Electric vehicle

Abstract

To suppress a sharp increase in motor revolution speed and suppress an excess current in a battery when a slip due to idling of a drive wheel occurs in rectangular wave voltage control.SOLUTION: An electric vehicle comprises: a motor; an inverter for driving the motor; a battery connected to the inverter; and a control device capable of executing rectangular wave voltage control to set a voltage phase obtained by adding, to a feedback term based on a deviation between a torque command of the motor and actual torque thereof, a feedforward term based on the torque command, and to control the inverter so that a rectangular wave voltage of the set voltage phase is applied to the motor. When a slip due to idling of a drive wheel is detected in the rectangular wave voltage control, the control device sets the feedforward term so as to offset the voltage phase in such a direction that the actual torque decreases relative to the torque command as compared to when the slip is not detected.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to electric vehicles. [Background technology]

[0002] A conventional electric vehicle of this type has been proposed that includes an AC motor, an inverter that converts DC voltage to AC voltage and applies it to the AC motor, and a control device having a square wave voltage control unit that sets a voltage phase by feedback control based on the torque deviation between the actual torque value and the torque command value and controls the inverter so that a square wave voltage of the set voltage phase is applied to the AC motor (see, for example, Patent Document 1). The square wave voltage control unit calculates the amount of torque change caused by changes in the motor operating state, calculates the ratio of the amount of torque change to the amount of voltage phase change to determine the amount of voltage phase shift, and shifts the integral term by feedback control that changes the voltage phase in accordance with the torque deviation according to the amount of voltage phase shift. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-148330 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the square wave voltage control unit of the electric vehicle described above does not have the effect of suppressing rotation disturbances caused by road surface irregularities, etc. Therefore, if slippage occurs due to spinning of the drive wheels while square wave voltage control is being executed, the rotation speed of the motor increases sharply, and there is a risk that an overcurrent will flow to the battery due to the sudden increase in motor output.

[0005] The electric vehicle of the present disclosure has a primary objective to suppress a sudden increase in the motor rotation speed and suppress an overcurrent in the battery when slippage occurs due to spinning of the drive wheels during square wave voltage control. [Means for solving the problem]

[0006] The electric vehicle of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] The electric vehicle of the present disclosure is an electric vehicle including a motor connected to drive wheels, an inverter that converts DC voltage to AC voltage and applies it to the motor, a battery connected to the inverter, and a control device capable of executing square wave voltage control that sets a voltage phase by adding a feedforward term based on a torque command to a feedback term based on the deviation between the torque command and actual torque of the motor, and controls the inverter so that a square wave voltage of the set voltage phase is applied to the motor, and the control device, when slip due to spin of the drive wheels is detected during the square wave voltage control, sets the feedforward term so as to offset the voltage phase in a direction that reduces the actual torque relative to the torque command more than when the slip is not detected.

[0008] In the electric vehicle disclosed herein, when slippage is detected, the torque output from the motor can be quickly reduced by setting the feedforward term, thereby suppressing a sudden increase in the motor rotation speed and suppressing an overcurrent in the battery that would otherwise occur due to a sudden increase in motor output. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an electric vehicle according to an embodiment of the present invention; [Figure 2] FIG. 4 is a functional block diagram of a square wave voltage control unit. [Figure 3] 10 is a flowchart illustrating an example of an FF term setting process. [Figure 4] FIG. 10 is an explanatory diagram showing FF term setting lines when slip determination is off and when slip determination is on. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an embodiment of the present disclosure will be described. Fig. 1 is a schematic configuration diagram of an electric vehicle 20 according to this embodiment. As shown in the figure, the electric vehicle 20 according to this embodiment includes a motor 32 for driving, an inverter 34, a battery 40, and an electronic control unit (hereinafter referred to as "ECU") 50 that controls the entire vehicle.

[0011] The motor 32 is configured as a synchronous generator motor having a rotor with a permanent magnet embedded therein and a stator around which a three-phase coil is wound. The rotor of the motor 32 is connected to a drive shaft 26 which is connected to the drive wheels 22 a, 22 b via a differential gear 24.

[0012] The inverter 34 is connected to the battery 40 via a power line 42. The inverter 34 has six transistors T11 to T16 as switching elements and six diodes D11 to D16 connected in anti-parallel to the corresponding transistors. The transistors T11 to T16 are arranged in pairs, two at a time, so as to be on the source side and two at the sink side of a positive line 42a and a negative line 42b of the power line 42. Each of the three-phase coils (U-phase, V-phase, and W-phase coils) of the motor 32 is connected to each of the connection points between the paired transistors T11 to T16. With a voltage applied to the power line 42, the motor 32 is rotated by applying a three-phase AC current to the three-phase coils through switching control of the transistors T11 to T16.

[0013] The battery 40 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. A positive terminal of the battery 40 is connected to a positive line 42a of a power line 42 via a reactor 41, and a negative terminal of the battery 40 is connected to a negative line 42b of the power line 42. The battery 40 may be connected to the power line 42 via a boost converter. A smoothing capacitor 44 is attached to the positive line 42a and the negative line 42b of the power line 42.

[0014] The ECU 50 is configured as a microprocessor centered around a CPU. In addition to the CPU, the ECU 50 includes a ROM for storing processing programs, a RAM for temporarily storing data, input / output ports, and communication ports. Signals from various sensors are input to the ECU 50 via input ports. Examples of signals input to the ECU 50 include a rotational position θm from a rotational position sensor (e.g., a resolver) 32a that detects the rotational position of the rotor of the motor 32, and phase currents Iu and Iv from current sensors 32u and 32v that detect the phase currents of the U and V phases of the motor 32. Other signals input to the ECU 50 include a voltage Vb of the battery 40 from a voltage sensor (not shown) attached between the terminals of the battery 40, a current Ib of the battery 40 from a current sensor (not shown) attached to the output terminals of the battery 40, and a voltage VH of the capacitor 44 (power line 42) from a voltage sensor 44a attached between the terminals of the capacitor 44. Further, signals input to the ECU 50 include an ignition signal from a start switch 60, a shift position SP from a shift position sensor 62 that detects the operating position of a shift lever 61, an accelerator opening Acc from an accelerator pedal position sensor 64 that detects the depression amount of an accelerator pedal 63, a brake pedal position BP from a brake pedal position sensor 66 that detects the depression amount of a brake pedal 65, a vehicle speed V from a vehicle speed sensor 68, and wheel speeds Vwr, Vwl from wheel speed sensors 69a, 69b attached to the drive wheels 22a, 22b. Various control signals are output from the ECU 50 via output ports. Examples of signals output from the ECU 50 include switching control signals to transistors T11 to T16 of the inverter 34.

[0015] In the electric vehicle 20 of this embodiment configured as described above, the ECU 50 sets a required torque Td* required of the drive shaft 26 based on the accelerator pedal position Acc from the accelerator pedal position sensor 64 and the vehicle speed V from the vehicle speed sensor 68. Next, the ECU 50 sets a torque command Tm* for the motor 32 so that the required torque Td* is output to the drive shaft 26. The ECU 50 then performs switching control of the transistors T11 to T16 of the inverter 34 so that the motor 32 is driven by the torque command Tm*.

[0016] The ECU 50 also calculates wheel accelerations αwr, αwl based on the wheel speeds Vwr, Vwl from the wheel speed sensors 69a, 69b, and performs slip determination based on the wheel accelerations αwr, αwl to determine whether slip due to spin has occurred at the drive wheels 22a, 22b. The slip determination is performed by determining that there is no slip (slip determination off) when the wheel accelerations αwr, αwl are less than a threshold value αref, and determining that there is slip (slip determination on) when the wheel accelerations αwr, αwl are equal to or greater than the threshold value αref. If the ECU 50 determines that there is slip, it controls the motor 32 so that the slip converges.

[0017] Next, the operation of the inverter 34 will be described. The ECU 50 controls the inverter 34 in one of a sinusoidal PWM (pulse width modulation) control mode, an overmodulation PWM control mode, and a square wave control mode. The sinusoidal PWM control mode is a control mode in which a PWM signal is generated by comparing a carrier wave (e.g., a triangular wave) with a sinusoidal voltage command to control the inverter 34. The overmodulation PWM control mode is a control mode in which a PWM signal is generated by comparing a carrier wave with a sinusoidal voltage command having an amplitude larger than that of the carrier wave to control the inverter 34. The square wave voltage control mode is a control mode in which a square wave pulse signal is generated by phase control of a square wave voltage to control the inverter 34. The square wave voltage control mode will be described in further detail below.

[0018] 2 is a functional block diagram of the square-wave voltage control unit 70. The square-wave voltage control unit 70 is a control unit that executes a square-wave voltage control mode and is realized by a program executed by the ECU 50 and calculation processing by electronic circuits (hardware) within the ECU 50. The square-wave voltage control unit 70 includes, as functional blocks, a power calculation unit 71, a torque calculation unit 72, a deviation calculation unit 73, an FB (feedback) term setting unit 74, an FF (feedforward) term setting unit 75, an adder 76, a square-wave generation unit 77, and a signal generation unit 78. The power calculation unit 71 calculates the power (motor power Pm) to be supplied to the motor 32 based on the phase currents Iu, Iv, and Iw and the phase voltages Vu, Vv, and Vw obtained from the U-phase current Iu and V-phase current Iv detected by the current sensors 32u and 32v. The torque calculation unit 72 calculates the torque (motor torque Tm) output from the motor 32 based on the motor power Pm calculated by the power calculation unit 71 and the rotational speed Nm of the motor 32 calculated from the rotational position θm detected by the rotational position sensor 32a. The deviation calculation unit 73 calculates the deviation between the motor torque Tm calculated by the torque calculation unit 72 and the torque command Tm* (torque deviation ΔTm = Tm* - Tm) and outputs it to the feedback term setting unit 74. The feedback term setting unit 74 sets the feedback term θb by the sum of a proportional control term obtained by multiplying the torque deviation ΔTm by a proportional gain and an integral control term obtained by multiplying the integral value of the torque deviation ΔTm by an integral gain. The FF term setting unit 75 sets the FF term θf based on the rotational speed Nm of the motor 32, the voltage VH of the capacitor 44, the torque command Tm*, and the slip determination. Details of the processing by the FF term setting unit 75 will be described later. An adder 76 adds the FB term θb and the FF term θf to set the voltage phase θ. A square wave generator 77 sets the phase voltage command values ​​Vu*, Vv*, and Vw* based on the voltage phase θ. A signal generator 78 generates a switching control signal based on the phase voltage command values ​​Vu*, Vv*, and Vw* and outputs it to the inverter 34. The inverter 34 controls the switching of the transistors T11 to T16 based on the switching control signal, thereby applying a square wave voltage according to the voltage phase θ to the motor 32.

[0019] Next, a detailed description will be given of the processing executed by the FF term setting unit 75. Fig. 3 is a flowchart showing an example of the FF term setting processing executed by the FF term setting unit 75 (ECU 50).

[0020] In the FF term setting process, the FF term setting unit 75 first inputs the slip determination (step S100), and determines whether the input slip determination is ON (slip is present) (step S102). The slip determination has been described above.

[0021] When the FF term setting unit 75 determines that the slip determination is OFF (no slip), it sets the FF term torque offset value to 0 (step S104). Then, the FF term setting unit 75 derives and sets the FF term θf corresponding to the torque command Tm* using a map (FF term setting line) that is offset in the torque axis direction from the normal map (actual torque line) by the set FF term torque offset value (step S108), and ends the FF term setting process. Here, the actual torque line is a map for setting the FF term θf such that the torque command Tm* matches the torque (actual torque) Tm actually output from the motor 32. When the slip determination is OFF, the FF term torque offset value is set to 0, and the FF term θf is set using the FF term setting line that is the same as the actual torque line. As described above, when the FF term θf is set by the FF term setting unit 75, the set FF term θf is input to the adder 76, where it is added to the FB term θb to set the voltage phase θ, and then input to the square wave generator 77. Then, a square wave generating unit 77 sets the respective phase voltage command values ​​Vu*, Vv*, Vw*, and a signal generating unit 78 generates a switching control signal to control the switching of the transistors T11 to T16 of the inverter 34. As a result, the motor 32 outputs a torque Tm that corresponds to the torque command Tm*.

[0022] On the other hand, if the FF term setting unit 75 determines that the slip determination is ON, it sets a positive predetermined value α to the FF term torque offset value (step S106).Then, the FF term setting unit 75 sets the FF term θf corresponding to the torque command Tm* using a map (FF term setting line) that is offset from the normal map (actual torque line) by the FF term torque offset value toward the high torque side of the torque shaft (step S108), and ends the FF term setting process.

[0023] FIG. 4 is an explanatory diagram showing the FF term setting lines when the slip determination is OFF and when the slip determination is ON. In the diagram, the dashed line (curved) is the actual torque line, and the solid line (curved) is the FF term setting line. When the slip determination is OFF, the FF term torque offset value is set to a value of 0, and the FF term setting line is set to the same line as the actual torque line, as shown in FIG. 4(a). Therefore, by using the FF term setting line to set the FF term θf corresponding to the torque command Tm* and performing square wave voltage control, it is possible to output torque Tm corresponding to the torque command Tm* from the motor 32. On the other hand, when the slip determination is ON, the FF term torque offset value is set to a positive predetermined value α, and the FF term setting line is set to a line offset by the predetermined value α toward the high torque side of the torque shaft from the actual torque line, as shown in FIG. 4(b). As a result, the torque output from the motor 32 due to the FF term θf' set using the FF term setting line becomes "Tm'" in the figure, which is smaller than the torque Tm output from the motor 32 due to the FF term θf set using the actual torque line. In other words, the torque output from the motor 32 can be reduced. Therefore, the rotation speed Nm of the motor 32 can be quickly reduced, and the generated slip can be resolved.

[0024] In this embodiment, a plurality of FF term setting lines are prepared for each rotation speed Nm of the motor 32 and each voltage VH of the capacitor 44. The FF term setting unit 75 selects one FF term setting line based on the rotation speed Nm and the voltage VH, then offsets the selected FF term setting line in accordance with the FF term torque offset value, and sets the FF term θf corresponding to the torque command Tm* using the FF term setting line after the offset.

[0025] In the electric vehicle 20 according to the embodiment described above, in the square wave voltage control mode, when slippage due to spinning of the drive wheels 22a, 22b is detected, the voltage phase θ is set by setting the FF term θf so that the voltage phase θ is offset in a direction that reduces the actual torque relative to the torque command Tm*, compared to when slippage is not detected, and the inverter 34 is controlled so that a square wave voltage with the set voltage phase θ is applied to the motor 32. This allows the torque of the motor 32 to be quickly reduced by setting the feedforward term. As a result, a sudden increase in the rotation speed of the motor 32 can be suppressed, and an overcurrent that would otherwise flow to the battery 40 due to a sudden increase in the output of the motor 32 can be suppressed.

[0026] In the above-described embodiment, the FF term setting unit 75 (ECU 50) sets the FF term torque offset value based on the slip determination, and derives and sets the FF term θf' corresponding to the torque command Tm* using an FF term setting line offset in the direction of the torque axis based on the FF term torque offset value. However, the FF term setting unit 75 may derive the FF term θf corresponding to the torque command Tm* using the actual torque line, and then correct (offset) the FF term θf based on the slip determination to set the FF term θf'.

[0027] In the above-described embodiment, the FF term setting unit 75 (ECU 50) sets the FF term torque offset value to a positive predetermined value α when the slip determination is ON. However, the FF term setting unit 75 may set a variable FF term torque offset value depending on the magnitude of slip (magnitude of wheel acceleration) when the slip determination is ON.

[0028] In the above-described embodiment, the electric vehicle 20 is configured to include a traction motor 32, an inverter 34, and a battery 40. However, the electric vehicle may be configured as a parallel or series type hybrid vehicle that includes an engine in addition to a traction motor.

[0029] The above describes the form for carrying out the present invention using examples, but the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms within the scope that does not deviate from the gist of the present invention. [Industrial Applicability]

[0030] The present invention can be used in the electric vehicle manufacturing industry and the like. [Explanation of symbols]

[0031] 20 electric vehicle, 22a, 22b drive wheels, 32 motor, 34 inverter, 40 battery, 50 electronic control unit (ECU), 70 square wave voltage control unit.

Claims

[Claim 1] An electric vehicle comprising: a motor connected to a drive wheel; an inverter that converts a DC voltage into an AC voltage and applies the AC voltage to the motor; a battery connected to the inverter; and a control device capable of performing square wave voltage control that sets a voltage phase by adding a feedforward term based on a torque command to a feedback term based on a deviation between a torque command and an actual torque of the motor, and controls the inverter so that a square wave voltage of the set voltage phase is applied to the motor, When slippage due to spinning of the drive wheels is detected in the rectangular wave voltage control, the control device sets the feedforward term so as to offset the voltage phase in a direction in which the actual torque decreases with respect to the torque command, compared to when the slippage is not detected. Electric vehicle.

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