JP5108327B2 - Vehicle control device - Google Patents

Description

  The present invention relates to a vehicle control device that controls a steering angle of at least one of a front wheel and a rear wheel.

  Conventionally, various vehicle steering angle control methods have been proposed. Patent Document 1 discloses a vehicle rear wheel steering angle control device including an actuator for rear wheel steering that is feedback-controlled. Specifically, Patent Document 1 discloses a rear wheel steering angle target differential value, a rear wheel steering angle target differential value for predicting an operating speed of an actuator, and a rear wheel steering angle target differential value of a second order differential for predicting an operating acceleration of an actuator. It is described that the actuator drive output is determined by adding feedforward compensation for compensating the rear wheel steering angle target value so as to suppress the response delay and the fluctuation of the actuator by using the value.

Further, Patent Document 2 discloses a technique for calculating while allowing a delay that can be practically ignored in following the actual turning angle to the target value while considering the dynamic characteristics of the actuator. Further, in Patent Literature 3, when the front wheel or the rear wheel is auxiliary-steered during steering of the steering wheel, the dynamic characteristics of the actuator are expressed by a pulse transfer function, and the steering angle actual value is predetermined with respect to the steering angle target value. A technique is disclosed in which the actual steering angle value of a wheel to be auxiliary steered is sufficiently brought close to the steering angle target value by following with a delay.
Japanese Patent No. 2587449 JP-A-3-31070 Japanese Patent Laid-Open No. 3-125669

  However, the configuration of any of the filters in Patent Documents 1 to 3 is based on the secondary characteristics of the motor that is an actuator, and is different from the primary delay characteristics based on the vehicle characteristics. For this reason, no consideration was given to the maneuverability and stability of the vehicle. Furthermore, none of Patent Documents 1 to 3 mentions the relationship between how to determine the target characteristic and the controller gain.

  The present invention has been proposed to solve the above-described problems, and an object thereof is to provide a vehicle control device capable of obtaining desired maneuverability and stability.

The vehicle control device according to the present invention includes a steering angle detection means for detecting a steering angle, a vehicle speed detection means for detecting a vehicle speed, a steering angle detected by the steering angle detection means, and a vehicle speed detected by the vehicle speed detection means. The first control amount calculation means for calculating the first control amount of the front wheels based on the first gain with respect to the steering angle calculated according to the steering angle, and the steering angle detected by the steering angle detection means against it, it has a second gain C ₁₁₀ for constants T ₁ and the steering angle when determined in accordance with the detected vehicle speed by the vehicle speed detecting means, and a transfer function that includes a filtering process using the Laplace operator s ( = C ₁₁₀ * s / (1 + T ₁ * s)) , the second control amount calculation means for calculating the second control amount of the front wheel, the steering angle detected by the steering angle detection means, and the vehicle speed detection Detected by means Third control amount calculating means for calculating a first control amount of the rear wheel based on a third gain for the steering angle calculated according to the vehicle speed, and the steering detected by the steering angle detecting means. relative angular, a fourth gain C ₂₁₀ for constant T ₂ and the steering angle when determined in accordance with the detected vehicle speed by the vehicle speed detecting means, and transmitting including a filter process using the Laplace operator s By a function (= C ₂₁₀ * s / (1 + T ₂ * s)), a fourth control amount calculating means for calculating the second control amount of the rear wheel, and the first and second control amount calculating means By adding the calculated first and second control amounts, the first addition means for calculating the target steering angle of the front wheels, and the first and second control amount calculation means calculated by the third and fourth control amount calculation means. And by adding the second control amount, A second adding means for calculating a target steering angle, said to be the target steering angle calculated by the first addition means to control the steering angle of the front wheels, the target calculated by the second addition means Steering angle control means for controlling the steering angle of the rear wheels so as to obtain a steering angle.

The first control amount calculation means calculates the first control amount of the front wheels based on the steering angle and the first gain with respect to the steering angle calculated according to the vehicle speed. Second control amount calculation means, with respect to the steering angle, have a second gain C ₁₁₀ for constants T ₁ and the steering angle when determined according to the vehicle speed, and the filtering process using the Laplace operator s The second control amount of the front wheel is calculated by the transfer function including (= C ₁₁₀ * s / (1 + T ₁ * s)) . The third control amount calculation means calculates the first control amount of the rear wheel based on the third gain for the steering angle, which is calculated according to the steering angle and the vehicle speed. The fourth control amount calculation means, with respect to the steering angle, and a fourth gain C ₂₁₀ for constant T ₂ and the steering angle when determined according to the vehicle speed, and the filtering process using the Laplace operator s The second control amount of the rear wheel is calculated using the transfer function (= C ₂₁₀ * s / (1 + T ₂ * s)). First addition means calculates a target steering angle of the front wheels by adding the first and second control amount of the front wheel. The second adding means calculates the rear wheel target steering angle by adding the first and second control amounts of the rear wheel. Then, the steering angle control means controls the front wheels so as to be the target steering angle of the front wheels, and controls the steering angle of the rear wheels so as to be the target steering angle of the rear wheels.

  Therefore, the vehicle control device of the present invention is based on the first control amount based on the steering angle and the first gain corresponding to the vehicle speed, and the transfer function having a predetermined time constant and the second gain with respect to the steering angle. By calculating the target steering angle by adding the second control amount that has been subjected to the filter processing represented, and controlling the steering angle of at least one of the front wheels and the rear wheels so as to be the target steering angle, The controllability and stability can be obtained.

  The vehicle control apparatus according to the present invention can obtain desired maneuverability and stability.

  Preferred embodiments of the present invention will be described in detail with reference to the drawings.

[Principle of the Invention]
Hereinafter, the principle of the present invention will be described.

(Control purpose)
Until now, efforts have been made to elucidate the ideal vehicle motion that the driver desires under various driving conditions using actual vehicles and driving simulators. Among them, the importance of dynamic characteristics of the yaw rate and lateral acceleration of the vehicle is shown, and it is pointed out that the characteristics of the yaw rate at low speed and the characteristics of lateral acceleration at high speed are important.

  In particular, the stability of the vehicle is related to the rising characteristics of yaw rate gain at low speed and yaw rate response to steering (linearity of yaw rate with respect to steering felt by the driver) and differential of lateral acceleration (transverse jerk) with respect to steering at high speed. Contributing to the safety evaluation is a major factor.

  In addition, the vehicle body slip angle during turning is considered to contribute to the evaluation of the stability and turning ability of the vehicle. At present, these ideal characteristics have not been quantitatively shown. However, at least the design of the controller that controls the vehicle motion requires that the dynamic characteristics of the yaw rate and lateral acceleration and the size of the vehicle body slip angle can be adjusted according to the vehicle speed.

As described above, the present invention satisfies the following four requirements.
(1) The steady gain of the yaw rate with respect to the steering wheel angle can be adjusted. (2) The response (phase) of the yaw rate with respect to the steering wheel angle can be adjusted. (3) The steady gain of the vehicle body slip angle with respect to the steering wheel angle can be adjusted. Be present (4) The rising characteristics of the lateral jerk can be adjusted with respect to the steering wheel angle (setting of the vehicle model)
A linear two-wheel model of a vehicle having front and rear wheel steers to be controlled is shown in Equation (1). β is the vehicle body slip angle, γ is the yaw rate, and δ _f and δ _r are the steering angles of the front and rear wheels, respectively. I _z is the yaw inertia of the vehicle, K _f and K _r are the cornering stiffnesses of the front and rear wheels, m is the vehicle weight, l is the wheel base, l _f and l _r are the distance from the vehicle center of gravity to the front and rear wheel axes, and v is the vehicle speed. It is.

Note that the upper equation of the equation (1) represents the equation of motion in the translation direction, and the lower equation represents the equation of motion in the yaw direction. When formula (1) is Laplace transformed and rearranged, formula (2) is obtained. Here, s is a Laplace operator, Δ _s (s) is a characteristic equation of the system expressed by equation (3), N _{1 to} N ₄ are numerator polynomials of the system, and are expressed by equations (4) to (7) You can write

Equation (6) shows the numerator of the transfer function from the steering angle of the front wheels to the yaw rate. Equation (7) shows the numerator of the transfer function from the steering angle of the rear wheel to the yaw rate. Therefore, according to the equations (2) to (7), the denominator of the transfer function corresponding to the vehicle speed is a part of the vehicle characteristics (N ₃ , N ₄ ).

Here, let us consider derivation of the front and rear and rear wheel steering angles for realizing the target vehicle body slip angle β ^* and the target yaw rate γ ^* described in the following formulas (8) and (9).

At this time, the target steady-state gains β ₀ ^* and γ ₀ ^* of the vehicle body slip angle and yaw rate are applied as in the following equations (10) and (11).

(Select control method)
Among the control purposes described above, the request for the steady characteristic uniquely determines the steady gain of the FF (feed forward) controller, but there are several methods for the request for the dynamic characteristic.

FIG. 1 is a Bode diagram of a transfer function from a steering angle of a general passenger car to a yaw rate. As the vehicle speed increases, the frequency at the resonance point decreases, and the peak gain increases greatly. Further, in a frequency region lower than the resonance frequency, the phase is delayed at a low speed and the phase is advanced at a high speed. As a conventional means for improving the responsiveness and stability of the yaw rate for a vehicle having such characteristics, there is a method of correcting the poles of the system. In this method, an FF controller (C _PolePlace ) is given as shown in equation (12).

In other words, the pole to be controlled is canceled at the zero point of the FF controller, and the resonance frequency of the system is corrected to a higher value (ω ^* ) and the damping is set to a larger value (ζ ^* ) by the pole of the FF controller. . However, _C0PolePlace is a steady gain of the controller. However, in such a controller, the denominator and numerator are quadratic polynomials, and as shown in FIG. 2, the gain characteristic has a peak, and the phase characteristic changes greatly in the vicinity thereof.

  Therefore, a controller design having the numerator polynomial of the system in the denominator of the controller is applied as a controller structure in which the controller does not have such a gain characteristic peak and can improve the response of the system. This is a method in which the zero point of the controlled object is canceled by the pole of the controller, and the zero point of the system is newly corrected by the zero point of the controller. However, as represented by the equations (4)-(7), since there is one zero to be controlled (numerator polynomial is first order), the controller denominator polynomial is also first order, and the gain characteristic of the controller has a peak. do not have. Therefore, it can be expected that the above-described self-excited vibration hardly occurs. Further, as will be described later, the structure of the controller is represented by the sum of a proportional term and a differential term, and parameter tuning is easy. Therefore, a controller using this method is designed.

(Design of front and rear wheel steering controllers)
Controllers that receive the steering wheel angle and output the front and rear wheel target rudder angles are C ₁ (s) and C ₂ (s), respectively. Here, C ₁ (s), C ₂ (s) are proportional terms C ₁₀ , C ₂₀ and numerator polynomials N ₃ (s), N ₄ (N It consists of differential terms C ₁₁ (s) and C ₂₁ (s) having s) in the denominator.

That is, C ₁₀ , C ₂₀ , C ₁₁₀ , and C ₂₁₀ are constant gains, and the controller is designed by determining these four gains. These gains finally become a map corresponding to information such as the vehicle speed. The differential filter has a value of s / N ₃ (s) and s / N ₄ (s) for each of the front and rear wheels, and constitutes a differential filter having a numerator polynomial of the system as a temporary delay coefficient.

Next, consider substituting Equations (14) and (15) into Equation (2) to realize β ^* and γ ^* given by Equations (8) and (9). Here, when N _* : (* = 1... 4) is written as in equation (16), equation (2) can be decomposed as in equations (17) to (20).

Here, the equation (18) is a term corresponding to the steady gain (β ₀ ^* , γ ₀ ^* ) of the vehicle body slip angle and the yaw rate, and can be written as the following equation (21).

When the equation (21) is solved, the proportional gains C ₁₀ and C _{20 of} the controller are obtained as in the equations (22) and (23).

  Next, attention is focused on the component (second line) relating to the yaw rate in the equation (17). The target value of the yaw rate is set as follows according to the equation (9).

Further, γ ₁ ^* is set as shown in equation (24).

Here, γ _12ws is the gain of the differential term of the yaw rate when _there is no control, and is given by equation (25).

That is, γ ₁ ^* is given here as Δγ times when there is no control. This is because the control amount is adjusted while considering the base performance of the vehicle by designating the amount of change from the state without control. However, the method of giving γ ₁ ^* is not limited to this, and it may be given as an absolute value or may be calculated from other characteristics.

When the components related to the yaw rate in the equation (17) are arranged using the already determined C ₁₀ , C ₂₀ and γ ₀ ^* , γ ₁ ^* , the equation (27) is obtained, and by solving this, (C ₁₁₀ + C ₂₁₀ ) Is obtained.

However, (gamma) _p (s) / (DELTA) _s (s) is a term regarding the yaw rate of (19) Formula.

Finally, consider the rise characteristics of lateral acceleration. By extracting the vehicle slip angle component from the equation (17) and rearranging the vehicle slip angle term of the equation (19) as β _p0 ≡N ₁ ′ C ₁₀ + N ₂ ′ C ₂₀ , the equation (30) is obtained. .

Expression (30) is an expression relating to the derivative of the slip angle, that is, the lateral acceleration. Here, since N _* (s) is a linear equation, the denominator of equation (30) is the second order, the numerator is the third order higher than the denominator, and the highest order term of the numerator is the derivative of the lateral acceleration. That is, it becomes the direct term of the horizontal jerk and determines the characteristics of the rise. The highest order term J _H of the numerator on the right side of the equation (30) becomes the equation (31).

Since N ₃ (s) is positive from Equation (6) and N ₄ (s) is negative from Equation (7), the right side denominator of Equation (30) is negative. Therefore, it can be said that the smaller the equation (31), the larger the direct term of the horizontal jerk and the faster the rise. C ₁₀ and C ₂₀ are already given by the equations (22) and (23), and in order to speed up the rise of the lateral jerk, (I _r C ₁₁₀ −l _f C ₂₁₀ ) may be increased. If (I _r C ₁₁₀ −l _f C ₂₁₀ ) is determined so that a desired lateral jerk is obtained, since (C ₁₁₀ + C ₂₁₀ ) is uniquely obtained by specifying γ ₁ ^* , C ₁₁₀ , C ₂₁₀ is obtained.

(Summary)
The design method of the controller was shown for the purpose of improving the maneuverability by the front and rear wheel active steering. The proposed controller has sufficient flexibility to adjust the steady state gain and responsiveness of the target yaw rate, the steady body slip angle, and the rising characteristics of the lateral jerk. Furthermore, the simple structure that can be reduced to the steering angle proportional and differential steer enables intuitive gain tuning from the vehicle motion, and is an effective method from the viewpoint of easy creation of vehicle characteristics.

[Specific Embodiment]
FIG. 3 is a block diagram showing a configuration of the vehicle control device according to the embodiment of the present invention. Rolling the vehicle control device, a steering angle sensor 11 for detecting a steering angle [delta] _MA, a vehicle speed sensor 12 for detecting the vehicle speed, the electronic control unit (ECU) 20 for calculating a front wheel steering angle and the rear wheel steering angle, the front wheel A front wheel steering actuator 31 for steering and a rear wheel steering actuator 32 for steering rear wheels are provided.

FIG. 4 is a block diagram showing the configuration of the ECU 20. ECU20 includes a gain calculation circuit 21 for multiplying the gain _{C 10} to gain _{C 10} operations to the steering angle [delta] _MA, a differentiating filter 22 performs a filtering process with respect to the steering angle [delta] _MA, and calculates the gain _{C 110} filters a gain calculating circuit 23 for multiplying the gain C ₁₁₀ to the output, an adder 24 which outputs a front-wheel steering angle [delta] _f by adding the output of the gain calculating circuit 21 and 23, and a.

Gain calculating circuit 21 uses the detected vehicle speed v by the vehicle speed sensor 12, calculates the gain C ₁₀ according to the above-described (22). In equation (22), β ₀ ^* is a steady gain of the vehicle body slip angle, and γ ₀ ^* is a steady gain of the yaw rate. The gain calculating circuit 21 multiplies the steering angle δ _MA detected by the steering angle sensor 11 by the gain C ₁₀ and outputs C ₁₀ · δ _MA .

Differential filter 22 has a characteristic of s _{/ N} 3 (s), by performing a primary differential filter processing with respect to the steering angle [delta] _MA, and outputs a _{δ MA · s / N 3 (} s). s is a Laplace operation element, and N ₃ (s) represents the above-described equation (6). When s / N ₃ (s) is transformed into the form of s / (1 + Ts), T represents the time constant of the differential filter 22.

Gain calculating circuit 23 calculates a gain _{C 110.} The gain C ₁₁₀ is obtained from the relationship of the expression (27) and the above-described (l _r C ₁₁₀ −l _f C ₂₁₀ ). Then, the gain calculation circuit 21 multiplies δ _MA · s / N ₃ (s) output from the differential filter 22 by the gain C ₁₁₀ and outputs C ₁₁₀ · δ _MA · s / N ₃ (s). To do.

The adder 24 adds C ₁₀ · δ _MA output from the gain calculation circuit 21 and C ₁₁₀ · δ _MA · s / N ₃ (s) output from the gain calculation circuit 23 to obtain (32 ) as shown in equation, and outputs a front-wheel steering angle [delta] _f as a target.

Further, ECU 20, as shown in FIG. 2, the gain calculating circuit 26 for multiplying by calculating the gain _{C 20} to the steering angle [delta] _MA gain _{C 20,} a differentiating filter 27 for filtering against the steering angle [delta] _MA comprises a gain calculation circuit 28 for multiplying the gain _{C 210} to the filter output and calculates the gain _{C 210,} an adder 29 for outputting a rear wheel steering angle [delta] _r by adding the output of the gain calculating circuit 26, the ing.

The gain calculation circuit 26 uses the vehicle speed v detected by the vehicle speed sensor 12 to calculate the gain C ₂₀ according to the above-described equation (23). Then, the gain calculation circuit 26 multiplies the steering angle δ _MA detected by the steering angle sensor 11 by the gain C ₂₀ and outputs C ₂₀ · δ _MA .

Differential filter 27 has a characteristic of s _{/ N} 4 (s), by performing a primary differential filter processing with respect to the steering angle [delta] _MA, and outputs a _{δ MA · s / N 4 (} s). s is a Laplace operation element, and N ₄ (s) represents the above-described equation (7). When s / N ₄ (s) is transformed into s / (1 + Ts), T represents the time constant of the differential filter 27.

The gain calculation circuit 28 calculates the gain C ₂₁₀ . The gain C ₂₁₀ is obtained from the relationship of the equation (27) and the above-mentioned (l _r C ₁₁₀ −l _f C ₂₁₀ ). Then, the gain calculation circuit 28 multiplies δ _MA · s / N ₄ (s) output from the differential filter 27 by the gain C ₂₁₀ and outputs C ₂₁₀ · δ _MA · s / N ₄ (s). To do.

The adder 29 adds C ₂₀ · δ _MA output from the gain calculation circuit 26 and C ₂₁₀ · δ _MA · s / N ₄ (s) output from the gain calculation circuit 28 to obtain (33 The target rear wheel steering angle δ _r is output as shown in the equation (1).

Then, the front wheel steering actuator 31 shown in FIG. 1, the steering angle of the actual front wheel to steer the front wheels so that the front wheel steering angle [delta] _f. The rear wheel steering actuator 32 steers the rear wheels as the steering angle of the actual rear wheel becomes the rear wheel steering angle [delta] _r.

Here, C ₁₀ and C ₂₀ are steady gains of the yaw rate with respect to the steering angle, respectively. (C ₁₁₀ + C ₂₁₀ ) indicates the response (phase) of the yaw rate with respect to the steering angle, as is apparent from the equation (27). Further, equation (30) represents the steady gain of the vehicle body slip angle with respect to the steering angle, and equation (31) represents the rising characteristic of the lateral jerk with respect to the steering angle. These can be adjusted by changing the values of predetermined parameters. That is, in the present embodiment, all the four requirements described in (Control Purpose) are satisfied. In other words, C ₁₀ , C ₁₁₀ , the time constants of the differential filters 22 and 27, and the differential gain according to the requirements of the steady gain of the yaw rate, the phase advance of the yaw rate, the steady gain of the vehicle body slip angle, and the rising characteristics of the lateral jerk. C ₁₁₀ and C ₂₁₀ are determined respectively.

  As described above, the vehicle control device according to the embodiment of the present invention detects the steering angle and the vehicle speed, and uses these detection results to determine the index (yaw rate gain and phase with respect to the steering angle) related to the steering performance. Since the index related to the sense of stability (rising of the lateral acceleration with respect to steering) can be set to an independent desired value, the steering performance can be improved. In addition, since the vehicle control device according to the present embodiment is controlled using a controller having a transfer function that does not have a frequency peak, induction of self-excited vibration of the steering system can be avoided.

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can also be applied to a design modified within the scope of the claims.

It is a Bode diagram of a transfer function from a steering angle of a general passenger car to a yaw rate. It is a figure which shows the transfer function of FF controller which corrects the resonant frequency and damping of a system. It is a block diagram which shows the structure of the vehicle control apparatus which concerns on embodiment of this invention. 2 is a block diagram showing a configuration of an ECU 20. FIG.

Explanation of symbols

11 Steering angle sensor 12 Vehicle speed sensor 20 ECU
21, 23, 26, 28 Gain calculation circuit 22, 27 Differential filter 24, 29 Adder

Claims (4)

Steering angle detection means for detecting the steering angle;
Vehicle speed detection means for detecting the vehicle speed;
A first control amount for the front wheels is calculated based on the steering angle detected by the steering angle detection means and the first gain for the steering angle calculated according to the vehicle speed detected by the vehicle speed detection means. First control amount calculating means for
Wherein with respect to the steering angle detected by the steering angle detection means, have a second gain C ₁₁₀ for constants T ₁ and the steering angle when determined in accordance with the detected vehicle speed by the vehicle speed detecting means, and Laplace A second control amount calculating means for calculating a second control amount of the front wheel by a transfer function (= C ₁₁₀ * s / (1 + T ₁ * s)) including a filter process using the child s ;
Based on the steering angle detected by the steering angle detection means and the third gain for the steering angle calculated according to the vehicle speed detected by the vehicle speed detection means, the first control amount of the rear wheels is calculated. A third control amount calculating means for calculating;
Wherein with respect to the steering angle detected by the steering angle detection means, having a fourth gain C ₂₁₀ for constant T ₂ and the steering angle when determined in accordance with the detected vehicle speed by the vehicle speed detecting means, and Laplace A fourth control amount calculating means for calculating a second control amount of the rear wheel by a transfer function (= C ₂₁₀ * s / (1 + T ₂ * s)) including a filter process using the child s ;
By adding the first and second control amount calculated by said first and said second control amount calculation means, a first adding means for calculating a target steering angle of the front wheels,
Second addition means for calculating a target steering angle of the rear wheel by adding the first and second control amounts calculated by the third and fourth control amount calculation means;
The first steering angle before wheels so that the target steering angle computed controlled by the addition means, controls the steering angle of the rear wheels so that the target steering angle calculated by said second addition means Steering angle control means,
A vehicle control device comprising: The vehicle control device according to claim 1, wherein the second control amount calculation means calculates a time constant that increases as the vehicle speed increases. The vehicle control device according to claim 1, wherein the second control amount calculation means calculates a time constant proportional to the vehicle speed. The vehicle characteristics of the vehicle to be controlled are such that the resonance frequency decreases and the peak gain becomes oscillating as the vehicle speed increases, the phase advances as the vehicle speed increases at a frequency lower than the resonance frequency, and at a frequency higher than the resonance frequency. It is expressed by the transfer characteristic from the steering angle to the yaw rate that the phase is delayed,
The vehicle control device according to claim 1, wherein a pole of a control system from a steering angle detected by the steering angle detection unit to a target steering angle calculated by the addition unit has a zero point of the vehicle characteristic.

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