METHOD AND DEVICE FOR CONTROLLING AN OPERATION OF AN ELECTRIC MOTOR

Abstract

In a method for controlling an operation of an electric motor, electric voltages applied to electric phases of the electric motor are generated and output in a modulation in a controlled manner dependent on a rotor position of the electric motor and a target/actual comparison of at least one first variable which characterizes a load on the electric motor or an actual rotational speed of the electric motor. A rotor position angle, which characterizes the rotor position, is complemented with a specified preliminary control angle and another regulated preliminary control angle component upon reaching a field weakening range of the electric motor so as to form a sum angle. The sum angle is used to characterize the rotor position in the modulation upon reaching the field weakening range. The disclosure also relates to a device for controlling an operation of an electric motor.

Claims

1-15. (canceled)

16. A method for controlling an operation of an electric motor, the method comprising: in a modulation, generating electric voltages which are applied to electric phases of the electric motor and outputting the electric voltages in a controlled fashion as a function of a rotor position of the electric motor and as a function of a setpoint/actual comparison of at least one first variable that characterizes a load of the electric motor or of an actual rotational speed of the electric motor; when a field-weakening range of the electric motor is reached, adding a predefined pilot-control angle and a further regulated pilot-control angle component to a rotor position angle, which characterizes a rotor position, to form a composite angle; and when the field-weakening range is reached, using the composite angle to characterize the rotor position in the modulation.

17. The method according to claim 16, which comprises determining that the field-weakening range has been reached when an upper limit of a degree of modulation which characterizes a predefined maximum amplitude of a motor voltage and/or a motor current is reached.

18. The method according to claim 17, which comprises, when the field-weakening range is reached, defining the degree of modulation at its upper limit, and carrying out the modulation of the electric voltages by regulating the pilot-control angle.

19. The method according to claim 16, which comprises determining the pilot-control angle as a function of an actual rotational speed and of at least one second variable, which characterizes a load of the electric motor, from a pilot-control angle characteristic diagram, and adding the further regulated pilot-control angle component to the pilot-control angle.

20. The method according to claim 16, wherein the pilot-control angle is predefined for an armature actuation range of the electric motor.

21. The method according to claim 16, wherein a maximum value of the pilot-control angle is predefined.

22. The method according to claim 21, wherein the pilot-control angle is predefined such that a regulation reserve is generated during the modulation for a voltage as a manipulated variable.

23. The method according to claim 16, which comprises using at least one of a rotational speed, a torque, and/or a motor current as the first variable the characterizes the load of the electric motor.

24. The method according to claim 19, which comprises using at least one of a currently requested motor voltage, a current direct current, a phase current which is determined from the direct current and a pulse duty factor, a measured phase current and/or a torque as a second variable that characterizes the load of the electric motor.

25. The method according to claim 16, which comprises generating the pilot-control angle characteristic diagram by determining pilot-control angles at rotational speed operating points and torque operating points of the electric motor at which at least one efficiency level of the electric motor is maximized.

26. The method according to claim 16, which comprises determining the voltages as a function of the composite angle in a space vector modulation.

27. A device for controlling an operation of an electric motor, the device comprising: a supply unit for a controlled outputting of electric voltages at electric phases of the electric motor; at least one detection unit coupled to said supply unit and configured for detecting a rotor position of the electric motor; at least one closed-loop controller for carrying out a setpoint/actual comparison of a first variable that characterizes a load of the electric motor; a memory having stored therein a pilot-control angle characteristic diagram; a control unit connected to said memory and configured for determining a pilot-control angle from the pilot-control angle characteristic diagram, in order to add a pilot-control angle and a further regulated pilot-control angle component to a rotor position angle, which characterizes the rotor position, to form a composite angle, for determining the voltages as a function of the composite angle when a field-weakening range of the electric motor is reached, and for controlling the outputting of the electric voltages to the electric phases of the electric motor by said supply unit.

28. The device according to claim 27, wherein said closed-loop controller is a rotational speed controller, a torque controller or a power controller or comprises the power controller.

29. The device according to claim 27, wherein said closed-loop controller includes a rotational speed controller, a torque controller or a power controller.

30. The device according to claim 27, wherein said supply unit comprises a bridge circuit.

31. The device according to claim 30, wherein said bridge circuit is a B6 bridge circuit.

Description

[0034] Exemplary embodiments of the invention are explained in more detail below with reference to drawings, of which:

[0035] FIG. 1 shows a schematic block diagram of a first exemplary embodiment of a control loop for the controlled sinusoidal actuation of an electric motor with field-weakening regulation according to the invention,

[0036] FIG. 2 shows a schematic flowchart of a first exemplary embodiment of a method according to the invention for controlling an operation of an electric motor with field-weakening regulation,

[0037] FIG. 3 shows a schematic block diagram of a second exemplary embodiment of a control loop for the controlled sinusoidal actuation of an electric motor with field-weakening regulation according to the invention,

[0038] FIG. 4 shows a schematic, detailed block diagram of the second exemplary embodiment of the control loop according to FIG. 3, and

[0039] FIG. 5 shows a schematic flowchart of a second exemplary embodiment of a method according to the invention for controlling an operation of an electric motor with field-weakening regulation.

[0040] Corresponding parts are provided with the same reference symbols in all the figures.

[0041] FIG. 1 shows a block diagram of a first exemplary embodiment of a control loop for the controlled block actuation or sinusoidal actuation of an electric motor 1 with field-weakening regulation of the electric motor 1.

[0042] In this context, a supply of power to individual motor windings of the electric motor 1 is controlled within the scope of a block or sinusoidal commutation by means of a control unit 2 by controlling a B6 bridge 3. Here, a high-side switch of a half bridge of the B6 bridge 3 and a low-side switch of the half bridge are connected (in a way not illustrated in more detail) within a commutation step for pulse width modulation. The commutation step is controlled here as a function of a rotor position of the electric motor 1.

[0043] In a detection unit 4, an actual rotational speed n.sub.act of the electric motor 1 is also determined and fed back, wherein an output voltage U.sub.out is set as a function of a setpoint rotational speed n.sub.setp of the electric motor 1 as the degree of modulation MG by means of a regulator 5 which is embodied as a rotational speed regulator, as a function of which output voltage U.sub.out the control unit 2 controls the B6 bridge 3.

[0044] In addition, the composite angle φ.sub.Σ is generated as a function of the actual rotational speed n.sub.act and of the variable G, which represents the load of the electric motor 1, on the basis of the pilot-control angle characteristic diagram KF and the rotor position angle φ, and is fed to the control unit 2 for space vector modulation RZM, which control unit 2 generates an actuation signal for the B6 bridge 3 on the basis of an amplitude of the voltage vector and an optimized commutation angle.

[0045] That is to say, in a simple motor actuation without phase current back-measurement, the electric voltages which are output to the electric motor 1 are modulated by means of the information of the rotor position and the predefined degree of modulation MG from the regulator 5 which is embodied as a rotational speed regulator. If, with this type of actuation, an armature actuation range of the electric motor 1 is exited in the direction of field weakening, that is to say a field-weakening range of the electric motor 1 is reached when an upper limit is reached by a predefined maximum amplitude of the output voltage U.sub.out and/or a motor current with or without regulating reserve, an additional pilot-control angle φ.sub.PA is generated starting from a pilot-control angle characteristic diagram KF for the commutation, by means of a subordinate pilot-control angle regulator 6. In this context, achieving a regulating reserve in the degree of modulation MG by optimizing the pilot-control angle φ.sub.PA is the main component, alongside the possibility of utilizing field weakening of the electric motor 1. A maximum permissible value of the pilot-control angle φ.sub.PA is provided in a limited fashion here preferably by means of an adjustable limit.

[0046] The pilot-control angle characteristic diagram KF is determined, in particular, in a data supply procedure of the entire system by determining pilot-control angles φ.sub.PA at rotational speed operating points and torque operating points of the electric motor 1 at which at least the efficiency level of the electric motor 1 is maximized, in particular a complete level of efficiency of electric motor 1 and the actuation electronics thereof. The pilot-control angle characteristic diagram KF is stored, in particular, in a memory (not illustrated) of the pilot-control angle regulator 6.

[0047] In the illustrated exemplary embodiment, the value of the pilot-control angle φ.sub.PA which is applied to the output of the pilot-control angle regulator 6 is added to the determined rotor position angle φ of the electric motor 1 to form a composite angle φ.sub.Σ, in particular added before the composite angle φ.sub.Σ is passed on for use for the modulation of the voltages for the electric motor 1.

[0048] In contrast to the illustration, the method according to the invention, the device according to the invention and the refinements thereof can also be used (in a manner not shown) in regulating structures with a subordinate power regulator or other regulating structures, for example for direct torque regulation, and is not restricted to the structure illustrated with rotational speed regulation.

[0049] FIG. 2 shows a flowchart of a possible first exemplary embodiment of a method according to the invention for controlling the operation of the electric motor 1 with field-weakening regulation.

[0050] In this context, in a first method step S1 the setpoint rotational speed n.sub.setp or, in a way which is not illustrated in more detail, a setpoint current or a setpoint torque is fed to the regulator 5 which is correspondingly embodied as a rotational speed regulator, power regulator or torque regulator and generates the output voltage U.sub.out in a second method step S2 as a function of the actual rotational speed n.sub.act, detected by means of the detection unit 4, of the actual current or of the actual torque.

[0051] In a third method step S3, for an armature actuation range of the electric motor 1 it is determined whether the degree of modulation MG is between the value “zero” and a predefined maximum value which characterizes the transition to the field-weakening range.

[0052] If this is the case (characterized by the reference symbol Y) the voltages are determined in a fourth method step S4 in a space vector modulation RZM as a function of the rotor position angle φ as a voltage vector, and in a fifth method step S5 they are output to the electric phases of the electric motor 1 in a controlled fashion.

[0053] If the degree of modulation MG exceeds the maximum value (characterized by the reference symbol N) which characterizes the transition to the field-weakening range, the rotor position angle φ is added to a pilot-control angle φ.sub.PA, additionally determined in a sixth method step S6 by means of the pilot-control angle regulator 6, to form the composite angle φ.sub.Σ. The voltages are determined as voltage vectors in the space vector modulation RZM as a function of the composite angle φ.sub.Σ, and are output in a controlled fashion to the electric phases of the electric motor 1.

[0054] FIG. 3 shows a block diagram of a second exemplary embodiment of a control loop for the controlled sinusoidal actuation of the electric motor 1 with field-weakening regulation according to the invention.

[0055] In this context, the control loop is embodied in such a way that in the case of the regulator output variable of the regulator 5 embodied as a rotational speed regulator 5.1 and a power regulator 5.2 it is possible to switch over situationally between the degree of modulation MG and the additive commutation angle, that is to say the composite angle φ.sub.Σ which is formed from the rotor position angle φ and the pilot-control angle φ.sub.PA. At the same time, the regulator parameters are adapted to the respective state.

[0056] In this context, when the upper limit of the degree of modulation MG is reached, the degree of modulation MG is defined, as it were “frozen”, at its upper limit, and the modulation of the electric voltages is carried out solely by regulating the pilot-control angle φ.sub.PA. Therefore, a further regulating difference between the rotational speed regulator 5.1 and the power regulator 5.2, which would bring about an increase in the regulator manipulated variable, is no longer added to the degree of modulation MG but is instead added as a pilot-control angle φ.sub.PA to the actual rotor position angle φ.

[0057] For this purpose, an alternating current I.sub.AC as regulator output variable of the rotational speed regulator 5.1 is fed, together with the degree of modulation MG fed via a signal conditioner 7 as a regulator output variable of the power regulator 5.2, to a multiplier 9 which generates a setpoint direct current I.sub.CC as a regulator input variable for the power regulator 5.2, as a function of said setpoint direct current I.sub.DC and an actual direct current I.sub.DC.sub._.sub.act the output of the power regulator 5.2 is connected to a switching means 8 in the actuation algorithm.

[0058] Furthermore, the pilot-control angle φ.sub.PA is determined on the basis of the determined actual rotational speed n.sub.act and an actual alternating current I.sub.AC-act, which characterizes the load of the electric motor 1 and is generated by means of a divider 10, and said pilot-control angle φ.sub.PA is added with the rotor position angle φ to form the composite angle φ.sub.Σ.

[0059] That is to say the regulator output of the power regulator 5.2 is switched over situationally between the degree of modulation MG and the pilot-control angle φ.sub.PA. The pilot-control angle φ.sub.PA from a pilot-control angle characteristic diagram KF which supplies only a minimum and operational-point-optimized pilot-control angle φ.sub.PA.sub._.sub.min for the armature actuation range, serves as the starting point for use as a pilot-control angle φ.sub.PA. This combines the advantage of rapid control with the property of a regulator 5 to eliminate persistent deviations.

[0060] This is illustrated in FIG. 4 in a detailed block diagram of the second exemplary embodiment of the control loop according to FIG. 3.

[0061] In this context, an actual rotational speed n.sub.act.sub._.sub.PA for the pilot-control angle characteristic diagram KF and an actual rotational speed n.sub.act.sub._.sub.nReg for the rotational speed regulator 5.1 as well as an actual rotor position angle φ.sub.act and a lag time rotor position angle φ.sub.LagTime are determined in a filtering operation and an angle- and rotational speed-calculating operation by means of the detection unit 5 from the sine values sin and cosine values cos of a rotational angle sensor which detects the position of the rotor of the electric motor 1.

[0062] Furthermore, in a process of triggering T values of an analog/digital converter from a current value I.sub.ADC and the degree of modulation MG an actual direct current I.sub.DC.sub._.sub.IReg is determined for feeding back for the power regulator 5.2, and an actual alternating current I.sub.motAC.sub._.sub.PA is determined for feeding back for the pilot-control angle characteristic diagram KF, wherein the switch 8 is switched as a function of exceeding of the maximum value MG.sub.max of the degree of modulation MG whether the setting of the voltages takes place solely on the basis of the pilot-control angle φ.sub.PA or on the basis of the composite angle φ.sub.Σ.

[0063] FIG. 5 shows a flowchart of a possible second exemplary embodiment of a method according to the invention for controlling the operation of the electric motor 1 with field-weakening regulation.

[0064] In this context, in contrast to the exemplary embodiment illustrated in FIG. 2, when the predefined maximum value MG.sub.max of the degree of modulation MG is undershot the load of the electric motor 1 is determined on the basis of a second variable, characterizing said load in a seventh method step S7, and the pilot-control angle φ.sub.PA is determined in an eighth method step S8, from the pilot-control angle characteristic diagram KF, and is fed to the space vector modulation RZM in the fourth method step S4. In particular, a currently requested motor voltage, a current direct current, a phase current which is determined from the direct current and a duty cycle factor, a measured phase current and/or a torque are used as the second variable.

[0065] When the predefined maximum value of the degree of modulation MG is exceeded, in a sixth method step S6 an additional pilot-control angle component φ.sub.PA.sub._.sub.reg is formed from the regulator manipulated variable and added to the pilot-control angle φ.sub.PA and the rotor position angle φ to form the composite angle φ.sub.Σ which is fed to the space vector modulation RZM in the fourth method step S4.

LIST OF REFERENCE SYMBOLS

[0066] 1 Electric motor [0067] 2 Control unit [0068] 3 B6 bridge [0069] 4 Detection unit [0070] 5 Regulator [0071] 5.1 Rotational speed regulator [0072] 5.2 Power regulator [0073] 6 Pilot-control angle regulator [0074] 7 Signal conditioner [0075] 8 Switch [0076] 9 Multiplier [0077] 10 Divider [0078] cos Cosine value [0079] I.sub.AC Alternating current [0080] I.sub.AC.sub._.sub.act Actual alternating current [0081] I.sub.ADC Current value [0082] I.sub.DC Setpoint direct current [0083] I.sub.DC.sub._.sub.act Actual direct current [0084] I.sub.DC-IReg Actual direct current [0085] I.sub.motAC.sub._.sub.PA Actual alternating current [0086] Y Yes [0087] KF Pilot-control angle characteristic diagram [0088] MG Degree of modulation [0089] MG.sub.max Maximum value [0090] N No [0091] n.sub.act Actual rotational speed [0092] n.sub.act.sub._.sub.nReg Actual rotational speed [0093] n.sub.act.sub._.sub.PA Actual rotational speed [0094] n.sub.setp Setpoint rotational speed [0095] RZM Space vector modulation [0096] S1 to S8 Method step [0097] sin Sine value [0098] T Triggering operation [0099] U.sub.out Output voltage [0100] φ Rotor position angle [0101] φ.sub.act Actual rotor position angle [0102] φ.sub.LagTime rotor position angle [0103] φ.sub.PA Pilot-control angle [0104] φ.sub.PA.sub._.sub.min Pilot-control angle [0105] φ.sub.PA.sub._.sub.reg Pilot-control angle component [0106] φ.sub.Σ Composite angle