Data processing: measuring – calibrating – or testing – Calibration or correction system – Speed
Reexamination Certificate
1998-08-21
2001-05-08
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Speed
C702S143000, C342S104000
Reexamination Certificate
active
06230107
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a vehicle speed detection system and more particularly to a vehicle speed detection system installed in a construction machine such as bulldozers to detect ground speed by use of a Doppler sensor.
BACKGROUND ART
A typical vehicle speed detection system for detecting the ground speed of a vehicle uses a Doppler sensor. This detection system is designed to emit electromagnetic waves (radio waves or ultrasonic waves) from the vehicle onto the ground at a specified beam depression angle &thgr; and to receive the electromagnetic waves which have been reflected off the ground. Based on these radiant and received waves, Doppler shift (beat wave frequency) f
d
is calculated, using the following equation.
f
d
=2f
t
·vcos &thgr;/C (1)
In this equation, f
t
is transmission frequency, C is electromagnetic wave propagation velocity (light velocity or sonic velocity) and v is actual vehicle speed.
This prior art vehicle speed detection system, however, suffers from the problem that when the actual speed of a vehicle is sensed by the Doppler sensor mounted on the vehicle body, the movements (pitching, vertical movement, yawing) of the vehicle body affect the Doppler sensor causing errors in speed detection so that the vehicle speed detection system cannot detect accurate ground speed.
Attempts to solve this problem are proposed in Japanese Patent Laid-Open Publication No. 53-17376 (1978) and No. 61-201176 (1986) which are directed to eliminating the effect of pitching angular velocity which most significantly affects speed detection. According to Japanese Patent Laid-Open Publication No. 53-17376, a plurality of Doppler sensors are mounted on a mobile unit and the speed of the mobile unit is determined by averaging, through mutual compensation, a plurality of Doppler signals sensed by the plurality of Doppler sensors. The detection system disclosed in Japanese Patent Laid-Open Publication No. 61-201176 is designed to calculate an error in speed detection from the angular velocity of the Doppler sensor with respect to the center of gravity of the vehicle and to correct a sensed ground speed based on the calculated error value.
Generally, the installation level of such a Doppler sensor, that is, the level at which such a Doppler sensor is installed when mounted on a vehicle body, is determined according to the specification of the sensor that is determined by the output power of the sensor.
Japanese Patent Laid-Open Publication No. 53-17376 directed to compensating for errors in speed detection due to the pitching of a vehicle requires a plurality of Doppler sensors, which leads to an increase in the manufacturing cost of the entire system. Japanese Patent Laid-Open Publication No. 61-201176 has the disadvantage that when the detection system is applied to a tracklaying vehicle such as bulldozers, the center of rotation of the vehicle varies according to the kind of operation being performed and to the terrain of the ground where the vehicle is traveling, which adversely affects the accuracy of correction.
Regarding the installation level of the Doppler sensor, if the Doppler sensor is mounted at a level in a vehicle such as a construction machine in accordance with the specification of the sensor, there is a strong likelihood that mud etc. may stick to the sensor causing a decrease in the signal strength of the sensor or the sensor may get damaged, hitting against rocks or stones.
It is conceivable that these problems may be solved by installation of a higher power sensor at a high position in a vehicle. However, use of a higher power sensor not only leads to higher cost but also causes disturbance to other working vehicles being operated in the same yard because of strong electromagnetic waves radiated from the high power sensor. Additionally, the output of the sensor higher than the specified value does not meet the requirement stipulated by the regulation.
The present invention is directed to overcoming the above problems and a first object of the invention is therefore to provide a vehicle speed detection system capable of correcting errors due to pitching of a vehicle body at low cost. A second object of the invention is to provide a vehicle speed detection system incorporating a Doppler sensor which can be installed at high levels in a vehicle without increasing the output power of the sensor.
DISCLOSURE OF THE INVENTION
The first object of the invention can be achieved by a ground speed detection system incorporating a Doppler sensor according to a first aspect of the invention, the detection system comprising:
(a) angular velocity detecting means for detecting the angular velocity of a vehicle with respect to the center of gravity of the vehicle while the vehicle is in pitching movement;
(b) center of rotation detecting means for detecting the center of rotation of the vehicle while the vehicle is in pitching movement; and
(c) vehicle speed correcting means for correcting the ground speed of the vehicle sensed by the Doppler sensor based on the center of rotation detected by the center of rotation detecting means in addition to the angular velocity detected by the angular velocity detecting means.
In the detection system according to the first aspect of the invention, the ground speed of the vehicle sensed by the Doppler sensor is corrected by the vehicle speed correcting means based on the angular velocity with respect to the center of gravity of the vehicle detected by the angular velocity detecting means. In this correction, a value of the center of rotation of the vehicle during pitching movement detected by the center of rotation detecting means is taken into account so that the correction is in conformity with the current center of rotation of the vehicle. In this way, the accuracy of the correction can be improved and accurate ground speed unaffected by the pitching movement of the vehicle can be calculated. The achievement of accurate ground speed enables it to obtain, for example, a quantitative value of the slippage rate of the crawler belts provided in a tracklaying vehicle and the accurate rate of shoe slippage (crawler belt slippage), in turn, allows improved control of the implement, engine and other parts.
The first object can be also achieved by a ground speed detection system incorporating a Doppler sensor according to a second aspect of the invention, the detection system comprising:
(a) angular velocity detecting means for detecting the angular velocity of a vehicle with respect to the center of gravity of the vehicle while the vehicle is in pitching movement and for detecting the angular velocity of the Doppler sensor being rotated; and
(b) vehicle speed correcting means for correcting the ground speed of the vehicle sensed by the Doppler sensor based on the angular velocity of the vehicle and the angular velocity of the Doppler sensor which have been detected by the angular velocity detecting means.
In the detection system according to the second aspect of the invention, the ground speed of the vehicle sensed by the Doppler sensor is corrected by the vehicle speed correcting means based on the angular velocity of the vehicle with respect to the center of gravity of the vehicle detected by the angular velocity detecting means. Since the Doppler sensor itself rotates following the pitching movement of the vehicle, the rotation of the Doppler sensor is taken into account in this correction. This improves the accuracy of the correction so that accurate ground speed which is unaffected by the pitching movement of the vehicle can be obtained.
The first object can be also achieved by a ground speed detection system incorporating a Doppler sensor according to a third aspect of the invention, the detection system comprising:
(a) angular velocity detecting means for detecting the angular velocity of a vehicle with respect to the center of gravity of the vehicle while the vehicle is in pitching movement and for detecting the angular velocity of the Doppler sensor being rotated;
(b) center of rotation detec
Kitahara Yasuo
Nagase Hidekazu
Yamamoto Shigeru
Armstrong Westerman Hattori McLeland & Naughton LLP
Hoff Marc S.
Komatsu Ltd.
Pretlow Demetrius
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