METHOD FOR MONITORING AN ANGULAR DISPLACEMENT SENSOR IN AN ELECTRICAL MACHINE

Abstract

Method for monitoring an angular displacement sensor of an electric machine rotor, the method comprising the steps: - acquiring a target torque (CCt) to be delivered, - acquiring a voltage (U) and a current (I) consumed by the electric machine, - acquiring an efficiency coefficient (μ) from a calibration table, - deducing a theoretical rotational speed, - calculating a theoretical angular stroke (θt) traveled during a reference time interval, - acquiring pulses resulting from the rotor rotation via the sensor, - counting the number of pulses detected during the time interval, - deducing a measured angular stroke (θm) traveled during the time interval, - calculating a difference in angular stroke between the measured and theoretical angular strokes, - triggering a machine reconfiguration if the difference in angular stroke is greater than a decision threshold. Figure 3

Description

Title of the invention: METHOD FOR MONITORING A DISPLACEMENT SENSOR ANGULAR IN AN ELECTRICAL MACHINE

[0001] The invention relates to a method for monitoring an angular displacement sensor of a rotor of an electric machine.

[0002] In an electric or hybrid vehicle, an electric machine is used to cause the vehicle to move in zero-emission mode.

[0003] The electrical machine in question comprises a rotor which rotates relative to a stator.

[0004] The electric machine includes an angular displacement sensor consisting of a rotating target, fixed in rotation to the rotor, and a stationary detection element arranged opposite the rotating target.

[0005] The rotating target includes lobes, projections or teeth whose passage is detected by the detection element (the latter is also called 'reading head').

[0006] Thus the angular displacement sensor of interest here makes it possible to determine the angular stroke of said rotor and the rotational speed of the rotor.

[0007] It should be noted that the angular displacement sensor does not allow for the determination of an absolute angular position. The angular displacement sensor detects pulses resulting from the passage of lobes in front of the detection element.

[0008] The sensor can also detect the direction of movement, e.g. forward or reverse.

[0009] The proper functioning of the angular displacement sensor is critical to ensure proper operation of the machine, to estimate the torque delivered by the electric machine and thus to ensure that the torque delivered to the wheels of the vehicle is consistent with the driver's intention expressed via the accelerator pedal.

[0010] It has already been proposed to verify the consistency of the information delivered by the sensor, for example for sensors that deliver sine and cosine information of the current angular position. Some simple failures of the angular displacement sensor can be detected by a likelihood test.

[0011] A need has arisen to propose a detection method that can detect early a failure of the angular displacement sensor, including in particular the detection of certain defects with random or intermittent occurrence.

[0012] In this context, the invention proposes a method for monitoring an angular displacement sensor of a rotor of an electric machine, the electric machine being Equipped with an angular displacement sensor and an inverter capable of providing instantaneous voltage and current consumption values, the process includes the following steps: - acquire a target torque to be delivered, - to acquire the voltage and current consumed by the electrical machine, - acquire a coefficient of performance from a calibration table, - to deduce a theoretical rotational speed, - calculate a theoretical angular displacement covered during a reference time period, - to acquire, via the angular displacement sensor, pulses resulting from the rotation of the rotor, - count the number of pulses detected by the sensor during the reference time period and, - to deduce a measured angular stroke covered during the reference time period, - calculate the difference in angular stroke between the measured angular stroke and the theoretical angular stroke. - trigger a reconfiguration of the machine if the difference in angular stroke is greater, in absolute value, than a first threshold.

[0013] Thanks to these provisions, it is possible to detect an inconsistency in the angular speed of the rotor at a very early stage. This inconsistency may be due, for example, to a random malfunction of the angular displacement sensor.

[0014] Advantageously, the correspondence between the theoretical rotational speed calculated using the voltage, current and efficiency coefficient parameters, and the rotational speed reported from the displacement sensor with the target on the rotor is checked in real time.

[0015] A target defect can be detected, for example a broken tooth, or a low-level signal processing defect affecting, for example, pulse shaping circuits.

[0016] According to an advantageous option, the calibration table is derived from measurements carried out during one or more previous characterization campaigns of the electrical machine.

[0017] Detailed knowledge of the efficiency coefficient q of the electrical machine makes it possible to calculate a precise theoretical value of rotational speed from the voltage and current consumed.

[0018] Usually the efficiency coefficient q is between 0.85 and 0.97 but my precise value depends on the operating conditions, hence the need to use a multidimensional calibration table.

[0019] According to one embodiment, the first threshold is calibrable and is preferably between 30° and 45°.

[0020] The tolerance for a point drift in the detection system can thus be adjusted. The angular tolerance can thus be adjusted to the value of the reference time interval.

[0021] According to one embodiment, the reference time interval is calibrable and is between 40 ms and 100 ms.

[0022] The responsiveness of the detection system can thus be adjusted. It is noted that the detection system is very responsive because it reacts in less than one second.

[0023] According to one embodiment, the reference time period is dependent on the theoretical rotation speed, and preferably the reference time period is generally decreasing as a function of the theoretical rotation speed.

[0024] The reference time interval must be sufficient to accurately measure the angular displacement via the sensor pulses. The reference time interval must be small enough to ensure a reliable response time. Hence the advantage of having at least a sufficiently large reference time interval for low rotational speeds, and at least a smaller reference time interval for higher rotational speeds.

[0025] According to one embodiment, the measured angular stroke (0m) is calculated as follows: 0m = Ntop x 360 / NN, where NN is the number of pulses per rotor revolution and Ntop is the number of pulses counted during the reference time period.

[0026] According to one embodiment, reconfiguring the machine involves stopping the operation of the electric machine. This ensures a high level of safety. Indeed, if the angular displacement sensor malfunctions, it cannot be ruled out that the torque delivered by the machine will not match that desired by the driver. In particular, producing a torque delivered by the machine that exceeds the driver's desired torque could pose a danger to the occupants, as well as to other motorists or pedestrians.

[0027] According to one embodiment, the electric machine is to be rehabilitated, subject to a rehabilitation condition, in order to restore its nominal control operation. Rehabilitation allows the electric machine to return to normal operation. The rehabilitation / restoration condition may be subject to intervention by the authorized after-sales network for the vehicle type in question.

[0028] The present invention also relates to a monitoring system for an angular displacement sensor of a rotor in an electric machine, comprising a motor control unit and a supervisory computer, the electric machine being equipped with an angular displacement sensor, an inverter capable of providing instantaneous values ​​of voltage and current consumed, the supervisor delivering a target torque to be delivered to the wheels, the control unit being configured to implement the process as defined previously.

[0029] According to one embodiment, the electric machine comprises a single rotor angular displacement sensor. This method advantageously avoids the need to install a redundant second sensor.

[0030] The present invention also relates to an electric or hybrid motor vehicle, comprising a monitoring system as defined above.

[0031] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: [Fig.1] schematically illustrates a synoptic diagram of an example of a monitoring system in which the monitoring method according to the present invention can be implemented; [Fig.2] schematically illustrates an example of a rotor angular displacement sensor; [Fig.3] represents a flowchart of an example of a monitoring method according to the present invention; [Fig.4] represents a graph linking the reference time interval to the rotational regime.

[0032] In the different figures, the same references designate identical or similar elements.

[0033] In [Fig. 1], certain elements of an electric or hybrid vehicle are shown schematically. The vehicle in question may be a passenger car, a utility vehicle, a van, a recreational vehicle, a minibus, a coach, a truck, etc.

[0034] The electric machine 1 is sized to move the vehicle in zero-emission mode, even though the vehicle in question includes an internal combustion engine. It is therefore an electric machine of a few tens of kilowatts.

[0035] The electric machine 1 is controlled by a control unit 4 via a power current block formed by an inverter 3. In the jargon, the control unit 4 is called Motor Control Unit (MCU for short).

[0036] An angular displacement sensor 2 is provided which includes a rotating part called the target and a stationary part.

[0037] The target 10 includes projections 11 which are formed like teeth or lobes.

[0038] On the housing, there is a reading head 12, also called stationary detection element, arranged opposite the rotating target 10.

[0039] There may be a second read head 13, in order to determine the direction of rotation of the target. For example, the pulses that are generated by the passage Teeth or lobes are offset in quadrature between the two reading heads, which allows for a very simple determination of the direction of rotation of the target.

[0040] Downstream of the rotor, a reducer R is provided, the output of which drives the wheel shafts via a differential not shown, and up to the wheels 7.

[0041] The monitoring system includes, in addition to the engine control unit 4, a supervisory computer 5. In the jargon, the supervisory computer 5 is sometimes called an eVCU.

[0042] The supervisory control unit 5 acquires the position of the accelerator pedal directly or indirectly and calculates a torque command to be delivered by the electric machine based on this. This torque command is denoted CCt.

[0043] Where appropriate, the supervisory computer 5 can arbitrate the torques to be supplied in the case where there is not only one electric machine (configuration with another electric machine or thermal engine).

[0044] The inverter 3 is configured to make available, in addition to the voltage prevailing at the stator windings, the current flowing in the windings, for example in each of the coils or the sum of the coil currents.

[0045] The respective real-time values ​​of voltage and current are denoted U and I.

[0046] Furthermore, the electrical machine 1 was characterized prior to use displayed here.

[0047] This characterization includes the determination of a coefficient of performance as a function of several parameters, it is therefore what is called a calibration table, here multidimensional.

[0048] The calibration table is derived from measurements carried out during one or more previous characterization campaigns of the electrical machine.

[0049] The efficiency coefficient is denoted by p. More precisely, Pmeca = Pelec x p, with Pmeca being the mechanical power, namely CC x co, and Pelec being the electrical power, namely U x I. It should be noted that CC is the mechanical torque delivered, and co is the rotational speed.

[0050] The efficiency coefficient p of the electric machine is measured on a test bench for each operating speed step co, for each torque step DC, for each voltage step U, for each supply current step I and for each stator temperature step Temp. One or more test and characterization campaigns of the electric machine 1 are thus carried out.

[0051] p = Fcalib (I, U, Temp, co, CC).

[0052] The mapping of the yield values ​​p recorded on the characterization bench is stored in a calibration table 8 in the memory of the control unit 4, MCU.

[0053] In view of the above, we have CC xco = Ux!xp. (x here denotes multiplication).

[0054] The theoretical rotational speed is calculated as follows: co = UxIxq / CC

[0055] The proposed process comprises the following steps, carried out iteratively.

[0056] The control unit 4 acquires the target torque CCt to be delivered to the wheels, from the supervisory computer 5.

[0057] The control unit 4 acquires the voltage U and a current I consumed by the electrical machine, which are instantaneous values.

[0058] The control unit 4 acquires the value of the efficiency coefficient p from the calibration table 8.

[0059] The control unit 4 deduces the theoretical rotation speed co, by the formula co = U x I xp / CCt.

[0060] The control unit 4 acquires a time horizon parameter called here the reference time interval, denoted DT. This parameter is calibrable or is subject to a logic of dependence on the rotation regime, which will be seen later.

[0061] The control unit 4 calculates the theoretical angular stroke 0t traveled during the reference time interval DT.

[0062] The aforementioned steps (boxes al and a2 of [Fig.3]) are carried out independently of the information delivered by the angular displacement sensor.

[0063] In parallel, the data delivered by the angular displacement sensor are of course exploited according to another branch of the process (boxes bl and b2 of [Fig.3])

[0064] The control unit 4 acquires, via the angular displacement sensor, pulses ('tops') resulting from the rotation of the rotor.

[0065] The control unit 4 counts the number of pulses detected by the sensor during the reference time interval DT.

[0066] The control unit 4 deduces the measured angular stroke, denoted 0m, traveled during the reference time interval DT. More precisely, 0m = Ntop x 360 / NN is calculated, where NN is the number of pulses per rotor revolution and Ntop is the number of pulses counted during the reference time interval. Here, the angles are expressed in degrees.

[0067] As illustrated in box c of [Fig. 3], the control unit 4 calculates a difference in angular stroke between the measured angular stroke 0m and the theoretical angular stroke 0t, in absolute value, i.e., Dif0 = 10m - 0tL

[0068] This difference in angular displacement DifO is compared to a first threshold denoted SD. The first threshold SD is calibrable. The first threshold SD is preferably between 30° and 45°.

[0069] If the angular stroke difference DifO remains below the first threshold SD, no particular action is taken, and the steps of the process are carried out again.

[0070] The steps are indeed iterative, the iteration period is on the order of ten milliseconds, or even less. According to one embodiment, the iteration period is on the order of 5 ms.

[0071] The control unit 4 sends this information back to the supervisor 5.

[0072] The supervisor 5 can trigger a reconfiguration of the machine if the difference of angular stroke, between the measured angular stroke 0m and the theoretical angular stroke 0t, is greater, in absolute value, than a first threshold SD.

[0073] Reconfiguring the machine (box labeled 91 in [Fig. 3]) may involve stopping the machine's operation. Information representing the fault in question is stored in the non-volatile memory of the control unit 4.

[0074] According to one possibility, the reference time interval DT is calibrable. According to another possibility, the reference time interval DT can be made dependent on the theoretical rotational speed co.

[0075] According to one example, the reference time interval DT is between 40 ms and 100 ms. The angular tolerance (threshold SD) can thus be adjusted to the value of the reference time interval DT.

[0076] According to one embodiment, a rehabilitation of the machine is planned, on a condition of rehabilitation.

[0077] The rehabilitation condition may be subject to intervention by the authorized after-sales network for the type of vehicle in question.

[0078] The rehabilitation condition may correspond to a new power supply cycle (e.g., new power-up).

[0079] As can be seen in [Fig.4], the process can be implemented from a minimum rotation speed of 50 revolutions per minute.

[0080] Still with reference to [Fig.4], the reference time period is generally decreasing as a function of the theoretical rotation speed.

[0081] As illustrated, this can be a series of steps (solid line) or an interpolation system (mixed line).

Claims

Demands

1. Method for monitoring an angular displacement sensor of a rotor of an electric machine (1), the electric machine being equipped with an angular displacement sensor (2), an inverter (3) capable of providing instantaneous values ​​of voltage and current consumed, the method comprising the steps: - acquiring a target torque (CCt) to be delivered, - acquiring a voltage (U) and a current (I) consumed by the electric machine, - acquiring an efficiency coefficient (q) from a calibration table (8), - deducing a theoretical rotational speed (œ), - calculating a theoretical angular stroke (0t) traveled during a reference time interval (DT), - acquiring, via the angular displacement sensor, pulses resulting from the rotation of the rotor, - counting the number of pulses detected by the sensor during the reference time interval and, - deducing a measured angular stroke (0m) traveled during the reference time interval (DT),- Calculate the difference in angular stroke between the measured angular stroke (0m) and the theoretical angular stroke (0t), - Trigger a machine reconfiguration if the difference in angular stroke is greater, in absolute value, than a first threshold (SD).

2. Method according to claim 1, characterized in that the calibration table (8) is derived from measurements carried out during one or more previous characterization campaigns of the electrical machine.

3. A method according to any one of claims 1 to 2, characterized in that the first threshold (SD) is calibrable and is preferably between 30° and 45°.

4. A method according to any one of claims 1 to 3, characterized in that the reference time interval (DT) is dependent on the theoretical rotation speed (œ), and preferably the reference time interval is generally decreasing as a function of the theoretical rotation speed.

5. A method according to any one of claims 1 to 4, wherein the measured angular stroke 0m is calculated as follows: 0m = Ntop x 360 / NN, where NN is the number of pulses per rotor revolution and Ntop is the number of pulses counted during the reference time interval (DT).

6. A method according to any one of claims 1 to 5, characterized in that the reconfiguration of the machine consists of stopping the operation of the electrical machine.

7. Method according to claim 6, characterized in that it provides for a rehabilitation of the electrical machine, on a rehabilitation condition, in order to restore a nominal operation of the control of the electrical machine.

8. Monitoring system for an angular displacement sensor of a rotor in an electric machine (1), comprising a control unit (4) of the electric machine and a supervisor computer (5), the electric machine being equipped with an angular displacement sensor (2), an inverter (3) capable of restoring the instantaneous values ​​of voltage and current consumed, the supervisor delivering a target torque to be delivered to the wheels, the control unit being configured to implement the method according to any one of claims 1 to 7.

9. Monitoring system according to claim 8, characterized in that the electric machine comprises a single rotor angular displacement sensor.

10. Electric or hybrid motor vehicle, comprising a monitoring system according to any one of claims 8 to 9.

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