DE102023131659A1 - Control of a rotary separator - Google Patents

Abstract

In a rotary separator for separating particles from a gas stream,
with a rotary-driven separator,
and with a BLDC motor for electrically rotating the separator,
and with control electronics that influence the speed of the BLDC motor,
proposes the invention,
that the motor is designed as a sensorless BLDC motor and
is therefore free of a sensor that detects the rotation angle position of the rotor,
and that the control electronics are designed to automatically switch between a control behavior and a regulation behavior,
such that
that a phase current with a fixed frequency is supplied to the BLDC motor in a controlled mode for starting,
and that after reaching a certain speed the BLDC motor operates in a controlled mode.

Description

The invention relates to a rotary separator and a method for controlling a rotary separator.

From the DE 10 2022 105 879 A1 A rotary separator, also known as a disc separator, is a generic type of separator used to separate liquid particles from hot gas. The separator rotor of the rotary separator has a plurality of separating discs. This disc separator uses a brushless direct current (BLDC) motor to drive the discs.

Other types of rotary separators or centrifuges, which are also electrically driven, are known from practice.

For the practical application of separators in commercial vehicles, it is known to use BLDC motors that feature a sensor for detecting the position of the BLDC motor's rotor. These sensors—e.g., Hall sensors—enable reliable motor start-up and high dynamic performance because the target state can always be compared with the actual state of the motor. In particular, the rotating magnetic field is optimally adjusted to the current position of the rotor, namely its rotational angle, and the motor can thus always be optimally controlled.

It is also known that sensorless BLDC motors are used in practice for separators in cars. These motors offer advantages over BLDC motors with sensors in terms of cost and, due to the smaller number of components, also in terms of robustness. However, firstly, not every start-up attempt with a sensorless BLDC motor may be successful, and secondly, the dynamics are limited because in both cases the circulating magnetic field is not – or at best only randomly – optimally matched to the current position of the rotor.

The invention is based on the object of improving a generic rotary separator so that it is both cost-effective and robust, while also exhibiting reliable start-up behavior and high dynamics. Furthermore, the invention is based on the object of providing a method for controlling an electrically driven rotary separator that enables reliable start-up behavior and high dynamics of the rotary separator when using a sensorless BLDC motor.

This object is achieved by a rotary separator according to claim 1 and by a method according to claim 10. Advantageous embodiments are described in the subclaims.

In other words, the invention proposes using a sensorless BLDC motor as the drive for a centrifuge, particularly in the form of a disc separator, so that the advantages of dispensing with a sensor come into play. To avoid the disadvantages of a sensorless BLDC motor as far as possible, the invention controls the BLDC motor using control electronics that operate as a controller when the BLDC motor starts up and later, once the BLDC motor has reached a certain speed, automatically switches to act as a closed-loop control. In control mode, a phase current with a fixed, predetermined frequency is supplied to the BLDC motor.

The invention is based on the assumption that such a phase current will most likely be sufficiently well-matched to the motor position, that the motor will start, and that the motor speed can then be increased even without being able to determine the rotor speed. After reaching a certain speed, the motor can then be operated in a controlled mode.

Even without a sensor, the behavior of the motor can be determined with sufficient accuracy based on electrical parameters of the BLDC motor, such as current consumption, inductances or a counter voltage, so that the rotor position can be determined with good accuracy and the parameters of the supplied phase current can be changed in a closed-loop control manner, and so that a high dynamic response can be achieved in the operation of the motor and thus also of a rotationally driven separation element of the centrifuge, e.g. the multiple separator plates of a plate separator.

Since there is a risk of an unsuccessful start-up attempt when starting the motor, the control electronics are advantageously designed to automatically detect such an unsuccessful start-up attempt, for example, based on the electrical parameters. In one embodiment, the control electronics are configured to decelerate the rotary-driven separator element after an unsuccessful start-up attempt, thus enabling a new start-up attempt to be initiated as quickly as possible. Deceleration is achieved with as little wear as possible, not through friction, but rather through a short circuit in the windings of the BLDC motor or through a magnetic field counteracting the rotation.

As an alternative to such active motor braking, in another embodiment, the control electronics are also configured to detect an unsuccessful motor start-up attempt. However, this alternative assumes that the rotor of the BLDC motor is coasting down and its speed is decreasing. Therefore, after an unsuccessful start-up attempt has been detected, the control electronics automatically reduce the power supply to the BLDC motor for a specific time interval, e.g., by reducing the power supply to zero during this time interval. After the time interval has elapsed, the control electronics automatically initiate a new start-up attempt for the BLDC motor.

In both alternative embodiments, in which the control electronics automatically initiate a new start-up attempt of the BLDC motor after a detected unsuccessful start-up attempt, the new start-up attempt can, for example, already be initiated when the BLDC motor's rotor is still running at a low speed. In one embodiment, however, the control electronics are configured such that they only initiate the new start-up attempt after the BLDC motor has come to a standstill, e.g., by selecting a sufficiently long time interval in the second alternative mentioned.

The renewed start-up attempt can be performed with the same parameters of the phase current supplied to the motor as during the previous start-up attempt. In one embodiment, however, the control electronics are configured to initially supply the BLDC motor with a phase current with modified parameters during a new start-up attempt, namely in the controlled mode. For example, the evaluation circuit can be configured to initially perform not just one, but several start-up attempts, always with the same parameters, and after a predetermined number of unsuccessful start-up attempts, to change the parameters of the phase current supplied to the motor in order to increase the probability of a successful start-up of the BLDC motor.

In order to record the number of unsuccessful start-up attempts, in one embodiment an error entry is automatically written to an electronic error log after the first unsuccessful start-up attempt. If the start-up attempt is again unsuccessful, the entry in the error log is automatically changed so that it represents the number of unsuccessful start-up attempts. For example, an additional entry can be written to the error log so that the number of entries corresponds to the number of unsuccessful start-up attempts. Or the value of the entry can be changed, for example from "1" to "2" or similar, so that although there is only a single entry in the error log, the value of this entry indicates the number of unsuccessful start-up attempts. Before a new start-up attempt is made, the error log is automatically read out so that, depending on the number of unsuccessful start-up attempts determined from this, the next start-up attempt can then be carried out automatically with changed parameters for the phase current supplied to the motor. After a successful start-up attempt, the error log can preferably be automatically reset. Alternatively, the value of the error memory can be assigned to another date so that the respective number of failed starts is retained in a later error log.

The control electronics can be designed as an integral component of the rotary separator; alternatively and preferably, it can be implemented in an external control unit, for example, in vehicles in one of the existing control units, e.g., the engine control unit. This not only advantageously reduces the manufacturing costs of the rotary separator, but also reduces the total number of required components in the vehicle, since the control unit is not only dedicated to the rotary separator but also controls other functions.

In one embodiment, the rotary separator is designed as a disc separator, with a separation element having several discs arranged on a common axis of rotation.

• 1 in Art eines Ablaufdiagramms ein Verfahren zur Ansteuerung eines mittels eines sensorlosen BLDC-Motors angetriebenen Rotationsabscheiders.

The invention is explained in more detail below using a purely schematic representation.

• 1 in the form of a flow chart, a method for controlling a rotary separator driven by a sensorless BLDC motor.

1 Figure 1 shows the first step, which is the starting of the rotary separator. This first step can, for example, be a start signal transmitted to the control electronics of the rotary separator, e.g., when a vehicle's internal combustion engine is started.

Step 2 involves accelerating the rotor either from a low speed or from standstill to a higher speed. This occurs in a controlled mode, also known as "open-loop mode," in which a phase current with fixed parameters is supplied to the BLDC motor, which is intended to rotate the separator element of the rotary separator.

Variations of step 2 consist of either repeating step 2 with the same phase current parameters when a new start-up attempt is initiated after an unsuccessful start-up attempt, or automatically varying the phase current during a subsequent start-up attempt, namely supplying the BLDC motor with modified parameters. Such a variation can, for example, occur automatically after the first unsuccessful start-up attempt, but possibly also only after a predetermined number of unsuccessful start-up attempts, e.g., two or three.

Step 3 of the process involves automatically checking whether the rotor start-up attempt was successful. This can be determined based on the electrical parameters automatically monitored by the control electronics. If the query result is "yes," the control electronics automatically switches from open-loop mode to closed-loop mode for operation of the rotary separator, which is shown as step 4 in the drawing.

However, if the query result is “No”, in the illustrated embodiment of the method, a message about the termination of the start-up attempt is automatically transmitted to a control unit (“ECU” = electronic control unit) of the vehicle according to step 5.

In addition, according to a step 6, the rotor of the BLDC motor is braked, which can be carried out either as an active braking process by a winding short circuit or as a passive braking process by waiting for a predetermined time interval during which the rotor gradually "runs down", i.e. reduces its speed due to a lack of energy supply.

Step 7 consists of waiting for the so-called pre-positioning of the BLDC motor's rotor. This time interval can be fixed and always constant. Alternatively, the time interval can be determined dynamically, for example, in the case of passive braking, depending on other measured parameters that influence the rotor's rotational resistance, such as temperature.

Step 8 consists of a second automatic query, namely checking whether the conditions for a new rotor start attempt are met. This condition can be the expiration of the aforementioned time interval or an automatically detected rotational movement of the rotor, which can be detected, for example, using electrical parameters. If the answer to the query is "no," steps 6 and 7 are repeated, followed by the query according to step 8.

However, if the answer to the second query is "yes," an entry is automatically written to an error log according to step 9. This creates an error counter so that the entry in the error log indicates the number of unsuccessful startup attempts. For example, a numerical value can be incremented by "1" starting from "0."

A subsequent step 10 consists of a third automatic query, namely whether the value in the error log—and thus the number of unsuccessful start-up attempts—has reached or exceeded a predetermined limit. If the answer to this query is "no," the process is repeated from the beginning, beginning with step 1. Depending on the number of unsuccessful start-up attempts, the parameters of the phase current supplied to the motor when the separator starts in controlled mode can be varied, as explained above for step 2.

However, if the answer to the query is "yes," meaning the number of unsuccessful start-up attempts has reached or exceeded a predetermined limit, a fourth automatic query is performed in step 11 to determine whether the boundary conditions for a start-up attempt are OK or not. These boundary conditions can, for example, be a specific temperature window or at least a minimum temperature, or values for a minimum electrical voltage and/or a maximum electrical voltage as the supply voltage.

As explained above, the query in step 11 only occurs if, according to the query in step 10, the error counter has reached or exceeded a certain limit. If the query in step 11 determines that the boundary conditions for a start-up attempt are OK, then, in view of the large number of unsuccessful start-up attempts, an error message is automatically transmitted to the vehicle's control unit mentioned above in step 12, for example by writing an error entry to a corresponding error memory in the control unit. This error entry can, for example, lead to an automatic functional restriction of the vehicle, e.g., with regard to the maximum achievable vehicle speed or the maximum achievable engine speed of an internal combustion engine, or the error entry can lead to an automatically triggered alarm, e.g., a request to visit a workshop.

In an alternative embodiment, the query described as step 11 can also be performed before each time the error memory is increased, for example before step 9. In this case, the increase in the error memory can also be made dependent on the query result, i.e. the entry in the error memory is only increased if the boundary conditions are OK. In a further alternative, the query described as step 11 can already take place before the separator is started - i.e. before step 1. The query described as step 11 can also be carried out at several points in the process. As an alternative to the exemplary embodiment described, a separate memory can also be provided for the results of the queries. Regardless of the point in the process at which the query described as step 11 is carried out, the entry in the error memory of the control unit in step 12 is preferably triggered when a certain number of false starts have occurred under correct boundary conditions.

If the minimum temperature is not reached or the temperature is outside the specified temperature window, and if the supply voltage is below the minimum voltage or above the maximum voltage, the query in step 11 is answered with "No" and the system automatically waits until the boundary conditions are OK according to step 14. Then, in step 15, the error entry in the error memory is automatically reset, i.e. the corresponding error counter is set to "0", and a new start-up attempt is automatically started, beginning with step 1. The error counter can be saved in a data record before being reset, or alternatively, the error counter can be omitted and the current value can be assigned to another date, for example a time value.

Reference symbols:

1

Step Start

2

Step Pre-positioning

3

Step acceleration

4

Query successful

5

Step switching

6

Step Message Cancel

7

Step Deceleration

8

Query conditions

9

Step error memory

10

Query error memory

11

Query boundary conditions

12

Step Error Message

14

Step Wait

15

Step Reset error message

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10 2022 105 879 A1 [0002]

Claims (18)

Rotary separator for separating particles from a gas stream, with a rotationally driven separation element, and with a BLDC motor for electrically rotating the separation element, and with control electronics influencing the speed of the BLDC motor, characterized in that the motor is designed as a sensorless BLDC motor and is therefore free of a sensor detecting the rotational angle position of the rotor, and in that the control electronics are set up to automatically switch between a control behavior and a control behavior in such a way that a phase current with a fixed predetermined frequency is supplied to the BLDC motor in a controlled mode for starting up, and that after a certain speed has been reached the BLDC motor is operated in a controlled mode. Rotary separator according to Claim 1 , characterized in that the control electronics are designed to detect electrical parameters of the BLDC motor and, based on these, to automatically switch from the controlled to the regulated mode. Rotary separator according to Claim 1 or 2 , characterized in that the control electronics are designed to detect an unsuccessful start-up attempt of the BLDC motor, to brake the separator element by short-circuiting the windings after an unsuccessful start-up attempt, and to start a new start-up attempt of the BLDC motor. Rotary separator according to Claim 1 or 2 , characterized in that the control electronics are designed to detect an unsuccessful start-up attempt of the BLDC motor, to reduce the energy supply to the BLDC motor for a certain time interval after an unsuccessful start-up attempt, and to start a new start-up attempt of the BLDC motor after the time interval has elapsed. Rotary separator according to Claim 4 , characterized in that the control electronics are designed to reduce the energy supply to the BLDC motor to zero in the event of an unsuccessful start-up attempt of the BLDC motor during the specific time interval. Rotary separator according to one of the Claims 3 until 5 , characterized in that the control electronics are designed to start a new start-up attempt after the BLDC motor has come to a standstill. Rotary separator according to one of the Claims 3 until 6 , characterized in that the control electronics are designed to supply a phase current with changed parameters to the BLDC motor in the controlled mode during a new start-up attempt. Rotary separator according to one of the preceding claims, characterized in that the control electronics are implemented as part of a higher-level control unit which is designed as a control device and can be mounted at a distance from the rotary separator and is also designed to control other functions beyond the rotary separator. Rotary separator according to one of the preceding claims, characterized in that the rotary separator is designed as a disc separator, wherein the separating element has a plurality of discs arranged on a common axis of rotation. A method for controlling a rotary separator electrically driven by a sensorless BLDC motor, comprising the following process steps: • To start up the BLDC motor, it is operated in a controlled mode by supplying it with a phase current with a fixed frequency. • Once the BLDC motor reaches a certain speed, it is operated in a regulated mode. • Electrical parameters of the BLDC motor are recorded and, based on these parameters, the motor automatically switches from the controlled to the regulated mode. Procedure according to Claim 10 , characterized in that an unsuccessful start-up attempt of the BLDC motor is automatically detected on the basis of the electrical parameters, and that after an unsuccessful start-up attempt the separator element is automatically braked, and that a new start-up attempt of the BLDC motor is then automatically started. Procedure according to Claim 11 , characterized in that the separating element is a short circuit in the windings of the BLDC motor is braked. Procedure according to Claim 10 , characterized in that an unsuccessful start-up attempt of the BLDC motor is automatically detected on the basis of the electrical parameters, and that after an unsuccessful start-up attempt for a certain time interval the energy supply to the BLDC motor is automatically reduced, and after the time interval has elapsed a new start-up attempt of the BLDC motor is automatically started. Procedure according to Claim 13 , characterized in that during the specified time interval the energy supply to the BLDC motor is reduced to zero. Method according to one of the Claims 11 until 14 , characterized in that a new start-up attempt is started after the BLDC motor has come to a standstill. Method according to one of the Claims 11 until 15 , characterized in that during a new start-up attempt, a phase current with changed parameters is supplied to the BLDC motor in the controlled mode. Method according to one of the Claims 11 until 16 , characterized in that in the event of a first unsuccessful start-up attempt, an error entry is automatically written into an electronic error memory, and in the event of a further unsuccessful start-up attempt, either an additional error entry is automatically written into the error memory or a value of the error entry is changed in such a way that the number of unsuccessful start-up attempts can be automatically read out from the error memory, and in the event of a successful start-up attempt, the error memory is automatically reset. Procedure according to Claim 17 , characterized in that when a certain number of unsuccessful start-up attempts is reached, the phase current supplied to the BLDC motor is automatically varied during the next start-up attempt.

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