control device

Abstract

The control device (10) of the present application starts slight brake control of generating a braking force to at least one of the front wheel (81) and the rear wheel (82) when the driving force of the vehicle (90) is increasing. The control device (10) estimates a force coefficient that indicates a relationship of the magnitude of the braking force to the magnitude of the pressing force generated by the friction brake device (70) during execution of the slight brake control. The control device (10) estimates the force coefficient of the wheel to which the braking force is applied by the slight brake control based on a deviation of the generated driving force based on the required value of the power source (91) from the actual driving force actually acting on the vehicle (90), and the pressing force corresponding to the wheel to which the braking force is applied by the slight brake control.

Description

Technical Field

[0001] This invention relates to a control device for vehicles equipped with friction braking systems. Background Technology

[0002] Patent Document 1 discloses a braking control device that estimates the degree of braking effect by relating the magnitude of the actual braking force to the wheel cylinder pressure when the brake pedal is depressed. Specifically, it is configured to actuate the brakes by estimating the degree of braking effect based on the deviation between the actual deceleration calculated from the front and rear acceleration based on detection signals from front and rear acceleration sensors and the estimated deceleration calculated based on the wheel cylinder pressure.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-196705

[0004] In the front and rear wheels of a vehicle, there are cases where the relationship between the pressure applied to the friction material and the braking force applied to the wheel differs. In the braking control device disclosed in Patent Document 1, the effectiveness of the brake is uniformly estimated without considering the differences between the front and rear wheels. Summary of the Invention

[0005] The main purpose of the control device for solving the above-mentioned problems is to be applied to a vehicle having a power source and a friction braking device. The power source generates driving force, and the friction braking device is a braking device that applies braking force to a wheel based on the pressure applied to a friction material pressed against a rotating body integral with the wheel. The control device is capable of adjusting the braking force applied to the front and rear wheels separately. The control device includes: a braking control unit that controls the friction braking device; and an estimation unit that estimates an effectiveness coefficient, which is a coefficient representing the relationship between the magnitude of the braking force and the magnitude of the pressing force. When the driving force is increasing, the braking control unit can initiate slight braking control that generates braking force on at least one of the front and rear wheels. During the execution of this slight braking control, the estimation unit estimates the effectiveness coefficient of the wheel to which braking force is applied by the slight braking control based on the deviation between the generated driving force and the actual driving force, and the pressing force corresponding to the wheel to which braking force is applied by the slight braking control. The generated driving force is a driving force based on a required value for the power source, and the actual driving force is the driving force actually acting on the vehicle.

[0006] In the above structure, as a control for applying braking force to estimate the efficiency coefficient, a slight braking control is performed. In the slight braking control, braking force is generated on at least one of the front and rear wheels. Then, the pressing force corresponding to the wheel to which braking force is applied is used to estimate the efficiency coefficient. Thus, the efficiency coefficients of the front wheels and the rear wheels can be identified and estimated.

[0007] Furthermore, slight braking control begins when the driving force is increasing. By applying slight braking control when the driving force is increasing, even if braking force is applied to at least one of the front and rear wheels, it is possible to reduce discomfort to the vehicle occupants or the effects of braking force such as vehicle pitching. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating one embodiment of a vehicle control device and a vehicle equipped with the control device.

[0009] Figure 2 This is a timing diagram illustrating the relationship between brake hydraulic pressure and the shift in driving force when braking force is applied during an increase in driving force.

[0010] Figure 3 It is a graph showing the relationship between brake hydraulic pressure, efficiency coefficient, and the reduction in driving force.

[0011] Figure 4 This is a flowchart illustrating the process of the control device performing a slight braking control action.

[0012] Figure 5 It is a diagram representing the mapping used to calculate the required braking force when performing slight braking control.

[0013] Figure 6 This is a flowchart illustrating the process by which the control device estimates its effectiveness coefficient.

[0014] Figure 7 This is a block diagram representing the efficiency coefficient estimation section.

[0015] Figure 8 It is a timing diagram showing the shift of braking force based on the slight braking control performed by the control device.

[0016] Figure 9 It is a timing diagram showing the shift of braking force in the slight braking control performed by the control device based on the modified example. Detailed Implementation

[0017] The following is for reference Figures 1 to 8 An embodiment of the control device will be described.

[0018] Figure 1 This refers to a vehicle 90 equipped with a power source 91, a friction braking device 70, and a control device 10. The control device 10 controls the friction braking device 70. The friction braking device 70 enables the vehicle 90 to generate friction braking force.

[0019] exist Figure 1 The diagram shows one of the front wheels 81 and one of the rear wheels 82 of the vehicle 90.

[0020] The vehicle 90 is equipped with a brake operating component 79. The brake operating component 79 can be operated by the driver of the vehicle 90. An example of the brake operating component 79 is a brake pedal.

[0021] The vehicle 90 may also be equipped with an automatic driving control device 30 that calculates command values ​​for enabling the vehicle 90 to drive automatically. The automatic driving control device 30 is capable of sending and receiving information with the control device 10.

[0022] <Power Source>

[0023] One example of the power source 91 provided by the vehicle 90 is an electric motor. The power source 91 is not limited to an electric motor; it can also be an internal combustion engine. Alternatively, both an electric motor and an internal combustion engine can be used as the power source 91. Furthermore, as a power source 91, it can also be an in-wheel motor in which an electric motor is installed in each of the wheels of the vehicle 90.

[0024] Friction Braking Device

[0025] The friction braking device 70 will be described. The friction braking device 70 includes braking mechanisms 73F and 73R corresponding to each wheel of the vehicle 90. Figure 1 In the example, the braking mechanism 73F corresponding to the front wheel 81 and the braking mechanism 73R corresponding to the rear wheel 82 are shown.

[0026] One example of a friction braking device 70 is a hydraulic braking device. The friction braking device 70, as a hydraulic braking device, includes a hydraulic generating device 71 and a brake actuator 72 that supplies brake fluid from the hydraulic generating device 71. A brake operating component 79 is connected to the hydraulic generating device 71. The hydraulic generating device 71 can generate hydraulic pressure corresponding to the amount of operation of the brake operating component 79 by the driver of the vehicle 90, i.e., the amount of braking operation. The hydraulic generating device 71 can also generate hydraulic pressure based on command values ​​calculated by the automatic driving control device 30.

[0027] The constituent elements of braking mechanisms 73F and 73R are common, therefore they are described using common reference numerals. Braking mechanisms 73F and 73R consist of a wheel cylinder 74, a rotating body 76 that rotates integrally with the wheel, and a friction material 75 capable of pushing against the rotating body 76. An example of braking mechanisms 73F and 73R is a disc brake. Braking mechanisms 73F and 73R can also be drum brakes.

[0028] Brake actuators 72 are connected to each wheel cylinder 74. For example, if the brake operating component 79 is operated, a corresponding amount of brake fluid is supplied to each wheel cylinder 74. In a hydraulic braking system, frictional braking force can be generated based on the hydraulic pressure, i.e., WC pressure, within the wheel cylinders 74 of the brake mechanisms 73F and 73R. The brake mechanisms 73F and 73R are configured such that the higher the WC pressure, the greater the force exerted on the rotating body 76 rotating integrally with the wheel to push the friction material 75. Each brake mechanism 73F and 73R can apply a greater braking force to the wheel as the WC pressure increases. WC pressure is an example representing the value of the pressing force exerted on the rotating body 76 to push the friction material 75.

[0029] The brake actuator 72 can independently change the hydraulic pressure of each wheel cylinder 74, so that the braking force applied to each wheel is different. The total braking force applied to the front wheel 81 by the braking mechanism 73F corresponding to the front wheel 81 is called the front wheel braking force. The total braking force applied to the rear wheel 82 by the braking mechanism 73R corresponding to the rear wheel 82 is called the rear wheel braking force.

[0030] <sensor>

[0031] Vehicle 90 is equipped with various sensors. Figure 1 As an example of various sensors, a hydraulic sensor 61, a front and rear acceleration sensor 62, and a wheel speed sensor 63 are shown. Detection signals from the various sensors are input to the control unit 10.

[0032] Hydraulic sensor 61 is a sensor that detects the pressing force of the friction material 75 in the friction braking device 70 being pushed against the rotating body 76. As an example, hydraulic sensor 61 can detect the WC pressure of each wheel cylinder 74 as the braking hydraulic pressure P. In this case, hydraulic sensor 61 is installed corresponding to each wheel cylinder 74. Furthermore, the value detected as braking hydraulic pressure P is not limited to WC pressure as long as it is the pressure corresponding to the pressing force.

[0033] The front and rear acceleration sensor 62 is a sensor that detects the acceleration of the vehicle 90 in the front and rear directions.

[0034] Wheel speed sensors 63 are sensors that detect wheel speed. Each wheel is individually installed with a wheel speed sensor 63. The vehicle speed can be calculated based on the wheel speed.

[0035] <Control Device>

[0036] The control device 10 will be described below. The control device 10 consists of multiple functional units that perform various controls. Figure 1 As an example of functional units, the following are shown: drive control unit 11, braking control unit 12, acquisition unit 13, friction material temperature estimation unit 14, storage unit 15, and efficiency coefficient estimation unit 20. The efficiency coefficient estimation unit 20 corresponds to the estimation unit that estimates the efficiency coefficient K. The various functional units included in the control device 10 can exchange and receive information with each other.

[0037] The vehicle 90 is not limited to having the control device 10, but may also have other control devices. In addition, some of the functional parts of the control device 10 may also be provided by other control devices.

[0038] Furthermore, the control device 10, the automatic driving control device 30, and other control devices may be any one of the following structures [a] to [c]. [a] A processor having one or more processors that execute various processes according to a computer program. The processor has a processing device. Examples of processing devices include CPUs, DSPs, and GPUs. The processor has memory. Examples of memory include RAM, ROM, and flash memory. The memory stores program code or instructions configured to enable the processing device to execute processes. Memory, or computer-readable medium, includes all usable media accessible by a general-purpose or special-purpose computer. [b] A hardware circuit having one or more hardware circuits that execute various processes. Examples of hardware circuits include ASICs (Application Specific Integrated Circuits), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays). [c] A circuit having a processor that executes a portion of the various processes according to a computer program, and hardware circuits that execute the remaining processes in the various processes.

[0039] The drive control unit 11 will be described. The drive control unit 11 is capable of controlling the power source 91. The drive control unit 11 can operate the power source 91 and transmit driving force to the drive wheels. For example, the drive control unit 11 can calculate a demand value on the power source 91 corresponding to the driver's operation of the accelerator control unit of the vehicle 90, and transmit driving force from the power source 91 based on the demand value. Alternatively, for example, the drive control unit 11 can also transmit driving force from the power source 91 based on the command value calculated by the automatic driving control device 30. The drive control unit 11 can calculate the driving force Fp generated as output by the power source 91 based on the demand value sent to the power source 91. For example, the driving force Fp can be calculated based on the workload of the electric motor mounted on the power source 91.

[0040] The brake control unit 12 will be described. The brake control unit 12 can control the friction brake device 70. The brake control unit 12 can activate the friction brake device 70 to generate braking force.

[0041] An example of the function of the braking control unit 12 will be explained.

[0042] The brake control unit 12 can calculate the required braking force BP as the required value of the braking force applied to the vehicle 90. For example, the required braking force BP can be calculated based on the operation amount of the brake operation component 79. Alternatively, the required braking force BP can also be obtained based on the command value calculated by the automatic driving control device 30.

[0043] The braking control unit 12 can calculate the front-to-rear distribution ratio 'a', which represents the proportion of the required braking force BP applied to the front wheels 81. The front-to-rear distribution ratio 'a' represents the proportion of the braking force applied to the front wheels 81 in the sum of the braking forces applied to the front wheels 81 and the braking forces applied to the rear wheels 82, i.e., the total braking force. The braking control unit 12 can calculate the required values ​​of the front wheel braking force and the rear wheel braking force based on the required braking force BP and the front-to-rear distribution ratio 'a'. Hereinafter, the required value of the front wheel braking force will be referred to as the required front wheel braking force BPf. The required value of the rear wheel braking force will be referred to as the required rear wheel braking force Bpr. For example, if the front-to-rear distribution ratio 'a' is "1", then the required front wheel braking force BPf is equal to the required braking force BP. Conversely, if the front-to-rear distribution ratio 'a' is "0", then the required rear wheel braking force Bpr is equal to the required braking force BP.

[0044] The brake control unit 12 can use a conversion coefficient Kb to convert between the required braking force and the target pressing force. The conversion coefficient Kb is a coefficient representing the relationship between the magnitude of the braking force and the magnitude of the pressing force. For example, the required front wheel braking force BPf can be converted into a target value of the WC pressure on the front wheel 81. Similarly, the required rear wheel braking force BPr can be converted into a target value of the WC pressure on the rear wheel 82. The brake control unit 12 activates the friction brake device 70 so that the generated pressing force follows the target value. The brake control unit 12 stores a pre-calculated value based on the specifications of the vehicle 90 and experimental data as the initial value of the conversion coefficient Kb.

[0045] The braking control unit 12 is capable of performing slight braking control. Details will be described later, but slight braking control is the control that generates braking force on at least one of the wheels, the front wheel 81 and the rear wheel 82, by performing coefficient estimation processing based on the efficiency coefficient estimation unit 20.

[0046] The acquisition unit 13 will be described below. The acquisition unit 13 is capable of calculating the state variables of the vehicle 90 based on detection signals from various sensors. For example, the acquisition unit 13 can calculate the brake hydraulic pressure P based on the detection signal from the hydraulic sensor 61. The acquisition unit 13 can calculate the front and rear acceleration Gx based on the detection signals from the front and rear acceleration sensors 62. The acquisition unit 13 can calculate the wheel speed based on the detection signals from the wheel speed sensor 63.

[0047] The acquisition unit 13 can calculate the vehicle weight M as the weight of the vehicle 90. The vehicle weight M takes into account not only the weight of the vehicle 90 itself, but also the weight of the passengers and cargo. For example, the vehicle weight M can be calculated using the driving force Fp and the front-rear acceleration Gx when the driving force Fp acts on the vehicle 90. The method for calculating the vehicle weight M is not particularly limited; it can also be calculated using the least squares method, or the arithmetic mean of multiple calculations can be used as the vehicle weight M.

[0048] The friction material temperature estimation unit 14 can estimate the temperature of the friction material 75. For example, it can estimate the temperature of the friction material 75 by accumulating the amount of temperature increase and temperature decrease. For example, it can calculate the amount of temperature increase based on the rate of decrease in wheel speed during vehicle braking and the WC pressure. For example, it can calculate the amount of temperature decrease based on the time the friction material 75 is not in contact with the rotating body 76.

[0049] The storage unit 15 will be described below. The storage unit 15 is capable of storing detection values ​​acquired from various sensors. In addition, the storage unit 15 is also capable of storing calculated values ​​generated by each functional unit.

[0050] The effectiveness coefficient estimation unit 20 will be described. The effectiveness coefficient estimation unit 20 is capable of performing coefficient estimation processing to estimate the effectiveness coefficient K. The effectiveness coefficient K is a coefficient representing the relationship between the magnitude of the braking force and the magnitude of the pressing force. In performing light braking control, the effectiveness coefficient estimation unit 20 performs coefficient estimation processing. In the coefficient estimation processing, based on the deviation between the generated driving force Fp and the actual driving force Fx actually acting on the vehicle 90, and the pressing force corresponding to the wheel to which braking force is applied by light braking control, the effectiveness coefficient K for the wheel to which braking force is applied by light braking control is estimated. The effectiveness coefficient estimation unit 20 can estimate the effectiveness coefficient K of the front wheel 81 and the effectiveness coefficient K of the rear wheel 82 respectively. Figure 7 As shown, the efficiency coefficient estimation unit 20 includes a deviation calculation unit 21, a variable pressure calculation unit 22, and an output unit 23.

[0051] <Utilization of the effectiveness coefficient>

[0052] The efficiency coefficient K estimated by the efficiency coefficient estimation unit 20 can be used as follows. For example, the efficiency coefficient K can be used to correct the conversion coefficient Kb stored in the brake control unit 12. For example, the brake control unit 12 can replace the efficiency coefficient K with the new conversion coefficient Kb. For example, the brake control unit 12 can adjust the front wheel braking force and the rear wheel braking force by adjusting the front-rear distribution ratio a based on the difference between the efficiency coefficient K of the front wheel 81 and the efficiency coefficient K of the rear wheel 82.

[0053] <Principles for Estimating the Power Coefficient>

[0054] use Figure 2 as well as Figure 3 The principle of estimating the power coefficient K by coefficient estimation is explained.

[0055] exist Figure 2 In the example shown, such as Figure 2 As shown in (a), the driving force is increased during the period from timing t1 to timing t2. Figure 2 In (a), the generated driving force Fp is shown as a solid line. The actual driving force Fx is shown as a dashed line. During the period from time t1 to time t2, when the generated driving force Fp increases, braking force is generated. Therefore, as... Figure 2 As shown in (b), brake hydraulic pressure P is generated during the period from timing t1 to timing t2. As a specific example of generating driving force Fp, it is, for example, the sum of the amounts of all wheels for the driving force transmitted from power source 91 to the contact surfaces of the wheels. As a specific example of actual driving force Fx, it is, for example, the sum of the amounts of all wheels for the driving force actually generated at the contact surfaces of the wheels.

[0056] Because a braking force is applied to vehicle 90 during the period from time t1 to time t2, therefore... Figure 2 As shown by the dashed line in (a), the actual driving force Fx acting on vehicle 90 is smaller than the generating driving force Fp. In this case, the greater the braking force, the smaller the actual driving force Fx relative to the generating driving force Fp. In other words, the greater the braking force, the greater the deviation between the generating driving force Fp and the actual driving force Fx, i.e., the driving force deviation ΔF.

[0057] That is, by using the deviation between the generated driving force Fp and the actual driving force Fx (i.e., the driving force deviation ΔF) and the variation in brake hydraulic pressure P, the actual braking force acting on the vehicle 90 can be estimated based on the driving force deviation ΔF corresponding to the variation in brake hydraulic pressure P. Thus, the relationship between brake hydraulic pressure P (i.e., the braking force) and the actual braking force can be determined.

[0058] Figure 3 This illustrates the relationship between the variation in braking hydraulic pressure P, i.e., the hydraulic pressure variation ΔP, and the driving force deviation ΔF. This relationship shows that the larger the hydraulic pressure variation ΔP, the larger the driving force deviation ΔF. Figure 3 As shown, it can be represented as an approximate straight line L. The slope of the approximate straight line L is equivalent to the efficiency coefficient K.

[0059] The efficiency coefficient K can be calculated, for example, using the least squares method. The calculation method based on the least squares method is explained using equations (1) to (3). In the least squares method, the efficiency coefficient K that minimizes the sum of squares error J shown in equation (1) is obtained.

[0060] [Formula 1]

[0061]

[0062] If we solve relation (Equation 1) to make relation (Equation 2) hold, then we can obtain relation (Equation 3).

[0063] [Equation 2]

[0064]

[0065] [Formula 3]

[0066]

[0067] The efficiency coefficient K can be calculated using the obtained relation (Equation 3).

[0068] Furthermore, the method for calculating the power coefficient K is not limited to the least squares method. The power coefficient K can also be calculated as an arithmetic mean, for example.

[0069] Light braking control

[0070] The details of the slight braking control performed by the braking control unit 12 are explained below. Slight braking control refers to a series of controls that activate the friction brake device 70 by performing the application and release processes described below.

[0071] Figure 4 The flowchart of the processing performed by the brake control unit 12 is shown. This processing routine is repeated every prescribed cycle.

[0072] If this processing routine begins, the braking control unit 12 first determines whether the start condition is met in step S101. For example, the braking control unit 12 can determine that the start condition is met if both condition A and condition B are met. (Condition A) The calculation of the vehicle weight M has been completed.

[0073] (Condition B) Driving force is increasing.

[0074] If the starting conditions are not met (S101: No), the braking control unit 12 temporarily terminates this processing routine.

[0075] On the other hand, if the starting condition is met (S101: Yes), the braking control unit 12 will move the processing to step S102.

[0076] In step S102, the brake control unit 12 begins the application process. During this process, the brake control unit 12 calculates the required braking force BP corresponding to the generated driving force Fp. Figure 5 The relationship between the driving force Fp and the required braking force BP is explained.

[0077] Figure 5 This is an example of a mapping that represents the relationship between the generated driving force Fp and the required braking force BP. The mapping representing this relationship is stored in the brake control unit 12.

[0078] according to Figure 5The relationship shown calculates the required braking force BP within the range where the generating driving force Fp is greater than or equal to the first driving force f1 and less than or equal to the third driving force f3. Within this range, the larger the generating driving force Fp is, the larger the required braking force BP is calculated. The second driving force f2 corresponds to a specified threshold related to the generating driving force Fp. Within the range where the generating driving force Fp is greater than the second driving force f2 and less than or equal to the third driving force f3, the larger the generating driving force Fp is, the smaller the required braking force BP is calculated. That is, the calculated required braking force BP is maximum when the generating driving force Fp is the second driving force f2. The maximum braking force bmax when the generating driving force Fp is the second driving force f2 is set to a value smaller than the braking force that balances the second driving force f2. Here, "balancing" means that, assuming a level road surface, the vehicle's 90° movement becomes "0" when the braking force counteracts the driving force. An example of the maximum braking force bmax is equivalent to 10% of the braking force that balances the second driving force f2.

[0079] Furthermore, the brake control unit 12 can arbitrarily set the front-to-rear distribution ratio 'a' during light braking control. If the front-to-rear distribution ratio 'a' during light braking control is fixed to "0" or "1", it is possible to select whether to apply the calculated required braking force BP to the front wheels 81 or the rear wheels 82. As an example, the brake control unit 12 can alternately perform light braking control that applies braking force only to the front wheels 81 and light braking control that applies braking force only to the rear wheels 82. Additionally, the brake control unit 12 can also vary the front-to-rear distribution ratio 'a' during light braking control. By setting the front-to-rear distribution ratio 'a' to a value greater than "0" and less than "1", braking force can be applied to both the front wheels 81 and the rear wheels 82.

[0080] Back Figure 4 If the processing begins in step S102 and the required braking force BP is calculated, the brake control unit 12 calculates the target value of the WC pressure based on the required braking force BP and the conversion coefficient Kb. Next, the brake control unit 12 activates the friction brake device 70 based on the target value of the WC pressure. As a result, the application of braking force begins.

[0081] If the processing begins in step S102, the braking control unit 12 moves the processing to step S103.

[0082] In step S103, the braking control unit 12 determines whether the termination condition is met. For example, the braking control unit 12 determines that the termination condition is met if a predetermined time has elapsed since the start of the application process.

[0083] Regarding the processing of step S103, the determination can also be performed as follows. The braking control unit 12 determines that the termination condition has been met even if a predetermined time has not elapsed since the start of the processing. For example, the braking control unit 12 can also determine that the termination condition has been met when the driving force decreases. Furthermore, the braking control unit 12 can also determine that the termination condition has been met when the driver intervenes in the operation of the braking operation component 79. Additionally, the braking control unit 12 can also determine that the termination condition has been met when the operating speed of the braking operation component 79 is faster than a predetermined deceleration operation determination value. The deceleration operation determination value can be set to a value that indicates the driver is seeking emergency braking when the operating speed is faster than the deceleration operation determination value. For example, the braking control unit 12 can also determine that the termination condition has been met when the driver operates the accelerator operation component faster than a predetermined acceleration operation determination value. The acceleration operation determination value can be set to a value that indicates the driver is seeking emergency acceleration when the operating speed is faster than the acceleration operation determination value. Furthermore, the braking control unit 12 can also determine that the termination condition has been met when the automatic driving control device 30 requests emergency braking or emergency acceleration.

[0084] If the termination condition is met (S103: Yes), the braking control unit 12 moves the process to step S104. On the other hand, if the termination condition is not met (S103: No), the braking control unit 12 repeats the process of step S103. The friction braking device 70 operates according to the applied process until the termination condition is met.

[0085] In step S104, the brake control unit 12 begins the elimination process. More specifically, the brake control unit 12 ends the application process and begins the elimination process. During the elimination process, the friction brake device 70 is activated to reduce the braking force applied by the application process to "0". For example, the brake control unit 12 reduces the braking force at a predetermined reduction rate. The brake control unit 12 may also reduce the braking force to "0" within a predetermined time from the start of the elimination process. If the elimination process begins, the brake control unit 12 ends this processing routine.

[0086] <Coefficient Estimation Processing>

[0087] The coefficient estimation process performed by the efficiency coefficient estimation unit 20 will be explained.

[0088] Figure 6 The flowchart of the process performed by the efficiency coefficient estimation unit 20 is shown. This process routine is repeated every prescribed period.

[0089] If this processing routine begins, in step S201, the efficiency coefficient estimation unit 20 first determines whether slight braking control is being performed. If slight braking control is not being performed (S201: No), the efficiency coefficient estimation unit 20 terminates this processing routine. On the other hand, if slight braking control is being performed (S201: Yes), the efficiency coefficient estimation unit 20 moves the processing to step S202.

[0090] In step S202, the efficiency coefficient estimation unit 20 determines whether the braking force is increasing. If the braking force applied to the wheel by slight braking control is increasing (S202: Yes), the efficiency coefficient estimation unit 20 moves the process to step S203.

[0091] In step S203, the efficiency coefficient estimation unit 20 calculates the driving force deviation ΔF and the hydraulic fluctuation ΔP. The efficiency coefficient estimation unit 20 temporarily stores the calculated values ​​and uses them to calculate the efficiency coefficient K. Figure 7 The calculation of driving force deviation ΔF and hydraulic fluctuation ΔP is explained.

[0092] like Figure 7 As shown, the efficiency coefficient estimation unit 20 acquires the generated driving force Fp via the acquisition unit 13. Furthermore, the efficiency coefficient estimation unit 20 acquires the vehicle weight M and the front-rear acceleration Gx via the acquisition unit 13. The efficiency coefficient estimation unit 20 calculates the actual driving force Fx by multiplying the vehicle weight M by the front-rear acceleration Gx. The generated driving force Fp and the actual driving force Fx are input to the deviation calculation unit 21 of the efficiency coefficient estimation unit 20. The deviation calculation unit 21 calculates the driving force deviation ΔF based on the generated driving force Fp and the actual driving force Fx. Alternatively, the deviation calculation unit 21 can use a correction value calculated to make the driving force deviation ΔF at the moment the light braking control begins "0" to calculate the driving force deviation ΔF.

[0093] Additionally, the efficiency coefficient estimation unit 20 acquires the brake hydraulic pressure P via the acquisition unit 13. The brake hydraulic pressure P is input to the variable pressure calculation unit 22 of the efficiency coefficient estimation unit 20. This brake hydraulic pressure P corresponds to the brake pressure P applied to the wheel by the applied light braking control. The variable pressure calculation unit 22 compares the input brake hydraulic pressure P with the previous brake hydraulic pressure P and calculates the hydraulic pressure variation ΔP as the variation in brake hydraulic pressure P.

[0094] Back Figure 6 If the driving force deviation ΔF and hydraulic fluctuation ΔP are calculated in step S203, the efficiency coefficient estimation unit 20 will move the processing to step S204.

[0095] On the other hand, in the process of step S202, if the braking force of the wheel to which the slight braking control is applied is not increasing (S202: No), the effectiveness coefficient estimation unit 20 moves the process to step S204. That is, if the braking force of the wheel to which the slight braking control is applied remains constant, or if the braking force is decreasing, the effectiveness coefficient estimation unit 20 does not perform the process of step S203 and proceeds to step S204.

[0096] In step S204, the efficiency coefficient estimation unit 20 determines whether the application process in the slight braking control has ended. If the application process has ended (S204: Yes), the efficiency coefficient estimation unit 20 moves the process to step S205.

[0097] On the other hand, if the application process has not ended (S204: No), the efficiency coefficient estimation unit 20 moves the process to step S202. Therefore, the processes of steps S202 to S204 are repeated until the application process ends. At this time, if the driving force deviation ΔF and hydraulic fluctuation ΔP are calculated through the process of step S203, the efficiency coefficient estimation unit 20 retains the values ​​of the driving force deviation ΔF and hydraulic fluctuation ΔP calculated up to the last time, and stores the calculated driving force deviation ΔF and hydraulic fluctuation ΔP. Thus, the calculated values ​​of driving force deviation ΔF and hydraulic fluctuation ΔP are accumulated.

[0098] In step S205, the efficiency coefficient estimation unit 20 estimates the efficiency coefficient K. The efficiency coefficient estimation unit 20 calculates the efficiency coefficient K based on the driving force deviation ΔF and hydraulic fluctuation ΔP accumulated by repeatedly executing the process of step S203.

[0099] like Figure 7 As shown, the driving force deviation ΔF and the hydraulic fluctuation ΔP are input to the output unit 23 of the efficiency coefficient estimation unit 20. The output unit 23 uses the driving force deviation ΔF and the hydraulic fluctuation ΔP to calculate the efficiency coefficient K based on equation (Equation 3). Return to... Figure 6 If the efficiency coefficient K is estimated in step S205, the efficiency coefficient estimation unit 20 ends the current processing routine.

[0100] like Figure 7 As shown, the efficiency coefficient estimation unit 20 can store the calculated efficiency coefficient K in the storage unit 15. At this time, the storage unit 15 can also store the state quantity of the vehicle 90 when calculating the efficiency coefficient K in a correlated manner. For example, the storage unit 15 can also store the temperature of the friction material 75 and the efficiency coefficient K in a correlated manner. The storage unit 15 can also store the temperature of the friction material 75, the efficiency coefficient K, and the vehicle speed in a correlated manner.

[0101] <Function and Effect>

[0102] The function and effects of this implementation method are explained.

[0103] exist Figure 8 In (a), an example is shown in which the increased driving force Fp is reduced to “0” and repeated three times.

[0104] exist Figure 8 In the example shown, at time t11, the start condition is determined to be met, and the application process of slight braking control begins (S102). Here, braking force is applied only to the front wheels 81. Therefore, as... Figure 8 As shown by the solid line in (b), the front wheel braking force BPf is required to increase from time t11. At time t12, the termination condition is determined to be met, the application process ends, and the elimination process begins (S104). Therefore, after time t12, the front wheel braking force BPf is required to decrease.

[0105] Here, for example, there is a situation where, if vehicle 90 is decelerating due to braking, the front-to-rear distribution ratio 'a' is set to suppress the pitching motion of vehicle 90. Therefore, if braking force is to be applied during deceleration for estimating the effectiveness coefficient K, it becomes difficult to make adjustments such as applying braking force only to one of the front wheels 81 or the rear wheels 82, or changing the front-to-rear distribution ratio 'a'. If the front-to-rear distribution ratio 'a' is changed during deceleration for estimating the effectiveness coefficient K, there are concerns that the pitching motion may increase, or that it may cause discomfort to the occupants of vehicle 90.

[0106] In contrast, the control device 10 initiates slight braking control for coefficient estimation when the driving force is increasing. Thus, even if braking force is applied to at least one of the front wheels 81 and the rear wheels 82, the effects of braking force, such as pitching of the vehicle 90 or discomfort to the occupants of the vehicle 90, can be mitigated.

[0107] Furthermore, in the slight braking control performed by the control device 10, the braking force BP is required to not exceed the driving force. Therefore, even when slight braking control is performed, it is difficult to suppress the acceleration of the vehicle 90.

[0108] exist Figure 8 At time t13, the driving force Fp increases again, and the braking force is applied. Here, braking force is applied only to the rear wheel 82. Therefore, as... Figure 8 As shown by the dashed line in (b), the rear wheel braking force BPr is required to increase from time t13. At time t14, the termination condition is determined to be met. After time t14, the rear wheel braking force BPr is required to decrease.

[0109] After time t15, treatment is applied only to the front wheels 81, requiring an increase in front wheel braking force BPf. After time t16, the front wheel braking force BPf is reduced due to the elimination of the treatment.

[0110] exist Figure 8 In the example shown, during the period from time t11 to time t12, the front wheel braking force BPf is required to increase. Therefore, during this period, the calculation of the driving force deviation ΔF and the hydraulic fluctuation ΔP is repeated (S203). The hydraulic fluctuation ΔP is calculated using the braking hydraulic pressure P corresponding to the pressing pressure applied to the front wheel 81. Then, if the processing ends at time t12, the effectiveness coefficient K of the front wheel 81 is estimated (S205).

[0111] Next, during the period from time t13 to time t14, the rear wheel braking force BPr is required to increase. Therefore, during this period, the hydraulic pressure variation ΔP is calculated using the braking hydraulic pressure P corresponding to the pressing pressure applied to the rear wheel 82. If the calculation of the driving force deviation ΔF and the hydraulic pressure variation ΔP is repeated and the processing ends at time t14, the effectiveness coefficient K of the rear wheel 82 is estimated.

[0112] Furthermore, during the period from time t15 to time t16, similarly to the period from time t11 to time t12, the hydraulic fluctuation ΔP is calculated using the braking hydraulic pressure P corresponding to the pressing pressure on the front wheel 81. Then, the effectiveness coefficient K for the front wheel 81 is estimated.

[0113] In the slight braking control performed by the control device 10, braking force is generated on at least one of the front wheel 81 and the rear wheel 82. Then, in the coefficient estimation process, the pressing force corresponding to the wheel on which the braking force is applied is used to estimate the effectiveness coefficient K. Thus, the effectiveness coefficient K of the front wheel 81 and the effectiveness coefficient K of the rear wheel 82 can be identified and estimated.

[0114] In the control device 10, the deviation between the generated driving force Fp and the actual driving force Fx, i.e., the driving force deviation ΔF, is used to estimate the efficiency coefficient K. In the vehicle 90 that uses an electric motor as the power source 91, the calculation accuracy of the generated driving force Fp is easily increased compared to the case where the power source 91 is an internal combustion engine. Therefore, in the vehicle 90 that uses an electric motor as the power source 91, the efficiency coefficient K can be estimated with relatively good accuracy.

[0115] In the control device 10, the driving force deviation ΔF and hydraulic fluctuation ΔP are calculated only when the braking force is increasing. That is, the driving force deviation ΔF and hydraulic fluctuation ΔP are used only when the braking force is increasing to estimate the effectiveness coefficient K. Therefore, the difference between the situation that increases the braking force and the situation that decreases the braking force does not affect the estimation of the effectiveness coefficient K. As a result, the hysteresis characteristics of the friction braking device 70 can be ignored when estimating the effectiveness coefficient K. According to the control device 10, the effectiveness coefficient K can be estimated with good accuracy.

[0116] According to the control device 10, the conversion coefficient Kb can be corrected using the effectiveness coefficient K. This corrects the relationship between braking pressure and braking force, suppressing the deviation between the required braking force BP and the actual braking force applied to the wheel. The same effect can be achieved when the effectiveness coefficient K is used as the new conversion coefficient Kb.

[0117] When the vehicle 90 is operated by a driver, even if there is a deviation between the required braking force BP and the actual braking force applied to the wheels, the driver can be expected to take action to eliminate the discomfort associated with the deviation. In contrast, when driving autonomously, it is difficult to expect driver intervention. Therefore, when driving autonomously, it is effective to estimate the efficiency coefficient K with good accuracy, as in the control device 10, and use the efficiency coefficient K to control the braking force.

[0118] If the relationship between braking force and pressure in the front wheel 81 differs significantly from that in the rear wheel 82, there is a concern that the actual front wheel braking force ratio applied according to the front-rear distribution ratio a may deviate from the ratio assumed based on the front-rear distribution ratio a. To address this, the control device 10 can adjust the front-rear distribution ratio a based on the difference between the efficiency coefficient K of the front wheel 81 and the efficiency coefficient K of the rear wheel 82. This prevents both the front and rear wheel braking force ratios from deviating from the desired ratios.

[0119] (Example of Change)

[0120] This embodiment can be modified and implemented as follows. This embodiment and the following modifications can be combined and implemented with each other within the scope of technical inconsistency.

[0121] In the above embodiment, an example is shown in which the application of braking force to the front wheel 81 and the application of braking force to the rear wheel 82 are alternately performed when the slight braking control is repeatedly executed. However, this is not a limitation; for example, the slight braking control that applies braking force to the front wheel 81 may be repeatedly executed multiple times.

[0122] In the above embodiment, an example is shown where braking force is applied to either the front wheel 81 or the rear wheel 82 during the period from the start of slight braking control to the end of the slight braking control. Alternatively, braking force can also be applied to both the front wheel 81 and the rear wheel 82 during slight braking control. Figure 9 Please provide an explanation.

[0123] exist Figure 9 In the example shown, at time t21, the start condition is determined to be met, and the application process of slight braking control begins (S102). Here, braking force is initially applied only to the front wheels 81. Figure 9 As shown by the solid line in (b), the front wheel braking force BPf is required to increase from time t21. Figure 9 As shown in (c), the pre- and post-allocation ratio a is "1" at this time.

[0124] like Figure 9 As shown in (c), starting from time t22, the pre- and post-allocation ratio a gradually decreases. As a result, as... Figure 9 As shown by the solid line in (b), the front wheel braking force BPf is required to begin to decrease. Furthermore, as... Figure 9 As shown by the dashed line in (b), the rear wheel braking force BPr is required to begin increasing. The front-to-rear distribution ratio a decreases to "0" at time t23.

[0125] Furthermore, at time t23, the termination condition is determined to be met, the application process ends, and the elimination process begins (S104). Therefore, after time t23, the rear wheel braking force BPr is required to decrease. The rear wheel braking force BPr is required to become "0" at time t24.

[0126] exist Figure 9 In the example shown, the period up to time t23 is the period during which the braking force BP is required to increase. The effectiveness coefficient K can also be estimated using a coefficient estimation process during the execution of such slight braking control. In this case, the hydraulic variation ΔP with respect to the front wheel 81 and the hydraulic variation ΔP with respect to the rear wheel 82 can be calculated taking into account the front-rear distribution ratio a.

[0127] • In the above embodiments, it is shown that in slight braking control, based on Figure 5 The example shown illustrates the required braking force BP in the mapping calculation. Alternatively, the increase in the required braking force BP can be set during the execution of slight braking control.

[0128] For example, it is possible to use Figure 5The vertical axis is set as a mapping of the required increase in braking force BP, and the required increase in braking force BP is calculated. That is, the required increase in braking force BP can be set based on the relationship between the generated driving force Fp and the required increase in braking force BP. In this case, the increase in braking force tends to continue during the application process. That is, it is difficult to generate periods where the braking force remains constant and periods where the braking force decreases during the application process. As a result, it is possible to suppress the lengthening of the period until the braking force applied by slight braking control increases. Therefore, it is possible to shorten the time until the estimation of the effectiveness coefficient K is completed. As a result, the duration of continuous slight braking control can be shortened. By performing slight braking control for a short time, it is difficult to hinder the acceleration of vehicle 90.

[0129] Furthermore, when the driving force Fp increases at a predetermined rate of increase Fps or higher, the required braking force BP can also be increased to the maximum braking force bmax at a preset rate of increase. This allows the required braking force BP to be increased at a preset rate even in light braking control. For example, if the rate of increase of the required braking force BP varies according to the rate of increase of the driving force Fp, there is a concern that the required braking force BP may increase with a delay or increase abruptly. In the case of abruptly increasing required braking force BP, the operating noise may increase along with the increase in required braking force BP. In contrast, if the rate of increase of the required braking force BP is set to a preset rate of increase as described above, the occurrence of a delay in the increase of required braking force BP or the increase in operating noise can be suppressed.

[0130] In the above embodiments, conditions A and B are exemplified as starting conditions for slight braking control, but the starting conditions are not limited to these. Starting conditions may also include a vehicle speed lower than a predetermined judgment speed. Starting conditions may also include a change in vehicle speed smaller than a predetermined change in speed. Starting conditions may also include a temperature of the friction material 75 lower than a predetermined judgment temperature.

[0131] In the above embodiment, as part of step S202, step S203 is performed when the braking force is increasing. Step S203 can also be performed when the braking force is above a predetermined braking force, in addition to when the braking force is increasing. In other words, the hydraulic fluctuation ΔP and driving force deviation ΔF during the period when the braking force is less than the predetermined braking force during the execution of slight braking control may not be used to estimate the effectiveness coefficient K.

[0132] • Even when braking force is increasing during slight braking control, the hydraulic fluctuation ΔP and driving force deviation ΔF during a 90° turn are not used to estimate the effectiveness coefficient K. During a 90° turn, the actual driving force Fx may decrease due to factors other than braking force. By excluding the hydraulic fluctuation ΔP and driving force deviation ΔF caused by this decrease in actual driving force Fx, error-causing factors can be eliminated, resulting in a more accurate estimation of the effectiveness coefficient K.

[0133] Furthermore, for example, it is possible to detect whether the vehicle 90 is turning based on the amount of operation of the steering control components. Alternatively, it is possible to detect the turning of the vehicle 90 based on the steering angle of the steering wheel. It is also possible to detect the turning of the vehicle 90 based on steering control commands from the automatic driving control unit 30.

[0134] In the above embodiment, the hydraulic pressure variation ΔP is calculated using the brake hydraulic pressure P detected by the hydraulic pressure sensor 61. For example, the hydraulic pressure variation ΔP can also be calculated based on the target value of the pressing pressure.

[0135] The termination condition for slight braking control is not limited to the conditions illustrated in the above embodiments. For example, even if no predetermined time has elapsed since the start of the process, the termination condition can be determined to be met once the vehicle at 90 has begun to turn.

[0136] In the above embodiment, a hydraulic braking device is exemplified as a friction braking device 70. However, it is not limited to a hydraulic braking device; a mechanical friction braking device that pushes friction material against a rotating body by mechanically transmitting the driving force of an electric motor can also be used. In this case, the magnitude of the pressure corresponds to the driving force of the electric motor. In such a structure, by using the variation in the driving force of the electric motor instead of the hydraulic variation ΔP in the above embodiment, the efficiency coefficient K can be estimated.

[0137] In the above embodiment, the temperature of the friction material 75 is estimated by the friction material temperature estimation unit 14. The temperature of the friction material 75 can also be obtained by a temperature sensor.

Claims

1. A control device applied to a vehicle having a power source and a friction braking device, wherein the power source generates driving force, and the friction braking device is a braking device that applies braking force to a wheel based on the pressure applied to a friction material pressed against a rotating body integral with the wheel, and is capable of separately adjusting the braking force applied to the front wheel and the rear wheel of the wheel, wherein... The aforementioned control device includes: Braking control unit, controls the aforementioned friction braking device; and The estimation department estimates the effectiveness coefficient, which is a coefficient representing the relationship between the magnitude of the braking force and the magnitude of the pressing force. When the driving force is increasing, the braking control unit can begin to apply slight braking control to at least one of the front and rear wheels. In performing the aforementioned slight braking control, the estimation unit estimates the efficiency coefficient of the wheel to which braking force is applied by the aforementioned slight braking control based on the deviation between the generated driving force and the actual driving force, and the pressing force corresponding to the wheel to which braking force is applied by the aforementioned slight braking control. The generated driving force is the driving force based on the required value of the aforementioned power source, and the actual driving force is the driving force that actually acts on the aforementioned vehicle.

2. The control device according to claim 1, wherein, In the aforementioned slight braking control, the braking control unit generates braking force on either the front wheel or the rear wheel.

3. The control device according to claim 1, wherein, In the aforementioned slight braking control, the braking control unit generates braking force on both the front and rear wheels based on the front-rear distribution ratio. The front-rear distribution ratio represents the proportion of the braking force applied to the front wheels in the total braking force, which is the sum of the braking force applied to the front wheels and the braking force applied to the rear wheels.

4. The control device according to any one of claims 1 to 3, wherein, If the aforementioned braking control unit initiates the aforementioned slight braking control, it performs a braking force application process, and after the application process is completed, it performs a process to reduce the braking force to "0" to terminate the slight braking control. When calculating the aforementioned effectiveness coefficient, the estimation unit uses the deviation between the generated driving force and the actual driving force during the period when the braking force is increasing.

5. The control device according to claim 4, wherein, In the above-described application process, the braking control unit calculates a value smaller than the braking force that balances the driving force as the required braking force for controlling the friction braking device.

6. The control device according to claim 5, wherein, In the above-mentioned application process, the braking control unit calculates the required braking force based on the generated driving force, and within the range where the generated driving force is below a predetermined threshold, the greater the generated driving force, the greater the calculated required braking force.

7. The control device according to claim 4, wherein, In the aforementioned slight braking control, if a predetermined time has elapsed since the start of the application process, the braking control unit ends the application process and begins the elimination process.

8. The control device according to claim 5 or 6, wherein, In the aforementioned slight braking control, if a predetermined time has elapsed since the start of the application process, the braking control unit ends the application process and begins the elimination process.

9. The control device according to claim 7, wherein, When the driving force decreases during the execution of the above-mentioned slight braking control, the braking control unit will end the above-mentioned application process and start the above-mentioned elimination process even if the prescribed time has not elapsed since the start of the above-mentioned application process.

10. The control device according to any one of claims 1 to 3, wherein, When the vehicle begins to turn during the aforementioned slight braking control, the estimation unit does not use the deviation between the generated driving force and the actual driving force during the turning period, or the pressing force, to calculate the effectiveness coefficient.

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