JP2005306249A - Vehicle steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle steering control device effectively suppressing upward movement of a vehicle body in rolling of the vehicle body without degrading the ride quality. <P>SOLUTION: The vehicle steering control device comprises: right, left, front, and rear wheels FL, FR, RL and RR supported in the vehicle body by a suspension mechanism 2; all-wheel independent steering control means 3 and 4 capable of independently controlling steering angles of the right, left, front, and rear wheels FL, FR, RL and RR; and a roll detecting means 5 for detecting a roll state of the vehicle body. When the vehicle body is detected to roll by a roll detecting means 5, the all-wheel independent steering control means 3 and 4 toe out at least either the right and left front wheels FL and FR or the right and left rear wheels RL and RR. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle steering control device that controls the steering angle of left and right front and rear wheels of a vehicle.

When the vehicle turns, the turning inertia force acts on the vehicle body toward the outside of the vehicle, and the vehicle body rolls. Also, when the road surface has undulations, rolls can occur on the vehicle body. [Patent Document 1] discloses a technique for suppressing this roll. The technique described in [Patent Document 1] suppresses an increase in the roll angle by steering the rear wheel when the roll angle becomes large.
JP-A-5-131946

  When the vehicle body is rolled, a phenomenon that the vehicle body is lifted may occur. This phenomenon is also expressed as jacked up. Jacking up raises the position of the center of gravity of the vehicle, which is undesirable in terms of vehicle maneuverability. The technique described in [Patent Document 1] described above considers only suppression of increase in roll angle, and does not consider suppression of bounce (upward movement of the vehicle body).

  Although there is a method of controlling the damping force of the suspension shock absorber in order to suppress the bounce of the vehicle body, it is difficult to control the damping force of the suspension shock absorber at a very low speed. Further, if the suspension shock absorber damping force is increased too much, there are problems that abnormal noise is generated from the suspension shock absorber or that the riding comfort is lumpy and worsened. For this reason, the suspension shock absorber damping force cannot be increased greatly. Accordingly, an object of the present invention is to provide a vehicle driving force control device that can effectively suppress the upward movement of the vehicle body when rolling the vehicle body without deteriorating riding comfort.

  The vehicle steering control device according to claim 1 includes left and right front and rear wheels supported on the vehicle body by a suspension mechanism, all-wheel independent steering control means capable of independently controlling the steering angles of the left and right front and rear wheels, and a vehicle body roll. Roll detecting means for detecting the state, and the all-wheel independent steering control means toe out at least one of the left and right front wheels or the left and right rear wheels when the roll detecting means detects that the vehicle body is rolling. It is characterized by letting. The vehicle only needs to have at least one wheel on each side in the front-rear and left-right directions. Needless to say, both the front and rear wheels may be toe-out.

  According to a second aspect of the present invention, in the vehicle steering control device according to the first aspect, when the all-wheel independent steering control means has a smaller body roll state as the body roll state detected by the roll detection means is larger. It is characterized by a large toe-out amount.

  The invention according to claim 3 is the vehicle steering control device according to claim 2, further comprising lateral acceleration detecting means for detecting lateral acceleration acting on the vehicle, wherein the all-wheel independent steering control means comprises: The toe-out amount is realized by distributing the right-wheel toe-out correction amount and the left-wheel toe-out correction amount, and the toe-out distribution of the left and right wheels is determined based on the vehicle lateral acceleration detected by the lateral acceleration detecting means.

  According to the vehicle steering control device of the first aspect, the left and right wheels are toe-out, thereby controlling the force to lift the vehicle body acting on the vehicle body (force to lower the vehicle body) to move the vehicle body upward. Suppress. Examples of the roll detection means include a stroke sensor that detects the distance between the vehicle body and the wheels, and a lateral acceleration sensor that detects lateral acceleration when the roll state is estimated from the lateral acceleration.

  According to the vehicle steering control device of the second aspect, the greater the roll state (the more remarkable), the greater the toe-out amount and the lower the force for lifting the vehicle body (the force for lowering the vehicle body). And the upward movement of the vehicle body is more effectively suppressed. Further, when the roll state is small, the toe-out amount for suppressing the upward movement of the vehicle body is small. For this reason, the smaller the roll state, the smaller the toe-out amount, and the tire wear can be suppressed, and the rotational resistance of the wheel can be reduced to suppress the deterioration of fuel consumption. In addition, the roll state is large (significant) means that the lateral inclination of the vehicle body with respect to the wheels is large.

  According to the vehicle steering control device of the third aspect, by distributing the toe-out amount to the left and right according to the lateral acceleration acting on the vehicle, the vehicle is reliably turned while suppressing the upward movement of the vehicle body. be able to. When turning, the vehicle turns by generating cornering power in a direction transverse to the wheel rotation direction. This cornering power depends on the wheel ground load, and the ground load depends on the vehicle lateral acceleration. In order to effectively generate a force that suppresses the upward movement of the vehicle body that acts by toe-out, it is preferable that the cornering forces generated on the left and right wheels are controlled to be as uniform as possible. The cornering force depends on the ground contact load of each wheel and the steering angle (toe-out amount) with respect to the vehicle body traveling direction. For this reason, by determining the left / right distribution ratio of the toe-out amount based on the lateral acceleration, it is possible to control the upward movement suppression of the vehicle body and the turning of the vehicle with a good balance.

  An embodiment of the vehicle steering control device of the present invention will be described below. A vehicle configuration diagram having the control device of the present embodiment is shown in FIG. As shown in FIG. 1, the vehicle 1 has four wheels: a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. Each wheel is supported by a vehicle body (not shown) via the suspension arm 2 (in the case of a strut suspension, it is supported by the vehicle body via a shock absorber). The vehicle 1 includes a four-wheel independent steering mechanism (a so-called 4WS system) that can independently control the steering angle of each wheel. An actuator 3 for changing the steering angle of each wheel is provided for each wheel.

  The main body of the actuator 3 is attached to the vehicle body, and a rod that extends and contracts using electric energy protrudes from the main body. The tip of this rod is pivotally connected to the hub carrier of each wheel. The steering angle of each wheel can be changed by extending and contracting the rod with electric power from a battery (not shown) based on a drive signal from the ECU 4 described later. A stroke sensor 5 is disposed between each suspension arm 2 and the vehicle body. Each stroke sensor 5 detects a suspension stroke for each of the left and right front and rear wheels. From this suspension stroke, the roll state of the vehicle body can be known. Here, the roll angle is obtained from the suspension stroke, and the roll state of the vehicle body is grasped by this roll angle. That is, the stroke sensor 5 functions as roll detection means.

  The stroke sensor 5 and the actuator 3 are connected to an electronic control unit (ECU) 4 that comprehensively controls the 4WS system. The ECU 4 is also connected with other sensors for detecting the amount of information necessary for controlling the 4WS system. Specifically, a yaw sensor 6 that detects yaw acting on the vehicle, a longitudinal G sensor 7 and a lateral G sensor 8 that respectively detect longitudinal acceleration and lateral acceleration acting on the vehicle, and the steering angle of the steering wheel operated by the driver A steering angle sensor 9 for detecting the wheel speed, a wheel speed sensor 10 for detecting the rotational speed of each wheel, and the like.

  Although only one wheel speed sensor 10 is illustrated in FIG. 1, the wheel speed sensor 10 is provided for each wheel, and the traveling speed (vehicle speed) of the vehicle 1 is detected from the detection results of the four wheel speed sensors. The steering angle of the four wheels is controlled based on the yaw, acceleration, steering wheel rudder angle, wheel speed, etc. detected by these sensors. That is, these sensors and the above-described ECU 4 and actuator 3 function as an all-wheel independent steering control means. Note that the accelerator opening, the amount of brake operation, the engine state, and the like may be used during front wheel steering.

  Next, toe-out control at the time of roll by this control apparatus will be described. In the all-wheel independent steering control, first, the basic steering amount of each wheel is determined based on the above-described various information amounts such as yaw and acceleration. Then, a toe-out correction amount for toe-out the front wheels and the rear wheels is determined according to the roll state, and this toe-out correction amount is reflected on the basic steering amount. That is, the toe-out state is formed during the roll by correcting the basic steering amount with the toe-out correction amount. The toe-out in the present invention refers to the distance connecting the front ends of the lines indicating the radii of the wheels on the plane parallel to the vehicle traveling direction through the centers of the pair of left and right wheels. A state longer than the distance. That is, not only when the vehicle is in a straight traveling state but also when the left and right wheels are in a steering state, the toe-out can occur.

  FIG. 2 schematically shows a jack-up phenomenon during turning (when a roll is generated). FIG. 2 is a diagram showing the vehicle 1 during a left turn from the rear. In FIG. 2, it turns from the front left side of the paper to the left side of the paper surface, and the right side in FIG. At this time, a turning inertia force indicated by an arrow X in FIG. Due to the relationship between the turning inertia force and the position of the center of gravity G of the vehicle, the vehicle body rolls so that the right side is lowered. In the turning outer wheel, when the resultant force of the lateral force (side force) at the tire contact point and the contact load is downward from the line connecting the tire contact point and the roll center, a force for lifting the vehicle body (jack-up force) is generated.

  Here, when the left and right wheels are toe-out, as shown in FIG. 3, the turning outer wheel is corrected toward the turning outer side, and the cornering force (approximate to the side force when the side slip angle is small) is reduced. As a result, jack-up power is reduced. In FIG. 3, the state of the tire before toe-out is indicated by a dotted line, and the state of the tire after toe-out correction is indicated by a solid line. For the sake of simplicity, the state before toe-out correction is shown here as a state in which neither toe-out nor toe-in is performed. On the other hand, the turning inner wheel is corrected toward the turning inside, and the cornering force increases, and accordingly, the jackdown force increases. As a result, the force for moving the vehicle body downward increases, and the upward movement of the vehicle body is suppressed.

  Next, how to determine the toe-out correction control amount and how to distribute the toe-out amount to the left and right wheels will be described. FIG. 4 schematically shows the flow at this time. In the following, the flow for determining the toe-out amount for one of the left and right front wheels and the left and right rear wheels will be described, but the same applies to the other. However, the map used due to the influence of vehicle weight distribution may be different.

  First, as shown in the “toe-out correction amount” on the left side of FIG. 4, the left and right wheel suspension stroke amounts are detected by the stroke sensor 5, and the average stroke amount is calculated therefrom. The average stroke amount is an average of left and right strokes and is an amount indicating how much the vehicle body is moving upward, that is, bounced. The bounce speed is calculated from the time variation of the average stroke length. Further, from the average stroke amount, the roll center height that is the height from the line (surface) connecting the left and right tire ground contact points of the roll center of the vehicle body is obtained.

The basic toe-out amount δ ₀ is obtained from the bounce speed and the roll center height of the vehicle body using the map shown in FIG. The basic toe-out amount δ ₀ is a toe-out amount per one wheel. As shown in FIG. 5, the basic toe-out amount δ ₀ increases as the roll center height decreases. This is because if the roll center height is low, the vertical force (jack-up suppressing force) generated by toe-out becomes small. In addition, the basic toe-out amount δ ₀ increases as the bounce speed increases. This is because a vertical force (jack-up suppressing force) proportional to the bounce speed is generated in order to increase the damping effect for suppressing jack-up.

The basic toe-out amount δ ₀ is set in proportion to the force F ^* acting toward the outside of the turn acting on the vehicle body. This is because the greater the outward force, the larger the toe-out amount and the lower the upward movement amount of the vehicle body. There is a relationship of the following formula (1) between the basic toe-out amount δ ₀ and the outward force F ^* . Here, Cn is a tire characteristic value, W is a wheel load, and both are constants determined by vehicle specifications. Cn = Cp / W, Cp is the cornering power, and W is the wheel load at the time of Cp measurement. Cp may be obtained directly with a load sensor, or may be obtained from, for example, an angle (tire slip angle) formed between the traveling direction of the vehicle and the direction of the tire. Here, the basic toe-out amount δ ₀ proportional to the outward force F ^* is obtained from the bounce speed and the roll center height of the vehicle body using the map of FIG.

Next, the left / right distribution of the determined basic toe-out amount δ ₀ is determined. When the toe-out is performed, the cornering force increases due to the increase in the steering angle on the turning inner wheel side, and the cornering force decreases due to the decrease in the steering angle on the turning outer wheel side. It is only necessary to compensate for the increase / decrease in the turning inner and outer wheels. However, if the determined basic toe-out amount δ ₀ is simply equally distributed to the left and right, a desired cornering force may not be obtained. Also, the ground contact load of the left and right wheels changes depending on the turning state, but the cornering force also changes if the ground contact load changes even at the same rudder angle.

Therefore, it is necessary to determine the left / right distribution in consideration of these matters. As shown in the “left / right distribution” in the center of FIG. 4, the lateral acceleration is first detected by the lateral G sensor 8. From the lateral acceleration, the ground load on the left and right wheels can be inferred. Therefore, Cp (cornering power: cornering force rising gradient [proportional part] with respect to tire side slip angle) of inner and outer wheels can be calculated from the detected lateral acceleration, and left and right (inner and outer) wheel distributions N _in and N _out are determined _therefrom. . Here, the inner ring side distribution N _in and the outer ring side distribution N _out are obtained directly from the lateral acceleration (turning acceleration) a using the map of FIG.

Note that there is a relationship of the following equation (2) between the left / right (inside / outside) wheel distributions N _in and N _out and the turning acceleration a. Here, m is the vehicle weight, H is the height of the center of gravity, T is the tread width, and J is the roll composition distribution, both of which are constants determined by the vehicle specifications. In addition, W _in the wheel load of the inner wheel, is W _out is a wheel load of turning the outer ring. Here, the basic toe-out amount δ ₀ proportional to the outward force F ^* is obtained from the bounce speed and the roll center height of the vehicle body using the map of FIG.

Then, the inner wheel side toe-out correction (steering angle) amount δ _in = δ ₀ × N _in and the outer wheel side toe-out correction (steering angle) amount δ _out = δ ₀ × N _out are calculated. As shown in FIG. 6, the outer wheel side toe-out correction (steering angle) amount δ _out decreases as the turning acceleration a increases. This is because, as the turning acceleration a increases, the ground load on the turning outer wheel increases, so that the cornering force can be secured even if the distribution on the outer ring side is reduced (the distribution on the inner ring side is increased accordingly). Further, the inner wheel side toe-out correction (steering angle) amount δ _in increases as the turning acceleration a increases. This is because, as the turning acceleration “a” increases, the ground contact load of the turning inner wheel decreases, and accordingly, the distribution on the inner wheel side is increased and the cornering force is secured by increasing the rudder angle. The inner ring Cp and the outer ring Cp are Cn × W _in and Cn × W _out , and the calculation of the inner ring Cp and the outer ring Cp in the “left-right distribution” in FIG. 4 is equivalent to the calculation of W _in and W _out. is there.

  On the other hand, as shown in “4WS” on the right side of FIG. 4, the steering angle of the steering wheel and other information (detected by the yaw sensor) detected by the steering angle sensor 9 of the left and right wheels (turning inner and outer wheels) by a normal 4WS system. Based on the vehicle yaw, the vehicle longitudinal acceleration detected by the longitudinal G sensor 7, the vehicle lateral acceleration a detected by the lateral G sensor 8, the vehicle speed detected by the wheel speed sensor 10, etc.) The rudder angle is determined. Since this is the same as a normal 4WS system, a detailed description thereof is omitted here.

Finally, the toe-out correction amounts δ _in and δ _{out of the} inner and outer wheels are reflected on the basic steering angle of the outer and inner wheels determined by the 4WS system, and the final steering angle is determined. In accordance with the determined steering angle, the ECU 4 drives the actuator 3 of each wheel to steer each wheel. Since the toe-out correction amounts δ _in and δ _out are reflected _{in the} final steering angle, the wheels are toe-out, and the upward movement of the vehicle body is suppressed as described above.

  In addition, this invention is not limited to embodiment mentioned above. For example, in the above-described embodiment, the roll state of the vehicle body is always detected, and the toe-out amount is always controlled according to the detected roll state (roll angle). That is, when rolls are generated, the toe-out is always controlled. However, the control may be performed such that the toe-out is performed only when the roll state becomes more significant than the predetermined roll state, for example, only when the roll angle is equal to or greater than the predetermined roll angle. Alternatively, the roll state may be determined based on the lateral acceleration instead of the roll angle, and control may be performed so that the toe-out is performed only when the lateral acceleration becomes a predetermined value or more.

It is a lineblock diagram of vehicles which have one embodiment of a vehicle steering control device of the present invention. It is a schematic diagram which shows the mode of the roll of a vehicle body. It is explanatory drawing which shows the wheel steering angle at the time of turning. It is explanatory drawing which shows the flow of wheel steering angle calculation in one Embodiment of the vehicle steering control apparatus of this invention. It is a map which shows the relationship between roll center height and bounce speed, and basic toe-out amount. It is a map which shows the relationship between turning acceleration and an inner-outer wheel distribution value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Suspension arm, 3 ... Actuator, 4 ... ECU, 5 ... Stroke sensor, 6 ... Yaw sensor, 7 ... Front-back G sensor, 8 ... Lateral G sensor, 9 ... Rudder angle sensor, 10 ... Wheel speed sensor, FL: front left wheel, FR: front right wheel, RL: rear left wheel, RR: rear right wheel.

Claims (3)

Left and right front and rear wheels supported by the vehicle body by a suspension mechanism;
All-wheel independent steering control means capable of independently controlling the steering angles of the left and right front and rear wheels;
Roll detecting means for detecting the roll state of the vehicle body,
The all-wheel independent steering control means toe-out at least one of the left and right front wheels or the left and right rear wheels when the roll detection means detects that the vehicle body is rolling.   The all-wheel independent steering control unit increases the toe-out amount as the vehicle body roll state detected by the roll detection unit is larger than when the vehicle body roll state is small. Vehicle steering control device. It further comprises a lateral acceleration detection means for detecting the lateral acceleration acting on the vehicle,
The all-wheel independent steering control means distributes the right-wheel toe-out correction amount and the left-wheel toe-out correction amount to realize the toe-out amount, and toe-out the left and right wheels based on the vehicle lateral acceleration detected by the lateral acceleration detecting means. The vehicle steering control device according to claim 2, wherein the distribution is determined.

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