Method for controlling a drive unit for a soil compactor, and drive unit for a soil compactor

Abstract

The present invention relates to a method for controlling a drive unit for a soil compactor having a ground contact plate, and to a drive unit designed to carry out the method, wherein the drive unit has a plurality n of electric motors (M1, M2, ..., Mn) that each carry at least one unbalance weight, and wherein the electric motors, during suitably synchronised operation, serve both for horizontal propulsion of the soil compactor and for generating a soil-compacting vertical shaking movement. The method is characterised, inter alia, in that a plurality of guide wave generators (LG1, LG2, ..., LGn), each for generating a virtual guide wave (VW1, VW2, ..., VWn), are provided, which are each assigned to an electric motor or to a group of electric motors. The virtual guide waves each represent the linear phase angle progression of a reference angular position of an electric motor rotating uninterruptedly at a constant basic speed and are synchronised with one another by means of a periodically emitted synchronisation pulse such that, with specification of individual phase offset values (Φoffset,M1, Φoffset,M2, ..., Φoffset,Mn) and of a basic speed (nspecification) for the respective electric motors and with determination of the actual phase position of each electric motor, precise phase regulation of all the electric motors is possible in order to implement an input movement command or other operating state command.

Description

[0001]Method for controlling a drive unit for a soil compactor and drive unit for a soil compactor The present invention relates to a method for controlling a drive unit for a soil compactor with a soil contact plate, wherein the drive unit has a plurality of electric motors, each carrying at least one unbalanced weight, and wherein the electric motors, when suitably synchronized, serve both for horizontal propulsion of the soil compactor and for generating a soil-compacting vertical vibrating movement. Furthermore, the present invention relates to a drive unit for a soil compactor with a soil contact plate, which is designed to carry out the method. Soil compactors with a soil contact plate, which are often also referred to as vibrating plates, and drive units acting as vibration generators for such soil compactors with several,Drives, particularly in the form of electric motors, each carrying at least one unbalanced weight (rotating around a rotational axis of the drive), are already known in a variety of designs from the prior art. In this regard, reference is made, for example, to the (unpublished) German patent application DE 102022127864.6 of the present patent applicant and the prior art cited below. It is well known (cf., for example, EP 1534439 B1) that with a suitable arrangement of two drives, each carrying an identical unbalanced weight, with the same orientation of the rotational axis and counter-rotating drive, the horizontal force components of the centrifugal forces generated by the two unbalanced weights acting on the ground contact plate can always cancel each other out if the relative phase position of the drives is adjusted so that the counter-rotating unbalanced weights have the same speed,that the horizontal force components of the centrifugal forces of the two unbalanced weights are always equal in magnitude and opposite in direction. At the same time, it can be ensured that the vertical force components of the centrifugal forces generated by the unbalanced weights, which oscillate between different directions, are always in the same direction and thus add up. Thus, by appropriately adjusting the relative phase position of the two drives, a vibration movement that is always oriented perpendicular to the ground can be generated without the soil compactor moving in a specific direction. The soil compactor can thus compact the soil while stationary. If, on the other hand, the relative phase position of the two unbalanced weights is adjusted, then operating conditions can also be realized with two similarly oriented drives, each with a rotation axis perpendicular to the forward direction of the soil compactor.in which the soil compactor (while simultaneously compacting the soil) moves forward or backward. It should be noted that the vertical force component of the added centrifugal force vectors of the individual unbalanced weights of the soil compactor's drive unit – with a suitable choice of phase shift between the unbalanced weights driven in opposite directions at the same speed – performs an oscillating upward and downward movement, so that the soil compactor's ground contact plate is partly pressed against the ground (the so-called compression phase) and partly pulled upward (the so-called flight phase) during operation.During the flight phase, it lifts off the ground at least partially or is significantly relieved of its load. The oscillation of the vertical force component of the combined centrifugal forces of all unbalanced weights ultimately ensures the desired soil compaction. If the horizontal component of the combined centrifugal forces of all unbalanced weights always points in a certain direction during the flight phase (or at least on average over the flight phase), then the soil compactor will ultimately be moved in that direction. In contrast, an opposite direction of the horizontal force component of the combined centrifugal force vectors of the unbalanced weights during the compression phase is insignificant or leads to a kind of repulsion effect.Because the soil compactor, pressed against the ground with its ground contact plate during the compression phase, is not (or only insignificantly) moved in the given direction of force by a force acting horizontally during this phase, and can then repel from this position during the transition to the flight phase in the direction of force acting horizontally at that time. This propulsion principle for soil compactors with a ground contact plate is well known and is explained in more detail below with reference to the figures. WO 2006 / 136446 A1 further explains that, to enable a lateral movement of a soil compactor (i.e., in a direction perpendicular or transverse to the forward direction), it can advantageously be provided that the vibration excitation device serving as the drive unit has at least four unbalanced masses, each of which is driven to rotate about a rotational axis.wherein the axes of rotation of at least two of the unbalanced masses are at an angle to the axis or axes of rotation of the other unbalanced masses. With such a drive unit, a soil compactor can also be driven to move sideways, provided that the individual drives carrying an unbalanced mass are driven at the same speed, but offset from each other by certain phase angles. The phase offset angles or values ​​of the individual drives to be set for such a driving condition, each of which represents a deviation of the angular position of a suitably defined reference point on the respective drive compared to a predetermined (and also co-rotating) reference angular position,depend on the specific arrangement and alignment of the drives. Furthermore, with the appropriately angled rotation axes of the unbalanced masses, rotational movements of the soil compactor around a vertical axis, as well as curves or slopes, are possible.This will be explained in more detail below with reference to the figures. For a drive unit with a plurality of drives, each carrying an unbalanced weight, with a specifically predefined arrangement of the rotational axes of the individual drives, a specific phase offset angle can then be specified for each drive – driven at the same speed – and, by evaluating the centrifugal force vectors of all unbalanced weights present at any given time, a resulting direction of travel and / or rotation for the soil compactor can be determined, and a distinction can also be made between flight phases and compression phases. Knowing the relationships already described, it is then easy to determine, for a specific number and arrangement of drives, each carrying an unbalanced weight,which compaction force (from the vertical oscillation) and direction of travel and / or rotation result from the selected phase offset angle. Thus, suitable phase offset angles can be determined for each drive, each carrying (at least) one unbalanced weight, for a desired travel command and / or operating state of the soil compactor. In practice, however, it has been shown that such a drive unit for a soil compactor is exposed to massive and unpredictable external disturbances, e.g., on inhomogeneous soils or when striking individual larger stones, which cause a shock to the oscillation system. Especially if, as is envisaged within the scope of the present invention, the drives carrying (at least) one unbalanced weight are designed as electric motors,This leads to a high control requirement to maintain the phase relationship of the individual electric motors required for a desired driving or operating state. It must also be taken into account that imprecise or too slow control interventions result in increased energy consumption and inaccurate driving behavior, which would be very disadvantageous for a drive unit equipped with multiple electric motors. Regarding the prior art, it should be noted that for an unbalanced vibrator for block making machines known from EP 0 999 020 A2, with which a vibrating table is set into vibration, it has already been proposed to provide control and / or regulation of the relative phase positions of the unbalanced shafts driven by at least one motor. When using multiple motors, it is proposed therethat either one of the motors is designed as a master drive and the others as slave drives, or that a virtual master drive is provided and all the motors are designed as slave drives. In the latter case, the virtual master drive transmits the rotational speed and rotor position to all slave drives, which facilitates the control properties and interchangeability of the electronic controllers. The motors used there, unlike the electric motors of the present invention, are not used for propulsion purposes. Against this background, the object of the present invention is to provide a novel method of the type mentioned above and a novel drive unit for a soil compactor with a ground contact plate.with which a particularly precise control or regulation of the individual electric motors can be achieved. According to a further aspect, the present invention and / or the advantageous embodiments thereof are also intended to provide such a method or such a drive unit that can be adapted in the simplest possible manner to differently designed soil compactors with possibly a different number of electric motors and possibly a different arrangement of the individual electric motors. The above object is achieved by a method according to claim 1 and a drive unit according to claim 11. The dependent claims relate to advantageous embodiments or further developments of the invention. The present invention thus relates firstly to a method for controlling a drive unit for a soil compactor with a ground contact plate,wherein the drive unit has a plurality of electric motors, each carrying (at least) one unbalanced weight, and wherein the electric motors, when suitably synchronized, serve both for horizontal propulsion of the soil compactor and for generating a soil-compacting vertical vibrating movement, which is characterized by the following steps: (A) Enabling the input of a travel command or other operating state command for the soil compactor by means of a suitable input unit (B) Specifying a base speed for all electric motors and specifying an individual phase offset value for each electric motor, taking into account the last input(s) made in step (A), by a central control unit of the drive unit (C) Transmitting the base speed from the central control unit to a plurality of guide shaft generators, each of which is assigned to an electric motor or a group of electric motors, andfor each electric motor from the plurality of electric motors, transmission of the base speed and the individual phase offset value from the central control unit to a phase controller assigned to the respective electric motor (D) generation of a virtual pilot wave by all pilot wave generators taking into account the base speed, whereby each virtual pilot wave represents the linear phase angle curve of a reference angular position (advantageously corresponding to the phase offset value zero) of an electric motor rotating undisturbed at a constant base speed (E) periodic transmission of a synchronization pulse from the central control unit to all pilot wave generators or periodic transmission of a synchronization pulse from a pilot wave generator serving as the master to all other pilot wave generators (F) synchronization of all virtual pilot waves using the periodically transmitted synchronization pulse,so that the virtual guide shafts of all guide shaft generators are synchronized (in particular in phase) and have the specified base speed (G) Phase control of all electric motors by means of a phase controller provided for each electric motor and acting on a motor controller of the respective electric motor, evaluating the current phase angle of the virtual guide shaft of the guide shaft generator assigned to the respective electric motor, the individual phase offset value of the respective electric motor, the current actual phase position of the respective electric motor determined by means of an angular position evaluation unit provided on each electric motor, and the base speed. A plurality of electric motors can be considered, in particular, the use of two, three, four, five, or six electric motors within the scope of the present invention.The invention can in principle also be implemented with even more motors. If, in step (A), the input of a travel command is to be enabled by means of a suitable input unit (e.g., in the form of a human-machine interface, HMI), it is preferably provided in this context that the input unit should enable the selection of a travel command from a certain number of possible travel commands. For autonomously or semi-autonomously operated soil compactors, the input (or specification) of certain travel commands can also be carried out via software, taking into account the current requirements. The specific design of the input unit can be suitably selected for the respective drive unit, taking into account the travel commands possible with it (e.g., as a touch display for selecting the available travel commands suitably displayed on the touch display, by suitably labeled control buttons or other control elements,as a joystick for specifying a direction of travel, as an adjustable thrust lever or rotary knob for selecting a desired travel speed or compaction force, and / or as a combination of various input devices already mentioned or known to those skilled in the art. Depending on the specific design of the drive unit and the specific arrangement and number of electric motors used, possible travel commands can be, for example, the travel commands "drive forward," "drive sideways to the left," "drive sideways to the right," "drive backward," each possibly graded according to the desired travel speed (fast, slow, possibly with intermediate steps). Furthermore, travel commands for "angled travel" in various directions,for "rotation left" (i.e., counterclockwise) or "rotation right" (i.e., clockwise), or for initiating cornering in different directions and / or with different curve radii. Other operating state commands may include, for example, specifying the desired compaction force ("strong compaction," "weak compaction," with intermediate stages if necessary). It should be noted thatthat the compaction force of a soil compactor of the type relevant to the present invention can typically be controlled via the base speed of the electric motors. When a specific compaction force is selected, the central control unit can thus predetermine a base speed corresponding to the desired compaction performance in each case in step (B). Furthermore, operating state commands can also be provided, for example, for carrying out a compaction-free run-up of the electric motors to a specific base speed and / or for a compaction-free pause with (continuing) running electric motors. It should be noted that soil compactors with a ground contact plate of the type in question here are typically operated in a speed range,which is above a critical resonance frequency or above a critical resonance range of the vibration system. When the electric motors are switched on and run up to the base speed selected during operation and the inevitable passage through the critical resonance range, this may lead to an uncontrollable build-up of vertical and / or horizontal vibrations of the soil compactor, which can be reliably avoided by selecting a compaction-free run-up. For this purpose, the relative phase position of the individual electric motors - i.e., the phase offset values ​​(typically specified as angles) of the individual electric motors - must be adjusted so thatthat the vertical components (and advantageously also the horizontal components) of the centrifugal force vectors of the unbalanced weights of all electric motors compensate each other at all times. During compression-free start-up, the base speed of the electric motors is then increased – within a certain transition period – to a base speed in the supercritical range, while specifying and maintaining these phase offset values. For compression-free pauses, the same phase offset values ​​are specified, whereby in this operating state the electric motors can continue to run at the given base speed. Since the system is not excited to vertical oscillations in this operating state,A compression-free pause proves to be comparatively energy-efficient and – depending on the duration of the pause – often consumes less energy than would be consumed by shutting down and later restarting the electric motors. Other possible operating state commands can be switching the drive unit on or off or, if necessary, an emergency shutdown or emergency stop procedure. It is understood that the aforementioned travel commands and operating state commands are not exhaustive and that the method according to the invention can also enable further or different travel and operating state commands if necessary. The central control unit is then responsible, according to step (B) of the method according to the invention, for determining from the last entered travel and / or operating state command,If necessary, taking into account the previously specified driving and / or operating state or the previously specified phase offset values ​​for the individual electric motors M1, M2, ..., Mn, a specification for the base speed of the electric motors and for the phase offset values ​​Φ , Φ , ..., Φ to be specified individually for each individual electric motor, which appropriately implements the currently entered driving or operating state command. For this purpose, at least one data set can preferably be stored in a memory unit assigned to the central control unit or integrated therein, in which specific target phase offset values ​​Θ , Θ , ..., Θ are stored for all electric motors for specific driving commands and / or operating state commands, depending on the specific arrangement and number of electric motors in the drive unit.with which the driving state or operating state corresponding to the respective driving command and / or operating state command can be achieved, and / or from which such target phase offset values ​​can be derived by the central control unit. If necessary, a specific basic speed or a specific basic speed curve for the electric motors (which may be driven in different directions of rotation depending on the specific design of the drive unit) can also be assigned to a specific driving or operating state command. Within the scope of the present invention, when a new driving or operating state command is input, a transition from a previously specified basic speed to a new target basic speed is to occur, it can typically be provided thatthat the central control unit successively and stepwise converts the base speed to be specified according to step (B) (and thus also to be transmitted to the pilot wave generators and phase controllers according to step (C)) from the previously specified value for the base speed to the target base speed in a transition period until this is reached. Furthermore, in an expedient embodiment of the invention, it can be provided that the central control unit, upon input of a new travel command or a new other operating state command according to step (A), is configured to specify the individual phase offset values ​​to be specified according to step (B) (and thus also to be transmitted to the phase controllers according to step (C), in a transition period successively and step by step from the previously specified phase offset values new phase offset values which either correspond to the respective target phase offset values correspond to or are equivalent to them. This enables particularly smooth and resource-saving transitions between different driving states or operating conditions, whereby during the transition period, not only a linear transition between different base speed or phase offset values ​​for the individual electric motors can be provided, but if necessary, a suitably curved course could also be provided. The duration of the transition period should be dimensioned such that, on the one hand, the soil compactor reacts with the desired dynamics to changed driving state or operating state commands and, on the other hand, that the phase control can easily follow the successively changing phase offset values ​​or base speed values ​​for the individual motors. What is meant by equivalent phase offset values ​​in the aforementioned sense will now be explained in more detail. Since ultimately the reference point orThe reference angular position defined for this purpose, against which a phase offset value (in the sense of an angle relative to the reference angular position, taking into account the direction of rotation of the respective electric motor) is to be determined or specified, can be chosen arbitrarily (provided that the reference point or the reference angular position is defined identically for each electric motor). It is clear that a tuple of n phase offset values ​​for a number n of electric motors is equivalent to that of another tuple of n phase offset values ​​in terms of the achievable driving and / or operating state, provided that each entry of the tuple is shifted by a difference value that is identical for each entry of the tuple. Thus, an equivalence relation can be defined, according to which a tuple of n phase offset values ​​(Φ ; Φ Φ ) is equivalent to any further tuple (Φ + δ; Φ + δ; ...; Φ + δ), in which each phase offset angle is shifted by a difference angle δ (identical for all entries), where the difference angle can be positive or negative (as can, of course, the individual phase offset values). During the transition to a new driving / operating state with corresponding target phase offset values ​​Θ , Θ , ..., Θ , the new phase offset values ​​(Φ , Φ ,..., Φ ) can preferably be specified as (Φ , Φ , ..., Φ ) = (Θ + δ, Θ + δ, ..., Θ + δ), where δ is chosen such that the maximum of the angular differences to be covered by each electric motor during the transition is minimized. Of course, it can then also be provided that the transition to the new phase offset values ​​takes place successively and step by step in a transition period, as already described above.In this case, the (target) tuple corresponding to the desired driving / operating state is corrected or selected by adding / subtracting a specific difference value δ in such a way that during the transition from the old to the new phase offset values, the maximum of all angular differences to be covered (in terms of amount) by the respective motors is minimized. This proves to be very advantageous from a control engineering perspective and particularly with regard to the energy efficiency of a suitably configured drive unit. Furthermore, this allows the time for a transition between two different driving states to be kept as short as possible. In a drive unit with only two electric motors, in which a transition from a previously specified driving / operating state with phase offset values. to one of the target phase offset values corresponding driving / operating state, the newly specified phase offset values according to simple optimization calculation to + δ, Θ + δ) can be selected with This always ensures that during the (advantageously step-by-step) transition from the phase offset value pair Both the phase offset angle of the first electric motor and the phase offset angle of the second electric motor must be changed by the same amount of difference angle, so that the phase angle differences to be covered during the transition are evenly distributed between both electric motors. This results in a transition that is optimized in every respect between different driving or operating states of a drive device operated according to the method according to the invention. If the method according to the invention is implemented in a drive system with any number of electric motors, a corresponding optimization can also always be carried out in order to minimize the maximum of the phase angle difference amounts to be covered by each electric motor during the transition.It can be shown that the above-mentioned value for Delta is easy to determine if first the phase offset values ​​for each different pair of electric motors (Mi, Mj) are determined with ^, ^ ∈. { 1, … , ^ ≠ ^ from the majority of electric motors. For each pair of electric motors, already find a suitable shift value that minimizes the phase angle difference to be bridged for the two electric motors considered. Among these values ​​δ ^,^ a value for δ can be found which achieves the desired optimization. To determine this value, simply ^,^ The resulting phase offset value differences for all electric motors and then their maximum are determined. For one (or possibly several) of these δ ^,^the maximum assumes a minimum value, which allows the control effort for a transition to the desired operating state to be optimized. Since soil compactors of the type in question here typically run on battery power, setting such optimized transitions between different driving / operating states proves to be extremely advantageous. Furthermore, it should be mentioned that – as far as the specific design of the drive unit and the given selection of driving / operating state commands allow – the target phase offset values ​​stored in the memory unit for the various driving or operating states can, if necessary, be stored in such a way that they are already optimized accordingly with regard to all transitions between any two different driving and / or operating states.Finally, it should be noted that the above-explained specification of corrected / optimized (target) phase offset values ​​for the individual electric motors is also considered an independent inventive concept that can be provided or implemented in any drive unit for a soil compactor with a ground contact plate, comprising a plurality of electric motors each carrying at least one unbalanced weight, regardless of how the current target phase position is specifically specified for the respective electric motor. The applicant therefore reserves the right to make this the subject of an independent patent claim, in which, in deviation from the presently claimed invention, a plurality of guide shaft generators that are to be synchronized with one another need not necessarily be provided.The transmission of the base speed currently specified by the central control unit and the individual (possibly successively changing) phase offset values ​​according to step (C) preferably takes place continuously or periodically (i.e. repeatedly at suitably specified time intervals), whereby it could also be provided that the specified values ​​are transmitted on an event-based basis, e.g. only in the event of a change in the previously applicable values. In the case of periodic transmission, the frequency must of course be suitably dimensioned so that, on the one hand, the soil compactor reacts with the desired dynamics to changing driving or operating state commands and, on the other hand, the phase control can easily follow the successively changing phase offset angles for the individual motors. The values ​​can be transmitted via a suitable communication interface (e.g. a CAN bus).Within the scope of the present invention, a plurality of guide shaft generators are provided, each of which is assigned either to an electric motor or to a group of electric motors, wherein the phase control of each electric motor is based on the virtual guide shaft of the guide shaft generator assigned to the respective electric motor.The virtual guide waves generated by the guide wave generators represent, as defined in step (D), each the linear phase angle curve of a reference angular position (advantageously corresponding to the phase offset value zero ("0")) of an electric motor rotating undisturbed at a constant base speed and, in a particularly expedient embodiment, as will be explained in more detail below with reference to Figure 8, can be designed as a counter incremented at a constant counter frequency, which counts up from a counter value 0 representing the phase angle 0° to a maximum value N representing the phase angle 360° and is reset to 0 when this maximum value (=overflow threshold) is reached.At typical base speeds in the range of several thousand revolutions per minute (bpm), the time interval for one complete revolution of the virtual control wave is a few tens of ms, for example 20 ms at 3000 rpm, during which significant load variations can occur for the individual electric motors in the event of external disturbances. Due to the individual generation of a virtual control wave for each individual electric motor or the generation of a plurality of virtual control waves, each of which is assigned to a group of, for example, two (or three) electric motors, and the synchronization of all virtual control waves according to step (F), particularly precise control of all electric motors is possible, which enables very fast control interventions by the phase controller even in the event of external disturbances.Compared to a system in which multiple motors orient themselves to a single virtual control wave, this offers the advantage that a single control wave generator serving as the master does not have to transmit corresponding data on the current value / angle of the virtual control wave to all motors for the phase control of all motors. Within the scope of the present invention, one control wave generator may also function as a master in a sense. However, this only needs to generate suitable synchronization pulses and transmit them to all other (slave) control wave generators, without the need for additional data to be exchanged between individual control wave generators (and / or the motor control units assigned to them).The synchronization pulse can be transmitted as a simple digital signal and is advantageously transmitted when an overflow threshold is reached, i.e., in particular, once per complete revolution of the virtual master control wave. As a result, the (slave) control wave generators receiving the synchronization pulse are also reset to the value 0 for synchronization purposes. Of course, other repetition rates for the synchronization pulse could also be selected. Within the scope of the present invention, each electric motor can advantageously be assigned a separate control wave generator, which is implemented in a motor control unit of the respective electric motor, which also includes the respective phase controller.Alternatively, at least one pilot wave generator can be provided, which is assigned to a group of preferably two electric motors and is provided in a motor group control unit that also includes all phase regulators for the electric motors of the respective group. The specific design of the individual motor control units and / or motor group controllers is, moreover, completely independent of the specific design of the drive unit and the number or arrangement of the electric motors used therein.Adaptation of the method according to the invention to differently designed drive units with different numbers / arrangements of electric motors is ultimately achieved by a different design / programming of the central control unit and the at least one data set provided in a memory unit, with which – depending on the number and arrangement of the electric motors provided in a specific drive unit – the target phase offset values ​​for the individual electric motors are specified for the driving / operating states possible with the respective drive unit, with which the respective driving / operating state can be set. Adaptation to input units that may be designed differently for different soil compactors for specifying the driving / operating state commands thus possible is also easily possible in this way.Regarding the phase control of the individual electric motors provided in step (G), it should be noted that this can be implemented in a particularly advantageous and simple manner by influencing a speed control that is typically provided for electric motors anyway. If an electric motor of the drive unit – e.g. due to an external disturbance – lags behind the angle of the virtual guide shaft shifted by the individual phase offset value in its current actual phase angle, the electric motor must be briefly accelerated (i.e., briefly operated at a higher speed) so that it again follows the phase angle curve of the virtual guide shaft shifted by the individual phase offset value as precisely as possible. If an electric motor of the drive unit – e.g.due to an external disturbance – its current actual phase angle leads the angle of the virtual master shaft shifted by the individual phase offset value, it must be briefly slowed down (i.e. briefly operated at a lower speed) so that it again follows the phase angle curve of the virtual master shaft shifted by the individual phase offset value as precisely as possible. Thus, the phase controllers assigned to the respective electric motors can advantageously output a target speed that deviates from the base speed by a correction value, which is fed to a motor controller of the respective electric motor designed as a speed controller, so that the electric motor is briefly accelerated or slowed down in order to follow the rotary movement specified by the virtual master shaft assigned to it and the individual phase offset value as quickly and precisely as possible.For the purpose of this control, conventional control technology, such as a PID controller, which is ideally suited in this case, can be used to ensure the desired control behavior with the highest possible precision. If an angular position evaluation unit is provided according to the invention for determining the actual phase position of each electric motor, the actual phase angle can be determined in a conventional manner known from the prior art, whereby contactless methods (based on optical, magnetic, or other measuring principles) also exist for this purpose.For this purpose, a suitable rotary angle sensor (hereinafter referred to synonymously as an encoder) or a resolver is suitable in an expedient embodiment of the invention. Sensorless methods also exist for determining the actual phase position of a motor, in which an evaluation of the control signals supplied to the electric motor allows a conclusion to be drawn about the current angular position of the electric motor, which would of course also be possible within the scope of the present invention. If the actual phase position of the electric motor is determined by the angle evaluation unit, an adjustment (or a suitable correction of the determined values) can of course preferably be carried out so that the actual phase position output by the angle evaluation unit at each electric motor advantageously refers to the same reference point of the respective electric motor as the reference angular position defined by the virtual guide shafts.In a particularly advantageous embodiment of the method according to the invention, it can be provided that the angle evaluation unit has an encoder for determining the actual phase angle of each electric motor, and that the phase control takes place iteratively in phase control cycles, wherein the rising and / or falling edge of each encoder signal or specific encoder signals (e.g., every mth encoder signal) is used as the trigger signal for a phase control cycle. Such an encoder-triggered start of a phase control cycle and the resulting comparison with the temporal resolution of the virtual master shaft, which can be set to virtually any desired high, enables the calculation of any phase deviation using maximum current data, wherein the virtual master shafts are not subject to speed fluctuations due to external influences.Of course, such phase control in phase control cycles can also be implemented using an angular position evaluation unit that does not have an encoder. A clearly definable event can then be used as a trigger signal for a phase control cycle. The current deviation of the target phase position (resulting from the addition of the current phase angle of the virtual control shaft assigned to the electric motor and the individual phase offset value) from the actual phase position determined by the encoder can advantageously be used as an input variable for the phase controller. This prevents the controller input from being subjected to a cyclically changing target value, which also reduces the load on the control loop and leads to energy-efficient operation of the soil compactor.In a further preferred embodiment of the invention, the method according to the invention finally has a further method step (H) as follows: (H) Repeatedly or continuously checking whether the drive unit is in an undesirable driving and / or operating state and, if an undesirable driving or operating state is detected, specifying a new base speed (ne) for all electric motors (M1, M2, ..., Mn) and / or new individual phase offset values. for all electric motors (M1, M2, ..., Mn) to eliminate the undesirable driving or operating condition. An undesirable operating condition can be determined, if necessary, with the aid of additional sensors (e.g., an acceleration sensor) and exists, for example, when the measured values ​​determined by the additional sensors are outside a standard range for normal operation, e.g., when excessive acceleration values ​​occur in a certain direction. Furthermore, an undesirable operating condition can also be detected, for example, when the phase control cannot establish a stable driving or operating condition within a certain time interval despite usual control interventions. In addition, using already available data, i.e., without additional sensors, e.g.By evaluating the power consumption or the phase currents of the electric motors used, an undesirable operating condition can be determined. In particular, it can be provided that, to eliminate the undesirable driving / operating condition, the central control unit predetermines suitable phase offset values ​​for the majority of electric motors, with which an operating condition with lower compaction or lower (driving or rotational) speed or even compaction- and propulsion-free operation of the soil compactor is set and / or that the base speed of the electric motors is adjusted (e.g., reduced) or, in extreme cases, shut down completely.As already mentioned above, the present invention also relates to a drive unit for a soil compactor with a ground contact plate, wherein the drive unit has an input unit for enabling the input of a travel command or other operating state command for the soil compactor and a plurality of electric motors, each carrying at least one unbalanced weight, which, when suitably synchronized, serve both for the horizontal propulsion of the soil compactor and for generating a soil-compacting vibrating movement, wherein each electric motor is assigned a separate phase controller and wherein the drive unit has a central electronic control unit and a plurality of guide wave generators and is set up to carry out a method according to the invention, as described above.The same aspects and advantageous developments that were already explained above in connection with the method according to the invention therefore apply to the drive unit according to the invention. Various exemplary embodiments of the invention are explained in more detail below with reference to the drawings. Fig. 1 shows, in three superimposed representations, schematic side views of a soil compactor with a ground contact plate and a drive unit with two electric motors driven in opposite directions, each carrying an unbalanced weight. Figs. 2a and 2b each show a schematic plan view of the soil compactor from Fig. 1 during forward and reverse travel, respectively. Figs. 3a to 3d each show a schematic plan view of a soil compactor with a ground contact plate and a drive unit with four electric motors driven in opposite directions, each carrying an unbalanced weight.4a - 4f various schematic plan views of soil compactors with a soil contact plate and a drive unit, each having two, three or four electric motors, each carrying an unbalanced weight, in different configurations, Fig. 5 an exemplary data set in which, for a soil compactor of the type in question with four electric motors, certain target phase offset values ​​are assigned to various driving and operating state commands, with which the respective driving / operating state can be realized, Fig. 6 a schematic circuit diagram to explain the method according to the invention and the system architecture of a drive unit set up to carry it out in a first exemplary embodiment, Fig.7 is a schematic circuit diagram to explain the method according to the invention and the system architecture of a drive unit set up to carry it out in a second exemplary embodiment, Fig. 8 is a representation to illustrate a virtual guide shaft and for synchronizing the virtual guide shafts, and Fig. 9 is a detailed representation of the phase control in a further exemplary embodiment of the present invention. Fig. 1 shows, in three superimposed representations, several schematic side views of a soil compactor BV in operation with a soil contact plate BK at different times, wherein, for the sake of better clarity, reference numerals are only inserted in the top left representation of the soil compactor BV.The soil compactor BV has a drive unit AE with two electric motors M1, M2, each carrying an unbalanced weight U1, U2, wherein the drive unit can be controlled using the method according to the invention. The two counter-rotating electric motors M1, M2 in the example shown, which are mounted in a suitable manner (not shown) on the ground contact plate BK, have a parallel axis of rotation - each perpendicular to the plane of the drawing - around which the respective unbalanced weight U1, U2 rotates in opposite directions according to arrows D1, D2, specifically at a speed that is the same for both electric motors M1, M2. The upper illustration in Fig. 1 shows a total of five views of the soil compactor BV from left to right at different times during half a revolution of the electric motors M1, M2.The phase offset values ​​Φ , Φ for the two electric motors M1, M2 are set so that both motors are operated with a phase difference ΔΦ = (Φ - Φ ) ​​= 0, whereby the electric motors M1, M2 are driven in opposite directions. The value pair (Φ , Φ ) can be selected as (0,0) for this purpose. The center of gravity of the respective unbalanced weight can be selected as the reference point for defining the reference angular position, so that in Fig. 1 above the respective centrifugal force vector F, F simultaneously also represents the reference angular position corresponding to the phase offset value zero. In the first view of the soil compactor BV shown on the left from the upper illustration in Fig.1, the unbalanced weights U1, U2 of both electric motors M1, M2 are oriented such that their center of gravity (or a radial center line through the respective unbalanced weight) lies exactly above the axis of rotation of the respective electric motor M1, M2, so that at this point in time the centrifugal force vectors F, F of both electric motors M1, M2 point exactly upwards. This means that a total force F directed vertically upwards acts on the soil compactor. In the second view of the soil compactor (from the upper illustration of Fig. 1), the unbalanced masses have already rotated by an angle of 45° in the respective direction of rotation D1, D2 of the two electric motors M1, M2, so that the respective centrifugal force vectors F, F of both electric motors M1, M2 now point diagonally upwards in different directions. In total, however, this results in a total force F on the soil compactor pointing exactly vertically upwards, but this is now lower than before.The horizontal components of the centrifugal force vectors F, F of both electric motors M1, M2 cancel each other out. In the third view of the soil compactor (from the upper illustration of Fig. 1), the unbalanced masses have already rotated by an angle of 90° in the respective rotational directions D1, D2 of the two electric motors M1, M2, so that the respective centrifugal force vectors F, F of both electric motors M1, M2 now point in different directions to the right and left, so that the resulting total force F is zero. In the fourth view from Fig. 1 above, the unbalanced masses U1, U2 have rotated another 45°, so that they now each point diagonally downwards and lead to a total force F directed vertically downwards. The fifth view from Fig.1 above shows the point in time at which the unbalanced masses have rotated 180° compared to the first view, so that the two centrifugal force vectors F, F and the total force F now point exactly vertically downwards. If one now mentally supplements these representations over the full rotation of the respective electric motors, then over a full rotation there results a total force that is always vertically aligned, oscillating, which means that the soil compactor is exposed to vertical upward and downward forces when stationary. With a sufficiently high speed of the two electric motors and appropriately dimensioned unbalanced weights, the soil compactor BV lifts off the ground intermittently (flight phase; this begins as soon as the vertical component of the total force acting on the soil compactor exceeds its gravity). Intermittently it is pressed against the ground (compression phase), which leads to soil compaction.The in-phase operation of the electric motors illustrated in the upper illustration of Fig. 1 results in soil compaction while stationary, i.e., without the soil compactor BV moving in a horizontal direction. The middle and lower illustrations of Fig. 1 illustrate a driving or operating state of the soil compactor, in which the two electric motors M1, M2 are operated with a phase difference of ΔΦ = (Φ - Φ ) ​​= +30° (central illustration of Fig. 1) and ΔΦ = (Φ - Φ ) ​​= -30° (lower illustration of Fig. 1). The middle illustration of Fig. 1 corresponds to operation of the drive unit AE with phase offset values ​​(Φ , Φ ) = (0, -30°), i.e., the phase position of the second electric motor M2 is always offset by an angle of 30° against its direction of rotation D2 compared to its specified reference angular position, which can be clearly seen when comparing the views below each other. The lower illustration of Fig.1 corresponds to operation of the drive unit AE with phase offset values ​​(Φ , Φ ) = (0, 30°), i.e. the phase position of the second electric motor M2 is always adjusted by an angle of 30° in the direction of rotation D2 compared to its specified reference angular position. It can be seen that when such phase differences are set, the total force F acting on the soil compactor is now directed diagonally upwards in certain time periods and diagonally downwards in certain time periods, so that it now also has horizontal components F, which are shown in the respective views. It is easy to see that the oscillating vertical component of the total force, with a suitable speed of the electric motors M1, M2, in turn leads to an up and down movement of the soil compactor BV with flight and compression phases, whereby in operation according to the middle illustration in Fig.1 (compared to the upper illustration), the relative phase position of the flight and compression phases is now shifted by 15°. In addition, it can be seen that when the soil compactor is operated according to the central illustration in Fig. 1 (with a phase shift ΔΦ = +30°), the horizontal force component F of the total force acting on the soil compactor BV always points to the right during the flight phase, which should correspond to the forward direction of the soil compactor. The soil compactor will therefore move a small amount in the forward direction in each flight phase. The horizontal force components directed to the left during the compression phase, on the other hand, have no effect in the opposite direction, since the soil compactor is pressed forcefully against the ground during this phase and the friction acting in the horizontal direction counteracts the horizontal force component pointing to the left.During the transition from the compression phase to the flight phase, the soil compactor can then, so to speak, push itself off the ground in a forward direction. When the soil compactor is operated according to the lower illustration in Fig. 1 (with a phase shift ΔΦ = -30°), the picture is exactly the opposite, as can easily be seen by mentally completing the missing views. The soil compactor is always moved to the left (i.e. in the reverse direction) during the flight phases. To illustrate the process described above for correcting or optimizing the target phase offset values ​​during the transition between different driving or operating states, it should also be mentioned that during the transition from stationary vibration with phase offset values. = (0°, 0°) to a soil compaction with simultaneous "forward travel" with target phase offset values = (0°, -30°) a correction can be made as follows. According to the formula mentioned above, the new phase offset values ​​can be set as follows: This results in new phase offset values ​​for the two electric motors M1, M2 so that for the desired transition, the phase position of the first electric motor must be adjusted by 15° in its direction of rotation and the phase position of the second electric motor by 15° against its direction of rotation, which can advantageously be done successively and step by step (e.g., linearly) within a suitable transition period. It is clear that the transition can be faster if the phase position of two electric motors is adjusted simultaneously by +15° or -15° than if the phase position of one electric motor (set by the phase offset value) has to be adjusted by 30°. This is also particularly energy-efficient because, with the driving state transition optimized in this way, the phase positions of the flight and compression phases are kept constant, whereas they would be shifted by 15° during the successive transition between phase offset values ​​(0.0) and (0.-30°), which would require additional energy. Fig.2a and 2b show again in a schematic top view of the soil compactor from Fig. 1 that with different settings of the phase position of the respective electric motors M1, M2 with unbalanced masses U1, U2, which each rotate about a rotational axis A1, A2 of the electric motor, travel commands for "moving forward" or "moving backward" can be set, so that - depending on the selection of the phase offset values ​​Φ , Φ - it can be driven to move forward according to the arrow in Fig. 2a or to move backward according to the arrow in Fig. 2b. Fig. 3a - 3d each show a schematic plan view of a soil compactor with a ground contact plate BK and a drive unit AE with a total of four electric motors M1, M2, M3, M4, each carrying an unbalance U1, U2, U3, U4, whose respective axes of rotation A1, A2, A3, A4 are all aligned parallel (perpendicular to the upward forward direction).The electric motors M2, M4 arranged on the left and the electric motors M1, M3 arranged on the right can each be regarded as a sub-unit, whereby each of these sub-units behaves like the drive unit AE of the soil compactor shown in Figs. 1, 2a, 2b when the motors M1 and M3 are driven in a suitable counter-rotating manner and the motors M2 and M4 are driven in a counter-rotating manner. Thus, if the left motors M2, M4 are operated with a phase shift of ΔΦ = (Φ - Φ ) ​​= -30° and the right motors M1, M3 are also operated with a phase shift of ΔΦ = (Φ - Φ ) ​​= -30°, then both the left motor pair M2, M4 and the right motor pair M1, M3 produce a forward-directed force, as shown in Fig. 3a by the corresponding arrows, so that the soil compactor as a whole is moved in a forward direction.Accordingly, when the motor pairs M2, M4 and M1, M3 are operated with a phase shift of -30° each, a backward force is produced for each motor pair, so that the soil compactor then moves backwards as a whole, as illustrated in Fig. 3b. However, if the left motor pair M2, M4 are operated to generate a forward force and the right motor pair M1, M3 are operated to generate a backward force, as illustrated in Fig. 3c, the soil compactor will rotate clockwise around a vertical axis. Accordingly, a counterclockwise rotation can be achieved if, as shown in Fig. 3d, the left motor pair M2, M4 are operated to generate a backward force on the soil compactor and the right motor pair M1, M3 are operated to generate a forward force.4a - 4d again show schematic top views of various soil compactors with differently designed drive units. As already discussed above, a drive unit corresponding to Fig. 4a with two electric motors M1, M2 can achieve forward or reverse travel. A drive unit with four electric motors according to Fig. 4b can, as also already discussed, achieve forward or reverse travel as well as a rotational movement in different directions around a vertical axis. Drive units with four electric motors M1, M2, M3, M4, in which the rotational axes A1, A2, A3, A4 of the electric motors M1, M2, M3, M4 are aligned at an angle to each other, can, in addition to forward and reverse travel and a rotational movement around a vertical axis, also achieve sideways travel to the left / right, which is shown in Figs. 4c ("O arrangement") and 4d ("X arrangement").A drive unit with three electric motors, whose centers (in plan view) lie on an equilateral triangle, can also cause forward / backward travel and sideways left / right travel, but not a rotational movement, as illustrated in Fig. 4e. Finally, a drive unit with three electric motors, whose centers (in plan view) lie on an isosceles but not equilateral triangle, can also additionally perform a rotational movement. Fig. 5 shows an example data set DS, presented here in the form of a table, in which, for a soil compactor of the type in question with four electric motors M1, M2, M3, M4, arranged as shown in Fig. 4c, specific target phase offset values ​​(as angles) for the individual electric motors are assigned to various travel and operating state commands, with which the respective travel / operating state can be realized.It is understood that, taking the above explanations into account, a person skilled in the art will naturally be able to create appropriate phase offset specifications for different arrangements of a plurality of electric motors (including both the arrangements already discussed and those not yet discussed) that correspond to suitable drive commands. The table in Fig. 5 should be self-explanatory; for the sake of clarity, it should be noted that phase offset values ​​according to the present invention do not necessarily have to be specified in angular units, but could also be specified, for example, in radians or any other suitable format.It should also be mentioned that, for example, phase offset values ​​for intermediate stages between slow and fast movement can also be derived from the given data set by forming suitable intermediate values ​​between the respective phase offset value tuples. Fig. 6 now illustrates the system architecture of a first exemplary embodiment of a drive unit configured to carry out the method according to the invention, which drive unit has a plurality of electric motors M1, M2, ..., Mn, each carrying an unbalanced weight and acting on a ground contact plate BK of a soil compactor BV. An input unit EE is initially provided, with which, according to method step (A), travel and / or other operating state commands for a soil compactor BV can be specified in a suitable manner, as already explained above.Furthermore, a central control unit ZS and a memory unit SE are provided, wherein at least one data set DS (cf. e.g. Fig. 5) is stored in the memory unit SE, in which data set DS, for specific driving commands and / or operating state commands, depending on the specific arrangement and number of electric motors in the drive unit, specific target phase offset values ​​Θ , Θ , ..., Θ for all electric motors M1, M2, ..., Mn are stored, with which the driving state or operating state corresponding to the respective driving command and / or operating state command can be achieved, and / or from which such target phase offset values ​​Θ , Θ , ..., Θ can be derived by the central control unit ZS. The drive unit further comprises a plurality of guide shaft generators LG1, LG2, ... LGn for generating a virtual guide shaft VW1, VW2, ..., VWn as required in step (D) of the method according to the invention, wherein in the embodiment shown in Fig.6, each electric motor M1, M2, ..., Mn is assigned exactly one pilot wave generator LG1, LG2, ..., LGn, and each virtual pilot wave VW1, VW2, ..., VWn represents the linear phase angle curve of an electric motor rotating undisturbed at a constant base speed. Furthermore, a phase controller PR1, PR2, ... PRn is provided for each electric motor, with one pilot wave generator and one phase controller each being formed or arranged in a motor control unit MS1, MS2, ... MSn assigned to the respective electric motor. Each pilot wave generator is configured to transmit the respective current phase angle Φ , Φ , ..., Φ of the virtual pilot wave VW1, VW2, ..., VWn generated by it to the phase controller PR1, PR2, ..., PRn assigned to it. Furthermore, for each motor there is a motor controller MR1, MR2, ..., MRn as well as a power electronics unit LE1, LE2, ... that electrically drives the respective electric motor M1, M2, ... Mn.LEn are provided, which can be combined in a motor control circuit MRK1, MRK2, ..., MRKn assigned to the respective motor M1, M2, ..., Mn. The respective motor control unit MS1, MS2, ..., MSn can be combined with the respective motor control circuit MRK1, MRK2, ..., MRKn as a structural unit to form a motor control and regulation unit MSR1, MSR2, ..., MSRn. Finally, each electric motor M1, M2, ..., Mn is provided with an angular position evaluation unit for determining the actual phase position of the electric motor. In the illustrated embodiment, this evaluation unit is formed by an encoder E1, E2, ..., En. Each encoder E1, E2, ..., En is configured to transmit the signal pulses it generates, from which the current actual phase position Φ , ..., Φ of its assigned electric motor can be determined, to the phase controller PR1, PR2, ..., PRn assigned to the respective electric motor. The individual guide wave generators LG1, LG2, ...LGn are connected by means of a data line designated by the reference symbol "sync pulse," via which a synchronization pulse can be transmitted. The central control unit ZS is configured, in accordance with method step (B) according to the invention, to determine a base speed n for all electric motors M1, M2, ..., Mn and an individual phase offset value, taking into account the last drive command or operating state command input (or inputs) made in step (A) and the target phase offset values ​​stored for this purpose in the memory unit SE. ..., Φ for each electric motor M1, M2, ..., Mn. Furthermore, the central control unit ZS is configured to iteratively transmit the (currently specified) base speed n to all guide shaft generators LG1, LG2, ... LGn as well as to all phase controllers PR1, PR2, ..., PRn in accordance with method step (C) according to the invention. Furthermore, the central control unit ZS is configured to transmit the (currently specified) phase offset value for each electric motor M1, M2, ..., Mn to be transmitted iteratively to the phase controller PR1, PR2, ... PRn assigned to the respective electric motor. In the exemplary embodiment shown, the pilot wave generator LG1 shown on the left is configured as the "master" pilot wave generator for the iterative generation and transmission of the synchronization pulse required according to method step (E), based on which all other pilot wave generators can synchronize the virtual pilot wave VW2, ..., VWn generated by them in accordance with method step (F) according to the invention, which will be explained in more detail below with reference to Fig. 8.It should be noted, however, that alternatively, corresponding synchronization pulses could also be transmitted from the central control unit ZS to the individual pilot wave generators, in which case the SyncPuls data line connecting the pilot wave generators would also have to be connected to the central control unit ZS. Each phase controller PR1, PR2, ..., PRn thus receives the currently specified base speed n and the current phase angle as input variables. the virtual control shaft VW1, VW2, ..., VWn assigned to it, the phase offset value Φ , Φ , ..., Φ transmitted to it by the central control unit ZS for the electric motor M1, M2, ... Mn assigned to it as well as the signals for the actual phase position transmitted to it by the respective encoder E1, E2, ..., En of the respective electric motor. The phase controllers PR1, PR2, ..., PRn are each configured, according to step (G) of the inventive method, to use the input variables supplied to them for the purpose of phase control to influence the motor controller MR1, MR2, ..., MRn of the electric motor M1, M2, ... Mn assigned to them, so that the latter follows the phase angle of the virtual pilot wave, shifted by the respective phase offset angle, as precisely as possible. Fig. 7 shows a second exemplary embodiment of the system architecture of a drive unit according to the invention with a total of four electric motors M1, M2, M3, M4, in which, in contrast to the exemplary embodiment according to Fig. 6, not each electric motor is assigned a separate pilot wave generator, but in which a total of two pilot wave generators LG-G1, LG-LG2 are provided, each assigned to a group of two motors M1, M2 or M3, M4.Each of the guide wave generators LG-G1, LG-G2 is set up to display the current phase angle. to transmit the virtual control wave VW-G1, VW-G2 generated by it to both phase controllers PR1, PR2 or PR3, PR4 assigned to it. Each of the control wave generators LG-G1, LG-G2 can in turn be designed or arranged together with the two phase controllers PR1, PR2 or PR3, PR4 assigned to it in a motor group control unit MS-G1, MS-G2 assigned to the respective group of electric motors. Furthermore, the respective motor group control unit MS-G1, MS-G2 and the motor control circuits MRK1, MRK2 or MRK3, MRK4 assigned to the electric motors of the respective group can be combined as a structural unit to form a motor group control and regulator unit MSR-G1, MSR-G2. The two guide wave generators LG-G1, LG-G2 can synchronize the virtual guide waves VW-G1, VW-G2 they generate in a similar manner, as already described, using a synchronization pulse transmitted via the sync pulse data line. All other aspects of the system shown in Fig.7 correspond – taking into account the given change in the system architecture – to those of the embodiment according to Fig. 6, so that reference is made to this to avoid repetition. Fig. 8 also illustrates the generation and synchronization of the virtual guide waves generated by the guide wave generators LG1, LG2, ..., LGn or LG-G1, LG-G2. Each virtual guide wave can be designed as a counter incremented with a constant counter frequency, which, starting from a counter value 0 representing the phase angle 0°, counts up at a constant counter frequency up to a maximum value N representing the phase angle 360° and is reset to 0 upon reaching this maximum value (=overflow threshold). When resetting the virtual guide wave of the guide wave generator LG1 or LG-G1 acting as the master (see also Fig.6 and 7), a synchronization pulse is sent from the master control wave generator to all (slave) control wave generators, forcing them to also reset their counter representing the virtual control wave to the value zero. If the virtual control wave of the slave control wave generator was previously slightly out of phase, then upon receipt of the synchronization pulse it will again run synchronously and in phase with the virtual control wave of the master control wave generator. Fig. 8 illustrates this for an initial synchronization in which the virtual control wave of the slave control wave generator was initially significantly out of phase. During operation, synchronization of the various control waves can then be ensured in the same way if asynchronous operation should occur, e.g. due to minor deviations in synchronicity and / or changes in the speed setting for the individual electric motors.However, it should be emphasized again that corresponding synchronization pulses could alternatively also be transmitted by the central control unit of a drive unit AE according to the invention, so that all guide wave generators LG1, LG2, ..., LGn, LG-G1, LG-G2 can then be configured as slave guide wave generators. For this purpose, the central control unit can also, if necessary, have a guide wave generator provided exclusively for the purpose of synchronizing the guide wave generators assigned to the individual electric motors. Finally, Fig. 9 shows further details of the exemplary embodiment of the phase control used in the context of the present invention.It can advantageously be provided that the values ​​supplied to one of the phase controllers PRn on the input side, namely the current phase angle Φ of the virtual master shaft VWn assigned to it, the phase offset value Φ transmitted to it by the central control unit ZS for the electric motor Mn assigned to it and the actual phase position Φ of the electric motor assigned to it transmitted to it by the respective encoder En, are processed as follows: By means of an adder or a suitable addition and subtraction circuit, an error signal can be generated. which represents the current deviation of the actual phase position of the electric motor Mn assigned to the phase controller PRn from the target phase position specified for it. From this error value Φ, a correction value n (with a positive or negative sign) for the motor speed can then be determined in a PID controller (if necessary taking the current base speed into account), which is added to the base speed n specified by the central control unit. This results in a current target speed n for the electric motor, which is fed to the motor controller MRn so that the motor controller MRn, which can also be designed as a PID controller, can regulate its speed accordingly, additionally taking into account the encoder signals transmitted to it from the encoder and suitably influencing its power electronics LEn.

Claims

1. Method for controlling a drive unit (AE) for a soil compactor (BV) with a soil contact plate (BK), wherein the drive unit has a plurality (n) of electric motors (M1, M2, ..., Mn) each carrying at least one unbalanced weight (U1, U2, ..., Un), and wherein the electric motors (M1, M2, ..., Mn) serve, when suitably synchronized, both for horizontal propulsion of the soil compactor and for generating a soil-compacting vertical vibrating movement, characterized by the following method steps: (A) Enabling the input of a travel command or other operating state command for the soil compactor by means of a suitable input unit (EE) (B) Specifying a basic speed (n Vorgabe ) for all electric motors (M1, M2, ..., Mn) and an individual phase offset value (Φ offset,M1 , Φ offset,M2 , ..., Φ offset,Mn) for each electric motor (M1, M2, ..., Mn) taking into account the last input(s) made in step (A) by a central control unit (ZS) of the drive unit (AE) (C) transmitting the basic speed (n Vorgabe ) from the central control unit (ZS) to a plurality of guide shaft generators (LG1, LG2, ..., LGn; LG-G1, LG-G2), each associated with an electric motor or a group of electric motors, and, for each electric motor (M1, M2, ..., Mn) of the plurality of electric motors (M1, M2, ..., Mn), transmitting the basic speed (n Vorgabe ) and the currently specified individual phase offset value (Φ offset,M1 , Φ offset,M2 , ..., Φ offset,Mn ) from the central control unit to 1 a phase controller (D) assigned to the respective electric motor; generation of a virtual control wave (VW1, VW2, ..., VWn; VW-G1, VW-G2)) by all control wave generators (LG1, LG2, ..., LGn; LG-G1, LG- G2) taking into account the basic speed (nVorgabe), whereby each virtual guide wave (VW1, VW2, ..., VWn; VW-G1, VW-G2) represents the linear phase angle profile of a reference angular position of an electric motor rotating undisturbed at a constant base speed (E) Periodic transmission of a synchronization pulse from the central control unit (ZS) to all guide wave generators (LG1, LG2, ..., LGn; LG-G1, LG-G2) or Periodic transmission of a synchronization pulse from a guide wave generator (LG1; LG-G1) serving as the master to all other guide wave generators (LG2, LG3, ..., LGn; LG-G2) (F) Synchronization of all virtual guide waves (VW1, VW2, ..., VWn; VW-G1, VW-G2) using the periodically transmitted synchronization pulse, so that the virtual guide waves of all guide wave generators are synchronized, in particular in phase, and have the specified base speed (G) Phase control of all electric motors (M1, M2, ..., Mn) by means of a phase controller (PR1, PR2, ..., PRn) provided for each electric motor and acting on a motor controller (MR1, MR2, ..., MRn) of the respective electric motor, evaluating - the current phase angle (Φ. Ref,M1 , Φ Ref,M2 , ..., Φ Ref,Mn ) of the virtual guide shaft (VW1, VW2, ..., 2 VWn; VW-G1, VW-G2) of the guide wave generator (LG1, LG2, ..., LGn; LG-G1, LG-G2) assigned to the respective electric motor (M1, M2, ..., Mn), - the currently specified individual phase offset value (Φ offset,M1 , Φ offset,M2 , ..., Φ offset,Mn ) of the respective electric motor, - the current actual phase position (Φ Ist,M1 , Φ Ist,M2 , ..., Φ Ist,Mn ) of the electric motor in question and - the base speed (n Vorgabe).

2. Method according to claim 1, characterized in that at least one data set (DS) is stored in a memory unit (SE) assigned to the central control unit (ZS) or integrated therein, in which data set, for specific travel commands and / or operating state commands, depending on the specific arrangement and number of electric motors in the drive unit, specific target phase offset values ​​(Θ offset,M1 , Θ offset,M2 , ..., Θ offset,Mn ) are stored for all electric motors (M1, M2, ..., Mn) with which the driving state or operating state corresponding to the respective driving command and / or operating state command can be achieved, and / or from which such target phase offset values ​​(Θ offset,M1 , Θ offset,M2 , ..., Θ offset,Mn ) by the central control unit.

3. Method according to claim 2, characterized in that 3 that the central control unit (ZS) is set up, upon input of a new travel command or a new other operating state command according to step (A), to determine the individual phase offset values ​​(Φ offset,M1 , Φ offset,M2 , ..., Φ offset,Mn ) in a transition period successively and step by step from the previously specified phase offset values ​​(Φ offset,M1,alt , Φ offset,M2,alt , ..., Φ offset,Mn,alt ) into new phase offset values ​​(Φ offset,M1,neu , Φ offset,M2,neu , ..., Φ offset,Mn,neu ) which correspond either to the respective target phase offset values ​​(Θ offset,M1 , Θ offset,M2 ,..., Θ offset,M1 ) or are equivalent to them.

4. Method according to claim 3, characterized in that the new phase offset values ​​(Φ offset,M1,neu , Φ offset,M2,neu ,..., Φ offset,Mn,neu ) can be specified as (Φ offset,M1,neu , Φ offset,M2,neu , ..., Φ offset,Mn,neu ) = (Θ offset,M1 + δ, Θ offset,M2 + δ, ..., Θ offset,M1+ δ), where δ is chosen such that the maximum of the angular differences to be covered by each electric motor during the transition is minimized.

5. Method according to one of the preceding claims, characterized in that according to step (E), one synchronization pulse is transmitted per complete revolution of a virtual master control wave, in particular upon completion of a complete revolution of the virtual master control wave.

6. Method according to one of the preceding claims, characterized in that 4 that each electric motor (M1, M2, ..., Mn) is assigned a separate pilot wave generator (LG1, LG2, ..., LGn), which is formed in a motor control unit (MS1, MS2, ..., MSn) of the respective electric motor, which also contains the respective phase regulator (PR1, PR2, ..., PRn).

7. Method according to one of claims 1 to 5, characterized in that at least one pilot wave generator (LG-G1, LG-G2) is provided, which is assigned to a group of preferably two electric motors (M1, M2; M3, M4) and which is provided in a motor group control unit (MS-G1, MS-G2) which also contains all phase regulators (PR1, PR2; PR3, PR4) for the electric motors of the respective group.

8. Method according to one of the preceding claims, characterized in that the phase regulators (PR1, PR2, ..., PRn) used in step (G) have a correction value (n offset ) from the base speed (n Vorgabe ) different target speed (n Soll), which is fed to a motor controller (MR1, MR2, ..., MRn) of the respective electric motor (M1, M2, ..., Mn), designed as a speed controller.

9. Method according to one of the preceding claims, characterized in that the angle evaluation unit for determining the actual phase angle of each electric motor (M1, M2, ..., Mn) has an encoder (E1, E2, ..., En), and that the phase control takes place iteratively in phase controller cycles, wherein the rising and / or falling edge of each encoder signal or specific encoder signals is used as the trigger signal for a phase controller cycle. 5 10. Method according to one of the preceding claims, characterized by the further method step (H) repeatedly or continuously checking whether the drive unit is in an undesirable driving and / or operating state, and, if an undesirable driving or operating state is detected, specifying a new basic speed (nVorgabe ) for all electric motors (M1, M2, ..., Mn) and / or new individual phase offset values ​​(Φ offset,M1 , Φ offset,M2 , ..., Φ offset,Mn) for all electric motors (M1, M2, ..., Mn) to eliminate the undesirable driving or operating condition.

11. Drive unit (AE) for a soil compactor (BV) with a ground contact plate, wherein the drive unit (AE) has an input unit (EE) for inputting driving commands and a plurality of electric motors (M1, M2, ..., Mn), each carrying at least one unbalanced weight (U1, U2, ..., Un), which, when suitably synchronized, serve both for horizontal propulsion of the soil compactor and for generating a soil-compacting vibrating movement, wherein each electric motor is assigned a separate phase controller (PR1, PR2, ..., PRn), wherein the drive unit has a central electronic control unit (ZS) and a plurality of guide wave generators (LG1, LG2, ..., LGn; LG-G1, LG-G2) and is configured to carry out a method according to one of claims 1-10. 6

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