JP5521943B2 - Vehicle total weight estimation device - Google Patents

Description

  The present invention relates to a total weight estimation device for a vehicle.

  2. Description of the Related Art Conventionally, there has been known an apparatus for detecting a sinking amount of a vehicle body with respect to an axle and estimating a vehicle loading weight (and hence a total weight) from the sinking amount (see Patent Document 1). In the device described in this document, at least the front wheel position and the rear wheel position are detected in order to accurately detect the amount of sinking of the vehicle body that is necessary to accurately obtain the total vehicle weight while eliminating the influence of the load bias on the vehicle body. One vehicle height sensor is required for each wheel position.

JP-A 63-63924

  In recent years, there are many vehicles equipped with a vehicle height sensor for adjusting the optical axis of a headlight. However, most of these mount the vehicle height sensor only at the rear wheel position. When estimating the total vehicle weight using the device described in the above document for a vehicle equipped with a vehicle height sensor only at the rear wheel position, the estimation error increases as the position of the center of gravity of the load shifts to the front of the vehicle body with respect to the rear wheel position. The problem may be that the increase is large.

  Incidentally, in recent years, there are many vehicles equipped with a steering torque sensor that detects the steering torque of a steering wheel operated by a driver, such as a vehicle equipped with an electric power steering device. The present inventor accurately estimates the total weight of the vehicle by effectively using the vehicle height sensor disposed at the rear wheel position mounted on many vehicles and the steering torque sensor mounted on many vehicles. As a result of studying whether there is a method to do so, the present invention has been achieved.

  An object of the present invention is to provide a vehicle total weight estimation device capable of accurately estimating a vehicle total weight by effectively using detection results of a vehicle height sensor and a steering torque sensor arranged at a rear wheel position.

  A total vehicle weight estimation apparatus according to the present invention includes a steering torque sensor that detects a steering torque, a front wheel slip angle calculation unit that calculates a slip angle of a front wheel, a vehicle height sensor that detects a vehicle height of a rear wheel position, A turning determination means for determining whether the vehicle is turning or not turning, and a longitudinal acceleration detection means for detecting a longitudinal acceleration of the vehicle.

  The vehicle gross weight estimating apparatus according to the present invention is characterized by comprising front wheel axle weight estimating means, rear wheel axle weight estimating means, and vehicle gross weight estimating means. Hereinafter, each means will be described in order.

  When it is determined that the vehicle is turning, the front wheel axle weight estimation means is configured as “a predetermined relationship among the steering torque, the front wheel slip angle, and the front wheel axle weight of the vehicle”. The front wheel axle weight of the vehicle is estimated based on the detected steering torque and the calculated front wheel slip angle. In the above relationship, “steering torque” can be rewritten as “self-aligning torque”.

  The relationship (see FIG. 4 to be described later) is a relationship obtained during vehicle turning in which self-aligning torque is generated. In other words, when the vehicle is turning, the front wheel axle load can be accurately estimated using the relationship. The front wheel axle weight estimation means is configured based on such knowledge.

  The rear wheel axle weight estimating means estimates the rear wheel axle weight of the vehicle based on the detected height of the rear wheel position when it is determined that the vehicle is not turning. In general, a vehicle height sensor that detects the vehicle height at the rear wheel position is disposed on one of the left and right sides of the rear wheel axle. Therefore, during turning of the vehicle, the rear wheel axle weight cannot be accurately estimated using the vehicle height sensor due to the influence of the centrifugal force acting on the vehicle. In other words, if the vehicle is not turning, the rear wheel axle weight can be accurately estimated using the vehicle height sensor. The rear wheel axle weight estimation means is configured based on such knowledge.

  The vehicle gross weight estimating means is configured to determine whether the difference between the longitudinal acceleration when the front wheel axle weight is estimated and the longitudinal acceleration when the rear wheel axle weight is estimated is equal to or less than a predetermined value. Based on the combination with wheel load, the total weight of the vehicle is estimated.

  The front wheel axle weight estimated by the front wheel axle weight estimating means (during vehicle turning) is reduced by an inertial force during vehicle acceleration and increased by an inertial force during vehicle deceleration as compared to when driving at a constant speed. Conversely, the rear wheel axle weight estimated by the rear wheel axle weight estimating means (during non-turning of the vehicle) increases by an inertial force during vehicle acceleration and decreases by an inertial force when the vehicle decelerates compared to when driving at a constant speed. To do. That is, the inertial force component is canceled out by calculating the sum of the estimated front wheel axle weight and rear wheel axle weight at the time of vehicle acceleration and vehicle deceleration.

  From the above, under the condition that the difference between the longitudinal acceleration when the front wheel axle weight is estimated and the longitudinal acceleration when the rear wheel axle weight is estimated is small, not only when driving at constant speed but also when accelerating and decelerating the vehicle. Even when the sum of the estimated front wheel axle weight and rear wheel axle weight can be a value that accurately represents the total vehicle weight. The vehicle total weight estimating means is configured based on such knowledge.

  According to the above configuration, estimation of the front wheel axle weight using the steering torque sensor and estimation of the rear wheel axle weight using the vehicle height sensor are performed individually at different timings during vehicle turning and vehicle non-turning, respectively. Based on the estimation result, the total vehicle weight can be accurately estimated.

  In a preferred aspect, a combination of the front wheel axle weight estimated when the longitudinal acceleration is within a predetermined range including zero and the rear wheel axle weight estimated when the longitudinal acceleration is within the predetermined range. Based on the above, the total vehicle weight is estimated.

  The front wheel axle weight estimation means may be configured not to execute the estimation of the front wheel axle weight when it is determined that the front wheel slip angle exceeds a predetermined value. The front wheel slip angle and the steering torque (self-aligning torque) are in a substantially proportional relationship when the front wheel slip angle is small, but the proportional relationship is lost when the front wheel slip angle is large (see FIG. 5 described later). The relationship (see FIG. 4) is a relationship obtained based on this proportional relationship. From the above, if the front wheel slip angle is large enough to break this proportional relationship, the front wheel axle load cannot be accurately estimated based on the relationship. The above configuration is based on such knowledge. According to this, the occurrence of a situation in which the total vehicle weight is incorrectly estimated based on the inaccurate front wheel axle weight is suppressed.

  Further, the front wheel axle weight estimation means may be configured not to execute the estimation of the front wheel axle weight when it is determined that the calculated time change rate of the front wheel steering angle exceeds a predetermined value. The above-described relationship (see FIG. 4) is a relationship obtained when traveling with a constant front wheel steering angle. When the time change rate of the front wheel rudder angle is large, the delay in the change of the steering torque (self-aligning torque) becomes large with respect to the change of the front wheel slip angle. As a result, the relationship cannot be maintained. From the above, when the time change rate of the front wheel rudder angle is large, the front wheel axle load cannot be accurately estimated based on the above relationship. The above configuration is based on such knowledge. According to this, the occurrence of a situation in which the total vehicle weight is incorrectly estimated based on the inaccurate front wheel axle weight is suppressed.

1 is a schematic configuration diagram of a vehicle equipped with a total vehicle weight estimation device according to an embodiment of the present invention. It is a flowchart which shows the flow of a process when a vehicle gross weight is estimated by the gross weight estimation apparatus shown in FIG. FIG. 3 is a graph showing a map that defines the relationship between rear wheel side vehicle height and rear wheel axle weight, which is referred to by the total weight estimation device shown in FIG. 1. 2 is a graph showing a map that defines the relationship between steering torque (self-aligning torque), front wheel slip angle, and front wheel axle weight, which is referred to by the total weight estimating device shown in FIG. 1. It is the graph which showed an example of the relationship between a front wheel slip angle and steering torque (self-aligning torque). It is the time chart which showed an example of the change of various physical quantities when a vehicle gross weight is estimated by the gross weight estimation apparatus shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a total vehicle weight estimation control device according to the present invention will be described with reference to the drawings.

(Constitution)
FIG. 1 shows a schematic configuration of a vehicle on which a total vehicle weight estimation device (hereinafter referred to as “the present device”) according to an embodiment of the present invention is mounted. As shown in FIG. 1, the present apparatus includes a vehicle height sensor HG that detects the vehicle height at the rear wheel position, and a steering torque sensor ST that detects the steering torque of the steering wheel SW. The vehicle height sensor HG is disposed on one of the left and right sides (in this example, the left side) of the rear wheel axle. The vehicle height sensor HG can be used for adjusting the optical axis of a vehicle headlight (not shown). The steering torque sensor ST is interposed in a steering shaft (steering column). The steering torque sensor ST can be used for controlling the electric power steering apparatus EPS.

  This apparatus includes a wheel speed sensor WS ** that detects the wheel speed of the wheel WH **, a longitudinal acceleration sensor GX that detects acceleration in the longitudinal direction of the vehicle (longitudinal acceleration), and a yaw rate sensor YR that detects the yaw rate of the vehicle. And a front wheel steering angle sensor FS for detecting the steering angle of the front wheels. Here, “**” comprehensively indicates “fl” (left front), “fr” (right front), “rl” (left rear), and “rr” (right rear).

  The apparatus also includes an electronic control unit ECU. The ECU is communicably connected to the various sensors described above. The ECU controls an actuator (not shown) for adjusting the optical axis of the headlight based on the output of the vehicle height sensor HG. The ECU controls an electric motor (not shown) in the EPS based on the output of the steering torque sensor ST. In addition, the ECU estimates the total weight of the vehicle based on the outputs of the various sensors described above.

(Estimated total vehicle weight)
Hereinafter, estimation of the total vehicle weight by the present apparatus will be described with reference to the flowchart shown in FIG. The routine shown by this flowchart is repeatedly executed by the ECU every elapse of a predetermined time (for example, 6 msec).

  First, in step 205, it is determined whether or not the absolute value of the longitudinal acceleration of the vehicle is within a minute range including zero. That is, it is determined whether or not the vehicle is traveling at a constant speed. In this determination, a value calculated based on the output of the longitudinal acceleration sensor GX may be used as the longitudinal acceleration, or a value calculated based on the output of the wheel speed sensor WS ** may be used. . However, the output of the longitudinal acceleration sensor GX may not show an accurate longitudinal acceleration when the vehicle body is tilted due to a load deviation when traveling on a slope. This is based on the fact that the vehicle body is affected by the gravitational component in the longitudinal direction of the vehicle due to the inclination from the horizontal to the pitching direction. In view of this point, in this determination, it is more preferable to use a value calculated based on the output of the wheel speed sensor WS ** as the longitudinal acceleration. In this example, it is assumed that the longitudinal acceleration takes a positive value during vehicle acceleration and takes a negative value during vehicle deceleration.

  Next, in step 210, the turning state of the vehicle is determined. Specifically, in this determination, it is determined whether the vehicle is turning or not turning (straightly traveling). The determination of “turning” is, for example, “a front wheel rudder angle is a predetermined value or more and a difference between a yaw rate calculated from the vehicle speed and the front wheel rudder angle (so-called rudder angle yaw rate) and an actual yaw rate is a predetermined value or less. "Can be made when the condition" is satisfied. The determination of “not turning” is, for example, that the condition that “the front wheel rudder angle is less than a predetermined value and the yaw rate (steering angle yaw rate) calculated from the vehicle speed and the front wheel rudder angle is less than a predetermined value” is satisfied. Can be made when. The front wheel rudder angle is obtained from the output of the front wheel rudder angle sensor FS, the vehicle speed is obtained from the output of the wheel speed sensor WS **, and the actual yaw rate is obtained from the output of the yaw rate sensor YR.

  First, a case where it is determined that the vehicle is “not turning” will be described. In this case, in step 215, the vehicle height on the rear wheel side is acquired based on the output of the vehicle height sensor HG. That is, in step 215, the vehicle height on the rear wheel side during constant speed traveling and non-turning is acquired.

  Subsequently, at step 220, the rear wheel axle load Wr is acquired based on MAP1 shown in FIG. 3 and the acquired rear wheel side vehicle height. As can be understood from MAP1, the rear wheel axle load Wr is calculated to be larger as the vehicle height on the rear wheel side is lower.

  In general, a vehicle height sensor for detecting the vehicle height at the rear wheel position is arranged on one of the left and right sides of the rear wheel axle (the vehicle height sensor HG in this example is on the left side of the rear wheel axle, see FIG. 1). Therefore, during turning of the vehicle, the rear wheel axle weight cannot be accurately estimated using the vehicle height sensor HG due to the influence of the centrifugal force acting on the vehicle. In other words, if the vehicle is not turning, the rear wheel axle weight can be accurately estimated using the vehicle height sensor HG. In step 220, the rear wheel axle load Wr can be accurately estimated based on such knowledge.

  Next, a case where it is determined that the vehicle is “turning” will be described. In this case, in step 225, the front wheel slip angle and the steering torque are acquired. That is, in step 225, “front wheel slip angle and steering torque” during constant speed traveling and turning are acquired. The front wheel slip angle can be calculated, for example, by adding the front wheel steering angle to the vehicle body slip angle obtained by integrating the difference between the yaw rate (steering angle yaw rate) calculated from the vehicle speed and the front wheel steering angle and the actual yaw rate. . The steering torque is obtained from the output of the steering torque sensor ST.

  Subsequently, at step 230, the front wheel axle load Wf is acquired based on MAP2 shown in FIG. 4 and the acquired front wheel slip angle and steering torque. In MAP2, “steering torque” can be rewritten as “self-aligning torque”.

  In general, under the condition that the front wheel axle weight is constant, as shown in FIG. 5, when the front wheel slip angle is within a predetermined value or less (see the usable range in FIG. 5), A relationship (proportional relationship) in which the torque (self-aligning torque) becomes larger is established. Further, under the condition that the front wheel slip angle is constant, the “relationship (proportional relationship) in which the steering torque (self-aligning torque) increases as the front wheel axle weight increases” is established. MAP2 defines these relationships.

  Specifically, the MAP 2 conducts an experiment for obtaining “relationship between the steering torque, the front wheel slip angle, and the front wheel axle weight” during the steady turning traveling (the vehicle speed and the front wheel rudder angle are constant). , And the front wheel axle load combination ”can be created based on data obtained by repeating various changes.

  The relationship shown in FIG. 4 is obtained during turning of the vehicle in which self-aligning torque is generated. In other words, if the vehicle is turning, the front wheel axle load can be accurately estimated using this relationship. In step 230, the front wheel axle load Wf can be accurately estimated based on such knowledge.

  As described above, in the state where the rear wheel axle weight Wr is acquired in step 220 and the front wheel axle weight Wf is obtained in step 230, the front wheel axle weight Wf and the rear wheel axle weight Wr are added in step 235. As a result, the total vehicle weight W is calculated.

  As described above, in this device, the front wheel axle load Wf using the steering torque sensor ST is estimated and the rear wheel axle load Wr using the vehicle height sensor HG is estimated at different timings of “turning” and “not turning”. The estimation is performed individually and accurately, and the total vehicle weight W can be accurately estimated based on the estimation results.

  FIG. 6 shows an example of changes in various physical quantities when the total vehicle weight W is estimated by the present apparatus. In this example, the vehicle speed is kept constant (longitudinal acceleration = 0). Prior to time t1, the vehicle is traveling straight (front wheel rudder angle = 0). After time t1, the steering wheel SW by the driver increases the front wheel rudder angle from zero, the front wheel rudder angle is maintained constant from time t2 to t3, and after time t3, the front wheel rudder angle is returned toward zero. ing. That is, the vehicle is “not turning” before time t1, and the vehicle is “turning” after time t1.

  In this case, before the time t1, the vehicle travels at a constant speed (“Yes” in step 205) and is not turning. Accordingly, the rear wheel axle load Wr is repeatedly acquired by the process of step 220 every time a predetermined time (for example, 6 msec) elapses until the time t1 (see the period indicated by A in FIG. 6). In this example, it is assumed that the front wheel axle weight Wf has not yet been acquired at this stage.

  After time t1, the vehicle travels at a constant speed (“Yes” in step 205) and is turning. Therefore, after the time t1, the front wheel axle load Wr can be repeatedly acquired by the process of step 230 every elapse of a predetermined time (for example, 6 msec).

  However, as described above, the relationship shown in FIG. 4 is a relationship obtained when the vehicle travels in a state where the front wheel rudder angle is constant. When the time change rate of the front wheel rudder angle is large, the delay in the change of the steering torque (self-aligning torque) becomes large with respect to the change of the front wheel slip angle. As a result, a case where the relationship shown in FIG. 4 cannot be maintained may occur. Therefore, when the time change rate of the front wheel steering angle is large, there is a possibility that the front wheel axle load cannot be accurately estimated based on the relationship shown in FIG.

  Based on this viewpoint, the front wheel rudder angle decreases (time change rate of the front wheel rudder angle is between time t1 and time t2 when the front wheel rudder angle increases (time change rate of the front wheel rudder angle exceeds a predetermined value). It is preferable not to acquire the front wheel axle load Wf after time t3 (which exceeds a predetermined value). That is, in this example, the front wheel rudder angle is substantially constant (the time change rate of the front wheel rudder angle is equal to or less than a predetermined value) between times t2 and t3 (period indicated by B in FIG. 6) for a predetermined time ( For example, it is preferable to repeatedly obtain the front wheel axle weight Wf every 6 msec).

  In addition, as shown in FIG. 5 described above, the front wheel slip angle and the steering torque (self-aligning torque) are approximately proportional to each other when the front wheel slip angle is small. The relationship breaks down. The relationship shown in FIG. 4 is a relationship obtained based on this proportional relationship. Therefore, when the front wheel slip angle is so large that the proportional relationship is broken (in FIG. 5, the upper limit of the usable range is exceeded), there is a possibility that the front wheel axle weight cannot be accurately estimated based on the relationship shown in FIG. Therefore, it is preferable not to acquire the front wheel axle weight Wf.

  In general, in a situation where the front wheel slip angle is so large that the proportional relationship is broken, the vehicle is often understeered. Therefore, understeer suppression control often intervenes in a vehicle in which understeer suppression control of the vehicle (for example, control for applying braking force to a wheel on the inside of a turn or reducing engine output) is executed. Therefore, based on the intervention of the understeer suppression control, it may be determined that “the front wheel slip angle has exceeded a predetermined value” and the acquisition of the front wheel axle load Wf may be stopped.

  As described above, in the example shown in FIG. 6, data of a plurality of rear wheel axle weights Wr (see A in FIG. 6) is acquired and stored before time t1, and a plurality of data is obtained at times t2 to t3. Data of the front wheel axle weight Wf (see B in FIG. 6) is acquired and stored. In this example, “total data of rear wheel axle weights Wr (rear wheel axle weight representative value Wr0 obtained from the data group of rear wheel axle weights Wr)” obtained by repeatedly acquiring and storing the vehicle total weight W before time t1 at time t3. And the sum of Wr0 and Wf0 based on the “data group of a plurality of front wheel axle weights Wf (the front wheel axle weight representative value Wf0 obtained from)” repeatedly acquired and stored at times t2 to t3. It has been calculated.

  In this case, the total vehicle weight W is obtained by adding the average value (Wr0) of the “data group of the plurality of rear wheel axle weights Wr” and the average value (Wf0) of the “data group of the plurality of front wheel axle weights Wf”, or The final value (Wr0) of the “data group of the plurality of rear wheel axle weights Wr” and the final value (Wf0) of the “data group of the plurality of front wheel axle weights Wf” can be calculated.

  Hereinafter, the vehicle total weight W is the above-described “data group of a plurality of rear wheel axle weights Wr (represented rear wheel axle weight representative value Wr0)” or “data group of a plurality of front wheel axle weights Wf (obtained from the front wheel axle weights obtained from Each time the “representative value Wf0)” is newly acquired, it can be sequentially updated using the average value or the latest value (Wr0 or Wf0) of the new data group.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the front wheel axle weight Wf and the rear wheel axle weight Wr estimated when the longitudinal acceleration is within a predetermined range including zero (that is, when traveling at a constant speed, see step 205 in FIG. 2) The total vehicle weight W is estimated based on the combination. On the other hand, the combination of the front wheel axle weight Wf and the rear wheel axle weight Wr in which the difference between the longitudinal acceleration when the front wheel axle weight Wf is estimated and the longitudinal acceleration when the rear wheel axle weight Wr is estimated is equal to or less than a predetermined value. The total vehicle weight W can be estimated based on the above. This is based on the following reason.

  That is, the front wheel axle load Wf is reduced by an inertial force when the vehicle is accelerating as compared to when driving at a constant speed, and is increased when the vehicle is decelerated by an inertial force when compared with when driving at a constant speed. The rear wheel axle load Wr increases by an inertial force when the vehicle is accelerated compared to when traveling at a constant speed, and decreases by an inertial force when the vehicle is decelerated compared with when traveling at a constant speed. That is, the inertial force component is canceled out by calculating the sum of the front wheel axle weight Wf acquired in step 230 and the rear wheel axle weight Wr acquired in step 220 regardless of whether the vehicle is accelerating or decelerating.

  Therefore, under the condition that the difference between the longitudinal acceleration when the front wheel axle weight Wf is estimated and the longitudinal acceleration when the rear wheel axle weight Wr is estimated is small, the vehicle acceleration / deceleration as well as the constant speed traveling is performed. Even so, the sum of the front wheel axle weight Wf and the rear wheel axle weight Wr can be a value that accurately represents the total vehicle weight W.

  In the example shown in FIG. 6, the total vehicle weight W is calculated at time t3, but “front wheel axle weight Wf data (front wheel axle weight representative value Wf0)” acquired and stored at time t2. And the “data group of a plurality of rear wheel axle weights Wr (rear wheel axle weight representative value Wr0 obtained from)” repeatedly acquired and stored continuously before time t1, The weight W may be calculated.

  ST ... Steering torque sensor, HG ... Vehicle height sensor, YR ... Yaw rate sensor, GX ... Longitudinal acceleration sensor, WS ** ... Wheel speed sensor, FS ... Front wheel steering angle sensor, ECU ... Electronic control unit

Claims (4)

A steering torque sensor for detecting a steering torque generated in a steering operation member operated by a driver of the vehicle;
Front wheel slip angle calculating means for calculating a slip angle of the front wheel of the vehicle;
A vehicle height sensor for detecting a vehicle height at a rear wheel position of the vehicle;
Turning determination means for determining whether the vehicle is turning or not turning;
Longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle;
When it is determined that the vehicle is turning, a predetermined relationship between the steering torque, the front wheel slip angle, and the front wheel axle weight of the vehicle, and the detected steering torque; Front wheel axle weight estimating means for estimating the front wheel axle weight of the vehicle based on the calculated front wheel slip angle;
Rear wheel axle weight estimating means for estimating the rear axle weight of the vehicle based on the detected height of the rear wheel position when it is determined that the vehicle is not turning;
Based on a combination of the front wheel axle weight and the rear wheel axle weight, in which a difference between the longitudinal acceleration when the front wheel axle weight is estimated and the longitudinal acceleration when the rear wheel axle weight is estimated is a predetermined value or less. Vehicle total weight estimating means for estimating the total weight of the vehicle,
A total weight estimation device for a vehicle comprising: The total vehicle weight estimation device according to claim 1,
The vehicle gross weight estimating means is
Based on a combination of the front wheel axle weight estimated when the longitudinal acceleration is within a predetermined range including zero and the rear wheel axle weight estimated when the longitudinal acceleration is within the predetermined range, A total vehicle weight estimation device configured to estimate a total vehicle weight. In the vehicle total weight estimation apparatus according to claim 1 or 2,
The front wheel axle weight estimation means includes
The front wheel axle load is estimated when it is determined that the calculated front wheel slip angle is equal to or less than a predetermined value, and it is determined that the calculated front wheel slip angle exceeds the predetermined value. A total vehicle weight estimation apparatus that sometimes does not perform estimation of the front wheel axle weight. A vehicle total weight estimation device according to any one of claims 1 to 3,
Front wheel rudder angle time change rate calculating means for calculating a time change rate of the rudder angle of the front wheel of the vehicle,
The front wheel axle weight estimation means includes
When it is determined that the calculated time change rate of the front wheel steering angle is equal to or less than a predetermined value, the front wheel axle weight is estimated, and the time change rate of the calculated front wheel steering angle satisfies the predetermined value. A total vehicle weight estimation device that does not perform the estimation of the front wheel axle weight when it is determined that the vehicle has exceeded the upper limit.

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