JP2007126057A - Tilt angle inferring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimally infer a tilt angle of a road on which a vehicle having, for example, an acceleration sensor and a wheel speed sensor runs by a tilt angle inferring device. <P>SOLUTION: This tilt angle inferring device infers a tilt angle of the road on which the vehicle having the acceleration sensor and the wheel speed sensor runs. For this reason, the tilt angle inferring device is provided with a tilt angle inferring means for inferring a tilt angle from the relation of a time differential value of wheel speed obtained from the wheel speed sensor and acceleration obtained from the acceleration sensor and a first control means for limiting increase incline of the time differential value when wheel speed is increased beyond a threshold value corresponding to a detection possible region of the wheel speed sensor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inclination angle estimation device that estimates an inclination angle of a road on which a vehicle having, for example, an acceleration sensor and a wheel speed sensor travels.

  In general, when starting or stopping on a slope, it is possible to detect and apply brakes when the vehicle slips in various scenes during travel, or to increase the creep from normal times. There is control. In this control, for example, when starting on a slope, a technique for estimating an inclination angle by subtracting an actual acceleration obtained from an acceleration sensor value and calculating a target driving force according to the inclination angle has been proposed. (See Patent Document 1).

JP 2005-67603 A

  However, for example, the following problem may occur in the technique disclosed in Patent Document 1 described above.

  That is, in the technique disclosed in Patent Document 1, it is indispensable to estimate the inclination angle in order to improve the controllability. In particular, the accelerator is returned while traveling in the upward direction on a slope, and the vehicle moves forward and backward. In a scene where the traveling direction changes, there is a possibility that the estimation of the tilt angle is erroneous. More generally, when a vehicle travels at a very low speed immediately after starting or immediately before stopping, noise is generated significantly in the output of the wheel speed sensor. There is a technical problem that it is difficult.

  The present invention has been made in view of the above-described problems, for example, and provides an inclination angle estimation device capable of estimating the inclination angle of a road with relatively high accuracy even when starting or stopping. Is an issue.

  In order to solve the above problems, a first inclination angle estimation device of the present invention is an inclination angle estimation device for estimating an inclination angle of a road on which a vehicle having an acceleration sensor and a wheel speed sensor travels, and the wheel speed sensor From the relationship between the time differential value of the wheel speed obtained from the acceleration and the acceleration obtained from the acceleration sensor, the inclination angle estimating means for estimating the inclination angle, and the wheel speed corresponds to a detectable region of the wheel speed sensor. And a first control unit that limits an increase gradient of the time differential value when accelerating to a threshold value or more.

  According to the first tilt angle estimating device of the present invention, for example, when the vehicle is running, stopped, or starting, the wheel speed obtained from the wheel speed sensor by the tilt angle estimating means including, for example, a controller or the like. The tilt angle is estimated from the relationship between the time differential value and the acceleration obtained from the acceleration sensor. Typically, the inclination angle of the road is estimated from the difference between the acceleration obtained from the acceleration sensor and the time differential value of the wheel speed, which is affected by gravity according to the inclination of the road. More specifically, the inclination angle θ is calculated using the fact that the value obtained by subtracting the time differential value of the wheel speed from the acceleration obtained from the acceleration sensor is proportional to the sine θ relating to the inclination angle θ. The The acceleration sensor is typically a one-dimensional or two-dimensional sensor, and may be a “front / rear sensor” that can detect at least the longitudinal acceleration of the vehicle, but may be 3 as long as it can detect the longitudinal acceleration of the vehicle. A dimensional acceleration sensor may be used.

  Here, in particular, the wheel speed sensor is composed of a sensor that mechanically and electromagnetically detects the wheel speed, such as a vehicle speed pulse generator, and therefore has a detectable region unique to each sensor. In other words, the wheel speed sensor can detect the wheel speed if the wheel speed is equal to or higher than the threshold corresponding to the detectable area (for example, the low speed area or higher), in other words, can be used with high precision or trial in a practical sense. Detectable to the extent. On the other hand, if the wheel speed is lower than the threshold (for example, lower than the low speed or very low speed range), the wheel speed sensor cannot detect the wheel speed, in other words, can withstand the trial with high accuracy or in a practical sense. It cannot be detected to the extent. The “threshold value” corresponding to such a detectable region is a value determined according to the type of sensor or, strictly speaking, depending on the individual sensor. For this reason, it is possible to specify the region of the speed that can be detected with a precision or withstand the trial in the product specification or the product standard by experimental, empirical, simulation, etc. A threshold value may be set in advance. Furthermore, this threshold value may be set as a fixed value at the time of shipment, or may be configured to be appropriately changed during use or inspection of the vehicle. In addition, a slight margin may be added to the threshold unique to the wheel speed sensor in a strict sense and used as the threshold.

  Therefore, according to the estimation of the inclination angle by the inclination angle estimation means described above, since the adverse effect of the noise of the wheel speed sensor is relatively large at the time of stopping, starting, etc., the inclination angle is accurately estimated. That is difficult or impossible in a practical sense. In particular, during acceleration immediately after starting, the adverse effect of noise of the wheel speed sensor is great even after the wheel speed reaches the detectable region. For this reason, if the output of the wheel speed sensor is simply removed from the non-detectable area, the wheel after the vehicle has started to reach the detectable area after the vehicle starts. The adverse effect on the estimated value of the tilt angle due to the noise of the speed sensor cannot be removed. Further, even if it is attempted to use such a filter as a filter, the noise is sometimes steep or large, so that it is often impossible in practice to effectively cut the noise.

  However, according to the first tilt angle estimation device of the present invention, for example, when starting from a stopped state, when the wheel speed is accelerated to a threshold value corresponding to the detectable region of the wheel speed sensor, for example, a controller or the like is used. The increasing slope of the time differential value is limited by the first control means provided. Then, from the relationship between the time differential value corrected so that the increase gradient is limited by the inclination angle estimation means and the acceleration obtained from the acceleration sensor, or the wheel speed corrected so that the increase gradient is limited. The tilt angle is estimated from the relationship between the time differential value and the acceleration obtained from the acceleration sensor. Therefore, when the vehicle shifts from the undetectable area of the wheel speed sensor to the detectable area of the wheel speed sensor immediately after the vehicle starts moving, the adverse effect on the estimated value of the inclination angle due to noise generated from the wheel speed sensor is noticeable. It becomes possible to reduce it.

  As a result, according to the first inclination angle estimation device of the present invention, it is possible to accurately estimate the inclination angle of a hill during acceleration in a very low speed region or a low speed region, for example. Thereby, for example, brake control, creep control, and the like when starting on a slope can be suitably performed according to the estimated inclination angle.

  In one aspect of the first inclination angle estimating device of the present invention, the first control means corrects the wheel speed so that the increase gradient is limited when the wheel speed accelerates to the threshold value or more. The tilt angle estimating means estimates the tilt angle from the relationship between the corrected time differential value of the wheel speed and the acceleration.

  According to this aspect, when the wheel speed is accelerated to a threshold value corresponding to the detectable range of the wheel speed sensor, the first control means corrects the wheel speed so that the increase gradient is limited. Then, the inclination angle estimation means estimates the inclination angle from the relationship between the corrected time differential value of the wheel speed and the acceleration obtained from the acceleration sensor. In this way, correction by the first control means and estimation by the inclination angle estimation means at the time of acceleration after starting, for example, by a relatively easy change process of correcting the wheel speed output from the wheel speed sensor. Can be done.

  Alternatively, in another aspect of the first tilt angle estimation device of the present invention, the first control means may be configured such that, when the wheel speed accelerates to the threshold value or more, the time differential value is limited so that the increase gradient is limited. The tilt angle estimating means estimates the tilt angle from the relationship between the corrected time differential value and the acceleration.

  According to this aspect, the time differential value of the wheel speed is corrected so that the increase gradient is limited by the first control means when the wheel speed accelerates to a threshold value corresponding to the detectable region of the wheel speed sensor. Is done. Then, the tilt angle is estimated by the tilt angle estimation means from the relationship between the corrected time differential value and the acceleration obtained from the acceleration sensor. As described above, correction by the first control means and estimation by the inclination angle estimation means are performed, for example, at the time of acceleration after starting by a relatively easy change process of correcting the time differential value of the wheel speed. Is possible.

  In order to solve the above problems, a second inclination angle estimation device of the present invention is an inclination angle estimation device that estimates an inclination angle of a road on which a vehicle having an acceleration sensor and a wheel speed sensor travels, and the wheel speed sensor From the relationship between the time differential value of the wheel speed obtained from the acceleration and the acceleration obtained from the acceleration sensor, the inclination angle estimating means for estimating the inclination angle, and the wheel speed corresponds to a detectable region of the wheel speed sensor. And second control means for fixing the time differential value to zero for a predetermined time when accelerating beyond a threshold value.

  According to the second tilt angle estimating device of the present invention, the tilt angle is estimated by the tilt angle estimating means as in the case of the first tilt angle estimating device described above. In particular, during acceleration immediately after starting, the adverse effect of noise of the wheel speed sensor is great even after the wheel speed reaches the detectable region.

  However, according to the second tilt angle estimating device of the present invention, for example, when starting from a stopped state, when the wheel speed is accelerated to a threshold value corresponding to the detectable region of the wheel speed sensor, for example, a controller or the like is used. The time differential value of the wheel speed is fixed to zero for a predetermined time by the second control means provided. Then, during this predetermined time, the tilt angle is estimated from the relationship between the time differential value of the wheel speed fixed to zero and the acceleration obtained from the acceleration sensor by the tilt angle estimating means. Therefore, when the vehicle shifts from the undetectable area of the wheel speed sensor to the detectable area of the wheel speed sensor immediately after the vehicle starts moving, the adverse effect on the estimated value of the inclination angle due to noise generated from the wheel speed sensor is noticeable. It becomes possible to reduce it.

  As a result, according to the second inclination angle estimation device of the present invention, it is possible to accurately estimate the inclination angle of a hill during acceleration in a very low speed region or a low speed region, for example. Thereby, for example, brake control, creep control, and the like when starting on a slope can be suitably performed according to the estimated inclination angle.

  In order to solve the above-described problem, a third inclination angle estimation apparatus of the present invention is an inclination angle estimation apparatus that estimates an inclination angle of a road on which a vehicle having an acceleration sensor and a wheel speed sensor travels, and the wheel speed sensor From the relationship between the time differential value of the wheel speed obtained from the acceleration and the acceleration obtained from the acceleration sensor, the inclination angle estimating means for estimating the inclination angle, and the wheel speed corresponds to a detectable region of the wheel speed sensor. And a third control means for limiting a decreasing gradient of the time differential value when the vehicle decelerates to a threshold value or less.

  According to the third tilt angle estimating apparatus of the present invention, the tilt angle is estimated by the tilt angle estimating means as in the case of the first tilt angle estimating apparatus described above. In particular, during deceleration immediately before the stop, after the wheel speed reaches from the detectable area to the undetectable area, the adverse effect of the noise of the wheel speed sensor is extremely large.

  Therefore, according to the estimation of the tilt angle by the tilt angle estimation means described above, the adverse effect of the noise of the wheel speed sensor is relatively large when decelerating to a very low speed region or when stopping completely. For this reason, it is difficult or impossible in a practical sense to accurately estimate the tilt angle.

  However, according to the third tilt angle estimating device of the present invention, when the wheel speed is reduced to a threshold value corresponding to the detectable region of the wheel speed sensor, for example, when stopping from a low speed state, for example, a controller or the like is used. The decreasing slope of the time differential value is limited by the third control means provided. Then, from the relationship between the time differential value corrected to limit the decrease gradient by the inclination angle estimation means and the acceleration obtained from the acceleration sensor, or the wheel speed corrected to limit the decrease gradient. The tilt angle is estimated from the relationship between the time differential value and the acceleration obtained from the acceleration sensor. Therefore, when the vehicle shifts from the detectable region of the wheel speed sensor to the undetectable region of the wheel speed sensor immediately before the vehicle stops or reaches the very low speed region, the inclination angle due to the noise generated from the wheel speed sensor is reduced. The adverse effect on the estimated value can be significantly reduced.

  As a result, according to the third tilt angle estimating device of the present invention, the tilt angle of the hill can be accurately estimated at the time of deceleration in a very low speed region or a low speed region, for example. Thereby, for example, brake control, creep control, etc. when stopping on a hill can be suitably performed according to the estimated inclination angle.

  In one aspect of the third inclination angle estimation device of the present invention, the third control means corrects the wheel speed so that the decreasing gradient is limited when the wheel speed is decelerated to the threshold value or less. The tilt angle estimating means estimates the tilt angle from the relationship between the corrected time differential value of the wheel speed and the acceleration.

  According to this aspect, when the wheel speed is reduced below the threshold corresponding to the detectable range of the wheel speed sensor, the wheel speed is corrected by the third control means so that the decreasing gradient is limited. Then, the inclination angle estimation means estimates the inclination angle from the relationship between the corrected time differential value of the wheel speed and the acceleration obtained from the acceleration sensor. As described above, correction by the third control means and estimation by the inclination angle estimation means at the time of deceleration immediately before stopping, for example, by a relatively easy change process of correcting the wheel speed output from the wheel speed sensor. Can be done.

  Alternatively, in another aspect of the third tilt angle estimating device of the present invention, the third control means is configured such that when the wheel speed is decelerated below the threshold value, the time differential value is limited so that the decreasing gradient is limited. The tilt angle estimating means estimates the tilt angle from the relationship between the corrected time differential value and the acceleration.

  According to this aspect, when the wheel speed is decelerated below the threshold corresponding to the detectable region of the wheel speed sensor, the time differential value of the wheel speed is corrected so that the decreasing gradient is limited by the third control means. Is done. Then, the tilt angle is estimated by the tilt angle estimation means from the relationship between the corrected time differential value and the acceleration obtained from the acceleration sensor. Thus, for example, correction by the third control means and estimation by the inclination angle estimation means at the time of deceleration immediately before the stop are performed by a relatively easy change process of correcting the time differential value of the wheel speed. Is possible.

  In another aspect of the third tilt angle estimating device of the present invention, the third control means limits the decreasing gradient so that the time differential value converges to zero over time.

  According to this aspect, the decreasing gradient of the time differential value can be limited by a relatively simple process such that the time differential value converges to zero (0). For example, by setting the larger one of the value obtained by subtracting a small amount b from the previous value of the time differential value and zero as the current time differential value, the wheel speed is not dependent on the wheel speed in this way. It is relatively easy to converge the time differential value to zero.

  Hereinafter, an embodiment embodying the present invention will be described in detail with reference to the drawings.

[Constitution]
First, the configuration of a vehicle provided with the tilt angle estimation device according to the present embodiment will be described with reference to FIG. FIG. 1 is a system diagram of a vehicle equipped with the tilt angle estimation device according to the embodiment.

  1, a vehicle 1 according to the embodiment includes a control device 100, a longitudinal G sensor 200, a wheel speed sensor 210, a drive mechanism (an engine 300, a differential gear device 310, an axle 320, a wheel 330), a braking mechanism (brake Actuator 400, master cylinder 410, master pressure sensor 420, wheel cylinder 430).

  The control device 100 is an example of the “tilt angle estimating means”, “first control means”, “second control means”, and “third control means” according to the present invention, and these are preferably known electronic devices. Control unit (Electronic Control Unit: ECU), central processing unit (Central Processing Unit: CPU), read-only memory (ROM) that stores control programs, read-and-write memory (Random Access Memory) that stores various data : RAM) etc. as a logical operation circuit. Furthermore, it is connected via a bus to an input port that receives input signals from various sensors such as the front and rear G sensor 200 and an output port that sends control signals to various actuators such as the brake actuator 400.

  The front-rear G sensor 200 is a sensor that detects an actual acceleration Gx in the front-rear direction of the vehicle 1 as an example of the “acceleration sensor” according to the present invention. The front-rear G sensor 200 is electrically connected to the control device 100, and the control device 100 is preferably configured to constantly monitor the sensor output.

  The wheel speed sensor 210 is a sensor that detects the rotational speeds (ie, wheel speeds) of the left and right wheels. The wheel speed sensor 210 is electrically connected to the control device 100 and is configured such that the detected wheel speed can be transmitted to the control device 100. The control device 100 estimates an inclination angle described later according to the transmitted wheel speed.

  The engine 300 is an example of an “internal combustion engine” according to the present invention. The engine 300 causes an air-fuel mixture to explode by a spark plug in a cylinder (not shown), and converts a reciprocating motion of a piston generated according to an explosive force into a rotational motion. It is configured to be possible. Torque generated by the engine 300 is transmitted to the wheel 300 via the differential gear device 310 and the axle 320.

  The differential gear device 310 is formed of, for example, a so-called differential gear, and has a torque transmission function as described above, and realizes smooth cornering by absorbing a rotational difference generated between the left and right wheels when the vehicle 1 turns, for example. It is a mechanism to do.

  The axle 320 is a shaft that connects the differential gear device 310 and the wheel 330 and rotates the wheel 330. In the independent suspension system that improves the followability to the road surface unevenness, an axle that allows the wheels 330 on both sides to freely move up and down is used.

  The wheel 330 is configured to rotate by receiving torque transmitted from the axle 320 and to drive the vehicle 1. In addition to the provision of the wheel cylinder 430 as a braking mechanism, the wheel speed is detected by the wheel speed sensor 210 and used for this control.

  The brake actuator 400 is electrically connected to the control device 100 and is configured to be able to adjust the braking mechanism by controlling the hydraulic pressure of each wheel cylinder 430 according to the upper control by the control device 100. Specifically, it functions as a braking mechanism that brakes the vehicle 1 by transmitting the hydraulic pressure of the brake oil to the wheel cylinder 430 via the master cylinder 410 and the brake actuator 400. Such a braking mechanism is used not only when the driver deliberately presses down the brake pedal during normal driving, but also automatically in response to falling on the slope as part of slope start support control. Sometimes used. The present invention proposes a technique that is particularly useful in the latter case.

  The master cylinder 410 is configured to be able to change the force corresponding to the amount of depression of the driver's brake petal to the hydraulic pressure of the brake oil.

  The master pressure sensor 420 is configured to be able to detect the hydraulic pressure of the brake oil converted by the master cylinder 410, and the output value is transmitted to the electrically connected control device 100. The master pressure transmitted to the control device 100 is used for controlling the brake actuator 400 and the like.

  The wheel cylinder 430 is provided in each wheel, and there are two types, a double-sided expansion type mainly including a piston on both sides, and a single-sided expansion type where the piston is only one side. Regardless of the type, the piston is spread by receiving the hydraulic pressure of the brake oil, and the vehicle 1 is braked.

  As described above, as shown in FIG. 1, the vehicle 1 according to this embodiment includes the front-rear G sensor 200 and the wheel speed sensor 210, and the wheel speed sensor 210 cannot be detected by the control device 100 analyzing their outputs. The wheel speed differential value (that is, the time differential value) during proper low-speed traveling is corrected as appropriate. Alternatively, the wheel speed itself that is the basis of the differential value of the wheel speed is corrected as appropriate. Therefore, the road inclination angle can be estimated with relatively high accuracy even when traveling on such a low-speed inclined road.

[Estimation formula for tilt angle θ]
Next, according to FIG. 2, the relationship between various physical quantities when the vehicle travels on an inclined road and an estimation formula for the inclination angle θ will be described below. FIG. 2 is a characteristic diagram showing various physical quantities when the vehicle travels on the road.

  In general, there is a relationship represented by the following expression (0-1) between the inclination angle of the road as shown in FIG. 2 and the acceleration of the vehicle 1 traveling on the road.

gSinθ = Gx−Dvx formula (0−1)
Here, g represents the gravitational acceleration, θ represents the inclination angle of the road on which the vehicle 1 is approaching, gSinθ represents the road surface direction component of the gravitational acceleration, and Gx represents the acceleration detected by the front and rear G sensor 200 (that is, Dvx indicates a time differential value (ie, expected acceleration) of the vehicle body speed Vx detected by the wheel speed sensor 210.

  In Formula (0-1), since the vehicle 1 is traveling on a road having an inclination angle θ as shown in FIG. 2, the vehicle surface component gSinθ of gravitational acceleration is actually detected by the front-rear G sensor 200. The actual acceleration Gx of the vehicle and the predicted acceleration Dvx of the vehicle 1 estimated from the wheel speed are shown as a difference. That is, in order to obtain the actual acceleration Gx, it is necessary to consider the influence of the road surface direction component of the gravitational acceleration corresponding to the inclination angle to the predicted acceleration Dvx.

  As described above, as shown in FIG. 2, the tilt angle estimation apparatus according to the present embodiment can indirectly estimate the tilt angle θ from other physical quantities by using the equation (0-1). However, when the wheel speed is a low speed that cannot be detected by the sensor, the following cautions are necessary. The present invention is a technique for suitably estimating the inclination angle θ even in the case of such a low speed.

[Comparison of the tilt angle estimation technique according to the comparative example and the tilt angle estimation technique according to the present invention]
Next, according to FIG. 3, the tilt angle estimation technique according to the comparative example and the tilt angle estimation technique according to the present invention are compared.

  FIG. 3 is a characteristic diagram for comparing the tilt angle estimation technique according to the comparative example and the tilt angle estimation technique according to the present invention. Differences in driving conditions or estimation methods are compared in the left column, the center column, and the right column. Here, each figure in the left column shows how the tilt angle during normal acceleration is estimated, and each figure in the center column shows when the traveling direction changes from forward to backward by the tilt angle estimation technique according to the comparative example. The manner in which the tilt angle is estimated is shown, and each figure in the right column shows the manner in which the tilt angle is estimated when the traveling direction changes from forward to backward by the tilt angle estimation technique according to the present invention.

  Here, the comparative example refers to a case where the inclination angle θ is estimated without using any of the first control unit, the second control unit, and the third control unit according to the present invention. ), The case where the inclination angle θ is estimated without using the equations (2-1) and (2-2).

  In addition, the four figures arranged in the upper and lower parts of each row are examples of “acceleration obtained from the acceleration sensor” according to the present invention in order from the top, the time change of the actual acceleration Gx (Gx-T diagram), the wheel speed Vx. Time change (Vx-T diagram), time change of predicted acceleration Dvx (Dvx-T diagram), which is an example of “time differential value of wheel speed obtained from wheel speed sensor” according to the present invention, and inclination angle component of gravitational acceleration The time change (gSinθ-T diagram) of gSinθ is shown. In each figure shown in FIG. 3, the horizontal axis is the time axis (T-axis) in all cases where the horizontal axis is not specified. Below, the characteristics in each case will be described in the order of the left column, the center column, and the right column.

  First, each figure in the left column shows how the road inclination angle during normal acceleration is estimated. Here, “normal acceleration” means that the vehicle is accelerating when the wheel speed Vx is large enough to be detected by the wheel speed sensor 210 (ie, the wheel speed sensor can be detected). Therefore, the road inclination angle θ can be estimated using either the inclination angle estimation technique according to the comparative example or the inclination angle estimation technique according to the present invention.

  The left column Gx-T diagram shows an example of a time change of the actual acceleration Gx in the case of normal traveling, and it can be seen that the actual acceleration Gx changes in a mountain from time t1 to t2.

  In the left column Vx-T diagram, the wheel speed Vx detected by the wheel speed sensor 210 increases with a change in the actual acceleration Gx from time t1 to time t2.

  The left column Dvx-T shows how the expected acceleration Dvx is derived by differentiating the wheel speed Vx of the vehicle 1. Here, the predicted acceleration Dvx changes like a mountain from the time t1 to the time t2, similarly to the Gx-T diagram, and Dvx = 0 before the time t1 and after the time t2. Comparing the left column Gx-T diagram and the left column Dvx-T diagram, although Gx and Dvx have the same or very close relative changes, there are some differences in absolute values. There is. In order to clarify this difference, the following left column gSinθ-T diagram was prepared.

  The left column gSinθ-T diagram shows the time change of the difference between the acceleration Gx and Dvx of the vehicle 1. This difference corresponds to the gravitational acceleration gSinθ corresponding to the inclination angle that the vehicle 1 receives when traveling on the road, as shown in the equation (0-1). Therefore, the road inclination angle θ can be derived by measuring the difference between the actual acceleration Gx and the wheel speed Vx.

  As described above, when the wheel speed Vx is sufficiently detected by the wheel speed sensor 210 as shown in the left column, the inclination angle θ can be estimated without any particular difficulty.

  However, as shown in the center row, the absolute value of the wheel speed Vx is smaller than the absolute value of the minimum detectable wheel speed a which is an example of the “threshold corresponding to the detectable region of the wheel speed sensor” according to the present invention. In this case, it is not as simple as the left column described above. This is because the wheel speed Vx is not accurately detected and steep noise occurs in Dvx. This will be described below. Here, the minimum detectable wheel speed threshold value a means the minimum wheel speed that can be detected by the wheel speed sensor 210 and is basically a value determined by the performance of the wheel speed sensor, for example, 0.8 km / Although it is h, it is the meaning which may be suitably changed by the advance of the kind of wheel speed sensor or sensor technology.

  First, the center Gx-T diagram shows that the vehicle 1 is moving at substantially equal acceleration.

  Here, for example, as shown in the center Vx-T diagram, while traveling on an inclined road in the upward direction, it is assumed that the traveling direction changes from forward to backward by returning the accelerator. In such a situation, the wheel speed Vx may fall below the minimum detectable wheel speed threshold value a before and after switching from forward to reverse. In particular, it can be seen that Vx changes abruptly immediately after time T = t3 (the moment when Vx falls below a) or immediately after time T = t4 (the moment when Vx falls below −a). The abrupt change in Vx does not mean that the wheel speed has actually changed in such a way that the wheel speed sensor 210 changes abruptly because the wheel speed sensor 210 cannot detect a value below the minimum detectable wheel speed threshold value a. It is only output.

  The center Dvx-T diagram is a diagram showing the time differential value of the actual acceleration Gx. Here, steep noise occurs immediately after T = t3 and T = t4. This noise does not mean that Dvx has actually made such a steep change, but merely because the inappropriate Vx below the minimum detectable wheel speed a is differentiated as it is. However, it is difficult to remove such noise by conventional filter processing.

  The central gSinθ-T diagram is also a diagram showing the difference between the central Gx-T diagram and the central Dvx-T diagram, and thus the noise in the above-mentioned central Dvx-T diagram is not removed. This is one of the causes for lowering the accuracy of tilt angle estimation according to the prior art. The effects of the present invention made to deal with such problems will be described below with reference to the drawings in the right column.

  Here, each figure in the right column represents detection results or calculation results of various physical quantities that lead to the estimation of the inclination angle θ according to the present invention. The right column Gx-T diagram and the right column Vx-T diagram are the same as the center column Gx-T diagram and the center column Vx-T diagram, respectively, and thus description thereof is omitted. That is, in this case as well, as in the case of the central row (prior art), the traveling direction changes from forward to backward by returning the accelerator while traveling in the upward direction on the road. The prior art under such circumstances should generate steep noise as seen in the center row.

  The cause of such noise is that the wheel speed sensor 210 cannot accurately detect the wheel speed Vx in the very low speed region. Therefore, in the right column Dvx-T diagram, the following formula (1-1), formula (2-1), and formula (2-2) are properly used according to the wheel speed Vx to correct the expected acceleration Dvx. Then, the inclination angle θ is estimated. Here, the expression (1-1) is used when the wheel speed Vx changes from the area that can be detected by the wheel speed sensor 210 to the area that cannot be detected, and conversely, the expression (2-1) and the expression (2) -2) is an expression used when the wheel speed Vx changes from a region that cannot be detected by the wheel speed sensor 210 to a region that can be detected.

Dvx (current value)
= Max ((Dvx (previous value) −b), 0) (Dvx (previous value) ≧ 0)
Or min ((Dvx (previous value) + b), 0) (Dvx (previous value) <0) Equation (1-1)
Dvx (current value) = 0 (period in which noise is expected) Formula (2-1)
Dvx (current value)
= Min ((Dvx (previous value) + c), Dvx (current operation value)) (Dvx (previous value) ≧ 0)
Or max ((Dvx (previous value) −c), Dvx (current calculation value)) (Dvx (previous value) <0) Equation (2-2)
In Expression (1-1), Dvx (current value) indicates an expected acceleration calculated this time based on the calculation result according to Expression (1-1), and Dvx (previous value) is expressed by Expression (1-1). Indicates the expected acceleration obtained by the previous calculation according to the above, and max (A, B) indicates the larger one of A and B. For example, when A> B, max (A, B) = A. Further, min (A, B) indicates the smaller value of A and B. For example, when A> B, min (A, B) = B. Further, b may indicate a constant obtained by experiment, experience, simulation, or the like as a value suitable for making Dvx asymptotic to 0, or the acceleration change of the vehicle 1 immediately before performing this processing A variable obtained from the above may be indicated.

  In Expression (2-1), the “period in which noise is expected to occur” is, for example, between time T = t4 and 20 [msec] in the figure, and the period in which noise actually occurs is experimental and experienced. Or a constant determined by simulation or the like, or may be a variable specifically determined according to the running state of the vehicle 1 or the like. This is to the extent that such noise may be freely determined as long as it is sufficiently small in practice.

  In Expression (2-2), Dvx (currently calculated value) is a time differential value of the wheel speed Vx detected this time by the wheel speed sensor 210. Therefore, if the wheel speed Vx changes sharply, noise may occur. is there. Further, c is a “gradient limiter”, that is, a change amount of the expected acceleration Dvx allowed between Dvx (previous value) and Dvx (current value), and Dvx (previous value) and Dvx (current calculated value). Is larger than c, Dvx (currently calculated value) is unduly too large, and such correction is applied. The value of the gradient limiter c may indicate a constant obtained experimentally, empirically, or by simulation as a value that is recognized as not abnormal as the amount of change in actual acceleration in actual driving, and may depend on the interval of loop calculation processing, etc. That is, it may be a required variable.

  According to the above three formulas, in the comparative example, steep noise that occurs when the wheel speed Vx changes from the region that can be detected by the wheel speed sensor 210 to the region that cannot be detected is reduced. Specifically, the control device 100 converges the predicted acceleration Dvx to 0 stepwise according to the equation (1-1) (see the right column Dvx-T diagram). Accordingly, gSinθ is suitably derived according to the equation (0-1) (see the right column gSinθ-T diagram).

  Further, when the wheel speed Vx changes from a region that cannot be detected by the wheel speed sensor 210 to a region that can be detected, any one of the above-described equations (2-1) and (2-2). For example, the noise of Dvx (currently calculated value) generated when the wheel speed Vx gradually increases from a very low speed that cannot be detected and exceeds the minimum detectable wheel speed threshold value a, for example, is preferably reduced. (See the right column Dvx-T diagram). Therefore, the predicted acceleration Dvx can be suitably obtained even when traveling at a very low speed. Accordingly, gSinθ is suitably derived according to the equation (0-1) (see the right column gSinθ-T diagram).

  As described above, as shown in FIG. 3, the inclination angle estimation device according to the present embodiment makes the accuracy of the inclination angle estimation as known in the prior art even when traveling at a very low speed, for example, lower than the minimum detectable wheel speed threshold value a. Compared to this, various vehicle motion control or driving support control in the speed region can be suitably performed.

  Next, specific operation processing according to the embodiment of the present invention will be described by classifying from the first embodiment to the third embodiment. Here, the first embodiment is a control example in the case where the wheel speed Vx of the vehicle 1 transitions from the detectable area of the wheel speed sensor 210 to the undetectable area (using Expression (1-1)). The second embodiment is a control example in the case where the wheel speed Vx of the vehicle 1 transitions from the undetectable region of the wheel speed sensor 210 to the detectable region (using Expression (2-1)). Furthermore, the third embodiment is also a control example in the case where the wheel speed Vx of the vehicle 1 transitions from the non-detectable area of the wheel speed sensor 210 to the detectable area (using Expression (2-2)).

[First Embodiment]
When the wheel speed Vx of the vehicle 1 transitions from the detectable area of the wheel speed sensor 210 to the undetectable area (for example, decelerates or stops to a very low speed), the inclination angle θ is estimated using the equation (1-1). The operation processing of the embodiment (first embodiment) will be described with reference to FIG. 4 in addition to FIGS. FIG. 4 is a flowchart showing an example of operation processing according to the first embodiment.

  In FIG. 4, first, the actual acceleration Gx is acquired by the longitudinal G sensor 200. (Step S1010) Then, in order to remove noise of the detected actual acceleration Gx, a filter process is performed on the actual acceleration Gx (step S1020).

Subsequently, the expected acceleration Dvx (current value) is acquired as described below. Here, if the wheel speed Vx is within the detectable range of the wheel speed sensor 210, the predicted acceleration Dvx (current value) can be used as the time differential value of the detected wheel speed Vx. Since it is a case where it changes from a setting of a form to an undetectable field, it is impossible to detect wheel speed Vx. Therefore, the expected acceleration Dvx (current value) is obtained using Equation (1-1). Specifically, first, it is determined whether Dvx (previous value) is 0 or more (step S1030). When it is determined that Dvx (previous value) is 0 or more (step S1030: YES), the larger one of “Dvx (previous value) −b” and 0 is acquired as Dvx (current value). (Step S1031). By repeating such processing, the expected acceleration Dvx changes step by step b without abrupt change, and finally converges to zero. Here, the initial value of Dvx (previous value), that is, the value of Dvx (previous value) when using formula (1-1) for the first time after transition from the detectable region to the undetectable region is preferably May adopt the time differential value of the immediately preceding wheel speed Vx. On the other hand, when it is determined that Dvx (previous value) is smaller than 0 (step S1030: NO), the smaller one of “Dvx (previous value) + b” and 0 is acquired as Dvx (current value). (Step S1032)
The value of gSinθ is obtained by substituting the actual acceleration Gx and the predicted acceleration Dvx (current value) acquired in this way into the equation (0-1) (step S1040). That is, the inclination angle θ is obtained.

  Therefore, according to the present embodiment, it is possible to appropriately estimate the inclination angle θ even when the wheel speed transitions from the detectable region of the wheel speed sensor to the undetectable region (for example, decelerates or stops to a very low speed). It becomes possible.

[Second Embodiment]
Subsequently, for the second embodiment, that is, when the wheel speed Vx of the vehicle 1 transitions from the undetectable region of the wheel speed sensor 210 to the detectable region (for example, stops or accelerates from a very low speed), the equation (2- The operation process when estimating the inclination angle θ using 1) will be described with reference to FIG. 5 in addition to FIGS. FIG. 5 is a flowchart showing an example of the operation process according to the second embodiment. In FIG. 5, the same steps as those in FIG. 4 are denoted by the same step numbers, and detailed description thereof is omitted as appropriate.

  Also in FIG. 5, first, the actual acceleration Gx is acquired by the longitudinal G sensor 200. (Step S1010) Then, in order to remove noise of the detected actual acceleration Gx, a filter process is performed on the actual acceleration Gx (step S1020).

  Subsequently, the expected acceleration Dvx (current value) is acquired as described below. First, whether or not the wheel speed Vx of the vehicle 1 is within a “period in which noise generation is expected” from the time when the wheel speed sensor 210 transitions from a non-detectable area to a detectable area of the wheel speed sensor 210 (ie, stops or accelerates from a very low speed) Is determined (step S2030). That is, it is determined whether or not it is within the “period in which noise generation is expected” after the wheel speed Vx becomes greater than the minimum detectable wheel speed threshold value a (+ α). For example, in FIG. 3, it is determined whether T = t4 is within 20 [msec]. Here, the “period in which noise generation is expected” refers to the “period in which noise generation is expected” according to Expression (2-1). In addition, (+ α) means that it is possible to make a determination with a slight margin as well as a determination based on a sensor performance limit value when performing the determination.

  Here, if it is within the “period in which noise generation is expected” (step S2030: Yes), the wheel speed Vx is in the detectable region, but the period in which noise generation is expected has not elapsed. It is considered that steep noise occurs in Dvx (currently calculated value) which is a time differential value of Vx. Accordingly, the predicted acceleration Dvx (current value) within this period is not Dvx (currently calculated value), but 0 (or a minute value corresponding thereto) (step S2031).

  On the other hand, if it is not within the “period in which noise generation is expected” (step S2030: No), the wheel speed Vx is in the detectable region and the period in which noise generation is expected has elapsed. It is considered that noise generated in the time differential value Dvx (currently calculated value) is subsided. Therefore, Dvx (currently calculated value) is adopted as the predicted acceleration Dvx (current value). Specifically, first, the wheel speed Vx is detected by the wheel speed sensor 210 (step S2032). The control device 100 obtains Dvx (currently calculated value) by differentiating the detected wheel speed Vx with respect to time (step S2033). Filter processing is performed on the acquired Dvx (currently calculated value) (step S2034). In this way, Dvx (currently calculated value) from which noise has been removed by greater or lesser is adopted as the predicted acceleration Dvx (current value) (step S2035).

  The value of gSinθ is obtained by substituting the actual acceleration Gx and the predicted acceleration Dvx (current value) acquired in this way into the equation (0-1) (step S1040). That is, the inclination angle θ is obtained.

  Therefore, according to the present embodiment, even when the wheel speed transitions from the undetectable region of the wheel speed sensor to the detectable region (for example, stops or accelerates from a very low speed), the inclination angle θ can be estimated appropriately. It becomes possible.

[Third Embodiment]
Subsequently, for the third embodiment, that is, when the wheel speed Vx of the vehicle 1 transitions from the undetectable region of the wheel speed sensor 210 to the detectable region (for example, stops or accelerates from a very low speed), the equation (2- In addition to FIGS. 1 to 5, the operation process when estimating the tilt angle θ using 2) will be described with reference to FIG. 6. FIG. 6 is a flowchart showing an example of the operation process according to the third embodiment. In FIG. 6, the same steps as those in FIGS. 4 and 5 are denoted by the same step numbers, and detailed description thereof will be omitted as appropriate.

  Also in FIG. 6, first, the actual acceleration Gx is acquired by the longitudinal G sensor 200. (Step S1010) Then, in order to remove noise of the detected actual acceleration Gx, a filter process is performed on the actual acceleration Gx (step S1020).

  Subsequently, the expected acceleration Dvx (current value) is acquired as described below. First, as in the second embodiment, Dvx (currently calculated value) is adopted as the predicted acceleration Dvx (current value). Specifically, first, the wheel speed Vx is detected by the wheel speed sensor 210 (step S2032). The control device 100 obtains Dvx (currently calculated value) by differentiating the detected wheel speed Vx with respect to time (step S2033). Filter processing is performed on the acquired Dvx (currently calculated value) (step S2034). Up to this point, the processing is the same as in the second embodiment.

  In the present embodiment, thereafter, an expected acceleration Dvx (current value) is acquired based on Dvx (current calculated value) acquired in the above processing and Expression (2-2). Specifically, first, it is determined whether Dvx (previous value) is 0 or more (step S1030). If it is determined that Dvx (previous value) is 0 or more (step S1030: YES), the smaller one of Dvx (current calculation value) and {Dvx (previous value) + c} is Dvx (current value). Value) (step S3031). This is because it is not appropriate for the amount of change in the predicted acceleration Dvx from the previous time to this time to exceed the gradient limiter c. Conversely, the gradient limiter c is defined as a reasonable amount of change in the expected acceleration Dvx. On the other hand, when it is determined that Dvx (previous value) is smaller than 0 (step S1030: NO), of Dvx (current calculation value) and {Dvx (previous value) -c}, whichever is greater is Dvx ( This value) is acquired (step S3032).

  The value of gSinθ is obtained by substituting the actual acceleration Gx and the predicted acceleration Dvx (current value) acquired in this way into the equation (0-1) (step S1040). That is, the inclination angle θ is obtained.

  Therefore, according to the present embodiment, even when the wheel speed transitions from the undetectable region of the wheel speed sensor to the detectable region (for example, stops or accelerates from a very low speed), the inclination angle θ can be estimated appropriately. It becomes possible.

  According to the embodiment described above, it is possible to appropriately estimate the inclination angle of the road on which the vehicle is traveling. The inclination angle estimated in this way can be used for the following requirements. That is, the vehicle motion control and the driving support control in a relatively low speed range, the abnormality detection determination of other sensors, or other traveling such as a DAC (Downhill Assist Control: DAC) or a low speed ACC (Adaptive Cruise Control: ACC). It can also be used for control. Further, when implementing the present invention, it is possible to use the wheel speed sensor 210 and the front / rear G sensor 200 which are essential in ABS (Antilock Break System: ABS) or VSC (Vehicle Stability Control: VSC), and the cost of hardware is reduced. Up is suppressed.

  Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and the inclination accompanying such a change. The angle estimation device is also included in the technical scope of the present invention.

1 is a system diagram of a vehicle equipped with a tilt angle estimation device according to an embodiment. It is a characteristic view showing various physical quantities when a vehicle drive | works a road. It is a characteristic view for comparing the inclination angle estimation technique according to the comparative example and the inclination angle estimation technique according to the present invention. It is a flowchart which shows an example of the operation | movement process which concerns on 1st Embodiment. It is a flowchart which shows an example of the operation process which concerns on 2nd Embodiment. It is a flowchart which shows an example of the operation process which concerns on 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 100 ... Control apparatus, 200 ... Front-back G sensor, 210 ... Wheel speed sensor, 300 ... Engine, 310 ... Differential gear apparatus, 320 ... Axle, 330 ... Wheel, 400 ... Brake actuator, 410 ... Master cylinder, 420 ... Master pressure sensor, 430 ... Wheel cylinder

Claims (8)

An inclination angle estimation device for estimating an inclination angle of a road on which a vehicle having an acceleration sensor and a wheel speed sensor travels,
From the relationship between the time differential value of the wheel speed obtained from the wheel speed sensor and the acceleration obtained from the acceleration sensor, an inclination angle estimating means for estimating the inclination angle;
Inclination angle estimation, comprising: first control means for limiting an increase gradient of the time differential value when the wheel speed is accelerated to a threshold value corresponding to a detectable region of the wheel speed sensor. apparatus. The first control means corrects the wheel speed so that the increase gradient is limited when the wheel speed accelerates to the threshold value or more,
2. The tilt angle estimation apparatus according to claim 1, wherein the tilt angle estimation means estimates the tilt angle from a relationship between the corrected time differential value of the wheel speed and the acceleration. The first control unit corrects the time differential value so that the increase gradient is limited when the wheel speed is accelerated to the threshold value or more,
2. The tilt angle estimation apparatus according to claim 1, wherein the tilt angle estimation means estimates the tilt angle from a relationship between the corrected time differential value and the acceleration. An inclination angle estimation device for estimating an inclination angle of a road on which a vehicle having an acceleration sensor and a wheel speed sensor travels,
From the relationship between the time differential value of the wheel speed obtained from the wheel speed sensor and the acceleration obtained from the acceleration sensor, an inclination angle estimating means for estimating the inclination angle;
And a second control means for fixing the time differential value to zero for a predetermined time when the wheel speed is accelerated to a threshold value corresponding to a detectable region of the wheel speed sensor. Angle estimation device. An inclination angle estimation device for estimating an inclination angle of a road on which a vehicle having an acceleration sensor and a wheel speed sensor travels,
From the relationship between the time differential value of the wheel speed obtained from the wheel speed sensor and the acceleration obtained from the acceleration sensor, an inclination angle estimating means for estimating the inclination angle;
Inclination angle estimation, comprising: a third control means for limiting a decrease gradient of the time differential value when the wheel speed is decelerated below a threshold corresponding to a detectable region of the wheel speed sensor. apparatus. The third control unit corrects the wheel speed so that the decreasing gradient is limited when the wheel speed is decelerated below the threshold value,
6. The tilt angle estimation apparatus according to claim 5, wherein the tilt angle estimation means estimates the tilt angle from a relationship between the corrected time differential value of the wheel speed and the acceleration. The third control unit corrects the time differential value so that the decreasing gradient is limited when the wheel speed is decelerated below the threshold value,
6. The tilt angle estimation apparatus according to claim 5, wherein the tilt angle estimation unit estimates the tilt angle from a relationship between the corrected time differential value and the acceleration. 8. The tilt angle estimation device according to claim 5, wherein the third control unit limits the decrease gradient so that the time differential value converges to zero with time. .

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