Diagnostic procedure and drive unit

Abstract

The invention relates to a diagnostic method for diagnosing detections in a controller for a multiphase electric drive (10), wherein the diagnostic method comprises: first activating (S1) a first phase (10.1) of the drive (10) to a first operating point; detecting a first common current (S2) across all phases (10.1, 10.2) of the drive (10) during the first activation (S1); second activating (S3) a second phase (10.2) of the drive (10) to a second operating point; detecting a second common current (S4) across all phases (10.1, 10.2) of the drive (10) during the second activation (S3); and determining a ratio (S5, S5.2) between the first common current and the second common current to diagnose detection of the first operating point and / or detection of the second operating point. The invention also relates to a drive unit (1).

Description

[0001] The invention relates to a diagnostic method for diagnosing detections in a control system for a multi-phase electric drive. The invention also relates to a drive unit.

[0002] Conventional diagnostic methods for diagnosing detections in a control system for electric drives are known from, for example, DE10061095A1 and DE102022210607A1.

[0003] DE 10 2004 040 052 A1 discloses a current-controlled inverter and a method for controlling a current-controlled inverter with three phase outputs. The method comprises the following steps: a) applying a test current signal to the first and second phase outputs of the three phase outputs and disconnecting the third phase output when the inverter is switched on for operation, b) measuring the test current signal and generating a measurement signal proportional to the measured test current signal for both the first and second phase outputs, c) determining a correction value dependent on these measurement signals, and d) controlling the inverter based on the determined correction value.

[0004] In DE 10 2016 215 711 A1, each phase of a three-phase electric motor is connected to an associated bridge circuit comprising two current valves to connect the phase to different potentials of an intermediate circuit. A method for determining phase currents through the phases comprises the steps of sampling a first voltage drop across a current valve associated with the first phase when the current valve is closed; sampling a second voltage drop across a current valve associated with the second phase when the current valve is closed; and determining the first phase current based on the first voltage, the second phase current based on the second voltage, and the third phase current based on the first and second phase currents. The determination of the first and second phase currents is balanced against a total current flowing through the three bridge circuits.

[0005] DE 10 2019 205 471 A1 discloses a method for verifying measured current strengths of currents supplied by a six-phase converter to at least one electrical machine, wherein each of the six phases of the at least one electrical machine is connected to a high-side switch and a low-side switch of the converter, wherein the high-side switches of the converter are connected to a first converter terminal and wherein the low-side switches of the converter are connected to a second converter terminal, wherein, in the course of at least one current measurement, a current strength of the corresponding phase current and a current strength of a sum current between the high-side switches and the first converter terminal are recorded for each of the six phases, wherein a verification is carried out depending on the recorded current strengths.whether the sum of the measured currents of the phases of the at least one electrical machine yields the value zero or at least substantially zero, and / or whether the sum of the measured currents of the phases of those phases whose high-side switches are closed corresponds to the measured current of the total current or at least substantially corresponds to it, and / or whether the sum of the measured currents of the phases of those phases whose low-side switches are closed corresponds to the negative value of the measured current of the total current or at least substantially corresponds to it, and wherein, depending on a result of the verification, it is determined whether all measured currents are correct or whether at least one of the measured currents is faulty.

[0006] DE 10 2011 086 177 A1 discloses a method for calibrating a multi-phase, in particular three-phase, inverter, which has a high-voltage switching element and a low-voltage switching element for each of its phases, as well as a current sensor for at least some of the phases. The following steps are proposed: - Switching off all switching elements - Switching on a high-voltage switching element of a first phase and a low-voltage switching element of a second phase, - Measuring the currents flowing through the first and second phases, - Calculating an average value from the measured currents, and - Calibrating the inverter based on the calculated average value.

[0007] DE 102 00 369 discloses a method for correcting the measurement signals in a three-phase current measurement with a current measuring device having three phase current measuring devices and an evaluation device.

[0008] Conventional solutions for fault detection in current-controlled electric drives utilize redundant sensors or sensors to detect short circuits and open connections. These redundant sensors allow for the plausibility checks of the individual measurement signals.

[0009] However, these known solutions have the disadvantage that, with the number of measured variables and redundant implementation, the unit costs and space requirements for such diagnostic systems increase. Furthermore, these known systems are not suitable for diagnosing drift in their measurement chain.

[0010] The object of the invention is to provide a diagnostic method that solves the aforementioned problems. In particular, it is an object of the invention to provide a diagnostic method that can diagnose drift in a measurement chain of an electric drive and that can be implemented with low costs and simple electronics. It is also an object of the invention to provide a drive unit that solves the aforementioned problems. The invention is intended, in particular, to provide a way to check the accuracy of several existing measurement chains for signals of a current-controlled electric drive without the effort in terms of cost and installation space increasing with the number of measurement signals required. Furthermore, the method should be insensitive to voltage and temperature fluctuations and, as a result, should not be affected by variations between individual components.

[0011] These problems are solved by the features of the independent claims. The dependent claims contain advantageous embodiments of the invention.

[0012] These tasks are solved in particular by the diagnostic method for diagnosing detections in a control system for a multiphase electric drive according to claim 1. The diagnostic method performs the following steps: - an initial activation of a first phase of the drive to a first operating point, - Detection of an initial common current across all phases of the drive during the initial control, - a second activation of a second phase of the drive to a second operating point, - Detection of a second common current across all phases of the drive during the second control, and - Determining a ratio between the first common current and the second common current to diagnose a detection of the first operating point and / or a detection of the second operating point.

[0013] Ideally, without errors or drift, the first common current should be approximately equal to the second common current. By relating the first common current to the second common current, errors, particularly drift, in the measurement of the first operating point and / or in the measurement of the second operating point are advantageously detected. In other words, this ratio advantageously performs a plausibility check for the measurement of the operating points, especially regulated output currents, of the phases. Furthermore, this ratio ensures that common effects for all phases, such as temperature fluctuations or supply voltage variations, are factored out, thus guaranteeing the robustness of the diagnosis against these effects.

[0014] The present diagnostic method, and in particular the drive mechanism, is not limited to two phases but can include any number of phases, for example, 3, 4, 5, or 6, preferably 3 or 6. The method can easily be extended to accommodate any number of phases (third activation, detection of a third common current, etc.). Advantageously, the ratio of the last two phases is calculated, for example, between the first and second common currents and between the second and third common currents, etc. In other words, a chain of the common currents of the phases is checked (one to two, three to two, four to three, etc.).

[0015] Advantageously, the ratio of the remaining phases is also determined, for example, between the first and third common currents. In other words, a ratio between all common currents is preferably determined (one to two, one to three, two to three, for example, in the case of three phases). Advantageously, the first and second operating points are essentially the same when the phases are first and secondly driven. The phases are advantageously regulated to essentially the same current value as their operating point. For example, the phases are regulated to 7.5 A as their operating point.

[0016] Advantageously, the first phase is set to zero during the second actuation, and the second phase is set to zero during the first actuation. In other words, the first phase is switched off during the actuation of the second phase, and the second phase is switched off during the actuation of the first phase. This ensures that the corresponding first or second common current flows exclusively through the first phase or the second phase. Here, a point in time "during the first / second actuation" corresponds to a point in time or a time interval at which the corresponding operating point is reached. In other words, the time intervals of the first operating point and the second operating point do not overlap. However, it is conceivable that, for example, the ramp-up to the second operating point might overlap with the decay of the first operating point, with both operating points never being reached simultaneously.In particularly advantageous examples, the operating points are separated from each other by 5 to 30 ms in time.

[0017] Preferably, the first and second control operations are each performed using a closed loop with the detected first operating point and the detected second operating point, respectively. The control operations are preferably performed using pulse-width modulation (PWM). In other words, the detected current values ​​of the operating points are used to control their current in a closed feedback loop. The diagnostic method according to the invention allows for the detection of errors or drift in these corresponding measurements.

[0018] In some preferred embodiments, the first and second drive stages are performed using a voltage-stabilized power supply. This voltage-stabilized power supply preferably includes a DC-DC converter and / or a filter to stabilize the voltage input. This configuration ensures that no voltage fluctuations occur at the source during the diagnostic process, further increasing the accuracy and robustness of the diagnostics.

[0019] Preferably, the ratio is determined by dividing the first common current (divided by the second common current) by the second common current (divisor). Particularly with a voltage-stabilized voltage source, the ratio is determined using only the common currents. This simplifies the diagnosis.

[0020] In some preferred configurations, the first and second actuations are performed using a variable voltage source. For example, the actuation might be performed using mains voltage. The term "variable voltage source" in this context means that the voltage source can generate fluctuations in the voltage it supplies, as is often the case with mains voltage. The diagnostic procedure then comprises the following steps: A first common voltage across all phases of the drive is measured during the first actuation. A second common voltage across all phases of the drive is measured during the second actuation. In the ratio determination step, the ratio between the first common power and the second common power is determined.The combined power is determined using the measured combined voltages and currents (P = U x I). This has the advantage that component costs can be reduced through a simpler voltage source, while fluctuations in the voltage supply are taken into account during diagnosis via the measured power.

[0021] Preferably, the diagnostic procedure further comprises the following steps: The specified ratio is compared with a predetermined threshold range. The drive is switched off if the specified ratio is outside the predetermined threshold range. An example threshold range is 0.8 to 1.25 inclusive. In other words, the drive is switched off if the specified ratio is outside the predetermined threshold range and the diagnostic system detects and / or outputs a fault or drift.

[0022] Preferably, the diagnostic procedure is carried out outside of regular operation of the drive, particularly during a start-up sequence. Preferably, the diagnostic procedure is performed in such a way that the control signals cause no or only minimal movement of the drive.

[0023] The present invention also relates to a control unit for a multi-phase electric drive, which has a controller and is configured to be connectable to the drive and wherein the controller is configured to perform the diagnostic procedure according to one of the previous embodiments.

[0024] The present invention further relates to a drive unit comprising a multi-phase electric drive, in particular a stepper motor. The drive unit also comprises a control unit for the drive, with at least one H-bridge circuit or a half-bridge circuit for each phase of the drive, an output current sensor at the output of each phase, and at least one controller, wherein the controller is connected to the respective H-bridge circuit for operating the phase and controls the H-bridge circuit by means of currents detected by the output current sensors. The drive unit also comprises a common current sensor, which is configured to detect a common current for all phases of the drive at a voltage source of the drive.Preferably, in addition to the output current sensors for each individual phase (number of output current sensors = number of phases), the drive unit has only one common current sensor that measures the current through all phases together. In other words, the total number of all current sensors is preferably the total number of all phases of the drive plus one; for example, in a three-phase drive, there are four current sensors: three for the phase outputs and one common current sensor. This configuration results in a drive unit where the plausibility, errors, or drift in the output current sensors can be detected without increasing redundancy with an increasing number of phases. This advantageously reduces the unit costs and the space required for the drive unit, while simultaneously increasing its robustness against measurement chain drift.

[0025] Preferably, in some applications, the drive comprises a unipolar stepper motor with a phase coil and a center tap. In this configuration, the drive has only one half-bridge per phase.

[0026] The controller of the drive unit is connected to the common current sensor and configured to perform the diagnostic procedure according to one of the above descriptions.

[0027] In this process, the output current sensors of the individual phases are preferably used for the corresponding control, while the common current sensor is used to determine the ratio of the common currents or the common powers.

[0028] Preferably, the drive unit comprises at least one of the aforementioned voltage sources. In the exemplary case where the drive unit comprises the variable voltage source, the drive unit further comprises a common voltage sensor configured to detect the common voltage for all phases of the drive, in particular an instantaneous common voltage for all phases of the drive. The detected values ​​for the common voltage are preferably used to determine the ratio of the common power outputs.

[0029] The aforementioned control unit and / or controller preferably includes a computing unit such as a CPU, µC, GPU, FPGA or the like.

[0030] Further details, advantages and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the drawing. It shows: Fig. 1 an electrical circuit diagram of a drive unit according to the present invention; Fig. 2 a schematic block diagram of a controller of the drive unit and a diagnostic method according to the present invention; Fig. 3 a diagram for representing controls according to the diagnostic method of the present invention.

[0031] An exemplary embodiment of the present invention is described with reference to the Fig. 1 to 3 explained, whereby the Fig. Figure 1 shows an electrical circuit diagram of a drive unit 1 according to the present invention, which Fig. Figure 2 shows a schematic block diagram of a controller 5 of the drive unit 1 and a diagnostic method according to the present invention and the Fig. Figure 3 shows a diagram illustrating controls according to the diagnostic method of the present invention.

[0032] The in Fig. The drive unit 1 shown in Figure 1 has a multi-phase drive 10. In the present example, the multi-phase drive 10 is a two-phase stepper motor. For the sake of simplicity, the following are shown in the Fig. 1 the two phases 10.1, 10.2 of the drive 10 are shown.

[0033] The drive unit 1 also includes a control unit 2 for controlling and operating the drive 10. The control unit 2 has two H-bridge circuits 3, one for each phase 10.1, 10.2 of the drive 10. The control unit 2 has two output current sensors 4, each of which is arranged at the output of one of the phases 10.1, 10.2 and detects the output current of each of the phases 10.1, 10.2.

[0034] Control unit 2 also includes a controller 5. As shown in a summary of the Fig. 1 with the Fig. As shown in Figure 2, the controller 5 is connected to the respective H-bridge circuit 3 for operating the corresponding phases 10.1 and 10.2. The controller 5 controls each H-bridge circuit 3 by means of an H-bridge driver 3.1. As explained below, the controller 5 controls the H-bridge circuits 3 using pulse-width modulation (PWM) and uses the respective output current, which is detected by the output current sensors 4.

[0035] Furthermore, the drive unit 1 has a common current sensor 6 and a voltage source 7. The common current sensor 6 detects a common current that flows through all phases 10.1, 10.2 of the drive 10.

[0036] The outputs, i.e., the measured values, of the output current sensors 4 are labeled "ADC0" for the first phase 10.1 and "ADC1" for the second phase 10.2 in the figures. An output of the common current sensor 6 is labeled "ADC2". These designations also refer to the inputs on the controller 5 in the diagram. Fig. Figure 2 shows the outputs of the controller 5, which are used for the PWM control of phases 10.1 and 10.2. These outputs are labelled "PWMA" for the first phase 10.1 and "PWMB" for the second phase 10.2, with each of these outputs being fed into two H-bridge drivers 3.1 (see Figure 2). Fig. 1).

[0037] The regular operation of the drive 10 is carried out by means of PWM control of the H-bridge circuits 3 as a closed circuit or feedback loop with the current values ​​recorded from the output current sensors 4.

[0038] The conventional difficulty here is that a drift or fault in the output current sensors 4 leads to a degradation in the efficiency of the drive 10. A fault can also lead to a failure to detect a step loss and negatively affect the positioning of the system. To detect such a drift or fault, the following exemplary diagnostic procedure is carried out, which is described below using the Fig. 2 and the Fig. 3 will be explained.

[0039] First, in step S0 a signal (“start up”) is sent to the controller 5, which signals that the diagnostic procedure, in particular as part of an initialization of the drive 10, is started (so-called start up).

[0040] An initial activation S1 of the first phase 10.1 of the drive 10 to a first operating point is performed. The first phase 10.1 of the drive 10 is thereby activated to the first operating point, as shown in Fig. 3 in a solid line, controlled via PWM. Fig. Figure 3 represents the regulated and output current values ​​of the individual phases 10.1, 10.2 in response to the control signals S1, S3, output by the output current sensors 4.

[0041] Simultaneously with the first activation of S1, a first common current across all phases 10.1, 10.2 of the drive 10 is detected using the common current sensor 6 S2. This is connected to the input “ADC2” in Fig. 2 shown.

[0042] A second activation S3 of the second phase 10.2 of the drive 10 to a second operating point is carried out, whereby this is in Fig. 3 is represented by a dashed line. Here, the first operating point and the second operating point are essentially the same current value, for example, approximately 7.5 to 7.8 A. Furthermore, the Fig. As can be seen from section 3, steps S1 and S2 are carried out one after the other, in particular not simultaneously or especially without temporal overlap.

[0043] Simultaneously with the second activation of S3, and after the detection of the first common current at S2, a second common current is detected at S4 (input “ADC2” in Fig. 2).

[0044] Subsequently, a ratio between the first common current and the second common current S5 is determined. The in Fig. The symmetry properties of the operating points shown in the diagram result in identical measurement results at the end of the diagnostic measurement chain for each of these excitation states, assuming the signal measurement chain (output current sensors) functions correctly. This similarity is verified by determining the ratio of the corresponding common currents.

[0045] Ideally, the ratio of the common currents to each other should be approximately one, as demonstrated by simply dividing the first common current by the second common current. This is because when S1 and S3 are activated, the other phase 10.1 and 10.2 are switched off, and the entire common current is therefore drawn from one phase. Due to the symmetrical activation of S1 and S3 (see...), this entire common current should be... Fig. 3) for both phases 10.1, 10.2 be identical, so that a ratio of one is calculated.

[0046] If the ratio deviates significantly from one, the diagnostic procedure indicates that there is an error or drift in the measurement chain.

[0047] For this purpose, the ratio is compared with a predetermined threshold range S6. In the present example, the threshold range is preferably between 0.8 and 1.25 inclusive.

[0048] If comparison S6 shows that the ratio determined in step S5 is outside the threshold range, drive 10 is switched off (S7) and an error signal is output. If comparison S6 shows that the ratio is within the threshold range and therefore there is no or only a small drift or error, regular operation of drive 10 is started, which in Fig. 3 is shown after the second activation of S3.

[0049] In the preceding explanation, the ratio was determined solely by means of the common currents S5. Here, the drive unit 1 has a voltage-stabilized voltage source 7, such as a DC-DC converter. This prevents fluctuations in the voltage supply, at which the common current is measured by the common current sensor 8.

[0050] In one modification of this configuration, the voltage source 7 of the drive unit 1 is variable. The voltage source 7 is, for example, a mains voltage, which may fluctuate. In this case, the drive unit also has a common voltage sensor 8, which is configured to detect the current output voltage of the voltage source 7.

[0051] The diagnostic procedure, as described in Fig.Figure 2 illustrates the following selective steps. A first common voltage across all phases 10.1, 10.2 of the drive 10 is detected during the first control S1 S8. A second common voltage across all phases 10.1, 10.2 of the drive 10 is detected during the second control S3 S9. In step S5, which determines the ratio, a modified step S5.2 determines the ratio between the first common power and the second common power. The common powers are each determined as the product of the detected common voltage and the detected common current. In this modification, the ratio is also determined by simple division (first power / second power). This takes into account the effects of fluctuations in the output of the variable voltage source 7.

[0052] The common voltage sensor 8 is advantageously integrated into the common current sensor 6, for example by means of a voltage drop across a resistor.

[0053] The diagnostic procedure and modification described above offer the following further advantages.

[0054] By using a voltage stabilizer as the voltage source 7, the process is independent of fluctuations in the supply voltage. Using the common voltage sensor 8 allows for a simpler voltage source 7, thereby reducing costs and space requirements.

[0055] Thanks to the use of consecutively excited, mutually symmetrical current states of the drive phases (operating points) to take their symmetry properties into account when validating the measurement chain parameters, a single diagnostic measurement path is sufficient to safeguard any number of phases n ≥ 2. In other words, only one additional current sensor 6 (optionally with an additional voltage sensor 8) is used, regardless of the number of phases 10.1, 10.2 of the drive 10. This reduces costs and space requirements.

[0056] The consecutive excitation states are selected to achieve sufficient sensitivity of the diagnostic measurement chain to the relevant phase signals. The current level is particularly important here, as the common current (supply current) is usually lower than the phase current. To fully utilize the detection resolution, the impressed phase currents should be higher than during normal operation. The time interval between excitations is preferably chosen so that only the common current of one phase is detected during the measurement.

[0057] Temperature effects are factored out using the ratio.

[0058] The method is also suitable for detecting unexpected asymmetries of the electric drive 10 between its phases 10.1 and 10.2. In combination with position monitoring, the electric drive 10 can be effectively protected by the present method.

[0059] In summary, the present diagnostic procedure performs a comparison between the different phases 10.1 and 10.2 of the electric drive 10 and utilizes its symmetry properties, thus significantly reducing cross-sensitivities to temperature, supply voltage, and a multitude of parameters subject to variation in the measurement chain. Due to the sequential approach of the diagnostic procedure, only one sensor 6 is required to monitor multiple measurement chain channels, and the need to implement each path of the measurement chain (each output current sensor 4) redundantly is eliminated.

[0060] In addition to the above written description of the invention, explicit reference is hereby made to the graphic representation of the invention in the figures for its supplementary disclosure. Reference symbol list 1 drive unit 2 Control unit 3 H-bridge circuit 4 Output current sensor 5 Controller 6 common current sensor 7 Voltage source 8 common voltage sensor 10 multi-phase electric drive 10.1 First phase of the drive 10.2 Second phase of the drive S0 Start S1 first activation of a first phase S2 Capturing a first common current S3 second activation of a second phase S4 Capturing a second common stream S5 Determining a ratio between common flows S5.2 Determining a relationship between joint services S6 Comparing the definite ratio S7 Switch off the drive S8 Detecting an initial common voltage S9 Capturing a second common voltage

Claims

[1] Diagnostic method for diagnosing detections in a controller for a multiphase electric drive (10), wherein the diagnostic method comprises: - a first activation (S1) of a first phase (10.1) of the drive (10) to a first operating point; - Detection of a first common current (S2) across all phases (10.1, 10.2) of the drive (10) during the first control (S1); - a second activation (S3) of a second phase (10.2) of the drive (10) to a second operating point; - Detection of a second common current (S4) across all phases (10.1, 10.2) of the drive (10) during the second control (S3); and - Determining a ratio (S5, S5.2) between the first common current and the second common current to diagnose a detection of the first operating point and / or a detection of the second operating point. [2] Diagnostic method according to claim 1, wherein the first operating point and the second operating point are essentially the same when first and secondly controlling (s1, S3) the phases (10.1, 10.2). [3] Diagnostic method according to one of the preceding claims, wherein the first actuation (S1) and the second actuation (S3) are each carried out by means of a closed circuit with the detected first operating point and with the detected second operating point, in particular by means of PWM. [4] Diagnostic method according to one of the preceding claims, wherein the first actuation (S1) and the second actuation (S3) are carried out by means of a voltage-stabilized voltage source (7), wherein the voltage source (7) in particular comprises a DC-DC converter and / or a filter. [5] Diagnostic method according to claim 4, wherein the ratio is a division of the first common current as dividend by the second common current as divisor. [6] Diagnostic method according to one of claims 1 to 3, wherein the first actuation (S1) and the second actuation (S3) are carried out by means of a variable voltage source (7), in particular by means of a mains voltage, the diagnostic method further comprising the steps: - Detection of a first common voltage (S8) across all phases (10.1, 10.2) of the drive (10) during the first control (S1); - Detection of a second common voltage (S9) across all phases (10.1, 10.2) of the drive (10) during the second control (S3); wherein - in the step of determining (S5.2) a relationship between a first joint performance and a second joint performance is determined. [7] Diagnostic method according to any of the preceding claims, further comprising the steps: - Comparing the specified ratio (S6) with a predetermined threshold range, in particular between 0.8 and 1.25 inclusive; and - Switching off the drive (S7) if the specified ratio is outside the predetermined threshold range. [8] Diagnostic method according to one of the preceding claims, wherein the diagnostic method is carried out outside of regular operation of the drive (10), in particular during a start-up. [9] Drive unit (1) comprising: - a multi-phase electric drive (10), in particular a stepper motor; - a control unit (2) with at least one H-bridge circuit (3) or a half-bridge circuit for each phase (10.1, 10.2), an output current sensor (4) at the output of each phase (10.1, 10.2) and at least one controller (5), wherein the controller (5) is connected to the respective H-bridge circuit (3) for operating the phase (10.1, 10.2) and controls the H-bridge circuit (3) by means of detected currents from the output current sensors (4); and - a common current sensor (6) which is configured to detect a common current for all phases (10.1, 10.2) of the drive (10) at a voltage source (7) of the drive (10), wherein the controller (5) is connected to the common current sensor (6) and is configured to perform the diagnostic method according to any one of claims 1 to 7.

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