JP6825515B2 - Suspension control system - Google Patents

Description

The present invention relates to a suspension control system mounted on a vehicle.

Skyhook damper control using a suspension that can change the damping force is known. In the skyhook damper control, the relative speed (hereinafter referred to as "stroke speed") between the sprung structure and the sprung structure connected via the suspension is estimated in order to generate the required damping force. There is a need. As a technique for estimating the stroke speed, for example, there is one described in Patent Document 1. In this document, in the method of estimating the stroke speed using an observer that uses the non-linear component of the damping force of the damper as the control input, this non-linear component is used as the spring force of the stabilizer due to the roll motion of the vehicle body and the lateral acceleration of the vehicle body. It has been proposed to compensate for the ground load fluctuation due to the roll motion based on the above and the ground load fluctuation due to the pitch motion based on the front-back acceleration.

Japanese Unexamined Patent Publication No. 2000-289424

In the above-mentioned conventional technique, the contact load fluctuation due to the pitch motion is taken into consideration as the force input to the spring of the suspension during acceleration / deceleration of the vehicle. However, the force input to the spring of the suspension during acceleration / deceleration of the vehicle is not only the amount of fluctuation in the ground contact load, but also the reaction force of the suspension due to acceleration / deceleration of the vehicle, for example. For this reason, in a configuration in which the stroke speed during acceleration / deceleration is estimated without considering the force other than the ground load fluctuation as the force input on the spring of the suspension during acceleration / deceleration of the vehicle, the estimation accuracy may be low. is there.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a suspension control system capable of improving the estimation accuracy of the stroke speed at the time of acceleration / deceleration of a vehicle in a vehicle provided with a suspension. ..

In order to solve the above problems, the present invention is applied to a suspension control system mounted on a vehicle. The suspension control system includes a suspension that connects the spring-loaded structure and the spring-loaded structure of the vehicle, and a control device that estimates the stroke speed, which is the relative speed between the spring-loaded structure and the spring-loaded structure. , Equipped with. The control device includes a spring-up vertical acceleration detecting means for detecting the spring-up vertical acceleration, which is the vertical acceleration of the spring-up structure, and a spring-up vertical acceleration detecting means for detecting the spring-up front-back acceleration, which is the front-back acceleration of the spring-up structure. Includes a longitudinal acceleration detecting means, a total value calculating means for calculating the total value of the forces input from the suspension to the sprung structure, and an observer configured based on the state space of the equation of motion based on the single-wheel model. .. The total value calculation means is a vertical force input to the sprung structure by calculating the ground contact load fluctuation of the vehicle due to the attitude change of the sprung structure using the sprung front-rear acceleration. The first force is calculated, and the driving force distribution or braking force distribution of the vehicle is used to apply the front-rear force input to the wheels due to the acceleration or deceleration of the vehicle to act on the suspension, which is the suspension reaction force . Calculate the second force , calculate the third force, which is the suspension reaction force due to the inertial force of the spring-loaded structure of the vehicle, and use the first force, the second force, and the third force. It is configured to calculate the total value. The observer is configured to output an estimated value of the stroke speed of the suspension by using the total value as a known input and the spring vertical acceleration as an input of the observed amount.

According to the suspension control system according to the present invention, when calculating the total value of the forces input from the suspension to the sprung structure, the change in the ground contact load of the vehicle due to the change in the attitude of the sprung structure and the acceleration of the vehicle Alternatively, the suspension reaction force generated by the front-rear force applied to the wheels due to deceleration acting on the suspension is used. As a result, the accuracy of calculating the force input from the suspension to the sprung structure during acceleration / deceleration of the vehicle is improved, so that the estimation accuracy of the stroke speed during acceleration / deceleration of the vehicle can be improved.

It is a figure which shows the structure of the vehicle which mounted the suspension control system which concerns on Embodiment 1. FIG. It is a figure which shows the model composition of the single wheel model observer of one degree of freedom. It is a control block diagram of a single wheel model observer. It is a figure for demonstrating the force acting at the time of acceleration / deceleration of a vehicle. 6 is a flowchart of a routine executed by the ECU of the first embodiment when estimating the stroke speed of the variable suspension. 6 is a flowchart of a routine executed by the ECU of the second embodiment when estimating the stroke speed of the variable suspension.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, when the number, quantity, quantity, range, etc. of each element is referred to in the embodiment shown below, the reference is made unless otherwise specified or clearly specified by the number in principle. The invention is not limited to these numbers. In addition, the structures, steps, and the like described in the embodiments shown below are not necessarily essential to the present invention, except when explicitly stated or clearly specified in principle.

Embodiment 1.
<Vehicle system configuration of the first embodiment>
Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a vehicle equipped with the suspension control system according to the first embodiment. In the following description, the traveling direction (front-back direction) of the vehicle 10 is defined as the X direction, the left-right direction of the vehicle 10 is defined as the Y direction, and the vertical direction of the vehicle 10 is defined as the Z direction. Further, the sign in the Z direction defines upward as "positive".

The vehicle 10 according to the first embodiment includes four wheels 12. In the four wheels 12, the front wheels and the rear wheels are arranged apart from each other in the X direction, and the left wheel and the right wheel are arranged apart from each other on the same axle extending in the Y direction. In the following description, when each wheel 12 is particularly distinguished, the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are referred to as wheels 12fr, 12fl, 12rr, and 12rl, respectively.

Each wheel 12 is provided with a variable suspension 14 and a spring-loaded vertical acceleration sensor 16. In the following description, when the variable suspensions 14 provided for the wheels 12fr, 12fl, 12rr, and 12rl are particularly distinguished, they are referred to as variable suspensions 14fr, 14fl, 14rr, and 14rl, respectively. Similarly, when the above-spring vertical acceleration sensors 16 provided for the wheels 12fr, 12fl, 12rr, and 12rl are particularly distinguished, they are referred to as the above-spring vertical acceleration sensors 16fr, 16fl, 16rr, and 16rl, respectively.

The variable suspension 14 is composed of an extension-dependent variable shock absorber and a spring whose damping force can be changed according to a driving current. The variable suspension 14 connects the sprung structure (body or the like) and the unsprung structure (wheels or the like) of the vehicle 10. Since the structure of the variable suspension 14 itself does not form the gist of the present invention, any structure can be adopted as long as the damping force can be controlled according to the control amount. Further, the control content may be arbitrary as long as the content suppresses the change in the posture of the vehicle.

The spring-loaded vertical acceleration sensor 16 is arranged in a spring-loaded structure near each wheel 12 of the vehicle 10 and detects acceleration in the vertical direction (Z direction) of the vehicle.

A sprung front-rear acceleration sensor 18 for detecting acceleration in the front-rear direction (X direction) of the vehicle is provided in the vicinity of the position of the center of gravity of the sprung-up structure of the vehicle 10.

The vehicle 10 according to the first embodiment includes an ECU 20 as a control device for the variable suspension 14. The ECU 20 estimates the stroke speed of the variable suspension 14 based on the signals input from each of the spring vertical acceleration sensor 16, the spring forward / backward acceleration sensor 18, and the variable suspension 14. In the following description, the sign of the stroke speed is defined as "positive" on the extension side and "negative" on the compression side of the variable suspension 14. Based on the estimated stroke speed, the ECU 20 controls the drive current value output to the variable suspension 14 so that the posture of the vehicle 10 is stabilized.

<Operation of the first embodiment>
The ECU 20 is configured to be capable of executing skyhook damper control using the variable suspension 14. The skyhook damper control individually determines the required damping force of the variable suspension 14 of each wheel 12 so that the posture of the body portion which is the spring-loaded structure of the vehicle 10 is stabilized. The damping force F _fc of the variable suspension 14 changes depending on the stroke speed, which is the relative speed between the sprung structure and the subspring structure, and the drive current value applied to the variable suspension 14. Therefore, in order to bring the damping force of the variable suspension 14 close to the required damping force, it is required to improve the estimation accuracy of the stroke speed.

An observer constructed based on the state space of the equation of motion based on the single-wheel model (hereinafter referred to as "single-wheel model observer") is used for estimating the stroke speed. Hereinafter, as an example of the single-wheel model observer, a stroke velocity estimation method using a single-wheel model observer with one degree of freedom that feeds back the vertical acceleration on the spring will be described.

FIG. 2 is a diagram showing a model configuration of a single-wheel model observer with one degree of freedom. In the example of the single-wheel model shown in this figure, the mass on the spring is M _b , the spring constant of the suspension is K _s , and the base damping coefficient of the shock absorber is C _s . Further, in the example of the single-wheel model shown in this figure, the force acting on the variable suspension 14 in the Z direction is f, the vertical displacement on the spring is Z _b , and the vertical displacement under the spring is Z _w .

When the state quantity x is as shown in the following equation (1), the observed quantity y is the sprung up and down acceleration Z _b ", f is the known input u, and Z _w is the unknown input w. The state equation and the observation equation of the one-degree-of-freedom single-wheel model are expressed as the following equations (2) and (3).

Here, the coefficient matrices A, B, C, D, G, and H in the above equations (2) and (3) are as follows.

Next, assuming that the estimated values of the state quantity x and the observable quantity y are x ^ and y ^, respectively, the state quantity estimation equation and the observable quantity estimation equation using the Kalman filter are as shown in the following equations (4) and (5). expressed.

Here, L is an observer gain, and is determined from the positively symmetric solution P of the Riccati equation shown in the following equation (6) to the following equation (7).

FIG. 3 is a control block diagram of the single wheel model observer. Hereinafter, the configuration of the single-wheel model observer for calculating the estimated value of the stroke speed, which is the estimated value x ^ of the state quantity x, will be described in more detail with reference to FIG. A force f is input to the single-wheel model observer 30 as a known input u. Since the control logic for calculating the force f is a feature of the system of the first embodiment, the description will be described later.

The known input u input to the single-wheel model observer 30 is input to the adder 36 after the coefficient matrix B is multiplied. In the adder 36, the calculation of the equation (4) is performed, and the time derivative value x ^'of the estimated value x ^ of the state quantity x is output. The output from the adder 36 is input to the integrator 38. The estimated value x ^ of the state quantity x output from the integrator is input to the adder 36 after the coefficient matrix A is multiplied.

Further, the estimated value x ^ of the state quantity x output from the integrator 38 is input to the adder 40 after the coefficient matrix C is multiplied. The product of the known input u and the coefficient matrix D is also input to the adder 40. In the adder 40, the calculation of the equation (5) is performed, and the estimated value y ^ of the observed amount y is output.

The estimated value y ^ of the observed amount y output from the adder 40 is input to the adder 42. The spring-up vertical acceleration Z _b ”as the observed amount y is also input to the adder 42. The adder 42 calculates the estimation error (y−y ^) of the observed amount y using these input values. The estimation error (yy ^) is input to the adder 36 after the observer gain L is multiplied.

By performing each calculation according to the above procedure for each wheel 12, the amount of state that can not be directly measured x, that is, estimating the stroke speed of the variable suspension _{14 (Z b '-Z w'} ) in each wheel 12 It will be possible.

<Characteristics of Embodiment 1>
Next, the features of the first embodiment will be described. When the vehicle 10 accelerates or decelerates, various forces act on the wheels 12. FIG. 4 is a diagram for explaining a force acting during acceleration / deceleration of the vehicle. As shown in this figure, the front-rear force F _x, which is the force in the front-rear direction (X direction) shown in the equation (8), acts on the vehicle during acceleration / deceleration. In the formula (8), M is the vehicle weight, and a _x is the acceleration in the front-rear direction (X direction) (hereinafter, referred to as "spring front-rear acceleration"). The vehicle weight M is a fixed value determined from the configuration of the vehicle 10, and a value previously stored in the memory of the ECU 20 is used. The sprung front-rear acceleration a _x is a _x ≧ 0 when the vehicle is accelerating, and a _x <0 when the vehicle is decelerating.

When the front-rear force F _x acts on the vehicle, the ground contact load acting on each wheel of the vehicle fluctuates. Assuming that the fluctuation of the ground contact load per wheel is ΔW _x , ΔW _x is expressed by the following equation (9). In equation (9), H is the height of the center of gravity of the sprung structure, and l is the wheelbase of the vehicle. These values H and l are fixed values determined from the configuration of the vehicle 10, and values stored in the memory of the ECU 20 in advance are used. The ground load fluctuation amount ΔW _x is a force in the vertical direction (Z direction), which is downward in the Z direction for the front wheels during acceleration and rear wheels during deceleration, and upward in the Z direction for the rear wheels during acceleration and front wheels during deceleration. Become.

Further, when the vehicle is accelerated, a front-rear force acts on the center of each wheel. The longitudinal force acting on the center of the front wheel one wheel and _{F XIF,} when the longitudinal force acting on the center of the rear wheel one wheel and _{F xIR,} longitudinal force _{F XIF, F xIR} the following equation (10) is represented by (11) To. In these equations, D _df indicates the front wheel drive force distribution, and D _dr indicates the rear wheel drive force distribution. These values D _df and D _dr are fixed values determined from the configuration of the vehicle 10, and values stored in the memory of the ECU 20 in advance are used.

On the other hand, when the vehicle is decelerating, a front-rear force acts on the ground contact points of each wheel. _Assuming that the front-rear force acting on the ground contact point of one front wheel is F _xJf and the front-rear force acting on the ground contact point of one rear wheel is F _xJr , the front-rear forces F _xJf and F _xJr are given by the following equations (12) and (13). expressed. In these equations, D _bf indicates the front wheel braking force distribution, and D _br indicates the rear wheel braking force distribution. These values D _bf and D _br are fixed values determined from the configuration of the vehicle 10, and values stored in the memory of the ECU 20 in advance are used.

Further, when the vehicle is accelerated or decelerated, the inertial force of the unsprung structure acts on the center of each wheel. _Assuming that the unsprung inertial force acting on one front wheel is F _xwf and the unsprung inertial force acting on the center of one rear wheel is F _xwr , the unsprung inertial forces F _xwf and F _xwr are given by the following equations (14) and (15). ). In these equations, M _wf indicates the unsprung mass of each front wheel, and M _wr indicates the unsprung mass of each rear wheel. These values M _wf and M _wr are fixed values determined from the configuration of the vehicle 10, and values stored in the memory of the ECU 20 in advance are used. The unsprung inertial forces F _xwf and F _xwr are _forces in the front-rear direction (X direction), which are negative _values during acceleration and positive _values during deceleration.

The forces shown in the above equations (9) to (15) are input to the springs of the variable suspension 14 of each wheel. The force in the Z direction input to the spring of the variable suspension 14 on the front wheel side by the ground load fluctuation ΔW _x is F _zxf1, and the force in the Z direction input to the spring of the variable suspension 14 on the rear wheel side is F _zxr1. Then, F _zxf1 and F _zxr1 are expressed by the following equations.

Longitudinal force _F xjf during deceleration _(a x _<0), when the reaction force of the variable suspension 14 and _{F zxf2, F zxr2} respectively by _{F xJr, F zxf2, F zxr2} is expressed by the following equation. In these equations, tanθ _Jf indicates the front wheel side anti-dive coefficient, and tanθ _Jr indicates the rear wheel side antilift coefficient. These values tanθ _Jf and tanθ _Jr are fixed values determined from the configuration of the vehicle 10, and values stored in the memory of the ECU 20 in advance are used.

Longitudinal force _F XIF during acceleration _{(a x} ≧ _0), if the respective reaction force _{F zxf3, F zxr3} variable suspension 14 by _{F xIr, F zxf3, F zxr3} is expressed by the following equation. In these equations, tanθ _If indicates the front wheel side antilift coefficient, and tanθ _Ir indicates the rear wheel side antisquart coefficient. These values tanθ _If and tanθ _Ir are fixed values determined from the configuration of the vehicle 10, and values stored in the memory of the ECU 20 in advance are used.

_Assuming that the reaction forces of the variable suspension 14 due to the unsprung inertial forces F _xwf and F _xwr are F _zxf4 and F _zxr4 , respectively, F _zxf4 and F _zxr4 are expressed by the following equations.

From the above, in each of the variable suspensions 14 on the front wheel side and the rear wheel side, the total values of the forces input on the spring during acceleration / deceleration of the vehicle (hereinafter referred to as "spring input") F _zxf and F _zxr are as follows. It becomes the street.

As described above, according to the above equations (24) to (27), it is possible to accurately calculate the spring input of the variable suspension 14 of each wheel during acceleration / deceleration of the vehicle 10.

In the estimation of the stroke speed using the single-wheel model observer described above, the force f in the Z direction acting on the variable suspension 14 is input as the known input u. The system of the first embodiment is characterized in that the above-mentioned sprung inputs F _zxf and F _zxr are reflected on this force f. Specifically, the force f includes the damping force F _fc of the variable suspension 14 and the spring input. Variable suspension 14fl, 14fr, 14rl, respectively _F Fcfl the damping force _{F fc} generated in the _14rr, F _fcfr, F _fcrl, When _{F FCRR,} variable suspension 14fl, 14fr, 14rl, the force _f fl acting on 14rr, f _fr , _frl , _frr are expressed by the following equation (28). In the following description, the force obtained by adding the spring input to the damping force is also referred to as a "total value". Since the sprung input F _zxf , F _zxr and the damping force F _fcfl , F _fcfr , F _fcl , and F _fcrr are all vector quantities in the Z direction, the total value of these is f _fl , f _fr , _frl , f _rr is also calculated as a vector quantity in the Z direction.

The calculation of equation (28) is performed by the adder 48 shown in FIG. Specifically, the adder 48 outputs a force f, which is the sum of the input damping force and the spring input, as a known input u.

The damping force F _fc fluctuates according to the drive current value and the stroke speed supplied to the variable suspension 14. The ECU 20 stores a map in which this relationship is defined. The estimated value of the stroke speed and the driving current value, which are the estimated values x ^ of the state quantity x, are input to the arithmetic unit 44 shown in FIG. The arithmetic unit 44 calculates the damping force F _fc corresponding to the drive current value and the estimated value of the stroke speed according to this map. The damping force F _fc includes a response delay element. Therefore, the damping force F _fc output from the arithmetic unit 44 is output to the adder 48 after the first-order delay of the damping force is corrected by the arithmetic unit 46.

Thus, sum _{f fl, f fr, f rl} , the _{f rr,} the force inputted to the spring of the variable suspension 14 is aggregated. As a result, the total value of the forces in the vertical direction (Z direction) input to the variable suspension 14 can be calculated with high accuracy, so that the estimation accuracy of the stroke speed can be improved.

<Specific processing of the first embodiment>
Next, with reference to the flowchart, a specific process executed when the system of the first embodiment estimates the stroke speed will be described. FIG. 5 is a flowchart of a routine executed by the ECU 20 when estimating the stroke speed of the variable suspension 14.

In this routine, first, the sensor signal of the spring-up vertical acceleration sensor 16 is A / D converted (step S1). In the following description, the values of the spring-loaded vertical acceleration sensors 16 _fr , 16 _fr , 16 _{r r} , and 16 _rl after A / D conversion are used for the detected accelerations Z ₁ ", Z ₂ ", Z ₃ ", and Z, respectively. _It is called ₄ ".

In the next step, from the sensor signals before and after the sprung acceleration sensor 18, longitudinal sprung acceleration a _x is detected (step S2). Next, the code determination is performed before and after the sprung acceleration _{a x} (step S3). Here, whether longitudinal sprung acceleration a _x is 0 or more is determined. As a result, when the establishment of a _x ≧ 0 is confirmed, it is determined that the vehicle 10 is in a state of acceleration or constant velocity, and the process proceeds to step S4.

In step S4, the spring input due to acceleration is calculated. Here, before and after the detected spring acceleration _{a x} expression in step S2 (16), (17) , (20), (21), (22), by substituting (23), ground load variation ΔW force _{F zxf1, F zxr1} by _x, the suspension reaction force due to the longitudinal force during acceleration _{F zxf3, F zxr3,} and suspension reaction force _{F zxf4, F zxr4} by unsprung inertia is calculated. Next, by substituting the calculated force into the equations (24) and (26), the spring-loaded inputs F _zxf and F _zxr at the time of acceleration are calculated.

On the other hand, if the establishment of a _x ≧ 0 is not recognized in step S3, it is determined that the vehicle 10 is in the deceleration state, and the process proceeds to step S5. In step S5, the spring input due to deceleration is calculated. Here, before and after the detected spring acceleration _{a x} expression in step S2 (16), (17) , (18), (19), (22), by substituting (23), ground load variation ΔW force by _{x F zxf1, F zxr1,} suspension reaction force _{F zxf2, F zxr2} by longitudinal force during deceleration, and the suspension reaction force _{F zxf4, F zxr4} by unsprung inertia is calculated. Next, by substituting the calculated force into the equations (25) and (27), the spring inputs F _zxf and F _zxr at the time of deceleration are calculated.

Next, the spring vertical acceleration at each wheel position is calculated (step S6). Here, first, according to the following equations (29) to (32) using the detected accelerations Z ₁ ", Z ₂ ", Z ₃ ", Z ₄ ", the vertical acceleration Zg "and the roll acceleration of the center of gravity of the sprung structure. Φg ”and pitch acceleration Θg” are calculated. In the following equations (29) to (32), L ₁ , L ₂ , L ₃ , L ₄ , and W ₁ , W ₂ , W ₃ , W ₄ Indicates the positions of the on-spring vertical acceleration sensors 16 _fr , 16 _fr , 16 _{r r} , and 16 _{rr in} the X direction and the Y direction, respectively. L _g and W _g are the positions of the spring-loaded structure. the center of gravity position in the X direction, and shows the center of gravity position in the Y direction. these values _{L i, W i (i =} 1,2,3,4), L g, W g is fixed determined from the sensor arrangement and the like The value, which is stored in the memory of the ECU 20 in advance, is used.

In step S6, the spring vertical acceleration Zb at each wheel position is then calculated. Here, according to the following equation (33), the spring vertical acceleration just above the variable suspensions 14fl, 14fr, 14rr, 14rr. Z _bfl ", Z _bfr ", Z _brl ", Z _brr " are calculated. In equation (33), T _f is the tread width of the front wheels, _Tr is the tread width of the rear wheels, and l _f is the distance between the front wheel shaft and the sprung center of gravity, and l _r is the distance between the rear wheel shaft and the sprung center of gravity. These values T _f , _Tr , L _f , and L _r are from the configuration of the vehicle 10. A fixed value that is fixed and is stored in the memory of the ECU 20 in advance is used.

The method for calculating the spring vertical acceleration Z _bfl ", Z _bfr ", Z _brl ", Z _brr " is not limited to the above. That is, for example, a known method using three spring-up vertical acceleration sensors 16 may be adopted.

In the next step, the drive current and the estimated value of the stroke speed of each variable suspension 14 are read, and the damping forces F _fcfl , F _fcfr , F _fcl , and F _fcrr corresponding to these values are specified from the map (step). S7).

In the next step, the on-spring inputs Fzxf and Fzxr calculated in step S4 or S5 and the damping forces F _fcfl , F _fcfr , F _fcl and F _fcrr calculated in step S7 are substituted into the above equation (28). it, the variable suspension 14fl, 14fr, 14rl, sum _f fl of the force acting on _{14rr, f fr, f rl,} f rr is calculated (step S8).

Next, the force was calculated at the step _{S8 f fl, f fr, f} rl, a _{f rr} a known input u, the spring calculated in step S1 vertical acceleration _{Z bfl ", Z bfr",} Z brl ", _{Z brr"} as observation quantity y, and by using a single-wheel model observer described above, the stroke speed of the state quantity _{x (Z b '-Z w'} ) is estimated (step S9).

As described above, according to the suspension control system of the first embodiment, as the force input to the spring of the variable suspension 14 by the front-rear force due to the acceleration / deceleration of the vehicle 10, the force F _zxf1 due to the contact load fluctuation amount ΔW _{x , F} zxr1, suspension reaction force _F Zxf2 by longitudinal force during _{deceleration, F zxr2,} suspension reaction force _F Zxf3 by longitudinal force during _{acceleration, F zxr3,} and suspension reaction force _F Zxf4 according unsprung inertial _{force, F zxr4} consider Will be done. As a result, the force (known input) input to the variable suspension 14 can be calculated with high accuracy, so that the stroke speed can be estimated with high accuracy using the single-wheel model observer.

The suspension control system of the first embodiment may apply a modified form as follows.

The suspension control system of the first embodiment described above is based on the premise that the deceleration of the vehicle 10 is performed by the friction brake, but strictly speaking, the engine brake also acts. When decelerating by the engine brake, the front-rear force acts on the center of the wheel 12. Therefore, the suspension reaction forces F _zxf2 and F _zxr2 due to the front-rear force during deceleration have different values between the deceleration by the friction brake and the deceleration by the engine brake. Therefore, the suspension control system of the first embodiment may distinguish between the deceleration by the engine brake and the deceleration by the friction brake according to the magnitude of the acceleration during deceleration. Specifically, for example, sprung longitudinal acceleration a _x calculates the deceleration times the suspension reaction force _{F zxf2,} F zxr2 by the engine brake is greater than a predetermined threshold during deceleration, the threshold below In the case of, the suspension reaction _forces F _zxf2 and F _zxr2 may be calculated as the deceleration by the friction brake. In the calculation of the suspension reaction _forces F _zxf2 and F _zxr2 during deceleration by the engine brake, _{tanθ If} and tanθ _Ir may be used _instead of _{tanθ Jf} and tanθ _Jr in the equations (18) and (19).

The suspension control system of the first embodiment described above may be applied to an in-wheel motor vehicle in which the driving force and the braking force are controlled by the in-wheel motor. However, in an in-wheel motor vehicle, the front-rear force during acceleration acts on the ground contact point of the wheel. Therefore, in the calculation of the suspension reaction _forces F _zxf3 and F _zxr3 , _{tanθ Jf} and tanθ _Jr may be used _instead of _{tanθ If} and tanθ _Ir in the equations (20) and (21).

If the observer is a single-wheel model observer, there are no restrictions on the number of degrees of freedom, how to take the equation of state, continuous system, discrete system, and the like. For example, the system may be configured to estimate the stroke speed using a two-degree-of-freedom single-wheel model observer. Further, the single-wheel model observer is not limited to a configuration using a continuous Kalman filter, and may be a configuration using a discrete Kalman filter.

In the suspension control system of the first embodiment, the "spring-up vertical acceleration detecting means" of the present invention is realized by the ECU 20 executing the processes of steps S1 and S6, and the ECU 20 executes the processes of step S2. As a result, the "spring front-rear acceleration detecting means" of the present invention is realized, and the "total value calculating means" of the present invention is realized by the ECU 20 executing the processes of steps S3 to S5, steps S7 and S8. ..

Embodiment 2.
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The suspension control system of the second embodiment includes an engine ECU that calculates a controlling driving force generated by an engine or a motor that is a driving force source of the vehicle 10, and a brake ECU that calculates a braking force generated in a brake other than a regenerative brake. It has the same configuration as the suspension control system of the first embodiment except that it is provided.

<Characteristics of Embodiment 2>
The features of the second embodiment will be described. The suspension system of the second embodiment is characterized in that the front-rear force acting on the wheels 12 is calculated by the engine ECU or the brake ECU. That is, in the engine ECU of the second embodiment, the front-rear force F _xIdf , F _xIdr acting on the center of each wheel 12 by the control drive of the engine or the motor, and the front-rear force F _xJdf , F acting on the ground contact point of each wheel 12. It is configured so that _xJdr can be calculated. The brake ECU is longitudinal force _F XIbf acting on the center of each wheel 12 by the braking by the brake, excluding the regenerative _{brake, F XIbr,} and longitudinal force _F XJbf acting to ground of each wheel _12, enables calculation of the _{F XJbr} It is configured in.

Suspension reaction force during deceleration _{F zxf2, F zxr2} and acceleration of the suspension reaction force _{F zxf3, F zxr3} is substituting the longitudinal force supplied from the engine ECU and the brake ECU to the following equation (34) - (37) It becomes possible to calculate by.

From the above, the sprung inputs F _zxf and F _zxr of each wheel 12 can be calculated by the following equations (38) and (39).

As described above, according to the above equations (38) and (39), the spring-loaded input of the variable suspension 14 of each wheel during acceleration / deceleration of the vehicle 10 is input by using the front-rear force supplied from the engine ECU and the brake ECU. , It becomes possible to calculate with high accuracy.

When the vehicle 10 is provided with a regenerative brake, the front-rear forces F _xIbf and F _xIbr acting on the center of each wheel 12 may be supplied from the ECU by braking by the regenerative brake. In this case, _instead of supplying the information from the brake ECU, the front-rear forces F _xJbp and F _xJbr acting on the ground contact point may be calculated according to the following equation.

<Specific processing of the second embodiment>
Next, with reference to the flowchart, a specific process executed when the system of the second embodiment estimates the stroke speed will be described. FIG. 6 is a flowchart of a routine executed by the ECU 20 when estimating the stroke speed of the variable suspension 14.

In this routine, first, the sensor signal of the spring-up vertical acceleration sensor 16 is A / D converted (step S11). In the next step, from the sensor signals before and after the sprung acceleration sensor 18, longitudinal sprung acceleration a _x is detected (step S12).

Then, before and after the detected spring acceleration _{a x} expression in step S12 (16), (17), (22), by substituting (23), the force _F Zxf1 by ground contact load variation _{ΔW x, F} zxr1 , And the suspension reaction forces F _zxf4 and F _zxr4 due to the unsprung inertial force are calculated (step S13).

Next, the front-rear force acting on the center of each wheel 12 is calculated (step S14). Here, specifically, the longitudinal force _F XIdf acting on the center of each wheel 12 by the braking operation of the engine or the _{motor, F XIdr} is calculated from the engine ECU. Further, the front-rear forces F _xIbf and F _xIbr acting on the center of each wheel 12 by braking by the brake excluding the regenerative brake are calculated from the brake ECU.

Next, the front-rear force acting on the ground contact point of each wheel 12 is calculated (step S15). Here, specifically, the front-rear forces F _xJdf and F _xJdr acting on the ground contact points of each wheel 12 by the controlled drive of the engine or the motor are calculated from the engine ECU. Further, the front-rear forces F _xJbf and F _xJbr acting on the ground contact point of each wheel 12 by braking by the brake excluding the regenerative brake are calculated from the brake ECU.

Next, the on-spring inputs F _zxf and F _zxr are calculated (step S16). Here, the suspension reaction _forces F _zxf2 , F _zxr2 , F _zxf3 , and F _zxr3 are calculated by first substituting the vertical forces calculated in steps S14 and S15 into the above equations (34) to (37). Then, the calculated suspension reaction _forces F _zxf2 , F _zxr2 , F _zxf3 , F _zxr3 and the forces F _zxf1 , F _zxr1 , F _zxf4 , F _zxr4 calculated in the above step S13 are _expressed by the above equations (38) and (39). By substituting into, the spring inputs F _zxf and F _zxr are calculated.

The processing of steps S17 to S20 of the routine shown in FIG. 6 is the same as the processing of steps S6 to S9 of the routine shown in FIG.

As described above, according to the suspension control system of the second embodiment, the front-rear force supplied from the engine ECU and the brake ECU is used to input the variable suspension 14 of each wheel on the spring during acceleration / deceleration of the vehicle 10. Is calculated. As a result, the force (known input) input to the variable suspension 14 can be calculated with high accuracy, so that the stroke speed can be estimated with high accuracy using the single-wheel model observer. In addition, the estimation accuracy of the stroke amount is improved by estimating the stroke speed with high accuracy.

In the suspension control system of the second embodiment, the "spring-up vertical acceleration detecting means" of the present invention is realized by the ECU 20 executing the processes of steps S11 and S17, and the ECU 20 executes the processes of step S12. As a result, the "spring front-rear acceleration detecting means" of the present invention is realized, and the "total value calculating means" of the present invention is realized by the ECU 20 executing the processes of steps S13 to S16, steps S18 and S19. ..

10 Vehicle 12 Wheels 14 Variable suspension 16 Spring-up vertical acceleration sensor 18 Spring-up front-back acceleration sensor 20 ECU
30 Single-wheel model observer 36, 40, 42, 48 Adder 38 Integrator 44, 46 Arithmetic

Claims (1)

Suspension control system installed in the vehicle
A suspension that connects the sprung structure and the unsprung structure of the vehicle,
A control device for estimating a stroke speed, which is a relative speed between the sprung structure and the unsprung structure, is provided.
The control device is
A spring-loaded vertical acceleration detecting means for detecting a spring-loaded vertical acceleration, which is a vertical acceleration of the spring-loaded structure,
An on-spring anteroposterior acceleration detecting means for detecting an on-spring anteroposterior acceleration, which is an acceleration in the anteroposterior direction of the sprung-up structure,
A total value calculation means for calculating the total value of the forces input from the suspension to the spring-loaded structure, and
Including an observer constructed based on the state space of the equation of motion based on a single-wheel model,
The total value calculation means is
Using the sprung front-rear acceleration, the change in the ground contact load of the vehicle due to the change in the attitude of the sprung structure is calculated, and this is the vertical force input to the sprung structure by the ground load fluctuation. Calculate one force,
Using the driving force distribution or braking force distribution of the vehicle , a second force, which is a suspension reaction force generated by the front-rear force input to the wheels due to the acceleration or deceleration of the vehicle acting on the suspension , is calculated. And
The third force, which is the suspension reaction force due to the inertial force of the unsprung structure of the vehicle, is calculated.
It is configured to calculate the total value using the first force, the second force, and the third force .
The observer is configured to output an estimated value of the stroke speed of the suspension by using the total value as a known input and the vertical acceleration on the spring as an input of an observed amount. ..

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