JPH0933546A - Detecting device of speed of carbody - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of detection of the speed of a carbody at the time of running of a vehicle. SOLUTION: This device is equipped with a laser light projecting means 5 which casts a laser light to a road surface whereon a vehicle runs, an image sensor 6 which reads a speckle pattern formed by the laser light cast from the laser light projecting means 5 and reflected and diffused by the road surface and an arithmetic processing part 15 computing an output of the image sensor 6. The speed of a carbody is calculated from the amount of shift after a unit time of the speckle pattern read by the image sensor 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle body speed detecting device for detecting a vehicle body speed when a vehicle is traveling.

[0002]

2. Description of the Related Art Recently, an anti-lock brake system that prevents the wheels from being locked during sudden braking to prevent the deterioration of braking performance due to the locking of the wheels, and the control of the slippage of the wheels on the road surface within an appropriate range. As a result, more and more vehicles are equipped with traction control systems that improve driving stability and drive force transmission efficiency.

In these anti-lock brake systems and traction control systems, the braking force is controlled so that the lock is avoided from the state where it is likely to lock, or the engine output is controlled so that the slip is within an appropriate range. In order to do so, the slip rate (slip rate) of each wheel is detected during traveling. Here, the slip ratio S _t, when the rotational speed V _t of the wheels, a vehicle speed (absolute speed) and V _F, are those calculated by the following equation (1). S _t = {(V _F −V _t ) / V _F } × 100 (1)

Here, the wheel rotation speed V _t is usually formed in a disk shape or a ring shape in which the axle is fitted in the center portion and integrally rotates with the wheel, and the rotation state is determined on the outer peripheral portion. A tone wheel (also referred to as a rotor) configured to include a rotation discriminating means, and fixedly mounted on the vehicle body side at a position close to the outer peripheral portion of the tone wheel to change the rotation speed of the tone wheel from the behavior of the rotation discriminating means. The rotation speed detection device is configured to include a rotation detection sensor that outputs a corresponding signal and an arithmetic processing unit that detects the rotation speed of the wheel equipped with the tone wheel from the output of the rotation detection sensor.

Further, a vehicle is equipped with a speedometer, and normally, the rotational speed V of the output shaft of the transmission for transmitting the engine output to the wheel side.
_S is detected and the speed V _S is displayed on the speedometer as the traveling speed of the vehicle. In the conventional case, the estimated vehicle body speed V _R calculated from the rotational speed V _S of the output shaft at the start of the brake operation or the deceleration of the speed V _S after the brake operation.
Is calculated as the vehicle speed V _F described above, and the slip ratio S _t is calculated.

[0006]

By the way, recently,
A high-sensitivity hydraulic control system that uses a piezo element as an actuator that controls the hydraulic pressure for braking has been researched.
It is expected that the capability of such a high-sensitivity hydraulic control system will be maximized to realize more accurate braking force control, and for that purpose, the above-described accuracy of detection of the slip ratio S _t is required. and in accordance with the capacity of the hydraulic control system in a high-sensitivity or high accuracy, it is indispensable to be able to detect more quickly the slip ratio S _t.

[0007] However, as described above, the detection of the conventional slip ratio S _t, the rotation of the transmission of the output shaft speed V _S and the velocity V _S vehicle speed V and the estimated vehicle speed V _R which is calculated from the deceleration or the like of These values are approximated as _F , and these speeds V _S and V _R have an error with respect to the actual vehicle body speed V _F , and the calculation process is increased to calculate the estimated vehicle body speed V _{R and the} like. From things such as
Or cause difficulties in the high accuracy of the detection accuracy of the slip ratio S _t, or a problem that shortening of the time required for detection of the slip ratio S _t becomes difficult occurs.

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems, and the slip ratio S of the wheels during traveling of the vehicle is S.
_In order to improve the detection accuracy of _t and at the same time shorten the time required to detect the slip ratio S _t , a vehicle body speed detection device capable of detecting a vehicle body speed close to an absolute speed is provided, and thus an antilock brake system is provided. And improve the slip ratio control performance in traction control systems.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser beam projection means for irradiating a traveling road surface with a laser beam in a vehicle body speed detecting device for detecting a vehicle body speed during traveling of the vehicle. An image sensor for reading a speckle pattern formed by a laser beam emitted from a laser beam projection means and reflected / diffused on a road surface, and an arithmetic processing unit for computing an output of the image sensor are provided, and the speckle read by the image sensor is provided. This is achieved by a vehicle body speed detecting device characterized in that the vehicle body speed is calculated from the amount of movement of the pattern after a unit time.

[0010]

According to the above configuration of the present invention, the speed used as the vehicle speed when calculating the slip ratio of the wheels is determined by the interference of the laser light reflected / diffused on the road surface on which the vehicle is actually traveling. It is calculated as the speckle pattern that is a light and dark pattern of stripes and calculated from the amount of movement of the speckle pattern after a unit time.Since it is a value that directly detects the amount of movement of the vehicle body on the road surface, it has been conventionally used. Compared with the estimated vehicle body speed calculated from the rotation speed of the output shaft and the deceleration of the speed, the error from the actual vehicle body speed can be made extremely small and the detection time can be shortened. .

[0011]

1 and 2 show an embodiment of a vehicle body speed detecting apparatus according to the present invention. FIG. 1 shows a vehicle body speed detecting apparatus 1 according to this embodiment on a vehicle body. FIG. 2 is a vehicle body side view showing a schematic arrangement, and FIG. 2 is a vehicle body side view.

The vehicle body speed detecting device 1 of this embodiment
Where V _t is the rotational speed of the wheels and S _t is the slip ratio of each wheel during traveling, the vehicle speed V is approximate to the absolute speed.
_{Although F} is calculated based on the above-mentioned formula (1), this method is characterized by the method of calculating the vehicle body speed V _F.

That is, since the vehicle body speed detecting device 1 detects the vehicle body speed V _F when the vehicle is traveling,
Laser light projection means 5 for irradiating the laser light 4 to the
It is emitted from this laser light projection means 5 and reflected on the road surface 3.
The image sensor 6 for reading the speckle pattern formed by the diffused laser beam 8 and the arithmetic processing unit 15 for calculating the output of the image sensor 6 are provided, and the speckle pattern read by the image sensor 6 after the unit time Δt is reached. The speed V _P (= L / Δt) is calculated from the movement amount L (see FIG. 3), and the calculated speed V _P is set as the vehicle body speed V _F.
It is used when calculating the slip ratio S _{t of the} wheel. In addition, the laser light projection means 5 and the image sensor 6 make the sensor unit 2
In this embodiment, as shown in FIG. 2, the sensor unit 2 is mounted at a position near the front end of the vehicle body frame 7.

The speckle pattern is a laser beam 4
When a rough surface is applied, the laser light 4
A difference occurs in the reach distance of the diffused light 8. Therefore, a phase difference occurs in the diffused light 8 reflected by the road surface 3 and an interference fringe is formed.

3 (a) and 3 (b) both show the speckle pattern P captured by the image sensor 6. As shown in FIG. However, (b) is a speckle pattern captured after the unit time Δt has elapsed from (a), and it can be seen that the speckle pattern has moved by 5 frames as compared with the state of (a). For example, if the length l of each bright and dark frame is 0.02 mm, the movement amount L after Δt time is L = 0.02 × 5 (frame) = 0.1 mm
Therefore, the velocity V _P treated as the vehicle body velocity V _F can be obtained from L / Δt.

On the other hand, the wheel rotation speed V _{t, which} is substituted into the above-mentioned equation (1) for calculating the slip ratio S _t , is a disk shape in which the axle 11 is fitted in the central portion and rotates integrally with the wheel 12. The tone wheel 13 that is formed and equipped with rotation determining means (for example, serration teeth) for determining the rotation state on the outer peripheral portion, and the body frame 7 side at a position close to the outer peripheral portion of the tone wheel 13. A rotation detection sensor 14 fixedly mounted on the rotation detection sensor 14 for outputting a signal corresponding to the rotation speed of the tone wheel 13 from the behavior of the rotation determination means.
Then, the rotation speed detection device 16 having the above-described arithmetic processing unit 15 for detecting the rotation speed of each wheel 12 equipped with the tone wheel 13 from the output of the rotation detection sensor 14 is obtained.

The arithmetic processing unit 15 also calculates the speed V _P and calculates the equation (1), and the slip ratio S _t calculated by the arithmetic processing unit 15 is the braking force. It is sent to a control circuit, etc. and used for controlling the slip ratio in an anti-lock brake system or a traction control system.

In the vehicle body speed detecting device 1 described above, each wheel 1
The speed V _P used as the vehicle speed V _F when calculating the slip ratio S _{t of} 2 is the road surface 3 on which the vehicle is actually traveling.
Is calculated as a speckle pattern P which is a light-dark pattern of interference fringes by the laser light 8 reflected and diffused on the road surface 3, and is calculated from a movement amount L of the speckle pattern P after a unit time Δt. since it is directly detected value of the movement amount on a road surface 3, as compared with the estimated vehicle speed V _R which is calculated from the deceleration or the like of the rotational speed V _S and the velocity V _S of the output shaft which has been conventionally used, The error from the actual vehicle speed V _F can be made extremely small, and the detection time can be shortened. As a result,
It is possible to improve the detection accuracy of the slip ratio S _t of the wheels 12 while the vehicle is running, and at the same time, shorten the time required to detect the slip ratio S _t , and improve the slip ratio control performance in the antilock brake system and the traction control system. It is possible to let

[0019]

According to the vehicle speed detecting apparatus of the present invention, the speed used as the vehicle speed when calculating the slip ratio of the wheels is obtained by reflecting / diffusing the road surface on which the vehicle is actually traveling. Captured as a speckle pattern that is a light-dark pattern of interference fringes by laser light, and calculated from the amount of movement of the speckle pattern after a unit time, since it is a value that directly detects the amount of movement of the vehicle body on the road surface, Compared with the estimated vehicle body speed calculated from the output shaft rotation speed and deceleration of the output shaft that have been used conventionally, it is possible to make the error from the actual vehicle body speed extremely small and shorten the detection time. Is possible and, as a result,
While improving the accuracy of detecting the slip ratio of the wheels while the vehicle is running, the time required to detect the slip ratio can be shortened, and the slip ratio control performance of the anti-lock brake system and traction control system can be improved. Become.

[Brief description of drawings]

FIG. 1 is a vehicle body plan view showing a schematic arrangement on a vehicle body of an embodiment of a vehicle body speed detecting device according to the present invention.

FIG. 2 is a vehicle body side view showing a schematic arrangement on the vehicle body of the vehicle body speed detecting device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of an absolute approximate speed calculated from a movement amount of a speckle pattern after a unit time in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vehicle speed detection device 2 Sensor part 3 Road surface 4 Laser light 5 Laser light projection means 6 Image sensor 7 Body frame 11 Axle 12 Wheel 13 Tone wheel 14 Rotation detection sensor 15 Calculation processing unit 16 Rotation speed detection device

Claims (1)

[Claims] 1. A vehicle body speed detecting device for detecting a vehicle body speed during traveling of a vehicle, comprising: a laser beam projecting means for irradiating a traveling road surface with laser light; and a laser beam projecting means for emitting a laser beam and reflecting on the road surface. An image sensor that reads a speckle pattern formed by diffused laser light and an arithmetic processing unit that calculates an output of the image sensor. The vehicle speed is calculated from the movement amount of the speckle pattern read by the image sensor after a unit time. A vehicle body speed detection device characterized by calculating