Sensor system for determining an exertion of force on a pedal, drive unit, sensor unit, and method for adjusting an assistance power of a drive unit

Abstract

The invention relates to a sensor system (18) comprising a sensor unit (16) for determining an exertion of force on a pedal (11) of a bicycle, the sensor unit (16) being connected for conjoint rotation to a bicycle crankset shaft (14) connected to the pedal, the sensor unit (16) comprising at least one sensor (22), which at the crankset shaft (14) detects a variable representing the exertion of force. The invention also relates to a drive unit for providing an assistance power for a bicycle comprising a sensor system (20), a sensor unit (16) comprising a ring (26) for connection with conjoint rotation to a crankset shaft (14) of a bicycle and a method for adjusting assistance power of a drive unit of a bicycle.

Description

[0001] Sensor system for determining a force exerted on a pedal, drive unit, sensor unit and method for adjusting a support power of a drive unit

[0002] The invention relates to a sensor system for determining a force exerted on a pedal according to patent claim 1. The invention further relates to a drive unit with such a sensor system according to patent claim 13 and a sensor unit according to patent claim 14. The invention also relates to a method for adjusting an assistance power of a drive unit according to patent claim 15.

[0003] For common bicycles with a drive unit—also called e-bikes, electric bikes, or pedelecs—it's common practice to adjust the assistance provided by the drive unit to the pedaling cadence and, more importantly, to the force exerted by the rider on the pedals. This adjusted assistance provided by the drive unit is intended to result in a comfortable and natural riding experience.

[0004] It is known from the prior art to determine the force acting on the pedal either using strain gauges or torque sensors. To determine the torque using torque sensors, a portion of the crankshaft is typically magnetized or coated with magnetic material (passive torque sensor), or a demagnetized material is used (active torque sensor). The torque acting on the crank is then determined using a non-rotating torque sensor mounted stationary on the frame.

[0005] Cadence is typically measured using Hall sensors. This, combined with the speed of the crankshaft, which may be measured by additional sensors or calculated, determines the current power output of the bicycle rider.

[0006] Magnet-based sensors, in particular, have the disadvantage of requiring comparatively large installation space. Furthermore, other magnetized components in the area of ​​the torque sensor can distort the measured values. This means that the individual components must undergo complex demagnetization processes during assembly of a bicycle or drive unit.

[0007] The aim of the present invention is to provide an alternative sensor system and an alternative method for adjusting an assistance power, which requires only little installation space and, in addition, can be installed particularly easily.

[0008] The object is achieved according to the invention with the features of the independent claims. Further embodiments and advantages are described in connection with the dependent claims.

[0009] A sensor system according to the invention comprises a sensor unit for detecting the force exerted on a bicycle pedal. The sensor unit is rotationally fixedly connected to a bicycle crankshaft connected to the pedal. The crankshaft is connected, in particular, to a first pedal and a second pedal via a crank. Actuating the pedal transmits torque to the crankshaft via the cranks. The crankshaft is, in particular, rotatably mounted in a bicycle frame. The sensor unit can be arranged directly on the crankshaft or indirectly connected to the crankshaft.

[0010] The sensor unit further comprises at least one sensor which detects a variable on the pedal crankshaft representing the exertion of force. A variable representing the exertion of force is understood here to be a variable which changes directly on the pedal crankshaft due to a change in the exertion of force on the pedal. If a person presses harder on the pedal, this leads, for example, to a change in the acceleration (angular acceleration or circumferential acceleration) of the pedal crankshaft, to a change in the rotational speed, a change in the angular velocity and also to a change in the circumferential speed of the pedal crankshaft. In this case, therefore, it is not the force exerted on the pedal that is directly detected, but at least a change in a measured variable on the pedal crankshaft triggered by the exertion of force. The measurement of the exertion of force is therefore carried out indirectly, e.g.via the change in the rotational speed of the crankshaft or the change in the peripheral speed (acceleration). Furthermore, the sensor unit does not detect the absolute force exerted on the crankshaft; rather, it only detects relative values ​​or a change in the force exerted on the crankshaft.

[0011] A bicycle typically has two pedals, and the sensor specifically measures the force transmitted from both pedals to the crankshaft. It may also be the case that the pedals are clipless, meaning force is exerted on the pedals throughout the entire pedal stroke.

[0012] Overall, the recorded measurement value representing the force exerted should be used to adjust the drive power of a drive unit. Adapted drive power means, in particular, that the drive power is adapted to the cyclical pedaling movement of the person. Accordingly, more support is provided by the drive unit in the phases of a pedaling 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 very top (position defined as 0) to horizontal (position defined here as n / 2), the force exerted increases, and from the horizontal to the bottom position (defined as n), the force exerted decreases again. With clipless pedals or when riding while standing, the pedaling profile can also be different. The drive power should be adjusted as synchronously as possible with the force exerted on the pedal.If a person applies more force to a pedal, e.g., when riding uphill or accelerating, this is detected by the sensor, and more assistance is provided by the drive unit. If the pedal is a clipless pedal, a force between n and 2n (upper position) can also be exerted on the pedal.

[0013] The advantage of a sensor system according to the invention with a sensor that rotates with the crankshaft is that, as explained below, the sensor system requires only a small amount of space. Furthermore, the concept is not based on magnetic sensors, meaning that magnetized components do not affect the measurement and no demagnetization is required. As described in more detail below, the sensor arrangement according to the invention also opens up new possibilities for detecting component load.

[0014] An acceleration sensor is used as the sensor. The acceleration sensor is located on the circumference of the crankshaft and rotates with it. Using the acceleration sensor, the acceleration of the crankshaft in the circumferential direction or a change in the circumferential speed of the crankshaft can be determined as a value representing the force exerted. A piezoelectric acceleration sensor or a micro-electromechanical system (MEMS) is used as the acceleration sensor. Such an acceleration sensor requires particularly little installation space.

[0015] Alternatively or in addition, at least one sensor is a yaw rate sensor. A microelectromechanical system (MEMS) can also be used as a yaw rate sensor, with a measuring principle that utilizes, for example, the Coriolis force, or one that operates optically. The yaw rate sensor can be used to determine a change in the angular velocity of the crankshaft, which also depends on how forcefully the pedal is pressed.

[0016] In a practical embodiment of the sensor system according to the invention, the at least one acceleration sensor is arranged on the pedal crankshaft in such a way that this acceleration sensor can detect acceleration in the tangential direction of the pedal crankshaft. "Tangential direction" means that the acceleration sensor detects acceleration in the direction of rotation of the pedal crankshaft. The acceleration transmitted from a pedal to the pedal crankshaft has a particularly pronounced effect in the tangential direction.

[0017] In particular, the at least one acceleration sensor is arranged on the pedal crankshaft in such a way that this acceleration sensor can detect an acceleration in the radial direction of the pedal crankshaft. An acceleration of the pedal crankshaft caused by a force applied to a pedal can also be detected in the radial direction. Furthermore, an acceleration of the entire bicycle in the longitudinal direction of the bicycle can also be detected in the radial direction.

[0018] Alternatively or additionally, the at least one acceleration sensor is arranged on the crankshaft in such a way that acceleration in the axial direction of the crankshaft can be detected by this acceleration sensor. The axial direction of the crankshaft corresponds to the transverse direction of the bicycle. A yaw rate sensor can also be arranged on the crankshaft in such a way that it detects rotation about the longitudinal direction of the bicycle (also known as rocking). This can be used, for example, to detect a back-and-forth tilt of the bicycle, as occurs when pedaling out of the saddle on a hill or when starting off. In this case, too, the assistance provided by the drive system can then be adjusted accordingly.

[0019] In particular, at least two or even all three of the aforementioned acceleration sensors are arranged on the pedal crankshaft. If several acceleration sensors are arranged on the pedal crankshaft, which measure acceleration in different directions, more precise measurement data can be obtained from a combination of the different acceleration data, which contribute to improving the support provided to the person by the drive unit. In particular, the acceleration in the longitudinal direction of the bicycle and in the direction of rotation can be determined more precisely from a combination of the recorded accelerations in the tangential direction and in the radial direction of the pedal crankshaft over one rotation of the pedal crankshaft. If the sensor unit comprises several acceleration sensors, these can also be integrated into a single component in a known manner. This component is also very compact and space-saving.

[0020] Alternatively or additionally, several rotation rate sensors can be arranged on the pedal crankshaft, which measure in different directions. A combination of this measured data can also be used to more precisely evaluate the force exerted on the pedal. In a further practical embodiment of the sensor system according to the invention, the at least one sensor is arranged on a ring. The ring is connected to the pedal crankshaft in a rotationally fixed manner. In particular, the ring is arranged to surround the outside of the pedal crankshaft, e.g. by means of a press fit. The at least one sensor can be easily connected to the pedal crankshaft via a ring and rotate with it. A structural modification of the pedal crankshaft is not necessary; standard available pedal crankshafts 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 extension in the axial direction or a ring that has a larger extension in the axial direction and is cylindrical.

[0021] In particular, the sensor unit has a plurality of sensors distributed around the circumference of the pedal crankshaft. In particular, a plurality of acceleration sensors are distributed around the circumference of the pedal crankshaft, which measure the acceleration in the same direction, and / or a plurality of yaw rate sensors that measure the angular velocity around the same axis. For example, two, three or more sensors can be distributed around the circumference, each of which records the acceleration of the pedal crankshaft in the direction of rotation. In particular, two or three acceleration sensors, which measure acceleration in different directions, can also be integrated into one component, with several of these integrated acceleration sensors being distributed around the circumference. The same applies to the yaw rate sensors.

[0022] By means of several sensors distributed around the circumference, it is possible in particular to detect wear or deformation and / or twisting of the crankshaft.

[0023] In particular, in conjunction with a ring described above, the arrangement of several sensors along this ring is easy to realize.

[0024] To further optimize measurement accuracy and thus the adjustment of the assistance level, the sensor unit can also be equipped with at least one magnetometer. The magnetometer can be used to determine the gravitational acceleration currently acting on the sensor. This is particularly advantageous for acceleration sensors. After compensating for the gravitational acceleration, a linear velocity can be calculated from the linear acceleration. Alternatively or additionally, an external cadence measurement can be performed as a reference measurement. This cadence measurement could be implemented on the sprocket using a light sensor or a Hall sensor.

[0025] In particular, three acceleration sensors and three angular rate sensors, each aligned orthogonally to each other, can be combined in a so-called IMU (inertial measurement unit). From the measured values ​​recorded by the acceleration sensors, the linear velocity can be determined by integration after compensation for gravitational acceleration, and the position of the respective IMU relative to a reference point can be determined by further integration. The integration of the three angular velocities determined by the angular rate sensors provides the orientation of the IMU (tilt) relative to a reference point.

[0026] In particular, several IMUs are distributed around the circumference of the pedal crankshaft and are arranged in particular on a ring that is connected to the pedal crankshaft in a rotationally fixed manner.

[0027] In a further 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 for supplying the sensor and / or for data transmission of the measured variable. By means of the slip ring, information or energy can be transmitted from components rotating relative to one another - in this case between the rotating sensor and a stationary, i.e., fixedly arranged power supply and / or control unit on a bicycle frame. Preferably, the at least one sensor is arranged on the front side or the front end side of a ring, the rear side or rear end side of which 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 (drum).The sliding contacts are connected via a sliding contact, in particular by means of brushes that are fixedly arranged on the frame of the bicycle.

[0028] The sensor system is particularly space-saving if the slip ring for the sensor system also serves as the slip ring for energy transmission and / or data transmission for a drive unit to provide assistance for the bicycle. The slip ring then has several poles, each of which is connected to the drive unit and / or to the at least one acceleration sensor. The arrangement described above is particularly suitable for co-rotating drive units arranged in the crankshaft.

[0029] Data transmission can also be carried out via telemetry, e.g. wirelessly via radio, WI_AN or Bluetooth.

[0030] It can also be provided that a reference acceleration sensor is mounted stationary on the frame of the bicycle. This acceleration sensor can be used, among other things, to compare the measured values ​​of the rotating sensor.

[0031] The invention also relates to a drive unit for providing assistance for a bicycle with a sensor system as described above. The drive unit is supplied with energy, in particular, via a battery / accumulator and assists the person on the bicycle during locomotion. It is, in particular, 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, the provision of an auxiliary torque to a hub (hub motor) is also conceivable.

[0032] The invention further comprises a sensor unit with a ring for rotationally fixed connection to a pedal crankshaft of a bicycle, wherein the ring has at least one sensor. The sensor is designed to detect a variable on the pedal crankshaft that represents the force exerted on a pedal. In particular, the at least one sensor is an acceleration sensor or a yaw rate sensor. 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 drive unit of a bicycle. The ring can be a closed ring or a ring with a slot, i.e. a ring section. A tubular, cylindrical ring or a drum is also referred to here as a ring.Such a cylindrical ring has a greater extension in the axial direction than a flat ring.

[0033] The invention also encompasses a method for adjusting the assistance power of a bicycle drive unit, in particular an electric assistance system. By means of at least one sensor connected to a pedal crankshaft in a rotationally fixed manner, a variable representing the force exerted on a pedal is detected on the pedal crankshaft, and the assistance power of the drive unit is adjusted depending on the detected variable. As already explained above, the force applied can be detected, in particular indirectly and simply, via the acceleration of the pedal crankshaft or the angular velocity of the pedal crankshaft, and the assistance power can be adjusted accordingly. The precise adjustment of the assistance power results in a particularly pleasant riding experience. For further advantages, reference is made to the above description.

[0034] In particular, an acceleration sensor measures the acceleration of the pedal crankshaft in the direction of rotation. The force exerted by the pedals has a particularly strong effect in the direction of rotation, or in the tangential direction of the pedal crankshaft, and can therefore be measured with particular precision.

[0035] Alternatively or in addition, the change in the rotational speed of the pedal crankshaft is recorded using a yaw rate sensor.

[0036] Furthermore, the movement of the bicycle in the longitudinal direction can be recorded using at least one acceleration sensor. This can be used, among other things, to determine the bicycle's speed. In particular, lateral acceleration of the bicycle, transverse to the longitudinal direction, is recorded using at least one acceleration sensor, and / or rotation of the bicycle around the longitudinal direction is recorded using a yaw rate sensor. This can be used, for example, to determine whether a person is riding out of the saddle and is subject to particularly high levels of stress, which in particular requires increased, adjusted assistance.

[0037] A rotation of the bicycle around its vertical direction can also be detected using at least one yaw rate sensor, which detects any yaw or roll of the bicycle and adjusts 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.

[0038] It can further be provided that an acceleration in the bicycle's vertical direction is determined from acceleration values ​​recorded by at least two acceleration sensors. In this case, "in the bicycle's vertical direction" means, in particular, that uphill and downhill rides of the bicycle can be identified. In the case of an uphill ride, i.e., an ascent, the assistance level can then also be adjusted and, in particular, increased. Alternatively or in addition to this, an incline caused, for example, by an uphill or downhill ride can also be determined using at least one yaw rate sensor. The incline can, in particular, also be recorded using the (co-rotating) magnetometer.

[0039] If several acceleration sensors and / or yaw rate sensors are arranged distributed around the circumference of the crankshaft, a deformation of the crankshaft can be determined based on their relative position. For this purpose, the position of each individual acceleration and / or yaw rate sensor is determined. If, for example, three acceleration sensors or IMUs are arranged evenly distributed around the circumference of the crankshaft, they form an equilateral triangle if the crankshaft is perfectly round. If the crankshaft deforms, the resulting triangle is also distorted. The deformation of the crankshaft can be used to draw conclusions about the load on the crankshaft and, in particular, whether the crankshaft should be replaced or repaired. By recording the relative positions, customized maintenance of the crankshaft can be carried out.

[0040] In a further practical embodiment of the method according to the invention, the measured acceleration values ​​are compared with measured acceleration values ​​from a reference sensor that is stationary connected to a bicycle frame. In particular, the acceleration in the longitudinal and / or vertical directions of the vehicle can be verified in this way, thus improving the accuracy of the acceleration values ​​for the acceleration in the direction of rotation of the pedal crankshaft.

[0041] Further practical embodiments and advantages are described below in conjunction with the figures. They show:

[0042] Fig. 1 a frame of a bicycle with a sensor system in a perspective view from the front,

[0043] Fig. 2 a sensor system in a perspective view from above,

[0044] Fig. 3 shows a sensor unit in a first embodiment in a front view,

[0045] Fig. 4 the sensor unit from Fig. 3 in a side view,

[0046] Fig. 5 shows the sensor unit from Figs. 3 and 4 in a rear view,

[0047] Fig. 6 shows a sensor system with a sensor unit according to the first embodiment in a perspective view,

[0048] Fig. 7 shows a sensor unit in a second embodiment in a front view,

[0049] Fig. 8 shows the sensor unit from Fig. 7 in a side view, Fig. 9 shows the sensor unit from Fig. 7 and 8 in a section along line IX-IX in Fig. 7

[0050] Fig. 10 shows a sensor system with a sensor unit according to the second embodiment in a perspective view,

[0051] Fig. 11 a sensor unit in a schematic representation,

[0052] Fig. 12 a diagram of the tangential forces,

[0053] Fig. 13a a sensor system with an intact crankshaft in a schematic representation, and

[0054] Fig. 13b shows the sensor system from Fig. 13a with a deformed crankshaft in a schematic representation.

[0055] Fig. 1 shows a frame 10 for a bicycle. Such a frame 10 is known from the prior art.

[0056] The frame 10 for the bicycle has two pedals (11), each connected to a pedal crank 12 with a crankshaft 14. The crankshaft 14 is rotatably mounted in the frame 10 and transmits the torque from the pedals 11 to the transmission 13 and subsequently to the rear wheel (not shown).

[0057] This bicycle is an electric bicycle featuring 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 in this case acts on the pedal crankshaft 14.

[0058] The pedal crankshaft 14, together with a sensor unit 16 (see, among others, Fig. 2), forms a sensor system 18. Furthermore, a second reference sensor 20 is arranged in a fixed position on the frame 10. Fig. 2 shows a sensor system 18 with a pedal crankshaft 14 and a sensor unit 16 connected in a rotationally fixed manner to the pedal crankshaft 14.

[0059] In conjunction with Figs. 3 to 5, a first embodiment of a sensor unit 16 is explained. The sensor unit 16 comprises a plurality of sensors 22, which are specifically integrated into three IMUs 24. Each IMU 24 comprises, in a single unit, three orthogonally aligned acceleration sensors and three yaw rate sensors. The three IMUs 24 are arranged on the front side of a ring 26. The ring 26 is a flat ring 26. The IMUs 24 are arranged at equal intervals, equidistantly, around the circumference of the ring 26.

[0060] In the side view in Fig. 4 it is clearly visible that the IMUs 24 are arranged on the front side of the ring 26 and protrude from it.

[0061] The ring 26 is a slip ring 28 and has four ring-shaped contacts 30 on the back (see Fig. 5), two contacts 30 being signal lines, one contact 30 being available for the power supply of the sensors 22 and one contact 30 being the ground contact.

[0062] The ring 26 also serves to arrange the at least one sensor 22, and here the multiple IMUs 24, on the pedal crankshaft 14. For this purpose, the ring 26 has three arcuate projections 32 on its inner side, extending over an arcuate section. The ring 26 is arranged on the outside of the pedal crankshaft 14. The diameter of the opening formed by the projections 32 is designed such that the ring 26 can be connected to the pedal crankshaft 14 by means of a press fit.

[0063] Fig. 6 shows a sensor system 18 comprising the pedal crankshaft 14 and the sensor unit 16 according to the first embodiment described above. It is clearly visible here that the ring 26 or the slip ring 28 is arranged surrounding the pedal crankshaft 14 and that the contacts 30 of the slip ring 28 are contacted by means of brushes via a readout unit 31 that is stationary and connected to the frame 10. In the following, the same reference numerals are used for identical or at least functionally equivalent elements to describe further embodiments.

[0064] In Figs. 7 to 10, a sensor unit 16 is shown in a second embodiment.

[0065] 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 acceleration sensors or IMUs 24. The ring 26 is a tubular cylindrical ring 26, as can be clearly seen in Figs. 8 to 10. The sensors 22 are arranged at equal intervals, equidistantly, around the inner circumference of the ring 26. The ring 26 has several hemispherical recesses 33 on its inside. The recesses 33 serve to create a certain elasticity. The slip ring 28 also has cable feedthroughs 36.

[0066] The ring 26 is a slip ring 28 and simultaneously serves to connect a drive unit located within the pedal crankshaft 14. The slip ring 28 has five ring-shaped contacts 30 on its outer surface (see Figs. 8 and 9). One contact 30 is the ground contact for the sensors 22, and one contact 30 supplies power to the sensors 22. Three additional contacts 30 are provided for the three phases of the drive unit, with the signal line for the sensors 22 being modulated onto one phase.

[0067] Fig. 10 shows a sensor system 18 comprising the pedal crankshaft 14 and the sensor unit 16 according to the second embodiment described above. Here, the ring 26 or slip ring 28 is also arranged surrounding the pedal crankshaft 14. The contacts 30 are now aligned parallel to the axial direction of the crankshaft 14 and are contacted by means of sliding contacts 35 via a readout unit 31 that is stationary and connected to the frame 10.

[0068] Fig. 11 schematically shows a sensor system 18 with an IMU 24, wherein the IMU 24 is arranged in a rotationally fixed manner on the pedal crankshaft 14. The direction of rotation of the pedal crankshaft 14 is indicated by the arrow 34. The IMU 24 rotates with the pedal crankshaft 14. By means of the three acceleration sensors 22 in the IMU 24, accelerations in three directions are measured: by means of a first acceleration sensor, an acceleration in the direction of rotation of the pedal crankshaft 14 (here a z) can be determined. From the acceleration in the direction of rotation, a force acting on a pedal 11 is inferred. Furthermore, a further acceleration sensor is used to measure the acceleration in the radial direction of the pedal crankshaft 14 (here a z ). From a y and a z The acceleration of the pedal crankshaft 14 can be determined particularly accurately. A third acceleration sensor measures an acceleration in the axial direction of the pedal crankshaft 14 (here a x ). This can be used, for example, to detect a rocking motion.

[0069] There are also three rotation rate sensors arranged, each of which detects a rotation around 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 crankshaft can be determined by the change in the twist, designated here as α.

[0070] The functional principle of the sensor system 18 is explained below in connection with Fig. 12.

[0071] In Fig. 12, the tangential force Ft acting on the pedal crankshaft 14 is plotted against the position t of the pedal crankshaft 14.

[0072] The course of the tangential force over approximately one and a half revolutions of the pedal crankshaft 14 is shown as an example in Fig. 12. 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 curve resulting at the pedal crankshaft 14 from the rotation of both pedals 11.

[0073] In the section from 0 to n / 2, the tangential force exerted by a person on a pedal 11 increases (see curve 40) and reaches its maximum at n / 2. From n / 2 to n, the tangential force exerted then decreases to 0. In the section from n via 3 / 2n to 0, the person does not exert any force on one pedal 11; rather, force must be exerted (via the other pedal 11) in order to move one pedal 11 back up. When pedaling out of the saddle, riding while standing, or using the bicycle with click pedals, the curve of the tangential force may deviate from the curve shown in Fig. 12. The assistance power can then be adapted to the respective curve.

[0074] By means of the sensor unit 16, this force curve can be determined and, in particular, changes in the strength of the force (here the amplitude) can be determined, which then also lead to an adjustment of the support power by the drive unit.

[0075] A further possibility offered by the sensor system 18 is described below in connection with Fig. 13a and Fig. 13b. Fig. 13a shows a cross-section of an intact, circular pedal crankshaft 14, on whose outer circumference three acceleration sensors 22 or three IMUs 24 are arranged at equal distances from one another. The three acceleration sensors 22 or three IMUs 24 form an isosceles triangle. In Fig. 13b, the pedal crankshaft 14 is shown deformed, with the original geometry indicated by a dashed line. The pedal crankshaft 14 is also twisted. This leads to a shift in the relative positions of the acceleration sensors 22 / the IMUs 24 (recognizable by the distorted triangle). Based on the deviation of the relative position from the target position in the case of a circular crankshaft 14, it can be concluded that the crankshaft 14 is deformed and / or twisted.

[0076] List of reference symbols

[0077] 10 frames

[0078] 11 Pedal

[0079] 12 crank

[0080] 13 gearboxes

[0081] 14 Crankshaft

[0082] 16 Sensor unit

[0083] 18 Sensor system

[0084] 20 Reference sensor

[0085] 22 Sensor

[0086] 24 IMU (inertial measurement unit)

[0087] 26 rings

[0088] 28 Slip ring

[0089] 30 Contact

[0090] 31 Reading unit

[0091] 32 lead

[0092] 33 Deepening

[0093] 34 Arrow (direction of rotation)

[0094] 35 sliding contact

[0095] 36 cable entry

[0096] 38 Curve

[0097] 40 curve

[0098] 42 Curve

Claims

Patent claims 1. 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 quantity representing the force exerted on the crank shaft (14).

2. Sensor system according to the preceding claim, characterized in that the at least one sensor (22) is an acceleration sensor.

3. Sensor system according to one of the preceding claims, characterized in that the at least one sensor (22) is a gyroscope.

4. Sensor system according to one of the two preceding claims, characterized in that the at least one acceleration sensor (22) 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).

5. Sensor system according to one of the three preceding claims, characterized in that the at least one acceleration sensor (22) is arranged on the pedal crank shaft (14) in such a way that acceleration in the radial direction of the pedal crank shaft (14) can be detected by means of this acceleration sensor (14).

6. Sensor system according to one of the four preceding claims, characterized in that the at least one acceleration sensor (22) 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) and / or that at least one yaw rate sensor (22) is arranged on the pedal crank shaft (14) in such a way that rotation about the longitudinal direction of the bicycle can be detected by means of this yaw rate sensor (22).

7. Sensor system according to one of the preceding claims, characterized in that the at least one sensor (22) is arranged on a ring (26).

8. Sensor system according to one of the preceding claims, characterized in that the sensor unit (16) has several sensors (22) arranged distributed over the circumference of the pedal crank shaft (14).

9. Sensor system according to one of the preceding claims, characterized in that the sensor unit (16) additionally comprises a magnetometer.

10. Sensor system according to one of the preceding claims, characterized in that a slip ring (28) is connected to the at least one sensor (22).

11. Sensor system according to the preceding claim, characterized in 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.

12. Sensor system according to one of the preceding claims, characterized in that a reference accelerometer (20) is arranged in a fixed position on a frame (10) of the bicycle.

13. Drive unit for providing support power for a bicycle with a sensor system (20) according to any one of the preceding claims 1 to 12.

14. Sensor unit comprising a ring (26) for rotationally fixed connection with a pedal crank shaft (14) of a bicycle, characterized in that the ring (26) has at least one sensor (22), wherein the sensor (22) is designed to detect a quantity representing the force exerted on a pedal (11) on the pedal crank shaft (14).

15. Method for adjusting the support power of a drive unit of a bicycle, characterized in that a quantity representing the force exerted on a pedal (11) is detected at the crank shaft (14) by means of at least one sensor (22) which is non-rotatably connected to a pedal crank shaft (14) and the support power of the drive unit is adjusted depending on the detected quantity.

16. Method according to the preceding claim, characterized in that the acceleration of the pedal crank shaft (14) is detected by means of an acceleration sensor (22).

17. Method according to one of the preceding claims, characterized in that the change in the rotational speed of the pedal crank shaft (14) is detected by means of a rotation rate sensor (22).

18. Method according to one of the preceding claims, characterized in that the movement of the bicycle in the longitudinal direction of the bicycle is detected by means of at least one acceleration sensor (22).

19. experienced according to one of the foregoing claims, characterized in that a lateral acceleration of the bicycle in the transverse direction 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 yaw rate sensor (22). A method according to one of the preceding claims, characterized in that a rotation about the vertical direction of the bicycle is detected by means of at least one yaw rate sensor (22). A method according to one of the preceding claims, characterized in that several acceleration sensors (22) and / or yaw rate sensors (22) are arranged distributed around a circumference of the crank arm (14) and a deformation of the crank arm (14) is determined based on their relative position. A method according to one of the preceding claims, characterized in that the measured values ​​are compared with measured acceleration values ​​of a reference sensor (20) stationary and connected to a frame (10) of the bicycle.

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