Method for controlling a drive motor of a bicycle and bicycle

Abstract

The present invention relates to a method for controlling a drive motor (10) of a bicycle (12) when the bicycle (12) is pushed by a user. The method comprises a step of detecting (40) a pushing force exerted by the user on the bicycle (12). Furthermore, the method comprises a step of controlling (42) the assistance output of the drive motor (10) depending on the detected pushing force. The invention also relates to a bicycle (12).

Description

[0001] The present invention relates to a method for controlling a drive motor of a bicycle when the bicycle, for example, a two-wheeler or tricycle, is pushed by a user. This also includes cargo bikes. Furthermore, the present invention relates to a bicycle.

[0002] Bicycles, such as city bikes, mountain bikes, or cargo bikes, are not only ridden by their riders, but are also occasionally pushed. For example, a bicycle is pushed onto a sidewalk to park. The bicycle is then pushed back onto the street to start riding. Bicycles are also often pushed by the rider in pedestrian zones or on steep paths. However, pushing can be uncomfortable for the rider.

[0003] For this reason, for example, many bicycles with an auxiliary motor have an assistance mode that can be activated when the user is pushing the bicycle. The auxiliary motor then provides drive power to assist the rider in pushing the bicycle. However, this assistance when pushing is provided with a fixed torque or a fixed speed. Optionally, different assistance levels can be selected, each with a fixed torque or a fixed speed. Nevertheless, the assistance provided by the auxiliary motor cannot be tailored to the user's specific needs in every situation. DE 10 2014 217 758 A1 discloses a drive aid for an electric vehicle that supports manual maneuvering using an electric motor and sensors that detect pulling or pushing by an operator.In the disclosed method, an assisting torque is generated depending on the sensor state in order to move the vehicle.

[0004] JP H11-59557 A discloses a motor-assisted bicycle that uses an electric motor to provide auxiliary propulsion power that corresponds to the walking speed and the pushing force of a person pushing. The bicycle is equipped with pushing force sensors and a controller that calculates the pushing force and controls the electric motor accordingly.

[0005] Based on the current state of the art, the object of the invention is to propose an improved method for controlling a drive motor of a bicycle when pushing the bicycle. This object is achieved by the method having the features of claim 1 and by the bicycle having the features of claim 9.

[0006] A first aspect relates to a method for controlling a drive motor of a bicycle when a user is pushing the bicycle. The drive motor can be designed, for example, as an auxiliary motor. The drive motor can be designed to provide a drive force to a driven wheel of the bicycle. The drive motor can be designed, for example, as an electric motor. The bicycle has two or more wheels. The bicycle can be designed, for example, as a pedelec. The bicycle can be designed, for example, as a cargo bike or touring bike. The bicycle has a saddle on which the user can sit while riding. When riding the bicycle, the rider can, for example, provide a drive force through muscle power on a pedal crankshaft. The bicycle can have a gear shift. When pushing the bicycle, the user is not sitting on the bicycle, for example.When pushing, the user can, for example, walk alongside the bike. When pushing, the user can, for example, grab the bike by its handlebars. When pushing, the user does not apply any muscle power to the bike's drivetrain. Instead, the user pushes the bike forward directly with their arms and legs.

[0007] The method includes a step of determining a pushing force exerted by the user on the bicycle. The pushing force can be the force with which the user pushes the bicycle. This force can frequently change depending on the surface, the desired pushing speed, or other circumstances during pushing. The pushing force can, for example, be directed in a forward direction.

[0008] The thrust force can be detected, for example, using a sensor device. For example, the sensor device can have a strain sensor, such as a strain gauge, which detects the deformation of a handlebar, a stem, or even a headset to detect the thrust force. The sensor device can, for example, have pressure sensors in the handlebar grips that detect the thrust force. The thrust force can also be determined, for example, mathematically based on one or more detected bicycle state variables. For example, the thrust force can be calculated or estimated using a model or with a trained AI depending on the gradient, the mass of the bicycle, the speed of the bicycle, the gear ratio, and alternatively or additionally, the bicycle acceleration. The method comprises a step of controlling an assistance power of the drive motor depending on the detected thrust force. The assistance power can, for example, correspond to a drive force provided by the drive motor when pushing the bicycle. For example, to control the assistance power, a motor torque, a motor speed, or both can be controlled depending on the detected thrust force. Optionally, when controlling the assistance power, a gear can also be set depending on the detected thrust force. The assistance power supports the user when pushing the bicycle. By controlling the assistance power depending on the detected thrust force, the assistance power can be adapted to the user pushing the bicycle.For example, the user no longer has to walk at a speed set by the drive motor when pushing, but the assistance level can be adjusted to the user's walking speed. The assistance level can be controlled, for example, by a control device such as an inverter.

[0009] In general, the assistance level can decrease, for example, if the pushing force decreases. Conversely, if the pushing force increases, the assistance level can also increase. This control is based on the idea that the user pushes harder against the bike if it is too slow for the desired running speed or if, for example, there is higher rolling resistance due to the surface. If the assistance level is too high, the running pace is slower, or the rolling resistance decreases, the pushing force applied by the user to the bike usually decreases because the bike begins to roll away from the user. In this case, reducing the assistance level can prevent the bike from rolling away from the user or the user from having to undesirably increase their running speed. This process therefore enables a great deal of pushing comfort.In addition, the risk of falling while pushing the bike can be particularly low. User support while pushing can be particularly high, for example, because the assistance level is adaptive. Furthermore, the pushing force required by the user to push the bike can be particularly consistent, as the system can compensate for varying rolling resistance, for example, caused by potholes, curbs, and roots.

[0010] The control of the support power of the drive motor as a function of the detected thrust force can be carried out in such a way that a sum of the thrust force exerted by the user on the bicycle and a drive force generated by the drive motor remains constant.

[0011] The recording of the pushing force and, alternatively or additionally, the control of the assistance performance depending on the recorded pushing force can only take place, for example, if an assistance mode for pushing has been activated beforehand. Otherwise, for example, no assistance for pushing can be provided by the drive motor or a fixed assistance can be provided. The assistance mode can therefore be an adaptive assistance mode for pushing. A non-adaptive assistance mode can also be activated. In addition, it can be provided that the strength of assistance can be adjusted in the assistance mode. With the same recorded pushing force, the user can receive more or less assistance when pushing depending on the selected assistance strength.

[0012] The drive motor torque is limited to a maximum torque. This prevents excessive assistance. The maximum torque can, for example, be fixed. The maximum torque is specified depending on a bicycle state variable. The bicycle state variable can be the same or a different bicycle state variable, depending on which the maximum speed and, alternatively or additionally, the maximum power are specified. For example, the maximum torque can be specified depending on the bicycle mass, the gradient, and, alternatively or additionally, the selected gear. In this way, a maximum torque can be specified that is adapted to the current load.

[0013] In a further embodiment of the method, it can be provided that the method comprises a step of comparing the detected thrust force with a thrust force threshold value. This comparison can be carried out, for example, using a microprocessor. During the control process, the assistance power can be increased if the detected thrust force is greater than the threshold value. During the control process, the assistance power can be reduced if the detected thrust force is less than the threshold value. This makes it possible to specify a constant total force for pushing the bicycle, provided that a pushing speed remains constant. For example, if the assistance power is increased, the thrust force applied by the user will decrease again. In this way, with a simple control process, a total driving force when pushing can be specified by the threshold value.The threshold can be adjustable, for example manually by the rider or depending on a bicycle state variable, such as the bicycle's mass. As long as the detected thrust corresponds to the threshold, the assistance power can remain the same. Optionally, a threshold range is specified, which is defined by a first and a second threshold. As long as the detected thrust lies between the two thresholds, the assistance power can remain the same. During control, the assistance power can be increased if the detected thrust is greater than the second threshold. During control, the assistance power can be reduced if the detected thrust is less than the first threshold. This can avoid frequent adjustment of the assistance power.The amount of increase or decrease in the assistance power can, for example, be determined depending on the difference between the detected thrust and the nearest threshold. Alternatively, the amount of increase or decrease in the assistance power can be fixed.

[0014] In a further embodiment of the method, it can be provided that the control of the support power of the drive motor includes an adjustment of the support power at a clock rate. This can prevent excessively frequent adjustments and / or unstable control. The clock rate can correspond to an adjustment frequency. The clock rate can, for example, correspond to a sensor rate for detecting the thrust force. The clock rate can, for example, be fixed or can be specified depending on a speed and / or the last detected thrust force.

[0015] In a further embodiment of the method, it can be provided that the assistance power of the drive motor is limited to a maximum power. This can avoid excessive assistance. For example, the maximum power can be selected so high that without the pushing force of the user, the bicycle cannot maintain its speed or even comes to a standstill after a certain time. The maximum power can, for example, be fixed. The maximum power can be specified depending on a bicycle state variable. For example, the maximum power can be specified depending on a mass. In this way, for example, an appropriate assistance power can be provided for both an empty and a fully loaded cargo bicycle.

[0016] In a further embodiment of the method, the speed of the drive motor can be limited to a maximum speed. This can prevent an excessively high pushing speed. The maximum speed can, for example, be fixed. The maximum speed can be specified depending on a bicycle state variable. For example, the maximum speed can be specified depending on a selected gear. Thus, the maximum speed can be used to specify a maximum speed up to which the drive motor assists when pushing, regardless of the gear.

[0017] In a further embodiment of the method, it can be provided that the drive motor's assistance in pushing the bicycle is terminated when the user applies a brake on the bicycle. For example, the drive motor can be deactivated when the brake is applied. For example, the assistance mode can be permanently deactivated when the brake is applied. To continue assisting pushing, reactivation may then be necessary, for example, by reselecting the assistance mode.

[0018] In a further embodiment of the method, it can be provided that the assistance for pushing the bicycle by the drive motor is deactivated if the detected pushing force is less than a minimum pushing force. The minimum pushing force can be fixed or, for example, determined as a function of a bicycle state variable. For example, a lower minimum pushing force can be set for downhill than for uphill. This can bring about a stop if the user no longer pushes the bicycle or only pushes it to a limited extent. For example, the assistance can only remain deactivated as long as the detected pushing force is less than the minimum pushing force. As soon as the pushing force is again equal to or greater than the minimum pushing force, the assistance for pushing the bicycle by the drive motor can be activated again.Alternatively or additionally, the drive motor's assistance for pushing the bike can be reactivated as soon as the bike speed is equal to or greater than a minimum speed. Alternatively or additionally, the drive motor's assistance for pushing the bike can be permanently deactivated if the bike speed is lower than a minimum speed. To continue assisting with pushing, reactivation may be necessary, for example, by reselecting the assistance mode.

[0019] A second aspect relates to a bicycle. The bicycle is designed to perform a method according to the first aspect. Further features, embodiments, and advantages can be found in the descriptions of the first aspect. Conversely, features, embodiments, and advantages of the second aspect also represent features, embodiments, and advantages of the first aspect.

[0020] The bicycle has a drive motor. For example, the drive motor can be designed as an electric motor, which can assist the rider while riding the bicycle by propelling the bicycle with muscle power. The bicycle can be designed as a pedelec. The bicycle has a detection device for detecting a pushing force exerted by the user on the bicycle when pushing. The bicycle has a control device for controlling the assistance power of the drive motor depending on the detected pushing force. This allows adaptive assistance to be provided to the user when pushing the bicycle. Fig. 1 illustrates a method for controlling a drive motor of a bicycle when the bicycle is pushed by a user. Fig. 2 shows a schematic top view of a bicycle.

[0021] Fig. 1 illustrates a method for controlling a drive motor 10 of a bicycle 12 when the bicycle 12 is pushed by a user. The bicycle 12 is shown in Fig. 2 is shown schematically in a top view. The bicycle 12 has two wheels 14. A rear one of the wheels 14 can be driven by the drive motor 10 when pushing the bicycle 12 to assist the user. It is also possible to drive the front wheel or both wheels, depending on the drive type of the bicycle 12. When riding the bicycle 12, the user pedals 16 to drive a crank 18 using muscle power. The rider can also be assisted by the drive motor 10.

[0022] When riding the bicycle 12, the rider usually sits on a saddle 20 and the driving force is applied solely by the rider via the pedals 16. When pushing, however, the user normally walks alongside the bicycle 12 and presses against the handlebars 22. The handlebars 22 have a grip 24 on each side and are connected to the front of the wheels 14 via a headset 26. In the embodiment shown, the headset 26 forms a sensor device. The sensor device detects a deformation of the handlebars 22 and thus a pushing force exerted by the user on the bicycle 12 when pushing the bicycle 12. This detection of the pushing force exerted by the user on the bicycle 12 represents a first step 40 of the Fig.1 for controlling the drive motor 10 of the bicycle 12 when the user pushes the bicycle 12. It is also possible to attach sensors to the handlebars and in the area of ​​the saddle 20, which detect a pushing force exerted by the user on the bicycle 12 if the user does not only push the handlebars.

[0023] In a further step 42, the assistance power of the drive motor 10 is controlled as a function of the detected thrust force by means of a control device, which here is designed as an integral part of the drive motor 10. If the detected thrust force is greater than a threshold value, the assistance power provided by the drive motor 10 is increased to relieve the rider's burden when pushing. If the detected thrust force is less than the threshold value, the assistance power provided by the drive motor 10 is reduced to prevent the bicycle 12 from rolling away due to excessive assistance when pushing. Reference symbol 10 Drive motor 12 bicycles 14 wheels 16 pedals 18 crank 20 saddle 22 handlebars 24 handle 26 Tax rate 40 Step: Determining a thrust force 42 Step: Control of support performance

Claims

[1] Method for controlling a drive motor (10) of a bicycle (12) when the bicycle (12) is pushed by a user, the method comprising at least the following steps: - detecting (40) a pushing force exerted by the user on the bicycle (12), and - controlling (42) an assisting power of the drive motor (10) as a function of the detected thrust, wherein a speed of the drive motor (10) is limited to a maximum speed, characterized by that the maximum speed is specified as a function of a bicycle state variable. [2] Method according to claim 1, characterized byin that the method comprises a step of comparing the detected thrust force with a thrust force threshold value, wherein during the control the assistance power is increased if the detected thrust force is greater than the threshold value and wherein during the control the assistance power is reduced if the detected thrust force is less than the threshold value. [3] Method according to claim 1 or 2, characterized by that the control of the support power of the drive motor (10) comprises an adjustment of the support power at a clock rate. [4] Method according to one of the preceding claims, characterized by that the support power of the drive motor (10) is additionally limited to a maximum power. [5] Method according to one of the preceding claims, characterized by that a motor torque of the drive motor (10) is additionally limited to a maximum torque. [6] Method according to claim 5, characterized bythat the maximum torque is specified as a function of a bicycle state variable. [7] Method according to one of the preceding claims, characterized by that support of pushing the bicycle (12) by the drive motor (10) is terminated when the user actuates a brake of the bicycle (12). [8] Method according to one of the preceding claims, characterized by that the support of pushing the bicycle (12) by the drive motor (10) is deactivated if the detected pushing force is less than a minimum pushing force. [9] Bicycle (12) with a drive motor (10), a detection device for detecting a thrust force exerted by the user on the bicycle (12) when pushing, and a control device for controlling an assistance power of the drive motor (10) as a function of the detected thrust force according to one of the preceding claims.

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