JP2007118898A - Braking/driving force controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a pitch rate of a vehicle when the vehicle passes a level difference or the like of a road surface even if the vehicle is an in-wheel motor type vehicle not capable of sufficiently obtaining effect of a suspension. <P>SOLUTION: This braking/driving force controller has: vertical acceleration sensors 21a, 21b, 21c, 21d detecting the pitch rate of the vehicle 10; and a controller 22 reducing a pitch moment generated around the gravity center of the vehicle by imparting different braking/driving force to front wheels Wfl, Wfr and rear wheels Wrl, Wrr. When fluctuation of the pitch rate is detected, the controller 22 reduces the driving force of one-side wheels of the front wheels Wfl, Wfr and the rear wheels Wrl, Wrr, and imparts the reduced driving force to the other-side wheels. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a braking / driving force control device for a vehicle, and more specifically, even if an in-wheel motor type vehicle in which the effect of a suspension is not sufficiently obtained, the pitch of the vehicle when the vehicle passes through a road surface step or the like. The present invention relates to a braking / driving force control device for a vehicle capable of reducing a rate.

  2. Description of the Related Art Conventionally, each drive wheel independent drive type electric vehicle has been provided in which motors are provided for a total of four wheels, front, rear, left and right, so that each drive wheel can be independently driven to rotate. A typical example of such an electric vehicle of each drive wheel independent drive type is an electric vehicle of a type in which a motor is embedded or integrated in each drive wheel, that is, an in-wheel motor type electric vehicle.

  In such a vehicle, depending on the state of occurrence of slip or tendency in each driving wheel, particularly the position and number of slips or driving wheels (slip wheels) exhibiting such tendency and other driving wheels (non-slip wheels). Thus, a technique for realizing four-wheel drive by motor torque control by determining a command value of output torque has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-295004

  By the way, since the in-wheel motor type vehicle according to Patent Document 1 is usually provided with a suspension, the vertical vibration (pitch rate) generated when the vehicle passes a step on the road surface is It is absorbed and reduced by this suspension.

  However, in a vehicle that does not have such a suspension, or a vehicle in which the suspension effect is not sufficiently obtained, such as a vehicle in which the suspension is broken, the vehicle is Since the generated pitch behavior cannot be sufficiently suppressed, there is a problem that the occupant feels uncomfortable feeling (acceleration / deceleration uncomfortable feeling) due to fluctuations in the pitch rate.

  The present invention has been made in view of the above, and even if the vehicle is an in-wheel motor type vehicle in which the effect of the suspension is not sufficiently obtained, the pitch rate of the vehicle can be adjusted when the vehicle passes through a road step or the like. An object of the present invention is to provide a vehicle braking / driving force control device that can be reduced.

  In order to solve the above-described problems and achieve the object, a braking / driving force control device for a vehicle according to claim 1 of the present invention includes at least pitch rate detection means for detecting the pitch rate of the vehicle, and the center of gravity of the vehicle. And a braking / driving force control means for applying a different braking / driving force to the wheels arranged before and after the wheel to reduce a pitch moment generated around the center of gravity.

  According to a second aspect of the present invention, there is provided a vehicle braking / driving force control device according to the first aspect of the present invention, wherein the variation in the pitch rate is detected by the pitch rate detecting means. The force control means reduces the driving force of one of the front wheels or the rear wheels, and applies the reduced driving force to the other wheel.

  According to a third aspect of the present invention, there is provided a vehicle braking / driving force control device according to the first or second aspect, wherein when the pitch rate variation is detected by the pitch rate detecting means, The braking / driving force control means applies different braking / driving forces to the left and right wheels of the vehicle at a predetermined cycle.

  According to a fourth aspect of the present invention, there is provided the vehicle braking / driving force control apparatus according to the third aspect, wherein the period is a period different from a yawing resonance point.

  According to the braking / driving force control device for a vehicle according to the present invention (claim 1), the front and rear wheels are different so as to reduce the pitch moment generated around the center of gravity of the vehicle when a change in the pitch rate of the vehicle is detected. Since the braking / driving force can be applied, the pitch rate of the vehicle can be reduced, and even if the pitch rate fluctuates, discomfort (according to acceleration / deceleration) felt by the occupant can be suppressed.

  According to the vehicle braking / driving force control apparatus (claim 2) according to the present invention, the pitch rate of the vehicle can be reduced without reducing the driving force of the entire vehicle.

  According to the braking / driving force control device for a vehicle according to the present invention (claim 3), by generating a yaw moment around the center of gravity of the vehicle, energy for generating a pitch angle for lifting the vehicle is absorbed in the yaw direction. Therefore, the sensation amount of the pitch rate can be reduced more than when the occupant feels only the pitch rate.

  According to the braking / driving force control device for a vehicle according to the present invention (claim 4), the attitude of the vehicle in the yaw direction is stabilized by issuing a control command at an early timing period different from the yawing resonance point. be able to.

  Embodiments of a braking / driving force control device for a vehicle according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a block diagram showing a braking / driving force control apparatus for a vehicle according to Embodiment 1 of the present invention. First, the overall configuration of the vehicle 10 will be described with reference to FIG. As shown in FIG. 1, the vehicle 10 includes four wheels: a left front wheel Wfl, a right front wheel Wfr, a left rear wheel Wrl, and a right rear wheel Wrr.

  Electric motors 11a, 11b, 11c, and 11d (in-wheel motors) are incorporated in these left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr. And the rotating shaft of each electric motor 11a, 11b, 11c, 11d is each assembled | attached integrally to hub 12a, 12b, 12, 12d.

  The electric motors 11a, 11b, 11c, and 11d incorporate a reduction gear (not shown), and the left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr are independently driven by their rotation.

  The electric motors 11a, 11b, 11c, and 11d also serve as knuckles, and are connected to the vehicle body BD via the lower arms 13a, 13b, 13c, and 13d, respectively.

  The lower arms 13a, 13b, 13c, and 13d are assembled at their inner ends so that the electric motors 11a, 11b, 11c, and 11d can be rotated about the longitudinal axis of the vehicle 10, respectively, and at the outer ends. Thus, the electric motors 11 a, 11 b, 11 c, and 11 d are assembled so as to be rotatable about the vertical axis of the vehicle 10.

  The electric motors 11a and 11b located on the left and right front wheels Wfl and Wfr are connected to the outer ends of the tie rods 15a and 15b via the knuckle arms 14a and 14b, respectively.

  The tie rods 15a and 15b are connected to both ends of the rack bar 16 at the respective inner ends. The rack bar 16 meshes with a pinion integrated with a steering shaft (not shown) in the steering gear box 17.

  Next, a braking / driving force control device that controls the braking force and driving force of the electric motors 11a, 11b, 11c, and 11d will be described. This braking / driving force control device includes vertical acceleration sensors 21a, 21b, 21c, and 21d, which are pitch rate detection means.

  The vertical acceleration sensors 21a, 21b, 21c, and 21d are assembled to, for example, the electric motors 11a, 11b, 11c, and 11d, and the accelerations in the vertical direction with respect to the absolute space of the left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr, respectively. It is for detection.

  In addition, the vertical acceleration is expressed as positive in the upward direction and negative in the downward direction. The vertical acceleration sensors 21a, 21b, 21c, and 21d are connected to a controller 22 that functions as a braking / driving force control unit and a braking / driving force control device.

  The left and right front and rear wheels Wfl, Wfr, Wrl, Wrr are provided with wheel speed sensors 32a, 32b, 32c, 32d for detecting the wheel speed. The wheel speed sensors 32a, 32b, 32c, and 32d are also connected to the controller 22.

  The controller 22 is constituted by a microcomputer whose main components are a CPU, a ROM, a RAM, and the like. And this controller 22 controls the braking / driving force of electric motor 11a, 11b, 11c, 11d by running the control program mentioned later.

  In addition to the vertical acceleration sensors 21a, 21b, 21c, and 21d, the controller 22 is connected to an accelerator sensor 23 and a brake sensor 24, and drives the electric motors 11a, 11b, 11c, and 11d, respectively. Drive circuits 25, 26, 27, and 28 are connected.

  The accelerator sensor 23 detects a depression amount of an accelerator pedal (not shown) and outputs a detection signal representing the depression amount. The brake sensor 24 detects a depression amount of a brake pedal (not shown) and outputs a detection signal indicating the depression amount.

  Electric power is supplied from the battery 29 to the drive circuits 25, 26, 27, 28, and current sensors 25a, 26a, 27a, which detect currents flowing through the electric motors 11a, 11b, 11c, 11d, 28a are connected to each other.

  The drive circuits 25, 26, 27, 28 control the electric motors 11 a, 11 b, 11 c, 11 d in cooperation with the current sensors 25 a, 26 a, 27 a, 28 a according to instructions from the controller 22 to control the left and right front and rear wheels Wfl, Wfr, Wrl and Wrr are controlled.

  In this case, the controller 22 receives the acceleration sensor 23 or the brake sensor 24 from the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr when the vertical excitation force (hereinafter referred to as vertical force) is not generated. The rotation of the electric motors 11a, 11b, 11c, and 11d is controlled via the drive circuits 25, 26, 27, and 28 according to the detection signal indicating the depression amount, and the left and right front and rear wheels Wfl, Wfr, Wrl, and Wrr are driven in the same manner. It is designed to be driven by force or braking force.

  On the other hand, as shown in FIGS. 5 to 6 which will be described later, when the vehicle 10 gets over the protrusion 42 on the road surface 40 while traveling, different vertical forces Fz are input to the left and right front and rear wheels Wfl, Wfr, Wrl, Wrr. 10 posture changes, that is, the pitch rate around the center of gravity G increases, which may cause discomfort to the passenger. In order to suppress this pitch rate, the controller 22 performs the following pitch control.

  Hereinafter, pitch control by applying different braking / driving forces to the front wheels Wfl, Wfr and the rear wheels Wrl, Wrr of the vehicle 10 will be described with reference to FIGS.

  Here, FIG. 2 is a flowchart showing the pitch control based on the difference in driving timing between the front and rear wheels, FIG. 3 is a left side view showing a running start state of the vehicle, and FIG. 4 is a plan view showing the vehicle shown in FIG. FIG. 5 is a left side view showing a state in which the vehicle starts to ride on the road surface projection, and FIG. 6 is a left side view showing a state in which different driving forces are distributed to the front wheels and the rear wheels.

  FIG. 7 is a graph showing an example of the time transition of the driving force distributed to the front wheels and the rear wheels, where the driving force on the front wheel side is indicated by a broken line and the driving force on the rear wheel side is indicated by a solid line. FIG. 8 is a graph showing a state in which the pitch angle is suppressed by the control. The case where the pitch control is performed is indicated by a thick solid line, and the case where the pitch control is not performed is indicated by a thin solid line.

  As shown in FIGS. 3 and 4, when the vehicle 10 starts running and before the left front wheel Wfl gets over the protrusion 42 of the road surface 40, no change in posture is seen in the vehicle 10, but FIG. As shown, since the vertical force Fz upward from the road surface 40 acts on the left front wheel Wfl when getting over the protrusion 42, the front portion of the vehicle 10 is lifted and a pitch angle θ is generated around the center of gravity G.

  At this time, since the vertical force Fz is input from the protrusion 42 of the road surface 40 to the vertical acceleration sensor 21a of the left front wheel Wfl (step S10), the vertical force Fz is estimated and calculated by the equation (1) (step S11).

Fz = mfl × afl (1)
Here, mfl is the mass of the left front wheel Wfl, and afl is the vertical acceleration of the left front wheel Wfl. The vertical force Fz is similarly estimated and calculated for the other wheels Wfr, Wrl, Wrr, and a total of four wheels is estimated (step S11).

  Next, the attitude of the vehicle 10 is estimated from the information on the vertical force Fz of the four wheels obtained in step S11 (step S12). That is, the pitch angle θ is calculated based on the equations (2) to (4).

ddθtt = (Fzf × lf−Fzr × lr) I (2)
dθt = ∫ddθtt (3)
θ = ∫dθt (4)
Here, Fzf is the vertical force (total value) of the left and right front wheels Wfl, Wfr, lf is the distance from the center of gravity G to the front wheel axis, Fzr is the vertical force (total value) of the left and right rear wheels Wrl, Wrr, and lr is from the center of gravity G. The distance to the rear wheel axis, I, is the moment of inertia of the vehicle 10 in the pitch direction.

Next, the pitch moment Mp necessary for the pitch control of the vehicle 10 is calculated from the pitch angle θ obtained in step S12 and the control gain according to the equation (5) (step S13).
Mp = Gain × θ (5)

  Then, the braking / driving force expressed by the equations (6) and (7) is distributed to the front wheels Wfl, Wfr and the rear wheels Wrl, Wrr of the vehicle 10 (step S14). That is, as shown in FIG. 6, a braking force ΔF (negative driving force) is applied to the front wheels Wfl, Wfr, and a driving force equal to the braking force ΔF is applied to the rear wheels Wrl, Wrr.

Front wheel Wfl, decrease in driving force on Wfr side = −gain × Mp (6)
Rear wheel Wrl, increase in driving force on Wrr side = gain × Mp (7)

  Next, the limit of the driving force to be distributed determined in step S14 is determined (step S15). Here, as described above, the absolute value of the braking force ΔF applied to the front wheels Wfl, Wfr and the driving force ΔF applied to the rear wheels Wrl, Wrr are made equal to each other, so that the total driving force of the vehicle 10 is increased. (Step S15).

  As a result, as shown in FIG. 7, the distributed braking / driving forces (−ΔF, + ΔF) cancel each other, so that the driving force of the entire vehicle 10 is not reduced.

  When the determination of the driving force limit in step S15 is completed, a driving force signal for outputting the braking / driving force is output (step S16), and the control is terminated. By performing such pitch control, as shown in FIG. 8, it was confirmed that the pitch angle θ was reduced as compared with the case where pitch control was not performed.

  As described above, according to the braking / driving force control device for the vehicle 10 according to the first embodiment, when fluctuations in the pitch rate of the vehicle 10 are detected, the front wheels Wfl, Wfr and the rear wheels Wrl, Wrr of the vehicle 10 are detected. In addition, since the predetermined braking / driving force is distributed to the vehicle 10 and within the range of the total driving force of the vehicle 10, the pitch rate can be reduced while the driving force of the entire vehicle 10 is maintained. Therefore, even if the pitch rate of the vehicle 10 varies, the discomfort (according to acceleration / deceleration) felt by the passenger is suppressed.

  Further, the vehicle 10 is not provided with a suspension because the torsional rigidity of the vehicle body BD can be utilized by allocating a predetermined braking / driving force to the front wheels Wfl, Wfr and the rear wheels Wrl, Wrr of the vehicle 10. In this case, the pitch rate can be reduced even when the suspension fails.

  In the second embodiment, when a change in the pitch rate of the vehicle 10 is detected, a predetermined braking / driving force is periodically applied to the left and right front wheels Wfl, Wfr of the vehicle 10, and a yaw moment around the center of gravity G of the vehicle 10 is detected. By generating (yaw angle γ), the sensation amount of the pitch rate can be reduced as compared to when the occupant feels only the pitch rate. In the following description, the same or corresponding parts as those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

  FIG. 9 is a flowchart showing pitch control based on a difference in drive timing between the left and right wheels according to the second embodiment of the present invention. FIG. 10 is a left side view showing how the pitch angle θ is reduced by generating a yaw moment. 11 is a plan view showing the vehicle shown in FIG. 10, and shows a state in which a braking / driving force is applied to the left and right front wheels to generate a yaw angle γ.

  FIG. 12 is a graph showing an example of time transition of the driving force distributed to the right wheel and the left wheel. The driving force on the right wheel side is indicated by a thin solid line, and the driving force on the left wheel side is indicated by a thick solid line. is there. FIG. 13 is a graph showing how the pitch angle is suppressed by the control. The case where the pitch control is performed is indicated by a thick solid line, and the case where the pitch control is not performed is indicated by a thin solid line.

  The state from the start of traveling of the vehicle 10 to the time of overcoming the protrusion 42 on the road surface 40 is as shown in FIGS. 3 to 5 described above. Moreover, since the control in the meantime is the same as that of step S10-S12 mentioned above, the same step number is attached | subjected and duplication description is abbreviate | omitted and it demonstrates from step S20.

If the attitude of the vehicle 10 is estimated in step S12, in order to shift the drive timing of the left and right front wheels Wfl, Wfr, the cycle of the driving force control to be distributed to the left and right front wheels Wfl, Wfr is determined by equation (8) ( Step S20).
Period = Gain / θ (8)

Next, the yaw moment My necessary for pitch control is calculated by the equation (9) (step S21).
My = Gain × θ (9)

Then, the braking / driving force expressed by the equations (10) and (11) is distributed to the left and right front wheels Wfl and Wfr (step S22). That is, a reverse driving force having the same absolute value is applied.
Decrease in driving force on the right front wheel Wfr side = −My / tread / 2 (10)
Increase in driving force on the left front wheel Wfl side = My / tread / 2 (11)

  Next, the limit of the driving force to be distributed determined in step S22 is determined (step S23). For example, an optimum threshold value is obtained in advance by experiments or the like to generate the yaw moment My necessary for suppressing the pitch rate generated by the vertical force Fz, and the amount of decrease in driving force on the right front wheel Wfr side and the left front wheel are determined. Both the increase in driving force on the Wfl side can fall within this threshold range. In the case where the driving force to be distributed exceeds this threshold, the threshold may be set as the upper limit.

  When the determination of the driving force limit in step S23 is completed, a driving force signal for outputting the braking / driving force is output (step S24). Then, as shown in FIG. 12, the control amounts of the left and right front wheels Wfl, Wfr are switched at regular time intervals (cycles) (step S25), and the control is terminated. By this replacement control, it is possible to generate a yaw moment My in a certain direction and a yaw moment My in the opposite direction.

  The command cycle is set at an early timing so as to be different from the yawing resonance point, that is, not to be the same as the yawing resonance point, in order to stabilize the posture of the vehicle 10 in the yaw direction.

  By periodically performing such pitch control, as shown in FIG. 11, the energy for generating the floating pitch angle θ is changed to the yaw direction, that is, the yaw angle γ (solid line) or the yaw angle γ ( It can be decreased in the direction of the broken line).

  As a result, schematically showing this, as shown in FIG. 10, the pitch angle θ can be reduced by, for example, the pitch angle Δθ. In addition, by performing such pitch control, it was possible to delay the generation of the pitch rate, and as shown in FIG. 13, it was confirmed that the pitch angle θ was reduced compared to the case where pitch control was not performed. .

  As described above, according to the braking / driving force control device for the vehicle 10 according to the second embodiment, when fluctuations in the pitch rate of the vehicle 10 are detected, predetermined braking / driving is applied to the left and right front wheels Wfl, Wfr of the vehicle 10. By applying force periodically and generating the yaw moment My around the center of gravity G of the vehicle 10, the sensation of the pitch rate can be reduced compared to when the occupant feels only the pitch rate.

  In the first and second embodiments, the control when the road surface 40 has the protrusion 42 has been described. However, the present invention is not limited to this. For example, when the road surface 40 has a recess, the front wheels Wfl, Wfr The present invention can be applied by changing the distribution degree of the braking / driving force to the rear wheels Wrl and Wrr, and the same effect as described above can be expected.

  Moreover, you may implement combining the said Example 1 and Example 2. FIG.

  As described above, the braking / driving force control device for a vehicle according to the present invention is useful for an in-wheel motor type vehicle in which the effect of the suspension cannot be sufficiently obtained, and particularly when the vehicle passes through a step on the road surface or the like. Suitable for vehicles aiming to reduce the pitch rate of the vehicle.

1 is a block diagram showing a braking / driving force control device for a vehicle according to Embodiment 1 of the present invention. FIG. It is a flowchart which shows the pitch control by the drive timing difference of front and rear wheels. It is a left view which shows the driving | running | working start state of a vehicle. FIG. 4 is a plan view showing the vehicle shown in FIG. 3. It is a left view which shows the state which the vehicle began to get on the protrusion of a road surface. It is a left view which shows the state which allocated different driving force to a front wheel and a rear wheel, respectively. It is a graph which shows the time transition example of the driving force allocated to a front wheel and a rear wheel. It is a graph which shows a mode that a pitch angle is suppressed by control. It is a flowchart which shows the pitch control by the drive timing difference of the right-and-left wheel which concerns on Example 2 of this invention. It is a left view which shows a mode that pitch angle (theta) is reduced by generating a yaw moment. It is a top view which shows the vehicle shown in FIG. It is a graph which shows the time transition example of the driving force allocated to a right wheel and a left wheel. It is a graph which shows a mode that a pitch angle is suppressed by control.

Explanation of symbols

10 Vehicle 11a, 11b, 11c, 11d Electric motor 21a, 21b, 21c, 21d Vertical acceleration sensor (pitch rate detection means)
22 Controller (braking / braking force control means, braking / braking force control device)
40 Road surface 42 Protrusion G Center of gravity θ Pitch angle γ Yaw angle Wfl Left front wheel Wfr Right front wheel Wrl Left rear wheel Wrr Right rear wheel Fz Vertical force from road surface projection Mp Pitch moment required for pitch control My Yaw moment required for pitch control

Claims (4)

At least pitch rate detecting means for detecting the pitch rate of the vehicle;
Braking / driving force control means for applying different braking / driving forces to the wheels arranged before and after the center of gravity of the vehicle, and reducing pitch moment generated around the center of gravity;
A braking / driving force control device for a vehicle, comprising:   When fluctuations in the pitch rate are detected by the pitch rate detection means, the braking / driving force control means reduces the driving force of one of the front wheels or the rear wheels and reduces the driving force. The braking / driving force control device for a vehicle according to claim 1, wherein the driving force is applied to the other wheel.   When the variation in the pitch rate is detected by the pitch rate detection means, the braking / driving force control means applies different braking / driving forces to the left and right wheels of the vehicle at a predetermined cycle. The braking / driving force control device for a vehicle according to claim 1 or 2.   4. The vehicle braking / driving force control device according to claim 3, wherein the cycle is a cycle different from a yawing resonance point.

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