JP3487333B2 - Body speed estimation device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed estimating apparatus, and more particularly, to a technique for estimating a vehicle speed using a longitudinal acceleration sensor. 2. Description of the Related Art In recent years, anti-skid brakes (ie, ABS) and traction controls (ie, TCL) are frequently used in vehicle speed information VB and wheel speed information VW.
Control the hydraulic pressure generating means or the throttle valve of the brake unit based on the slip ratio λ calculated based on the above, thereby avoiding the locking of the wheels at the time of sudden braking or sudden acceleration and stopping the vehicle early and safely or It is possible to take off. The vehicle speed VB used here is
Is usually determined from the wheel speed VW.
Of the plurality of obtained wheel speeds VW, for example, the fastest one is set as a reference wheel speed VWB, and the vehicle speed VB is used as the reference wheel speed VWB.
It is assumed that. However, when the vehicle is suddenly braked or accelerated on a low μ road, the wheels tend to lock or idle, and in such a case, the vehicle speed VB is accurately calculated based on the wheel speed information VW. It is difficult to estimate. Therefore, a longitudinal acceleration sensor (front and rear G
Sensors) and integrating the output of the longitudinal acceleration sensor to estimate the vehicle speed VB.
For example, as shown in FIG. 4, when the reference wheel speed VWB (solid line) suddenly changes (in this case, suddenly decreases) at the time of sudden braking or sudden acceleration on a low μ road, the longitudinal acceleration sensor detects the sudden change. The vehicle speed VB is estimated based on this information (broken line), thereby improving the accuracy of the vehicle speed VB. It has also been proposed to estimate the vehicle speed VB based only on information from the longitudinal acceleration sensor. However, as described above, when the vehicle speed VB is estimated on the basis of information from the longitudinal acceleration sensor while the reference wheel speed VWB is rapidly changing, the reference wheel speed is usually increased. After detecting that the speed VWB has suddenly changed, the information from the longitudinal acceleration sensor is taken in to obtain the vehicle speed VB.
As shown in FIG. 4, the vehicle speed VB (broken line) temporarily follows the sudden change of the reference wheel speed VWB, and is smaller (or larger) than the actual vehicle speed (dot-dash line) as a whole. It is not preferable because it may be estimated. In this regard, on the other hand, Japanese Patent Publication No. 3-598
As disclosed in Japanese Patent Application Publication No. 65-65, first, a wheel speed peak value at the start of deceleration due to braking is set as an initial value, and then the integral value of the longitudinal acceleration is subtracted to reduce the pseudo vehicle speed (vehicle speed V).
A device for estimating B) has been considered, whereby the vehicle speed VB can be estimated more accurately. However, the device disclosed in the publication is intended for anti-skid control, and is not always applicable to vehicles without an anti-skid mechanism. [0010] Further, in the device disclosed in the publication or the like,
Only the wheel speed (wheel speed VW) is used as a reference. Therefore, in the case where the wheels are already slipping at the start of deceleration, the initial value is smaller than the actual vehicle speed, and based on the initial value. It is highly possible that the estimated vehicle speed VB is not always accurate. Further, detection information from the longitudinal acceleration sensor and other detection means often includes a detection error. Therefore, when braking is performed for a long time, the vehicle speed as an integral value of the detection information is obtained. The error is included in VB as an accumulated error, and the vehicle speed VB may deviate significantly from the actual vehicle speed. In particular, when estimating the vehicle speed VB based on information from the longitudinal acceleration sensor, the output of the longitudinal acceleration sensor is usually subjected to a filtering process before the vehicle speed VB is obtained. Although it is good when the vehicle is running, for example, when the vehicle is suddenly braked or accelerated on a high μ road, as shown in FIG. There is also a problem that it is inadvertently estimated to be larger (or smaller) than the actual vehicle speed (dashed line). The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a vehicle speed estimating apparatus capable of accurately estimating the vehicle speed even during sudden braking. According to the first aspect of the present invention, the longitudinal acceleration of a vehicle is detected by a longitudinal acceleration detecting means, and the longitudinal acceleration is calculated by an integrating circuit. It is integrated, estimated as the vehicle speed, and output. Meanwhile, at this time, has been detected peripheral speed of the wheels by the wheel speed detection means, one had during braking of the vehicle
During acceleration, the longitudinal acceleration is corrected by the correction means based on the difference between the peripheral speed and the vehicle speed output from the integration circuit. Therefore, the estimated value of the vehicle speed calculated based on the longitudinal acceleration of the vehicle detected by the longitudinal acceleration detecting means is always suitably corrected according to the peripheral speed of the wheels. Therefore, while the detection error of the longitudinal acceleration detecting means is eliminated, sudden braking or rapid acceleration is performed on a high μ road, and the vehicle decelerates without slipping of the wheels or accelerates without idling of the wheels, as in the related art. It is prevented that the vehicle speed is estimated to be larger or smaller than the actual speed due to a phase delay or the like, and the vehicle speed is accurately estimated based on the longitudinal acceleration. Thereby, the reliability of the vehicle speed based on the longitudinal acceleration is improved. Further, the longitudinal acceleration of the vehicles are corrected based on the correction amount continuously updated by storing the retained and updating means in the storage means, further, the correction amount of updating by said updating means update The suspension means is configured to be suspended when the peripheral speed of the wheel changes suddenly. Accordingly, when the vehicle slips or idles due to sudden braking or sudden acceleration on a low μ road, the peripheral speed of the wheel suddenly changes. In such a case, it is preferable to update the correction amount. The correction is suspended, and the correction is performed based on the stored correction amount. Therefore, when suddenly braking on a low μ road and suddenly accelerating, it is surely prevented that the vehicle speed is estimated to be smaller or larger than the actual one following the change in the peripheral speed of the wheels as in the past, It is always possible to accurately and stably estimate the vehicle speed. An embodiment of the present invention will be described below with reference to the drawings. Referring to FIG. 1, there is shown a control circuit diagram of the vehicle speed estimating apparatus according to the present invention. Hereinafter, the configuration of the vehicle speed estimating apparatus according to the present invention will be described with reference to FIG. As shown in FIG. 1, the vehicle speed estimating apparatus is constituted, for example, in an electronic control unit (ECU) 1 mounted on a vehicle, and has, on its input side, a front and rear G mounted on the vehicle. Sensors (longitudinal acceleration detecting means) 2 and peripheral velocities VW1, VW2, V of each wheel (not shown)
A wheel speed sensor (wheel speed detecting means) 4 for detecting W3 and VW4 respectively is connected. Note that these peripheral velocities V
W1, VW2, VW3, and VW4 indicate, for example, the peripheral velocities of the front left wheel, front right wheel, rear left wheel, and rear right wheel, respectively. The output information from the front / rear G sensor 2 is supplied to an integration circuit 6, where the information is integrated and the acceleration information is replaced with vehicle speed information. The integration circuit 6 is provided with a filter circuit for eliminating disturbances and the like. Therefore, output information from the front and rear G sensors 2 is filtered by the filter circuit so that highly accurate vehicle speed information can be obtained. Have been. The peripheral speed information V from the wheel speed sensor 4
W1, VW2, VW3, and VW4 are supplied to the reference wheel speed setting device 8, and the reference wheel speed setting device 8 sets the largest value among the peripheral speed information VW1, VW2, VW3, and VW4. This is selected and set as the reference wheel speed VWB. The vehicle speed information from the integrating circuit 6 is compared with the reference wheel speed VWB and is subtracted from the reference wheel speed VWB.
Is input to the error corrector (correction means) 12 via the. That is, as described above, the front and rear G sensor 2
Includes a difference, while the reference wheel speed VWB from the wheel speed sensor 4 is relatively accurate during normal driving, and therefore, the detection information from the front-rear G sensor 2 is determined based on the reference wheel speed VWB. Correct it. More specifically, the error corrector 12 has a function of storing a correction amount corresponding to the above-mentioned error (storage means) and a function of converting the correction amount from speed information to acceleration information and outputting the same. The output value converted into the acceleration information is added to the detection value from the front and rear G sensor 2 to compensate for the error. Note that the correction amount held in the error corrector 12 is constantly updated when the switch 10 is turned on (the state indicated by the broken line), and is always set to an appropriate value (update means). As a result, the vehicle speed information output from the integration circuit 6 is made appropriate, and the vehicle speed VB is accurately estimated. The vehicle speed VB can be used as a parameter for various controls (for example, the anti-skid control). The reference wheel speed VWB is supplied to the switch 10 via a differentiating circuit 14, and the switch 10 is turned on in accordance with the differential value of the reference wheel speed VWB, that is, the reference wheel acceleration.
It is designed to operate off. Specifically, the switch 10 sets the reference wheel acceleration to a predetermined value G1 (for example, -1.
0G) or less (update suspending means), and thereafter, it is set to be on when it exceeds a predetermined value G2 (for example, -0.8G). The operation and effect of the vehicle speed estimating apparatus thus configured according to the present invention will be described below. First, a description will be given of a case where the vehicle is suddenly braked while traveling on a low μ road. Referring to FIG. 2, similarly to FIG.
This shows how the vehicle speed VB changes with time when the vehicle is suddenly braked on a road. The following description will be made with reference to FIG. When the vehicle is suddenly braked on a low μ road, the deceleration is detected by the longitudinal G sensor 2, and the deceleration is converted into vehicle body speed information by the integration circuit 6. Since the deceleration is not so large at the time when the vehicle starts sudden braking, the switch 10 is turned on (broken line) at this time, and therefore the vehicle speed information is stored in the switch 1.
After that, it is supplied to the error corrector 12. As a result, the deceleration information from the front-rear G sensor 2 is corrected by the output from the error corrector 12, that is, the detection error of the front-rear G sensor 2 is eliminated, the vehicle speed information becomes appropriate, and the vehicle speed VB Is accurately estimated. Then, the wheel slips and the reference wheel speed V
When the differential value of WB, that is, the reference wheel acceleration becomes equal to or less than a predetermined value G1 (for example, -1.0 G), the switch 10 is turned off (solid line), and the error correction device 12 of the correction amount based on the reference wheel speed VWB is used. Input to is blocked. In other words, when the wheel slips and the reference wheel speed VWB is greatly attenuated, the reference wheel speed VWB is no longer accurate, and in such a case, the updating of the correction amount is interrupted. ,
The deceleration information from the longitudinal G sensor 2 is corrected based on the correction amount before the start of the slip stored in the error corrector 12. Thus, in FIG. 2, the reference wheel speed VWB
Is a solid line, the vehicle speed VB is indicated by a dashed line, and the actual vehicle speed is indicated by a dashed line.
Even when the wheel slips and the reference wheel speed VWB is greatly reduced, the vehicle speed VB is maintained at the reference wheel speed VWB.
Satisfactorily decreases along the actual vehicle speed without following the decrease in the vehicle speed. The switch 10 in the off state (solid line) while the wheel is slipping is turned on again (dashed line) when the reference wheel acceleration becomes larger than a predetermined value G2 (for example, -0.8 G). ), Whereby the updating of the correction amount is restarted. Next, a case in which the vehicle suddenly brakes while traveling on a high μ road will be described. Referring to FIG. 3, as in FIG.
This shows how the vehicle speed VB changes with time when the vehicle is suddenly braked on a road. The following description will be made with reference to FIG. When the vehicle suddenly brakes on a high μ road,
The deceleration is detected by the longitudinal G sensor 2, and the deceleration is used as vehicle speed information by the integration circuit 6. When the vehicle starts sudden braking, the front and rear G sensor 2
Is corrected by the output from the error corrector 12, that is, the detection error of the front-rear G sensor 2 is eliminated, the vehicle speed information becomes appropriate, and the vehicle speed VB is corrected.
Is accurately estimated. However, as described above, the filter circuit is interposed in the integration circuit 6, and the filter processing in the filter circuit takes a little time, and therefore, the variation amount of the reference wheel speed VWB is large. And a phase delay occurs in the processing, and the vehicle body speed VB tends to be higher than the actual vehicle speed. However, in this regard, in the vehicle speed estimating apparatus of the present invention, the deceleration information from the longitudinal G sensor 2 is corrected by the output from the error corrector 12. That is, the deceleration information is reduced by an amount corresponding to the vehicle speed information being larger than the reference wheel speed VWB. Therefore, the vehicle speed information is also appropriate, and the vehicle speed VB is accurately estimated. Thus, in FIG. 3, the vehicle speed VB is indicated by a broken line, and the actual vehicle speed is indicated by a dashed line. However, even when sudden braking is performed on a high μ road, The vehicle body speed VB decreases favorably along with the actual vehicle body speed. As described above, the vehicle speed estimating apparatus according to the present invention mainly uses the deceleration information from the longitudinal G sensor 2 and corrects the deceleration information based on the reference wheel speed VWB. The speed VB is obtained, and the correction amount is constantly updated. When the wheel slips during the rapid braking on the low μ road, the updating of the correction amount is interrupted, and while the wheel is slipping, the deceleration information is corrected by the correction amount before the start of the slip. I am trying to do it. Therefore, not only when the vehicle is traveling normally but also during a sudden braking, the vehicle speed is always accurately adjusted to the actual vehicle speed by correcting the detection error of the front and rear G sensor 2 and the phase delay of the filtering process. VB can be obtained. Even when the reference wheel speed VWB is temporarily largely attenuated due to sudden braking on a low μ road, the vehicle speed VB is always maintained at a good value. Can be held along. Therefore, when the vehicle speed VB is used as a parameter of the anti-skid control (ABS), the control accuracy of the anti-skid control can be improved. In the above embodiment, the description has been made mainly on the case of sudden braking of the vehicle. However, the present invention can be applied to the case of rapid acceleration of the vehicle. That is, when the vehicle is rapidly accelerated on a high μ road, the phase delay of the filtering process can be corrected so that the vehicle speed VB is not reduced. Is idle and the reference wheel speed V
Even in the case where the WB temporarily increases greatly, the vehicle body speed VB can always be kept satisfactorily along the actual vehicle speed. Therefore, even when the vehicle speed VB is used as a parameter of the traction control (TCL), the control accuracy of the traction control can be improved. As is apparent from the above description, claim 1
According to the vehicle speed estimating device of
At times, the estimated value of the vehicle body speed calculated based on the longitudinal acceleration of the vehicle can always be suitably corrected according to the peripheral speed of the wheels. Accordingly, it is possible to eliminate the detection error of the longitudinal acceleration detecting means, and to perform a rapid braking or a rapid acceleration on a high μ road, and when the vehicle is decelerated or accelerated without slipping or idling of the wheels, the phase is reduced as in the conventional case. It is possible to prevent the vehicle speed from being estimated to be higher or lower than the actual speed due to a delay or the like, and to accurately estimate the vehicle speed based on the longitudinal acceleration. Therefore, it is possible to improve the reliability of the vehicle speed based on the longitudinal acceleration. When the vehicle slips or idles due to sudden braking or acceleration on a low μ road, the peripheral speed of the wheel changes suddenly. In such a case, it is preferable to update the correction amount. And the correction can be performed based on the stored correction amount. Therefore, during rapid braking and rapid acceleration on a low μ road, it is ensured that the vehicle speed is estimated to be smaller or larger than the actual vehicle speed following the change in the peripheral speed of the wheels as in the prior art. Thus, accurate and stable estimation of the vehicle speed can be always realized even when the wheels slip or idle. Therefore, the reliability of the vehicle speed based on the longitudinal acceleration can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a control circuit diagram of a vehicle speed estimation device according to the present invention. FIG. 2 is a graph showing a time change of the vehicle body speed VB when sudden braking is performed on a low μ road, and is a diagram for explaining an effect of the present invention. FIG. 3 is a graph showing a time change of a vehicle body speed VB when sudden braking is performed on a high μ road, and is a diagram illustrating an effect of the present invention. FIG. 4 is a graph showing a time change of a vehicle body speed VB when sudden braking is performed on a low μ road, and is a diagram for explaining a problem of the related art. FIG. 5 is a graph showing a time change of the vehicle body speed VB when sudden braking is performed on a high μ road, and is a diagram for explaining a problem of the conventional technology. [Description of Signs] 1 Electronic control unit (ECU) 2 Front / rear G sensor (Longitudinal acceleration detecting means) 4 Wheel speed sensor (Wheel speed detecting means) 6 Integration circuit 8 Reference wheel speed setting device 10 Switch (Update suspending means) 12 Error Corrector (correction means) 14 Differentiator (update interruption means)

Claims (1)

(57) [Claim 1] A longitudinal acceleration detecting means for detecting a longitudinal acceleration of a vehicle, an integrating circuit for integrating the longitudinal acceleration detected by the longitudinal acceleration detecting means and converting the acceleration into a vehicle body speed, A wheel speed detecting means for detecting a peripheral speed of a wheel; and a vehicle speed output from the integrating circuit, which is compared with the peripheral speed detected by the wheel speed detecting means during braking or acceleration of the vehicle. And a correcting means for correcting the longitudinal acceleration based on a difference between the vehicle speed and the vehicle speed. The correcting means comprises: a storing means for storing and holding a correction amount of the longitudinal acceleration; and a peripheral speed detected by the wheel speed detecting means. Updating means for continuously updating the correction amount on the basis of: when the peripheral speed detected by the wheel speed detecting means suddenly changes, updating of the correction amount by the updating means is interrupted. Vehicle speed estimating device characterized by comprising an updating interruption means.