Brake control device for a vehicle

Abstract

Brake control device (BCS) for a vehicle, which actuates an electric motor (MTR) on the basis of a set pressure force (Fpt) corresponding to a required braking force for a vehicle wheel (WH) of a vehicle and generates a braking force in the vehicle wheel (WH) by pressing a friction element (MS) against a rotary element (KT) that is fixed to the vehicle wheel (WH), with: a control circuit (DRV) that controls the electric motor (MTR); a control unit (ECU) that controls the actuator circuit (DRV) based on the target pressure force (Fpt); and a rotary angle sensor (MKA) that detects a rotary angle (Mka) of the electric motor (MTR), wherein the control unit (ECU) sets a current limiting circuit (Cis) of a current characteristic of a d-axis current and a q-axis current of the electric motor (MTR) based on a specification of the control circuit (DRV), characterized by the fact that The electronic control unit (ECU) calculates a voltage limiting circuit (Cvs) of the current characteristic based on the rotation angle (Mka), calculates a d-axis setpoint current (Idt) and a q-axis setpoint current (Iqt) based on a correlation between the current limiting circuit (Cis) and the voltage limiting circuit (Cvs), and controls the drive circuit (DRV) based on the d-axis setpoint current (Idt) and the q-axis setpoint current (Iqt).

Description

Technical area

[0001] The present invention relates to a brake control device for a vehicle. Background of the invention

[0002] JP 2008 - 184 057 A discloses a "configuration in which a target brake fluid pressure calculation means M1 calculates a target brake fluid pressure to be generated in a slave cylinder, a differentiation means M2 calculates a target brake fluid pressure change rate by differentiating the target brake fluid pressure with respect to time, a field current calculation means M3 calculates a field current command value of an electric motor that drives the slave cylinder based on the target brake fluid pressure change rate, and an electric motor control means M4 executes field weakening control on the electric motor based on the field current command value.A case where the target brake fluid pressure change rate is large indicates an emergency in which a braking force needs to be increased quickly, and the responsiveness of generation of the braking force can be improved by promptly operating the slave cylinder and increasing the rotational speed of the electric motor with an increase in the field current command value and the weak field amount of the electric motor at that time" for the purpose of "increasing the responsiveness of generation of the braking force without increasing the size of the electric motor driving an electric braking force generating device".

[0003] JP 2012-131293 A discloses a "configuration in which the drive of a motor drive cylinder 13, which applies brake fluid pressure to a wheel cylinder, is controlled by executing field weakening control when a deviation Δθ between an actual motor angle θm and a target motor angle θt obtained in response to a brake operation amount is large. For example, when a motor angle (a rotation amount) is used as an operation amount of an electric actuator, the motor angle can be detected with high accuracy by a simple and inexpensive known rotation sensor or the like, a motor angle change range is broadened, and a brake responsiveness can thus be easily increased.Furthermore, since there is no influence of a change in load intensity, a deviation of the motor angle occurs in a transient state immediately after the start of the field weakening control, field weakening control can be continuously executed, a change in a motor responsiveness characteristic is reduced, thus a stable responsiveness characteristic can be obtained" for the purpose of "further enhancing the responsiveness of generation of the braking force by the electric actuator with a simple configuration".

[0004] The applicant has developed a brake control device for a vehicle that generates braking torque by an electric motor and suppresses excessive slip of a vehicle wheel at the time of starting the execution of a slip suppression control for the vehicle wheel. Specifically, as described in JP 2014-51198 A, "vehicle wheel slip suppression control" for reducing the braking torque of the vehicle wheel is executed by controlling the electric motor based on the amount of slip of the vehicle wheel. Further, "sudden stop control" for suddenly stopping the rotation of the electric motor based on the amount of slip of the vehicle wheel is executed. The sudden stop control is started under a condition that the vehicle wheel slip suppression control is not being executed.As the sudden stop control, “control for gradually changing the energization amount of the electric motor by a predetermined energization limit value according to a speed reduction direction of the electric motor” may be executed.

[0005] JP 2008-184057 A and JP 2012-131293 A disclose "field weakening control (also referred to as magnetic flux weakening control)" that is performed by flowing a current from a d-axis of the electric motor. In a three-phase brushless motor, a d-axis current and a q-axis current can be controlled independently. For this reason, there is a desire to further suppress excessive slip of the vehicle wheel at the time of starting the execution of the vehicle wheel slip suppression control by appropriately controlling these currents.

[0006] Document DE 10 2014 010 362 A1 describes a current control device of a synchronous motor, which includes a brake control device according to the preamble of claim 1. Specifically, a current control device for a synchronous motor is described, which includes a calculation unit for calculating a preliminary d-phase current command; a voltage amplitude calculation unit for calculating a magnitude of a voltage command vector in a previous duty cycle; a voltage ratio calculation unit for determining a voltage ratio between the magnitude of the voltage command vector and a maximum output voltage of an amplifier; a target d-phase current calculation unit, which obtains a d-phase current command in the previous duty cycle and calculates a target d-phase current command from the voltage ratio and the d-phase current command;a correction value calculation unit that determines a correction value by passing a difference between the preliminary d-phase current command and the target d-phase current command through a low-pass filter; and an adder that adds the correction value to the d-phase current command in the current sampling period to calculate a new d-phase current command. Brief summary of the inventionTechnical problem

[0007] An object of the invention is to provide a brake control device for a vehicle using a three-phase brushless motor capable of more effectively suppressing excessive vehicle wheel slip at the time of starting a vehicle wheel slip suppression control for suppressing vehicle wheel slip.

[0008] This object is achieved by a brake control device according to claim 1. Advantageous further developments are specified in the dependent claims. Solution to the problem

[0009] A brake control device for a vehicle according to an aspect of the invention drives an electric motor (MTR) based on a target pressing force (Fpt) corresponding to a demand braking force for a vehicle wheel (WH) of a vehicle, and generates a braking force in the vehicle wheel (WH) by pressing a friction element (MS) against a rotation element (KT) fixed to the vehicle wheel (WH). The brake control device for the vehicle includes a vehicle wheel speed sensor (VWA) that detects a speed (Vwa) of the vehicle wheel (WH), a rotation angle sensor (MKA) that detects a rotation angle (Mka) of the electric motor (MTR), a drive circuit (DRV) that drives the electric motor (MTR), and a controller (ECU) that controls the drive circuit (DRV) based on the target pressing force (Fpt).

[0010] In the brake control device for the vehicle according to an embodiment of the invention, the control unit (ECU) sets a current limiting circuit (Cis) of a dq-axis current characteristic of the electric motor (MTR) based on a specification of the drive circuit (DRV); calculates a voltage limiting circuit (Cvs) of the dq-axis current characteristic based on the rotation angle (Mka); calculates a slip state amount (Slp) indicating a slip degree of the vehicle wheel (WH) based on the rotational speed (Vwa) of the vehicle wheel (WH); executes slip suppression control for reducing the slip degree of the vehicle wheel (WH) based on the slip state amount (Slp);It calculates a d-axis target current (Idt) and a q-axis target current (Iqt) based on a correlation between the current limiting circuit (Cis) and the voltage limiting circuit (Cvs) at the time of starting the execution of the slip suppression control, and it controls the drive circuit (DRV) based on the d-axis target current (Idt) and the q-axis target current (Iqt). Specifically, the control unit (ECU) calculates an intersection point (Pxb) between the current limiting circuit (Cis) and the voltage limiting circuit (Cvs), and calculates the d-axis target current (Idt) and the q-axis target current (Iqt) based on the intersection point (Pxb).

[0011] In a state where the electric motor MTR is rotating at a high speed in the normal rotation direction, the electric motor MTR attempts to continue rotation due to the inertia moment of the rotor of the electric motor MTR in a situation where a vehicle wheel slip suppression control, such as an anti-skid control or anti-lock brake control, is initiated. To suppress excessive vehicle wheel slip, the speed of the electric motor MTR immediately becomes "0," thus requiring the electric motor to be driven in the reverse rotation direction.

[0012] According to the configuration described above, dq-axis target currents Idt and Iqt are determined based on an intersection point Pxb (corresponding to the current in the reverse rotation direction) between a current limiting circuit Cis and a voltage limiting circuit Cvs. The intersection point Pxb indicates an operating point at which the output of the electric motor MTR in the reverse rotation direction of the electric motor MTR becomes maximum. For this reason, the electric motor MTR can be stopped and reversed in the most effective manner. As a result, the responsiveness of the vehicle wheel slip suppression control is improved, and excessive vehicle wheel slip due to the inertia moment of the electric motor MTR can be suppressed.

[0013] In the brake control device for the vehicle according to an aspect of the invention, the control device (ECU) controls the drive circuit (DRV) based on the correlation between the current limiting circuit (Cis) and the voltage limiting circuit (Cvs) in a non-execution state in which the slip suppression control is not executed, increasing the current limiting circuit (Cis) in the execution start state rather than the current limiting circuit (Cis) in the non-execution state.

[0014] According to the configuration described above, the current limiting circuit Cis exceeds an allowable current value iqm, increasing it to an increased allowable current value iqn for a short time. Therefore, the electric motor MTR is more effectively stopped and reversed after the temperature rise of the electric motor MTR and the drive circuit DRV is suppressed. As a result, excessive vehicle wheel slip can be suppressed.

[0015] The brake control device for the vehicle according to an embodiment of the invention further comprises a current sensor (IMA) that detects a current value (Ima) of the drive circuit (DRV), wherein the control device (ECU) calculates a d-axis actual current (Ida) corresponding to a d-axis element of the current value (Ima) and a q-axis actual current (Iqa) corresponding to a q-axis element of the current value (Ima) based on the current value (Ima) and the rotation angle (Mka), calculates a counter electromotive force (ω·ϕ) of the electric motor (MTR) based on the rotation angle (Mka), calculates a target voltage (Edqs) based on a deviation (eId) between the d-axis target current (Idt) and the d-axis actual current (Ida), a deviation (eIq) between the q-axis target current (Iqt) and the q-axis actual current (Iqa) and the back electromotive force (ω·φ) and controls the drive circuit (DRV) based on the target voltage (Edqs).

[0016] The control of the electric motor MTR is achieved through voltage control (i.e., voltage control corresponding to current control) based on a deviation eId between the d-axis command current Idt and a d-axis actual current Ida, and a deviation eIq between the q-axis command current Iqt and a q-axis actual current Iqa. According to the configuration described above, the influence of the back electromotive force (back electromotive voltage) generated by the rotation of the electric motor MTR in the voltage control is compensated. For this reason, it is possible to decelerate the electric motor MTR more effectively and quickly. Short description of the drawing Fig. 1 shows an overall configuration diagram of a vehicle equipped with a brake control device BCS for a vehicle according to the invention. Fig. 2 shows a functional block diagram for describing a processing of a control device ECU. Fig. 3 shows a flowchart for describing processings of a vehicle wheel slip suppression control block FSC and a target pressing force calculation block FPT. Fig. 4 is a flowchart for describing a first processing example of a target current calculation block IMT (specifically, a flow of processing when vehicle wheel slip suppression control is not executed). Fig. 5 is a flowchart for describing a first processing example of the target current calculation block IMT (specifically, a flow of processing when the vehicle wheel slip suppression control is executed). Fig. 6 shows a characteristic diagram for describing the first processing example of the target current calculation block IMT. Fig. 7 shows a flowchart for describing a second processing example of the target current calculation block IMT. Fig. 8 shows a characteristic diagram for describing the second processing example of the target current calculation block IMT. Fig. 9 shows a schematic diagram for describing processing of a switching control block SWT and a drive circuit DRV of a three-phase brushless motor. Fig. 10 is a timing chart for describing an operation and effect of the brake control device BCS for the vehicle according to the invention. Embodiment of the invention <Gesamtkonfiguration einer Bremssteuerungsvorrichtung für ein Fahrzeug gemäß der Erfindung>

[0017] With reference to an overall configuration diagram according to Fig. 1, a brake control device (BCS) according to the invention is described. In the following description, components, calculation processes, signals, characteristics, and values ​​indicated by the same reference numerals represent the same functions. Therefore, a repeated description is omitted.

[0018] A vehicle including a brake control device BCS is equipped with a brake operating element BP, a brake operating amount sensor BPA, a control unit ECU, a brake master cylinder MC, a stroke simulator SSM, a simulator cut-off valve VSM, a pressurizing unit KAU, a changeover valve VKR, a brake master cylinder pipe HMC, a wheel cylinder pipe HWC, and a pressurizing cylinder pipe HKC. Furthermore, each vehicle wheel WH of the vehicle is equipped with a brake caliper CP, a wheel cylinder WC, a rotary element KT, and a friction element MS.

[0019] The brake operating member (e.g., a brake pedal) BP is a member used by a driver to reduce vehicle speed. When the brake operating member BP is operated, a braking torque for the vehicle wheel WH is adjusted, generating a braking force in the vehicle wheel WH. Specifically, a rotating member (e.g., a brake disc) KT is fixed to the vehicle wheel WH of the vehicle. The brake caliper CP is arranged to clamp the rotating member KT. Then, the brake caliper (simply referred to as a caliper) CP is provided with the wheel cylinder WC. When a fluid pressure within the wheel cylinder WC of the caliper CP is adjusted (increased or decreased), a piston within the wheel cylinder WC moves (moves forward or backward) with respect to the rotating member KT.Due to the movement of the piston, the friction element (e.g., a brake pad) MS is pressed against the rotating element KT to generate a pressing force. The rotating element KT and the vehicle wheel WH are fixed by a fixed shaft DS to rotate together. Therefore, a braking torque (braking force) is generated in the vehicle wheel WH due to a friction force generated by the pressing force. Thus, the braking force (the demand braking force) required for the vehicle wheel WH is achieved in response to a target value of the pressing force.

[0020] The brake operation amount sensor (also simply referred to as an operation amount sensor) BPA is provided in the brake operation member BP. An operation amount Bpa of the brake operation member (brake pedal) BP by the driver is detected by the operation amount sensor BPA. Specifically, at least one of a fluid pressure sensor for detecting a pressure of the master cylinder MC, an operation displacement sensor for detecting an operation displacement of the brake operation member BP, and an operation force sensor for detecting an operation force of the brake operation member BP is employed as the brake operation amount sensor BPA. In other words, the operation amount sensor BPA is a general term for the master cylinder fluid pressure sensor, the operation displacement sensor, and the operation force sensor.Thus, the brake application amount Bpa is determined based on at least one of the fluid pressure of the master cylinder MC, the application displacement of the brake application element BP, and the application force of the brake application element BP. The application amount Bpa is input to the control unit ECU.

[0021] A control device (electronic control unit) ECU includes an electrical circuit board on which a microprocessor or the like is mounted, and a control algorithm programmed in the microprocessor. The control device ECU controls the pressurizing unit KAU (specifically, an electric motor MTR), the cut-off valve VSM, and the changeover valve VKR based on the brake application amount Bpa. Specifically, a signal (Sux or the like) for controlling the electric motor MTR, the cut-off valve VSM, and the changeover valve VKR is calculated based on the programmed control algorithm and output from the control device ECU.

[0022] When the brake application amount Bpa becomes a predetermined value bp0 or more, the control unit ECU outputs a drive signal Vsm, in which the cutoff valve VSM is set to an open position, and a drive signal Vkr, in which the switching valve VKR connects the pressurizing cylinder pipe HKC to the wheel cylinder pipe HWC, to the electromagnetic valves VSM and VKR, respectively. In this case, the brake master cylinder MC is connected to the simulator SSM, and a pressurizing cylinder KCL is connected to the wheel cylinder WC.

[0023] The control unit ECU calculates a drive signal (Sux or the like) for driving the electric motor MTR based on the operation amount Bpa, a rotation angle Mka, and an actual pressing force Fpa (for example, the fluid pressure a of the pressurizing cylinder KCL), and outputs the drive signal to the drive circuit DRV. Here, the brake operation amount Bpa is detected by the brake operation amount sensor BPA, the actual rotation angle Mka is detected by a rotation angle sensor MKA, and the actual pressing force Fpa is detected by a pressing force sensor FPA. The pressurizing unit KAU, which is driven by the electric motor MTR, controls (maintains, increases, or decreases) the pressure of the brake fluid within the wheel cylinder WC.

[0024] The brake master cylinder MC is mechanically connected to the brake actuator BP through a brake rod BRD. Through the brake master cylinder MC, the operating force (brake pedal force) of the brake actuator BP is changed according to the brake fluid pressure. When the brake master cylinder pipe HMC is connected to the brake master cylinder MC and the brake actuator BP is actuated, the brake fluid is expelled (pressurized) from the brake master cylinder MC to the brake master cylinder pipe HMC. The brake master cylinder pipe HMC is a fluid path connecting the brake master cylinder MC and the changeover valve VKR.

[0025] The stroke simulator (also simply referred to as the simulator) SSM is provided to generate the operating force in the brake operating member BP. The simulator cut-off valve (also simply referred to as a cut-off valve) VSM is provided between the simulator SSM and a fluid pressure chamber within the brake master cylinder MC. The cut-off valve VSM is an electromagnetic two-position valve having an open position and a closed position. The brake master cylinder MC is connected to the simulator SSM when the cut-off valve VSM is in the open position, and the brake master cylinder MC is isolated from the simulator SSM (in a non-connection state) when the cut-off valve VSM is in the closed position. The cut-off valve VSM is controlled by the drive signal Vsm from the control unit ECU.An electromagnetic valve of a normally closed type or a normally closed type (NC valve) can be used as the VSM shut-off valve.

[0026] A piston and an elastic element (e.g., a compression spring) are provided within the simulator SSM. Brake fluid moves from the brake master cylinder MC to the simulator SSM, and the piston is pushed by the flowing brake fluid. A force is applied to the piston by the elastic element in a direction that prevents the flow of the brake fluid. The elastic element generates the operating force (e.g., the brake pedal depression force) at the time of actuation of the brake operating element BP. <<Druckbeaufschlagungseinheit KAU> >

[0027] The pressurizing unit KAU discharges (pressurizes) brake fluid to the pressurizing cylinder pipe HKC using the electric motor MTR as a power source. Then, the pressurizing unit KAU applies braking torque (braking force) to the vehicle wheel WH by pressing (pressurizing) the friction element MS against the rotating element KT due to this pressure. In other words, the pressurizing unit KAU generates a force (pressing force) for pressing the friction element MS against the rotating element KT through the electric motor MTR. The pressurizing unit KAU includes the electric motor MTR, the drive circuit DRV, a power transmission mechanism DDK, a pressurizing shaft KSF, a pressurizing cylinder KCL, a pressurizing piston PKC, and the pressing force sensor FPA.

[0028] The MTR electric motor is a power source for adjusting (increasing or decreasing) the brake fluid pressure within the wheel cylinder WC through the pressure cylinder KCL. A three-phase brushless motor is used as the MTR electric motor. The MTR electric motor includes three coils CLU, CLV, and CLW, corresponding to U, V, and W phases, respectively, and is controlled by the drive circuit DRV. The MTR electric motor is equipped with a rotation angle sensor MKA, which detects the rotor position (rotation angle) Mka of the MTR electric motor. The rotation angle Mka is input to the control unit ECU.

[0029] The drive circuit DRV is an electrical circuit board on which a switching element (a power semiconductor device) for driving the electric motor MTR is mounted. Specifically, the drive circuit DRV is provided with a three-phase bridge circuit, and the power supply state to the electric motor MTR is controlled based on the drive signal (Sux or the like). The drive circuit DRV is provided with a current sensor (e.g., a current sensor) IMA that detects an actual current Ima (a general designation of respective phases) to the electric motor MTR. The current (detection value) Ima of each phase is input to the control unit ECU.

[0030] The power transmission mechanism DDK decelerates the rotational power of the electric motor MTR, converts the rotational power into linear power, and outputs the linear power to the pressurizing shaft KSF. Specifically, the power transmission mechanism DDK is equipped with a deceleration device (not shown), and the rotational power output from the electric motor MTR is decelerated and output to a screw element (not shown). Then, the rotational power is converted into the linear power of the pressurizing shaft KSF by the screw element. That is, the power transmission mechanism DDK is a rotary motion / linear motion conversion mechanism.

[0031] The pressurizing piston PKC is fixed to the pressurizing shaft KSF. The pressurizing piston PKC is inserted into an inner hole of the pressurizing cylinder KCL, forming a combination of the piston and the cylinder. Specifically, the outer periphery of the pressurizing piston PKC is provided with a sealing member (not shown), ensuring fluid tightness with respect to the inner hole (inner wall) of the pressurizing cylinder KCL. That is, the pressurizing chamber Rkc filled with the brake fluid is formed by the partitioning of the pressurizing cylinder KCL and the pressurizing piston PKC.

[0032] Within the pressurizing cylinder KCL, the volume of the pressurizing chamber Rkc changes as the pressurizing piston PKC moves in the axial direction. With this volume change, the brake fluid moves between the pressurizing cylinder KCL and the wheel cylinder WC through the brake pipes (fluid paths) HKC and HWC. The fluid pressure within the wheel cylinder WC is adjusted due to the loading and unloading of the brake fluid from the pressurizing cylinder KCL. As a result, the pressing force of the friction element MS relative to the rotary element KT is adjusted.

[0033] For example, a fluid pressure sensor that detects the fluid pressure Fpa of the pressurizing chamber Rkc is provided in the pressurizing unit KAU (specifically, the pressurizing cylinder KCL) as the pressing force sensor FPA. The fluid pressure sensor (i.e., the pressing force sensor) FPA is fixed to the pressurizing cylinder KCL to be integrated as the pressurizing unit KAU. The pressing force detection value Fpa (i.e., the fluid pressure of the pressurizing chamber Rkc) is input to the control unit ECU. As described above, the pressurizing unit KAU has been described.

[0034] A "state where the wheel cylinder WC is connected to the brake master cylinder MC" and a "state where the wheel cylinder WC is connected to the pressurizing cylinder KCL" are switched by the switching valve VKR. The switching valve VKR is controlled based on the drive signal Vkr output from the control unit ECU. Specifically, when the brake operation is not performed (the case of "Bpa < bp0"), the wheel cylinder pipe HWC communicates with the brake master cylinder pipe HMC through the switching valve VKR and is not communicated with (isolated from) the pressurizing cylinder pipe HKC. Here, the wheel cylinder pipe HWC is a fluid path connected to the wheel cylinder WC.When the brake operation is performed (that is, a state of “Bpa ≥ bp0”), the changeover valve VKR is energized based on the drive signal Vkr, the communication between the wheel cylinder pipe HWC and the master cylinder pipe HMC is interrupted, and the wheel cylinder pipe HWC is in communication with the pressurizing cylinder pipe HKC. <Verarbeitung der Steuerungseinrichtung ECU>

[0035] With reference to a functional block diagram according to Fig. 2 describes processing of the control device (electronic control unit) ECU. Furthermore, as described above, the components, calculation processing, signals, characteristics, and values ​​indicated by the same reference numerals represent the same functions.

[0036] In the control unit ECU, the control of the electric motor MTR and the excitation of the electromagnetic valves VSM and VKR are carried out based on the actuation amount Bpa of the brake operating element BP. The electric motor MTR is controlled by the control circuit DRV. The control circuit DRV (the three-phase bridge circuit) includes switching elements SUX, SUZ, SVX, SVZ, SWX, and SWZ (also referred to simply as "SUX to SWZ"). In the control unit ECU, the control signals Sux, Suz, Svx, Svz, Swx, and Swz (also referred to simply as "Sux to Swz") are calculated, and the switching elements SUX to SWZ are controlled based on the control signals. Furthermore, the control signals Vsm and Vkr are determined in the control unit ECU, and the electromagnetic valves VSM and VKR are controlled based on the control signals.

[0037] The control device ECU includes a command pressing force calculation block FPS, a vehicle wheel slip suppression control block FSC, a target pressing force calculation block FPT, a command current calculation block IMS, a pressing force control block FFB, a target current calculation block IMT, a switching control block SWT and an electromagnetic valve control block SLC.

[0038] In the command pressing force calculation block FPS, a command pressing force Fps is calculated based on the brake operation amount Bpa and a calculation map (a calculation map) CFps. Here, the command pressing force Fps indicates a target value of the fluid pressure (corresponding to the pressing force) generated by the pressurizing unit KAU. Specifically, in the calculation map CFps, the command pressing force Fps is calculated to be "0 (zero)" in a range where the brake operation amount Bpa is greater than or equal to "0 (corresponding to a case where the brake operation is not performed)" and less than a predetermined value dp0, and the command pressing force Fps is calculated to monotonously increase from "0" corresponding to an increase in the operation amount Bpa in a range where the operation amount Bpa is greater than or equal to the predetermined value bp0.Here, the predetermined value bp0 is a value corresponding to an “idle” of the brake operating element bp, and is referred to as an “idle value”.

[0039] In the vehicle wheel slip suppression control block FSC, an adjustment pressing force Fsc is calculated based on a vehicle wheel speed Vwa of each vehicle wheel WH. The adjustment pressing force Fsc is a target value for executing the vehicle wheel slip suppression control. Here, "vehicle wheel slip suppression control" is used to improve vehicle stability by independently and separately controlling the slip states of four vehicle wheels WH of the vehicle. For example, the vehicle wheel slip suppression control is at least one of an anti-skid control (anti-lock control) and a braking force distribution control (electronic braking force distribution control). In the vehicle wheel slip suppression control block FSC, the adjustment pressing force Fsc is calculated for executing at least one of the anti-skid control and the braking force distribution control.

[0040] In the vehicle wheel slip suppression control block FSC, the adjustment pressing force Fsc for the anti-skid control is calculated. Specifically, the adjustment pressing force Fsc for executing the anti-skid control is calculated so as to prevent vehicle wheel lock based on the acquisition result (the vehicle wheel speed Vwa) of the vehicle wheel speed sensor VWA provided in each vehicle wheel WH. For example, a vehicle wheel slip state amount Slp (a control variable indicating the deceleration slip state of the vehicle wheel) is calculated based on the vehicle wheel speed Vwa. Then, an adjustment pressing force Fsc is determined based on the vehicle wheel slip state amount Slp.

[0041] Here, the vehicle wheel slip state amount Slp is a state amount or a state quantity (a variable) indicating the slip degree of the vehicle wheel WH. For example, the vehicle wheel slip state amount Slp is calculated based on at least one of the vehicle wheel slip speed and the vehicle wheel deceleration speed. Here, the vehicle wheel slip speed is calculated based on a difference between the vehicle wheel speed Vwa and a "vehicle body speed Vxa calculated based on the vehicle wheel speed Vwa of each vehicle wheel WH of the vehicle." Further, the vehicle wheel deceleration speed is calculated by differentiating the vehicle wheel speed Vwa with respect to time.Then, the adjustment pressing force Fsc is calculated such that the anti-skid control is started at a time when the vehicle wheel slip state amount Slp exceeds a predetermined amount slx and the command pressing force Fps decreases. Here, the predetermined amount slx is a certain threshold value (a constant) for determining whether the anti-skid control is to be executed.

[0042] Similarly, in the vehicle wheel slip suppression control block FSC, the adjustment pressing force Fsc is calculated to perform the braking force distribution control for suppressing the vehicle wheel slip of the rear wheel based on the acquisition result (the vehicle wheel speed Vwa) of the vehicle wheel speed sensor VWA. Specifically, the adjustment pressing force Fsc of the rear wheel is determined based on the slip state amount Slp of the rear wheel with respect to the slip state amount Slp of the front wheel. Specifically, the adjustment pressing force Fsc is calculated such that the braking force distribution control is started at a time point when a difference between the front wheel slip speed and the rear wheel slip speed exceeds the predetermined speed slz and the command pressing force Fps is uniformly maintained.Here, the predetermined speed slz is a certain threshold value (a constant) for determining whether the braking force distribution control is to be executed.

[0043] In the target pressing force calculation block FPT, a target pressing force Fpt is calculated based on the command pressing force Fps and the adjustment pressing force Fsc. Here, the target pressing force Fpt indicates a final target pressing force and corresponds to a demand braking force for the vehicle wheel WH. When the vehicle wheel slip suppression control is not executed, the command pressing force Fps is directly determined as the target pressing force Fpt. When the vehicle wheel slip suppression control is executed, the command pressing force Fps is adjusted by the adjustment pressing force Fsc, so that the final target pressing force Fpt is calculated. For example, when the anti-skid control is executed in the vehicle wheel slip suppression control block FSC, the command pressing force Fps is adjusted to decrease by the adjustment pressing force Fsc to prevent the vehicle wheel from locking.Furthermore, when the braking force distribution control is executed in the vehicle wheel slip suppression control block FSC, the command pressing force Fps is adjusted by the adjustment pressing force Fsc to be maintained, so that an increase in rear wheel slip is suppressed. Detailed processing of the vehicle wheel slip suppression control block FSC and the target pressing force calculation block FPT will be described below.

[0044] In the command current calculation block IMS, a command current Ims of the electric motor MTR is calculated based on the target pressing force Fpt and a predetermined calculation characteristic (a calculation map) CIms. Here, the command current Ims is a target value of a current for controlling the electric motor MTR. In the calculation characteristic CIms, the command current Ims is determined such that the command current Ims increases monotonically from "0" as the target pressing force Fpt increases from "0."

[0045] In the pressing force control block FFB, a compensation current Ifp of the electric motor MTR is calculated based on the pressing force command value (e.g., the target fluid pressure) Fpt and the pressing force actual value (the fluid pressure detection value) Fpa, which are control state variables. Since an error in the pressing force is generated only by control based on the command current Ims, compensation for the error is performed in the pressing force control block FFB. The pressing force control block FFB includes a comparison calculation and a compensation current calculation block IFP.

[0046] Through the comparison calculation, the target value Fpt (corresponding to the demand braking force of the vehicle wheel WH) and the actual value Fpa (corresponding to the actually generated braking force) of the pressing force are compared. Here, the actual value Fpa of the pressing force is a detection value detected by a pressing force sensor FPA (for example, the fluid pressure sensor that detects the fluid pressure of the pressurizing cylinder KCL). In the comparison calculation, a deviation (a pressing force deviation) eFp between the target pressing force (the target value) Fpt and the actual pressing force (the detection value) Fpa is calculated. The pressing force deviation eFp is input to the compensation current calculation block IFP as a control variable.

[0047] The compensation current calculation block IFP comprises a proportional element block, a differential element block, and an integral element block. In the proportional element block, the pressing force deviation eFp is multiplied by a proportional gain Kp to calculate the proportional element of the pressing force deviation eFp. In the differential element block, the pressing force deviation eFp is differentiated, and the result is multiplied by a differential gain Kd to calculate the differential element of the pressing force deviation eFp. In the integral element block, the pressing force deviation eFp is integrated, and the result is multiplied by an integral gain Ki to calculate the integral element of the pressing force deviation eFp. The proportional element, the differential element, and the integral element are then added to calculate the compensation current Ifp.That is, in the compensation current calculation block IFP, a so-called PID control based on the pressing force is executed based on the comparison result (the pressing force deviation eFp) between the target pressing force Fpt and the actual pressing force Fpa, so that the actual pressing force (the detection value) Fpa is consistent with the target pressing force (the set value) Fpt (that is, the deviation eFp approaches “0 (zero)”).

[0048] In the command current calculation block IMT, the command current Ims, a command current (a command current vector) Imt, which is a final command value of a current, is calculated based on the compensation current (the compensation value due to the pressing force control) Ifp and the rotation angle Mka. The command current Imt is a dq-axis vector and includes a d-axis element (also referred to as a "d-axis command current") Idt and a q-axis element (also referred to as a "q-axis command current") Iqt. Furthermore, the command current Imt is also referred to as a command current vector (Idt, Iqt). Detailed processing of the command current calculation block IMT is described below.

[0049] In the target current calculation block IMT, the sign (positive or negative value) of the target current Imt is determined based on the rotation direction of the electric motor MTR (i.e., the pressing force increase / decrease direction). Furthermore, the magnitude of the target current Imt is calculated based on the rotational power to be output to the electric motor MTR (i.e., the pressing force increase / decrease amount). Specifically, when the pressing force is increased, the sign of the target current Imt is calculated as a positive sign (Imt>0), and the electric motor MTR is driven in the normal rotation direction. Meanwhile, when the pressing force is decreased, the sign of the target current Imt is determined as a negative sign (Imt<0), and the electric motor is driven in a reverse rotation direction.Further, the output torque (rotational power) of the electric motor MTR is controlled to increase as the absolute value of the target current Imt decreases, and the output torque is controlled to decrease as the absolute value of the target current Imt decreases.

[0050] In the switching control block SWT, the drive signals Sux to Swz for performing pulse width modulation on the switching elements SUX to SWZ are calculated based on the target current Imt (Igt, Iqt). Based on the target current Imt and the rotation angle Mka, a target value Imt (a general term for target voltages Eut, Evt, and Ebt of respective phases) of each of the U-, V-, and B-phase voltages is calculated. A duty cycle Dtt (a general term for duty cycles Dut, Dvt, and Dwt of respective phases) of a pulse width of each phase is determined based on the target voltage Imt of each phase. Here, the "duty cycle" is a ratio of an ON time to one cycle, with "100%" corresponding to full power supply.Then, the drive signals Sux to Swz are calculated based on the duty cycle (the set value) Dtt to determine whether the switching elements SUX to SWZ constituting the three-phase bridge circuit should be set to an ON state (a power supply state) or an OFF state (a non-power supply state). The drive signals Sux to Swz are output to the drive circuit DRV.

[0051] The energization or de-energization states of six switching elements SUX to SWZ are individually controlled by six control signals Sux to Swz. Since the energization time per unit time of each switching element increases as the duty cycle Dtt (a general term for the respective phases) increases, a larger current flows to the coils CLU, CLV, and CLW. Thus, the rotational power of the electric motor MTR is adjusted to be large.

[0052] In the drive circuit DRV, a current sensor IMA (a general name for current sensors IUA, IVA, and IWA of respective phases) is provided in each phase, and the actual current Ima (a general name for the actual currents Iua, Iva, and Iwa of respective phases) is detected. The detected value Ima (a general name) of each phase is input to the switching control block SWT. Then, a so-called current control is performed so that the detected value Ima of each phase is consistent with the set value Imt. Specifically, the duty cycle Dtt (a general name for the duty cycles Dut, Dvt, and Dwt of respective phases) is individually corrected (fine-tuned) based on a deviation eIm between the actual current Ima and the set current Imt of each phase, so that the current deviation eIm approaches "0." Through current control, high-precision motor control can be achieved.

[0053] In the electromagnetic valve control block SLC, the drive signals Vsm and Vkr for controlling the electromagnetic valves VSM and VKR are calculated based on the brake application amount Bpa. When the application amount Bpa is less than the idle value bp0 (specifically, in a case where "Bpa = 0"), the drive signal Vsm is determined such that the simulator cut-off valve VSM is located at the open position in response to the non-brake application state (for example, when the cut-off valve VSM is an NC valve, the drive signal Vsm indicates non-energization). At the same time, in the case of "Bpa < bp0," the drive signal Vkr is calculated such that the "master cylinder MC is in communication with the wheel cylinder WC and the pressurizing cylinder KCL is isolated from the wheel cylinder WC (referred to as a non-energization state)."

[0054] A time point after the brake application amount Bpa has increased so that the brake application amount Bpa becomes greater than or equal to the idle value bp0 corresponds to the brake application state, and the drive signal Vsm is determined such that the cutoff valve VSM changes from the closed position to the open position at that time (at the brake application start time). If the cutoff valve VSM is an NC valve, an energization command is started as the drive signal Vsm at the brake application start time. Further, the drive signal Vkr is determined at the brake application start time such that the master cylinder MC is isolated from the wheel cylinder WC and the pressurizing cylinder KCL is in communication with the wheel cylinder WC (which is referred to as an energization state). <Verarbeitungen des Fahrzeugradschlupfunterdrückungssteuerungsblocks FSC und des Solldrückkraftberechnungsblocks FPT>

[0055] With reference to the flow chart according to Fig. 3, the processing of the vehicle wheel slip suppression control block FSC and the target pressing force calculation block FPT are described.

[0056] In step S110, the vehicle wheel speed Vwa of each of the four vehicle wheels WH of the vehicle is read. The vehicle wheel speed Vwa is detected by the vehicle wheel speed sensor Vwa provided in each vehicle wheel WH. In step S120, the vehicle body speed Vxa is calculated based on the vehicle wheel speed Vwa.

[0057] For example, a maximum value of four vehicle wheel speeds Vwa is used as the vehicle body speed Vxa.

[0058] In step S130, the vehicle wheel slip state amount Slp of each vehicle wheel WH is calculated based on the vehicle wheel speed Vwa. The vehicle wheel slip state amount Slp is a state amount or a state quantity (a variable) indicating the slip degree of the vehicle wheel WH. For example, a slip speed, which is a deviation between the vehicle body speed Vxa and the vehicle wheel speed Vwa, is substituted as the vehicle wheel slip state amount Slp. Further, a vehicle wheel deceleration speed obtained by differentiating the vehicle wheel speed Vwa is substituted as the vehicle wheel slip state amount Slp. That is, the vehicle wheel slip state amount Slp is calculated based on at least one of the vehicle wheel slip speed and the vehicle wheel deceleration speed.Here, the vehicle wheel slip ratio is calculated by non-dimensioning the vehicle wheel slip speed by the vehicle body speed Vxa, and the vehicle wheel slip ratio can be used as a parameter of the vehicle wheel slip state amount Slp.

[0059] In step S140, it is determined whether the "vehicle wheel slip suppression control execution condition is satisfied or not." If the vehicle wheel slip suppression control is the anti-skid control, it is determined whether the "vehicle wheel slip state amount Slp exceeds the predetermined amount slx or not." Here, the predetermined amount slx is a determination threshold for the anti-skid control, and it is a predetermined value. Further, if the vehicle wheel slip suppression control is the braking force distribution control, it is determined whether a "difference between the front wheel slip speed and the rear wheel slip speed exceeds the predetermined speed slz or not (or whether a difference between the front wheel slip ratio and the rear wheel slip ratio exceeds the predetermined value slz or not)."Here, the predetermined speed slz is a determination threshold for the braking force distribution control, and is a predetermined value.

[0060] If the vehicle wheel slip suppression control execution condition is satisfied and the determination in step S140 is affirmative (a case of "YES"), the processing proceeds to step S150. Meanwhile, if the vehicle wheel slip suppression control execution condition is not satisfied and the determination in step S140 is negative (a case of "NO"), the processing proceeds to step S170.

[0061] In step S150, a control flag FLsc is set to "1." The control flag FLsc is a signal indicating the execution / non-execution state of the vehicle wheel slip suppression control; it is set to "1" in the execution state and to "0" in the non-execution state. Thus, the control flag FLsc is switched from "0" to "1" at the time of starting the vehicle wheel slip suppression control. Further, the control flag FLsc is switched from "1" to "0" at the time of ending the vehicle wheel slip suppression control.

[0062] In step S160, the adjustment pressing force FLsc is calculated based on the vehicle wheel slip state amount Slp. The adjustment pressing force Fsc is a target pressing force value used to calculate the final target pressing force Fpt by adjusting the command pressing force Fps. When the vehicle wheel slip suppression control is anti-skid control, the adjustment pressing force Fsc is determined such that the vehicle wheel slip does not become excessive. Further, when the vehicle wheel slip suppression control is braking force distribution control, the adjustment pressing force Fsc is determined such that the rear wheel slip comes within a predetermined range of the front wheel slip.

[0063] In step S170, the command pressing force Fps and the actual pressing force Fpa are read. The command pressing force Fps is calculated based on the brake application amount Bpa.

[0064] In step S180, the target pressing force Fpt is calculated based on the command pressing force Fps, the actual pressing force Fpa, and the adjustment pressing force Fsc. When the vehicle wheel slip suppression control is not executed and the determination in step S140 is negative, "FLsc = 0" and "Fsc = 0" are satisfied. In this case, in step S180, the command pressing force Fps is directly determined as the target pressing force Fpt. Then, the pressing force control is executed based on the target pressing force Fpt (= Fps) and the actual pressing force Fpa.

[0065] When the vehicle wheel slip suppression control is executed (when the determination in step S140 is affirmative), the target pressing force Fpt of the current calculation period is calculated based on the target pressing force Fpt of the previous calculation period and the adjustment pressing force Fsc of the current calculation period in step S180. That is, the target pressing force Fpt of the current calculation period is determined by adjusting the adjustment pressing force Fsc of the current calculation period with reference to the target pressing force Fpt of the previous calculation period.

[0066] Specifically, in step S180, the target pressing force Fpt is determined based on the actual pressing force Fpa and the adjustment pressing force Fsc at a vehicle wheel slip suppression control start time point (i.e., a corresponding calculation period). Specifically, in the calculation period in which the control flag FLsc changes from "0" to "1", the actual pressing force Fpa of the current calculation period (i.e., the control start time point) is set as a reference, and the target pressing force Fpt of the current calculation period is calculated by adding the adjustment pressing force Fsc of the current calculation period thereto. In other words, the target pressing force Fpt is calculated by correcting the command pressing force Fps to quickly decrease to the value of the actual pressing force Fpa at the control execution start time point at the time of starting the execution of the vehicle wheel slip suppression control.

[0067] In step S190, the target pressing force (current value) Fpt is stored according to step S180. The stored target pressing force Fpt is used as a reference for calculating the target pressing force Fpt in the next calculation period. That is, a new target pressing force Fpt (of the current calculation period) is determined by correcting the past target pressing force Fpt (calculated in the previous calculation period) by the adjustment pressing force Fsc after the vehicle wheel slip suppression control start time.

[0068] When the brake operating element BP is rapidly applied, the follow-up of the actual pressing force Fpa with respect to an increase in the command pressing force Fps is slow with respect to time. However, at the time point (the calculation period) when the vehicle degree slip suppression control starts, the target pressing force Fpt is determined by rapidly reducing the command pressing force Fps to the value of the actual pressing force Fpa at that time. For this reason, since the interference between the pressing force control and the vehicle wheel slip suppression control is avoided, the actual pressing force Fpa decreases with high responsiveness. As a result, it is possible to suppress the occurrence of excessive vehicle wheel slip due to the follow-up delay.Furthermore, even if the command pressing force Fps is large during the execution of the vehicle wheel slip suppression control, the actual pressing force Fpa is controlled by referring to the target pressing force (the previous value) Fpt calculated at the previous calculation period. Therefore, the vehicle wheel slip suppression control can be continued appropriately. <Erstes Verarbeitungsbeispiel des Sollstromberechnungsblocks IMT>

[0069] A first processing example of the target current calculation block IMT will be described with reference to the flowcharts according to the Fig. 4 and Fig. 5 and the characteristic diagram according to Fig. 6. This corresponds to Fig. 4 a processing during the non-execution of the vehicle wheel slip suppression control, wherein Fig. 5 corresponds to processing during execution of the vehicle wheel slip suppression control. < <Ablauf der Verarbeitung während der Nicht-Ausführung der Fahrzeugradschlupfunterdrückungssteuerung > >

[0070] First, a flow of processing of the target current calculation block IMT during non-execution of the vehicle wheel slip suppression control will be described with reference to the flowchart of Fig. 4 described.

[0071] In step S210, the command current Ims, the compensation current Ifp, the rotation angle Mka, the current limiting circuit Cis, and the control flag FLsc are read. Here, the current limiting circuit Cis is set in advance based on the allowable current (the maximum current value to be supplied as power) ipm of the switching elements SUX to SWZ (components of the drive circuit DRV) in the current characteristic (dq-axis plane) of the q-axis current and the d-axis current of the electric motor MTR. That is, the current limiting circuit Cis is determined from the specification of the drive circuit DRV (specifically, the current ratings iqm of the switching elements SUX to SWZ). Here, the predetermined value iqm is referred to as a "maximum q-axis current value."

[0072] In step S220, a compensation command current Imr is calculated based on the command current Ims and the compensation current Ifp based on the pressing force control. Here, the compensation command current Imr is a command current compensated based on the pressing force control. Specifically, the compensation command current Imr is determined by adding the compensation current Ifp to the command current Ims (Imr = Ims + Ifp).

[0073] In step S230, an electrical angular velocity ω of the electric motor MTR is calculated based on the detection value (rotation angle) Mka of the rotation angle sensor MKA. Specifically, the electrical angular velocity ω is determined by converting the rotation angle (mechanical angle) Mka into an electrical angle θ and differentiating the electrical angle θ with respect to time. Here, the "mechanical angle Mka" corresponds to the rotation angle of the output shaft of the electric motor MTR. Furthermore, the "electrical angle θ" is an angle in which one cycle of the magnetic field of the electric motor MTR is expressed as 2π [rad]. Furthermore, the electrical angle θ can be directly detected by the rotation angle sensor MKA.

[0074] In step S240, it is determined whether or not the "vehicle wheel slip suppression control is being executed (that is, whether the control flag FLsc is "1" or "0")". If "FLsc = 1" is satisfied and the determination in step S240 is affirmative (a case of "YES"), the processing proceeds to step S50 (see (A)). Meanwhile, if "FLsc = 0" is satisfied and the determination in step S240 is negative (a case of "NO"), the processing proceeds to step S250.

[0075] In step S250, the voltage limiting circuit Cvs is calculated based on the electrical angular velocity θ of the electric motor MTR. Specifically, the voltage limiting circuit Cvs is calculated based on the "predetermined values ​​of a power supply voltage (i.e., voltages of a storage battery BAT and a generator ALT) Iba, a phase inductance (i.e., inductances of the coils CLU, CLV, and CLW) L, and the number of flux connections (i.e., a magnetic strength) Φ" in the dq-axis current characteristic (Idt-Iqt plane) of the electric motor MTR, and the "electrical angular velocity ω of the electric motor MTR calculated from the rotation angle Mka." The radius of the voltage limiting circuit Cvs decreases as the rotational speed dMk of the electric motor MTR increases, and the radius of the voltage limiting circuit Cvs increases as the rotational speed dMk decreases.

[0076] In step S260, two points Pxa (Idx, Iqx) and Pxb (Idx - Iqx) at which the current limiting circuit Cis intersects the voltage limiting circuit Cvs on the dq-axis current plane are calculated based on the current limiting circuit Cis and the voltage limiting circuit Cvs. Here, the values ​​Idx and Iqx (or -Iqx) are variables indicating the dq-axis coordinates of the intersection points Pxa and Pxb. Furthermore, an intersection point Pxa (Idx, Iqx) corresponds to the normal rotation direction of the electric motor MTR and is referred to as a "first intersection point Pxa." Furthermore, an intersection point Pxb (Idx, -Iqx) corresponds to the reverse rotation direction of the electric motor MTR and is referred to as a "second intersection point Pxb." Two intersection points Pxa and Pxb are also referred to as one “intersection point Px” as a general term.

[0077] The overlap region between the current limiting circuit Cis and the voltage limiting circuit Cvs is actually a current range (also called an "energizable region") that can be reached by current control. Thus, even if a command different from the energizable region is given, the current command cannot actually be achieved in current control. Furthermore, when the rotational speed dMk is low (for example, when the electric motor MTR is stopped), the intersection point Px (a general term for Pxa and Pxb) does not exist in some cases.

[0078] In step S270, it is determined whether the "compensation command current Imr is greater than or equal to "0" or not." That is, it is determined whether the "compensation command current Imr commands the normal rotation direction or the reverse rotation direction of the electric motor MTR." If "Imr ≥ 0" and the determination in step S270 is affirmative (a case of "YES"), the processing proceeds to step S280. Meanwhile, if "Imr < 0" and the determination in step S270 is negative (a case of "NO"), the processing proceeds to step S310.

[0079] In step S280, it is determined whether the "current limiting circuit Cis is included in the voltage limiting circuit Cvs or not" or whether the "first intersection point Pxa (Idx, Iqx) exists in the first quadrant of the dq-axis current plane or not." Here, the "first quadrant" is a region where both the d-axis current and the q-axis current are positive. If the determination in step S280 is affirmative (a case of "YES"), processing proceeds to step S300. Meanwhile, if the determination in step S280 is negative (a case of "NO"), processing proceeds to step S290.

[0080] In step S290, it is determined whether the "compensation instruction current Imr is greater than or equal to the q-axis coordinate Iqx (of the variable) of the first intersection point Pxa" based on the compensation instruction current Imr and the coordinate (Idx, Iqx) of the first intersection point Pxa. If the determination in step S290 is affirmative (a case of "YES"), processing proceeds to step S400. Meanwhile, if the determination in step S290 is negative (a case of "NO"), processing proceeds to step S410.

[0081] In step S300, it is determined whether the "compensation command current Imr is less than or equal to the q-axis intercept iqm (the maximum q-axis current value) of the current limiting circuit Cis" based on the compensation command current Imr and the current limiting circuit Cis. If the determination in step S300 is affirmative (a case of "YES"), the processing proceeds to step S430. Meanwhile, if the determination in step S300 is negative (a case of "NO"), the processing proceeds to step S440.

[0082] In step S310, it is determined whether the "current limiting circuit Cis is included in the voltage limiting circuit Cvs or not" or whether the "second intersection point Pxb (Idx, -Iqx) is included in the fourth quadrant of the dq-axis current plane or not." Here, the "fourth quadrant" is a region where the d-axis current is positive and the q-axis current is negative. If the determination in step S310 is affirmative (a case of "YES"), processing proceeds to step S330. Meanwhile, if the determination in step S310 is negative (a case of "NO"), processing proceeds to step S320.

[0083] In step S320, it is determined whether the compensation instruction current Imr is smaller than the q-axis coordinate -Iqx (the variable) of the second intersection point Pxb or not based on the compensation instruction current Imr and the coordinate (Idx, -Iqx) of the second intersection point Pxb. If the determination in step S320 is affirmative (a case of "YES"), the processing proceeds to step S450. Meanwhile, if the determination in step S320 is negative (a case of "NO"), the processing proceeds to step S460.

[0084] In step S330, it is determined whether the "compensation command current Imr is less than the q-axis intercept -iqm (the minimum q-axis current value) of the current limiting circuit Cis" based on the compensation command current Imr and the current limiting circuit Cis. If the determination in step S330 is affirmative (a case of "YES"), the processing proceeds to step S480. Meanwhile, if the determination in step S330 is negative (a case of "NO"), the processing proceeds to step S490.

[0085] In step S400, the d-axis command current Idt is determined as an intersection d-axis coordinate Idx (which is a variable and is also referred to as a "first intersection d-axis coordinate"), and the q-axis command current Iqt is determined as an intersection q-axis coordinate Iqx (which is a variable and is also referred to as a "first intersection q-axis coordinate") (that is, "Idt = Idx, Iqt = Iqx"). In step S410, a voltage limiting circuit d-axis coordinate Ids (which is a variable and is simply referred to as a "limiting circuit d-axis coordinate") is calculated based on the compensation command current Imr and the voltage limiting circuit Cvs. Specifically, the limiting circle d-axis coordinate Ids is a d-axis coordinate of an intersection point of the voltage limiting circle Cvs, where “Iqt = Imr”.That is, the coordinate indicates a value (a coordinate) of the d-axis command current Idt when the compensation command current Imr is supplied to the q-axis command current Iqt in the voltage limiting circuit Cvs (see equation (2) described below). Then, in step S420, the d-axis command current Idt is determined to coincide with the voltage limiting circuit d-axis coordinate Ids, and the q-axis command current Iqt is determined to coincide with the compensation command current Imr (that is, "Idt = Ids, Iqt = Imr").

[0086] In step S430, the d-axis command current Idt is determined to be "0," and the q-axis command current Iqt is determined to be the maximum q-axis current value ipm (the predetermined value) (i.e., "Idt = 0, Iqt = iqm"). In step S440, the d-axis command current Idt is determined to be "0," and the q-axis command current Iqt is determined to be the same as the compensation command current Imr (i.e., Idt = 0, Iqt = Imr).

[0087] In step S450, the d-axis command current Idt is determined as an intersection d-axis coordinate Idx (which is a variable and also referred to as a "second intersection d-axis coordinate"), and the q-axis command current Iqt is determined as an intersection q-axis coordinate Iqx (which is a variable and also referred to as a "second intersection q-axis coordinate") (that is, "Idt = Idx, Iqt = -Iqx"). In step S460, similarly to step S410, the limiting circuit d-axis coordinate Ids (a value of the d-axis command current Idt in the voltage limiting circuit Cvs in the case of "Iqt = Imr") is calculated based on the compensation command current Imr and the voltage limiting circuit Cvs.Then, in step S470, the d-axis command current Idt is determined to coincide with the limiting circle d-axis coordinate Ids, and the q-axis command current Iqt is determined to coincide with the compensation command current Imr (that is, “Idt = Ids, Iqt = Imr”).

[0088] In step S480, the d-axis target current Idt is determined to be "0," and the q-axis target current Iqt is determined to be a minimum q-axis current value -iqm (a predetermined value) (i.e., "Idt = 0, Iqt = -iqm"). In step S490, the d-axis target current Idt is determined to be "0," and the q-axis target current Iqt is determined to be the same as the compensation command current Imr (i.e., Idt = 0, Iqt = Imr). As described above, a flow of processing during non-execution of the vehicle wheel slip suppression control has been described. <<Ablauf der Verarbeitung während einer Ausführung der Fahrzeugradschlupfunterdrückungssteuerung> >

[0089] Next, a flow of processing of the target current calculation block IMT during the execution of the vehicle wheel slip suppression control will be described with reference to the flowchart of Fig. 5. Since the processing from step S210 to step S240 is the same, a description thereof is omitted.

[0090] The processing from step S550 to step S630 is the same as that from step S250 to S330. Furthermore, the processing from step S700 to step S790 is the same as that from step S400 to step S490 at the time of determining the dq-axis target currents Idt and Iqt. Thus, processing during non-execution of the vehicle wheel slip suppression control described with reference to Fig. 4, as a processing during the execution of the vehicle wheel slip suppression control described with reference to Fig. 5. Specifically, in the first half of each step symbol, one in which "S2" is replaced with "S5", "S3" is replaced with "S6", and "S4" is replaced with "S7" corresponds to the description of the processing during the execution of the vehicle wheel slip suppression control. < <Sollstromvektor Imt (Idt, Iqt) einer Korrelation des Strombegrenzungskreises Cis und des Spannungsbegrenzungskreises Cvs> >

[0091] Next, a processing for determining a target current vector Imt (Idt, Iqt) (i.e., a processing from step S400 to step S490 and a processing from step S700 to step S790) is carried out with reference to the characteristic diagram according to Fig. 6. Furthermore, steps S400 to S440 and steps S700 to S740 correspond to a case where the electric motor MTR is driven in the normal rotation direction (i.e., "Imr ≥ 0"). Furthermore, steps S450 to S490 and steps S750 to S790 correspond to a case where the electric motor MTR is driven in the reverse rotation direction (i.e., "Imr < 0").

[0092] The current limiting circuit Cis is determined based on the maximum rating (rated current iqm) of the switching element constituting the drive circuit DRV (specifically, a bridge circuit BRG). Here, the maximum rating is determined as the maximum allowable values ​​of the current flowing in the switching element (a power MOSFET or the like), the applicable voltage, the electrical power loss, and the like.

[0093] Specifically, the current limiting circuit Cis is expressed as a circle centered on an origin O (a point corresponding to "Idt = 0 and Iqt = 0") in the dq-axis current characteristic (Idt-Iqt plane). Furthermore, the radius of the current limiting circuit Cis is the allowable current value iqm (the predetermined value) of each of the switching elements SUX to SWZ. That is, the current limiting circuit Cis intersects the q-axis at the points (0, iqm) and (0, -iqm), while intersecting the d-axis at the points (-iqm, 0) and (iqm, 0). The current limiting circuit Cis in the dq-axis current characteristic is determined by an equation (1). Idt2+Iqt2=iqm2

[0094] Furthermore, the voltage limiting circuit Cvs in the dq-axis current characteristic of the electric motor MTR is determined by an equation (2). {Idt+(Φ / L)}2+Iqt2={Eba / (L⋅ω)}2

[0095] Here, "Eba" indicates the power supply voltage (i.e., the voltages of the storage battery BAT and the generator ALT), "L" indicates the phase inductance, and "Φ" indicates the number of flux connections (the magnetic strength). Furthermore, "ω" indicates the electrical angular velocity of the electric motor MTR. Furthermore, the electrical angular velocity ω indicates an amount of change of the electrical angle θ (an angle at which one cycle of the magnetic field of the electric motor MTR is expressed as 2π [rad]) of the electric motor MTR with time, and is calculated from the rotation angle Mka.

[0096] The voltage limiting circuit Cvs is expressed as a circle in which the coordinate of the center point Pcn is (idc, 0) (-(Φ / L), 0) and the radius is "Eba" / (L ω). The power supply voltage Eba is a predetermined value (a constant), and the electrical angular velocity ω increases as the speed dMk increases. For this reason, the radius of the voltage limiting circuit Cvs decreases as the speed dMk increases. In contrast, the radius of the voltage limiting circuit Cvs increases as the speed dMk decreases.

[0097] A case where the rotational speed dMk (i.e., the electrical angular velocity ω) of the electric motor MTR is relatively large is indicated by the voltage limiting circuit Cvs:a. In this state, in the correlation between the current limiting circuit Cis and the voltage limiting circuit Cvs:a, the current limiting circuit Cis and the voltage limiting circuit Cvs:a intersect each other at two points Pxa:a and Pxb:a. In this state, since a first intersection point Pxa:a exists in the second quadrant and a second intersection point Pxb:a exists in the third quadrant, the determination processing in steps S280, S310, S580, and S610 is negative.

[0098] Furthermore, at two intersection points Pxa and Pxb, the intersection point Pxa (the first intersection point), where the q-axis target current Iqt is positive, corresponds to the normal rotation direction of the electric motor MTR. Furthermore, at two intersection points Pxa and Pxb, the intersection point Pxb (the second intersection point), where the q-axis target current Iqt is negative, corresponds to the reverse rotation direction of the electric motor MTR.

[0099] In this state, the determination processing in steps S290 and S590 is positive in the case where "Imr = iq1 (> Iqx)" is set, so the electric motor MTR is driven in the normal rotation direction. Then, in steps S400 and S700, "Idt = Idx and Iqt = Iqx" are determined. That is, the target current vector Imt is limited to a first intersection d-axis coordinate Idx and a first intersection q-axis element Iqx of respective elements of the dq axes based on the coordinate (Idx, Iqx) of the first intersection point Pxa.

[0100] Furthermore, in the case of "Imr = iq4 (< -Iqx)", the determination processing in steps S320 and S620 is positive, so the electric motor MTR is driven in the reverse rotation direction. Then, in steps S450 and S750, "Idt = Idx and Iqt = -Iqx" are determined. That is, the target current vector Imt is limited to a second intersection d-axis coordinate Idx and a second intersection q-axis element -Iqx of respective elements of the dq axes based on the coordinate (Idx, -Iqx) of the second intersection point Pxb.

[0101] When supplying power to the electric motor MTR, the dq-axis current that can actually flow during current control corresponds to a region (a shaded region and an energizable region) where the current limiting circuit Cis and the voltage limiting circuit Cvs overlap. If control is performed while deviating from the energizable region, the driving of the electric motor MTR becomes insufficient, and an overload (a load exceeding a rated current) may be temporarily applied to the switching element.

[0102] The intersection point Pxa:a and Pxb:a on the boundary of the energizable region indicates a point at which the output (which is a work amount per unit time and a work rate) becomes maximum. Therefore, when the rotational speed dMk is relatively high and the absolute value of the compensation command current Imr is relatively large, a vector Imt:1 (a vector directed from the origin O to the first intersection point Pxa:a) and a vector Imt:4 (a vector directed from the origin O to the second intersection point Pxb:a) are determined as the command current Imt, so that the output (work rate) of the electric motor MTR becomes maximum.

[0103] The first intersection point Pxa:a, where the q-axis command current Iqt is positive, indicates a maximum output point when the electric motor MTR is driven in the normal rotation direction. For example, when the brake actuator BP is rapidly applied and the electric motor MTR is rapidly accelerated from a stop state, the first intersection point Pxa:a is determined as the command current vector Imt:1. Since the command current vector Imt (Idt, Iqt) is determined as the first intersection point Pxa (Idx, Iqx), the actual pressing force Fpa can be most effectively increased with high responsiveness.

[0104] The second intersection point Pxb:a, where the q-axis target current Iqt is negative, indicates a maximum output point when the electric motor MTR is driven in the reverse rotation direction. For example, when the electric motor MTR is quickly stopped by starting the vehicle wheel slip suppression control while the electric motor MTR is driven in the normal rotation direction, the second intersection point Pxb:a is determined as the target current vector Imt:4. Since the target current vector Imt (Idt, Iqt) is determined as the second intersection point Pxb (Idx, -Iqx), the actual pressing force Fpa can be reduced in the most effective way with high responsiveness.

[0105] Meanwhile, when the absolute value of the compensation command current Imr is relatively small (for example, a case of "Imr = iq2 (< Iqx)" and "Imr = iq5 (> -Iqx)"), the determination processing in steps S290, S320, S590, and S620 is negative. Then, in steps S410, S460, S710, and S760, the voltage limiting circuit d-axis coordinate Ids is calculated based on the compensation command current Imr and the voltage limiting circuit Cvs. The limiting circuit d-axis coordinate Ids indicates a value (coordinate) of the d-axis command current Idt when the q-axis command current Iqt is the compensation command current Imr in the voltage limiting circuit Cvs. Specifically, the compensation command current Imr is applied to the q-axis command current Iqt of equation (2), and the calculated d-axis command current Idt is substituted as the limiting circle d-axis coordinate Ids. In steps S420, S470, S720, and S770, "Idt = Ids and Iqt = Imr" are determined.That is, since the q-axis current is limited by the limiting circuit d-axis coordinate Ids, the target current Imt is determined as vectors Imt: 2 and Imt: 5. In this case, too, since the d-axis target current Idt is sufficiently ensured in the energizable region, the responsiveness of the electric motor MTR can be improved. In addition, since the d-axis target current Idt is set to the voltage limiting circuit Cvs, the electric motor MTR is effectively controlled, thus reducing heat generation.

[0106] A case where the rotational speed dMk is relatively small is indicated by the voltage limiting circuit Cvs:b. In this state, the current limiting circuit Cis intersects the voltage limiting circuit Cvs:b at the points Pxa:b and Pxb:b in the correlation between the current limiting circuit Cis and the voltage limiting circuit Cvs:b. In this state, since the first intersection point Pxa:b exists in the first quadrant and the second intersection point Pxb:b exists in the fourth quadrant, the determination processing in steps S280, S310, S580, and S610 is positive.

[0107] In this state, the determination processing in steps S300 and S600 is positive in the case of "Imr = iq3 (> iqm)", which is set so that the electric motor MTR is driven in the normal rotation direction. Then, in steps S430 and S730, "Idt = 0 and Iqt = iqm" are determined. That is, a vector Imt: 3 (a vector directed from the origin O to the point (0, iqm)) is calculated as the target current vector Imt. Furthermore, the determination processing in steps S330 and S630 is positive in the case of "Imr = iq6 (< -iqm)", which is set so that the electric motor MTR is driven in the reverse rotation direction. Then, in steps S480 and S780, "Idt = 0 and Iqt = -imq" are determined.

[0108] When the speed dMk is relatively low, magnetic flux weakening control is not required, and "Idt = 0" is set. The d-axis current and the q-axis current have a balance relationship. Therefore, by setting the d-axis command current Idt to "0," it is possible to maximize the q-axis command current Iqt, which acts in the torque direction during energization of the electric motor MTR.

[0109] A case where the rotational speed dMk remains low and the electric motor MTR is substantially stopped is indicated by a voltage limiting circuit Cvs:c. In this state, the current limiting circuit Cis is included in the voltage limiting circuit Cvs:c, and there is no intersection point Px. Thus, the determination processing in steps S280, S310, S580, and S610 is positive as described above. Further, the determination processing in steps S300, S330, S600, and S630 is negative. Then, in steps S440, S490, S740, and S790, "Idt = 0 and Iqt = Imr" are determined. Also, in this case, the magnetic flux weakening control is not required, and the electric motor MTR is driven only based on the required compensation command current Imr (i.e., the request torque).

[0110] Furthermore, when the rotational speed dMk is relatively low, a point (0, iqm) and (0, -iqm) located on the boundary of the energizable region becomes a maximum output point. Therefore, when the absolute value of the compensation command current Imr exceeds the maximum q-axis current value Iqm, the absolute value of the compensation command current Imr is limited by the maximum q-axis current value (the rated current value) Iqm. Meanwhile, when the absolute value of the compensation command current Imr is less than the maximum q-axis current value Iqm, the limitation of the compensation command current Imr is not performed, and the compensation command current Imr is directly set as the q-axis element of the command current vector Imt. <Zweites Verarbeitungsbeispiel des Sollstromberechnungsblocks IMT>

[0111] A second processing example of the target current calculation block IMT will be explained with reference to the flowchart according to Fig. 7 and the characteristic diagram according to Fig. 8. In the second processing example, the current limiting circuit Cis is increased for a predetermined time tkz from a time when the vehicle wheel slip suppression control starts, thus further improving the responsiveness of the operation for stopping and reversing the electric motor MTR. <<Ablauf der Verarbeitung> >

[0112] First, a flow of processing (particularly when the vehicle wheel slip suppression control is executed) will be described with reference to the flowchart shown in Fig. 7. Here, since a processing step indicated by the same reference numeral as that according to the first processing example is the same as that of the first processing example, a corresponding description will be omitted. In the second processing example, a processing block (S576 or the like) indicated by a dashed line is different from that of the first processing example (see Fig. 5) have been added or changed.

[0113] In the first processing example, the first and second intersection points Pxa and Pxb are calculated in step S560 regardless of the rotation direction of the electric motor MTR. However, in the second processing example, when the electric motor MTR rotates in the normal rotation direction, the first intersection point Pxa is calculated in step S575. Meanwhile, when the electric motor MTR rotates in the reverse rotation direction, the second intersection point Pxb is calculated in step S576. This is because the current limiting circuit Cis is enlarged to stop and reverse the electric motor MTR at the initial stage of the vehicle wheel slip suppression control. These processings will be described in detail below.

[0114] If the processing in step S570 is negative, processing proceeds to step S576. In step S576, the current limiting circle Cis is enlarged. Specifically, the radius of the current limiting circle Cis is changed to the value iqn larger than the maximum q-axis current value iqm. The maximum q-axis current value iqm is the allowable current value of each of the switching elements SUX to SWZ, but the switching elements SUX to SWZ are energized at a value exceeding the allowable current value iqm only for a short time. Here, the value iqn is a predetermined value and is referred to as the "enlarged allowable current value."

[0115] In step S577, the second intersection point Pxb (Idx, -Iqx) is calculated based on the enlarged current limiting circuit Cis and the voltage limiting circuit Cvs. In step S610, it is determined whether or not the "current limiting circuit Cis is included in the voltage limiting circuit Cvs" or whether or not the "second intersection point Pxb (Idx, -Iqx) is present in the fourth quadrant (the d-axis current indicates a region of a positive sign and the q-axis current indicates a region of a negative sign) of the dq-axis current plane" based on the enlarged current limiting circuit Cis and the second intersection point Pxb (Idx, -Iqx). If the determination in step S610 is affirmative (a case of "YES"), the processing proceeds to step S630. After step S630, the same processing as that according to the first processing example is executed.

[0116] Meanwhile, if the determination in S610 is negative (a case of "NO"), the processing proceeds to step S615. In step S615, it is determined whether or not the "intersection d-axis coordinate Idx is less than or equal to a value idc" or whether or not the "voltage limiting circuit Cvs is included in the current limiting circuit Cis" based on the second intersection point Pxb (Idx, -Iqx) or the like. Here, the value idc indicates the d-axis coordinate of the center of the voltage limiting circuit Cvs. If the determination in S615 is negative (a case of "NO"), the processing proceeds to step S620. After step S620, the same processing as that according to the first processing example is executed.

[0117] If the determination in step S615 is affirmative (a case of "YES"), processing proceeds to step S616. In step S616, it is determined whether or not the "compensation command current Imr is less than or equal to the vertex q-axis coordinate Iqp" based on the compensation command current Imr and the vertex q-axis coordinate Iqp. Here, the vertex q-axis coordinate Iqp indicates a q-axis coordinate (a variable) of a point (a vertex Pqp (idc, -Ipq)) at which the absolute value of the q-axis coordinate becomes maximum in the overlap portion of the current limiting circuit Cis and the voltage limiting circuit Cvs. If the determination in S616 is affirmative (a case of "YES"), processing proceeds to step S800. Meanwhile, when the determination in step S616 is negative (a case of “NO”), the processing proceeds to step S810.

[0118] In step S800, the d-axis command current Idt is determined as idc, and the q-axis command current Iqt is determined as the vertex q-axis coordinate -Iqp (the variable) (i.e., "Idt = idc, Iqt = -Iqp"). In step S810, the voltage limiting circuit d-axis coordinate Ids (the variable) is calculated based on the compensation command current Imr and the voltage limiting circuit Cvs. Then, in step S820, the d-axis command current Idt is determined as the voltage limiting circuit d-axis coordinate Ids, and the q-axis command current Iqt is determined as the compensation command current Imr (i.e., "Idt = Ids, Iqt = Imr"). < <Sollstromvektor Imt (Idt, Iqt) der Korrelation beziehungsweise Wechselbeziehung zwischen dem Strombegrenzungskreis Cis und dem Spannungsbegrenzungskreis Cvs> >

[0119] Next, a characteristic of the second processing example will be described with reference to the characteristic diagram according to Fig. 8. In the second processing example, the current limiting circuit Cis is enlarged to exceed the allowable current value iqm only for a short period of time immediately after the execution of the vehicle wheel slip suppression control starts.

[0120] When the vehicle wheel slip suppression control is not executed, the current limiting circuit Cis:e is determined based on the allowable current value iqm. In step S576, a current limiting circuit Cis:f is determined based on the increased allowable current value iqn (> iqm) until the predetermined time tkz has elapsed from the vehicle wheel slip suppression control start time. Specifically, the current limiting circuit Cis:f is determined by replacing the value iqm according to equation (1) with the increased allowable current value iqn. Here, the increased allowable current value iqn is a predetermined value.

[0121] As the current limiting circuit Cis is enlarged from the current limiting circuit Cis:e to the current limiting circuit Cis:f, two intersection points Px change. Specifically, the first and second intersection points Pxa:e and Pxb:e change to the first and second intersection points Pxa:f and Pxb:f. That is, the first and second intersection points Pxa and Pxb move farther away from the q-axis. Since the enlargement of the current limiting circuit Cis corresponds to the stopping and reversing of the electric motor MTR, the second intersection point Pxb:f is considered at the time of a determination of the target current vector Imt (Idt, Iqt). If the determination in step S610 is negative, the processing proceeds to step S615.

[0122] By determining whether the "intersection d-axis coordinate Idx is less than or equal to the value idc" in step S615, it is determined whether the second intersection Pxb is farther from or closer to the q-axis with respect to the "line Lcn passing through the center Pcn (idc, 0) and parallel to the q-axis." If "Idx < idc" and the second intersection Pxb is farther from the q-axis with respect to the line Lcn, as indicated by the second intersection Pxb: f, the processing proceeds to step S616.

[0123] In step S616, it is determined whether the compensation command current Imr is greater than or equal to the vertex q-axis coordinate Iqp. Here, the vertex q-axis coordinate Iqp is the q-axis coordinate of the vertex Pqp (idc, -Ipq) where the absolute value of the q-axis coordinate becomes maximum in a section where the current limiting circuit Cis overlaps the voltage limiting circuit Cvs. Specifically, the vertex Pqp is an intersection point between the line Lcn ("Idt = idc") and the voltage limiting circuit Cvs.

[0124] When the compensation command current Imr (a negative value) is relatively small and "Imr ≤ Iqp" is satisfied, "Idt = idc and Iqt = -Iqp" are calculated in step S800. For example, a command current vector Imt: 6 (a vector directed from the origin O to the vertex Pqp) is determined in the case of "Imr = iq7". The vertex Pqp is an operating point at which the electric motor MTR is most effectively driven. For this reason, compared with a case where the command current vector Imt is determined by the second intersection point Pxb: f, it is possible to more appropriately stop and reverse the electric motor MTR and suppress heat generation.

[0125] When the compensation command current Imr (a negative value) is relatively small and "Imr ≤ Iqp" is not satisfied, the limiting circuit d-axis coordinate Ids is calculated in step S810. Similar to the first processing example, the limiting current d-axis coordinate Ids indicates a value of the d-axis command current Idt when the q-axis command current Iqt of the voltage limiting circuit Cvs is the compensation command current Imr. Specifically, the limiting circuit d-axis coordinate Ids is calculated by applying the compensation command current Imr to the q-axis command current Iqt according to Equation (2). Then, "Idt = Ids and Iqt = Imr" are calculated in step S820. For example, the target current vector Imt: 7 is determined in the case of “Imr = iq8”.Since the d-axis command current Idt is sufficiently ensured in the energizable region, the response sensitivity for stopping and reversing the electric motor MTR is improved, thus reducing the generation of heat.

[0126] In the second processing example, the current limiting circuit Cis is enlarged to the increased allowable current value iqn to exceed the allowable current value iqm, but the continuation time is limited to a short time (within the predetermined time tkz). That is, the current limiting circuit is returned to the current limiting circuit Cis calculated using the allowable current value imq (the enlargement of the current limiting circuit Cis is stopped) after the predetermined time tkz has elapsed from the vehicle wheel slip suppression control start time. Thus, the temperature rise of the electric motor MTR and the drive circuit DRV is small.

[0127] Furthermore, the enlargement of the current limiting circuit Cis may be terminated (stopped) based on the rotational speed dMk. For example, the enlargement of the current limiting circuit Cis continues when the rotational speed dMk continues to be higher than or equal to a predetermined rotational speed dmz (a positive sign), and is terminated when the rotational speed dMk is lower than the predetermined rotational speed dmz. That is, the enlargement of the current limiting circuit Cis is terminated at a time point when the rotational speed dMk of the electric motor MTR changes from a state where the rotational speed is higher than or equal to the predetermined rotational speed dmz to a state where the rotational speed is lower than the predetermined rotational speed dmz, thereby returning to the original current limiting circuit Cis.Since the increase in the current limiting circuit Cis is limited for a shorter time, an increase in the temperature of the electric motor MTR and the drive circuit DRV can be suppressed.

[0128] Improving the responsiveness for stopping and reversing the electric motor MTR immediately after the start of the vehicle wheel slip suppression control is particularly necessary when the rotational speed dMk before the start of the control is very high. Thus, the enlargement of the current limiting circuit Cis is permitted when the rotational speed dMk is higher than or equal to a predetermined rotational speed dmx (a positive sign) at the vehicle wheel slip suppression control start time, and the enlargement of the current limiting circuit Cis is prohibited when the rotational speed dMk is lower than the predetermined rotational speed dmx at this time. Since the current limiting circuit Cis is only enlarged when the required minimum limit is increased in response to the rotational speed dMk of the electric motor MTR, an increase in the temperature of the electric motor MTR and the drive circuit DRV can be more reliably suppressed. <Verarbeitung des Umschaltsteuerungsblocks SWT und der Ansteuerungsschaltung DRV des bürstenlosen Drei-Phasen-Motors>

[0129] With reference to the schematic diagram according to Fig. Figure 7 describes the processing of the switching control block SWT and the drive circuit DRV of the brushless three-phase motor. The brushless three-phase motor MTR comprises three coils (windings): a U-phase coil CLU, a V-phase coil CLV, and a W-phase coil CLW. The electric motor MTR is equipped with the rotation angle sensor MKA, which detects the rotation angle (rotor position) Mka of the electric motor MTR. The rotation angle Mka is input to the switching control block SWT of the control unit ECU. <<Verarbeitung des Umschaltsteuerungsblocks SWT> >

[0130] First, processing of the switching control block SWT is described. In the switching control block SWT, the control signals Sux, Suz, Svx, Svz, Swx, Swz (i.e., Sux to Swz) of the switching elements SUX, SUZ, SVX, SVZ, SWX, SWZ (i.e., SUX to SWZ) of the three-phase bridge circuit BRG are determined based on the target current Imt, the actual current value (the detection value) Ima, and the rotation angle Mka (the detection value) of the electric motor MTR.

[0131] In the switching control block SWT, a duty cycle (a ratio of ON time to one cycle) of the pulse width is determined based on the magnitude of the command current Imt and a predetermined characteristic (a calculation map). At the same time, the rotation direction of the electric motor MTR is determined based on the sign (positive or negative sign) of the command current Imt. For example, the rotation direction of the electric motor MTR is set such that the normal rotation direction is a positive (plus) value and the reverse rotation direction is a negative (minus) value. Since a final output voltage is determined by the input voltage (the voltage of the storage battery BAT) and the duty cycle Dtt, the rotation direction and output torque of the electric motor MTR are determined.Specifically, since the energization time per unit time in the switching element increases as the duty cycle Dtt increases, a larger current flows to the electric motor MTR, thus the output (rotational power) becomes larger.

[0132] The switching control block SWT includes a first conversion calculation block IHA, a target voltage calculation block EDQ, a no-interference control block HKC, a correction voltage calculation block EDQS, a second conversion calculation block EMT, a target duty cycle calculation block DTT, and a drive signal calculation block SDR. The electric motor MTR is controlled by a so-called vector control.

[0133] In the first conversion calculation block IHA, a converted actual current Iha is calculated based on the actual current Ima and the rotation angle Mka. The converted actual current Iha is obtained by converting the actual current Ima from three phases to two phases and from a fixed coordinate to a rotational coordinate. The converted actual current Iha is a vector in the dq-axis (a rotor-fixed coordinate) and is obtained by the d-axis element (also called a "d-axis actual current") Ida and the q-axis element (also called a "q-axis actual current") Iqa.

[0134] In the first conversion calculation block IHA, the actual current Ima is converted from three phases to two phases. The actual current Ima is a general designation of the respective phases (U, V, and W phases) of the bridge circuit BRG and specifically includes a U-phase actual current Iua, a V-phase actual current Iva, and a W-phase actual current Iwa. To handle three signals simultaneously, calculation in a three-dimensional space is required. To simplify the calculation, the three-phase actual current Ima (Iua, Iva, Iwa) is converted into a two-phase actual current Ina (Iα, Iβ) (a so-called Clarke transformation) by utilizing the fact that "Iua + Iva + Iwa = 0" is established in the ideal three-phase alternating current.

[0135] The three-phase actual currents (detected values) Iua, Iva, and Iwa are converted into two-phase actual currents Iα and Iβ using the Clarke transformation. That is, the actual currents Iua, Iva, and Iwa of symmetrical three-phase alternating current (three-phase alternating current with phases shifted by 120°) are converted into actual currents Iα and Iβ of two-phase alternating current.

[0136] Furthermore, in the first conversion calculation block IHA, the converted actual current Iha is calculated by performing a coordinate conversion from a fixed coordinate (a stationary coordinate) to a rotational coordinate based on the rotation angle Mka. The converted actual current Iha is formed by the d-axis element (the d-axis actual current) Ida and the q-axis element (the q-axis actual current) Iqa. That is, since the current value Ina subjected to the Clarke transformation corresponds to a current flowing to the rotor, the coordinate is converted to the rotor-fixed coordinate (which is a rotational coordinate and a dq-axis coordinate) (a so-called Park transformation). Based on the rotor rotation angle Mka from the rotation angle sensor MKA, the fixed coordinate is converted into the rotation coordinate (dq-axis coordinate), and the actual current Iha (Ida, Iqa) is determined after the coordinate conversion.

[0137] In the target voltage calculation block EDQ, a target voltage vector Edq is calculated based on the target current vector Imt (Idt, Iqt) and the actual current Iha (Ida, Iqa), which undergoes a Park transformation. In the vector control, a so-called current control is performed such that the "dq-axis elements Idt and Iqt of the target current" match the "dq-axis elements Ida and Iqa of the actual current." Thus, in the target voltage calculation block EDQ, PI control is performed based on the deviation (current deviation) between the "dq-axis target currents Idt and Iqt" and the "dq-axis actual currents Ida and Iqa." In PI control, P control (which is proportional control in response to the deviation between the setpoint and the actual value) and I control (which is integral control in response to the integral value of the deviation) are executed in parallel.

[0138] Specifically, in the target voltage calculation block EDQ, the target voltage Edq is determined such that the current deviation between the target current Imt and the converted actual current decreases based on the deviation with respect to Iha (i.e., the deviation approaches "0"). The target voltage Edq is a vector for the dq axes and includes a d-axis element (also referred to as a "d-axis target voltage") Edt and a q-axis element (also referred to as a "q-axis target voltage") Eqt.

[0139] In the no-interference control block HKC, an interference element is calculated to correct the target voltages Edt and Eqt. This is because not only the d-axis current but also the q-axis current changes (referred to as an "interference element") when the d-axis voltage increases. The interference element is also present in the q-axis current. In addition, the counter electromotive force is also considered in the no-interference control block HKC. This is because the counter electromotive force is generated to decrease the magnitude of a current when the electric motor MTR rotates.

[0140] Specifically, in the no-interference control block HKC, the q-axis current interference compensation element is calculated as "-ω·Iqt·L" based on the electrical angular velocity ω, the q-axis command current Iqt, and the coil / inductance L. Similarly, the d-axis current interference compensation element is calculated as "ω·Idt·L." Furthermore, the back electromotive force compensation element is calculated as "ω·Φ" based on the electrical angular velocity ω and the field magnetic flux Φ of the magnet. Then, each calculation result is input to the correction voltage calculation block EDQS as the compensation value Hkc.

[0141] In the correction voltage calculation block EDQS, a correction voltage vector Edqs (Eds, Eqs) is calculated based on the target voltage vector Edq (Edt, Eqt) and the compensation value Hkc. Here, the correction voltage vector Edqs (Eds, Eqs) is a target vector of a final voltage obtained by correcting the target voltage vector Edq using the compensation value Hkc. Specifically, the d-axis element Eds and the q-axis element Eqs of the correction voltage Edqs are calculated by equations (3) and (4) given below. Eds=Edt−ω⋅lqt⋅L Eqs=Eqt+ω⋅ldt⋅L+ω⋅Φ

[0142] Furthermore, a second expression according to equation (3) is a compensation expression for the q-axis current interference. Furthermore, a second expression according to equation (4) is a compensation expression for the d-axis current interference, and a third corresponding expression is a compensation expression for the counter electromotive force.

[0143] In the second conversion calculation block EMT, the final target voltage Emt is calculated based on the correction voltage vector Edqs and the rotation angle Mka. The target voltage Emt is a general designation of the respective phases of the bridge circuit BRG and includes a U-phase target voltage Eut, a V-phase target voltage Evt, and a W-phase target voltage Ewt.

[0144] First, in the second conversion calculation block EMT, the correction voltage vector Edqs is inversely converted from the rotational coordinate to the fixed coordinate based on the rotation angle Mka, so that the two-phase target voltages Eα and Eβ are calculated (a so-called inverse Park transformation). Then, the two-phase target voltages Eα and Eβ are inversely converted into the three-phase target voltages Emt (the target voltage values ​​Eut, Evt, and Ewt of the respective phases) through the space vector transformation.

[0145] In the target duty cycle calculation block DTT, a duty cycle (a target value) Dtt of each phase is calculated based on the target voltage Emt of each phase. The duty cycle Dtt is a general designation of respective phases and includes a U-phase duty cycle Dut, a V-phase duty cycle Dvt, and a W-phase duty cycle Dwt. Specifically, the duty cycle Dtt is calculated according to a calculation characteristic CDtt to monotonically increase from "0" as the target voltage value Emt of each phase increases from "0".

[0146] In the drive signal calculation block SDR, signals Sux to Swz for driving the switching elements SUX to SWZ, which constitute respective phases of the bridge circuit BRG, are determined based on the duty cycle Dtt. Based on the drive signals Sux to Swz, the ON / OFF states of the switching elements SUX to SWZ are switched, and the electric motor MTR is driven. As described above, the processing of the switching control block SWT has been described. <<Ansteuerungsschaltung DRV> >

[0147] Next, the drive circuit DRV is described. The drive circuit DRV includes the three-phase bridge circuit BRG and a stabilizing circuit LPF. The drive circuit DRV is an electrical circuit that drives the electric motor MTR and is controlled by the switching control block SWT.

[0148] The bridge circuit BRG (also called an inverter circuit) includes six switching elements (power transistors) SUX, SUZ, SVX, SVZ, SWX, and SWZ (SUX to SWZ). Based on the control signals Sux, Suz, Svx, Svz, Swx, and Swz (Sux to Swz) of the respective phases from the switching control block SWT within the control circuit DRV, the bridge circuit BRG is controlled, thereby adjusting the output of the electric motor MTR.

[0149] Six switching elements SUX to SWZ are elements capable of turning part of the electric circuit on or off. For example, MOS-FETs and IGBTs are used as the switching elements SUX to SWZ. In the brushless motor MTR, the switching elements SUX to SWZ, which form the bridge circuit BRG, are controlled based on the detection value Mka of the rotation angle (rotor position). Then, the directions (i.e., the excitation directions) of the currents of the coils CLU, CLV, and CLW of three phases (U, V, and W phases) are sequentially switched, thereby rotationally driving the electric motor MTR. That is, the rotation direction (the normal rotation direction or the reverse rotation direction) of the brushless motor MTR is determined by a relationship of an excitation position with respect to the rotor.Here, the normal rotation direction of the electric motor MTR is a rotation direction of the pressing force Fpa using the pressurizing unit KAU, and the reverse rotation direction of the electric motor MTR is a rotation direction corresponding to a reduction in the pressing force Fpa.

[0150] The current sensor IMA (a general term), which detects the actual current Ima (a general term for each phase) between the bridge circuit BRG and the electric motor MTR, is provided in three phases (U, V, and W phases). Specifically, the U-phase current sensor IUA detects the U-phase actual current Iua, the V-phase current sensor IVA detects the V-phase actual current Iva, and the W-phase current sensor IWA detects the W-phase actual current Iwa in the respective phases. The detected phase currents Iua, Iva, and Iwa are respectively input to the switching control block SWT.

[0151] Then, the current control described above is executed in the switching control block SWT. Based on the deviation eIm between the actual current Ima and the target current Imt, the duty cycle Dtt is corrected (fine-tuned). Through current control, control is performed such that the actual value Ima matches the target value Imt (i.e., the current deviation eIm approaches "0"). As a result, highly accurate motor control can be achieved.

[0152] The drive circuit DRV receives electrical power from the electrical power source (the storage battery BAT, the generator ALT). To reduce the variation in the supplied electrical power (the voltage), the drive circuit DRV is provided with the stabilizing circuit LPF. The stabilizing circuit LPF is a so-called LC circuit configured by combining at least one capacitor (capacitor) and at least one reactor (coil). As described above, the drive circuit DRV has been described. <Betrieb und Wirkung>

[0153] With reference to the timing diagram according to Fig. 10, the operation and effect of the brake control device BCS for the vehicle according to the invention are described. A case is assumed in which the vehicle wheel slip suppression control (for example, the anti-skid control) is started while the actual pressing force Fpa is increased when a driver suddenly operates the brake operating element BP. For high-precision control by current control, Fig. 10 the q-axis command current Iqt overlaps the q-axis actual current Iqa and the d-axis command current Idt overlaps the d-axis actual current Ida.

[0154] At time t0, a driver suddenly starts operating the brake operating member BP, so that the brake operating amount Bpa starts increasing from "0." After time t1, the brake operating amount Bpa is constantly maintained at a value bp1. According to an increase in the brake operating amount Bpa, the command pressing force Fps is calculated as indicated by a dot-dashed line, where the command pressing force Fps is directly determined as the target pressing force Fpt (i.e., "Fpt = Fps"). That is, the target pressing force Fpt increases from "0" to a value fp1 corresponding to the value bp1. However, since there is a time delay at the time of activating the electric motor MTR (which starts rotation in the normal rotation direction), the actual pressing force Fpa increases from "0" with a gentle slope compared to the target pressing force Fpt, as indicated by a solid line.

[0155] When the electric motor MTR is stopped or rotated at a low speed, magnetic flux weakening control is unnecessary. For this reason, immediately after the start of the brake application (immediately after time t1), the d-axis currents Idt and Ida become "0", and only the q-axis currents Iqt and Iqa are generated. Then, as the speed of the electric motor MTR increases, the d-axis command current Idt decreases from "0" toward a value -id2 (the absolute value of the d-axis command current Idt increases). Since the d-axis command current Idt and the q-axis command current Iqt have a balance relationship, the q-axis command current Iqt decreases from the maximum q-axis current value iqm.

[0156] The vehicle wheel slip state amount Slp increases with an increase in the actual pressing force Fpa. Then, at a time t2 when the actual pressing force Fpa reaches a value fp2, an anti-skid control start condition is satisfied, and the anti-skid control is started. At the anti-skid control execution start time t2, the target pressing force Fpt suddenly decreases from the command pressing force Fps to the value fp2 of the actual pressing force Fpa at the time t2. That is, the target pressing force Fpt is calculated such that the command pressing force Fps is corrected to decrease based on the actual pressing force Fpa (the value fp2) at the time of starting the slip suppression control (the time t2). Specifically, the command pressing force Fps is corrected to decrease to the “value fp2 of the actual pressing force Fpa at the time of starting the control”, and then the final target pressing force Fpt is determined.Then, the target pressing force Fpt after time t2 is calculated by referring to the target pressing force Fpt at time t2.

[0157] Furthermore, the target current vector Imt is determined based on the correlation between the current limiting circuit Cis and the voltage limiting circuit Cvs such that the movement of the electric motor MTR in the normal rotation direction is suddenly stopped and the corresponding movement in the reverse rotation direction is started at time t2. Specifically, the target current vector Imt (Idt, Iqt) is determined while being limited by the second intersection d-axis coordinate Idx and the second intersection q-axis coordinate Iqx (see step S750 according to Fig. 5 and the target current vector Imt: 4 according to Fig. 6).

[0158] Since the sudden stop of the electric motor MTR is effectively commanded at time t2, the actual pushing force Fpa slightly exceeds the value fp2 to the value fp3, and then rapidly decreases. At time t3, the target pushing force Fpt is the same as the actual pushing force Fpa. After time t3, the target pushing force Fpt is repeatedly increased or decreased, so that the vehicle wheel slip state amount Slp enters a suitable range. That is, the general anti-skid control continues.

[0159] The final target pressing force Fpt is calculated by correcting the command pressing force Fps based on the actual pressing force (detection value) Fpa at the time of starting the execution of the slip suppression control. For this reason, the deviation eFp between the target pressing force Fpt and the actual pressing force Fpa at the time of starting the execution of the slip suppression control does not occur. As a result, it is possible to appropriately prevent a problem in which a decrease in the actual pressing force Fpa due to the interference between the pressing force control and the vehicle wheel slip suppression control is disturbed. That is, it is possible to suppress excessive vehicle wheel slip due to a time lag in an increase in the pressing force at the time of starting the execution of the slip suppression control.

[0160] In addition, the target current vector Imt (Idt, Iqt) is determined based on the correlation between the current limiting circuit Cis and the voltage limiting circuit Cvs at the time of starting the execution of the slip suppression control. Specifically, the second intersection point Pxb (Idx, -Iqx) between the current limiting circuit Cis and the voltage limiting circuit Cvs is calculated, and the second intersection point Pxb is calculated as the target current vector Imt (Idt, Iqt). Here, the second intersection point Pxb (Idx, -Iqx) is one where the q-axis target current Iqt is commanded in the reverse rotation direction (the q-axis target current Iqt has a negative sign) between two intersection points Pxa and Pxb.An overlapping section between the current limiting circuit Cis and the voltage limiting circuit Cvs is an energizable region of the electric motor MTR, where the second intersection point Pxb (Idx, -Iqx) is an operating point where the electric motor MTR is most effectively driven in the reverse rotation direction. For this reason, the electric motor MTR moving in the normal rotation direction is immediately stopped and driven in the reverse rotation direction. As a result, the vehicle wheel slip suppression control can be performed such that the excessive vehicle wheel slip is suppressed and the slip state amount Slp enters a suitable range.

[0161] Furthermore, the current limiting circuit Cis can be increased only for a short time immediately after the start of the vehicle wheel slip suppression control. For example, as indicated by a dashed line, the q-axis target current Iqt decreases from "0" to an increased allowable current value -iqn (< -iqm) at time t2. The electric motor MTR is stopped and driven in the reverse rotation direction with higher responsiveness when the current limiting circuit Cis is increased. As a result, since the exceedance of the actual pushing force Fpa is suppressed, the occurrence of excessive vehicle wheel slip can be appropriately suppressed. <Andere Ausführungsbeispiele>

[0162] Other embodiments will be described below. In other embodiments, the same effect as described above (instantaneously stopping the electric motor MTR in the rotating state and suppressing excessive vehicle wheel slip) is also obtained.

[0163] In the above-described embodiment, the case of calculating the voltage limiting circuit Cvs using equation (2) has been exemplified. When calculating the voltage limiting circuit Cvs, a voltage drop due to the current flowing to the electric motor MTR can be considered. The voltage drop is considered as "(R·Iqa) / (L·ω)" in the d-axis current and is calculated as "(R·Ida) / (L·ω)" in the q-axis current. Specifically, the voltage limiting circuit Cvs is calculated in equation (5). {ldt+(Φ / L)+(R⋅Iqa) / (L⋅ω)}2+{(R⋅Ida) / (L⋅ω)−Iqt}2={Eba / (L⋅ω)}2

[0164] Here, "Eba" indicates the power supply voltage (i.e., the voltages of the storage battery BAT and the generator ALT), "L" indicates the phase inductance, "Φ" indicates the number of flux connections (magnetic strength), and "R" indicates the wiring / winding resistance. Furthermore, "ω" indicates the electrical angular velocity of the electric motor MTR, which is calculated based on the rotation angle Mka. Furthermore, "Ida" indicates the d-axis actual current, and "Iqa" indicates the q-axis actual current, which are calculated based on the detection value Ima of the current sensor IMA (see Fig. 7).

[0165] In equation (3), the voltage drop is considered based on the dq-axis actual currents Ida and Iqa. Instead of the dq-axis actual currents Ida and Iqa, the dq-axis command currents Idt[n-1] and Iqt[n-1] of the previous calculation period are substituted. That is, the dq-axis command currents Idt[n] and Iqt[n] of the current calculation period can be calculated by considering the voltage drop based on the dq-axis command currents Idt[n-1] and Iqt[n-1] of the previous calculation period. Here, the symbol [n] at the end of the symbol indicates the current calculation period, and the symbol [n-1] indicates the previous calculation period. Specifically, in equation (6), the voltage limiting circuit Cvs is calculated. {Idt[n]+(Φ / L)+(R⋅Iqt[n−1]) / (L⋅ω)}2+{(R⋅Idt[n−1]) / (L⋅ω)−Iqt[n]}2={Eba / (L⋅ω)}2

[0166] As shown in equation (5) or equation (6), the control of the electric motor MTR can be achieved with higher accuracy by taking the voltage drop into account.

[0167] In the above-described embodiment, the electrical angular velocity ω is calculated by calculating the electrical angle θ based on the rotation angle Mka (the mechanical angle) of the electric motor MTR, and differentiating the electrical angle θ with respect to time in calculating the electrical angular velocity ω of the electric motor MTR. That is, the electrical angular velocity ω is determined in an order according to “Mka→0→w.” Instead, the rotational speed dMk may be calculated based on the rotational angle Mka, where the electrical angular velocity ω may be calculated based on the rotational speed dMk. That is, the electrical angular velocity ω may be determined in an order according to “Mka→dMk→w.” In any case, however, the voltage limiting circuit Cvs of the dq-axis current characteristic is calculated based on the rotational angle Mka detected by the rotational angle sensor MKA.

[0168] In the above-described embodiment, a configuration of the disc-type brake device (disc brake) has been described by way of example. In this case, the friction element MS is a brake pad, and the rotating element KT is a brake disc. Instead of the disc-type brake device, a drum-type brake device (drum brake) may be employed. In the case of the drum brake, the brake drum is employed instead of the brake caliper CP. Further, the friction element MS is a brake shoe, and the rotating element KT is a brake drum.

[0169] In the above-described embodiment, a case in which a braking force is applied to one vehicle wheel WH by the pressurizing unit KAU has been described as an example. However, a braking force may be generated at a plurality of vehicle wheels WH by the pressurizing unit KAU. In this case, the plurality of wheel cylinders WC are connected to the fluid path HWC.

[0170] Furthermore, the pressurizing cylinder KCL can be one having two fluid pressure chambers defined by pressurizing pistons. That is, the pressurizing cylinder KCL uses a tandem-type configuration. Then, two wheel cylinders WC of four vehicle wheels WH are connected to one fluid pressure chamber, and the other two wheel cylinders WC of four vehicle wheels WH are connected to the other fluid pressure chamber. Accordingly, a so-called longitudinal-type or diagonal-type fluid configuration can be formed, in which the pressurizing cylinder KCL is used as a fluid pressure source.

[0171] In the above-described embodiment, a configuration of the fluid pressure type brake control device in which the rotational power of the electric motor MTR is converted into the fluid pressure of the wheel cylinders WC by a brake fluid and a braking force is generated in the vehicle wheel WH has been exemplified. Instead, an electric / mechanical brake control device that does not use the brake fluid may be employed. In this case, the KAU is mounted on the brake caliper CP. Further, as the pressing force sensor FPA, a thrust sensor is employed instead of the fluid pressure sensor. For example, the thrust sensor may be provided between the power transmission mechanism DDK and the pressurizing piston PKC, as represented by "(FPA)" in FIG. Fig. 1 is specified.

[0172] Further, a composite type configuration in which a fluid pressure type pressurizing unit using a brake fluid is employed for a front wheel and an electric / mechanical pressurizing unit is employed for a rear wheel may be formed.

Claims

[1] A brake control device (BCS) for a vehicle that drives an electric motor (MTR) based on a target pressing force (Fpt) corresponding to a demand braking force for a vehicle wheel (WH) of a vehicle and generates a braking force in the vehicle wheel (WH) by pressing a friction element (MS) against a rotary element (KT) fixed to the vehicle wheel (WH), comprising: a control circuit (DRV) that controls the electric motor (MTR); a control device (ECU) that controls the drive circuit (DRV) based on the target pressing force (Fpt); and a rotation angle sensor (MKA) that detects a rotation angle (Mka) of the electric motor (MTR), wherein the control device (ECU) sets a current limiting circuit (Cis) of a current characteristic of a d-axis current and a q-axis current of the electric motor (MTR) based on a specification of the drive circuit (DRV), characterized by , that the control device (ECU) calculates a voltage limiting circuit (Cvs) of the current characteristic based on the rotation angle (Mka), calculates a d-axis target current (Idt) and a q-axis target current (Iqt) based on a correlation between the current limiting circuit (Cis) and the voltage limiting circuit (Cvs), and controls the drive circuit (DRV) based on the d-axis target current (Idt) and the q-axis target current (Iqt). [2] Brake control device (BCS) for the vehicle according to claim 1, further comprising: a vehicle wheel speed sensor (VWA) which detects a speed (Vwa) of the vehicle wheel (WH), wherein a slip state amount (Slp) indicating a degree of slip of the vehicle wheel is calculated based on the speed (Vwa) of the vehicle wheel (WH), and a slip suppression control for reducing the degree of slip of the vehicle wheel (WH) is executed based on the slip state amount (Slp), and wherein a d-axis target current (Idt) and a q-axis target current (Iqt) are calculated based on a correlation between the current limiting circuit (Cis) and the voltage limiting circuit (Cvs) at the time of starting the execution of the slip suppression control. [3] A brake control device for the vehicle according to claim 1 or 2, wherein the control device (ECU) calculates an intersection point between the voltage limiting circuit (Cvs) and the current limiting circuit (Cis) in the correlation and calculates the d-axis target current (Idt) based on the intersection point. [4] A brake control device for the vehicle according to any one of claims 1 to 3, further comprising: a current sensor (IMA) that detects a value (Ima) of a current flowing in the control circuit, wherein the control device calculates a d-axis actual current (Ida) corresponding to a d-axis element of the current value (Ima) and a q-axis actual current (Iqa) corresponding to a q-axis element of the current value (Ima) on the basis of the current value (Ima) and the rotation angle (Mka), calculates a counter electromotive force (ω·Φ) of the electric motor (MTR) on the basis of the rotation angle (Mka), calculates a target voltage (Edqs) based on a deviation (eId) between the d-axis target current (Idt) and the d-axis actual current (Ida), a deviation (eIq) between the q-axis target current (Iqt) and the q-axis actual current (Iqa) and the counter electromotive force (ω·Φ), and the drive circuit (DRV) based on the target voltage (Edqs). [5] A brake control device for the vehicle according to claim 2, wherein the control device (ECU) controls the drive circuit (DRV) based on the correlation between the current limiting circuit (Cis) and the voltage limiting circuit (Cvs) even in a non-execution state in which the slip suppression control is not executed, and enlarges the current limiting circuit (Cis) in the execution start state rather than the current limiting circuit (Cis) in the non-execution state.

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