Electric vehicle control device

Abstract

To provide a control device of an electric vehicle which can suppress destruction of a capacitive element of an inverter associated with failsafe control.SOLUTION: A control device of an electric vehicle comprises: a pressure-resistant map acquisition unit which acquires a pressure-resistant map showing a relation between voltage of a capacitive element for smoothing DC power input in an inverter and durable time; a voltage information acquisition unit which acquires voltage information showing the voltage of the capacitive element; a timer unit which counts time; and a short-circuit control unit which performs winding short-circuit control for short-circuiting windings of a drive motor when the capacitive element is non-durable on the basis of the pressure-resistant map, the voltage information, and time in which the voltage shown by the voltage information continues, counted by the timer unit when an operation of the inverter is stopped by failsafe.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] In a conventional electric vehicle equipped with an engine and a drive motor driven by electric power generated by the engine, a technique is known in which, in the event of a failure in a motor drive device equipped with an inverter, the operation of the inverter is stopped as a fail-safe control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6296169 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, when the inverter operation is stopped by fail-safe control, the drive motor enters an uncontrolled state with its output released. At this time, the capacitance element used to smooth the DC power input to the inverter is charged by the back electromotive force of the drive motor. This may result in an overvoltage being applied to the capacitance element, which may lead to destruction.

[0005] An object of the present invention is to provide a control device for an electric vehicle that can prevent damage to the capacitance elements of an inverter that occurs due to fail-safe control. [Means for solving the problem]

[0006] In order to achieve the above object, the control device for an electric vehicle according to the present invention is a control device for an electric vehicle including an engine, a battery that stores electric power obtained by converting power of the engine, an inverter that converts DC power output from the battery into AC power, and a drive motor that uses the AC power output from the inverter to supply drive power for running drive wheels, the control device comprising: a voltage resistance map acquisition unit that acquires a voltage resistance map showing the relationship between the voltage of a capacitance element that smooths the DC power input to the inverter and a durable time; and a voltage information acquisition unit that acquires voltage information showing the voltage of the capacitance element. a temperature information acquiring unit that acquires temperature information indicating a temperature of the drive motor; and a rotation speed information acquiring unit that acquires rotation speed information indicating a rotation speed of the drive motor. and a short-circuit control unit that performs winding short-circuit control to short-circuit a winding of the drive motor if the capacitance element is not durable, based on the withstand voltage map, the voltage information, and the duration of time that the voltage indicated by the voltage information has continued, when the operation of the inverter is stopped by a fail-safe. During the winding short-circuit control, if the voltage of the capacitive element acquired by the voltage information acquisition unit is equal to or lower than a first threshold, the temperature of the drive motor acquired by the temperature information acquisition unit is equal to or higher than a second threshold, and the rotation speed of the drive motor acquired by the rotation speed information acquisition unit is equal to or lower than a third threshold, the short-circuit control unit cancels the winding short-circuit control.

[0007] With this configuration, it is possible to determine whether the inverter's capacitance element is in an unsustainable state based on the breakdown voltage map, the capacitance element voltage, and the duration of the capacitance element voltage. If the capacitance element is in an unsustainable state, winding short-circuit control is performed to stop the application of the back electromotive force of the drive motor to the capacitance element. This makes it possible to prevent damage to the inverter's capacitance element due to fail-safe control. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent damage to the capacitance elements of the inverter due to fail-safe control. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of a configuration of a main part of a hybrid vehicle. [Figure 2] FIG. 2 is a diagram illustrating an example of a schematic configuration of the second inverter. [Figure 3]FIG. 3 is a diagram showing an example of the relationship between the three-phase voltage of the drive motor and the voltage of the smoothing capacitor. [Figure 4] FIG. 4 is a diagram showing an example of the relationship between the vehicle speed and the voltage of the back electromotive force of the drive motor at the time of shutdown. [Figure 5] FIG. 5 is a diagram showing an example of a pressure resistance map. [Figure 6] FIG. 6 is a diagram illustrating an example of functions of the MG-ECU. [Figure 7] FIG. 7 is a timing chart showing an example of the operation of the HEV-ECU and the MG-ECU when an internal failure occurs in the PCU. [Figure 8] FIG. 8 is a flowchart showing an example of the operation of the MG-ECU. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a control device for a hybrid vehicle according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0011] 1 is a diagram showing an example of the configuration of the main parts of a hybrid vehicle 1 according to this embodiment. The hybrid vehicle 1 is equipped with a series hybrid system 10. The hybrid system 10 includes an engine 11, a generator motor (MG1) 12, a drive motor (MG2) 13, a battery 14, and a PCU (Power Control Unit) 15.

[0012] The engine 11 is, for example, a gasoline engine.

[0013] The generator motor 12 is, for example, a permanent magnet synchronous motor. The rotating shaft of the generator motor 12 is mechanically connected to the crankshaft of the engine 11 via a gear (not shown). For example, an output gear of the engine 11 is supported on the crankshaft of the engine 11 so as not to rotate relative to the crankshaft, and an output gear of the engine 11 is supported on the rotating shaft of the generator motor 12 so as not to rotate relative to the crankshaft, and the output gear of the engine 11 and the motor gear are meshed.

[0014] The drive motor 13 is, for example, a permanent magnet synchronous motor that is larger than the generator motor 12. A rotating shaft of the drive motor 13 is connected to a drive system 16 of the hybrid vehicle 1. The drive system 16 includes a differential gear, and the power of the drive motor 13 is transmitted to the differential gear and then distributed and transmitted from the differential gear to drive wheels 17 consisting of left and right front or rear wheels. This causes the left and right drive wheels 17 to rotate, causing the hybrid vehicle 1 to move forward or backward.

[0015] Battery 14 stores the electric power obtained by converting the power of engine 11. For example, battery 14 is a battery pack made up of a combination of multiple secondary batteries. The secondary batteries are, for example, lithium ion batteries. Battery 14 outputs, for example, DC power of approximately 200 to 350 V.

[0016] The PCU 15 is a unit for controlling the driving of the generator motor 12 and the drive motor 13, and includes a first inverter 21, a second inverter 22, and a converter .

[0017] When starting the engine 11, the DC power output from the battery 14 is boosted by the converter 23, the boosted DC power is converted into AC power by the first inverter 21, and the AC power is supplied to the generator motor 12. This causes the generator motor 12 to perform power running, and the engine 11 is motored (cranked) by the generator motor 12. When the rotation speed of the crankshaft of the engine 11 has increased to the rotation speed required for starting due to motoring, the ignition plug of the engine 11 is sparked, and the engine 11 starts.

[0018] When the hybrid vehicle 1 is traveling, the drive motor 13 is operated in a power running mode, and the drive motor 13 generates power.

[0019] When the output required of the drive motor 13 is smaller than the output of the battery 14, the hybrid vehicle 1 runs in EV mode. That is, the engine 11 is stopped, power generation by the generator motor 12 is not performed, and power is supplied from the battery 14 to the drive motor 13, which is then driven by the power.

[0020] Furthermore, when the remaining capacity of the battery 14 falls below a predetermined level, the generator motor 12 operates to generate electricity while the engine 11 is running, regardless of whether the drive motor 13 is running or stopped. At this time, AC power from the generator motor 12 is converted to DC power by the first inverter 21, and the DC power output from the first inverter 21 is stepped down by the converter 23. The stepped-down DC power is supplied to the battery 14, thereby charging the battery 14.

[0021] When the hybrid vehicle 1 decelerates, the drive motor 13 undergoes regenerative operation, and power transmitted from the drive wheels 17 to the drive motor 13 is converted into AC power. At this time, the drive motor 13 acts as a resistance in the traveling drive system, and this resistance acts as a braking force (regenerative braking force) that brakes the hybrid vehicle 1. At this time, in the PCU 15, the AC power supplied from the drive motor 13 to the second inverter 22 is converted into DC power by the second inverter 22, and the DC power output from the second inverter 22 is stepped down by the converter 23. The stepped-down DC power is then supplied to the battery 14, thereby charging the battery 14.

[0022] The ECU 31 is a control device that controls the hybrid vehicle 1. The ECU 31 includes a plurality of ECUs, such as an HEV-ECU 100 that controls the hybrid system 10, and an MG-ECU 200 that controls the motor system, such as the generator motor 11, the drive motor 13, and the PCU 15. The ECUs are connected to each other via electrical communication lines such as a CAN (Controller Area Network) so that they can communicate with each other.

[0023] Next, a description will be given of the portion of this embodiment relating to fail-safe control in the event of a failure of the PCU 15. The MG-ECU 200 of this embodiment stops (shuts down) the operation of the second inverter 22 as fail-safe control in the event of an internal failure of the PCU 15. FIG. 2 is a diagram showing an example of a schematic configuration of the second inverter 22. As shown in FIG. 2, the second inverter 22 includes a smoothing capacitor C (corresponding to a "capacitance element") for smoothing the input DC power, six transistors S1 to S6, and six diodes D1 to D6 that correspond one-to-one to the six transistors and are connected in parallel in the reverse direction of the corresponding transistors. A full-bridge circuit is configured by the combination of the six transistors and the six diodes D1 to D6.

[0024] In this example, the three upper transistors S1 to S3 are referred to as the first upper arm transistor S1, the second upper arm transistor S2, and the third upper arm transistor S3, respectively. The three lower transistors S4 to S6 are referred to as the first lower arm transistor S4, the second lower arm transistor S5, and the sixth lower arm transistor S6, respectively. The first upper arm transistor S1 and the first lower arm transistor S4 are paired and connected in series, and their connection point (node) is connected to one of the three phases (u, v, w) of the drive motor 13. The second upper arm transistor S2 and the second lower arm transistor S5 are paired and connected in series, and their connection point (node) is connected to one of the three phases (u, v, w) of the drive motor 13. The third upper arm transistor S3 and the sixth lower arm transistor S6 are paired and connected in series, and their connection point (node) is connected to one of the three phases (u, v, w) of the drive motor 13.

[0025] The six diodes D1 to D6 are referred to as the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, and the sixth diode D6, respectively. The first diode D1 is connected in parallel in the reverse direction to the first upper arm transistor S1. The second diode D2 is connected in parallel in the reverse direction to the second upper arm transistor S2. The third diode D3 is connected in parallel in the reverse direction to the third upper arm transistor S3. The fourth diode D4 is connected in parallel in the reverse direction to the first lower arm transistor S4. The fifth diode D5 is connected in parallel in the reverse direction to the second lower arm transistor S5. The sixth diode D6 is connected in parallel in the reverse direction to the third lower arm transistor S6.

[0026] If an internal failure occurs in the PCU 15, the MG-ECU 200 performs fail-safe control by stopping the operation of the transistors S1 to S6 (stopping the operation of the second inverter 22). This causes the drive motor 13 to enter an uncontrolled (output-disconnected) state, and the smoothing capacitor C is charged by the back electromotive force of the drive motor 13 via the full-bridge circuit. FIG. 3 is a diagram showing an example of the relationship between the three-phase voltage and the voltage VH of the smoothing capacitor C (the voltage applied between the electrodes), and the direction of the current indicated by the arrow in FIG. 2 corresponds to the state at time t shown in FIG. 3.

[0027] FIG. 4 is a diagram showing an example of the relationship between vehicle speed and the voltage of the back electromotive force (back electromotive voltage) of the drive motor 13 during shutdown due to the fail-safe function of the PCU 15. As shown in FIG. 4, it can be seen that the back electromotive voltage of the drive motor 13 during shutdown is proportional to the vehicle speed. FIG. 5 is a diagram showing an example of a withstand voltage map showing the relationship between the voltage of the smoothing capacitor C and the endurance time. As shown in FIG. 5, when the voltage exceeds V1, the endurance time shortens proportionally. For example, when the voltage of the smoothing capacitor C is V2 (700 V, for example), the endurance time is about 60 seconds. This means that if the voltage applied to the smoothing capacitor C continues for 60 seconds or more, the withstand voltage limit may be exceeded, leading to overvoltage breakdown (meaning that the capacitor cannot withstand the voltage).

[0028] The MG-ECU 200 of this embodiment determines whether the smoothing capacitor C is unsustainable based on the withstand voltage map, the voltage VH of the smoothing capacitor C, and the time during which the voltage VH is continuously applied to the smoothing capacitor C. If the smoothing capacitor C is unsustainable, winding short-circuit control is performed to short-circuit the windings of the drive motor 13, thereby preventing overvoltage breakdown of the smoothing capacitor C. The specific configuration of the MG-ECU 200 will be described below.

[0029] Fig. 6 is a diagram showing an example of functions of MG-ECU 200. As shown in Fig. 6, MG-ECU 200 has a fail-safe control unit 210, a withstand voltage map acquisition unit 220, a voltage information acquisition unit 230, a timer unit 240, a temperature information acquisition unit 250, a rotation speed information acquisition unit 260, a short-circuit control unit 270, and a discharge control unit 280. In this example, the functions illustrated in Fig. 7 are realized by a processor executing a program stored in a non-volatile memory, but the present invention is not limited to this, and for example, some or all of these functions may be realized by a dedicated hardware circuit (e.g., a semiconductor integrated circuit).

[0030] In the example of FIG. 6, only functions necessary for explaining the main parts of this embodiment are illustrated, but the functions of the MG-ECU 200 are not limited to these.

[0031] When an internal failure occurs in the PCU 15, the fail-safe control unit 210 performs fail-safe control to shut down the second inverter 22. More specifically, the fail-safe control unit 210 stops the operation of the transistors S1 to S6 included in the second inverter 22.

[0032] The withstand pressure map acquisition unit 220 acquires the withstand pressure map described above. The withstand pressure map may be stored in any location, and may take various forms depending on design conditions, etc. For example, the withstand pressure map may be stored in the ROM 202, in a memory external to the MG-ECU 200, or in an external device such as a server.

[0033] The voltage information acquisition unit 230 acquires the voltage VH of the smoothing capacitor C. The timekeeping unit 240 has a timekeeping function. The temperature information acquisition unit 250 acquires temperature information indicating the temperature of the drive motor 13. The rotation speed information acquisition unit 260 acquires rotation speed information indicating the rotation speed of the drive motor 13.

[0034] When the operation of the second inverter 22 is stopped by the fail-safe control unit 210, the short-circuit control unit 170 performs winding short-circuit control to short-circuit the windings of the drive motor 13 if the smoothing capacitor C is not durable, based on the withstand voltage map acquired by the withstand voltage map acquisition unit 220, the voltage information acquired by the voltage information acquisition unit 230, and the duration of time for which the voltage VH indicated by the voltage information has continued, as measured by the timer unit 240. For example, in the withstand voltage map of FIG. 5, if the state in which the voltage VH of the smoothing capacitor C is V2 continues for 60 seconds, it is determined that the smoothing capacitor C is not durable. In this case, the short-circuit control unit 170 performs winding short-circuit control. The winding short-circuit control may be any control that short-circuits three phases of the drive motor 13, and may be, for example, control that simultaneously transitions the first upper arm transistor S1, the second upper arm transistor S2, and the third upper arm transistor S3 to the ON state, or control that simultaneously transitions the first lower arm transistor S4, the second lower arm transistor S5, and the third lower arm transistor S6 to the ON state.

[0035] Furthermore, during winding short-circuit control, if the voltage VH of the smoothing capacitor C is equal to or lower than the first threshold and the temperature of the drive motor 13 acquired by the temperature information acquisition unit 250 is equal to or higher than the second threshold, the short-circuit control unit 270 cancels the winding short-circuit control. If the drive motor 13 is short-circuited, the drive motor 13 will be heated by a short-circuit current, which may cause demagnetization or burnout of the windings due to overheating. Therefore, if the voltage VH of the smoothing capacitor C is equal to or lower than the first threshold indicating a voltage that does not pose a risk of overvoltage breakdown (for example, a voltage equal to or lower than voltage V1 in FIG. 5 ) and the temperature of the drive motor 13 is equal to or higher than the second threshold indicating a temperature that may cause winding burnout, the winding short-circuit control is canceled, thereby protecting the drive motor 13.

[0036] Furthermore, when the rotation speed of the drive motor 13 acquired by the rotation speed information acquisition unit 260 is equal to or less than a third threshold value, the short-circuit control unit 270 cancels the winding short-circuit control.

[0037] Continuing with the explanation of Fig. 6, the discharge control unit 280 controls the discharge of the smoothing capacitor C. For example, the discharge control unit 280 can promote the discharge of the smoothing capacitor C by powering the generator motor 11 (active discharge). The smoothing capacitor C is also discharged via a discharge resistor (not shown) (passive discharge).

[0038] 7 is a timing chart showing an example of the operation of the HEV-ECU 100 and the MG-ECU 200 when an internal failure occurs in the PCU 15. In FIG. 7, the IGCT activation signal, which is one of the internal signals of the HEV-ECU 100, is a signal that indicates whether the ignition switch is in an on or off state. SMRB and SMRG are signals that indicate whether power is being supplied from the battery 14 to the converter 23. When SMRB and SMRG are in an on state, this indicates that power is being supplied from the battery 14 to the converter 23, and when they are in an off state, this indicates that power supply from the battery 14 to the converter 23 is being cut off.

[0039] 7 means the voltage VH of the smoothing capacitor C. In the example of FIG. 7, an internal failure occurs in the PCU 15, the system voltage VH rises, and reaches a voltage exceeding the first threshold. When the time has passed since the voltage resistance map indicates that overvoltage breakdown will occur, the MG-ECU 200 performs winding short-circuit control. Thereafter, the temperature of the drive motor 13 rises and reaches a second threshold (≦critical temperature). If the rotation speed is equal to or lower than the third threshold and the system voltage VH has fallen to equal to or lower than the first threshold, the MG-ECU 200 releases the winding short-circuit control.

[0040] After the winding short-circuit control is released, the system voltage rises again and exceeds the first threshold. When the time has passed since the voltage resistance map indicated that overvoltage breakdown would occur, MG-ECU 200 performs winding short-circuit control again. MG-ECU 200 continues to monitor the state of drive motor 13, and releases winding short-circuit control if the temperature of drive motor 13 again reaches the second threshold, the rotation speed is equal to or lower than the third threshold, and system voltage VH is equal to or lower than the first threshold. If the system voltage does not show an increasing tendency after the release of winding short-circuit control, the motor short-circuit necessity determination flag, which indicates whether or not a determination is required as to whether or not to short-circuit drive motor 13, is turned off.

[0041] 8 is a flowchart showing an example of the operation of MG-ECU 200 when an internal failure occurs in PCU 15. Explanations of portions that overlap with the above functional explanations will be omitted where appropriate. As shown in FIG. 8, first, when second inverter 22 is shut down by fail-safe control unit 210 (step S1: Yes), voltage information acquisition unit 230 acquires voltage information (step S2).

[0042] The short-circuit control unit 270 determines whether the voltage VH (the voltage VH of the smoothing capacitor C) indicated by the voltage information acquired in step S2 exceeds the first threshold value (step S3). If the result of step S3 is positive (step S3: Yes), the timer unit 240 starts timing (step S4), and the voltage information acquisition unit 230 acquires voltage information (step S5).

[0043] The short-circuit control unit 270 determines whether or not the voltage VH indicated by the voltage information acquired in step S5 exceeds the first threshold value (step S6). If the result of step S6 is positive (step S6: Yes), the short-circuit control unit 270 determines whether or not there is a possibility that the component withstand voltage of the smoothing capacitor C will be exceeded (whether or not it will be unsustainable) based on the withstand voltage map and the elapsed time (step S7).

[0044] If the result of step S7 is positive (step S7: Yes), the short-circuit control unit 270 performs winding short-circuit control, and the discharge control unit 280 performs discharge control of the smoothing capacitor C (control related to passive discharge and active discharge) (step S8). After step S8, the temperature information acquisition unit 250 acquires temperature information (step S9). Then, the short-circuit control unit 270 determines whether the temperature indicated by the temperature information acquired in step S8 is equal to or higher than a second threshold (step S10). If the result of step S10 is positive (step S10: Yes), the voltage information acquisition unit 230 acquires voltage information (step S11). Then, the short-circuit control unit 270 determines whether the voltage VH indicated by the voltage information acquired in step S11 is equal to or lower than a first threshold (step S12).

[0045] If the result of step S12 is positive (step S12: Yes), the rotation speed information acquisition unit 260 acquires rotation speed information (step S13). Then, the short circuit control unit 270 determines whether the rotation speed indicated by the rotation speed information acquired in step S13 is equal to or less than a third threshold value (step S14).

[0046] If the result of step S14 is positive (step S14: Yes), the discharge control unit 280 stops the discharge control, and the short-circuit control unit 270 releases the winding short-circuit control (step S15).

[0047] As described above, when the operation of the second inverter 22 is stopped due to a fail-safe caused by an internal failure of the PCU 15, the MG-EU 200 of this embodiment uses a breakdown voltage map showing the relationship between the voltage VH of the smoothing capacitor C and the endurance time to monitor the voltage VH of the smoothing capacitor C and the application time of the voltage VH, and determines whether the smoothing capacitor C is beyond its endurance. If the smoothing capacitor C is beyond its endurance, the drive motor 13 This makes it possible to prevent breakdown of the smoothing capacitor C of the second inverter 22 due to fail-safe control caused by an internal failure of the PCU 15.

[0048] Furthermore, when the drive motor 13 is short-circuited by the above-described winding short-circuit control, the drive motor 13 heats up due to the short-circuit current, which may cause demagnetization or burnout of the windings due to overheating. Therefore, as described above, the MG-EU 200 of this embodiment can protect the drive motor 13 by canceling the winding short-circuit control when the voltage VH of the smoothing capacitor C is equal to or lower than the first threshold value indicating a voltage that does not pose a risk of overvoltage breakdown, and when the temperature of the drive motor 13 is equal to or higher than the second threshold value indicating a temperature that may cause winding burnout or the like.

[0049] Although the embodiments of the present invention have been described above, the above-described embodiments are presented as examples and are not intended to limit the scope of the present invention. This novel embodiment can be embodied in various other forms. Furthermore, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Furthermore, this embodiment is included within the scope and spirit of the invention, and is also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0050] 1 Hybrid vehicle 10 Hybrid System 11 Engine 12 Generator motor (MG1) 13 Drive motor (MG2) 14 Battery 15 PCU 16 Drivetrain 17 Drive wheels 21 First inverter 22 Second inverter 23 Converter 31 ECU 100 HEV-ECU 200MG-ECU 201 processor 202 ROM 203 RAM 204 I / F section 210 Fail-safe control unit 220 Pressure resistance map acquisition section 230 Voltage information acquisition unit 240 Timing section 250 Temperature information acquisition section 260 Rotational speed information acquisition unit 270 Short-circuit control section 280 Discharge control unit

Claims

[Claim 1] A control device for an electric vehicle including an engine, a battery that stores electric power obtained by converting power of the engine, an inverter that converts DC power output from the battery into AC power, and a drive motor that uses the AC power output from the inverter to supply drive power for driving drive wheels, a withstand voltage map acquisition unit that acquires a withstand voltage map that indicates a relationship between a voltage of a capacitance element for smoothing DC power input to the inverter and a durable time; a voltage information acquiring unit that acquires voltage information indicating a voltage of the capacitive element; a temperature information acquisition unit that acquires temperature information indicating the temperature of the drive motor; a rotation speed information acquisition unit that acquires rotation speed information indicating the rotation speed of the drive motor; a timing unit that measures time; a short-circuit control unit that performs winding short-circuit control to short-circuit a winding of the drive motor if the capacitance element is not durable, based on the withstand voltage map, the voltage information, and the duration of the voltage indicated by the voltage information measured by the timer unit, when the operation of the inverter is stopped by a fail-safe function; Equipped with the short-circuit control unit cancels the winding short-circuit control when, during the winding short-circuit control, the voltage of the capacitive element acquired by the voltage information acquisition unit is equal to or lower than a first threshold, the temperature of the drive motor acquired by the temperature information acquisition unit is equal to or higher than a second threshold, and the rotation speed of the drive motor acquired by the rotation speed information acquisition unit is equal to or lower than a third threshold. Control device for electric vehicles.

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