Control unit with a current module for determining a generator current.

Abstract

The present invention relates to a control unit (1) for controlling an electric machine (2) to which a pedaling torque (MTret) at an angular velocity (θ) can be supplied by means of a pedal crank, comprising: a pedal resistance module (3) configured and adapted to determine, from a pedaling parameter (kTW), a pedal resistance quantity that supports or counteracts the pedaling torque (MTret), in particular a pedal resistance current (ITW) that flows through an electrical coil of the electric machine (2); an inertia module (4) configured and adapted to determine, from a change in the angular velocity (θ) of the pedal, an inertia quantity, in particular an inertia current (IInertia) that flows through the electrical coil of the electric machine (2);and a current module (5) configured and adapted to determine a generator current (IG) of the electric machine (2) based on the pedal resistance and the inertia. The invention further relates to a method for controlling an electric machine.

Description

Technical FieldThe present invention relates to a control unit for controlling an electric machine, to which a pedaling torque can be supplied at an angular speed by means of a pedal crank.Prior ArtElectrically operated vehicles, such as bicycles, particularly chainless cargo bicycles, are enjoying increasing popularity. An electric drive can be provided in the region of a wheel hub. This can draw its power from a traction battery unit. In an assisting manner, a generator provided in a region of a pedal-driven crank driven by muscle power can supply power to the traction battery unit.In the patent specification DE 10 2020 131 674 B3 an electric drive system is disclosed in which a mechanical pedaling power is supplied to a generator which transmits a power to an electric motor without chains. Due to the chainless transmission, a pedaling feel does not correspond to the one who a user would identify mechanically coupled drive systems. Accordingly, that specification aims to improve haptic pedaling feel. It proposes to determine a generator setpoint torque M G, soll as a function of the rotational speed of a drive wheel and the rotational speed of a generator. This is transmitted to the generator as a torque specification. On the other hand, a drive motor setpoint torque M A, soll is determined from the generator setpoint torque M G, soll as a function of which the control of the electric motor takes place. In this respect, the actual rotational speed of the drive wheel serves as a determination variable for the electric drive torque.The laid-open specification DE 10 2013 012 208 A1 discloses a further electric drive system for a vehicle operated with muscle power. This laid-open specification aims at causing a pedaling resistance in a crank such that the pedaling feeling during a start from standstill is equal to the pedaling feeling of a vehicle conventionally operated with muscle power. For this purpose, it proposes a system in which the current intensity of the electric motor is to be determined from the actual rotational speed of the drive wheel.International Publication WO 2015 / 128818 A1 discloses a further electric drive train. A counter torque of a generator determines the generator current that is supplied to a drive motor. Power parameters of the drive motor are supplied to a control unit in order to vary the generator current based thereon.SUMMARY OF THE INVENTIONIt is an object of the present invention to provide an improved control unit for controlling an electric machine, to which a pedaling torque can be supplied at an angular speed by means of a pedal crank, and a method for controlling an electric machine, to which a pedaling torque can be supplied at an angular speed by means of a pedal crank. In particular, the invention aims to create a round pedaling feel corresponding to that of a purely mechanical drive. Furthermore, the invention can aim in particular to provide a robust solution which is low in terms of control and regulation. Furthermore, the invention can have the object of enabling an efficient control adapted to human physiology.The object is achieved by a control unit and a method having the features of the independent claims. Advantageous refinements emerge from the dependent claims, the description and the figures.Accordingly, a control unit for controlling an electric machine, to which a pedaling torque can be supplied at an angular speed by means of a pedal crank, is proposed. The electric machine can be provided in the region of the crank. The pedal crank can be part of a load bicycle, in particular a chainless load bicycle, or a wheelchair or fitness device, for example. At a free end of the pedal crank, a pedal can be provided on which a muscle force of a user acts. By a circular movement of the crank pedal, the pedaling moment can be initiated. The crank can be composed of two crank arms, at the free ends of which a pedal is provided. The power that can be supplied to the electric machine can result from the product of the pedaling torque with the angular speed. The electric machine may function as a generator or as an electric motor depending on an operating state of the electric machine. The operating state of the electric machine may correspond to the operating state of a powertrain of the chainless load bicycle. The operating state may vary from various factors, such as the angular velocity of the crank and / or a user input. The control unit can actuate the electric machine by means of power electronics.The control unit has a pedaling resistance module which is configured and adapted to determine a pedaling resistance variable supporting the pedaling torque or counteracting the pedaling torque, in particular to determine a pedaling resistance current which flows through an electric coil of the electric machine, at least from a pedaling parameter. The pedaling resistance current can be positive, thus flowing out of the electric machine and thus counteract the pedaling torque, or negative, thus flowing into the electric machine and thus supporting the pedaling torque. In particular, the pedaling resistance variable can be determined exclusively on the basis of the pedaling parameter. The pedaling parameter is a parameter that the control unit uses to determine the pedaling resistance quantity. It can be determined within the pedal resistance module on the basis of an input variable, such as the angular speed, the pedal torque or an adjustable generator stage, for example, or can be supplied to the pedal resistance module from the outside. The pedal parameter can also be constant or constant within the respectively set generator stage. The pedaling resistance module can be a functional unit which receives as input variable the pedaling parameter or a parameter correlating therewith, such as the angular speed or an adjustable generator stage, and determines from this as output variable the pedaling resistance variable. The adjustable generator stage may simulate a transmission gear, as described in more detail below. The electric coil of the electric machine can be composed of a plurality of partial coils. The current flowing through the electric coil of the electric machine may cause a magnetic field that assists or counteracts the pedaling torque depending on the operating state. A generator voltage that is present in the electrical coil may be lower than a battery voltage provided by a traction battery unit. The generator current can thus differ from a battery current. In order that a current can flow in the electrical coil, a mechanical resistance of the coil and in particular of the power electronics must be overcome. An output power output by the electric machine in an operating state may result from the product of the generator voltage with a generator current. The ratio of the output power and the supplied power may correspond to the process efficiency of the electric machine. The pedal resistance variable, in particular the pedal resistance current, can counteract the pedal torque in an operating state. It can thus generate a pedaling feel for a user, which results at least partially from a pedaling resistance as known from a mechanically driven system. The pedaling resistance magnitude maps a pedaling resistance feeling that a user would experience a mechanical drive.The control unit further comprises an inertia module configured and adapted to determine an inertia quantity, in particular to determine an inertia current, flowing through the electric coil of the electric machine, at least from a change in the angular speed of the pedal. In particular, the inertia variable can be determined exclusively on the basis of the change in the angular velocity. The inertia module can be a functional unit which receives the change in the angular velocity as an input variable and determines the inertia variable as an output variable therefrom. The inertia variable, in particular the inertia current, can counteract the pedaling torque in an operating state. It can thus generate a pedaling feel for a user, which results at least partially from an inertia as known from a mechanically driven system. The inertia variable differs in its determination from the pedaling resistance variable, so that the inertia and the pedaling resistance can be determined separately from each other. Of course, the inertia variable and the pedaling resistance variable may have the same amount and / or the same sign in a certain operating state. The inertia quantity maps an inertia feel that a user would experience in a mechanical drive.The control unit further comprises a current module configured and adapted to determine a generator current of the electric machine based on the pedaling resistance quantity and the inertia quantity, wherein the generator current is determined in particular exclusively based on the pedaling resistance quantity and the inertia quantity. The generator current numbers the electric current which flows out of the electric machine or flows into the electric machine depending on the respective operating state. In the latter case, the generator current can also be referred to as electric motor current. The generator current is determined in particular based on the pedal resistance current and the inertia current. The current module can be a functional unit which receives as input variables the pedal resistance variable and the inertia variable and determines from this as output variable the generator current. The generator current maps the pedaling resistance feeling and the inertia feeling that a user would experience in a mechanical drive. The generator current can communicate with a traction battery unit, in particular with the interposition of a power converter, such as a rectifier or a converter. If the generator current is positive, it can be supplied to the traction battery unit, if it is negative, it can be obtained from the traction battery unit. The generator current can also be supplied to an electric drive.The control unit is thus able to determine a generator current that maps the pedaling resistance feeling and the inertia feeling. Since these depend on different factors, the current module takes into account both the pedaling resistance quantity and the inertia quantity. Thus, from the pedaling parameter and the change of the angular velocity, a generator current can be determined which generates a magnetic field in the coil. This counteracts the pedaling moment in such a way that a user has a round pedaling feel which corresponds to that of a purely mechanical drive. The round pedaling feel results in particular from the control unit taking into account factors simulating pedaling resistance and factors simulating inertia separately from each other. The fact that the generator current can be determined in particular exclusively on the basis of the pedal resistance variable and the inertia variable contributes to providing a robust solution which is low in terms of control and regulation. A real inertia occurs in the electric machine, for example due to the mass of the components in the electric machine involved in the transmission of force. The real inertia is very low. Because the generator current varies with the change in the angular velocity, inertia is additionally simulated. The simulated inertia gives the user a real pedaling feel. Moreover, it adapts the behavior of the electric machine to human physiology. This is because at a top dead center, thus at 0° or 360° of the circular movement of the crank, and at a bottom dead center, thus at 180° of the circular movement of the crank, the pedaling moment is very low, for physiological reasons, compared to the pedaling moment at 90° and 270° of the circular movement of the crank. The simulated inertia may help the crank move at top dead center and bottom dead center without requiring a pedaling torque.When a human being applies a pedaling moment to the pedals of the crank, the energy applied usually varies. First, an applied pedaling force can depend, for example, on whether the user wishes to drive more quickly or more slowly and correspondingly exerts more or less pedaling force rafts on the pedals. Yet, human physiology requires a low frequency, double waveform per pedal revolution because human physiologically is unable to produce a uniform pedaling moment throughout the pedal revolution. The control unit according to the disclosure enables the following application case in such a pedaling behavior: the pedal crank is positioned at 90° in a standstill at a starting point. The angular velocity is initially zero. A user now steps into the pedals and thus generates a pedaling moment. In order to enable the electric machine to start up, the mechanical resistance thereof, for example the resistance of the coil and of the power electronics, must first be overcome. If the resistance of the electric machine is overcome and the crank moves at a certain angular speed, the pedaling torque of the user is converted at the certain angular speed by the electric machine into current which leaves the electric machine, so that the generator current is now positive. In the electric machine, the pedaling torque of the user is opposed by a pedaling resistance torque and, provided that the change in the angular velocity is not zero, a moment of inertia. The pedaling resistance torque correlates with the pedaling resistance current, which results from the pedaling parameter. The moment of inertia correlates with the inertial current resulting from the change in angular velocity. If the pedal crank now arrives at 180°, for example, the pedal moment generated by the user is very low or even zero for physiological reasons. As the pedaling torque decreases, the angular velocity has decreased. The reduction in angular velocity causes an inertial current to be supplied to the electric machine. The inertial current acts in the direction other than the pedaling resistance current in this situation. Depending on how large the inertia current and the pedal resistance current are, the generator current can leave the electric machine, i.e. be positive, or be supplied to the electric machine, i.e. be negative. Because the inertia current is supplied to the electric machine, the pedal crank can be moved beyond the bottom dead center even in the absence of a pedal torque. The supplied inertial flow thus simulates an inertia actually occurring in a mechanical system and physiologically optimizes the pedal crank. The control unit can thus dispense with converting an introduced pedaling torque into a current leaving the electric machine in order instead to realistically map the inertia. The thermal efficiency of the electric machine may thus be decreased to cause the round pedaling feel. If, for example, the user stops walking and thus no longer generates a pedaling torque, the generator current can be switched from the positive direction out of the electric machine into the negative direction into the electric machine in order to simulate the inertia in a real manner.In one embodiment, the pedaling parameter is determined at least partially from the angular velocity, in particular it corresponds to the angular velocity. Alternatively or concomitantly, the pedaling parameter is determined at least partially from a generator stage, which can be communicated to the control unit by a user. The pedaling parameter may be determined within the pedaling resistance module. It can be proportional to the angular speed, for example. Alternatively or concomitantly, the pedaling parameter can take account of a generator stage which can be communicated to the control unit by a user. The generator stage can simulate a transmission gear that the user specifies to the control unit. In a first gear, the pedaling parameter is, for example, such that the resulting pedaling resistance current is lower than in the second gear, where it is again smaller than in a third gear, and so on. Thus, the control unit of a user can wake up the impression of different gears. The pedal parameter can depend, for example, on the one hand on the respective gear, and therefore on the respective generator stage, and on the other hand on the angular speed. The relationship between the angular velocity and the tread parameter may be linear or progressive. In a simple embodiment, the pedal parameter is independent of the angular speed and is determined exclusively from the selectable transmission stage.In one embodiment, the current module determines the generator current by the current module adding the pedal resistance current and the inertia current in a directional manner to determine the generator current. The direction-dependent addition takes into account whether the respective current is positive or negative. The generator current which leaves the electric machine can thus be determined by means of a sum image. The addition contributes the current module to a low-control and low-regulation solution.In one embodiment, the pedaling resistance current is positive above a threshold value of the angular velocity and the pedaling torque and flows out of the electric machine, while the pedaling resistance current is negative below the threshold value of the angular velocity and the pedaling torque and flows into the electric machine. Thus, the control unit is adapted to control the pedal resistance current and the generator current influenced thereby according to the internal resistances of the electric machine. The threshold value of the angular velocity and the pedaling torque may be less than 45° per second and Newton-meters. The control unit is thus able to determine a positive pedal resistance current even at a low threshold value.In one embodiment, the inertial current is positively determined with an increase in angular velocity and flows out of the electric machine. Alternatively or concomitantly, the inertial current is determined to be negative with a decrease in angular velocity and flows into the electric machine. The inertial current is positively determined as the angular velocity increases to produce an opposing moment of inertia to the angular velocity that counteracts the pedaling moment and induces a flow of current out of the electric machine. The inertia current is determined to be negative as the angular velocity decreases to generate a moment of inertia acting in the direction of the angular velocity that assists the pedaling torque and induces a current flow into the electric machine. This contributes to a round and realistic pedaling feel.In one embodiment, in a state in which an amount of negative inertial current is greater than an amount of pedal resistance current, the electric machine is controlled to function as an electric motor, i.e., to be in motor operation. The control unit can actuate the electric machine in accordance with the determination carried out in the current module in such a way that current is drawn from a drive battery unit and a torque supporting the pedaling torque is exerted by the electric machine.In one embodiment, in a state in which an amount of the inertial current is less than an amount of the positive pedal resistance current, the electric machine is controlled in such a way that it functions as a generator, that is to say is in a generator mode. The control unit can actuate the electric machine in accordance with the determination carried out in the current module in such a way that an intermediate circuit and a drive battery unit are supplied with current, so that a torque counteracting the pedaling torque is exerted by the electric machine. The pedaling resistance current is positive as soon as it is above the threshold value of the angular velocity and the pedaling torque. If its magnitude is greater than that of the inertia current, regardless of whether it generates a supporting or counteracting moment of inertia, the electric machine is controlled in such a way that it generates current and thus functions as a generator.In one embodiment, the control unit is subject to a timing system in which control commands can be transmitted to the electric machine, the timing system being between 100 Hz and 40 kHz, in particular between 200 Hz and 3 kHz. The control commands from the control unit to the electric machine can be transmitted via power electronics, which can be directly connected to the coil of the electric machine. The high-frequency clocking, which is preferably between 1 kHz and 3 kHz, ensures that the electric machine can be adapted to varying environmental conditions in the millisecond range. In particular for the pedaling moment varying due to human physiology with progressive angular velocity, the high-frequency clocking can contribute to bringing about the round pedaling feel and to making possible an efficient actuation adapted to the human physiology.In one embodiment, the control unit is an independent system which contains power electronics and which is capable of transmitting control commands to the electric machine independently, in particular without further control commands from other control units, on the basis of the pedaling parameter and the change in the angular speed. The control unit can thus have a control loop which is limited to the electric machine. This reduces the dependencies of the control unit on other influence variables, which contributes to a low-control and low-control solution and provides a robust control unit.In one embodiment, the inertia module uses an inertia parameter to determine the inertial current in addition to the change in angular velocity, wherein the inertia parameter is determined in particular at least partially by a generator stage that can be communicated to the control unit by a user. The inertia parameter, as well as the change in angular velocity, may be directional. Thus, a direction of rotation of the crank and a direction of travel of the chainless load bicycle are taken into account in the determination of the inertial current. The inertia parameter may be determined within the inertia module. The generator stage may simulate a transmission gear that the user specifies to the control unit, as described above. The pedal parameter can depend, for example, on the one hand on the respective gear, and therefore on the respective generator stage, and on the other hand on the change in the angular speed. The relationship between the change in angular velocity and the inertia parameter may be linear or progressive. In a simple embodiment, the inertia parameter is independent of the generator stage and is determined exclusively from the change in the angular speed.In one embodiment, the control unit is configured and adapted to drive the electric machine such that the inertial current flows through the same coil of the electric machine as the pedaling resistance current. The coil of the electric machine can be composed of a plurality of partial coils. From the inertial current and the pedaling resistance current, the generator current is determined. By both flowing through the same coil, the particular generator current can be efficiently conducted through the electric machine.In one embodiment, the inertial module is configured and adapted to, upon receipt of a release signal, set the inertial current to zero upon a change in angular velocity. The release signal may be triggered by the electric machine changing from generator operation to motor operation, as described above. As soon as the electric machine changes back into the generator mode, the opening signal can be canceled. The generator current may correspond to the pedal resistance current after receiving the opening signal. The opening signal can be detected by the power electronics of the electric machine.In one embodiment, the release signal is triggered by a negative angular velocity and / or by a state in which the pedal does not have any contact with a user. The negative angular velocity may result from the user stepping backwards. In this case, the simulated inertia may be disadvantageous, so that it is resolved by the resolution signal and the inertial current set to zero by it. The control unit can also receive a signal that the user is no longer touching the pedals. In this case, the mapping of a real pedaling feel is pleasing. Consequently, the control unit can dispense with involving the inertia variable in the generator current.In one embodiment, the control unit is configured and adapted to determine a control signal, which is provided to an electric drive, on the basis of the angular speed and / or the pedaling torque. In particular, the control signal may indicate to the electric drive how much power it draws from the traction battery unit. This contributes to an efficient and chain-free drive.In one embodiment, the disclosure relates to a system, in particular a trackless load bicycle, including a control unit according to the disclosure, the electric machine according to the disclosure, and a traction battery unit electrically connected to the electric machine. The control unit is adapted and configured to, in a first determination by the current module, in particular if the positive pedaling resistance current is greater than the inertial current, allow the generator current to flow from the electric machine to the traction battery unit, and in a second determination by the current module, in particular if the pedaling resistance current is less than the negative inertial current, allow the generator current to flow from the traction battery unit to the electric machine. The system contributes to a round and realistic pedaling feel. Depending on the respective ambient conditions, the electric machine can be used variably as a generator or as an electric motor. Efficiency expressions can be accepted in this case in order to configure the pedaling feel as real as possible.In one embodiment, the system has an electric drive configured and adapted to drive the system, in particular the chainless load bicycle, wherein the electric drive is connected to the electric machine and / or the traction battery unit. The electric machine, the drive battery unit and the electric drive can be connected to one another by means of an intermediate circuit. The electric drive can ensure that the system can be driven comfortably, with application of no muscle force or only a very low muscle force.The disclosure further relates to a method for controlling an electric machine, to which a pedaling torque can be supplied at an angular speed by means of a pedal crank. The method comprises the step of obtaining a pedaling parameter and determining a pedaling resistance quantity based on the pedaling parameter. This step may be performed by the treading module. The method further includes the step of obtaining a change in angular velocity of the pedal and determining the amount of inertia based on the change in angular velocity of the pedal. This step may be performed by the inertial module. The method further includes the step of determining a generator current of the electric machine based on the pedaling resistance magnitude and the inertia magnitude. The pedaling resistance quantity may be the pedaling resistance current, the inertia quantity may be the inertia current. The features, effects and advantages disclosed above in connection with the control unit apply, where applicable, to the method.In one embodiment, the method further comprises the step of obtaining a break-up signal and determining the generator current taking into account the break-up signal. The release signal may be triggered by the electric machine changing from generator operation to motor operation, as described above. As soon as the electric machine changes back into the generator mode, the opening signal can be canceled. The generator current may correspond to the pedal resistance current after receiving the opening signal. In one embodiment, the release signal is triggered by a negative angular velocity and / or by a state in which the pedal does not have any contact with a user. The negative angular velocity may result from the user stepping backwards. In this case, the simulated inertia may be disadvantageous, so that it is resolved by the resolution signal and the inertial current set to zero by it. The control unit can also receive a signal that the user is no longer touching the pedals. In this case, the mapping of a real pedaling feel is pleasing. Consequently, the control unit can dispense with involving the inertia variable in the generator current.Brief Description of the FiguresPreferred further embodiments of the invention are explained in more detail by the following description of the figures. The following are shown: FIG. 1 is a schematic view of a load bicycle; FIG. 2 is a schematic view of a generator unit as well as the incoming and outgoing currents; FIG. 3 is a schematic view for determining a generator current; FIG. 4 is a schematic view of a powertrain; and FIG. 5 shows a schematic relationship between a pedal torque and a position of a pedal crank.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTSExemplary embodiments are described below with reference to the figures. Identical, similar or identically acting elements are provided with identical reference numerals in the different figures.FIG. 1 schematically shows a chainless load bicycle 100. The load bicycle 100 is configured to transport loads of, for example, several hundred kilograms. In the region of a crank, a generator unit 110 is mounted, which has a control unit 1 and an electric machine 2. The generator unit 110 can convert a pedaling power introduced by a user via the crank into electric power, which it supplies to a traction battery unit 120 via a cable 130. The generator unit 110 may further draw current from the traction battery unit 120 to drive the crank and thus function as an electric motor. The traction battery unit 120 is further coupled to an electric drive 140 configured and adapted to drive the trackless load bicycle 100.FIG. 2 schematically shows the generator unit 110 and its connection to a torque unit 150. The generator unit 110 has the control unit 1 and the electric machine 2. Torque unit 150 may include a crank having a pedal in communication with a shaft of electric machine 2. Via the pedal and the crank, a user can supply a pedaling torque M Tret at an angular speed ω to the torque unit 150. The torque unit 150 passes the power, which can be composed of the product of the pedaling torque M Tret with the angular velocity ω, to the electric machine 2, which in this case functions as a generator. Further, the torque unit 150 may be driven by the electric machine 2, in which case the electric machine 2 functions as an electric motor.The control unit 1 receives an input signal from the torque unit 150. For example, the control unit 1 may obtain the angular velocity ω as well as a temporal change ω of the angular velocity. The angular speed ω can be supplied to a pedaling resistance module 3 which, for example, determines a pedaling parameter k TW and / or the pedaling resistance variable from this and optionally from further parameters. The pedaling parameter may be constant and selected by a user. The pedaling resistance module 3 can determine a pedaling resistance variable from the pedaling parameter k TW. The pedal resistance variable can be, for example, a pedal resistance current I TW. The pedal resistance current I TW is supplied as an input variable to a current module 5. The change in the angular velocity can be fed to an inertia module which determines an inertia variable from this and optionally from further parameters. The inertia variable can be, for example, an inertia current I Inertia. The inertial current I Inertia is supplied to the current module 5 as a further input variable, the current module 5 can determine a generator current I G from the pedal resistance current I TW and the inertial current I Inertia. For example, the current module 5 can add the pedal resistance current I TW and the inertia current I Inertia depending on the direction, i.e. taking into account their signs, in order to obtain the generator current I G. By taking into account both the angular speed ω and its change over time in order to determine the generator current I G the control unit 1 can simulate both a pedaling resistance and an inertia of a mechanical system in a real-world manner.The control unit 1 can specify the generator current I G to the electric machine 2. For example, power electronics of the control unit 1 can directly determine, in particular adjust, the current flowing in a coil of the electric machine 2. Depending on the respective values of the pedaling resistance variable and the inertia variable, the generator current I G may be positive, i.e., flow out of the electric machine 2, for example, into the traction battery unit 120, or negative, i.e., flow into the electric machine 2, for example, from the traction battery unit 120.Consider the following application: At a starting point, the crank is positioned at 90° at a standstill. The angular velocity ω is initially zero. A user now steps into the pedals and thus generates a pedaling torque M Tret. In order for the electric machine 2 to be able to start up, its electrical resistance, for example the electrical resistance of the coil and of the power electronics, must first be overcome. If the electrical resistance of the electric machine 2 is overcome and the crank moves at a certain angular speed ω 1, the pedaling torque M Tret of the user is converted at the certain angular speed ω 1by the electric machine 2 into current which leaves the electric machine 2, so that the generator current I G is now positive. In the electric machine 2, the pedaling torque M Tret of the user is opposed by a pedaling resistance torque M TW and, if the change in the angular velocity is not zero, a moment of inertia M Inertia. The pedaling resistance torque M TW correlates with the pedaling resistance current I TW, which results from the pedaling parameter k TW. The moment of inertia M Inertia correlates with the inertial current I Inertia, which results from the change in the angular velocity ω. If the pedal crank now arrives at 180°, for example, the pedal moment generated by the user is very low or even zero for physiological reasons. As the pedaling torque M Tret decreases, the angular velocity ω has decreased. The reduction in the angular velocity ω causes an inertial current I Inertia, which is supplied to the electric machine 2. The inertia current I Inertia acts in the direction other than the pedaling resistance current I TW. in this situation. Depending on how large the inertial current I Inertia and the pedal resistance current I are TW the generator current I G can leave the electric machine 2, i.e. be positive, or be supplied to the electric machine 2, i.e. be negative. Because the inertial current I Inertia is supplied to the electric machine 2, the pedal crank can be moved beyond the bottom dead center even in the absence of the pedal torque M Tret. The supplied inertial current I Inertia thus simulates an inertia actually occurring in a mechanical system and physiologically optimizes the pedal crank. The control unit 1 can thus dispense with converting an introduced pedaling torque M Tret into a current leaving the electric machine 2, in order instead to realistically map the inertia. The thermal efficiency of the electric machine 2 can thus be reduced in order to cause the round feeling of pedaling. If, for example, the user stops walking and thus no longer generates a pedaling torque M Tret the generator current I G can be converted from the positive direction out of the electric machine 2 into the negative direction into the electric machine 2 in order to simulate inertia in a real-world manner.FIG. 3 schematically shows the determination of the pedaling resistance current I TW and the inertia current I Inertia. The pedaling resistance current I TW is determined using the pedaling parameter k TW. The pedaling parameter k TW can be determined from the angular velocity ω, for example via a linear or a progressive relationship between the angular velocity ω and the pedaling parameter k TW. The pedaling parameter k TW may also correspond to the angular velocity ω. The pedaling parameter k TW may further depend on a generator stage. For example, a user can inform the control unit 1 in which gear the electric machine 2 is to be operated and thus specify a generator stage. In a first gear, the pedaling parameter k TW is the smallest, and as the number of gears increases, the value of the pedaling parameter k TW. increases. For example, the user can specify three to seven, in particular five, generator stages. Within each generator stage, the tread parameter k TW can in turn depend on the angular speed. The inertial current I Inertia is determined with the aid of the change over time in the angular velocity and optionally via an inertial parameter k Inertia. The inertia parameter k Inertia can also depend on the respective generator stage.Once the pedal resistance current I TW and the inertia current I Inertia are determined, they are added up via a sum image in order to obtain the generator current I G. When the angular velocity is accelerated, the inertial current I Inertia is positive. When the angular velocity is decelerated, the inertial current I Inertia is negative. The pedal resistance current I TW is generally positive. In particular at low rotational speeds, i.e. in a starting state, the pedal resistance current I TW can also be negative. The pedaling resistance current I TW and the inertial current I Inertia are added in a direction dependent manner, i.e., with their respective signs. If the sum is positive, the electric machine 2 serves as a generator, if the sum is negative, the electric machine 2 serves as an electric motor.FIG. 4 shows a drive train with the generator unit 110 which supplies an output current, which is G depending on the respective generator current I, to an intermediate circuit 160 as a circuit for electrically connecting the drive train. The drive battery unit 120 and the electric drive 140 are connected to the intermediate circuit 160. The drive battery unit 120, the intermediate circuit 160 and the electric drive 140 are controlled by a central control unit 170. This is formed separately from the control unit 1. In an alternative embodiment, not shown, the control unit 1 is part of the central control unit 170.FIG. 5 shows a section of a typical profile of the pedaling torque M Tret as a function of the position of the pedal crank. If the pedal crank is at 0°, the pedal torque M Tret is minimal. Up to the position of 90°, the pedaling moment M Tret increases in a wave-like manner. As soon as the maximum is reached at 90°, the pedaling torque M Tret decreases again up to the position at 180°. A 360° pedal revolution is thus subject to a low-frequency double waveform. In a mechanical system, inertia acts on the pedal crank during each pedal revolution because the pedal torque M Tret is applied at a continuously varying angular speed. This behavior can faithfully reproduce the control device according to the disclosure.Where applicable, all individual features illustrated in the exemplary embodiments can be combined with one another and / or interchanged without departing from the scope of the invention.List of reference characters1 Control unit 2 electric machine 3 pedaling resistance module 4 inertia module 5 current module 100 chainless load bicycle 110 generator unit 120 traction battery unit 130 electric cable 140 electric drive 150 torque unit 160 intermediate circuit 170 central control device ω angular velocity M Tret pedaling torque k TW pedaling parameter I TW pedaling resistance current k Inertia inertia parameter I Inertia inertia currentReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2020 131 674 B3

[0003] DE 10 2013 012 208 A1

[0004] WO 2015 / 128818 A1

[0005]

Claims

Control unit (1) for controlling an electric machine (2) to which a pedaling torque (M Tret) can be supplied at an angular speed (ω) by means of a pedal crank, comprising: - a pedaling resistance module (3) which is configured and adapted to determine from a pedaling parameter (k TW) a pedaling resistance variable supporting the pedaling torque (M Tret) or counteracting the pedaling torque (M Tret) in particular to determine a pedaling resistance current (I TW) which flows through an electric coil of the electric machine (2); an inertia module (4) configured and adapted to determine an inertia variable, in particular to determine an inertia current (I Inertia) flowing through the electric coil of the electric machine (2) from a change in the angular velocity (ω) of the pedal; and a current module (5) configured and adapted to determine a generator current (I G) of the electric machine (2) based on the pedaling resistance variable and the inertia variable.Control unit (1) according to Claim 1, wherein the pedaling parameter (k TW) is determined at least partially from the angular speed (ω), in particular corresponds to the angular speed (ω); and / or the pedaling parameter (k TW) is determined at least partially from a generator stage, which can be communicated to the control unit (1) by a user.Control unit (1) according to one of the preceding claims, wherein the current module (5) adds the pedal resistance current (I TW) and the inertia current (I Inertia) depending on the direction in order to determine the generator current (I G).Control unit (1) according to one of the preceding claims, wherein the pedaling resistance current (I TW) is positive above a threshold value of the angular velocity (ω) and the pedaling torque (M Tret) and flows out of the electric machine (2), and the pedaling resistance current (I TW) is negative below the threshold value of the angular velocity (ω) and the pedaling torque (M Tret) and flows into the electric machine (2); wherein in particular the threshold value of the angular velocity (ω) and the pedaling torque (M Tret) is less than 45° per second and Newton-meters.Control unit (1) according to one of the preceding claims, wherein the inertial current (I Inertia) is determined positively with an increase in the angular speed (ω) and flows out of the electric machine (2) and / or is determined negatively with a decrease in the angular speed (ω) and flows into the electric machine (2).The control unit (1) according to claim 5, wherein the electric machine (2) is driven to function as an electric motor in a state where an amount of the negative inertial current (I Inertia) is larger than an amount of the pedaling resistance current (I TW).Control unit (1) according to Claim 5 or 6, wherein the electric machine (2) is driven in such a way that it functions as a generator in a state in which an amount of the inertial current (I Inertia) is less than an amount of the positive pedal resistance current (I TW).Control unit (1) according to one of the preceding claims, which is subject to a timing in which control commands can be transmitted to the electric machine (2), the timing being between 100 Hz and 40 kHz, in particular between 200 Hz and 3 kHz.Control unit (1) according to one of the preceding claims, which is a stand-alone system which contains power electronics and which is capable of transmitting control commands to the electric machine (2) independently on the basis of the pedaling parameter (k TW) and the change in the angular speed (ω).Control unit (1) according to one of the preceding claims, wherein the inertia module (4) uses, in addition to the change in the angular velocity (ω), an inertia parameter (k Inertia) in order to determine the inertia current (I Inertia) wherein the inertia parameter (k Inerta) is determined in particular at least partially by a generator stage which can be communicated to the control unit (1) by a user.Control unit (1) according to one of the preceding claims, configured and adapted to drive the electric machine (2) such that the inertial current (I Inertia) flows through the same coil of the electric machine (2) as the pedaling resistance current (I TW).Control unit (1) according to any one of the preceding claims, wherein the inertial module (4) is configured and adapted to set the inertial current (I Inertia) to zero upon a change in angular velocity (ω) upon receipt of a release signal.Control unit (1) according to claim 12, wherein the release signal is triggered by a negative angular velocity (ω) and / or by a state in which the pedal does not have any contact with a user.Control unit (1) according to any of the preceding claims, configured and adapted to determine, based on the angular velocity (ω) and / or the pedaling torque (M Tret) a control signal provided to an electric drive (140).A system, in particular a chainless load bicycle (100), comprising - a control unit (1) according to any one of the preceding claims; - the electric machine (2); and - a traction battery unit (120) electrically connected to the electric machine (2); wherein the control unit (1) is adapted and configured to, in a first determination by the current module (5), allow the generator current (I G) to flow from the electric machine (2) to the traction battery unit (120) and, in a second determination by the current module (5), allow the generator current (I G) to flow from the traction battery unit (120) to the electric machine (2).The system according to claim 15, further comprising an electric drive (140) configured and adapted to drive the system, in particular the chainless load bicycle (100), wherein the electric drive (140) is connected to the electric machine (2) and / or the traction battery unit (120).Method for actuating an electric machine (2) to which a pedaling torque (M Tret) can be supplied at an angular speed (ω) by means of a pedal crank, having the steps: - obtaining a pedaling parameter (k TW) and determining a pedaling resistance variable based on the pedaling parameter (k TW); - obtaining a change of an angular speed (ω) of the pedal and determining the inertia variable based on the change of the angular speed (ω) of the pedal; and - determining a generator current (I G) of the electric machine (2) based on the pedaling resistance variable and the inertia variable.Method according to claim 17, further comprising the step of: obtaining a break-up signal and determining the generator current (I G) taking into account the break-up signal.

Images