JP2009078759A - Suspension controller for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suspension controller for vehicle capable of properly changing distribution of vertical load of inner and outer wheels of an automobile A during turning by the control force given to the wheels 3 to control its behavior during turning in the optimum manner. <P>SOLUTION: This suspension controller for vehicle controls an electromagnetic actuator 2 per wheel 3 in accordance with the predetermined rule for controlling actuator so that deviations of yaw rate ϕ' and amount of side slip V<SB>y</SB>which occur during turning from target values become the minimum values. The optimum rule for controlling actuator and minimizing the integration of function L having at least the term expressing degree of the deviation of yaw rate, the term expressing degree of the deviation of amount of side slip, the term expressing the energy to be transmitted to a vehicle body B and the wheel 3 to be controlled from the electromagnetic actuator 2, and the term expressing balance of total energy of the vehicle body B and the wheel 3 is used as the rule for controlling actuator. The characteristics for controlling behavior of the automobile A are corrected by changing a value of weighting factor κ of controllability and stability included in the optimum rule for controlling actuator based on a running condition of the automobile A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a suspension control device that applies control force to wheels suspended on a vehicle body, thereby changing the load distribution of inner and outer wheels to control the turning behavior of the vehicle.

  Conventionally, as this type of suspension control device, for example, an electromagnetic suspension device disclosed in Patent Document 1, a suspension is stroked by an actuator (such as a linear motor or a ball screw mechanism) disposed between a vehicle body and a wheel. What is made to let you do is known.

Further, in the vehicle suspension device described in Patent Document 2, the damping force of the shock absorber of each wheel is variably controlled during turning of the vehicle to increase the roll rigidity, and at that time, rolls are performed on the front wheel side and the rear wheel side. The behavior of the vehicle in the yaw direction is controlled by making a difference in the degree of change in rigidity and making a difference in the cornering force between the front and rear wheels.
Japanese Patent Laid-Open No. 2007-083813 JP-A-9-109641

  By the way, by applying the control force to the wheel using an actuator as in the former conventional example (Patent Document 1) and increasing or decreasing the ground load, the ground load of the inner and outer wheels on the front wheel side and the rear wheel side of the vehicle, respectively. If the distribution is adjusted, the behavior of the yaw direction of the vehicle is controlled by making the difference in the cornering force by differentiating the roll rigidity on the front wheel side and the rear wheel side as in the latter conventional example (Patent Document 2). Can do.

  However, in the latter conventional example, the control constant k1 is switched to a higher value k2 during the turning of the vehicle in the damping force control of the shock absorber. It is hard to say what can be controlled. That is, if the yaw moment acting on the vehicle by the control is insufficient, the followability (steerability) to the steering cannot be sufficiently increased, while if the yaw moment is too large, the behavior may be disturbed. It is.

  In view of such a point, an object of the present invention is to appropriately change the ground load distribution of the inner and outer wheels during turning of the vehicle by at least the vertical control force applied to the wheels, thereby controlling the controllability and behavior stability of the vehicle. It is to realize the optimal turning behavior control that balances the above.

  In order to achieve the above object, according to the present invention, the actuator is controlled in accordance with an optimal control law that achieves both the controllability and stability of the vehicle, and the controllability in the control law is determined based on the running state of the vehicle. In addition, the weighting of stability is changed.

  That is, the invention of claim 1 detects a running state amount representing a running state of a vehicle for a vehicle suspension control device in which at least a vertical control force is applied to a wheel suspended on a vehicle body by an actuator. Based on the running state quantity detection means and the detected running state quantity, the actuator is controlled according to a predetermined control law, and the grounding load distribution of the inner and outer wheels during turning is changed by increasing or decreasing the grounding load of the wheel by the control force. And a behavior control means for controlling the turning behavior of the vehicle, the control law is an optimal control law that achieves both the controllability and stability of the vehicle, and a weighting coefficient that changes the weighting of the control law. Based on the detected running state quantity of the vehicle, the weighting coefficient value of the control law is changed and the behavior control characteristics are corrected. Those having a control characteristic correcting means that.

  In the vehicle suspension control device having the above-described configuration, the actuator is controlled according to a predetermined control law by the behavior control means while the vehicle is turning, and at least a vertical control force is applied to one or more wheels. The ground load changes. This makes it possible to change the ground load distribution of the inner and outer wheels in a turning vehicle, and to control the turning behavior of the vehicle by adjusting the cornering force on at least one of the front wheel side and the rear wheel side. .

  At this time, if the predetermined control law is an optimal control law that achieves both the maneuverability and stability of the vehicle, a control force determined in accordance with the control law is applied to the wheels, so that driving such as steering steering is performed. Appropriate turning behavior control is performed with high followability to the operation and without disturbing the behavior.

  In addition, the control law has a weighting factor that changes the weighting of the controllability and stability of the vehicle, and the value of the weighting factor is changed by the control characteristic correcting means based on the running state of the vehicle. Thus, the balance between maneuverability and stability will be further optimized. In other words, it is possible to realize optimal turning behavior control that takes into account the running state as well as the controllability and stability of the vehicle.

  Specifically, for example, a steering angle sensor for detecting the steering angle of the steering wheel or the steering wheel is provided, and if the change rate is higher than a predetermined value based on at least the change rate of the steering angle, the weight is given by the control characteristic correction unit. What is necessary is just to correct | amend the value of a coefficient so that maneuverability may become higher (Claim 3). In this way, for example, when the driver steers suddenly to avoid a collision, the vehicle's behavior follow-up performance is improved, and a more reliable collision avoidance can be achieved.

  On the other hand, for example, when the steering angle change rate of the steering wheel or steering wheel is lower than a predetermined value, the vehicle is considered to travel slowly along a gentle curve, and its behavior is desired to be highly stable, Since it is preferable that the tracking performance with respect to steering is rather low from the viewpoint of riding comfort and the like, in this case, the value of the weighting factor may be corrected by the control characteristic correcting means so that the stability becomes higher.

  By the way, in general, it is difficult to derive the optimal control law analytically, and in order to actually perform the optimal control as described above, the optimal control problem must be solved in real time. It was thought. In this regard, the inventor of the present application has proposed a method for analytically deriving an optimal control law that asymptotically stabilizes the system, focusing on the energy balance of the control target, as will be described in detail later. If a control law is used, the above-described control can be realized.

  That is, for example, the control law of the vehicle behavior control includes at least a term representing the magnitude of deviation from the target value of yaw rate, a term representing the magnitude of deviation from the target value of the vehicle side slip amount, and an actuator. It is calculated | required as what minimizes the integral of the function which has the term showing the transmission energy to the vehicle body and wheel which are controlled objects, and the term showing the total energy balance of this vehicle body and wheel, expressed.

However, U is a target value of the vertical load variation of the wheel by the control force, U _A is the yaw moment acting on the vehicle by the lateral force of the wheel when not applied with the control input, U _B, the unit control input Is the yaw moment acting on the vehicle by the lateral force of the wheels. Φ ′ is a yaw rate, and can be detected by a yaw rate sensor. ^tar φ ′ is the target yaw rate, and is obtained from, for example, the vehicle speed and the steering angle. Furthermore, κ, r ₁ , and r ₃ are control weighting factors, respectively, and can be set in advance by experiment, analysis, or the like so as to obtain desirable control characteristics.

More U _A specifically-formula (A), for example, the formula: (B), U _B is represented by formula (C).
U _A = l _f [(μW ₁ −aW ₁ ² ) Γ ₁ + (μW ₂ −aW ₂ ² ) Γ ₂ ] (B)
U _B = l _f [(μ-2aW ₁ ) Γ _1- (μ-2aW ₂ ) Γ ₂ ]
-L _r [-(μ-2aW ₃ ) Γ ₃ + (μ-2aW ₄ ) Γ ₄ ] (C)
In formulas (B) and (C), l _f and l _r are distances in the front-rear direction from the center of gravity of the vehicle body to the front wheels and the rear wheels, respectively, and a is a constant determined by the characteristics of the tire. It is set based on specifications. The road surface friction coefficient μ is estimated by, for example, a conventionally known method from the vehicle speed and the engine output. W ₁ , W ₂ ,... Represent the ground load of each wheel, and are estimated from, for example, the vehicle speed and the steering angle. Further, Γ ₁ , Γ ₂ ,... Represent the ratio of the lateral force of each wheel to the maximum value, and are estimated using a tire model such as a magic formula, for example.

The U _B, for example, as in the formula (C), and represents the magnitude of the yaw moment due to the control input, the control law of the formula (A), it weight coefficient κ is multiplied. Increasing the value of the weighting factor κ apparently increases the yaw moment due to the control input in the control law of the equation (A), so that the ground load change amount U obtained according to the control law becomes smaller. However, since the value of U _B does not actually change and the yaw moment due to the control input does not increase particularly, the amount of change U becomes smaller as described above, so the yaw moment actually decreases. Thus, the behavior change of the vehicle with respect to the steering is small, that is, the behavior stability is increased.

  That is, if the value of the weighting factor κ is increased, the weight of stability in the behavior control of the vehicle is increased. On the other hand, if the value of the weighting factor κ is decreased, the weight of controllability is increased. The behavior control characteristic may be corrected by changing the value of the weight coefficient κ according to the running state of the vehicle.

  By the way, the wheel that increases or decreases the ground load by applying the control force by the optimal control as described above may be at least one wheel such as a front wheel inward of turning, but preferably the front wheel or the rear wheel. In either of the above, the ground contact load of one of the inner and outer rings is increased and the other is decreased (Claims 5 and 6). In this way, the distribution of the ground load of the inner and outer rings can be changed efficiently. At that time, from the viewpoint of speeding up the control calculation, it is preferable to make the increase / decrease change amount of the contact load of the inner and outer rings the same.

  More preferably, the grounding load of one of the inner and outer wheels on the front side of the vehicle is increased and the other is decreased, and the grounding load of the inner and outer wheels on the rear side of the vehicle is decreased and the actuator is controlled to increase the other. (Claim 7) In this way, the direction of the ground load change of the inner and outer rings is reversed on the front side and the rear side of the vehicle, so the roll moment acting on the vehicle is also reversed and the behavior The vibration around the roll axis of the vehicle due to the control can be suppressed. In this case also, it is preferable that the amount of change in increase / decrease in the ground load of each wheel is the same.

  As described above, according to the suspension control device for a vehicle according to the present invention, at least the vertical control force is applied to the wheels by the actuator to change the ground load distribution of the inner and outer wheels during the turning of the vehicle. Therefore, the actuator is controlled in accordance with an optimal control law that achieves both controllability and stability of the vehicle, and based on the running state of the vehicle. By changing the weighting of the maneuverability and stability, it is possible to realize the optimum turning behavior control that takes into account the running state of the vehicle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

(Schematic configuration of suspension control device)
FIG. 1 schematically shows an automobile A (vehicle) equipped with a suspension control device S according to the present invention. In this example, as shown in FIG. 1 (a), front and rear suspensions 1 _FR , 1 _FL , 1 _RR and 1 _RL are provided with electromagnetic actuators 2, 2,. Each of the suspensions 1 _FR , 1 _FL ,... Is a so-called unsprung member including a suspension member (not shown) such as a wheel 3 (tire 3a, wheel 3b) and a wheel support that supports the wheel 3 (tire 3a, wheel 3b). The electromagnetic actuator 2 is connected to the vehicle body B via a spring 4 (which may be a leaf spring, a torsion bar, an air spring or the like) and a shock absorber 5 and provided between the coil spring 4 and the vehicle body B in parallel. Thus, at least a vertical control force is applied to the wheel 3.

As schematically shown in FIG. 2B, the suspension 1 is mechanically connected to the member 6 on the spring (mainly the mass shared by the vehicle body B) by the coil spring 4 and the shock absorber 5 in the suspension 1. It can be regarded as a vibration system with two degrees of freedom. In the example of the figure, the mass under the spring is represented as M ₁ , the spring constant of the tire 3a is represented as K ₁ , the spring constant of the coil spring 4 is represented as K ₂ , the damping coefficient of the shock absorber 5 is represented as C, and the mass over the spring is M _2. It expresses.

Further, the unevenness of the road surface on which the wheel 3 is grounded, that is, the vertical displacement is represented as q ₀ , the unsprung vertical displacement is represented as q ₁ , and the upward and downward displacement is represented as q _2. Is represented as u. The electromagnetic actuator 2 driven corresponding to the control amount u gives a control force in the vertical direction under the spring, while giving a reaction force in the opposite direction to the spring. The control force generated by the electromagnetic actuator 2 has a positive value in the direction in which the unsprung and sprung parts are pushed apart from each other, and a negative value in the direction in which both are pulled.

  As an example of the electromagnetic actuator 2, a linear motor is used, and a permanent magnet is disposed on a rod connected under the spring, and a driving coil is disposed on the spring so as to surround the rod. The forward / backward driving force of the rod is controlled by power supply control to the driving coil, and the control force is applied to the unsprung and the unsprung respectively. Of course, you may connect a rod on a spring.

Then, the controller 10 controls the electromagnetic actuators 2, 2,... For each wheel 3, 3,. As schematically shown in FIG. 2, the vehicle body B of the automobile A has an acceleration in the vertical direction corresponding to the mounting portion (on the spring) of the suspension 1 _FR , 1 _FL ,. , which detects q ₂ ″, and stroke sensors 12, 12,... which detect a stroke q _s (= q ₂ −q ₁ ) of the suspension 1.

Further, a vehicle speed sensor 13 for detecting a running speed (vehicle speed) V _x of the automobile A, _'the lateral acceleration sensor 14 for detecting a same yaw rate phi' the lateral acceleration V _y and yaw rate sensor 15 for detecting, the steering And a rudder angle sensor 16 for detecting the angle δ. However, the type of sensor is not limited to the above, for example, if the computed vehicle speed V _x on the basis of an output from a known wheel speed sensor, may not be the vehicle speed sensor 13. In this embodiment, the sensors 13 to 16 together with a travel state amount detection unit 10b of the controller 10 described later constitute a travel state amount detection means for detecting the travel state amount of the automobile A.

The controller 10 receives signals from the sensors 11-16, etc., and controls the electromagnetic actuators 2, 2,... For each of the wheels 3, 3,..., That is, the suspensions 1 _FR , 1 _FL ,. The stroke of the suspension 1 is positively changed by the control force generated. Specifically, it absorbs input due to road surface irregularities, etc., reduces vibration transmission to the vehicle body B, and suppresses changes in the posture of the vehicle due to inertial forces so that both ride comfort and exercise performance are compatible at a high level. .

Further, the controller 10 controls the electromagnetic actuators 2, 2,... For each of the suspensions 1 _FR , 1 _FL ,... According to a predetermined control law, and the ground load of the wheel 3 is controlled by the generated control force. By increasing or decreasing, the ground load distribution of the inner and outer wheels is changed while the vehicle A is turning, and the turning behavior is controlled.

That is, in this embodiment, the ground loads W _i (i = 1, 2,...) Of the front and rear left and right four wheels 3, 3,. as shown in, for example, if the increase maneuverability of the car a in the left turn, increases ground load W ₁ in the left front wheel is turning inner (friction circle radius indicating put hatching in FIG enlarge the front wheel ) and, with decreasing on the right front wheel is turning outer, as the rear wheel side reduces the turning inner (left rear wheel), the ground load W _3, increases in outer turning wheel (right rear wheel), the suspension 1 The electromagnetic actuators 2, 2... Are controlled for each of _FR 1, 1 _FL ,. At that time, in order to reduce the amount of calculation related to the control as much as possible and increase the responsiveness, the increase / decrease amounts of the ground loads W ₁ , W ₂ ,... I have to.

Thus the vertical load W ₁ of the inner turning wheel is increased at the front wheel, the ground load W ₂ of the outer turning wheel is decreased, the nonlinearity of the tire grip force 3a, turning inner as shown in FIG. (B) Since the increase in the lateral force is larger than the decrease in the lateral force of the outer ring, the lateral force on the front wheel side including the inner and outer rings 3 and 3 is increased and the cornering force is increased. On the other hand, on the rear wheel side, the ground contact load distribution changes toward the outer side of the turn as opposed to the front wheel side, and although not shown, the lateral force of the inner and outer wheels combined decreases and the cornering force also decreases. Therefore, the yaw moment (the counterclockwise yaw moment φ in the example in the figure) increases, and the maneuverability of the automobile A that follows the steering is improved.

Although detailed explanation is omitted, if a control force is applied in the opposite direction to change the ground loads W ₁ , W ₂ ,... Of the wheels 3, 3,. While the cornering force on the side is reduced, the cornering force on the rear wheel side is increased, so that the yaw moment is reduced and the turning behavior of the vehicle A changes toward stability.

More specifically, the controller 10 includes an unsprung vertical displacement q ₁ for each suspension 1 _FR , 1 _FL ,... Based on signals from the acceleration sensors 11, 11,. The suspension state quantity detector 10a calculates the speed q ₁ ′ and acceleration q ₁ ″, the vertical displacement q ₂ on the spring and the speed q ₂ ′, that is, the suspension state quantity indicating the operating state of the suspension 1. It has been.

In addition, the controller 10 performs vehicle speed V _x , lateral acceleration V _y ′, yaw rate φ ′, steering steering angle based on signals from the vehicle speed sensor 13, lateral acceleration sensor 14, yaw rate sensor 15, steering angle sensor 16, and the like. δ and the like are detected, and the road surface friction coefficient μ and the ground loads W ₁ , W ₂ ,..., the side slip angles β ₁ , β ₂ ,..., or the lateral forces Y ₁ , Y ₂ ,. Is calculated, that is, a traveling state amount detection unit 10b that detects various traveling state amounts representing the traveling state of the automobile A is provided.

Further, the controller 10 includes two control amount calculation units 10c and 10d that calculate control outputs to the electromagnetic actuators 2, 2,... Based on the calculation results of the two state quantity detection units 10a and 10b. Yes. The first control amount calculation unit 10c, the electromagnetic actuator 2, 2 as ... suspension 1 _{FR, 1} FL by the operation of, _... aggressively to stroke, to absorb an input from irregularities of road surface or the like, the wheels And a control amount for driving the electromagnetic actuators 2, 2,... So as to suppress vibration of the vehicle body B.

On the other hand, the behavior control amount calculation unit 10d, which is the second control amount calculation unit, changes the ground load distribution of the inner and outer wheels of the turning vehicle A as described with reference to FIG. A control amount u for controlling the turning behavior is calculated so as to achieve both stability. Then, the control amounts calculated by the two control amount calculation units 10c and 10d are added together according to a predetermined cooperative logic and output to the electromagnetic actuators 2, 2,... For each suspension 1 _FR , 1 _FL ,. (U _opt ).

  In addition, the controller 10 of this embodiment has a behavior control characteristic based on the current running state of the automobile A detected as described above, specifically, a balance between maneuverability and stability in the behavior control. A correction control unit 10e for correction is also provided. The functions of the suspension state quantity detection unit 10a, the running state quantity detection unit 10b, the first and second control amount calculation units 10c and 10d, and the correction control unit 10e are controlled by a CPU of the controller 10 according to a predetermined program. In this sense, the controller 10 includes the units 10a to 10e in the form of a software program.

In particular, as a feature of the present invention, the behavior control amount calculation unit 10d which is the second control amount calculation unit includes the yaw rate φ ′ and the side slip amount (the vehicle lateral speed V _{y in} the turning behavior control of the automobile A as described above. Are controlled by electromagnetic actuators 2, 2,... So that both maneuverability and stability are compatible, and energy consumption for driving the actuators is as much as possible. Control laws are set to suppress. In other words, the control law is an optimal control law as described in detail below.

(How to find the optimal control law)
Next, the control law set in the behavior control amount calculation unit 10d of the controller 10 as described above, in particular, a method for deriving such an optimal control law, that is, a solution method for the optimal control problem will be described in detail.

-Basic concept-
First, the basic concept will be explained. In general, in the optimal control problem, the characteristics of the controlled object are described by an equation of motion, and a control law is determined that maximizes or minimizes the evaluation function defined from various viewpoints for the system that controls this. Usually, it is not easy to derive such a control law analytically.

  In this regard, the inventors of the present application, as a method for analytically solving a relatively wide range of optimal control problems including nonlinear systems of mechanical dynamics systems, pay attention to the energy balance of the control target and control rules that asymptotically stabilize the system. We have devised a method that can easily guide you.

  In this method, the characteristic of the controlled object is not described by the equation of motion, but the balance equation (1) of the total input / output power of the controlled object is used as follows. This equation (1) is a vector display of the equation of motion for each degree of freedom of the system, and this is multiplied by the velocity vector. The input power includes not only control input but also disturbance input. Since the control target is not limited to passive elements, there is an energy source inside, and if this affects the movement, it is treated as a disturbance input.

In the above equation (1), d, e, q, u, ν, zεR ⁿ , MεR ^{n × n} are positive definite inertia matrices, and n is the degree of freedom of the controlled object. q is a generalized coordinate, u is a control input, and the number of independent actuators is n. ν is a force input disturbance, and z is a displacement input disturbance. u and ν act directly on inertia, and z acts on inertia via unsprung. d is Coriolis force, centrifugal force, damping force, etc., e is potential force.

  Even if the object to be controlled is non-linear, if the control device is rationally designed, u can be directly applied to M as shown in equation (1). Assuming a rationally designed mechanical system, the following evaluation function J is considered for this system.

In Equation (2), g is a scalar function that gives an evaluation of control performance, and u ^T q ′ is the power applied from the actuator of the control device to the controlled object, that is, the energy transmitted from the actuator. r is a weight coefficient and is a positive definite value. This method is intended for real-time control and assumes a finite evaluation interval. Finding the control amount u (t) that minimizes the equation (2) is the optimal control problem.

  First, in order to obtain the necessary conditions for optimal control, a scalar function L as shown in the following equation (3) is defined. In this equation, κ is an undetermined constant. The inside of {} on the right side is the same as the left side of the equation (1) and is the total power balance of the controlled object, so it satisfies the energy conservation law and is always zero. Therefore, the condition for minimizing the integral (functional) of the function L represented by the equation (3) gives the condition for minimizing the equation (2).

  Therefore, the following equation (4) in which the variational principle with q as a variable is applied to the integral of L gives a necessary condition for optimal control with respect to the control input u. Since L is a linear expression with respect to u, ∂L / ∂u has no meaning, and the following equation (4) includes all information related to control. However, since L includes two derivatives of q, in the following equation, a third term is added to a general Euler equation.

  When the equation (4) is integrated and the integration constant is set to zero, the following equation (5) is obtained. The equation (3) is substituted into the equation (5), and the first to third terms on the left side are sequentially set to the first. If it is written as ~ 3 lines, the following equation (6) is obtained. Then, the control law is obtained from the equation (6) as in the following equation (7).

  Thus, since the relationship between q and u that minimizes the evaluation function J can be directly derived, the process of solving the two-point boundary value problem using the principle of optimality as in the conventional general method is unnecessary. Become. κ is an undetermined constant, but when κ = 0, u is determined only by the parameters of the evaluation function, whereas when κ = ∞, u is determined only by the parameter to be controlled. , For u to be optimal, must be a non-zero finite value.

  The first line of the equation (7) is control for the external force ν and q dependency of inertia, the second line is control for Coriolis force, centrifugal force and damping force, and the third line is potential force and its q dependency and external force z. The fourth line is a control for reducing the evaluation function. Equation (7) includes an unexecuted calculus term. However, if all external forces and state quantities can be detected or estimated, these can be executed in real time.

  Although the integral constant is set to zero in the above formula (5), it can be seen from the above results that the integral constant gives a constant bias to the control law, so that it is appropriate to set it to zero. The same applies to the integral in equation (7).

  Further, in the equation (7), it is assumed that the number of actuators and the degree of freedom of the system are the same, and the following processing is necessary when the number of actuators is small. For example, when the actuator is placed between two independent inertias, the constraint condition is included in the control vector, and the optimal control law is obtained by weighting and adding the two control laws. Good.

That is, if u _i and u _{i + 1} are optimal control rules when they are derived as independent controls, and ρ _i and ρ _{i + 1} are weighting factors, then control output u _opt = ρ _i u _i + ρ _{i + 1} u _{i + 1} and Become. Note that the values of the weight coefficients ρ _i and ρ _{i + 1} are not theoretically derived, but depend on the structural features of the controlled object.

-Suspension system-
In accordance with the above concept, a method for obtaining the control amount u for behavior control of the automobile A in the suspension control device S of this embodiment, that is, a control law for realizing optimum behavior control is derived. First, the equation of motion of the vehicle model shown in FIG. 4 is expressed as the following equations (8) to (10). Equation (8) represents the balance of longitudinal forces in the motion coordinate system of the car A, Equation (9) represents the balance of the lateral forces, and Equation (10) represents the balance of yaw moments.

In the above formulas (8) to (10), m is the mass of the vehicle, I is the moment of inertia around the center of gravity, V _x is the vehicle speed, that is, the longitudinal speed of the automobile A, and V _y is the lateral speed. In addition, X _i (i = 1, 2,...), Y _i (i = 1, 2,...) Are the longitudinal force and lateral force at the respective wheels 3, 3,. In this order, i corresponds to the front wheel 3 on the inner side of the turn, the front wheel 3 on the outer side of the turn, the rear wheel 3 on the inner side of the turn, and the rear wheel 3 on the outer side of the turn. Further, l _f and l _r represent distances in the front-rear direction from the center of gravity of the vehicle body to the front wheels 3 and 3 and the rear wheels 3 and 3, respectively.

A power balance equation corresponding to the equation (1) is created by multiplying the motion equations (8) to (10) for each degree of freedom by a velocity component. That is, the equation (8) is multiplied by the longitudinal velocity V _x , the equation (9) is multiplied by the lateral velocity V _y , the equation (10) is multiplied by the yaw rate φ ′, and these are added together to obtain the following equation ( 11) get.

Here, the target of the turning behavior control of this embodiment is the deviation of the yaw rate φ ′ generated in the automobile A during the turning from the target value ^tar φ ′ (yaw rate deviation) and the target of the side slip amount, that is, the lateral speed V _y . Since the deviation (side slip amount deviation) from the value ^tar V _y is minimized, the function g giving the evaluation of controllability in the evaluation function J of the equation (2) is expressed by the following equation (12). . The scalar function L of the equation (3) is expressed by the following equation (13) using the power balance equation of the equation (11).

In the equations (12) and (13), the constant κ functions as a weighting factor for changing the control characteristics as will be described later. R ₁ , r ₂ , and r ₃ are weighting factors that are set in advance so as to obtain desired control characteristics, and r ₁ and r ₂ are respectively multiplied by the yaw rate deviation and the skid amount deviation, The evaluation function J has a meaning of changing those weights. On the other hand, r ₃ corresponds to the weighting coefficient of the third term on the right side of the equation (13), that is, the term representing the transmitted energy from the electromagnetic actuator 2, and has the meaning of changing the weight of the energy consumption in the evaluation function J.

In order to obtain the condition for minimizing the evaluation function J of the equation (12), the condition for minimizing the integral (functional) of the function L of the equation (13) may be obtained as described above. Since the lateral force Y _i (i = 1, 2,...) Of each wheel 3, 3,... Is included in the expression (13), in this embodiment, a well-known magic formula model is used to The wheel lateral force is estimated as shown in equation (14).

Incidentally, each of the wheels 3,3, ... contact load _W 1, _{W 2} of, ... can be estimated from, for example, the vehicle speed _{V x} and the steering angle δ or the like, an acceleration sensor 11, 11, ... and the stroke sensor 12, It can also be estimated based on the detected values of 12,. Similarly, the sideslip angles β ₁ , β ₂ ,... Of the wheels 3, 3,... Can be estimated from the traveling direction of the automobile A and the steering angle δ obtained by integrating the yaw rate φ ′, for example. Further, a, B (Stiffness Factor), and C (Shape Factor) are constants determined by the tire characteristics, respectively, and appropriate values thereof are obtained by an exploratory method.

  In order to obtain a condition for minimizing the integration of the function L in the equation (13), the equation (14) is substituted into the equation (13), and the following equation corresponding to the equation (4) is obtained. Apply (15). As a result, a control law (necessary condition) for an analytical solution that does not include an integral can be obtained as in equation (7).

Here, as described above with reference to FIG. 3, in this embodiment, the electromagnetic actuators 2, 2, 2, 2, 2,... Control ... In this way, the ground contact loads of the wheels 3, 3,... Are W ₁ + U at the front wheel 3 inside the turning, W ₂ -U at the front wheel 3 outside the turning, W ₃ -U at the rear wheel 3 inside the turning, and turning. Since the outer rear wheel is W ₄ + U, the control law only needs to determine the ground contact load change amount U common to all the wheels 3, 3,.

Therefore, although detailed explanation is omitted, the following equations (16) to (18) are obtained by arranging the control law obtained from the equations (13) to (15) as described above for the ground load change amount U. In equations (17) and (18), Γ ₁ , Γ ₂ ,... Are the ratios of the lateral forces Y ₁ , Y ₂ ,... To the maximum values D ₁ , D ₂ ,. Represents. In addition, D ₁ , D ₂ ,... Are represented as D _i = (μW _i −aW _i ² ), and θ _i = (1 / D _i ) × (∂Y _i / ∂φ _i ′). (I = 1, 2,...)

Comparing the first to fourth terms on the right side of the equation (17), the values of the second to fourth terms are sufficiently smaller than the first term and can be ignored. Similarly, since the third and fourth terms on the right side of the equation (18) can be ignored, the equations (17) and (18) can be simplified and expressed as the following equations (19) and (20). The U _A of the formula (19) represents a yaw moment generated by the lateral force of the front wheels 3, 3 when not applied with the control input, U _B of the formula (20), all when applying a unit control input The yaw moment generated by the lateral force of the wheels 3, 3,. U _A and U _B vary depending on the roll stiffness of the elements of the suspensions 1 _FR , 1 _FL ,..., The current roll size, and the like.

The derivation of the control law by this method is up to the equations (16), (19), and (20), which give the necessary conditions for optimal control. The undetermined constants κ, r ₁ , and r ₃ in equation (16) are weighting factors that affect the control characteristics as described above. For r ₁ and r ₃ , the desired control characteristics are obtained. A value that minimizes the function J may be obtained in advance by an exploratory method using experiment, analysis, or the like. As described above, increasing the value of r ₁ increases the weight of the yaw rate deviation, and increasing the value of r ₃ increases the weight of the energy consumption.

  The control law thus derived is a function L of the equations (3) and (13), that is, a term representing the magnitudes of the yaw rate deviation and the side slip amount deviation of the vehicle A, and the electromagnetic actuator 2 to be controlled ( This is an optimal control law that minimizes the integral of the function L having a term representing the energy transmitted to the vehicle body B and the wheel 3) and a term representing the total energy balance of the controlled object. If the electromagnetic actuators 2, 2,... Of the wheels 3, 3,... Are controlled so that the ground load change amount U is obtained, both the followability to the steering of the vehicle A and the behavioral stability can be achieved while suppressing energy consumption. It is possible to realize appropriate turning behavior control.

  Furthermore, in this embodiment, as specifically described below, the value of the weighting coefficient κ in the above equation (16) is changed based on the rate of change of the steering angle δ, and thus the vehicle A The behavior control characteristics (specifically, the balance between maneuverability and stability) can be changed in consideration of the traveling state, and more appropriate control can be performed.

That is, as is apparent from the equation (20), U _B mainly represents the yaw moment acting on the automobile A in accordance with the unit control input. In equation (16), since the weighting factor kappa is multiplied by the U _B, apparently by increasing kappa, but the yaw moment due to the control input will increase, control law in the equation (16) is steered Therefore, the ground load change amount U obtained in accordance with this control law changes in a direction in which the yaw moment decreases (that is, the ground load change amount U becomes a smaller value).

However, even if the weighting factor κ is increased, the value of U _B does not change, so the magnitude of the yaw moment that actually acts on the automobile A by control does not change. For this reason, if the ground contact load change amount U controlled as described above becomes smaller, the yaw moment actually acting on the automobile A becomes smaller, the followability to steering steering is reduced, and the behavior of the automobile A is also reduced. This increases the stability.

  That is, if the value of the weighting factor κ in the equation (16) is increased, the characteristic of the turning behavior control of the car A is changed to a value that emphasizes the behavioral stability rather than the followability to steering. If the value of κ is made smaller, it will be changed to one that emphasizes maneuverability rather than stability.

(Specific example of suspension control)
Next, the control of the electromagnetic actuators 2, 2,... By the controller 10, in particular, the calculation of the control amount u in the behavior control amount calculation unit 10d will be specifically described based on the flowchart shown in FIG.

First, in step S1 after the start of the illustrated flow, mainly signals from the sensors 13 to 16 are input, and at least the vehicle speed V _x , lateral acceleration V _y ′, yaw rate φ ′, steering steering angle δ, and the like travel. The state quantity is detected, and in the subsequent step S2, for example, the road surface friction coefficient μ is estimated from the vehicle speed V _x and the engine output, and the wheels 3, 3,... Are calculated from the vehicle speed V _x and the steering angle δ, for example. Estimates the ground loads W ₁ , W ₂ ,.

Subsequently, in step S3, for example, the sideslip angles β ₁ , β ₂ ,... Of the wheels 3, 3,... Are estimated from the vehicle speeds V _x , V _y and the steering angle δ, and the road surface friction coefficient μ and the ground load W The lateral forces Y ₁ , Y ₂ ,... Of the wheels 3, 3,... Are estimated using the above-described equation (14) together with the estimated values of ₁ , W ₂ ,. In the subsequent step S4, Γ ₁ , Γ ₂ ,... Are calculated based on the estimated values of the lateral forces Y ₁ , Y ₂ ,... And the maximum values D ₁ , D ₂ ,. Then, U _A and U _B are calculated using equations (19) and (20).

Subsequently, in step S5, a target yaw rate ^tar φ ′ is calculated from the vehicle speed V _x and the steering angle δ, for example, and a deviation from the actual yaw rate φ ′ (yaw rate deviation ^tar φ′−φ ′) is obtained. In step S6, the value of the weighting factor κ is read from a preset table based on the running state of the vehicle, specifically, for example, the rate of change of the steering angle δ, and is set in the above equation (16).

  As an example, as shown in FIG. 6, the value of the weighting coefficient κ is associated with the rate of change Δδ (change amount per hour) of the steering angle δ, and becomes larger as the rate of change Δδ is lower. The higher the value is, the smaller the value is set. That is, the low rate of change Δδ of the steering angle δ is, for example, a situation where the vehicle is traveling slowly on a gentle curve, and the stability of the behavior of the automobile A is preferably high, and the following capability with respect to steering is also preferable. This is because the lower one is advantageous in terms of ride comfort and the like.

  On the other hand, for example, when the driver suddenly steers the steering wheel to avoid a collision, the highest priority is to avoid a collision with an obstacle by sufficiently increasing the tracking ability of the behavior change of the automobile A with respect to the steering. In this case, since the behavioral stability may be slightly impaired, the weight coefficient κ is set to be smaller as the steering angle change rate Δδ is higher. In the table, the value of the weighting factor κ may not be set so as to change continuously according to the change in the steering angle change rate Δδ, and may change in a stepped manner, for example.

Subsequent to step S6, in step S7, U _A and U _B calculated in step S4 and the yaw rate deviation ( ^tar φ′−φ ′) calculated in step S5 are substituted into the equation (16). A common ground load change amount U (target value) is calculated for the wheels 3, 3,. Then, on the basis of the ground load change amount U and the current ground loads W ₁ , W ₂ ,... Of the wheels 3, 3,. ,... Are calculated.

In addition, the control amount for vibration suppression calculated by the first control amount calculation unit 10c is added to the actuator control amount u for behavior control thus calculated, and in step S9, each wheel 3, 3, The amount of power supplied to the electromagnetic actuators 2, 2,. Then, the control signal u _opt corresponding to the power supply amount is output and the process returns.

  The procedure of Steps S1 to S3 is performed by the travel state amount detection unit 10b of the controller 10, and the procedure of Steps S4 to S8 is performed by the behavior control amount calculation unit 10d. In particular, the process of changing the weighting coefficient κ according to the steering angle change rate Δδ in step S6 is performed by the correction control unit 10e.

(Action / Effect)
Therefore, according to the vehicle suspension control device of this embodiment, during the turning of the automobile A, as described above, based on the control amount u calculated by the behavior control amount calculation unit 10d of the controller 10, each wheel 3, 3, ... each of the electromagnetic actuator 2, 2, ... control is performed, the respective wheels 3,3, required control force is applied to ..., their vertical load _{W 1, W} 2, ... will increase or decrease.

For example, if the vehicle behavior changes slightly delayed with respect to the steering, along with increasing the vertical load W ₁ of the front wheel 3 of the turning inner, to reduce the vertical load W ₂ in the front wheels 3 of the turning outer, ground The load distribution changes efficiently toward the inside of the turn, increasing the cornering force. On the other hand, reducing the vertical load W ₃ in the wheel 3 after the turning inward to increase the wheel 3 in vertical load W ₄ after turning the outer, ground load allocation change efficiently turning outward toward, cornering force Becomes smaller. Therefore, the yaw moment in the turning direction is increased and the followability to steering is improved.

On the other hand, if the behavior change with respect to steering is large, the control force of the electromagnetic actuators 2, 2,... Is applied in the opposite direction, and the ground loads W ₁ , W _{2 of the} wheels 3, 3,. ,... Change in the opposite direction, the yaw moment is reduced and the behavior stability of the automobile A is increased.

  In this embodiment, the electromagnetic actuators 2, 2,... Are controlled so that the yaw rate deviation and the side slip amount deviation are minimized to achieve both the controllability and stability of the automobile A. As a result, the turning behavior of the car A controlled by the control force of the electromagnetic actuators 2, 2,... Is suitable for driving operation in terms of both yaw rate and skid, and both maneuverability and stability are compatible. To come.

  Since such an optimal control law is analytically derived in advance and stored in the memory of the controller 10 in the form of a control arithmetic expression, unlike the prior art, sufficient responsiveness for suspension control of the vehicle A can be ensured. . In particular, in this embodiment, the amount of calculation related to control is reduced as much as possible by making the ground load change amount U that is the control target value common to all the wheels 3, 3,. Easy to secure.

  Thus, the optimal control basically achieves compatibility between the controllability and stability in the behavior control of the automobile A, and in this embodiment, the steering weight value κ of the control in the optimal control law is further steered. The correction is made based on the change rate Δδ of the angle δ, and the balance of maneuverability and stability can be changed to a more appropriate one depending on the running state, for example, the steering response is particularly high during sudden steering. .

  In addition, in the turning behavior control of this embodiment, as described above, in the front wheels 3 and 3 and the rear wheels 3 and 3 of the automobile A, the ground load is increased on one of the inner and outer wheels and decreased on the other to decrease the ground. The load distribution is changed, and the change in the ground load distribution between the inner and outer rings is reversed on the front wheel side and the rear wheel side. As a result, the cornering force of the front and rear wheels 3 and 3 can be changed in the opposite direction, and the yaw moment can be applied more efficiently. In addition, the roll moment acting on the vehicle body B is also changed in the opposite direction. Therefore, there is an effect of suppressing vibration around the roll axis caused by behavior control.

(Other embodiments)
The configuration of the suspension control device according to the present invention is not limited to the above-described embodiment, and includes various other configurations. That is, for example, in the above-described embodiment, the electromagnetic actuators 2, 2,... Are provided in the suspensions 1 _FR , 1 _FL ,. Only the electromagnetic actuators 2 and 2 may be provided.

  In addition to the linear motor exemplified as the actuator, for example, an hydraulic / pneumatic cylinder, a piezoelectric element, or the like can be used, and an electric motor and a ball screw mechanism can be combined to form an actuator.

  In addition, as described above, in the front wheels 3 and 3 and the rear wheels 3 and 3 of the automobile, the ground load is increased on one of the inner and outer wheels and decreased on the other, and the ground load distribution is efficiently changed. Such a change in the ground load distribution between the inner and outer wheels is reversed on the front wheel side and the rear wheel side, but is not limited thereto.

  That is, for example, only one of the front wheels 3 and 3 or the rear wheels 3 and 3 may increase the ground contact load of one of the inner and outer wheels and decrease the other, or the front wheel 3 or the like. The ground contact load may be changed only in one wheel inside the turn. When changing the ground load of the plurality of wheels 3, 3,..., It is not necessary to make the change amounts the same.

Further, the specific embodiment of the suspension control is merely an example. For example, U _A and U _B expressed by the equations (19) and (20) are expressed by the equations (17) and (17), respectively. 18) or an approximate expression different from Expressions (19) and (20).

In the above-described embodiment, the value of the coefficient κ that changes the weight of the controllability and stability in the control law is changed according to the steering angle change rate Δδ. Δδ not limited to, for example, the vehicle speed _{V x,} lateral acceleration _V y ', yaw rate phi', the road surface friction coefficient mu, or each wheel 3,3, ... contact load _W 1, _{W 2} of, ..., the side slip angle beta ₁ , Β ₂ ,..., Lateral force Y ₁ , Y ₂ ,.

  Further, the control law of Expression (16) is also an example, and a control law that minimizes the evaluation function defined from various viewpoints can be used in addition to the exemplified evaluation function J. However, such a control law minimizes the integral of a function (function L in equations (3) and (13)) obtained by adding a term representing the total energy balance of the control target to the term of the evaluation function, as in the above embodiment. It is preferable that

  Furthermore, the suspension control device according to the present invention can be applied to vehicles other than automobiles.

  The suspension control device according to the present invention controls an actuator used in a so-called active suspension according to a predetermined optimal control law, and appropriately changes the ground load distribution of the inner and outer wheels of the vehicle, thereby controlling the turning behavior thereof. This makes it possible to achieve optimal control that achieves both stability and stability, and is therefore suitable for mounting in automobiles.

FIG. 2 is a diagram schematically showing an automobile (a) equipped with a suspension control device according to the present invention and a suspension (b). It is a block diagram which shows schematic structure of a suspension control apparatus. FIG. 6 is a conceptual diagram (a) of behavior control by a change in contact load distribution, and an explanatory diagram (b) in which a lateral force changes according to increase / decrease in contact load distribution of inner and outer rings. It is a block diagram of the vehicle model used for derivation | leading-out of a control law. It is a flowchart figure which shows the calculation procedure of a behavior control amount. It is a conceptual diagram of the table which set the value of the weighting coefficient in association with the steering angle change rate.

Explanation of symbols

A car (vehicle)
B Body S Suspension control device 1 Suspension 2 Electromagnetic actuator 3 Wheel 3a Tire 3b Wheel 4 Coil spring 5 Shock absorber 10 Controller 10a Suspension state quantity detection unit 10b Running state quantity detection unit (running state quantity detection means)
10c 1st controlled variable calculating part 10d 2nd controlled variable calculating part (behavior control means)
10e Correction control unit (control characteristic correction means)
DESCRIPTION OF SYMBOLS 11 Vehicle body vertical acceleration sensor 12 Suspension stroke sensor 13 Vehicle speed sensor (Driving state amount detection means)
14 Lateral acceleration sensor (traveling state quantity detection means)
15 Yaw rate sensor (running state quantity detection means)
16 Rudder angle sensor (traveling state quantity detection means)

Claims (7)

A suspension control device for a vehicle in which at least a vertical control force is applied to a wheel suspended on a vehicle body by an actuator,
Travel state amount detection means for detecting a travel state amount representing the travel state of the vehicle;
The actuator is controlled in accordance with a predetermined control law based on the detected running state quantity, and the ground contact load distribution of the inner and outer wheels during turning is changed by increasing / decreasing the ground contact load of the wheel by the control force. A behavior control means for controlling the turning behavior,
The control law is an optimal control law that achieves both the maneuverability and stability of the vehicle, and has a weighting coefficient that changes their weighting.
A suspension control apparatus for a vehicle, comprising: control characteristic correction means for correcting a behavior control characteristic by changing a value of the weighting factor of the control law based on the detected vehicle running state quantity. The control rules for vehicle behavior control include at least a term representing the magnitude of deviation from the target value of yaw rate, a term representing the magnitude of deviation from the target value of the vehicle side slip amount, and the body to be controlled from the actuator. And a term representing the transmitted energy to the wheel and a term representing the total energy balance of the vehicle body and the wheel are obtained as those that minimize the integral of the function, and are represented by the following formula (A):

However, U is a target value of the vertical load variation of the wheel by the control force, U _A is the yaw moment acting on the vehicle by the lateral force of the wheel when not applied with the control input, U _B, the unit control input Is the yaw moment acting on the vehicle by the lateral force of the wheel, φ ′ is the yaw rate, ^tar φ ′ is the target yaw rate, and κ, r ₁ and r ₃ are the control weighting factors, respectively. The vehicle suspension control apparatus according to claim 1. A steering angle sensor for detecting the steering angle of the steering wheel or steering wheel;
3. The vehicle-use vehicle according to claim 2, wherein the control characteristic correction unit corrects the weight coefficient κ so that the value of the weighting coefficient κ becomes smaller if the change rate is higher than a predetermined value based on at least the detected change rate of the steering angle. Suspension control device. A steering angle sensor for detecting the steering angle of the steering wheel or steering wheel;
4. The control characteristic correction unit according to claim 2, wherein the control characteristic correction unit corrects the weight coefficient κ so that the value of the weighting coefficient κ is increased if the change rate is lower than a predetermined value based on at least the detected change rate of the steering angle. The vehicle suspension control device described in 1.   The behavior control means controls the actuator so that the ground contact load of one of the inner and outer wheels on the front side of the vehicle increases, the other decreases, and the increase / decrease amount is the same. The vehicle suspension control device described.   The behavior control means controls the actuator so that the ground contact load on one of the inner and outer wheels on the rear side of the vehicle increases, the other decreases, and the increase / decrease amount is the same. The vehicle suspension control device described in 1.   The behavior control means is configured such that one of the ground loads on the inner and outer wheels on the front side of the vehicle is increased and the other is decreased, the one ground load on the inner and outer wheels on the rear side of the vehicle is decreased, and the other is increased. The vehicle suspension control device according to any one of claims 1 to 4, wherein the actuator is controlled so that the amount of increase / decrease in the ground load of each wheel is the same.

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