Control device, fan, fan system, and method for controlling fans of a fan system

Abstract

The invention relates to a control device (10) for controlling fans of a fan system, to a fan (7), to a fan system having a control device of this type, and to a corresponding method for controlling fans of a fan system. The invention also relates to a fan having a control circuit. The control device (10) is designed to determine, for each fan, a phase offset between an oscillation caused by interaction of the fans and a rotational reference point of the particular fan on the basis of sensor signals from the fans (7), and to temporarily adjust a rotational speed of a fan (7) on the basis of the phase offsets of the fans of the fan system in order to shift the phase offset of the fan.

Description

[0001] CONTROL UNIT, FAN, FAN SYSTEM AND METHOD FOR CONTROLLING FANS OF A FAN SYSTEM

[0002] The invention relates to a control unit for controlling fans of a fan system.

[0003] The invention further relates to a fan with such a control unit, as well as a fan system with such a control unit.

[0004] The invention further relates to a corresponding method for controlling fans of a fan system.

[0005] The invention further relates to a fan with a control circuit.

[0006] Fan systems with multiple fans of the type in question have been known in practice for years. In fan systems with multiple mechanically coupled fans, the fans influence each other's vibrations. The main cause of undesirable vibrations is excitation due to imbalance in individual fans.

[0007] Since the fans in a multi-fan system are typically operated synchronously, their rotational speeds differ only minimally due to the shared analog or digital control. This difference in rotational speed is primarily attributable to manufacturing tolerances. With analog control, the difference is greater than with digital control, but these differences have a negligible impact on airflow. However, this slight difference in rotational speed can lead to observed vibrations within the system, which gradually build up and then decay. This is explained by the fact that the slight difference in rotational speed causes the relative positions of the rotating excitation vectors of each individual fan in the system to change.This results in mutual reinforcement ("oscillation") when the oscillation phases are aligned, and damping ("cancellation") of the oscillation amplitudes when they are aligned in opposite directions. Whether the oscillation phases are aligned or in opposite directions depends on the vibration mode and order. In a first-order oscillation, an opposite orientation occurs with a 180° offset; for other orders, this may occur with a different offset. These effects can develop or change over several seconds to minutes, depending on the magnitude of the rotational speed difference.

[0008] If the rotational frequency of all fans in the system is kept constant, the phase shift to each other also remains constant, thus also the vibrational influence and therefore the vibrational state of the individual devices and the multi-fan system.

[0009] In extreme cases, excessively high vibration amplitudes or regular periods of excessive vibration amplitudes can lead to damage to the fans and / or peripheral components. EP 3282202 B1, for example, discloses a method for determining these resonance effects by measuring the pulsation of the current consumption at a given rotational speed, thus enabling maintenance or replacement of the respective fan mounting. However, this approach is reactive, meaning that only damage that has already been detected can be repaired retrospectively.

[0010] For example, US7282873B2 discloses the use of mutually canceling interference of pressure waves to reduce noise emission and vibration of a system with at least two computer fans.

[0011] The present invention is therefore based on the objective of designing and further developing a fan system of the type mentioned at the outset in such a way that resonance effects are avoided or the effects of resonance effects are mitigated.

[0012] According to the invention, the aforementioned problem is solved by the features of claim 1. Accordingly, the control unit in question is designed to control fans of a multi-fan fan system and to determine, based on sensor signals from the fans, a respective phase shift between an oscillation caused by the interaction of the fans and a rotational reference point of the respective fan. The control unit is also designed to temporarily adjust the rotational speed of a fan based on the phase shifts of the fans of the fan system in order to shift the phase shift of the fan.

[0013] In accordance with the invention, it has first been recognized that the phase shift of a fan relative to a reference point can be shifted by briefly changing the rotational speed of the fan relative to the phase shift of other fans. In particular, the brief or intermittent adjustment of the rotational speed allows the phase shift of the fan to be shifted in such a way that the relative phase shift between two fans has a damping rather than an amplifying effect with respect to the jointly generated oscillation. Determining the phase shifts relative to a reference, namely the oscillation caused by the interaction of the fans, and thus the relative phase shift between two fans, makes it possible to selectively adjust the phase shift of one of the fans in order to achieve the desired effect, i.e., the damping or cancellation of the oscillation.This can improve the acoustics and smooth running of the fan system on the one hand, and on the other hand prevent the fan system from being damaged by vibration in the long term.

[0014] In particular, the control unit can be designed to shift the phase shift of the fan by temporarily adjusting its rotational speed relative to the phase shift of a second fan, such that the phase shift of the first fan has a predetermined ratio to that of the second fan. This predetermined ratio can be selected to dampen the vibration. This leads to the aforementioned improvement in acoustics and prevents damage to the fan system.

[0015] In principle, the control unit can be implemented to directly control the fan speeds. In this case, the control unit can, for example, be configured to (directly) specify the fan's rotational speed in order to adjust it temporarily. Alternatively, the rotational speed can be adjusted indirectly by instructing the respective fan to set a desired phase shift. In this case, the control unit can be configured to specify the desired phase shift for the fan in order to trigger the temporary adjustment of the fan's rotational speed.

[0016] For example, the specified ratio can correspond to a phase difference of approximately 180° for the excitation effects (roughly between 180° and 190°, or between 175° and 185°) relative to the oscillation caused by the interaction of the fans. Such a phase difference leads to a damping of the oscillation.

[0017] As an alternative to controlling the fans to a predetermined phase difference, such as a predetermined phase difference of 180°, a model or digital twin can be used to determine a phase shift (and thus, in particular, one or more phase differences relative to the phase shift of the other fans) that exhibits improved acoustic properties or improved vibration damping properties. The control unit can therefore be configured to calculate a desired phase shift of the fan using a digital twin or model of the fan system and shift the fan's phase accordingly.In particular, the control unit can be configured to determine, using the digital twin or model of the fan system, a desired state of the fan system that exhibits lower vibrations when viewed as a whole than at least one other state of the fan system, and to determine the desired phase shift of the fan based on this desired state. In other words, a global optimization can be performed in which at least one phase shift is adjusted to dampen or eliminate the vibration caused by the interaction of the fans. For example, the techniques shown in WO 2019 / 149324 A1 or WO 2019 / 149326 A1 can be used to create such a digital twin or model and to determine the desired phase shift.

[0018] Alternatively or additionally to a targeted shift of the phase shift, an iterative method can also be used, in which the fan's phase shift is moved in small steps in one direction or the other until a termination condition is reached. In other words, the control unit can be designed to shift the fan's phase shift using an iterative method. This iterative method can be based, in particular, on how the oscillation changes as a result of shifting the phase shift. If the oscillation increases when shifted in a first direction, then in the next iteration the phase shift can be moved in a second direction opposite to the first. If the oscillation decreases when shifted in the first direction, then in the next iteration the phase shift can also be moved in the first direction.Thus, the control unit can be configured to maintain, reverse, or terminate the iterative process based on a sensor signal from an accelerometer. For example, the control unit can be configured to adjust the step size of the phase shift based on the accelerometer signal. The accelerometer signal is used to determine the amplitude (and phase) of the oscillation. If the iterative process reaches a local or global minimum—that is, shifts in either direction result in an amplification of the oscillation—the termination condition is met. Alternatively, a jump shift can be performed to determine whether the minimum is local or global.

[0019] In the preceding examples, it was simplified to show that the phase shift of a fan is being changed. Preferably, however, the proposed procedure is applied to several fans simultaneously. In particular, the fans can be controlled in groups to shift the phase shift of a group together, for example, to ultimately achieve two groups of fans whose phase difference is 180°. The control unit can therefore be designed to shift the phase shift of a group of fans together. A hierarchical approach can be used. If a number of fans in a fan system are divided into subgroups, the procedure can be applied separately for each subgroup. Once an optimal – i.e., low-vibration – alignment or phase shift has been found for a subgroup, this group behaves like a single fan when subsequently controlled synchronously.Thus, in a further step, subgroups can be aligned against each other and an optimal alignment / phase offset can be determined here as well.

[0020] There are several ways to determine the rotational reference point of a given fan. In this context, a rotational reference point is a predefined point in the fan's rotation, such as a point used as the zero point in the fan's control system. For example, fans can be controlled by position sensors, and the control unit can be configured to determine the rotational reference point of a given fan based on a signal from the sensor or based on the fan's internal state derived from the sensor. Alternatively, an external position sensor, such as an external optical, magnetic sensor-based, or electrical sensor, can be used for each fan to determine its position and thus its rotational reference point.In other words, the control unit can be configured to determine the rotation reference point based on a sensor signal from an external (optical, magnetic sensor-based, or electrical) position sensor. Furthermore, the control unit can be configured to determine the rotation reference point of a specific fan based on a sensor signal derived from the back-induced voltages of the fan's electric motor. The control unit can receive these signals or sensor signals from the respective fans or determine them itself, for example, based on the control or power supply signals provided to the respective fan by the control unit. Alternatively, the analysis of the respective signals can be performed by a control circuit within the respective fans.These control circuits can provide the control unit with information about, for example, the respective rotation reference point or the phase shift of the respective fan. Furthermore, it is conceivable that the respective signals, sensor signals, position information, rotation reference points, and / or vibration information are recorded synchronously, for example by the control unit or a separate measuring unit that includes or is coupled to a multiple sensor.

[0021] The vibration caused by the interaction of the fans, and in particular its temporal evolution, can be detected using suitable sensors. One sensor that can be used for this purpose is an accelerometer. Thus, the control unit, or a control circuit of the respective fan, can be designed to determine the temporal evolution of the vibration caused by the interaction of the fans based on a sensor signal from an accelerometer. An accelerometer can be used to determine vibrations by capturing the acceleration data of the vibrating object. The sensor signal provided by the accelerometer contains a digital representation of the acceleration of the sensor, and therefore also of the fan to which the sensor is attached, along one or more axes.The sensor signal can be analyzed in the time domain by the control unit and / or the fan's control circuitry to determine the amplitude, frequency, and other characteristics of the vibration. Additionally, the control unit or the fan's control circuitry can analyze the acceleration data in the frequency domain to exclude vibrations generated by individual fans, but not by their combined effect. If part of the analysis is performed by the control circuitry of the individual fans, the control unit can obtain the relevant information, such as amplitude and frequency, from the respective sensor circuitry. This allows the temporal evolution of the vibration caused by the combined effect of the fans to be determined, and a vibration reference point to be established, which can be used as a reference for determining the phase shift.Finally, the control unit can determine the respective phase offset between the rotation reference point and the oscillation reference point (approximately the point with the maximum oscillation amplitude).

[0022] The presented control unit can, for example, include an interface for communication with other components of the fan system, such as for providing control, current, and / or voltage signals to the respective fans and for receiving sensor signals from the respective sensors, and / or for communicating with the control circuitry of the respective fans. The control unit can also include a processor or microcontroller configured to provide the functionality of the control unit in conjunction with the interface. The processor or microcontroller is connected to the interface, and the control unit communicates with the other components of the fan system via the interface. Furthermore, the interface can be used to communicate with devices outside the fan system.

[0023] In principle, a single control unit is sufficient to control or regulate all fans in the fan system. Alternatively, an approach can be chosen in which each fan comprises its own control unit or control circuit that controls the phase shift of that fan, in conjunction with the control units or control circuits of the other fans. In the first case, the control unit can be part of a fan or, independently of the fans, part of the fan system. In the second case, each fan can comprise a control unit or control circuit, or the respective control units can be assigned to the respective fan separately. The invention thus also relates to a fan comprising the aforementioned control unit, as well as to a fan system with a plurality of fans and the control unit.

[0024] The invention further relates to a corresponding method for controlling fans of a fan system. The method comprises determining, based on sensor signals from the fans, a respective phase shift between an oscillation caused by the interaction of the fans and a rotational reference point of the respective fan. The method includes temporarily adjusting the rotational speed of a fan based on the phase shifts of the fans of the fan system in order to shift the phase shift of the fan.

[0025] It is evident that the method maps the functions provided by the control unit. Accordingly, additional functions and features described in connection with the control unit can also be incorporated into the method. However, the method is not limited to execution by a single control unit. In particular, the method can also be carried out by multiple components that communicate with each other.

[0026] Furthermore, it is evident that the method can be implemented as a computer program. For example, the invention can also relate to a computer program comprising instructions that, when executed by a computer, cause it to carry out the method.

[0027] In some embodiments, a large part of the respective functionality can be provided by a control circuit for each fan. In particular, determining the zero reference (i.e., the rotational reference point) or the position of the imbalance (i.e., the phase shift) on the fan can be performed by the control circuit. In this case, the control unit combines the information from several fans and returns target angles for the imbalances, i.e., the desired phase shifts, to the fans. These fans can then independently achieve the target angle. This creates a hybrid system. Either the control unit, via explicit control of the time-limited rotational speed adjustment, or the fan itself, using a controller, can adjust the relative position of the imbalance vectors.

[0028] One aspect of the invention relates to a fan comprising a motor and a control circuit. The control circuit is configured to receive a control signal regarding a desired phase shift between a rotational reference point of the motor and an oscillation, in particular an oscillation caused by the interaction of several fans. The control circuit can further be configured to temporarily adjust the rotational speed of the motor to achieve the desired phase shift. This approach allows much of the complexity to be shifted from the control unit to the control circuits of the individual fans. This, for example, enables the control unit to be used with a large number of different fans, since the logic for adjusting the phase shift is provided by the fan itself.Additionally, the control circuit can provide the control unit with the relevant parameters for controlling the respective phase shifts. Specifically, the control circuit can be configured to determine the rotation reference point and, optionally, transmit information about the rotation reference point to a control unit for controlling fans of a fan system. Additionally or alternatively, the control circuit can be configured to determine the phase shift between the rotation reference point of the motor and the vibration caused by the interaction of several fans and, optionally, transmit information about the phase shift to the control unit. Both the determination of the rotation reference point and the determination of the phase shift (and the underlying vibration) can be performed using the techniques described with respect to the control unit.

[0029] Within the scope of this disclosure, a fan is an air-conveying device for generating a differential pressure and / or volume flow. A control unit is a unit for executing commands and control steps. A fan system is a combination of one or more fans, including their peripherals. A phase difference describes the difference in phase between two signals of the same frequency. A rotational frequency difference describes the difference in rotational frequency between two fans. An excitation effect corresponds to a superposition of oscillations of the same frequency from different sources (e.g., fans), which, taking coupling behavior into account, result in an overall oscillation. A phase shift is a relative alignment of excitation effects from at least two fans with respect to each other.

[0030] There are now various ways to advantageously develop and further refine the teaching of the present invention. For this purpose, reference is made, on the one hand, to the claims subordinate to claims 1 and 13, and on the other hand, to the following explanation of preferred embodiments of the invention with reference to the drawings. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawings, generally preferred embodiments and further developments of the teaching are also explained. In the drawings, Figures 1a to 1c show a three-stage method for determining a phase shift between a rotational reference point of a fan and an oscillation generated by the interaction of several fans;

[0031] Figures 2 and 3 illustrate the phase shift between the rotation reference point of a fan and the vibration generated by the interaction of several fans;

[0032] Figures 4a to 4c show the determination of a desired phase shift of a fan for a fan system with two fans;

[0033] Fig. 5 shows a schematic diagram of a fan system; and

[0034] Fig. 6 shows a flowchart of a process or procedure for

[0035] Eliminating or reducing vibrations.

[0036] The present invention relates to the targeted synchronization and desynchronization of vibration excitation vectors in multi-fan systems. A control unit is used to determine the vibration excitation vectors, also referred to as phase shift, of the fans in a multi-fan system relative to an oscillation caused by the interaction of the fans. By determining the vibration excitation vector of each individual fan in a multi-fan system, their relative phase positions can be determined. By selectively and minimally changing the rotational frequency of a fan, the vibration excitation vector, i.e., the phase shift, of the respective fan can be shifted, thus changing its relative phase position with the other fans. Once the desired phase position is reached, the fan is operated again at a constant rotational frequency to prevent further phase shifts.The aim of this method is to align the balancing excitation vectors relative to each other in such a way as to minimize the overall vibration load. The following section first explains how the phase shift can be determined as a balancing excitation vector. Fans are frequently operated with permanent magnet synchronous motors (PMSMs). PMSMs, in turn, require information about the rotor's position, or a position within an electrical pole, in order to operate. This information can be provided either via a position sensor as an electrical component or through a mathematical method that infers the position within the pole based on the back-induced voltages. Depending on the number of pole pairs of the electric machine, the challenge lies in deducing the actual position in the mechanical system from the position in the electrical system (also called the observer position).By counting the known number of pole pairs, it is possible to deduce the mechanical position of the rotor from the electrical observer position during PMSM operation. Thus, the control unit can determine the rotor's position, and therefore the rotational reference point of the respective fan, using an internal or external position sensor (such as a photoelectric sensor) as a rotor position reference or based on the aforementioned mathematical method. Alternatively, a Halbach rotor (or other types of magnetic sensors) can be used for position determination. When using a Halbach rotor, for example, a magnetic signature can be introduced, which allows the rotor position to be detected by magnetic sensors. The phase shift is based on an offset between the rotational reference point of the fan, such as the internal zero point of the fan, and a reference point of the oscillation phase.

[0037] The order indicates the multiplier for how many oscillations occur within one rotor rotation. In the case of the 1st order, the oscillation period corresponds to one mechanical revolution. To synchronize the information between the oscillation and rotation patterns, a significant event is defined. In the examples in Figures 1a to 4, the observer angle at maximum oscillation is used as the reference point for the oscillators, and thus as the reference for the phase shift. This requires that both signal references are time-synchronized.

[0038] Figures 1a to 1c show a three-stage procedure for determining the phase shift between a rotational reference point of a fan and an oscillation generated by the interaction of several fans. Figure 1a shows an initial run, assuming that the fan is operated in resonance in single-fan mode, i.e., U = S (U = imbalance, S = mode shape). Here, the position of the imbalance U, i.e., the position of the maximum oscillation displacement of the current oscillation period, relative to a zero reference 0°, is determined, and thus the phase shift, as angle α. Figures 1b and 1c relate to multi-fan operation in resonance. In Figure 1b, the position of the mode shape S relative to the zero reference 0° is determined as angle β, and in Figure 1c, the position of the imbalance U relative to the mode shape S, and thus the phase shift, is determined as angle γ, where γ = β - α.The vibration mode S represents a superimposed vibration mode consisting of the components of the fan itself and its exciting neighbors.

[0039] Figures 2 and 3 illustrate the relationship between rotation and vibration in a further way. They show the phase shift between the rotational reference point of a fan and the vibration generated by the interaction of several fans. In Figures 2 and 3, axis 1 (x-axis) represents time, while the y-axis represents the vibration and rotational motion, respectively. Figures 2 and 3 also show the rotor signal 2: in Figure 2 as a sinusoidal curve, and in Figure 3 as a straight line between 0° and the observer angle at time to + 360°, i.e., a mechanical rotation of the rotor measured from to. Curve 3 represents the vibration signal, intersection point 4 represents the rotor's zero position, and intersection point 5 represents the maximum vibration displacement of the considered vibration period. Figures 2 and 3 also show the phase shift between the zero position 4 and the vibration displacement 5.This phase shift corresponds, with reference to Figs. 1a to 1c, to the angle β. For the first order, the mechanical angle at the maximum oscillation velocity corresponds to the sum of the signal phase (in degrees) and Obs(to), i.e., the observer angle at time to.

[0040] The angles, i.e., the phase shift, can be adjusted by changing the rotational speed as follows. Angle adjustment describes the change in the relative position of two rotors to each other. To adjust the angle, the rotational speed (rotational frequency) of at least one fan is temporarily changed to achieve a change in position / angle. The "rotation time" at a different rotational frequency is calculated using the following formula:

[0041] 60 * <5 tls] = -

[0042] Arpm * 360

[0043] Here, ö (as shown in Fig. 4c) corresponds to the angle to be rotated, i.e., the desired phase shift, and arpm to the speed difference between the two rotors. Experience has shown that a correction can be implemented for more precise adjustment of the desired angle. The positions / angles can be adjusted from either rotor at a higher or lower rotational frequency. In other words, the control unit can increase or decrease the rotational speed (i.e., the rotational speed) of the fan to shift the fan's phase offset.

[0044] In many embodiments, the control unit functions as a controller, and in particular as an angle controller, by regulating one or more rotors to a target angular position. To achieve this, the control unit performs an angular adjustment, i.e., a shift in the phase offset, on one or more rotors. The controller can act in a higher-level manner to combine information from multiple rotors. With regard to the vibration mode, the controller can adjust the unbalance vectors to be opposite to each other (i.e., offset by 180°) for maximum cancellation. The control unit thus sets the phase difference between the phase offsets (or unbalance vectors) of two fans to a predetermined ratio, such as a phase difference of 180° relative to the vibration caused by the interaction of the fans. The common vibration mode of the two fans serves as a "reference coordinate system." The procedure is shown in Figures 4a to 4c.

[0045] Figures 4a to 4c show the adjustment of the phase difference based on the unbalance vectors / angles U1 and U2 of devices (fans) 1, shown in Figure 4a, and 2, shown in Figure 4b. U1 and U2 can be plotted in a diagram as shown in Figures 4a to 4c. Figures 4a to 4c illustrate the determination of a desired phase shift for a fan in a two-fan system. In Figures 4a and 4b, the unbalance vectors U1 and U2, along with their respective relevant angles a, β, and y, are determined analogously to Figures 1a to 1c. Figure 4c shows how, starting from U1 (the phase shift of the first device), the target phase shift U2 of the second device and the angle θ between U2 and U2 are calculated. The U2 target is chosen such that it corresponds to U1 + 180° in the vibration mode coordinate system. In reality, this results in a counter-rotating vibration mode with the unbalances aligned.To achieve the target imbalance U2-target, U2 must be rotated by the angle θ relative to Ui. In other words, the phase shift of the second device is shifted by the angle θ relative to the phase shift of the second device and with respect to the vibration caused by the interaction of the fans.

[0046] As an alternative or supplement to the targeted setting of a specific phase shift, an iterative approach can also be used. In other words, the control unit can shift the fan's phase shift using an iterative process. This serves to gradually improve or optimize the vibration state of a system. Within the iterative process, different alignment states of individual components in the system are tested, the resulting vibration states are measured, and evaluated in comparison to the previous state. Based on this evaluation, a decision is made as to whether the direction of action should be maintained, reversed, or the process terminated.Thus, the control unit can be configured to maintain, reverse, or complete the direction in which the phase shift is shifted, based on a sensor signal from an accelerometer or another sensor signal representing the resulting vibration states, with respect to the iterative process. Ideally, the iterative process works when it can be clearly traced which action causes which change (i.e., one device performs one action). Even groups of devices that behave synchronously (i.e., each performs the same relative action) can be considered a single device. Therefore, the relative vibration optimum of one group can be optimized against the relative vibration optimum of a second group.

[0047] Furthermore, a method using a digital twin or a model-based approach can be applied. In such a method, the control unit can calculate a desired phase shift (i.e., target imbalance vector) of the fan using a digital twin or model of the fan system and shift the fan's phase shift accordingly. The behavior of a fan system with multiple fans based on a defined angular change is represented by a model. The model can be created using various methods, such as data-driven (e.g., using machine learning), mathematical-physical, or a combination thereof. In this approach, possible subsequent states (e.g., all possible subsequent states) are predicted by the model at a current measurement point, and the best possible subsequent state is selected and implemented.Thus, using the digital twin or model of the fan system, a desired state of the fan system can be determined that exhibits lower vibrations than at least one other state of the fan system (preferably than all other states). The desired phase shift of the fan can then be determined based on the desired state of the fan system. The model can also be used for predictions further than one step into the future to reach the global vibration minimum, and thus the desired state.

[0048] The control or regulation of the respective phase shift is performed by the control unit, which is part of a fan system. Fig. 5 shows a schematic diagram of a fan system. The fan system comprises several fans 7, each of which is assigned an accelerometer 8 for determining the oscillation. In some cases, the fans may also each include a control circuit. The control circuits, which may be coupled to the respective accelerometers, are also shown in Fig. 5 as part of the block 8. The fan system further includes the control unit 10 as a control unit, which communicates with the fans 7 and the accelerometers 8 via digital communication 9. The control unit 10 is optionally also connected to application peripherals 11 via analog and / or digital communication 12.The control unit 10 can, for example, perform synchronous position and vibration recording across multiple devices 7 (fans). The control unit 10 can be used as an end device for networked monitoring and implemented as an external, separate unit, as a cloud application, or as a master (assigned to a fan) within a system. The control unit 10 controls the vibration behavior of the fan system by means of angle control to set a desired angular position on the device.

[0049] For this purpose, the control unit 10 can, for example, perform the method shown in Fig. 6. Fig. 6 shows a flowchart of a process or method for eliminating or reducing vibrations. The method includes determining 13 the position of the imbalance, i.e., the phase shift, on all rotors. The method further includes determining 14 the alignment of several imbalance positions relative to each other. The method further includes determining 15 the target alignment of several imbalance positions relative to each other. Finally, the method includes aligning 16 the position of the rotors relative to each other. The respective components of the method have already been explained in connection with Figs. 1a to 4c.

[0050] The present invention was evaluated in test systems with four fans. The imbalance vector was determined by means of a mark on the impeller and the 3M method for operational balancing. With digital control of the fans, the relative rotor position between individual units could be achieved by a brief, minimal difference in rotational speed. This could be verified by a video recording of the marks on the impeller.

[0051] It has been proven that the rotors, and therefore the imbalance vectors, of different fans can change their relative positions. The speed at which the rotors' orientation changes relative to each other can be adjusted via the speed difference between the two fans. The following formula can be used for this purpose:

[0052] 60 * <5 tls] = -

[0053] Arpm * 360

[0054] The evaluation demonstrated that the relative position of the rotors, and thus the unbalance vectors, has a direct and significant influence on the resulting vibrations. Vibration optimizations were observed with synchronized unbalance vectors, while vibration anomalies were found with desynchronized unbalance vectors. With desynchronized unbalance vectors, the vibration values ​​measured by the accelerometers were approximately five times higher than with synchronized unbalance vectors. The present invention provides a method for achieving overall vibration optimization in applications with multiple fans by selectively aligning the unbalance vectors of the individual fans. The present invention differs from a resonance controller (active vibration management) in that the operating point, or...The desired rotational frequency of the fans can be maintained. Furthermore, no operating ranges are temporarily or permanently blocked, thus enabling continued use of the fans' entire operating range. The present invention therefore represents a further development and improvement of the resonance controller and provides a method for balancing with an internal vibration sensor. It is based on the analysis of vibrations in multi-fan systems. It enables the reduction of vibration amplitudes of vibration modes in which multi-fan systems can oscillate, as well as high vibrations in multi-fan systems. The invention also provides a systematic approach to vibration reduction without changing the operating point of the system.

[0055] Regarding further advantageous embodiments of the device according to the invention, reference is made to the general part of the description and to the attached claims in order to avoid repetition.

[0056] Finally, it should be expressly pointed out that the exemplary embodiments of the device according to the invention described above serve only to discuss the claimed teaching, but do not limit it to these exemplary embodiments.

[0057] Reference symbol list Timeline Rotor signal Vibration signal Zero position of the rotor Maximum vibration displacement Phase shift fan Accelerometer, control circuit Digital communication control unit Application Peripherals Analog / digital communication Determining the location of the imbalance Determining the orientation of multiple unbalanced positions relative to each other Determining a target alignment of several unbalanced positions relative to each other Aligning the position of the motors relative to each other

Claims

Claims 1. Control unit for controlling fans of a fan system, designed to determine, based on sensor signals from the fans, a respective phase shift between an oscillation caused by an interaction of the fans and a rotation reference point of the respective fan, and to temporarily adjust a rotation speed of a fan based on the phase shifts of the fans of the fan system in order to shift the phase shift of the fan.

2. Control device according to claim 1, characterized in that the control device is designed to shift the phase shift of the fan by temporarily adjusting the rotational speed relative to the phase shift of a second fan such that the phase shift of the fan to the phase shift of the second fan has a predetermined ratio.

3. Control unit according to claim 2, characterized in that the predetermined ratio corresponds to a phase difference of 180° with respect to the vibration caused by the interaction of the fans.

4. Control unit according to one of claims 1 to 3, characterized in that the control unit is configured to specify the rotational speed of the fan in order to adjust the rotational speed of the fan temporarily, or characterized in that the control unit is configured to specify a desired phase shift for the fan in order to trigger a temporary adjustment of the rotational speed by the fan.

5. Control unit according to one of claims 1 to 4, characterized in that the control unit is designed to calculate a desired phase shift of the fan using a digital twin or model of the fan system and to shift the phase shift of the fan according to the desired phase shift.

6. Control unit according to claim 5, characterized in that the control unit is configured to determine, by means of the digital twin or model of the fan system, a desired state of the fan system which, viewed as a whole, exhibits lower vibrations than at least one other state of the fan system, and to determine the desired phase shift of the fan based on the desired state of the fan system.

7. Control unit according to one of claims 1 to 6, characterized in that the control unit is designed to shift the phase shift of the fan by means of an iterative method.

8. Control unit according to claim 7, characterized in that the control unit is configured to maintain, reverse the direction in which the phase shift is shifted, or complete the iterative process based on a sensor signal from an acceleration sensor with respect to the iterative process.

9. Control unit according to one of claims 1 to 8, characterized in that the control unit is designed to shift the phase shift of a group of fans together.

10. Control unit according to one of claims 1 to 9, characterized in that the control unit is configured to determine the rotation reference point of a respective fan based on a sensor signal of a position sensor of the fan, based on a sensor signal of an external position sensor or based on a sensor signal based on back-induced voltages of an electric motor of the fan.

11. Control unit according to one of claims 1 to 10, characterized in that the control unit is designed to determine a temporal profile of the oscillation caused by the interaction of the fans based on a sensor signal from an accelerometer, and to determine the respective phase shift based on the temporal profile of the oscillation caused by the interaction of the fans.

12. Fan comprising the control unit according to any one of claims 1 to 11.

13. Fan system comprising a plurality of fans and the control unit according to any one of claims 1 to 11.

14. Method for controlling fans of a fan system, comprising determining, based on sensor signals of the fans, a respective phase shift between an oscillation caused by an interaction of the fans and a rotation reference point of the respective fan, and temporarily adjusting a rotation speed of a fan based on the phase shifts of the fans of the fan system in order to shift the phase shift of the fan.

15. Fan comprising a motor and a control circuit, wherein the control circuit is configured to obtain a control signal about a desired phase shift between a rotation reference point of the motor and an oscillation, in particular an oscillation caused by an interaction of several fans, and to adjust a rotation speed of the motor in the meantime to achieve the desired phase shift.

16. Fan according to claim 15, characterized in that the control circuit is configured to determine the rotation reference point and to transmit information about the rotation reference point to a control unit for controlling fans of a fan system, and / or characterized in that the control circuit is configured to determine the phase shift between the rotation reference point of the motor and the vibration caused by an interaction of several fans and to transmit information about the phase shift to the control unit.

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