Method and drive module for detecting, quantifying and compensating for engagement faults of strain wave gearing

Abstract

The invention relates to a method for detecting and quantifying an engagement failure of a strain wave gear arrangement comprising a wave generator, a rigid outer ring having inner teeth, and an elastically deformable transmission ring having outer teeth engaging with the inner teeth of the outer ring, the method comprises the following method steps:-measuring a torque curve over time on the deformable transmission ring,-detecting an engagement failure on the basis of the measured torque curve,-determining the number of teeth skipped during the detected engagement failure on the basis of the measured torque,-calculating the angle of rotation of the outer ring corresponding to the determined number of teeth.

Description

Technical Field

[0001] The invention relates to a method for detecting and quantifying a meshing fault of a strain wave gearing and a method for compensating a meshing fault of a strain wave gearing in a drive system. Furthermore, the invention relates to a drive module having a strain wave gearing. Background Art

[0002] Strain wave gearing (also called strain wave drive, elliptical center gearing) enables almost play-free power transmission at high transmission ratios and is therefore particularly suitable for applications requiring precise movements and small space requirements. Since high torques can be generated by relatively small motors due to the high transmission ratios, very compact drive mechanisms, for example for automatic machinery, can be constructed using strain wave gearing.

[0003] The main components of a strain wave gearing are a wave generator ("wave generator"), a rigid outer ring with internal teeth ("circular spline"), and a transmission ring with external teeth ("flexspline") arranged between the wave generator and the rigid outer ring. In contrast to rigid gearing, the torque transmission between the wave generator and the outer ring is based on elastic deformation, in which the transmission ring is deformed into an oval shape by the wave generator so that the transmission ring engages with the outer ring on two opposite sides of its circumference. When the wave generator rotates, the transmission ring rolls on the outer ring so that the torque is transmitted between the transmission ring and the outer ring through the interlocking teeth. Therefore, the transmission ratio of the transmission is determined by the difference in the number of teeth on the transmission ring and the outer ring.

[0004] If excessive torque is applied during operation, for example when the gearbox is working under high resistance, the engagement between the transmission ring and the outer ring can be at least partially lost, so that the teeth of the transmission ring jump over the teeth of the outer ring ("ratchet effect"). Although the rotation of the transmission ring and the rotation of the outer ring are strictly coupled during normal operation, this engagement failure temporarily leads to an uncontrolled relative rotation between the two rings. This produces an unknown angular offset on the output side compared to the drive side, making it impossible to accurately control the angular position. Since the condition of the transmission does not indicate whether and to what extent such an engagement failure has occurred, it is more difficult to find the cause of subsequent faults.

[0005] In this context, a method is known from JP 2021014876 A in which the torque acting on the output side of the strain wave gearing is measured and compared with two threshold values. Exceeding the first threshold value indicates a coupling fault, while exceeding the second threshold value indicates a possible buckling of the transmission ring. A disadvantage of this method is that the critical torque ("ratchet torque") at which a coupling fault may occur varies from transmission to transmission. On the other hand, this simple threshold method cannot reliably determine whether a coupling fault has actually occurred, whether the temporarily occurring high torque has been reduced without interference, and to what extent the coupling fault has occurred. Summary of the invention

[0006] Against this background, the object is to provide a method by which the stability of a drive mechanism, in particular an automatic machine, with a strain wave gearing can be increased.

[0007] The object is achieved by a method for detecting and quantifying engagement faults of a strain wave gear device, the strain wave gear device comprising an input-side wave generator, an output-side rigid outer ring with internal teeth, and an elastically deformable transmission ring with external teeth that engage with the internal teeth of the outer ring, wherein the method comprises the following method steps:

[0008] -Measurement of the time-varying torque curve on the deformable transmission ring,

[0009] - detection of engagement faults based on the measured torque curve,

[0010] - determining the number of teeth skipped during the detected engagement fault based on the torque measurement, and

[0011] - Calculation of the angular offset between the transmission ring and the outer ring corresponding to the determined number of teeth.

[0012] Furthermore, the object is achieved by a method for compensating for an engagement fault of a strain wave gearing in a drive system, in particular a drive system of an automatic machine, the strain wave gearing comprising an input-side wave generator, an output-side rigid outer ring with internal teeth, and an elastically deformable transmission ring with external teeth engaging with the internal teeth of the outer ring, wherein the drive system has a rotary encoder for measuring the rotational position of the wave generator of the strain wave gearing, wherein the method for detecting and quantifying an engagement fault according to one of the preceding claims is performed and the calculated angular offset is transmitted to an evaluation unit connected to the rotary encoder, which compensates for the engagement fault based on the calculated angular offset.

[0013] The detection of a coupling fault is based on a torque curve measured over time on a deformable transmission ring. This represents the dynamic behavior of the torque transmission before and during the coupling fault. Usually, an excessively high torque is built up before the coupling fault, which ultimately causes the teeth of the transmission ring to disengage from the outer ring and jump over the teeth of the outer ring. The accumulated torque is reduced significantly within a short period of time. This reduction in torque can be used as a characteristic signal of a coupling fault in the method according to the invention and enables a reliable detection of the coupling fault.

[0014] In the method according to the invention, the number of skipped teeth or tooth engagements between the transmission ring and the outer ring during the engagement fault is determined based on the torque curve. The engagement fault can have several skipped teeth or tooth engagements, wherein the skipped teeth can be detected based on predefined parameters. According to the invention, the angular offset between the transmission ring and the outer ring is determined based on the determined number of skipped teeth, wherein the angular offset corresponds to the angular offset defined by the skipped teeth or tooth engagements. The angular offset corresponds to the angular offset occurring between the input-side wave generator and the output-side outer ring of the strain wave gearing. In the method according to the invention for compensating for the engagement fault, the determined angular offset is transmitted to an evaluation unit connected to a rotary encoder. The evaluation unit then compensates for the occurrence of the engagement fault based on the calculated angular offset. This can improve the stability of the drive system with the strain wave gearing.

[0015] The wave generator of the strain wave gearing is formed in particular by a disk, which is connected to the drive shaft and has an oval shape, for example an elliptical shape. The disk preferably has a rolling bearing that is contracted onto its circumference, which rolling bearing has a thin, elastically deformable raceway and several rolling elements. The transmission ring can be, for example, cup-shaped or top-hat-shaped ("top hat"-shaped), i.e. the transmission ring is formed in particular by a cylindrical wall of a cup-shaped or top-hat-shaped bushing, which can be made of steel, for example. These are therefore common design options for transmission rings, which common design options can be used to preload the transmission ring relative to the wave generator. In particular, the time-varying torque curve can be analyzed and evaluated via the evaluation unit, the change of the measured value over time can be determined and compared with a reduction threshold value. For example, the rate of change over time can be determined in particular by forming a difference or a numerical derivative of the torque measurement value and compared with the reduction threshold value. It is also conceivable that the comparison checks whether the measured torque decreases by at least a predetermined amount within a predetermined time period. The reduction threshold value can in particular be a relative reduction threshold value, i.e. a comparison is made to check whether the measured torque has decreased by at least a predetermined percentage. If the reduction threshold value is exceeded, a warning signal is triggered which can in particular be transmitted to an external data processing unit, such as a monitoring and control unit of the strain wave gearing.

[0016] In addition, during the detection, the measured torque can be compared with at least one torque threshold, wherein only when the torque threshold is detected to be exceeded, the measured torque is determined to decrease over time and compared with the reduction threshold. The torque threshold is used to distinguish between load peaks generated during normal operation and excessive torques that indicate or signal an engagement fault. For example, during the start or stop process, the transmission must overcome the inertia of the load connected to the outlet side or the output side, which can cause a short increase in torque (start / stop torque). If an obstacle appears on the output side, for example, if an automatic mechanical arm actuated by a gearbox hits an obstacle, the transmission will briefly resist high resistance (collision torque) before the collision is recorded. At very high torques, the mechanical load capacity of the transmission ring will eventually be exceeded, resulting in buckling of the transmission ring (buckling torque, torsional buckling, torsional bending buckling). The ratchet torque is between the collision torque and the buckling torque, and the ratchet torque usually triggers an engagement fault. The torque threshold used in the method can, for example, correspond to a collision torque or a ratchet torque. Preferably, the torque threshold is between the collision torque and the buckling torque, or between the collision torque and the ratchet torque. In particular, the torque threshold can be adapted to the transmission independently, for example by triggering one or more engagement faults in a controlled manner before commissioning and selecting the threshold value according to the torque generated during the engagement fault. It is also conceivable that first a comparison is made with a first torque threshold and, if the first torque threshold is exceeded, a comparison is made with a second torque threshold that is higher than the first torque threshold. In particular, the first torque threshold can correspond to a crash torque, while the second torque threshold can correspond to a ratchet torque.

[0017] In a further advantageous embodiment of the detection according to the invention, a single torque threshold value for the strain wave gearing is determined at the start of the method and a comparison of the measured torque is performed by means of the single torque threshold value, wherein the single torque threshold value is in particular determined by a controlled triggering of at least one, preferably several, engagement faults. In other words, the measured torque is compared with the single torque threshold value, wherein an exceeding of the single torque threshold value is detected and triggers an increase in the sampling rate of the torque sensor. The single torque threshold value is determined by one or more targeted experiments. For example, the single threshold value can be determined such that the single threshold value is higher than a torque value generated during normal operation (e.g. a start / stop torque).

[0018] The angular offset between the transmission ring and the outer ring determined in the method for detection and quantification according to the invention can be used in a further method step for compensating for misalignment. The rotary encoder can determine the position of the wave generator while recording the torque, so that the position of the engagement fault can be determined based on this position. This value combined with the determined angular offset of the outer ring can be transmitted to an evaluation unit. Based on the determined position of the rotary encoder on the wave generator, the evaluation unit can accurately determine the rotational position of the outer ring when the engagement fault occurred. The evaluation unit can use the angular offset to correct the measured value of the rotary encoder, wherein the angular offset caused by the so-called "slipping" of the teeth on the outer ring can be compensated by "resetting" the rotary encoder without moving the drive module. When the rotary encoder is "reset", the angular offset can be included in the current position determination by the rotary encoder, wherein the angular offset can be added to the current position or subtracted from the current position. Advantageously, the "resetting" of the rotary encoder allows continued precise positioning on the output side, wherein the stability of the strain wave gearing is improved. In addition, downtimes of machines with built-in strain wave gearing and inaccuracies in the rotational position on the outer ring due to engagement faults can be reduced.

[0019] In an alternative embodiment, the rotary encoder is attached to the input-side rotor shaft or directly to the input-side drive module, preferably an electric motor.

[0020] According to a preferred embodiment, it is provided that the torque curve over time is realized by means of a torque sensor arranged on a deformable transmission ring, which preferably has one or more strain gauges. The sensor data from the torque sensor can thus provide data for the torque curve. Therefore, a plurality of torque sensors creates a more reliable system, wherein preferably a torque sensor with a high measurement accuracy is used. The torque sensor can, for example, be attached to the transmission ring or incorporated into the transmission ring. In particular, the transmission ring can have a strain-sensitive structure or coating, with which the applied torque can be measured via the torsion generated by the transmission ring. It is also conceivable that a compensating strain gauge can be used, wherein this can be used to compensate for temperature fluctuations. During highly dynamic operation, the temperature inside the strain wave gearing can increase, which can distort the torque curve. A compensating strain gauge can be arranged inside the strain wave gearing, wherein the compensating strain gauge is not subjected to any mechanical stress, but is subjected to the same temperature. This enables the evaluation unit to compensate for distortions caused by temperature fluctuations.

[0021] According to a preferred embodiment, it is provided that measuring the torque curve over time comprises measuring the direction of rotation and / or the torque amount of the wave generator. Existing sensors can be used to determine the direction of rotation of the wave generator, wherein the direction of rotation is particularly important when outputting the rotation angle of the outer ring. The direction of rotation of the outer ring can be determined based on the determined direction of rotation of the wave generator and the transmission ratio, wherein this can require the use of the determined rotation angle of the outer ring. Alternatively, the direction of rotation of the wave generator can be transmitted directly, or a rotary encoder with a Hall sensor, for example, can determine the direction of rotation of the wave generator.

[0022] According to a preferred embodiment, it is provided that the occurrence of damped vibrations is identified in the measured torque curve in order to detect an engagement fault. When the ratchet torque is exceeded and when "slipping" occurs, the torque curve of the engagement fault can be represented as a damped vibration. On the one hand, this engagement fault can already be detected via a threshold value, but on the other hand, the engagement fault can alternatively be detected based on a characteristic vibration shape. Thus, the torque increases or decreases rapidly until the ratchet torque is exceeded or fallen below. When the tooth "slips", the measured torque initially drops until the teeth of the outer toothing meet the teeth of the inner toothing again. The teeth can collide with each other when slipping, causing short-term vibrations, which are quickly stopped by the engagement and power supply of the wave generator. This can depict the characteristic course of damped vibrations.

[0023] According to a preferred embodiment, it is provided that the number of consecutive damped oscillations in the measured torque curve is determined in order to determine the number of teeth skipped during the detected engagement fault. An engagement fault can have several skipped teeth, wherein the number of skipped teeth is particularly important for the calculation of the rotation angle. In order to be able to accurately determine the rotation angle of the outer ring, the number of teeth skipped within an engagement fault can be determined in the event of several damped oscillations.

[0024] In a particularly preferred embodiment, it is checked whether the teeth skipped during the engagement fault are arranged adjacent to each other. A plurality of skipped teeth can be regarded as an engagement fault only if the skipped teeth are directly adjacent to each other. If the teeth between two skipped teeth are not skipped, these events can be understood as two different engagement faults.

[0025] According to another preferred embodiment, the rotation angle is calculated as Where Δzs is the number of skipped teeth, Δzc is the number of teeth of the inner teeth of the outer ring, and i is the transmission ratio. From the measured torque curve and the resulting skipped teeth, the angular offset between the transmission ring and the outer ring caused by the engagement fault can be determined. This value can be forwarded to the evaluation unit.

[0026] According to a preferred embodiment, it is provided that the rotational position of the outer ring at which the engagement fault occurred is determined based on the rotational position of the wave generator, wherein the rotational position is stored together with the torque value determined when the engagement fault occurred and optionally together with the number of teeth skipped during the detected engagement fault for later comparison. Such a comparison can be used to identify defective teeth or severely worn teeth.

[0027] According to another preferred embodiment, it is provided that it is checked whether the torque at the point when the engagement fault occurs is less than the stored torque at the same rotational position of the outer ring in the case of the previously detected engagement fault. The rotary encoder data and other data can be stored in an internal storage unit. Advantageously, the data can be used in the case of repeated engagement faults, wherein the engagement faults occurring at the same rotational position can be compared with each other and can be an indicator of the service life and wear of the strain wave gearing. Repeated engagement faults at the same rotational position on the outer ring can indicate severe local wear of the teeth or tooth damage. In this way, the torque curves of these engagement faults can be compared with each other, wherein strong deviations between the torque curves can indicate damage or severe wear. With increasing operating time, several engagement faults can occur at the same tooth position, wherein the later-occurring engagement fault should have a smaller torque increase or decrease or a gentler torque curve slope than the previously occurring engagement fault. The torque comparison can involve the ratchet torque at the first skipped tooth of the engagement fault, or the maximum torque at the first skipped tooth of the engagement fault, or if several teeth are skipped, the average torque value of several damped vibrations of the engagement fault. In a particularly preferred embodiment, the magnitude of the torques is compared so that the sign is irrelevant when comparing the data. In addition, this simplifies the comparison and the target search by pre-defining criteria during the comparison.

[0028] The problem mentioned at the outset is further solved by a drive module with a strain wave gearing, the drive module comprising an input-side wave generator, an output-side rigid outer ring with internal teeth, and an elastically deformable transmission ring with external teeth engaging with the internal teeth of the outer ring, wherein the drive module is configured to perform the following method steps:

[0029] -Measurement of the time-varying torque curve on the deformable transmission ring,

[0030] - detection of engagement faults based on the measured torque curve,

[0031] - determining the number of teeth skipped during the detected engagement fault based on the torque measurement, and

[0032] - Calculation of the angular offset between the transmission ring and the outer ring corresponding to the determined number of teeth.

[0033] The same advantages as described above in connection with the method according to the invention can be achieved by the drive module according to the invention. The advantageous designs and features described in connection with the method can also be applied—alone or in combination—to the drive module according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further details and advantages of the invention are described below with reference to the exemplary embodiments shown in the accompanying drawings. In the drawings:

[0035] Figure 1 An exemplary embodiment of an automatic machine is shown schematically;

[0036] Figure 2 shows a schematic cross-sectional view of a strain wave gearing, and intact tooth engagement during operation;

[0037] Figure 3 shows a schematic engagement failure and deformation of a transmission ring for measuring torque;

[0038] Figure 4 A cross-sectional view of the strain wave gearing device showing the input side;

[0039] Figure 5 A cross-sectional view of a strain wave gearing device showing the output side;

[0040] Figure 6 shows the torque curve over time in the case of a coupling failure;

[0041] Figure 7 A schematic sensor system is shown, and

[0042] Figure 8 A schematic flow chart for detecting, quantifying and compensating for joint faults is shown. DETAILED DESCRIPTION

[0043] Figure 1 A schematic diagram shows an embodiment of an automatic machine designed as an industrial automatic machine 200 having several arm segments 201, each of which is rotatably connected via a drive module 100 according to the invention. Even though the industrial automatic machine 200 shown here comprises three arm segments 201 and three drive modules 100, embodiments of industrial automatic machines 200 with a different number of arm segments 201 and drive modules 100, for example four, five, six or seven arm segments and drive modules, can also be envisaged. In addition, the drive module 100 can be used for any automatic machine connection.

[0044] Figure 2The typical structure of a strain wave gearing 10 is schematically shown. The main components of the strain wave gearing 10 are a wave generator 13, a rigid outer ring 11 with internal teeth 1 ("circular spline"), and a flexible transmission ring 12 with external teeth 2 ("flex spline") arranged between the wave generator and the rigid outer ring. The wave generator 13 is formed by an oval disk connected to the drive shaft, on the circumference of which several rolling elements 14 (not shown) are arranged, which roll on the inside of the transmission ring 12. The flexible transmission ring 12 is engaged with the outer ring 11 via the wave generator 13, wherein each individual tooth of the transmission ring 12 moves out of the gap between two teeth of the outer ring 11 during a rotation of 180° of the wave generator 13 and moves into the corresponding gap immediately following it (indicated by arrows 3 in section 4). In this way, the transmission ring 12 rotates relative to the outer ring 11 in the direction opposite to the rotation of the wave generator 13, wherein torque is transmitted between the two rings 11 and 12. The output of the strain wave gear device 10 can be realized either via the transmission ring 12 (when the outer ring 11 is fixed) or via the outer ring 11 (when the transmission ring 12 is fixed).

[0045] Due to excessive torque, the engagement between the gear teeth 1, 2 may be temporarily lost, so that the teeth of the transmission ring 12 may jump over several teeth of the outer ring 11 during a so-called engagement failure 62 (indicated by arrow 62). Although the strict relationship between the corresponding rotation angles is maintained during normal operation by the gears between the rings 11, 12, this engagement failure leads to an uncontrolled relative rotation and a resulting angular offset 64 (see Figure 6 ).

[0046] Figure 3The dynamic deformation of the transmission ring 12 in different stages of an engagement fault is schematically shown. The transmission ring 12 is designed as a top hat-shaped bushing ("top hat") (see left figure), the upper edge of which has an outer tooth 2, which in turn engages with the inner tooth 1 of the outer ring 11. The degree of deformation of the cylindrical wall of the transmission ring 12 at three consecutive time points and the corresponding state of the gears 1, 2 are shown. The position of the outer ring 11 is marked by the reference point 34 at the upper edge of the transmission ring 12, while the lines 36, 37, 38 represent the corresponding torsion of the transmission ring 12. In the first stage, the engagement between the rings 1, 2 is still intact, but the torque is constantly increasing due to the elastic torsion 36 of the transmission ring 12. As the torsion increases, the torsional stiffness of the transmission ring 12 increases, so that the torque increases sharply and finally reaches the maximum value of the torque at the deformation 37. When this critical value is reached, the engagement fault 62 is triggered, wherein the engagement of the gear teeth 1, 2 is at least partially cancelled, the torsion rebounds and the outer tooth 2 jumps relative to the inner tooth 1. After the jump, the line 38 no longer ends at the reference point 34 as before, but has an angular offset from the reference point, which corresponds to the resulting offset 2, 3 between the rotation angles of the two rings. Based on this twisting, the torque can be measured by means of a torque sensor 15, for example one or more strain gauges, and is presented as a torque curve 60 over time (see Figure 6 ) in the form of utilization.

[0047] Figure 4 An embodiment of a drive module 100 for moving an arm section 201 of an industrial robot 200 is shown, which can be configured according to Figure 1 The drive module 100 is used in an industrial automatic machine 200. The drive module 100 includes a transmission device designed as a strain wave gear device 10, an electric motor 20 and a brake device 30. Another component of the drive module 100 according to this embodiment is an electronic unit 40. The wave generator 13 is formed by an oval disk, and several rolling elements 14 are arranged on the circumference of the wave generator, and the rolling elements roll on the inner side of the transmission ring 12.

[0048] The wave generator 13 of the strain wave gearing 10 is coupled to an electric motor 20, in this case to a rotor shaft 21 of the electric motor 20. The electric motor 20 can be designed as an axial flow machine or as a radial flow machine.

[0049] The rotor shaft 21 and therefore the wave generator 13 are further coupled to a brake device 30, by means of which the rotor shaft 21 can be decelerated and / or fixed. The rotor shaft 21 is also coupled to a position sensor 50, which can be used to determine the position of the rotor shaft 21, in this case the angular position of the rotor shaft. The position sensor 50 is preferably designed as an optical or magnetic rotary encoder or a rotary angle encoder. By the combination of the torque sensor 15 and the position sensor 50, the amount of torque between the rings 11, 12 and the direction of rotation of the wave generator can be detected.

[0050] Figure 5 Shown according to Figure 4 Details of the strain wave gearing 10 of the drive module 100. It can be seen that a torque sensor 15 is arranged on the elastically deformable transmission ring 12, with the help of which the torque applied to the transmission ring 12 is measured. The torque sensor 15 according to the present embodiment comprises one or more strain gauges, by means of which the applied torque can be measured via the strain gauges and via the torsion of the transmission ring 12 caused thereby. The torque sensor 15 is connected to an evaluation unit 41 of the drive module 100, which continuously or quasi-continuously receives the measured values ​​of the torque sensor 15. In this embodiment, the evaluation unit 41 is designed as a part of the electronic unit 40, see Figure 4 .

[0051] Figure 6 A torque curve 50 is shown as a function of time. The detection of an engagement fault can be accomplished via the inclination of the torque curve 60 and / or via a threshold value. A significant increase or decrease in torque and / or a sharp increase or decrease in the inclination of the measured torque curve 60 allows the detection of an engagement fault 62. During an engagement fault 62, one or more teeth may be skipped, wherein the number of skipped teeth is determined in the method according to the invention. According to the invention, the angular offset 64 resulting from the engagement fault is calculated as a function of the number of teeth skipped during the engagement fault 62. The rotation angle of the outer ring describes the difference between the rotational position measured by the position sensor 50 and the actual rotational position caused by the engagement fault 62.

[0052] The necessity of the method according to the invention is achieved by Figure 6 64 shown in FIG. 6A . If a critical value of the ratchet torque 61 is exceeded, a coupling fault 62 may occur. In this case, the coupling fault 62 has three skipped teeth, wherein each skipped tooth produces a damped vibration 62' in the torque curve 60. The angular offsets 63 produced by the teeth within the coupling fault 62 add up to the full angular offset of the coupling fault 64, wherein it is of particular interest to compensate for this misalignment produced by the coupling fault 62.

[0053] Based on the measured torque curve 60 and the already explained criteria for detecting an engagement fault 62, an engagement fault 62 is detected from the damped vibrations 62' generated by the skipped teeth. The engagement fault 62 can have one or more damped vibrations 62', from which the number of skipped teeth is determined. This number is required for calculating the angular offset of the outer ring 11 relative to the transmission ring 12, which corresponds to the angular offset 64 between the input and the output of the strain wave gearing. The number of skipped teeth is determined in the evaluation unit 41 and is calculated using the formula The rotation angle of the outer ring 11 is calculated, where Δzs is the number of skipped teeth, Δzc is the number of teeth of the inner teeth 1 of the outer ring 11, and i is the transmission ratio. If the skipped teeth generating the damped vibrations 62' are arranged adjacent to each other, multiple damped vibrations 62' are counted as only one engagement fault 62.

[0054] Figure 7 A sensor system 300 is shown, which has an evaluation unit 41 and a torque sensor 15. The system 300 is also supported by data from a position sensor 50. The evaluation unit 41 arranged in the system 300 comprises a filter and amplifier 301, an analog / digital converter 302, a microprocessor 303 and an internal storage unit 304. The internal storage unit 304 is capable of storing the torque measured during the engagement fault 62 and the associated measurement position. When the engagement fault occurs at the same position, the magnitude of the torque can be compared based on the position. The data from the position sensor 50 provides the rotational position of the transmission ring 12. The detection and quantification of the angular offset of the outer ring 12 relative to the transmission ring enables the rotary encoder or position sensor 50 to be "reset" so that the evaluation unit 41 knows the actual position of the outer ring 12. The compensation of the angular offset 64 increases the stability of the drive module to misalignment and can therefore increase the service life of such a module. Even if the strain wave gearing 10 has an extended service life and a high degree of wear, it is possible to accurately control the outer ring 11 or the arm section 201 of the exemplary automatic machine 200.

[0055] The internal memory unit 304 within the evaluation unit 41 stores the rotational position at which the engagement fault 62 occurs and the torque value determined when the engagement fault 62 occurs, and optionally stores the number of teeth skipped during the detected engagement fault 62. The internal memory unit 304 may be included in the microprocessor 303. The evaluation unit 40 may also include two or more analog / digital converters 302, as well as filters and amplifiers 301, wherein the number of these elements may depend on the number of input variables. For example, it is conceivable that the position sensor 50 and the torque sensor 15 each have their own signal converter 302 and filter and amplifier 301 within the evaluation unit 41. In addition, the preferred embodiment may have other physical quantities as input quantities, which are particularly used to compare the torque curve 60 during the engagement fault 62. For example, the system 300 may include a temperature sensor and a pressure sensor. Temperature is particularly relevant for consideration of the torque curve 60, because the strain gauges preferably used (such as the torque sensor 15) are very sensitive to temperature. The influence of temperature may be an important factor in the comparability of the data. In Figure 7 In an embodiment of the invention, the rotation angle of the outer ring calculated by the microprocessor 303 is transmitted to the electric motor 20 located on the input side, wherein the control is carried out in a targeted manner taking into account the rotation angle to be compensated.

[0056] Figure 7 The purpose of the evaluation unit 41 shown in FIG. 4 is to evaluate the measurement data of the torque sensor and to determine how many teeth were skipped during the engagement fault.

[0057] The following will use Figure 8 The flowchart in explains an embodiment of a method 400 for compensating an angular offset. In a first method step 401, a coupling fault 62 is detected. Subsequently, in a second method step 402, the direction of rotation is then detected using the described method for detection and quantification, and the number of skipped teeth is determined. The direction of rotation of the electric motor 20 can be determined via a position sensor 50 or a speed sensor on the electric motor 20. In a third method step 403, the angle of rotation of the outer ring 11 is determined. The compensation angle or the angular offset is determined by the formula explained above.

[0058] If these method steps have been completed, a first query 404 determines to what extent a meshing fault 62 has already occurred at the same position on the outer ring 11. If the first query 405' is negative, the method jumps to a fourth method step 408 and the calculated rotation angle is transmitted to the electric motor 20 and / or a "reset" of the position sensor 50 is performed. If the first query 405 is positive, the process continues with a second query 406. In the second query 406, it is determined whether the ratchet torque in the current meshing fault 62 has decreased compared to the ratchet torque of the previous meshing fault 62 at the same position, wherein in the present embodiment, the quantity of the torque curve 60 is used. Alternatively, it is also possible to consider the maximum value of the first damped vibration 62' of the meshing fault, or the average value of a plurality of damped vibrations within the meshing fault 62. This comparison of the ratchet torques of the meshing faults 62 occurring at the same position is supported by the internal storage unit 304. The comparison of these ratchet torques enables the evaluation unit 41 to estimate the wear and potential service life of the strain wave gearing 10. Furthermore, such a comparison may be used to detect damage of teeth in the strain wave gearing 10. It is conceivable that the evaluation unit 41 provides a user with an evaluation of the condition, wear and / or estimated remaining service life of the strain wave gearing 10 based on the comparison of the torques.

[0059] If the second query 407' is negative, it can be assumed that there is damage in the strain wave gearing 10, so the process continues to an alternative fourth method step 409. In this alternative fourth method step 409, an error message is displayed to the user. Furthermore, it is conceivable to introduce several stages so that the system 300 can assume a smaller damage situation and only output an error message if the ratchet torque increases slightly in the case of a subsequent engagement fault 62 compared to a previous engagement fault 62 at the same position. On the other hand, if the ratchet torque increases significantly, the system 300 can be controlled to an emergency stop so that no further damage occurs in the strain wave gearing 10.

[0060] If the second query 407 is positive, the process proceeds to the fourth step 408 and continues as already explained. Alternatively, in a preferred embodiment, an error message can be issued despite the positive second query 407 if the ratchet torque is significantly lower than the previous ratchet torque. For this purpose, a third query is required that can classify the exact drop or increase in the ratchet torque. A sharp drop can also indicate damage or severe wear of the teeth of the strain wave gearing 10.

[0061] Reference numerals list

[0062] 1 Internal teeth

[0063] 2 External teeth

[0064] 3 Movement of external teeth

[0065] 4. Incision

[0066] 10 Strain wave gearing

[0067] 11 Outer Ring

[0068] 12 Transmission ring

[0069] 13 Wave Generator

[0070] 14 Rolling elements

[0071] 15. Torque sensor

[0072] 20 Electric Motor

[0073] 21 Rotor shaft

[0074] 30 Braking device

[0075] 34 Reference Points

[0076] 36, 37, 38 deformation lines

[0077] 40 electrical units

[0078] 41 evaluation units

[0079] 50 Position Sensor

[0080] 60 Torque Curve

[0081] 61 Ratchet torque

[0082] 62 Engagement failure

[0083] 62' Damping Vibration

[0084] 63 According to the angle offset of the skipped tooth

[0085] 64 Angular offset due to joint failure

[0086] 100 Driver Module

[0087] 200 Automatic machinery

[0088] 201 Arm section

[0089] 300 Sensor System

[0090] 301 Filters and Amplifiers

[0091] 302 analog / digital converter

[0092] 303 Microprocessor

[0093] 304 Internal storage unit

[0094] 400 Method for compensating for angular offset

[0095] 401 First method step

[0096] 402 Second method step

[0097] 403 Third Method Step

[0098] 404 First Query

[0099] 405 The first query is positive

[0100] 405' The first query is negative

[0101] 406 Second query

[0102] 407 The second query is positive

[0103] 407' The second query is negative

[0104] 408 Fourth Method Step

[0105] 409 Alternative Fourth Method Step

Claims

1. A method for detecting and quantifying an engagement fault (62) of a strain wave gear device (10), the strain wave gear device comprising an input-side wave generator (13), an output-side rigid outer ring (11) having inner teeth (1), and an elastically deformable transmission ring (12) having outer teeth (2) engaging with the inner teeth (1) of the outer ring (11), wherein: The method comprises the following method steps: - measuring a torque curve (60) on the deformable transmission ring (12) as a function of time, - detecting an engagement fault (62) based on the measured torque curve (60), - determining the number of teeth skipped during the detected engagement fault (62) based on the measured value of the torque, - calculating the angular offset between the transmission ring (12) and the outer ring (11) corresponding to the determined number of teeth.

2. The method according to claim 1, characterized in that The torque curve (60) over time is realized by means of a torque sensor (15) arranged on the deformable transmission ring (12), the torque sensor preferably having one or more strain gauges.

3. The method according to one of the preceding claims, characterized in that Measuring the torque curve (60) over time includes measuring the direction of rotation and / or the amount of torque of the wave generator (13).

4. The method according to one of the preceding claims, characterized in that The presence of damped vibrations is identified in the measured torque curve (60) to detect the engagement fault (62).

5. The method according to claim 4, characterized in that The number of consecutive damped oscillations (62') in the measured torque curve (60) is determined to determine the number of teeth skipped during the detected engagement fault (62).

6. The method according to one of the preceding claims, characterized in that The angular offset is calculated as in, Δzs is the number of teeth skipped, Δzc is the number of teeth of the inner teeth (1) of the outer ring (11), and i is the transmission ratio.

7. A method for compensating for an engagement fault (62) of a strain wave gear device (10) in a drive system, in particular a drive system of an automatic machine (200), the strain wave gear device (10) comprising an input-side wave generator (13), an output-side rigid outer ring (11) with inner teeth (1), and an elastically deformable transmission ring (12) with outer teeth (2) engaging with the inner teeth (1) of the outer ring (11), wherein: The drive system has a rotary encoder for measuring the rotational position of the wave generator (13) of the strain wave gearing (10), wherein the method for detecting and quantifying a meshing fault (62) according to one of the preceding claims is performed and the calculated angular offset is transmitted to an evaluation unit (41) connected to the rotary encoder, which compensates for the meshing fault (62) based on the calculated angular offset.

8. The method according to claim 7, characterized in that The rotational position of the outer ring (11) at which the engagement fault (62) occurred is determined based on the rotational position of the wave generator (13), wherein the rotational position is stored together with the torque value determined at the point when the engagement fault (62) occurred, and optionally together with the number of teeth skipped during the detected engagement fault (62), for later comparison.

9. The method according to claim 8, characterized in that It is checked whether the torque at the point when the engagement fault (62) occurs is less than the stored torque at the same rotational position of the outer ring (11) in the case of a previously detected engagement fault (62).

10. A drive module (100), the drive module having a strain wave gear device (10), the strain wave gear device comprising an input-side wave generator (13), an output-side rigid outer ring (11) having inner teeth (1), and an elastically deformable transmission ring (12) having outer teeth (2) engaging with the inner teeth (1) of the outer ring (11), wherein: The driving module (100) is configured to perform the following method steps: - measuring the torque curve of the deformable transmission ring (12) as a function of time, - detecting an engagement fault (62) based on the measured torque curve (60), - determining the number of teeth skipped during the detected engagement fault (62) based on the torque measurement, and - calculating the angular offset between the transmission ring (12) and the outer ring (11) corresponding to the determined number of teeth.

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