MXPA99007456A - Tracc line vibration analyzer - Google Patents

Abstract

A diagnostic tool that analyzes the vibrations in the traction line to measure and characterize the torsional vibrations in the traction line of a vehicle. An electronic control unit and a sensor cooperate to measure speed fluctuations that occur between the passage of adjacent teeth of a rotating gear. These time measurements are the basis for the displacement, velocity and acceleration calculations, which, combined with the information of the rotational order of the traction arrow, can be used to indicate the source of excessive torsional vibrations in the traction line.

Description

TRACTION LINE VIBRATION ANALYZER BACKGROUND AND SUMMARY OF THE INVENTION This invention relates in general to the diagnosis of vehicle vibrations, and in a more particular way, to a system and method for measuring and evaluating torsional vibration in a traction line of a vehicle. The problems of torsional vibration of the traction line are a significant source of premature failures of the components of the traction line, as well as complaints of customers for noise and vibration, especially on heavy-duty trucks. Damaged drive line components are often replaced in the field without resolving the root cause of the fault, and only to result in a similar failure in the future. Noise and vibration problems are routinely solved by changing the components of the traction line until the problem seems to be resolved, even in cases where the problem may not even be related to the traction line. - Both situations produce high warranty costs for the component supplier and the OEM, and increase the lost time of the fleet owner's truck. To eliminate this prevailing "trial and error" approach to solving the problems of the truck pulling line, the traction line vibration analyzer (DVA) of the present invention was developed to quantitatively measure and evaluate the torsional vibration of the traction line. To do this, the vibration analyzer of the traction line measures the cyclical variations in the speed of the rotating components of the transmission line, and correlates the amplitude of torsional vibration with the rotation order of the transmission shaft. These variations of speed are converted into information of displacement and acceleration, and are separated according to the harmonic order of the transmission shaft, in order to measure the response of the line of traction to the torsional excitations of the motor and the universal joint. . Using previously selected or calculated orders of interest, the magnitudes of detected vibrations in terms of acceleration are compared with previously determined thresholds to help a test technician identify potential vibration problems, determine the source of any problems encountered, and Select an appropriate remedy for each problem. The vibration analyzer of the traction line was designed to work both as a torsional vibration analysis instrument, and as a simple field tool to quickly solve problems. An experienced operator of the traction line vibration analyzer can perform a vibration analysis of the complete traction line in less than half a day. The implementation of the traction line vibration analyzer in a laptop personal computer provides portability and makes it possible for service technicians to use it in a variety of ways to diagnose and resolve torsional vibration problems. These and other features and advantages of the present analyzer will become clearer when reviewing the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of the present invention, implemented as a decampoo diagnostic tool. Figure 2 is a graphic representation of the signal produced by the magnetic speed sensor of the present analyzer. Figure 3 is a graphic representation of the signal shown in Figure 2, after being converted to a square waveform. Figure 4 is a graphic representation of a graph produced by the vibration analyzer of the traction line, which illustrates the measured speed and acceleration of the traction line, for a traction line system under test. Figure 5 is a graph similar to that of Figure 4, of the same traction line, after a soft clutch was installed to remedy the excessive torsional vibration. Figure 6 is "a graph produced by the traction line vibration analyzer to indicate the magnitudes of the real-time traction line vibrations." Detailed Description of the Preferred Embodiment Form Turning now to the drawings, and in particular to Figure 1, the present traction line vibration analyzer (DVA) is generally indicated at 10. The vibration analyzer of the traction line 10 includes a sensor for measuring the rotational speed of a particular component of the line of traction, in the currently preferred embodiment of the invention, a magnetic speed sensor 12. The sensor 12 is a non-contact magnetic sensor, such as a variable reluctance sensor, which provides speed or time data in the form of a train In this case, the sensor 12 is one that is already present inside most modern class 8 truck transmissions, such as the trac 14, to provide a signal from the vehicle's speedometer, and can be easily reached from behind the transmission. An appropriate signal conditioning unit 16 can also be provided to filter and reduce noise at the signal output from sensor 12. Sensor 12 provides a clean tachometer sinewave signal of 16 pulses per revolution (one pulse per tooth) of a 16-tooth wheel rotating with the output arrow of the transmission 14) 18, as illustrated graphically in Figure 2. Note that a signal peak 18a is created by a strong magnetic field that occurs when a tooth near the sensor 12, and a valley 18b is created when the sensor is placed between the passing teeth. While the sensor 12 measures the rotational speed at the output of the transmission 14, it is sensitive to all sources of significant torsional excitation of the line of traction. Although the location of the transmission output is usually not the highest torsional vibration point in the line of traction, it has been shown to be sufficiently active torsionally under vibration excited in both the motor and the universal joint, to accurately assess the behavior torsional of the traction line. However, in an alternative way, any other suitable elements could be provided to accurately measure the rotational speed of a component of particular interest of the traction line. For example, an alternative embodiment may include a similar magnetic sensor adapted to measure the rotational speed between the teeth passing from a suitable test attachment fixed for testing purposes to the component of interest of the particular tension line, such as a yoke of entry or exit of a driving or traction axle of a vehicle. An optional sensor could also be used to indicate the passage of marks or indentations made on a particular rotating component of the traction line. The sensor 12 is electrically coupled by means of a conductor 20 to an electronic control unit based on microprocessor (ECU) 22, preferably through the signal conditioning unit 16. The unit 16 can also be configured to provide power for the electronic control unit 22, such as through the cigarette lighter of the vehicle 21. The electronic control unit 22 may include a personal computer, preferably a portable laptop computer, or any other suitable processor. The electronic control unit 22 in the present exemplary embodiment is implemented outboard of the vehicle in a diagnostic field test application, but with the required energy of the computer, and alternatively, design choices could be implemented permanently on board a vehicle as a separate processor or as part of the driver or transmission of the vehicle engine. The electronic control unit 22 includes a high-speed continuous period counter board for generating accurate time pulses of a uniform frequency associated with the measurements obtained by the sensor 12. In effect, the number of pulses between the detected step of each tooth. It can be seen that at very high revolutions per minute, this information is acquired very quickly. The time measurement for each tooth is related to the instantaneous angular velocity of the tensile line at the point of measurement. Consequently, a gear with n teeth makes it possible to measure angular velocity per revolution of the gear. The following definitions apply to the present transmission line vibration measurement system:? T = measurement of time between the consecutive teeth of the gear; N = number of data samples (preferably a power of 2); ? T = 2p / n = angular displacement between any consecutive teeth of the gear; dT / dt =? T /? t = instantaneous angular velocity of the traction line; ? N * (? T) = average angular velocity of the traction line N - l? (? tj) j = 0 K-, = order value for the spectral line j. The conversion of the sensor output signal illustrated in Figure 2 to a square waveform, as graphically shown in Figure 3, is a way in which the electronic control unit 22 can perform the quantization of the time that it passes between each pair of adjacent teeth. This "time between teeth" can be represented as? T. However, in an alternative way, any other suitable method known to those skilled in the art can also be used to determine? T from signal 18. Knowing that the angular displacement between two adjacent teeth is equal to 2p divided between the number of teeth, the angular velocity d © / dt can be easily calculated. Because the velocity measurements are uniformly separated in terms of the rotation angle of the gear, the application of a discrete Fourier transform for the velocity data of the angle domain results in a data transformation to the order domain. This can be done in any suitable method, in the currently preferred mode by a commonly available commercial FFT (fast Fourier transformation) software package executed in the electronic control unit 22. The Fourier transformation is particularly useful, because it makes possible the calculation of the torsional displacement and the magnitudes of acceleration in the line of traction as a function of the harmonic order of rotation of the transmission shaft. Because the velocity measurements are uniformly separated in terms of? T, the application of a discrete Fourier transformation to this domain domain data results in the transformation to the order domain. Because the entered data contains real values only, the double-sided Fast Fourier transformation block (positive as well as negative order) has real and imaginary components, which are equal. Without considering the data of negative order, the function of the fast Fourier transformation puts the real and imaginary components R-. and I3 in separate blocks that have a total of 1 + N / 2 elements with the index j = 0.1, ..., N / 2. Therefore, the relationship between the order I and the index j is: K, = j 2_ J ÍL 2 -Kmax = - = maximum order K = - = order resolution N 0 The vibration analyzer of the traction line 10 can calculate all the orders of vibrations of the traction arrow up to half the number of teeth of the gear. Accordingly, the vibration analyzer of the traction line 10 is sensitive to the torsionals excited by the joint U, which are of second order constant in all transmission gears. The vibration excited by the motor can be analyzed in all transmission gears up to a maximum gear ratio equal to half the number of teeth divided by the vibration order of the engine crankshaft. For example, the fundamental firing order of the engine for a six-cylinder, four-cycle engine is the third order of the crankshaft. With a sixteen-tooth gear, the vibration analyzer of the traction line 10 could thus analyze the motor trip data in all gear ratios less than 2.67. Because the torsionals excited by the motor are of greater concern in high-range transmission gears, therefore, a gear or a sixteen-tooth wheel is suitable. In addition, order resolution can be improved by increasing the sample size. For example, using the same gear and a sample size of 256, the vibration analyzer of the traction line 10 will record 16 rotations of the arrow, and can resolve the torsional vibration to the nearest 1/16 order. In each rotation order of the crankshaft, the electronic control unit 22 produces speed magnitude data. From this speed data, displacement and acceleration can also be calculated, in a manner well known to those having experience in this field. After the real and imaginary components are normalized, the magnitude of the speed spectrum for each component of K ° order is calculated from: = = magnitude of speed From the above, the angular velocity magnitude spectrum, the displacement, the torsional displacement magnitudes and acceleration in the traction line are calculated as a function of the harmonic order of rotation. This is derived as follows: - | = Ak * cos (?? * t) ?? = * sin (?? * t)? v substituting? k =? * K in the equations for the maximum displacement (magnitude), speed, and acceleration: t A? dt fd? ^ However, the details of these calculations are provided in SAE Document Number 942324 entitled "DVA-A New Tool for the Trucking Industry", McGovern et al., submitted on November 8, 1994, incorporated herein as reference. These preferred values are formatted and plotted on a suitable visual display device 24 coupled with, or part of, the electronic control unit 22. One way of presenting the information to the vibration analyzer operator of the traction line is in the manner illustrated in the graphs of Figures 4 and 5. As shown therein, the speed of the pull line (in rpm) is plotted over time in Figures 4a and 5a. One skilled in the art will readily appreciate that a line of traction rotating at a perfectly constant rotation free of torsional vibration would produce a straight horizontal line on this graph. The acceleration and displacement calculated in relation to the rotation order of the transmission shaft are plotted in Figures 4a and 5a. Preferably, the orders of particular interest, and the magnitude of acceleration for these orders, are also indicated to the operator of the traction line vibration analyzer, numerically at 26. In addition, numerous additional visual displays of information can also be provided. graphical and / or numerical to the operator of the vibration analyzer of the traction line in 26. The torsional vibration of the traction line is induced from two primary sources: the torsional ones of the motor that appear in the fundamental firing frequency of the motor, and its harmonics, and the universal joints that operate with angles of work that are not zero. The traction train system responds to this torsional excitation by winding and unwound in a dynamic manner. A certain amount of this torsional activity is always present, and generally does not represent a danger to the components of the traction line. However, if the excitation frequency is coincident with a torsional resonant frequency of the traction line, serious amplification of the torsional lines of the traction line can occur. The traction line consists of numerous components that can be modeled dynamically as a separate system containing spring and mass elements. In theory, the pull line will produce a resonant frequency for each degree of freedom in the mode. However, only the second torsional mode is considered here, because it is the only resonant mode of the line of traction that is in the frequency range, so that it is excited regularly by the forced inputs from the motor and the universal boards. The second torsional mode is described as the rotary components of the transmission and the torsionally axis springing in phase over the clutch springs and the arrow, with nodules on the steering wheel and wheels. Although the front-drive shaft is usually the anti-nodule of the system, high torsional displacements can be consistently measured during resonance at the output of the transmission. The data obtained in each rotation order of the transmission shaft can be compared by the electronic control unit 22 with previously determined thresholds, above which it is considered that the torsional vibrations are excessive. The vibrations measured above the previously established threshold can be visually indicated to the operator of the vibration analyzer of the traction line, through flashes or a colored visual display 24. Acceptable threshold levels of vibration can be calculated or determined in an empirical manner, and more likely will differ with the combinations of the components of the pull line. Although different calculations can be made from the basic rotary speed measurements obtained, only those belonging to the second torsional mode are considered in the example mode of the vibration analyzer of the traction line 10, because it is the only one resonant mode of the pull line that is in the frequency range, so that it is excited regularly by the forced inputs from the motor and the universal joints. However, the vibration analyzer of the traction line 10 can evaluate higher and lower torsional traction line modes within the basic response constraints defined by the maximum order of vibration and order resolution, as described previously. The second torsional mode usually has a frequency from 20 to 100 Hz, but most commonly occurs between 30 and 70 Hz in high-range transmission gears. The second mode increases its frequency as the numerical proportion of the transmission gear increases, resulting in the lowest resonant frequency in the upper gear. The amplitude of resonant vibration is the highest in the upper gear, and decreases progressively in its amplitude for the lower gears. The internal combustion engine is the most dominant torsional exciter in the traction line. The combustion process produces a dynamic torque waveform that creates an oscillating dynamic torque of the line of traction, and torsional displacements. The dynamic torque waveform of the motor is comprised mostly of the firing frequency of the fundamental motor, but there is also a measurable torque component in the harmonics 0.5, 1.5, and 2.0 of the firing frequency the motor. For a typical six-cylinder engine with four cycles, the trip comes three times per revolution of the crankshaft (third order). Therefore, the harmonics of 0.5, 1.5, and 2.0 would represent the crankshaft orders of 1.5, 4.5, and 6.0, respectively. Crankshaft orders of 4.5 and 6.0 normally do not present a problem, because they are of a frequency too high to excite the second torsional mode of the traction line. However, if the third order of the crankshaft is coincident in its frequency with the second torsional mode, a significant resonant amplification can be presented, and therefore, the third order is of a particular interest. In a similar way, the crankshaft excitation of order 1.5 is also a concern, because it will be coincident with the resonant frequency at some speed in the operated range of the primary motor. In some cases, the excitation of the crankshaft of order 1.5 is of sufficient amplitude to create a "damaging cyclic load, and consequently, it is also of interest." The torsional effects of the non-zero working angles in the universal joints will include a rotating oscillatory output speed given a constant input speed, varying at the speed of two cycles per revolution of the arrow.As a consequence, second-order accelerations are also of interest.Therefore, significant torsional accelerations in the second order indicate work angles of the joint U that are not zero.A shifting of the universal joint by some angle of work will produce a torsional acceleration in the output yoke approximately equal to the angle of the joint squared, multiplied by the speed of the yoke input to the square The torsional effect can be canceled by assembling the gasket U downstream in phase and with the same operating angle The m together U in series (and in phase), approximate the kinematic equation for the resulting output torsional acceleration given by: where ? = rotating speed of the input shaft (in radians / second), and working angle of the joint (in radians). The highest torsional acceleration will be obtained in the upper gear at the higher speeds of the transmission shaft. The traction train responds to these torsional excitations by winding and discharging in a dynamic way. A certain amount of this torsional activity is always present, and does not represent a danger to the components of the traction line. However, if the excitation frequency is coincident with a torsional resonant frequency of the traction line, a serious amplification of the torsional lines of the traction line can occur. Excessive universal joint torsionals can cause continuous state vibration problems as well as resonant excitation. Continuous state problems normally occur at highway cruising speeds, and cause excessive torsional accelerations of the transmission shaft and components. If the torsionals of the joint are sufficient to excite the second torsional mode at resonant velocity, even higher torsional displacements can be developed. In order to use the vibration analyzer of the traction line 10, an operator of the vibration analyzer of the traction line or preferential testing technician connects the conductor 20 to the sensor 12. The truck can be driven, and the data they can be recorded and stored in a memory device for later use, or they can be processed in real time. Preferably, a graph, such as that shown in Figure 6, is provided in the visual display 24, in order to indicate, in real time, to the technician, at what speed and in which gears the torsional vibrations are more prevalent. This visual display of real-time speed preferably has sufficient response to indicate torsional activity in real time. Figure 6 illustrates the real-time visual display screen for a traction line experiencing firing excitation of the second torsional mode motor of the traction line. Using this screen, the operator of the traction line vibration analyzer can cycle rapidly through each transmission gear under different operating conditions and load in search of excessive torsionals (indicated by speed variations that exceed a certain limit). If excessive torsional activity is encountered, the operator of the traction line vibration analyzer immediately acquires data for further processing. This saves a lot of time, and eliminates the need to obtain large amounts of data at all speeds and in all gears. The torsional activity of the traction line can be treated in several ways, including reducing the amplitude of the excitation source, changing the resonant speed below the operating range of the motor, or providing sufficient damping of the transmission line to attenuate the torsional response . The preferred treatment depends on the nature of the problem. By using the vibration analyzer of the traction line 10 to identify the source of vibration, the appropriate remedy can be selected. Referring again to Figures 4 and 5, Figure 4 illustrates measurements taken from a line of traction exhibiting a significant fourth-order vibration. Figure 5 illustrates measurements from the same line of traction after the proper damping was achieved, with a significant decrease in fourth-order vibration. Additional detail is provided with respect to this example in the embedded SAE document. To increase the accuracy, it may also be preferable to average the data (as long as the rotating speed remains constant), as well as add data from the order 1-15 / 16 and the order 2-1 / 16, with the data of order 2.0. The same can also be applied to the information obtained in the other orders of interest. Accordingly, the vibration analyzer of the traction line 10 provides a convenient and simple solution for many vehicle vibration problems. In this way, the sources of the vibrations can be pointed out in order to eliminate the costly and inefficient trial and error repair methods of the traction line. The vibration analyzer of the traction line is configured to allow a vehicle to be tested, and the results are analyzed, in only a couple of hours, thus minimizing the lost time of the vehicle. Additionally, the vibration analyzer of the traction line 10 can also be used as an engineering tool to study the torsional vibration in the traction lines of vehicles, to be used in the design of traction lines, as well as to be introduced to the traction lines. engine and transmission control algorithms. The foregoing description discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize, from this description, and from the accompanying drawings and the appended claims, that certain changes, modifications, and variations may be made therein without departing from the spirit and scope of the invention, as is defined in the following claims

Claims (3)

1. A tool for measuring and analyzing torsional vibration based on the order of a rotating component in a vehicle traction line, comprising: a sensor for measuring an instantaneous velocity of a traction line component under test and generating signals from speed; a processor electrically coupled to said sensor for receiving said speed signals from said sensor and for processing said speed signals in rotational acceleration measurements, said processing including calculating the amplitudes of said rotational acceleration measurements at each of one or more predetermined frequencies , said frequencies tracking the rotation order of said rotating component; and screen means for representing said amplitudes of said rotational acceleration measurements with their respective rotation commands. The tool of claim 1, wherein said rotating component in a vehicle drive line is an output arrow of the transmission. The tool of claim 2, wherein said processing is carried out using a fast Fourier transform.