Vehicle motion detecting apparatus

Abstract

The present invention provides a vehicle motion detecting apparatus that can satisfy a required detection accuracy with a simple architecture and at a low cost, and also maintain reliability of an applied external apparatus. The vehicle motion detecting apparatus 100 of the present invention has a motion detecting section 10 that detects a motion of a vehicle and a malfunction detecting section 20 that detects a malfunction of the motion detecting section 10, and is characterized in that the motion detecting section 10 is a 6-axis inertial sensor as the first multi-axis inertial sensor that is capable of detecting accelerations in directions of three axes and angular velocities about three axes.

Claims

1. A vehicle motion detecting apparatus comprising: a motion detecting section that detects a motion of a vehicle; and a malfunction detecting section for detecting a malfunction of the motion detecting section and that includes a first multi-axis inertial sensor configured to detect, for three axes that are mutually orthogonal, accelerations in directions of the three axes and angular velocities about at least two of the three axes, respectively, and wherein the malfunction detecting section includes a plurality of other sensors and a computing section that is electrically connected to the first multi-axis inertial sensor, wherein the computing section performs a comparison operation between a detection value of the first multi-axis inertial sensor and a detection value of the plurality of other sensors, and determines a malfunction of the first multi-axis inertial sensor based on a comparison value obtained by the comparison operation.

2. The vehicle motion detecting apparatus according to claim 1, wherein the plurality of other sensors includes: a second multi-axis inertial sensor that is capable of detecting at least an acceleration in a front-back direction, an acceleration in a lateral direction, and a roll rate of a vehicle; a wheel speed sensor; and a pressure sensor.

3. The vehicle motion detecting apparatus according to claim 2, wherein the detection value of the plurality of other sensors with which the malfunction detecting section performs the comparison operation with the detection value of the first multi-axis acceleration sensor is a detection value obtained by at least one of the group consisting of the second multi-axis inertial sensor, the wheel speed sensor and the pressure sensor.

4. The vehicle motion detecting apparatus according to claim 2, wherein the pressure sensor is a brake fluid pressure sensor that is capable of sensing a brake fluid pressure of the vehicle, the brake fluid pressure sensor being provided in a braking control system for which the vehicle motion detecting apparatus is used.

5. The vehicle motion detecting apparatus according to claim 4, wherein, in a case where the malfunction detecting section has judged that there is a malfunction, the braking control system is forcibly stopped.

6. The vehicle motion detecting apparatus according to claim 2, wherein the vehicle is a two-wheeled vehicle, and the wheel speed sensor is capable of detecting at least one of the wheel speeds of the two-wheeled vehicle.

7. The vehicle motion detecting apparatus according to claim 1, further comprising an alerting device that informs a driver of a determination result of the malfunction detecting section.

8. A sensor correcting means that corrects an output value of the first multi-axis inertial sensor depending on a discrimination result of the malfunction detecting section.

9. The vehicle motion detecting apparatus according to claim 1, wherein, when the malfunction detecting section determines that there is a malfunction, the motion detecting section does not send out at least one detection value of the first multi-axis inertial sensor.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a block diagram schematically showing a configuration of a vehicle motion detecting apparatus according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) An embodiment of the present invention will now be described with reference to FIG. 1. Components and arrangements described below should not be considered as limiting the present invention, and may be altered and modified within the scope of the present invention.

(3) A vehicle motion detecting apparatus 100 shown in FIG. 1 is used for a braking control system 70 of a vehicle, particularly a two-wheel vehicle, and includes a motion detecting section 10 that detects a motion of the vehicle and a malfunction detecting section 20 for detecting a malfunction of the motion detecting section 10. Note that, in FIG. 1, the vehicle motion detecting apparatus 100 is indicated by a region surrounded by a dotted line.

(4) The motion detecting section 10 includes a first multi-axis inertial sensor 11 that is capable of detecting, for three axes that are mutually orthogonal, accelerations in directions of the three axes and angular velocities about at least two axes among these three axes, respectively. Defining a longitudinal (front-back) direction of the vehicle as an x-axis direction, a lateral (right-left) direction as a y-axis direction, and a vertical (up-down) direction as a z-axis direction, the first multi-axis inertial sensor 11 is a 6-axis inertial sensor serving as a multi-axis inertial sensor that is capable of detecting accelerations a.sub.x1, a.sub.y1, a.sub.z1 for three axes and angular velocities .sub.x1, .sub.y1, .sub.z1 about three axes, the accelerations for three axes and the angular velocities about three axes consisting of accelerations in three-axis directions of an x-axis direction acceleration a.sub.x1, a y-axis direction acceleration a.sub.y1 and a z-axis direction acceleration a.sub.z1, as well as angular velocities about three axes of an angular velocity about an x-axis (roll rate) x, an angular velocity about a y-axis (pitch rate) y, and an angular velocity about a z-axis (yaw rate) z. The first multi-axis inertial sensor 11 as a 6-axis inertial sensor includes three acceleration sensors and three angular velocity sensors, and each of the six sensors detects the accelerations for the three axes a.sub.x1, a.sub.y1, a.sub.z1 and the angular velocities about the three axes .sub.x1, .sub.y1, .sub.z1, respectively. The first multi-axis inertial sensor 11 is, in order to particularly reduce equipment cost, preferably a low-cost consumer 6-axis inertial sensor provided with three acceleration sensors and three angular velocity sensors, which is used in, for example, vehicle navigation systems and telematics systems.

(5) The malfunction detecting section 20 includes a plurality of sensors (other sensors). It is preferable that the malfunction detecting section 20 includes a 3-axis inertial sensor (second multi-axis inertial sensor) 30 that is capable of detecting the angular velocity about the x-axis .sub.x2, the y-axis direction acceleration a.sub.y2 and the z-axis direction acceleration a.sub.z2, among the accelerations for three axes a.sub.x2, a.sub.y2, a.sub.z2, and angular velocities about three axes .sub.x2, .sub.y2, .sub.x2, a wheel speed sensor 40 and a pressure sensor 50.

(6) Also, it is preferable that the malfunction detecting section 20 includes a microcomputer as a computing section that is electrically connected to the malfunction detecting section 20 internally or externally as shown FIG. 1. As this computing section, in FIG. 1, it is preferable that two microcomputers 60 and 60A are provided, and it is preferable that the microcomputer 60 is provided with an algorithm for receiving and performing a comparison operation between the detection values a.sub.x1, a.sub.y1, a.sub.z1, .sub.x1, .sub.y1, .sub.z1 of the accelerations and angular velocities for the six axes obtained by the first multi-axis inertial sensor 11, and the detection values a.sub.x2, a.sub.y2, a.sub.x2, .sub.x2, .sub.y2, .sub.x2 obtained by the malfunction detecting section 20.

(7) For example, in an embodiment shown in FIG. 1, the malfunction detecting section 20 includes the 3-axis inertial sensor 30 that are preferably used for motion stability braking control of the vehicle, the wheel speed sensor 40 and the pressure sensor 50. The 3-axis inertial sensor 30 directly detects accelerations for two axes and an angular velocity about one axis of the angular velocity .sub.x2 about the x-axis, the y-axis direction acceleration a.sub.y2 and the z-axis direction acceleration a.sub.x2. The wheel speed sensor 40 measures wheel speeds v.sub.x of at least two wheels, and the x-axis direction acceleration a.sub.x2 is detected by differentiating the measured wheel speeds v.sub.x with respect to time in the second CPU 60A, which is a microcomputer. And, the pressure sensor 50, which is preferably a brake fluid pressure sensor 50 which is a component of the braking control system 70, can estimate the angular velocity .sub.y2 about the y-axis of the car body by comparing measured fluid pressures P of front and rear wheels. The first CPU 60 receives and performs a comparison operation between the angular velocity .sub.x2 about x-axis, the y-axis direction acceleration a.sub.y2, and the z-axis direction acceleration a.sub.z2 detected by the 3-axis acceleration sensor 30, the x-axis direction acceleration a.sub.x2 detected by the wheel speed sensor 40, and the angular velocity .sub.y2 about the y-axis estimated by the brake fluid pressure sensor 50 and the detected values a.sub.x1, a.sub.y1, a.sub.x1, .sub.x1, .sub.y1, .sub.z1 of each of the accelerations and angular velocities obtained by the first multi-axis inertial sensor 11 of the motion detecting section 10, to thereby discriminate a malfunction of the first multi-axis inertial sensor 11.

(8) In FIG. 1, illustrated is the embodiment in which, in order to increase malfunction detection accuracy, the detected values obtained in the malfunction detecting section 20 are subject to the comparison operation with all of the detected values obtained with the 3-axis inertial sensor 30, the wheel speed sensor 40 and the pressure sensor 50. However, according to the present invention, the configuration may be altered to a configuration in which a comparison operation is performed using a detected value obtained by at least one of the 3-axis inertial sensor 30, the wheel speed sensor 40 and the pressure sensor 50.

(9) Accordingly, in a case where the result of the comparison operation in the first CPU 60 shows a predetermined mismatch between the detected values which are from the motion detecting section 10 and the malfunction detecting section 20 and corresponding with each other, the first CPU 60 determines that the detected values of the accelerations and the angular velocities detected by the first multi-axis inertial sensor 11 that is a 6-axis inertial sensor are abnormal. In this case, a command is submitted from the first CPU 60 to the braking control system 70 to operate in a fail-safe mode.

(10) In a case where it is determined by the first CPU that at least one of the detection values of the accelerations and angular velocities detected by the first multi-axis inertial sensor 11 is abnormal, the detection values of the accelerations and the angular velocities detected by the first multi-axis inertial sensor 11 are not sent to the braking control system 70. In this case, all detection values of the first multi-axis inertial sensor 11 are not sent to the braking control system 70, or at least one detection value that has indicated a malfunction of the first multi-axis inertial sensor 11 are not sent to the braking control system 70. Also, in this case, the braking control system 70 may stop the braking control and inform the driver of the stoppage of the braking control. Thus, it is possible to avoid a braking control by the braking control system 70 based on a false detection result of the motion of the two-wheeled vehicle, and it is also possible to prevent the braking control system 70 from impairing safety and reliability.

(11) Note that, FIG. 1 shows a configuration including two microcomputers, i.e., the first CPU 60 and the second CPU 60A, but the configuration may include only one microcomputer, i.e., the first CPU 60.

(12) As another embodiment, the 3-axis inertial sensor may be a so-called 3-axis gyroscope sensor (3-axis angular velocity sensor) that detects the angular velocities about three axes, i.e., the angular velocity about the x-axis (roll rate) .sub.x1, the angular velocity about the y-axis (pitch rate) .sub.y1 and the angular velocity about the z-axis (yaw rate) .sub.z1.

(13) Further, the first multi-axis inertial sensor 11 may have five-axis inertial sensors that respectively detect accelerations for three axes and angular velocities about two axes including accelerations in three directions, i.e., an x-axis direction acceleration a.sub.x1, a y-axis direction acceleration a.sub.y1 and a z-axis direction acceleration a.sub.z1, as well as angular velocities about two of three axes, i.e., an angular velocity about an x-axis (roll rate) x, an angular velocity about a y-axis (pitch rate) y, and an angular velocity about a z-axis (yaw rate) z.

(14) The pressure sensor 50 of the malfunction detecting section 20 is, from the viewpoint of reducing equipment cost or the like, preferably a brake fluid pressure sensor of the braking control system. Further, in order to inform the driver of the detection of a malfunction of the first multi-axis inertial sensor 11, it is preferable that the malfunction detecting section 20 is further provided with, for example, an alerting means 80 such as an alarm display and an alarm tone.

INDUSTRIAL APPLICABILITY

(15) According to the present invention, it is possible to provide a vehicle motion detecting apparatus which is used for a braking control system of a vehicle, particularly a two-wheeled vehicle, that can detect a malfunction of the multi-axis inertial sensor with a simple structure and at low cost by employing a consumer low-cost 6-axis inertial sensors used in, for example, vehicle navigation systems and telematics systems as a multi-axis sensor used for a braking control system of a vehicle and by employing the malfunction detecting section detecting a malfunction of the 6-axis inertial sensor.

List of Reference Signs

(16) 10 motion detecting section 11 first multi-axis inertial sensor 20 malfunction detecting section 30 3-axis acceleration sensor 40 wheel speed sensor 50 pressure sensor (or brake fluid pressure sensor) 60 microcomputer (or first CPU) 60A microcomputer (or second CPU) 70 braking control system (or ABS ECU) 80 alerting means 90 output signal 100 vehicle motion detecting apparatus