Vehicle control apparatus

Abstract: A vehicle behavior during driving is correctly grasped by computing and map-retrieving from on output signal (ωy) of an angular velocity sensor (2) for detecting the angular velocity of the vehicle. A vehicle control apparatus of the present invention can correctly compensate an output signal (ωy) having an error owing to the secular change or temperature change, etc. by using a zero-point calculation means (6) for calculating a zero-point signal (ωy0) and an angular velocity correction means (7) for correcting the output signal (ωy) of the angular velocity sensors (2).

Description: FIELD OF THE INVENTION AND RELATED ART STATEMENT 1.FIELD OF THE INVENTION The present invention relates to a vehicle control apparatus for controlling a vehicle posture by changing the damping force of shockabsorber so as to get the driving stability and riding comfort in response to the driving state of the vehicle. 2.DESCRIPTION OF THE RELATED ART When a vehicle passes over a big projection of an uneven road, the vehicle receives a great shock from the projection in a vertical direction of the vehicle. This great shock received by the vehicle is called a bottoming motion. When a vehicle is driving on an undulated surface road, the vehicle makes periodical motion in a vertical direction by resonance of the sprung suspension. This periodical motion of the vehicle is called a bouncing motion. Inventors of the present invention have disclosed a suspension control apparatus for decreasing such a bottoming motion and the bouncing motion in EP-A-428 096, which is part of the prior art according to Art.54(3)EPC. The suspension control apparatus which was disclosed by the inventors has a pitch angular velocity sensor for detecting the bottoming motion or the bouncing motion. Thereby, the vehicle behavior is grasped and the damping force of the shockabsorbers is controlled in response to the vehicle behavior. As a result, the driving stability and riding comfort have been improved by the above-mentioned suspension control apparatus. Furthermore, EP-A-424 843, which is part of the prior art according to Art.54(3)EPC, discloses another suspension control apparatus which was invented by the inventors of the present invention. This suspension control apparatus has a yaw angular velocity sensor for detecting the rolling motion of the vehicle during cornering or turning. Thereby, the vehicle behavior during turning is grasped and the damping force of the shockabsorbers are controlled in response to the turning vehicle behavior. A pitch angular velocity, which is detected by the above-mentioned pitch angular velocity sensor, is an angular velocity in a rotation about a lateral axis (pitch axis) of the vehicle. A yaw angular velocity, which is detected by the above-mentioned yaw angular velocity sensor, is an angular velocity in a rotation about a vertical line (yaw axis) at the center of the vehicle. FIG.12 shows a characteristic diagram of output signals of these angular velocity sensors. A line C in FIG.12 shows a typical characteristic of an output signal of the angular velocity sensor for sensing the angular velocity of the vehicle. As shown by the line C, when the angular velocity is "0", that is, the vehicle is moving on a straight line or at a stop, the angular velocity sensor issues a zero-point signal ωy0 to indicate the zero-point of the angular velocity. However, the zero-point signal ωy0 issued at a straight line moving or a stop of the vehicle is liable to change owing to a secular change and/or temperature change, etc. For example, when the above-mentioned line C is drifted to a line D or E, the angular velocity sensor issues another zero-point signal ωy1 or ωy2 in spite of that the vehicle is moving on the straight line or at the stop. As a result, the exact angular velocity of the vehicle can not be precisely detected by the conventional angular velocity sensor, and the suspensions of the vehicle can not be correctly controlled in response to the vehicle posture. WO-A-89/00927 discloses a vehicle control apparatus according to the preamble of claim 1 comprising a vehicle speed sensor detecting the speed of the vehicle; a vehicle attitude sensor in form of an acceleration sensor; a zero-point calculation means which detects a normal state of the vehicle by using output signals of the vehicle speed sensor and output signals of the vehicle attitude sensor, and which calculates a zero-point signal of the vehicle attitude sensor; correction means which corrects the output signal of the vehicle attitude sensor by using the zero-point signal calculated by the zero-point calculation means; a turning state inference means which infers a rolling state of the vehicle from the corrected signal of the correction means and the output signal of the vehicle speed sensor, and further produces output signals for controlling to decrease the rolling state; and shock absorber means whereof damping force is adjusted in response to output signals from the turning state inference means. OBJECT AND SUMMARY OF THE INVENTION An object of the present invention is to provide a vehicle control apparatus which can correctly correct the drift value of the zero-point signal of the angular velocity sensor receiving the secular change and/or temperature change, etc. The above-mentioned object is achieved by a vehicle control apparatus according to claim 1. While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a perspective view showing principal parts of a first embodiment of a vehicle control apparatus of the present invention in a vehicle shown with alternate long and short dash lines. FIG.2 is a block diagram of the vehicle control apparatus shown in FIG.1. FIG.3 is a flowchart of operation of the first embodiment of the vehicle control apparatus. FIG.4 is a block diagram of a second embodiment of the vehicle control apparatus of the present invention. FIG.5 is a characteristic diagram of the output signal of an angular velocity sensor of the vehicle control apparatus shown in FIG.4. FIG.6 is a flowchart of operation of the second embodiment of the vehicle control apparatus. FIG.7 is a block diagram of a third embodiment of the vehicle control apparatus of the present invention. FIG.8 is a characteristic diagram of a low-pass digital filter of the third embodiment of the vehicle control apparatus. FIG.9 is a waveform of an input signal of the low-pass digital filter of the third embodiment. FIG.10 is a waveform of an output signal of the low-pass digital filter of the third embodiment. FIG.11 is a flowchart of operation of the third embodiment of the vehicle control apparatus. FIG.12 is a characteristic diagram of the angular velocity sensor. It will be recognized that some or all of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of the elements shown. DESCRIPTION OF THE PREFERRED EMBODIMENTS 〈FIRST EMBODIMENT〉 Hereafter, a first embodiment of the vehicle control apparatus of the present invention is elucidated with reference to the accompanying drawings of FIGs. 1 through 3. A suspension control apparatus as the first embodiment of the vehicle control apparatus controls a rolling state of the vehicle during turning. FIG.1 is a perspective view showing a principal part of the suspension control apparatus which is disposed in a vehicle 11 shown with alternate long and short dash lines. The suspension control apparatus comprises a vehicle speed sensor 1, a yaw angular velocity sensor 2, shockabsorbers 3, actuators 4 and a controller 5. The vehicle speed sensor 1, which is disposed in a front grill adjacent a speed meter, produces a signal responding to the vehicle speed by detecting the revolution speed of an output shaft of a gearbox in the vehicle 11. The yaw angular velocity sensor 2 is provided to detect an angular velocity of rotation about a vertical line substantially at the center of the vehicle 11, that is about a yaw axis B of the vehicle 11. The directions of the rotation are shown with an arrow A in FIG.1. The yaw angular velocity sensor 2, for instance described in U.S. Pat. No. 4,671,112 which is issued June 9, 1987 and filed by same assignee is usable. The shockabsorbers 3 damp the force received by wheels of the vehicle 11. The actuators 4, which are provided on the shockabsorbers 3, control the damping force of these shockabsorbers 3. The controller 5, which is disposed in appropriate space, such as under the back seat or in the trunk, produces the output signal for controlling the damping force of the shockabsorber 3. The actuator 4 operates the shock absorber 3 by receiving a signal which is produced by the controller 5 in response to the output signals of the vehicle speed sensor 1 and the yaw angular velocity sensor 2. FIG.2 is a block diagram of the suspension control apparatus of the first embodiment. As shown in FIG.2, the controller 5 is constituted by an arithmetic unit 10 and an operation circuit 9. The arithmetic unit 10 comprises a zero-point calculation means 6, an angular velocity correction means 7 and a turning state inference means 8. The zero-point calculation means 6 detects a straight line driving state on the flat surface of the road or a stopping state (thereafter, such state is abbreviated to normal state) by using output signals V of the vehicle speed sensor 1 and output signals ωy of the yaw angular velocity sensor 2. The zero-point calculation means 6 calculates a value of a zero-point signal ωy0 of the yaw angular velocity sensor 2. In other words, the zero-point calculation means 6 regards an output signal of the yaw angular velocity sensor 2 as the zero-point signal ωy0 when the vehicle 11 is in the normal state. The angular velocity correction means 7 calculates a deviation between the calculated zero-point signal ωy0 and the detected output signal ωy of the yaw angular velocity sensor 2, and calculates a corrected value ωyA for the yaw angular velocity sensor 2. The turning state inference means 8 infers a rolling state of the turning vehicle 11 from the output signal V of the vehicle speed sensor 1 and the above-mentioned corrected value ωyA of the angular velocity correction means 7, and produces an output signal for controlling to decrease the rolling state. Table 1 below shows the map of operating parameters for the turning state inference means 8 wherein the inferred rolling state caused by the turning vehicle is issued by retrieving the map by using the output signal V of the vehicle speed sensor 1 and the corrected value ωyA of the yaw angular velocity sensor 2. DUMP 0, DUMP 1, DUMP 2, ---, DUMP 10 in the Table 1 indicate different relative damping rates of the shockabsorber 3. DUMP 0 is usually the damping rate during the while the vehicle is normally driving (i.e. straight). The damping rate DUMP0 is given by the following equation (1): DUMP0 = C 2 M·K where C is the damping coefficient (unit: N·sec. / m) of the shockabsorber 3 during the while the vehicle is normally driving (i.e. straight), M is the sprung mass (unit: N·sec. 2 / m), and K is the spring constant (unit: N / m) of the suspension. DUMP 0, DUMP 1, DUMP 2, ---, DUMP 10 are set up to satisfy the following inequity (2): DUMP 0 < DUMP 1 < DUMP 2 < DUMP 3 < DUMP 4 < DUMP 5 < DUMP 6 < DUMP 7 < DUMP 8 < DUMP 9 < DUMP 10 Table 2 below shows the operating parameters which are found preferable through experiments. As shown in FIG.2, the operation circuit 9 which receives the output signal of the turning state inference means 8 produces signals for driving each actuator 4. The actuators 4 control the damping force of the shockabsorbers 3. The arithmetic unit 10, which includes the zero-point calculation means 6, the angular velocity correction means 7 and the turning state inference means 8, comprises an A/D converter and a logical circuit having a CPU, a ROM and a RAM. Apart from the above-mentioned first embodiment wherein the rolling state of the vehicle 11 during the turning is inferred with the above-mentioned map, a modified embodiment may be such that the rolling state of the vehicle is inferred by computing the output signal V of the vehicle speed sensor 1 and the output signal ωy of the yaw angular velocity sensor 2. FIG.3 shows a flowchart in the arithmetic unit 10 of the controller 5 of the suspension control apparatus in accordance with the present invention. In step 501 of FIG.3, the output signal V from the vehicle speed sensor 1 and the output signal ωy from the yaw angular velocity sensor 2 are detected. Next, in step 502, it is judged whether an absolute value of a change rate ΔV of the vehicle speed V is on or below the predetermined change rate ΔVc, e.g. 0.1km/h/sec. In case of being below the predetermined change rate ΔVc, that is when the below-mentioned inequity (3) |ΔV| ≦ ΔVc is satisfied by the detected change rate ΔV, it is judged whether an absolute value of a change rate Δωy of the yaw angular velocity is on or below the predetermined change rate Δωyc, e.g. 0.3deg/sec/sec. In case of being below the predetermined change rate Δωyc, that is when the below-mentioned inequity (4) |Δωy| ≦ Δωyc is satisfied by the detected change rate Δωy, the arithmetic unit 10 judges that the vehicle 11 is in the normal state. When the arithmetic unit 10 judges "YES" in step 503, it is judged whether the normal state is continued for a predetermined time interval T m , e.g. 5 sec. or not, in step 504. When the normal state is continued for the predetermined time interval T m or more, the arithmetic unit 10 judges that the yaw angular velocity of the vehicle 11 is substantially of a negligible value, e.g. substantially at a "zero-point" of the yaw angular velocity, and the sequence thereafter goes to step 505. In step 505, the zero-point calculation means 6 calculates an average of the output signals ωy from the yaw angular velocity sensor 2, and the calculated average value is stored as a new value of the zero-point signal ωy0. The sequence thereafter goes to step 506 so as to keep the damping force of the shockabsorbers 3 at the usual damping rate. In the above-mentioned steps 502 and 503, when the arithmetic unit 10 judges "NO", that is, the vehicle 11 is not in the normal state, the zero-point signal calculation routine has been finished and a timer for detecting the duration of the normal state is reset in step 507. In step 508, the angular velocity correction means 7 corrects the detected output signal ωy of the yaw angular velocity sensor 2 by using the corrected value ωyA given by the following equation (5): ωyA = ωy - ωy0 The corrected value ωyA of the yaw angular velocity is calculated by using the zero-point signal ωy0 stored in the arithmetic unit 10. In step 509, it is judged, by using the corrected value ωyA calculated in step 508, whether the vehicle 11 is turning or not. When the arithmetic unit 10 judges "YES" in step 509, that is, the vehicle 11 is in a turning state, the sequence thereafter goes to step 510. In step 510, the turning state inference means 8 infers the rolling state during turning by retrieving the map (the aforementioned Table 1) with the output signal V of the vehicle speed sensor 1 and the corrected value ωyA of the yaw angular velocity sensor 2. As a result, the suspension control apparatus of the first embodiment makes a control to increase the damping force of the shock-absorbers 3 in step 511. On the contrary, when the arithmetic unit 10 in step 509 judges "NO", the damping force of the shock-absorbers 3 is kept at the ordinary damping rate during normal driving (straight) in step 506. Thus, according to the first embodiment of the vehicle control apparatus of the present invention, the drift value of the detected zero-point signal owing to the secular change and/or the temperature change, etc. can be precisely corrected by function of the vehicle control apparatus, which comprises a zero-point calculation means for calculating a zero-point signal of an angular velocity sensor by using average data of output signals of an angular velocity sensor, and an angular velocity correction means for calculating a deviation between the output signals detected by the angular velocity sensor and the calculated zero-point signal in the zero-point calculation means. As a result, the suspensions of the vehicle can be correctly controlled by the vehicle control apparatus of the present invention. 〈SECOND EMBODIMENT〉 Hereafter, a second embodiment of the vehicle control apparatus of the present invention is elucidated with reference to the accompanying drawings of FIGs. 4 through 6. A suspension control apparatus as the second embodiment of the vehicle control apparatus also controls the rolling state of the vehicle during turning, using an output signal corrected by means of the change rate of the zero-point signal, apart from using the output signal in the normal state in the first embodiment. Corresponding parts and components to the first embodiment are shown by the same numerals and marks, and the description thereon made in the first embodiment similarly applies. Differences and features of this second embodiment from the first embodiment are as follows. FIG.4 is a block diagram of the suspension control apparatus of the second embodiment. As shown in FIG.4, the controller 5 of the second embodiment is constituted by an arithmetic unit 100 and an operation circuit 9. The arithmetic unit 100 comprises a zero-point calculation means 16, an angular velocity correction means 17 and a turning state inference means 18. The zero-point calculation means 16 detects a straight line driving state on the flat surface of the road or a stopping state (hereafter, such state is abbreviated to normal state) by using output signals V of a vehicle speed sensor 1 and output signals ωy of a yaw angular velocity sensor 2. The zero-point calculation means 16 calculates a change rate Δωy of the value of a zero-point signal ωy0 of the yaw angular velocity sensor 2 (at the time T) and a drift value ωd of the zero-point signal ωy0 of the yaw angular velocity sensor 2. The angular velocity correction means 17 corrects the detected output signal ωy of the yaw angular velocity sensor 2, and calculates a corrected value ωyA for the yaw angular velocity sensor 2. The turning state inference means 18 infers the rolling state of the turning vehicle 11 from the output signal V of the vehicle speed sensor 1 and the corrected value ωyA of the angular velocity correction means 17, and thereby produces an output signal for controlling to decrease the rolling state by retrieving the map (the aforementioned Table 1 in the first embodiment). The operation circuit 9 which receives the output signal of the turning state inference means 18 produces signals for driving each actuator 4. The actuators 4 control the damping force of the shock-absorbers 3. FIG.5 is a characteristic diagram of output signals from the yaw angular velocity sensor 2 in the suspension control apparatus of the second embodiment. FIG.6 is a flowchart of operation of the second embodiment. In FIG.5, when the vehicle 11 is in the normal state at the time indicated by a normal state time Tn, the yaw angular velocity sensor 2 issues an output signal ωyn. When the vehicle 11 is in the next normal state at the time indicated by a next normal state time Tn+1, the yaw angular velocity sensor 2 may issue a drifted output signal ωyn+1 owing to the secular change and/or temperature change and so on. As shown in FIG.5, the output signal ωy of the yaw angular velocity sensor 2 is drifting at a substantially constant change rate. Therefore, the change rate Δωy and a drift value ωd of the yaw angular velocity sensor 2 is calculated by the following equations in the zero-point calculation means 16. The change rate Δωy1 of the zero-point signal ωy0 between the normal state time Tn and the next normal state time Tn+1 is given by the following equation (6): Δωy1 = (ωyn+1 - ωyn) / (Tn+1 - Tn) and the drift value ωd of the zero-point signal ωy0 at the present time T after the normal state time Tn+1 is given by the following equation (7): ωd = Δωy1 × (T - Tn+1) Therefore, a present zero-point signal ωy0 of the yaw angular sensor 2 is given by the following equation (8): ωy0 = ωd + ωyn+1 When the vehicle 11 is in the next normal state at the time indicated by a normal state time Tn+2, the yaw angular velocity sensor 2 issues another output signal ωyn+2. The new change rate Δωy2 of the zero-point signal ωy0 between the previous normal state time Tn+1 and the normal state time Tn+2 is calculated by the zero-point calculation means 16 in the same way as by the aforementioned equation (6). Thereafter, a zero-point signal ωy0 and a drift value ωd after the normal state time Tn+2 are calculated by using the new change rate Δωy2 as by aforementioned equations (7) and (8). FIG.6 show a flowchart of the arithmetic unit 100 of the controller 5 in the suspension control apparatus of the second embodiment in accordance with the present invention. In step 701 of FIG.6, the output signal V from the vehicle speed sensor 1 and the output signal ωy from the yaw angular velocity sensor 2 are detected. Next, in step 702, it is judged whether a change rate ΔV of the vehicle speed V is on or below the predetermined change rate ΔVc (e.g. 0.1 km/h/sec). When the aforementioned formula (3) in the first embodiment is satisfied by the detected change rate ΔV, it is judged whether a change rate Δωy of the yaw angular velocity is on or below the predetermined change rate Δωyc (e.g. 0.3deg/sec/sec) in step 703. When the aforementioned formula (4) is satisfied by the detected change rate Δωy, the arithmetic unit 100 judges that the vehicle 11 is in the normal state. When the arithmetic unit 100 judges "YES" in step 703, it is judged whether the normal state is continued for a predetermined time interval Tm (e.g. 5 sec.) or not in step 704. When the normal state is continued for the predetermined time interval Tm over, the arithmetic unit 100 judges that the yaw angular velocity of the vehicle 11 is substantially zero, namely, at a "zero-point" of the yaw angular velocity, the sequence thereafter goes to step 705. In step 705, the detected output signal ωy of the yaw angular velocity sensor 2 is stored as new zero-point signal (ωy0=ωy). Next, in step 706, the zero-point calculation means 16 calculates the change rate Δωy of the yaw angular velocity by the aforementioned formula (6). The sequence thereafter goes to step 707 so as to keep the damping force of the shockabsorbers 3 at the usual damping rate. In the above-mentioned step 702 or 703, when the arithmetic unit 100 judges "NO", that is, the vehicle 11 is not in the normal state, the zero-point signal calculation routine has been finished and a timer for detecting the duration of the normal state is reset in step 708, and the sequence goes to step 709. When the arithmetic unit 100 judges "NO" in step 704, the drift value ωd and zero-point signal ωy0 are calculated by the formulas (7) and (8) in the zero-point calculation means 16 in step 709. The drift value ωd is calculated by using the change rate Δωy stored at the previous zero-point calculation routine. In step 710, the detected output signal ωy of the yaw angular velocity sensor 2 is corrected to the corrected value ωyA by calculating the aforementioned formula (5) in the angular velocity correction means 17. In step 711, it is judged by the corrected value ωyA calculated in step 710 whether the vehicle 11 is turning or not. When the arithmetic unit 100 judges "YES" in step 711, that is, the vehicle 11 is in turning state, the sequence thereafter goes to step 712. In step 712, the turning state inference means 18 infers the rolling state during turning by retrieving the map (the aforementioned Table 1) with the output signal V of the vehicle speed sensor 1 and the corrected value ωyA of the yaw angular velocity sensor 2. As a result, the suspension control apparatus of the second embodiment controls to increase the damping force of the shock-absorbers 3 in step 713. On the contrary, when the arithmetic unit 100 in step 711 judges "NO", the damping force of the shock-absorbers 3 is kept at the ordinary damping rate during normal driving (straight), in step 707. Thus, according to the second embodiment of the vehicle control apparatus of the present invention, the deviation of the zero-point signal of the angular velocity sensor can be precisely calculated by function of the vehicle control apparatus which infers the drift value of the zero-point signal during driving from the changing ratio of the zero-point signal which is detected during moving the vehicle on straight line or at a stop. As a result, the suspensions of the vehicle can be appropriately controlled in response to the vehicle driving state. 〈THIRD EMBODIMENT〉 Hereafter, a third embodiment of the vehicle control apparatus of the present invention is elucidated with reference to the accompanying drawings of FIG. 7 to 11. A suspension control apparatus as the third embodiment of the vehicle control apparatus also controls the rolling state of the vehicle during turning, using an output signal of a low-pass filter of a zero-point calculation means 26, apart from using an output signal corrected by means of the change rate of the zero-point signal. Corresponding parts and components to the first embodiment are shown by the same numerals and marks, and the description thereon made in the first embodiment similarly applies. Differences and features of this third embodiment from the first embodiment are as follows. FIG.7 is a block diagram of the suspension control apparatus of the third embodiment. As shown in FIG.7, the controller 5 of the third embodiment is constituted by an arithmetic unit 200 and an operation circuit 9. The arithmetic unit 200 comprises a zero-point calculation means 26, an angular velocity correction means 27 and a turning state inference means 28. The zero-point calculation means 26, which comprises a low-pass digital filter, eliminates undesirable output signals for detecting a change of the zero-point signal ωy0 of the yaw angular velocity sensor 2. The undesirable output signals of the yaw angular velocity sensor 2 are generated owing to the rolling and the vibrating of the vehicle 11. The zero-point calculation means 26 detects the drifted zero-point signal ωy0 owing to the secular change and/or the temperature change, etc. The angular velocity correction means 27 corrects the detected output signal ωy of the yaw angular velocity sensor 2, and calculates a corrected value ωyA of the yaw angular velocity sensor 2. The turning state inference means 28 infers the rolling state of the moving vehicle 11 from the output signal V of the vehicle speed sensor 1 and the corrected value ωyA of the angular velocity correction means 27, and thereby produces an output signal for controlling to decrease the rolling state by retrieving the map (the aforementioned table 1 in the first embodiment). The operation circuit 9 which receives the output signal of the turning state inference means 28 produces signals for driving each actuator 4. The actuators 4 control the damping force of the shock-absorbers 3. FIG.8 shows a typical gain characteristics of the low-pass digital filter of the zero-point calculation means 26 in the third embodiment. As shown in FIG.8, the low-pass digital filter attenuates inputted signals having higher frequencies than the predetermined cut-off frequency fc, or eliminates them. The function of the low-pass digital filter for calculating a zero-point signal ωy0(n) is shown by the following equation (9): ωy0(n) = A·ωy(n)+A·ωy(n-1)+B·ωy0(n-1) wherein A and B are constants decided by the low-pass digital filter, and given by the following equations: A = T/(2τ +T), B = (2τ-T)/(2τ+T), τ = 1/2π · fc, and T is a sampling period in the low-pass digital filter. Apart from the above-mentioned embodiment wherein the low-pass digital filter having a simple equation shown by formula (9) is used in the zero-point calculation means 26, a modified embodiment may be such that a low-pass digital filter having a quadratic equation or a low-pass analog filter is used in the zero-point calculation means 26. FIG.9 shows a waveform of the input signal to the low-pass digital filter, and FIG.10 shows a waveform of the output signal from the low-pass digital filter. Since the cutoff frequency fc, e.g. 10 mHz, is set at a frequency lower than the frequency of the above-mentioned undesirable signals owing to the rolling or the vibrating of the moving vehicle 11, the undesirable signals which are detected by the yaw angular velocity sensor 2 are eliminated by the low-pass digital filter. As a result, the change of the zero-point signal ωy0 owing to the secular change and/or temperature change, etc. is distinctly shown in the output signal of the low-pass digital filter as shown by FIG.10. FIG.11 shows a flowchart in the arithmetic unit 200 of the controller 5 in the suspension control apparatus of the third embodiment in accordance with the present invention. In step 1001 of FIG.11, the output signal V from the vehicle speed sensor 1 and the output signal ωy from the yaw angular velocity sensor 2 are detected. Next, in step 1002, the undesirable output signals of the yaw angular velocity sensor 2 owing to the rolling and the vibrating of the vehicle 11 are eliminated by the zero-point calculation means 26 which comprises the low-pass digital filter and the change of the zero-point signal ωy0 is detected by calculating the aforementioned formula (9). The zero-point signal ωy0 which is calculated by the zero-point calculation means 26 is stored in the arithmetic unit 200 as a new zero-point signal ωy0 for correction. In step 1003, the angular velocity correction means 27 corrects the detected output signal ωy of the yaw angular velocity sensor 2 to the corrected value ωyA by calculating the aforementioned formula (5) shown in the first embodiment. In step 1004, it is judged by using the corrected value ωyA calculated in step 1003 whether the vehicle 11 is turning or not. When the arithmetic unit 200 judges "YES" in step 1004, that is, the vehicle 11 is in turning state, the sequence thereafter goes to step 1005. In step 1005, the turning state inference means 28 infers the rolling state during turning by retrieving the map (the aforementioned Table 1) with the output signal V of the vehicle speed sensor 1 and the corrected value ωyA of the yaw angular velocity sensor 2. As a result, the suspension control apparatus of the third embodiment controls to increase the damping force of the shockabsorbers 3 in step 1006. On the contrary, when the arithmetic unit 200 in step 1004 judges "NO", the damping force of the shock-absorbers 3 is kept at the usual damping rate during normally driving straight in step 1007. Thus, according to the third embodiment of the vehicle control apparatus of the present invention, the drift value of the zero-point signal can be precisely detected in a driving state by function of the vehicle control apparatus which removes the undesirable output signal of the angular velocity sensor in response to the rolling and vibrating of the driving vehicle, and calculates the drift value owing to the secular change and/or the temperature change, etc. As a result, the suspension of the vehicle can be appropriately controlled every time in response to the vehicle driving state. Apart from the above-mentioned first, second and third embodiments wherein the damping force of the shock-absorbers 3 is controlled to decrease the rolling of the moving vehicle 11 by using the yaw-angular velocity detected by the yaw angular velocity sensor 2, a modified embodiment may be such that the damping force of the shockabsorbers 3 is controlled by using a pitch angular velocity, or by using a combined signal of two angular velocity signals in the yaw, roll and pitch angular velocity. Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the scope of the invention.

Claims: A vehicle control apparatus comprising: a vehicle speed sensor (1) for detecting the speed (V) of a vehicle (11); at least one attitude sensor (2) for detecting an attitude of said vehicle (11); a zero-point calculation means (6, 16, 26) which detects a normal state of said vehicle (11) by using output signals (V) of said vehicle speed sensor (1) and output signals (ωy) of said attitude sensor (2), and which calculates a zero-point signal (ωy0) of said attitude sensor (2); a correction means (7, 17, 27) which corrects said output signal (ωy) of said attitude sensor (2) by using said zero-point signal (ωy0) calculated by said zero-point calculation means (6, 16, 26); a turning state inference means (8, 18, 28) which infers a rolling state of said vehicle (11) in response to a corrected signal (ωyA) of said correction means (7, 17, 27) and said output signal (V) of said vehicle speed sensor (1) and further produces output signals for controlling to decrease the rolling state; and shockabsorber means (3, 4) whereof the damping force is adjusted in response to output signals from said turning state inference means (8, 18, 28), characterized in that said attitude sensor is an angular velocity sensor (2) for detecting an angular velocity about a pitch axis, a yaw axis or a roll axis of said vehicle (11). A vehicle control apparatus in accordance with claim 1, wherein said zero-point calculation means (6, 16, 26) regards an average of said output signals (ωy) of said angular velocity sensor (2) in a normal state as zero-point signal (ωy0). A vehicle control apparatus in accordance with claim 1 or 2, wherein said zero-point calculation means (6, 16, 26) calculates a zero-point signal (ωy0) of said angular velocity sensor (2) when a change rate (Δωy) of the detected angular velocity is on or below a predetermined change rate (Δωyc). A vehicle control apparatus in accordance with claim 1, wherein said zero-point calculation means (16) infers a drift value (ωd) and a zero-point signal (ωy0) from a change rate (Δωy) of the detected angular velocity. A vehicle control apparatus in accordance with claim 1, wherein said zero-point calculation means (26) which comprises a low-pass filter having a predetermined cut-off frequency eliminates signals which are output by said angular velocity sensor (2) owing to the rolling and the vibrating of said vehicle (11); and said angular velocity correction means (27) corrects the output signal (ωy) of said angular velocity sensor (2) during driving.

Inventors: OKUDA EIICHIRO, TAKIGAWA MASUO, OKUDA, EIICHIRO, TAKIGAWA, MASUO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1991
Main classification: B60G17
IPC codes: B62D7, B60G17