Method for controlling a drive train, drive train and vehicle

Abstract

A method for controlling a drive train (4) of a vehicle (2) is described, wherein the drive train (4) has at least one shaft (6) which is accelerated when the vehicle (2) is driven by a driver, wherein the drive train (4) has a drive motor (12) for providing drive force to assist the driver of the vehicle (2) in driving the vehicle (2). The method comprises determining (S1) an angular acceleration of the shaft (6) and controlling (S2) the drive motor (12), wherein the assistance by the drive motor (12) is switched on or off depending on the determined angular acceleration. Furthermore, a drive train (4) for a vehicle (2) and a vehicle (2) having such a drive train (4) are described.

Description

[0001] The present invention relates to a method for controlling a vehicle's drivetrain. Furthermore, the present invention relates to a vehicle's drivetrain and to a vehicle with such a drivetrain, wherein the vehicle can be powered at least temporarily by muscle power.

[0002] Vehicles that can be propelled at least temporarily by muscle power, such as bicycles, e-bikes, pedelecs, or cargo bikes, may also have a drive motor to assist propulsion. For example, a pedelec, as a muscle-powered vehicle, may have an electric motor to provide assistance. The assistance provided by the drive motor must be controlled. For safety reasons, the assistance may only be provided when the rider is pedaling. To determine whether the rider is pedaling, rider torque can be measured. Rider torque is the torque applied by the rider to the vehicle's crankshaft to propel the vehicle using muscle power. Methods and systems are known in the art that control the drive motor based on the rider torque.

[0003] For example, DE 10 2022 132 256 A1 describes how a driver's torque is detected by a sensor and the drive motor is controlled accordingly. Such a sensor for detecting driver torque increases the system complexity of the vehicle. Furthermore, such a sensor can fail or detect an incorrect value for driver torque.

[0004] DE 10 2010 048 592 A1 relates to a bottom bracket system for pedelecs with a mid-drive motor concept, which enables control of the motor power, especially at high motor power and long gear ratios, through the measurement of torque and crank speed on both sides and the integration of a freewheel between the crankshaft and the drive sprocket.

[0005] DE 10 2009 000 919 A1 relates to a method for operating a motor-assisted bicycle in which the desired drive support is determined by a dynamic evaluation of the angular velocity and / or angular acceleration of the pedal crank, wherein a control and / or regulating device infers the torque requirement taking into account further operating parameters.

[0006] The object of the invention, starting from the prior art, is to improve the control of the drive motor of a vehicle that is at least temporarily powered by muscle power. This object is achieved by the subject matter with the features of the independent claims. Advantageous further developments are described in the dependent claims.

[0007] The invention relates, in a first aspect, to a method for controlling the drivetrain of a vehicle. The vehicle can be, for example, a bicycle, e-bike, pedelec, or cargo bike. The method for controlling the drivetrain can be a method for controlling a drive motor, such as an electric motor of the drivetrain. Steps of the method can, for example, be carried out using a control device of the vehicle.

[0008] The drivetrain includes a shaft that is accelerated when the vehicle is propelled by a rider. This shaft can be the vehicle's crankshaft. Crank arms can be rigidly connected to the crankshaft. For example, two crank arms can be rigidly connected to the crankshaft, with a pedal rotatably mounted at one end of each crank arm. The crankshaft can therefore also be called a pedal crank. The crankshaft is rotatably mounted to the vehicle's frame by means of a bearing. This bearing can be a rolling bearing, such as a ball bearing, a needle bearing, or a roller bearing. The rider's power is transmitted via the crankshaft to propel the vehicle.

[0009] The shaft can be directly connected to the crankshaft. The shaft can be at least indirectly connected to the crankshaft, for example via a gearbox. The shaft can be mechanically coupled to the crankshaft. When the rider propels the vehicle using muscle power, the shaft can be accelerated along with the crankshaft. An acceleration of the shaft, such as angular or rotational acceleration, can be directly correlated with an acceleration of the crankshaft; for example, the accelerations can be linearly related. For instance, the acceleration of the shaft can be identical to the acceleration of the crankshaft.

[0010] The powertrain includes a drive motor to provide propulsion power to assist the driver in driving the vehicle. The drive motor can be an electric motor. The drive motor can be used to relieve the driver while driving and, alternatively or additionally, to increase the vehicle's range. The drive motor can be configured to provide propulsion power to relieve the driver. For example, propulsion power can be provided by the driver through muscle power applied to the pedals and crank arm, and propulsion power provided by the drive motor can also be used to drive the vehicle. The propulsion power provided by the drive motor can thus relieve the driver.

[0011] The method involves determining the angular acceleration of the shaft. A time-dependent profile of the angular acceleration can be determined, for example, for time-equidistant values. For instance, a discrete-time function can be determined as the angular acceleration. The angular acceleration of the pedal crank shaft can be determined. The determination of the angular acceleration can be performed directly or indirectly. The angular acceleration can be determined directly using a sensor. Alternatively or additionally, the angular acceleration can be determined indirectly, depending on another measured quantity.

[0012] The method further includes controlling the drive motor, whereby the drive motor's assistance is activated and deactivated depending on a specific angular acceleration. For example, an initial angular acceleration value can be determined at a specific time, and the drive motor can be controlled such that the assistance is activated based on this initial angular acceleration. This initial angular acceleration can correspond to a value indicating that the rider is pedaling. When the assistance is activated, drive power is provided by the drive motor to propel the vehicle and, for example, transferred to a driven wheel.

[0013] For example, a second angular acceleration can be determined at a later time than the first. This second angular acceleration can differ from the first in sign and, alternatively or additionally, in magnitude. The second angular acceleration might correspond to a value indicating that the rider is not pedaling and, for example, is merely resting their feet on the pedals. For instance, the sign of the second angular acceleration could be different from the sign of the first. The drive motor can then be controlled such that, depending on this second angular acceleration, the assistance provided by the drive motor is deactivated. When the assistance is deactivated, for example, no drive power is provided by the drive motor to propel the vehicle.

[0014] This method makes it particularly easy to detect when the rider is pedaling and, depending on this, to switch the assistance from the drive motor on or off. Pedaling can be determined by measuring the angular acceleration of the shaft, which is at least indirectly connected to the crank axle that is directly accelerated by the rider while pedaling. As described in the previous example, the first value of the angular acceleration is determined, thus indicating that the rider is pedaling. If the second value of the angular acceleration is determined—for example, a value opposite in sign to the first—it is determined that the rider is not pedaling. Then the drive motor and, alternatively or additionally, its assistance are switched off.

[0015] According to the law of conservation of angular momentum, there is a relationship between the sum of all torques acting on a shaft, the shaft's moment of inertia, and the shaft's angular acceleration. Thus, the sum of the applied torques equals the shaft's moment of inertia multiplied by the shaft's angular acceleration. The angular acceleration of the shaft, and therefore of the pedal crank (which is indirectly accelerated by the shaft), is positively correlated with a rider torque acting on the shaft, for example, on the pedal crank. The rider torque can be the torque applied by the rider to propel the vehicle. The shaft's moment of inertia can be predetermined and stored as a hard-coded value on the control unit. By determining the angular acceleration, the rider torque can be deduced.Therefore, steering can be carried out in at least indirect dependence on the driver's torque, without the need to directly measure the driver's torque.

[0016] Deactivating the drive motor's assistance when the rider is not pedaling may be necessary to increase the safety of such vehicles. Compared to conventional methods, which use a torque sensor to measure and determine the rider's torque applied to the crank axle, this method allows for particularly simple detection of rider pedaling. This is achieved by determining the angular acceleration. Determining rider torque with a dedicated torque sensor is typically comparatively complex due to rotating parts on the crank axle. Furthermore, the necessary installation space for such a torque sensor is required, which can increase development and production costs as well as system complexity.Adding such a sensor to the vehicle also necessitates an increase in the number of electrical and electronic interfaces required to connect the sensor to the vehicle's existing power supply and to communicate with other electronic units. Furthermore, like any component, such a sensor can malfunction or fail, potentially reducing the vehicle's reliability, availability, and safety. The method described here reduces the number of sensors and electrical and electronic interfaces required. Often, a sensor for measuring another parameter is already present, and the angular acceleration can be determined based on this measurement.

[0017] Some vehicles powered at least partially by muscle power have a freewheel between the crank axle and the driven wheel. The freewheel can be open or closed. When the freewheel is closed, power applied to the crank axle can be transferred to the driven wheel to propel the vehicle. When the freewheel is open, no power is transferred from the crank axle to the driven wheel to propel the vehicle. Similarly, when no power is transferred, no rider torque is applied to the crank axle, as there is no resistance while pedaling. For example, if the vehicle is already moving before the rider begins pedaling, the freewheel is open.When the rider begins pedaling, the freewheel is still open, and the crank arm exhibits a non-zero angular acceleration. After a specific rotation of the crank arm through a certain angle, the freewheel engages. Drive force is then transmitted, and a non-zero rider torque is applied to the crank arm. Therefore, the angular acceleration of the arm is non-zero at a given moment, while no rider torque is yet being applied. This method allows for earlier detection of whether the rider is pedaling compared to conventional methods, taking into account the rider torque.According to this, the method offers a way to switch the support from the drive motor on or off depending on the rider's pedaling, and at the same time the detection time of pedaling can be reduced, which can improve comfort and safety, for example.

[0018] Detection accuracy can also be improved by eliminating the need to wait for rider torque to be applied. Safety can be enhanced by allowing the rider to rely on the motor's assistance switching on or off based on pedaling activity. Furthermore, determining angular acceleration is generally less complex than determining torque at the crank axle, for example, because fewer additional sensors are required on the vehicle.

[0019] According to a further embodiment, the method can be characterized in that, during steering, assistance from the drive motor can be engaged when the specific angular acceleration exceeds a first threshold. Engaging the assistance can involve the drive motor providing power. The first threshold can, for example, be defined such that the angular acceleration is greater than the first threshold when the rider begins pedaling. For instance, the rider can begin pedaling, and thus the angular acceleration can exceed the first threshold.

[0020] Thus, depending on the first threshold value, which can be stored as a hard-coded value on the vehicle's control unit, an objective limit for activating the drive motor's assistance can be defined. This allows the point in time when pedaling begins to be detected. Therefore, this method enables event detection of the start of pedaling by determining the angular acceleration.

[0021] According to a further embodiment, the method can be characterized in that, during control, the assistance provided by the drive motor can be switched off when the specified angular acceleration falls below a second threshold. Switching off the assistance can mean ceasing the provision of driving force by the drive motor. The second threshold can be the same as or different from the first threshold. The first and second thresholds can be different. For example, the first and second thresholds can have opposite signs. The magnitude of the first threshold can be the same as or different from the magnitude of the second threshold.

[0022] This allows the point at which pedaling ceases to be detected. Therefore, this method can be used to implement event detection regarding the cessation of pedaling by determining the angular acceleration.

[0023] For example, the angular acceleration can be positive at a first point in time and exceed the first threshold, which can also be positive. This indicates that the driver is pedaling at that first point in time and applying muscle power to propel the vehicle. For example, the driver can begin pedaling, and thus the angular velocity of the shaft can increase. In this case, the angular acceleration can be positive at that first point in time. At a later, second point in time, the driver can stop pedaling, and the angular acceleration can be negative. This angular acceleration can fall below the second threshold, which can also be negative. This indicates, for example, that the driver is no longer pedaling.

[0024] For example, a hysteresis effect can be provided by the method if the magnitudes of the first and second thresholds are different. The magnitude of the first threshold can be greater than the magnitude of the second. If the magnitude of the first threshold is greater than the magnitude of the second, for instance, the assistance can only be engaged at a higher angular acceleration, whereas the assistance can be disengaged at a lower angular acceleration. This ensures, for example, that the assistance only engages when the rider generates a certain minimum acceleration of the shaft by applying muscle force to the pedals and crank axle, thus causing the angular acceleration to exceed this first threshold.Simultaneously, the smaller value of the second threshold ensures that the rider doesn't have to stop pedaling as quickly as they started. Then the assistance can be switched off. This allows the deactivation of the assistance by the drive motor to be defined and controlled via the second threshold.

[0025] Furthermore, the method is characterized by the ability to determine an additional measurement variable on the drivetrain. This additional measurement variable could be, for example, the rotational speed of a wheel or the longitudinal acceleration of the vehicle. The measurement variable can be directly measured, for instance, using a sensor. Alternatively or additionally, the measurement variable can be approximated, for example, using an approximation method based on the additional measurement variable. The control of the drive motor can then be carried out based on this additional measurement variable. This control can be performed based on both the additional measurement variable and, furthermore, on the determined angular acceleration.Thus, the switching on or off of the support by the drive motor can be carried out depending on both the specific angular acceleration and the specific other measured variable.

[0026] This can, for example, further improve accuracy. Alternatively or additionally, the process can be made more reliable, as redundancy can be implemented. This can reduce the reliability, availability, and safety of the vehicle.

[0027] To determine the additional measured variable, a torque is measured at the shaft using a torque sensor. This allows the determination of the additional measured variable. The torque sensor can have one or more strain gauges. The shaft can be the crank arm. The torque at the crank arm can be rider torque. The drive motor can be controlled based on the measured torque. This control of the drive motor, and thus, for example, the activation or deactivation of the motor's assistance, can be based on either the determined angular acceleration or the measured torque.

[0028] This allows for redundancy in the control process of the drive motor and its assistance through activation or deactivation. This improves the safety, availability, and reliability of the process and, consequently, the vehicle. This can be advantageous for safety-critical functions, such as the activation or deactivation of the drive motor assistance. Such a method can also reduce the time delay present in conventional methods before the freewheel engages, which rely solely on a torque sensor to measure the driver's torque and activate or deactivate the drive motor assistance accordingly. With the method presented here, activation or deactivation can, for example, initially be performed solely based on a specific angular acceleration.Within a specific time window, this control of the assistance and the drive motor can then be checked in relation to the measured torque. This also allows the measured rider torque to be used to control the drive motor, switching the assistance on or off, thereby reducing the time delay between starting pedaling and engaging the freewheel by means of the determined angular acceleration.

[0029] The drive motor is controlled based on a specific angular acceleration when a torque sensor's measuring range is exceeded. For example, the drive motor can be controlled based on a specific angular acceleration only when, or exactly when, the torque sensor's measuring range is exceeded. This measuring range can be a predefined area within which the torque sensor can measure the torque at the shaft with a predefined high level of confidence. During control, the assistance can be switched on or off based on the specific angular acceleration when the torque sensor's measuring range is exceeded.

[0030] This allows, for example, the torque sensor to be used to determine the driver's torque, and the drive motor to be controlled based on this measured torque, provided the measuring range is not exceeded. If the measuring range is not exceeded, the torque can be measured with a high level of confidence. If the measuring range is exceeded, the torque can no longer be measured with a high level of confidence. In this case, the specific angular acceleration can be used to control the drive motor instead. This enables the drive motor to be controlled even outside the measuring range of the torque sensor, although the torque sensor itself cannot measure torque with a high level of confidence. This allows for the installation of a simple torque sensor that enables torque measurement within a specific measuring range.At the same time, higher torques are possible, for example, higher rider torques at the crank axle, which do not need to be directly measured for control purposes. Instead, the angular acceleration can be determined, which correlates at least with the torque. This allows control to be performed even outside the measurement range.

[0031] Additionally or alternatively, a determination is made as to whether a fault condition of the torque sensor exists, for example, at least one fault condition. A fault condition can include a failure or malfunction of the torque sensor. Determining whether a fault condition exists can be carried out by means of a device. The device can be the control unit for executing steps of the procedure. Alternatively or additionally, the device can be the torque sensor itself. Controlling the drive motor can be carried out depending on the specified angular acceleration, for example, if, only if, or exactly if a fault condition exists, for example, at least one fault condition. During control, switching on or off the assistance can be carried out depending on the specified angular acceleration if a fault condition exists, for example, at least one fault condition.

[0032] This allows the control to be performed based on a specific angular acceleration if the torque sensor malfunctions, for example, if it has failed. This increases the reliability of the drive motor control by using the specific angular acceleration instead of the torque measured by the torque sensor. This can improve the safety, reliability, and availability of such a vehicle.

[0033] A second aspect of the present invention relates to a drive train for a vehicle. The vehicle can be a bicycle, e-bike, pedelec, or cargo bike that is powered, at least temporarily, by muscle power. The drive train can include a shaft that is accelerated when the vehicle is propelled by a rider. For example, the shaft can be mechanically connected to the crank arm. Crank arms can be non-rotatably connected to the crank arm. For example, two crank arms can be non-rotatably connected to the crank arm, with a pedal rotatably mounted at one end of each crank arm. The crank arm can thus also be referred to as the pedal crank. The crank arm can be rotatably mounted on the vehicle's frame by means of a bearing.The bearing can be a rolling bearing, for example a ball bearing, a needle bearing, or a roller bearing. The pedal crank shaft allows the rider's driving force to propel the vehicle.

[0034] Furthermore, the powertrain may include a drive motor, such as an electric motor, to provide propulsion power to assist the driver in driving the vehicle. The drive motor may be designed to relieve the driver of effort while driving and to increase the vehicle's range. Additionally, the drive motor may be designed to provide propulsion power to relieve the driver.

[0035] The drive train may include a means for determining the angular acceleration of the shaft. The drive train may include one or more means for determining the angular acceleration. Furthermore, the drive train may include a control device for controlling the drive motor. The assistance provided by the drive motor can be switched on and off depending on the determined angular acceleration, either alternatively or additionally.

[0036] This allows the drive train to be configured to switch the relief or support provided by the drive motor on or off depending on the angular acceleration of the shaft. Further features, embodiments, and advantages are described in the first aspect. Conversely, features, embodiments, and advantages of the second aspect also represent features, embodiments, and advantages of the first aspect.

[0037] According to a further embodiment, the drive train can be characterized in that the control device can be configured to perform steps of a method according to an embodiment of the first aspect of the present invention. The drive train can be configured to perform all steps of the method according to an embodiment of the first aspect. For example, the means for determining the acceleration and the control device can be jointly configured to perform all steps of the method according to an embodiment of the first aspect. Furthermore, the drive train can include a torque sensor for measuring a torque on the shaft.

[0038] According to a further embodiment, the drivetrain can be characterized in that it includes a sensor for measuring an angular signal of the shaft. The angular signal can be measured as a time-dependent progression, for example, with angular values ​​at time-equidistant intervals between the individual angular values. The sensor can be configured to measure the crank angle of the crank arms of the pedal crank shaft. The control device can be configured as the means for determining the angular acceleration as a function of the measured angular signal. The angular acceleration can be determined by approximate two-stage time differentiation of the angular signal. Thus, the crank angle can be measured using a sensor that is often already present in conventional vehicles. The angular acceleration can then be determined based on this measurement.For example, a dedicated sensor for angular acceleration is not required. This can reduce the complexity of the powertrain and thus increase reliability.

[0039] According to a further embodiment, the drive train can be characterized in that it includes a sensor for measuring the cadence of the shaft. The cadence can be measured as a time-dependent progression, for example, with cadence values ​​at equidistant intervals between the individual values. The sensor can be configured to measure the cadence of the pedal crank shaft. The cadence can be an angular velocity, for example, the crank angular velocity of the pedal crank shaft. The control device can be configured to determine the angular acceleration as a function of the cadence. The angular acceleration can be determined by approximating it with a simple time-dependent differentiation of the cadence. The advantages of the previous embodiment also apply to this embodiment.

[0040] The determination of angular acceleration using approximate differentiation can be performed using a numerical method. This determination can be approximate. For example, a numerical method can determine the angular acceleration using the difference quotient. A numerical method can also determine the angular acceleration using a differentiating low-pass filter, such as a differentiating IIR or FIR low-pass filter. For example, the cadence, as a discrete function of time with time-equidistant intervals between the measured cadence values, can be easily differentiated over time. Alternatively, the angular signal, as a discrete function of time with time-equidistant intervals between the measured angular signal values, can be differentiated twice over time. For this, the difference quotient can be determined twice.Alternatively, the differentiating low-pass filter can be applied in two stages. For this, the low-pass filter can be a single differentiating low-pass filter. Alternatively, a double differentiating low-pass filter, such as an IIR or FIR low-pass filter, can be used. This double differentiating low-pass filter is, for example, applied in a single stage.

[0041] A third aspect of the present invention relates to a vehicle with a drive train according to an embodiment of the second aspect of the present invention. The vehicle can be a bicycle, e-bike, pedelec, or cargo bike that is powered at least temporarily by muscle power. Further features, embodiments, and advantages of each aspect are described in the descriptions of the first and second aspects, respectively. Conversely, features, embodiments, and advantages of the third aspect also represent features, embodiments, and advantages of the first and second aspects, respectively.

[0042] Fig. Figure 1 schematically shows the steps of a procedure for controlling the powertrain of a vehicle.

[0043] Fig. Figure 2 schematically shows a vehicle with a drive train and a control device for executing the schematically described Fig. 1. The steps of the procedure for controlling the powertrain are shown.

[0044] Fig. Figure 1 schematically shows the steps of a procedure for controlling a powertrain 4 of a vehicle 2. Fig. Figure 2 schematically shows such a vehicle 2, which can be propelled at least temporarily by muscle power, with such a drive train 4. The drive train 4 has a shaft 6 which is accelerated when the vehicle 2 is propelled by a driver of the vehicle 2. According to one embodiment, the shaft 6 is a pedal crank shaft of the vehicle 2. The pedal crank shaft is rotatably mounted on a frame of the vehicle 2 by means of a bearing of the vehicle 2. The pedal crank shaft also has pedals (not shown) which are rotatably arranged on crank arms (not shown) of the pedal crank shaft. The bearing is a roller bearing. Furthermore, the drive train 4 has a drive motor 12 for providing propulsion power to assist a driver of the vehicle 2 when propelling the vehicle 2.

[0045] Furthermore, the drive train 4 includes a sensor 13 for measuring S5 an angular signal of the shaft 6. According to one embodiment, the sensor 13 is configured to measure S5 a crank angle of the pedal crank shaft. The sensor 13 is arranged on the frame of the vehicle 2.

[0046] Furthermore, the drive train 4 includes a sensor 14 for measuring S6 of the cadence of the shaft 6. According to one embodiment, the sensor 14 is configured to measure S6 of the cadence of the pedal crank shaft. The sensor 14 is arranged on the frame of the vehicle 2.

[0047] Furthermore, the drive train 4 includes a torque sensor 15 for measuring S3.1 of a torque at the shaft 6. The torque sensor 15 is configured to determine S3 of another measured quantity at the drive train 4. When determining S3 of the other measured quantity, a measurement S3.1 of a torque at the shaft 6 is performed using the torque sensor 15. According to one embodiment, the torque sensor 15 is configured to measure S3.1 of a rider torque at the crank axle. This determines the other measured quantity. The torque sensor 15 is arranged on the shaft 6. The torque sensor 15 has at least one strain gauge for measuring S3.1 of the torque.

[0048] According to one embodiment, the drive train 4 includes sensor 13 for measuring the angle signal S5, sensor 14 for measuring the cadence S6, and torque sensor 15 for measuring the torque S3.1. In an alternative embodiment, the drive train includes two of the sensors 13, 14, and the torque sensor 15. In another alternative embodiment, the drive train 4 includes either sensor 13 for measuring the angle signal S5, sensor 14 for measuring the cadence S6, or torque sensor 15 for measuring the torque S3.1.

[0049] The drive train 4 also includes a control device 16. The control device 16 is communicatively connected to the sensors 13, 14, the torque sensor 15 and the drive motor 12.

[0050] The drive train 4 further comprises a means for determining S1 of the angular acceleration of the shaft 6. The control device 16 is configured as the means for determining S1 of the angular acceleration. According to one embodiment, the control device 16 is configured to determine S1 of the angular acceleration as a function of the measured angular signal. According to another embodiment, the control device 16 is configured to determine S1 of the angular acceleration as a function of the measured cadence.

[0051] The determination of the angular acceleration S1 is carried out approximately. According to one embodiment, a numerical method is used to determine the angular acceleration profile from a measured profile of the angular signal. According to another embodiment, a numerical method is used to determine the angular acceleration profile from a measured profile of the cadence. The numerical method is a time differentiation method. Simple or double time differentiation is performed by the control device 16. According to one embodiment, simple differentiation of the cadence is performed to determine the angular acceleration. According to another embodiment, double differentiation of the angular signal is performed to determine the angular acceleration. According to yet another embodiment, both simple and double differentiation are performed.This increases the accuracy in determining S1, the angular acceleration. According to one embodiment, either simple or double differentiation is performed. This reduces the computational effort required to determine S1, the angular acceleration.

[0052] The control device 16 is configured to control S2 of the drive motor 12. The assistance provided by the drive motor 12 is switched on or off depending on the specified angular acceleration. The control device 16, the sensors 13, 14, and the torque sensor 15 are configured to perform steps of the schematically shown in Fig. to carry out the procedure shown in 1.

[0053] During control operation S2, the assistance provided by the drive motor 12 is activated (S2.1) when the specified angular acceleration exceeds a first threshold. Furthermore, during control operation S2, the assistance provided by the drive motor 12 is deactivated (S2.2) when the specified angular acceleration falls below a second threshold. In the illustrated embodiment, the magnitude of the first threshold is greater than the magnitude of the second threshold. The first threshold has a positive sign, and the second threshold has a negative sign. In an alternative embodiment, the magnitude of the first and the magnitude of the second threshold are identical.

[0054] Furthermore, the control S2 of the drive motor 12 is carried out as a function of a further measured variable. The control S2 of the drive motor 12 is carried out as a function of the determined torque, which was measured by the torque sensor 15. This implements redundancy in the method. The control S2 of the drive motor 12 as a function of the angular acceleration is verified using the determined torque. In an alternative embodiment, the control S2 of the drive motor 12 is carried out as a function of the determined torque, and the control S2 of the drive motor 12 as a function of the determined angular acceleration implements redundancy in the control S2.

[0055] According to one embodiment, the control S2 of the drive motor 12 is performed depending on the specified angular acceleration when a measuring range of the torque sensor 15 is exceeded. The measuring range defines a region in which the measured torque values ​​have a high confidence level. Outside the measuring range, the measured torque values ​​have a lower confidence level. Thus, according to one embodiment, the control S2 is performed depending on the torque measured by the torque sensor 15 and independently of the angular acceleration when the measuring range is not exceeded. If the measured torque is outside the measuring range, and therefore the measuring range is exceeded, the control S2 of the drive motor 12 is performed depending on the specified angular acceleration and independently of the measured torque.

[0056] In one embodiment, a determination S4 is performed to determine whether a fault condition exists in the torque sensor 15. In another embodiment, the determination S4 is performed by the control device 16. This means that the determination S4 is performed by a different element than the torque sensor 15, thus reducing its susceptibility to errors. In yet another embodiment, the determination S4 is performed using the torque sensor 15, thus reducing the requirements for the control device 16. In yet another embodiment, the determination S4 is performed by both the control device 16 and the torque sensor 15. In yet another embodiment, either the determination S4 is performed by the control device 16 or by the torque sensor 15. A fault condition includes both a simple fault of the torque sensor 15, such as incorrect calibration, and a complete failure of the torque sensor 15.If a fault condition exists, the control of the drive motor 12 S2 is carried out depending on the specified angular acceleration. According to one embodiment, the control of S2 is carried out depending on the measured torque and independently of the specified angular acceleration when no fault condition exists. If a fault condition exists, the control of S2 is carried out independently of the measured torque and depending on the specified angular acceleration.

[0057] With such a method and such a drive train 4, precise and rapid detection and determination of the rider's pedaling in the vehicle 2 is made possible. Thus, the method and the drive train 4 are configured to detect and determine pedaling more accurately and quickly than known methods and drive trains that detect pedaling solely based on measuring the rider's torque at the crank arm 6. This increases safety when using the vehicle 2 with such a drive train 4 controlled by such a method. Switching the assistance provided by the drive motor 12 on or off is therefore carried out more quickly compared to known methods and drive trains that switch the assistance on or off solely based on the measured rider torque. Reference sign 2 vehicles 4 Powertrain 6 wave 12 Drive motor 13 Sensor for measuring an angular signal of the shaft 14 Sensor for measuring the cadence of the wave 15 Torque sensor 16 Control device S1 Determining the angular acceleration of the wave S2 Controlling the drive motor S2.1 Activating support from the drive motor S2.2 Switching off support from the drive motor S3 Determining another measured variable on the powertrain S3.1 Measuring a torque on the shaft S4 Determine if the torque sensor is faulty S5 Measuring the angle signal of the wave S6 Measuring the cadence of the wave

Claims

[1] Method for controlling a drive train (4) of a vehicle (2), wherein the drive train (4) has at least one shaft (6) which is accelerated when the vehicle (2) is driven by a driver, wherein the drive train (4) has a drive motor (12) for providing drive power to assist the driver of the vehicle (2) when driving the vehicle (2), wherein the method comprises the steps: determining (S1) an angular acceleration of the shaft (6); and controlling (S2) the drive motor (12), wherein the assistance provided by the drive motor (12) is switched on or off depending on the determined angular acceleration, wherein a further measurement (S3) is carried out on the drive train (4), and wherein the control (S2) of the drive motor (12) is carried out depending on the further measurement, wherein a measurement (S3) is carried out when determining (S3) the further measurement.1) a torque on the shaft (6) is carried out with a torque sensor (15), and that the control (S2) of the drive motor (12) is carried out depending on the measured torque, . characterized by , that the control (S2) of the drive motor (12) is carried out depending on the specific angular acceleration when a measuring range of the torque sensor (15) is exceeded, and / or characterized by , that a determination (S4) is carried out to determine whether a fault condition of the torque sensor (15) exists, and that the control (S2) of the drive motor (12) is carried out depending on the determined angular acceleration if a fault condition exists. [2] Method according to claim 1, characterized by , that during control (S2) an activation (S2.1) of the support by the drive motor (12) is carried out when the certain angular acceleration exceeds a first threshold value. [3] Method according to any one of the preceding claims, characterized by , that during control (S2) a shutdown (S2.2) of the support by the drive motor (12) is carried out if the specified angular acceleration falls below a second threshold value. [4] Drive train (4) for a vehicle (2), wherein the drive train (4) has at least one shaft (6) which is accelerated when the vehicle (2) is driven by a driver, wherein the drive train (4) has a drive motor (12) for providing drive power to assist the driver of the vehicle (2) when driving the vehicle (2), wherein the drive train (4) has a means for determining (S1) an angular acceleration of the shaft (6), wherein the drive train (4) has a control device (16) for controlling (S2) the drive motor (12), and wherein the assistance provided by the drive motor (12) is switched on or off depending on the determined angular acceleration. [5] Drive train (4) according to claim 4, characterized by , that the control device (16) is configured to perform steps of a method according to any one of claims 1 to 3. [6] Powertrain (4) according to one of claims 4 or 5, characterized by , that the drive train (4) has a sensor (13) for measuring (S5) an angular signal of the shaft (6) and that the control device (16) is set up as the means for determining (S1) the angular acceleration as a function of the measured angular signal. [7] Powertrain (4) according to any one of claims 4 to 6, characterized by , that the drive train (4) has a sensor (14) for measuring (S6) a cadence of the shaft (6) and that the control device (16) is set up as the means for determining (S1) the angular acceleration as a function of the measured cadence. [8] Vehicle (2) with a drive train (4) according to any one of claims 4 to 7.

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