Method for operating a drive system to avoid interference in voltage wave gearboxes

Abstract

Method for operating a drive system, wherein the drive system comprises an electric machine (20) and a voltage wave gear (10) which has a shaft generator (13) coupled to the electric machine (20), a rigid outer ring (11) with an internal toothing (1) and an elastically deformable transmission ring (12) with an external toothing (2) which engages with the internal toothing (1) of the outer ring (11), wherein the method comprises the following process steps: Measuring a torque applied to the transmission ring (12) using a torque sensor (15), Detecting an intervention fault (62) based on the measured torque and Storing a critical torque value that occurred during the intervention fault (62), Determining a torque threshold (63) that is less than or equal to the critical torque value and Controlling the electric machine (20) such that the torque exerted on the transmission ring (12) is less than the torque threshold value (63), characterized by the fact that the electric machine (20) is additionally controlled in such a way that if the torque threshold value (63) or the stored critical torque value is exceeded, the electric machine is operated in a freewheeling state.

Description

[0001] The invention relates to a method for operating a drive system, wherein the drive system comprises an electric machine and a voltage wave gear. The invention further relates to a drive system comprising an electric machine and a voltage wave gear.

[0002] Strain wave gearing (also known as harmonic drive or wave gearing) enables virtually backlash-free power transmission with a high gear ratio and is therefore particularly suitable for applications requiring precise movements and a small footprint. Because the high gear ratio allows for the generation of high torques with relatively small motors, strain wave gearing enables the creation of very compact drive mechanisms, which are used, for example, in robotics.

[0003] A stress-wave transmission consists primarily of a wave generator, a rigid outer ring (circular spline) with internal teeth, and a flex spline transmission ring with external teeth positioned between them. Unlike rigid transmissions, the transmission of torque between the wave generator and the outer ring is based on elastic deformation. The wave generator deforms the transmission ring into an oval shape, causing it to engage with the outer ring on two opposite sides of its circumference. As the wave generator rotates, the transmission ring rolls on the outer ring, and the interlocking teeth transmit torque between the transmission and outer rings. The transmission ratio is determined by the difference in the number of teeth on the transmission and outer rings.

[0004] If excessive torque is applied during operation, for example, when the gearbox is working against high resistance, the engagement between the transmission ring and the outer ring can be at least partially lost, causing the teeth of the transmission ring to skip over the teeth of the outer ring ("ratcheting"). While the rotation of the transmission ring and the outer ring are strictly coupled during normal operation, such a failure of engagement leads to a temporary, uncontrolled relative rotation between the two rings. This creates an unknown angular offset on the output side compared to the input side, making precise control of the angular position impossible. Furthermore, since the condition of the gearbox does not reveal whether such a failure of engagement has occurred, troubleshooting the subsequent malfunction is made more difficult.

[0005] In this context, JP 2021014876 A discloses a method in which the torque acting on the output side of a tension shaft drive is measured and compared with two threshold values. Exceeding the first threshold value serves as an indication of a clutch failure, while exceeding the second threshold value indicates possible buckling of the transmission ring. A disadvantage of this method is, firstly, that the critical torque (ratcheting torque), at which a clutch failure is highly likely to occur, varies from drive to drive. Secondly, such a simple threshold method cannot reliably determine whether a clutch failure actually occurred or whether the temporarily occurring high torque was dissipated without any issues.Furthermore, these interference faults can lead to damage in the tension wave drive, with interference faults becoming a self-reinforcing phenomenon as operating time increases. Locally increased wear on the gear teeth of the tension wave drive and high output torques required in repetitive operating cycles lead to an increased potential for local interference faults.

[0006] DE 10 2021 113 139 B3 describes a method for operating a robotic system with a gearbox and a sensor device, which determines the torque applied to the gearbox. The method includes a determination step and a calibration step, whereby the robot's operating parameters are adjusted depending on the calibration.

[0007] JP 2021-14 876 A describes a fault detection device for a shaft transmission with a torque detector on an output side of the shaft transmission and a determination unit for determining the failure of the shaft transmission based on the torque detected by the torque detector.

[0008] DE 10 2019 210 795 A1 describes a stress wave gearbox with a vibration sensor, the signals of which are used to determine load data and / or to make statements about the gearbox condition and / or to detect critical operating conditions.

[0009] Against this background, the task arises to provide a procedure and a system that can reduce the probability of interventional complications occurring.

[0010] The problem is solved by a method for operating a drive system, wherein the drive system comprises an electric machine and a voltage wave gear, which has a shaft generator coupled to the electric machine, a 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 process steps: - Measuring the torque exerted on the transmission ring using a torque sensor, - Detecting an intervention fault based on the measured torque and storing a critical torque value that occurred during the intervention fault, - Determining a torque threshold that is less than or equal to the critical torque value and - Controlling the electric machine in such a way that the torque exerted on the transmission ring is less than the torque threshold value.

[0011] Furthermore, this task is solved by a drive system comprising an electric machine and a voltage wave gear, which includes a shaft generator coupled to the electric machine, a 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 drive system is configured to perform the following process steps: - Measuring the torque exerted on the transmission ring using a torque sensor, - Detecting an intervention fault based on the measured torque and storing a critical torque value that occurred during the intervention fault, - Determining a torque threshold that is less than or equal to the critical torque value and - Controlling the electric machine in such a way that the torque exerted on the transmission ring is less than the torque threshold value.

[0012] If a malfunction is detected based on the measured torque, the critical torque value that occurred during the malfunction is stored. This torque value can correspond to a ratchet torque. According to the invention, after the detection of an engagement fault and the storage of the critical torque value, a torque threshold value is determined which is less than or equal to the critical torque value. Subsequently, the electric machine is controlled such that the torque exerted on the transmission ring is less than or equal to the level of the previously determined torque threshold value. This method according to the invention makes it possible to significantly reduce the probability of further engagement faults occurring. In a particularly preferred case, a further engagement fault can be completely avoided by the method and drive system according to the invention.

[0013] The shaft generator of the voltage wave drive is formed, in particular, by a disk with an oval, for example elliptical, shape connected to a drive shaft. The disk preferably has a rolling bearing shrunk onto its circumference, comprising a thin, elastically deformable raceway and several rolling elements. The transmission ring can be, for example, cup-shaped or silk-hat-shaped; that is, the transmission ring is formed, in particular, by a cylindrical wall of a cup-shaped or silk-hat-shaped bushing, which can be made, for example, of steel. These are common design options for the transmission ring, which allow for a preload of the transmission ring relative to the shaft generator.In particular, the measured torque can be analyzed and evaluated by an evaluation unit that determines the rate of change of the torque and compares it to a decrease threshold. For example, a rate of change over time can be determined and compared to the decrease threshold, especially by calculating the difference or numerically differentiating the torque measurements. It is also conceivable that the comparison checks whether the measured torque has decreased by at least a predetermined amount within a specified time period. The decrease threshold can, in particular, be a relative decrease threshold, meaning that the comparison checks whether the measured torque has decreased by at least a predetermined percentage.If the acceptance threshold is exceeded, a warning signal is triggered, which can be transmitted in particular to an external data processing unit, such as a control and monitoring unit of the voltage wave drive.

[0014] The detection of a misalignment can be based on the temporal profile of the measured torque at the deformable transmission ring. This reflects the dynamic behavior of the torque transmission before and during the misalignment. Typically, an excessively high torque builds up prior to the misalignment, eventually causing the teeth of the transmission ring to lose engagement with the outer ring and skip its teeth. The accumulated torque is then rapidly reduced. This decrease in torque can serve as a characteristic signature of a misalignment and enable its reliable detection.

[0015] Furthermore, during detection, the measured torque can be compared with at least one threshold value. The decrease in the measured torque over time is only determined and compared with the threshold value if an exceedance of the threshold value is detected. The threshold value serves to distinguish between load peaks occurring during normal operation and excessively high torques that indicate or precede a malfunction. For example, during each start-up or stop-down process, the transmission must overcome the inertia of the load coupled to the output or driven side, which manifests itself as 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 collides with an obstacle, the gearbox briefly works against high resistance (impact torque) before the impact is registered. At very high torques, the mechanical load-bearing capacity of the transmission ring is eventually exceeded, causing it to buckle (buckling torque). The ratcheting torque lies between the impact torque and the buckling torque, and this is typically where engagement malfunctions are triggered. The threshold value used in the method can, for example, correspond to the impact torque or the ratcheting torque. Preferably, the threshold value lies between the impact torque and the buckling torque or between the impact torque and the ratcheting torque.

[0016] In the method according to the invention, the critical torque value, for example the ratchet torque, which occurred during the engagement fault, can be stored in an internal storage unit in or on the voltage wave gear, wherein this unit can be arranged in the evaluation unit of the input-side electric machine. Alternatively or additionally, it is conceivable that the critical torque value, in particular the critical ratchet torque, can be transmitted to an external storage unit via a wired or wireless connection.

[0017] According to a preferred embodiment, the torque threshold is determined based on the detected critical torque. The detected critical torque is preferably included in the determination of the torque threshold. For example, a safety factor is stored in an evaluation unit, defining a relationship between the detected critical torque and the torque threshold to be determined. For instance, the torque threshold can be determined as a predetermined percentage of the detected critical torque. To maintain the efficiency and effectiveness of the stress wave drive, this percentage should not be too low, as the drive would otherwise only be able to deliver a fraction of the required torque. For example, the percentage can be chosen between 80% and 95%.The safety factor or percentage can be adjusted by the evaluation unit during operation or be a fixed, empirically determined value. The embodiment with a variable safety factor or percentage is particularly advantageous, as it can be assessed more conservatively, for example, with increasing service life. With progressive service life and increasing wear, the probability of a failure increases. Therefore, the safety factor or percentage can be chosen lower in a tension wave drive with a long operating time to prevent a recurrence of a failure. In a tension wave drive with only a few operating hours, the safety factor or percentage can be chosen higher, as a failure is less likely.Alternatively, a safety margin can be stored in the evaluation unit, for example an absolute value that defines the torque threshold as the difference between the detected critical torque and the absolute value.

[0018] According to a preferred embodiment, further engagement faults are detected based on the measured torque, and the additional critical torque values ​​occurring during these faults are stored. The torque threshold is then determined based on these stored critical torque values. In this context, an engagement fault describes a "slippage" of the teeth of the transmission ring relative to the teeth of the outer ring. In such a fault, one or more teeth may be skipped, and the teeth must be arranged adjacent to each other. The torque threshold is then determined based on several, in particular all, stored critical torque values.In this way, the torque threshold can be lowered further, for example, if another intervention fault occurs at a critical torque that is below the currently used torque threshold. For instance, a lowest critical torque value can be determined from several critical torque values ​​and then used to determine the torque threshold.

[0019] According to a preferred embodiment, an initial critical torque value is determined and stored during the initial commissioning or manufacturing of the drive system, and the torque threshold is additionally determined based on this initial critical torque value. Since even a single instance of interference can cause increased wear, it is highly desirable to avoid interference for as long as possible. A torque threshold preset before initial operation reduces the probability of interference occurring, particularly during the first few hours of operation. Thus, a torque threshold can be determined or set based on experimentally obtained data from manufacturing, empirical data, or data obtained during the initial commissioning of the drive system.In particular, during an experimental test series, initial critical torque values ​​can be determined, which serve as the basis for the first torque threshold value.

[0020] According to a preferred embodiment, when a malfunction is detected, a torque curve and / or a load curve are additionally stored, and the torque threshold is further determined based on the stored torque or load curve. Storing the torque or load curve makes it possible to identify whether torque and / or load maxima occur repeatedly, particularly when certain areas, especially teeth, of the internal and / or external gearing are in mesh with each other. This allows for the early detection of wear in these specific areas, especially teeth. If wear is detected in a particular area, the torque threshold can be selected to minimize further wear in this area or to reduce the risk of a malfunction occurring in this area.

[0021] In a preferred embodiment, the drive system includes a position sensor, the position of which is stored when a malfunction occurs. The position sensor allows the malfunction to be attributed to a specific area, in particular a tooth, of the transmission ring.

[0022] According to the invention, at least one control parameter is set to control the electric machine depending on the determined torque threshold value; namely, a control parameter that influences the acceleration and / or deceleration behavior of the electric machine. Alternatively, the control parameter can influence the cycle time for a duty cycle.

[0023] According to a preferred embodiment, the electric machine is additionally controlled such that it enters a freewheeling state when an overload torque threshold greater than the determined torque threshold is exceeded and / or when a predetermined overload torque increase is exceeded. The freewheeling state describes a condition in which the electric machine provides no input torque. The electric machine can be switched off, thus acting as a damper. The freewheeling state is relevant not only for protecting the voltage wave drive but also for personal safety in applications where the drive system is used in the arm of a collaborative robot.Such collaborative robots work closely with a person, for example, and the person can be protected by putting the electric machine into freewheeling mode in the event of a collision with the robot.

[0024] In the voltage wave transmission, the transmission ring is preferably fixed. The wave generator can form the input of the voltage wave transmission, and the rigid outer ring the output. Both the wave generator and the outer ring are preferably rotatably mounted.

[0025] Further details and advantages of the invention will be explained below with reference to the exemplary embodiment shown in the drawings. This shows: Fig. 1. An exemplary embodiment of a robot in a schematic representation; Fig. 2 a schematic sectional view of a tension wave gear, as well as a tooth mesh intact in operation; Fig. 3 a schematic interference fault, as well as a deformation of a transmission ring for measuring a torque; Fig. 4 a sectional view of a drive system; Fig. 5 a sectional view of a stress wave gear; Fig. 6. A first torque curve with an intervention fault, based on which a torque threshold value is determined, and a further torque curve taking into account the determined torque threshold value; Fig. 7 a second torque curve with an intervention fault based on which a torque threshold value is determined and a further torque curve taking into account the determined torque threshold value; Fig. 8 a load cycle of a drive system; Fig. 9 an excerpt of the load cycle' from Fig. 8; Fig. 10 a control loop for the drive system and Fig. 11 a schematic flowchart of an embodiment of the inventive method for operating a drive system.

[0026] Fig. Figure 1 shows a schematic representation of an embodiment of an industrial robot 200 with several arm segments 201, each rotatably connected via drive modules 100. Although the industrial robot 200 shown here has three arm segments 201 and three drive modules 100, embodiments 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, one drive module 100 can be used for any of the robot's joints. Such industrial robots 200 are often used as collaborative robots that work in close cooperation with humans.

[0027] In the Fig. Figure 2 schematically depicts a typical configuration of a stress wave drive 10. The main components of the stress wave drive 10 are a shaft generator 13, a rigid outer ring 11 ("circular spline") with internal teeth 1, and a flexible transmission ring 12 ("flexspline") with external teeth 2 arranged between them. The shaft generator 13 is formed by an oval disk connected to a 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 by the shaft generator 13, whereby each individual tooth of the transmission ring 12 is moved out of a gap between two teeth of the outer ring 11 and into the next gap during a 180° rotation of the shaft generator 13 (indicated by arrow 3 in section 4).In this way, the transmission ring 12 rotates relative to the outer ring 11 in the opposite direction to the rotation of the shaft generator 13, thereby transmitting a torque between the two rings 11 and 12. The output of the tension shaft drive 10 can be provided either via the transmission ring 12 (with the outer ring 11 fixed) or via the outer ring 11 (with the transmission ring 12 fixed). In the following, the output of the tension shaft drive is described as being provided via the outer ring 11.

[0028] As a consequence of excessively high torque, the engagement between the gear teeth 1 and 2 can be temporarily lost, so that one tooth of the transmission ring 12 can skip several teeth of the outer ring 11 during a so-called misalignment 62 (indicated by arrow 62). While in normal operation the gearing between the rings 11 and 12 maintains a strict relationship between the respective angles of rotation, such a misalignment results in an uncontrolled relative rotation and a consequent angular displacement 64.

[0029] In Fig. Figure 3 schematically depicts the dynamic deformation of the transmission ring 12 during various phases of the engagement failure. The transmission ring 12 is designed as a cylindrical, hat-shaped bushing (“silk-hat”) (see figure on the left), the upper edge of which has the external teeth 2, which in turn engage with the internal teeth 1 of the outer ring 11. The degree of deformation of the cylindrical wall of the transmission ring 12 is shown at three successive time points, along with the corresponding state of the teeth 1 and 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 lines 36, 37, and 38 represent the corresponding twisting of the transmission ring 12. In the first phase, the engagement between rings 1, 2 is still intact, but an increasingly strong torque builds up due to the elastic twisting 36 of the transmission ring 12.As the twist increases, the torsional stiffness of the transmission ring 12 also increases, causing the torque to rise sharply and finally reach its maximum value at deformation 37. Upon reaching this critical value, a disengagement 62 is triggered, in which the engagement of the gear teeth 1, 2 is at least partially disengaged, the twist rebounds, and the external gear 2 jumps relative to the internal gear 1. After the jump, the line 38 no longer ends at the reference point 34 as before, but exhibits an angular offset from it, corresponding to the resulting offset between the rotation angles 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 displayed as a torque curve 60 (see figure 60). Fig. 6) be made usable over time.

[0030] In the Fig. Figure 4 shows an embodiment of a drive module 100 for moving an arm segment 201 of an industrial robot 200, which is used in the industrial robot 200 according to Fig. 1. The drive module 100 comprises a gearbox designed as a voltage wave gearbox 10, an electric machine 20, and a braking device 30. A further component of the drive module 100 according to the exemplary embodiment is an electronic unit 40. The wave generator 13 is formed by an oval disk on the circumference of which several rolling elements 14 are arranged, which roll on the inside of the transmission ring 12.

[0031] The wave generator 13 of the voltage wave gear 10 is coupled to the electric machine 20, here to the rotor shaft 21 of the electric machine 20. The electric machine 20 can be designed as an axial flux machine or as a radial flux machine.

[0032] The rotor shaft 21, and thus also the shaft generator 13, is coupled to the braking device 30, by means of which the rotor shaft 21 can be decelerated and / or locked in position. The rotor shaft 21 is also coupled to a position sensor 50, which can determine the position, in this case the angular position, of the rotor shaft 21. The position sensor 50 is preferably designed as an optical or magnetic rotary encoder or rotary angle encoder. The torque sensor 15 and the position sensor 50 allow the magnitude of the torque between the rings 11 and 12 and the direction of rotation of the shaft generator to be determined.

[0033] Fig. Figure 5 shows a detail of the tension wave gear 10 of the drive module 100. Fig. 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. According to the exemplary embodiment, the torque sensor 15 comprises 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 electronic unit 40, cf. Fig. 4.

[0034] In Fig. 6 and Fig. Figure 7 shows two torque curves 60 and 60' over time t that can occur during the execution of the method according to the invention. The first torque curve 60 represents an operating situation in which an engagement fault 62 occurs and is detected. The second torque curve 60' represents a corresponding operating situation in which the electric machine is controlled as a result of the detected engagement fault 62 such that the torque at the transmission ring 12 is less than a torque threshold value 63, which is determined based on a critical torque value that occurred during the engagement fault.

[0035] The torque exerted on the transmission ring 12 is measured using one or more torque sensors 15. The interference fault 62 is detected based on the measured torque. The interference fault 62 is in Fig. 6 and Fig. 7 each recognizable as a damped oscillation. The critical torque value occurring during a malfunction 62, for example the ratchet torque 61, which is present when teeth 1 and 2 first "slip," is stored. The torque threshold value 63 is then determined based on the critical torque value, whereby this value is less than or equal to the critical torque value 61. As shown by the second torque curve 60', the electric machine is then controlled such that the torque exerted on the transmission ring 12 is less than the fixed torque threshold value 63.

[0036] The difference between the in Fig. embodiment shown in 6 and in Fig. In the embodiment shown in Figure 7, the second torque curve 60', 60'' is established when the electric machine is driven with the torque threshold value 63. While the second torque curve 60' according to Fig. 6 exhibits the same phases of torque increase and decrease as the first torque curve 60, the second torque curve 60'' follows according to Fig. 7 results from a control strategy in which the phases of torque rise and fall are changed compared to the first torque curve 60. Such a modified control strategy can be achieved, for example, by adapting control parameters used to control the electric machine.

[0037] Fig. Figure 8 illustrates the changes in a speed profile during an exemplary operating cycle 80 of a drive system that can result from changes in control parameters, such as those related to Fig. 7 were explained. This work cycle 80 represents a repetitive task of a drive system. A first speed profile 81 is shown, which corresponds to the first torque profile 62. As a result of determining the torque threshold 63 and changing the control parameters, a second speed profile 62 results for the same work cycle, which corresponds in particular to the second torque profile 60''.

[0038] In Fig. 8 shows that in the second speed profile 82 the acceleration and braking behavior has changed compared to the first speed profile 81. Fig. Figure 9 shows a section 83 of the processes 81, 82 from Fig. 8. It can be seen that the second rotational speed profile 82 has an initially lower acceleration (84') than the first rotational speed profile 81, which transitions into an increased acceleration (84'') compared to the first rotational speed profile 81 and ends at the end of the acceleration process (84''') again in a lower acceleration than in the first rotational speed profile 81.

[0039] In Fig. Figure 10 shows an exemplary control system 1000 for a drive system. The control system 1000 comprises a position controller 70, a speed controller 71, a current controller 72, an inverter 73, a frequency converter 74, a speed-to-velocity converter 75, the electric machine 20, the position sensor 50, the voltage wave gear 10, and the torque sensor 15. The control system 1000 is designed such that it includes three cascaded control loops. The first control loop is the position control loop 70'. In addition, the control system 1000 has a speed control loop 71' and a current control loop 72'.

[0040] The torque threshold value determined within the framework of the method according to the invention can be taken into account in the current control loop. The torque threshold value 63 can be supplied to the current controller 72, so that the control of the electric machine 20 is such that the torque exerted on the transmission ring 12 is lower than the torque threshold value 63. If control parameters are changed in the method depending on the determined torque threshold value 63, these changes can affect the speed controller 71, and optionally also the position controller 70.

[0041] Fig.Figure 11 shows a flowchart of an embodiment of a method for preventing interference faults 300. In an optional first process step 301, an initial torque threshold can be defined during the initial commissioning of the drive system or during its manufacture. This threshold is then considered as the upper limit of the torque at the transmission ring 12 when controlling the electric machine. The initial torque threshold can be determined by measuring an initial critical torque value or based on empirical data from identical drive systems. The torque threshold 63 can thus be preset before the initial commissioning of the drive system, thereby preventing the occurrence of an initial interference fault 62 at an early stage of operation.

[0042] After commissioning of the drive system, malfunctions can still occur, for example due to wear, even at a predetermined torque threshold. In a second process step 302, such a malfunction 62 can be detected. For this purpose, the torque exerted on the transmission ring 12 is measured using a torque sensor 15. In a third process step 303, the critical torque value that occurred during the malfunction 62 is stored.

[0043] In a first query 304, it is checked whether the measured torque is greater than a predefined overload torque threshold or whether the increase in the measured torque is greater than a predefined overload torque increase. If either of these thresholds is exceeded, the electric machine is put into a freewheeling state 309. Following the transition to the freewheeling state 309, a fifth process step 310 checks whether the current torque value is acceptable for the drive system or still significantly too high. If the torque value is too high, an emergency shutdown is initiated in the sixth process step 311.

[0044] If query 305' is negative, procedure 300 continues with a second query 306. The second query 306 checks whether the current torque exceeds the stored ratchet torque 61. The stored ratchet torque 61 describes the last critical torque or a plurality of stored critical torques that have occurred. If the second query 307 is positive, the process jumps directly to the sixth step 311, which initiates an emergency shutdown.

[0045] If the second query 307' is negative, the process proceeds to the fourth step 308. The fourth step 308 comprises the normal operation of the drive system by controlling the electric machine 20 such that the torque exerted on the transmission ring 12 is less than the determined torque threshold value 63.

[0046] If several intervention faults 62 occur during the operation of the drive system, all critical torque values ​​occurring during these intervention faults 62 are stored. The torque threshold value 63 used in the control process step 308 is then determined based on all stored critical torque values, for example, by determining the lowest critical torque value and using it to determine the torque threshold value. Reference symbol list 1 Internal toothing 2 External teeth 3 Movement of a tooth of the external toothing 4 Excerpt 10 voltage wave gears 11 Outer ring 12 transmission ring 13 Wave generator 14 rolling elements 15 Torque sensor 20 electric machine 21 Rotor shaft 30 Brake system 34 Reference point 36, 37, 38 Deformation lines 40 electronic unit 41 Evaluation unit 50 Position sensor 60 Torque curve 60' new torque curve 60'' alternative new torque curve 61 ratchet torque 62 Interventional disorder 63 new torque threshold 70-position controller 70' Position Control Loop 71 Speed ​​controllers 71' Speed ​​control loop 72 current controllers 72' Current control loop 73 inverters 74 converters 75 Speed-to-Speed ​​Converter 80 duty cycle 81 Speed ​​curve 82 new speed curve 83 Excerpt of the processes 84', 84'', 84''' changed acceleration 100 drive module 200 robots 201 Arm segment 300 methods for avoiding interventional complications 301 first procedural step 302 second procedural step 303 third procedural step 304 first query 305 positive first query 305' negative first query 306 second query 307 positive second query 307' negative second query 308 fourth procedural step 309 Freewheel condition 310 fifth procedural step 311 sixth procedural step 1000 control for a drive system

Claims

[1] Method for operating a drive system, wherein the drive system comprises an electric machine (20) and a voltage wave transmission (10) comprising a wave generator (13) coupled to the electric machine (20), a rigid outer ring (11) with an internal toothing (1) and an elastically deformable transmission ring (12) with an external toothing (2) which engages with the internal toothing (1) of the outer ring (11), wherein the method comprises the following process steps: Measuring a torque applied to the transmission ring (12) using a torque sensor (15), Detecting an intervention fault (62) based on the measured torque and Storing a critical torque value that occurred during the intervention fault (62), Determining a torque threshold (63) that is less than or equal to the critical torque value and Controlling the electric machine (20) such that the torque exerted on the transmission ring (12) is less than the torque threshold value (63), characterized by , that the electric machine (20) is additionally controlled in such a way that if the torque threshold value (63) or the stored critical torque value is exceeded, the electric machine is operated in a freewheeling state. [2] Method according to claim 1, characterized by , that the determination of the torque threshold (63) is carried out on the basis of the detected critical torque. [3] Method according to claim 2, characterized by, that further intervention disturbances (62) are detected based on the measured torque, and the further critical torque values ​​occurring in these intervention disturbances (62) are stored, whereby the torque threshold value (63) is additionally determined based on the stored further critical torque values. [4] Method according to claim 2 or 3, characterized by , that during the initial commissioning of the drive system or during the manufacture of the drive system an initial critical torque value is determined and stored and the torque threshold value (63) is additionally determined on the basis of the initial critical torque value. [5] Method according to any one of the preceding claims, characterized by, that when detecting the intervention fault (62) a torque curve and / or a load curve is additionally stored and the torque threshold value (63) is additionally determined on the basis of the stored torque curve and / or load curve. [6] Method according to any one of the preceding claims, characterized by , that to control the electric machine (20) at least one control parameter is set depending on the determined torque threshold value (63), namely a control parameter that influences the acceleration behavior and / or the braking behavior of the electric machine (20). [7] Drive system comprising an electric machine (20) and a voltage wave gear (10) comprising a wave generator (13) coupled to the electric machine (20), a rigid outer ring (11) with an internal toothing (1) and an elastically deformable transmission ring (12) with an external toothing (2) which engages with the internal toothing (1) of the outer ring (11), wherein the drive system is configured to perform the following process steps: Measuring a torque applied to the transmission ring (12) using a torque sensor (15), Detecting an intervention fault (62) based on the measured torque and Storing a critical torque value that occurred during the intervention fault (62), Determining a torque threshold (63) that is less than or equal to the critical torque value and Controlling the electric machine (20) such that the torque exerted on the transmission ring (12) is less than the torque threshold value (63) Controlling the electric machine (20) such that if the torque threshold (63) or the stored critical torque value is exceeded, the electric machine is operated in a freewheeling state.

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