Method for determining the rotational parameters of a rotation angle, as well as an electric motor

Abstract

Method (16) for determining the rotational parameters of at least one rotational angle (y) of a rotor (14) of an electric motor (10) rotatable relative to a stator (12), which is dependent on a rotational speed (θ), comprising the following steps: Determining (20) a first phase voltage (ud) and a first phase current (id) each with respect to a d-direction and a second phase voltage (uq) and a second phase current (iq) each with respect to a q-direction of the rotor-fixed dq coordinate system; Applying (22) a calculation algorithm (24) with a calculation (26) of the first phase voltage (ud) as a modeled first phase voltage (ud,m) and the second phase voltage (uq) as a modeled second phase voltage (uq,m) at least dependent on the first and second phase currents (id, iq), at least one electrical motor parameter (P), the rotational speed (θ;) and the rotation angle (y) and with an iterative calculation (27) of the rotational speed (w) as calculated rotational speed (Δi) and of the rotational angle (y) as calculated rotational angle (Δi) depending on the determined first and second phase voltage (ud, uq) and the modeled first and second phase voltage (ud,m, uq,m), output (28) of the calculated rotational angle (Δi) as output calculated rotational angle (Δr) and calculation (30) of the rotational speed (w) as output calculated rotational speed (Δr) from the output calculated rotational angle (Δr) omitting a direct calculation from the calculated rotational speed (Δi), characterized in that the calculation algorithm (24) applies a first relationship (32) which provides a first voltage difference (Δ;ud) between the determined first phase voltage (ud) and the modeled first phase voltage (ud,m), and the iterative calculation (27) of the rotation angle (y) with the first relationship (32) is carried out by using the rotation angle (Δi-1) previously calculated in a preceding calculation step and changing it in a calculation step by a rotation angle difference (ΔΔΔ) such that the first voltage difference (ΔΔud) is reduced.

Description

The invention relates to a method for determining the rotational parameter according to claim 1.If the rotor of an electric motor rotates and thus enough counter-induced voltage is available, it is known in permanently excited synchronous motors to use a method based on a voltage model based on voltage equations of the electrical phase voltages for the purpose of determining the rotational parameter. The phase voltages are measured on the one hand and calculated as modeled phase voltages via the voltage model on the other hand. The electrical phase currents and electrical motor parameters continue to enter into this voltage model. Voltage errors in the dq coordinate system are calculated from the difference between the respective measured and the modeled phase voltages. The rotation angle and the rotation speed are calculated by reducing the tension errors.In M. Brodatzki, J. Sicher, J. Koib and M. Braun, "Position and Speed Estimation Algorithm for Permanent Magnet Synchronous Machines Avoiding Nonlinear Magnetic Effects," 10th International Conference on Power Electronics and ECCE Asia (ICPE 2019-ECCE Asia), 2019, pp. 1-8, an iterative calculation is described which calculates four voltage errors in the d direction and the q direction in a calculation step starting from a solution for the rotational angle and the rotational speed from the preceding calculation step by changing the rotational angle and the rotational speed. By using the two-dimensional-sentinel method, the calculated rotational angle and rotational speed are calculated as a solution of the nonlinear equation system of the voltage model.If the motor parameters used in the voltage model are incorrectly assumed, for example because of temperature influences, an erroneous and / or delayed calculation of the calculated rotational angle and the calculated rotational speed can occur.In ICHIKAWA, Shinji [et al.]: Sensorless controls of salty-poles permanently magnetically synchronous motors using extended electron motif force models. In: Electrical Engineering in Japan, Vol. 146, 2004, H. 3, P. 55-64. - issn 0424-7760 (p); 1520-6416 (E). DOI: 10.1002 / eej. 10257. URL: https: / / online library.wiley.com / doi / epdf / 10.1002 / eej.10257 [retrieved on 2024-02-07], a mathematical model for synchronous motors and a sensorless control method based thereon that enables rotor position determination without approximation is described.The object of the present invention is to determine the rotational parameters of the electric motor more accurately, more easily and quickly.At least one of these objects is achieved by a method for determining the rotational parameter with the features according to claim 1. As a result, the angle of rotation can be determined more accurately and quickly. Model inaccuracies in the stress model can be better compensated. The calculation of the angle of rotation and / or the speed of rotation can be more independent of temperature influences.The electric motor may be disposed in a vehicle. The vehicle may be a motor vehicle. The electric motor can provide a drive power for moving the vehicle and / or a drive power for operating a vehicle component. The vehicle component can be an auxiliary unit, in particular a fluid pump. The fluid pump may be a hydraulic pump.The electric motor can be operated in a sensorless operation. The method may be carried out during sensorless operation of the electric motor. The electric motor can be operated exclusively in a sensorless operation. Sensorless operation is understood to mean operation without including a rotation angle measured with a sensor, for example a position sensor.The electric motor can be controlled via at least three motor phases. The electric motor may be a brushless DC motor. The electric motor may be a permanent magnet synchronous AC motor.The output calculated rotational speed may be calculated as a time-dependent change in the output calculated rotational angle.The modeled first phase voltage and the modeled second phase voltage may be calculated by a voltage model. The modeled first phase voltage u d,m can be calculated as a function of the first phase current i d and the second phase current i q as follows: with the directional inductances L d, L q and the electrical resistance R s of the stator as the electrical motor parameter P, respectively.The modeled second phase voltage u q,m can be calculated with the voltage model as follows: with the flux linkage ψ EM of the rotor as a further motor parameter P'.The first and second phase voltages in the dq coordinate system can be calculated from the phase voltages in the stator-fixed coordinate system. The electric motor may have three motor phases. The phase voltages in the stator-fixed coordinate system can accordingly form three phase voltages.The output as the output calculated rotation angle may be the output from the calculation algorithm.The output calculated rotational speed may be calculated immediately as a time change of the output calculated rotational angle.The output calculated rotational angle and / or the output calculated rotational speed can be used for controlling a rotational operation of the electric motor, in particular in a current control.In a preferred embodiment of the invention, it is advantageous if an output of the calculated rotational speed for calculating the output calculated rotational speed is omitted. The calculated rotational speed can be used exclusively for internal calculation in the calculation algorithm. The output of the calculated rotational speed can relate to an output from the calculation algorithm, in particular after completion of the iterative calculation.In a preferred embodiment of the invention, it is provided that the determination of the first and / or second phase voltage is carried out by estimation from a current regulation of the first and second phase currents. As a result, the method can be carried out more cost-effectively. The first and / or second phase voltage can alternatively or additionally be determined by measuring the corresponding phase voltage.The first and / or second phase voltage can be measured directly or indirectly.According to the invention, it is provided that the calculation algorithm uses a first relationship which specifies a first voltage difference between the ascertained first phase voltage and the modeled first phase voltage. The first relationship can specify the first voltage difference Δu d as a function of the ascertained first phase voltage u d and the modeled first phase voltage u d,m as follows:According to the invention, it is provided that the iterative calculation of the angle of rotation is carried out with the first relationship by using the angle of rotation y calculated previously in a preceding calculation step i-1 and changing it by an angle of rotation difference Δγ in a calculation step in such a way that the first voltage difference is reduced. The iterative calculation of the angle of rotation to reduce the first voltage difference Δu d can be implemented by iteratively adapting the angle of rotation with the following dependency:In a specific embodiment of the invention, it is advantageous if the reduction of the first voltage difference is achieved exclusively by iterative adaptation of the angle of rotation. An iterative adaptation of the rotational speed, in particular by introducing a rotational speed difference, can be omitted in this case.In a specific embodiment of the invention, it is advantageous if the calculation algorithm uses a second relationship which specifies a second voltage difference between the ascertained second phase voltage and the modeled second phase voltage. The second relationship can specify the second voltage difference Δu q as a function of the ascertained second phase voltage u q and the modeled second phase voltage u q,m as follows:In a specific embodiment of the invention, it is advantageous if the iterative calculation of the rotational speed is carried out with the second relationship by using the rotational speed ω i-1 calculated beforehand in a preceding calculation step and changing it by a rotational speed difference Δω in a calculation step in such a way that the second voltage difference Δu q is reduced. The iterative calculation of the rotational speed can be implemented by iteratively adapting the rotational speed with the following dependency:If the further motor parameter P' used in the modeled second phase voltage u q,m is temperature-dependent and not exactly known or unknown during the rotational operation of the rotor, the iterative calculation with the second relationship can bring about a reduction in the second voltage difference by iteratively adapting the calculated rotational speed ω i and the rotational speed ω i calculated thereby can be used in the first relationship for calculating the calculated rotational angle.The calculated rotational speed can thus be used as an internally calculated rotational speed for compensating uncertainties in the further motor parameter P'. The calculation algorithm can compensate for possible model uncertainties due to unknownly changed engine parameters, such as the further engine parameter P'.If the further motor parameter P' is inaccurate, for example, the iterative calculation can still find an equilibrium with the second relationship if the rotational speed is adjusted in the opposite direction as the change of the further motor parameter by the iterative calculation. If the further motor parameter P' becomes smaller, for example, the iterative calculation will calculate a greater rotational speed. This property of finding an equilibrium with the second relationship can be utilized in the feedback of the rotational speed for the next calculation step of the iterative calculation.In an advantageous embodiment of the invention, it is provided that the reduction of the second voltage difference is achieved exclusively by iterative adaptation of the rotational speed. An iterative adaptation of the angle of rotation, in particular by introducing an angle of rotation difference, can be omitted in this case.Furthermore, within the scope of the invention, for achieving at least one of the objects specified above, an electric motor having the features according to claim 10 is proposed. As a result, the electric motor can be operated more comfortably and efficiently.Further advantages and advantageous embodiments of the invention result from the description of the figures and the figures.DESCRIPTION OF THE FIGURESThe invention will be described in detail below with reference to the drawings. They show in detail: FIG. 1 : An electric motor in a specific embodiment of the invention. FIG. 2 : A method for determining rotational parameters in a specific embodiment of the invention.FIG. 1 shows an electric motor in a specific embodiment of the invention. The electric motor 10 comprises a stator 12 and a rotor 14 rotatable with respect thereto by changing a rotation angle γ. The rotor 14 has a rotation speed ω changing the rotation angle γ during a rotation operation. The electrical quantities, such as a phase voltage or a phase current, can be specified in the dq coordinate system fixed to the rotor.FIG. 2 shows a method for determining rotational parameters in a specific embodiment of the invention. The method 16 for determining the rotational parameter is applied to a rotational operation of the electric motor, for example as shown in FIG. 1, in which the rotor rotates with respect to the stator by changing the rotational angle γ depending on the rotational speed ω of the rotor. The method 16 comprises the steps of:determining 20 a first phase voltage u d and a first phase current i d each with respect to a d-direction, and a second phase voltage u q and a second phase current i q each with respect to a q-direction of the rotor-fixed dq coordinate system,Application 22 of a calculation algorithm 24 with a calculation 26 of the first phase voltage u d as modeled first phase voltage u d,m and the second phase voltage u q as modeled second phase voltage u q,m at least depending on the first and second phase currents i d, i q, at least one electric motor parameter P, the rotational speed ω and the rotational angle γ,Iterative calculation 27 of the rotational speed ω as the calculated rotational speed ω i and of the rotational angle γ as the calculated rotational angle γ i depending on the modeled first and second phase voltages u d,m, u q,m,output 28 of calculated rotation angle γ i as output calculated rotation angle γ r andCalculation 30 of the rotational speed ω as the output calculated rotational speed ω r from the output calculated rotational angle γ r omitting immediate calculation from the calculated rotational speed ω i.The calculated rotational speed ω i is thus used exclusively internally to the calculation of the calculated rotational angle γ i. An output of the calculated rotational speed ω i for calculating 30 the output calculated rotational speed ω r is thus omitted.The first and second phase voltages u d u q can be estimated from a current regulation of the first and second phase currents i d, i q.In the calculation algorithm 24, a first relationship 32 indicating a first voltage difference Δu d between the determined first phase voltage u d and the modeled first phase voltage u d,m and a second relationship 34 indicating a second voltage difference Δu q between the determined second phase voltage u q and the modeled second phase voltage u q,m are applied.The iterative calculation 27 of the rotation angle γ with the first relationship 32 is carried out by using the rotation angle γ i-1 calculated previously in a preceding calculation step and changing it by a rotation angle difference Δγ in the current calculation step in such a way that the first voltage difference Δu d is reduced. The reduction of the first voltage difference Δu d is achieved in particular exclusively by the iterative adaptation of the angle of rotation γ i. An iterative adaptation of the rotational speed ω i is omitted in this case.The iterative calculation 27 of the rotational speed ω with the second relationship 34 is carried out by using the rotational speed ω i-1 calculated previously in a preceding calculation step and changing it by a rotational speed difference Δω in the current calculation step in such a way that the second voltage difference Δu q is reduced. The reduction of the second voltage difference Δu q is achieved in particular exclusively by the iterative adaptation of the rotational speed ω i. An iterative adaptation of the angle of rotation γ i is omitted in this case.The output calculated rotational speed ω r and the output calculated rotational angle γ r may be respectively calculated from the calculated rotational angle γ i by a filter 32.List of reference characters10 Electric motor 12 Stator 14 Rotor 16 Method 20 Ascertainment 22 Application 24 Calculation algorithm 26 Calculation 27 Iterative calculation 28 Output 30 Calculation 32 First relationship 34 Second relationship P Electric motor parameter Δu d First voltage difference Δu q Second voltage difference Δγ Angle of rotation difference Δω Angle of rotation difference γ Angle of rotation γ i Calculated angle of rotation γ r Output Calculated angle of rotation γ i-1 Previously Calculated angle of rotation ω Speed of rotation ω i Calculated speed of rotation ω r Output Calculated speed of rotation ω i-1 Previously Calculated speed of rotation i d First phase current i q second phase current u d first phase voltage u q second phase voltage u d,m modeled first phase voltage u q,m modeled second phase voltage

Claims

Method (16) for determining the rotational parameter of at least one rotational angle (y) of a rotor (14) of an electric motor (10), which rotor can be rotated with respect to a stator (12), which rotational angle can be varied as a function of a rotational speed (ω), having the following steps: determining (20) a first phase voltage (u d) and a first phase current (i d) in each case with respect to a d-direction and a second phase voltage (u q) and a second phase current (i q) in each case with respect to a q-direction of the dq coordinate system fixed to the rotor, Application (22) of a calculation algorithm (24) with a calculation (26) of the first phase voltage (u d) as modeled first phase voltage (u d,m) and the second phase voltage (u q) as modeled second phase voltage (u q,m) at least depending on the first and second phase currents (i d, i q), of at least one electric motor parameter (P), the rotational speed (ω) and the rotational angle (y) and with an iterative calculation (27) of the rotational speed (w) as the calculated rotational speed (ω i) and of the rotational angle (y) as the calculated rotational angle (γ i) depending on the determined first and second phase voltages (u d, u q) and the modeled first and second phase voltages (u d,m, u q,m), outputting (28) the calculated rotational angle (γ i) as the output calculated rotational angle (γ r) and calculating (30) the rotational speed (w) as the output calculated rotational speed (ω r) from the output calculated rotational angle (γ r) omitting an immediate calculation from the calculated rotational speed (ω i), characterized in that the calculation algorithm (24) applies a first relationship (32) which indicates a first voltage difference (Δu d) between the determined first phase voltage (u d) and the modeled first phase voltage (u d,m), and the iterative calculation (27) of the angle of rotation (y) with the first relationship (32) is carried out by using the angle of rotation (γ i-1) calculated beforehand in a preceding calculation step and changing it by an angle of rotation difference (Δγ) in a calculation step in such a way that the first voltage difference (Δu d) is reduced.Method (16) according to Claim 1, characterized in that an output of the calculated rotational speed (ω i) for calculating the output calculated rotational speed (ω r) is omitted.Method (16) according to Claim 1 or 2, characterized in that the determination (20) of the first and / or second phase voltage (u d, u q) is effected by estimation from a current regulation of the first and second phase current (i d, i q).Method (16) according to one of Claims 1 to 3, characterized in that the reduction of the first voltage difference (Δu d) is achieved exclusively by iterative adaptation of the angle of rotation (γ i).Method (16) according to any one of claims 1 to 4, characterised in that the calculation algorithm (24) applies a second relationship (34) indicative of a second voltage difference (Δu q) between the determined second phase voltage (u q) and the modeled second phase voltage (u q,m).Method (16) according to Claim 5, characterized in that the iterative calculation (27) of the rotational speed (w) with the second relationship (34) takes place by using the rotational speed (ω i-1) calculated beforehand in a preceding calculation step and, in a calculation step, changing it by a rotational speed difference (Δω) in such a way that the second voltage difference (Δu q) is reduced.Method (16) according to Claim 6, characterized in that the reduction of the second voltage difference (Δu q) is achieved exclusively by iterative adaptation of the rotational speed (ω i).Electric motor (10) having a stator (12) and a rotor (14) which can be rotated with respect to the latter by changing a rotation angle (y), the rotation angle (y) of which can be determined by determining the rotation parameter by means of a method (16) of the preceding claims.

Images