Method, evaluation unit and system for determining the direction of rotation and / or for detecting interference faults in a tension wave gear using strain sensors

Abstract

The invention relates to a method, an evaluation unit, and a system for determining the direction of rotation in a stress wave gear, wherein the stress wave gear comprises an elastic transmission element with external teeth, a shaft generator, and a rigid outer ring with internal teeth, wherein the elastic transmission element is an elastic transmission element with a first strain sensor arrangement comprising at least one first strain sensor and a second strain sensor arrangement comprising at least one further strain sensor, wherein the first strain sensor arrangement is formed in the undeformed elastic transmission element essentially in the circumferential direction of a first circle with a first diameter, and the second strain sensor arrangement is formed in the undeformed elastic transmission element essentially in the circumferential direction of a second circle with a second diameter.wherein the at least one first strain sensor on the first circle is arranged offset by an angle of substantially 45° relative to the at least one first further strain sensor.

Description

[0001] The invention relates to a method for determining the direction of rotation in a tension wave drive and / or for detecting engagement faults in the tension wave drive. The invention further relates to an evaluation unit configured to perform the method for determining the direction of rotation and / or detecting engagement faults in a tension wave drive. The invention also relates to a system comprising an evaluation unit and an elastic transmission element of the tension wave drive. Background of the invention

[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] The main components of a stress wave drive are a wave generator, a rigid outer ring (circular spline) with internal teeth, and an elastic transmission element (flexspline) with external teeth positioned between them. The transmission of torque between the wave generator and the outer ring is based on elastic deformation. The wave generator deforms the elastic transmission element into an ellipse, so that the elastic transmission element engages with the outer ring on two opposite sides of its circumference. As the wave generator rotates, the elastic transmission element rolls on the outer ring, and the interlocking teeth between the elastic transmission element and the outer ring transmit torque between them. The transmission ratio is determined by the difference in the number of teeth on the transmission ring and the outer ring.

[0004] During operation, excessively high torque can occur, for example, when the gearbox is operating under heavy load. This can lead to a misalignment between the transmission element and the outer ring, causing the teeth of the transmission element to skip over the teeth of the outer ring (ratcheting). Under normal operating conditions, the transmission element rotates with a constant tooth feed. However, a misalignment results in a temporary, uncontrolled relative rotation between the outer ring and the transmission element. This leads to an unknown angular offset relative to the input side, making precise control of the angular position impossible. The gearbox's condition does not reveal whether such a misalignment has occurred, thus complicating the search for the cause of the fault.

[0005] In this context, a method is known from publication JP 7 394 551 B2 in which an arrangement of strain gauges is used to measure the torque acting on the output side of a stress wave gear, to compare it with two threshold values, and to correct the torque value by compensating for a shear load acting on the elastic transmission element. However, publication JP 7 394 551 B2 does not describe a strain measurement for detecting changes in the tooth engagement in the stress wave gear.

[0006] DE 102022 128 423 B3 describes a method for detecting and quantifying a meshing fault in a tension wave drive. This includes measuring a torque profile over time on the deformable transmission ring, detecting a meshing fault based on the measured torque profile, determining the number of teeth skipped during the detected meshing fault based on the torque measurement, and calculating a rotation angle of the outer ring corresponding to the determined number of skipped teeth.

[0007] WO 2024 / 082116 A1 describes a stress wave drive with a wave generator and a plurality of sets of torque sensors. Each set of torque sensors comprises a plurality of strain gauges, with each set of torque sensors being configured to measure the torque transmitted by the drive during rotation of the flex spline.

[0008] DE 10 2018 125 079 A1 describes an elastic transmission element of a stress wave drive. This element has external teeth and at least one strain gauge for measuring mechanical stress on the elastic transmission element. The strain gauge extends over a cylindrical surface or an axial side surface. Disclosure of the invention

[0009] Against this background, the task is to provide a method, an evaluation unit for carrying out the method and a system consisting of the evaluation unit and an elastic transmission element, by which or with which the determination of the direction of rotation and the detection of interference disturbances in the gearing of the tension wave drive is possible with minimal effort.

[0010] The problem is solved by a method for determining the direction of rotation and for determining interference disturbances in a stress wave transmission, wherein the stress wave transmission comprises an elastic transmission element with external teeth and a first strain sensor arrangement having at least one first strain sensor and a second strain sensor arrangement having at least one further strain sensor, and by an evaluation unit configured to perform the method for determining the direction of rotation and for determining interference disturbances, and by a system consisting of the evaluation unit and the elastic transmission element.

[0011] According to the invention, the method for determining the direction of rotation and for determining interferences in a tension wave gear is characterized in that, in a first step, it is determined whether a first sensor signal of the at least one first strain sensor of the first strain sensor arrangement increases or decreases at a first time point, and in a second step, it is determined whether, at the first time point, the difference between a second sensor signal of the at least one first further strain sensor of the second strain sensor arrangement and a DC component of the second sensor signal is positive or negative, and in a third step, the direction of rotation in the tension wave gear is determined, at least using the information determined in the first step and at least using the information determined in the second step.wherein, in particular, the direction of rotation of the wave generator is deduced from the sequence and / or order and / or arrangement of the first strain sensor arrangement relative to the second strain sensor arrangement on the elastic transmission element and the information determined in the first step and the information determined in the second step.

[0012] The elastic transmission element in the system according to the invention, comprising an elastic transmission element and an evaluation unit configured to carry out the method according to the invention, has the first strain sensor arrangement in the undeformed elastic transmission element in such a way that the first strain sensor arrangement is formed essentially in the circumferential direction of a first circle with a first diameter, and it has the second strain sensor arrangement in the undeformed elastic transmission element in such a way that the second strain sensor arrangement is formed essentially in the circumferential direction of a second circle with a second diameter, wherein the at least one first strain sensor on the first circle is arranged offset by an angle of essentially 45° relative to the at least one first further strain sensor on the second circle.

[0013] This results in the advantage of the inventive method, the inventive evaluation unit configured for carrying out the inventive method and the inventive system that the direction of rotation can be determined with less effort from the combination of the information about the slope of the first sensor signal of the at least one first strain sensor at the first time and the information about the difference between the second sensor signal of the at least one first further strain sensor and a DC component of the second sensor signal at the first time.

[0014] According to an advantageous embodiment of the invention, the DC component of the second sensor signal is zero.

[0015] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is viewed from the drive side of the tension wave gear, is arranged clockwise by essentially 45° relative to another strain sensor of the second strain sensor arrangement, and that a decreasing signal value of the sensor signal of the strain sensor at a given time and a negative value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time, is used to conclude that the shaft generator is rotating clockwise from the viewpoint of the drive side of the tension wave gear.

[0016] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is arranged clockwise by essentially 45° relative to another strain sensor of the second strain sensor arrangement when viewed from the drive side of the tension wave gear, and that a counterclockwise rotation of the wave generator, as viewed from the drive side of the tension wave gear, is inferred from a decreasing signal value of the sensor signal of the strain sensor at a given time and from a positive value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time.

[0017] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is arranged counterclockwise by substantially 45° relative to another strain sensor of the second strain sensor arrangement when viewed from the drive side of the voltage wave gear, and that a decreasing signal value of the sensor signal of the strain sensor at a given time and a negative value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time, is used to conclude that the wave generator is rotating counterclockwise from the viewpoint of the drive side of the voltage wave gear.

[0018] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is arranged counterclockwise by essentially 45° relative to another strain sensor of the second strain sensor arrangement when viewed from the drive side of the tension wave gear, and that a clockwise rotation of the wave generator is inferred from a decreasing signal value of the sensor signal of the strain sensor at a given time and from a positive value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time.

[0019] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is viewed from the drive side of the tension wave gear, is arranged clockwise by essentially 45° relative to another strain sensor of the second strain sensor arrangement, and that a counterclockwise rotation of the wave generator, from the viewpoint of the drive side of the tension wave gear, is inferred from an increasing signal value of the sensor signal of the strain sensor at a given time and from a negative value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time.

[0020] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is viewed from the drive side of the tension wave gear, is arranged clockwise by essentially 45° relative to another strain sensor of the second strain sensor arrangement, and that a clockwise rotation of the wave generator, from the viewpoint of the drive side of the tension wave gear, is inferred from an increasing signal value of the sensor signal of the strain sensor at a given time and from a positive value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time.

[0021] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is arranged counterclockwise by essentially 45° relative to another strain sensor of the second strain sensor arrangement when viewed from the drive side of the tension wave gear, and that a clockwise rotation of the wave generator, as viewed from the drive side of the tension wave gear, is inferred from an increasing signal value of the sensor signal of the strain sensor at a given time and from a negative value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time.

[0022] According to an advantageous embodiment of the invention, it is provided that a strain sensor of the first strain sensor arrangement, which is arranged counterclockwise by essentially 45° relative to another strain sensor of the second strain sensor arrangement when viewed from the drive side of the tension wave gear, and that a counterclockwise rotation of the wave generator, as viewed from the drive side of the tension wave gear, is inferred from an increasing signal value of the sensor signal of the strain sensor at a given time and from a positive value of the difference between the signal value of the other strain sensor and a DC component of the signal of the other strain sensor at a given time.

[0023] According to an advantageous embodiment of the invention, it is provided that, in order to determine the slope of the sensor signal of a strain sensor of the first strain sensor arrangement and / or the slope of the sensor signal of another strain sensor of the second strain sensor arrangement, in particular the slope of the sensor signal of the at least one first strain sensor of the first strain sensor arrangement, the difference between two temporally successive values ​​of the sensor signal of a strain sensor of the first strain sensor arrangement or of the sensor signal of another strain sensor of the second strain sensor arrangement is calculated, wherein, for the calculation of the difference, the earlier value of the two successive values ​​is subtracted from the later value.

[0024] According to an advantageous embodiment of the invention, it is provided that a positive sign of the difference between two successive values ​​of the sensor signal of a strain sensor of the first strain sensor arrangement and / or of the sensor signal of another strain sensor of the second strain sensor arrangement indicates an increasing sensor signal of the strain sensor of the first strain sensor arrangement or an increasing sensor signal of the other strain sensor of the second strain sensor arrangement. According to an advantageous embodiment of the invention, it is provided that a negative sign of the difference between two successive values ​​of the sensor signal of a strain sensor of the first strain sensor arrangement and / or of the sensor signal of another strain sensor of the second strain sensor arrangement indicates a decreasing sensor signal of the strain sensor of the first strain sensor arrangement or a decreasing sensor signal of the other strain sensor of the second strain sensor arrangement.

[0025] According to an advantageous embodiment of the invention, it is provided that the first diameter of the first circle is not equal to the second diameter of the second circle, wherein the first circle is located in particular within the second circle or the second circle is located in particular within the first circle.

[0026] For the implementation of the method according to the invention, it is possible that the first strain sensor arrangement comprises a second strain sensor, a third strain sensor, and a fourth strain sensor, wherein the first strain sensor is arranged diametrically opposite to the second strain sensor, and the third strain sensor is arranged diametrically opposite to the fourth strain sensor, wherein the first strain sensor is arranged on the first circle offset by 90° relative to the third strain sensor and on the first circle offset by 90° relative to the fourth strain sensor, and the second strain sensor is arranged on the first circle offset by 90° relative to the third strain sensor and on the first circle offset by 90° relative to the fourth strain sensor.

[0027] For the implementation of the method according to the invention, it is possible that the second strain sensor arrangement comprises a second further strain sensor, a third further strain sensor, and a fourth further strain sensor, wherein the first further strain sensor is arranged diametrically opposite to the second further strain sensor, and the third further strain sensor is arranged diametrically opposite to the fourth further strain sensor, wherein the first further strain sensor is arranged on the second circle offset by 90° relative to the third further strain sensor and on the second circle offset by 90° relative to the fourth further strain sensor, and the second further strain sensor is arranged on the second circle offset by 90° relative to the third further strain sensor and on the second circle offset by 90° relative to the fourth further strain sensor.

[0028] According to an advantageous embodiment of the invention, it is provided that, in order to detect interference disturbances in the tension wave transmission, the bending strain of the elastic transmission element is determined along a strain direction and / or that it is checked whether the bending strain of the elastic transmission element exceeds a first threshold value, wherein the first threshold value is equal to the value of the bending strain that occurs when an interference of the tooth engagement begins and / or that it is checked whether the bending strain of the elastic transmission element exceeds a second threshold value, wherein the second threshold value is equal to the value of the bending strain that occurs when the tooth engagement is displaced by one tooth and / or that it is checked whether the bending strain of the elastic transmission element falls below the first threshold value.

[0029] For the implementation of the method according to the invention, it is possible that the elastic transmission element has an additional strain sensor, wherein the additional strain sensor is arranged in the undeformed state of the elastic transmission element, in particular completely on a third circle with a third diameter.

[0030] For the implementation of the method according to the invention, it is possible for the elastic transmission element to have an additional strain sensor, in particular one extending over the entire circumference of the elastic transmission element. This makes it advantageously possible to check whether threshold values ​​of the total strain have been exceeded, instead of local strain values ​​of the elastic transmission element according to the invention.

[0031] A further aspect of the invention is an evaluation unit configured to execute the methods according to the invention. The evaluation unit according to the invention can achieve the same technical effects, advantages, and configurations as already described in connection with the methods according to the invention.

[0032] A further object of the invention is a system comprising an evaluation unit according to the invention and an elastic transmission element with external teeth, wherein the elastic transmission element is an elastic transmission element with a first strain sensor arrangement comprising at least one first strain sensor and a second strain sensor arrangement comprising at least one further strain sensor, wherein the first strain sensor arrangement in the undeformed elastic transmission element is formed essentially in the circumferential direction of a first circle with a first diameter and the second strain sensor arrangement in the undeformed elastic transmission element is formed essentially in the circumferential direction of a second circle with a second diameter.wherein the at least one first strain sensor is arranged on the first circle offset by an angle of essentially 45° relative to the at least one first further strain sensor. The system according to the invention can achieve the same technical effects, advantages and embodiments as already described in connection with the method according to the invention.

[0033] In a preferred embodiment of the invention, strain gauges are used as strain sensors for the elastic transmission element, such that the strain gauges extend mainly in the circumferential direction around the elastic transmission element and have only a small radial extension. Optionally, the elastic transmission element can include further components, contacts, or conductors for processing or transmitting the sensor signals from the strain gauges.

[0034] According to an advantageous embodiment of the invention, quarter and / or half and / or full bridge circuits of strain gauges are used as strain sensor circuits.

[0035] According to an advantageous embodiment of the invention, the elastic transmission element has external teeth, and the first strain sensor arrangement is formed in the undeformed elastic transmission element essentially at a first radial distance to an axis of symmetry of the undeformed elastic transmission element and essentially in the circumferential direction, and the second strain sensor arrangement is formed in the undeformed elastic transmission element essentially at a second radial distance to an axis of symmetry of the undeformed elastic transmission element and essentially in the circumferential direction.

[0036] According to an advantageous embodiment of the invention, the elastic transmission element has a radially inwardly directed second strain sensor arrangement, wherein the second strain sensor arrangement in particular has a first further, a second further, a third further and a fourth further strain sensor.

[0037] According to an advantageous embodiment of the invention, the elastic transmission element between the first strain sensor arrangement and the second strain sensor arrangement has an additional strain sensor, in particular an additional strain sensor extending over the entire circumference of the elastic transmission element and / or an additional strain sensor circulating around the entire circumference of the elastic transmission element according to the invention.

[0038] According to an advantageous embodiment of the invention, the elastic transmission element has, starting from the first strain sensor arrangement and starting from the second strain sensor arrangement, an additional strain sensor directed radially inwards, in particular an additional strain sensor extending over the entire circumference of the elastic transmission element according to the invention and / or an additional strain sensor circulating around the entire circumference of the elastic transmission element according to the invention.

[0039] According to an advantageous embodiment of the invention, the elastic transmission element has, in a radial direction from outside to inside, first a first strain sensor arrangement, in particular comprising four strain sensors, then a second strain sensor arrangement, in particular comprising four further strain sensors, and then an additional strain sensor, in particular one extending over the entire circumference of the elastic transmission element according to the invention and / or one circulating around the entire circumference of the elastic transmission element according to the invention.

[0040] According to an advantageous embodiment of the invention, the elastic transmission element has, in a radial direction from outside to inside, first a first strain sensor arrangement, in particular comprising four strain sensors, then an additional strain sensor, in particular extending over the entire circumference of the elastic transmission element according to the invention and / or circulating around the entire circumference of the elastic transmission element according to the invention, and then a second strain sensor arrangement, in particular comprising four further strain sensors.

[0041] According to an advantageous embodiment of the invention, the elastic transmission element has, in a radial direction from the inside to the outside, first an additional strain sensor, in particular one extending over the entire circumference of the elastic transmission element according to the invention and / or one circumferentially around the entire circumference of the elastic transmission element according to the invention, then a first strain sensor arrangement, in particular comprising four strain sensors, and then a second strain sensor arrangement, in particular comprising four further strain sensors.

[0042] Further details and advantages of the invention will be explained below with reference to the exemplary embodiments shown in the drawings. These show: Fig. 1a a wave generator and an elastic transmission element with a strain sensor arrangement with four strain sensors according to the prior art in a schematic sectional view Fig. 1b the sensor signals of the four strain sensors of an elastic transmission element according to the prior art with the ambiguity of the rotation angle of the shaft generator occurring in the prior art Fig. 2 the dedoidal state of the gearing as a result of a failure to engage, as occurs in elastic transmission elements in the prior art, in schematic sectional view Fig. 3 a first embodiment of an elastic transmission element according to the invention in a schematic sectional view; Fig. 4a a second embodiment of an elastic transmission element according to the invention in a schematic sectional view; Fig. 4b the sensor signals of the eight strain sensors in the second embodiment of an elastic transmission element according to the invention and the resulting uniqueness in the determination of the angle Fig. 5 a third embodiment of an elastic transmission element according to the invention in a schematic sectional view. Fig. 6 a fourth embodiment of an elastic transmission element according to the invention in a schematic sectional view. Fig. 7 a fifth embodiment of an elastic transmission element according to the invention in a schematic sectional view. Fig. 8 a sixth embodiment of an elastic transmission element according to the invention in a schematic sectional view. Fig. 9 two states of tooth engagement in error-free operation (first line) and the three phases of an engagement malfunction (second line)

[0043] In the various figures, identical parts are always marked with the same reference symbols and are therefore usually only named or mentioned once.

[0044] Fig. Figure 1a shows a schematic sectional view of the prior art of a wave generator 5 and an elastic transmission element 1 with a strain sensor arrangement comprising four strain sensors. The strain sensor arrangement includes a first strain sensor 2.1, a second strain sensor 2.2, a third strain sensor 2.3, and a fourth strain sensor 2.4, wherein the first strain sensor 2.1 is arranged diametrically opposite to the second strain sensor 2.2, and the third strain sensor 2.3 is arranged diametrically opposite to the fourth strain sensor 2.4. It is also indicated that the angle of rotation Θ between the major axis of the wave generator 5 and a vertical axis is to be measured.

[0045] Fig. Figure 1b shows a schematic representation of the four sensor signals 2.1', 2.2', 2.3' and 2.4' of the four strain sensors 2.1, 2.2, 2.3 and 2.4 of an elastic transmission element 1 according to the prior art and with the ambiguity in determining the direction of rotation of the shaft generator 5 that occurs in the prior art. Also shown are the four measured values ​​2.1", 2.2", 2.3", and 2.4". Due to the symmetry of the signals, an unambiguous determination of the direction of rotation is not possible.

[0046] Fig. Figure 2 shows a schematic representation of a ratcheting fault between the external teeth 1' of an elastic transmission element 1 and the internal teeth 6' of a rigid outer ring 6 of a stress wave gear according to the prior art. One of the contact points along the main axis of the wave generator has shifted by one tooth towards the shorter axis. This condition is also known as a dedoidal state.

[0047] Fig. Figure 3 shows a schematic sectional view of a first embodiment of an elastic transmission element 1 according to the invention. The elastic transmission element has a first strain sensor arrangement 2 with four strain sensors: a first strain sensor 2.1, a second strain sensor 2.2, a third strain sensor 2.3, and a fourth strain sensor 2.4. The first strain sensor 2.1 and the second strain sensor 2.2 are arranged diametrically opposite to each other, and the third and fourth strain sensors 2.4 are arranged diametrically opposite to each other. The strain sensors 2.1, 2.2, 2.3, and 2.4 are arranged along an outer circle on the elastic transmission element 1. The first strain sensor 2.1 is also offset by an angle of 90° relative to both the third strain sensor 2.3 and the fourth strain sensor 2.4 on the outer circle. The second strain sensor 2.The second strain sensor 2 is also arranged on the outer circle at an angle of 90° to both the third strain sensor 2.3 and the fourth strain sensor 2.4. Radially extending inwards from the first strain sensor arrangement, the elastic transmission element 1 also features a second strain sensor arrangement 3 with four further strain sensors: a first further strain sensor 3.1, a second further strain sensor 3.2, a third further strain sensor 3.3, and a fourth further strain sensor 3.4. The first further strain sensor 3.1 and the second further strain sensor 3.2 are arranged diametrically opposite to each other, and the third further strain sensor 3.3 and the fourth further strain sensor 3.4 are also arranged diametrically opposite to each other. The further strain sensors 3.1, 3.2, 3.3, and 3.4 are arranged along an inner circle on the elastic transmission element 1.The first additional strain sensor 3.1 is also arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second additional strain sensor 3.2 is likewise arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second strain sensor arrangement 3 is rotated by an angle of 45° relative to the first strain sensor arrangement 2, thus enabling a unique determination of the direction of rotation (see . Fig. 4a and Fig. 4b). Furthermore, the circumferential direction U along which the strain sensors are arranged is shown.

[0048] Fig. Figure 4a shows a schematic sectional view of a second embodiment of an elastic transmission element 1 according to the invention, comprising a first strain sensor arrangement 2, a second strain sensor arrangement 3, and a shaft generator 5. It is also shown that the angle between the major main axis of the shaft generator 5 and a vertical axis is measured. The schematic sectional view shown corresponds to the view from the drive side of the tension shaft transmission.

[0049] Fig. Figure 4b shows a schematic representation of the four sensor signals 2.1', 2.2', 2.3' and 2.4' of the four strain sensors 2.1, 2.2, 2.3 and 2.4 and the four further sensor signals 3.1', 3.2', 3.3' and 3.4' of the four further strain sensors 3.1, 3.2, 3.3 and 3.4 of an elastic transmission element 1 according to the invention. Also shown are the four measured values ​​2.1", 2.2", 2.3" and 2.4" of the four strain sensors 2.1, 2.2, 2.3 and 2.4 measured at a first time point and the four further measured values ​​3.1", 3.2", 3.3" and 3.4" of the four further strain sensors 3.1, 3.2, 3.3 and 3.4 also measured at a first time point. 3.4. Due to the phase shift of the signals, a unique determination of the direction of rotation is possible. The direction of rotation at a given time is determined based on the slope of at least one of the four sensor signals 2.1', 2.2', 2.3' or 2.4' and based on the signal value of at least one of the four other sensor signals 3.1', 3.2', 3.3' or 3.4'.4' minus the DC component of at least one of the four other sensor signals 3.1', 3.2', 3.3' or 3.4'. From first information about the sign of the slope of at least one of the four sensor signals 2.1', 2.2', 2.3', or 2.4' at the given time, and from second information about the sign of the difference between the signal value of at least one of the four other sensor signals 3.1', 3.2', 3.3', or 3.4' and the DC component of at least one of the four other sensor signals 3.1', 3.2', 3.3', or 3.4' at the given time, the direction of rotation can be determined – based on the known arrangement of the strain sensors 2.1, 2.2, 2.3, and 2.4 relative to the other strain sensors 3.1, 3.2, 3.3, and 3.4 on the elastic transmission element 1. In the embodiment shown here, the first sensor signal 2 has a negative slope.1' always occurs together with a negative value of the difference between the signal value of the first further sensor signal 3.1' and the DC component of the first further sensor signal 3.1', while a positive slope of the first sensor signal 2.1' always occurs together with a positive value of the difference between the signal value of the first further sensor signal 3.1' and the DC component of the first further sensor signal 3.1'. From this, based on the known relative position of the strain sensors on the elastic transmission element, it can be clearly concluded that the shaft generator rotates counterclockwise from the drive side.

[0050] Fig. Figure 5 shows a schematic sectional view of a third embodiment of an elastic transmission element 1 according to the invention. The elastic transmission element has a first strain sensor arrangement 2 with four strain sensors: a first strain sensor 2.1, a second strain sensor 2.2, a third strain sensor 2.3, and a fourth strain sensor 2.4. The first strain sensor 2.1 and the second strain sensor 2.2 are arranged diametrically opposite to each other, and the third and fourth strain sensors 2.4 are arranged diametrically opposite to each other. The strain sensors 2.1, 2.2, 2.3, and 2.4 are arranged along an outer circle on the elastic transmission element 1. The first strain sensor 2.1 is also offset by an angle of 90° relative to both the third strain sensor 2.3 and the fourth strain sensor 2.4 on the outer circle. The second strain sensor 2.The second strain sensor 2 is also arranged on the outer circle at an angle of 90° to both the third strain sensor 2.3 and the fourth strain sensor 2.4. Radially extending inwards from the first strain sensor arrangement, the elastic transmission element 1 also features a second strain sensor arrangement 3 with four further strain sensors: a first further strain sensor 3.1, a second further strain sensor 3.2, a third further strain sensor 3.3, and a fourth further strain sensor 3.4. The first further strain sensor 3.1 and the second further strain sensor 3.2 are arranged diametrically opposite to each other, and the third further strain sensor 3.3 and the fourth further strain sensor 3.4 are also arranged diametrically opposite to each other. The further strain sensors 3.1, 3.2, 3.3, and 3.4 are arranged along an inner circle on the elastic transmission element 1.The first additional strain sensor 3.1 is also arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second additional strain sensor 3.2 is likewise arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second strain sensor arrangement 3 is rotated by an angle of 45° relative to the first strain sensor arrangement 2, thus enabling a unique determination of the direction of rotation (see . Fig. 4a and Fig. 4b). Also shown is a strain direction B along which the strain is measured and compared with strain threshold values ​​for detecting interferences. Furthermore, a section of a strain gauge is shown. The section shows the schematic setup of the strain gauge.

[0051] Fig. Figure 6 shows a schematic sectional view of a fourth embodiment of an elastic transmission element 1 according to the invention. The elastic transmission element has a first strain sensor arrangement 2 with four strain sensors: a first strain sensor 2.1, a second strain sensor 2.2, a third strain sensor 2.3, and a fourth strain sensor 2.4. The first strain sensor 2.1 and the second strain sensor 2.2 are arranged diametrically opposite to each other, and the third and fourth strain sensors 2.4 are arranged diametrically opposite to each other. The strain sensors 2.1, 2.2, 2.3, and 2.4 are arranged along an outer circle on the elastic transmission element 1. The first strain sensor 2.1 is also offset by an angle of 90° relative to both the third strain sensor 2.3 and the fourth strain sensor 2.4 on the outer circle. The second strain sensor 2.The second strain sensor 2 is also arranged on the outer circle at an angle of 90° to both the third strain sensor 2.3 and the fourth strain sensor 2.4. Radially extending inwards from the first strain sensor arrangement, the elastic transmission element 1 also features a second strain sensor arrangement 3 with four further strain sensors: a first further strain sensor 3.1, a second further strain sensor 3.2, a third further strain sensor 3.3, and a fourth further strain sensor 3.4. The first further strain sensor 3.1 and the second further strain sensor 3.2 are arranged diametrically opposite to each other, and the third further strain sensor 3.3 and the fourth further strain sensor 3.4 are also arranged diametrically opposite to each other. The further strain sensors 3.1, 3.2, 3.3, and 3.4 are arranged along an inner circle on the elastic transmission element 1.The first additional strain sensor 3.1 is also arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second additional strain sensor 3.2 is likewise arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second strain sensor arrangement 3 is arranged rotated by an angle of 45° relative to the first strain sensor arrangement 2, thus enabling a unique determination of the direction of rotation of the shaft generator 5 (see figure). Fig. 4a and Fig. 4b). Also shown is an additional strain sensor 4, which is located between the first strain sensor arrangement and the second strain sensor arrangement.

[0052] Fig. Figure 7 shows a schematic sectional view of a fifth embodiment of an elastic transmission element 1 according to the invention. The elastic transmission element has a first strain sensor arrangement 2 with four strain sensors: a first strain sensor 2.1, a second strain sensor 2.2, a third strain sensor 2.3, and a fourth strain sensor 2.4. The first strain sensor 2.1 and the second strain sensor 2.2 are arranged diametrically opposite to each other, and the third and fourth strain sensors 2.4 are arranged diametrically opposite to each other. The strain sensors 2.1, 2.2, 2.3, and 2.4 are arranged along an outer circle on the elastic transmission element 1. The first strain sensor 2.1 is also offset by an angle of 90° relative to both the third strain sensor 2.3 and the fourth strain sensor 2.4 on the outer circle. The second strain sensor 2.The second strain sensor 2 is also arranged on the outer circle at an angle of 90° to both the third strain sensor 2.3 and the fourth strain sensor 2.4. Radially extending inwards from the first strain sensor arrangement, the elastic transmission element 1 also features a second strain sensor arrangement 3 with four further strain sensors: a first further strain sensor 3.1, a second further strain sensor 3.2, a third further strain sensor 3.3, and a fourth further strain sensor 3.4. The first further strain sensor 3.1 and the second further strain sensor 3.2 are arranged diametrically opposite to each other, and the third further strain sensor 3.3 and the fourth further strain sensor 3.4 are also arranged diametrically opposite to each other. The further strain sensors 3.1, 3.2, 3.3, and 3.4 are arranged along an inner circle on the elastic transmission element 1.The first additional strain sensor 3.1 is also arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second additional strain sensor 3.2 is likewise arranged on the inner circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second strain sensor arrangement 3 is arranged rotated by an angle of 45° relative to the first strain sensor arrangement 2, thus enabling a unique determination of the direction of rotation of the shaft generator 5 (see Figure 5). Fig. 4a and Fig. 4b). Also shown is an additional strain sensor 4, which is arranged radially from the outside to the inside, facing inwards after the first strain sensor arrangement 2 and after the second strain sensor arrangement 3.

[0053] Fig. Figure 8 shows a schematic sectional view of a sixth embodiment of an elastic transmission element 1 according to the invention. The elastic transmission element has a first strain sensor arrangement 2 with four strain sensors: a first strain sensor 2.1, a second strain sensor 2.2, a third strain sensor 2.3, and a fourth strain sensor 2.4. The first strain sensor 2.1 and the second strain sensor 2.2 are arranged diametrically opposite to each other, and the third and fourth strain sensors 2.4 are arranged diametrically opposite to each other. The strain sensors 2.1, 2.2, 2.3, and 2.4 are arranged along an inner circle on the elastic transmission element 1. The first strain sensor 2.1 is also offset by an angle of 90° relative to both the third strain sensor 2.3 and the fourth strain sensor 2.4 on the inner circle. The second strain sensor 2.The second strain sensor 2 is also arranged on the inner circle at an angle of 90° to both the third strain sensor 2.3 and the fourth strain sensor 2.4. Radially extending outwards from the first strain sensor arrangement, the elastic transmission element 1 also features a second strain sensor arrangement 3 with four further strain sensors: a first further strain sensor 3.1, a second further strain sensor 3.2, a third further strain sensor 3.3, and a fourth further strain sensor 3.4. The first further strain sensor 3.1 and the second further strain sensor 3.2 are arranged diametrically opposite to each other, and the third further strain sensor 3.3 and the fourth further strain sensor 3.4 are arranged diametrically opposite to each other. The further strain sensors 3.1, 3.2, 3.3, and 3.4 are arranged along an outer circle on the elastic transmission element 1.The first additional strain sensor 3.1 is also arranged on the outer circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second additional strain sensor 3.2 is likewise arranged on the outer circle offset by an angle of 90° relative to the third additional strain sensor 3.3 and the fourth additional strain sensor 3.4. The second strain sensor arrangement 3 is rotated by an angle of 45° relative to the first strain sensor arrangement 2, thus enabling a unique determination of the direction of rotation of the shaft generator 5 (see Figure 5). Fig. 4a and Fig. 4b). Also shown is an additional strain sensor 4, which is arranged radially from the outside to the inside, after the second strain sensor arrangement 3 and after the first strain sensor arrangement 2 facing inwards.

[0054] Fig.Figure 9 schematically depicts two successive states of tooth engagement during fault-free operation (first row) and the three phases of an engagement failure (second row). The first sub-figure of the second row (second row, left) shows how – for example, due to an excessively high input torque – the outer teeth of an elastic transmission element separate from the inner teeth of a rigid outer ring, known as the pre-ratcheting phase. The second sub-figure of the second row (second row, center) shows how a displacement of one tooth occurs as a result of the continuing rotation of the shaft generator, known as the mid-ratcheting phase (first slip). The third sub-figure of the second row (second row, right) shows how the previous offset of the shaft generator is reversed by a jump back one tooth, known as the mid-ratcheting phase (second slip). Reference symbol list 1 elastic transmission element 1' External gearing 2 first strain sensor arrangement 2.1 First strain sensor 2.2 Second strain sensor 2.3 Third strain sensor 2.4 fourth strain sensor 2.1' first sensor signal 2.2' second sensor signal 2.3' third sensor signal 2.4' fourth sensor signal 2.1" first measurement 2.2" second measurement 2.3" third measurement 2.4" fourth measurement 3 second strain sensor arrangement 3.1 First additional strain sensor 3.2 Second additional strain sensor 3.3 Third additional strain sensor 3.4 fourth additional strain sensor 3.1' first further sensor signal 3.2' second additional sensor signal 3.3' third additional sensor signal 3.4' fourth additional sensor signal 3.1" first further measurement 3.2" second further measurement 3.3" third further measurement 3.4" fourth further measurement 4 additional strain sensors 5-wave generator 6 rigid outer ring 6' Internal teeth B Direction of expansion U circumferential direction Θ Rotation angle

Claims

[1] Method for determining the direction of rotation in a stress wave gear, wherein the stress wave gear comprises an elastic transmission element (1) with an external toothing (1') and a shaft generator (5) and a rigid outer ring (6) with an internal toothing (6'), wherein the elastic transmission element (1) comprises an elastic transmission element (1) with a first strain sensor arrangement (2) comprising at least one first strain sensor (2.1) and a second strain sensor arrangement (3) comprising at least one first further strain sensor.1) comprising a strain sensor arrangement (3), wherein the first strain sensor arrangement (2) is formed in the undeformed elastic transmission element (1) substantially in the circumferential direction of a first circle with a first diameter, and the second strain sensor arrangement (3) is formed in the undeformed elastic transmission element (1) substantially in the circumferential direction of a second circle with a second diameter, wherein the at least one first strain sensor (2.1) is arranged on the first circle offset by an angle of substantially 45° relative to the at least one first further strain sensor (3.1). characterized by that the procedure comprises the following steps: -- In a first step, it is determined whether a first sensor signal of the at least one first strain sensor (2.1) of the first strain sensor arrangement (2) increases or decreases at a first time point, -- in a second step, it is determined whether at the first time point the difference between a second sensor signal of the at least one first further strain sensor (3.1) of the second strain sensor arrangement (3) and a DC component of the second sensor signal is positive or negative, -- In a third step, the direction of rotation in the voltage wave gear is determined, at least using the information obtained in the first step and at least using the information obtained in the second step. [2] System comprising an evaluation unit configured to perform a method according to claim 1 and an elastic transmission element (1) with external teeth (1'), wherein the elastic transmission element (1) is an elastic transmission element (1) with a first strain sensor arrangement (2) comprising at least one first strain sensor (2.1) and a second strain sensor arrangement (3) comprising at least one first further strain sensor (3.1), wherein the first strain sensor arrangement (2) is formed in the undeformed elastic transmission element (1) substantially in the circumferential direction of a first circle with a first diameter and the second strain sensor arrangement (3) is formed in the undeformed elastic transmission element (1) substantially in the circumferential direction of a second circle with a second diameter, wherein the at least one first strain sensor (2.1) is arranged on the first circle offset by an angle of substantially 45° relative to at least one first further strain sensor (3.1). [3] System according to claim 2, characterized by, that the first strain sensor arrangement (2) comprises a second strain sensor (2.2) and a third strain sensor (2.3) and a fourth strain sensor (2.4), wherein the first strain sensor (2.1) is arranged diametrically opposite to the second strain sensor (2.2) and the third strain sensor (2.3) is arranged diametrically opposite to the fourth strain sensor (2.4), wherein the first strain sensor (2.1) is arranged on the first circle offset by 90° relative to the third strain sensor (2.3) and on the first circle offset by 90° relative to the fourth strain sensor (2.4), and the second strain sensor is arranged on the first circle offset by 90° relative to the third strain sensor (2.3) and on the first circle offset by 90° relative to the fourth strain sensor (2.4). [4] System according to one of claims 2 or 3, characterized by, that the second strain sensor arrangement (3) comprises a second further strain sensor (3.2) and a third further strain sensor (3.3) and a fourth further strain sensor (3.4), wherein the first further strain sensor (3.1) is arranged diametrically opposite to the second further strain sensor (2.2) and the third further strain sensor (3.3) is arranged diametrically opposite to the fourth further strain sensor (3.4), wherein the first further strain sensor (3.1) is arranged on the second circle offset by 90° relative to the third further strain sensor (3.3) and on the second circle offset by 90° relative to the fourth further strain sensor (3.4) and the second further strain sensor (3.2) is arranged on the second circle offset by 90° relative to the third further strain sensor (3.3) and on the second circle offset by 90° relative to the fourth further strain sensor (3.4).

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