Sensor system for detecting force applied to a pedal, drive unit, sensor unit and method for adjusting the support power of a drive unit

Abstract

Sensor system with a sensor unit (16) for determining a force exerted on a pedal (11) of a bicycle, characterized in that the sensor unit (16) is rotationally fixed to a crank shaft (14) of the bicycle connected to the pedal (11), wherein the sensor unit (16) comprises at least one sensor (22) which detects a measured quantity representing the force exertion on the crank shaft (14), wherein the at least one sensor (22) is an acceleration sensor, and wherein the sensor (22) is connected to a drive unit such that the support power of the drive unit can be adapted as a function of a change in the measured quantity representing the force exertion triggered by the force exertion on the crank shaft (14), wherein the sensor system comprises at least two of the following sensors (20, 22): - an acceleration sensor (22) which is arranged on the pedal crank shaft (14) in such a way that an acceleration of the pedal crank shaft (14) in the tangential direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (22), - an acceleration sensor (22) which is arranged on the pedal crank shaft (14) in such a way that an acceleration in the radial direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (14), - an acceleration sensor (22) which is arranged on the pedal crank shaft (14) in such a way that acceleration in the axial direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (22), - a reference accelerometer (20) which is fixedly mounted on a frame (10) of the bicycle.

Description

[0001] The invention relates to a sensor system for detecting the application of force to a pedal according to claim 1. The invention further relates to a drive unit with such a sensor system according to claim 13 and a sensor unit according to claim 14. The invention also relates to a method for adjusting the support level of a drive unit according to claim 15.

[0002] On conventional bicycles with a drive unit – also called e-bikes, electric bicycles, or pedelecs – it is standard practice to adjust the assistance provided by the drive unit to the pedaling cadence and, above all, to the force exerted by the rider on the pedals. This adjusted assistance from the drive unit is intended to result in a pleasant and natural riding experience.

[0003] It is known from the prior art to determine the force acting on the pedal using torque sensors. To determine the torque, a portion of the crank axle is typically magnetized or provided with magnetic material (passive torque sensor), or a demagnetized material is used (active torque sensor). The torque acting on the crank is then determined by means of a non-rotating torque sensor fixed to the frame.

[0004] From DE 10 2014 203 632 A1 a measuring device for a bottom bracket arrangement is known, wherein the measuring device determines a rotational speed and / or a torque based on the bearing forces occurring.

[0005] From DE 10 2012 104 061 B4 a bicycle force measuring device is known for measuring a pedaling force on a crankshaft.

[0006] From DE 10 2020 206 102 A1 a crank angle estimation device is known, with a torque sensor.

[0007] From US 20 130 024 137 A1 a torque sensor for arrangement on a pedal crank shaft is known, wherein the torque sensor comprises a grid of strain gauges.

[0008] From US patent 20,100,093,494 A1, a device is known for measuring and monitoring a torque exerted by a cyclist while pedaling. The device has one or more sensor elements for detecting the angular position of a crank arm and / or a torque exerted on it.

[0009] From US 20 100 024 590 A1 a sensor for detecting the force on a pedal is known, whereby the sensor is intended to be used to improve training and increase performance.

[0010] The cadence is usually determined using Hall sensors. From this, together with the rotational speed of the crank axle, which may be measured by additional sensors or calculated, the power output of the bicycle user is determined.

[0011] Magnet-based sensors, in particular, have the disadvantage of requiring a relatively large amount of installation space. Furthermore, other magnetized components in the vicinity of the torque sensor can distort the measured values. This means that during the assembly of a bicycle or drive unit, the individual components must undergo complex demagnetization processes.

[0012] The aim of the present invention is to provide an alternative sensor system and an alternative method for adjusting support performance, which requires little installation space and can also be installed particularly easily.

[0013] The problem is solved according to the invention by the features of the independent claims. Further embodiments and advantages are described in connection with the dependent claims.

[0014] A sensor system according to the invention comprises a sensor unit for detecting the application of force to a bicycle pedal. The sensor unit is rotationally fixed to a crank arm of the bicycle connected to the pedal. The crank arm is, in particular, connected to a first pedal and a second pedal via a crank arm. Actuation of the pedal transmits a torque to the crank arm via the crank arms. The crank arm is, in particular, rotatably mounted in a bicycle frame. The sensor unit can be arranged directly on the crank arm or indirectly connected to it.

[0015] The sensor unit further comprises at least one sensor that detects a quantity representing the force exerted on the crank arm. This sensor is an accelerometer and is connected to a drive unit in such a way that the assistance output of the drive unit can be adjusted depending on the detected quantity. A quantity representing the force exerted is understood here to be a quantity that changes directly at the crank arm when the force applied to the pedal is altered. For example, if a person pedals harder, this leads to a change in the acceleration of the crank arm, a change in its rotational speed, a change in its angular velocity, and also a change in its circumferential speed.The system in question does not directly measure the force applied to the pedal, but rather detects at least a change in a measured variable at the crank axle triggered by the application of force. The force applied is therefore measured indirectly, for example, via the change in the rotational speed of the crank axle or the change in its circumferential speed (acceleration). Furthermore, the sensor unit does not measure the absolute force applied to the crank axle; instead, it only determines relative values ​​or changes in the force applied to the crank axle.

[0016] A bicycle typically has two pedals, and the sensor specifically detects the force exerted by both pedals on the crank arm. The pedals may also be clipless pedals, meaning force is applied to them throughout a complete pedal stroke.

[0017] The measured quantity representing the force exerted is used to adjust the drive power of a drive unit. Adjusted drive power means, in particular, that the drive power is adapted to the cyclical pedaling motion of the rider. Accordingly, more support is provided by the drive unit during the phases of a pedal cycle in which the most force is exerted on a pedal. The force exerted is generally greatest when the pedal is in a horizontal position. From the top position (defined as 0) to the horizontal position (defined here as Π / 2), the force exerted increases, and from the horizontal position to the bottom position (defined as Π), the force exerted decreases again. With clipless pedals or when riding while standing, the pedaling profile may differ. The drive power should be adjusted as synchronously as possible with the force exerted on the pedal.Even if a person applies more force to a pedal, for example when cycling uphill or accelerating, this is detected by the sensor and the drive unit provides more assistance. If the pedal is a clipless pedal, force can also be exerted on the pedal between position Π and 2Π (upper position).

[0018] The advantage of a sensor system according to the invention with a sensor rotating with the crank axle is that the sensor system – as explained below – requires sensors that occupy only a small installation space. Furthermore, the concept is not based on magnetic sensors, meaning that magnetized components do not affect the measurement and no demagnetization is necessary. As described in more detail below, the sensor arrangement according to the invention also opens up new possibilities for measuring component load.

[0019] In this case, an accelerometer serves as the sensor. The accelerometer is positioned around the circumference of the crank arm and rotates with it. Using the accelerometer, the acceleration of the crank arm in the circumferential direction, or a change in its circumferential speed, can be determined as a quantity representing the force exerted. A piezoelectric accelerometer or a microelectromechanical system (MEMS) is particularly suitable as the accelerometer. Such an accelerometer requires very little installation space.

[0020] Alternatively or additionally, at least one sensor is a gyroscope. A microelectromechanical system (MEMS) can also be used as the gyroscope, whose measuring principle utilizes, for example, the Coriolis force, or which operates optically. The gyroscope can determine a change in the angular velocity of the crank axle, which also depends on the force applied to the pedals.

[0021] In a practical embodiment of the sensor system according to the invention, the at least one acceleration sensor is arranged on the crank arm such that acceleration in the tangential direction of the crank arm can be detected by means of this acceleration sensor. Tangential direction means that the acceleration sensor detects acceleration in the direction of rotation of the crank arm. The acceleration transmitted from a pedal to the crank arm has a particularly pronounced effect in the tangential direction.

[0022] In particular, the at least one acceleration sensor is arranged on the crank axle in such a way that acceleration in the radial direction of the crank axle can be detected by means of this acceleration sensor. Acceleration of the crank axle caused by force being applied to a pedal can also be detected in the radial direction. Furthermore, acceleration of the entire bicycle in the longitudinal direction can also be detected in the radial direction.

[0023] Alternatively or additionally, at least one acceleration sensor is positioned on the crank axle in such a way that acceleration in the axial direction of the crank axle can be detected. The axial direction of the crank axle corresponds to the lateral direction of the bicycle. A gyroscope can also be positioned on the crank axle in such a way that it detects rotation around the longitudinal direction of the bicycle (also known as wobble). This can detect, for example, the swaying of the bicycle, such as occurs when standing up to pedal uphill or when starting off. The assistance provided by the drive system can then be adjusted accordingly.

[0024] In particular, at least two or even all three of the aforementioned acceleration sensors are arranged on the crank arm. If several acceleration sensors are arranged on the crank arm, measuring acceleration in different directions, more precise measurements can be obtained from a combination of the various acceleration data, contributing to improved support for the rider by the drive unit. Specifically, a combination of the accelerations measured in the tangential and radial directions of the crank arm over one revolution of the crank arm allows for a more accurate determination of acceleration in the longitudinal direction and in the direction of rotation of the bicycle. If the sensor unit comprises several acceleration sensors, these can also be integrated into a single component in a known manner. This component remains very compact and space-saving.

[0025] Alternatively or additionally, several rotation rate sensors can be arranged on the crank axle, measuring in different directions. A more precise evaluation of the force exerted on the pedal can also be achieved by combining these measurement data.

[0026] In another practical embodiment of the sensor system according to the invention, the at least one sensor is arranged on a ring. The ring is rotationally fixed to the crank axle. In particular, the ring is arranged to surround the crank axle externally, e.g., by means of an interference fit. The at least one sensor can be easily connected to the crank axle via the ring and rotate with it. No structural modification of the crank axle is required; standard crank axles can be used. The ring can be a closed ring or a slotted ring (ring section). The ring can be a flat ring with a small axial dimension or a ring with a larger axial dimension and a cylindrical shape.

[0027] In particular, the sensor unit comprises several sensors distributed around the circumference of the crank arm. Specifically, several acceleration sensors are distributed around the circumference of the crank arm, measuring acceleration in the same direction, and / or several angular rate sensors are distributed around the circumference, measuring angular velocity about the same axis. For example, two, three, or more sensors can be distributed around the circumference, each detecting the acceleration of the crank arm in the direction of rotation. In particular, two or three acceleration sensors measuring acceleration in different directions can also be integrated into a single component, with several of these integrated acceleration sensors distributed around the circumference. The same applies to the angular rate sensors.

[0028] By means of several sensors distributed around the circumference, it is particularly possible to detect wear or deformation and / or twisting of the pedal crank shaft.

[0029] Particularly in conjunction with a ring described above, the arrangement of several sensors along this ring is easy to implement.

[0030] To further optimize measurement accuracy and thus the adjustment of the assistance power, the sensor unit can also include at least one magnetometer. The magnetometer can determine the acceleration due to gravity acting on the sensor. This is particularly advantageous for accelerometers. After compensating for the acceleration due to gravity, a linear velocity can be calculated from the linear acceleration. Alternatively or additionally, an external cadence measurement can be performed as a reference. This cadence measurement could be implemented on the gear ring using a light sensor or a Hall sensor.

[0031] In particular, three accelerometers and three gyroscopes, each orthogonally aligned to the others, can be combined in a so-called IMU (inertial measurement unit). From the measured values ​​acquired by the accelerometers, the linear velocity can be determined by integration after compensating for gravitational acceleration. The position of the respective IMU relative to a reference point can then be determined by further integration. Integrating the three angular velocities determined by the gyroscopes yields the orientation (tilt) of the IMU relative to a reference point.

[0032] In particular, several IMUs are arranged distributed around the circumference of the pedal crank shaft and, in particular, are arranged on a ring that is non-rotatably connected to the pedal crank shaft.

[0033] In another practical embodiment of the sensor system according to the invention, a slip ring is connected to the at least one sensor. The slip ring serves in particular for energy transmission to power the sensor and / or for data transmission of the measured quantity. Information or energy can be transmitted via the slip ring between components rotating relative to each other – in this case, between the rotating sensor and a stationary power supply and / or control unit, i.e., fixed in place on a bicycle frame. Preferably, the at least one sensor is arranged on the front or front end face of a ring whose rear end face has sliding contacts. Alternatively, the at least one sensor can be arranged on the inside of the slip ring and the sliding contacts on the outside. The above is particularly suitable for a tubular, cylindrical ring.The sliding contacts are contacted via a sliding contact, in particular by means of brushes that are fixedly arranged on the frame of the bicycle.

[0034] The sensor system is particularly space-saving when the slip ring for the sensor system simultaneously serves as the slip ring for energy transmission and / or data transmission for a drive unit to provide assistance to the bicycle. The slip ring then has multiple poles, each connected to the drive unit and / or to the at least one accelerometer. The arrangement described above is particularly suitable for co-rotating drive units located in the crankshaft.

[0035] It may also be possible to have an additional reference accelerometer permanently mounted on the bicycle frame. This accelerometer can be used, among other things, to compare the readings of the rotating sensor.

[0036] The invention also relates to a drive unit for providing assistance to a bicycle with a sensor system as described above. The drive unit is powered, in particular, by a battery and assists the cyclist in propulsion. It is specifically an electric drive unit. The type of assistance is possible in various, already known ways. In particular, the drive unit provides an auxiliary torque that acts on the pedal crank (also referred to as a mid-drive motor). Alternatively, providing an auxiliary torque to a hub (hub motor) is also conceivable.

[0037] The invention further comprises a sensor unit with a ring for a rotationally fixed connection to a bicycle crank axle, the ring having at least one sensor. The sensor is designed to detect a quantity representing the force exerted on a pedal at the crank axle. In particular, the at least one sensor is an accelerometer or a gyroscope. The ring is, in particular, a slip ring by means of which the sensor can be supplied with energy and / or by means of which the sensor is controlled and the measured values ​​can be transmitted. The sensor is, in particular, connected to a control unit for a bicycle drive unit. The ring can be a closed ring or a ring with a slot, i.e., a ring segment. A tubular, cylindrical ring or a drum is also referred to here as a ring.Such a cylindrical ring has a greater extent in the axial direction than a flat ring.

[0038] The invention also includes a method for adjusting the assistance output of a bicycle drive unit, in particular an electric assist system. A quantity representing the force exerted on a pedal is detected at the crank shaft by means of at least one sensor non-rotatably connected to the crank arm, and the assistance output of the drive unit is adjusted accordingly. As explained above, the force is detected indirectly and simply via the acceleration or angular velocity of the crank arm, and the assistance output is adjusted accordingly. The acceleration of the crank arm is detected by means of an accelerometer, and the sensor is connected to a drive unit in such a way that the assistance output of the drive unit is adjusted depending on the detected quantity.

[0039] The precisely adjusted level of assistance results in a particularly pleasant riding experience. For further advantages, please refer to the description above.

[0040] In particular, the acceleration sensor detects the acceleration of the crank arm in the direction of rotation. The force exerted via the pedal has a particularly strong effect in the direction of rotation, or tangentially, of the crank arm, and can therefore be measured with exceptional accuracy.

[0041] Alternatively or additionally, the change in the rotational speed of the pedal crank shaft is detected using a rotation rate sensor.

[0042] Furthermore, at least one accelerometer can be used to detect the bicycle's longitudinal movement. This allows, among other things, the bicycle's speed to be determined.

[0043] Using at least one accelerometer, the system detects, in particular, the lateral acceleration of the bicycle, perpendicular to its longitudinal direction, and / or it detects the bicycle's rotation around its longitudinal direction using a gyroscope. This allows, for example, the system to detect whether a person is riding standing up and pedaling, indicating a particularly high level of exertion that requires increased, adjusted assistance.

[0044] At least one yaw rate sensor can also detect rotation of the bicycle around its vertical direction, thereby identifying any yaw or wobble and adjusting the assistance level accordingly. If the sensors detect an unstable riding situation, the assistance level can be reduced, and other components such as brakes or ABS can be additionally activated / controlled.

[0045] Furthermore, it can be provided that acceleration in the uphill direction of the bicycle is determined from acceleration values ​​recorded by at least two accelerometers. Uphill acceleration in this context means, in particular, that the bicycle's ascents and descents can be identified. In the case of an uphill climb, the assistance level can then be adjusted and, in particular, increased. Alternatively or additionally, an incline caused, for example, by an uphill or downhill climb, can also be determined using at least one yaw rate sensor. The incline can also be detected, in particular, using the (rotating) magnetometer.

[0046] If multiple accelerometers and / or yaw rate sensors are arranged around the circumference of the crankshaft, their relative positions can be used to determine any deformation of the crankshaft. This involves determining the position of each individual accelerometer and / or yaw rate sensor. For example, if three accelerometers or IMUs are evenly distributed around the circumference of the crankshaft, they form an equilateral triangle when the crankshaft is perfectly round. If the crankshaft deforms, this triangle will also be distorted. The deformation of the crankshaft allows conclusions to be drawn about the stress on the crankshaft and, in particular, whether it should be replaced or repaired. By measuring the relative positions, a customized maintenance plan for the crankshaft can be implemented.

[0047] In a further practical embodiment of the method according to the invention, the measured acceleration values ​​are compared with measured acceleration values ​​of a reference sensor that is stationary and connected to the frame of the bicycle. In particular, the acceleration in the longitudinal direction of the vehicle and / or in the vertical direction of the vehicle can thus be verified, and the accuracy of the acceleration values ​​for the acceleration in the direction of rotation of the crank axle can also be improved.

[0048] Further practical embodiments and advantages are described below in connection with the figures. They show: Fig. 1. A bicycle frame with a sensor system in a perspective view from a slanted front view, Fig. 2 a sensor system in a perspective view from a slanted top, Fig. 3 a sensor unit in a first embodiment in a front view, Fig. 4 the sensor unit Fig. 3 in a side view, Fig. 5 the sensor unit from the Fig. 3 and Fig. 4 in a rear view, Fig. 6 a sensor system with a sensor unit according to the first embodiment in a perspective view, Fig. 7 a sensor unit in a second embodiment in a front view, Fig. 8 the sensor unit Fig. 7 in a side view, Fig. 9 the sensor unit Fig. 7 and Fig. 8 in a section along line IX-IX in Fig. 7 Fig. 10 a sensor system with a sensor unit according to the second embodiment in a perspective view, Fig. 11 a sensor unit in a schematic representation, Fig. 12 a diagram of the tangential forces, Fig. 13a a sensor system with an intact pedal crank axle in a schematic representation, and Fig. 13b the sensor system from Fig. 13a with a deformed pedal crank shaft in a schematic representation.

[0049] In Fig. Figure 1 shows a frame 10 for a bicycle. Such a frame 10 is known from the prior art.

[0050] The bicycle frame 10 has two pedals (11), each connected to a crank arm 14 via a crank shaft 12. The crank shaft 14 is rotatably mounted in the frame 10 and transmits the torque from the pedals 11 to the gearbox 13 and subsequently to the rear wheel (not shown).

[0051] The bicycle in question is an electric bicycle, which has a drive unit (not visible here) and a battery (also not visible) to supply power to the drive unit. The drive unit provides an auxiliary torque which acts on the crank axle 14.

[0052] The pedal crank shaft 14 forms together with a sensor unit 16 (see, among others, Fig. 2) a sensor system 18. Furthermore, a second reference sensor 20 is fixedly arranged on the frame 10.

[0053] In Fig. Figure 2 shows a sensor system 18 with a pedal crank shaft 14 and a sensor unit 16 which is non-rotatably connected to the pedal crank shaft 14.

[0054] In connection with the Fig. In Sections 3 to 5, a sensor unit 16 in a first embodiment is described. The sensor unit 16 comprises several sensors 22, which are specifically integrated into three IMUs 24. Each IMU 24 comprises three orthogonally oriented accelerometers and three gyroscopes in a single unit. The three IMUs 24 are arranged on the front surface of a ring 26. The ring 26 is a flat ring. The IMUs 24 are arranged equidistantly around the circumference of the ring 26.

[0055] In the side view in Fig. 4 It is clearly visible that the IMUs 24 are arranged on the front of the ring 26 and protrude from it.

[0056] Ring 26 is a slip ring 28 and has on the back (cf. Fig. 5) four ring-shaped contacts 30, wherein two contacts 30 are signal lines, one contact 30 is available for the power supply of the sensors 22 and one contact 30 is the ground contact.

[0057] The ring 26 also serves to mount the at least one sensor 22, and in this case, the multiple IMUs 24, on the crank arm 14. For this purpose, the ring 26 has three arc-shaped projections 32 on its inner side, extending over an arc segment. The ring 26 is mounted on the outside of the crank arm 14. The diameter of the opening formed by the projections 32 is designed such that the ring 26 can be press-fitted to the crank arm 14.

[0058] In Fig. Figure 6 shows a sensor system 18, which comprises the crank arm 14 and the sensor unit 16 according to the first embodiment described above. It is clearly visible that the ring 26 or slip ring 28 is arranged surrounding the crank arm 14 and that the contacts 30 of the slip ring 28 are contacted by means of brushes via a readout unit 31 which is stationary and connected to the frame 10.

[0059] In the following, the same reference numerals are used to describe further embodiments for identical or at least functionally equivalent elements as are used to describe the first embodiment.

[0060] In the Fig. Figures 7 to 10 show a sensor unit 16 in a second embodiment.

[0061] The sensor unit 16 also comprises several sensors 22. The three sensors 22 are arranged on the inside of the ring 26. The sensors 22 can be simple accelerometers or IMUs 24. The ring 26 is a tubular cylindrical ring 26, as shown in Fig. 8 to 10 are clearly visible. The sensors 22 are arranged at equal intervals, equidistant around the inner circumference of the ring 26. The ring 26 has several hemispherical recesses 33 on its inner surface. The recesses 33 serve to provide a certain degree of elasticity. In addition, the slip ring 28 has cable glands 36.

[0062] The ring 26 is a slip ring 28 and also serves here to connect a drive unit, which is arranged inside the pedal crank axle 14. The slip ring 28 has on its outer side (see Fig. 8 and Fig. 9) five ring-shaped contacts 30. One contact 30 is the ground contact for the sensors 22 and one contact 30 serves to supply power to the sensors 22. Three further contacts 30 are provided for the three phases of the drive unit, with the signal line for the sensors 22 modulated onto one phase.

[0063] In Fig. Figure 10 shows a sensor system 18, which comprises the crank arm 14 and the sensor unit 16 according to the second embodiment described above. Here, the ring 26 or the slip ring 28 is also arranged surrounding the crank arm 14. The contacts 30 are now aligned parallel to the axial direction of the crank arm 14 and are contacted via a readout unit 31, which is stationary and connected to the frame 10, by means of sliding contacts 35.

[0064] In Fig. Figure 11 schematically shows a sensor system 18 with an IMU 24, the IMU 24 being fixed to the crank arm shaft 14. The direction of rotation of the crank arm shaft 14 is indicated by arrow 34. The IMU 24 rotates with the crank arm shaft 14. Accelerations in three directions are measured by means of the three accelerometers 22 in the IMU 24: an acceleration in the direction of rotation of the crank arm shaft 14 (here a) can be measured by means of a first accelerometer. z ) are determined. The acceleration in the direction of rotation is used to infer, in particular, a force acting on a pedal 11. Furthermore, another acceleration sensor serves to measure the acceleration in the radial direction of the pedal crank axle 14 (here a z ). From a y and a zThe acceleration of the pedal crank shaft 14 can be determined with particular accuracy. A third acceleration sensor measures an acceleration in the axial direction of the pedal crank shaft 14 (here a x This can be used, for example, to detect a standing kick.

[0065] In addition, three gyroscopes are arranged, each of which detects a rotation about the axes a x , a y , a z The individual angles are then designated as α, β, γ. For example, the rotational speed of the pedal crank axle can be determined from the change in the twist, here designated as α.

[0066] The operating principle of sensor system 18 is described below in conjunction with Fig. 12 explained.

[0067] In Fig. 12 is the tangential force Ft acting on the pedal crank shaft 14 plotted against the position t of the pedal crank shaft 14.

[0068] The course of the tangential force over approximately one and a half revolutions of the pedal crank shaft 14 is in Fig. Figure 12 is shown as an example. The dashed line 38 and the dash-dotted line 40 each indicate the course of the tangential force for one pedal 11. The solid line 42 is the force course that results at the crank axle 14 from rotation with both pedals 11.

[0069] In the section from 0 to Π / 2, the tangential force exerted by a person on pedal 11 increases (see curve 40) and reaches its maximum at Π / 2. From Π / 2 to Π, the tangential force exerted then decreases to 0. In the section from Π through 3 / 2Π to 0, the person exerts no force on one pedal 11; rather, force must be exerted (via the other pedal 11) to move the first pedal 11 back up.

[0070] In the case of standing pedaling, riding while standing, or using clipless pedals, the course of the tangential force can vary from that in Fig. The course shown in section 12 may differ. The support provided can then be adjusted to the respective course.

[0071] The sensor unit 16 can be used to determine this force profile and, in particular, to detect changes in the strength of the force (here the amplitude), which then lead to an adjustment of the support power by the drive unit.

[0072] Another possibility offered by sensor system 18 is described below in connection with Fig. 13a and Fig. 13b described. Fig. Figure 13a shows a cross-section of an intact, circular pedal crank shaft 14, on the outer circumference of which three acceleration sensors 22 or three IMUs 24 are arranged at equal intervals. The three acceleration sensors 22 or three IMUs 24 form an isosceles triangle. Fig. Figure 13b shows the crankshaft 14 deformed, with the original geometry indicated by a dashed line. The crankshaft 14 is also twisted. This leads to a shift in the relative positions of the accelerometers 22 and the IMUs 24 (recognizable by the distorted triangle). Based on the deviation of the relative position from the target position when the crankshaft 14 is circular, a deformation and / or twisting of the crankshaft 14 can be inferred. Reference symbol list 10 frames 11 Pedal 12 Crankshaft 13 gearboxes 14 Crankshaft 16 sensor units 18 Sensor system 20 Reference Sensor 22 Sensor 24 IMU (inertial measurement unit) 26 rings 28 Slip ring 30 Contact 31 reading unit 32 lead 33 In-depth study 34 Arrow (direction of rotation) 35 Sliding contact 36 Cable entry 38 Curve 40 Curve 42 Curve

Claims

[1] Sensor system with a sensor unit (16) for detecting a force being applied to a pedal (11) of a bicycle, characterized by , that the sensor unit (16) is rotationally fixed to a crank shaft (14) of the bicycle connected to the pedal (11), wherein the sensor unit (16) comprises at least one sensor (22) which detects a measured quantity representing the force exertion on the crank shaft (14), wherein the at least one sensor (22) is an acceleration sensor, and wherein the sensor (22) is connected to a drive unit such that the support power of the drive unit can be adapted as a function of a change in the measured quantity representing the force exertion triggered by the force exertion on the crank shaft (14), wherein the sensor system comprises at least two of the following sensors (20, 22): - an acceleration sensor (22) which is arranged on the pedal crank shaft (14) in such a way that an acceleration of the pedal crank shaft (14) in the tangential direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (22), - an acceleration sensor (22) which is arranged on the pedal crank shaft (14) in such a way that an acceleration in the radial direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (14), - an acceleration sensor (22) which is arranged on the pedal crank shaft (14) in such a way that acceleration in the axial direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (22), - a reference accelerometer (20) which is fixedly mounted on a frame (10) of the bicycle. [2] Sensor system according to the preceding claim, characterized by , that at least one sensor (22) is a gyroscope. [3] Sensor system according to one of the preceding claims, characterized by , that at least one rotation rate sensor (22) is arranged on the crank axle (14) in such a way that a rotation about the longitudinal direction of the bicycle can be detected by means of this rotation rate sensor (22). [4] Sensor system according to one of the preceding claims, characterized by that the at least one sensor (22) is arranged on a ring (26). [5] Sensor system according to any one of the preceding claims, characterized by , that the sensor unit (16) has several sensors (22) distributed around the circumference of the pedal crank shaft (14). [6] Sensor system according to one of the preceding claims, characterized by , that the sensor unit (16) additionally includes a magnetometer. [7] Sensor system according to one of the preceding claims, characterized by , that a slip ring (28) is connected to the at least one sensor (22). [8] Sensor system according to the preceding claim, characterized by , that the slip ring (28) is simultaneously the slip ring for energy transmission and / or data transmission for a drive unit to provide support power for the bicycle. [9] Drive unit for providing support power for a bicycle with a sensor system (20) according to any one of the preceding claims 1 to 8. [10] Sensor unit comprising a ring (26) for rotationally fixed connection with a pedal crank shaft (14) of a bicycle, wherein the ring (26) is arranged to surround the pedal crank shaft (14) on the outside, characterized by , that the ring (26) has at least two of the following sensors (22): - an acceleration sensor (22) so that an acceleration of the pedal crank shaft (14) in the tangential direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (22), - an acceleration sensor (22) so that acceleration in the radial direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (14), - an acceleration sensor (22) so that acceleration in the axial direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (22), wherein the sensor (22) is designed to detect a quantity representing the force exerted on a pedal (11) at the pedal crank shaft (14). [11] Method for adjusting the support power of a drive unit unit of a bicycle, characterized by , that by means of at least one sensor (22) connected to a crank shaft (14) in a rotationally fixed manner, a measured quantity representing the force exerted on a pedal (11) is detected at the crank shaft (14), and the support power of the drive unit is adjusted as a function of a change in the measured quantity representing the force exerted on the crank shaft (14) triggered by the force exerted on the crank shaft (14), wherein the acceleration of the crank shaft (14) is detected by means of an acceleration sensor (22), and wherein the sensor (22) is connected to a drive unit in such a way that the support power of the drive unit is adjusted as a function of the detected quantity, wherein at least two of the following four process steps are carried out: - An acceleration of the pedal crank shaft (14) in the tangential direction of the pedal crank shaft (14) is detected by means of an acceleration sensor (22), - an acceleration in the radial direction of the pedal crank shaft (14) is detected by means of an acceleration sensor (22), - an acceleration in the axial direction of the pedal crank shaft (14) is detected by means of an acceleration sensor (22), - the measured values ​​are compared with measured acceleration values ​​of a reference sensor (20) that is stationary and connected to a frame (10) of the bicycle. [12] Method according to the preceding claim, characterized by , that the change in the rotational speed of the pedal crank shaft (14) is detected by means of a rotation rate sensor (22). [13] Method according to any of the preceding claims, characterized by , that the movement of the bicycle in the longitudinal direction of the bicycle is detected by means of at least one acceleration sensor (22). [14] Method according to any of the preceding claims, characterized by, that a lateral acceleration of the bicycle in the transverse direction of the bicycle is detected by means of at least one acceleration sensor (22) and / or a rotation about the longitudinal direction of the bicycle is detected by means of at least one gyroscope (22). [15] Method according to any of the preceding claims, characterized by , that a rotation about the bicycle's up-turn direction is detected by means of at least one gyroscope (22). [16] Method according to any of the foregoing claims, characterized by , that several acceleration sensors (22) and / or angular rate sensors (22) are arranged distributed around a circumference of the pedal crank shaft (14) and a deformation of the pedal crank shaft (14) is determined on the basis of their relative position.

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