Control device of electric vehicle

Abstract

To provide a control device of an electric vehicle which can estimate target torque of a motor for controlling DC current value of an inverter to target electric current value over wide operating range at sufficient precision without requiring a memory with high capacity.SOLUTION: A control device of an electric vehicle is configured so as to comprise a torque estimation value calculation part 21 which calculates torque estimation value representing estimation value of torque of a motor 2 for setting DC current value of an inverter 4 as target current value and a torque estimation value correction part 22 which estimates efficiency of a motor 2 on the basis of torque estimation value and rotational speed of the motor 2 and corrects the torque estimation value on the basis of the estimated efficiency of the motor 2 and the target current value. The torque estimation value corrected by the torque estimation value correction part 22 is referred to as the torque estimation value before correction and then the torque estimation value corrected at prescribed frequency by the torque estimation correction part 22 is referred as the target torque of the motor 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for an electric vehicle. [Background technology]

[0002] Conventionally, Patent Document 1 proposes that in a control device for a hybrid vehicle equipped with a battery including a lithium-ion secondary battery, the vehicle's power performance and fuel economy can be improved by providing a battery protection processing unit that performs protection processing to protect the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-71622 Summary of the Invention [Problem to be solved by the invention]

[0004] In EV (Electric Vehicle) systems and HEV (Hybrid Electric Vehicle) systems, power management, particularly controlling the inverter's DC current value to a target current value, is an important function, such as limiting the amount of charge / discharge that can be performed to protect the battery and ensuring the current consumption of the electrical load.

[0005] There are two methods for estimating the motor torque for controlling the inverter's DC current value to a target current value: The first method estimates the motor torque for controlling the inverter's DC current value to a target current value using a conversion equation between electrical power and mechanical power that uses an efficiency value expressed as a single constant.

[0006] The second method calculates the efficiency value from a three-dimensional map consisting of three axes: torque, rotational speed, and voltage, and estimates the motor torque to control the inverter's DC current value to the target current value using a conversion equation between electrical power and mechanical power using the calculated efficiency value.

[0007] However, the first method does not comprehensively consider the efficiency characteristics of the inverter that drives the motor, so while it can ensure sufficient accuracy at a specific operating point, the accuracy drops significantly at operating points away from the specific operating point.As such, the first method has the problem of being unable to estimate the motor target torque, which is used to control the inverter's DC current value to the target current value, with sufficient accuracy over a wide range.

[0008] On the other hand, the second method can ensure sufficient accuracy even at operating points far from a specific operating point, and can therefore estimate the motor's target torque for controlling the inverter's DC current value to the target current value with sufficient accuracy over a wide range. However, it has the drawback of requiring a large amount of memory for the map used to calculate the efficiency value.

[0009] An object of the present invention is to provide a control device for an electric vehicle that can estimate the target torque of a motor for controlling the DC current value of an inverter to a target current value with sufficient accuracy over a wide range of coverage, without requiring a large capacity memory. [Means for solving the problem]

[0010] The control device for an electric vehicle according to the present invention is a control device for an electric vehicle provided with a motor that is a drive source of the vehicle, a battery that supplies power to the motor, and an inverter that performs power conversion between the motor and the battery, and is equipped with a torque estimation value calculation unit that calculates a torque estimation value that represents an estimate of the torque of the motor so that the DC current value of the inverter becomes a target current value, and a torque estimation value correction unit that estimates the efficiency of the motor based on the rotational speed of the motor and the torque estimation value, and corrects the torque estimation value based on the estimated efficiency of the motor and the target current value, and is configured so that the torque estimation value corrected by the torque estimation value correction unit is set to the torque estimation value before correction, and the torque estimation value corrected a predetermined number of times by the torque estimation value correction unit is set to the target torque of the motor. [Effects of the Invention]

[0011] The present invention can provide a control device for an electric vehicle that can estimate the target torque of a motor for controlling the DC current value of an inverter to a target current value with sufficient accuracy over a wide range of coverage, without requiring a large capacity memory. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with a control device for an electric vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a flowchart showing the torque estimation operation of the control device for an electric vehicle according to one embodiment of the present invention. [Figure 3] FIG. 3 is a graph for explaining the operation of the control device for an electric vehicle according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] A control device for an electric vehicle according to one embodiment of the present invention is provided with a motor as a drive source of the vehicle, a battery that supplies power to the motor, and an inverter that performs power conversion between the motor and the battery, and includes: a torque estimate calculation unit that calculates a torque estimate representing an estimate of motor torque for setting a DC current value of the inverter to a target current value; and a torque estimate correction unit that estimates motor efficiency based on the motor rotation speed and the torque estimate and corrects the torque estimate based on the estimated motor efficiency and the target current value, wherein the torque estimate corrected by the torque estimate correction unit is used as the torque estimate before correction, and the torque estimate corrected a predetermined number of times by the torque estimate correction unit is used as the target torque of the motor. As a result, the control device for an electric vehicle according to the embodiment of the present invention can estimate the target torque of the motor for controlling the DC current value of the inverter to the target current value with sufficient accuracy over a wide range without requiring a large-capacity memory. [Example]

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle equipped with a control device for an electric vehicle according to an embodiment of the present invention will now be described with reference to the drawings.

[0015] As shown in FIG. 1, the vehicle 1 is an electric vehicle including a motor 2, a battery 3, an inverter 4, an electric load 5, and an ECU (Electronic Control Unit) 6.

[0016] The motor 2 has a function as an electric motor that rotates when power is supplied from the battery 3 to drive the vehicle 1, and a function as a generator that converts the rotational force of the drive wheels of the vehicle 1 into electric power. In this embodiment, the motor 2 functions as a drive source for the vehicle 1.

[0017] Hereafter, the drive current and drive torque are positive, and the generated current and generated torque are negative. For example, when the current values ​​are 5A and 7A, the minimum value is 5A, and when the current values ​​are -5A and -7A, the maximum value is -5A.

[0018] The battery 3 is configured by a rechargeable secondary battery, such as a lithium-ion battery. The battery 3 stores power charged from an external source and power generated by the motor 2. The power stored in the battery 3 is supplied to the motor 2, the electrical load 5, etc.

[0019] The inverter 4 is controlled by the ECU 6 to convert DC power supplied from the battery 3 into three-phase AC power to be supplied to the motor 2. The inverter 4 is also controlled by the ECU 6 to convert the three-phase AC power supplied from the motor 2 into DC power to be supplied to the battery 3.

[0020] The ECU 6 is composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, input ports, and output ports.

[0021] The ROM of this computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the ECU 6. That is, the CPU executes the program stored in the ROM using the RAM as a work area, causing the computer unit to function as the ECU 6 in this embodiment.

[0022] Various sensors are connected to the input port of the ECU 6, including a rotational speed sensor 11 that detects the rotational speed of the motor 2 (hereinafter also simply referred to as the "motor rotational speed"), a battery sensor 12 that detects the state of the battery 3, such as the discharge / charge current of the battery 3 and the voltage between the terminals of the battery 3, and an inverter voltage sensor 13 that detects the voltage between the positive and negative wires of the inverter 4 (hereinafter also simply referred to as the "inverter voltage").

[0023] The output port of the ECU 6 is connected to various control objects including the inverter 4. The ECU 6 controls the various control objects connected to the output port based on information obtained from various sensors connected to the input port.

[0024] For example, the ECU 6 has the functions of a torque estimation value calculation unit 21 that calculates an estimated value of the torque of the motor 2 (hereinafter also simply referred to as the "torque estimation value") to set the DC current value of the inverter 4 (hereinafter also simply referred to as the "inverter current value") to the target current value It, and a torque estimation value correction unit 22 that corrects the torque estimation value.

[0025] An initial efficiency value map M1 in which the efficiency of the motor 2 (hereinafter also simply referred to as "motor efficiency") η is associated with the inverter current value is stored in the ROM of the ECU 6. The ECU 6 uses the initial efficiency value map M1 to calculate an initial value η0 of the motor efficiency η from the target current value It.

[0026] The ECU 6 executes a torque estimation value calculation process to calculate a torque estimation value Tg based on the target current value It, the inverter voltage E, the initial value η0 of the motor efficiency η, and the motor rotation speed N, according to the following equation (1).

[0027] Tg×N=E×It×η0 (1)

[0028] After calculating the torque estimate value Tg, the ECU 6 executes a torque estimate value correction process to correct the torque estimate value Tg as described below.

[0029] An efficiency map M2 in which motor efficiency η is associated with the motor rotation speed N and the torque (hereinafter simply referred to as "motor torque") Tm of the motor 2 is stored in the ROM of the ECU 6. The ECU 6 estimates the motor efficiency η from the motor rotation speed N and the torque estimate value Tg using the efficiency map M2.

[0030] Depending on the characteristics of the motor 2, even if the motor rotation speed N and motor torque Tm do not change, the motor efficiency η changes depending on the inverter voltage E. For this reason, a correction map M3 in which a correction value Δη for the motor efficiency η is associated with the inverter voltage E, the motor rotation speed N, and the motor torque Tm is stored in the ROM of the ECU 6. The ECU 6 determines the correction value Δη for the motor efficiency η using the correction map M3.

[0031] The ECU 6 corrects the motor efficiency η estimated using the efficiency map M2 with the correction value Δη determined using the correction map M3. Specifically, the ECU 6 corrects the motor efficiency η by adding the correction value Δη determined using the correction map M3 to the motor efficiency η estimated using the efficiency map M2.

[0032] The ECU 6 calculates the inverter current value Ip from the inverter voltage E, the torque estimation value Tg, the motor efficiency η, and the motor rotation speed N according to the following equation (2).

[0033] Tg×N=E×Ip×η (2)

[0034] The ECU 6 corrects the operating point of the motor 2, which is determined by the torque estimation value Tg and the corrected current value Ic, by performing a current value correction in which the minimum value of the inverter current value Ip calculated based on equation (2) and the target current value It is determined as the corrected current value Ic (hereinafter simply referred to as the "corrected current value").

[0035] The ECU 6 calculates the torque estimation value Tg from the corrected current value Ic, the inverter voltage E, the motor efficiency η, and the motor rotation speed N based on the following equation (3), thereby correcting the torque estimation value Tg.

[0036] Tg×N=E×Ic×η (3)

[0037] The ECU 6 uses the torque estimate Tg corrected by the torque estimate correction process described above as the torque estimate before correction, and sets the torque estimate Tg corrected a predetermined number of times by the torque estimate correction process as the target torque of the motor.

[0038] In this way, after calculating the torque estimation value Tg, the ECU 6 executes the torque estimation value correction process, and executes the torque estimation value correction process a predetermined number of times, using the torque estimation value Tg after correction by the torque estimation value correction process as the torque estimation value before correction.

[0039] The predetermined number of times is set to a value that allows the torque estimation value Tg to fall within an allowable range for the ideal target torque value, and is set to three times in this embodiment. That is, in this embodiment, the torque estimation value correction process is executed four times.

[0040] When performing the torque estimation value correction process using the torque estimation value Tg after correction by the torque estimation value correction process as the torque estimation value before correction, the ECU 6 determines the minimum value between the inverter current value Ip and the target current value It as the corrected current value Ic in the first and third current value corrections, but determines the maximum value between the inverter current value Ip and the target current value It as the corrected current value Ic in the second current value correction.

[0041] In this way, when the torque estimation value correction process is performed using the torque estimation value Tg after correction by the torque estimation value correction process as the torque estimation value before correction, the ECU 6 prevents the corrected current value Ic from converging in a region lower than the target current value It by alternately determining the minimum and maximum values ​​of the inverter current value Ip and the target current value It as the corrected current value Ic.

[0042] If the corrected current value Ic converges in a region lower than the target current value It, it is possible to prevent the corrected current value Ic from exceeding the target current value It, but from the perspective of energy management, this will result in a power shortage or excess power.

[0043] On the other hand, by alternately determining the minimum and maximum values ​​of the inverter current value Ip and the target current value It as the corrected current value Ic, the corrected current value Ic can be converged so that it does not bias toward either a region higher or lower than the target current value It.

[0044] From the viewpoint of battery protection, it is desirable that the minimum value between the inverter current value Ip and the target current value It be determined as the corrected current value Ic in the fourth and final torque estimated value correction process.

[0045] As described above, even if the torque estimation value Tg is calculated without performing current value correction, the inverter current value can be converged to the target current value It. However, there is a possibility that the inverter current value will not converge and will continue to exceed the target current value It. Therefore, although this can be used for energy management purposes, it cannot be used for protecting the battery 3 by preventing the inverter current value from exceeding the target current value It.

[0046] In this way, the control device for an electric vehicle according to this embodiment can be used for both energy management and protection of the battery 3. On the other hand, if the purpose is to use the control device for an electric vehicle according to this embodiment for either energy management or protection of the battery 3, the current value correction may be omitted or the processing content of the current value correction may be changed in order to simplify the processing.

[0047] The torque estimation operation by the ECU 6 configured as above will be described with reference to Fig. 2. The torque estimation operation described below is repeatedly performed over a period during which the ECU 6 controls the inverter 4 so as to drive the motor 2.

[0048] First, in S1, the ECU 6 executes a torque estimation value calculation process to calculate a torque estimation value Tg from the target current value It, the inverter voltage E, the initial value η0 of the motor efficiency η, and the motor rotation speed N. After executing the process of S1, the ECU 6 executes a process of S2.

[0049] In S2, the ECU 6 uses the efficiency map M2 to estimate the motor efficiency η from the motor rotation speed N and the torque estimation value Tg. After executing the process of S2, the ECU 6 executes the process of S3.

[0050] In S3, the ECU 6 resets the value of a correction number counter, which indicates the number of times the torque estimation value correction process has been executed, to 0. After executing the process of S3, the ECU 6 executes the process of S4. In S4, the correction value Δη of the motor efficiency η is determined using the correction map M3. After executing the process of S4, the ECU 6 executes the process of S5.

[0051] In S5, the ECU 6 corrects the motor efficiency η estimated using the efficiency map M2 with the correction value Δη determined using the correction map M3. After executing the process of S5, the ECU 6 executes the process of S6.

[0052] In S6, the ECU 6 calculates the inverter current value Ip from the inverter voltage E, the torque estimation value Tg, the motor efficiency η, and the motor rotation speed N. After executing the process of S6, the ECU 6 executes the process of S7.

[0053] In S7, the ECU 6 corrects the operating point of the motor 2 determined by the torque estimation value Tg and the corrected current value Ic by performing a current value correction in which the minimum or maximum value of the inverter current value Ip and the target current value It is determined as the corrected current value Ic according to the value of the correction count counter.

[0054] In this embodiment, when the value of the correction number counter is 0, 1, or 3, the ECU 6 determines the minimum value between the inverter current value Ip and the target current value It as the corrected current value Ic, and when the value of the correction number counter is 2, the ECU 6 determines the maximum value between the inverter current value Ip and the target current value It as the corrected current value Ic. After executing the process of S7, the ECU 6 executes the process of S8.

[0055] In S8, the ECU 6 corrects the torque estimation value Tg by calculating the torque estimation value Tg from the corrected current value Ic, the inverter voltage E, the motor efficiency η, and the motor rotation speed N. After executing the process of S8, the ECU 6 executes the process of S9.

[0056] In S9, the ECU 6 adds 1 to the value of the correction number counter. After executing the process of S9, the ECU 6 executes the process of S10. In S10, the ECU 6 determines whether the value of the correction number counter is 4 or more.

[0057] If it is determined in S10 that the value of the correction number counter is 4 or greater, the ECU 6 executes the process of S11. If it is determined in S10 that the value of the correction number counter is not 4 or greater, the ECU 6 executes the process of S4. In S11, the ECU 6 controls the inverter 4 using the torque estimation value Tg as the target torque. After executing the process of S11, the ECU 6 ends the torque estimation operation.

[0058] In this way, the torque estimation operation by the ECU 6 ensures the estimation accuracy of the torque estimate value Tg because the operating point of the motor 2 converges to an ideal operating point as shown in Fig. 3. Therefore, the ECU 6 controls the inverter 4 using the finally obtained torque estimate value Tg as the target torque, thereby achieving highly accurate energy management control and battery protection control.

[0059] As described above, the control device for an electric vehicle according to this embodiment uses the torque estimate corrected by the torque estimate corrector 22 as the torque estimate before correction, and uses the torque estimate corrected a predetermined number of times by the torque estimate corrector 22 as the target torque of the motor 2, and therefore can estimate the target torque of the motor 2 for controlling the inverter current value to the target current value It with sufficient accuracy over a wide range.

[0060] Furthermore, the control device for an electric vehicle according to this embodiment can calculate with sufficient accuracy the target torque of the motor 2 even in an ECU that does not have a sufficient map capacity. As a result, the control device for an electric vehicle according to this embodiment can perform energy management with high accuracy and protect the battery 3 with high accuracy, thereby improving fuel efficiency and system performance.

[0061] Furthermore, the control device for an electric vehicle according to this embodiment determines a correction value Δη for the motor efficiency η using the correction map M3, and corrects the motor efficiency η estimated using the efficiency map M2 with the correction value Δη. Therefore, even if the motor efficiency η varies depending on the inverter voltage E, the target torque of the motor 2 for controlling the inverter current value to the target current value It can be estimated with sufficient accuracy over a wide coverage range.

[0062] Furthermore, the control device for an electric vehicle according to this embodiment calculates the initial value η0 of the motor efficiency η from the target current value It using the initial efficiency value map M1, and therefore, the number of times that the torque estimation value corrected by the torque estimation value correcting unit 22 is corrected as the torque estimation value before correction can be reduced.

[0063] Furthermore, the control device for an electric vehicle according to this embodiment can reduce the map capacity by controlling on a current basis while using the efficiency map M2 and the output conversion formulas shown in equations (1) to (3), and can improve the estimation accuracy of the target torque of the motor 2.

[0064] Furthermore, when correcting the operating point of the motor 2, the control device for an electric vehicle according to this embodiment determines the corrected current value Ic from the inverter current value Ip and the target current value It, so that even if the operating point fails to converge as a result of correcting the torque estimation value Tg a predetermined number of times by the torque estimation value correction unit 22, the operating point can be compensated.

[0065] In addition, the control device for an electric vehicle according to this embodiment can stabilize the calculation time of the target torque of the motor 2 and the processing load of the ECU 6 by setting the number of corrections by the torque estimation value correction unit 22 to a predetermined number regardless of the result of comparison between the target current value It and the corrected current value I.

[0066] Furthermore, the control device for an electric vehicle according to this embodiment does not feed back the estimated results of the inverter current value or the values ​​detected by the inverter current sensor, so it is possible to ensure the ability to follow changes in the target current value It and the stability of control, and it is possible to reduce the development man-hours required to adapt the feedback parameters.

[0067] Furthermore, the control device for an electric vehicle according to this embodiment can be configured without requiring a sensor for detecting an inverter current value, a sensor for ensuring the estimation accuracy of an inverter current estimated value, or a sensor at all.

[0068] Furthermore, in the control device for an electric vehicle according to this embodiment, if there is a concern that the accuracy may be deteriorated due to the inverter voltage E depending on the characteristics of the motor 2, this can be addressed by correcting the correction map M3, and therefore the configuration can be highly scalable.

[0069] In the above-described embodiment, in order to make the invention easier to understand, the description has been given on the assumption that the inverter 4 is controlled by the ECU 6 so that the motor 2 is driven. However, the control device for an electric vehicle according to this embodiment is configured to operate in the same way as when the inverter 4 is controlled by the ECU 6 so that the motor 2 is driven, even when the inverter 4 is controlled by the ECU 6 so that the motor 2 generates electricity.

[0070] For example, similar to the initial efficiency value map M1, an initial efficiency value map M11 in which the power generation efficiency of the motor 2 (hereinafter also simply referred to as "motor power generation efficiency") ρ is associated with the inverter current value is stored in the ROM of the ECU 6, and the ECU 6 executes a torque estimation value calculation process that calculates a torque estimation value Tg based on the following equation (4) from the target current value It, the inverter voltage E, the initial value ρ0 of the motor power generation efficiency ρ, and the motor rotation speed N.

[0071] Tg×N×ρ0=E×It (4)

[0072] Similarly to the efficiency map M2, an efficiency map M12 in which the motor power generation efficiency ρ is associated with the motor rotation speed N and the motor torque Tm is stored in the ROM of the ECU 6, and the motor power generation efficiency ρ is estimated from the motor rotation speed N and the torque estimation value Tg using the efficiency map M12.

[0073] Similarly to the correction map M3, a correction map M13 in which a correction value Δρ of the motor power generation efficiency ρ is associated with the inverter voltage E, the motor rotation speed N, and the motor torque Tm is stored in the ROM of the ECU 6, and the ECU 6 determines the correction value Δρ of the motor power generation efficiency ρ using the correction map M13.

[0074] The ECU 6 calculates the inverter current value Ip from the inverter voltage E, the torque estimation value Tg, the motor power generation efficiency ρ, and the motor rotation speed N according to the following equation (5).

[0075] Tg×N×ρ=E×Ip (5)

[0076] When performing the torque estimation value correction process using the torque estimation value Tg after correction by the torque estimation value correction process as the torque estimation value before correction, the ECU 6 determines the maximum value between the inverter current value Ip and the target current value It as the corrected current value Ic in the first and third current value corrections, but determines the minimum value between the inverter current value Ip and the target current value It as the corrected current value Ic in the second current value correction.

[0077] In this way, when the motor is driven, the first and third current value corrections are made to the minimum value, and the second current value correction is made to the maximum value, whereas when the motor is generating power, the first and third current value corrections are made to the maximum value, and the second current value correction is made to the minimum value.

[0078] From the viewpoint of battery protection, it is desirable that in the fourth and final torque estimated value correction process, the maximum value between the inverter current value Ip and the target current value It be determined as the corrected current value Ic.

[0079] The ECU 6 calculates the torque estimation value Tg from the corrected current value Ic, the inverter voltage E, the motor power generation efficiency ρ, and the motor rotation speed N based on the following equation (6), thereby correcting the torque estimation value Tg.

[0080] Tg×N×ρ=E×Ic (6)

[0081] From the above explanation, the torque estimation operation that is repeatedly executed over the period during which the inverter 4 is controlled by the ECU 6 so that the motor 2 generates electricity can be easily understood based on the torque estimation operation described with reference to Figure 2, so an explanation of this will be omitted.

[0082] The initial efficiency value map M1 in this embodiment may be a simple map with a low density.Instead of storing the initial efficiency value map M1 in the ROM of the ECU 6, the initial value η0 of the motor efficiency η may be stored as a fixed value in the ROM of the ECU 6.

[0083] Furthermore, instead of calculating the correction value Δη of the motor efficiency η using the correction map M3, the ECU 6 may correct the motor efficiency η estimated using the efficiency map M2 using a mathematical expression that represents the relationship between the inverter voltage E and the motor efficiency η. This configuration can reduce the storage capacity of the correction map M3.

[0084] Furthermore, for example, even other physical quantities such as voltage values ​​can be controlled by the ECU 6 by converting them into direct current using Ohm's law, etc. In addition, any physical quantity that can be converted into direct current can be controlled by the ECU 6 without exception.

[0085] Alternatively, the density of the efficiency map M2 may be reduced, and the ECU 6 may estimate the motor efficiency η from the motor rotation speed N and the torque estimate value Tg by nonlinear interpolation using a spline function or the like.

[0086] In this way, it is also possible to replace the efficiency map M2 with a model formula such as a nonlinear function, for example, a thin plate smoothing spline.

[0087] Furthermore, the ECU 6 in the embodiment may be configured by a system controller, or may be configured by a motor controller that controls the motor 2 via the inverter 4.

[0088] While the present invention has been described with reference to an embodiment thereof, it will be apparent that modifications may be made thereto without departing from the scope of the present invention, and the present invention is disclosed with the understanding that equivalents of such modifications are intended to be encompassed within the scope of the appended claims. [Explanation of symbols]

[0089] 1 vehicle 2 motors 3 Battery 4 inverters 21 Torque estimation value calculation unit 22 Torque estimation value correction unit

Claims

1. a motor that is a drive source for the vehicle; a battery for supplying power to the motor; an inverter that performs power conversion between the motor and the battery, a torque estimation value calculation unit that calculates a torque estimation value representing an estimate of a torque of the motor for setting the DC current value of the inverter to a target current value; a torque estimation value correction unit that estimates an efficiency of the motor based on a rotation speed of the motor and the torque estimation value, and corrects the torque estimation value based on the estimated efficiency of the motor and the target current value, a torque estimation value corrected by the torque estimation value correction unit as a torque estimation value before correction, and a torque estimation value corrected a predetermined number of times by the torque estimation value correction unit as a target torque of the motor.

2. 2. The control device for an electric vehicle according to claim 1, wherein the torque estimation value calculation unit calculates the torque estimation value from the target current value, a voltage of the inverter, an initial value of efficiency of the motor, and a rotation speed of the motor.

3. 3. The control device for an electric vehicle according to claim 2, wherein the torque estimation value calculation unit calculates the initial value of the efficiency of the motor from the target current value using an initial efficiency value map in which the efficiency of the motor is associated with the DC current value of the inverter.

4. The torque estimation value correction unit estimating the efficiency of the motor using an efficiency map in which the efficiency of the motor is correlated with the rotational speed and torque of the motor; calculating a DC current value of the inverter based on the estimated efficiency and the torque estimation value; 2. The control device for an electric vehicle according to claim 1, wherein the torque estimated value is corrected by determining one of the calculated current value and the target current value as the corrected current value of the inverter, thereby correcting an operating point of the motor determined by the torque of the motor and the corrected current value.

5. 5. The control device for an electric vehicle according to claim 4, wherein the torque estimated value correction unit determines a correction value for the motor efficiency using a correction map in which correction values ​​for the motor efficiency are associated with the inverter voltage, the motor rotation speed, and the motor torque, and corrects the motor efficiency estimated using the efficiency map with the correction value.

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