JP4182944B2 - Vehicle motor traction control device - Google Patents

Description

  The present invention relates to a motor traction control device for a vehicle that is applied to a hybrid vehicle, an electric vehicle, and the like and in which at least one motor is installed in a power source that drives wheels.

In hybrid vehicles and electric vehicles equipped with a motor as the power source for driving the wheels, when the wheels are driven and slipped, the motor over-rotates in accordance with the driving slip of the wheels and an overcurrent is generated in the motor drive circuit. In order to protect the parts, it is necessary to converge the drive slip with good response. The motor traction control device for converging the driving slip for the purpose of protecting the component predicts that the driving slip occurs when the change rate (angular acceleration) of the rotational angular velocity of the driving wheel is equal to or higher than a predetermined value, and reduces the motor torque. And driving slip that occurs with an increase in motor torque is prevented (see, for example, Patent Document 1).
JP-A-10-304514

  However, in the conventional motor traction control device described above, priority is given to component protection on a low-μ road where driving slip is likely to occur, and if the occurrence of driving slip is predicted, a large motor torque is reduced by a high control gain (fixed value). Since the control amount is provided, the motor torque is reduced when the driving slip occurs. However, when the angular acceleration of the driving wheel is lowered due to the reduction of the motor torque, the increase of the motor torque is permitted and the slip occurs again. When the generation and convergence of the slip are repeated in the wheels of the drive wheels and the wheel speed rotation fluctuates, there is a problem that front and rear G hunting in which the vehicle front and rear G fluctuates due to the reaction force. In particular, since a vehicle equipped with a motor as a power source for driving wheels has a fast torque response by the motor, such a phenomenon is more likely to occur than an engine vehicle.

  The present invention has been made paying attention to the above problem, and provides a motor traction control device for a vehicle that can achieve both protection of parts and prevention of front and rear G hunting regardless of the level of road surface friction coefficient. With the goal.

In order to achieve the above object, in the motor traction control device for a vehicle according to the present invention, at least one motor provided in a power source for driving the wheel, and a driving slip of the wheel are detected, and the wheel grip is controlled by motor torque down control. A motor traction control device for a vehicle comprising:
A road surface friction coefficient equivalent value estimating means for estimating a road surface friction coefficient equivalent value is provided,
The motor traction control means sets the control gain of the motor traction control to a high value when the road surface friction coefficient equivalent value indicates a low friction coefficient, and to a lower value as the high friction coefficient is indicated. Based on the value obtained by multiplying the slip amount by the motor torque down control amount ,
The motor traction control means limits the maximum motor torque based on a sum of a value obtained by multiplying the control gain and the slip amount of the wheel and a value obtained by accumulating the difference between the slip amount and the slip determination threshold while the slip is continued. A limit torque is calculated, and when slip occurs, a value obtained by subtracting the limit torque from the required motor torque is used as a motor torque down control amount .

  Therefore, in the motor traction control device for a vehicle according to the present invention, in the motor traction control means, the control gain of the motor traction control is set to a high value when the road surface friction coefficient equivalent value shows a low friction coefficient. The motor torque down control amount is calculated based on a value obtained by multiplying the set control gain and the slip amount. That is, for example, when a driving slip having the same slip amount occurs, the motor gain is reduced so that the control gain is high when traveling on a low μ road and the control gain is low when traveling on a high μ road. The control amount becomes larger as the road becomes lower. Therefore, for example, when slip occurs when traveling on a low μ road, the slip converges with good response due to a large motor torque-down control amount, and the over-rotation of the motor is suppressed. On the other hand, when slipping occurs on high-μ roads, a small motor torque-down control amount causes gradual but reliable reduction of the drive wheel speed and grip recovery. After convergence, the driver suddenly depresses the accelerator. As long as there is no such thing, the occurrence of re-slip is suppressed. As a result, it is possible to achieve both the protection of parts and the prevention of front and rear G hunting regardless of the level of the road surface friction coefficient.

  Hereinafter, the best mode for realizing a motor traction control device for a vehicle according to the present invention will be described based on Examples 1 to 3 shown in the drawings.

First, the drive system configuration of the hybrid vehicle will be described.
FIG. 1 is an overall system diagram showing a drive system of a hybrid vehicle to which the motor traction control device of Embodiment 1 is applied. As shown in FIG. 1, the drive system of the hybrid vehicle in the first embodiment includes an engine E, a first motor generator MG1, a second motor generator MG2 (motor), an output sprocket OS, and a power split mechanism TM. Have.

  The engine E is a gasoline engine or a diesel engine, and the opening degree of a throttle valve and the like are controlled based on a control command from an engine controller 1 described later.

The first motor generator MG1 and the second motor generator MG2 are synchronous motor generators in which a permanent magnet is embedded in a rotor and a stator coil is wound around a stator. Based on a control command from the motor controller 2 described later, Each is controlled independently by applying a three-phase alternating current generated by the control unit 3.
Both of the motor generators MG1 and MG2 can operate as electric motors that are rotated by receiving power supplied from the battery 4 (hereinafter, this state is referred to as “powering”), and the rotor is rotated by an external force. If it is, the battery 4 can be charged by functioning as a generator that generates electromotive force at both ends of the stator coil (hereinafter, this state is referred to as regeneration).

  The power split mechanism TM is configured by a simple planetary gear having a sun gear S, a pinion P, a ring gear R, and a pinion carrier PC. And the connection relationship of the input / output member with respect to the three rotating elements (sun gear S, ring gear R, and pinion carrier PC) of the simple planetary gear will be described. A first motor generator MG1 is connected to the sun gear S. A second motor generator MG2 and an output sprocket OS are connected to the ring gear R. An engine E is connected to the pinion carrier PC via an engine damper ED. The output sprocket OS is connected to the left and right front wheels via a chain belt CB, a differential and a drive shaft (not shown).

Due to the above connection relationship, the first motor generator MG1 (sun gear S), the engine E (planet carrier PC), the second motor generator MG2 and the output sprocket OS (ring gear R) are arranged in this order on the alignment chart shown in FIG. It is possible to introduce a rigid lever model (a relationship in which three rotational speeds are always connected by a straight line) that can simply express the dynamic operation of a simple planetary gear.
Here, the “collinear diagram” is a velocity diagram used in a simple and easy-to-understand method of drawing instead of the method of obtaining by equation when considering the gear ratio of the differential gear, Take the number of rotations (rotation speed) of the rotating elements, take each rotating element on the horizontal axis, and set the interval between each rotating element to the collinear lever ratio (1: λ) based on the gear ratio λ of the sun gear S and ring gear R It arrange | positions so that it may become.

Next, the control system of the hybrid vehicle will be described.
As shown in FIG. 1, the control system of the hybrid vehicle in the first embodiment includes an engine controller 1, a motor controller 2, a power control unit 3, a battery 4 (secondary battery), a brake controller 5, and an integrated controller. 6.

  The integrated controller 6 receives input information from an accelerator opening sensor 7, a vehicle speed sensor 8, an engine speed sensor 9, a first motor generator speed sensor 10, and a second motor generator speed sensor 11. Brought about. Note that the vehicle speed sensor 8 and the second motor generator rotation speed sensor 11 are for detecting the output rotation speed of the same power split mechanism TM, so the vehicle speed sensor 8 is omitted and the second motor generator rotation speed sensor 11 The sensor signal may be used as a vehicle speed signal.

  The brake controller 5 includes a front left wheel speed sensor 12, a front right wheel speed sensor 13, a rear left wheel speed sensor 14, a rear right wheel speed sensor 15, and a steering angle sensor 16 (steering angle detection means). The master cylinder pressure sensor 17 and the brake stroke sensor 18 provide input information.

  The engine controller 1 responds to an engine operating point (Ne) according to a target engine torque command or the like from an integrated controller 6 that inputs an accelerator opening AP from an accelerator opening sensor 7 and an engine speed Ne from an engine speed sensor 9. , Te), for example, is output to a throttle valve actuator (not shown).

  The motor controller 2 receives the motor of the first motor generator MG1 in response to a target motor generator torque command or the like from the integrated controller 6 that inputs the motor generator rotational speeds N1 and N2 from the motor generator rotational speed sensors 10 and 11 by the resolver. A command for independently controlling the operating point (N1, T1) and the motor operating point (N2, T2) of the second motor generator MG2 is output to the power control unit 3. The motor controller 2 uses information on the battery S.O.C that indicates the state of charge of the battery 4.

  The power control unit 3 constitutes a power supply system high voltage system capable of supplying power to both motor generators MG1 and MG2 with less current. As shown in FIG. 5, a joint box 3a and a boost converter 3b A drive motor inverter 3c, a generator generator inverter 3d, and a capacitor 3e. A drive motor inverter 3c is connected to the stator coil of the second motor generator MG2. A generator generator inverter 3d is connected to the stator coil of the first motor generator MG1. The joint box 3a is connected to a battery 4 that is discharged during power running and charged during regeneration.

  The brake controller 5 performs ABS control according to a control command to a brake hydraulic pressure unit 19 that independently controls the brake hydraulic pressure of the four wheels during low-μ road braking, sudden braking, and the like. At the time of braking by the brake, regenerative brake cooperative control is performed by issuing a control command to the integrated controller 6 and a control command to the brake hydraulic pressure unit 19. The brake controller 5 includes wheel speed information from the wheel speed sensors 12, 13, 14, 15, steering angle information from the steering angle sensor 16, braking operation from the master cylinder pressure sensor 17 and the brake stroke sensor 18. Quantity information is entered. And based on these input information, a predetermined calculation process is performed and the control command by the process result is output to the integrated controller 6 and the brake hydraulic pressure unit 19. A front left wheel wheel cylinder 20, a front right wheel wheel cylinder 21, a rear left wheel wheel cylinder 22, and a rear right wheel wheel cylinder 23 are connected to the brake fluid pressure unit 19.

  The integrated controller 6 manages the energy consumption of the entire vehicle and has a function for running the vehicle with the highest efficiency. The integrated controller 6 performs engine operating point control by a control command to the engine controller 1 during acceleration running or the like. In addition, the motor generator operating point control is performed by a control command to the motor controller 2 at the time of stopping, running, braking, or the like. The integrated controller 6 includes the accelerator opening AP, the vehicle speed VSP, the engine speed Ne, the first motor generator speed N1, and the second motor generator speed N2 from the sensors 7, 8, 9, 10, and 11. Entered. And based on these input information, a predetermined calculation process is performed and the control command by the process result is output to the engine controller 1 and the motor controller 2. FIG. The integrated controller 6 and the engine controller 1, the integrated controller 6 and the motor controller 2, and the integrated controller 6 and the brake controller 5 are connected by bidirectional communication lines 24, 25, and 26, respectively, for information exchange.

Next, driving force performance will be described.
As shown in FIG. 2 (b), the driving force of the hybrid vehicle of the first embodiment includes the engine direct driving force (the driving force obtained by subtracting the generator driving amount from the total engine driving force) and the motor driving force (both motor generators MG1). , Driving force by the sum of MG2). As shown in FIG. 2A, the maximum driving force is configured such that the lower the vehicle speed, the greater the motor driving force. In this way, since the vehicle does not have a transmission and travels by adding the direct driving force of the engine E and the motor driving force that is electrically converted, the full power of the accelerator pedal is fully opened from low speed to high speed from the state of low steady driving power. Until now, it is possible to control the driving force seamlessly in response to the driver's request (torque on demand).
In the hybrid vehicle of the first embodiment, the engine E, the motor generators MG1 and MG2, and the left and right front wheels are connected without a clutch through the power split mechanism TM. Further, as described above, most of the engine power is converted into electric energy by a generator, and the vehicle is driven by a motor with high output and high response. For this reason, for example, when driving on a slippery road surface such as an ice burn, when the driving force of the vehicle changes suddenly due to wheel slip or wheel lock during braking, the power control unit 3 is protected from excessive current. Alternatively, it is necessary to protect parts from the pinion over-rotation of the power split mechanism TM. On the other hand, motor traction control that utilizes the high-output and high-response motor characteristics, developed from the component protection function, detects wheel slip instantaneously, recovers the grip, and runs the vehicle safely. Is adopted.

Next, the braking force performance will be described.
In the hybrid vehicle of the first embodiment, the kinetic energy of the vehicle is converted into electric energy by operating the second motor generator MG2 operating as a motor as a generator (generator) during braking by an engine brake or a foot brake. Then, a regenerative braking system that recovers and reuses the battery 4 is adopted.
As shown in Fig. 3 (a), the general regenerative brake cooperative control in this regenerative brake system calculates the required braking force with respect to the brake pedal depression amount, regardless of the magnitude of the required braking force. The required braking force is shared by the regenerative component and the hydraulic component.
In contrast, the regenerative brake cooperative control employed in the hybrid vehicle of the first embodiment calculates the required braking force with respect to the brake pedal depression amount as shown in FIG. 3 (b), and calculates the calculated required braking force. On the other hand, the regenerative brake is given priority, and as long as the regenerative portion can cover it, the regenerative portion is expanded to the maximum without using the hydraulic component. Thereby, especially in a traveling pattern in which acceleration / deceleration is repeated, energy recovery efficiency is high, and energy recovery by regenerative braking is realized up to a lower vehicle speed.

Next, the vehicle mode will be described.
As the vehicle mode in the hybrid vehicle of the first embodiment, as shown in the collinear diagram of FIG. 4, “stop mode”, “start mode”, “engine start mode”, “steady travel mode”, “acceleration mode” Have
In the “stop mode”, as shown in FIG. 4A, the engine E, the generator MG1, and the motor MG2 are stopped. In the “start mode”, as shown in FIG. 4 (2), the vehicle starts by driving the motor MG2 . In the “engine start mode”, as shown in FIG. 4 (3), the sun gear S rotates to start the engine E by the generator MG1 having a function as an engine starter. In the “steady travel mode”, as shown in FIG. 4 (4), the vehicle travels mainly by the engine E, and power generation is minimized in order to increase efficiency. In the “acceleration mode”, as shown in FIG. 4 (5), the engine E is rotated and the generator MG1 starts generating power. The electric power of the battery 4 is used to increase the driving force of the motor MG2. In addition, it accelerates.
In reverse running, in the “steady running mode” shown in FIG. 4 (4), if the rotation speed of the generator MG1 is increased while the increase in the rotation speed of the engine E is suppressed, the rotation speed of the motor MG2 becomes negative. Transition and reverse travel can be achieved.

  At the time of start-up, when the ignition key is turned, the engine E starts, and after the engine E is warmed up, the engine E stops immediately. When starting or at a light load, when starting or when going down a gentle hill that runs at a very low speed, the fuel is cut in areas where engine efficiency is low, and the engine stops and the motor MG2 runs. During normal travel, the driving force of the engine E is driven directly by one of the wheels by the power split mechanism TM, while the other drives the generator MG1 and assists the motor MG2. At the time of full open acceleration, power is supplied from the battery 4 and further driving force is added. When decelerating or braking, the wheel drives the motor MG2 and acts as a generator to perform regenerative power generation. The collected electrical energy is stored in the battery 4. When the charge amount of the battery 4 decreases, the generator MG1 is driven by the engine E and charging is started. When the vehicle is stopped, the engine E is automatically stopped except when the air conditioner is used or when the battery is charged.

Next, the motor traction control device according to the first embodiment will be described.
FIG. 6 is a block diagram showing the motor traction control device of the first embodiment incorporated as a control program in the integrated controller 6 (motor traction control means).
As shown in FIG. 6, the motor traction control device of the first embodiment includes a required motor torque calculation block 60, a road surface μ estimation block 61 (road surface friction coefficient equivalent value estimation means), a control gain setting block 62, an angular acceleration. Calculation block 63, angular acceleration amount calculation block 64, angular acceleration slip amount calculation block 65, angular acceleration slip amount integrated value calculation block 66, adder 67, limit torque calculation block 68, and motor torque selection block 69 And.

  This motor traction control device sets a high value when the road surface friction coefficient μ, which estimates the control gain α of the motor traction control, shows a low friction coefficient, and sets a low value as the high friction coefficient shows, and sets the set control gain. A motor torque down control amount is calculated based on a value obtained by multiplying α by angular acceleration ω ′ (slip amount). That is, the slip amount multiplied by the control gain α is the angular acceleration ω ′ of the drive wheel to which the second motor generator MG2 is connected. More specifically, the sum (δ + αω) of a multiplication value of the control gain α and the angular acceleration ω ′ of the wheel and a value δ obtained by integrating the difference between the angular acceleration ω ′ and the angular acceleration slip determination threshold ω′slip while the slip continues. Based on '), the limit torque TMlim that limits the maximum motor torque is calculated, and when slip occurs, the value obtained by subtracting the limit torque TMlim from the requested motor torque TMdrv is used as the motor torque down control amount.

Next, the operation will be described.
[Motor traction control process]
FIG. 7 is a flowchart showing the flow of the motor traction control process executed by the integrated controller 6 according to the first embodiment. Each step will be described below.

In step S1, a required motor torque TMdrv obtained by subtracting the engine sharing torque Te from the required drive torque f (AP, ω) is calculated in the required motor torque calculation block 60, and the process proceeds to step S2.
When traveling using only the second motor generator MG2 as a drive source, the engine sharing torque Te becomes zero, and when traveling using the second motor generator MG2 and the engine E as a driving source, the engine sharing torque Te is directly applied to the engine. This is the driving force (see FIG. 2).

  In step S2, in the road surface μ estimation block 61, FIG. 8 and a road surface friction coefficient μ estimation method (described later, wheel speeds VW1 to VW4 of each wheel and braking / driving forces F1 to F4 per unit load are obtained, and these wheel speeds The points for each wheel representing the combinations of VW1 to VW4 and braking / driving forces F1 to F4 per unit load are described on two-dimensional coordinates, a straight line representing these points is obtained, and the road surface friction coefficient μ is calculated based on the gradient. To estimate the road surface friction coefficient μ, and the process proceeds to step S3.

In step S3, the control gain setting block 62 calculates the control gain α of the motor traction control based on the estimation information of the road surface friction coefficient μ, and the process proceeds to step S4.
As shown in FIG. 9, the control gain α is set to a high value when the estimation information of the road surface friction coefficient μ indicates a low friction coefficient, and is set to a lower value as the high friction coefficient is indicated.

  In step S4, in the angular acceleration calculation block 63 and the angular acceleration amount calculation block 64, the angular acceleration amount α · ω ′ is calculated by multiplying the control gain α and the angular acceleration ω ′ (= dω / dt). The process proceeds to S5.

  In step S5, when the angular acceleration ω 'exceeds the angular acceleration slip determination threshold value ω'slip, it is determined that a slip has occurred. When the slip occurs, the process proceeds to step S6, and when the slip converges, the process proceeds to step S7.

  In step S6, the angular acceleration slip amount (ω′−ω′slip) is calculated in the angular acceleration slip amount calculation block 65 and the angular acceleration slip amount integrated value calculation block 66 based on the determination that slip is occurring in step S6. An angular acceleration slip amount integrated value δ, which is a time integral value, is calculated, and the process proceeds to step S8.

  In step S7, based on the determination that slip convergence has occurred in step S6, the angular acceleration slip amount integrated value calculation block 66 resets the angular acceleration slip amount integrated value δ (δ = 0), and the process proceeds to step S8.

  In step S8, in the adder 67 and the limit torque calculation block 68, based on the sum (δ + α · ω ′) of the angular acceleration amount α · ω ′ and the angular acceleration slip amount integrated value δ, as shown in FIG. The limit torque TMlim, which decreases as the value of (δ + α · ω ′) increases, is calculated, and the process proceeds to step S9.

In step S9, one of the requested motor torque TMdrv calculated in step S1 and the limit torque TMlim calculated in step S8 is selected by select low in the motor torque selection block 69, and the process proceeds to step S10. .
That is, as shown in FIG. 10, at the time of slip when the limit torque TMlim is selected by select low, the difference between the requested motor torque TMdrv and the limit torque TMlim becomes the motor torque reduction amount.

  In step S10, the torque value selected in step S9 is output to the motor controller 2 as a target motor torque command, and the process proceeds to return.

[Estimation of road surface μ]
The estimation of the road surface μ in step S2 of FIG. 7 (road surface μ estimation block 61) is performed by the following method.
The change characteristic of the road surface friction coefficient μ with respect to the wheel slip ratio S (in other words, the braking / driving force of the wheel) is as shown by a solid line in FIG. As shown in FIG. 8A, it is known as indicated by a one-dot chain line. In either case, the maximum value μmax of the road surface friction coefficient is different, but exhibits characteristics having almost the same tendency. It is well known that the above relationship holds true not only in the region of S ≦ So during acceleration but also in the region of S ≧ −So during braking as shown in FIG. 8A. Is the fact of

  Then, in the region of the region below the wheel slip rate So in which the change characteristic of the road surface friction coefficient μ with respect to the wheel slip rate S can be regarded as almost linear, FIG. 8 (b) expressed by the wheel speed and the braking / driving force per unit load. ) When the combinations of the wheel speeds VW1 to VW4 of the wheels 1 to 4 and the braking / driving forces F1 to F4 per unit load are plotted for each wheel on the two-dimensional coordinates of), the four points generated by the plot are As indicated by a solid line in FIG. The wheel speed value at the point where the straight line and the wheel speed (VW) axis of the two-dimensional coordinate intersect is the vehicle body speed Vx itself, and the slope of the straight line with respect to the wheel speed (VW) axis is shown in FIG. This is the driving stiffness k of the vehicle corresponding to the rising gradient of the road surface friction coefficient μ with respect to the horizontal axis (wheel slip ratio S) of (a).

  Here, as is clear from the comparison between the solid line characteristic and the one-dot chain line characteristic shown in FIG. 8 (a), between the driving stiffness k and the maximum value μmax of the road surface friction coefficient, for example, FIG. 8 (c) And the maximum friction coefficient μmax is an absolute slippage difficulty of the road surface (in this specification, since this absolute slippage difficulty is also a general term, the road surface friction coefficient From this, the road surface friction coefficient μ, which is the absolute difficulty of slipping on the road surface, is estimated from the slope of the straight line (driving stiffness k) with respect to the wheel speed (VW) axis in FIG. 8 (b). can do.

Therefore, in Example 1, the wheel speeds VW1 to VW4 and the braking / driving forces F1 to F4 per unit load are obtained for the wheels in the linear region that are not greatly slipped. The points for each wheel representing the combination of VW1 to VW4 and braking / driving forces F1 to F4 per unit load are shown on the two-dimensional coordinates as shown in Fig. 8 (b), and a straight line representing these points is obtained. The vehicle speed Vx and the road surface friction coefficient μ are estimated in the manner described above.
[Background of traction control]
Including JP-A-6-229264, JP-A-5-312061, etc., when a drive slip occurs in a drive wheel, torque reduction control is performed to adjust the drive torque applied to the drive wheel according to the drive slip state. A number of vehicle traction control devices to be implemented have been announced.

When the vehicle traction control device adopts a system for controlling the driving torque of the engine, the following points may be problematic when the vehicle is traveling at a low speed, particularly when starting.
In order to keep the driving slip generated when the driver performs excessive accelerator operation at the time of starting, it is desirable to start the traction control as early as possible. For this purpose, the slip reference value (slip target value or slip threshold, It is necessary to detect the driving slip as early as possible by setting a low value to the following). Especially at low vehicle speeds, the operation delay time of the engine, transmission, etc. is large, so detection of early driving slip is necessary. Is effective in suppressing driving slip.
However, if the slip reference value is set low at low vehicle speeds, the driving torque will be reduced too much, and in some cases the engine speed will be extremely low and engine vibration will increase, resulting in poor driving feeling. If the engine speed is too low, the engine may stall (is stalled). As a result, the slip reference value at the initial stage of slip needs to be set to a high value.

  However, if the slip reference value at the initial stage of the slip is set to a high value, under steering on an icy road, under steering occurs in the FF vehicle, over steering occurs in the FR vehicle, and the secondary battery and When this control is used in an electric vehicle using a drive motor, etc., power generation by the generator cannot catch up, resulting in an increase in the amount of power taken from the secondary battery, resulting in a large current. May occur.

In order to solve the above problems, Japanese Patent Laid-Open Nos. 60-104428 and 62-265430 have been proposed, and these include slip reference values when the vehicle speed (vehicle speed) is low. A technique is disclosed in which the slip determination level is changed so as to allow more drive slips (a determination direction in which slipping occurs more).
Further, as described in JP-A-5-312061, after the start of drive torque adjustment by the drive torque adjustment means, the slip reference value is changed to a value higher than the initially set value, thereby improving driving feeling and engine stall. A technique for preventing the above is disclosed. However, in these prior arts, power and current are not considered.

  On the other hand, Japanese Patent Laid-Open No. 10-304514 discloses a technique (angular acceleration control) for improving responsiveness in the initial stage of slip, not the slip ratio. This technique is often applied to a vehicle using a motor as a unit for generating a driving force, such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle.

  The basis of this technology is a configuration that predicts that drive slip will occur when the rate of change (angular acceleration) of the rotational angular velocity of the drive wheels is greater than or equal to a predetermined value, and reduces the motor torque. With this configuration, it is possible to prevent a drive slip that occurs with an increase in motor torque.

Here, the reason why “angular acceleration control” that suppresses slip with high responsiveness in the early stage of generation of drive slip in a hybrid vehicle using a motor as a unit that generates drive force will be described.
If there is no motor traction control device and the drive slips, the power generation of the engine cannot catch up and the motor draws more current from the battery. Therefore, an overcurrent is generated in the motor drive circuit, and the elements on the circuit are damaged. For example, in the power control unit 3 of the first embodiment, as shown by the arrow in FIG. 5, when an overcurrent flows through the capacitor 3e, the fuse of the joint box 3a and the switching circuit of the boost converter 3b are damaged. There is a case. Moreover, in a hybrid vehicle or a fuel cell vehicle, overcurrent tends to flow as the motor output (motor output ratio) is larger than that of the secondary battery. In addition, overvoltage and overcurrent flow more easily as the output of the engine and fuel cell (engine output ratio) is larger than that of the secondary battery. There is a relationship.
Therefore, in order to reliably protect the parts, it is necessary to perform motor traction control that converges the drive slip with good response by "angular acceleration control" in which torque is limited when slipping.

  However, in the conventional "angular acceleration control", priority is given to component protection on low-μ roads where drive slip is likely to occur, and if drive slip is predicted, motor torque can be reduced significantly by a high control gain (fixed value). The control amount was given. For this reason, for example, when the driving wheel speed increases due to the occurrence of driving slip at the time point (1) shown in FIG. 11, the motor torque decreases, and the driving wheel speed also decreases as the motor torque decreases. This decrease in the drive wheel wheel speed passes after the time point (2) in the target control range (optimum slip amount range) in FIG. 11 (b) and further decreases to the time point (3) of the vehicle body speed level. If the increase in motor torque is permitted by shifting the vehicle body speed level after the time point (3), the driving wheel speed increases again from the time point (4) to the time point (5). Situation occurs, and the slip generation and slip convergence operations are repeated after the time point (5).

In other words, in the case of “angular acceleration control”, although overcurrent can be prevented, as shown in FIG. 11B, the actual control range extends to a region where the cornering power is low (3) with respect to the target control range where the cornering power is high. Since the wheel potential has not been used up to the maximum as shown in FIG. 12, when the output decrease of the driving torque is large and the driving wheel speed sticks to the vehicle speed as shown in FIG. There is a problem that (stumbling) occurs.

  In the case of “angular acceleration control”, as shown in FIG. 11 and FIG. 12, when the generation of slip (large slip amount) and slip convergence (small slip amount) are repeated in the driving wheel and the wheel speed rotation fluctuates, There is a problem that front-rear G hunting occurs in which the front-rear G of the vehicle fluctuates due to the reaction force.

[Motor traction control function]
The following points were noted in the motor traction control device of the hybrid vehicle of Example 1.
On low-μ roads with a small friction circle, driving slip is generated with a slight accelerator depression amount, so the transmission torque from the driving wheel to the road surface itself is small, so slip generation and convergence are repeated, and the wheel speed Even if the rotation fluctuates, the front / rear G hunting is so small that passengers including the driver do not feel uncomfortable.
On the other hand, on a high μ road with a large friction circle, driving slip occurs with a strong accelerator depression amount, and the fluctuation range of the transmission torque from the wheel of the driving wheel to the road surface increases, and slip generation and convergence occur. If the wheel speed rotation is repeated, the front / rear G hunting occurs to the extent that the occupant including the driver feels uncomfortable.

  Therefore, when the control gain of motor traction control is given as a fixed value, setting it to a large value can achieve component protection as in the conventional “angular acceleration control”, but front and rear G hunting is not possible on high μ roads. It becomes a problem. In addition, when the control gain of motor traction control is given as a fixed value, setting it to a small value can prevent front and rear G hunting, but in low-μ roads where drive slip is likely to occur, the component due to torque delay response delay Protection cannot be achieved. That is, “part protection” and “preventing front / rear G hunting” are in a trade-off relationship that if one is established, the other is not established.

  Focusing on the above points, in the first embodiment, the control gain α of the motor traction control is set according to the road surface friction coefficient μ, and the motor torque down control is performed based on the value obtained by multiplying the set control gain α and the angular acceleration ω ′. By calculating the amount, it is possible to achieve both the protection of parts and the prevention of front and rear G hunting regardless of the road friction coefficient μ.

  That is, when a driving slip occurs, the flow proceeds to step S1, step S2, step S3, step S4, step S5, step S6, step S8, step S9, and step S10 in the flowchart of FIG.

That is, in step S3, the control gain α is calculated according to the road surface μ estimated in step S2. As shown in FIG. 9, the control gain α is the highest value on extremely low μ roads such as icy and snowy roads, and gradually decreases as the road surface μ increases, such as rainy roads and dry roads. The
For example, when a driving slip occurs with the same angular acceleration ω ′ and the same angular acceleration slip amount integrated value δ, the control gain α is set to a high value when traveling on a low μ road, and the control gain α is low when traveling on a high μ road. As shown in FIG. 10, the motor torque down control amount becomes larger as the road becomes lower, as shown in FIG.

  Therefore, for example, when a drive slip occurs during traveling on a low μ road, the drive slip converges with a good response due to a large motor torque down control amount, and the over-rotation of the second motor generator MG2 is suppressed, and the component protection function is provided. Achieved. As for the front / rear G hunting, although the driving wheel speed fluctuates due to the control hunting, as described above, in the case of a low μ road, the transmission torque from the wheel of the driving wheel to the road surface itself is small. Front and rear G hunting by force is not a problem.

  On the other hand, when a driving slip occurs on a high μ road, the driving wheel speed is gradually reduced by a small motor torque down control amount, but the driving wheel speed is surely reduced and the grip is recovered. As shown, after the first driving slip converges, it shows a characteristic that varies gently along the driven wheel speed. The occurrence of re-slip is suppressed as long as the driver does not suddenly depress the accelerator. In other words, when driving on high μ roads, by protecting the parts by converging the driving slip utilizing the grip performance of the wheels, suppressing the strong gradient that the control overshoots, and controlling the recovery of the wheel grips well, Control hunting itself that causes front and rear G hunting can be prevented.

Next, the effect will be described.
In the vehicle motor traction control device of the first embodiment, the effects listed below can be obtained.

  (1) A vehicle motor comprising: at least one motor provided in a power source for driving the wheel; and motor traction control means for detecting a driving slip of the wheel and recovering the grip of the wheel by motor torque down control. In the traction control device, road surface friction coefficient equivalent value estimation means for estimating a road surface friction coefficient equivalent value is provided, and the motor traction control means has a control gain of motor traction control when the road surface friction coefficient equivalent value indicates a low friction coefficient. Is set to a high value and set to a low value to indicate a high friction coefficient, and the motor torque down control amount is calculated based on the value obtained by multiplying the set control gain and slip amount. Therefore, regardless of the road friction coefficient μ Thus, it is possible to achieve both protection of parts and prevention of front and rear G hunting.

  (2) Since the motor traction control means sets the slip amount multiplied by the control gain α to the angular acceleration ω ′ of the drive wheel to which the second motor generator MG2 is connected, the component protection is ensured by predicting the occurrence of the drive slip. Can be achieved.

  (3) The motor traction control means is a value δ obtained by multiplying a difference between the control gain α and the angular acceleration ω ′ of the wheel and the angular acceleration ω ′ and the angular acceleration slip determination threshold ω′slip while the slip continues. Based on the sum (δ + αω '), the limit torque TMlim that limits the maximum motor torque is calculated. When the driving slip continues on the μ road without converging, the motor torque down control amount can be gradually increased to promote early convergence of the driving slip.

  (4) The road surface friction coefficient equivalent value estimation means obtains wheel speeds VW1 to VW4 and braking / driving forces F1 to F4 per unit load of each wheel, and these wheel speeds VW1 to VW4 and braking / driving forces per unit load. The road surface used in motor traction control to express the points for each wheel representing the combination of F1 to F4 on two-dimensional coordinates, to obtain a straight line representing these points, and to estimate the road surface friction coefficient μ based on the gradient Highly accurate road surface friction coefficient information can be obtained as the friction coefficient information.

  The second embodiment is an example in which the limited motor torque output value during the slip is used as a road surface friction coefficient equivalent value. In addition, since the structure of Example 2 is the same as that of Example 1, illustration and description are abbreviate | omitted.

  The operation will be described. FIG. 14 is a flowchart showing the flow of the motor traction control process executed by the integrated controller 6 of the second embodiment.

  In step S22, the road surface μ estimation block 61 obtains a limited motor torque output value (= current torque) during slipping, and the process proceeds to step S23.

In step S23, a control gain α for motor traction control is calculated based on the current torque in the control gain setting block 62, and the process proceeds to step S24.
As shown in FIG. 15, the control gain α is set to a low value when the current torque indicates a high value, and is set to a higher value as the current torque indicates a lower value. . Steps S21 and S24 to S30 are the same steps as steps S1 and S4 to S10 in FIG.

  In the second embodiment, the reason why the current torque is set to the road surface friction coefficient equivalent value will be described. Considering the friction circle indicating the allowable limit of the longitudinal force and lateral force of the wheel, the friction circle becomes smaller as the road becomes lower, and slip occurs beyond the allowable limit when torque exceeding the friction circle is applied to the drive wheels. In other words, the lower the μ road, the smaller the torque that is allowed during driving slip. Therefore, it can be estimated that the smaller the current torque during slip control (= the torque in the slip limit region) is, the lower the friction coefficient is, and conversely, the greater the current torque during slip control is, the greater the road surface is. It can be estimated that the friction coefficient is high μ. Since other operations are the same as those in the first embodiment, description thereof is omitted.

Next, the effect will be described.
In the vehicle motor traction control device of the second embodiment, in addition to the effects (1), (2), (3) of the first embodiment, the following effects can be obtained.

  (5) The road surface friction coefficient equivalent value estimation means uses the current torque, which is a limited motor torque output value during slip, as the road surface friction coefficient equivalent value, so that the motor can be obtained by a simple method of simply acquiring the current torque. Accurate road surface friction coefficient information can be obtained for use in traction control.

  The third embodiment is an example in which the motor torque output value at the start of slip is set to a road surface friction coefficient equivalent value.

  The operation will be described. FIG. 16 is a flowchart showing the flow of the motor traction control process executed by the integrated controller 6 of the third embodiment.

  In step S32, the road surface μ estimation block 61 acquires the motor torque at the start of slip, and the process proceeds to step S33.

In step S33, the control gain setting block 62 calculates a control gain α for motor traction control based on the motor torque at the start of slip, and the process proceeds to step S34.
As shown in FIG. 17, the control gain α is set to a value corresponding to the road surface friction coefficient corresponding to the motor torque at the start of slip, and is set to a low value when the motor torque at the start of slip shows a high value. The lower the torque, the higher the value. Steps S31 and S34 to S40 are the same steps as steps S1 and S4 to S10 in FIG.

  In the third embodiment, the reason why the motor torque at the start of slip is set to the road surface friction coefficient equivalent value will be described. Similar to the second embodiment, the friction circle indicating the allowable limit of the longitudinal force and lateral force of the wheel can be examined. The smaller the motor torque at the start of the slip (= the torque in the slip limit region), the smaller the road surface friction coefficient. Can be estimated as low μ, and conversely, as the motor torque at the start of slip increases, the road surface friction coefficient can be estimated as high μ. In addition, by setting the motor torque at the start of slip to a value equivalent to the road surface friction coefficient, the required performance characteristic for motor traction control, which is important for component protection, is to estimate the road surface friction coefficient with good response from the start of slip. Can also be satisfied.

Next, the effect will be described.
In the vehicle motor traction control device of the third embodiment, in addition to the effects (1), (2), and (3) of the first embodiment, the following effects can be obtained.

  (6) Since the road surface friction coefficient equivalent value estimating means uses the motor torque output value at the start of slip as the road surface friction coefficient equivalent value, the motor traction control is performed by a simple method of only acquiring the motor torque at the start of slip. Thus, it is possible to obtain road surface friction coefficient information with good response that achieves suppression of initial driving slip.

  As mentioned above, although the motor traction control apparatus of the vehicle of this invention has been demonstrated based on Example 1-Example 3, it is not restricted to these Examples about a concrete structure, Each of Claims Design changes and additions are permitted without departing from the scope of the claimed invention.

  In Examples 1 to 3, as road surface friction coefficient equivalent value estimation means, points for each wheel representing a combination of braking / driving forces per wheel speed and unit wheel load are represented on two-dimensional coordinates, and these points are representative. Means for estimating a road surface friction coefficient by obtaining a straight line to be used, Means for limiting a motor torque output value during slipping to be equivalent to a road surface friction coefficient, Means for setting a motor torque output value at the start of slip to a value equivalent to a road surface friction coefficient However, as long as it is a means for estimating the road surface friction coefficient equivalent value, road surface friction coefficient equivalent value estimation means other than those shown in the first to third embodiments may be used.

  In the first to third embodiments, an example in which the motor traction control unit uses the angular acceleration of the driving wheel connected to the motor as the slip amount multiplied by the control gain has been described. Alternatively, other slip amounts such as a value obtained by combining two or more of these may be used. In short, any slip amount that calculates the motor torque down control amount based on multiplication with the set control gain may be used.

  In the first to third embodiments, an example of application to a hybrid vehicle including one engine, two motor generators, and a power split mechanism is shown. However, the motor traction control device of the present invention is a hybrid including another power unit structure. In short, any vehicle such as a car, an electric vehicle, a fuel cell vehicle, a motor 4WD vehicle, etc., which is equipped with at least one motor as a power source for driving wheels can be applied.

1 is an overall system diagram illustrating a hybrid vehicle to which a motor traction control device according to a first embodiment is applied. FIG. 2 is a driving force performance characteristic diagram and a driving force conceptual diagram in a hybrid vehicle to which the motor traction control device of Embodiment 1 is applied. It is a contrast characteristic figure showing the braking force performance by regenerative cooperation in the hybrid car to which the motor traction control device of Example 1 was applied. It is an alignment chart which shows each vehicle mode in the hybrid vehicle to which the motor traction control device of Example 1 was applied. FIG. 2 is a block diagram illustrating a motor drive control system (battery, power control unit, first motor generator, second motor generator) of the hybrid vehicle according to the first embodiment. It is a block diagram which shows the motor traction control apparatus integrated as a control program in the integrated controller of Example 1. 3 is a flowchart illustrating a flow of a motor traction control process executed by the integrated controller according to the first embodiment. It is a figure which shows the road surface friction coefficient characteristic, the braking / driving force characteristic per unit wheel load, and the maximum friction coefficient characteristic for demonstrating the estimation method of the road surface friction coefficient of Example 1. FIG. FIG. 6 is a control gain characteristic diagram with respect to a road surface μ estimated in the first embodiment. FIG. 6 is a limit torque characteristic diagram calculated according to the sum of an angular acceleration slip amount integrated value δ and an angular acceleration amount αω ′ in the first embodiment. It is a driving wheel wheel speed characteristic and cornering power characteristic figure in the conventional angular acceleration control. It is a time chart which shows each characteristic of the accelerator opening degree, vehicle speed, and driving wheel vehicle speed at the time of using the motor traction control based on the conventional angular acceleration. 3 is a time chart showing characteristics of driven wheels and drive wheels in motor traction control in Embodiment 1; 6 is a flowchart illustrating a flow of a motor traction control process executed by an integrated controller according to a second embodiment. FIG. 10 is a control gain characteristic diagram with respect to the current torque in the second embodiment. 10 is a flowchart illustrating a flow of a motor traction control process executed by an integrated controller according to a third embodiment. FIG. 10 is a control gain characteristic diagram with respect to torque at the start of slip in Example 3.

Explanation of symbols

E engine
MG1 1st motor generator
MG2 Second motor generator
OS output sprocket
TM power split mechanism 1 engine controller 2 motor controller 3 power control unit 4 battery 5 brake controller 6 integrated controller 60 required motor torque calculation block 61 road surface μ estimation block (road surface friction coefficient equivalent value estimation means)
62 Control gain setting block 63 Angular acceleration calculation block 64 Angular acceleration amount calculation block 65 Angular acceleration slip amount calculation block 66 Angular acceleration slip amount integrated value calculation block 67 Adder 68 Limit torque calculation block 69 Motor torque selection block 7 Accelerator opening sensor 8 Vehicle speed sensor 9 Engine speed sensor 10 First motor generator speed sensor 11 Second motor generator speed sensor 12 Front left wheel speed sensor 13 Front right wheel speed sensor 14 Rear left wheel speed sensor 15 Rear right wheel speed sensor 16 Steering Angle sensor 17 Master cylinder pressure sensor 18 Brake stroke sensor 19 Brake fluid pressure unit 20 Front left wheel wheel cylinder 21 Front right wheel wheel cylinder 22 Rear left wheel wheel cylinder 23 Rear right wheel wheel cylinder

Claims (5)

A motor traction control device for a vehicle, comprising: at least one motor provided in a power source for driving the wheel; and motor traction control means for detecting a driving slip of the wheel and recovering the grip of the wheel by motor torque down control. In
A road surface friction coefficient equivalent value estimating means for estimating a road surface friction coefficient equivalent value is provided,
The motor traction control means sets the control gain of motor traction control to a high value when the road surface friction coefficient equivalent value indicates a low friction coefficient, and sets the control gain to a lower value as the high friction coefficient indicates. Calculate the motor torque down control amount based on the value multiplied by the slip amount ,
The motor traction control means limits the maximum motor torque based on a sum of a value obtained by multiplying the control gain and the slip amount of the wheel and a value obtained by accumulating the difference between the slip amount and the slip determination threshold while the slip is continued. A motor traction control device for a vehicle, wherein a limit torque is calculated, and a value obtained by subtracting the limit torque from the required motor torque when a slip occurs is used as a motor torque down control amount . In the vehicle motor traction control device according to claim 1,
The motor traction control device according to claim 1, wherein the motor traction control means uses the slip amount multiplied by the control gain as an angular acceleration of a driving wheel to which the motor is connected. In the motor traction control device for a vehicle according to claim 1 or 2,
The road surface friction coefficient equivalent value estimating means expresses a point for each wheel representing a combination of braking / driving force per wheel speed and unit wheel load on a two-dimensional coordinate, and obtains a straight line representing these points to determine the road surface. A motor traction control device for a vehicle characterized by estimating a friction coefficient . In the vehicle motor traction control device according to claim 1,
The road surface friction coefficient equivalent value estimation means sets a limited motor torque output value during slipping as a road surface friction coefficient equivalent value . In the vehicle motor traction control device according to claim 1,
The road surface friction coefficient equivalent value estimation means uses a motor torque output value at the start of slip as a road surface friction coefficient equivalent value .

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