In-wheel motor vehicle

Abstract

To make it possible to appropriately make sure of a situation when one of left and right driving wheels 12RL and RR falls into a slipping state, and the other falls into a locked state in an in-wheel motor vehicle 10, and make it possible to get out of the situation.SOLUTION: An in-wheel motor vehicle includes in-wheel motors 14RL and RR, and active suspensions 16RL and RR suspending left and right driving wheels, respectively. When it is determined that one of the left and right driving wheels is in a locked state, and the other is in a slipping state, suspension control means controls the active suspension so as to lower a position of the other of the left and right driving wheels which is in the slipping state, thereby bringing the wheel in the slipping state into contact with a road surface, or increasing its ground load to increase road surface reaction force, so that driving torque is transmitted to the road surface.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle such as an automobile equipped with in-wheel motors (in-wheel motor vehicle), and more particularly, to a configuration for increasing the driving force of a vehicle in a situation where one of the left and right drive wheels is spinning and the other is locked in an in-wheel motor vehicle.

Background Art

[0002] A vehicle equipped with in-wheel motors that individually drive each drive wheel is advantageous in that drive control for each drive wheel can be individually executed in various modes according to the situation of each drive wheel. For example, in Patent Document 1, in an electric vehicle in which each wheel is driven and rotated by a motor, when the presence of a wheel slipping on the road surface is detected, the supply of power to the motor that drives and rotates this wheel is cut off, thereby suppressing wasteful power consumption. Then, when the amount of compression of the suspension that transmits the load of the vehicle body to the wheel changes by a predetermined amount or more when the steering angle of the wheel changes by a predetermined angle or more, it is determined that the wheel is in contact with the ground and the cutoff of the power supply is released. Also, when the presence of a wheel slipping on the road surface is detected, if the change in the amount of compression of the suspension is equal to or greater than a predetermined value, it is determined that the wheel has come off the ground, and the power supply is cut off to suppress wasteful power consumption. If the change in the amount of compression is less than the predetermined value, it is determined that the wheel is in a stacked state, and the wheel is steered left and right so that it can escape from the stacked state. A configuration has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a in-wheel motor vehicle as described above, since the two wheels are not connected, the left and right drive wheels can be in different rotational states. When one of the left and right drive wheels floats from the road surface and enters a spinning state, the torque transmitted from the vehicle to the road surface is halved, resulting in a decrease in the driving performance or uphill performance of the vehicle. In that case, if the other of the left and right drive wheels is rotating, the vehicle can move, and it is expected that the spinning state of the one drive wheel will be resolved. However, if the driving torque is insufficient and the other drive wheel enters a locked state, the vehicle will stop, and the situation cannot be resolved. Therefore, in an in-wheel motor vehicle, when one of the left and right drive wheels is in a spinning state and the other is in a locked state, it is advantageous to have a control configuration that allows for a quick escape from that situation. In this regard, when the drive wheels are simply slipping, there are cases where only one drive wheel is slipping (for example, a combination of a normal road surface and a low-μ road), and cases where both wheels are slipping (for example, a snowy road or a muddy road). In such cases, unlike the situation where one of the left and right drive wheels is in a spinning state and the other is in a locked state, the vehicle may be allowed to continue running as it is. Therefore, in the above control configuration for escaping from the situation where one of the left and right drive wheels is in a spinning state and the other is in a locked state, it is preferable that not only can it be determined that one of the left and right drive wheels is slipping, but also that the other is locked.

[0005] Thus, one problem of the present invention is to provide a control configuration in an in-wheel motor vehicle that can appropriately identify the situation when one of the left and right drive wheels is in a spinning state and the other is in a locked state, and can escape from that situation.

Means for Solving the Problem

[0006] According to the present invention, the above problem is solved by an in-wheel motor vehicle including in-wheel motors that generate driving torque for each of the left and right drive wheels and active suspensions that suspend each of the left and right drive wheels, Drive wheel state determination means for determining that one of the left and right drive wheels is in a locked state and the other of the left and right drive wheels is in a slip state; Suspension control means for separately controlling the active suspensions of each of the left and right drive wheels including When the drive wheel state determination means determines that one of the left and right drive wheels is in a locked state and the other of the left and right drive wheels is in a slip state, the suspension control means is configured to control the corresponding active suspension so as to lower the position of the other of the left and right drive wheels in the slip state. A vehicle achieved by

[0007] In the configuration of the above vehicle, the in-wheel motor and the active suspension may be of any type, and may be of the type commonly used in vehicles such as automobiles equipped with in-wheel motors. When the vehicle is four-wheel drive, in-wheel motors are equipped on all wheels, and when it is front-wheel drive or rear-wheel drive, in-wheel motors are equipped on each of the left and right front wheels or left and right rear wheels. In the drive wheel state determination means, the determination of the locked state and the slip state of the left and right drive wheels may be executed in various modes. Typically, for example, it may be made based on the magnitude of the torque output by the motor of each wheel and the rotational speed of the wheel or the motor. Specifically, in one of the left and right drive wheels, when the rotational speed of the wheel or the motor is 0 or substantially 0 despite torque being output from the motor, that drive wheel is determined to be in a locked state. In that state, of the left and right drive wheels HeIn a vehicle, when torque is output from a motor and the wheel or the motor is rotating at a rotational speed exceeding a predetermined rotational speed, it may be determined that one of the left and right drive wheels is in a locked state and the other is in a slipping state. Note that the fact that one drive wheel is in a locked state may be determined by detecting that the vehicle speed is 0 or substantially 0, or the wheel speed of the driven wheel is 0 or substantially 0, or from GPS information, even though torque is being output from the motor of one drive wheel. When the suspension control means lowers the position of the drive wheel in a slipping state, the active suspension may be controlled to extend.

[0008] According to the above configuration, in a in-wheel motor vehicle, when one of the left and right drive wheels is locked and the other is slipping, the position of the slipping wheel is lowered. As a result, if the wheel is floating, it comes into contact with the ground, or it is expected that the ground contact load of the slipping wheel increases. Thereby, the road surface reaction force is restored, the driving force acting on the vehicle is restored, and the driving performance or climbing performance is improved. And with this configuration, even if one of the left and right drive wheels floats from the road surface and the torque transmitted from the vehicle to the road surface becomes half of the magnitude that can be originally applied, the vehicle can quickly escape from that situation. Note that the fact that the position of the wheel in a slipping state has been lowered and it has come into contact with the road surface or the ground contact load has increased and the road surface reaction force has been generated may be determined by detecting that the rotational speed of that wheel or the motor has decreased (when a road surface reaction force is generated or increased in a wheel that is idling or slipping, the rotational speed thereof decreases).

[0009] In the above configuration, when one of the left and right drive wheels is locked and the other is slipping, before operating the active suspension, the magnitude of the torque of the slipping wheel may be reduced so as to suppress wasteful power consumption. Further, the lowering of the position of the slipping wheel by the active suspension may be executed at an arbitrary degree, for example, gradually by a predetermined amount. After the operation of the active suspension, when the rotational speed of the wheel whose position has been lowered falls below a predetermined value and it is determined that the road surface reaction force of the wheel has been restored, the magnitude of the torque of the wheel may be increased (it may be returned to the magnitude before reduction).

Advantages of the Invention

[0010] According to the above configuration of the present invention, in an in-wheel vehicle, when one wheel floats and spins, and drive torque is not transmitted from that wheel to the road surface, resulting in a decrease in driving performance or uphill climbing performance, the spinning wheel is grounded by operating the active suspension, or the ground contact load is increased, thereby restoring the road surface reaction force and enabling drive torque to be transmitted to the road surface, so that the driving performance or uphill climbing performance can be quickly restored. In such a configuration, for example, restoration of driving performance or uphill climbing performance can be achieved without performing control such as changing the steering angle of the spinning wheel. Further, in the above configuration, when adopting a mode of confirming that one drive wheel is locked and then confirming that the other is slipping, the situation where one of the left and right drive wheels is in a spinning state and the other is in a locked state can be distinguished from the case where only one drive wheel is slipping or both wheels are slipping, so that useless operation of the active suspension can be avoided. The configuration of the present invention is expected to be applied to various in-wheel vehicles.

[0011] Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments of the present invention.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Explanation of Reference Numerals

[0013] 10…Vehicle 12FL, FR, RL, RR…Wheels 14RL, RR…In-wheel Motors 16FL, FR, RL, RR…Active Suspensions 50…Computer Device 62…GPS Device (Optional)

Best Mode for Carrying Out the Invention

[0014] Configuration of the vehicle Referring to FIG. 1(A), in one in-wheel motor vehicle 10 of a preferred embodiment of the present invention, the left and right front wheels 12FL and 12FR and the left and right rear wheels 12RL and 12RR are each suspended from the vehicle body by suspensions 16FL, FR, RL, RR (which may be active suspensions of a normal configuration. For driven wheels, they do not have to be active suspensions in the present embodiment.). In the left and right rear wheels 12RL and 12RR serving as drive wheels, in-wheel motors 14RL and RR for rotationally driving each of them are provided. Therefore, in a normal mode, the vehicle 10 responds to the depression of an accelerator pedal (not shown) by the driver or to the acceleration / deceleration request of an arbitrary control device (not shown) such as a driving assistance device or an automatic driving device, and the left and right rear wheels 12RL and 12RR are rotated by the in-wheel motors 14RL and RR to apply driving torque to the road surface, thereby moving forward or backward. Note that the in-wheel motor may be further mounted on the left and right front wheels or on the left and right front wheels only. Also, the vehicle 10 is normally equipped with a steering device (not shown) for controlling the steering angle of the wheels and a braking device (not shown) for generating braking force for each wheel. As the steering device, a power steering device that transmits the rotation of a steering wheel (not shown) operated by the driver to the tie rod (not shown) while multiplying the rotational torque to steer the front wheels 12FL and 12FR may be employed. The braking device may be of any type that applies braking force to each wheel in response to the depression of a brake pedal (not shown) by the driver.

[0015] The operation control of the in-wheel motors 14RL and RR and the suspensions 16FL, FR, RL, and RR according to the above-described embodiment is executed by the computer device 50. The computer device 50 may include a computer having a CPU, a ROM, a RAM, and an input / output port device, which are interconnected by a normal two-way common bus, and a drive circuit. The configuration and operation of each part of the device of the present embodiment described later may be realized by the operation of the computer device 50 according to a program. Detection values from various sensors for detecting the operation amount or depression amount of the accelerator pedal, the state of the wheels such as the wheel speed Vwi (i = FL, FR, RL, RR) from the wheel speed sensors of each wheel, and the motion state of the vehicle, etc. are input to the computer device 50. Note that GPS information from the GPS device 62 may be used to detect the vehicle speed. Although not shown, various parameters necessary for various controls to be executed in the vehicle of the present embodiment, for example, various detection signals such as the depression amount of the brake pedal, the steering angle, the yaw rate, and the lateral acceleration, are input to the computer device 50, and various control commands may be output to the corresponding devices. Then, based on the above various inputs from the computer device 50, control commands Crl and Crr for adjusting the output torque (drive torque) of the in-wheel motors 14RL and RR, and a control command cs for adjusting the operation amount of the suspensions 16FL, FR, RL, and RR are transmitted to the corresponding parts.

[0016] Configuration of the vehicle control system Referring to FIG. 1(B), in the configuration of the control system related to the characteristic configuration in the present embodiment in the computer device 50, generally speaking, a drive torque determination unit, a left drive wheel control unit, a right drive wheel control unit, and a suspension control unit are provided.

[0017] More specifically, the drive torque determination unit basically receives the depression amount of the accelerator pedal or the acceleration / deceleration request (not shown) of any control device such as a driving assistance device or an autonomous driving device, determines the drive torque (or driving force) to be generated in the vehicle, and transmits the drive torque target values Twrl and Twrr to be generated by the left wheel motor 14RL and the right wheel motor 14RR to the left drive wheel control unit and the right drive wheel control unit. The left drive wheel control unit and the right drive wheel control unit are each configured to give control commands Crl and Crr for generating the drive torque target value to the left wheel motor 14RL and the right wheel motor 14RR. In particular, in this embodiment, the drive torque determination unit is configured to refer to the wheel speed of each wheel (in the purpose of this embodiment, only that of the drive wheels) or the rotational speeds of the left wheel motor 14RL and the right wheel motor 14RR in order to detect the case where one of the left and right drive wheels is in a locked state and the other is in a slip state, as will be described later. Also, in a certain aspect, the vehicle speed may be determined from the time change of the vehicle position information obtained by the GPS device 62, and whether the vehicle is stopped or not may be determined with reference to such vehicle speed. The suspension control unit is basically configured to control the operation amount of the suspension so as to control the damping force, stroke, vehicle height, etc. of the suspension in a normal manner. In particular, in the characteristic operation in this embodiment, as will be described later, when one of the left and right drive wheels is in a locked state and the other is in a slip state, the suspension control unit is configured to operate the suspension that suspends the wheel in the slip state so as to lower the position of the wheel in the slip state (away from the vehicle body downward).

[0018] Operation of the vehicle control system (1) Outline of Control As described in the "Summary of the Invention" section, in an in-wheel motor vehicle, since the rotations of the left and right drive wheels are completely independent, when one of the left and right drive wheels floats from the road surface and enters a spinning or slipping state, the torque transmitted from the vehicle to the road surface is provided only from the other drive wheel, and the torque transmitted from the vehicle to the road surface is halved. As a result, when the driving force or climbing force is insufficient, the other drive wheel enters a locked state, and the vehicle stops. As it is, it may be difficult to escape from such a situation. Therefore, in the present embodiment, when one of the left and right drive wheels enters a locked state and the other enters a slipping state (spinning state - a state where no driving force is substantially transmitted to the road surface), the suspension is actuated to execute control to lower the position of the slipping wheel. According to such a control configuration, in the slipping wheel, if the wheel is floating from the road surface, the position of the wheel drops to make it contact the ground, and if the wheel is slipping, the ground contact load increases. As a result, the road surface reaction force in the slipping wheel returns or increases, the torque transmitted from the vehicle to the road surface returns or increases, and it is expected that the driving performance or climbing performance of the vehicle will recover. In detecting the situation where one of the left and right drive wheels enters a locked state and the other enters a slipping state, typically, as described below, after detecting that one of the left and right drive wheels has entered a locked state, it may be configured to detect that the other is in a slipping state. In that case, on a patchy road where the road surface friction coefficients on the left and right are different, even if one of the left and right drive wheels is slipping, the situation where propulsion force is obtained by the other wheel, or on a snowy road or muddy road where propulsion force is obtained even when both wheels are slipping, it is possible to distinguish and detect the situation where one of the left and right drive wheels enters a locked state and the other enters a slipping state.

[0019] (2) Processing Procedure of the Device Referring to FIG. 2, in the control of the in-wheel motor vehicle according to the present embodiment, first, it is determined that one of the left and right drive wheels is in a locked state (step 1). Here, for example, in either one of the left and right drive wheels, when the output torque Twi of the motor (i is either RL or RR) exceeds a predetermined value Two that may be appropriately set, and the wheel speed Vwi of the wheel or the magnitude of the rotational speed of the motor is substantially 0, for example, less than a predetermined small positive number ε, it may be determined that the wheel is in a locked state. Here, the predetermined value Two for the output torque Twi may be set to a value at which the wheel should rotate to a sufficient extent if the output torque Twi is greater than the predetermined value. Also, the predetermined small positive number for the wheel speed Vwi of the wheel or the magnitude of the rotational speed of the motor may be set to an appropriate value that can determine that the wheel and the motor are not rotating if the wheel speed Vwi of the wheel or the magnitude of the rotational speed of the motor is less than the predetermined small positive number ε. In such a determination, when the output torque Twi of the motor exceeds the predetermined value Two and the wheel speed Vwi of the wheel or the magnitude of the rotational speed of the motor is substantially 0, although the motor generates a driving torque and the driving torque acts on the road surface by the wheel, the wheel and the motor stop. Therefore, it can be determined that the driving torque for advancing the vehicle is insufficient and the vehicle is stopped.

[0020] In the above step 1, if it is determined that one of the left and right drive wheels is in a locked state, then next, it is determined that the other of the left and right drive wheels is in a slip state. Here, for example, in the other of the left and right drive wheels, the output torque Twj of the motor (j is the one that is not i among RL or RR) exceeds a predetermined value Two set as appropriate, and when the wheel speed Vwj of the wheel or the magnitude of the rotational speed of the motor is significantly rotating, for example, exceeds a predetermined value Vwo, it may be determined that the wheel is in a slip state. Here, the predetermined value Vwo for the wheel speed Vwi of the wheel or the magnitude of the rotational speed of the motor may be set to an appropriate value that can determine that the wheel and the motor are rotating if the wheel speed Vwi of the wheel or the magnitude of the rotational speed of the motor exceeds the predetermined value Vwo. In such a determination, when the output torque Twj of the motor exceeds the predetermined value Two and the wheel speed Vwj of the wheel or the magnitude of the rotational speed of the motor is significantly rotating, although the vehicle is stopped, the wheel and the motor are rotating, so it can be determined that the wheel is floating from the road surface or the wheel is spinning or slipping because the road surface friction coefficient is low.

[0021] When the situation where one of the left and right drive wheels is in a locked state and the other is in a slip state is detected by the above steps 1 and 2, first, a flag Fs indicating that situation is set to 1 (step 3), and then the output torque of the wheel j in the slip state may be reduced (step 4). Here, reducing the output torque of the wheel j is to save wasted power and to avoid a sharp increase in the road surface reaction force when the position of the wheel j is lowered later and the ground load of the wheel increases. After that, the suspension of the wheel j is actuated and the position of the wheel j is lowered (step 5). Here, the lowering range of the position of the wheel j may be appropriately set so as not to lower it too much at once.

[0022] After the position of wheel j is lowered by the above process, the determination in step 1 is executed again. When it is determined that wheel i is still in the locked state (step 1), the rotational state of wheel j is evaluated in step 2. Here, since the drive torque has already been reduced in the previous cycle, step 2 may result in a no. However, when the wheel speed Vwj of the wheel or the magnitude of the motor rotation speed is still above the predetermined value Vwo (step 6), steps 4 and 5 may be repeated, and further reduction of the drive torque and lowering of the position of wheel j may be executed. This process may be repeatedly executed until the locked state of wheel i is released in step 1 or until the wheel speed Vwj of the wheel or the magnitude of the motor rotation speed falls below the predetermined value Vwo in step 6.

[0023] In step 6, when the wheel speed Vwj of wheel j or the magnitude of the motor rotation speed falls below the predetermined value Vwo, the floating wheel j comes into contact with the ground, or the ground contact load of the slipping wheel j increases, and a road surface reaction force is generated or increased in wheel j, that is, it can be determined that the state has returned to a state where the drive torque can be transmitted. Then, an increase or return of the reduced drive torque of wheel j may be executed (step 7). As a result, it is expected that the drive torque acting on the vehicle increases, the vehicle starts to move, and the locked state of wheel i is also released.

[0024] If wheel i is not locked from the beginning (step 1), the flag Fs is not set to 1 (step 8), and no special process is executed. On the other hand, if the flag Fs is set to 1 in the previous processing cycle and then the locked state is released, since the torque of wheel j is reduced, an increase or return of the drive torque is executed (step 9), the flag Fs is set to 0 (step 10), and a series of processes ends.

[0025] Thus, according to the above control process, in an in-wheel motor vehicle, when one of the left and right drive wheels floats from the road surface and enters an idling state or a slip state, and the other enters a locked state, an operation is executed to lower the position of the wheel that is idling or slipping. As a result, the road surface reaction force of that wheel is restored, enabling the vehicle to quickly escape from a situation where one of the left and right drive wheels is in a locked state and the other is in a slip state, thereby achieving an improvement in the driving performance or climbing performance of the in-wheel vehicle.

[0026] The above description has been made in relation to the embodiments of the present invention. However, many modifications and changes are easily possible for those skilled in the art. It is obvious that the present invention is not limited only to the embodiments illustrated above, and can be applied to various devices without departing from the concept of the present invention.

Claims

【Claim 1】 An in-wheel motor vehicle comprising in-wheel motors that generate driving torque for each of left and right drive wheels and active suspensions that suspend each of the left and right drive wheels, a drive wheel state determination means for determining that when driving torque is being generated by the left and right drive wheels, one of the left and right drive wheels is in a locked state and the other of the left and right drive wheels is in a slip state, and a suspension control means for separately controlling the active suspensions of each of the left and right drive wheels is included, wherein when the drive wheel state determination means determines that one of the left and right drive wheels is in a locked state and the other of the left and right drive wheels is in a slip state, after reducing the driving torque of the other of the left and right drive wheels in the slip state, the suspension control means is configured to control the corresponding active suspension so as to lower the position of the other of the left and right drive wheels in the slip state.

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