Method and control device for controlling a drive motor of a muscle-powered vehicle

Abstract

A method (S4) for controlling a drive motor (4) of a muscle-powered vehicle (2) is described. The method comprises determining (S1) a nominal setpoint for the rotational speed of a shaft (6) connected to the drive motor (4) and determining (S2) a threshold for the magnitude of the setpoint as a function of a specific temperature of an element (8) of the vehicle (2). Furthermore, the method comprises determining (S3) a setpoint for the rotational speed of the shaft (6), wherein the setpoint is the determined nominal setpoint if the magnitude of the nominal setpoint is less than the threshold for the magnitude of the setpoint, and otherwise the setpoint is determined such that the magnitude of the setpoint corresponds to the determined threshold and the sign of the setpoint corresponds to the sign of the determined nominal setpoint.The method further includes controlling (S4) the drive motor (4) depending on the determined setpoint of the speed. A control device (10) is also described, which is configured to execute such a method.

Description

Technical area

[0001] The present invention relates to a method for controlling a drive motor of a human-powered vehicle. Furthermore, the present invention relates to a control device configured to carry out this method. Furthermore, the present invention relates to a drive train having such a control device and further to a vehicle having such a drive train. State of the art

[0002] Human-powered vehicles have drive motors to support the muscular power of a driver. A vehicle designed as a pedelec has an electric machine as the drive motor. Such a drive motor provides a specific speed to drive the vehicle. The higher the provided speed, the greater the power loss of the drive motor. If the speed is too high, this can lead to overheating of the drive motor and thus to reduced efficiency or thermal destruction of the drive motor. For this reason, such drive motors are controlled using derating functions that limit the power of the drive motor to prevent such overheating. DE 10 2022 200 541 A1, for example, describes how a derating function is modeled depending on several parameters. For this purpose, an expected thermal load for future points in time is determined.The drive motor is then controlled using the derating function modeled in this way. Furthermore, DE 10 2021 213 526 A1 describes a method for operating an electric bicycle. Furthermore, WO 2020 / 064 324 A1 describes an electric pedelec bottom bracket drive. Description of the invention

[0003] The object of the invention is to provide an improved method for controlling a drive motor of a human-powered vehicle. This object is achieved by a method having the features of independent claim 1. Furthermore, this object is achieved by a control device configured to carry out such a method. Furthermore, this object is achieved by a drive train having such a control device and by a human-powered vehicle having such a drive train.

[0004] In a first aspect, the present invention relates to a method for controlling a drive motor of a human-powered vehicle. The human-powered vehicle can be, for example, a bicycle, an e-bike, a pedelec, or a cargo bike. The drive motor can be, for example, an electric machine. The method for controlling the drive motor can be a method for operating the drive motor. The drive motor can be speed-controlled and, alternatively or additionally, speed-regulated. The drive motor can be part of a drive train of the vehicle. The drive motor can relieve or assist a driver of the vehicle when driving or pushing the vehicle by providing drive force. The method can be a computer-implemented method. A control device as part of the vehicle can be configured to carry out steps of the method.The vehicle may have a crank and pedals to absorb muscle power as driving force.

[0005] The method involves determining a nominal setpoint of the rotational speed of a shaft connected to the drive motor. Alternatively or in addition to the step of determining the nominal setpoint, the method may include a step of reading in the nominal setpoint. For example, the nominal setpoint can be determined by another method and read in as the first step of this method in the step of reading in. The determination of the nominal setpoint can be carried out independently of the temperature. The nominal setpoint can be a desired setpoint of the rotational speed of the shaft. In this step of determination, one or more nominal setpoints of the rotational speed of the shaft can be determined, for example as the time course of the nominal setpoint of the rotational speed of the shaft.When determining the nominal setpoint of a shaft speed, a single value or, alternatively, a time profile of the nominal setpoint of the shaft speed can be determined. The nominal setpoint can be referred to as the nominal value of the setpoint of a speed. The shaft can be connected directly or indirectly to the drive motor.

[0006] The method comprises determining a threshold value for an absolute value of the target speed value as a function of a specific temperature of an element of the vehicle. The determination can be a determination of one or more threshold values ​​for an absolute value of the target speed value. In this case, for example, a threshold value for a specific point in time or, for example, a temporal progression of threshold values ​​can be determined. If multiple threshold values ​​are determined, the threshold values ​​for the absolute values ​​of target speed values ​​can be determined. The determined temperature can be a predetermined temperature, such as a temperature progression of the element of the vehicle, such as a part of the vehicle's drive motor. The determined temperature can be less than or equal to a maximum temperature that may prevail at the element without risking overheating of the element and, alternatively or additionally, of the drive machine.The threshold value should then be determined, for example, in such a way that this maximum temperature at the element is never exceeded. For example, the determination should be carried out in such a way that the following applies at any time: ϑ≤ϑmax, where ϑ is the specific temperature and ϑ max the maximum temperature.

[0007] Furthermore, the method involves determining a target value for the rotational speed of the shaft. If the amount of the nominal target value is less than the threshold value for the amount of the target value, the determined target value is the nominal target value. In an alternative embodiment, the determined target value can be the nominal target value if the amount of the nominal target value is less than or equal to the threshold value for the amount of the target value. The determination can include comparing the nominal target value with the threshold value. When determining the target value, a single target value can be determined, or alternatively, multiple target values of the shaft can be determined, for example, as the time course of the target value of the rotational speed of the shaft. Then, for example, multiple determined nominal target values can be compared with multiple determined threshold values for amounts of the target value, for example, as time courses.Otherwise, for example, if the nominal setpoint value is greater than or equal to the threshold value for the nominal setpoint value, the setpoint is determined such that the setpoint value corresponds to the specified threshold value and the sign of the setpoint value corresponds to the sign of the specified nominal setpoint value. This can also be performed for individual values ​​or for a temporal progression of setpoints.

[0008] The method further comprises controlling the drive motor as a function of the determined target speed value. If, for example, multiple target speed values ​​are determined, for example as a temporal progression of the target speed value, the drive motor can be controlled as a function of the multiple determined target speed values, such as the determined temporal progression of the target speed value. The control can be a control and, alternatively or additionally, a regulation of the drive motor. In this case, the speed at the shaft can, for example, be set close to the determined target speed value.

[0009] With such a method for controlling the drive motor, a derating function can be implemented. This allows the drive power, provided here, for example, by controlling the drive motor using the speed, to be limited in order to prevent the drive motor from overheating. The method can therefore be used to derate the drive motor. By controlling the drive motor depending on the determined target speed, the power of the drive motor can be effectively limited and reduced. Derating can prevent unwanted performance losses and, alternatively or additionally, unwanted wear of the drive motor, since overheating of the drive motor can be prevented. Furthermore, endangering a user of the vehicle due to an excessively high surface temperature of the element can be prevented.Under normal circumstances, i.e. when the magnitude of the nominal value is less than the threshold value for the magnitude of the setpoint, the nominal setpoint can be passed on and used as a specific setpoint to control the drive motor. At the same time, the speed and thus the power of the drive motor can be automatically restricted and limited if the magnitude of the nominal setpoint is not less than the threshold value and, for example, overheating would be imminent if the nominal setpoint were used as the speed setpoint for control. The threshold value is then used to control the drive motor as the setpoint, with the direction of rotation of the shaft defined by the nominal setpoint being used for control. Thus, nominal operation and derating operation can be provided with the method. A situational limitation of the power of the drive motor can be implemented using the method.Situational can mean that in every situation where the nominal setpoint can be used to control the drive motor, this should also be used and the power of the drive motor should therefore not be limited or restricted. This means that the method can be combined with other methods and implementations for speed control; for example, another method can independently provide a nominal setpoint for the speed. With the method presented here, this nominal setpoint can then be read in, for example, and either used to control the setpoint or the power of the drive motor can be limited using the method. This means that this method can be integrated into several different control devices for controlling different drive motors in different vehicles. This can reduce development effort.The method thus provides a well-partitionable method for controlling the drive motor, as it does not place any special requirements on, for example, higher-level methods for speed control, for example, for determining a nominal setpoint. Furthermore, the method does not place any special requirements on, for example, lower-level methods for determining currents and, alternatively or additionally, voltages for controlling the drive motor. The nominal setpoint can be determined independently of the setpoint for the absolute value of the speed setpoint. The nominal setpoint can be determined using a variety of possible methods. Regardless of the specific method used to determine the nominal setpoint, the method for controlling the drive motor can be used for derating. This method for derating can therefore be combined with a variety of different methods for determining the nominal setpoint.This can further reduce development effort. This allows the actual logic for controlling the drive motor during normal operation, such as determining the nominal setpoint, to be performed independently of the described method for controlling the drive motor for derating, i.e., for physically limiting the drive motor's power. The determined nominal setpoint used to control the drive motor therefore does not automatically prevent the element's maximum temperature from being exceeded, for example. However, comparing it with the threshold value performed by this method does, for example, result in such a power limitation. This further reduces development effort because the nominal setpoint can be determined independently.

[0010] According to a further embodiment, the method can be characterized in that the nominal setpoint can be determined as a function of a measured speed on the vehicle. The nominal setpoint can be proportional to the measured speed on the vehicle. Alternatively or additionally, the nominal setpoint can converge towards a value proportional to the measured speed. Converging here can mean an asymptotic approach and, alternatively or additionally, a tendency towards an approximation between the nominal setpoint and a value proportional to the measured speed. As an alternative to the measured speed, the speed on the vehicle can be estimated.

[0011] Thus, the method can be used to determine a nominal setpoint, or alternatively, multiple nominal setpoints, such as a temporal progression of the nominal setpoint, depending on the situation, depending on a measured speed. The method can thus be used to synchronize the bicycle's speeds, for example, when the nominal setpoint converges to the measured speed.

[0012] According to a further embodiment, the method can be characterized in that the determination of the nominal setpoint is carried out as a function of a measured rotational speed of a crank of the vehicle. The rotational speed of the crank can be referred to as cadence. The rotational speed at the vehicle's crank can be measured, for example, using a rotational speed sensor on the crank. The measured rotational speed can, for example, be a rotational speed applied by the driver of the vehicle, for example, by pedaling.

[0013] For example, the method can implement pedal assist to support the driving force applied by the driver to the vehicle's pedals using muscle power. This method can increase comfort because the nominal speed setpoint, for example, converges to a value proportional to the cadence applied by the driver, thus preventing the pedals from striking the driver's feet due to the pedal assist.

[0014] According to a further embodiment, the method can be characterized in that the determination of the nominal setpoint is carried out as a function of a measured rotational speed of a driven wheel of the vehicle. The driven wheel can be a rear wheel of the vehicle configured as a pedelec. A sensor can be configured to measure the rotational speed of the driven wheel. The driven wheel can be mechanically operatively connected to the shaft.

[0015] For example, the method can implement push assistance to support the driving force applied by the driver to the vehicle's handlebars using muscle power. This method can increase comfort because the nominal setpoint of the speed, for example, converges to the speed of the driven wheel, applied by the driver to the vehicle's handlebars using muscle power, thus preventing the handlebars from hitting the driver's hands due to push assistance. For example, the nominal setpoint can be kept constant to maintain a constant speed and thus a constant vehicle speed during push assistance.

[0016] According to a further embodiment, the method can be characterized in that the determination of the nominal setpoint can be carried out depending on a transmission ratio of the vehicle. The transmission ratio can be a ratio between the speed applied by the driver to the vehicle's crank and the nominal setpoint speed. Alternatively or additionally, the transmission ratio is the ratio between the speed of the driven wheel and the nominal setpoint. The transmission ratio can define a relationship between the speed of the shaft and the speed of the vehicle, such as the cadence or the speed of the driven wheel. The transmission ratio can be part of a proportional relationship between the nominal setpoint and the measured speed. The following formulas show the relationship between the nominal setpoint speed and the measured speed: ωref,nom=kpedl ωpedl ωref,nom→kpedl ωpedl ωref,nom=kwhl ωwhl ωref,nom→kwhl ωwhl

[0017] Where ω ref,nom the nominal speed setpoint, k pedl is the ratio between the speed applied by the driver to the vehicle's crank and the nominal speed setpoint. k whl is the ratio between the speed of the driven wheel and the nominal speed setpoint. ω pedl is the measured speed at the crank and ω whl For example, is the measured speed at the driven wheel. According to the first and third equations above, there is a proportional relationship between the measured speed and the nominal setpoint. According to the second and fourth equations, the nominal setpoint converges to the measured value. For example, as time increases, an asymptotic convergence or approximation of the left side of the formula to the right side of the formula can occur.

[0018] The method can thus be used for different vehicles with different gear ratios, and for a single vehicle with different gear ratios, for example, due to a vehicle's gearshift. A nominal target value can then be determined depending on the situation.

[0019] According to a further embodiment, the nominal setpoint can be determined depending on a user input. For example, the adjustment of a lever on the vehicle's handlebars can be read in and determined as user input. For example, the user can specify that the vehicle should be pushed slowly or faster in Eco or Sport mode. The nominal setpoint of the speed can be determined depending on the user input. For example, the nominal setpoint can be specified by the user input and, for example, determined in such a way that the nominal setpoint is kept constant. The nominal setpoint can be determined, for example, independently of a measured speed at the driven wheel of the vehicle. With regard to the above four formulas, for example, ω whlThe speed of a vehicle wheel can be determined based on user input and is independent of the measured speed of the driven wheel. Thus, the push assistance can be implemented in such a way that the push assistance can be adjusted and, for example, specified by the user.

[0020] According to a further embodiment, the method can be characterized in that the determination of the nominal setpoint can be carried out recursively. The determination of the nominal setpoint can be carried out statefully. For example, a first nominal setpoint can be determined for a first point in time and a second nominal setpoint can be determined for a second point in time later than the first. The determination of the second nominal setpoint can be dependent on the determined first nominal setpoint. In this case, unless the nominal setpoint has previously been used as the setpoint, nominal setpoints can be determined as the method continues to run depending on specific speed setpoints. These nominal setpoints can thus be overwritten, for example with specific threshold values ​​with amounts of the speed setpoint.This can, for example, limit changes to consecutive nominal setpoints. This can result in consecutive nominal setpoints changing only at a limited rate, which can lead to more comfortable use of the vehicle.

[0021] Furthermore, determining the threshold value includes determining a power loss of the drive motor using a first mapping. The first mapping maps the power loss of the drive motor and environmental parameters to the temperature. For example, the first mapping can be an operator, such as a differential operator. The first mapping can also represent a power loss map. The relationship between the temperature, the power loss, and environmental parameters can be represented by the following formula: ϑ=Φ[P,ψ]

[0022] Here, ϑ is the temperature, for example, the temperature of the vehicle element, Φ is the first mapping formed as an operator, and ψ are the environmental parameters. The environmental parameters can include, for example, ambient temperature, air humidity, vehicle speed, temperature values, and alternatively or additionally, values ​​of time derivatives of the temperature at a specific point in time. These environmental parameters can influence the relationship between a temporal progression of the power loss and the temperature. The first mapping formed as an operator can map temporal progressions of the power and the environmental parameters onto a temporal progression of the temperature. To determine the power loss, a permissible target curve for the temperature is selected, for example, expressed by the following equation: ϑlim≤ϑmax

[0023] For example, at any given time a limited temperature ϑ lim be less than or equal to the maximum permissible temperature ϑ max For example, it can also apply for any point in time that the permissible target curve ϑ lim equal to the maximum permissible temperature ϑ max The previously mentioned specific temperature of the element, on which the determination of the threshold value for an amount of the setpoint speed depends, can, for example, be the permissible setpoint curve of the temperature ϑ lim Furthermore, determining the threshold value includes determining the threshold value using a second mapping that maps the speed and drive motor parameters to the power loss of the drive motor. The second mapping can be configured as a function, as represented by the following equation: P=γ(ω,ξ) P is the power loss of the drive motor, y is the second mapping, designed as a function, which can map the speed ω and drive motor parameter ξ to the power loss. The function γ can represent a power loss map between the power loss, the speed ω, and the drive motor parameters ξ. The drive motor parameters ξ can, for example, include the temperature of the drive motor and, alternatively or additionally, a torque of the shaft connected to the drive motor. These drive motor parameters can affect the power, in this case power loss, of the drive motor in addition to the speed. The second mapping, designed as a function, for example, can be strictly monotonically increasing with the speed, as expressed as follows: ∂γ∂|ω|>0

[0024] This means that the power increases as the speed increases.

[0025] Advantageously, the method can therefore use physical models and relationships in the form of the first and second mappings to control the drive motor. This makes it possible to achieve a high level of accuracy when determining the speed setpoint. This allows derating to be implemented effectively and efficiently, so that the method for controlling the drive motor can achieve a convenient derating function with comfortable and high driving comfort. Furthermore, this method can be highly reused. Due to the physical models formed by the first and second mappings, the method can be combined with various other methods for controlling the drive motor and determining the nominal setpoint. The method can therefore also be combined with other steps for determining a nominal setpoint for new applications.This minimizes further development effort. Furthermore, calibration of this method is particularly simple because only a few parameters based on physical models are required to execute the method, such as environmental parameters and drive motor parameters. This reduces the development effort of the method. Simpler and better calibration of the parameters can also lead to a better coordinated transition between normal operation and derating operation. This can also increase driving comfort. Furthermore, parameterization can be simplified and accelerated, for example on a test bench. Especially in comparison to previous derating methods, which are not based on physical-mathematical models with physical parameterization, this can result in significantly fewer parameters having to be parameterized on a test bench.This can then lead to fewer malfunctions in the field using the method presented here due to a more suitable calibration for fewer parameters.

[0026] According to a further embodiment, the method can be characterized in that determining the power loss can comprise inverting the first mapping, wherein the inverted first mapping can be evaluated using a specific function. For this purpose, for example, the first mapping designed as an operator can be approximately left-invertible with respect to the power loss. This can mean that the approximately left-inverse Φ̂ -1 of Φ with respect to the power loss exists such that the following equation applies: Φ^−1[Φ[P,ψ]]=P

[0027] This should be at least approximately fulfilled. Thus, the curve of the power loss P lim to achieve the temperature curve ϑlim can be estimated using the following equation: Plim=Φ^−1[ϑlim,ψ]

[0028] The operator Φ̂ -1 Interpolation functions can contain characteristics and, alternatively or additionally, characteristic maps. Interpolation functions can contain regressors. Regressors can be polynomials. Regressors can be radial basis functions. The rewritten equation can be expressed using an explicit expression for Φ̂ -1 be evaluated. For this purpose, the underlying mathematical model, i.e., the first mapping that maps the power loss of the drive motor and loss parameters to the temperature, can be invertible without solving a differential equation for the power loss. For example, the mathematical model can be differentially flat. An explicit representation can be used for the power loss according to the equation just defined: Plim=α(δ−τ0ϑlim(0),δ−τ1ϑlim(1),...,δ−τnϑlim(n),δ−τψψ) where α is, for example, a function, the notation ϑlim(i) the i-th time derivative of ϑ lim For example, ϑlim(0)=ϑlim δ can be a temporal shift operator. For example, the notation (δ τ f)(t) = f(t - τ). τ i with i = 0, ..., n and τ ψ can be dead times. This makes it particularly easy to evaluate the equation for the power loss, as, for example, solving a differential equation is no longer necessary. The dead times τ i with i = 0, ..., n and alternatively or additionally τ ψ can be 0 according to the explicit representation above. This can have the advantage, for example, that no prediction is required for the corresponding quantities. ϑ limcan be chosen as a constant function, which further simplifies the evaluation of the equation described above, since all derivatives of ϑlim(i) with order i>0 are identically equal to 0. The function α can contain interpolation functions. Interpolation functions can contain characteristic curves and, alternatively or additionally, characteristic maps. Interpolation functions can contain regressors. Regressors can be polynomials. Regressors can be radial basis functions. Means for determining values ​​of ψ can be available. Means for prediction and thus, for example, forecasting values ​​of parameters of ψ can be available. Determinations of values ​​of parameters of ψ, i.e. the environmental parameters ψ, can be carried out using sensors. Determinations of values ​​of ψ can include the evaluation of mathematical models. Mathematical models can include machine learning models. Prediction of values ​​of parameters ψ can capture constant extrapolation of determined values ​​of parameters of ψ into the future. Prediction of values ​​of parameters of ψ can include regressors.Regressors can be polynomials. Regressors can be radial basis functions. Prediction of values of parameters ψ can include numerical simulation. Prediction of values of parameters ψ can include evaluating mathematical models. Mathematical models can include machine learning models. Prediction of values of parameters ψ can be performed by state observers. State observers can include linear or non-linear Kalman filters or particle filters. State observers, linear Kalman filters, non-linear Kalman filters and alternatively or additionally particle filters can include mathematical models. Mathematical models can be machine learning models. Values of parameters ψ can be received via a signal interface. Values of parameters ψ can be determined by data processing units. Data processing units can be integrated into the drive motor.Data processing units can be integrated into the drive train and alternatively or additionally into the vehicle and mechanically connected to it. Alternatively, data processing units can be geographically independent of the vehicle. Data processing units can be, for example, a PC, a server, a central computer of the vehicle, a mobile phone or a smartwatch. Values ​​of parameters ψ can be determined using map data and alternatively or additionally using weather information, for example by determining ambient temperature, humidity and alternatively or additionally using map and weather data. For this purpose, the vehicle's coordinates can be determined, for example using satellite navigation or by localization using neighboring radio transmitters and alternatively or additionally radio receivers.

[0029] According to a further embodiment, determining the threshold may comprise inverting the second mapping. From the monotonicity condition defined above regarding the function γ, the threshold may be determined using the following equation: |ω|≤γ−1(Plim,ξ) where γ -1 a left inverse of γ with respect to the speed. Thus, the speed can be determined such that the temperature never exceeds the maximum permissible temperature. In an example case, the temperature ϑ lim equal to the maximum permissible temperature ϑ max In a preferred representation, the threshold |ω ref | lim can be determined using the following equation: |ωref|lim=γ−1(Plim,ξ)

[0030] The function γ -1can contain interpolation functions. Interpolation functions can contain characteristic curves or characteristic maps. Interpolation functions can contain regressors. Regressors can be polynomials. Regressors can be radial basis functions. Means can be present for determining values ​​of parameters ξ, which can be drive motor parameters. Means can be present for predicting values ​​of parameters ξ. Determinations of values ​​of parameters ξ can be carried out using sensors. Determinations of values ​​of parameters ξ can include the evaluation of mathematical models. Mathematical models can include machine learning models. Predictions of values ​​of parameters ξ can include constant extrapolation of determined values ​​of parameters ξ into the future. Predictions of values ​​of parameters ξ can include regressors. Regressors can be polynomials. Regressors can be radial basis functions.Predictions of values ​​of parameters ξ can include numerical simulations. Predictions of values ​​of parameters ξ can include the evaluation of mathematical models. Mathematical models can include machine learning models. Predictions of values ​​of parameters ξ can be made using state observers. State observers can include linear or nonlinear Kalman filters or particle filters. State observers, linear Kalman filters, nonlinear Kalman filters and, alternatively or additionally, particle filters can include mathematical models. Mathematical models can be machine learning models. Values ​​of parameters ξ can be received via a signal interface. Values ​​of parameters ξ can be determined by data processing units. Data processing units can be integrated into the drive motor. Data processing units can be integrated into the drive train.Data processing units can be mechanically connected to the vehicle. Data processing units can be locally independent of the vehicle. Data processing units can be a PC, server, central computer of the vehicle, a mobile phone or a smart watch.

[0031] Accordingly, the target values of the rotational speed can be determined via the following relationship. |ωref,nom|≤|ωref|lim

[0032] Here, the absolute value of the nominal target value |ω ref,nom | is compared with the threshold values for the absolute value of the target value of the rotational speed |ω ref | lim If the inequality described above holds, the nominal target values are used as the target values of the rotational speed ω ref i.e.: ωref=ωref,nom. Otherwise, the following relationship applies: ωref={|ωref|lim,if ωref,nom≥0,−|ωref|lim,if ωref,nom<0

[0033] A second aspect of the present invention relates to a computer program. The computer program may consist of steps of embodiments of the method shown in the first aspect of the present invention.

[0034] A third aspect of the present invention relates to a machine-readable data carrier with such a computer program.

[0035] A fourth aspect of the present invention relates to a control device configured to carry out a method according to an embodiment of the first aspect of the present invention. The control device may have a read-in interface. Thus, for example, nominal setpoints determined with another control device can be read in to then be used in the further steps of this method described here for derating and controlling the drive motor. For example, if the nominal setpoints are merely read in with the method described here, the nominal setpoints can be determined with another control device, for example a control device of the drive motor or the drive train. Alternatively, this other control device for determining the nominal setpoints can also be a PC, a server, a central computer of the vehicle, a mobile phone, or a smartwatch.Furthermore, the control device can have an output interface. This allows the method to provide specific values, such as the target speed, for example, for other control devices and for other methods. Alternatively or additionally, these specific values ​​can be transmitted and stored. Alternatively or additionally, these specific values ​​can be sent, further processed, and alternatively or additionally visualized. For this purpose, a display can be provided, for example, on the vehicle's handlebars, on the smartwatch with an application, on the mobile phone with an application, on the server, on the PC, or on the vehicle's central computer to display these specific values.For example, when derating is active, the derating can be signaled to the user visually, acoustically, or haptically via vibration on the drive motor, the drive train, or, for example, on the display of the vehicle's driver as the vehicle's control unit, or on another control device such as a smartwatch or the user's mobile phone. Alternatively or additionally, information can be displayed, processed, and alternatively or additionally stored, indicating when the derating was active and how intensively it was intervened, for example, how much the specified target value deviated from the nominal target value.

[0036] A fifth aspect of the present invention relates to a drive train comprising a drive motor, a shaft connected thereto, and a control device according to an embodiment of the fourth aspect of the present invention. The drive train may, for example, comprise a sensor for measuring a rotational speed of the shaft and, alternatively or additionally, a sensor for measuring a torque of the shaft.

[0037] A sixth aspect of the present invention relates to a human-powered vehicle with a drive train according to an embodiment of the fifth aspect of the present invention. Such a vehicle can be, for example, an e-bike or a pedelec, for example a cargo bike. Short description of the characters Fig. 1 schematically shows steps of a method for controlling a drive motor of a muscle-powered vehicle. Fig. 2 shows schematically a muscle-powered vehicle with a drive train and a control device for carrying out the functions schematically shown in Fig. 1 shown steps of the procedure. Detailed description of embodiments

[0038] Fig. 1 schematically shows steps of a method for controlling S4 a drive motor 4 of a muscle-powered vehicle 2. Schematically in Fig. 2, the vehicle 2 is shown with a control device 10, which is arranged to schematically Fig. 1. Furthermore, a drive train 12 is shown as part of the vehicle 2, which drive train 12 comprises the drive motor 4, a shaft 6 mechanically connected thereto, and the control device 10. The control device 10 is communicatively connected to the drive motor 4. Furthermore, in Fig.2 schematically shows an element 8 of the vehicle 2, here a part of the drive motor 4. In the embodiment shown, the vehicle 2 is a pedelec with a drive motor 4 designed as an electric motor for drive assistance. The element 8 is a stator of the drive motor 4. In addition, the vehicle 2 has a crank 16, which has a sensor (not shown) for measuring a rotational speed of the crank 16, also referred to as cadence. Furthermore, the vehicle 2 has a driven wheel 18, which has a sensor (not shown) for measuring a rotational speed of the wheel 18. Both the crank 16 and the driven wheel 18 are part of the drive train 12. The sensors of the crank 16 and the wheel 18 are communicatively connected to the control device 10.

[0039] The method comprises determining S1 a nominal target value of a rotational speed of the shaft 6 connected to the drive motor 4. The determination S1 is carried out as a function of a measured rotational speed of the vehicle 2. In this case, a rotational speed applied by a driver of the vehicle 2 is measured at the crank 16 of the vehicle 2. The determination S1 is carried out as a function of the measured rotational speed of the crank 16 when the driver is driving the vehicle 2. In this case, pedal assistance is carried out. If the driver is not driving and pushes the vehicle 2 by applying force to a handlebar of the vehicle 2, push assistance is carried out. In this case, the determination S1 is carried out as a function of a measured rotational speed of the driven wheel 18.

[0040] Furthermore, the determination of S1 of the nominal setpoint is carried out depending on a gear ratio of vehicle 2. The gear ratio is a ratio between the speed measured on vehicle 2 and the nominal setpoint of the speed. The following formulas describe the relationship when determining S1 of the nominal setpoint: ωref,nom=kpedl ωpedl ωref,nom→kpedl ωpedl ωref,nom=kwhl ωwhl ωref,nom→kwhl ωwhl

[0041] Where ω ref,nom the nominal speed setpoint, k pedl is the ratio between the speed applied by the driver to the crank 16 of the vehicle 2 and the nominal speed setpoint. k whl is the ratio between the speed of the driven wheel 18 and the nominal speed setpoint. ω pedı is the measured speed at the crank 16 and ω whlis the measured speed at the driven wheel 18. In the embodiment shown here, the nominal setpoint is determined as a value proportional to the measured speed, i.e., when an equation is used to determine S1 of the nominal setpoint, as defined above by the first and third expressions. In an alternative embodiment, the nominal setpoint should converge to the product of the gear ratio and the measured speed, as defined above by the second and fourth expressions. The first and second expressions relate to pedal assistance, and the third and fourth expressions relate to walking assistance.

[0042] In one embodiment, the determination S1 of the nominal setpoint is performed recursively, wherein the determination S1 is stateful. The determined nominal setpoint depends on previously determined nominal setpoints.

[0043] The method further comprises determining S2 a threshold value for an amount of the target value of the rotational speed as a function of a specific temperature of the element 8 of the vehicle 2. By determining S2, the following condition is to be achieved at all times: ϑ≤ϑmax

[0044] Determining S2 of the threshold value includes determining S2.1 a power loss of the drive motor 4 using a first mapping. The first mapping is configured as an operator Φ. The first mapping maps the power loss P of the drive motor 4 and environmental parameters ψ to the temperature ϑ. The first mapping is described by the following formula: ϑ=Φ[P,ψ]

[0045] Furthermore, determining S2 includes determining S2.2 the threshold value using a second mapping. The second mapping is configured as a function γ. This second mapping maps the speed ω and drive motor parameter ξ to the power loss P of the drive motor 4. The following relationship defines the second mapping: P=γ(ω,ξ)

[0046] Determining S2.1 the power loss involves inverting S2.1.1 of the first figure. The power loss P lim is represented by the following formula: Plim=Φ^−1[ϑlim,ψ]

[0047] The inverted first mapping, Φ̂ -1 is evaluated using a specific function. An explicit representation can be used for the power loss: Plim=α(δ−τ0ϑlim(0),δ−τ1ϑlim(1),…,δ−τnϑlim(n),δ−rψψ)

[0048] Here, α is a function, ϑlim(i) is the i-th time derivative of ϑ lim . δ is a temporal shift operator and τ i with i=0, ..., n and τ ψ are dead times. Furthermore, threshold values ​​for the magnitudes of setpoints of the speed |ω ref | lim determined by the following inequality: |ωref|lim≤γ−1(Plim,ξ)

[0049] In the embodiment shown here, the following formula is used to determine the threshold values ​​in order to be able to determine the highest possible speed as the target value: |ωref|lim=γ−1(plim,ξ)

[0050] Thus, threshold values ​​at a given permissible temperature ϑ lim , and thus certain power loss P lim maximum. The determination S2.2 of the threshold value comprises inverting S2.2.1 the second mapping γ in order to match the inverted second mapping γ -1 to determine threshold values.

[0051] Furthermore, the method comprises determining S3 a setpoint value of the rotational speed ω ref of wave 6. This is done via the following relationship: ωref={ωref,nom,falls|ωref,nom|≤|ωref|lim|ωref|lim,falls|ωref,nom|>|ωref|limand ωref,nom≥0,−|ωref|lim,falls|ωref,nom|>|ωref|limand ωref,nom<0

[0052] The equation shown above means that the setpoint of the speed ω ref the determined nominal setpoint ω ref,nom is determined if an amount of the nominal setpoint |ω ref,nom | is less than or equal to the threshold value for an amount of the setpoint |ω ref | lim. For this purpose, a comparison of the nominal setpoint and the threshold value is carried out during determination S3. In the embodiment shown here, nominal setpoints are also determined as setpoints of the speed if the magnitude of the nominal setpoint is equal to the threshold value for the magnitude of the setpoint. In another embodiment, only nominal setpoints are determined as setpoints if the magnitudes of the nominal setpoints are smaller than the threshold values ​​of the magnitudes of the setpoint. Otherwise, i.e. if the relationship |ωref,nom|≤|ωref|lim does not hold, the setpoint is determined such that an amount of the setpoint corresponds to the determined threshold value and a sign of the setpoint corresponds to a sign of the determined nominal setpoint.

[0053] The method further comprises controlling S4 the drive motor 4 as a function of the determined target speed. The control device 10 is configured to determine control parameters for the control S4 as a function of the determined target speed. The control device 10 is further configured to send these determined control parameters to the drive motor 4. During this control S4, the drive motor 4 is controlled such that the speed of the shaft 6 is adjusted to the determined target speed. In an alternative embodiment, the speed of the shaft 6 converges towards the determined target speed.

[0054] The method performs control S4 of the drive motor 4, determining the target speed value and thus implementing a derating function. The target speed value is determined in such a way that the speeds of the shaft 6 and the crank 16 are synchronized during pedal assistance and, alternatively, the speeds of the shaft 6 and the driven wheel 18 are synchronized during push assistance. This increases driving comfort for the driver of the vehicle 2, since the pedals of the crank 16 are neither pushed into the driver's legs by the control S4 of the drive motor 4, nor does the vehicle 2 impart a shock via the handlebars to the driver when pushing. Reference symbol 2 vehicles 4 drive motor 6 Wave 8 elements 10 Control device 12 Drivetrain 16 Crank 18 driven wheel S1 Determining a nominal setpoint of a speed S2 Determining a threshold value for an amount of the setpoint speed S2.1 Determining the power loss of the drive motor S2.1.1 Inverting the first image S2.2 Determining the threshold using a second image S2.2.1 Inverting the second image S3 Determining a setpoint for the shaft speed S4 Control of the drive motor

Claims

[1] Method for controlling (S4) a drive motor (4) of a muscle-powered vehicle (2), comprising the steps of: determining (S1) a nominal setpoint value of a rotational speed of a shaft (6) connected to the drive motor (4); determining (S2) a threshold value for an amount of the setpoint value of the rotational speed as a function of a specific temperature of an element (8) of the vehicle (2); wherein determining (S2) the threshold value comprises determining (S2.1) a power loss of the drive motor (4) by means of a first mapping which maps the power loss of the drive motor (4) and environmental parameters to the temperature, and further determining (S2.2) the threshold value by means of a second mapping which maps the speed and drive motor parameters to the power loss of the drive motor (4); determining (S3) a setpoint value for the speed of the shaft (6), wherein the determined nominal setpoint value is determined as the setpoint value if an amount of the nominal setpoint value is less than the threshold value for an amount of the setpoint value, and otherwise the setpoint value is determined such that an amount of the setpoint value corresponds to the determined threshold value and a sign of the setpoint value corresponds to a sign of the determined nominal setpoint value; and controlling (S4) the drive motor (4) as a function of the determined setpoint value of the speed. [2] Method according to claim 1, characterized by that the determination (S1) of the nominal setpoint is carried out as a function of a measured speed on the vehicle (2). [3] Method according to claim 2, characterized bythat the determination (S1) of the nominal setpoint is carried out as a function of a measured speed of a crank (16) of the vehicle (2). [4] Method according to claim 2, characterized by that the determination (S1) of the nominal setpoint is carried out as a function of a measured rotational speed of a driven wheel (18) of the vehicle (2). [5] Method according to one of claims 2 to 4, characterized by that the determination (S1) of the nominal setpoint is carried out as a function of a gear ratio of the vehicle (2). [6] Method according to one of the preceding claims, characterized by that the determination (S1) of the nominal setpoint is carried out depending on a user input. [7] Method according to one of the preceding claims, characterized by that the determination (S1) of the nominal setpoint is carried out recursively. [8] Method according to one of the preceding claims, characterized bythat determining (S2.1) the power loss comprises inverting (S2.1.1) the first mapping, wherein the inverted first mapping is evaluated by means of a specific function. [9] Method according to one of the preceding claims, characterized by that determining (S2.2) the threshold value comprises inverting (S2.2.1) the second mapping. [10] Control device (10) which is arranged to carry out a method according to the preceding claims. [11] Drive train (12) with a drive motor (4), a shaft (6) connected thereto and a control device (10) according to claim 10. [12] Muscle-powered vehicle (2) with a drive train (12) according to claim 11.

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