JP2004067096A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device for obtaining a suitable steering characteristic corresponding to various operating conditions. <P>SOLUTION: The number of rotations of each wheel is taken in an ECU1 in a step 110. In a step 120, a steering angle is taken, and an angular rate is calculated and taken using the steering angle. In a step 130, a number of rotation of an engine is taken, and an engine rotation acceleration is calculated and taken using the number of rotation of the engine. In a step 140, a lateral G is taken, and a yaw rate is taken in a step 150. In a step 160, signals from a stop lamp SW21 are taken, and signals from a mode switching SW23 are taken in a step 170. In a step 180, suspension rigidity is controlled on the basis of the signals taken by the ECU1, and a power steering assist volume is controlled in a step 190. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a power steering device capable of obtaining suitable steering characteristics according to a driving state of a vehicle.

It has been known that steering characteristics such as steering stability and steering feeling of a vehicle can be changed by changing steering characteristics of a power steering device. For example, when the assisting force (steering assist force) in power steering is reduced, the response at the time of steering becomes dull and the steering feeling becomes dull. Conversely, when the assisting force is increased, the response becomes sharp. The steering feeling becomes sharp.

As an example of changing the steering characteristics, for example, the steering operation force is changed according to the vehicle speed, the steering is increased at high speed to increase the straight running stability, and the steering is reduced at low speed to improve turning performance. Things are known. In recent years, a change in steering characteristics caused by a change in suspension characteristics can be expressed by sharpness of response and a magnitude of a steering force, and a change in steering characteristics caused by a change in steering characteristics is also the same. Focusing on the sharpness of the response and the fact that it can be expressed by the magnitude of the steering force, the control of the combination of the change in the suspension characteristics and the change in the steering characteristics enhances the steering characteristics and further increases the steering characteristics. A technique has been proposed in which the change is offset and the change is reduced (see JP-A-59-106371).

However, in the above-described technology, it is not always necessary to sufficiently obtain steering characteristics such as steering stability and steering feeling of a vehicle that can appropriately cope with various driving states such as when receiving a crosswind or turning. Therefore, further improvement was desired. The present invention has been made to solve the above-described problem, and has as its object to provide a power steering device that can obtain suitable steering characteristics in accordance with various driving states.

In order to achieve this object, a first aspect of the present invention provides a power steering apparatus for adjusting an assist amount, which is an auxiliary steering force applied to a steering wheel, as illustrated in FIG. A steering angle detecting means for detecting a steering angle, a vehicle body state detecting means for detecting a lateral G or a yaw rate, a vehicle speed calculating means for calculating a vehicle speed based on the wheel speed detected by the wheel speed detecting means, Based on the vehicle speed and the steering angle detected by the vehicle speed detection means and the steering angle detection means, a vehicle state calculation means for calculating a reference lateral G or yaw rate; and a reference lateral G or a yaw rate calculated by the vehicle body state calculation means. Based on the yaw rate and the lateral G or yaw rate detected by the vehicle body state detecting means, the assist of power steering is determined. And an assist amount setting means for setting the amount of a power steering apparatus comprising the the gist.

The invention according to claim 2 estimates the road surface μ based on the reference lateral G or yaw rate calculated by the vehicle body state calculating means and the lateral G or yaw rate detected by the vehicle body state detecting means. The power steering apparatus according to claim 1, wherein the power steering assist amount is set based on the following.

The invention of claim 3 is the gist of the power steering apparatus according to claim 1 or 2, wherein the assist amount of the power steering is reduced as the road surface μ is smaller.

According to the first aspect of the present invention, the vehicle speed is calculated based on the wheel speed detected by the wheel speed detecting means, and the lateral G or the standard G based on the vehicle speed and the steering angle detected by the vehicle speed detecting means and the steering angle detecting means. The yaw rate is calculated, and the assist amount of the power steering is set based on the lateral G or yaw rate of the reference calculated by the vehicle body state calculating means and the lateral G or yaw rate detected by the vehicle body state detecting means. That is, since the assist amount is set based on the calculated lateral G or yaw rate of the reference and the detected lateral G or yaw rate, the signal of the wheel speed used in the ABS control is used in accordance with the driving state of the vehicle. It is possible to suitably control the power steering device.

According to the second aspect of the present invention, the road surface μ is estimated based on the reference lateral G or yaw rate calculated by the vehicle body state calculating means and the lateral G or yaw rate detected by the vehicle body state detecting means, and based on the estimated road surface μ. Thus, the power steering assist amount is set, so that the power steering device can be suitably controlled according to the road surface condition.

According to the third aspect of the present invention, since the assist amount of the power steering is reduced as the road surface μ is smaller, the steering stability and the steering feeling in an unstable state where the vehicle is slippery are improved.

In order to further clarify the configuration and operation of the present invention described above, preferred embodiments of the present invention will be described below. FIG. 2 shows a vehicle provided with the power steering device of the present embodiment. The driving state of the vehicle is detected by various sensors, and various actuators are driven and controlled based on the detected driving state. Control such as power steering assist amount control and suspension rigidity control, which will be described later, is performed.

As shown in FIGS. 2 and 3, in the present embodiment, as sensors, a wheel speed sensor 7 for detecting the rotation speed of each wheel, an engine rotation speed sensor 9 for detecting the rotation speed of the engine, and a steering wheel 11 A steering angle sensor 13 for detecting the rotation angle (steering angle) of the vehicle, a vertical G sensor 15 for detecting the vertical acceleration (G), a lateral G sensor 17 for detecting the lateral G, a yaw rate sensor 19 for detecting the yaw rate, A stop lamp switch (hereinafter, switch is referred to as SW) 21 for detecting that a brake pedal is depressed, and a mode switching SW 23 for switching a setting state of a damping force between a sports mode and a normal mode are provided.

Further, as an actuator, a hydraulic motor 25 and a hydraulic pump 27 for supplying (assisting) a hydraulic pressure for driving the power steering 3, a damping force switching actuator 29 for switching a damping force of the shock absorber 5, and an abnormality such as disconnection of a sensor. And a warning lamp 31 for notifying the user.

The electronic control unit (ECU) 1 receives signals from the sensors, performs various calculations based on the signals, and outputs control signals to the actuators. Next, a basic control procedure of the power steering apparatus according to the present embodiment having the above-described configuration will be described with reference to a flowchart of FIG.

First, initialization is performed in step 100 of FIG. 4, and in subsequent step 110, the wheel speed of each wheel is taken into the ECU 1 based on a signal from the wheel speed sensor 7. The wheel speed sensor 7 may be a sensor used for ABS control.

In the following step 120, the steering angle is captured based on the signal from the steering angle sensor 13, and the angular velocity of the steering angle is calculated and captured using the steering angle. In the following step 130, the engine rotational speed is acquired based on the signal from the engine rotational speed sensor 9, and the engine rotational acceleration is calculated and acquired using the engine rotational speed.

In the following step 140, the horizontal G is captured based on the signal from the horizontal G sensor 17, and in the subsequent step 150, the yaw rate is captured based on the signal from the yaw rate sensor 19. In the following step 160, a signal from the stop lamp SW21 is fetched, and in the following step 170, a signal from the mode switching SW23 is fetched.

In the following step 180, suspension rigidity control, which will be described in detail later, is performed based on the signal taken in by the ECU 1 as described above, and in step 190, power steering assist amount control, which is also described in detail later, is performed. Return to 110.

Next, various control processes performed in this embodiment will be sequentially described in detail.

(1) Vehicle Speed Sensitive Control of Power Steering As shown in FIG. 5, in this processing, in step 200, the wheel speed of each wheel is taken in based on a signal from the wheel speed sensor 7.

In step 210, the vehicle speed is calculated according to the wheel speed to be used, as shown in Table 1 below.

In the following step 220, an assist amount which is a steering assist force of the power steering is calculated. When calculating the assist amount, the calculation method is slightly different depending on which of the vehicle speed calculation methods (1) to (10) in Table 1 is used.

Specifically, in the case of (1) (using the wheel speed of one wheel as it is), the assist amount is calculated using a map indicating the relationship between the vehicle speed and the assist amount as shown in FIG. 6, for example. . Thus, the assist amount can be obtained by the simplest calculation. The map in FIG. 6 is set so that the assist amount decreases as the vehicle speed increases. However, when the vehicle is moving at a high speed, it is necessary to turn the steering wheel so much. Because it does not.

(2) In the case of (2) (using a filter), the influence of the unevenness of the road surface can be removed by the filter, so that the wheel speed can be detected more accurately, and therefore, the assist amount can be accurately obtained. In the case of (3) (the average value of the left and right wheels), when the vehicle turns, the vehicle speed can be calculated more accurately, and the assist amount can be accurately obtained.

In the case of (4) (drive wheel; maximum value of left and right wheels), acceleration slip can be detected by selecting the maximum value. Therefore, in this case, as shown in FIG. 6, a smaller assist amount is set as the vehicle speed increases, and the steering force increases during acceleration slip, thereby improving safety.

In the case of (5) (the minimum value of the left and right wheels), by selecting the minimum value, a brake lock state (for example, a single wheel lock state) can be detected. Therefore, in this case, as shown in FIG. 7, a smaller assist amount is set for a lower vehicle speed, and the steering force is increased when the brake is locked, so that safety is improved.

In the case of (6) (4 wheel average value), for example, when the vehicle turns, the vehicle speed can be calculated more accurately, and the assist amount can be calculated more accurately. In the case of (7) (the maximum value of four wheels), the acceleration slip can be detected by selecting the maximum value in the same manner as in (4). Therefore, in this case, as shown in FIG. 6, a smaller assist amount is set as the vehicle speed increases, and the steering force increases during acceleration slip, thereby improving safety.

In the case of (8) (the minimum value of the four wheels), the brake lock state can be detected by selecting the minimum value as in the case of (5). Therefore, in this case, as shown in FIG. 7, a smaller assist amount is set for a lower vehicle speed, and the steering force is increased when the brake is locked, so that safety is improved.

In the case of (9) (the maximum value of the average of the front two wheels and the average of the rear two wheels), it is possible to detect the acceleration slip by selecting the maximum value as in the above (4) and (7). it can. Therefore, in this case, as shown in FIG. 6, a smaller assist amount is set as the vehicle speed increases, and the steering force increases during acceleration slip, thereby improving safety.

In the case of (10) (the minimum value of the average of the two front wheels and the average of the two rear wheels), the brake lock state is detected by selecting the minimum value in the same manner as in the above (5) and (8). Can be. Therefore, in this case, as shown in FIG. 7, a smaller assist amount is set for a lower vehicle speed, and the steering force is increased when the brake is locked, so that safety is improved.

{Circle around (2)} In the following step 230, the calculated assist amount is output, and the present process is ended once. As described above, in the present process, the vehicle speed is calculated using the wheel speed, and the assist amount is reduced as the vehicle speed increases, so that there is an effect that steering characteristics such as steering stability and steering feeling are improved.

In the case where the wheel speed of not only one wheel but also two wheels or four wheels is used, the accuracy of detecting the vehicle speed is further improved, and an effect that a more suitable assist amount can be set can be obtained. Furthermore, by using the average value, the maximum value, and the minimum value of each wheel speed, there is an advantage that the detection accuracy of the vehicle speed is improved corresponding to various driving states, and a more suitable assist amount can be set.

(2) Control according to the magnitude of the sprung and / or unsprung resonance frequency component of the fluctuation of the wheel speed As shown in FIG. To capture the wheel speed of each wheel.

In the following step 310, a sprung resonance frequency component (e.g., 1 Hz to 2 Hz) and an unsprung resonance frequency component (e.g., 10 Hz to 20 Hz) are extracted from the fluctuation of the wheel speed using a frequency filter. Here, when the sprung resonance frequency component is 1 Hz to 2 Hz, the vehicle shows a fluttering (tilt) state. On the other hand, when the unsprung resonance frequency component is 10 Hz to 20 Hz, the vehicle flutters ( The state of the vehicle is unstable, which is not preferable. Either the sprung resonance frequency component or the unsprung resonance frequency component may be extracted, or both may be extracted.

In the following step 320, the assist amount is calculated using a map as shown in FIG. 9 according to the extracted sprung or lower resonance frequency component. In this case, separate maps are used for the sprung portion and the unsprung portion, but a map is used in which the assist amount decreases as the signal intensity of the resonance frequency component increases. This is because the steering force is increased as the flapping state or the flapping state becomes more remarkable, thereby improving the steering stability and the steering feeling. When both the sprung and unsprung resonance frequency components are used, the steering stability and the steering feeling are further improved by setting the assist amount using the smaller one of the two values.

(4) In the subsequent step 330, the calculated assist amount is output to perform the assist control, and the present process is temporarily terminated. Here, one example of the control of the assist amount is shown in FIG. As shown in FIG. 10, when the signal strength of the sprung / unsprung resonance frequency component exceeds the control start threshold (point A), the assist amount is reduced at a fixed rate from the basic assist amount based on vehicle speed sensitivity. , A target value set corresponding to the maximum value (point B) of the sprung / unsprung resonance frequency component. Similarly, when the maximum value (point C) becomes larger than the point B during the predetermined period T from the start of the control, the assist amount is reduced at a constant rate from the time of the point C, and the magnitude of the point C is reduced. The next target value set corresponding to this is made to follow. After that, when the predetermined period T ends, a process of increasing the assist amount at a fixed rate and returning to the basic assist amount is performed.

As described above, in the present process, the sprung resonance frequency component indicating the vertical movement of the vehicle body due to the unevenness of the road surface is extracted from the fluctuation of the wheel speed, and the assist amount is determined according to the magnitude of the sprung resonance frequency component. Is controlling. Specifically, since the assist amount decreases as the sprung resonance frequency component increases, it is possible to prevent the vehicle from tilting and improve steering stability and steering feeling.

Similarly, the unsprung resonance frequency component is extracted from the fluctuation of the wheel speed, and the assist amount is reduced as the unsprung resonance frequency component increases, so that the flapping of the vehicle is prevented, and the steering stability and the steering are improved. Feeling can be improved.

(3) Control at the time of traveling on a low μ road surface As shown in FIG. 11, in this processing, in step 400, the wheel speed of each wheel is taken in based on a signal from the wheel speed sensor 7.

In the following step 405, the vehicle speed is calculated using this wheel speed in the same manner as in step 210. In the following step 410, the steering angle is acquired based on the signal from the steering angle sensor 13.

In the following step 420, the lateral G or yaw rate is taken in based on the signal from the lateral G sensor 17 or the yaw rate sensor 19. In this case, the lateral G and the yaw rate may be estimated from the difference between the left and right wheel speeds by calculation, instead of the actual measurement, as in the following equations (1) and (2).

・ Horizontal G = (V02−V12) / 2 · T · g (1)
・ Yaw rate = (V0−V1) / T (2)
However, V0: right wheel speed, V1: left wheel speed, T: trad, g; gravitational acceleration In the next step 430, calculation of the reference lateral G or the reference yaw rate is performed. The reference lateral G and the reference yaw rate can be calculated as the lateral G and the yaw rate when an ideal trace is performed from the calculated vehicle speed and steering angle.

In the following step 440, μ (coefficient of friction) of the road surface is estimated based on each difference between the reference lateral G or yaw rate and the actually measured or estimated lateral G or yaw rate. That is, the larger the difference between the normative (lateral G, yaw rate) value and the actually measured or estimated (lateral G, yaw rate) value, the more the vehicle body is slipping (oversteer or understeer state). It is determined that μ is small.

In the following step 450, the assist amount is calculated using a map as shown in FIG. 12 according to the estimated μ of the road surface. In this case, it is predicted that the smaller the μ of the road surface, the more slippery and unstable the road is. Therefore, a map is used in which the smaller the μ of the road surface, the smaller the assist amount, and the smaller the μ of the road surface, the heavier the steering force. Improves steering stability and steering feeling.

(4) In the following step 460, the calculated assist amount is output to perform the assist control, and the present process is ended once. As described above, in this process, the reference lateral G or the reference yaw rate is obtained from the vehicle body speed and the steering angle, and the lateral G or the yaw rate is detected from the lateral G sensor 17 or the yaw rate sensor 19, and the difference between the reference value and the measured value is obtained. Since the road surface state is determined from the road surface μ to estimate the road surface μ and the assist amount is reduced when the road is a low μ road, the steering stability and the steering feeling on the low μ road can be improved.

Similarly, the μ of the road surface is estimated from the reference lateral G or the reference yaw rate obtained from the vehicle body speed and the steering angle, and the lateral G or the yaw rate estimated from the difference between the left and right wheel speeds. Since the assist amount is reduced, steering stability and steering feeling on a low μ road can be improved.

(4) One-wheel Lock, Control on Running on Low μ Road Surface, and Running on Puddle Road Surface As shown in FIG. 13, in this processing, in step 500, the wheels of each wheel are Capture speed.

In the following step 510, the difference between the wheel speeds of the left and right wheels is calculated. In the following step 520, an assist amount is calculated using a map as shown in FIG. 14 according to the calculated wheel speed difference between the left and right wheels. In this case, as the wheel speed difference between the left and right wheels is larger, it is predicted that the wheel speed difference between the left and right wheels is more likely to be slippery and unstable, for example, when one wheel is locked, when running on a low μ road surface, and when running on a puddle road surface. A map is used in which the larger the amount, the smaller the assist amount is, and the steering force is increased to improve the steering stability and the steering feeling.

(4) In the following step 530, the calculated assist amount is output to perform the assist control, and the present process is ended once. As described above, in the present process, when the wheel speeds of the left and right wheels are high, it is determined that the vehicle is in a slippery and unstable state such as one-wheel lock, traveling on a low μ road surface, and traveling on a puddle road surface. In such a case, since the assist amount is reduced, the steering stability and the steering feeling in an unstable road surface state can be improved.

(5) Control Corresponding to Steering State As shown in FIG. 15, in this processing, in step 600, the wheel speed of each wheel is taken in based on the signal from the wheel speed sensor 7.

In the following step 605, the vehicle speed is calculated in the same manner as in the above-described step 210, using the taken wheel speed. In the following step 610, the steering angle is acquired based on the signal from the steering angle sensor 13. Alternatively, a steering angular velocity is calculated and taken in using the steering angle.

In the following step 620, it is determined based on the acquired steering angle or steering angular velocity and the vehicle speed whether or not the steering state (frequent steering is performed) is an unstable corrected steering state. In other words, as shown by the hatching in FIG. 16, the frequency (the ratio within the predetermined time) of traveling in the region indicated by the predetermined range of the vehicle speed and the predetermined range of the steering angle (or the steering angular speed) is not less than the predetermined frequency. Is determined to be in the corrected steering state. If an affirmative determination is made here, the process proceeds to step 630, while if a negative determination is made, the process proceeds to step 640.

In step 630, since the steering is in the corrected steering state, a correction amount of an assist amount described later is calculated in order to perform more stable steering, and the process proceeds to step 640. This correction amount is for reducing the assist amount. Therefore, a method of reducing the assist amount by a certain amount in one calculation, a method of increasing the amount of reducing the assist amount as the vehicle speed increases, and For example, a method of reducing the assist amount by a predetermined amount over a certain period can be adopted.

In step 640, a process of setting the assist amount is performed using a map as shown in FIG. 17A according to the steering angle or the steering angular velocity. Specifically, by using a map in which the assist amount decreases as the steering angle or the steering angular velocity increases, the steering force increases as the steering angle or the steering angular velocity increases, thereby improving the steering stability and steering feeling. Let it. Further, here, the assist amount is set according to the vehicle speed using a map having a different tendency such as a high speed region, a medium speed region, and a low speed region. Specifically, each map is set so that the assist amount becomes smaller as the vehicle speed increases. Alternatively, as shown in FIG. 17B, the assist amount may be set using a three-dimensional map including the steering angle or the steering angular speed, the vehicle speed, and the assist amount.

(4) If the correction amount is calculated in step 630, a process of subtracting the correction amount from the assist amount set as described above is performed. In the following step 640, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in the present processing, the assist amount decreases as the vehicle body speed and the steering angle (or the steering angular speed) increase, so that the steering stability and the steering feeling in an unstable state such as turning or lane change, for example, are obtained. Can be improved. In this process, the correction steering state is learned, and when it is determined from the steering frequency that the vehicle is in the correction steering state, the correction amount is corrected so as to decrease the assist amount. In addition, steering stability and steering feeling in an unstable state such as a disturbance of a cross wind can be improved.

(6) Control During Acceleration As shown in FIG. 18, in this processing, in step 700, the wheel speed of each wheel is taken in based on the signal from the wheel speed sensor 7.

In the following step 705, the vehicle speed is calculated in the same manner as in the above-mentioned step 210, using the taken wheel speed. In the following step 710, the engine speed is taken in based on the signal from the engine speed sensor 9.

In the following step 720, an engine rotational acceleration is calculated using the obtained engine rotational speed. In the following step 730, based on the calculated engine rotational acceleration, a process for setting the assist amount is performed using a map as shown in FIG. Specifically, by using a map in which the assist amount decreases as the engine rotational acceleration increases, the steering force increases as the acceleration state becomes more remarkable (that is, as the engine rotational acceleration increases), and the steering stability increases. And improve the steering feeling. Further, here, the assist amount is set according to the vehicle speed using a map having a different tendency such as a high speed region, a medium speed region, and a low speed region. Specifically, each map is set so that the assist amount becomes smaller as the vehicle speed increases.

Alternatively, as shown in FIG. 19 (b), the assist amount may be set using a three-dimensional map including the engine rotational acceleration, the vehicle speed, and the assist amount. In the following step 740, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in this processing, the assist amount decreases as the engine rotational acceleration increases, so that the steering stability and the steering feeling in an unstable state such as during acceleration can be improved. Further, in this processing, not only the engine rotational acceleration but also the vehicle speed is taken into account, and the assist amount is reduced as the engine rotational acceleration and the vehicle speed increase, so that the steering stability and the steering feeling can be further improved. .

(7) Control during acceleration and deceleration (1)
As shown in FIG. 20, in this process, in step 800, the wheel speed of each wheel is fetched based on the signal from the wheel speed sensor 7.

(4) In the following step 810, the vehicle speed is calculated in the same manner as in step 210 described above, using the acquired wheel speed. In the following step 820, the vehicle body longitudinal acceleration, which is the longitudinal (acceleration or deceleration) acceleration of the vehicle body, is calculated using the vehicle body speed.

In the following step 830, the assist amount is set based on the vehicle longitudinal acceleration. Specifically, as shown in FIG. 21A, by using a map in which the assist amount decreases as the vehicle body longitudinal acceleration increases, the more the acceleration or deceleration state becomes remarkable (that is, the greater the vehicle body longitudinal acceleration increases). The steering force is increased to improve steering stability and steering feeling. Further, here, the assist amount is set according to the vehicle speed using a map having a different tendency such as a high speed region, a medium speed region, and a low speed region. Specifically, each map is set so that the assist amount becomes smaller as the vehicle speed increases.

Alternatively, as shown in FIG. 21B, the assist amount may be set using a three-dimensional map including the vehicle longitudinal acceleration, the vehicle speed, and the assist amount. In the following step 840, the assist control is performed by outputting the calculated assist amount, and the present process is ended once.

As described above, in this processing, the assist amount decreases as the vehicle longitudinal acceleration (absolute value) increases, so that the steering stability and the steering feeling in an unstable state such as acceleration or deceleration are improved. can do. In addition, in this processing, not only the vehicle longitudinal acceleration but also the vehicle speed is taken into consideration, and the assist amount is reduced as the vehicle longitudinal acceleration and the vehicle speed increase, so that the steering stability and the steering feeling can be further improved. .

Note that, in the case of this processing, the processing may be executed only at a speed lower than the predetermined vehicle speed. This is in order to appropriately cope with such a state, since a low speed is likely to cause an unstable state such as pitching due to a sudden torque fluctuation or the like.

(8) Control during acceleration and deceleration (2)
As shown in FIG. 22, in this process, in step 900, the wheel speed of each wheel is fetched based on the signal from the wheel speed sensor 7.

In the following step 910, the vehicle speed is calculated in the same manner as in the above-described step 210, using the taken wheel speed. In the following step 910, the temporal change rate of the average value of the left and right wheel speeds is calculated using the wheel speeds taken in step 900.

In the following step 920, the assist amount is set based on the temporal change rate of the average value of the left and right wheel speeds. Specifically, as shown in FIG. 23A, by using a map in which the assist amount decreases as the change rate increases, the acceleration or deceleration state becomes more remarkable (ie, as the change rate increases, ) Steering force is increased to improve steering stability and steering feeling. Further, here, the assist amount is set according to the vehicle speed using a map having a different tendency such as a high speed region, a medium speed region, and a low speed region. Specifically, each map is set so that the assist amount becomes smaller as the vehicle speed increases.

Alternatively, as shown in FIG. 23 (b), the assist amount may be set using a three-dimensional map including the change rate, the vehicle speed, and the assist amount. In the following step 940, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in the present process, the assist amount decreases as the temporal change rate of the average value of the left and right wheel speeds increases, so that the steering stability in an unstable state such as during acceleration or deceleration is improved. The steering feeling can be improved. Further, in this processing, not only the change rate but also the vehicle speed is taken into consideration, and the assist amount is reduced as the change rate and the vehicle speed increase, so that the steering stability and the steering feeling can be further improved.

Note that in the case of this processing, the processing may be performed only at a predetermined vehicle speed or higher. This is because in a low-speed range, it is not relatively necessary to attach importance to the steering stability, and the operability is facilitated.

(9) Combined control with suspension control (Part 1)
As shown in FIG. 24, in this processing, in step 1000, the wheel speed of each wheel is fetched based on the signal from the wheel speed sensor 7.

In the following step 1010, the vehicle speed is calculated in the same manner as in step 210 described above, using the obtained wheel speed. In the following step 1020, various sensors for suspension stiffness control (vehicle speed sensitive control, anti-roll control, anti-dive control, anti-squat control, pitch, bounce vibration control) shown in Tables 2 and 3 below are used. It takes in signals and performs necessary operations. Specifically, as shown in Table 2 below, for example, a steering angle, a steering angular velocity, an engine rotation speed, an engine rotation acceleration, a stop lamp SW21, a lateral G, a yaw rate, a vertical G, a height sensor (not shown) Each data such as relative displacement with the car body is taken.

In the following step 1030, the target damping force (by changing the orifice area of the shock absorber) required to perform the respective suspension stiffness control as shown in Tables 2 and 3 based on the acquired data. Set.

で は In the following step 1040, the assist amount is set based on the target damping force. Specifically, as shown in FIG. 25A, by using a map in which the assist amount decreases as the target damping force increases, the steering force increases as the target damping force increases. As a result, the suspension stiffness control and the power steering control act in combination, and the steering stability and the steering feeling are further improved.

As shown in FIG. 25B, using a three-dimensional map including the target damping force, the vehicle speed, and the assist amount, the assist amount decreases as the vehicle speed increases as well as the target damping force. May be set as follows. In the following step 1050, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in the present process, the assist amount is reduced as the target damping force in the various suspension stiffness controls increases, so that the steering stability and the steering feeling are further improved as compared with the control that simply performs the power steering control. be able to.

In addition, in the present process, not only the target damping force but also the vehicle speed is taken into consideration, and the assist amount is reduced as the target damping force and the vehicle speed increase, so that the steering stability and the steering feeling can be further improved. it can. In this process, the suspension stiffness control is performed by calculating the target damping force. However, separately from this, the target value of the spring constant of the air spring, the target value of the control of the hydraulic stabilizer, or the target value of the vehicle height control Or the like may be calculated, and control may be performed using the calculated rigidity target value.

(10) Combined control with suspension control (part 2)
As shown in FIG. 26, in this processing, in step 1100, the wheel speed of each wheel is fetched based on the signal from the wheel speed sensor 7.

In the following step 1110, the vehicle speed is calculated in the same manner as in step 210 described above, using the taken wheel speed. In the following step 1120, based on the signal from the mode switch SW23, data indicating whether the current suspension setting mode is the (soft-eye) normal mode or the (soft-eye) sports mode is fetched.

In the following step 1130, the assist amount is set based on the state of this mode and the vehicle speed. More specifically, as shown in FIG. 27A, in both the normal mode and the sports mode, the assist amount is set to decrease as the vehicle speed increases, but in the sports mode, the normal mode is set. The assist amount is set lower than in the case of. That is, the steering force is set heavier in the sport mode. As a result, the suspension stiffness control and the power steering control act in combination, and the steering stability and the steering feeling are further improved.

As shown in FIG. 27B, using the three-dimensional map including the target damping force, the vehicle speed, and the assist amount described above, not only the mode, but also the assist as the target damping force and the vehicle speed increase. The amount may be set to be small. In the following step 1140, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in the present process, the assist amount is adjusted according to the operation state of the mode switching SW 23, so that the steering stability and the steering feeling can be further improved as compared with the control of simply performing the power steering control. . In addition, in this processing, not only the state of the mode but also the target damping force and the vehicle speed are taken into consideration, and the assist amount is reduced as the target damping force and the vehicle speed are increased, so that the steering stability and the steering feeling are further improved. Can be improved.

In this process, the suspension stiffness control is performed by calculating the target damping force. However, separately from this, the target value of the spring constant of the air spring, the target value of the control of the hydraulic stabilizer, or the target value of the vehicle height control Or the like may be calculated, and control may be performed using the calculated rigidity target value.

(11) Combined control with suspension control according to the tilting state and unsprung state of the vehicle, as shown in FIG. 28, in this processing, in step 1200, the wheels Capture wheel speed.

In the following step 1210, the vehicle speed is calculated based on the wheel speed. In the following step 1220, in the same manner as in step 310 described above, the resonance frequency component on the spring (for example, 1 Hz to 2 Hz) and the resonance frequency component below the spring (for example, 10 Hz to 20 Hz). Here, when the sprung resonance frequency component is 1 Hz to 2 Hz, the vehicle shows a fluttering (tilt) state. On the other hand, when the unsprung resonance frequency component is 10 Hz to 20 Hz, the vehicle flutters ( The state of the vehicle is unstable, which is not preferable. Either the sprung resonance frequency component or the unsprung resonance frequency component may be extracted, or both may be extracted.

In the following step 1230, a target stiffness value is calculated in accordance with the extracted sprung or sprung resonance frequency component in order to perform suitable vehicle control related to suspension stiffness control, that is, to suppress tilt and flutter. Specifically, for example, a target damping force of the shock absorber is calculated.

In the following step 1240, a control signal based on the calculated target damping force is output to the damping force switching actuator 29. In the following step 1250, the assist amount is set based on the target damping force. Specifically, using a map as shown in FIG. 29A, the setting is made such that the assist amount decreases as the target damping force increases. As a result, the suspension stiffness control and the power steering control act in combination, and the steering stability and the steering feeling are further improved.

As shown in FIG. 29B, using a three-dimensional map including the target damping force, the vehicle speed and the assist amount, the assist amount is set to decrease as the target damping force and the vehicle speed increase. May be. In the following step 1260, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in the present process, the suspension stiffness control is performed by extracting the sprung / lower resonance frequency components, setting the target damping force so as to suppress the tilt and flutter, and according to the target damping force. Since the assist amount is adjusted, steering stability and steering feeling can be further improved as compared with the control of simply performing power steering control.

In addition, in this processing, not only the target damping force but also the vehicle speed is taken into consideration, and the assist amount is reduced as the vehicle speed increases, so that the steering stability and the steering feeling can be further improved. In this process, the suspension stiffness control is performed by calculating the target damping force. However, separately from this, the target value of the spring constant of the air spring, the target value of the control of the hydraulic stabilizer, or the target value of the vehicle height control Or the like may be calculated, and control may be performed using the calculated rigidity target value.

(12) Combined Control with Suspension Control According to Steering State As shown in FIG. 30, in this processing, in step 1300, the wheel speed of each wheel is taken in based on the signal from the wheel speed sensor 7.

In the following step 1310, the vehicle speed is calculated based on the wheel speed. In the following step 1320, the steering angle is acquired based on the signal from the steering angle sensor 13, as in step 120 described above. The angular velocity may be calculated and taken in using the steering angle.

In the following step 1330, in order to perform suitable control of the vehicle with respect to the suspension stiffness control according to the acquired steering angle and / or steering angular velocity, that is, to control the unstable vehicle when the steering is largely or rapidly performed. A stiffness target value that suppresses the operation is calculated. Specifically, for example, a target damping force of the shock absorber is calculated.

In the following step 1340, a control signal based on the calculated target damping force is output to the damping force switching actuator 29. In the following step 1350, the assist amount is set based on the target damping force. Specifically, using a map as shown in FIG. 31A, the setting is made such that the assist amount decreases as the target damping force increases. As a result, the suspension stiffness control and the power steering control act in combination, and the steering stability and the steering feeling are further improved.

As shown in FIG. 31B, using a three-dimensional map including the target damping force, the vehicle speed, and the assist amount, setting is made such that the assist amount decreases as the target damping force and the vehicle speed increase. May be. In the following step 1360, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in this processing, the target damping force is set based on the steering angle and / or the steering angular velocity to perform the suspension stiffness control, and the assist amount is adjusted according to the target damping force. Steering stability and steering feeling can be further improved as compared with the control of simply performing power steering control during turning or lane change.

In addition, in this processing, not only the target damping force but also the vehicle speed is taken into consideration, and the assist amount is reduced as the vehicle speed increases, so that the steering stability and the steering feeling can be further improved. In this process, the suspension stiffness control is performed by calculating the target damping force. However, separately from this, the target value of the spring constant of the air spring, the target value of the control of the hydraulic stabilizer, or the target value of the vehicle height control Or the like may be calculated, and control may be performed using the calculated rigidity target value.

(13) Combined Control with Suspension Control According to Steering State As shown in FIG. 32, in this processing, in step 1400, the wheel speed of each wheel is fetched based on the signal from the wheel speed sensor 7.

In the following step 1410, the vehicle speed is calculated based on the wheel speed. In the following step 1415, the engine speed is taken in based on the signal from the engine speed sensor 9. In the following step 1420, the engine rotational acceleration is calculated based on the engine rotational speed.

In the following step 1430, a signal from the stop lamp SW21 is taken in to detect a brake operation. In the following step 1440, the vehicle body longitudinal acceleration, which is the longitudinal (acceleration or deceleration) acceleration of the vehicle body, is estimated using the engine rotational acceleration. Here, instead of using the engine rotation acceleration, the vehicle body longitudinal acceleration may be obtained using the vehicle body speed in the same manner as in step 820 described above.

In the following step 1450, in order to perform suitable vehicle control relating to suspension stiffness control in accordance with the vehicle longitudinal acceleration and the state of the stop lamp SW21, that is, to control an unstable vehicle when sudden acceleration or sudden braking is performed. A stiffness target value that suppresses the operation is calculated. Specifically, for example, a target damping force of the shock absorber is calculated.

In the following step 1460, a control signal based on the calculated target damping force is output to the damping force switching actuator 29. In the following step 1470, the assist amount is set based on the target damping force. Specifically, using a map as shown in FIG. 33 (a), the setting is made so that the assist amount decreases as the target damping force increases. As a result, the suspension stiffness control and the power steering control act in combination, and the steering stability and the steering feeling are further improved.

As shown in FIG. 33 (b), using a three-dimensional map including the target damping force, the vehicle speed and the assist amount, setting is made such that the assist amount decreases as the target damping force and the vehicle speed increase. May be. In the following step 1480, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in the present process, the target damping force is set based on the vehicle longitudinal acceleration and the state of the stop lamp SW21, the suspension stiffness is controlled, and the assist amount is adjusted according to the target damping force. For example, in the case of sudden acceleration, sudden braking, or the like, steering stability and steering feeling can be further improved as compared with control that simply performs power steering control.

In addition, in this processing, not only the target damping force but also the vehicle speed is taken into consideration, and the assist amount is reduced as the vehicle speed increases, so that the steering stability and the steering feeling can be further improved. In this process, the suspension stiffness control is performed by calculating the target damping force. However, separately from this, the target value of the spring constant of the air spring, the target value of the control of the hydraulic stabilizer, or the target value of the vehicle height control Or the like may be calculated, and control may be performed using the calculated rigidity target value.

(14) Control at the time of disconnection of wheel speed sensor As shown in FIG. 34, in this process, in step 1500, the wheel speed of each wheel is taken in based on the signal from the wheel speed sensor 7.

In the following step 1510, the disconnection state of the wheel speed sensor 7 is detected as shown in Table 4 below.

In the following step 1520, it is determined whether or not there is a disconnection. If it is determined that the disconnection has occurred, the process proceeds to step 1530. If it is determined that the disconnection has not occurred, the process proceeds to step 1540. In step 1530, the vehicle speed is calculated according to the normal wheel speed as shown in Table 5 below.

On the other hand, in step 1540, the vehicle speed is calculated from the information of all the wheels. In the following step 1550, the assist amount is set according to the calculated vehicle speed. In the following step 1560, the calculated assist amount is output to perform the assist control, and the present process is ended once.

As described above, in the present process, the disconnection of the wheel speed sensor 7 is detected, and the correct vehicle speed is calculated based on the output from the normal wheel speed sensor 7, thereby appropriately controlling the power steering. Can be. Further, since a plurality of wheel speeds are detected and used, there is an effect that the redundancy of the system is increased and the reliability is improved.

Note that the present invention is not limited to the above-described embodiment at all, and it goes without saying that the present invention can be implemented in various modes within the scope of the present invention.

FIG. 2 is a schematic configuration diagram illustrating the configuration of the first aspect of the invention. FIG. 2 is an explanatory diagram illustrating a hardware configuration according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating an electrical configuration of the embodiment. 5 is a flowchart illustrating basic processing of the embodiment. It is a flowchart which shows the process using the wheel speed of (1). 4 is a graph illustrating a relationship between an assist amount and a vehicle speed in the process of (1). 9 is a graph showing another relationship between the assist amount and the vehicle speed in the processing of (1). It is a flowchart which shows the process using the resonance frequency component of (2). 9 is a graph showing a relationship between an assist amount and a resonance frequency component of the process (2). 6 is a graph illustrating a relationship between an assist amount and a resonance frequency component of the process (2). It is a flowchart which shows the process using horizontal G etc. of (3). It is a graph which shows the relationship between the assist amount of processing of (3), and horizontal G etc. It is a flowchart which shows the process using the right and left wheel speed difference of (4). It is a graph which shows the relationship between the assist amount of the process of (4), and the wheel speed difference on either side. It is a flowchart which shows the process according to the steering state of (5). It is a graph which shows the correction steering state of the processing of (5). It is a graph which shows the relationship between the assist amount of a process of (5), a steering state, and a vehicle body speed. It is a flowchart which shows the process using engine rotation acceleration of (6). It is a graph which shows the relationship between the assist amount of processing of (6), engine rotational acceleration, and vehicle speed. It is a flowchart which shows the process using the vehicle body longitudinal acceleration of (7). It is a graph which shows the relationship between the assist amount of the process of (7), the vehicle longitudinal acceleration, and the vehicle speed. It is a flowchart which shows the process using the change rate of the average value of right and left wheel speed of (8). It is a graph which shows the relationship between the assist amount of the process of (8), the change rate of the average value of right and left wheel speed, and vehicle speed. It is a flowchart which shows the process using the target damping force of the suspension control of (9). In the process (9), (a) is a graph showing the relationship between the assist amount and the target damping force, and (b) is a graph showing the relationship between the assist amount, the target damping force and the vehicle speed. It is a flowchart which shows the process using the mode switching SW of (10). In the process (10), (a) is a graph showing the relationship between the assist amount, the mode, and the vehicle speed, and (b) is a graph showing the relationship between the assist amount, the target damping force, and the vehicle speed. It is a flowchart which shows the process using the resonance frequency component and target damping force of (11). In the processing of (11), (a) is a graph showing the relationship between the assist amount and the target damping force, and (b) is a graph showing the relationship between the assist amount, the target damping force and the vehicle speed. It is a flowchart which shows the process using a steering state and target damping force of (12). In the process (12), (a) is a graph showing the relationship between the assist amount and the target damping force, and (b) is a graph showing the relationship between the assist amount, the target damping force, and the vehicle speed. It is a flowchart which shows the process using acceleration etc. and target damping force of (13). In the process (13), (a) is a graph showing the relationship between the assist amount and the target damping force, and (b) is a graph showing the relationship between the assist amount, the target damping force, and the vehicle speed. It is a flowchart which shows the process at the time of detecting the abnormality of a sensor of (14).

Explanation of reference numerals

1. Electronic control unit (ECU)
3 ... Power steering 5 ... Shock absorber 7 ... Wheel speed sensor 9 ... Engine rotation speed sensor 13 ... Steering angle sensor 15 ... Vertical G sensor)
17: Horizontal G sensor 19: Collate sensor 21: Stop lamp SW
23: Mode switching SW
25 ... Hydraulic motor 29 ... Damping force actuator

Claims (3)

In a power stearing device that adjusts an assist amount, which is an auxiliary steering force applied to a steering,
Wheel speed detecting means for detecting wheel speed,
Steering angle detecting means for detecting a steering angle,
Body state detecting means for detecting the lateral G or the yaw rate;
Based on the wheel speeds detected by the wheel speed detection means, a vehicle speed calculation means for calculating a vehicle speed,
Based on the vehicle speed and the steering angle detected by the vehicle speed detection unit and the steering angle detection unit, a vehicle state calculation unit that calculates a standard lateral G or yaw rate,
Assist amount setting means for setting an assist amount for power steering based on the lateral G or yaw rate of the reference calculated by the vehicle body state calculating means and the lateral G or yaw rate detected by the vehicle body state detecting means;
A power steering device comprising: A road surface μ is estimated based on the reference lateral G or yaw rate calculated by the vehicle body state calculating means and the lateral G or yaw rate detected by the vehicle body state detecting means. The power steering apparatus according to claim 1, wherein an assist amount is set. The power steering apparatus according to claim 1 or 2, wherein the assist amount of the power steering is reduced as the road surface μ decreases.

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