JP2007176260A - Brake control device and controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve braking performance by improving the estimation precision of a tire-and-road surface friction coefficient. <P>SOLUTION: A tire-and-road surface friction coefficient estimation means 10 estimates a maximum friction coefficient between a wheel and a road surface in accordance with the information of a rate of a change of the deceleration of a vehicle and braking from vehicle body speed obtained by a vehicle body speed detection means. A target slip ratio computation means 20 computes a target slip ratio on the basis of a maximum friction coefficient estimated value estimated by a friction coefficient estimation means 14. A braking force control means 30 outputs a braking force applied on each of wheels in accordance with the vehicle body speed, wheel speed and the target slip ratio. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an automobile brake control apparatus and control method, and more particularly, to an automobile brake control apparatus and control method for controlling a brake by estimating a maximum friction coefficient between tire road surfaces.

  In order to suppress the increase in the number of vehicle accidents in recent years, research and development of preventive safety technology for preventing accidents such as vehicle collision prevention devices and ABS (Anti-Lock Brake System) has been promoted in each manufacturer. In the vehicle collision prevention device, ABS, etc., the brake pressure applied to each wheel is controlled according to the vehicle state, but if the brake pressure is not controlled according to the road surface condition during traveling, the wheel will lock and the vehicle behavior will be It can become unstable and rather dangerous.

Therefore, for example, as described in JP-A-7-17346, the brake pressure Pi, the wheel acceleration αi, and the wheel slip ratio Si are measured a plurality of times, and the obtained data set (Pi, αi, Si; i = 1 to n), a coefficient C ₁ is obtained by the least square method from an equation consisting of Pi = C ₁ × Si + C ₂ × αi, and the coefficient of friction between tire roads μ is calculated from μ = a × C ₁ using a constant a. The method of seeking is known.

Japanese Patent Laid-Open No. 7-17346

  However, in the method described in JP-A-7-17346, the relationship between the maximum friction coefficient μ between the tire road surfaces and the slip ratio Si is linearly approximated. This is because the linearity is relatively strong in the region where the slip ratio is small. However, as the slip ratio increases and approaches the maximum friction coefficient between tire roads, the nonlinearity becomes stronger, so the error increases and the accuracy of the estimated tire road surface printing coefficient deteriorates. .

  An object of the present invention is to improve the estimation accuracy of the tire road surface friction coefficient and improve the braking performance.

(1) In order to achieve the above object, the present invention provides a wheel speed detecting means for obtaining a wheel speed that is a speed from a rotational speed of a wheel, and a vehicle body that obtains a vehicle body speed that is a speed with respect to a road surface in the traveling direction of the vehicle. The actual slip ratio of the wheel is calculated from the speed detection means, the wheel speed determined by the wheel speed detection means and the vehicle speed determined by the vehicle speed detection means, and the preset target slip ratio and the actual slip ratio are calculated. A brake control device having a brake control means for obtaining a braking force command value of the wheel based on the wheel braking means for adding a braking force to the wheel based on the braking force command value obtained by the brake control means, The brake control means includes a friction coefficient estimation means for estimating a maximum friction coefficient between the wheel and the road surface based on a vehicle speed change rate obtained by the vehicle speed detection means and brake information; Based on the maximum friction coefficient estimating value estimated by the number estimation means, is obtained by so and a target slip ratio calculating means for calculating said target slip ratio.
With this configuration, it is possible to improve the estimation accuracy of the tire road surface friction coefficient and improve the braking performance.

  (2) In the above (1), preferably, the friction coefficient estimating means stores a representative relationship between a rate of change of the deceleration and a maximum friction coefficient between the wheel and the road surface, and the calculation is performed. The maximum printing coefficient is estimated by interpolating the stored representative relationship from the rate of change in deceleration.

  (3) In the above (2), preferably, the information on the brake is a brake pressure when the brake is depressed, and the friction coefficient estimating means has a rate of change of the deceleration for each of a plurality of brake pressures. And a representative relationship of the maximum friction coefficient between the wheel and the road surface, and based on the brake pressure detected by the brake pressure sensor, a plurality of stored change rates of the deceleration The maximum printing coefficient is estimated by selecting one from the representative relationship of the maximum friction coefficient between the wheel and the road surface, and interpolating the stored representative relationship from the obtained rate of change in deceleration. It is what you do.

  (4) In the above (2), preferably, the brake information is a stroke amount of a brake pedal when the brake is depressed, and the friction coefficient estimating means is configured to reduce the decrease for each of a plurality of brake stroke pressures. A representative relationship between a rate of change in speed and a maximum friction coefficient between the wheel and the road surface is stored, and a plurality of the decelerations stored based on the brake stroke detected by the brake stroke sensor are stored. The maximum friction coefficient is selected by interpolating the stored representative relationship from the calculated rate of change in deceleration and selecting one from the typical relationship between the rate of change in the maximum friction coefficient between the wheel and the road surface. The printing coefficient is estimated.

  (5) In the above (2), preferably, the information on the brake is a brake torque requested by a driver, and the friction coefficient estimating means determines the rate of change of the deceleration and the speed for each of a plurality of brake torques. A representative relationship of a maximum friction coefficient between a wheel and the road surface is stored, and based on the brake torque detected by the brake torque sensor, a plurality of stored change rates of the deceleration and the wheel are stored. One of the representative relations of the maximum friction coefficient between the road surface and the road surface, and the maximum printing coefficient is estimated by interpolating the stored representative relation from the obtained rate of change in deceleration. It is a thing.

  (6) In the above (1), preferably, the deceleration change rate calculation means calculates a change in vehicle deceleration using the vehicle body speed calculated by the vehicle body speed detection means. is there.

  (7) In the above (1), preferably, the deceleration change rate calculating means calculates a deceleration change in a predetermined time from a point in time when deceleration occurs in the vehicle by a driver's brake pedal operation. Is.

(8) Further, in order to achieve the above object, the present invention calculates the actual slip ratio of the wheel from the wheel speed that is the speed from the rotational speed of the wheel and the vehicle body speed that is the speed with respect to the road surface in the traveling direction of the vehicle. A brake control method for calculating a braking force command value of a wheel based on a preset target slip ratio and the actual slip ratio, wherein a change in deceleration of the vehicle is calculated, and based on the deceleration change rate Then, a maximum friction coefficient between the wheel and the road surface is estimated, and the target slip ratio is calculated based on the estimated maximum friction coefficient estimated value.
With this method, it is possible to improve the estimation accuracy of the tire road surface friction coefficient and improve the braking performance.

  According to the present invention, it is possible to improve the estimation accuracy of the tire road surface friction coefficient and improve the braking performance.

Hereinafter, the configuration and operation of the brake control device according to the first embodiment of the present invention will be described with reference to FIGS.
First, the system configuration of the brake control device according to the present embodiment will be described with reference to FIG.
FIG. 1 is a block diagram showing a system configuration of a brake control device according to a first embodiment of the present invention.

  The brake control device 1 is responsible for function control and various arithmetic operations of the entire device, and is performed by a vehicle body speed sensor 2, a brake pressure sensor 3, and wheel speed sensors 4FL, 4FR, 4RL, 4RR via an input / output interface. Various detected state signals are inputted, and a control signal is outputted to the wheel braking means 5FL, 5FR, 5RL, 5RR. Here, the wheel braking means 5FL, 5FR, 5RL, 5RR are hydraulically driven brakes. The illustration of the input / output interface is omitted.

  The vehicle body speed sensor 2 detects the vehicle body speed VI. Instead of directly detecting with a sensor, the vehicle body speed VI may be obtained by estimation. The brake pressure sensor 3 detects a brake pressure Pm generated when the driver steps on the brake pedal. Wheel speed sensors 4FL, 4FR, 4RL, 4RR detect wheel speeds Vw_FL, Vw_FR, Vw_RL, Vw_RR of each wheel. In addition, when referring to all the wheel speeds of the four wheels, the wheel speeds Vw_FL, Vw_FR, Vw_RL, and the average value of Vw_RR are used to refer to the wheel speeds Vw.

  The wheel braking means 5FL, 5FR, 5RL, 5RR applies a braking force to the wheel based on the braking force calculated by the brake control device 1. Here, the system is driven by hydraulic pressure, but a system driven by a motor may be used.

  The brake control device 1 includes a tire road surface friction coefficient estimating means 10, a target slip ratio calculating means 20, and a braking force control means 30. The tire road surface friction coefficient estimating means 10 receives the vehicle body speed VI and the brake pressure Pm, and outputs a maximum friction coefficient μmax. The target slip ratio calculating means 20 receives the maximum friction coefficient μmax and outputs a target slip ratio Starget. The braking force control means 30 receives the vehicle body speed VI, the wheel speed Vw, and the target slip ratio Starget, and outputs the braking force applied to each wheel.

Next, the configuration and operation of the tire road surface friction coefficient estimating means 10 of the brake control device according to the present embodiment will be described with reference to FIGS. 2 and 3.
FIG. 2 is a block diagram showing the configuration of the tire road surface friction coefficient estimating means of the brake control device according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram of a method for calculating the rate of change in vehicle deceleration by the brake control device according to the first embodiment of the present invention. In FIG. 2, the same reference numerals as those in FIG. 1 denote the same parts.

  The tire road surface friction coefficient estimation means 10 includes a MAP storage means 11, an actual vehicle deceleration calculation means 12, an actual vehicle deceleration change rate calculation means 13, and a maximum friction coefficient μmax calculation means 14.

  The MAP storage unit 11 stores the relationship between the actually measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate. In FIG. 3, the horizontal axis indicates time, the vertical axis indicates deceleration, the solid line indicates vehicle deceleration when braking on a road surface having three maximum friction coefficients μmax, and the dotted line is between Δt. The inclination of the vehicle body deceleration, that is, the rate of change of the vehicle body deceleration is shown. However, the driver's brake operation method is almost the same. FIG. 3 shows that the vehicle body deceleration change rate increases as the maximum friction coefficient μmax increases, and the MAP storage means 11 utilizes this relationship.

  The relationship between the actually measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate is shown in FIG. 3 on the road surface where the actually measured maximum friction coefficient μmax_data is measured in advance, after a predetermined time Δt from the start of the brake operation (when the deceleration occurs). This is obtained by stepping on the brake pedal so that the brake pressure becomes a predetermined value Pm_1 and measuring the vehicle body deceleration change rate during the predetermined time Δt at this time. As shown in the MAP storage unit 11 in FIG. 2, the vehicle body deceleration change rate is measured by stepping on the brake pedal so that the brake pressure Pm_1 is obtained even on a plurality of road surfaces having different measured maximum friction coefficients μmax_data. One map showing the relationship between the actually measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate at the brake pressure Pm_1 can be created. Further, the vehicle body deceleration change rate is measured in the same manner as in the case of the brake pressure Pm_1 by setting the brake pressure to a different value other than Pm_1 (Pm_i: i = 2 to n), so that Pm_i ( n maps showing the relationship between the actually measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate when i = 1 to n) can be created. The created n maps are stored in the MAP storage unit 11 and selected by comparing the brake pressure Pm detected by the brake pressure sensor 3 with the brake pressure Pm_i using the brake pressure Pm_i as a parameter.

  In FIG. 2, when the vehicle body speed VI detected by the vehicle body speed sensor 2 is input to the tire road surface friction coefficient estimating unit 10, the vehicle body deceleration calculating unit 12 calculates the vehicle body deceleration. Further, the actual vehicle deceleration change rate calculation means 13 calculates the actual vehicle deceleration change rate from the vehicle deceleration determined by the actual vehicle deceleration calculation means 12. The actual vehicle deceleration calculated in this way is sent to the maximum friction coefficient μmax calculating means 14. On the other hand, when the brake pressure Pm detected by the brake pressure sensor 3 is inputted, it is sent to the MAP storage means 11.

  The MAP storage unit 11 selects a map indicating the relationship between the actual maximum friction coefficient μmax_data and the vehicle body deceleration change rate at the brake pressure Pm_k (1 ≦ k ≦ n) closest to the brake pressure Pm. As another method for selecting a map, for example, when there is a relationship of brake pressure Pm_k−1 ≦ Pm ≦ Pm_k, a linear map is obtained using a map at the time of brake pressure Pm_k−1 and a map at the time of brake pressure Pm_k. A map at the time of the brake pressure Pm may be newly created by interpolation, and this map may be selected. The map selected in this way is sent to the maximum friction coefficient μmax calculating means 14.

  The maximum friction coefficient μmax calculation means 14 is linear using the actual vehicle deceleration change rate obtained by the actual vehicle deceleration change rate calculation means 13, the vehicle body deceleration change rate on the map, and the actually measured maximum friction coefficient μmax_data. The maximum friction coefficient μmax is calculated by interpolation.

Next, the operation of the target slip ratio calculating means 20 of the brake control device according to the present embodiment will be described with reference to FIG.
FIG. 4 is an explanatory diagram of the principle in the target slip ratio calculating means of the brake control device according to the first embodiment of the present invention.

  Next, the operation of the target slip ratio calculating means 20 will be described. One of the target slip ratios calculated by the target slip ratio calculating means 20 is a slip ratio at which the braking force is maximized. One method for calculating the slip ratio at which the braking force is maximized is to use an equation of force in the longitudinal direction generated by the tire, which is derived from a brush model, which is a dynamic model of the tire.

FIG. 4 shows a state of deformation of the tread rubber on the ground contact surface due to side slip during braking. In the figure, θ is the slip direction of the tire contact surface at an arbitrary point A within the tire contact surface, σx is the longitudinal force acting on the point A, σy is the lateral force acting on the point A, and σ is the front and back. Direction force σx and lateral force σy, Fx is the longitudinal force acting on the entire tire contact surface, Fy is the lateral force acting on the entire tire contact surface, F is the force in the previous direction Expressed as the resultant force of Fx and lateral force Fy. At this time, the angle formed between σ and σx acting on the point A is the slip direction θ of the tire contact surface. Here, if it is approximated that the slip direction is θ in the entire area of the tire contact surface, the angle formed by Fx and F acting on the entire tire contact surface is also θ. Therefore, the resultant force F of the longitudinal force Fx and the lateral force Fy generated by the tire can be expressed by the following equation (1).

However,

Here, s: slip ratio, Fz: wheel load, β: vehicle side slip angle, Ks: longitudinal tire stiffness, Kβ: lateral tire stiffness, θ: tire slip direction, μs: static friction coefficient, μd: Dynamic friction coefficient.

  The longitudinal tire stiffness Ks and the lateral tire stiffness Kβ may be substituted with predetermined values, but may be corrected using values output by the tire condition estimating means for estimating the tire condition. It is. In addition, the wheel load Fz may be a value that is corrected by using vehicle body deceleration in the front-rear direction and the lateral direction with respect to a value unique to the vehicle. Here, the resultant force F during straight braking, that is, Fx, is derived, but also in the case of turning, the vehicle body side slip angle β and the slip direction θ of the tire contact surface detected using various detection devices are expressed by Equation (1). It can be obtained by substituting.

The resultant force F at the time of straight braking is obtained by substituting the slip direction θ = 0 of the tire contact surface and the vehicle body side slip angle β = 0 as

here,

In other words, equation (2) can be transformed into the following equation (3).

Here, -Fx is a force in the direction opposite to the traveling direction, that is, a braking force. That is, by dividing both sides of the equation (3) by Fz, the tire road surface friction coefficient μ can be derived as shown in the following equation (4).

Here, since s takes a value in the range of 0 ≦ s ≦ 1, (Equation 4) is

At the maximum. Therefore, the maximum friction coefficient μmax is expressed by the following equation (5).

Incidentally, the relationship of μd = α · μs (0 <α <1) is generally known between the static friction coefficient μs and the dynamic friction coefficient μd. From this relationship and the equation (5), the static friction coefficient μs and the dynamic friction coefficient μd are obtained from the estimated maximum friction coefficient μmax. Therefore, the slip ratio when the braking force is maximized during the straight braking, that is, the target slip ratio s is obtained by the following equation (6).

Note that the slip ratio at which the braking force is maximized during turning can be obtained in the same manner.

  Next, the operation of the braking force control means 30 will be described. The braking force control means 30 does not perform feedback control or the like while the wheel speed Vw exceeds the ABS start threshold Vwsp set based on the target slip ratio after the driver performs the braking operation, and the brake pressure Pm Based on the above, the braking force is calculated. Then, when the wheel speed Vw once falls below the ABS start threshold value Vwsp, the ABS operates, and the following calculation is performed until the wheel speed Vw becomes zero and the vehicle body speed becomes zero, or the brake pressure Pm becomes zero. Do. The braking force control means 30 includes an actual slip ratio obtained from the vehicle speed VI and the wheel speed Vw detected by the vehicle speed sensor 2 and the wheel speed sensor 4, and a target slip ratio calculated by the target slip ratio calculation means 20. Feedback control regarding the slip ratio is performed so that the difference is zero, and the braking force of each wheel is calculated. However, when the difference between the actual slip ratio and the target ratio is greater than a predetermined value, the predetermined braking force may be directly calculated instead of the feedback control.

Next, an overall control calculation operation of the brake control device 1 of the brake control device according to the present embodiment will be described with reference to FIGS. 5 and 6.
FIG. 5 is a flowchart showing an overall control calculation operation of the brake control device 1 of the brake control device according to the first embodiment of the present invention. FIG. 6 is a timing flowchart during the control calculation operation by the brake control device 1 of the brake control device according to the first embodiment of the present invention. The vertical axis in FIG. 6 (A) indicates the speed (km / h), the vertical axis in FIG. 6 (B) indicates the brake pressure (Mpa), and the horizontal axis indicates time.

  In step S1 of FIG. 5, the brake control device 1 determines the start of the driver's brake operation (time t0 in FIG. 6) and the occurrence of vehicle deceleration. At this time, time T = 0.

  Next, in step S2, the actual vehicle deceleration calculation means 12 measures the vehicle deceleration and time T. In step S3, determination is made according to time T. If the time T is less than the predetermined value Δt, the process returns to step S2, and the vehicle body deceleration and the time T are continuously measured.

  When the time T exceeds the predetermined value Δt, in step S4, the actual vehicle body deceleration change rate calculating means 13 calculates the vehicle body deceleration change rate.

  Next, in step S5, the maximum friction coefficient μmax calculating means 14 calculates the maximum friction coefficient μmax (time t1 in FIG. 6).

  Next, in step S6, the target slip ratio calculating means 20 calculates the target slip ratio. Also, Vwsp is set based on this target slip ratio. Next, in step S7, the braking force control means 30 determines whether or not AB step S is started. If the wheel speed Vw exceeds the ABS determination threshold value VwSp, the process proceeds to step S9. In step S9, the braking force control means 30 converts the brake pressure applied by the driver into the braking force as it is.

  If the wheel speed Vw is below the ABS determination threshold value Vwsp, the process proceeds to step S8. In step S8, the braking force control means 30 makes a determination based on the wheel speed Vw and the brake pressure applied by the driver. If it is determined in step S8 that the wheel speed Vw = 0 or the brake pressure is zero, the process proceeds to step S9.

  On the other hand, if the wheel speed Vw = 0 or the brake pressure is neither zero, the process proceeds to step S10. Here, the braking force control means 30 calculates the braking force based on the difference between the actual slip ratio and the target slip ratio.

  By the above control, as shown in FIG. 6, the maximum friction coefficient μmax is estimated at time t1 before the wheel is locked, the ABS start threshold value Vwsp is set, and the wheel speed Vw is changed to the ABS start threshold value Vwsp at time t2. If below, start ABS.

  As described above, in the present embodiment, the road surface friction coefficient is obtained by using the representative relationship between the vehicle body deceleration change rate and the maximum friction coefficient stored in advance based on the brake operation amount and the vehicle speed of the driver. The maximum friction coefficient of the running road surface can be accurately estimated without being affected by the nonlinearity of the slip ratio. In addition, by causing the wheel slip ratio to follow the target slip ratio obtained based on the estimated maximum friction coefficient, it is possible to prevent wheel lock caused by the driver's sudden braking operation, etc., and to improve the braking performance. Can do.

Next, the configuration and operation of the brake control device according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 7 is a block diagram showing a system configuration of a brake control device according to the second embodiment of the present invention.

  In the embodiment shown in FIG. 1, the wheel braking means 5 ′ is driven by hydraulic pressure, but in this embodiment, the wheel braking means 5 ′ (wheel braking means 5FL ′, 5FR ′, 5RL ′, 5RR) is used. ') Is a system driven by a motor.

  In the case of a system driven by a motor, a brake pedal stroke sensor 6 that detects the degree of depression of the driver's brake pedal, that is, a pedal stroke amount, can be used instead of the brake pressure sensor 3 shown in FIG. . Here, a case where the brake pedal stroke sensor 6 is used will be described.

  The brake control device 1A includes a tire road surface friction coefficient estimating means 10A, a target slip ratio calculating means 20, and a braking force control means 30A.

  The tire road surface friction coefficient estimating means 10A has MAP storage means similar to the MAP storage means 11 shown in FIG. A map showing the relationship between the actually measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate stored in the MAP storage means can also be created using the brake pedal stroke amount for a predetermined time Δt from the time of vehicle body deceleration occurrence. it can. The method for creating the map is the same as that described with reference to FIG. 3, and is as follows. On the road surface where the actually measured maximum friction coefficient μmax_data is measured in advance, the brake pedal is stepped on so that the brake stroke amount for a predetermined time Δt from the time of deceleration occurrence becomes the predetermined value ST_1, and the vehicle body deceleration change rate during Δt at this time It is obtained by measuring. By measuring the vehicle body deceleration change rate by stepping on the brake pedal so that the brake stroke amount ST_1 becomes the same even on a plurality of road surfaces having different actual maximum friction coefficients μmax_data, One map showing the relationship between the vehicle body deceleration change rate can be created. Further, by measuring the vehicle body deceleration change rate in the same manner as in the case of the brake stroke amount ST_1 by setting the brake stroke amount to a different value other than ST_1 (ST_i: i = 2 to n), N maps showing the relationship between the actual maximum friction coefficient μmax_data and the vehicle body deceleration change rate when the brake stroke amount ST_i (i = 1 to n) can be created.

  The tire road surface friction coefficient estimating means 10A compares the brake stroke amount ST detected by the brake stroke amount sensor 6 with the brake stroke amount ST_i, using the brake stroke amount ST_i as a parameter, for the created n maps. It is selected by. Further, as another method for selecting a map, for example, when there is a relationship of ST_k-1 ≦ ST ≦ ST_k (1 ≦ k ≦ n−1), the map at the time of the brake stroke amount ST_k−1 and the brake stroke amount ST_k. It is also possible to newly create a map at the time of the brake pedal stroke amount ST by performing linear interpolation using the map at the time, and select this map.

  When the vehicle body speed VI detected by the vehicle body speed sensor 2 is input, the tire road surface friction coefficient estimating unit 10A calculates the vehicle body deceleration in the actual vehicle body deceleration calculating unit 12 as shown in FIG. Further, the actual vehicle deceleration change rate calculation means 13 as shown in FIG. 2 calculates the actual vehicle deceleration change rate from the vehicle deceleration obtained by the actual vehicle deceleration calculation means 12. The actual vehicle deceleration calculated in this way is sent to the maximum friction coefficient μmax calculating means 14 as shown in FIG. On the other hand, when the brake pedal stroke amount ST_1 detected by the brake pedal stroke sensor 6 is input, it is sent to the MAP storage means as shown in FIG.

  The MAP storage means selects a map indicating the relationship between the measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate at the brake pedal stroke amount ST_k (1 ≦ k ≦ n) closest to the brake pedal stroke amount ST_1. The map selected in this way is sent to the maximum friction coefficient μmax calculating means 14.

  The maximum friction coefficient μmax calculating means 14 as shown in FIG. 2 includes the actual vehicle deceleration change rate obtained by the actual vehicle deceleration change rate calculating means 13, the vehicle body deceleration change rate on the map, and the actually measured maximum. The maximum friction coefficient μmax is calculated by linear interpolation using the friction coefficient μmax_data.

  The target slip ratio calculating means 20 receives the maximum friction coefficient μmax and outputs a target slip ratio Starget. Further, the braking force control means 30A is necessary for controlling the motor type wheel braking means 5FL ′, 5FR ′, 5RL ′, 5RR ′ with the vehicle body speed VI, the wheel speed Vw, and the target slip ratio Starget as inputs. The braking force applied to each wheel is output.

  Also in this embodiment, a non-linear relationship between the road surface friction coefficient and the slip ratio is obtained by using a typical relationship between the vehicle body deceleration change rate and the maximum friction coefficient stored in advance based on the driver's brake operation amount and the vehicle body speed. It is possible to accurately estimate the maximum friction coefficient of the traveling road surface without being affected by the property. In addition, by causing the wheel slip ratio to follow the target slip ratio obtained based on the estimated maximum friction coefficient, it is possible to prevent wheel lock caused by the driver's sudden braking operation, etc., and to improve the braking performance. Can do.

Next, the configuration and operation of the brake control device according to the third embodiment of the present invention will be described with reference to FIG.
FIG. 8 is a block diagram showing a system configuration of a brake control device according to the third embodiment of the present invention.

  In the embodiment shown in FIG. 7, the brake pedal stroke sensor 6 that detects the degree of depression of the driver's brake pedal is used. However, the brake control device 1 </ b> B of this embodiment allows the driver to depress the pedal. Is used, that is, the brake torque sensor 7 for detecting the brake torque requested by the driver.

  The brake control device 1B includes tire road surface friction coefficient estimation means 10B, target slip ratio calculation means 20, and braking force control means 30A.

  The tire road surface friction coefficient estimating means 10B has MAP storage means similar to the MAP storage means 11 as shown in FIG. A map showing the relationship between the actually measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate stored in the MAP storage means can also be created using the brake torque Tq for a predetermined time Δt from the time of vehicle body deceleration occurrence. . The method for creating the map is the same as that shown in FIG. 3 and is as follows. On the road surface where the actual maximum friction coefficient μmax_data was measured in advance, the brake pedal was stepped on so that the brake torque for a predetermined time Δt from the time of deceleration occurrence becomes a predetermined value Tq_1. It is obtained by measuring. By measuring the vehicle body deceleration change rate by stepping on the brake pedal so that the brake torque Tq_1 becomes the brake torque Tq_1 even on a plurality of road surfaces having different actual maximum friction coefficients μmax_data, the actual maximum friction coefficient μmax_data and the vehicle body decrease at the brake torque Tq_1 One map showing the relationship of speed change rate can be created. Furthermore, by measuring the vehicle body deceleration change rate in the same manner as that for the brake torque Tq_1 by setting the brake torque to a different value other than Tq_1 (Tq_i: i = 2 to n), Tq_i ( n maps showing the relationship between the actually measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate when i = 1 to n) can be created. The created n maps are selected by comparing the brake torques Tq and Tq_i detected by the brake torque sensor 7 with Tq_i as a parameter. As another method of map selection, for example, when there is a relationship of Tq_k-1 ≦ Tq ≦ Tq_k (1 ≦ k ≦ n−1), a map at Tq_k1 and a map at Tq_k are used. There is also a method of creating a new map at the time of brake torque Tq by performing linear interpolation and selecting this map.

  When the vehicle body speed VI detected by the vehicle body speed sensor 2 is input, the tire road surface friction coefficient estimating unit 10B calculates the vehicle body deceleration in the actual vehicle body deceleration calculating unit 12 as shown in FIG. Further, the actual vehicle deceleration change rate calculation means 13 as shown in FIG. 2 calculates the actual vehicle deceleration change rate from the vehicle deceleration obtained by the actual vehicle deceleration calculation means 12. The actual vehicle deceleration calculated in this way is sent to the maximum friction coefficient μmax calculating means 14 as shown in FIG. On the other hand, when the brake torque Tq detected by the brake torque sensor 7 is input, it is sent to the MAP storage means as shown in FIG.

  The MAP storage means selects a map indicating the relationship between the measured maximum friction coefficient μmax_data and the vehicle body deceleration change rate at the brake pedal stroke amount ST_k (1 ≦ k ≦ n) closest to the brake pedal stroke amount ST_1. The map selected in this way is sent to the maximum friction coefficient μmax calculating means 14.

  The maximum friction coefficient μmax calculating means 14 as shown in FIG. 2 includes the actual vehicle deceleration change rate obtained by the actual vehicle deceleration change rate calculating means 13, the vehicle body deceleration change rate on the map, and the actually measured maximum. The maximum friction coefficient μmax is calculated by linear interpolation using the friction coefficient μmax_data.

  The target slip ratio calculating means 20 receives the maximum friction coefficient μmax and outputs a target slip ratio Starget. Further, the braking force control means 30A is necessary for controlling the motor type wheel braking means 5FL ′, 5FR ′, 5RL ′, 5RR ′ with the vehicle body speed VI, the wheel speed Vw, and the target slip ratio Starget as inputs. The braking force applied to each wheel is output.

Also in this embodiment, a non-linear relationship between the road surface friction coefficient and the slip ratio is obtained by using a typical relationship between the vehicle body deceleration change rate and the maximum friction coefficient stored in advance based on the driver's brake operation amount and the vehicle body speed. It is possible to accurately estimate the maximum friction coefficient of the traveling road surface without being affected by the property. In addition, by causing the wheel slip ratio to follow the target slip ratio obtained based on the estimated maximum friction coefficient, it is possible to prevent wheel lock caused by the driver's sudden braking operation, etc., and to improve the braking performance. Can do.

It is a block diagram which shows the system configuration | structure of the brake control apparatus by the 1st Embodiment of this invention. It is a block diagram which shows the structure of the friction coefficient between tire road surface estimation means of the brake control apparatus by the 1st Embodiment of this invention. It is explanatory drawing of the calculation method of the change rate of the vehicle body deceleration by the brake control apparatus by the 1st Embodiment of this invention. It is principle explanatory drawing in the target slip ratio calculating means of the brake control apparatus by the 1st Embodiment of this invention. It is a flowchart which shows the control calculation operation | movement of the whole brake control apparatus 1 of the brake control apparatus by the 1st Embodiment of this invention. It is a timing flowchart at the time of the control calculation operation | movement by the brake control apparatus 1 of the brake control apparatus by the 1st Embodiment of this invention. It is a block diagram which shows the system configuration | structure of the brake control apparatus by the 2nd Embodiment of this invention. It is a block diagram which shows the system configuration | structure of the brake control apparatus by the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A, 1B ... Brake control device 2 ... Body speed sensor 3 ... Brake pressure sensor 4FL, 4FR, 4RL, 4RR ... Wheel speed sensor 5FL, 5FR, 5RL, 5RR ... Wheel brake means 6 ... Brake pedal stroke sensor 7 ... Brake Torque sensor 10 ... Tire road surface friction coefficient estimating device 11 ... MAP storage device 12 ... Real vehicle deceleration calculation device 13 ... Real vehicle deceleration change rate calculation device 14 ... Tire road maximum friction coefficient (μmax) calculation device 20 ... Target Slip rate calculating device 30 ... braking force control device

Claims (8)

Wheel speed detection means for obtaining a wheel speed, which is a speed from the rotation speed of the wheel;
Vehicle body speed detecting means for obtaining a vehicle body speed which is a speed with respect to a road surface with respect to a traveling direction of the vehicle;
The actual slip ratio of the wheel is calculated from the wheel speed obtained by the wheel speed detecting means and the vehicle body speed obtained by the vehicle body speed detecting means, and the wheel control is performed based on the preset target slip ratio and the actual slip ratio. Brake control means for obtaining a power command value;
A brake control device having wheel braking means for adding braking force to a wheel based on a braking force command value obtained by the brake control means,
The brake control means includes
Friction coefficient estimating means for estimating a maximum friction coefficient between the wheel and the road surface based on the rate of change in deceleration of the vehicle and information on the brake from the vehicle body speed obtained by the vehicle body speed detecting means;
A brake control device comprising: target slip ratio calculating means for calculating the target slip ratio based on a maximum friction coefficient estimated value estimated by the friction coefficient estimating means. The brake control device according to claim 1, wherein
The friction coefficient estimating means stores a representative relationship between a rate of change of the deceleration and a maximum friction coefficient between the wheel and the road surface,
A brake control device, wherein a maximum printing coefficient is estimated by interpolating the stored representative relationship from the obtained rate of change in deceleration. The brake control device according to claim 2, wherein
The information on the brake is a brake pressure when the brake is depressed,
The friction coefficient estimating means stores, for each of a plurality of brake pressures, a representative relationship between a rate of change of the deceleration and a maximum friction coefficient between the wheel and the road surface,
Based on the brake pressure detected by the brake pressure sensor, one is selected from a representative relationship of a plurality of stored change rates of the deceleration and the maximum friction coefficient between the wheel and the road surface, A brake control device, wherein a maximum printing coefficient is estimated by interpolating the stored representative relationship from the obtained rate of change in deceleration. The brake control device according to claim 2, wherein
The brake information is the stroke amount of the brake pedal when the brake is depressed,
The friction coefficient estimating means stores a representative relationship between a rate of change of the deceleration and a maximum friction coefficient between the wheel and the road surface for each of a plurality of brake stroke pressures.
Based on a brake stroke detected by the brake stroke sensor, one is selected from a representative relationship of a plurality of stored change rates of the deceleration and a maximum friction coefficient between the wheel and the road surface, A brake control device, wherein a maximum printing coefficient is estimated by interpolating the stored representative relationship from the obtained rate of change in deceleration. The brake control device according to claim 2, wherein
The brake information is brake torque requested by the driver,
The friction coefficient estimating means stores, for each of a plurality of brake torques, a representative relationship between a rate of change of the deceleration and a maximum friction coefficient between the wheel and the road surface,
Based on the brake torque detected by the brake torque sensor, one is selected from a representative relationship of a plurality of stored change rates of the deceleration and the maximum friction coefficient between the wheel and the road surface, A brake control device, wherein a maximum printing coefficient is estimated by interpolating the stored representative relationship from the obtained rate of change in deceleration. The brake control device according to claim 1, wherein
The brake control device, wherein the deceleration change rate calculating means calculates a change in vehicle deceleration using the vehicle body speed calculated by the vehicle body speed detecting means. The brake control device according to claim 1, wherein
The brake control apparatus according to claim 1, wherein the deceleration change rate calculating means calculates a change in deceleration in a predetermined time from a point in time when deceleration occurs in the vehicle by a driver's brake pedal operation. Calculate the actual slip ratio of the wheel from the wheel speed that is the speed from the rotational speed of the wheel and the vehicle body speed that is the speed with respect to the road surface in the traveling direction of the vehicle,
A brake control method for calculating a braking force command value of a wheel based on a preset target slip ratio and the actual slip ratio,
Calculating the change in deceleration of the vehicle,
Based on this deceleration change rate and brake information, estimate the maximum friction coefficient between the wheel and the road surface,
A brake control method, wherein the target slip ratio is calculated based on the estimated maximum friction coefficient estimated value.

Images