Method, carrier and device for fast closed-loop control of average value of controlled variables

Abstract

The invention relates to a method for closed-loop control of a controlled variable to a given reference variable, wherein the actual value and / or the measured actual value of the controlled variable is subject to fluctuation effects with a specific periodicity, the controlled variable being readjusted only if a control difference exists between the reference variable and an average value of the actual value of the controlled variable averaged over a periodic time period, wherein the measured values ​​M1 to M n The specific measurement time points t1 to t2 in a specific controller cycle within each periodic period duration are n It is determined that these measured values ​​are related to or correspond to the corresponding actual values ​​of the controlled variable and / or are suitable for determining therefrom a control difference between the reference variable and the average value of the actual value of the controlled variable. According to the invention, at each specific measuring time t1 to t n The invention also relates to a corresponding carrier and a device.

Description

Technical Field

[0001] The invention relates to a method for closed-loop control of a controlled variable to a given reference variable according to the preamble of independent claim 1 . Background Art

[0002] In the case of methods of the general type, the actual value and / or the measured actual value of the controlled variable is subject to fluctuation effects with a certain periodicity. This is the case, for example, when the speed of a drive motor for driving an eccentric drive or a diaphragm pump or a piston pump or a unidirectional lifting and / or conveying system or a mechanism for applying a load in only one direction of movement is to be controlled in a closed loop. This is also the case if the rotary encoder used to determine the rotor position and the speed of the drive motor exhibits, for example, pitch errors or inaccuracies, which the measured actual value of the controlled variable is periodically affected by and deviates from the actual value of the controlled variable. Such inaccuracies may occur, for example, when the encoder is loaded.

[0003] Furthermore, in the case of a method of the general type, the controlled variable is only readjusted if there is a control difference between the reference variable and the average value of the actual value of the controlled variable averaged over a periodic time period. For this purpose, the measured values ​​M1 to M n Each periodic time period lasts from the specific measurement time point t1 to t n The measured values ​​are determined to be correlated with or correspond to the respective actual values ​​of the controlled variable and / or adapted to thereby determine a control difference between the reference variable and an average value of the actual values ​​of the controlled variable. The number n of measurement time points within the periodic time period corresponds to the number n of associated measured values.

[0004] The prior art discloses fast classical controllers that attempt to compensate for fluctuations in the controlled variable during the load period. Considering a speed controller, for example, this has the following effect: during phases where the load absorbs little energy or even returns energy to the drive, closed-loop control will result in unnecessary deceleration, while during phases where more energy is needed to manage the load, additional energy must be supplied to compensate for the immediately preceding deceleration phase. In this case, the system fails to benefit from the load's high moment of inertia. However, very soft or slow closed-loop control, or drives with open-loop control rather than closed-loop control, allow for larger speed variations during the load period and thus also benefit from the load's high moment of inertia. However, soft closed-loop control may be too slow to respond to changes in the reference variable or the mean controlled variable. Drives with open-loop control rather than closed-loop control may not even react to changes in the mean controlled variable or changes in the load.

[0005] Methods of this general type are known, for example, from EP 2498395 A2. This document describes a closed-loop control method for the speed of an electric motor, in which the average value of the actual speed is used to establish a lookup table with pulse width modulation values ​​adapted to the expected load on the motor for the next revolution. The method known from this document is relatively complex and requires a high level of computing power. Furthermore, the response time of the closed-loop control can be improved. Summary of the Invention

[0006] The object of the present invention is therefore to provide a method of a generic type which allows a fast reaction to changes in the mean value of a controlled variable and, in doing so, avoids the above-mentioned problems of conventional fast controllers and requires little computing power.

[0007] This object is achieved by the features of independent claim 1. According to these features, in the case of a method according to the preamble of independent claim 1, when at each specific measuring time t1 to t n There are creative solutions when it comes to determining control differences and, when necessary, readjusting the controlled variables.

[0008] The actual sampling rate of the sensor for determining the actual value of the controlled variable or the corresponding dependent variable is preferably equal to the controller cycle, but can also deviate from the controller cycle, so that the actual measurement time point can deviate from the measurement time point that lies within the control cycle and the measured value can therefore only have approximate validity.

[0009] Advantageous embodiments of the method according to the invention are subject matter of the dependent claims.

[0010] According to a particularly preferred embodiment of the method according to the present invention, a difference is calculated between the measured value at the current measurement time and the corresponding measured value of the previous cycle recorded at the previous n measurement time points to determine the control difference. The control difference is derived from this difference. If the duration of the period of the cycle does not change but remains constant, the current measured value is compared with the measured value recorded one period earlier. This embodiment does not require significant computing power. The control difference can be determined quickly with the aid of inexpensive hardware. If the difference between the measured value at the current measurement time point and the corresponding measured values ​​recorded at the previous n measurement time points is zero, it can be assumed based on the simplified determination of the control difference that no control difference exists.

[0011] According to an alternative embodiment of the method according to the invention, it is also possible to calculate the actual mean value of the controlled variable from the measured value at the current measurement time and the n-1 measured values ​​at the previous n-1 measurement time points to determine the control difference. To calculate the control difference, the difference between the reference variable and this mean value can then be calculated. This embodiment requires slightly more computing power.

[0012] According to another preferred embodiment of the method according to the present invention, the controller cycle is selected such that at least six measurement time points lie within the duration of the cycle period. This requirement preferably also applies to the actual sampling rate of the sensor used to determine the actual value of the controlled variable or the corresponding dependent variable. This embodiment ensures that the measured values ​​allow a meaningful and correct control difference to be determined. According to a particularly preferred embodiment, the controller cycle is selected such that at least 12 measurement time points lie within the duration of the cycle period. According to another preferred embodiment, the sampling time of the controller cycle is at most 1 ms.

[0013] According to another preferred embodiment of the method according to the invention, the duration of the periodic intervals is continuously determined by evaluating the measured values. The determination of the periodic interval duration is further preferably performed by the same controller unit that is also used to control the controlled variable. On the one hand, this increases reliability, and on the other hand, it keeps the cost of the necessary hardware low. According to alternative embodiments of the method according to the invention, a periodic fixed cycle can be predetermined for the controller unit, or an external source that transmits the interval duration to the controller unit can be used.

[0014] According to a particularly preferred embodiment of the method according to the invention, the actual value of the controlled variable is influenced by a fluctuating load with a specific load period.

[0015] According to another particularly preferred embodiment of the method according to the invention, the measured actual value of the controlled variable is influenced by periodic measurement errors within the measurement period, in particular pitch errors or inaccuracies in the gauge of the rotary encoder. Preferably, the rotary encoder is a magnetic, optical, inductive or capacitive rotary encoder.

[0016] According to another particularly preferred embodiment, the method relates to a method for closed-loop control of a drive motor, the controlled variable being the speed of the drive motor.

[0017] The invention further provides a machine-readable data carrier having a program, wherein the data carrier is associated with a motor control unit for driving an electric motor, and wherein the program comprises a sequence of instructions which, when executed by a processor, results in the execution of a method according to the invention, in particular according to one of the above-described embodiments.

[0018] In addition, the present invention also provides a motor control unit for driving a motor, wherein the motor control unit is configured and adapted to execute the method according to the present invention, in particular the method according to one of the above embodiments.

[0019] Furthermore, the present invention also provides a drive motor comprising a rotor and a motor control unit according to the present invention. According to a particularly preferred embodiment, the drive motor is an electric motor.

[0020] According to a preferred embodiment of the present invention, the drive motor includes at least one sensor for detecting the position, orientation, or speed of the rotor, wherein the motor control unit is configured to calculate the control difference based on the measured values ​​provided by the sensor. In this respect, it is particularly advantageous when the drive motor is an electric motor and the sensor is a Hall effect sensor, whose signal is also used for commutating the electric motor. This embodiment ensures reasonable production costs.

[0021] According to another embodiment, the motor control unit is configured to calculate the control difference by an algorithm for determining the position, orientation, or speed of the rotor, based on the values ​​generated by the parameters inductance and electromagnetic force, without the use of sensors. The algorithm in question is a so-called sensorless control algorithm of the type described in patent applications EP 2 924 870 A1 and EP 3 288 175 A1. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The embodiments of the present invention will be described in detail below based on the accompanying drawings.

[0023] Figure 1 A schematic flow chart showing a method for closed-loop control of the speed of an electric motor according to the present invention, and

[0024] Figure 2 The associated speed curve of the electric motor is shown.

[0025] In the following description, identical components will be identified with identical reference numerals. If a figure includes a reference numeral which is not dealt with in detail in the description associated with that figure, reference is made to the preceding or following description of the figure. DETAILED DESCRIPTION

[0026] Figure 1 A schematic flow chart of a method according to the invention for closed-loop speed control of an electric motor 1 connected to a fluctuating load with a specific load period (e.g. a diaphragm pump or piston pump) is shown. Alternatively, however, the flow chart shown here can also be applied to rotary encoders whose gauges exhibit pitch errors or inaccuracies within a specific measurement period. Figure 2, which shows the actual speed curve of the motor over time t, showing two complete consecutive time periods T1 and T2. It can be easily seen that the actual speed reaches a maximum value at the beginning and end of each period. These are therefore periodically repeating load characteristics, which lead to corresponding periodically repeating speed characteristics of the motor. In the case shown, the time period duration is unchanged. The time period duration T2 therefore corresponds to the time period duration T1. The method works optimally if the load variation is related to the rotation angle of the drive and exhibits a single or multi-periodic nature to the speed of the motor. However, at this point, reference is made to the fact that the method according to the invention will also be suitable for use if the position and / or time period duration of the load variation vary slowly relative to the controller cycle and / or sampling rate. Similarly, the load variation characteristics may also vary slowly relative to the controller cycle and / or sampling rate.

[0027] For commutation purposes, Figure 1 The electric motor 1, shown only schematically in FIG, has at least one Hall sensor, whose sensor signal can be used to determine the rotor position or rotor speed and, in the case of the method according to the invention, to determine the actual speed average value averaged over the period duration T of the load period. To this end, the sensor signal is fed to a speed determination unit 2, which also takes into account the period duration T for determining the average speed. In some systems, the motor control unit can be operated with a fixed, predetermined period duration in certain cases. However, it is usually necessary to continuously determine the period duration and transmit it to the speed determination unit 2. This can be done by the motor control unit itself, in particular by suitable evaluation of the sensor signals, or by an external evaluation unit.

[0028] exist Figure 2 In the case of the embodiment shown in FIG. 1 , the controller period and / or sampling rate has been chosen so that there are a total of 12 measurements (M1 to M2 over a period of time T1). 12 ; In the period T2, it is from M1' to M 12 ') For each load period, there are 12 specific time points (t1 to t2 in the period T1) 12 ; In the time period T2, from t1' to t 12 At each specific time point, the average value of the motor speed can be calculated based on the corresponding current measurement value and the eleven measurement values ​​measured immediately before. Figure 1 As shown in , this average value can then be compared with the corresponding reference variable w corresponding to the target speed. The corresponding resulting control difference is fed to the actual controller 3 of the motor control unit. This controller in turn transmits the corresponding default value to the inverter 4, which provides voltage to the individual phases of the electric motor 1.

[0029] Instead of calculating the average value of the motor speed at each measurement time point based on the current measurement value and the eleven measurement values ​​recorded immediately before, as Figure 2 As shown in , the control difference can also be determined alternatively by calculating the difference between the current measured value and the measured value of the previous load period recorded at the previous 12 measuring time points. In this regard, Figure 2 If the difference between the measured value at the current measurement time and the corresponding measured values ​​at the 12 previously recorded measurement time points is equal to zero, it can be assumed based on the simplified determination of the control difference that no control difference exists.

[0030] Reference Signs List

[0031] 1. Drive motor / electric motor

[0032] 2 Speed ​​determination unit

[0033] 3 Controller

[0034] 4 Inverter

[0035] T, T1, T2 Period duration of the period or load period and / or measurement period

[0036] t1 to t n The measurement time points during the first period

[0037] t1' to t n ' The measurement time point during the second period

[0038] M1 to M n Measured values ​​during the first period

[0039] M1' to M n 'Measured value during the second period

[0040] n number of measurement points / measurement values

[0041] w Reference variable (target value of speed)

Claims

1. A method for closed-loop control of a controlled variable to a given reference variable (w), wherein the actual value and / or the measured value of the controlled variable is influenced by fluctuation effects with a specific periodicity, wherein the controlled variable is readjusted only if a control difference exists between the reference variable (w) and the average value of the actual value of the controlled variable averaged over the periodic time duration (T, T1, T2), The measured values ​​(M1 to M n 、M1' to M n ') A specific measurement time point (t1 to t2) in a specific controller cycle within the duration of each periodic period n , t1' to t n '), which measured values ​​are related to or correspond to respective actual values ​​of the controlled variable and / or are adapted to determine therefrom a control difference between the reference variable (w) and an average value of the actual values ​​of the controlled variable, It is characterized in that At each specific measurement time point (t1 to t n , t1' to t n ') to determine the control difference and readjust the controlled variable; The method is a closed-loop control method for a drive motor (1), and the controlled variable is the speed of the drive motor.

2. The method according to claim 1, wherein To determine the control difference, a difference value is calculated between the measured value at the current measuring time and the corresponding measured value of the preceding period recorded at the previous n measuring times, from which the control difference is derived.

3. The method according to claim 1, wherein: To determine the control difference, the actual mean value of the controlled variable is calculated from the measured value at the current measurement time point and the n-1 measured values ​​at the previous n-1 measurement time points.

4. The method according to claim 1, wherein The controller cycle is selected so that at least six measurement time points (M1 to M2) n 、M1' to M n ') is within the periodic duration (T, T1, T2).

5. The method according to claim 4, wherein The controller cycle is selected so that at least twelve measurement time points (M1 to M2) n 、M1' to M n ') is within the periodic duration (T, T1, T2).

6. The method according to claim 1, wherein The periodic duration (T, T1, T2) of the periodicity is determined by evaluating the measured values ​​(M1 to M2). n 、M1' to M n ') to be continuously determined.

7. The method according to claim 1, wherein The actual value of the controlled variable is affected by a fluctuating load having a specific load period.

8. The method according to claim 1, wherein The measured value of the controlled variable is affected by periodic measurement errors within the measurement period.

9. The method according to claim 8, wherein The measured value of the controlled variable is affected by pitch errors or inaccuracies in the gauge of the rotary encoder.

10. A machine-readable data carrier having a program, characterized in that The data carrier is associated with a motor control unit of a drive motor (1), and wherein the program comprises a sequence of instructions which, when executed by a processor, results in the execution of a method according to one of claims 1 to 9.

11. A motor control unit for driving a motor (1), characterized in that The motor control unit is configured and adapted to perform the method according to one of claims 1 to 9 .

12. A driving motor (1), characterized in that: The drive motor (1) comprises a rotor and a motor control unit according to claim 11.

13. The driving motor according to claim 12, wherein: The drive motor (1) comprises at least one sensor for detecting the position or location or speed of the rotor, wherein the motor control unit is configured to calculate the control difference based on the measurement values ​​provided by the sensor.

14. The drive motor (1) according to claim 13, characterized in that The drive motor (1) is an electric motor, and the sensor is a Hall sensor, whose signal is also used to commutate the electric motor.

15. A drive motor (1) comprising a rotor and a motor control unit, configured and adapted to perform the method according to one of claims 1 to 7, characterized in that The drive motor (1) is an electric motor, and the motor control unit is further configured to calculate the control difference based on values ​​generated thereof on the basis of parameters inductance and electromagnetic force by an algorithm for determining the position or location or speed of the rotor without using sensors.

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