System and method for measurement and / or compensation on a strain wave gear
Patent Information
- Application Number
- PCT/EP2026/058677
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-26
- Filing Date
- 2026-03-26
- Publication Date
- 2026-10-01
Smart Images
Figure EP2026058677_01102026_PF_FP_ABST
Abstract
Description
[0001] Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0002] 1
[0003] Title: System and method for measuring and / or compensating on a stress wave gear
[0004] The invention relates to a system for measuring and / or compensating on a stress wave gear according to the preamble of claim 1. It further relates to a method for measuring and / or compensating on a stress wave gear and a stress wave gear.
[0005] The performance requirements of modern powertrains are becoming increasingly difficult to meet using only components from conventional drive technology. These requirements can only be met by incorporating advanced mechatronic elements and methods.
[0006] Voltage wave gears, or wave gears, are frequently used in drive trains as reduction gears to, for example, convert the rapid rotation of an electric motor at low torque into a slow, precise movement at high torque. This conversion is required, for example, in robots (industrial, cobots, medical), machine tools, or in the aerospace industry. Specific applications often give rise to further requirements, such as measuring the (output-side) torque, compensating for the inherent transmission error (vibration excitation by the gear), active damping of (externally excited) vibrations, or adaptable torsional stiffness (damper function, "variable stiffness actuator").
[0007] Actuator functions (error compensation, active damping) are currently often implemented via the main drive or electric motor. However, this is significantly limited by the achievable bandwidth in terms of electrical and mechanical time constants. Current sensor solutions for torque measurement often utilize... Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0008] 2
[0009] Additional structures that cause additional and detrimental compliance in the system.
[0010] From WO 2021 / 239317 A1, a drive device is known which comprises a drive motor with a drive shaft rotatable about a central axis. It further comprises a base and a gear unit with a stationary element, an input element, and an output element, wherein the input element of the gear unit is rotationally fixed to the drive shaft of the drive motor. It further comprises at least one solid-state actuator with a first end fixed to the base and a second end fixed to the stationary element of the gear unit. The gear unit can be designed as a tension wave drive. A piezoelectric element can be arranged between the base and the stationary element of the tension wave drive.
[0011] US 2018 / 0239327A1 describes a position control device for an actuator equipped with a strain-wave gearbox, comprising a closed-loop control system for feedback on the position of a load shaft and for driving and controlling a motor to position the load shaft at a target position. The closed-loop control system incorporates an H°° compensator designed such that, when a generalized system with angular transmission errors in the strain-wave gearbox is assumed as the disturbance input, the Hoo values of a transfer function from the disturbance input of the generalized system to a control output are a predetermined value or less. Mechanical vibrations during the positioning process, caused by the disturbance error in the strain-wave gearbox, can be reliably suppressed.
[0012] Based on the disadvantages described above, the invention aims to provide a system for measuring and / or compensating on a Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0013] 3
[0014] To provide a stress wave drive in which the sensory and / or actuator properties of the stress wave drive are improved. Furthermore, a corresponding method should be provided. In addition, an improved stress wave drive should be specified.
[0015] These and other tasks are solved with a system for measuring and / or compensating on a stress wave gear according to claim 1 and a method for measuring and / or compensating on a stress wave gear according to claim 11.
[0016] The system comprises a stress wave drive, including at least the components flexspline, circular spline, and wave generator, wherein a smart element, which consists at least partially of a smart material, is arranged in and / or on at least one component of the stress wave drive. The system further comprises a measurement and / or control unit, which is connected to the at least one smart element via a signal path.
[0017] Preferred embodiments of the invention can be found in the dependent claims and furthermore in the following description, which in particular includes various embodiments as described in the appended claims. The person skilled in the art will understand that each embodiment described in the following description is covered and encompassed by the subject matter of the appended claims. The embodiments, features, and combinations of features described herein in connection with the invention, as well as the combinations of features specified in the appended claims, and also any combination of features mentioned and described in connection with the embodiments, are deemed to be disclosed herein, or at least to be derivable by the person skilled in the art. In particular, each feature and each combination of Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0018] 4
[0019] Features in the embodiments described herein may, for example, be claimed in a different combination, in particular in a different claim category, at least because the person skilled in the art will recognize that each combination of the features mentioned herein is suitable for solving the underlying problem.
[0020] Furthermore, any feature and any combination of features in the claims and in the description below can be used and claimed independently of the specific claimed subject matter, independent of claim dependencies and cross-references, and independent of the claim category in which the feature is claimed. For example, it can be provided in any combination selected from one or more claims, one or more of the embodiments listed below, and / or the accompanying figures.
[0021] A person skilled in the art will immediately recognize that a feature, embodiment, effect or advantage described herein in connection with the system according to the invention may, individually, simultaneously or alternatively, be a feature, embodiment, effect or advantage of the method according to the invention and vice versa.
[0022] The invention is based on the consideration that in many applications where stress wave gears are used, particularly in reduction operation in drive trains, measuring forces and torques to determine process variables or as input variables for specific control algorithms, or even actively introducing forces / movements into the gear to compensate for transmission errors and / or for active vibration damping, can achieve a significant improvement in precision and reliability in the drive train. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0023] 5
[0024] In particular, the compensation of transmission errors can improve the accuracy of the voltage wave drive. Known closed-loop control systems for transmission error compensation, such as those described in US 2018 / 0239327A1, measure the transmission error and perform motor control to compensate for it. Since the transmission error is speed-dependent, high-frequency motor control is required at high speeds. The bandwidth of a motor control is limited primarily by sensory factors, such as the resolution and sampling rate of motor feedback angle measurement systems like encoders; electrical factors, such as the clock frequency of PWM-based power stages; and mechanical factors, such as the inertia of the rotating shafts. Motor controllers with higher cutoff frequencies are significantly more expensive, and losses increase.
[0025] As has now been recognized, the desired improvements can be achieved by using smart elements integrated into a voltage wave drive in such a way that they enable targeted and demand-based measurement and / or force application. Smart elements, especially piezoelectric elements, exhibit a wide bandwidth from low to the required high frequencies and can be used as sensors for detection and as actuators for compensating transmission errors. Piezoelectric elements achieve a frequency many times higher than that of the main motor, but with only small strokes. One insight of the invention was that these properties, or rather this trade-off, allow the treatment or compensation of transmission errors directly in the voltage wave drive, where they originate.
[0026] The applicant further acknowledged that while the use of smart elements entails higher costs and somewhat more complex mounting, it results in a significant improvement in the accuracy of the tension wave drive. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0027] 6
[0028] This is made possible because transmission errors in all frequency ranges that occur can be reliably compensated.
[0029] The present invention addresses several individual aspects within the context of these requirements, namely, firstly, the sensor-based detection of forces and torques for determining process variables or as input for specific control algorithms, etc. Furthermore, it enables the application of forces / movements with a high bandwidth for compensating transmission errors, for active vibration damping, for overcoming static friction, for achieving variable (torsional) stiffness, or similar technical functions. Finally, the use of "smart materials," e.g., piezoelectric sensors / actuators, enables a technical solution for both requirement classes (sensory and actuator) with just one system. The measuring and / or control unit can measure and / or apply forces / torques occurring in the stress wave drive to increase the precision of the stress wave drive.
[0030] Within the scope of the present invention, "smart materials" refers in particular to materials whose properties spontaneously adapt to the prevailing environmental conditions. For the purposes of this invention disclosure, the term refers specifically to materials in which this adaptation can be brought about in a targeted and controlled manner. Known examples of these are piezoelectric materials, electrorheological fluids, and shape-memory alloys.
[0031] The flexspline can be cup-shaped or constructed using a silk-hat design. The wave generator can have an elliptical cross-section with a major and a minor ellipse axis. In other configurations, the wave generator can also exhibit threefold symmetry in its cross-section. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0032] 7
[0033] In an advantageous embodiment, the measuring and / or control unit is set up and configured to compensate for transmission errors in the voltage wave transmission, in particular through pure control, i.e., open loop.
[0034] The transmission accuracy of a gearbox describes the absolute positional error at the output. The measurement is preferably performed using a high-resolution measuring system during a complete rotation of the output element. The direction of rotation is not reversed. The transmission accuracy is defined as the sum of the magnitudes of the maximum positive and negative differences between the theoretical and actual output angles. The transmission error is the difference between the theoretical and actual output angles that occurs at any given time.
[0035] Like other gear drives, a tension wave gear drive does not exhibit perfect angular transmission. Rather, an angular error arises as the difference between the actual (measurable) output angle and the theoretical output rotation angle. The theoretical output rotation angle, in turn, is derived from the actual (measurable) input angle and the nominal gear ratio "R". Thus, the angular transmission error A<|) = 4>ab-c|)an / R applies. This relationship is described, for example, as "transmission accuracy" or "transmission accuracy (TA)." Tension wave gear drives have a very high degree of contact in the gear teeth. Therefore, unlike spur gear drives, the pitch error does not play a role in the angular transmission quality. Instead, longer-wavelength effects, such as the cumulative pitch error or influences from eccentricity errors, come into play.
[0036] Preferably, the measuring and / or control unit is configured and designed to use the smart element as a sensor for a measurement in a measuring operating mode and to detect at least one error in the measurement. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0037] 8
[0038] to identify gear movement and generate an inverse error from it, and to superimpose this inverse error in an actuation mode by using the smart element as an actuator of the gear movement.
[0039] The system can preferably perform measurements at regular intervals in measurement mode, so that the currently existing error, which can change over time, can be detected regularly. Advantageously, the error is also regularly compensated in update mode by superimposing an inverse error.
[0040] At least one error is preferentially identified as at least one periodic oscillation. For example, a wave gear can exhibit a periodic transmission error (with a fundamental period of "2" or "3" in the case of a wave generator with threefold symmetry, as well as its harmonics). If an opposing micro-movement is generated by the smart elements, a significantly smoother motion is produced. This results in increased accuracy and reduced vibration excitation.
[0041] In the tension wave gear, an overall periodic error pattern develops, depending on the drive angle. Each tooth engagement area (2 or 3) results in one period in the fundamental wave. Harmonics are also possible.
[0042] The at least one identified error is preferably parameterized by means of a number of harmonic parameters, wherein the inverse error is parameterized by means of these parameters or functions of these parameters.
[0043] Overall, the error function can be described mathematically with sufficient accuracy using a few harmonic parameters. These parameters can be... Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0044] 9
[0045] A single, short-term measurement (using the smart elements as sensors) or a measurement taken at specific intervals (drift effects) can identify the angular error. An "inverse error" can then be calculated and superimposed on the gearbox movement by the smart elements (now acting as actuators). This allows for compensation of the angular error through open-loop control. Time-division multiplexing between measurement and actuation during operation, as in closed-loop control, is therefore unnecessary. The inverse error is preferably designed such that controlling the smart element based on the inverse error precisely compensates for the vibrations caused by transmission errors. It preferably corresponds to an inverted error function; that is, when the error function has a minimum, the inverse error function has a corresponding maximum, and vice versa.
[0046] The stress wave drive of the system preferably comprises a disk-shaped double ring with an outer flange and with an inner flange arranged inside the outer flange when viewed radially, wherein the inner flange has a plurality of recesses along its circumference in which radially inwardly pointing projections of the outer flange are arranged, and wherein a smart element is arranged circumferentially between at least one wall of a projection and a wall of a recess.
[0047] In an alternative preferred embodiment, the stress wave drive of the system comprises a tubular double ring with a first flange and a second flange, wherein the first flange has a plurality of axial first projections and the second flange has a plurality of second projections, and wherein the two flanges are arranged opposite each other such that the projections of the first flange and the projections of the second flange alternate circumferentially, and wherein a smart element is arranged circumferentially between at least one first projection and a second projection. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0048] 10
[0049] Preferably a housing is provided, wherein the first flange of the double ring is connected to the housing and the second flange of the double ring is connected to the circular spline or is designed as a combined component, in particular in one piece, or wherein an output element is provided and wherein the first flange of the double ring is connected to the housing and the second flange of the double ring is connected to the originally provided component, the circular spline or the flex spline, or is designed as a combined component, in particular in one piece.
[0050] The voltage wave gearbox is preferably operated in two-shaft operation (stationary gearbox) in reduction mode, in which the wave generator acts as a fast drive and the flexspline or circular spline as a slow output (most positioned component, therefore no circumferential cables).
[0051] Preferably a housing is provided, wherein the first flange of the double ring is connected to the housing and the second flange of the double ring is connected to the circular spline or is designed as a combined component, in particular in one piece, or wherein an output element is provided and wherein the first flange of the double ring is connected to the output element and the second flange is connected to the flex spline or is designed as a combined part, in particular in one piece.
[0052] The Flexspline can be designed in a silk-hat construction with a collar, whereby a plurality of smart elements are applied to the collar as an active layer.
[0053] The invention also relates to a method for measuring and / or compensating on a stress wave drive, which comprises at least the components flexspline, circular spline and wave generator, wherein a smart [device] is integrated in and / or on at least one component of the stress wave drive. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0054] 11
[0055] An element, which consists at least partially of a smart material, is arranged. The smart element is controlled to compensate for unwanted dynamics of the tension wave drive.
[0056] In a preferred embodiment of the method, the smart element is controlled to compensate for unwanted dynamics of the stress wave drive.
[0057] Particularly favored is the compensation of transmission errors in the voltage wave transmission.
[0058] Advantageously, at least one signal from a smart element is captured, and this signal is used to control a smart element.
[0059] Preferably, in a measurement step, at least one error of the transmission movement is measured and identified using the smart element, from which an inverse error is generated, and in an actuation step, this inverse error is superimposed on the transmission movement using the smart element as an actuator.
[0060] The measurement step and / or the update step are preferably performed multiple times, especially at regular intervals. This allows for adjustments to be made to accommodate transmission errors that change over time, thus providing optimized handling of transmission errors.
[0061] The at least one fault is advantageously identified as at least one periodic oscillation. The fault can, in particular, be a single fundamental wave or a fundamental wave with harmonics. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0062] 12
[0063] The at least one identified error is preferably parameterized by means of a number of harmonic parameters, wherein the inverse error is parameterized by means of these parameters or functions of these parameters.
[0064] The invention also relates to a stress wave drive, in particular for a system described above, comprising at least the components flexspline, circular spline and wave generator. A smart element, which consists at least partially of a smart material, is arranged in and / or on at least one component of the stress wave drive, wherein the respective smart element is preferably a piezo element.
[0065] The tension wave drive is thus enhanced to improve its sensory and / or actuator properties. Furthermore, targeted treatment of transmission errors is enabled, allowing them to be addressed or compensated for directly at their source, thereby increasing the accuracy of the tension wave drive.
[0066] Advantageously, the respective smart element is a piezo element.
[0067] Piezoelectric elements exhibit a rapid response to mechanical stress and electrical signals. They can be built small and are lightweight, making them easy to integrate into various materials and structures.
[0068] Piezoelectric elements have no moving parts, making them low-wear and suitable for extreme environmental conditions. They exhibit a high force and frequency bandwidth and can therefore generate both very small and very large forces with a high bandwidth.
[0069] In a preferred embodiment, the tension wave drive comprises a disk-shaped double ring with an outer flange and with a Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0070] 13
[0071] viewed in a radial direction, the inner flange is arranged inside the outer flange, wherein the inner flange has a plurality of recesses along its circumference in which radially inwardly pointing projections of the outer flange are arranged, and wherein a smart element is arranged circumferentially between at least one wall of a projection and a, in particular adjacent, wall of a recess.
[0072] In a preferred embodiment, a smart element is arranged between all walls of a projection and each adjacent wall of a recess.
[0073] In a further preferred embodiment, the stress wave gear comprises a tubular double ring with a first flange and a second flange, wherein the first flange has a plurality of axial first projections and the second flange has a plurality of second projections, and wherein the two flanges are arranged opposite each other such that the projections of the first flange and the projections of the second flange alternate circumferentially, and wherein a smart element is arranged circumferentially between at least one first projection and a second projection.
[0074] Advantageously, in this preferred embodiment, the double ring also comprises six smart elements, thereby realizing sufficiently spatially resolved actuators or sensors along the circumference of the double ring for many applications. Furthermore, advantageous actuator functions are enabled. Piezo stack actuators can effectively generate pressure, but not tension, unless they are pre-tensioned. Consequently, to generate a rotational component, actuators are required for each of the two directions of rotation. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0075] 14
[0076] Preferably, a housing is provided, wherein the first flange of the double ring is connected to the housing and the second flange of the double ring is connected to the circular spline, or is formed as a combined component; or wherein an output element is provided, and wherein the first flange of the double ring is connected to the output element and the second flange is connected to the flex spline, or is formed as a combined part. The double ring thus acts as a connecting element between the housing and the circular spline, or between the output element and the flex spline. The smart elements in the double ring enable measurements and / or actuation at this connection, thereby improving the operation of the stress wave drive.
[0077] The smart element preferably has a cylindrical shape. This cylindrical shape results in a uniform stress distribution, making it mechanically stable and able to withstand high compressive or tensile loads. Alternatively, and preferably, the smart element is formed as a stacked actuator from square discs, resulting in a rod-shaped element with a square cross-section.
[0078] The Flexspline is advantageously designed in a silk-hat construction with a collar, whereby a plurality of smart elements are applied to the collar as an active layer.
[0079] The technical solutions described above can be used either purely as sensors, e.g., for measuring torque, or for control (sensory / actuator). The dual "sensory / actuator" function can be implemented either with separate elements or via time-division multiplexing. A single smart element can also contain two sub-elements, each performing one of the two functions. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0080] 15
[0081] In one application example, an external vibration can be dampened. If such a vibration is detected, the smart elements can be used to generate an antiphase torsional vibration, which is superimposed on the macroscopic rotary motion of the gearbox.
[0082] The smart elements are preferably arranged at an angle of 45° to the radial collar direction. Torsion in shafts or disks generates shear, so stresses and strains act in the 45° direction. This arrangement allows for advantageous sensor functions. Due to the arrangement in the "plus" or "minus" 45° direction, the smart elements experience, for example, strains or compressions (negative strains), i.e., quantities with opposite signs, which are well suited for differential input.
[0083] In this variant, shear effects in an annular membrane are used to achieve a relative rotational effect, which is why the active structures are arranged at ±45° to the radial direction.
[0084] The advantages of the invention lie particularly in the fact that a high bandwidth can be achieved in actuator functions using a smart materials solution. Furthermore, higher energy efficiency is possible if only a portion of the (rotating) masses needs to be dynamically accelerated. In sensor solutions for torque measurement, a smart materials solution with higher stiffness can be implemented.
[0085] Furthermore, it is possible to implement energy harvesting (time-division multiplexed energy harvesting or sensor function). The smart materials solution can be realized via an additional mechanical structure, such as an intermediate flange or shaft. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0086] 16
[0087] Advantageously, direct integration into an existing component is also possible (gearbox components: wave generator, flexspline, circular spline / peripheral components: housings, shafts, flanges).
[0088] The invention can be used in a variety of application areas, in particular in drive trains with wave gears in installation kits, units, actuators or in applications where the simultaneous use of sensory (e.g. torque) and additional actuator (e.g. active damping) functions offers advantages or is even necessary for the desired performance, for example in high-precision, low-vibration drives, systems with force feedback control, etc., or also in cobots.
[0089] Further objectives, advantages, features, and applications of the present invention will become apparent from the following description of an exemplary embodiment with reference to the drawing. All features described and / or illustrated, individually or in any meaningful combination, constitute the subject matter of the present invention, even independently of their compilation in the claims or their cross-references. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0090] 17
[0091] Some of these show schematically:
[0092] Figure 1 shows a disc-shaped double ring with smart elements in a perspective view;
[0093] Figure 2 shows the double ring according to Figure 1 in a front view;
[0094] Figure 3 shows the double ring according to Figure 1 in a section;
[0095] Figure 4 shows a tubular double ring with smart elements in a perspective view;
[0096] Figure 5 shows the tubular double ring according to Figure 4 in a first section;
[0097] Figure 6 shows the tubular double ring according to Figure 4 in a second section;
[0098] Figure 7 shows a section of a voltage wave drive with smart sensors / actuators in a preferred embodiment;
[0099] Figure 8 shows a section of a voltage wave drive with smart sensors / actuators in a further preferred embodiment;
[0100] Figure 9 shows a flexspline in silk-hat construction with an active layer of smart elements, and
[0101] Figure 10 shows a periodic signal of a transmission error.
[0102] Identical or equivalent components are shown in the following figures of the drawing based on an embodiment with Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0103] 18
[0104] Reference symbols have been added to improve readability. For clarity, not all components are marked with reference symbols if identical or equivalent components are already marked with reference symbols.
[0105] A disc-shaped double ring 2, shown in perspective in Figure 1, has an outer flange 6 and an inner flange 10 arranged inside the outer flange 6 when viewed radially. The inner flange 10 has a plurality of recesses 14 along its circumference, in each of which radially inwardly projecting projections 18 of the outer flange 6 are arranged. In this case, three recesses 14 are provided.
[0106] Between each wall 22 of a projection 18 and a wall 26 of a recess 14 directly adjacent to it on its circumference, a smart element 30 is arranged, so that in the present embodiment there are a total of six smart elements 30. The respective smart element 30 is configured as a sensor and / or actuator. In this example, the respective smart element 30 is configured as a piezoelectric element.
[0107] Figure 2 shows the disc-shaped double ring 2 according to Figure 1 in a front view and Figure 3 shows it in a section.
[0108] Figure 4 shows a tubular double ring 34 having a first flange 38 and a second flange 42. The first flange 38 has a plurality of axial first projections 46 and the second flange 42 has a plurality of second projections 50.
[0109] The two flanges 38, 42 are arranged opposite each other, such that the projections 46 of the first flange 38 and the projections 50 of the second flange 42 alternate circumferentially. A gap is formed circumferentially between at least one first projection 48 and one second projection 50. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0110] 19
[0111] smart element 30 is arranged such that, in the preferred embodiment shown, six smart elements 30 are provided. In this case, each smart element 30 is designed as a piezoelectric element.
[0112] The tubular double ring 34 is shown in a first section in Figure 5 and in a second section in Figure 6.
[0113] A tension wave transmission 60 in a preferred embodiment is shown in partial detail in Figure 7, in which a compensating mechanism based on the tubular double ring 34 shown is integrated.
[0114] The stress wave gear 60 has a pot-shaped flex spline 64, a wave generator 68 and a circular spline 72.
[0115] In a known configuration, the Flexspline 64 has an external toothing 76 which engages with an internal toothing 80 of the Circular Spline 72.
[0116] The stress wave drive 60 has a shaft generator 68 arranged within the flexible flexspline 64 for deforming the flexspline 64 in the radial direction. The deformation of the flexspline 64 creates a positive-locking, torque-transmitting connection between the circular spline 72 and the flexspline 64 at, in particular, two opposing points on the flexspline 64.
[0117] In the reduction operation of the voltage wave gear 60, i.e., during speed reduction, the shaft generator 68, which is particularly elliptically shaped, serves as the drive element. Via a rolling bearing, particularly a thin-section bearing, the shaft generator 68 deforms the flexspline 64, which is in mesh with the circular spline 72. As the shaft generator 68 rotates, the tooth engagement area shifts. Since the flexspline 64 has fewer teeth, in particular two fewer, than the circular spline 72, it rotates. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0118] 20
[0119] During half a revolution of the shaft generator 68, the flexspline 64 rotates relative to the circular spline 72, specifically by the angle of one tooth pitch, and during a full revolution by the angle of two tooth pitches. With the circular spline 72 stationary, the flexspline 64 rotates in the opposite direction to the rotation of the shaft generator 68.
[0120] In a tension wave gear 60 operating in standard reduction mode, the circular spline 72 is fixed to the frame. However, when using a compensation mechanism according to the present invention, the circular spline 72 is combined with one of the flanges 42 of a tubular double ring 34 described above as a single component or manufactured in one piece. The other flange 38 is fixed to a housing 84.
[0121] The main output motion of the tension wave gear 60 is superimposed on the flex spline 64 with the compensation applied via the circular spline 72. In this way, for example, cyclic transmission errors of the tension wave gear 60 can be compensated, resulting in highly accurate synchronization. Active damping of externally excited vibrations can also be implemented.
[0122] Figure 7 shows a measuring and / or control unit 90, which is connected to at least one smart element 30 via a signal transmission system. The voltage wave gear 60 and the measuring and / or control unit 90 together form a system 94 for measuring and / or compensating a voltage wave gear.
[0123] A tension wave gear 60 in a further preferred embodiment is shown in section in Figure 8, in which a compensating mechanism based on the disc-shaped double ring 2 shown is integrated. While the tubular double ring 34 can be used effectively in pot gears (see Figure 7), the disc-shaped double ring 2 can be advantageous for a silk-hat gear, since the Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0124] 21
[0125] Flexspline 64 has a larger diameter due to the outwardly designed flange 98.
[0126] The sensor-actuator unit and the flexspline flange 98 have a similar aspect ratio. The output bearing (e.g., crossed roller bearing) can be arranged between them, which is not shown in Figure 8.
[0127] The tension wave gear 60 according to Figure 8 has a flex spline 64 designed in a silk-hat configuration with a flange 98 or collar, a shaft generator 68, and a circular spline 72. In a known embodiment, the flex spline 64 has an external toothing 76 which engages with an internal toothing 80 of the circular spline 72.
[0128] The stress wave drive 60 has a shaft generator 68 arranged within the flexible flexspline 64 for deforming the flexspline 64 in the radial direction. The deformation of the flexspline 64 creates a positive-locking, torque-transmitting connection between the circular spline 72 and the flexspline 64 at, in particular, two opposing points on the flexspline 64.
[0129] In the reduction operation of the voltage wave gear 60, i.e., during speed reduction, the shaft generator 68, which is particularly elliptically shaped, serves as the drive element. Via a rolling bearing, particularly a thin-section bearing, the shaft generator 68 deforms the flexspline 64, which is in mesh with the circular spline 72. As the shaft generator 68 rotates, the tooth engagement area shifts. Since the flexspline 64 has fewer teeth, in particular two fewer, than the circular spline 72, the flexspline 64 rotates relative to the circular spline 72 by an angle of one tooth pitch during half a revolution of the shaft generator 68, and by an angle of two tooth pitches during a full revolution. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0130] 22
[0131] The outer flange 6 of the disc-shaped double ring 2 is fixed. The inner flange 10 is combined or integrated with the circular spline 72.
[0132] In a tension wave gear 60 operating in standard reduction mode, the circular spline 72 is fixed to the frame. However, when using a compensation mechanism according to the present invention, the circular spline 72 is combined with the flange 10 of the disc-shaped double ring 2 described above as a single component or manufactured in one piece. The other flange 6 is fixed to a housing 84.
[0133] The main output motion of the tension wave gear 60 is superimposed on the flex spline 64 with the compensation applied via the circular spline 72. In this way, for example, cyclic transmission errors of the tension wave gear 60 can be compensated, resulting in highly accurate synchronization. Active damping of externally excited vibrations can also be implemented.
[0134] Figure 8 shows a measuring and / or control unit 90 which is connected to at least one smart element 30 via a signal transmission system. The voltage wave gear 60 and the measuring and / or control unit 90 together form a system 94 for measuring and / or compensating a voltage wave gear.
[0135] The measuring and / or control unit 90 is set up and designed to compensate for transmission errors in the voltage wave transmission, in particular by means of pure control, i.e. open loop.
[0136] The measuring and / or control unit 90 is configured and designed to use the smart element as a sensor for a measurement in a measuring operating mode and to identify at least one error in the gearbox movement in the measurement and to derive an inverse error from it. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0137] 23
[0138] generate and, in an actuation mode, superimpose this inverse error by using the smart element as an actuator of the gear movement.
[0139] The system or the measuring and / or control unit 90 can preferably perform measurements at regular intervals in measuring mode, so that the currently existing error, which can change over time, can be detected regularly. Advantageously, the error is also regularly compensated in actuation mode by superimposing an inverse error. The measuring and / or control unit 90 preferably identifies the error as at least one periodic oscillation. The error is identified, for example, as a pure fundamental oscillation or as a fundamental oscillation with harmonic overtones.
[0140] The measuring and / or control unit 90 parameterizes the identified error using a number of harmonic parameters, whereby the inverse error is parameterized using these parameters or functions thereof. Overall, the error function can be described mathematically with sufficient accuracy using just a few harmonic parameters. These parameters can be identified once or at specific intervals (drift effects) from a short-term measurement (using the smart elements 30 as sensors). An "inverse error" can then be calculated and superimposed on the gearbox movement by the smart elements (now acting as actuators). Thus, compensation of the angular error can be achieved through pure control (open loop). A time-division multiplexed switching between measurement and actuation during operation, as in closed loop control, is therefore unnecessary.
[0141] Figure 9 shows a flexspline 64 constructed using a silk-hat design with a flange 98. Sensor / actuator structures made of smart elements 30 are applied directly to the flange 98 as an active layer. In the variant shown, shear effects are mitigated in a... Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE
[0142] 24
[0143] An annular membrane is used to achieve a relative rotational effect, which is why the active structures are arranged at ±45° to the radial direction. Due to the arrangement in the "plus" or "minus" 45° direction, the smart elements experience strains or compressions (negative strains), i.e., quantities with opposite signs, which are well suited for a differential input.
[0144] Figure 10 shows an example diagram of a transmission error. The input angle in degrees is shown on the x-axis 120. The output angle error in arcsec is shown on the y-axis 124. A first vertical line 128 corresponds to an angle of 0° and thus zero revolutions, while a second vertical line 132 corresponds to an angle of 360° and thus one revolution. A curve 136 represents the transmission error, which is given by a periodic wave-like curve, in particular a sinusoidal curve. This curve 136 shows the pure second-order fundamental wave without harmonics or other components.
[0145] Since long-wave effects, such as the sum of pitch errors or influences from eccentricity errors, come into play in voltage wave drives, an overall periodic error pattern develops as shown in Figure 10, depending on the drive angle. Each tooth engagement area (2 or 3) results in one period in the fundamental wave. Harmonics are also possible. Overall, the error function can be described mathematically with sufficient accuracy using a few harmonic parameters. Our reference: H003P118PCT 26.03.2026
[0146] Applicant: Harmonic Drive SE
[0147] 25
[0148] Reference numeral list
[0149] 2 disc-shaped double rings
[0150] 6 outer flange
[0151] 10 inner flange
[0152] 14 Exclusion
[0153] 18 lead
[0154] 22 Wall
[0155] 26 Wall
[0156] 30 smart elements
[0157] 34 tubular double ring
[0158] 38 first flange
[0159] 42 second flange
[0160] 46 lead
[0161] 50 lead
[0162] 60 voltage wave gears
[0163] 64 Flexspline
[0164] 68 Wave generator
[0165] 72 Circular Spline
[0166] 76 External gearing
[0167] 80 internal teeth
[0168] 84 cases
[0169] 90 Measuring and / or control unit 94 System
[0170] 98 flange
[0171] 100 membrane
[0172] 120 x-axis
[0173] 124 y-axis
[0174] 128 first vertical line
[0175] 132 second vertical line
[0176] 136 Curve
Claims
Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE 26 Patent claims 1. System (94) for measuring and / or compensating on a stress wave gear (60), comprising - a stress wave transmission (60) comprising at least the components flex spline (64), circular spline (72) and wave generator (68), wherein a smart element (30), which consists at least partially of a smart material, is arranged in and / or on at least one component (64, 68, 72) of the stress wave transmission (60); - a measuring and / or control unit (90) which is connected to at least one smart element (30) via signal technology.
2. System (94) according to claim 1 , characterized in that the measuring and / or control unit (90) is set up and designed to compensate for transmission errors in the voltage wave transmission (60), in particular by means of pure control.
3. System (94) according to claim 2, characterized in that the measuring and / or control unit (90) is set up and configured to use the smart element (30) as a sensor for a measurement in a measuring mode and to identify at least one error of the transmission movement in the measurement and to generate an inverse error from it and to superimpose this inverse error in an actuation mode by using the smart element as an actuator of the transmission movement.
4. System (94) according to claim 3, characterized in that the at least one fault is identified as at least one periodic oscillation. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE 27 5. System (94) according to claim 4, characterized in that the at least one identified error is parameterized by means of a number of harmonic parameters, and wherein the inverse error is parameterized by means of these parameters or functions of these parameters.
6. System (94) according to one of claims 1 to 5, characterized in that the respective smart element (30) is a piezo element.
7. System (94) according to one of claims 1 to 6, comprising a disk-shaped double ring (2) with an outer flange (6) and with an inner flange (10) arranged inside the outer flange (6) when viewed radially, wherein the inner flange (10) has a plurality of recesses (14) along its circumference in which radially inwardly projecting projections (18) of the outer flange (6) are arranged, and wherein a smart element (30) is arranged circumferentially between at least one wall (22) of a projection (18) and a wall (26) of a recess (14).
8. System (94) according to any one of claims 1 to 6, comprising a tubular double ring (34) with a first flange (38) and a second flange (42), wherein the first flange (38) has a plurality of axial first projections (46) and the second flange (42) has a plurality of second projections (50), and wherein the two flanges (38, 42) are arranged opposite each other such that the projections (46) of the first flange (38) and the projections (50) of the second flange (42) alternate circumferentially, and wherein a smart element (30) is arranged circumferentially between at least one first projection (46) and a second projection (50). Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE 28 9. System (94) according to claim 7 or 8, characterized in that a housing (84) is provided, wherein the first flange (38) of the double ring (34) is connected to the housing (84) and the second flange (42) of the double ring (34) is connected to the circular spline (72) or is formed as a combined component, or wherein an output element is provided and wherein the first flange (38) of the double ring (34) is connected to the housing (84) and the second flange (42) of the double ring (34) is connected to the originally provided component, the circular spline (72) or the flex spline (64), or is formed as a combined component, in particular in one piece.
10. System (94) according to one of claims 1 to 6, characterized in that the flexspline (64) is designed in a silk-hat construction with a collar, wherein a plurality of smart elements (30) are applied as an active layer on the collar.
11. Method for measuring and / or compensating on a stress wave drive (60), which comprises at least the components flex spline (64), circular spline (72) and wave generator (68), wherein a smart element (30), which consists at least partially of a smart material, is arranged in and / or on at least one component (64, 68, 72) of the stress wave drive (60), characterized in that the smart element (30) is controlled to compensate for undesired dynamics of the stress wave drive (60).
12. Method according to claim 11, wherein transmission errors in the voltage wave transmission (60) are compensated.
13. Method according to claim 11 or 12, characterized in that at least one signal from a smart element (30) is detected. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE 29 where this signal is taken into account for controlling a smart element (30).
14. Method according to claim 13, characterized in that in a measuring step at least one error of the transmission movement is measured and identified by means of the smart element (30) and wherein an inverse error is generated therefrom, wherein in an actuation step this inverse error is superimposed by means of the smart element (30) as actuator of the transmission movement.
15. Method according to claim 14, characterized in that the at least one fault is identified as at least one periodic oscillation.
16. Method according to claim 15, characterized in that the at least one identified error is parameterized by means of a number of harmonic parameters, and wherein the inverse error is parameterized by means of these parameters or functions of these parameters.
17. Voltage wave transmission (60), in particular for a system (94) according to one of claims 1 to 10, comprising at least the components Flexspline (64), Circular Spline (72) and wave generator (68), characterized in that a smart element (30), which consists at least partially of a smart material, is arranged in and / or on at least one component (64, 68, 72) of the voltage wave transmission (60), wherein the respective smart element (30) is preferably a piezo element.
18. Voltage wave gear (60) according to claim 17, comprising a disk-shaped double ring (2) with an outer flange (6) and with a radially viewed interior of the outer ring. Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE 30 flange (6) arranged inner flange (10), wherein the inner flange (10) has a plurality of recesses (14) along its circumference in which radially inwardly pointing projections (18) of the outer flange (6) are arranged, and wherein a smart element (30) is arranged circumferentially between at least one wall (22) of a projection (18) and one wall (26) of a recess (14).
19. Tension wave transmission (60) according to claim 17, comprising a tubular double ring (34) with a first flange (38) and a second flange (42), wherein the first flange (38) has a plurality of axial first projections (46) and the second flange (42) has a plurality of second projections (50), and wherein the two flanges (38, 42) are arranged opposite each other such that the projections (46) of the first flange (38) and the projections (50) of the second flange (42) alternate circumferentially, and wherein a smart element (30) is arranged circumferentially between at least one first projection (46) and a second projection (50).
20. Tension wave gear (60) according to claim 19, characterized in that a housing (84) is provided, wherein the first flange (38) of the double ring (34) is connected to the housing (84) and the second flange (42) of the double ring (34) is connected to the circular spline (72) or is formed as a combined component, or wherein an output element is provided and wherein the first flange (38) of the double ring (34) is connected to the output element and the second flange (42) is connected to the flex spline (64) or is formed as a combined part.
21. Tension wave gear (60) according to claim 19 or 20, characterized in that the flex spline (64) is in silk-hat construction with Our reference: H003P118PCT 26.03.2026 Applicant: Harmonic Drive SE 31 is formed in a collar, wherein a plurality of smart elements (30) are applied to the collar as an active layer.