Braking control device

Abstract

To improve controllability of wheel brake force.SOLUTION: A brake control device 70 includes: an indication value acquisition part 101 for acquiring brake indication values BPfIv and BPrIv for brake devices 21 to 24 provided on wheels of a vehicle; a brake force acquisition part 103 for acquiring wheel brake forces BPfR and BPrR imparted to the wheels by the brake devices 21 to 24; a brake characteristic derivation part 107 for deriving brake characteristics BCF and BCR of the brake devices 21 to 24, on the basis of the brake indication values BPfIv and BPrIv and the wheel brake forces BPfR and BPrR acquired during traveling of the vehicle; and a brake control part 111 for controlling the brake devices 21 to 24 on the basis of the brake characteristics BCF and BCR derived by the brake characteristic derivation part 107.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a brake control device applied to a vehicle. [Background technology]

[0002] Patent Document 1 discloses a device that estimates vehicle braking characteristics, which are the relationship between the braking torque applied to a vehicle by the brake system and the brake fluid pressure of the brake system, based on the brake fluid pressure of the vehicle's brake system and the deceleration of the vehicle. This device controls the braking force of the entire vehicle based on the estimated vehicle braking characteristics. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2018 / 0201243 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, consider a case where braking force is applied to wheels by operating braking devices provided on the wheels. The vehicle braking characteristics of Patent Document 1 indicate the relationship between the braking torque applied to the vehicle by the brake system and the brake fluid pressure of the brake system. Therefore, although the device of Patent Document 1 can derive the brake fluid pressure of the brake system corresponding to the braking force to be applied to the vehicle (target total braking force), it cannot accurately control the brake fluid pressure of the braking devices provided on each wheel corresponding to the braking force to be applied to the wheels. An object of the present invention is to provide a braking control device that improves the controllability of the braking force applied to the wheels. [Means for solving the problem]

[0005] A braking control device for solving the above problem includes an instruction value acquisition unit that acquires a braking instruction value, which is an instruction value for a braking device provided on a wheel of a vehicle; a braking force acquisition unit that acquires a wheel braking force, which is the braking force applied to the wheel by the braking device; a braking characteristic derivation unit that derives the relationship between the braking instruction value and the wheel braking force as the braking characteristic of the braking device based on the braking instruction value acquired by the instruction value acquisition unit and the wheel braking force acquired by the braking force acquisition unit while the vehicle is traveling; and a braking control unit that controls the braking device based on the braking characteristic derived by the braking characteristic derivation unit.

[0006] In the braking control device, the braking characteristics of the braking devices provided on the wheels are derived based on a braking command value for the braking devices provided on the wheels and the wheel braking force applied to the wheels by the braking devices operated in accordance with the braking command value.The braking control device then controls the braking devices provided on the wheels based on the derived braking characteristics.This improves the controllability of the braking force applied to the wheels. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an outline of a vehicle equipped with a braking control device according to an embodiment. [Figure 2] FIG. 2 is a plan view showing a rear wheel braking device provided on the rear wheels of a vehicle. [Figure 3] FIG. 3 is a block diagram showing the functional configuration of the braking control device. [Figure 4] FIG. 4 is a flowchart showing the braking characteristic derivation process. [Figure 5] FIG. 5 is a flowchart showing the braking force control process. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a braking control device will be described below with reference to FIGS. <Vehicle> FIG. 1 is a schematic diagram showing an outline of a vehicle 10 equipped with a braking control device 70. The vehicle 10 is equipped with wheels and braking devices provided on the wheels. The vehicle 10 is equipped with a left front wheel 11, a right front wheel 12, a left rear wheel 13, and a right rear wheel 14 as wheels. The vehicle 10 is equipped with a braking device 21 for the left front wheel 11, a braking device 22 for the right front wheel 12, a braking device 23 for the left rear wheel 13, and a braking device 24 for the right rear wheel 14 as braking devices. These braking devices 21 to 24 are controlled by a braking control device 70. Of the multiple braking devices 21 to 24, the braking devices 23 and 24 correspond to the "rear wheel braking devices 23 and 24" provided on the rear wheels 13 and 14, and the braking devices 21 and 22 correspond to the "front wheel braking devices 21 and 22" provided on the front wheels 11 and 12.

[0009] <Braking device for front wheels> The front wheel braking devices 21, 22 are electric braking devices equipped with an electric motor 25 that is driven in response to a command from the braking control device 70. The braking devices 21, 22 apply a friction braking force that corresponds to the driving amount of the electric motor 25.

[0010] <Brake device for rear wheels> 2 is a plan view showing the rear wheel braking devices 23, 24. The rear wheel braking devices 23, 24 are drum-type braking devices. More specifically, the rear wheel braking devices 23, 24 are drum-type electric braking devices. The rear wheel braking devices 23, 24 include a back plate 31 fixed to the body of the vehicle 10 and a brake drum 32 attached to the axle of the vehicle 10. While the brake drum 32 rotates integrally with the rear wheels 13, 14, the back plate 31 is fixed to the body.

[0011] The back plate 31 is a metal plate with an axle hole 31a formed in the center for passing the axle through. The brake drum 32 has a cylindrical portion 321. The cylindrical portion 321 is cylindrically shaped with the axle at its center. Hereinafter, the inner peripheral surface 32a of the cylindrical portion 321 will be referred to as the "inner peripheral surface 32a of the brake drum 32."

[0012] The rear wheel braking devices 23, 24 include an actuating device 33, a first brake shoe 35, and a second brake shoe 36. The actuating device 33, the first brake shoe 35, and the second brake shoe 36 are each disposed inside the brake drum 32. The first brake shoe 35 and the second brake shoe 36 are each disposed so that the axle is located between the first brake shoe 35 and the second brake shoe 36.

[0013] The actuator 33 is disposed above the axle of the vehicle and between the first brake shoe 35 and the second brake shoe 36. The actuator 33 is operated using an electric motor 34 as a power source. Specifically, the actuator 33 operates in response to the driving of the electric motor 34 to press both brake shoes 35, 36 against the inner circumferential surface 32a of the brake drum 32.

[0014] The first brake shoe 35 and the second brake shoe 36 each have a friction material 37. When the actuating device 33 is activated, the friction materials 37 of both brake shoes 35, 36 are pressed against the inner peripheral surface 32a of the brake drum 32.

[0015] A return spring 39 and an anchor 40 are provided between the first brake shoe 35 and the second brake shoe 36. The return spring 39 biases the brake shoes 35, 36 to move them away from the inner peripheral surface 32a of the brake drum 32. The anchor 40 is disposed on the opposite side of the axle from the actuator 33. The anchor 40 is fixed to the back plate 31.

[0016] When both brake shoes 35, 36 are pressed against the brake drum 32 by the actuation of the actuating device 33, a first load is input from the first brake shoe 35 to the anchor 40, and a second load is input from the second brake shoe 36 to the anchor 40. The difference between the first load and the second load correlates with the frictional braking force applied to the rear wheels 13, 14 by the braking devices 23, 24.

[0017] The anchor 40 is provided with a load sensor 41 that outputs a signal indicating the difference between the first load and the second load as an electric signal to the braking control device 70. The load sensor 41 is, for example, a strain gauge. Therefore, the load sensor 41 detects distortion of a component of the anchor 40 that corresponds to the difference between the first load and the second load, and outputs a signal corresponding to the distortion as an electric signal.

[0018] In this embodiment, the anchor 40 limits the movement of the brake shoes 35, 36 in the rotational direction of the brake drum 32. Therefore, the anchor 40 corresponds to a "limiting portion."

[0019] <Vehicle detection system> As shown in Fig. 1, vehicle 10 is equipped with a detection system including a plurality of wheel speed sensors 51, 52, 53, 54, a longitudinal acceleration sensor 55, and a brake sensor 56. Wheel speed sensors 51 to 54 detect wheel speeds VW, which are the rotational speeds of corresponding wheels 11 to 14. Longitudinal acceleration sensor 55 detects longitudinal acceleration GX of vehicle 10. Brake sensor 56 detects operation information related to the operation of the brake pedal by the driver of vehicle 10. Brake sensor 56 includes, for example, a sensor that detects the amount of brake pedal operation by the driver as operation information, and a sensor that detects the operating force input to the brake pedal by the driver as operation information.

[0020] <Brake control device> As shown in Fig. 1, signals are input to the braking control device 70 from the various sensors described above. The braking control device 70 derives a vehicle speed VS, which is the traveling speed of the vehicle 10, based on a wheel speed VW, which is a detection value of the plurality of wheel speed sensors 51-54. The braking control device 70 detects a required value of braking force for the vehicle based on a detection value of the brake sensor 56. The braking control device 70 then controls the plurality of braking devices 21-24 based on the detection values ​​of the sensors and values ​​derived by processing the detection values.

[0021] The friction braking force applied to the wheels 11-14 by the braking devices 21-24 is referred to as the "wheel braking force," and the braking force of the entire vehicle 10 is referred to as the "vehicle braking force." The vehicle braking force includes wheel braking forces applied to the multiple wheels 11-14 and braking forces other than the wheel braking forces. Examples of other braking forces include engine braking, regenerative braking force, and resistance braking force, which is braking force caused by running resistance.

[0022] The braking control device 70 includes an execution unit 71, a first storage unit 72, and a second storage unit 73. For example, the execution unit 71 is a CPU. The first storage unit 72 stores various control programs executed by the execution unit 71. The second storage unit 73 stores the calculation results of the execution unit 71, etc.

[0023] 3, the execution unit 71 executes the control program of the first storage unit 72, thereby functioning as an instruction value acquisition unit 101, a braking force acquisition unit 103, a state acquisition unit 105, a braking characteristics derivation unit 107, and a braking control unit 111. In addition, a part of the storage area of ​​the second storage unit 73 functions as a braking characteristics storage unit 109.

[0024] <Indication value acquisition section> The instruction value acquisition unit 101 acquires braking instruction values ​​BPfIv, BPrIv which are instruction values ​​for the braking devices 21-24. The braking instruction value BPfIv is a braking instruction value for the front wheel braking devices 21, 22, and the braking instruction value BPrIv is a braking instruction value for the rear wheel braking devices 23, 24. As will be described in detail later, when the braking devices 21-24 are operated to apply wheel braking forces to the wheels 11-14, the braking control unit 111 derives the braking instruction values ​​BPfIv, BPrIv. Therefore, the instruction value acquisition unit 101 acquires the braking instruction values ​​BPfIv, BPrIv derived by the braking control unit 111. In this case, the instruction value acquisition unit 101 acquires a plurality of braking instruction values ​​BPfIv, BPrIv corresponding to the plurality of braking devices 21-24.

[0025] <Brake force acquisition section> The braking force acquisition unit 103 acquires wheel braking forces BPfR, BPrR applied to the plurality of wheels 11-14 by the braking devices 21-24 when the braking devices 21-24 are operating in accordance with the braking command values ​​BPfIv, BPrIv. The wheel braking force applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 is the wheel braking force BPfR, and the wheel braking force applied to the rear wheels 13, 14 by the rear wheel braking devices 23, 24 is the wheel braking force BPPrR.

[0026] First, the derivation of the wheel braking force BPrR will be explained. As described above, the rear wheel braking devices 23, 24 have a load sensor 41, which outputs an electrical signal corresponding to the friction braking force applied to the rear wheels 13, 14 by the braking devices 23, 24. The braking force acquisition unit 103 then derives the wheel braking force BPrR based on the electrical signal output from the load sensor 41. Therefore, the rear wheel braking devices 23, 24 correspond to the "first braking device," the rear wheels 13, 14 to which wheel braking force is applied by the rear wheel braking devices 23, 24 correspond to the "first wheel," and the wheel braking force BPrR corresponds to the "first wheel braking force."

[0027] Next, the derivation of the wheel braking force BPfR will be described. The front wheel braking devices 21, 22 do not have a sensor equivalent to the load sensor 41. Therefore, the braking force acquisition unit 103 derives the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 based on the vehicle braking force BPC and the wheel braking force BPrR applied to the rear wheels 13, 14 by the rear wheel braking devices 23, 24.

[0028] Specifically, the braking force acquisition unit 103 derives the vehicle braking force BPC based on the longitudinal acceleration GX, which is the detection value of the longitudinal acceleration sensor 55. At this time, the braking force acquisition unit 103 derives a larger value as the deceleration of the vehicle 10 indicated by the longitudinal acceleration GX is larger, as the braking force acquisition unit 103 derives a larger value as the vehicle braking force BPC. For example, the braking force acquisition unit 103 derives the product of the absolute value of the longitudinal acceleration GX and the weight WGT of the vehicle 10 as the vehicle braking force BPC. Then, the braking force acquisition unit 103 acquires the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 based on a braking force difference DBP, which is the difference between the sum of the wheel braking forces BPrR applied to the two rear wheels 13, 14 and the vehicle braking force BPC. For example, the braking force acquisition unit 103 acquires a larger value as the wheel braking force BPfR is larger, as the braking force difference DBP is larger. Therefore, the front wheel braking devices 21, 22 correspond to the "second braking device", the front wheels 11, 12 to which wheel braking force is applied by the front wheel braking devices 21, 22 correspond to the "second wheel", and the wheel braking force BPfR corresponds to the "second wheel braking force".

[0029] The deceleration of the vehicle 10 also varies depending on engine braking, regenerative braking force, and the running resistance RR of the vehicle 10. The running resistance RR includes acceleration resistance, air resistance, gradient resistance, and rolling resistance. The acceleration resistance is proportional to the acceleration (in this case, deceleration) of the vehicle 10 and the weight WGT of the vehicle 10. The air resistance increases as the square of the vehicle speed VS increases. The gradient resistance is proportional to the road surface gradient θ, which is the gradient of the road surface on which the vehicle 10 is running. The rolling resistance is proportional to the weight WGT of the vehicle 10 and the μ value of the road surface, etc.

[0030] Therefore, in this embodiment, the braking force acquisition unit 103 acquires the wheel braking force BPfR based on the engine braking, the regenerative braking force, and the running resistance RR of the vehicle 10. Specifically, the braking force acquisition unit 103 acquires the engine braking and the regenerative braking force from another control device that controls the engine braking and the regenerative braking force. The braking force acquisition unit 103 also derives the running resistance RR based on the weight WGT of the vehicle 10, the deceleration of the vehicle 10 (i.e., the longitudinal acceleration GX), the vehicle speed VS, and the road surface gradient θ, and derives the resistance braking force BPRR, which is the braking force caused by the running resistance RR, so that it increases as the running resistance RR increases. When the sum of the engine braking, the regenerative braking force, and the resistance braking force BPRR is defined as the other braking force BPA, the braking force acquisition unit 103 acquires a larger value as the wheel braking force BPfR increases as the calculated value, which is the value obtained by subtracting the other braking force BPA from the braking force difference DBP, increases.

[0031] <Status acquisition section> The state acquisition unit 105 acquires a predetermined state PS of the current vehicle 10. The predetermined state PS is a state of the vehicle 10 in which the braking characteristics BC of the braking system, which is the relationship between the braking command values ​​BPfIv, BPrIv and the wheel braking forces BPfR, BPrR, can change. The braking characteristics BC can change depending on the vehicle speed VS, the device temperature TPbp, which is the temperature of the braking system, and the ground load of the wheels to which wheel braking force is applied by the braking system. The device temperature TPbp can be estimated based on the outside air temperature, the vehicle speed VS, the operating time of the braking system, etc. The ground load of the wheels changes depending on the deceleration of the vehicle 10 (i.e., the longitudinal acceleration GX). Specifically, as the deceleration of the vehicle 10 increases, the ground load of the front wheels 11, 12 increases, while the ground load of the rear wheels 13, 14 decreases. Therefore, the state acquisition unit 105 acquires a predetermined state PS(x, y, z) of the vehicle 10 based on the vehicle speed VS, the device temperatures TPbp of the braking devices 21 to 24, and the deceleration (i.e., the longitudinal acceleration GX) of the vehicle 10. "x", "y", and "z" are integers equal to or greater than 1.

[0032] In the predetermined state PS(x,y,z), "x" is a value corresponding to the current vehicle speed VS, "y" is a value corresponding to the device temperature TPbp, and "z" is a value corresponding to the longitudinal acceleration GX. For example, if the vehicle speed VS is a value within the first vehicle speed region, "x" is 1, and if the vehicle speed is a value within the second vehicle speed region, "x" is 2. For example, if the device temperature TPbp is a value within the first temperature region, "y" is 1, and if the device temperature TPbp is a value within the second temperature region, "y" is 2. For example, if the longitudinal acceleration GX is a value within the first acceleration region, "z" is 1, and if the longitudinal acceleration GX is a value within the second acceleration region, "z" is 2. Therefore, if the vehicle speed VS is a value within the first vehicle speed region, the device temperature TPbp is a value within the second temperature region, and the longitudinal acceleration GX is a value within the third acceleration region, the state acquisition unit 105 acquires the predetermined state PS(1,2,3) as the current predetermined state of the vehicle 10.

[0033] <Brake characteristics derivation part> The braking characteristic deriving unit 107 derives braking characteristics BC of the braking devices 21-24 based on the braking command values ​​BPfIv, BPrIv acquired by the command value acquiring unit 101 while the vehicle 10 is traveling and the wheel braking forces BPfR, BPrR acquired by the braking force acquiring unit 103. The braking characteristics BC are the relationship between the braking command values ​​BPfIv, BPrIv for the braking devices 21-24 and the wheel braking forces BPfR, BPrR applied to the wheels 11-14 by the braking devices 21-24 operating in accordance with the braking command values ​​BPfIv, BPrIv.

[0034] Specifically, the braking characteristics deriving unit 107 derives the axle input axial force Fb based on the braking command values ​​BPfIv, BPrIv. The axle input axial force Fb is an axial force input to the axle from the braking devices 21-24 that operate based on the braking command values ​​BPfIv, BPrIv. The axle input axial force Fb is proportional to the braking command values ​​BPfIv, BPrIv. Therefore, the braking characteristics deriving unit 107 can derive the axle input axial force Fb by converting the braking command values ​​BPfIv, BPrIv into axial forces of the axle. Then, the braking characteristics deriving unit 107 derives the braking characteristics BC of the braking devices 21-24 using the following relational expression (Equation 1): In the relational expression (Equation 1), "BPR" is the wheel braking force, so when deriving the braking characteristic BCR of the rear wheel braking devices 23, 24, the wheel braking force BPrR is substituted for "BPR", and when deriving the braking characteristic BCF of the front wheel braking devices 21, 22, the wheel braking force BPfR is substituted for "BPR". Also, "RS" is the wheel diameter, and "Ra" is the effective braking diameter of the wheel.

[0035]

number

[0036] The braking characteristic deriving unit 107 derives, as braking characteristics BC, braking characteristics BCF of the front wheel braking devices 21, 22 and braking characteristics BCR of the rear wheel braking devices 23, 24. More specifically, the braking characteristic deriving unit 107 derives braking characteristics BCF of the front wheel braking device 21, braking characteristics BCF of the front wheel braking device 22, braking characteristics BCR of the rear wheel braking device 23, and braking characteristics BCR of the rear wheel braking device 24. For example, the braking characteristic deriving unit 107 can derive the braking characteristic BCF of the front wheel braking device 21 based on a braking command value BPfIv for the front wheel braking device 21 and a wheel braking force BPfR applied to the left front wheel 11 by operating the front wheel braking device 21 in accordance with the braking command value BPfIv.

[0037] Then, the braking characteristic derivation unit 107 stores the derived braking characteristics BC of the braking devices 21 to 24 in the braking characteristic storage unit 109. At this time, the braking characteristic derivation unit 107 stores the current predetermined state PS(x, y, z) of the vehicle 10 acquired by the state acquisition unit 105 and the derived braking characteristics BC of the braking devices 21 to 24 in the braking characteristic storage unit 109 in an associated state.

[0038] <Braking characteristics memory section> The braking characteristic storage unit 109 stores braking characteristics BC for each of the predetermined states PS of all expected vehicles 10. The stored contents of the braking characteristic storage unit 109 are updated every time the braking characteristic derivation unit 107 derives a braking characteristic BC. For example, when the braking characteristic derivation unit 107 derives the braking characteristic BCF of the front wheel braking device 21 in the predetermined state PS(1,1,1), the braking characteristic BCF of the front wheel braking device 21 in the predetermined state PS(1,1,1) is rewritten in the braking characteristic storage unit 109. At the time of shipping the vehicle 10, initial values ​​determined from the specifications of the vehicle 10 are stored in the braking characteristic storage unit 109 as the braking characteristics BC for each of the predetermined states PS of all expected vehicles 10.

[0039] <Braking control unit> The braking control unit 111 controls the braking devices 21-24 based on the braking characteristics BCF, BCR of the braking devices 21-24 derived by the braking characteristics derivation unit 107. The braking control unit 111 reads out the braking characteristics BCF, BCR corresponding to the current predetermined state PS(x, y, z) of the vehicle 10 acquired by the state acquisition unit 105 from the braking characteristics storage unit 109. The braking control unit 111 derives braking command values ​​BPfIv, BPrIv based on the wheel braking forces BPfR, BPrR acquired by the braking force acquisition unit 103 and the braking characteristics BCF, BCR read out from the braking characteristic storage unit 109. Then, the braking control unit 111 controls the braking devices 21-24 based on the derived braking command values ​​BPfIv, BPrIv.

[0040] The following describes how the braking command value BPrIv for the rear wheel braking devices 23, 24 is derived. The braking control unit 111 acquires the wheel braking force BPrR applied to the rear wheels 13, 14 by the rear wheel braking devices 23, 24. Here, the wheel braking force BPrR acquired by the braking control unit 111 is a braking force corresponding to the electrical signal output from the load sensor 41 of the rear wheel braking devices 23, 24.

[0041] Next, the braking control unit 111 derives a target braking force BPrTr, which is a target value of the wheel braking force, based on the acquired wheel braking force BPrR. Specifically, the braking control unit 111 acquires a required braking force BPrRq, which is a required value of braking force set based on the detection value of the brake sensor 56, braking control, etc. The required braking force BPrRq is a required value of wheel braking force to be applied to the rear wheels 13, 14. The braking control unit 111 derives the target braking force BPrTr by correcting the required braking force BPrRq based on the result of comparison between the wheel braking force BPrR and the previous value BPrTrA of the target braking force BPrTr. Because the target braking force BPrTr is derived at predetermined intervals, the previous value BPrTrA of the target braking force is the target braking force BPrTr derived in the previous cycle. When the wheel braking force BPrR is smaller than the previous value BPrTrA of the target braking force, the braking control unit 111 derives the target braking force BPrTr by increasing the required braking force BPrRq. The amount of increase in the required braking force BPrRq increases as the difference between the wheel braking force BPrR and the previous value BPrTrA of the target braking force increases. On the other hand, when the wheel braking force BPrR is larger than the previous value BPrTrA of the target braking force, the braking control unit 111 derives the target braking force BPrTr by decreasing the required braking force BPrRq. The amount of decrease in the required braking force BPrRq increases as the difference between the wheel braking force BPrR and the previous value BPrTrA of the target braking force increases.

[0042] The braking control unit 111 derives a braking command value BPrIv for the rear wheel braking devices 23, 24 based on the derived target braking force BPrTr and the braking characteristics BCR of the rear wheel braking devices 23, 24. Specifically, the braking control unit 111 derives the braking command value BPrIv by dividing the target braking force BPrTr by the braking characteristics BCR.

[0043] Next, a description will be given of how the braking command value BPfIv for the front wheel braking devices 21, 22 is derived. The braking control unit 111 acquires the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22.

[0044] The braking control unit 111 derives the target braking force BPfTr based on the acquired wheel braking force BPfR. Specifically, the braking control unit 111 derives the target braking force BPfTr by correcting the required braking force BPfRq based on the comparison result between the wheel braking force BPfR and the previous value BPfTrA of the target braking force BPfTr. If the wheel braking force BPfR is smaller than the previous value BPfTrA of the target braking force, the braking control unit 111 derives the target braking force BPfTr by increasing the required braking force BPfRq. The amount of increase in the required braking force BPfRq increases as the difference between the wheel braking force BPfR and the previous value BPfTrA of the target braking force increases. On the other hand, if the wheel braking force BPfR is larger than the previous value BPfTrA of the target braking force, the braking control unit 111 derives the target braking force BPfTr by decreasing the required braking force BPfRq. The amount of reduction correction of the required braking force BPfRq at this time increases as the difference between the wheel braking force BPfR and the previous value BPfTrA of the target braking force increases.

[0045] The braking control unit 111 derives a braking command value BPfIv for the front wheel braking devices 21, 22 based on the derived target braking force BPfTr and the braking characteristics BCF of the front wheel braking devices 21, 22. Specifically, the braking control unit 111 derives the braking command value BPfIv by dividing the target braking force BPfTr by the braking characteristics BCF.

[0046] <Braking characteristics derivation process> The braking characteristic derivation process, which is a process flow for deriving the braking characteristics BCF and BCR of the braking devices 21 to 24, will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the braking characteristic derivation process. A control program corresponding to the braking characteristic derivation process is repeatedly executed by the execution unit 71 at a predetermined interval when applying braking force to the vehicle 10.

[0047] In step S11, the execution unit 71 functions as the instruction value acquisition unit 101 to acquire the braking instruction value BPrIv for the rear wheel braking device 23 and the braking instruction value BPrIv for the rear wheel braking device 24.

[0048] In step S13, the execution unit 71 functions as the braking force acquisition unit 103 to acquire the wheel braking force BPrR applied to the rear wheels 13, 14 by the rear wheel braking devices 23, 24. The acquired wheel braking force BPrR is a friction braking force applied to the rear wheels 13, 14 by the operation of the rear wheel braking devices 23, 24 based on the braking command value BPrIv acquired in step S11. The execution unit 71 acquires the wheel braking force BPrR applied to the left rear wheel 13 by the rear wheel braking device 23 based on the electrical signal output from the load sensor 41 of the rear wheel braking device 23, and acquires the wheel braking force BPrR applied to the right rear wheel 14 by the rear wheel braking device 24 based on the electrical signal output from the load sensor 41 of the rear wheel braking device 24.

[0049] In step S15, the execution unit 71 functions as the braking characteristic derivation unit 107 to derive the braking characteristic BCR of the rear wheel braking devices 23, 24. Specifically, the execution unit 71 derives the braking characteristic BCR of the rear wheel braking device 23 based on the braking command value BPrIv for the left rear wheel 13 acquired in step S11 and the wheel braking force BPrR for the left rear wheel 13 acquired in step S13. The execution unit 71 also derives the braking characteristic BCR of the rear wheel braking device 23 based on the braking command value BPrIv for the right rear wheel 14 acquired in step S11 and the wheel braking force BPrR for the right rear wheel 14 acquired in step S13.

[0050] In step S17, the execution unit 71 functions as the instruction value acquisition unit 101 to acquire the braking instruction value BPrIv for the rear wheel braking device 23 and the braking instruction value BPrIv for the rear wheel braking device 24.

[0051] In step S19, the execution unit 71 functions as the braking force acquisition unit 103 to acquire the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22. The acquired wheel braking force BPfR is the friction braking force applied to the front wheels 11, 12 by the operation of the front wheel braking devices 21, 22 based on the braking command value BPfIv acquired in step S11. The execution unit 71 derives the wheel braking force BPfR based on the longitudinal acceleration GX, the wheel braking force BPrR acquired in step S13, and other braking forces BPA. In this case, the execution unit 71 separately derives the wheel braking force BPfR applied to the left front wheel 11 by the front wheel braking device 21 and the wheel braking force BPfR applied to the right front wheel 12 by the front wheel braking device 22.

[0052] In step S21, the execution unit 71 functions as the braking characteristic derivation unit 107 to derive the braking characteristic BCF of the front wheel braking devices 21, 22. Specifically, the execution unit 71 derives the braking characteristic BCR of the front wheel braking device 21 based on the braking command value BPfIv for the left front wheel 11 acquired in step S17 and the wheel braking force BPfR for the left front wheel 11 acquired in step S19. The execution unit 71 also derives the braking characteristic BCF of the front wheel braking device 22 based on the braking command value BPfIv for the right front wheel 12 acquired in step S17 and the wheel braking force BPfR for the right front wheel 12 acquired in step S19.

[0053] In step S23, the execution unit 71 functions as the braking characteristic derivation unit 107, thereby storing the braking characteristics BCR, BCF derived in step S15 and step S21 in a storage area of ​​the second storage unit 73 that functions as the braking characteristic storage unit 109. At this time, the execution unit 71 stores the braking characteristics BCR, BCF in the second storage unit 73 in a state associated with the current predetermined state PS(x, y, z) of the vehicle 10 that is acquired by functioning as the state acquisition unit 105. Then, the execution unit 71 ends the current processing.

[0054] <Braking force control processing> The braking force control process, which is a process flow for operating the braking devices 21 to 24, will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the braking force control process. A control program corresponding to the braking force control process is repeatedly executed by the execution unit 71 at a predetermined cycle.

[0055] The execution unit 71 functions as the braking control unit 111 and executes steps S41 to S47 shown in FIG. 5. In step S41, the execution unit 71 derives a target braking force BPfTr for the front wheels 11, 12 based on a required braking force BPfRq for the front wheels 11, 12 and the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22. Specifically, the execution unit 71 derives the target braking force BPfTr by correcting the latest value of the required braking force BPfRq based on the difference between the previous value of the required braking force BPfRq and the previous value of the wheel braking force BPfR. The execution unit 71 also derives the target braking force BPrTr for the rear wheels 13, 14 based on the required braking force BPPrRq for the rear wheels 13, 14 and the wheel braking force BPPrR applied to the rear wheels 13, 14 by the rear wheel braking devices 23, 24. Specifically, the execution unit 71 derives the target braking force BPrTr by correcting the latest value of the required braking force BPrRq based on the difference between the previous value of the required braking force BPrRq and the previous value of the wheel braking force BPrR.

[0056] In step S43, the execution unit 71 derives a braking command value BPfIv for the front wheels 11, 12 based on the target braking force BPfTr for the front wheels 11, 12 and the braking characteristics BCF of the front wheel braking devices 21, 22. At this time, the execution unit 71 derives the braking command value BPfIv based on the braking characteristics BCF corresponding to the current predetermined state PS(x, y, z) of the vehicle 10.

[0057] In step S45, the execution unit 71 derives a braking command value BPrIv for the rear wheels 13, 14 based on the target braking force BPrTr for the rear wheels 13, 14 and the braking characteristics BCR of the rear wheel braking devices 23, 24. At this time, the execution unit 71 derives the braking command value BPrIv based on the braking characteristics BCR corresponding to the current predetermined state PS(x, y, z) of the vehicle 10.

[0058] In step S47, the execution unit 71 activates the front wheel braking devices 21, 22 based on the braking command value BPfIv derived in step S43. The execution unit 71 also activates the rear wheel braking devices 23, 24 based on the braking command value BPrIv derived in step S45. Thereafter, the execution unit 71 ends the current processing.

[0059] <Operation of this embodiment> This section explains the operation of ABS, a braking control system. ABS stands for "Anti-lock Braking System."

[0060] When ABS is executed, the wheel braking force applied to the wheels by the braking devices is reduced to eliminate deceleration slip of the wheels. In this embodiment, the brake control device 70 grasps the braking characteristics BCF, BCR of the multiple braking devices 21-24, and therefore can accurately derive the wheel braking forces BPfR, BPrR of the multiple wheels 11-14. As a result, the wheel braking force can be quickly reduced to a braking force that can eliminate deceleration slip of the wheels. At this time, excessive reduction in wheel braking force can be prevented, and therefore, the deceleration of the vehicle 10 can also be prevented from becoming too small. In other words, because the wheel braking force applied to the wheels that are the target of ABS can be appropriately controlled, the amount of slip of the wheels can be appropriately adjusted during ABS execution.

[0061] Next, the operation during service braking will be described. In recent years, the front and rear braking force distribution is sometimes changed during service braking in order to suppress pitching behavior of the vehicle 10 during service braking. In this case, unless the braking characteristics BCF, BCR of the multiple braking devices 21-24 are known, there is a risk that the deceleration of the vehicle 10 will change significantly when the front and rear braking force distribution is changed.

[0062] In this regard, in this embodiment, the brake control device 70 grasps the braking characteristics BCF, BCR of the brake devices 21 to 24, and therefore can accurately derive both the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 and the wheel braking force BPrR applied to the rear wheels 13, 14 by the rear wheel braking devices 23, 24. Therefore, even if the front / rear braking force distribution is changed during service braking, changes in the deceleration of the vehicle 10 can be suppressed. Therefore, during service braking, changes in the deceleration of the vehicle 10 can be suppressed while pitching behavior of the vehicle 10 can be suppressed.

[0063] <Effects of this embodiment> (1) The braking characteristics BCF, BCR of the braking devices 21-24 are derived based on the braking command values ​​BPfIv, BPrIv for the braking devices 21-24 and the wheel braking forces BPfR, BPrR when the braking devices 21-24 are operated in accordance with the braking command values ​​BPfIv, BPrIv. The braking characteristics BCF, BCR derived in this manner are not the braking characteristics of the entire vehicle but the braking characteristics of the braking devices 21-24. Therefore, after deriving the braking characteristics BCF, BCR of the braking devices 21-24, the brake control device 70 can improve the controllability of the wheel braking force by operating the braking devices 21-24 based on the braking characteristics BCF, BCR.

[0064] (2) The braking characteristics BCF, BCR of the braking devices 21-24 may change depending on the predetermined state PS of the vehicle 10 at that time. Therefore, in this embodiment, the braking characteristics BCF, BCR of the braking devices 21-24 are derived for each predetermined state of the vehicle 10. Then, when the braking devices 21-24 are operated, the braking devices 21-24 are controlled based on the braking characteristics BCF, BCR corresponding to the current predetermined state PS of the vehicle 10. This further improves the controllability of the wheel braking force.

[0065] For example, since the braking characteristics BCF, BCR of the braking devices 21-24 can change depending on the vehicle speed VS, the braking characteristics BCF, BCR are derived for each vehicle speed range. Therefore, when controlling the braking devices 21-24, the braking characteristics BCF, BCR according to the vehicle speed range can be used. Therefore, it is possible to suppress variations in the controllability of the wheel braking force caused by changes in the vehicle speed VS.

[0066] Furthermore, for example, since the braking characteristics BCF, BCR of the braking devices 21-24 can change depending on the device temperature TPbp, the braking characteristics BCF, BCR are derived for each device temperature range. Therefore, when controlling the braking devices 21-24, the braking characteristics BCF, BCR according to the device temperature TPbp can be used. Therefore, it is possible to suppress variations in the controllability of the wheel braking force caused by changes in the device temperature TPbp.

[0067] Furthermore, for example, the braking characteristics BCF, BCR of the braking devices 21-24 may change depending on the ground loads of the wheels 11-14. The ground loads of the wheels 11-14 correlate with the deceleration of the vehicle 10 (i.e., the longitudinal acceleration GX). Therefore, the braking characteristics BCF, BCR are derived for each range of the longitudinal acceleration GX. Therefore, when controlling the braking devices 21-24, the braking characteristics BCF, BCR according to the range of the longitudinal acceleration GX can be used. Therefore, it is possible to suppress variations in the controllability of the wheel braking force caused by changes in the ground loads of the wheels 11-14.

[0068] (3) The front wheel braking devices 21, 22 may be of a different type from the rear wheel braking devices 23, 24. For example, the rear wheel braking devices 23, 24 may be drum-type braking devices, while the front wheel braking devices 21, 22 may be disc-type braking devices. In this case, the front wheel braking devices 21, 22 and the rear wheel braking devices 23, 24 have completely different braking characteristics. Furthermore, even if the front wheel braking devices 21, 22 are of the same type as the rear wheel braking devices 23, 24, the braking characteristics of the front wheel braking devices 21, 22 and the rear wheel braking devices 23, 24 may differ if the degree of wear of the braking device components differs due to differences in frequency of use, etc.

[0069] In this embodiment, the braking characteristics BCF of the front wheel braking devices 21, 22 and the braking characteristics BCR of the rear wheel braking devices 23, 24 are derived separately. When the front wheel braking devices 21, 22 are operated to apply wheel braking force to the front wheels 11, 12, the front wheel braking devices 21, 22 are controlled based on the braking characteristics BCF of the front wheel braking devices 21, 22. When the rear wheel braking devices 23, 24 are operated to apply wheel braking force to the rear wheels 13, 14, the rear wheel braking devices 23, 24 are controlled based on the braking characteristics BCR of the rear wheel braking devices 23, 24. This makes it possible to improve the controllability of the wheel braking force at both the front wheels 11, 12 and the rear wheels 13, 14.

[0070] (4) While the rear wheel braking devices 23, 24 have a load sensor 41, the front wheel braking devices 21, 22 do not have a sensor that outputs an electrical signal corresponding to the wheel braking force. However, in this embodiment, the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 can be derived based on the vehicle braking force BPC and the wheel braking force BPrR applied to the rear wheels 13, 14. Therefore, even if the front wheel braking devices 21, 22 do not have the above-mentioned sensor, the braking characteristic BCF of the front wheel braking devices 21, 22 can be derived.

[0071] (5) The wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 is derived taking into consideration other braking forces BPA. This allows the wheel braking force BPfR to be derived with high accuracy, and therefore the braking characteristic BCF of the front wheel braking devices 21, 22 to be derived with high accuracy.

[0072] (6) In this embodiment, the target braking force BPrTr for the rear wheels 13, 14 is derived based on the output signal of the load sensor 41. Therefore, the load sensor 41 can be said to be an essential sensor for deriving the target braking force BPrTr. In this embodiment, the braking characteristic BCR is derived by using a value (in this case, the target braking force BPrTr) derived based on the electrical signal output from the load sensor 41. In other words, it is not necessary to provide a new sensor other than the load sensor 41 in the rear wheel braking devices 23, 24 to derive the braking characteristics BCF, BCR. Therefore, the controllability of the wheel braking force for the rear wheels 13, 14 can be improved without increasing the cost of the rear wheel braking devices 23, 24.

[0073] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0074] In the rear wheel braking devices 23, 24, the load sensor 41 may be provided in a location other than the anchor 40, as long as it is provided in a location where a load is input from the brake shoes 35, 36 when the brake shoes 35, 36 are pressed against the brake drum 32.

[0075] The rear wheel braking devices 23, 24 may be devices equipped with wheel cylinders as actuating devices. In this case, when brake fluid is supplied to the wheel cylinders, the first brake shoe 35 and the second brake shoe 36 are pressed against the inner circumferential surface 32a of the brake drum 32, thereby applying a frictional braking force to the rear wheels 13, 14. Even in this configuration, the load sensor 41 can output an electrical signal corresponding to the wheel braking force BPrR.

[0076] The rear wheel braking device does not have to be a drum type braking device as long as it has a sensor that can output an electrical signal corresponding to the wheel braking force BPrR. The front wheel braking device may be a braking device that does not include the electric motor 25 but includes a wheel cylinder. In this case, the vehicle 10 may be a vehicle that includes an electric pressure device that can supply brake fluid to both the wheel cylinder of the front wheel braking device provided on the left front wheel 11 and the wheel cylinder of the front wheel braking device provided on the right front wheel 12. Examples of the electric pressure device include an electric cylinder and an electric pump.

[0077] In the above embodiment, the braking characteristics BCF, BCR of the braking devices 21, 22 are derived at predetermined intervals while the vehicle 10 is traveling, but this is not limiting. For example, the braking characteristics BCF, BCR may be derived only once per trip of the vehicle 10. Also, for example, the braking characteristics BCF, BCR may be derived only once every few months.

[0078] The front wheel braking device may be a braking device equipped with a sensor that outputs an electrical signal corresponding to the wheel braking force BPfR, similar to the rear wheel braking devices 23, 24. In this case, in step S19 shown in Fig. 4, the wheel braking force BPfR can be derived in the same manner as in step S15.

[0079] If the μ value of the friction material of the braking device can be detected or estimated, the wheel braking forces BPfR and BPrR may be calculated based on the μ value of the friction material. For example, the wheel braking forces BPfR and BPrR may be calculated as a value corresponding to the product of the μ value of the friction material, the wheel ground load, and the wheel diameter (i.e., tire diameter). In this case, the braking device does not need to be equipped with a sensor that outputs an electrical signal corresponding to the wheel braking force.

[0080] If the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 is derived based on engine braking, it is not necessary to consider regenerative braking force, nor is it necessary to consider resistance braking force BPRR, which is braking force caused by running resistance RR. When the wheel braking force BPfR is derived without considering regenerative braking force, the vehicle may be a vehicle that has only the engine as a power source out of the engine and motor generator.

[0081] If the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 is derived based on the regenerative braking force, it is not necessary to take engine braking into consideration, and it is not necessary to take resistance braking force BPRR into consideration. When the wheel braking force BPfR is derived without taking engine braking into consideration, the vehicle may be equipped with only the motor generator as a power source out of the engine and the motor generator.

[0082] If the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 is derived based on the resistance braking force BPRR, it is not necessary to take engine braking or regenerative braking force into consideration.

[0083] In the above embodiment, the braking characteristics BCF, BCR corresponding to each of a plurality of vehicle speed ranges are derived, and the braking devices 21-24 are controlled based on the braking characteristics BCF, BCR corresponding to the current vehicle speed VS, but this is not limiting. That is, the braking characteristics BCF, BCR used to control the braking devices 21-24 do not have to be changed according to the vehicle speed VS.

[0084] In the above embodiment, the braking characteristics BCF and BCR corresponding to each of the ranges of the device temperature TPbp are derived, and the braking devices 21 to 24 are controlled based on the braking characteristics BCF and BCR corresponding to the current device temperature TPbp, but this is not limiting. That is, the braking characteristics BCF and BCR used to control the braking devices 21 to 24 do not have to be changed according to the device temperature TPbp.

[0085] In the above embodiment, the braking characteristics BCF, BCR corresponding to each of the multiple deceleration ranges of the vehicle 10 are derived, and the braking devices 21-24 are controlled based on the braking characteristics BCF, BCR corresponding to the current deceleration, but this is not limiting. That is, the braking characteristics BCF, BCR used to control the braking devices 21-24 do not have to be changed according to the deceleration of the vehicle 10.

[0086] In the above embodiment, the braking characteristics BCF, BCR are derived for each predetermined state PS of the vehicle 10, and the braking devices 21-24 are controlled based on the braking characteristics BCF, BCR corresponding to the predetermined state PS at that time, but this is not limited to this. That is, only one braking characteristic BC may be derived for one braking device. In this case, the braking characteristic BC used to control the braking devices does not change even if the predetermined state PS of the vehicle 10 changes.

[0087] In the above embodiment, the braking characteristics BCR of the rear wheel braking device 23, which is the braking device for the left rear wheel 13, and the braking characteristics BCR of the rear wheel braking device 24, which is the braking device for the right rear wheel 14, are derived separately, but this is not limitative. That is, a braking characteristic common to the rear wheel braking device 23 and the rear wheel braking device 24 may be derived as the braking characteristics BCR of the rear wheel braking device.

[0088] In the above embodiment, the braking characteristics BCF of the front wheel braking device 21, which is the braking device for the left front wheel 11, and the braking characteristics BCF of the front wheel braking device 22, which is the braking device for the right front wheel 12, are derived separately, but this is not limitative. In other words, a braking characteristic common to the front wheel braking device 21 and the front wheel braking device 22 may be derived as the braking characteristics BCF of the front wheel braking device.

[0089] If the rear wheel braking devices 23, 24 are controlled based on the braking characteristic BCR of the rear wheel braking devices 23, 24, it is not necessary to use the braking characteristic BCF of the front wheel braking devices 21, 22 when controlling the front wheel braking devices 21, 22. Even in this case, the wheel braking force BPrR applied to the rear wheels 13, 14 by the rear wheel braking devices 23, 24 can be controlled with high accuracy.

[0090] Conversely, if the front wheel braking devices 21, 22 are controlled based on the braking characteristic BCF of the front wheel braking devices 21, 22, it is not necessary to use the braking characteristic BCR of the rear wheel braking devices 23, 24 when controlling the rear wheel braking devices 23, 24. Even in this case, the wheel braking force BPfR applied to the front wheels 11, 12 by the front wheel braking devices 21, 22 can be controlled with high precision.

[0091] The braking control device 70 may be configured as a circuit including one or more processors operating according to a computer program, one or more dedicated hardware circuits such as dedicated hardware for performing at least some of the various processes, or a combination thereof. Dedicated hardware may include, for example, an application-specific integrated circuit (ASIC). The processor includes a CPU and memory such as RAM and ROM, which stores program code or instructions configured to cause the CPU to perform processes. The memory, i.e., storage medium, includes any available medium accessible by a general-purpose or dedicated computer.

[0092] <Other technical ideas> Next, the technical ideas that can be understood from the above-described embodiment and modified examples will be described. (A) the braking characteristic deriving unit derives a plurality of braking characteristics corresponding to a plurality of vehicle speeds, It is preferable that the braking control unit controls the braking device based on the braking characteristics corresponding to the current vehicle speed.

[0093] (b) the braking characteristic deriving unit derives a plurality of braking characteristics corresponding to each of the plurality of temperatures of the braking device; It is preferable that the braking control unit controls the braking device based on the braking characteristics corresponding to the current temperature of the braking device.

[0094] (c) the braking characteristic deriving unit derives a plurality of braking characteristics corresponding to each of a plurality of decelerations of the vehicle (or ground contact loads of the wheels); It is preferable that the braking control unit controls the braking device based on the braking characteristics corresponding to the current deceleration of the vehicle (or the ground contact load of the wheel).

[0095] (d) It is preferable that the braking characteristic derivation unit individually derives the braking characteristics of the front wheel braking device provided on the left front wheel of the front wheels, the braking characteristics of the front wheel braking device provided on the right front wheel of the front wheels, the braking characteristics of the rear wheel braking device provided on the left rear wheel of the rear wheels, and the braking characteristics of the rear wheel braking device provided on the right rear wheel of the rear wheels.

[0096] (e) the braking characteristic derivation unit deriving the braking characteristics common to the front wheel braking device provided on the left front wheel of the front wheels and the front wheel braking device provided on the right front wheel of the front wheels as the braking characteristics of the front wheel braking device; It is preferable to derive the braking characteristics common to the rear wheel braking device provided on the left rear wheel of the rear wheels and the rear wheel braking device provided on the right rear wheel of the rear wheels as the braking characteristics of the rear wheel braking device.

[0097] (e) It is preferable that the braking force acquisition unit acquires the second wheel braking force based on at least one of engine braking, the regenerative braking force of the vehicle, and the braking force caused by the running resistance of the vehicle, the vehicle braking force, and the first wheel braking force.

[0098] The expression "at least one" used herein means "one or more" of the desired options. As an example, the expression "at least one" used herein means "only one option" or "both of two options" if the number of options is two. As another example, the expression "at least one" used herein means "only one option" or "any combination of two or more options" if the number of options is three or more. [Explanation of symbols]

[0099] 10...Vehicle 11,12...Front wheels 13,14...Rear wheels 21,22…Front wheel braking device 23,24…Rear wheel braking device 32...Brake drum 35,36...Brake shoes 40...Anchor (an example of a restriction) 41...Load sensor 70...Brake control device 101...Indication value acquisition unit 103...Braking force acquisition section 107...Braking characteristic derivation section 111...Braking control unit

Claims

1. an instruction value acquisition unit that acquires a braking instruction value that is an instruction value for a braking device provided on a wheel of the vehicle; a braking force acquisition unit that acquires a wheel braking force, which is a braking force applied to the wheel by the braking device; a braking characteristic deriving unit that derives a relationship between the braking command value and the wheel braking force as a braking characteristic of the braking device, based on the braking command value acquired by the command value acquisition unit and the wheel braking force acquired by the braking force acquisition unit while the vehicle is traveling; a braking control unit that controls the braking device based on the braking characteristics derived by the braking characteristics derivation unit, The vehicle includes, as the braking devices, a first braking device provided on a first wheel among the wheels and a second braking device provided on a second wheel among the wheels, the first braking device includes a sensor that outputs an electrical signal that correlates with the wheel braking force applied to the first wheel by the first braking device; The braking force acquisition unit deriving a first wheel braking force, which is the wheel braking force applied to the first wheel by the first braking device, based on the electrical signal output from the sensor; acquiring a second wheel braking force, which is the wheel braking force applied to the second wheel by the second braking device, based on a difference between a vehicle braking force, which is the braking force applied to the vehicle, and the first wheel braking force; The braking characteristic derivation unit deriving the braking characteristics of the first braking device based on the braking command value for the first braking device and the first wheel braking force acquired by the braking force acquisition unit; deriving the braking characteristics of the second braking device based on the braking command value for the second braking device and the second wheel braking force acquired by the braking force acquisition unit; The braking control unit controlling the first braking device based on the braking characteristics of the first braking device derived by the braking characteristics derivation unit; a braking control device that controls the second braking device based on the braking characteristics of the second braking device derived by the braking characteristics derivation unit;

2. the braking force acquisition unit acquires the first wheel braking force for each period; The braking control unit periodically deriving a target braking force, which is a target value of the first wheel braking force, based on the first wheel braking force acquired by the braking force acquisition unit; 2. The braking control device according to claim 1, wherein the braking command value for the first braking device is derived based on the braking characteristics of the first braking device derived based on the first wheel braking force acquired in a period prior to the current period and the target braking force derived in the current period.

3. the first braking device is a drum-type braking device that applies a braking force to the wheel by pressing a brake shoe against a brake drum, the sensor outputs, as the electrical signal, a signal indicative of a load input from the brake shoe to a limiting section that limits movement of the brake shoe in the rotational direction of the brake drum; The braking characteristic deriving unit derives the braking characteristic of the first braking device based on the electrical signal.

3. The braking control device according to claim 1 or 2.

4. the braking characteristic deriving unit derives a plurality of braking characteristics corresponding to a plurality of predetermined states of the vehicle, 4. The brake control device according to claim 1, wherein the brake control unit controls the brake device based on the braking characteristic corresponding to the predetermined current state of the vehicle.

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