provides for correcting derived distance between the reference surface and the surface of the roller for compensating displacement of the reference surface according to the axial displacement thereof. The corrected distance Z i (L) at the fully shifted position is derived by the equation Z' i (L) = Z i (L) + a 1 x i + b 1 where coefficients a and b are derived so as to minimize Δ, defined in the following equation: where Z i (0)(i = 1 to 10) are the measured values at the initial positions. The corrected roller profile indicative distance values W i at any of the intermediate points shifted through a distance ℓ is derived by modifying the distance value Z i (ℓ) (i = 1, 2,..,10) according to the following equation: W i = Z i (ℓ) + a 2 x i + b 2 where a 2 = 1 9 {-Z 10 (ℓ) + Z 1 (ℓ) + Q' 9 2L 2 ℓ (ℓ - L) - Q' 10 L 2 (ℓ + L)(ℓ - L) - Q' 3 2L 2 ℓ (ℓ - L) + Q' 2 L 2 ℓ ℓ - 2L } b 2 = 1 9 {-10Z 1 (ℓ) + Z 10 (ℓ) + 5Q' 3 L 2 ℓ (ℓ - L) - 10Q' 2 L 2 ℓ (ℓ - 2L) - Q' 9 2L 2 ℓ (ℓ - L) + Q' 10 L 2 (ℓ + L) ℓ - L } Q i (shown in Fig. 15) (i = 1 to 11) being derived from the following equation: Q i = Z i (0) :i = 1 = {Z' i-1 (L) + Z i (0)}/2 :i = 2 - 10 = Z' 10 (L) :i = 11 Q' i (i = 1 to 11) being derived from the following equation: Q' i = Q i - {(Q 11 - Q 1 ) x (i - 1)/10 + Q 1 }. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood from the detailed description given herebelow and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding only. In the drawings: Fig. 1 is a block diagram of an ultra-sonic sensor which may be incorporated in the monitoring system according to the invention. Fig. 2 is an enlarged section through a sensor head in the ultra-sonic sensor of Fig. 1; Fig. 3 is a timing chart of operation of the ultra-sonic sensor of Fig. 1; Fig. 4 is a block diagram of a modified embodiment of an ultra-sonic sensor which may be incorporated in the monitoring system according to the invention. Fig. 5 is a graph of output of the sensor of Figs. 1 and 4; Fig. 6 is a comparatory graph illustrating the effects of the ultra-sonic sensors of Figs 1 and 4 the invention; Fig. 7 is a fragmentary block diagram showing an embodiment of a roller profile monitoring system as an application of ultra-sonic sensor systems. Fig. 8 is a graph of the results of measurement performed by the roller profile monitoring system of Fig. 7; Fig. 9 shows an embodiment of a roller profile monitoring system; Fig. 10 is an enlarged longitudinal section through an auxiliary sensor employed in the roller profile monitoring system of Fig. 9; Fig. 11 is a diagram of the operating principles of the roller profile monitoring system of Fig. 9; Fig. 12 is a graph of the results of measurement performed by the system of Fig. 9; Fig. 13 shows a preferred embodiment of a roller profile monitoring system according to the present invention; Fig. 14 is a diagram of the operating principles of the roller profile monitoring system of Fig. 13; and Fig. 15 is a graph of the results of measurement performed by the roller profile monitoring system of Fig. 13. DESCRIPTION OF THE DRAWINGS Figs. 1 and 2 show an ultra-sonic sensor for measuring the elapsed time between transmission of ultra-sonic waves and reception of an ultra-sonic waves reflected by a surface of an object, to which the distance is to be measured. The ultra-sonic waves transmitted by the sensor to the target surface will be hereafter referred to as "transmitted waves" and the ultra-sonic waves reflected by the target surface will be hereafter referred to as "reflected waves". In the shown embodiment, the transmitted waves and the reflected waves pass through a fluid stream, such as a water jet. The path for the ultra-sonic waves defined by the fluid stream will be hereafter referred to as "ultra-sonic wave path". It should be appreciated that, although the shown embodiment employs a water jet to forming the ultra-sonic wave path, other appropriate fluids, such as oil, air and so forth may be the medium for the ultra-sonic wave. The ultra-sonic sensor has a sensor head 11. The sensor head 11 is provided with a water jet nozzle 12 for discharging a water jet. The water jet nozzle 12 has a port 12a connected to a water supply circuit (not shown), through which pressurized water is supplied. A vibrator 13 which is designed to oscillate at ultra-sonic frequencies produces the transmitted wave and resonates when the reflected wave is received. The vibrator 13 is placed at a given distance from the surface of an object 14, the distance d₁ to which is to be measured, as shown in Fig. 2. The surface of the object to be monitored will be hereafter referred to as "target surface". The water jet is directed toward the target surface to form the ultra-sonic wave path. An annular reflector plate 15 is disposed within the ultra-sonic wave path. The reflector plate 15 is separated from the vibrator 13 by a predetermined distance d₀. The reflector plate 15 is made of essentially disc-shaped metal plate with a central circular opening having a diameter ⊘₁ slightly smaller than the diameter ⊘₀ of the ultra-sonic beam. Therefore, the edge of the central opening of the reflector plate 15 extends into the path of the ultra-sonic beam and reflects part of the ultra-sonic beam. The rest of the ultra-sonic beam from the vibrator 13 passes through the central opening of the reflector plate 15 and reaches the target surface. As will be appreciated from Figs. 1 and 2, the reflector plate 15 is closer to the vibrator 13 than the target surface. In order to generate the ultra-sonic waves, the vibrator 13 is associated with a driver circuit 17, which is, in turn, connected for input from a primary pulse generator 16. The driver circuit 17 receives a primary pulse from the primary pulse generator 16 and outputs a drive signal P a to the vibrator 13. The drive signal P a has a frequency substantially corresponding to the frequency of the primary pulse and to the desired oscillation or vibration frequency of the vibrator 13. In other words, the vibrator 13 is driven at an ultra-sonic frequency in synchronism with the primary pulse. The vibrator 13 is, on the other hand, connected for output to a receiver 18 to which it sends a vibration indicative signal when it resonates in response to a reflected wave. Although it is not shown in the drawings, the receiver 18 is provided with an amplifier to amplify the received vibration indicative signal and transmits the amplified signal to mixers 21 and 22. The mixers 21 and 22 are also connected for input from delayed pulse generators 19 and 20, which are, in turn, connected for input from the primary pulse generator 16. The delayed pulse generators 19 and 20 produce delayed pulses S b and S c with respectively predetermined delay times relative to the primary pulse. The delayed pulse generator 19 produces a delay approximately corresponding to the expected elapsed time between transmission of the ultra-sonic waves by the vibrator 13 and reception of the ultra-sonic waves reflected by the reflector plate 15. The elapsed time between transmission of the ultra-sonic waves by the vibrator 13 and reception of the ultra-sonic waves reflected from the reflector plate 15 will be referred to hereafter as "reference times". The delayed pulse P b from the delayed pulse generator 19 has a pulse width wide enough to cover all possible reference times. On the other hand, the delayed pulse generator 20 produces a delay approximately corresponding to an elapsed time between transmission of the transmitted waves and reception of waves reflected by the target surface. The elapsed time between transmission of the transmitted wave and receipt of the reflected wave will be hereafter referred to as "reflection time". The pulse width of the delayed pulse P c from the delayed pulse generator 20 is selected to be wide enough to cover all possible reflection times. The mixer 21 receives the delayed pulse S b and is responsive to the vibration indicative signal from the receiver 18 in the presence of the delayed pulse S b from the delayed pulse generator 19, to produce a mixer signal S d . Similarly, the mixer 22 receives the delayed pulse S c and is responsive to the vibration indicative signal from the receiver 18 in the presence of the delayed pulse S c from the delayed pulse generator 20, to produce a mixer signal S e . The mixer signal from the mixer 21 is fed to a pulse counter 24. The pulse counter 24 is connected to a clock generator 23 to receive clock pulses and counts the latter. The pulse counter 24 is responsive to the mixer signal S d to latch its counter value and to send a reference time indicative signal which is representative of the reference time. Similarly, the mixer signal from the mixer 22 is fed to a pulse counter 25. The pulse counter 25 is also connected to a clock generator 23 to receive clock pulses and counts the latter. The pulse counter 25 is responsive to the mixer signal S e to latch its counter value and to output a reflection time indicative signal which is representative of the reflection time. An arithmetic circuit 26 receives the reference time indicative signal from the pulse counter 24 and the reflection time indicative signal from the pulse counter 25. The arithmetic circuit 26 processes the reference time indicative signal to derive the transmission velocity of ultra-sonic waves through the water jet on the basis of the known distance d₀ between the vibrator 13 and the reflector plate 15 and reference time indicative signal value. The reflection time indicative signal is processed on the basis of the derived transmission velocity to derive the distance d₁ between the vibrator 13 and the target surface. The arithmetic circuit 26 thus derives an output signal having a value representative of the derived distance d₁. Fig. 3 shows the timing chart showing operation of the ultra-sonic sensor as set forth above. In the operation, both of the delayed pulse generators 19 and 20 are triggered by the primary pulse generator before the driver circuit 17. Thus, both of the delayed pulse generators 19 and 20 output the delayed pulses S b and S c with the predetermined pulse widthes. In the presence of both of the delayed pulses S b and S c ' the driver circuit 17 outputs the driver signal S a . The driver signal S a is output to the vibrator 13 to drive the latter and to the receiver 18. The receiver 18 outputs a vibration indicative signal to the mixers 21 and 22. Therefore, the mixers 21 and 22 transmit signals S d and S e substantially corresponding to the signal received by the receiver 18 to the corresponding pulse counters 24 and 25. The pulse counters 24 and 25 are triggered by the signals S d and S e from the mixers 21 and 22 to start counting clock pulses. After a given delay following the primary pulse, the delayed pulse generator 19 again outputs the delayed pulse S b (P b ). As set forth above, this delay approximately corresponds to the reference time. Shortly after the rising edge of the delayed pulse S b (P b ), the vibrator 13 will be driven to vibrate by the ultra-sonic waves reflected by the reflector plate 15. Due to the presence of the delayed pulse S b (P b ) from the delayed pulse generator 19, the mixer 21 produce the mixer signal S d . The pulse counter 24 is responsive to the mixer signal S d from the mixer 21 to latch its counter value and output the reference time indicative signal to the arithmetic circuit 26. The value of the reference time indicative signal corresponds to the counter value of the pulse counter 24 and, in addition, is representative of the reference time. After a given delay following the primary pulse, the delayed pulse generator 20 again outputs the delayed pulse S c (P c ). As set forth above, this delay approximately corresponds to the reflection time. Shortly after the rising edge of the delayed pulse S c (P c ), the vibrator 13 is driven to vibrate by the ultra-sonic waves reflected from the surface of an object 14. Due to the presence of the delayed pulse S c (P c ) from the delayed pulse generator 20, the mixer produce the mixer signal S e . The pulse counter 25 is responsive to the mixer signal S e from the mixer 22 to latch its counter value and output the reflection time indicative signal to the arithmetic circuit 26. The value of the reflection time indicative signal corresponds to the counter value of the pulse counter 25 which, in turn, is representative of the reflection time. The arithmetic circuit 26 derives the transmission velocity C of the ultra-sonic wave through the water jet according to the following equation (2), in terms of the reference time T₀ measured with respect to the ultra-sonic wave reflected by the reflector plate 15, and the known distance d₀ between the reflector plate 15 and the vibrator 13: C = d 0 /(T 0 - Δ) where Δ is a relatively short elapsed time required for transmission of the primary pulse and/or the drive signal to the vibrator through a conductive line and so on. Based on the transmission velocity C derived according to the equation (2), the distance d₁ from the vibrator 13 to the target surface is derived by the equation (3) in terms of the reflection time T₁: d 1 = (T 1 - Δ) x C The arithmetic circuit 26 outputs an output signal based on the derived distance d₁ through an output device 27. It should be noted that the primary pulse generator 16 produces a primary pulse with a 20-nsec rising transition. The vibrator 13 employed in the shown embodiment operates at a vibration frequency of approximately 10 MHz. On the other hand, the clock generator 23 employed in the shown embodiment produces clock pulses at 1 GHz. In general, the transmission velocity of the ultra-sonic waves through the water is approximately 1,500 m/sec. Therefore, by utilizing a clock frequency of 1 GHZ, the system will have a resolution of better than 1 µm. This allows precise measurement of the distance to the target surface. According to the shown embodiment, since the reflector plate 15 is provided within the ultra-sonic wave path through which the waves from the vibrator are transmitted, the reference time is measured at substantially the same water temperature. This satisfactorily prevents error in the velocity of sound in water due to temperature differences. In addition, by deriving the sonic velocity based on the known distance and the reference time, errors which would otherwise occur due to use of a constant or fixed sonic velocity value can be avoided. Fig. 4 shows a modified of ultra-sonic sensor. In this modification the mixer 21 and the pulse counter 24 are commonly used for measurement of the reference time and the reflection time. In this embodiment, the mixer 21 is commonly connected for input from the delayed pulse generators 19 and 20 through a switching relay 31. The switching relay 31 selectively connects one of the delayed pulse generators 19 and 20 to the mixer 21 to transmit the delayed pulse from the corresponding one of the delayed pulse generators. According to this modification, two cycles of transmission of the ultra-sonic waves, reception of the reflected ultra-sonic waves, and measurement of elapsed time between transmission and receiption of the ultra-sonic waves are performed to measure both the reference time and reflection time. Specifically, in the first cycle, the mixer 21 is be connected to the delayed pulse generator 19 to receive the delayed pulse therefrom. This enbales the mixer 21 to respond to the vibration indicative signal produced upon reception of the ultra-sonic wave reflected by the reflector plate 15. Thus, the reference time can be measured according to substantially the same procedure as set out with respect to the foregoing preferred embodiment. Then, in the second cycle, the switching relay 31 is switched to connect the mixer 21 to the delayed pulse generator 22. As a result, the mixer 22 is enabled to respond to the reflected wave received by the vibrator 13. Therefore, in the second cycle, the reflection time can be measured by latching the counter value of the pulse counter 24 upon reception of the vibration indicative signal from the receiver 18. The arithmetic circuit 26 thus derives the sonic velocity C through the water based on the result of measurement in the first cycle, and the distance d₁ to the target surface based on the derived sonic velocity C and the reflection time measured in the second cycle. This modification simplifies the structure of the ultra-sonic sensor system by eliminating the mixer 22 and the pulse counter 25. This also serves to reduce the cost of construction of the ultra-sonic sensor. Fig. 5 shows practical results of measurement of the distance to the target surface, in which the target surface is offset step-by-step by 50 µm, As will be seen from Fig. 5, error of measurement is ± 2 µm. This proves that precise measurement of the distance to the target surface is possible using such ultra-sonic sensors. Fig. 6 shows the results of an experiment checking the effect of temperature dependent correction on the distance measurement. The experiment Was performed by varying the water temperature over the range of 5 °C to 45 °C. As can be seen in Fig. 6, when there is no temperature dependent correction, an error of about 1,000 µm exists in the results of measurement. On the other hand, by performing temperature dependent correction, the error becomes less than ± 5 µm. Therefore, an accuracy better than 10 times higher can be obtained by with the temperature dependent correction. Fig. 7 shows one example of application of the aforementioned ultra-sonic sensor to monitor the profile of a roller such as a roller employed in a rolling mill. The roller profile monitoring system illustrated in Fig. 7 comprises a pair of roller-chock frames 2 which rotatably support opposite ends of a roller 1. The roller chock frames 2 are connected to a base 3 through rubber dampers 4, by means of fastening bolts 5. The dampers are provided to absorb shock exerted on the roller chock frames 2 and/or the roller 1. The base 3 has a reference plane 3a lying substantially parallel to the longitudinal axis of the roller 1. a rail 6 is mounted on the reference plane 3a and extends substantially parallel to the roller axis. The sensor head 11 is slidably or movably mounted on the rail 6 for movement therealong. The sensor head 11 is associated with a drive mechanism to be driven to move along the rail 6. The driving mechanism comprises an electric motor 7a and a threaded propelling shaft 7b which is engageable with a threaded opening (not shown) formed in the sensor head 11 so as to drive the sensor head through a distance corresponding to the rotation thereof when driven by the motor 7a. Although a specific driving mechanism for the sensor head 11 has been illustrated in Fig. 7, it can be constructed in various ways. For instance, the sensor head 11 can be driven by a driving belt which is, in turn, driven by the motor 7a, with an appropriate power transmission mechanism. A dust-proof cover 8a of expandable and flexible construction, such as a bellows sheet, is provided to cover the drive mechanism and the reference surface 3a of the base 3. The space defined between the reference surface 3a and the dust proof cover 8a communicates with a purge air source 8b. A purge air from the purge air source 8b is introduced into the space to protecting the drive mechanism and the sensor head 11 from heat, water and dust. The sensor head 11 is also connected to a water source 8c via a water supply circuit 8d. In the preferred construction, the water supply circuit 8d comprises a flexible hose so as to allow movement of the sensor head 11 along the rail 6. The water from the water source 8c is preferably pressurized to a predetermined pressure so as to form a water jet 9 when discharged through the water jet nozzle 12 shown in Fig. 2. The ultra-sonic sensor circuit, denoted by the reference numeral "10A" and designed as disclosed with reference to Fig. 1, is connected for output to an arithmetic/control unit 41. The arithmetic/control unit 41 is also connected for input from a pulse counter 43 which is, in turn, connected for input from an encoder 42. The encoder 42 produces a pulse in response to a predetermined angle of rotation of the propelling shaft 7B. The pulses from the encoder 42 are counted by the pulse counter 43. The pulse counter 43 produces a counter signal which is indicative of its counter value and, thus indicative of the position of the sensor head 11 along the rail 6. Based on the counter signal from the pulse counter 43, the arithmetic/control unit 41 derives the axial position of the target surface with respect to the roller axis. In cases where the roller axis is inclined with respect to the reference surface 3a of the base, an inclination-dependent correction for the axial position of the target surface may be performed for higher accuracy of the derived data. Thus, the arithmetic/control unit 41 receives distance indicative data from the ultra-sonic sensor circuit 10a and target surface position indicative data from the pulse counter and outputs those data to a profile display unit 44. The arihtmetic/control unit 41 also sends a drive control signal to the electronic motor 7a. The target surface position indicative counter signal from the pulse counter may serve as a feedback signal in determining the angular displacement of the propeller shaft needed to shift the sensor head 11 to the next scanning point according to a predetermined schedule. In practice, the arithmetic/control unit 41 corrects the distance and axial position data at the end of the axial shift of the sensor head 11. Specifically, during rolling, the axial ends of the roller are free from wear and should lie at the same distance from the reference surface when the roller axis is substantially parallel to the reference surface. Therefore, by comparing the distances to the ends, the correction values for both axial position data and distance data can be derived. Alternatively, it would also be possible to set the roller 1 up so that the roller axis lies substantially parallel to the reference surface by setting the roller to have the same distance from the reference surface at both ends. In this case, the distance to each end can be precisely measured by the ultra-sonic sensor system as set forth above. Fig. 8 shows the results of monitoring of the roller profile. In Fig. 8, the line A shows raw data of scanning of the distance to the roller surface from the sensor head 11. On the other hand, line B shows smoothed data in which the data of line A is processed by averaging to avoid vibration of the base and influence of eccentricity and vibration of the roller as it rotates. As will be appreciated herefrom, the roller profile monitoring system clearly reveals a roller crown of about 100 µm. Fig. 9 shows an embodiment of a roller profile monitoring system. In this modification, a plurality of ultra-sonic sensors are employed to monitor the roller profile. The ultra-sonic sensor comprises primary sensors 118A, 118B, 118C, 118D and 118E designed to transmit ultra-sonic waves toward corresponding parts of the roller surface and aligned parallel to the roller axis at given intervals between adjacent sensors, and auxiliary sensors 120A, 120B, 120C, 120D and 120E. The auxiliary sensors 120A, 120B, 120C, 120D and 120E are coupled to corresponding primary sensors 118A, 118B, 118C, 118D and 118E at the same axial positions. The auxiliary sensors 120A, 120B, 120C, 120D and 120E are designed to transmit ultra-sonic waves in the opposite direction to the transmission direction of the ultra-sonic waves from the primary sensors 118A, 118B, 118C, 118D and 118E. In the preferred construction, each pair of the primary and secondary sensors 118A and 120A, 118B and 120B, 118C and 120C, 118D and 120D and 118E and 120E are fixed to each other and supported by a base 113. The base 113 has a reference surface 114 lying substantially parallel to the axis of the roller 111. The base 113 is preferably made from a hollow steel pipe or the like so as to define therein a space 115 for receiving the assemblies of the primary and secondary sensors. The internal space 115 of the base 113 is filled with water supplied by way of a water supply system which comprises a water source 112, such as a water reservoir, a water pump 123 and a water flowmeter 124. A wire 116 is stretched through the internal space 115 of the base 113 so as to cross all of the ultra-sonic wave paths. One end of the wire 116 is rigidly fixed to the base 113 and the other end is connected to a spring 117 serving as a tensioner. The wire 116 is guided by guides 116a to extend parallel to the roller axis. The spring 117 exerts a given tension on the wire 116 to hold the wire straight. In the preferred construction, the wire is a piano wire 1 mm in diameter and the spring 117 has a tension of 30 kg to 40 kg. In this case, if the tension should deviate by as much as 10%, the deviation of the straightness of the wire 116 will be equal to or less than 5 µm. It should be appreciated that the primary sensors 118A, 118B, 118C, 118D and 118E have the same construction as disclosed with reference to Figs. 1 to 4, and are designed to direct water jets onto corresponding points of the roller surface. The water jets are generated by the water pressure introduced into the inner space 115 of the base and discharged through the sensor heads of the primary sensor. The water in the inner space 115 of the base 113 also serves as the ultra-sonic wave transmission medium for the auxiliary sensors 120A, 120B, 120C, 120D and 120E. Furthermore, the water in the inner space 115, serves to cool the base and to absorb vibrations of wire. The primary sensors 118A, 118B, 118C, 118D and 118E are connected to respectively corresponding sensor circuits 119A, 119B, 119C, 119D and 119E, each of which has substantially the same circuitry as disclosed with respect to Fig. 1 or Fig. 4. Similarly, the secondary sensors 120A, 120B, 120C, 120D and 120E are connected to respectively corresponding sensor circuits 121A, 121B, 121C, 121D and 121E, each of which also have substantially the same circuitry as disclosed with reference to Fig. 1 or Fig. 4. Therefore, the primary sensors 118A, 118B, 118C, 118D and 118E are designed to measure the distance to the corresponding points on the roller surface. On the other hand, the auxiliary sensors 120A, 120B, 120C, 120D and 120E are responsive to the ultra-sonic waves reflected by the wire 116 to measure the distance to the wire 116. As set forth above, since tension is constantly applied to the wire 116 by means of the spring 117, the wire 116 is held substantially straight. Therefore, if the base 113 is somewhat deformed, which results in deformation of the reference surface 114, the deformation can be monitored by measuring the distance to the wire 116 at each measurement point. The deformations detected by measurement of the distances to the different points on the wire 116 yield correction values for correcting the distance values derived on the basis of the measurements performed by the primary sensors. This allows precise measurement of the roller profile while eliminating the influence of deformation of the base 113. The sensor circuits 119A, 119B, 119C, 119D, 119E and 121A, 121B, 121C, 121D and 121E are connected for output to a scanner circuit 125. The scanner circuit 125 is, in turn, connected for output to an arithmetic circuit 126 which is associated with a display unit 127. The scanner 125 selectively connects one of the sensor circuits to the arithmetic circuit 126 to indroduce distance indicative data from the connected one of the sensor circuits for derivation of the distance based thereon. The arithmetic operations performed by the arithmetic circuit 126 are substantially the same as disclosed with respect to Fig. 1 or Fig. 4. In practical measurement, each sensor 118A, 118B, 118C, 118D, 118E and 120A, 120B,120C, 120D, 120E cyclically measures the distance at given intervals, e.g. 200 µsec. intervals. The scanner circuit 125, first, passes the distance indicative signals from the sensor circuits 119A, 119B, 119C,. 119D and 119E in sequence. The arithmetic circuit 127 derives the respective distances P₁, P₂, P₃, P₄ and P₅ based on the distance indicative signals from the sensor circuits 119A, 119B, 119C, 119D and 119E. Subsequently, the scanner circuit 125 introduces the distance indicative signals from the sensor circuits 121A, 121B, 121C, 121D and 121E to the arithmetic circuit 126. The arithmetic circuit 126 derives the distances S₁, S₂, S₃, 5₄ and S₅ to the wire 116 at respectively corresponding points. The distance values derived in the arithmetic circuit 126 are used to derive the distance Z i (i = 1, 2 ...5) from an axis x parallel to the axis of the roller 111 to the target surface at each of the measurement points, by the following equation: Z i = P i + S i + U i It should be noted that the distances U₁, U₂, U₃, U₄ and U₅ are derived beforehand by measuring the profile of a reference roller with a known profile. Specifically, by measuring the known profile of the reference roller, the values U i can be arithmetically derived by measuring P i and S i . Therefore, the distance U i from the wire 116 to the axis x becomes a known value for each measuring point. As will be appreciated herefrom, since the axis x is an imaginary axis established as set forth above, the profile can be observes by measuring the distances P i and S i at each of the measurment points. Therefore, by the disclosed arrangement, influence of deformation of the base 113 or angular shift of the roller axis can be satisfactorily and successfully avoided. Figs. 12(A) and 12(B) show the results of measurements performed by the roller profile monitoring system of Fig. 9. Fig. 12(A) shows a results of measurements performed under normal conditions, which substantially match with the results of measurements performed by micrometer. Fig. 12(B) shows a result of another measurement, in which a 20-kg load is applied for the base to intentionally deform of the base 113. As will be seen from 12(B), the distance P i derived on the basis of the distance indicative data from the primary sensor is influenced by the deformation (about 100 µm) of the base. However, the distance value S i of the auxiliary sensors clearly reflect the deformation of the base. Therefore, the distance Z i as corrected value of the distance value P i with the correction value derived based on the distance value S i becomes substantially correspond to the result shown in Fig. 12(A). Fig. 13 shows of the preferred embodiment of the roller profile monitoring system according to the invention. In this embodiment, the base 113 is slidingly or movably supported by guides 134 to allow axial movement of the base 113. The base 113 is also associated with a driving means 132 capable of axially moving the former. The driving means 132 is associated with a position sensor 133 which detects the axial position of the drive means and thus detects the position of the base 113. In practice, the driving means 132 is intended to axially shift the base 113 to an extent approximately corresponding to the spacing between the sensor assemblies, which each comprise a primary sensor 118 and a auxiliary sensor 120. In the shown embodiment, 10 sensor assemblies are arranged on the base 113 at 20-cm intervals. Therefore, the driving means 132 can drive the base 113 as far as approximately 20 cm. The velocity of axial motion of the base 113 is controlled to be within the range of 10 mm/sec to 200 mm/sec. Preferably, the base 113 is driven at constant velocity throughout its travel. As shown in Fig. 14, when the base 113 is shifted from its initial position through the distance ℓ, the distances R₁(ℓ), R₂(ℓ) ... R₁₀(ℓ) are derived from the results of measurement by the primary sensors 118A, 118B... 118J, and the distance S₁(ℓ), S₂(ℓ)... S₁₀(ℓ) are derived from the results of measurement by the auxiliary sensors 120A, 120B... 120J. In order to simplify the following description, it is assumed that the wire 116 extends substantially parallel to the x-axis in Fig. 14 and thus the distance value U i is constant over all measurement points. Therefore, the roller profile indicative distance value Z i after correction at each of the measurement points can be expressed by the following equation: Z i = R i + S i Therefore, the roller profile indicative distance value Z i (ℓ) at each measurement point when the base 113 is shifted to the extent ℓ can be expressed... Z i (ℓ) = R i (ℓ) + S i (ℓ) The x-coordinate, i.e. the axial coordinate, of the measurement points are ℓ, L + ℓ, 2L + ℓ....9L + ℓ. Shifting the base 113 through a distance corresponding to the axial spacing L of the sensor assemblies, allows the roller profile indicative distance values Z i to form a sequence of roller surface contour values covering fixed axial points. For precise measurement of the roller profile, it is necessary to correct the roller profile indicative distance value Z i , taking into account the displacement of the sensor assemblies perpendicular to the x-axis and variation of relative inclination between the sensor and the roller surface. The correction process will be described hereafter in terms of the roller profile indicative distance value Z i (L) at the fully-shifted position of the base 113. The correction is given by the equation... Z' i (L) = Z i (L) + a 1 x i + b 1 where coefficients a and b are derived so as to minimize Δ, defined in the following equation: where Z i (0)(i = 1 to 10) are the measured values at the initial positions. Then, Q i (shown in Fig. 15) (i = 1 to 11) is derived from the following equation : Q i = Z i (0) :i = 1 = {Z' i-1 (L) + Z i (0)}/2 :i = 2 - 10 = Z' 10 (L) :i = 11 Then, Q' i (i = 1 to 11) can be derived from the following equation: Q' i = Q i - {(Q 11 - Q 1 ) x (i - 1)/10 + Q 1 } Q' i (i = 1 to 11) is the roller profile indicative distance value at each of the measurement points given by the x-coordinates x = 0, L, 2L, ..., 10L. Interpolation in the regions (0, L) and (9L, 10L) can be performed according to the following equations: Z= Q' 3 2L 2 x x - L - Q' 2 L 2 x x - 2L : region (0, L) Z = Q' 9 2L 2 x - 9L x - 10L - Q' 10 L 2 x - 8L x - 10L : region (9L, 10L) Then, the roller profile indicative distance values W i at any of the intermediate points shifted through a distance ℓ is derived by modifying the distance value Z i (ℓ) ( i = 1, 2,...10) according to the following equation: W i = Z i (ℓ) + a 2 x i + b 2 where a 2 = 1 9 {-Z 10 (ℓ) + Z 1 (ℓ) + Q' 9 2L 2 ℓ (ℓ - L) - Q' 10 L 2 (ℓ + L)(ℓ - L) - Q' 3 2L 2 ℓ (ℓ - L) + Q' 2 L 2 ℓ ℓ - 2L } b 2 = 1 9 {-10Z 1 (ℓ) + Z 10 (ℓ) + 5Q' 3 L 2 ℓ (ℓ - L) - 10Q' 2 L 2 ℓ (ℓ - 2L) - Q' 9 2L 2 ℓ (ℓ - L) + Q' 10 L 2 (ℓ + L) ℓ - L } The value W i may be derived at any intermediate measuring points according to the foregoing procedure. Based on the values W i , coordinates (X i , Z i ) at respective measuring points offset by P ∞i are derived by: X i = ℓ + L x (i - 1) Z i = W i Therefore, the derived coordinates of the sequential measurement points form a continuous curve representing the roller profile, as shown in Fig. 15. As will be appreciated herefrom, the preferred embodiment of the roller profile monitoring system allows accurate measurement and monitoring of the roller profile. Therefore, the present invention fulfills all of the objects and advantages sought therefor.

Claims: A system for monitoring the profile of a roller (111) having a longitudinal axis in a rolling mill, wherein a base (113) with a reference surface (114) extends in the same direction as the roller (111) does along the longitudinal axis, wherein at each of a predetermined number of measuring points (0 to 10L, in fig. 15) equidistant along an axis (x) parallel to said longitudinal axis of the roller, a distance from the reference surface (114) to the roller (111) is determined by measuring a time taken for ultra-sonic waves to travel through a jet of hydraulic fluid to the roller (111) from an ultra-sonic sensor (118A-118J) on the reference surface (114), the number of measuring points including two remotest initial (0) and terminal (10L) end points which are adjacent to the axial ends of the roller, respectively, characterized in that a plurality (10 in figs.13 to 15) of such ultra-sonic sensors (118A-118J) are arranged equidistant on the reference surface (3A, 114) of the base (113) that is shiftable between an initial position (broken line position in Fig.13) where the plurality of ultra-sonic sensors (118A to 118J) are at such positions as to allow measurements of distance at that measuring points of the predetermined number of measuring points which exclude the terminal end point (10L) and a fully shifted position (continuous line position in Fig.13) where the plurality of ultra-sonic sensors (118A to 118J) are at such positions as to allow measurements of distance at that measuring portion of the predetermined number of measuring points that excludes the initial end point (0) ; a first group of distance data (Z i (0) i = 1 to 10), (top of Fig.15) is derived from results of distance measurements with the base (113) at the initial position thereof, a second group of distance data (Z j (L) , j = 1 to 10) is derived from results of distance measurements with the base (113) at the fully shifted position thereof ; the second group of data are modified with due consideration of correction factors related to motion of the base (113) from the initial position to the fully shifted position and set as the modified second group of data (Z'j(L), j = 1 to 10) ; one data of the first group and the corresponding one data of the modified second group for the common measuring point are processed to give an average and set as a processed data (Q₂ to Q₁₀), a data of the first group for the initial end point (0) is unmodified and set as a processed data for the initial end point, a data of the modified second group for the terminal end point (10L) is set as a processed data (Q₁₁) for the terminal end point (10L) ; each of the processed data for one measuring point is subtracted by a value resulting form multiplying a subtraction (Q₁₁-Q₁) of the processed data (Q₁) for the initial end point (Q₁) from the processed data (Q₁₁) for the terminal end point (Q₁₁) with a ratio [(i-1)/n, where : i = 1...11, n = 10)] of the distance of the one measuring point from the initial end point to the total distance of the terminal end point from the initial end point, and then interconnected to generate a contour of the monitored profile of the roller (111). A system as claimed in claim 1, characterized in that a reference wire (116) is streched along the axis (x) and spaced from the longitudinal axis of the roller (111) more than the reference surface (113) is, and that a plurality of auxiliary ultra-sonic sensors (120A to 120J) are connected to the corresponding main ultra-sonic sensors (118A to l18J), respectively, to direct ultra-sonic waves to the referen<ce wire (116). A system as claimed in claim 2, characterized in that each of the distance data is derived from combining the result of measurement of distance to the reference wire (116) using one of the auxiliary ultra-sonic sensors (120A to 120J) with the result of measurement of distance using the corresponding one of the ultra-sonic sensors (118A to 118J). A system as claimed in claim 2 or 3, characterized in that the reference wire (116) extends through a body of hydraulic fluid (115). A system as claimed in claim 1 or 3, characterized in that the modified second group of data (Z' j (L), where: j = 1 to 10) can be expressed by the following equation, Z' j (L) = Z j (L) + a 1 x i + b 1 where : Z j (L) is the second group of data, and a₁ and b₁ are coefficients derived to minimize Δ (delta), defined by the following equation, where : Z i (0) (i = 1 to 10) is the result of distance measurement when the reference surface is at the initial position.

Inventors: ISHIKAWA FUMIHIKO, OHKI TOSHIO, ICHIKAWA, FUMIHIKO, OHKI, TOSHIO, ICHIKAWA, FUMIHIKO C/O TECHNICAL RESEARCH DIV., OHKI, TOSHIO C/O CHIBA WORKS
Applicants: KAWASAKI STEEL CO, KAWASAKI STEEL CORPORATION
Application year: 1986
Main classification: G01S15
IPC codes: G01S15, B21B38, G01B17, G01S7