Method for controlling an electric motor when speed measurement anomalies occur - Patents.com

Abstract

A method for controlling a synchronous electric motor comprising generating 400 a torque reference from a mechanical set point, measuring 405 a position, determining a speed of the motor, measuring 410 a current generated by the motor, generating 445 a voltage reference from the torque reference, and generating 450 a control voltage from the reference voltage. The method comprises monitoring for anomalies in the position measurement and adapting 440 an electrical control gain in response to detecting or not detecting 435 an anomaly in the measurement of the position of the electric motor, where the voltage reference is dependent on the value of the electrical control gain.

Description

[Technical field]

[0001] The present invention relates to control of electric motors, and more particularly to control of electric motors that tracks anomalies in the measurement of the rotor speed of the electric motor. [Background technology]

[0002] In control systems configured to control electric motors configured for speed or position, rotor speed sensors are commonly used to develop robust and efficient control laws.

[0003] If position information becomes unavailable, the system becomes inoperable due to lack of information to replace the measurements. If an anomaly occurs during a controlled movement, an immediate reaction is required to continue this movement and maintain the expected performance level.

[0004] There are different methods of controlling electric motors without sensors that can be divided into two categories: on the one hand, methods that operate from electrical quantities applied or measured on the electric motor, which can be instantaneous quantities or quantities averaged over a period depending on the power stage and its control strategy, and on the other hand, methods that operate from high frequency components of electrical quantities that are superadded to the main control.

[0005] The principle of controlling an electric motor without a position sensor from elementary electrical quantities comprises a motor driven with a voltage by an electrical control, as shown diagrammatically in Figure 1. The electrical control receives as inputs measurements of the current in the motor, values ​​of the motor speed estimated from the motor voltage and current, and a mechanical torque reference provided by a mechanical control, which determines the mechanical torque reference from the speed or position reference, the speed estimate and the control parameters of the electrical control.

[0006] As shown diagrammatically in FIG. 2, the principle of controlling an electric motor without a position sensor from high-frequency electrical quantities differs from that of FIG. 1 in that a high-frequency module is provided upstream of the motor and estimations are made regarding the speed or position of the motor.

[0007] In the definition of known electrical system architectures, the presence of a position or speed measurement is known at the time of configuration of the control system. It is at this stage that the choice is made in the control unit to manage or not manage the position or speed measurement.

[0008] This control law is configured to operate with the information given by the position sensor or without this information. Reconfiguration from one to the other can only be performed after a shutdown phase. This induces the current movement to terminate in an uncontrolled way. A faulty position / speed measurement produces, via regulation, voltages at the motor that do not correspond to the motor's state. This can lead to a series of incorrect behaviors that need to be captured through different monitoring functions.

[0009] Known systems only propose to generate a warning or a fault when a fault is detected. Summary of the Invention [Problem to be solved by the invention]

[0010] The main objective of the invention is therefore to propose a solution for reconfiguring the motor control modes in flight to compensate for motor position sensor failures. In-flight reconfiguration of the motor control modes means reconfiguration during operation, i.e. reconfiguring the motor control modes while keeping the motor and its control means in operation. [Means for solving the problem]

[0011] According to a first object of the invention, a method for controlling a synchronous electric motor is proposed, comprising generating a mechanical torque reference from a mechanical setpoint, measuring a position, determining a speed of the electric motor from the measured position, measuring a current generated by the electric motor, generating a voltage reference from the mechanical torque reference, and generating a control voltage from the reference voltage.

[0012] The method further comprises monitoring for anomalies in the measurement of the position of the electric motor and adapting an electrical control gain in response to detecting or not detecting an anomaly in the measurement of the position of the electric motor, the generated voltage reference being dependent on a value of the electrical control gain.

[0013] The method according to the invention therefore makes it possible to provide continuity of control of the voltage of the electric motor even in the presence of a major fault, which is the loss of information on the measured value of the position of the motor. Through detection of the fault and thus adaptation of the gains, reconfiguration of the electrical control means and, alternatively, of the current reference, it is possible to guarantee the performance of the mechanical movement of the electric motor, without having to stop the motor and without having to stop the control, i.e. without having to turn off and reset the control of the motor.

[0014] Monitoring for anomalies in the position measurement of an electric motor further comprises controlling the consistency of the position or speed information with the current information.

[0015] Current information refers to data from current measurements and data from transformations of current measurements.

[0016] In one aspect of the method, monitoring for anomalies in measurements of the position of the electric motor comprises estimating a speed determined from measurements of the motor's position and current measured across the motor, comparing the estimated speed to the determined speed, and reporting a measurement anomaly depending on the result of the comparison against a detection threshold.

[0017] According to another object of the invention, an electrical control system for a synchronous electric motor is proposed, comprising a mechanical control block configured to receive a mechanical set point and to deliver a mechanical torque reference, an electrical control block configured to deliver a voltage reference as a function of the torque reference delivered by the mechanical control block, a power block configured to deliver a control voltage to the electric motor as a function of the voltage reference delivered by the electrical control block, a position sensor of the rotor of the electric motor controlled by the electrical system, and means for measuring the current across the electric motor controlled by the electrical control system.

[0018] According to one general feature of the system according to the invention, the electronic control block comprises: means for detecting anomalies in the measurements of the position sensor; a module for adapting an electrical control gain configured to adapt the gain in response to detecting or not detecting an anomaly in the measurement of the position of the electric motor; and a control module configured to deliver a voltage reference from the mechanical torque reference, the current measured across the electric motor, and the electrical control gain delivered by the adaptation module (94).

[0019] In a first aspect of the invention, the anomaly detection means comprises a module for estimating the speed of the motor from the motor voltage and current, a comparator configured to compare the determined speed with the speed measured by the sensor, and a module for reporting a measurement anomaly depending on the result of the comparison against a detection threshold.

[0020] In a second aspect of the system according to the invention, the power control block further comprises a power converter.According to another object of the invention, an electric system is proposed, comprising an electric motor coupled to a load and an electric control system as defined above coupled to the electric motor.

[0021] Other characteristics and advantages of the invention will become apparent from the description given below with reference to the attached drawings, which show one exemplary embodiment without any limiting nature. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 shows diagrammatically an electrical system 1 comprising a synchronous electric motor 2 and a control circuit 4 according to an embodiment of the present invention. [Diagram 2] FIG. 2 shows generally in more detail the electrical control system 4 for the synchronous electric motor 2 of FIG. [Diagram 3] FIG. 3 is a more detailed schematic diagram of the electrical control block 9 of FIG. [Figure 4] FIG. 4 shows a schematic flow chart of a control method implemented by an electrical control system 4 for a synchronous electric motor 2 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] FIG. 1 shows diagrammatically an electrical system 1 comprising a synchronous electric motor 2 with permanent magnets, connected to a load 3 , and an electrical control system 4 coupled to the electric motor 2 .

[0024] The electrical control system 4 for the synchronous electric motor 2 comprises a control assembly 5, a position sensor 6 configured to measure the speed of the rotor of the synchronous electric motor 2, and means for measuring the voltage and current across the synchronous electric motor 2.

[0025] As shown in FIG. 2, which illustrates a schematic of an electrical control system 4 for a synchronous electric motor 2, a control assembly 5 receives a mechanical set point Cm and determines a mechanical torque reference R C a mechanical control block 8 configured to deliver a torque reference R delivered by the mechanical control block 8; C Voltage reference R as a function of T and a voltage reference R delivered by the electrical control block 9.T as a function of the control voltage T C and a power block 10 configured to supply the electric motor 2 with

[0026] As shown in FIG. 3, which is a more detailed schematic representation of the electrical control block 9, the electrical control block 9 comprises means 92 for detecting anomalies in the measurements of the position sensor 6, a module 94 for adapting the electrical control gains, which is configured to adapt the electrical control gains depending on the detection or non-detection of an anomaly in the measurements of the position of the synchronous electric motor 2, and a mechanical reference R C from the current measured across the electric motor 2 by the measuring means 7 and the electrical control gain delivered by the adaptation module 94, a voltage reference R T and a control module 96 configured to deliver

[0027] Furthermore, the anomaly detection means 92 comprise a module 922 for estimating the motor speed from the motor voltage and current, a comparator 924 configured to compare the determined speed with the speed measured by the position sensor 6, and a module 926 for reporting measurement anomalies depending on the result of the comparison against a detection threshold.

[0028] 4 represents a flow chart of the control method implemented by the electrical control system 4 for the synchronous electric motor 2. The method comprises a first step 400 of generating a mechanical torque reference from a mechanical set point, followed in a second step 405 by a measurement of the position using the position sensor 6 and a determination of the speed of the electric motor 2 from the position measurement, followed in step 410 by a measurement of the current generated by the electric motor 2.

[0029] Then, a monitoring of anomalies in the measurements of the position sensor 6 is performed. For this purpose, in step 430, the consistency of the position or speed information and the current information is controlled and in step 435, it is determined whether there are any anomalies between the position or speed information and the current information. The information consistency control comprises in particular an estimation of the speed or position of the motor from an electrical quantity such as the current generated by the motor and a comparison of this estimated speed or position with a measured position or a speed determined from the measured position, which comparison may be performed by calculating the difference between the estimated speed and the measured speed and by making sure that this gap remains limited to the expected variation range with respect to the measurement noise and the regulation dynamics.

[0030] Following the control of the consistency of the information, in step 420 it is possible to deliver an estimate of the speed of the electric motor 2, in particular from the measurements of the position of the motor and of the current measured across the motor.

[0031] In the following step 445 the voltage reference of the selected electrical control gain is sent to the power block 10 .

[0032] Finally, in step 450 , the voltage block delivers a control voltage to the synchronous electric motor 2 .

[0033] The estimation of the speed of a synchronous electric motor 2 with permanent magnets can be made in different ways from the electrical quantities (voltage and current) of the electric motor.

[0034] The mathematical model below represents the modeling of a synchronous electric motor with surface permanent magnets (without salient poles) and the physical quantities of the three phases S1, S2, S3, the resistance R S , the current on each of the phases i S1 , i S2 , i S3 , the voltage on each of the phases u S1 , u S2 , u S3 , and the electric flux φ on each of the phases S1 , φ S2 , φ S3 has.

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[0035] In the steady state, the above quantities (u S1 , u S2 , u S3 ) is a sine quantity phase shifted by 2π / 3.

[0036] By constructing an electric machine, i S1 +i S2 +i S3 It is known that =0.

[0037] By applying the Clarke transformation to the three-phase quantities, i.e., by applying the following two transformation matrices:

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[0038] The following relationship is obtained:

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[0039] i Sγ By the construction =0,

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[0040] The model shows that this third component has no functional role to the extent that the current magnitude is zero and this component does not participate in torque generation. A conventional two-phase system is described as follows:

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[0041] i Sγ By the construction =0,

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[0042] At steady state, the quantity (u Sα , u Sβ ) is a sinusoidal quantity phase shifted by π / 2.

[0043] By substituting the flux variables, the equations of a permanent magnet synchronous electric motor without salient poles are obtained.

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[0044] The model below represents in matrix form a synchronous electric motor having permanent magnets in the following fixed reference frame:

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[0045] In the following notation:

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[0046] With the mechanical and electrical conditions established, the system reaches a steady-state equilibrium. The motor is driven by the load torque constraint τ EM = τ LOAD It rotates at a speed of ω=dθ / dt under The torque formula is as follows:

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[0047] This results in the following formula:

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[0048] This variable allows

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[0049] In reality, it is not possible to know the phase θ specifically from the electrical signals taken individually. It is possible to estimate the pulsation of the electrical signals, an image of the velocity, i.e., the derivative of the position.

[0050] To estimate the speed from the phase of an electrical quantity, for example, the angle of the voltage vector may be calculated by directly calculating the inverse of the tangent function.

[0051] It is also possible to use a PLL (Phase lock loop) type algorithm.

[0052] In all cases there is a phase shift φ between the phase of the electrical quantities (which depends primarily on the control strategy) and the rotor position, which must be taken into account in the previous equations for the rotating reference frame. This gives:

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[0053] The speed of the electric motor can also be determined from the amplitude of the electrical quantities. From equation 38 above, the current speed estimate based on the voltage amplitude and the current amplitude can also be developed by solving

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[0054] Note that in the previous equations, there is no objection to using quantities in a fixed reference frame instead of a rotating reference frame.

[0055] The previous equation gives us two solutions, one positive and one negative. We can remove the ambiguity by choosing a speed whose sign matches the direction of motion of the voltage vector (if its phase increases or decreases).

[0056] To construct the dynamic estimation, we employ a model of the motor in a fixed reference frame (equations (23) and (24)) to obtain the speed

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[0057]

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[0058] Then we can build the observer.

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[0059] The quantity that corresponds to the speed estimate

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[0060]

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[0061] Classical studies of this system have shown the convergence of a speed estimator based on electrical quantities (Eq. 53) towards the actual speed.

[0062] The consistency of the position or speed measurements can be verified by a comparison of the information obtained from the speed measurement on the one hand and the information obtained from the speed estimation on the other hand. The speed estimate can be directly a value obtained from an electrical quantity such as equation (41) or equation (52), or a static or dynamic combination of speed measurements and speed estimates from these electrical quantities can be used. The verification of the consistency consists for example in calculating the gap between the two pieces of information and in defining an acceptable threshold of the difference between these two estimates, which must be equal in the steady state, for example 1 Hz.

[0063] Conventional control of a permanent magnet electric motor consists of calculating a reference voltage vector in the control reference frame:

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[0064] gain matrix

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[0065] Then the reference voltage is

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[0066] The invention thus makes it possible to provide continuity of control of the voltage of the electric motor even in the presence of a gross fault in which information about the measurement of the motor's position is lost. Detection of the fault and reconfiguration of the electrical control means through adaptation of the gains and, alternatively, of the current reference, then makes it possible to guarantee the performance of the mechanical movement of the electric motor.

[0067] In other words, the invention consists in controlling this motion and thereby reconfiguring the motor control mode during flight to compensate for position sensor failures. This on-the-fly reconfiguration is made possible by the invention by controlling the consistency of the speed / position information with respect to electrical measurements and adapting the controls depending on the consistency of these measurements.

[0068] The present invention therefore proposes control of the consistency of speed / position measurement information with respect to electrical measurements, enabling detection of position measurement anomalies from electrical / mechanical behavior analysis without speed / position measurement information, reconfiguration of electrical and mechanical control units for controlling movement, and adaptive control between control means having information on speed / position measurement values ​​and control means having information on measurements of electrical quantities.

Claims

1. A method for controlling a synchronous electric motor, The aforementioned method, Generation of a mechanical torque reference from a mechanical setpoint (400), The measurement of the position of the synchronous electric motor (405), Determination of the speed of the synchronous electric motor from the measured value of the aforementioned position, Measurement of the current generated by the synchronous electric motor (410), The generation of a voltage reference from the aforementioned mechanical torque reference (445), A method for controlling a synchronous electric motor, comprising generating a control voltage from a reference voltage (450), The aforementioned method, Monitoring of abnormalities in the measurement of the position of the synchronous electric motor, The system further includes adjustment of the electrical control gain (440) in response to the detection or non-detection (435) of an abnormality in the measurement of the position of the synchronous electric motor, A method wherein the voltage reference depends on the value of the electrical control gain, and monitoring for abnormalities in the measurement of the position of the synchronous electric motor includes control (430) of the consistency between the position or speed information and the current information.

2. The monitoring of abnormalities in the measurement of the position of the synchronous electric motor is as follows: Estimation of the speed of the synchronous electric motor from the speed determined from the current measurement taken across the position and the synchronous electric motor (420), A comparison between the estimated speed and the measured speed, The method according to claim 1, further comprising reporting a measurement anomaly (435) in accordance with the result of the comparison with respect to a detection threshold.

3. An electrical control system (4) for a synchronous electric motor (2), The aforementioned electrical control system (4) is The mechanical setpoint (Cm) is received and the mechanical torque reference (R Ｃ A mechanical control block (8) configured to send out ) Voltage reference (R) is a function of the torque reference sent by the mechanical control block (8). Ｔ An electrical control block (9) configured to send out ) The voltage reference (R) sent out by the electrical control block (9) Ｔ A control voltage (T) is supplied to the synchronous electric motor (2) as a function of ). Ｃ A power block (10) configured to send out ) The position sensor (6) of the rotor of the synchronous electric motor (2) controlled by the electrical control system (4), An electrical control system (4) for a synchronous electric motor (2) comprising means (7) for measuring current across the synchronous electric motor (2) controlled by the electrical control system (4), The aforementioned electrical control block (9) further, Means (92) for detecting abnormalities in the measurement of the position sensor (6) by controlling the consistency between position or velocity information and current information, A module (94) for adjusting the electrical control gain is configured to adjust the electrical control gain in response to the detection or non-detection of an abnormality in the position measurement of the synchronous electric motor, An electrical control system (4) for a synchronous electric motor (2), comprising a control module (96) configured to output a voltage reference from a mechanical torque reference, a current measured across the synchronous electric motor, and an electrical control gain output by a compatible module (94).

4. The means (92) for detecting the abnormality is, A module (922) for estimating the speed of the synchronous electric motor from the voltage and current of the synchronous electric motor, A comparator (924) configured to compare the determined speed with the speed measured by the position sensor, The electrical control system (4) according to claim 3, further comprising a module (926) that reports a measurement anomaly in accordance with the result of the comparison with respect to a detection threshold.

5. The electrical control system (4) according to claim 3, wherein the power block (10) further comprises a power converter.

6. An electrical system (1) comprising a synchronous electric motor (2) connected to a load (3), and an electrical control system (4) according to any one of claims 3 to 5, connected to the synchronous electric motor (2).

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