Control device of electric vehicle

Abstract

To provide a control device of an electric vehicle which can quickly determine whether a driving wheel is idling.SOLUTION: An electric vehicle includes: a motor serving as a drive force source; a drive shaft connected to the motor; and a driving wheel connected to an end of the drive shaft. A control device of the electric vehicle calculates a drive shaft torque which is an actual torque acting on the drive shaft based on a value obtained by subtracting an inertia torque of the motor from an actual torque generated in the motor (Step S1) and determines that the driving wheel is idling when a value, obtained by subtracting the drive shaft torque from a torque which corresponds to a command torque for controlling the motor and is transmitted to the drive shaft, is larger than a predetermined torque determined in advance (Step S2).SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a control device for an electric vehicle equipped with a motor as a driving force source. [Background technology]

[0002] When traveling on a wavy or uneven road or going over a step, the drive wheels spin and then touch the ground. In such cases, the reaction force acting on the drive wheels decreases during spinning, causing the rotational speed of the drive wheels to increase. At this time, the rotational speed of the drive power source increases with a delay relative to the rotational speed of the drive wheels, causing torsion in the drive shaft as the rotational speed of the drive wheels increases. Furthermore, during spinning, the actual rotational speed of the drive wheels is faster than the rotational speed of the drive wheels corresponding to the vehicle speed. Therefore, when the vehicle touches the ground again, the rotational speed of the drive wheels drops sharply, causing torsion in the drive shaft. In order to suppress vibrations and component damage associated with such torsion in the drive shaft, the control devices described in Patent Documents 1 to 3 are configured to detect wheel spin.

[0003] The control device described in Patent Document 1 is a control device for a vehicle equipped with an engine as a driving force source, and is configured to integrate the rate of increase of the engine rotation speed from when it exceeds a first threshold until it falls below the first threshold, and to determine that the wheels have slipped when the integrated value exceeds a second threshold.

[0004] The control device described in Patent Document 2 is a control device for an electric vehicle equipped with a motor as a driving force source, and is configured to extract a predetermined frequency component of the detected motor rotation speed and determine whether or not the vehicle is spinning, focusing on the fact that the magnitude of inertia on the tire side in an inertial system differs between when the tire is on the ground and when the tire is spinning.

[0005] Furthermore, the control device described in Patent Document 3 is a control device for an electric vehicle equipped with a motor as a driving force source, and is configured to determine that the rotational speed of the motor fluctuates (pulsates) as a result of resonance of a transmission mechanism that transmits torque from the motor to the tires, determine the rotational jerk by differentiating the pulsating rotational speed of the motor twice, and determine that the tires are spinning if the rotational jerk is a positive value. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-64037 [Patent Document 2] Japanese Patent Publication No. 2020-145863 [Patent Document 3] Japanese Patent Publication No. 2021-167139 Summary of the Invention [Problem to be solved by the invention]

[0007] The control device described in Patent Document 1 determines that a wheel has slipped when the integrated value of the rate of increase of the engine rotation speed during a period in which the rate of increase is equal to or greater than a first threshold value exceeds a second threshold value. In other words, even if a wheel has slipped, wheel slip is not determined until the integrated value of the rate of increase of the engine rotation speed exceeds the second threshold value. Therefore, until wheel slip is determined, control to eliminate slip is not executed, which may cause vibration due to twisting of the drive shaft or reduce the durability of parts such as the drive shaft.

[0008] The present invention has been devised in view of the above technical problems, and has as its object to provide a control device for an electric vehicle that can quickly determine whether the drive wheels are spinning. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a control device for an electric vehicle having a motor as a driving force source, a drive shaft connected to the motor, and drive wheels connected to the ends of the drive shaft, the control device including a controller for controlling the motor, the controller including a torque calculation unit for calculating drive shaft torque, which is the actual torque acting on the drive shaft, and a spin determination unit for determining that the drive wheels are spinning when the value obtained by subtracting the drive shaft torque from the torque transmitted to the drive shaft in accordance with a command torque for controlling the motor is greater than a predetermined torque.

[0010] In the present invention, the torque calculation unit may calculate the drive shaft torque based on a value obtained by subtracting an inertia torque of the motor from an actual torque generated by the motor.

[0011] In the present invention, the spin determination unit may determine that the drive wheels are spinning when the rate of change of the drive shaft torque is greater than a predetermined rate of change of torque.

[0012] In the present invention, the spin determination unit may determine that the drive wheels are spinning when the rate of change of the torsion angle of the drive shaft is greater than a predetermined rate of change.

[0013] In the present invention, the spin determination unit may determine that the drive wheels are spinning when the angular acceleration of the drive wheels is greater than a predetermined angular acceleration.

[0014] In addition, the present invention may further include an ammeter that detects the current flowing through the motor, and the torque calculation unit may determine the actual torque generated by the motor based on the current value detected by the ammeter.

[0015] In addition, this invention may further include a sensor that detects the rotation angle of the motor, and the torque calculation unit may calculate the inertia torque of the motor based on the angular acceleration corresponding to the rotation angle of the motor detected by the sensor and the moment of inertia of the motor.

[0016] In addition, in this invention, the controller may include a limit torque calculation unit that calculates a limit command torque for limiting the angular acceleration of the drive wheels to an angular acceleration equal to or less than a predetermined limit angular acceleration, and a command torque calculation unit that selects the limit command torque calculated by the limit torque calculation unit as the command torque for controlling the motor when the spin determination unit determines that the drive wheels are spinning.

[0017] In this invention, the limit torque calculation unit may include an angular acceleration selector that selects the smaller of the actual angular acceleration of the drive wheel and the predetermined limit angular acceleration, and a feedback controller that calculates the limit command torque based on the difference between a target wheel speed of the drive wheel based on the angular acceleration selected by the angular acceleration selector and the actual wheel speed of the drive wheel. [Effects of the Invention]

[0018] In an electric vehicle according to the present invention, the motor and drive wheels are connected via a drive shaft. Therefore, when the drive wheels spin, the frictional force between the drive wheels and the road surface decreases, causing the rotational speed of the drive wheels and the motor to increase. In such a case, the electromotive force generated by the motor increases, causing the voltage applied to the motor to decrease relatively, thereby reducing the current flowing through the motor. This reduces the actual torque of the motor. Conversely, the angular acceleration of the motor increases, causing the inertia torque of the motor to increase. In other words, when the drive wheels spin, the drive shaft torque changes significantly. Therefore, the control device according to the present invention calculates the drive shaft torque and determines that the drive wheels are spinning when the value obtained by subtracting the calculated drive shaft torque from the torque transmitted to the drive shaft according to the command torque of the motor is greater than a predetermined torque, thereby enabling rapid detection of drive wheel spin. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram schematically illustrating an example of an electric vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating a configuration for connecting a motor and a drive wheel. [Figure 3] FIG. 2 is a block diagram illustrating a functional configuration of a controller according to an embodiment of the present invention. [Figure 4] FIG. 4 is a block diagram for explaining the functional configuration of a torque calculation unit. [Figure 5] 10 is a time chart showing an example of a change in drive shaft torque calculated by a torque calculation unit when the command torque of the motor is kept constant and the vehicle travels on an undulating road or a rough road. [Figure 6] FIG. 4 is a block diagram for explaining the functional configuration of a limit torque calculation unit. [Figure 7] FIG. 2 is a block diagram for explaining the functional configuration of a command torque calculation unit. [Figure 8]4 is a flowchart illustrating an example of control executed by a controller in the embodiment of the present invention. [Figure 9] 5 is a time chart for explaining a change in the rotation speed of a driving wheel when a control example according to an embodiment of the present invention is executed. [Figure 10] 4 is a block diagram for explaining the functional configuration of a spin determination unit that determines whether a drive wheel is spinning in accordance with the rate of change of the torsion angle of the drive shaft. FIG. [Figure 11] FIG. 4 is a block diagram for explaining the functional configuration of a torsional angular velocity calculation unit. [Figure 12] 3 is a block diagram for explaining the functional configuration of a spin determination unit that determines whether a drive wheel is spinning in accordance with the wheel speed. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments are merely examples of specific embodiments of the present invention and are not intended to limit the scope of the present invention.

[0021] An example of an electric vehicle according to an embodiment of the present invention is shown in FIG. 1. The electric vehicle (hereinafter simply referred to as the vehicle) Ve shown in FIG. 1 is a four-wheel-drive electric vehicle in which a motor is connected to each wheel, and is equipped with four motors: a right front motor 2Fr connected to the right front wheel 1Fr, a left front motor 2Fl connected to the left front wheel 1Fl, a right rear motor 2Rr connected to the right rear wheel 1Rr, and a left rear motor 2Rl connected to the left rear wheel 1Rl. The vehicle Ve shown in FIG. 1 is a so-called inboard type vehicle in which the motors 2Fr, 2Fl, 2Rr, and 2Rl are fixed (supported) to the vehicle body. Note that the electric vehicle according to an embodiment of the present invention may also be a so-called in-wheel type electric vehicle in which the motors are built into the wheels. The vehicle may also be a two-wheel drive electric vehicle having a right front motor 2Fr connected to the right front wheel 1Fr and a left front motor 2Fl connected to the left front wheel 1Fl, with the pair of front wheels being the drive wheels, or a two-wheel drive electric vehicle having a right rear motor 2Rr connected to the right rear wheel 1Rr and a left rear motor 2Rl connected to the left rear wheel 1Rl, with the pair of rear wheels being the drive wheels.

[0022] The above-mentioned motors 2Fr, 2Fl, 2Rr, and 2Rl are configured in the same manner as motors used as driving power sources in conventional electric vehicles and hybrid vehicles. That is, they can be configured as motor generators that function not only as motors that output driving torque when supplied with electric power, but also as generators that convert at least a portion of the power into electric power when the output shaft (rotor shaft) is rotated. Specifically, they can be configured as synchronous motors, induction motors, or the like.

[0023] 1, the vehicle Ve shown in FIG. 1 has the same configuration for connecting the right front wheel 1Fr and the right front motor 2Fr, the same configuration for connecting the left front wheel 1Fl and the left front motor 2Fl, the same configuration for connecting the right rear wheel 1Rr and the right rear motor 2Rr, and the same configuration for connecting the left rear wheel 1Rl and the left rear motor 2Rl. Therefore, in the following description, the right front wheel 1Fr, the left front wheel 1Fl, the right rear wheel 1Rr, and the left rear wheel 1Rl will not be distinguished from each other and will simply be referred to as drive wheels 1. Furthermore, the right front motor 2Fr, the left front motor 2Fl, the right rear motor 2Rr, and the left rear motor 2Rl will not be distinguished from each other and will simply be referred to as motors 2. Furthermore, the components provided between the drive wheel 1 and the motor 2 are designated by common names without specifying whether they are front, rear, left, or right, and the reference symbols in the figures are given with "F" for the front components, "R" for the rear components, "r" for the right-side components, and "l" for the left-side components.

[0024] FIG. 2 shows a schematic diagram of a configuration for connecting a drive wheel 1 and a motor 2. An externally toothed drive gear 4 is connected to an output shaft 3 of the motor 2, and a driven gear 5 having a larger diameter (i.e., a greater number of teeth) than the drive gear 4 is meshed with the drive gear 4. One end of a drive shaft 6 is connected to the driven gear 5, and the drive wheel 1 is connected to the other end of the drive shaft 6. Therefore, the rotational speed of the motor 2 is reduced according to the gear ratio between the drive gear 4 and the driven gear 5, and the output torque of the motor 2 is amplified and transmitted to the drive wheel 1. In other words, the drive gear 4 and the driven gear 5 constitute a reduction mechanism 7.

[0025] The vehicle Ve is also provided with a power storage device (Batt) 8 and an inverter (INV) 9. The power storage device 8 is configured with a secondary battery (including an all-solid-state battery) such as a lithium-ion battery or a nickel-metal hydride battery, similar to power storage devices provided in conventional electric vehicles and hybrid vehicles. The inverter 9 is configured with a plurality of transistors and diodes, and is configured to convert DC power output from the power storage device 8 into AC power and output it to the motor 2 by controlling the switching signals of the transistors.

[0026] Furthermore, the vehicle Ve is provided with various sensors, such as a resolver 10 that detects the rotation angle of the motor 2, an ammeter 11 that detects the current flowing through a coil (not shown) that constitutes the motor 2, and a wheel speed sensor 12 that detects the rotation speed of the drive wheels 1, and is also provided with an electronic control device (hereinafter referred to as a controller) 13 to which signals from these sensors 10, 11, and 12 are input.

[0027] Like controllers installed in conventional vehicles, this controller 13 is mainly composed of a microcomputer, and is configured to determine target values ​​for the torque and rotational speed of the motor 2 based on input signals and pre-stored arithmetic expressions and maps, and to output command signals corresponding to these target values ​​to the inverter 9.

[0028] This controller 13 is configured to determine whether the drive wheels 1 are spinning, and when the drive wheels 1 are spinning, to control the motor 2 so as to suppress an increase in the rotational speed of the drive wheels 1. Fig. 3 is a block diagram for explaining the functional configuration of the controller 13, and the controller 13 shown in Fig. 3 is configured by a torque calculation unit 14, a spin determination unit 15, a limit torque calculation unit 16, and a command torque calculation unit 17.

[0029] The torque calculation unit 14 calculates the torque Tm_act that is actually output from the motor 2 (hereinafter referred to as the actual torque) and the angular acceleration dθm of the motor 2. ^2 / dt ^2 Based on this, the torque Tds acting on the drive shaft 6 (hereinafter referred to as drive shaft torque) is estimated. Specifically, as shown in FIG. 4, the system is configured to include a drive shaft torque estimator 18 and a filter 19. The drive shaft torque estimator 18 stores the following equation (1): Tds=Gr(Tm_act-Im·dθm ^2 / dt ^2 ) …(1)

[0030] Here, Gr in equation (1) is the gear ratio of the reduction gear mechanism 7, and Im is the moment of inertia predetermined according to the structure of the motor 2. In addition, when the drive wheels 1 spin freely and the rotation speed increases, the rotation angle of the rotor may differ from the intended rotation angle. In such a case, the actual torque Tm_act differs from the command torque Tm_com for controlling the motor 2. Therefore, the actual torque Tm_act is calculated based on the detection value of the ammeter 11 provided in the motor 2. In addition, the angular acceleration dθm of the motor 2 ^2 / dt ^2 can be obtained by twice differentiating the rotation angle θm of the motor 2 detected by the resolver 10. As described above, equation (1) calculates the drive shaft torque Tds based on the actual torque Tm_act of the motor 2 and the inertia torque of the motor 2. However, the drive shaft torque Tds calculated as described above contains noise. For this reason, a filter 19 such as a low-pass filter is provided to attenuate high-frequency components above a predetermined frequency.

[0031] Figure 5 shows a schematic example of changes in the drive shaft torque Tds calculated by the torque calculation unit 14 when the vehicle travels on an undulating or bumpy road with the command torque Tm_com of the motor 2 kept constant. At time t0 in Figure 5, a constant torque continues to act on the drive shaft 6 because the vehicle is traveling on a flat road.

[0032] At time t1, the drive wheel 1 starts to spin. Therefore, the friction force generated between the road surface and the drive wheel 1 decreases so as to suppress the increase in the rotation speed of the drive wheel 1. In other words, the reaction torque opposing the torque of the motor 2 decreases. Therefore, the drive wheel 1 spins and the rotation speed of the drive wheel 1 increases, and the rotation speed of the motor 2 also increases accordingly. In other words, the angular acceleration dθm of the motor 2 ^2 / dt ^2 As a result, at time t1, the drive shaft torque Tds begins to decrease.

[0033] When the drive wheel 1 touches the road surface at time t2, a frictional force is generated between the road surface and the drive wheel 1. This frictional force acts in the direction of decreasing the rotational speed of the drive wheel 1, which increased when the wheel was spinning. Therefore, when the drive wheel 1 touches the road surface, the rotational speed of the drive wheel 1 decreases rapidly, and the rotational speed of the motor 2 also decreases accordingly. In other words, the angular acceleration dθm of the motor 2 ^2 / dt ^2 becomes a negative value. As a result, at time t2, the drive shaft torque Tds begins to increase.

[0034] Then, the rotation speed of the motor 2 reaches a rotation speed corresponding to the rotation speed of the drive wheel 1 when the drive wheel 1 contacts the road surface without slipping, and the rotation speed of the motor 2 becomes constant. ^2 / dt ^2 becomes zero. Therefore, the torque acting on the drive shaft 6 from the motor 2 becomes equivalent to the command torque Tm_com. Meanwhile, since the drive shaft 6 has a predetermined elastic coefficient, when twisting occurs, an elastic torque is generated in the direction to eliminate the twist. In other words, the drive shaft torque Tds pulsates. Therefore, from time t3 in Figure 5, the drive shaft torque Tds begins to decrease due to the elastic torque.

[0035] As described above, the drive wheel 1 repeatedly spins and touches the ground, and the elastic torque acting in a direction to eliminate the torsion of the drive shaft 6 causes the drive shaft torque Tds to pulsate.

[0036] The spin determination unit 15 is configured to determine whether or not the drive wheels 1 are spinning based on the change in the drive shaft torque Tds. Specifically, it is configured to determine whether or not the drive wheels 1 are spinning based on whether or not the drive shaft 6 is twisted and whether or not the drive shaft torque Tds is changing suddenly. Whether or not the drive shaft 6 is twisted can be determined based on whether or not the following formula (2) is satisfied, and whether or not the drive shaft torque Tds is changing suddenly can be determined based on whether or not the following formula (3) is satisfied. |Tm_com×Gr-Tds|>A …(2) |ΔTds / Δt|>B …(3)

[0037] Here, A in equation (2) is a threshold value for determining whether torsion has occurred in the drive shaft 6, and may be a fixed value determined in advance through experiments or a variable value that varies based on the command torque Tm_com, vehicle speed, etc. Furthermore, B in equation (3) is a threshold value for determining whether the torque of the drive shaft 6 has changed due to the drive wheels 1 spinning, and may be a fixed value determined in advance through experiments or a variable value that varies based on the command torque Tm_com, vehicle speed, etc. This threshold B can be set to a value greater than the rate of change in torque of the drive shaft 6 that occurs during sudden acceleration or deceleration, for example. The threshold A corresponds to the "predetermined torque" in this embodiment of the present invention, and threshold B corresponds to the "torque change rate" in this embodiment of the present invention.

[0038] Furthermore, ΔTds / Δt in equation (3) is the difference ΔTds between the drive shaft torque Tds(n-1) calculated last time in a calculation cycle and the drive shaft torque Tds(n) calculated this time, divided by the calculation cycle (time) Δt. In other words, it is the rate of change of the drive shaft torque Tds. Furthermore, the command torque Tm_com in equation (2) is the command torque Tm_com calculated in the previous calculation cycle in step S3 or step S6 in a control example described later.

[0039] The spin determination unit 15 is configured to determine whether the drive wheels 1 are spinning or not, and also to determine whether the drive wheels 1 have grounded again. Specifically, the spin determination unit 15 is configured to determine whether the drive wheels 1 have grounded again based on whether the following formulas (4) and (5) are satisfied. |Tm_com×Gr-Tds| <C …(4) |ΔTds / Δt| <D …(5)

[0040] Here, C and D in equations (4) and (5) are thresholds for determining whether the vehicle has re-contacted the ground. These may be predetermined fixed values ​​or variable values ​​that vary based on the command torque Tm_com, vehicle speed, etc. Furthermore, when the drive wheels 1 re-contact the ground, the torque acting on the drive shaft 6 based on the command torque Tm_com of the motor 2 is substantially equal to the drive shaft torque Tds calculated by equation (1). Therefore, equation (4) is calculated to determine whether the torsion of the drive shaft 6 has been resolved. Therefore, threshold C may be the same value as threshold A or a different value. Similarly, when the drive wheels 1 re-contact the ground, more specifically, when the drive wheels 1 begin to contact the road surface, the frictional force generated between the drive wheels 1 and the road surface acts on the drive shaft 6 as a resistance torque that reduces the pulsation associated with the torsion of the drive shaft 6, thereby reducing the rate of change of the drive shaft torque Tds. Therefore, equation (5) is calculated. Therefore, threshold D is set to a value smaller than threshold B.

[0041] The limit torque calculation unit 16 is configured to calculate a motor torque for suppressing an increase in rotation speed due to spinning of the drive wheels 1. Specifically, as shown in Fig. 6, the limit torque calculation unit 16 is configured by a difference calculation unit 20, an angular acceleration selector 21, an integrator 22, and a feedback controller 23.

[0042] The difference calculator 20 is configured to calculate the rotational acceleration (angular acceleration) of the drive wheel 1 from the difference between the previous rotational speed (actual wheel speed) of the drive wheel 1 on the calculation cycle detected by the wheel speed sensor 12 and the current rotational speed (actual wheel speed) of the drive wheel 1.

[0043] The angular acceleration selector 21 is configured to select (set) an angular acceleration for suppressing an increase in the rotational speed of the drive wheels 1, and is configured to receive the rotational acceleration of the drive wheels 1 calculated by the difference calculator 20 (hereinafter referred to as the actual angular acceleration) and a predetermined limit angular acceleration as an upper limit value of the angular acceleration of the drive wheels 1, and to select the angular acceleration with the smaller value between the actual angular acceleration and the limit angular acceleration. In other words, the angular acceleration selector 21 is configured to upper limit guard the angular acceleration of the drive wheels 1.

[0044] The integrator 22 is configured to set a target wheel speed by integrating the angular acceleration selected by the angular acceleration selector 21 .

[0045] The feedback controller 23 is configured to determine a limiting command torque Tm_com_lim for the motor 2. Specifically, the controller 23 calculates a difference between the target wheel speed and the actual wheel speed, differentiates the difference, and multiplies the differentiated value by the moment of inertia of the motor 2 to determine a feedback torque for making the actual wheel speed follow the target wheel speed. The controller 13 is also provided with a drive torque calculation unit (not shown) that calculates the drive torque of a conventional vehicle. This drive torque calculation unit is configured to calculate a drive torque (drive force) that the driver requests for the vehicle Ve based on the operation amount of an accelerator operation unit such as an accelerator pedal and the vehicle speed. The feedback controller 23 is configured to calculate a limiting command torque Tm_com_lim for the motor 2 by adding the feedback torque to a required torque Tm_com_req for the motor 2 that corresponds to the required drive torque.

[0046] The command torque calculation unit 17 is configured to select (calculate) a command torque for the motor 2 depending on whether or not the drive wheels 1 are spinning. Specifically, as shown in Fig. 7 , the command torque calculation unit 17 receives a signal indicating whether or not the drive wheels 1 are spinning from the spin determination unit 15, a required torque Tm_com_req from the drive torque calculation unit, and a limit command torque Tm_com_lim for the motor 2 from the limit torque calculation unit 16. When the command torque calculation unit 17 receives a signal indicating that the drive wheels 1 are spinning from the spin determination unit 15, the command torque calculation unit 17 outputs the limit command torque Tm_com_lim received from the limit torque calculation unit 16 as the command torque Tm_com for the motor 2, and when the command torque calculation unit 17 receives a signal indicating that the drive wheels 1 are not spinning from the spin determination unit 15, the command torque calculation unit 17 outputs the required torque Tm_com_req received from the drive torque calculation unit as the command torque Tm_com for the motor 2.

[0047] The controller 13 performs switching control of the inverter 9 based on the command torque Tm_com of the motor 2 output from the command torque calculation unit 17, in the same way as in conventional motor control.

[0048] Fig. 8 shows a flowchart for explaining an example of control executed by the controller 13. In the control example shown in Fig. 8, first, the drive shaft torque Tds is calculated (step S1). This step S1 is executed by the torque calculation unit 14. That is, the actual torque Tm_act of the motor 2 and the angular acceleration dθm of the motor 2 are calculated. ^2 / dt ^2 The drive shaft torque Tds is calculated based on the inertia torque corresponding to the rotational speed.

[0049] Next, it is determined whether any of the drive wheels 1 is spinning (step S2). This step S2 can be determined by the spin determination unit 15. That is, it is determined whether the above formulas (2) and (3) are satisfied.

[0050] If the answer to step S2 is negative because none of the drive wheels 1 are spinning, the required torque Tm_com_req input from the drive torque calculation unit is set as the command torque Tm_com for the motor 2 (step S3), and this routine is temporarily terminated. This step S3 can be executed by the command torque calculation unit 17.

[0051] On the other hand, if the answer to step S2 is YES because any of the drive wheels 1 is spinning, the limiting command torque Tm_com_lim of the motor 2 connected to the spinning drive wheel 1 is calculated. Specifically, first, a target wheel speed of the spinning drive wheel 1 is calculated (step S4), and then a limiting command torque Tm_com_lim of the motor 2 is calculated based on the target wheel speed (step S5). Steps S4 and S5 are executed by the limiting torque calculation unit 16. That is, the actual angular acceleration of the drive wheel 1 is calculated by the difference calculation unit 20, and then the angular acceleration selector 21 selects the smaller angular acceleration from the angular acceleration of the drive wheel 1 or the limiting angular acceleration. Then, the integrator 22 sets the target wheel speed based on the selected angular acceleration. Furthermore, the limiting command torque Tm_com_lim of the motor 2 is calculated based on the difference between the target wheel speed and the actual wheel speed and the required torque Tm_com_req of the motor 2.

[0052] Then, the limiting command torque Tm_com_lim of the motor 2 calculated in step S5 is set as the command torque Tm_com of the motor 2 (step S6), and this routine is temporarily ended. This step S6 can be executed by the command torque calculation unit 17.

[0053] In this control example, the presence or absence of spinning of the drive wheels 1 is determined before calculating the limiting command torque Tm_com_lim. However, the present invention may also be configured to determine the presence or absence of spinning of the drive wheels 1 after calculating the limiting command torque Tm_com_lim, and based on the determination result, set either the required torque Tm_com_req or the limiting command torque Tm_com_lim as the command torque Tm_com of the motor 2.

[0054] FIG. 9 shows a time chart illustrating the difference in change in the rotational speed (wheel speed) of the drive wheels 1 when the above control example is executed and when the control example is not executed while traveling on an uneven road. When the above control example is executed, if the drive shaft torque Tds changes due to the drive wheels 1 spinning, a limiting command torque Tm_com_lim is immediately calculated, and the limiting command torque Tm_com_lim is set as the command torque Tm_com of the motor 2. This limiting command torque Tm_com_lim is a torque that is determined with the limit angular acceleration determined to suppress changes in the rotational speed of the wheel as its upper limit, so the command torque Tm_com of the motor 2 is immediately reduced. Therefore, even if the drive wheels 1 spin and the reaction torque acting from the road surface on the drive wheels 1, i.e., the torque acting in a direction to reduce the rotational speed of the drive wheels 1, decreases, the torque transmitted from the motor 2 to the drive wheels 1 is limited, thereby suppressing an increase in the rotational speed of the drive wheels 1 during spinning, as shown by the solid line in FIG. 9.

[0055] In contrast, if the above control example is not executed, in other words, if the torque of the motor 2 is kept constant while traveling on an uneven road, a constant torque is output from the motor 2 even when the drive wheels 1 spin, causing the rotational speed of the drive wheels 1 to increase rapidly. This is because the reaction torque corresponding to the frictional force acting on the drive wheels 1 from the road surface, i.e., the torque acting in a direction to slow the rotational speed of the drive wheels 1, decreases relatively. Therefore, the rotational speed of the drive wheels 1 increases when the wheels spin, as shown by the dashed line in Figure 9.

[0056] As described above, when the drive wheel 1 spins, the frictional force generated between the drive wheel 1 and the road surface decreases, and the rotational speed of the drive wheel 1 and the motor 2 also increases. In such a case, the electromotive force generated by the motor 2 increases, and the voltage applied to the motor 2 becomes relatively small, so the current flowing through the motor 2 decreases. As a result, the actual torque Tm_act of the motor 2 decreases. Conversely, the angular acceleration dθm of the motor 2 ^2 / dt ^2 As a result, the inertia torque of the motor 2 increases. Therefore, the actual torque Tm_act of the motor 2 decreases, while the angular acceleration dθm of the motor 2 decreases. ^2 / dt ^2 As the inertia torque corresponding to the command torque Tm_com increases, the amount of change in the drive shaft torque Tds increases. In other words, when the drive wheels 1 spin, the drive shaft torque Tds changes significantly. Therefore, by calculating the difference between the drive shaft torque Tds and the torque acting on the drive shaft 6 determined according to the command torque Tm_com, it is possible to quickly determine whether the drive wheels 1 are spinning. As a result, the torque of the motor 2 can be limited to suppress an increase in the rotational speed of the drive wheels 1, which makes it possible to suppress vibrations and damage to parts associated with torsion of the drive shaft 6, or to suppress a decrease in the torque transmitted from the motor 2 to the drive wheels 1 when the wheels re-contact the ground due to torsion of the drive shaft 6.

[0057] Furthermore, by determining whether or not a wheel spin has occurred using the difference between the drive shaft torque Tds and the torque acting on the drive shaft 6 determined according to the command torque Tm_com as a parameter, and also by determining whether or not a wheel spin has occurred using the rate of change of the drive shaft torque Tds as a parameter, it is possible to prevent erroneous determination of whether or not a wheel spin has occurred during sudden acceleration or deceleration, even in situations where the drive shaft torque Tds increases, such as during sudden acceleration or deceleration, without the need to determine such sudden acceleration or deceleration through other control, etc. In other words, a series of controls can be used to properly determine whether or not a wheel spin has occurred at the drive wheels 1, and the control can be prevented from becoming complicated.

[0058] The slip determination unit 15 in the embodiment of the present invention may determine slip of the drive wheels 1 based on the rate of change of the torsion angle of the drive shaft 6 instead of the rate of change (ΔTds / Δt) of the drive shaft torque Tds. Fig. 10 shows a block diagram for explaining the functional configuration of the slip determination unit 15. The slip determination unit 15 shown in Fig. 10 is configured to receive signals from the torque calculation unit 14 and the torsion angular velocity calculation unit 24.

[0059] This torsional angular velocity calculation unit 24 is configured to calculate the rate of change of the torsion angle of the drive shaft 6. A block diagram for explaining the functional configuration of this torsional angular velocity calculation unit 24 is shown in Fig. 11, and the torsional angular velocity calculation unit 24 shown in Fig. 11 is made up of a differentiator 25, a multiplier 26, a difference calculator 27, and a filter 28. The differentiator 25 determines the rotational speed ωm of the motor 2 by time differentiating the rotational angle θ of the motor 2 detected by the resolver 10.

[0060] The multiplier 26 determines the input rotation speed of the drive shaft 6 by multiplying the rotation speed ωm of the motor 2 determined by time differentiation by the differentiator 25 by the reciprocal of the gear ratio Gr of the reduction mechanism 7.

[0061] The differentiator 27 calculates the rate of change of the torsion angle of the drive shaft 6 (torsion angular velocity) from the difference between the input side rotation speed and the output side rotation speed of the drive shaft 6, and subtracts the rotation speed (wheel speed) ωw of the drive wheels 1 detected by the wheel speed sensor 12 from the input side rotation speed of the drive shaft 6 multiplied by the reciprocal of the gear ratio Gr by the multiplier 26.

[0062] Similarly to the filter 19, the filter 28 is configured with a low-pass filter or the like for attenuating high-frequency components above a predetermined frequency, and is configured to remove noise contained in the torsional angular velocity input from the differentiator 27.

[0063] That is, the torsional angular velocity calculation unit 24 calculates the torsional angular velocity ωds of the drive shaft 6 by the following equation (6). ωds=ωm×1 / Gr-ωw …(6)

[0064] The spin determination unit 15 determines whether or not the drive wheels 1 are spinning based on the drive shaft torque Tds calculated by the torque calculation unit 14 and the torsional angular velocity ωds of the drive shaft 6 calculated by the torsional angular velocity calculation unit 24. Specifically, it is determined that the drive wheels 1 are spinning when the following equations (2) and (7) are satisfied. |Tm_com×Gr-Tds|>A …(2) |ωds|>E …(7)

[0065] Here, E in equation (7) is a threshold value for determining whether the rate of change of the torsional angle of the drive shaft 6 has increased due to spinning of the drive wheels 1, and may be a fixed value determined in advance through experiments or the like, or may be a variable value that varies based on the command torque Tm_com, vehicle speed, etc. This threshold value E can be set to a value greater than the torsional angular velocity of the drive shaft 6 that occurs during sudden acceleration or deceleration, for example. This threshold value E corresponds to the "predetermined rate of change" in this embodiment of the present invention.

[0066] The spin determination unit 15 is configured to determine whether the drive wheels 1 are spinning or not, and also to determine whether the drive wheels 1 have grounded again. Specifically, the spin determination unit 15 is configured to determine whether the drive wheels 1 have grounded again based on whether the following formulas (4) and (8) are satisfied. |Tm_com×Gr-Tds|<C …(4) |ωds|> F …(8)

[0067] Here, F in equation (8) is a threshold value for determining whether the vehicle has touched the ground again, and may be a predetermined fixed value or a variable value that varies based on the command torque Tm_com, the vehicle speed, etc. Furthermore, the threshold value F may be set to a value smaller than the threshold value E in equation (7).

[0068] Even when determining whether the drive wheels 1 are spinning based on the torsional angular velocity ωds of the drive shaft 6 instead of the rate of change (ΔTds / Δt) of the drive shaft torque Tds as described above, it is possible to prevent erroneous determination of whether the drive wheels 1 are spinning during sudden acceleration or deceleration in a situation where the drive shaft torque Tds increases, such as during sudden acceleration or deceleration, without determining such sudden acceleration or deceleration through other control. In other words, it is possible to properly determine whether the drive wheels 1 are spinning through a series of controls, and it is possible to prevent the controls from becoming complicated.

[0069] The spin determination unit 15 in the embodiment of the present invention may determine spin of the drive wheels 1 based on the rate of change of the wheel speed ωw, i.e., the angular acceleration of the drive wheels 1, instead of the rate of change (ΔTds / Δt) of the drive shaft torque Tds or the torsional angular velocity ωds of the drive shaft 6. Fig. 12 is a block diagram for explaining the functional configuration of the spin determination unit 15. The spin determination unit 15 shown in Fig. 12 is configured to receive signals from the torque calculation unit 14 and the wheel speed sensor 12.

[0070] Then, the spin determination unit 15 determines whether or not the drive wheels 1 are spinning based on the drive shaft torque Tds calculated by the torque calculation unit 14 and the wheel speed ωw detected by the wheel speed sensor 12. Specifically, it is determined that the drive wheels 1 are spinning when the following equations (2) and (9) are satisfied. |Tm_com×Gr-Tds|>A …(2) |Δωw / Δt|>G …(9)

[0071] Here, G in equation (9) is a threshold value for determining whether the rate of change (angular acceleration) of the wheel speed ωw has increased due to spinning of the drive wheels 1. It may be a fixed value determined in advance through experiments or a variable value that varies based on the command torque Tm_com, vehicle speed, etc. This threshold value G can be set to a value greater than the torsional angular velocity of the drive shaft 6 that occurs during sudden acceleration or deceleration. This threshold value G corresponds to the "predetermined angular acceleration" in this embodiment of the present invention. The rate of change Δωw / Δt of the wheel speed ωw is the difference between the wheel speed ωw(n-1) detected last time during a calculation cycle and the wheel speed ωw(n) detected this time, divided by the calculation cycle (time).

[0072] The spin determination unit 15 is configured to determine whether the drive wheels 1 are spinning or not, and also to determine whether the drive wheels 1 have touched the ground again. Specifically, the spin determination unit 15 is configured to determine whether the drive wheels 1 have touched the ground again based on whether the following formulas (4) and (10) are satisfied. |Tm_com×Gr-Tds| <C …(4) |Δωw / Δt| <H …(10)

[0073] Here, H in equation (10) is a threshold value for determining whether the vehicle has grounded again, and may be a predetermined fixed value or a variable value that varies based on the command torque Tm_com, the vehicle speed, etc. Furthermore, the threshold value H may be set to a value smaller than the threshold value F in equation (9).

[0074] As described above, even when determining whether the drive wheels 1 are spinning based on the rate of change (Δωw / Δt) of the wheel speed ωw instead of the rate of change (ΔTds / Δt) of the drive shaft torque Tds or the torsional angular velocity ωds of the drive shaft 6, even under circumstances in which the drive shaft torque Tds increases, such as during sudden acceleration or deceleration, it is possible to prevent erroneous determination of whether the drive wheels 1 are spinning during sudden acceleration or deceleration without determining such sudden acceleration or deceleration through other control. In other words, it is possible to properly determine whether the drive wheels 1 are spinning through a series of controls, and it is possible to prevent the controls from becoming complicated.

[0075] The electric vehicle in the embodiments of the present invention is not limited to an electric vehicle equipped only with a motor as a driving force source. It may also be a parallel hybrid vehicle configured to drive one of a pair of front wheels or a pair of rear wheels with an engine and drive the other with a motor, or a series hybrid vehicle configured to convert engine power into electricity with a generator and supply that electricity to a motor to drive the drive wheels. In other words, any vehicle may be used as long as one of the drive wheels and the motor are mechanically coupled at all times. In addition, in each of the control examples described above, the drive shaft torque is calculated based on the torque actually output from the motor and the inertia torque of the motor. However, if the drive shaft torque can be directly detected by, for example, providing a torque sensor on the drive shaft, the detected torque may be used as the drive shaft torque. [Explanation of symbols]

[0076] 1 drive wheel 2 motors 4 drive gear 5 Driven gear 6 drive shaft 10 Resolver 11 Ammeter 12 Wheel speed sensor 13 Controller 14 Torque calculation unit 15 Idling detection section 16. Limit torque calculation section 17 Command torque calculation unit 18 Drive shaft torque estimator 20 Difference calculator 21 Angular acceleration selector 22 Integrator 23 Feedback Controller 24 Angular velocity calculation section 25 Differentiator 26 Multiplier 27 Differentiator Vehicle

Claims

1. A control device for an electric vehicle including a motor as a driving force source, a drive shaft connected to the motor, and a drive wheel connected to an end of the drive shaft, a controller for controlling the motor; The controller a torque calculation unit that calculates a drive shaft torque that is an actual torque acting on the drive shaft; and a spin determination unit that determines that the drive wheels are spinning when a value obtained by subtracting the drive shaft torque from the torque transmitted to the drive shaft according to a command torque for controlling the motor is greater than a predetermined torque. A control device for an electric vehicle.

2. The control device for an electric vehicle according to claim 1, The torque calculation unit calculates the drive shaft torque based on a value obtained by subtracting the inertia torque of the motor from the actual torque generated by the motor. A control device for an electric vehicle.

3. The control device for an electric vehicle according to claim 1, The spin determination unit determines that the drive wheels are spinning when the rate of change of the drive shaft torque is greater than a predetermined rate of change of torque. A control device for an electric vehicle.

4. The control device for an electric vehicle according to claim 1, The spin determination unit determines that the drive wheels are spinning when the rate of change of the torsion angle of the drive shaft is greater than a predetermined rate of change. A control device for an electric vehicle.

5. The control device for an electric vehicle according to claim 1, The wheel spin determination unit determines that the drive wheels are spinning when the angular acceleration of the drive wheels is greater than a predetermined angular acceleration. A control device for an electric vehicle.

6. The control device for an electric vehicle according to claim 2, further comprising an ammeter for detecting a current flowing through the motor; The torque calculation unit calculates the actual torque generated by the motor based on the current value detected by the ammeter. A control device for an electric vehicle.

7. The control device for an electric vehicle according to claim 2, a sensor for detecting a rotation angle of the motor; The torque calculation unit calculates the inertia torque of the motor based on the angular acceleration corresponding to the rotation angle of the motor detected by the sensor and the moment of inertia of the motor. A control device for an electric vehicle.

8. The control device for an electric vehicle according to any one of claims 1 to 7, The controller a limit torque calculation unit that calculates a limit command torque for limiting the angular acceleration of the drive wheels to an angular acceleration equal to or less than a predetermined limit angular acceleration; a command torque calculation unit that selects the limit command torque calculated by the limit torque calculation unit as a command torque for controlling the motor when the spin determination unit determines that the drive wheels are spinning; A control device for an electric vehicle.

9. The control device for an electric vehicle according to claim 8, the limit torque calculation unit includes: an angular acceleration selector that selects an angular acceleration having a smaller value between an actual angular acceleration of the drive wheels and the predetermined limit angular acceleration; a feedback controller that calculates the limiting command torque based on the difference between a target wheel speed of the drive wheels based on the angular acceleration selected by the angular acceleration selector and an actual wheel speed of the drive wheels. A control device for an electric vehicle.

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