Drive with drive controller and motor encoder with memory unit for correction parameters

Abstract

The invention relates to a motor encoder (DSR) for a drive controller (DCR) having a converter (CVT), wherein the motor encoder (DSR) determines raw measurement values (RSG) for the angular position (AGL) of a rotor shaft (DRS). The motor encoder has an integrated memory unit (MEM) for first correction parameters (CRP) for correcting the angular position (AGL) by means of a first correction function (CPF), a measurement scale (MBD) for mounting on the rotor shaft (DRS), a sensor (SNR) for determining the angular position, a motor encoder bearing (BDS), and an encoder shaft (IME). The bearing (BDS) defines a first axis of rotation (AXP) and the measurement scale (MBD) is attached to the encoder shaft (IME), the first correction parameters (CRP) compensate for an error caused by an offset between the first axis of rotation (AXP) and the sensor (SNR), and the memory unit (MEM) and the processor (CPU) of the drive controller (DCR) form a functional module (FMD) which converts raw measurement values (RSG) into corrected angular positions (AGL). According to the invention, the encoder shaft (IME) is connected to the rotor shaft (DRS) in a rotationally rigid manner, the rotor shaft (DRS) is mounted along a second axis of rotation (AXS), the two axes of rotation (AXP, AXS) have an offset (ORS), and second correction parameters (CRS) in the second memory unit (MES) compensate for the error caused by said offset by means of a second correction function (CPF).

Description

[0001] 202401474 Foreign version

[0002] 1

[0003] Description

[0004] Motor encoder, drive and drive control

[0005] The present invention relates to a motor sensor for a drive control system with an inverter, wherein the motor sensor is configured to determine raw measured values ​​of an angular position of a rotor shaft of a drive. The invention further relates to a drive control system with a motor sensor and an inverter, wherein the motor sensor is configured to determine raw measured values ​​of an angular position of a rotor shaft of a drive. The invention further relates to a drive system comprising a corresponding drive control system.

[0006] A motor sensor, also known as a speed sensor or position sensor, is an electronic component typically used in a motor to acquire information about the rotational speed and position of the rotor shaft. The position here primarily refers to the angular orientation of the rotor shaft, that is, the angle of the rotor shaft relative to its rotation around the axis of rotation intended for normal operation.

[0007] The motor encoder typically consists of a sensor and a measuring element, usually a magnetic ring or a toothed disc attached directly or indirectly to the rotor shaft. The term "measuring element" is used here because this component physically embodies the angular increment of the measurement, for example, by means of the tooth spacing in the case of a toothed disc. The sensor detects the signals from the magnetic ring or toothed disc as they move past it. These signals are then converted into electrical impulses and transmitted to a drive controller.

[0008] The drive control unit uses information from the motor encoder to monitor and control motor operation. Primarily, the drive control unit regulates the speed, ensuring that the drive receives the necessary energy to achieve the target speed under load. By accurately measuring the speed and rotor position, the motor encoder enables precise control of the drive, contributing to improved performance and efficiency.

[0009] Motor encoders can be used, for example, in electric motors to acquire information about the rotor position or speed. This information can be used to optimize the control and regulation of the electric motor, improve efficiency, or enable safety functions. 202401474 Foreign version

[0010] 2

[0011] Furthermore, motor encoders are used in various industrial machines, robots, precision instruments and other systems where the accurate measurement of rotational movement or position is crucial.

[0012] There are various types of motor sensors, which can vary depending on the application. These include, for example, optical or magnetic sensors that can detect the movement or position of a rotor, as well as inductive or capacitive sensors that can provide information about the rotational movement or position.

[0013] Overall, motor encoders are used in a wide variety of motors and applications where accurate measurement of the position or speed of rotating components is required.

[0014] The accuracy of the position determination achieved by the motor encoder can vary depending on the type of sensor and the specific application. Generally, the position determination is very precise and can offer high resolution.

[0015] However, it is important to note that the accuracy of the position determination depends not only on the motor encoder itself, but also on other factors such as signal processing in the drive control system, the quality of the electrical connections, and potential disturbances or inaccuracies in the motor's operation. Therefore, the actual accuracy values ​​can vary depending on the specific circumstances and the quality of the components.

[0016] A drive control system of the type described above is already known from EP 3669 241 B1. During special operation of the drive, EP 3669 241 B1 provides that the rotor shaft is accelerated to a specific initial speed and then coasts to a stop without force in order to obtain position measurements that are used to determine correction parameters for position determination. The invention follows at least partially the same approach with regard to determining the correction parameters. For information on determining the correction parameters, the person skilled in the art is referred to the disclosure in EP 3669 241 B1, unless the present disclosure explicitly describes a different procedure.

[0017] However, the state of the art, including the procedure according to EP 3669 241 B1, also has some disadvantages. Some disadvantages and limitations are:

[0018] The motor encoder is only calibrated in combination with the inverter in its fully installed state, 202401474 Foreign version

[0019] 3

[0020] The motor encoder initially delivers significantly erroneous values ​​because, according to the current state of the art, the correction values ​​are stored in a correction value memory of the drive control – i.e., in the inverter. If the motor is replaced, the correction values ​​must be recalculated.

[0021] Access by the inverter or drive control to the motor encoder is a safety risk that is technically unacceptable depending on the application.

[0022] US20230130262A1 discloses a sensor for measuring angular positions with correction parameters, without a motor encoder for drive controllers, without a specific mechanical arrangement with the encoder shaft bearings and without two-axis offset compensation.

[0023] US20200378798A1 describes an angle sensor that stores offset and amplitude correction values ​​in memory to correct rotation angle estimates during operation.

[0024] US20200378798A1 does not disclose a motor encoder specifically for a drive controller with an inverter, multiple rotational axes with specific offsets, or separate correction parameters for different types of mechanical misalignments.

[0025] TSUKASA WATANABE ET AL: "Self-calibratable rotary encoder", JOURNAL OF PHYSICS: CONFERENCE SERIES, INSTITUTE OF PHYSICS PUBLISHING, BRISTOL, GB, Vol. 13, No. 1, 1 January 2005, describes a self-calibratable rotary encoder system with multiple sensor heads mounted on a rotary platform to enable precise angle measurement. While it addresses angular deviation and calibration to improve accuracy, it lacks a specific disclosure of stored data.

[0026] Correction parameters, offset compensation of two axes, or integration with a drive controller.

[0027] The object of the present invention is therefore to address one of the above-mentioned problems, to improve the general state of the art and to provide an alternative to what is known previously.

[0028] To solve the problem, the invention proposes a motor encoder, a drive control, and a drive of the type mentioned above, which are further developed according to the invention. 202401474 Foreign version

[0029] 4

[0030] Specifically, it is proposed that the motor encoder has an integrated memory, in which first correction parameters for correcting the angular position are stored using a first correction function.

[0031] The invention provides that the motor encoder has a scale for mounting on the rotor shaft and a sensor for determining the angular position of the rotor shaft by means of the scale, wherein the motor encoder has a motor encoder bearing and an encoder shaft, wherein the motor encoder bearing defines a first axis of rotation of the encoder shaft, wherein the scale is attached to the encoder shaft, wherein the first correction parameters are provided to compensate for only an error in the determination of the angular position caused by an offset of the first axis of rotation of the scale to the sensor by means of the first correction function.

[0032] According to the invention, a drive control with such a motor encoder is further proposed, wherein the drive control has a processor, wherein the memory and the processor together form a functional module, wherein the functional module is designed and prepared such that the processor converts the raw measured values ​​of the motor encoder to corrected angular positions using the first correction parameters and the first correction function, and the drive control controls the drive on the basis of the corrected angular positions.

[0033] According to the invention, a drive with a drive control is further proposed, wherein the encoder shaft is torsionally rigidly connected to the rotor shaft at the motor encoder, wherein the rotor shaft is rotatably mounted along a second axis of rotation, wherein the first axis of rotation and the second axis of rotation have an offset relative to each other, wherein second correction parameters are stored in a second memory, wherein the second correction parameters are provided to compensate only for an error in the determination of the angular position of the rotor shaft caused by the offset of the second axis of rotation to the first axis of rotation by means of a second correction function.

[0034] According to the invention, the motor encoder is proposed to have a scale for mounting on the rotor shaft and a sensor for determining the angular position of the rotor shaft by means of the scale. 202401474 Foreign version

[0035] 5

[0036] Preferably, it is proposed that the calibration module be designed such that a suitable operating state of the drive for calibration must be met as a necessary condition for activating the calibration mode of the calibration module.

[0037] Preferably, it is proposed that the functional module be designed such that a suitable operating state of the drive for calibration must be met as a necessary condition for activating the calibration mode of the functional module.

[0038] Preferably, it is proposed that the suitable operating condition provides that the drive is accelerated to a speed above a minimum speed and that the drive control is parameterized such that no force influences on the rotor shaft are caused by the drive control during calibration.

[0039] Preferably, it is proposed that during calibration, the drive control checks whether the current rotational speed of the rotor shaft reaches or falls below a minimum speed based on the respective raw measurement values, and when the minimum speed is reached or fallen below, the determination and temporary storage of the raw measurement values ​​is stopped and the processor determines the second correction parameters from the raw measurement values ​​measured up to that point.

[0040] The invention is described in more detail below using a specific embodiment for clarification. The figures show:

[0041] Figure 1: a schematic, simplified representation of a drive comprising a drive control and a motor encoder according to the invention,

[0042] Figure 2: a section detail, which is shown as ll-ll in Figure 1,

[0043] Figure 3: a flowchart illustrating the cascaded error corrector according to the invention,

[0044] Figures 4 and 6: each a representation of the motor encoder error over time, Figure 5: a spectral analysis of the motor encoder error.

[0045] Figure 1 shows a DRV drive with a DCR drive controller comprising a DSR motor encoder and a CVT inverter. The DSR motor encoder is configured to first determine raw measured values ​​RSG of the angular position AGL of a DRS rotor shaft of a DRV drive. The DSR motor encoder has a dimensioned representation MBD for mounting on the DRS rotor shaft. A sensor SNR measures the AGL of the DRS rotor shaft using the dimensioned representation MBD. 202401474 Foreign version

[0046] 6

[0047] The measuring element MBD is attached to the rotor shaft DRS by means of an encoder shaft IME. The motor encoder DSR has its own motor encoder housing SCS, which is attached to a housing CAS of the drive DRV. The encoder shaft IME of the motor encoder DSR, which serves as a mechanical transmission element between the rotor shaft DRS and the measuring element MBD, is torsionally rigidly attached to the rotor shaft DRS by means of a coupling CPL and rotatably mounted in the motor encoder housing SCS by means of a motor encoder bearing BDS, approximately coaxial to the rotor shaft DRS.

[0048] One source of error in determining the angular position AGL is an offset OMS of the measuring element MBD relative to the first axis of rotation AXP of the encoder shaft IME, such that the measuring element MBD is not mounted concentrically to the first axis of rotation AXP and, consequently, its distance to the stationary sensor SNR varies over the revolution. In other words, the measuring element MBD wobbles or wobbles during its rotation. This source of error is internal to the motor encoder DSR.

[0049] Another source of error is an offset ORS of the second axis of rotation of the rotor shaft DRS relative to the first axis of rotation AXP of the encoder shaft IME of the motor encoder DRS. This offset is almost unavoidable within the limits of technical accuracy and distorts the determination of the angular position AGL by the motor encoder DSR.

[0050] The first-mentioned source of error is addressed according to the invention with an error correction mechanism, which is specifically assigned to the motor encoder DSR. The motor encoder DSR has an integrated first memory MEP. This first memory MEP is attached to the motor encoder and is in data transmission communication with a processor CPU. Preferably independently of the drive DRV and the inverter CVT, first correction parameters CRP are determined, which are intended to compensate only for the motor encoder DSR's internal error in determining the angular position AGL by means of a first correction function CPF. Such calibration—i.e., the determination of the first correction parameters CRP—can be performed on a separate test bench, for example, against a reference sensor.In principle, a procedure analogous to that proposed in EP 3 669241 B1 is also possible – i.e., determining the correction parameters CRP and CRS during force-free operation – for example, during free coasting from high speed. However, this option is primarily intended for correcting the second source of error explained below. 202401474 Foreign version.

[0051] 7

[0052] The second source of error – namely the offset ORS of the first rotary axis AXP to the second rotary axis AXS – is stored in a second memory MES using a second correction function CSF and compensated for by means of a second correction parameter CRS. The second memory can be – as shown in Figure 1 – part of the first memory attached to the motor encoder DRS or physically assigned to the drive controller DCR.

[0053] The respective computational correction of the errors can be carried out using the first and second correction parameters CRP, CRS - read from the first memory MEP or second memory MES - and using the first or second correction function CPF, CSF by means of a processor CPU, whereby the processor CPU can be assigned to the drive control DCR, as shown in Figure 4.

[0054] The error compensation process is schematically illustrated in Figure 3. The error compensation is essentially cascaded, such that first the motor encoder DSR internal errors are calculated and then this simply corrected angular position AGL' is corrected again for the error arising due to the offset of the rotor shaft to the encoder shaft.

[0055] Figure 3 illustrates the procedure in three steps (a), (b), (c):

[0056] (a) The first correction step (a) involves recording the raw RSG measurement value using the SNR sensor of the DRS engine sensor;

[0057] (b) In a second step, an initial error correction is carried out under:

[0058] - Reading the first correction parameter CRP from the first memory MEP and

[0059] - Calculating the simply corrected angular position AGL' using the first correction parameter CRP and applying the first correction function CPF using the processor CPU

[0060] (c) In a third step, a second error correction is carried out under

[0061] - Reading the second correction parameter CRP from the second memory MES and

[0062] - Calculating the corrected angular position AGL using the second correction parameter CRP and applying the second correction function CSF using the processor CPU. 202401474 Foreign version

[0063] 8

[0064] These corrections (b), (c) are calculated additively one after the other, so that the simply corrected angular position AGL' is calculated to the fully corrected angular position AGL due to the further correction.

[0065] The second error correction is carried out in detail as described below and already explained in more detail in EP 3 669241 B1.

[0066] The error measured during inverter operation encompasses inaccuracies caused by the integration of the DSR motor encoder into the DRV drive, specifically deviations in the alignment of the IME encoder shaft, DRS rotor shaft, and CPL coupling from ideal coaxial alignment. Such a correction is more accurate than correcting only the DSR motor encoder alone. Extensive measurements with a reference encoder are unnecessary. The correction can also be applied additively to a previously performed compensation of the DRV's internal error on a test bench. This stepwise approach significantly increases the accuracy of a DRV drive with a DSR motor encoder.

[0067] The procedure for determining the second correction parameter CRS proceeds in the following steps:

[0068] - Creating an operating state that allows for the determination of the motor sensor fault,

[0069] - Determination of the motor encoder fault from the measured values ​​recorded in the inverter

[0070] - Storing the fault for motor sensor correction in the first memory MEP of the motor sensor DSR.

[0071] Regarding the first step, it should be noted that various operating conditions are possible from which the motor encoder error can be determined. For example, the drive can be allowed to coast down from high speed (pulses removed) and the motor encoder position recorded. The signal is then cleaned of its large-signal component (e.g., by estimating the least-squares polynomial curve and subtracting it from the signal), and the remaining small-signal is the motor encoder error. Alternatively, the DSR motor encoder can be operated in controlled mode at medium speed, and the motor encoder error can be calculated from the motor encoder position and the motor torque.

[0072] An operating condition that allows for a very precise calculation of the motor encoder error occurs when the DRV drive is brought to the highest possible speed and the speed controller is parameterized so that the motor torque no longer significantly influences the system behavior at frequencies of the motor speed and above. The motor encoder error can then be determined by spectral analysis of the measured synchronization deviation. 202401474 Foreign version

[0073] 9

[0074] This procedure is illustrated in Figures 4, 5 and 6.

[0075] The first correction parameter CRP is determined by measuring the motor sensor DSR on a test bench; the correction is determined from the difference to the measured values ​​of a reference sensor of the test bench and stored in the motor sensor DSR in the first memory MEP.

[0076] After compensating for the motor encoder's internal error, the following aspects limit the achievable precision of the overall system (motor encoder DSR + drive DRV):

[0077] - The influence of mounting the DSR motor sensor in the DRV drive and the clutch cannot be compensated, as only the DSR motor sensor is treated on the test bench.

[0078] - The installation of the DSR engine sensor on the test bench creates an error that is not actually present in the DSR engine sensor, but is included in the correction table and thus reduces the quality.

[0079] Figure 4 – left side – shows the measured synchronization error of a servo motor at 3000 rpm over a period of 0.5 seconds. This represents 25 rotor shaft revolutions. The speed controller is set sufficiently low to assume that the physical (actual) synchronization of the drive DRV over a single revolution is nearly perfect. Therefore, the fluctuation of the measured value at frequencies corresponding to low integer multiples of the motor speed is an error in the motor encoder DSR. The slow fluctuation of the synchronization error can be attributed, among other things, to the non-constant friction of mechanical bearings. Figure 4 – right side – shows in detail the synchronization error of the angular position AGL over a period of 100 ms – i.e., 5 rotor shaft revolutions. Figure 5 shows the spectral analysis of the synchronization error, dominated by first- and second-order errors.Accordingly, the second correction parameter CRS is set. Figure 6 shows the representation of Figure 4 in comparison with the motor sensor error before BFR correction and after AFT correction using the first and second correction parameters CRP and CRS.

[0080] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

202401474 Foreign version Patent claims 1. Motor encoder (DSR) for a drive control (DCR) with an inverter (CVT), wherein the motor encoder (DSR) is configured to determine raw measured values ​​(RSG) of an angular position (AGL) of a rotor shaft (DRS) of a drive (DRV), wherein the motor encoder (DSR) has an integrated memory (MEM) wherein first correction parameters (CRP) for correcting the angular position (AGL) by means of a first correction function (CPF) are stored in the memory (MEM), wherein the motor encoder (DSR) has a scale (MBD) for mounting on the rotor shaft (DRS), and has a sensor (SNR) for determining the angular position (AGL) of the rotor shaft (DRS) by means of the scale (MBD), wherein the motor encoder has a motor encoder bearing (BDS) and an encoder shaft (IME), wherein the motor encoder bearing (BDS) defines a first axis of rotation (AXP) of the encoder shaft (IME), wherein the encoder shaft (IME) The physical form (MBD) is attached, with the first correction parameters (CRP) provided,to compensate for an error in the determination of the angular position (AGL) caused by an offset of the first axis of rotation (AXP) of the measuring instrument (MBD) to the sensor SNR by means of the first correction function (CPF), wherein the drive control (DCR) has a processor (CPU), wherein the memory (MEM) and the processor (CPU) together form a functional module (FMD), wherein the functional module (FMD) is designed and prepared such that the processor (CPU) converts the raw measured values ​​(RSG) of the motor encoder (DSR) to corrected angular positions (AGL) by means of the first correction parameters (CRP) and the first correction function (CPF), and the drive control (DCR) controls the drive (DRV) on the basis of the corrected angular positions (AGL), characterized in that the encoder shaft (IME) is torsionally rigidly connected to the motor encoder (DSR) with the rotor shaft (DRS), wherein the rotor shaft (DRS) rotates along a second axis of rotation (AXS) is rotatably mounted,wherein the first axis of rotation (AXP) and the second axis of rotation (AXS) have an offset (ORS) relative to each other, wherein second correction parameters (CRS) are stored in a second memory (MES), wherein the second correction parameters (CRP) are provided to only one due to, 202401474 Foreign version 11. To compensate for the error in determining the angular position (AGL) of the rotor shaft (DRS) caused by the offset of the second axis of rotation (AXS) to the first axis of rotation (AXP) using a second correction function (CPF).

2. Drive (DRV) according to claim 1, wherein a calibration module (KMD) is configured such that a calibration mode (CLM) for calibrating (CLR) the determination (DTM) of the angular position (AGL) of the rotor shaft (DRS) can be activated (ACT), wherein the calibration (CLR) comprises a determination (DTM) of the second correction parameters (CRS) of the second correction function (CSF), wherein the function module (FMD) is prepared for the purpose of calibration (CLR) to perform the following steps: (a) Activation (ACT) of the calibration mode (CLM) of the calibration module (KMD), (b) Determination (DTM) of the second correction parameter (CRP), (c) Storage (STR) of the second correction parameter (CRP) in a second memory (MES).

3. Drive (DRV) according to claim 2, wherein the calibration module (KMD) is designed such that, for the activation (ACT) of the calibration mode (CLM), an operating state (OPC) of the drive (DRV) suitable for calibration (CLR) must be met as a necessary condition.

4. Drive (DRV) according to claim 3, wherein the suitable operating state (OPC) provides that the drive (DRV) is accelerated to a speed (RPM) above a minimum speed (MRP) and the drive control (DCR) is parameterized such that no force influences on the rotor shaft (DRS) are caused by the drive control (DCR) during the calibration (CLR).

5. Drive (DRV) according to any one of the preceding claims 2 to 4, wherein the drive control (DCR) during calibration (CLR) checks, based on the respective raw measurement values ​​(RSG), whether a current rotational speed (RPM) of the rotor shaft (DRS) reaches or falls below a minimum rotational speed (RPN), and when the minimum rotational speed (RPN) is reached or fallen below, the determination and temporary storage of the raw measurement values ​​(RSG) is stopped and the processor (CPU) determines the second correction parameters (CRP) from the raw measurement values ​​(RSG) measured up to that point.

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