DE102022128423B3 - Method and a drive module for detecting, quantifying and compensating for a meshing fault in a voltage wave transmission - Google Patents

Abstract

The invention relates to a method for detecting and quantifying a meshing fault of a voltage wave transmission comprising a shaft generator, a rigid outer ring with internal teeth and an elastically deformable transmission ring with external teeth which is in engagement with the internal teeth of the outer ring, the method comprising the following method steps :- Measuring a temporal torque curve on the deformable transmission ring, - Detecting a meshing disturbance based on the measured torque curve, - Determining a number of teeth skipped during the detected meshing disturbance based on the measurement of the torque, - Calculating an angle of rotation of the outer ring, which corresponds to the determined number of teeth .

Description

The invention relates to a method for detecting and quantifying a meshing fault of a voltage wave gear and a method for compensating for a meshing fault of a voltage wave gear in a drive system. The invention further relates to a drive module with a voltage wave transmission.

Tension wave gears (also wave gears, sliding wedge gears; “strain wave gearing” or “harmonic drive”) enable almost backlash-free power transmission with a high gear ratio and are therefore particularly suitable for applications that require precise movements and a small space requirement. Since high torques can be generated with relatively small motors due to the high transmission ratio, very compact drive mechanisms can be implemented using voltage wave gears, which are used, for example, in robotics.

The main components of a voltage wave gearbox are a wave generator, a rigid outer ring (“circular spline”) with internal teeth and a transmission ring (“flexspline”) with external teeth arranged in between. In contrast to rigid gears, the transmission of torque between the shaft generator and the outer ring is based on elastic deformation, in which the transmission ring is deformed into an oval by the shaft generator in such a way that it is in engagement with the outer ring on two opposite sides of its circumference. Due to the rotation of the shaft generator, the transmission ring rolls on the outer ring, so that a torque is transmitted between the transmission ring and the outer ring through the interlocking teeth. The transmission ratio of the gearbox is determined by the difference in the number of teeth on the transmission ring and the outer ring.

If an excessively strong torque occurs during operation, for example if the gearbox works against a 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 (“ratcheting”). While the rotation of the transmission ring and that of the outer ring are strictly coupled in normal operation, an uncontrolled relative rotation between the two rings temporarily occurs in the event of such a disruption in engagement. This creates an unknown angular offset on the output side compared to the drive side, which makes precise control of the angular position impossible. Since it is not possible to determine from the condition of the transmission whether and to what extent such a malfunction has occurred, the search for the cause of the subsequent malfunction is made more difficult.

From the JP 2021014876 A In this context, a method is known in which the torque acting on the output side of a voltage shaft transmission is measured and compared with two threshold values. Exceeding the first threshold serves as an indication of a malfunction, while exceeding the second threshold indicates possible buckling of the transmission ring. The disadvantage of this method is, on the one hand, that the critical torque (“ratcheting torque”), at which a meshing fault is highly likely to occur, varies from gearbox to gearbox. On the other hand, such a simple threshold value method cannot be used to reliably determine whether an engagement fault has actually occurred, whether the high torque that occurred at times was reduced without disruption and to what extent the engagement fault has occurred.

The DE 11 2004 002 907 B4 describes a wave gear drive with a tooth profile that avoids ratcheting at high (speed) reductions.

Against this background, the task is to provide a method with which the robustness of a drive mechanism with a voltage wave transmission, in particular of a robot, can be increased.

• - Messen eines zeitlichen Drehmomentverlaufs an dem verformbaren Übertragungsring,
• - Detektieren einer Eingriffsstörung anhand des gemessenen Drehmomentverlaufs,
• - Ermitteln einer Anzahl während der detektierten Eingriffsstörung übersprungener Zähne anhand der Messung des Drehmoments und
• - Berechnen eines Winkelversatzes zwischen dem Übertragungsring und dem Außenring, welcher der ermittelten Anzahl an Zähnen entspricht.

The object is achieved by methods for detecting and quantifying a meshing fault of a voltage wave transmission, which comprises an input-side shaft generator, an output-side, rigid outer ring with internal teeth and an elastically deformable transmission ring with external teeth which is in engagement with the internal teeth of the outer ring, wherein the Process includes the following process steps:

• - measuring a torque curve over time on the deformable transmission ring,
• - Detecting a malfunction based on the measured torque curve,
• - Determining a number of teeth skipped during the detected engagement fault based on the measurement of the torque and
• - Calculating an angular offset between the transmission ring and the outer ring, which corresponds to the determined number of teeth.

Furthermore, this object is achieved by a method for compensating for a meshing disturbance of a voltage wave transmission in a drive system, in particular a robot, wherein the voltage wave transmission comprises an input-side wave generator, an output-side, rigid outer ring with internal teeth and an elastically deformable transmission ring with external teeth which engage with the internal toothing of the outer ring, wherein the drive system has a rotary encoder for measuring the rotational position of the shaft generator of the voltage shaft gear, wherein a method for detecting and quantifying a meshing disturbance is carried out according to one of the preceding claims and the calculated angular offset is transmitted to an evaluation unit connected to the rotary encoder which compensates for the interference interference based on the calculated angular offset.

The detection of the engagement fault is based on a measured torque curve over time on the deformable transmission ring. This reflects the dynamic behavior of the torque transmission before and during the engagement fault. Typically, in the run-up to the engagement disruption, an excessively high torque builds up, which ultimately leads to the teeth of the transmission ring losing engagement with the outer ring and jumping over its teeth. The accumulated torque is greatly reduced within a short period of time. In the method according to the invention, this decrease in torque can serve as a characteristic signature of an engagement fault and enable the engagement fault to be reliably detected.

In the method according to the invention, the number of teeth or tooth meshes between the transmission ring and the outer ring that are skipped due to the engagement fault is determined based on the torque curve. An engagement fault can have several skipped teeth or tooth engagements, whereby a skipped tooth can be recognized based on predefined parameters. According to the invention, an angular offset between the transmission ring and the outer ring is determined from the determined number of skipped teeth, this angular offset corresponding to the angular offset defined by the skipped teeth or tooth meshes. This angular offset corresponds to the angular offset that occurs between the input-side shaft generator and the output-side outer ring of the voltage shaft gear. In the method according to the invention for compensating for the interference interference, the determined angular offset is transmitted to the evaluation unit, which is connected to the rotary encoder. The evaluation unit then compensates for the occurrence of the intervention interference based on the calculated angular offset. As a result, the robustness of the drive system having voltage wave gears can be improved.

The wave generator of the voltage wave transmission is formed in particular by a disk with an oval, for example elliptical, shape connected to a drive shaft. The disk preferably has a roller bearing shrunk on its circumference with a thin, elastically deformable race and several rolling elements. The transmission ring can, for example, be designed in the shape of a cup or a cylinder hat, i.e. the transmission ring is formed in particular by a cylindrical wall of a top-shaped or cylinder hat-shaped bushing, which can be made of steel, for example. These are common design options for the transmission ring, with which a pretension of the transmission ring relative to the wave generator can be achieved. In particular, the torque curve over time can be analyzed and evaluated via an evaluation unit, the change in the measured values over time can be determined and compared with a decrease threshold value. For example, a temporal rate of change can be determined and compared with the decrease threshold value, in particular by forming a difference or a numerical derivation of the torque measurement values. It is also conceivable that the comparison checks whether the measured torque decreases by at least a predetermined amount within a predetermined period of time. The decrease threshold value can in particular be a relative decrease threshold value, i.e. the comparison checks whether the measured torque has decreased by at least a predetermined percentage. If the decrease threshold value is exceeded, a warning signal is triggered, which can be transmitted in particular to an external data processing unit, such as a monitoring and control unit of the voltage wave transmission.

Furthermore, during detection, the measured torque can be compared with at least one torque threshold value, with the temporal decrease in the measured torque only being determined and compared with the decrease threshold value when an exceedance of the torque threshold value is detected. The torque threshold value is used to be able to distinguish the load peaks that occur during normal operation from excessively high torques that indicate or herald a malfunction. For example, the transmission must control the mass inertia of the output or output side during the starting and stopping process overcome coupled load, which manifests itself in a briefly increased torque (start/stop torque). If an obstruction occurs on the output side, for example if a robot arm actuated by the gearbox hits an obstacle, the gearbox briefly works against a high resistance (impact torque) before the impact is registered. At very high torques, the mechanical load capacity of the transmission ring is ultimately exceeded, so that it buckles (buckling torque, torsional buckling moment, bending-torsional buckling moment, “buckling torque”). Between the starting torque and the buckling torque lies the ratcheting torque, at which engagement faults are typically triggered. The torque threshold value used in the method can correspond, for example, to the kicking torque or the ratcheting torque. Preferably, the torque threshold is between the kicking torque and the buckling torque or between the kicking torque and the ratcheting torque. In particular, the torque threshold value can be individually tailored to the transmission, for example by triggering one or more engagement faults in a controlled manner before commissioning and the threshold value is selected depending on the torque that occurs during the engagement faults. It is also conceivable to first carry out a comparison with a first torque threshold value and, if it is exceeded, to carry out a comparison with a second torque threshold value which is higher than the first torque threshold value. In particular, the first torque threshold value may correspond to the starting torque, while the second torque threshold value corresponds to the ratchet torque.

In a further advantageous embodiment of the detection according to the invention, an individual torque threshold value for the voltage wave transmission is determined at the beginning of the method and the comparison of the measured torque is carried out using the individual torque threshold value, the individual torque threshold value being determined in particular by at least one, preferably several, controlled triggering of engagement faults . In other words, the measured torque is compared with an individual torque threshold value, whereby an exceedance of the individual torque threshold value is detected and an increase in a sampling rate of the torque sensor is triggered by exceeding the individual torque threshold value. The individual torque threshold is determined through one or more targeted experiments. For example, the individual threshold value can be determined so that it is above the torque values that occur during normal operation (e.g. start/stop torque).

The angular offset between the transmission ring and the outer ring determined in the method according to the invention for detecting and quantifying can be used in a further method step to compensate for the misalignment. A rotary encoder can determine the position of the shaft generator while recording the torque, so that the position of the interference fault can be assigned based on this position. This value in combination with the determined angular offset of the outer ring can be transferred to the evaluation unit. From the determined position of the rotary encoder on the shaft generator, the evaluation unit can determine exactly the rotational position of the outer ring at which the engagement fault occurred. The evaluation unit can correct the measured value of the rotary encoder using the angular offset, whereby the angular offset, which occurs due to the so-called “slipping” of the teeth on the outer ring, can be compensated for by “resetting” the rotary encoder without moving the drive module. When “resetting” the encoder, the angular offset can be taken into account in the current position determination by the encoder, whereby the angular offset can either be added to or subtracted from the current position. Advantageously, exact positioning can continue to take place on the output side by “resetting” the rotary encoder, thereby increasing the robustness of the voltage shaft gear. The downtime of a machine with a built-in tension shaft gear and inaccuracies in the rotational position on the outer ring due to interference can also be minimized.

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

According to a preferred embodiment, it is provided that the torque curve over time takes place by means of a torque sensor arranged on the deformable transmission ring, which preferably has one or more strain gauges. The sensor data from the torque sensor can provide the data for the torque curve. Multiple torque sensors create a more reliable system, with preference being given to using torque sensors with high measurement accuracy. The torque sensor can, for example, be attached to the transmission ring or integrated into the transmission ring. In particular, the transmission ring can have an expansion have a sensitive structure or coating with which the applied torque can be measured via the resulting torsion of the transmission ring. It is also conceivable that a compensation strain gauge can be used, which can serve to compensate for temperature fluctuations. During highly dynamic operation, the temperatures within the voltage shaft transmission can rise, which could distort the torque curve. A compensation strain gauge can be arranged within the tension shaft gear, which does not experience any mechanical stress but does experience the same temperatures. This makes it possible for the evaluation unit to equalize the distortion caused by the temperature fluctuation.

According to a preferred embodiment, it is provided that measuring the torque curve over time includes measuring a direction of rotation of the shaft generator and/or an amount of the torque. The direction of rotation of the wave generator can be determined using the existing sensors, with the direction of rotation being of particular relevance when outputting the angle of rotation of the outer ring. The direction of rotation of the outer ring can be determined from the determined direction of rotation of the shaft generator and the translation, which may be required to use the determined angle of rotation of the outer ring. Alternatively, the direction of rotation of the wave generator can be transmitted directly or a rotary encoder, for example having a Hall sensor, can determine the direction of rotation of the wave generator.

According to a preferred embodiment, it is provided that an event of a damped oscillation is recognized in the measured torque curve in order to detect the engagement disturbance. When the ratchet torque is exceeded and “slips”, the torque curve of the engagement fault can produce a damped oscillation. On the one hand, this intervention disturbance can already be recognized via the threshold values, but on the other hand, the intervention disturbance can alternatively be recognized based on the characteristic vibration shape. The torque increases or decreases briefly until the ratchet torque is exceeded or fallen below. When the teeth “slip,” the measured moment first drops until a tooth on the external toothing hits a tooth on the internal toothing again. The teeth can collide when slipping, causing a brief vibration that is quickly dampened by the engagement and the power supply from the wave generator. This can depict the characteristic course of the damped oscillation.

According to a preferred embodiment, it is provided that in order to determine the number of teeth skipped during the detected engagement disturbance, a number of successive damped oscillations in the measured torque curve is determined. A meshing fault can have several skipped teeth, with the number of skipped teeth being of particular relevance for calculating the angle of rotation. In order to be able to precisely determine the angle of rotation of the outer ring, the number of skipped teeth can be determined within the engagement fault with several damped vibrations occurring.

In a particularly preferred embodiment, a check is made during a meshing disruption to see whether the skipped teeth are arranged next to one another. An interference failure with multiple skipped teeth can only be considered as such if the teeth are skipped right next to each other. Unless a tooth is skipped between two skipped teeth, these events can be understood as two different engagement failures.

wobei Δzs die Anzahl übersprungener Zähne Δzc die Anzahl Zähne der Innenverzahnung des Außenrings und i das Übersetzungsverhältnis ist. Aus dem gemessenen Drehmomentverlauf und den daraus ermittelten übersprungenen Zähnen kann der Winkelversatz zwischen Übertragungsring und Außenring, bedingt durch die Eingriffsstörung, ermittelt werden. Dieser Wert kann an eine Auswerteeinheit weitergeleitet werden.According to a further preferred embodiment it is provided that the angle of rotation is calculated as $\Delta \theta =\left(\frac{360°}{\Delta \mathrm{e.g}c}\cdot \Delta \mathrm{e.g}s\right)/i,$

where Δzs is the number of skipped teeth, Δzc is the number of teeth of the internal teeth of the outer ring and i is the gear ratio. From the measured torque curve and the skipped teeth determined from it, the angular offset between the transmission ring and the outer ring, caused by the interference interference, can be determined. This value can be forwarded to an evaluation unit.

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

According to a further preferred embodiment, it is provided that a check is made as to whether a torque when the engagement fault occurs is smaller than a stored torque at the same rotational position of the outer ring in the event of a previously detected engagement fault. The encoder data and other data can be stored in one internal storage unit. This data can advantageously be used in the event of repeated engagement faults, whereby the engagement faults occurring at the same rotational position can be compared with one another and can be an indicator of the service life and wear of the tension shaft gear. Repeatedly occurring engagement problems at the same rotational position on the outer ring can indicate severe local wear on a tooth or damage to a tooth. In this way, the torque curves of these interference faults can be compared with each other, whereby strong deviations between the torque curves can indicate damage or heavy wear. As the duration of operation increases, several engagement faults can occur at the same tooth position, whereby a engagement fault that occurs at a later point in time should have a smaller increase or decrease in torque or a flatter gradient in the torque curve than a previously occurring engagement fault. The comparison of the torque can relate either to the ratchet torque at the first skipped tooth of a meshing fault or the maximum torque at the first skipped tooth of a meshing fault or the averaged torque value from the several damped oscillations of a meshing fault if several teeth are skipped. In a particularly preferred embodiment, the magnitude of the torques is compared so that the signs are not relevant when comparing the data. This also simplifies the comparison and targeted query using predefined criteria during a comparison.

• - Messen eines zeitlichen Drehmomentverlaufs an dem verformbaren Übertragungsring,
• - Detektieren einer Eingriffsstörung anhand des gemessenen Drehmomentverlaufs,
• - Ermitteln einer Anzahl während der detektierten Eingriffsstörung übersprungener Zähne anhand der Messung des Drehmoments und
• - Berechnen eines Winkelversatzes zwischen dem Übertragungsring und dem Außenring, welcher der ermittelten Anzahl an Zähnen entspricht.

The problem mentioned at the outset is further solved by a drive module with a voltage shaft gear, which comprises an input-side wave generator, an output-side, rigid outer ring with internal teeth and an elastically deformable transmission ring with external teeth which is in engagement with the internal teeth of the outer ring, the drive module is configured to carry out the following procedural steps:

• - measuring a torque curve over time on the deformable transmission ring,
• - Detecting a malfunction based on the measured torque curve,
• - Determining a number of teeth skipped during the detected engagement fault based on the measurement of the torque and
• - Calculating an angular offset between the transmission ring and the outer ring, which corresponds to the determined number of teeth.

The drive module according to the invention can achieve the same advantages that were previously described in connection with the method according to the invention.

The advantageous configurations and features described in connection with the method can also be used - alone or in combination - in the drive module according to the invention.

• 1 ein Ausführungsbeispiel eines Roboters in einer schematischen Darstellung;
• 2 eine schematische Schnittansicht eines Spannungswellengetriebes, sowie einen im Betriebsfall intakten Zahneingriff;
• 3 eine schematische Eingriffsstörung, sowie eine Verformung eines Übertragungsringes zur Messung eines Drehmoments;
• 4 eine Schnittansicht eines Spannungswellengetriebes eingangsseitig;
• 5 eine Schnittansicht eines Spannungswellengetriebes ausgangsseitig;
• 6 ein Drehmomentverlauf über die Zeit mit einer Eingriffsstörung;
• 7 ein schematisches Sensorsystem und
• 8 ein schematisches Flussdiagramm zum Erkennen, Quantifizieren und Kompensieren einer Eingriffsstörung.

Further details and advantages of the invention will be explained below using the exemplary embodiment shown in the drawings. This shows:

• 1 an exemplary embodiment of a robot in a schematic representation;
• 2 a schematic sectional view of a tension shaft gear, as well as a tooth mesh that is intact during operation;
• 3 a schematic engagement fault and a deformation of a transmission ring for measuring a torque;
• 4 a sectional view of a voltage shaft transmission on the input side;
• 5 a sectional view of a voltage shaft transmission on the output side;
• 6 a torque curve over time with a meshing failure;
• 7 a schematic sensor system and
• 8th a schematic flow diagram for detecting, quantifying and compensating for an intervention failure.

1 shows a schematic representation of an exemplary embodiment of a robot designed as an industrial robot 200 with several arm segments 201, each of which is rotatably connected via drive modules 100 according to the invention. Even if the industrial robot 200 shown here has three arm segments 201 and three drive modules 100, configurations of the industrial robot 200 with a different number of arm segments 201 and drive modules 100 are conceivable, for example four, five, six or seven each. Furthermore, a drive module 100 can be used for any robot joints.

In the 2 A typical structure of a voltage wave transmission 10 is shown schematically. The main components of the voltage shaft transmission 10 are a shaft generator 13, a rigid outer ring 11 (“circular spline”) with internal toothing 1 and a flexible transmission ring 12 (“flexspline”) with external toothing 2 arranged between them. The shaft generator 13 is provided by a, Oval disk connected to a drive shaft is formed, 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 brought into engagement with the outer ring 11 by the shaft generator 13, with each individual tooth of the transmission ring 12 being moved out of a gap between two teeth of the outer ring 11 and into the respective subsequent gap during a 180 ° rotation of the shaft generator 13 migrates (indicated by arrow 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, with a torque being transmitted between the two rings 11 and 12. The output of the voltage shaft gear 10 can take place either via the transmission ring 12 (with a fixed outer ring 11) or via the outer ring 11 (with a fixed transmission ring 12). In the following, the output of the tension shaft gear is formed by the outer ring 11.

As a result of an excessively high torque, the engagement between the toothings 1, 2 can be temporarily lost, so that a tooth of the transmission ring 12 can jump over several teeth of the outer ring 11 during a so-called engagement fault 62 (indicated by the arrow 62). While in normal operation a strict relationship between the respective angles of rotation is maintained by the toothing between the rings 11, 12, such a disruption in engagement results in an uncontrolled relative rotation and a resulting angular offset 64 (see 6 ).

In 3 the dynamic deformation of the transmission ring 12 is shown schematically in different phases of the engagement failure. The transmission ring 12 is designed as a cylinder hat-shaped bushing (“silk-hat”) (see illustration on the left), the upper edge of which has the external toothing 2, which in turn is brought into engagement with the internal toothing 1 of the outer ring 11. The degree of deformation of the cylindrical wall of the transmission ring 12 is shown at three consecutive times together with the associated state of the toothings 1, 2. The position of the outer ring 11 is marked by a reference point 34 on the upper edge of the transmission ring 12, while the lines 36, 37, 38 represent the associated twisting of the transmission ring 12. In the first phase, the engagement between the rings 1, 2 is still intact, but the elastic twist 36 of the transmission ring 12 builds up an ever-increasing torque. As the twist increases, the torsional rigidity of the transmission ring 12 increases, so that the torque rises steeply and finally reaches its maximum value at the deformation 37. When this critical value is reached, an engagement fault 62 is triggered, in which the engagement of the toothings 1, 2 is at least partially canceled, the twisting snaps back and the external toothing 2 jumps relative to the internal toothing 1. After the jump, the line 38 no longer ends at the reference point 34, as before, but has an angular offset from this, which corresponds to the resulting offset between the angles of rotation of the two rings 2, 3. Based on this rotation, a torque can be measured using a torque sensor 15, for example one or more strain gauges, and in the form of a torque curve 60 (see 6 ) can be made usable over time.

In the 4 an embodiment of a drive module 100 for moving an arm segment 201 of an industrial robot 200 is shown, which is in the industrial robot 200 according to 1 can be used. The drive module 100 comprises a gear designed as a voltage wave gear 10, an electric motor 20 and a braking device 30. Another component of the drive module 100 according to the exemplary embodiment is an electronics unit 40. The wave generator 13 is formed by an oval disk, on the circumference of which several rolling elements 14 are arranged are that roll on the inside of the transmission ring 12.

The wave generator 13 of the voltage wave gear 10 is coupled to the electric motor 20, here with the rotor shaft 21 of the electric motor 20. The electric motor 20 can be designed as an axial flux machine or as a radial flux machine.

The rotor shaft 21 and thus also the wave generator 13 are further coupled to the braking device 30, by means of which the rotor shaft 21 can be delayed and/or fixed. The rotor shaft 21 is also coupled to a position sensor 50, via which a position, here an angular position, of the rotor shaft 21 can be determined. The position sensor 50 is preferably designed as an optical or magnetic rotary encoder or rotary angle encoder. From 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 shaft generator can be detected.

5 shows a detail of the voltage shaft gear 10 of the drive module 100 4 . It can be seen that a torque sensor 15 is arranged on the elastically deformable transmission ring 12, by means of which the torque exerted on the transmission ring 12 is measured. The torque sensor 15 according to the off The exemplary embodiment includes one or more strain gauges with which the applied torque can be measured via the resulting torsion of the transmission ring 12. The torque sensor 15 is connected to an evaluation unit 41 of the drive module 100, which continuously or quasi-continuously receives measured values from the torque sensor 15. In the exemplary embodiment, the evaluation unit 41 is designed as part of the electronics unit 40, cf. 4 .

In 6 a torque curve 50 is shown over time. The detection of an engagement fault can occur on the one hand via the gradient of the torque curve 60 and/or via a threshold value. A significant increase or decrease in torque and/or a steep increase or decrease in the gradient of the measured torque curve 60 allows the engagement fault 62 to be recognized. During an engagement fault 62, one or more teeth can be skipped, the number of skipped teeth being determined in the method according to the invention. According to the invention, an angular offset 64, which was generated by this engagement disturbance, is calculated from the number of skipped teeth during a meshing disturbance 62. The angle of rotation 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.

The necessity of the method according to the invention is made clear by the in 6 angular offset 64 shown. An engagement fault 62 can occur if the critical value of the ratchet torque 61 is exceeded. In this case, the engagement fault 62 has three skipped teeth, with each skipped tooth generating a damped oscillation 62 'in the torque curve 60. The angular offsets 63 generated by a tooth within a meshing disruption 62 add up to the complete angular offset for a meshing disruption 64, whereby it is of particular interest to compensate for this misalignment generated by the meshing disruption 62.

wobei Δzs die Anzahl übersprungener Zähne Δzc die Anzahl Zähne der Innenverzahnung 1 des Außenrings 11 und i das Übersetzungsverhältnis ist, der Drehwinkel des Außenringes 11 berechnet. Eine Pluralität von gedämpften Schwingungen 62' zählt lediglich als eine Eingriffsstörung 62 sofern die übersprungenen Zähne, welche die gedämpften Schwingungen 62' erzeugen, nebeneinander angeordnet sind.Based on the measured torque curve 60 and the criteria already explained for detecting a meshing fault 62, a meshing 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 when 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 output of the voltage wave gear. The number of skipped teeth is determined in the evaluation unit 41 and using the formula $\Delta \theta =\left(\frac{360°}{\Delta \mathrm{e.g}c}\cdot \Delta \mathrm{e.g}s\right)/i,$

where Δzs is the number of skipped teeth, Δzc is the number of teeth of the internal toothing 1 of the outer ring 11 and i is the transmission ratio, the angle of rotation of the outer ring 11 is calculated. A plurality of damped vibrations 62' only counts as a meshing interference 62 if the skipped teeth that generate the damped vibrations 62' are arranged next to one another.

7 shows a sensor system 300, which has an evaluation unit 41 and a torque sensor 15. This system 300 is further supported by data from the 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 enables the storage of torques measured during an engagement fault 62 and the torques measured therefor positions. Based on the position, the amounts of torque can be compared in the event of interference faults occurring at the same positions. 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 “reset” of the rotary encoder or position sensor 50, so that the real position of the outer ring 12 is known to the evaluation unit 41. The compensation of the angular offset 64 increases the robustness of the drive module against misalignment and can thus increase the service life of such a module. Even with a progressive service life and highly advanced wear in the tension shaft gear 10, precise control of the outer ring 11 or an arm segment 201 of an exemplary robot 200 could be possible.

The internal storage unit 304, within the evaluation unit 41, stores the rotational position at which a meshing fault 62 occurred together with the determined torque value when the meshing fault 62 occurred, and optionally the number of teeth skipped during the detected meshing fault 62. The internal storage unit 304 may be included in the microprocessor 303. The evaluation unit 40 can also have two or more analog/digital converters 302, as well as filters and amplifiers 301, whereby the number of these elements can depend on the number of input variables. For example, it would be conceivable that the position sensor 50 and the torque sensor 15 each have their own signal converter 302 and a filter and amplifier 301 within the evaluation unit 41. In addition, a preferred embodiment could have further physical variables as input variables, these being used in particular to compare the torque curves 60 during the engagement disturbances 62. For example, the system 300 could include a temperature sensor and a pressure sensor. The temperature is particularly relevant for the consideration of the torque curve 60, since the strain gauges that are preferably used (as a torque sensor 15) are very sensitive to temperature. The influence of temperature could be a significant factor in the comparability of the data. The rotation angle of the outer ring calculated by the microprocessor 303 is in the embodiment 7 passed on to the electric motor 20 positioned on the input side, which is controlled specifically, taking into account the angle of rotation to be compensated.

A task of the in 7 The evaluation unit 41 shown is to evaluate the measurement data from the torque sensor and determine how many teeth were skipped during a meshing fault.

Using the flowchart in 8th An exemplary embodiment of a method for compensating the angular offset 400 will be explained below. In a first method step 401, an intervention fault 62 is detected. The direction of rotation is then detected and the number of skipped teeth is determined in a second method step 402 using the described method for detection and quantification. The direction of rotation of the electric motor 20 can be determined either via the position sensor 50 or via a speed sensor on the electric motor 20. In the 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 already explained above.

If these procedural steps have been completed, the first query 404 determines to what extent an engagement 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 the fourth method step 408 and passes on the calculated angle of rotation to the electric motor 20 and/or carries out a “reset” of the position sensor 50. If the first query 405 is positive, a second query 406 is advanced. In the second query 406 it is determined whether the ratchet torque in the current engagement fault 62 has reduced compared to the ratchet torque in the previous engagement fault 62 at the same position, with the amount of the torque curve 60 being used in this embodiment. Alternatively, it would also be possible to consider the maxima of the first damped oscillation 62' of an engagement disturbance or to consider an average value from a plurality of damped oscillations within an engagement disturbance 62. This comparison of the ratchet torques of engagement faults 62 that occurred at the same positions is supported via the internal storage unit 304. The comparison of these ratchet torques enables the evaluation unit 41 to estimate the wear of the tension shaft gear 10 and the potential service life. Furthermore, damage to the teeth in the tension wave gear 10 can be determined using this comparison. It would be conceivable for the evaluation unit 41 to give the user an assessment of the condition, wear and/or the estimated remaining service life of the tension shaft gear 10 based on the comparison of the torques.

If the second query 407' is negative, it can be assumed that there is damage in the voltage wave transmission 10, so that an alternative fourth method step 409 is proceeded to. In this 409, an error message is displayed for the user. Furthermore, it is conceivable to install several stages, so that a system 300 could assume a small case of damage in the event of a small increase in the ratchet torque in the event of a later engagement fault 62 compared to the previous engagement fault 62 at the same position and only output an error message. On the other hand, if the ratchet torque increases significantly, the system 300 can be controlled into an emergency stop so that no further damage can occur within the tension shaft gear 10.

If the second query 407 is positive, the fourth method step 408 is advanced and continued as already explained. Alternatively, in a preferred embodiment, an error message could be issued despite a positive second query 407 if the ratchet torque is significantly lower than the previous ratchet torque. A third query would then be required for this, which can classify the exact decrease or increase in the ratchet torque. A sharp drop could also indicate damage or significant wear on the teeth of the tension shaft gear 10.

List of reference symbols:

1

Internal gearing

2

External gearing

3

Movement of a tooth in the external toothing

4

Detail

10

Tension wave gear

11

Outer ring

12

transmission ring

13

Wave generator

14

rolling elements

15

Torque sensor

20

Electric motor

21

Rotor shaft

30

Braking device

34

reference point

36,37, 38

Deformation lines

40

Electrical unit

41

Evaluation unit

50

Position sensor

60

Torque curve

61

Ratchet torque

62

Intervention interference

62'

dampened vibration

63

Angular offset depending on a skipped tooth

64

Angular misalignment due to an engagement fault

100

Drive module

200

robot

201

arm segment

300

Sensor system

301

Filters and amplifiers

302

Analog/digital converter

303

microprocessor

304

internal storage unit

400

Method for compensating an angular misalignment

401

first step of the process

402

second procedural step

403

third step of the process

404

first query

405

positive first query

405'

negative first query

406

second query

407

positive second query

407'

negative second query

408

fourth step of the process

409

alternative fourth process step

Claims (10)

Method for detecting and quantifying a meshing fault (62) of a voltage wave transmission (10), which has an input-side shaft generator (13), an output-side, rigid outer ring (11) with internal teeth (1) and an elastically deformable transmission ring (12) with external teeth ( 2), which is in engagement with the internal toothing (1) of the outer ring (11), the method comprising the following method steps: - Measuring a temporal torque curve (60) on the deformable transmission ring (12), - Detecting an engagement fault (62) based on the measured torque curve (60), - Determining a number of teeth skipped during the detected engagement fault (62) based on the measurement of the torque, - Calculating an angular offset between the transmission ring (12) and the outer ring (11), which corresponds to the determined number of teeth. Procedure according to Claim 1 , characterized in that the torque curve (60) over time takes place by means of a torque sensor (15) arranged on the deformable transmission ring (12), which preferably has one or more strain gauges. Method according to one of the preceding claims, characterized in that measuring the temporal torque curve (60) comprises measuring a direction of rotation of the wave generator (13) and/or an amount of the torque. Method according to one of the preceding claims, characterized in that an event of a damped oscillation (62') is recognized in the measured torque curve (60) in order to detect the engagement disturbance (62). Procedure according to Claim 4 , characterized in that in order to determine the number of teeth skipped during the detected engagement disturbance (62), a number of successive damped oscillations (62 ') in the measured torque curve (60) is determined. Method according to one of the preceding claims, characterized in that the angular offset is calculated as $\Delta \theta =\left(\frac{360°}{\Delta \mathrm{e.g}c}\cdot \Delta \mathrm{e.g}s\right)/i,$

where Δzs is the number of skipped teeth, Δzc is the number of teeth of the internal toothing (1) of the outer ring (11) and i is the transmission ratio. Method for compensating for a meshing fault (62) of a tension shaft gear (10) in a drive system, in particular a robot (200), wherein the tension wave gear (10) has an input-side shaft generator (13), an output-side, rigid outer ring (11) with an internal toothing (1 ) and an elastically deformable transmission ring (12) with external teeth (2) which engage with the internal teeth (1) of the outer ring (11), the drive system comprising a rotary encoder for measuring the rotational position of the wave generator (13) of the voltage wave gear ( 10), wherein a method for detecting and quantifying an engagement fault (62) is carried out according to one of the preceding claims and the calculated angular offset is transmitted to an evaluation unit (41) connected to the rotary encoder, which detects the engagement fault (62) based on the calculated angular offset compensated. Procedure according to Claim 7 , characterized in that a rotational position of the outer ring (11) at which the engagement fault (62) occurred is determined based on the rotational position of the shaft generator (13), the rotational position together with the determined torque value when the engagement fault (62) occurs, and optionally stored together with the number of teeth skipped during the detected engagement fault (62) for later comparison. Procedure according to Claim 8 , characterized in that it is checked whether a torque when the engagement fault (62) occurs is smaller than a stored torque at the same rotational position of the outer ring (11) in the event of a previously detected engagement fault (62). Drive module (100) with a voltage wave gear (10), which comprises an input-side wave generator (13), an output-side, rigid outer ring (11) with internal teeth (1) and an elastically deformable transmission ring (12) with external teeth (2), which is in engagement with the internal toothing (1) of the outer ring (11), the drive module (100) being configured to carry out the following method steps: - Measuring a torque curve over time on the deformable transmission ring (12), - Detecting an engagement fault (62) based on the measured torque curve (60), - Determining a number of teeth skipped during the detected engagement fault (62) based on the measurement of the torque and - Calculating an angular offset between the transmission ring (12) and the outer ring (11), which corresponds to the determined number of teeth.

Images