Method for controlling an electric motor in case of a speed measurement anomaly

Abstract

Method for controlling an electric motor in case of a speed measurement anomaly. Method for controlling a synchronous electric motor comprising generating (400) a torque reference from a mechanical setpoint, measuring (405) the position and determining the motor speed, measuring (410) the current generated by the motor, generating (445) voltage references from the torque reference, and generating (450) control voltages from the reference voltages. It includes monitoring for a position measurement anomaly, adapting (440) the electrical control gains based on whether or not (435) a position measurement anomaly of the electric motor is detected, and in that the voltage references depend on the values ​​of the electrical control gains. Figure for the abstract: Fig. 4

Description

Title of the invention: Method for controlling an electric motor in case of a speed measurement anomaly technical field

[0001] The invention relates to the control of an electric motor and more particularly to the control of an electric motor following an anomaly in the measurement of the speed of its rotor. Previous technique

[0002] For a control system configured to control an electric motor configured in speed or position, a rotor speed sensor is generally used in order to build a robust and efficient control law.

[0003] When the position information becomes unusable, the system becomes inoperative due to a lack of information to replace the measurement. When the anomaly occurs during a controlled movement, it is necessary to react instantly to continue the movement and maintain the expected level of performance.

[0004] There are different methods of controlling a sensorless electric motor which can be classified into two categories: on the one hand, methods operating from electrical quantities as applied or measured on an electric motor, the electrical quantities being able to be instantaneous quantities or quantities averaged over a period of time which depends on the power stage and its control strategy, and, on the other hand, methods operating from high frequency components of electrical quantities, added to the main control.

[0005] As schematically illustrated in [Fig. 1], the principle of controlling an electric motor without a position sensor based on fundamental electrical quantities comprises a motor driven by voltage via an electrical controller. The electrical controller receives as input a measurement of the current in the motor, a value of the motor speed estimated from the motor voltage and current, and a mechanical torque reference provided by a mechanical controller. The mechanical controller determines the mechanical torque reference from a speed or position reference, the speed estimate, and control parameters of the electrical controller.

[0006] As schematically illustrated in [Fig. 2], the principle of controlling an electric motor without a position sensor using high-frequency electrical quantities differs from the principle of [Fig. 1] in that it includes a high-frequency module upstream of the motor and the estimation performed is based on the speed or the engine position.

[0007] In defining the architectures of known electrical systems, the presence of a position or speed measurement is known at the time of the control system configuration. It is in this phase that the choice is made of a controller that manages or does not manage the position or speed measurement.

[0008] The control law is configured either to operate with the information provided by the position sensor, or it is configured to operate without this information. Reconfiguration from one to the other can only occur after a shutdown phase. This results in the ongoing movement ending uncontrollably. A faulty position / speed measurement will, through the control system, generate voltages on the motor that do not correspond to the motor's state. This can induce a range of undesirable behaviors that must be captured through various monitoring functions.

[0009] In known systems, when a fault is detected, it is only proposed to generate a warning or a fault. Description of the invention

[0010] The main purpose of the present invention is therefore to provide a solution for reconfiguring the motor control mode on the fly, to compensate for the failure of a motor position sensor.

[0011] In 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 the position and determining the speed of the electric motor from the position measurement, measuring the current generated by the electric motor, generating voltage references from the mechanical torque reference, and generating control voltages from the reference voltages.

[0012] The method further includes monitoring an anomaly in the position measurement of the electric motor, adapting the electrical control gains according to whether or not an anomaly in the position measurement of the electric motor is detected, the generated voltage references depending on the values ​​of the electrical control gains.

[0013] The method according to the invention thus makes it possible to provide continuous control of the electric motor voltage even in the presence of a major failure, namely the loss of motor position measurement information. Detecting the failure and then reconfiguring the electrical control means by adapting the gains, and alternatively the current reference, ensures the performance of the electric motor's mechanical movement.

[0014] In one aspect of the method, monitoring an anomaly in the position measurement of the electric motor includes estimating the speed of the electric motor from the speed determined from the position measurement and the current measured at the motor terminals, comparing the estimated speed to the determined speed, and reporting a measurement anomaly based on the result of the comparison against a detection threshold.

[0015] 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 setpoint and 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 rotor position sensor of the electric motor that said electrical system controls, and means for measuring the current at the terminals of the electric motor controlled by the electrical control system.

[0016] According to a general feature of the system according to the invention, the electrical control unit further comprises: - a means of detecting a measurement anomaly in the position sensor, - an electrical control gain adaptation module configured to adapt the gains based on whether or not a position measurement anomaly of the electric motor is detected, and - a control module configured to deliver voltage references from the mechanical torque reference, the current measured across the electric motor terminals, and the electrical control gains delivered by the adaptation module (94).

[0017] In a first aspect of the system according to the invention, the anomaly detection means includes a motor speed estimation module from the motor voltage and current, a comparator configured to compare the determined speed to the speed measured by the sensor, and a measurement anomaly reporting module based on the result of the comparison with a detection threshold.

[0018] In a second aspect of the system according to the invention, the power control block further includes a power converter.

[0019] According to another object of the invention, an electrical system is proposed comprising an electric motor coupled to a load, and an electrical control system as defined above coupled to the electric motor. Brief description of the drawings

[0020] Other features and advantages of the present invention will become apparent from the description given below, with reference to the attached drawings which illustrate an example of an embodiment without any limiting character.

[0021] [Fig-1] Fig.1 schematically represents an electrical system 1 comprising a synchronous electric motor 2 and a control circuit 4 according to one embodiment of the invention.

[0022] [Fig.2] Figure [Fig.2] schematically presents in more detail an electrical system of control 4 of the synchronous electric motor 2 of the [Fig.l].

[0023] [Fig.3] Fig.3 is a schematic representation in more detail of a block of electrical control 9 of the [Fig.2].

[0024] [Fig.4] Figure 4 schematically presents a flowchart of a process of control implemented by the electrical control system 4 of the synchronous electric motor 2 according to an embodiment of the invention. Description of embodiments

[0025] Figure 1 schematically represents an electrical system 1 comprising a permanent magnet synchronous electric motor 2 coupled to a load 3 and an electrical control system 4 coupled to the electric motor 2.

[0026] The electrical control system 4 of the synchronous electric motor 2 includes 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 at the terminals of the synchronous electric motor 2.

[0027] As illustrated in [Fig.2] which schematically presents in more detail an electrical control system 4 of the synchronous electric motor 2, the control assembly 5 comprises a mechanical control block 8 configured to receive a mechanical setpoint Cm and deliver a mechanical torque reference Rc, an electrical control block 9 configured to deliver a voltage reference RT as a function of the torque reference Rc delivered by the mechanical control block 8, and a power block 10 configured to deliver a control voltage Tc to the electric motor 2 as a function of the voltage reference RT delivered by the electrical control block 9.

[0028] As illustrated in [Fig. 3], which schematically represents an electrical control block 9 in more detail, the electrical control block 9 comprises a means 92 for detecting a measurement anomaly of the position sensor 6, an electrical control gain adaptation module 94 configured to adapt the gains according to whether or not a position measurement anomaly of the synchronous electric motor 2 is detected, and a control module 96 configured to deliver voltage references RT from the mechanical reference Rc, of the current measured at terminals of the electric motor 2 by the current measurement means 7, and the electrical control gains delivered by the adaptation module 94.

[0029] In addition, the anomaly detection means 92 includes a module 922 for estimating the motor speed from the motor voltage and current, a comparator 924 configured to compare the determined speed to the speed measured by the position sensor 6, and a module 926 for reporting a measurement anomaly based on the result of the comparison with a detection threshold.

[0030] Figure 4 shows a flowchart of a control process implemented The operation is carried out by the electrical control system 4 of the synchronous electric motor 2. The method comprises a first step 400 of generating a mechanical torque reference from a mechanical setpoint. In a second step 405, a position measurement is then performed using the position sensor 6 and the speed of the electric motor 2 is determined from the position measurement, and, in a step 410, the current generated by the electric motor 2 is measured.

[0031] Next, an anomaly measurement monitoring of the position sensor 6 is performed. To this end, in step 430, the consistency of the position or speed information with the current information is checked, and whether or not an anomaly exists between said information is determined in step 435. The information consistency check includes, in particular, an estimation of the speed or position of the motor from electrical quantities such as the current generated by the motor and a comparison of this estimated speed or position with the measured position or a speed determined from the measured position. This comparison can be carried out by calculating the difference between the estimated speed and the measured speed and verifying that this difference remains limited to a range of variation expected with regard to measurement noise and the control dynamics.

[0032] Following the check of the consistency of the information, in a step 420, an estimate of the speed of the electric motor 2 can be provided from the position measurements and the current measured at the terminals of the motor in particular.

[0033] In a subsequent step 445, the voltage references for the selected electrical control gains are delivered to the power block 10.

[0034] Finally, in a step 450, the voltage block delivers a control voltage to the synchronous electric motor 2.

[0035] Estimating the speed of the permanent magnet synchronous electric motor 2 from the electrical quantities (voltage and current) of the electric motor can be done in different ways.

[0036] The following mathematical model represents a modeling of a synchronous electric motor with surface permanent magnets (without protrusion) with the physical quantities of three phases S1, S2, S3, with the resistance Rs, the current i on each of the phases isl, iS2, is3, and the voltage on each of the phases us[, uS2, us3, and the electric flux on each of the phases<pSi, Ç> s2, q>s3- [Math 1] A <psi + Rs iSi - usi [Math 2] A <ps2 + rs is2="Us2" [math 3] am 4- is3="uS3" avec le flux q>expressed by the magnetic coupling matrix equation: [Math 4] / LM 'isi\ vte / cos(0) \ COS^-^) \œs(e-Ç) / With M representing the value of the mutual stator inductance, and L representing the value of the self-stator inductance, <1> M represents the steady-state flux value, and 0 represents the position of the magnet. The electromagnetic torque rEM is expressed by the following equation: [Math 5] Tem = - nP ■ <|)M ■ ( isl ■ sin ( 0 ) + iS2 ■ sin ( 0 - ^ ) + iS3 ' sin (0 ' ¥ ) ) With np representing the number of pole pairs.

[0037] In steady state, the quantities (us[, uS2, us3) are sinusoidal quantities phase-shifted by 2ir / 3.

[0038] We know from the construction of the electrical machine that iSi+ iS2 + is3 = 0.

[0039] By applying the Clarke transform to the three-phase quantities, that is to say by applying the following two transformation matrices: [Math 6] [Math 7] we can define for each quantity X a new coordinate vector (or variables): [Math 8]

[0040] We obtain the following relationships: [Math 9] A <p^ + Rs iS(7 = uSh [Math 10] ^ <psp+Rs isf5 = usp [Math 11] A^ + Rs iSY = uSy Given that, by construction, iSx = 0, and [Math 12] / Ldq 0 0 0 ^Sa isp + (b. . ' ^cos(O) ' sin(0) 0 Ldq ' 0 0 Ly 1 ÂSy \ 0 / [Math 13] i -sin(0) ' tem ~ 3 . 2 nP- A . 'Sapy cos(6) ' o / Where Ldq = LM, and L7 = L + 2.M.

[0041] This model shows that the third component has no functional role since the current quantity is zero and this component does not participate in torque generation. The following is the representation of the classic two-phase system: [Math 14] A + Rs iSa = Usu [Math 15] A + Rs iSi3 - Usp Given that, by construction, iSx = 0, and [Math 16] (pSa = LdqiSa + • cos (0) [Math 17] (p^ = Ldqisp + • sin (6) [Math 18] Tem = | np(- sin (6) ■ iSa + cos (0) • isp) In steady state, the quantities (usa, usp) are sinusoidal quantities phase-shifted by jt / 2.

[0042] By substituting the flux variables, we obtain the equations for the permanent magnet synchronous motor without protrusions: [Math 19] = Usct+ w ■<Dm • sin(e) -Rs [Math 20] - Usp- u> • ' cos( #) - Rs isp [Math 21] A0=w (It [Math 22] Tem = | np ( - sin ( 8 ) • iSa + cos ( 8 ) ) <t>M The following model represents, in matrix form, a permanent magnet synchronous electric motor in the following fixed coordinate system: [Math 23] A0 — dt [Math 24] ( J ) = - Rs • ( J ) - «> • J • 9) • ( *" ) + ( J; ) [Math 25] _3n TEM - 0 / / \ 'sp / With the following notations: [Math 26] Usap = ( , the motor voltage, [Math 27] / \, the current of the US|> ' hSap = • w

[0043]

[0044] motor, 0, the position of the magnet, co, the speed of the magnet, and the matrices: | Math 281, / 0 -IV Mi o) [Math 29] A0) = œsA0.1 + sinAe.} = / cosAS - smA6\. sinAO cosAO / In steady-state mechanical and electrical regimes, the system reaches stationary equilibrium. The motor rotates at a speed co = dO / dt under a load torque constraint rEM = r load*. The following expression for the torque: [Math 30] tEM " 5 ' nP ■ allows the current to be expressed in a general form: [Math 31] / iSa\ . = R(0) ■ VKsp / w With [Math 32] ]„ — and ID any value (which is often fixed by the controller). Then comes the expression: [Math 33] which allows you to write [Math 34] Zip With the variables [Math 35] (¾)V) 'i< (^)(M

[0045] In practice, it is not possible to know the phase 0 precisely from the individual electrical signals. It is possible to estimate the angular frequency of the electrical signals, a representation of the velocity, that is to say, the derivative of the position.

[0046] To estimate the speed from the phase of the electrical quantities, it is sufficient to calculate the angle of the voltage vector with a direct calculation of the inverse of the tangent function for example.

[0047] It is also possible to use a PLL (Phase lock loop) type algorithm.

[0048] In all cases, there is a phase shift $ between the phase of the quantities electrical components and the rotor position (which depends primarily on the control strategy) must be taken into account in the preceding expressions of the rotating frame of reference. come : [Math 36] / Ksa) d / ü \ (\[Math 37] = R(0-(p)- VSp / Hq / / They» 1 / One \ and [Math 38] (¾) =«'■.?■ W (!") +RS- (ij + x-.'-R^) ■ (^)

[0049] The speed of the electric motor can also be determined from the amplitudes of the electrical quantities. From expression [Math 38], an estimate of the speed can also be extracted, this time based on the amplitude of the voltage and current, by solving the following equation: [Math 39] ( (UD-RS-ID) +œ-Ldq-lQ) + ( (Uq-Rs■ Iq) - w■ Ldq■ ID) = co2■ That is to say [Math 40] (^-L^-flB + I^))-^+2^-(lD-UQ-IQ-UD)-MU^^^ And [Math 41] -L^Pk±JU^ —------------— ---------- With : [Math 42] P# ~ / p ■ UQ - Iq • UD[Math 43] PA = ID ■ UD + Iq • Ug[Math 44] I2 = il + / |,l Malh 45] OT o

[0050] Note that there is no objection to using the quantities in the fixed frame instead of a rotating frame in the preceding formulas.

[0051] The preceding expression gives two solutions (one positive, one negative). It is possible to resolve the indeterminacy by selecting the velocity whose sign is consistent with the direction of motion of the tension vector (whether its phase increases or decreases).

[0052] By using the engine model in the fixed frame (equations [Math 23] and [Math 24]), to construct a dynamic estimate, we choose to place ourselves in a frame rotating at the speed: [Math 46] A0=^avcc: [Math 47] M / ¾) [Math 48] I — Kl ü I ■ I Vsp / v 7 \1q / / UD \ We then have: W [Math 49] A0=a,[Math5O] Aq — gj[Math 51] v vq / v \uq /

[0053] We can then construct the observer: [Math 52] M ( 6 ) " - ( R r Z ♦ -^)-(1)-^(^) + (^) + ^-((^)-(1)) \ / < ' \ 1 \ / / [Math 53] da _ / / ID \ / Ç> \ j II remains to define the structure of the gains which guarantees that the quantity ô, corresponding to the velocity estimate, tends towards œ. With the notation -- X - X' al°rs 'a difference between the motor model and the observer can to write: [Math 54] ^Ô0^Ôœ[Math55] + ¼[M-ÔO-ôœ-UM+OCe) vq / v 17 W \ 0 / \ 0 / [Math 56] [Math 57] 2Cp = - Rs ■ 1 + Kpq ■ J[Math 58] / 0 \ leads to ~ KI ' \kIQ / [Math 59] Ldq ■ £SID = ( Ldq ■ S + KPQ ) • SIq + œ ■ 4>M ■ 60[Math 60] Ld(|'^ôlQ= - (Uiq'tà + KpQ) • 6Id-(|>m-ôœ[Math 61] -K{q'ÔIq-

[0054] The classical study of this system shows the convergence of the velocity estimator based on electrical quantities [Math 53] towards the actual speed.

[0055] Comparing the information obtained by measuring the velocity with the information obtained by estimating the velocity allows for validation of the consistency of the position or velocity measurement. The velocity estimate can be a value obtained directly from electrical quantities, for example [Math 41] or [Math 52]; it is also possible to use a static or dynamic combination of the velocity measurement and the velocity estimate from electrical quantities. Validating consistency involves, for example, calculating the difference between the two pieces of information and defining an acceptable threshold for the difference between these two estimates, which must be equal in steady state, for example, 1 Hz.

[0056] A conventional control method for a permanent magnet electric motor consists of calculating a reference voltage vector in the following control frame:

[0057] [Math 62] T rREF - w ■ -7 ■ Ljq ■ \UQ / [Math 63] œs - œ [Math 64] ™0s = ws / tREF 4) rREF / tref\ I 'D tREF Uq / M + UCTRL-D 0 / \UcRTL-Q / With [Math 65] / UCTRL.D \ UcRTL-Q [Math 66] dpx CTRL-P tREF UQ UID ^IQ / tREF t ï _ XD - H) CTRL-I ' tREF t Uq 'tQ / where / UqEF\ corresponds to the reference voltage, corresponds to the angular frequency of t tREF \ UQ / control reference, 0s corresponds to the pulsation of the control reference, l^1'1 tREF UQ

[0058] corresponds to the reference current, / it corresponds to the motor current in the W control reference, and æ corresponds to the estimated speed of the motor. The gains matrices ^ctrl-p and [Math.62][Math63][Math64]With [Math65][Math66] CTRL-I are to be calculated to ensure control performance. This performance depends on the estimated velocity dynamics. A set of gains ( [Math.62][Math63][Math64]With[Math65][Math66] "^-CTRL-P [Math.62][Math63][Math64]With [Math65][Math66] ^CTRL-I ) by speed estimation strategy, whether the estimated speed of the motor comes from measurement, or from an estimation strategy based on electrical quantities, or a mix of both.

[0059] The reference voltage is then transformed into the three voltages to be applied to the phases of the motor, in two steps:

[0060] from a rotation of the angle of the control frame

[0061] / uJEF\ / cos0s -sin0s\ / üpEF\ UnQs cos0s / *U§EF /

[0062] [Math.67] then with [Math7] / « S1 \ m US2 =Pafi^123- UpEF KJ [ 0 /

[0063] The invention thus makes it possible to provide continuous control of the electric motor voltage even in the presence of a major failure, namely the loss of motor position measurement information. Detecting the failure and then reconfiguring the electrical control system by adapting the gains, and alternatively the current reference, ensures the performance of the electric motor's mechanical movement.< / t>

Claims

Claims

1. Method for controlling a synchronous electric motor, comprising a generation (400) of a mechanical torque reference from a mechanical setpoint, a measurement (405) of the position of the electric motor and a determination of the speed of the electric motor from the position measurement, a measurement (410) of the current generated by the electric motor, a generation (445) of the voltage references from the mechanical torque reference, and a generation of the control voltages (450) from the reference voltages, characterized in that it further comprises a monitoring of a position measurement anomaly of the electric motor, an adaptation (440) of the electrical control gains as a function of the detection or not (435) of a position measurement anomaly of the electric motor, and in that the voltage references depend on the values ​​of the electrical control gains,monitoring an anomaly in the position measurement of the electric motor comprising a check (430) of the consistency of the position or speed information with the current information.,

2. The method of claim 1, wherein monitoring an electric motor position measurement anomaly comprises estimating (420) the speed of the electric motor from the speed determined from the position measurement and the current measured at the motor terminals, comparing the estimated speed to the measured speed, and reporting (435) a measurement anomaly based on the result of the comparison with respect to a detection threshold.

3. Electrical control system (4) of a synchronous electric motor (2) comprising a mechanical control unit (8) configured to receive a mechanical setpoint (Cm) and deliver a mechanical torque reference (Rc), an electrical control unit (9) configured to deliver a voltage reference (RT) as a function of the torque reference delivered by the mechanical control unit (8), a power unit (10) configured to deliver a control voltage (Tc) to the electric motor (2) as a function of the voltage reference (RT) delivered by the electrical control unit (9), a position sensor (6) of the rotor of the electric motor (2) that said electrical control system (4) controls, and means (7) for measuring the current at the terminals of the electric motor (2) controlled by said electrical control system (4). control (4), characterized in that the electrical control block (9) further comprises: - a means (92) for detecting a measurement anomaly of the position sensor (6) via a check of the consistency of the position or speed information with the current information, - a module (94) for adapting the electrical control gains configured to adapt the gains according to the detection or not of a position measurement anomaly of the electric motor, - a control module (96) configured to deliver voltage references from the mechanical torque reference, the current measured at the terminals of the electric motor, and the electrical control gains delivered by the adaptation module (94).

4. Electrical control system (4) according to claim 3, wherein the anomaly detection means (92) comprises a module (922) for estimating the speed of the motor from the voltage and the current of the motor, a comparator (924) configured to compare the determined speed with the speed measured by the sensor, and a module (926) for signaling a measurement anomaly as a function of the result of the comparison with respect to a detection threshold.

5. An electrical control system (4) according to one of claims 3 or 4, wherein the power control unit (10) further comprises a power converter.

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

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