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Detecting Misalignment of a Claw Clutch Using Vibration Measurements

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Coupling misalignment is a fairly common fault in rotating machines and causes excessive loads to bearings and other machine components. In general, misalignment and its severity can be detected reliably using vibration measurements. Misalignment is typically detected on the basis of the velocity spectrum. An increase in amplitude at rotational frequency and its harmonics are an indication of misalignment or a bent shaft. However, the behaviour of a claw clutch (jaw coupling) is very different as compared with a conventional elastic coupling. This paper presents the results of research where the detection of claw clutch misalignment is investigated based on acceleration signals. Real order derivatives and lp norms are calculated from the signals. In a test rig, which is used in this study, different degrees of misalignment are generated by moving a motor in the horizontal direction with steps of 0.1 mm. The tests were carried out at five rotational frequencies. Studies show that after a certain level of misalignment, the claw clutch gives rise to impacts that induce high frequency vibrations.
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... In references (1,2,3,4) Lahdelma et al. have defined real order derivatives and integrals of function (1) by replacing n ∈ N with a real number α ∈ R ...
... Norm (17) can be generalised with weight factors, which we choose to be 1/N (3,4) . Generalised norm l p is 1 N weighted l p norm ...
... Lahdelma presented in 1992 (19) the measurement index, or M IT index, utilising rms values of displacement and its derivatives and integrals of order n ∈ N. Later it has been generalised to l p norms and real order derivatives and integrals (3,4) . Thus it is formulated as ...
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Fractional calculus and generalised norms provide a powerful toolkit for analysing vibration from rotating machines. They have been used effectively in the condition monitoring of immobile machines. A harsh environment and varying operating conditions complicate the reliable condition monitoring of mobile machines in underground mining industry. In this paper, we focus on the condition monitoring of the front axle of a load haul dumper and the numerical calculation of complex order derivatives and integrals. Measurements are performed with accelerometers, which measure horizontal and vertical vibrations near the planetary gearboxes. A tachometer records the rotational speed of the drive shaft, which is essential for recognising different operation stages of the machine. We describe how the mentioned difficulties can be overcome and what real order derivatives and generalised norms can reveal about the condition of the axle. An improved algorithm for the numerical calculation of complex order derivatives and integrals is given.
... The motor and the driven shaft are coupled by means of a claw clutch with a four-tooth elastic element (spider). More information on the test rig can be found in Lahdelma and Laurila, 2012), where the same test rig has been used. ...
... Coupling misalignment of the claw clutch causes impacts and invokes high frequency vibrations as shown in earlier studies (Laurila and Lahdelma, 2013;Lahdelma and Laurila, 2012). Figure 5 shows projections of the signals x (3.4+i) in the z plane, when different rates of coupling misalignment occur. ...
... The weighted l p norm was utilised in the vibration signal analysis in order to evaluate the levels of vibration signals and the stress of the cutter. It is defined by (Lahdelma and Laurila, 2012), ...
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The papers published in these proceedings are presented in the International Conference on Maintenance, Condition Monitoring and Diagnostics, and Maintenance Performance Measurement and Management, MCMD 2015 and MPMM 2015, to be arranged in Oulu, Finland, in 30th September – 1st October, 2015. Arranged by the University of Oulu and POHTO – The Institute for Management and Technological Training, the present conference is supported by a variety of Finnish industrial enterprises.
... More information on the test rig and the original measurements can be found in (31) . We have studied the detection of the offset misalignment of a claw clutch in (32) . Figure 1 shows the relative peak values of the x (3) signals in the case of motor offset and rotational frequency changes. ...
... The relative jerk peak or x(3) p values when the rotational frequency of the motor and offset misalignment changes(32) . ...
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... The motor and the driven shaft are coupled by means of a claw clutch with a four-tooth elastic element (spider). More information on the test rig can be found in (7,8) , where the same test rig has been used. ...
... For example, when the unbalance mass is doubled from 5.5 g to 11 g, the diameter of the circle is doubled too from 200 µm/s 0.4+i to 400 µm/s 0.4+i . Coupling misalignment of the claw clutch causes impacts and invokes high frequency vibrations as shown in earlier studies (4,8) . Figure 5 shows projections of the signals x (3.4+i) in the z plane, when different rates of coupling misalignment occur. ...
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... The motor and the driven shaft are coupled by means of a claw clutch with a four-tooth elastic element (spider). More information on the test rig can be found in (Lahdelma et al., 2011;Lahdelma and Laurila, 2012), where the same test rig has been used. ...
... Coupling misalignment of the claw clutch causes impacts and invokes high frequency vibrations as shown in earlier studies (Laurila and Lahdelma, 2013;Lahdelma and Laurila, 2012). Figure 5 shows projections of the signals x (3.4+i) in the z plane, when different rates of coupling misalignment occur. ...
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... The weighted l p norm has been applied for several cases of fault detection. This norm has proved to be an effective tool in condition monitoring and it can be applied to any type of signal (4,9,10,11,12) . It is defined by ...
... Moreover, we end up with (5), when w 1 = w 2 = ... = w N = 1 N . This is the l p norm, which Lahdelma introduced in (12) , and it is defined by ...
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... Unstable running of an electric motor [26,62,67] Bearing faults [26,[66][67][68][69]72,[84][85][86][87][88][89][90]93,94,98] Bent shaft [88] Misalignment [88,91,92] Cavitation [95][96][97] Poor lubrication [91] A laboratory experiment is examined in which automatic diagnostics were used with acceleration and jerk signals. The outer race of a rolling bearing contained the faults shown in Table 6 [69,87,94] . ...
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... where all the weight factors are equal to N 1 , has been proved to be an efficient indicator in condition monitoring Juuso, 2011a, 2011b;Lahdelma et al., 2010;Lahdelma and Laurila, 2012). ...
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