JP7095465B2 - Vehicle speed estimation device - Google Patents

Description

The present disclosure relates to a vehicle speed estimation device.

Conventionally, there is known a technique of detecting a wheel rotation speed with a sensor and estimating a vehicle speed as a vehicle speed based on the detected wheel rotation speed.

Japanese Unexamined Patent Publication No. 11-192930

In the above technology, for example, when a wheel slips on a slippery road surface (so-called low μ road), the wheel rotation speed decreases and the difference between the wheel rotation speed and the actual vehicle speed increases. , The reliability of the wheel rotation speed is reduced. As a result, the accuracy of vehicle speed estimation is reduced.

On the other hand, for example, a method of detecting the acceleration in the front-rear direction of the vehicle and estimating the vehicle speed based on the integral of the acceleration without relying on the rotation speed of the wheels has been proposed. However, in this method, it is necessary to provide a new sensor called a front-rear acceleration sensor for detecting the acceleration in the front-rear direction of the vehicle, which causes inconveniences such as an increase in cost and a complicated configuration.

Therefore, one of the problems of the present disclosure is to provide a vehicle speed estimation device capable of improving the vehicle speed estimation accuracy when a wheel slip occurs with a simple configuration that does not require a new sensor. be.

The vehicle speed estimation device according to the present disclosure is, for example, a vehicle speed estimation device for estimating the speed of a vehicle provided with a braking force applying unit that applies braking force to the front and rear wheels of the vehicle, and is at least one of the front wheels and the rear wheels. When one wheel slips and the acceleration operation for accelerating the vehicle is not performed, the increase control that increases the braking force by using at least one wheel where the slip occurs as the control target wheel, One of the control unit that executes the decrease control that reduces the braking force and the increase / decrease control that repeats, and the rotation speed of the wheel to be controlled and the rotation speed of the wheels other than the control target wheel during the execution of the increase / decrease control. It includes an estimation unit that estimates the speed of the vehicle based on the larger one. The braking force applying unit is separate from the electric parking brake that generates the parking braking force by the electric actuator on one of the front and rear wheels and the parking braking force on at least one of the front and rear wheels. Includes regular brakes that generate regular braking force. The increase / decrease control is executed by the electric parking brake. In the control unit, the electric parking brake is parked on the rear wheels in response to the change from the state in which the normal brake can generate the normal braking force on both the front and rear wheels to the state in which the normal braking force can be generated only on the front wheels. When slip is generated by generating power and the acceleration operation for accelerating the vehicle is not performed, the increase / decrease control is executed by driving the electric actuator.

According to the above-mentioned vehicle speed estimation device, during execution of the increase / decrease control, the rotation speed of the wheel to be controlled and the rotation speed of the wheels other than the control target wheel, whichever is larger, that is, the one closer to the actual vehicle speed. Since the vehicle speed is estimated based on this, it is possible to improve the estimation accuracy of the vehicle speed when a wheel slip occurs with a simple configuration that does not require a new sensor.

FIG. 1 is an exemplary and schematic block diagram showing a schematic configuration of a vehicle according to an embodiment. FIG. 2 is an exemplary and schematic cross-sectional view showing the configuration of the brake device provided on the rear wheel of the vehicle according to the embodiment. FIG. 3 is an exemplary and schematic block diagram showing the function of the vehicle speed estimation device according to the embodiment. FIG. 4 is an exemplary and schematic diagram showing an example of a vehicle speed estimation method executed by the vehicle speed estimation device according to the embodiment. FIG. 5 is an exemplary and schematic diagram showing another example of the vehicle speed estimation method executed by the vehicle speed estimation device according to the embodiment. FIG. 6 is an exemplary and schematic flowchart showing a series of processes executed by the vehicle speed estimation device according to the embodiment for increase / decrease control. FIG. 7 is an exemplary and schematic flowchart showing a series of processes executed by the vehicle speed estimation device according to the embodiment for estimating the vehicle speed. FIG. 8 is an exemplary and schematic flowchart showing details of increase / decrease control executed by the vehicle speed estimation device according to the embodiment.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The configurations of the embodiments described below, and the actions and results (effects) brought about by the configurations are merely examples, and are not limited to the contents described below.

First, the configuration of the embodiment will be described.

FIG. 1 is an exemplary and schematic block diagram showing a schematic configuration of a vehicle 100 according to an embodiment. Hereinafter, as an example, an example in which the technique of the embodiment is applied to a vehicle 100 as a four-wheeled automobile having front wheels FL and FR and rear wheels RL and RR will be described. Further, in the following, if it is not necessary to distinguish between them, the front wheels FL and FR and the rear wheels RL and RR may be collectively referred to as wheels.

As shown in FIG. 1, the vehicle 100 according to the embodiment has a normal brake 1 that generates a braking force in response to a driver's depression of the brake pedal 3, and a braking force that is generated by an EPB motor 10 separately from the normal brake 1. It has two types of braking devices (braking force applying portions), that is, an electric parking brake 2 that generates a braking force. The electric parking brake may also be referred to as an EPB (Electric Parking Break). In the following, if necessary, the braking force generated by the regular brake 1 may be described as the regular braking force, and the braking force generated by the electric parking brake 2 may be described as the parking braking force.

In the example shown in FIG. 1, the normal brake 1 is configured to apply braking force to all the wheels of the front wheels FL and FR and the rear wheels RL and RR, and the electric parking brake 2 is configured to apply braking force to the rear wheels RL. And RR are configured to apply braking force only. Although details will be described later, both the regular brake 1 and the electric parking brake 2 have a structure in which a braking force due to frictional force is applied to the wheels by pressing the brake pads 11 against the brake discs 12 that rotate together with the wheels. ing.

Note that FIG. 1 illustrates, as an example, a configuration in which the electric parking brake 2 applies braking force only to the rear wheels RL and RR, but in the technique of the embodiment, the electric parking brake 2 has the front wheels FL and FR. It can also be applied to a configuration in which braking force is applied only to.

The regular brake 1 includes a master cylinder 5 that generates pressure (hydraulic pressure) based on a brake operation such as depression of the brake pedal 3 by a driver, and a negative pressure booster 4 that amplifies the force of the brake operation by using negative pressure. And have. The normal brake 1 transmits the hydraulic pressure in the master cylinder 5 corresponding to the depression force of the brake pedal 3 amplified by the negative pressure booster 4 to the wheel cylinders 6 provided on each wheel, so that the hydraulic pressure is applied to the wheels. Apply braking force. The negative pressure of the negative pressure booster 4 is generated, for example, in response to the intake air of an engine (not shown).

Here, in the example shown in FIG. 1, a hydraulic pressure control circuit 7 is provided between the master cylinder 5 and the wheel cylinder 6. This hydraulic pressure control circuit 7 includes a solenoid valve, a pump, and the like, and realizes various controls such as ESC (Electronic Stability Control) for improving the safety of the vehicle 100, such as adjusting the braking force by the normal brake 1. It is provided to do. The hydraulic pressure control circuit 7 is driven based on the control of the ESC-ECU (Electronic Control Unit) 8.

On the other hand, the electric parking brake 2 drives the EPB motor 10 as an electric actuator provided in the caliper 13 based on the control of the EPB-ECU 9, so that the front wheel FL and FR are separately from the braking force of the regular brake 1. Apply braking force. Therefore, in the embodiment, as shown in FIG. 2 below, both the normal braking force by the regular brake 1 and the parking braking force by the electric parking brake 2 can be applied to the rear wheel RL and RR.

FIG. 2 is an exemplary and schematic cross-sectional view showing the configuration of the rear wheel RL and the brake device provided on the rear wheel RL of the vehicle 100 according to the embodiment. FIG. 2 shows a specific example of the structure of the rear wheel RL and the RR caliper 13.

First, a mechanism for increasing or decreasing the normal braking force by the normal brake 1 will be briefly described.

As shown in FIG. 2, in the embodiment, the body 14 of the wheel cylinder 6 is provided with a hole 14b for introducing the brake fluid into the hollow portion 14a inside the body 14. The hollow portion 14a is provided with a piston 19 that can reciprocate along the inner peripheral surface of the body 14. The piston 19 is formed in a bottomed cylindrical shape, and a brake pad 11 facing the brake disc 12 is provided at the bottom of the piston 19.

Here, inside the body 14 of the wheel cylinder 6, a seal member 22 for suppressing leakage of the brake fluid from between the outer peripheral surface of the piston 19 and the inner peripheral surface of the body 14 is provided. .. As a result, the hydraulic pressure generated in the hollow portion 14a is applied to the end surface of the piston 19 on the side opposite to the brake pad 11.

With the above structure, when the brake pedal 3 is depressed as the operation of the normal brake 1, hydraulic pressure due to the brake fluid is generated in the hollow portion 14a, and the direction of pressing the brake pad 11 (paper surface of FIG. 2). The piston 19 moves to the left). Then, when the piston 19 moves in the direction of pressing the brake pad 11, the brake pad 11 comes into contact with the brake disc 12 and is pressed against the brake disc 12, and the wheel corresponding to the brake disc 12 is subjected to a normal braking force due to frictional force. ..

On the contrary, when the operation of releasing the depression of the brake pedal 3 is performed as the operation of the normal brake 1, the hydraulic pressure in the hollow portion 14a decreases and the pressing of the brake pad 11 is released (to the right of the paper in FIG. 2). ), The piston 19 moves. Then, when the piston 19 moves in the direction of releasing the pressing of the brake pad 11, the pressing force of the brake pad 11 against the brake disc 12 is weakened, and the braking force applied to the wheel corresponding to the brake disc 12 is reduced. .. When the brake pad 11 is completely separated from the brake disc 12, the normal braking force applied to the brake disc 12 becomes zero.

Next, the mechanism by which the parking braking force is increased or decreased by the electric parking brake 2 will be briefly described.

As shown in FIG. 2, in the embodiment, the EPB motor 10 is fixed to the body 14 of the wheel cylinder 6. A spur gear 15 is connected to the drive shaft 10a of the EPB motor 10. As a result, when the EPB motor 10 is driven and the drive shaft 10a rotates, the spur gear 15 also rotates with the drive shaft 10a as the center of rotation.

Further, a spur gear 16 having a rotating shaft 17 is meshed with the spur gear 15. The rotary shaft 17 is located at the center of rotation of the spur gear 16, and is supported by the O-ring 20 and the bearing 21 provided in the insertion hole 14c while being inserted into the insertion hole 14c of the body 14 of the wheel cylinder 6. Has been done.

Here, a male screw groove 17a is formed on the outer peripheral surface of the end portion of the rotating shaft 17 opposite to the spur gear 16. The male thread groove 17a is screwed with the female thread groove 18a provided on the inner peripheral surface of the bottomed cylindrical linear motion member 18 that reciprocates inside the piston 19. As a result, when the spur gear 15 is rotated by the drive of the EPB motor 10, the rotary shaft 17 rotates together with the spur gear 16, and the linear motion member 18 is rotated by the meshing between the male screw groove 17a and the female screw groove 18a. Moves back and forth in the axial direction of.

The linear motion member 18 has a detent structure in relation to the rotating shaft 17, so that even if the rotating shaft 17 rotates, it does not rotate together with the rotating shaft 17. Similarly, the piston 19 also has a detent structure in relation to the linear motion member 18, so that even if the linear motion member 18 rotates about the rotation shaft 17, it does not rotate together with the linear motion member 18. Structure.

As described above, in the embodiment, a motion conversion mechanism for converting the rotation of the EPB motor 10 into the reciprocating movement of the linear motion member 18 inside the piston 19 is provided. When the drive of the EPB motor 10 is stopped, the linear motion member 18 stops at the same position due to the frictional force due to the engagement between the male screw groove 17a and the female screw groove 18a.

With the above structure, when the EPB motor 10 rotates in the positive direction when the electric parking brake 2 is operated, the linear motion member 18 moves in the direction of contact with the piston 19 (to the left of the paper in FIG. 2). Then, when the linear motion member 18 and the piston 19 come into contact with each other while the brake pad 11 is pressed against the brake disc 12, the piston 19 is supported by the linear motion member 18, so even if the brake pedal 3 (see FIG. 1) is used. Even if the depression of the hollow portion 14a is released and the hydraulic pressure of the hollow portion 14a is reduced, the parking braking force applied to the wheels is maintained (locked) as it is.

On the contrary, when the EPB motor 10 rotates in the opposite direction, the linear motion member 18 moves in the direction away from the piston 19 (to the right of the paper in FIG. 2). Then, when the linear motion member 18 is separated from the piston 19, the pressing of the brake pad 11 against the brake disc 12 by the piston 19 is weakened by that amount, and the parking braking force applied to the wheels is gradually released (released). I will go.

As described above, in the embodiment, the mechanism for applying the braking force to the front wheel FL and FR is partially shared by the regular brake 1 and the electric parking brake 2.

Returning to FIG. 1, the ESC-ECU 8 is configured as a microcomputer equipped with, for example, a processor and a memory, and controls the hydraulic pressure control circuit 7 by executing a program stored in the memory or the like by the processor. Realize various functions of. The ESC-ECU 8 is communicably connected to the EPB-ECU 9 via an in-vehicle network or the like.

Further, like the ESC-ECU 8, the EPB-ECU 9 is also configured as a microcomputer equipped with, for example, a processor and a memory, and controls the EPB motor 10 by executing a program stored in the memory or the like by the processor. Realize various functions to do.

In the embodiment, the EPB-ECU 9 has, for example, the output of a stroke sensor 23 that detects a stroke as an operation amount of an accelerator pedal (not shown) for performing an acceleration operation for accelerating the vehicle 100, or the output of each wheel of the vehicle 100. Information based on the output of the speed sensor 24 that detects the rotation speed is acquired, and the acquired information can be used for controlling the EPB motor 10.

In the embodiment, the speed sensor 24 includes a speed sensor 24FL that detects the rotation speed of the front wheel FL, a speed sensor 24FR that detects the rotation speed of the front wheel FR, and a speed sensor 24RL that detects the rotation speed of the rear wheel RL. Four speed sensors 24RR, which detect the rotation speed of the rear wheel RR, are provided.

By the way, in the vehicle 100 provided with the speed sensor 24 as described above, the vehicle speed is generally obtained based on the rotation speed of the wheel as the detection result of the speed sensor 24.

However, when a wheel slip occurs on a slippery road surface (so-called low μ road), for example, the wheel rotation speed decreases, so that the difference between the wheel rotation speed and the actual vehicle speed increases, and the wheel rotation speed increases. Reliability is reduced.

Here, it is known that when the slip as described above occurs, for example, anti-lock control for recovering the slip is executed by repeatedly increasing or decreasing the braking force applied to the wheels. However, if the braking force applied to the wheels is repeatedly increased or decreased, the rotation speed of the wheels also increases and decreases accordingly. As a result, the rotation speed of the wheels and the actual vehicle speed deviate from each other, and the reliability of the rotation speed of the wheels is reliable. The sex is reduced.

As described above, when the wheel slips, the reliability of the wheel rotation speed decreases. Then, when the reliability of the rotation speed of the wheel is lowered, the estimation accuracy of the vehicle speed is lowered by the above-mentioned general method simply using the detection result of the speed sensor 24.

On the other hand, for example, there is known a method of detecting the acceleration in the front-rear direction of the vehicle 100 and estimating the vehicle speed based on the integral of the acceleration without relying on the rotation speed of the wheels. However, in this method, it is necessary to provide a new sensor called a front-rear acceleration sensor for detecting the acceleration in the front-rear direction of the vehicle 100, which causes inconveniences such as an increase in cost and a complicated configuration.

Therefore, the EPB-ECU 9 according to the embodiment executes a predetermined control program stored in a memory or the like by a processor, and realizes a vehicle speed estimation device 300 having a function as shown in FIG. 3 below. With a simple configuration that does not require a new sensor, it is possible to improve the estimation accuracy of the vehicle speed when wheel slip occurs.

FIG. 3 is an exemplary block diagram showing the function of the vehicle speed estimation device 300 according to the embodiment. As shown in FIG. 3, the vehicle speed estimation device 300 according to the embodiment includes a sensor information acquisition unit 301, an actuator control unit 302, and a vehicle speed estimation unit 303. In the embodiment, a part or all of the functions shown in FIG. 3 may be realized by dedicated hardware (circuit).

The sensor information acquisition unit 301 acquires sensor information based on the outputs of various sensors provided in the vehicle 100, such as the stroke sensor 23 and the speed sensor 24.

The actuator control unit 302 controls the EPB motor 10. For example, the actuator control unit 302 can rotate the EPB motor 10 in the forward direction, rotate it in the reverse direction, or stop it in order to control the position of the linear motion member 18.

The vehicle speed estimation unit 303 estimates the vehicle speed as the speed of the vehicle 100 based on the sensor information acquired by the sensor information acquisition unit 301.

Here, in the embodiment, the vehicle speed estimation unit 303 is basically configured to estimate the vehicle speed by a conventional estimation method based on the output of the speed sensor 24 acquired as sensor information. More specifically, the vehicle speed estimation unit 303 obtains the second highest rotation speed of the four wheels based on the outputs of the four speed sensors 24FL, 24FR, 24RL, and 24RR, and the second highest rotation speed is obtained. It is configured to estimate the vehicle speed based on the large rotational speed.

According to the conventional estimation method using the second largest rotation speed, it is possible to obtain an accurate vehicle speed as long as the reliability of the rotation speed of the wheels does not decrease. However, as described above, when the wheel slips on a low μ road or the like, the reliability of the wheel rotation speed decreases, so that it is not possible to obtain an accurate vehicle speed by the conventional estimation method. be.

Therefore, in the embodiment, the actuator control unit 302 slips at least one of the front wheels FL and FR and the rear wheels RL and RR, and the acceleration operation for accelerating the vehicle 100 is not performed. By driving the EPB motor 10, an increase / decrease control that repeats an increase control for increasing the parking braking force and a decrease control for decreasing the parking braking force is executed. Then, while the vehicle speed estimation unit 303 is executing the increase / decrease control, the rotation speed of the rear wheels RL and RR as one wheel and the rotation speed of the front wheels FL and FR as the other wheel, whichever is larger. Estimate the vehicle speed based on. According to such an estimation method, it is possible to obtain an estimation result closer to the actual vehicle speed, as described below.

FIG. 4 is an exemplary and schematic diagram showing an example of a vehicle speed estimation method executed by the vehicle speed estimation device 300 according to the embodiment. The example shown in FIG. 4 corresponds to time changes of various parameters starting immediately after the increase / decrease control is executed according to the occurrence of wheel slip in the state where the acceleration operation is not performed.

More specifically, in the example shown in FIG. 4, the solid line L400 corresponds to the time change of the actual vehicle speed. Further, the alternate long and short dash line L401a corresponds to the time change of the rotation speed of one of the front wheels FL and FR, and the two-dot chain line L401b corresponds to the time change of the rotation speed of the other of the front wheels FL and FR. Further, the alternate long and short dash line L402a corresponds to the time change of the rotation speed of one of the rear wheels RL and RR, and the two-dot chain line L402b corresponds to the time change of the rotation speed of the other of the rear wheels RL and RR.

In the example shown in FIG. 4, as a result of the increase / decrease control being executed according to the occurrence of wheel slip in the state where the acceleration operation is not performed, the rotational speeds of the front wheels FL and FR gradually decrease (one point). The rotational speeds of the chain line L401a and the two-dot chain line L401b) and the rear wheels RL and RR alternately increase and decrease (see the one-dot chain line L402a and the two-dot chain line L402b). In the example shown in FIG. 4, the timing of increasing / decreasing the rotation speed of the rear wheel RL and the timing of increasing / decreasing the rotation speed of the rear wheel RR do not overlap, but in the embodiment, both are at least a part. It may overlap at the timing.

In the example shown in FIG. 4, when the conventional estimation method of estimating the vehicle speed based on the rotation speed of the second largest of the rotation speeds of the four wheels is applied, the rotation speed of the front wheel FL or FR (single point chain line L401a or two). The vehicle speed will be estimated based on the point chain line L401b). However, since the rotation speeds of the front wheels FL and FR both deviate greatly from the actual vehicle speed (see the solid line L400), the conventional estimation method can obtain an estimation result deviating from the actual vehicle speed. become.

Therefore, in the example shown in FIG. 4, it is based on the larger of the rotational speeds of the front wheels FL and FR and the larger of the rotational speeds of the rear wheels RL and RR. The vehicle speed is estimated. In the following, for the sake of simplicity, "the larger of the rotation speeds of the front wheels FL and FR" is simply referred to as "the rotation speed of the front wheels FL and FR", and "the rotation speed of the rear wheels RL and RR". The larger of the two may be simply referred to as "rear wheel RL and RR rotation speed".

With the above estimation, in the example shown in FIG. 4, the estimation result as shown by the solid line L403 can be obtained. The estimation result shown by the solid line L403 is closer to the actual vehicle speed (see the solid line L400) than the estimation result obtained by the above-mentioned conventional estimation method (see the one-dot chain line L401a or the two-dot chain line L401b). According to the example shown in, it is possible to improve the estimation accuracy of the vehicle speed when the wheel slip occurs.

Thus, in the example shown in FIG. 4, the rotation speeds of the rear wheels RL and RR are taken into consideration in the section where the rotation speeds of the rear wheels RL and RR are larger than the rotation speeds of the front wheels FL and FR. Minutes, an estimation result closer to the actual vehicle speed can be obtained as compared with the conventional estimation method in which only the rotation speed of either the front wheel FL or FR is taken into consideration in all sections. However, since the rotation speeds of the rear wheels RL and RR increase / decrease according to the increase / decrease control, when the vehicle speed is estimated based on the rotation speeds of the rear wheels RL and RR, the rotation speeds of the rear wheels RL and RR decrease sharply. After that, the discrepancy between the estimated result and the actual vehicle speed may become large.

Therefore, as an example different from the example shown in FIG. 4, the embodiment is based on the actual vehicle speed, not the rotation speed of the rear wheels RL and RR, after the rotation speeds of the rear wheels RL and RR are sharply reduced. It is also possible to obtain a vehicle speed closer to the actual vehicle speed as an estimation result by using a rotation speed preset so that the deviation between the two is smaller.

That is, in the embodiment, the vehicle speed estimation unit 303 is a case where the rotation speeds of the rear wheels RL and RR are larger than the rotation speeds of the front wheels FL and FR based on the estimation method as exemplified in FIG. 5 below. However, when the value indicating the degree of decrease in the rotation speeds of the rear wheels RL and RR becomes larger than the threshold value, the rotation speeds of the rear wheels RL and RR or more at the timing when the value indicating the degree of decrease becomes larger than the threshold value. The speed of the vehicle can be estimated based on the rotation speed preset in. As the value indicating the degree of decrease, for example, the time derivative (absolute value) can be used.

FIG. 5 is an exemplary and schematic diagram showing another example of the vehicle speed estimation method executed by the vehicle speed estimation device 300 according to the embodiment. Similar to the example shown in FIG. 4, the example shown in FIG. 5 also has various parameters starting immediately after the increase / decrease control is executed according to the occurrence of wheel slip in the state where the acceleration operation is not performed. Respond to changes over time.

In the example shown in FIG. 5, the meanings of the solid line L400, the alternate long and short dash line L401a, the alternate long and short dash line L401b, the alternate long and short dash line L402a, and the alternate long and short dash line L402b are the same as those shown in FIG. That is, also in the example shown in FIG. 5, the rotation speeds of the front wheels FL and FR gradually decrease as a result of the increase / decrease control being executed according to the occurrence of wheel slip, as in the example shown in FIG. (See one-dot chain line L401a and two-dot chain line L401b), the rotational speeds of the rear wheels RL and RR alternately increase and decrease (see one-dot chain line L402a and two-dot chain line L402b).

The example shown in FIG. 5 is shown in FIG. 4 in the basic concept of estimating the vehicle speed based on the larger of the rotational speeds of the front wheels FL and FR and the rotational speeds of the rear wheels RL and RR. Similar to the example. However, in the example shown in FIG. 5, as described above, even when the rotation speeds of the rear wheels RL and RR are larger than the rotation speeds of the front wheels FL and FR, the rotation speeds of the rear wheels RL and RR When the value indicating the degree of decrease becomes larger than the threshold value, the speed of the vehicle is estimated based on the rotation speed preset so that the deviation from the actual vehicle speed becomes smaller. Therefore, according to the example shown in FIG. 5, the estimation result as shown in the following solid line L503 can be obtained.

In the solid line L503, the point P501 is one of the points where the rotation speed of one of the rear wheel RL and the RR (see the alternate long and short dash line L402a) sharply decreases, and the value indicating the degree of decrease in the rotation speed becomes larger than the threshold value. Represents. Therefore, in the example shown in FIG. 5, at the point P501, the vehicle speed estimation method is previously based on the estimation method based on the larger of the rotation speeds of the front wheels FL and FR and the rotation speeds of the rear wheels RL and RR. Switch to the estimation method based on the set rotation speed.

Here, in a situation where the acceleration operation is not performed as in the example shown in FIG. 5, the actual vehicle speed (see the solid line L400) gradually decreases with the passage of time. Therefore, in order to correspond to such an actual change in vehicle speed, the above-mentioned preset rotation speed decreases with the passage of time with a degree of decrease smaller than the above-mentioned threshold value (points P501 and P502 on the solid line L503). See the section between and).

By the way, on the solid line L503, at the point P502, after the vehicle speed estimation method is switched at the point P501, the rotation speed of the other of the rear wheel RL and the RR (see the two-dot chain line L402b) is higher than the preset rotation speed. It represents one of the points that grows. Therefore, after the point P502, it is better to estimate the vehicle speed based on the rotation speed of the other of the rear wheel RL and RR than to estimate the vehicle speed based on the preset rotation speed (solid line L400). See)) closer estimation results are obtained.

Therefore, in the example shown in FIG. 5, the estimation method based on the larger of the rotation speeds of the front wheels FL and FR and the rotation speeds of the rear wheels RL and RR is changed to the estimation method based on the preset rotation speed. When the rotation speeds of the rear wheels RL and RR become higher than the preset rotation speeds after switching, the vehicle speed is estimated based on the rotation speeds of the rear wheels RL and RR.

In the solid line L502, there are other points where the vehicle speed estimation method is switched in the same manner as the points P501 and P502, but the switching of the vehicle speed estimation method at those points is the same as in the points P501 and P502. Since there is, the description is omitted here.

As described above, according to the example shown in FIG. 5, it is possible to avoid a large discrepancy between the estimated result and the actual vehicle speed, particularly after the rotation speeds of the rear wheels RL and RR are sharply reduced. , It is possible to improve the estimation accuracy of the vehicle speed.

By the way, in the above description, as an example of the situation where slip occurs, it is assumed that the vehicle 100 travels on a low μ road. However, in the embodiment, as another example of the situation where slip occurs, the function of the rear wheel RL and the RR side of the normal brake 1 is lost, that is, the normal brake 1 has the front wheels FL and FR and the rear wheel RL and Electric parking as a result of driver operation or automatic control depending on the change from the state where the normal braking force can be generated for both the RR to the state where the normal braking force can be generated only for the front wheels FL and FR. A situation is also assumed in which the brake 2 generates a parking braking force on the rear wheels RL and RR.

Even in the latter situation described above, the braking force of the rear wheels RL and RR is also transmitted to the front wheels FL and FR via the center differential (not shown), resulting in a decrease in the rotational speeds of the front wheels FL and FR. The reliability of the wheel rotation speed is reduced. Even in such a situation, according to the embodiment, the basic concept of estimating the vehicle speed based on the larger of the rotation speeds of the front wheels FL and FR and the rotation speeds of the rear wheels RL and RR. Based on the above, it is possible to obtain a vehicle speed closer to the actual vehicle speed.

Next, the control operation of the embodiment will be described in more detail.

FIG. 6 is an exemplary and schematic flowchart showing a series of processes executed by the vehicle speed estimation device 300 according to the embodiment for increase / decrease control.

As shown in FIG. 6, in the embodiment, first, in step S601, the condition that the actuator control unit 302 of the vehicle speed estimation device 300 has a wheel slip and the acceleration operation is not performed is satisfied. Determine if you did. This determination is made based on the sensor information acquired by the sensor information acquisition unit 301.

If it is determined in step S601 that the condition that the wheel slips and the acceleration operation is not performed is satisfied, the process proceeds to step S602. Then, in step S602, the actuator control unit 302 of the vehicle speed estimation device 300 executes the increase / decrease control by the electric parking brake 2. The details of the increase / decrease control executed in step S602 will be described later. Then, the process ends.

If it is determined in step S602 that the condition that the wheel slips and the acceleration operation is not performed is not satisfied, the increase / decrease control as in step S602 is not executed. The process ends as it is.

Here, in the embodiment, while the increase / decrease process of step S602 shown in FIG. 6 is being executed, a series of processes shown in FIG. 7 may be repeatedly executed.

FIG. 7 is an exemplary and schematic flowchart showing a series of processes executed by the vehicle speed estimation device 300 according to the embodiment for estimating the vehicle speed. The series of processes shown in FIG. 7 corresponds to the vehicle speed estimation method already described with reference to FIG. The inequality sign in some of the series of processes shown in FIG. 7 may be replaced with an inequality sign with an equal sign.

As shown in FIG. 7, in the embodiment, first, in step S701, whether or not the vehicle speed estimation unit 303 of the vehicle speed estimation device 300 has a rotation speed of the rear wheels RL and RR higher than the rotation speed of the front wheels FL and FR. Judge.

When it is determined in step S701 that the rotation speeds of the rear wheels RL and RR are equal to or lower than the rotation speeds of the front wheels FL and FR, the vehicle speed estimated based on the rotation speeds of the front wheels FL and FR is the rear wheel RL. And it can be determined that the vehicle speed is closer to the actual vehicle speed than the vehicle speed estimated based on the rotation speed of the RR. Therefore, in this case, the process proceeds to step S702, and in step S702, the vehicle speed estimation unit 303 of the vehicle speed estimation device 300 estimates the vehicle speed based on the rotation speeds of the front wheels FL and FR. Then, the process returns to step S701.

On the other hand, when it is determined in step S701 that the rotation speeds of the rear wheels RL and RR are larger than the rotation speeds of the front wheels FL and FR, the vehicle speed estimated based on the rotation speeds of the rear wheels RL and RR is higher. It can be determined that the vehicle speed is closer to the actual vehicle speed than the vehicle speed estimated based on the rotation speeds of the front wheels FL and FR. Therefore, in this case, the process proceeds to step S703, and in step S703, the vehicle speed estimation unit 303 of the vehicle speed estimation device 300 estimates the vehicle speed based on the rotation speeds of the rear wheels RL and RR.

Then, in step S704, the vehicle speed estimation unit 303 of the vehicle speed estimation device 300 determines whether or not the value indicating the degree of decrease in the rotational speeds of the rear wheels RL and RR is larger than the threshold value. As described above, as the value indicating the degree of decrease, for example, the time derivative (absolute value) can be used.

When it is determined in step S704 that the value indicating the degree of decrease in the rotation speeds of the rear wheels RL and RR is equal to or less than the threshold value, the estimated result of the vehicle speed and the actual vehicle speed are obtained along with the sharp decrease in the rotation speeds of the rear wheels RL and RR. It can be judged that it is unlikely that a situation will occur in which the divergence from the above will increase sharply. Therefore, in this case, the process returns to step S703, and the estimation of the vehicle speed based on the rotation speeds of the rear wheels RL and RR is executed.

On the other hand, when it is determined in step S704 that the value indicating the degree of decrease in the rotation speeds of the rear wheels RL and RR is larger than the threshold value, the estimation results and the actual vehicle speeds are accompanied by a sharp decrease in the rotation speeds of the rear wheels RL and RR. It can be judged that there is a high possibility that a situation will occur in which the deviation from the vehicle speed of the vehicle increases sharply. Therefore, in this case, the process proceeds to step S705, and in step S705, the vehicle speed estimation unit 303 of the vehicle speed estimation device 300 is based on a rotation speed preset so that the deviation from the actual vehicle speed becomes smaller. Estimate the vehicle speed.

Then, in step S706, the vehicle speed estimation unit 303 of the vehicle speed estimation device 300 determines whether or not the rotation speeds of the rear wheels RL and RR are higher than the above-mentioned preset rotation speeds.

When it is determined in step S706 that the rotation speeds of the rear wheels RL and RR are equal to or less than the preset rotation speeds, the deviation between the vehicle speed estimated based on the rotation speeds of the rear wheels RL and RR and the actual vehicle speed Can be judged to be still large. Therefore, in this case, the process returns to step S705, and the estimation of the vehicle speed based on the preset rotation speed is executed.

On the other hand, when it is determined in step S706 that the rotation speeds of the rear wheels RL and RR are higher than the preset rotation speeds, the vehicle speed estimated based on the rotation speeds of the rear wheels RL and RR and the actual vehicle speed are used. It can be judged that the divergence of is small. Therefore, in this case, the process proceeds to step S707, and in step S707, the vehicle speed estimation unit 303 of the vehicle speed estimation device 300 estimates the vehicle speed based on the rotation speeds of the rear wheels RL and RR. Then, the process returns to step S701.

In this way, a series of processes corresponding to the vehicle speed estimation method already described with reference to FIG. 5 is executed.

Since the vehicle speed estimation method already described with reference to FIG. 4 does not take into consideration the degree of decrease in the rotational speeds of the rear wheels RL and RR, steps S704 to S707 of the series of processes shown in FIG. 7 are executed. Not done. That is, in the vehicle speed estimation method already described with reference to FIG. 4, the process is executed according to the flowchart in which the process returns to step S701 after step S703 in FIG. 7.

FIG. 8 is an exemplary and schematic flowchart showing details of increase / decrease control executed by the vehicle speed estimation device 300 according to the embodiment. The series of processes shown in FIG. 8 is executed when the process proceeds to S602 in FIG.

As shown in FIG. 8, in the embodiment, first, in step S801, the actuator control unit 302 of the vehicle speed estimation device 300 is applied to the front wheels FL and FR as the control target wheels by rotating the EPB motor 10 in the forward direction. Performs increasing control to increase the parking braking force.

Then, in step S802, the actuator control unit 302 of the vehicle speed estimation device 300 determines whether or not the wheels (front wheel FL and FR) are locked.

If it is determined in step S802 that the wheel is not locked, the process proceeds to step S803. Then, in step S803, the actuator control unit 302 of the vehicle speed estimation device 300 executes holding control for holding the parking braking force applied to the front wheel FL and FR as it is. Then, the process returns to step S802.

On the other hand, if it is determined in step S802 that the wheel is locked, the process proceeds to step S804. Then, in step S804, the actuator control unit 302 of the vehicle speed estimation device 300 executes reduction control for reducing the parking braking force applied to the front wheel FL and FR by rotating the EPB motor 10 in the reverse direction.

Then, in step S805, the actuator control unit 302 of the vehicle speed estimation device 300 determines whether or not the lock of the wheels (front wheel FL and FR) has been released, that is, whether or not the wheels have returned from the lock.

If it is determined in step S805 that the wheel lock has not been released yet, the process returns to step S804.

On the other hand, if it is determined in step S805 that the wheel lock is released, the process returns to step S801.

As described above, in the embodiment, the increase / decrease control is realized by appropriately repeating the increase control, the holding control, and the decrease control. The increase / decrease control can be terminated when the wheel slip is eliminated.

As described above, the vehicle speed estimation device 300 according to the embodiment includes an electric parking brake 2 that generates a parking braking force by the EPB motor 10 on the rear wheels RL and RR, and front wheels FL and FR and rear wheels RL and RR. It is a device that estimates the vehicle speed as the speed of the vehicle 100 provided with the normal brake 1 that generates a normal braking force separate from the parking braking force on both sides. The vehicle speed estimation device 300 includes an actuator control unit 302 and a vehicle speed estimation unit 303. The actuator control unit 302 drives the EPB motor 10 when at least one of the front wheels FL and FR and the rear wheels RL and RR slips and the acceleration operation for accelerating the vehicle 100 is not performed. Therefore, the increase / decrease control that repeats the increase control for increasing the parking braking force and the decrease control for decreasing the parking braking force is executed. The vehicle speed estimation unit 303 estimates the vehicle speed based on the larger of the rotation speeds of the rear wheels RL and RR and the rotation speeds of the front wheels FL and FR during the execution of the increase / decrease control.

According to the vehicle speed estimation device 300 according to the embodiment, during the execution of the increase / decrease control, the rotation speed of the rear wheels RL and RR and the rotation speed of the front wheels FL and FR, whichever is larger, that is, the actual vehicle speed Since the vehicle speed is estimated based on the closer one, it is possible to improve the estimation accuracy of the vehicle speed when a wheel slip occurs with a simple configuration that does not require a new sensor.

Further, in the vehicle speed estimation device 300 according to the embodiment, the vehicle speed estimation unit 303 rotates the rear wheels RL and RR even when the rotation speeds of the rear wheels RL and RR are larger than the rotation speeds of the front wheels FL and FR. When the value indicating the degree of decrease in speed becomes larger than the threshold value, the rotation speed is set to a preset rotation speed equal to or higher than the rotation speed of the rear wheels RL and RR at the timing when the value indicating the degree of decrease becomes larger than the threshold value. Based on this, the vehicle speed can be estimated. According to such a configuration, when the rotation speeds of the rear wheels RL and RR suddenly decrease and the deviation from the actual vehicle speed suddenly increases, the actual vehicle speed is based on the preset rotation speed. It is possible to estimate a closer vehicle speed.

Further, in the vehicle speed estimation device 300 according to the embodiment, the above-mentioned preset rotation speed may decrease with the passage of time with a degree of decrease smaller than the above-mentioned threshold value. According to such a configuration, the preset rotation speed can be changed in time according to the actual vehicle speed that decreases with the passage of time because the acceleration operation is not performed.

Further, in the vehicle speed estimation device 300 according to the embodiment, the vehicle speed estimation unit 303 rotates the rear wheels RL and RR when the rotation speeds of the rear wheels RL and RR become larger than the above-mentioned preset rotation speeds. Estimate the vehicle speed based on the speed. According to such a configuration, when the rotation speeds of the rear wheels RL and RR are closer to the actual vehicle speed than the preset rotation speeds, the rotation speeds of the rear wheels RL and RR are estimated as the vehicle speed. It can be properly selected as a basis.

In the above-described embodiment, the electric parking brake 2 is used to realize the increase / decrease control, and the vehicle speed is based on the larger of the rotation speeds of the front wheels FL and FR and the rotation speeds of the rear wheels RL and RR. The configuration for estimating is illustrated. However, as a modification, the increase / decrease control is realized by using the regular brake 1 without using the electric parking brake 2, and either the rotation speeds of the front wheels FL and FR and the rotation speeds of the rear wheels RL and RR are used. A configuration in which the vehicle speed is estimated based on the larger one is also conceivable. However, in the vehicle speed estimation technique as described above, the increase / decrease control is realized by using the electric parking brake 2 which tends to cause an extreme change in the rotation speed of the wheels because the EPB motor 10 performs sinusoidal drive. It is particularly effective for configurations such as morphology.

Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples and are not intended to limit the scope of the invention. The novel embodiment described above can be implemented in various forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. Further, the above-described embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 Regular brake 2 Electric parking brake 10 EPB motor (electric actuator)
100 Vehicle 300 Vehicle speed estimation device 302 Actuator control unit (control unit)
303 Vehicle speed estimation unit (estimation unit)
FL, FR Front wheels (wheels)
RL, RR rear wheel (wheel)

Claims (4)

A vehicle speed estimation device that estimates the speed of a vehicle provided with a braking force applying unit that applies braking force to the front and rear wheels of the vehicle.
When at least one of the front wheels and the rear wheels slips and the acceleration operation for accelerating the vehicle is not performed, the at least one wheel in which the slip occurs is controlled. As a wheel, a control unit that executes an increase / decrease control that repeats an increase control that increases the braking force and a decrease control that decreases the braking force.
During the execution of the increase / decrease control, an estimation unit that estimates the speed of the vehicle based on the larger of the rotation speed of the control target wheel and the rotation speed of the wheels other than the control target wheel.
Equipped with
The braking force applying portion includes an electric parking brake that generates a parking braking force by an electric actuator on one of the front wheels and the rear wheels, and the parking on at least one of the front wheels and the rear wheels. Including a regular brake that generates a regular braking force separate from the braking force,
The increase / decrease control is executed by the electric parking brake.
The control unit responds to the change from the state in which the normal brake can generate the normal braking force to both the front wheels and the rear wheels to the state in which the normal braking force can be generated only in the front wheels. When the parking brake generates the parking braking force on the rear wheels to generate the slip and the acceleration operation for accelerating the vehicle is not performed, the increase / decrease is performed by driving the electric actuator. A vehicle speed estimator that performs control . When the value indicating the degree of decrease in the rotation speed of the controlled object wheel becomes larger than the threshold value, the estimation unit of the controlled object wheel at the timing when the value indicating the degree of decrease becomes larger than the threshold value. Estimating the speed of the vehicle based on a rotation speed preset above the rotation speed.
The vehicle speed estimation device according to claim 1. The preset rotation speed decreases with the passage of time with a degree of decrease smaller than the threshold value.
The vehicle speed estimation device according to claim 2. When the rotation speed of the control target wheel becomes larger than the preset rotation speed, the estimation unit estimates the speed of the vehicle based on the rotation speed of the control target wheel.
The vehicle speed estimation device according to claim 2 or 3.

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