Vehicle braking system

Abstract

To provide a braking device for a vehicle, capable of appropriately executing control in response to switching between braking force-increasing operation and decreasing operation in the control of an electric brake having hysteresis characteristics.SOLUTION: A torque command calculation unit 401 in a braking force control unit calculates a torque command value Trq* for a motor on the basis of required braking force which is given by a command from the outside. The relationship between the torque of the motor and braking force generated in an electric brake has hysteresis characteristics. When the torque increases, the braking force increases along a positive efficiency line. When the torque decreases, the braking force decreases along an inverse efficiency line. A specific controller (load controller) 48 in the torque command calculation unit 401 calculates the torque command value Trq* so that an actual load F approaches a load command value F*. A control adjuster 471 adjusts a parameter for control calculation in the specific controller 48, or at the input side or output side of the specific controller 48, during increasing operation, decreasing operation, or a transition between the increasing operation and decreasing operation.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a vehicle braking device.

Background Art

[0002] Conventionally, in an electric brake device for a vehicle in which the relationship between the torque of a motor and the pressing force applied to a brake disk from a motion conversion mechanism has a hysteresis characteristic, a technique for controlling the drive of the motor so that the magnitude of the pressing force reaches a target value is known.

[0003] For example, in the electric brake device disclosed in Patent Document 1, the motor control device controls the drive current of the motor based on the magnitude of the pressing force detected by a load sensor. The relationship between the motor torque and the pressing force has a hysteresis characteristic. When the motor control device applies and holds the pressing force to the brake disk, it increases the torque of the motor along the positive efficiency line until the pressing force rises to a predetermined value greater than the target value, and then decreases the torque of the motor along the negative efficiency line until the pressing force decreases to the target value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In this specification, the vertical axis of the hysteresis diagram is described as the "correlation quantity of braking force". In Patent Document 1, the pressing force detected by the load sensor corresponds to the actual braking force that the electric brake actually outputs. Also, the load command value in Patent Document 1 corresponds to the required braking force. In the prior art of Patent Document 1, by moving the operating point from the positive efficiency line to the negative efficiency line to hold the braking force, the current for driving the motor during the holding of the braking force can be reduced.

[0006] In controlling electric brakes with hysteresis characteristics, compared to cases without hysteresis characteristics, a larger torque change is required during the transition from increasing to decreasing braking force, and from decreasing to increasing braking force, which could lead to response delays. Furthermore, if the control gain of the PI controller is set to be the same for increasing and decreasing braking force, there is a risk of overshoot during decreasing braking force. In addition, unnecessary switching between increasing and decreasing braking force across the target braking force value could lead to torque pulsation.

[0007] The present invention was created in view of the above-mentioned points, and its purpose is to provide a vehicle braking device that can appropriately perform control in accordance with the switching between increasing and decreasing braking force in the control of an electric brake having hysteresis characteristics. [Means for solving the problem]

[0008] The vehicle braking system of the present invention is mounted on a vehicle (900) in which multiple electric brakes (81-84) are provided on each wheel, which convert the torque output by a motor (60) into linear power by a linear motion mechanism (85) and press against the corresponding wheels (91-94) to generate braking force.

[0009] The vehicle braking system includes a torque command calculation unit (401-404) and a current command calculation unit (50), and a braking force control unit (400) that controls the braking force generated by each electric brake. The torque command calculation unit calculates the motor's torque command value (Trq) based on the requested braking force commanded from an external source. * The current command calculation unit calculates the current command value (I) to energize the motor based on the torque command value. * ) is calculated.

[0010] The electric brake is equipped with a load sensor (71) that detects the actual load (F), which is the braking load actually pressed against the wheel, or a position sensor (72, 73) that detects the actual rotation angle of the motor or the actual stroke of the linear motion mechanism (θ, X).

[0011] The relationship between motor torque and the braking force generated in the electric brake exhibits a hysteresis characteristic: when torque increases, the braking force increases along the positive efficiency curve; when torque decreases from the turning point where it changes from increasing to decreasing to the holding critical value, the braking force is maintained constant; and when torque decreases from the holding critical value, the braking force decreases along the negative efficiency curve.

[0012] We define the operation of increasing the motor torque along the positive efficiency line as "increase operation," the operation of maintaining braking force at any operating point between the positive efficiency line and the negative efficiency line as "maintaining operation," and the operation of decreasing the motor torque along the negative efficiency line as "decrease operation."

[0013] The first of the present invention ~Third In this embodiment, the torque command calculation unit includes a specific controller (48) and control adjusters (471, 472, 473). The specific controller calculates the torque command value so as to bring the actual load detected by the load sensor closer to the load command value, or so as to bring the actual position detected by the position sensor closer to the position command value. The control adjusters are used during increasing operation, decreasing operation, or increasing and decreasing operation. motion During the transition to the next operation, the parameters of the control calculation in the specific controller, or on the input or output side of the specific controller, are adjusted. For example, the torque command calculation unit of the first embodiment calculates the torque command value calculated by the specific controller and the feedforward term (Trq) of the torque command value set by the control regulator. * The FF) is output to the current command calculation unit. The current command calculation unit calculates the current command value so that the actual torque (Trq), which is the torque actually output by the motor, approaches the sum of the torque command value and the feedforward term. The control regulator decreases the value of the feedforward term when transitioning from increasing operation to decreasing operation, and increases the value of the feedforward term when transitioning from decreasing operation to increasing operation.

[0014] The first of the present invention ~Third In this embodiment, in the control of an electric brake having hysteresis characteristics, the control can be appropriately implemented by adjusting the parameters of the control calculation in accordance with the switching between increasing and decreasing braking force.

[0015] This invention fourIn this embodiment, the torque command calculation unit includes a specific controller (48) and a dead zone setter (43). The specific controller calculates a torque command value so as to bring the actual load detected by the load sensor closer to the load command value, or so as to bring the actual position detected by the position sensor closer to the position command value. The dead zone setter sets a predetermined range as a dead zone so as to consider the load deviation, which is the difference between the load command value input to the specific controller and the actual load, or the position deviation, which is the difference between the position command value and the actual position, as zero if it is within a predetermined range including zero.

[0016] This invention four In this configuration, setting a dead zone prevents unnecessary switching between increasing and decreasing operations. [Brief explanation of the drawing]

[0017] [Figure 1] Configuration diagrams of vehicles equipped with the vehicle braking systems of each embodiment. [Figure 2] Block diagram of the braking force control for the electric brakes corresponding to each wheel. [Figure 3] (a) Schematic diagram of the pads of an electric brake, (b) Characteristic diagram of pad load and pad position. [Figure 4] A diagram showing the hysteresis characteristics between motor torque and braking force. [Figure 5] Block diagram of the torque command calculation unit and current command calculation unit of the first embodiment. [Figure 6] A diagram illustrating the calculation of maximum and minimum torque. [Figure 7] A diagram showing the change in the feedforward term during the transition from decreasing to increasing motion. [Figure 8] Flowchart of the feedforward term adjustment process. [Figure 9] Block diagram of the torque command calculation unit of the second embodiment. [Figure 10] Flowchart of the gain adjustment process. [Figure 11] A diagram showing a comparative example to a combined embodiment of the first and second embodiments. [Figure 12] A diagram illustrating the effects of a combined embodiment of the first and second embodiments. [Figure 13] Block diagram of the torque command calculation unit of the third embodiment. [Figure 14] A diagram showing the dead zone setting according to the basic embodiment of the third embodiment. [Figure 15] A figure showing (a) positive-negative symmetric and (b) positive-negative asymmetric dead zone settings according to other embodiments of the third embodiment. [Figure 16] Flowchart for dead zone adjustment process. [Figure 17] A diagram of a comparative example to the third embodiment. [Figure 18] A diagram illustrating the effects of the third embodiment. [Figure 19] Block diagram of the torque command calculation unit of the fourth embodiment. [Modes for carrying out the invention]

[0018] Multiple embodiments of the present invention will be described with reference to the drawings. In multiple embodiments, substantially identical components are denoted by the same reference numerals and their descriptions are omitted. The following first to fourth embodiments will be collectively referred to as "this embodiment." The vehicle braking device of this embodiment is mounted on a vehicle in which multiple electric brakes are provided on each wheel, converting the torque output by a motor into linear power using a linear motion mechanism and pressing it against the corresponding wheel to generate braking force. The vehicle braking device includes a braking force control unit that controls the braking force generated by each electric brake.

[0019] [Vehicle configuration] Referring to Figures 1 to 3(b), the configuration of the vehicle 900 and electric brakes 81-84 on which the vehicle braking system 30 of this embodiment is mounted will be described. As shown in Figure 1, the vehicle 900 is a four-wheeled vehicle having two rows of left and right pairs of wheels 91, 92, 93, and 94 in the front and rear directions. The front left and right wheels 91 and 92 are labeled "FL" and "FR," and the rear left and right wheels 93 and 94 are labeled "RL" and "RR." Multiple (four in this example) electric brakes 81, 82, 83, and 84 are provided corresponding to each wheel 91, 92, 93, and 94. Hereafter, four consecutive reference numerals will be abbreviated as "wheels 91-94" and "electric brakes 81-84," respectively.

[0020] The vehicle braking system 30 includes a braking force control unit 400. The braking force control unit 400 controls the braking force generated by each electric brake 81-84 based on a requested braking force commanded from an external source. The requested braking force is commanded by the driver's brake operation or a braking signal from a driver assistance device. From each electric brake 81-84, a load sensor signal F (solid line) detecting the pressing load of the brake pad, or position sensor signals θ and X (dashed lines) detecting the operating position of the motor or linear motion mechanism are input to the braking force control unit 400.

[0021] In this embodiment, the control configuration of each electric brake 81-84 is the same. Figure 2 illustrates the control configuration of the electric brake by the braking force control unit 400, using one of the electric brakes 81-84 as an example.

[0022] Each electric brake 81-84 includes a motor 60, a linear motion mechanism 85, and a caliper 86. The motor 60 is, for example, a permanent magnet type three-phase brushless motor, and outputs torque by a drive current supplied from the braking force control unit 400. The linear motion mechanism 85 is an actuator that converts the output rotation of the motor 60 into linear motion while reducing its speed. The rotation angle θ of the motor 60 and the stroke X of the linear motion mechanism 85 are proportional. In this way, each electric brake 81-84 converts the torque output by the motor 60 into linear force by the linear motion mechanism 85 and presses it against the corresponding wheel 91-94 to generate braking force.

[0023] The output torque of the motor 60 acts on the pads 87 of the caliper 86 via the linear motion mechanism 85. As the pads 87 move and press against the discs 88 of each wheel 91-94, braking force is generated by friction. The braking force is released when the pads 87 move away from the discs 88.

[0024] Referring to Figures 3(a) and (b), the characteristics of the pad 87 of the electric brake 81-81 shown in section IIIa of Figure 2 will be supplemented. As shown in Figure 3(a), the pad 87 has spring-like characteristics, and the pressing force Fd by the linear motion mechanism 85 and the reaction force Fr corresponding to the amount of strain act in opposite directions. As shown in Figure 3(b), the pad position X based on the stroke of the linear motion mechanism 85 and the pad load F are approximately proportional. If the pad position changes by ΔX due to a change in the rotation angle Δθ of the motor 60, the pad load changes by ΔF. Note that only in Figure 3(b), the symbol "ΔF" indicates the change in load. This has a different meaning from the "ΔF" used in Figure 5 and below to indicate the load deviation between the load command value and the actual load.

[0025] Returning to Figure 2, the braking force control unit 400 includes a torque command calculation unit 40, a current command calculation unit 50, and an inverter 55. The torque command calculation unit 40 calculates the torque command value Trq of the motor 60 based on the requested braking force commanded from the outside. * The current command calculation unit 50 calculates the current command value I to energize the motor 60 based on the torque command value. * Perform the calculation.

[0026] The inverter 55 converts the DC power from the battery 15 into AC power, and sets the current command value I * AC power corresponding to this is supplied to the motor 60. Note that the detailed configuration of current feedback and other components from the current command calculation unit 50 to the inverter 55 is omitted. Using general motor control technology, the inverter 55 switches according to a switching signal such as PWM control.

[0027] In a basic embodiment, the electric brakes 81-84 are equipped with a load sensor 71 that detects the actual load F, which is the braking load actually pressed against the wheels 91-94. The actual load F detected by the load sensor 71 is input to the torque command calculation unit 40. The torque command calculation unit 40 adjusts the torque command value Trq so that the actual load F approaches the load command value calculated based on the required braking force. * It has a load controller that calculates the torque. In the description of the first to fourth embodiments, it is assumed that the torque command calculation unit 40 is configured to perform load control by the load controller.

[0028] However, the electric brakes 81-84 of other embodiments may include an angle sensor 72 shown by a dashed line, or a stroke sensor 73 shown by a double dashed line. The angle sensor 72 detects the actual angle θ, which is the actual rotation angle of the motor 60. The stroke sensor 73 detects the actual stroke X, which is the actual stroke of the linear motion mechanism 85.

[0029] The angle sensor 72 and stroke sensor 73 are collectively referred to as "position sensors," and the actual angle θ and actual stroke X are collectively referred to as "actual position." The actual positions θ and X detected by the position sensors 72 and 73 are input to the torque command calculation unit 40. The torque command calculation unit 40 adjusts the torque command value Trq so that the actual positions θ and X approach the position command value calculated based on the required braking force. * The system may have a position controller that calculates the load. In this specification, a load controller or a position controller is defined as a "specific controller". In the torque command calculation unit of the first to fourth embodiments, a load controller 48 is used as the "specific controller".

[0030] Next, referring to Figure 4, the relationship between motor torque and braking force in this configuration of electric brake will be explained. The braking force correlates with the brake pad load. Hereinafter, "torque" simply refers to the torque output by the motor 60, and "load" simply refers to the pressing load by the pad 87. Figure 4 corresponds to Figure 10 of Patent Document 1 (Japanese Patent No. 6080682).

[0031] The relationship between the torque of the motor 60 and the braking force generated in the electric brakes 81-84 has a hysteresis characteristic. When the torque increases, the braking force increases along the positive efficiency line. When the torque decreases from the turning value Tconv where the torque changes from increasing to decreasing to the holding critical value Tcr, the braking force is held constant. When the torque decreases from the holding critical value Tcr, the braking force decreases along the reverse efficiency line.

[0032] In the prior art of Patent Document 1, the torque of the motor is increased until the magnitude of the load detected by the load sensor reaches a value "greater than the target value F * by a predetermined offset value dF". Thereafter, the drive current of the motor is controlled so that the torque of the motor is decreased until the magnitude of the load detected by the load sensor reaches the target value F * During the process of decreasing the torque of the motor, the load F, that is, the braking force, is held.

[0033] The operation of increasing the torque and the braking force along the positive efficiency line is defined as an "increasing operation", the operation of holding the braking force at an arbitrary operating point between the positive efficiency line and the reverse efficiency line is defined as a "holding operation", and the operation of decreasing the torque and the braking force along the reverse efficiency line is defined as a "decreasing operation".

[0034] [[ID=X]] As disclosed in Patent Document 1, in the control of an electric brake having a hysteresis characteristic, compared with the case where there is no hysteresis characteristic, a large torque change is required when transitioning from the increasing operation of the braking force to the decreasing operation, and when transitioning from the decreasing operation to the increasing operation, and there is a possibility of a response delay. Also, if the control gains of the PI controller are set to be the same for the increasing operation and the decreasing operation, there is a possibility of overshoot occurring during the decreasing operation. Further, due to an unnecessary switching between the increasing operation and the decreasing operation across the braking force target value, there is a possibility of torque pulsation occurring.

[0035] Therefore, the vehicle braking device 30 of this embodiment aims to appropriately control the switching between increasing and decreasing braking force in the control of an electric brake having hysteresis characteristics. The means of solving this can be broadly divided into the first to third embodiments and the fourth embodiment.

[0036] The torque command calculation unit 40 in the first to third embodiments is used during increasing operation, decreasing operation, or increasing and decreasing operation. motion The system includes a "control adjuster" that adjusts the parameters of the control calculations in the load controller, or on the input or output side of the load controller, during the transition between operations. Next, the detailed configuration for each embodiment will be described. In the first to third embodiments, the reference numerals for the torque command calculation unit and the control adjuster are numbered according to the embodiment, with the third digit following "40" and "47".

[0037] In the torque command calculation unit 401 of the first embodiment, the control regulator 471 controls increasing and decreasing operations. motion During the transition to the operation, the torque command value Trq is used as a parameter in the control calculation on the output side of the load controller. * Adjust the feedforward term.

[0038] In the torque command calculation unit 402 of the second embodiment, the control adjuster 472 adjusts the control gain as a parameter for the control calculation of the load controller during increasing and decreasing operations.

[0039] In the torque command calculation unit 403 of the third embodiment, the control adjuster 473 adjusts the upper and lower limits of the dead zone as parameters for the control calculation on the input side of the load controller during increasing and decreasing operations.

[0040] (First Embodiment) The first embodiment will be described with reference to Figures 5 to 8. As shown in Figure 5, the torque command calculation unit 401 of the first embodiment has a load command calculation unit 41, a load deviation calculator 42, and a load controller 48, as well as a control adjuster 471. The current command calculation unit 50 has a torque deviation calculator 52 and a torque controller 53.

[0041] The load command calculation unit 41 calculates the load command value F based on the required braking force. * The load deviation calculator 42 calculates the actual load F detected by the load sensor 71 and the load command value F. * The load deviation ΔF(=F * -F) is calculated and output to the load controller 48. The load controller 48 adjusts the load deviation ΔF to approach zero, that is, the actual load F to the load command value F. * Torque command value Trq * Perform the calculation.

[0042] The control regulator 471 calculates the hysteresis width W_hys in the torque-braking force map, as described later. The control regulator 471 also calculates the feedforward term Trq of the torque command value. * Set _FF and output it to the torque deviation calculator 52 of the current command calculation unit 50. Below is the feedforward term Trq of the torque command value. * _FF is simply "feedforward term Trq * Write "_FF".

[0043] The control regulator 471 acquires the actual load F and load deviation ΔF and estimates the current operating point on the map and the direction of increase or decrease in braking force. The control regulator 471 then determines whether it is a transition from increasing to decreasing action or a transition from decreasing action, and sets the feedforward term Trq. * Adjust _FF.

[0044] The torque deviation calculator 52 of the current command calculation unit 50 receives the torque command value Trq calculated by the load controller 48. * The feedforward term Trq set by the control regulator 471 * _FF and the actual torque Trq, which is the torque actually output by the motor 60, are input. For example, in a permanent magnet type three-phase brushless motor, the actual torque Trq of the motor 60 is estimated from the d-axis current and q-axis current using the number of pole pairs, magnetic flux, d-axis inductance, and q-axis inductance. Alternatively, the actual torque Trq of the motor 60 may be detected by a torque sensor.

[0045] The torque deviation calculator 52 calculates the torque command value Trq. * and the feedforward term Trq * The torque deviation ΔTrq (=Trq) is obtained by subtracting the actual torque Trq of motor 60 from the sum with FF. * +Trq * It is calculated as _FF-Trq). The torque controller 53 adjusts the torque deviation ΔTrq to approach zero, that is, the actual torque Trq to the torque command value Trq. * and the feedforward term Trq * The current command value I should be adjusted to approximate the sum with FF. * Perform the calculation.

[0046] Referring to Figure 6, the storage of the maximum torque Trq_max and minimum torque Trq_min by the control regulator 471, and the calculation of the hysteresis width W_hys will be explained. In the torque-braking force map of Figure 6, the white circles on the positive efficiency line indicate the maximum torque Trq_max, and the hatched circles on the negative efficiency line indicate the minimum torque Trq_min. The control regulator 471 stores each load command value F * The maximum torque Trq_max and minimum torque Trq_min corresponding to these values ​​are stored. The control regulator 471 also calculates the "hysteresis width W_hys," which is the difference between the maximum torque Trq_max and the minimum torque Trq_min.

[0047] For example, during the manufacturing process or initial operation, the control regulator 471 sets the load command value F * The torque is moved in the order of "0 → maximum torque → 0" and the maximum torque Trq_max and minimum torque Trq_min are stored. The map may be updated as appropriate each time the power is turned on, each time an operation is performed, etc. Also, as in the prior art of Patent Document 1, the load command value F * When performing a holding operation that involves over-operating and then returning, the control regulator 471 may store the torque values ​​at the start of the over-operation and at the end of the return operation. In this case, it is efficient as it is not necessary to store the entire map.

[0048] Next, referring to Figure 7, the feedforward term Trq corresponds to the transition direction between increasing and decreasing operations.* Let's explain the adjustment of _FF. The control regulator 471 controls the absolute value of the change in the feedforward term |ΔTrq * Set _FF| to be less than or equal to the hysteresis width W_hys. The absolute value of the change in the feedforward term is |ΔTrq|. * The intention is that _FF| should not exceed the hysteresis width W_hys, and the length of the block arrow indicating the change in the feedforward term is illustrated to be slightly shorter than the hysteresis width W_hys.

[0049] During the transition from increasing to decreasing operation, the control regulator 471 controls the Trq feedforward term Trq * The value of _FF is reduced. In other words, the change ΔTrq is the difference between the changed value of the feedforward term and the value before the change. * _FF is negative. When transitioning from a decreasing operation to an increasing operation, the control regulator 471 sets the Trq feedforward term Trq * Increase the value of _FF. In other words, the change in the feedforward term ΔTrq. * _FF is positive.

[0050] Referring to the flowchart in Figure 8, the feedforward term adjustment process performed by the control regulator 471 will be explained. In the flowchart, the symbol "S" represents a step.

[0051] In S11, the control regulator 471 stores the maximum torque Trq_max and minimum torque Trq_min corresponding to the held braking force, and calculates the hysteresis width W_hys, which is the difference between the maximum torque Trq_max and the minimum torque Trq_min. In S12, the control regulator 471 calculates the absolute value of the change in the feedforward term during the transition between increasing and decreasing operations |ΔTrq * Set _FF| to be less than or equal to the hysteresis width W_hys.

[0052] In S13, it is determined whether it is a transition from an increasing operation to a decreasing operation. If the answer in S13 is YES, then in S14 the control regulator 471 sets the feedforward term Trq *The value of _FF is reduced. In S15, it is determined whether it is a transition from a decreasing operation to an increasing operation. If YES in S15, in S16 the control regulator 471 sets the feedforward term Trq * Increase the value of _FF.

[0053] In addition, in the modified version of the first embodiment, the absolute value of the change in the feedforward term |ΔTrq is calculated, including cases where the hysteresis width W_hys is not calculated at all. * _FF| can be set to a fixed value, for example, regardless of the hysteresis width W_hys. In that case, steps S11 and S12 of the flowchart will not be performed.

[0054] In the first embodiment, when transitioning between an increasing operation and a decreasing operation, a feedforward term Trq is set according to the direction of the transition. * By increasing or decreasing the value of _FF, the response delay associated with switching operations can be reduced. Also, the absolute value of the change in the feedforward term |ΔTrq * By setting _FF| to less than or equal to the hysteresis width W_hys, an inappropriate torque command value Trq can be avoided due to excessive adjustment. * This prevents the calculation of the absolute value of the change in the feedforward term |ΔTrq. * By setting _FF| to be equivalent to the hysteresis width W_hys, the response delay associated with operation switching can be reduced to almost zero.

[0055] (Second Embodiment) The second embodiment will be described with reference to Figures 9 and 10. As shown in Figure 9, the torque command calculation unit 402 of the second embodiment includes a load command calculation unit 41, a load deviation calculator 42, and a load controller 48, as well as a control adjuster 472. Furthermore, the load controller 48 of the second embodiment calculates the torque command value Trq by performing a control calculation including proportional-integral control (hereinafter referred to as "PI control"). * This is the calculation performed. For example, the specific controller 48 may perform PID control including differential control.

[0056] The control regulator 472 acquires the load deviation ΔF and estimates the direction of increase or decrease in braking force from the sign of the load deviation ΔF. In other words, the control regulator 472 determines whether the current operation is an increasing operation, a decreasing operation, or a holding operation. Furthermore, the control regulator 472 may acquire the actual load F and estimate the current operating point on the map.

[0057] In the map shown in Figure 4, if the slopes of the positive efficiency line and the negative efficiency line are different, using common control gains Kp and Ki may not yield optimal control performance. Therefore, the control regulator 472 changes at least one of the proportional gain Kp or integral gain Ki of the load controller 48 depending on whether it is increasing or decreasing. Preferably, the control regulator 472 makes the proportional gain Kp and integral gain Ki of the load controller 48 greater in the increasing operation than in the decreasing operation.

[0058] Furthermore, the control regulator 472 does not necessarily change both the proportional gain Kp and the integral gain Ki; it may change only one of them. Also, after switching between increasing and decreasing operation, processing such as resetting the integral term may be performed.

[0059] Referring to the flowchart in Figure 10, the gain adjustment process performed by the control regulator 472 will be explained. Here, the control regulator 472 changes both the proportional gain and the integral gain, Kp and Ki, in the same increasing or decreasing direction.

[0060] In S23, it is determined whether an increasing operation is in progress. If the answer in S23 is YES, in S24 the control regulator 472 sets the control gains Kp and Ki to be greater than the values ​​during the decreasing operation. In S25, it is determined whether a decreasing operation is in progress. If the answer in S25 is YES, in S26 the control regulator 472 sets the control gains Kp and Ki to be less than the values ​​during the increasing operation.

[0061] In the second embodiment, the braking force can be appropriately controlled by switching the control gains Kp and Ki in accordance with the switching between increasing and decreasing operations. The control regulator 472 may also switch either the proportional gain Kp or the integral gain Ki according to the operation as described above. In this case, the other gain may be fixed or changed in the opposite direction.

[0062] Next, referring to Figures 11 and 12, the effects of the combined embodiment of the first and second embodiments will be explained in comparison with the comparative example. In the comparative example shown in Figure 11, the feedforward term Trq * -FF and control gains Kp and Ki are not adjusted. The load command value F is shown in the upper part of each figure. * The dashed line shows the change in the actual load F (solid line), and the lower section shows the change in torque.

[0063] Load command value F * The load increases from time t0 to time t1, and then decreases from time t1 to time t4. During the period up to time t1, the actual load F along the positive efficiency curve is equal to the load command value F. * The load increases to the target holding load Fhold in response, and the torque increases to the maximum torque Trq_max. In the comparative example, from time t1 to time t2, the torque decreases due to the holding operation, while the actual load F is held at the target holding load Fhold. From the standpoint of the responsiveness of the load F, during this time, the load command value F * A response delay occurs in the actual load F in response to the decrease in [the specified value].

[0064] When the torque drops to the minimum torque Trq_min at time t2, the holding operation ends, and the actual load F becomes the load command value F. * It drops sharply to this point. At this time, if the control gain is set to the same level as during the increase operation in an attempt to reduce the response delay during the decrease operation, an overshoot of the actual torque is likely to occur when switching to the decrease operation, and at the same time, the actual load F also overshoots. After that, the actual torque recovers, and at time t3, the decreased load command value F * When it matches the actual load F, the actual load F is equal to the load command value F * It follows the curve and decreases along the inverse efficiency curve.

[0065] In the combined embodiment of the first and second embodiments shown in Figure 12, at time t1 when the torque reaches the maximum torque Trq_max, along with the transition from increasing to decreasing operation, a feedforward term Trq equal to the hysteresis width W_hys is generated. * _FF decreases. As a result, the torque instantly drops to the minimum torque Trq_min. In other words, the operating point instantly shifts from the positive efficiency line to the negative efficiency line, so there is no response delay due to the holding action of the braking force.

[0066] In the combined embodiment, different control gains Kp and Ki can be set for increasing and decreasing operations. Therefore, by making the control gains Kp and Ki in the decreasing operation smaller than those in the increasing operation, overshoot during the switch to the decreasing operation is suppressed. Thus, an appropriate balance between controllability and responsiveness can be achieved.

[0067] (Third embodiment) The third embodiment will be described with reference to Figures 13 to 18. As shown in Figure 13, the torque command calculation unit 403 of the third embodiment includes a load command calculation unit 41, a load deviation calculator 42, and a load controller 48, as well as a dead zone setter 43 and a control adjuster 473.

[0068] The dead zone setter 43 is installed between the load deviation calculator 42 and the load controller 48. The dead zone setter 43 sets a predetermined range as a dead zone so that the load deviation ΔF input to the load controller 48 is considered to be zero if it is within a predetermined range including zero. The dead zone setter 43 outputs the processed load deviation ΔF# to the load controller 48.

[0069] The control regulator 473 acquires the load deviation ΔF and estimates the direction of increase or decrease of the braking force from the sign of the load deviation ΔF. In other words, the control regulator 473 determines whether the current operation is an increasing operation, a decreasing operation, or a holding operation. Furthermore, as shown by the dashed line, the control regulator 473 also determines the load command value F *Alternatively, at least one of the actual loads F may be obtained, and the other may be calculated by adding or subtracting the load deviation ΔF. The control regulator 473 may estimate the current operating point on the map based on the actual load F. Load command value F * Examples of control methods using this will be discussed later.

[0070] Here, we will reconfirm the definition of the sign of the load deviation ΔF in this embodiment. The load deviation ΔF in this embodiment is equal to the load command value F * It is defined as the value obtained by subtracting the actual load F from the load command value. In increasing motion, if the load deviation ΔF is positive, the load command value F * If the value is not reached and the load deviation ΔF is negative, the load command value F * This means it exceeds a certain value. The opposite is true for decreasing actions.

[0071] The following explanation assumes the above definition of the sign of the load deviation ΔF. However, in other embodiments, the sign of the load deviation ΔF may be defined in reverse, in which case the following explanation should be interpreted by reversing the sign as appropriate.

[0072] The control regulator 473 changes the dead zone for increasing and decreasing operations. Figure 14 shows the dead zone setting according to the basic embodiment of the third embodiment. In increasing operations, the control regulator 473 sets a dead zone DZi where the upper limit is zero only in the negative region of the load deviation ΔF. * It reaches the load command value F * When it exceeds this value, the load deviation ΔF changes from positive to negative. Then, the control system attempts to reduce the negative load deviation ΔF to zero, and switches to a decreasing operation. By setting a dead zone DZi with a lower limit value LL in the negative region of the load deviation ΔF, the actual load F becomes equal to the load command value F. * Even if it exceeds the limit, the system prevents switching to a decreasing operation within the range of the dead zone DZi. Furthermore, since the dead zone DZi is not set in the positive region of the load deviation ΔF, the actual load F is equal to the load command value F. * The increasing motion can be maintained with high precision until the moment it reaches that point.

[0073] Furthermore, the control regulator 473 sets a dead zone DZd where the lower limit is zero only in the positive region of the load deviation ΔF during the decreasing operation. * It reaches the load command value F * When it falls below a certain value, the load deviation ΔF changes from negative to positive. Then, the control system attempts to make the positive load deviation ΔF zero, and switches to an increasing operation. Therefore, by setting the dead zone DZd of the upper limit value UL in the positive region of the load deviation ΔF, the load command value F * Even if it falls below a certain value, the system will not switch to increasing operation within the range of the dead zone DZd. Furthermore, since the dead zone DZd is not set in the negative region of the load deviation ΔF, the actual load F is equal to the load command value F. * The decreasing motion can be maintained with high precision until the moment it reaches that point.

[0074] In the basic embodiment, by combining a negative dead zone DZi during increasing motion and a positive dead zone DZd during decreasing motion, the actual load F becomes equal to the load command value F. * Within a predetermined range spanning across these parameters, frequent switching between increasing and decreasing operations is prevented.

[0075] Figures 15(a) and 15(b) show dead zone settings according to other embodiments of the third embodiment. In the example shown in Figure 15(a), the dead zone DZ is set symmetrically across zero, that is, the absolute values ​​of the upper limit and the lower limit are equal (|UL|=|LL|). In the example shown in Figure 15(b), the dead zone DZ is set asymmetrically across zero, that is, the absolute values ​​of the upper limit and the lower limit are different (|UL|≠|LL|).

[0076] As shown in Figure 15(a), the control regulator 473 controls the load command value F * The larger the value, the wider the dead zone DZ may be set. This allows the width of the dead zone DZ to be appropriately adjusted according to the magnitude of the required braking force, for example, the load command value F * The ratio of the dead zone DZ to the load command value F can be set to be approximately constant. This also applies to setting the upper and lower limits of the dead zone provided in either the positive or negative region. In other words, the control regulator 473 controls the load command value F *The larger the value of the dead zone, the larger the absolute value of the upper limit UL or lower limit LL may be set.

[0077] Referring to the flowchart in Figure 16, the dead zone adjustment process performed by the control regulator 473 will be explained. Here, we assume an example in which, according to the basic embodiment shown in Figure 14, a dead zone is set only in either the negative or positive region of the load deviation ΔF depending on whether the operation is increasing or decreasing.

[0078] In S33, it is determined whether an increasing operation is in progress. If the answer in S33 is YES, in S34 the control regulator 473 sets the dead zone DZi to only the negative region of the load deviation ΔF. In S35, it is determined whether a decreasing operation is in progress. If the answer in S35 is YES, in S36 the control regulator 473 sets the dead zone DZd to only the positive region of the load deviation ΔF.

[0079] In the third embodiment, by switching the dead zone in conjunction with the switching between increasing and decreasing operations, it is possible to prevent unnecessary switching between increasing and decreasing operations.

[0080] Next, referring to Figures 17 and 18, the effects of the third embodiment will be explained in comparison with the comparative example. In the comparative example shown in Figure 17, no dead zone is set. The load command value F is shown in the upper part of each figure. * The dashed line shows the change in the actual load F (solid line), and the lower section shows the change in torque.

[0081] Load command value F * The load increases from time t5 to time t6, then remains constant at Fconst during the stop period from time t6 to time t7, and increases again from time t7. In the comparative example, during the stop period, the actual load F is equal to the load command value F * In an attempt to follow, the load command value F * Each time it exceeds a certain value, the torque switches between increasing and decreasing. Accordingly, the torque repeatedly increases and decreases across the hysteresis width W_hys. Even if the absolute value of the load deviation |ΔF| is small, the torque command value Trq *Large changes in this can occur as periodic pulsations, potentially increasing the load on the load controller 48 or causing noise and electromagnetic interference.

[0082] In the third embodiment shown in Figure 18, a dead zone DZi in the negative region is set during the increasing operation, so if the load deviation ΔF during the stop period is greater than the lower limit LL, switching to the decreasing operation is prevented. Similarly, during the decreasing operation, a dead zone DZd in the positive region is set, so if the load deviation ΔF during the stop period is less than the upper limit UL, switching to the increasing operation is prevented. Therefore, the torque command value Trq when the load deviation ΔF is within the range from the lower limit LL to the upper limit UL. * It can suppress the pulsation.

[0083] (Fourth Embodiment) Referring to Figure 19, the fourth embodiment will be described. The torque command calculation unit 404 of the fourth embodiment has a load command calculation unit 41, a load deviation calculator 42, and a load controller 48, as well as a dead zone setter 43, similar to the third embodiment. However, in the fourth embodiment, the direction of operation and the load command value F * Regardless of the size, the upper and lower limits and width of the dead zone are fixed. The upper and lower limits may be set symmetrically or asymmetrically.

[0084] In the fourth embodiment, by setting a dead zone, it is possible to prevent unnecessary switching between increasing and decreasing operations.

[0085] (Other embodiments) (a) The vehicle on which the vehicle braking device of the present invention is installed is not limited to a four-wheeled vehicle having two rows of left and right pairs of wheels in the longitudinal direction of the vehicle, but may also be a six-wheeled or more vehicle having three or more rows of wheels in the longitudinal direction of the vehicle.

[0086] (b) In the torque command calculation unit of the above embodiment, the load controller 48, which is a "specific controller", calculates the load command value F based on the actual load F detected by the load sensor 71. * Torque command value Trq *The torque command calculation unit of another embodiment calculates the torque command value Trq so that the actual positions θ and X detected by position sensors 72 and 73 approach the position command value. * The calculation may be performed. In that case, the braking force correlates with position θ and X, and position θ and X are used as the vertical axes of the hysteresis diagram corresponding to Figures 4 and 6. Also, the "load command value" and "actual load" in the above embodiment are interpreted as "position command value" and "actual position." The deviation between the position command value and the actual position becomes the "position deviation."

[0087] In the third embodiment, the position deviation is defined as the value obtained by subtracting the actual position from the position command value. The dead zone setter sets a predetermined range as a dead zone so that the position deviation is considered to be zero when the position deviation input to the position controller is within a predetermined range including zero. In the basic embodiment of the third embodiment, the control adjuster sets a dead zone DZi only in the negative region of the position deviation during increasing operation, and sets a dead zone DZd only in the positive region of the position deviation during decreasing operation. A configuration combining load control and position control may also be adopted.

[0088] The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit.

[0089] The braking force control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the braking force control unit and its method described herein may be implemented by a dedicated computer provided by configuring a processor by one or more dedicated hardware logic circuits. Alternatively, the braking force control unit and its method described herein may be implemented by one or more dedicated computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium. [Explanation of symbols]

[0090] 30. Vehicle braking systems, 400... Braking force control unit, 40 (401-404) ... Torque command calculation unit, 43 ... Dead zone setting device, 47 (471, 472, 473) ... Control regulator, 48. Load controller (specific controller), 50...Current command calculation section, 60...motor, 81-84...Electric brakes, 85...Linear drive mechanism, 900...vehicles, 91-94...wheels.

Claims

1. A vehicle braking system mounted on a vehicle (900) in which a plurality of electric brakes (81-84) are provided on each wheel, which convert the torque output by a motor (60) into direct force by a linear motion mechanism (85) and press against the corresponding wheels (91-94) to generate braking force, Based on the requested braking force commanded from an external source, the torque command value (Trq) of the motor is controlled. ＊ A torque command calculation unit (401) calculates the torque command value, and a current command value (I) that energizes the motor based on the torque command value. ＊ It includes a current command calculation unit (50) that calculates the current command, and a braking force control unit (400) that controls the braking force generated by each of the electric brakes, The electric brake is equipped with a load sensor (71) that detects the actual load (F), which is the braking load actually pressed against the wheel, or position sensors (72, 73) that detect the actual rotation angle of the motor or the actual position (θ, X), which is the actual stroke of the linear motion mechanism. The relationship between the torque of the motor and the braking force generated in the electric brake has a hysteresis characteristic in which, as the torque increases, the braking force increases along the positive efficiency curve; as the torque decreases from the turning point where it changes from increasing to decreasing to the holding critical value, the braking force is maintained at a constant level; and as the torque decreases from the holding critical value, the braking force decreases along the negative efficiency curve. If we define the operation of increasing the torque and braking force of the motor along the positive efficiency line as an increasing operation, the operation of maintaining the braking force at any operating point between the positive efficiency line and the negative efficiency line as a maintaining operation, and the operation of decreasing the torque and braking force of the motor along the negative efficiency line as a decreasing operation, then, The torque command calculation unit, A specific controller (48) calculates the torque command value so as to bring the actual load detected by the load sensor closer to the load command value, or so as to bring the actual position detected by the position sensor closer to the position command value, A control adjuster (471) adjusts the parameters of the control calculation on the input or output side of the specific controller during the increase operation, the decrease operation, or the transition between the increase operation and the decrease operation. It has, The torque command calculation unit outputs the torque command value calculated by the specific controller and the feedforward term (Trq * _FF) of the torque command value set by the control regulator to the current command calculation unit. The current command calculation unit calculates the current command value such that the actual torque (Trq), which is the torque actually output by the motor, approaches the sum of the torque command value and the feedforward term. The control regulator is a vehicle braking device that decreases the value of the feedforward term when transitioning from the increasing operation to the decreasing operation, and increases the value of the feedforward term when transitioning from the decreasing operation to the increasing operation.

2. The aforementioned control regulator is The hysteresis width (W_hys), which is the difference between the maximum torque on the positive efficiency line and the minimum torque on the negative efficiency line corresponding to the held braking force, is calculated. The vehicle braking device according to claim 1, wherein the absolute value of the change in the feedforward term during the transition between the increasing operation and the decreasing operation is set to be less than or equal to the hysteresis width.

3. A vehicle braking system mounted on a vehicle (900) in which a plurality of electric brakes (81-84) are provided on each wheel, which convert the torque output by a motor (60) into direct force by a linear motion mechanism (85) and press against the corresponding wheels (91-94) to generate braking force, Based on the requested braking force commanded from an external source, the torque command value (Trq) of the motor is controlled. ＊ A torque command calculation unit (402) calculates the torque command value, and a current command value (I) that energizes the motor based on the torque command value. ＊ It includes a current command calculation unit (50) that calculates the current command, and a braking force control unit (400) that controls the braking force generated by each of the electric brakes, The electric brake is equipped with a load sensor (71) that detects the actual load (F), which is the braking load actually pressed against the wheel, or position sensors (72, 73) that detect the actual rotation angle of the motor or the actual position (θ, X), which is the actual stroke of the linear motion mechanism. The relationship between the torque of the motor and the braking force generated in the electric brake has a hysteresis characteristic in which, as the torque increases, the braking force increases along the positive efficiency curve; as the torque decreases from the turning point where it changes from increasing to decreasing to the holding critical value, the braking force is maintained at a constant level; and as the torque decreases from the holding critical value, the braking force decreases along the negative efficiency curve. If we define the operation of increasing the torque and braking force of the motor along the positive efficiency line as an increasing operation, the operation of maintaining the braking force at any operating point between the positive efficiency line and the negative efficiency line as a maintaining operation, and the operation of decreasing the torque and braking force of the motor along the negative efficiency line as a decreasing operation, then, The torque command calculation unit, A specific controller (48) calculates the torque command value so as to bring the actual load detected by the load sensor closer to the load command value, or so as to bring the actual position detected by the position sensor closer to the position command value, A control adjuster (472) adjusts the parameters of the control calculation on the input or output side of the specific controller during the increase operation, the decrease operation, or the transition between the increase operation and the decrease operation, It has, The specific controller of the torque command calculation unit calculates the torque command value by a control calculation including proportional-integral control. The control regulator is a vehicle braking device that changes at least one of the proportional gain or integral gain of the specific controller with the increasing operation and the decreasing operation.

4. The vehicle braking device according to claim 3, wherein the control regulator makes at least one of the proportional gain or integral gain of the specific controller greater in the increasing operation than in the decreasing operation.

5. A vehicle braking system mounted on a vehicle (900) in which a plurality of electric brakes (81-84) are provided on each wheel, which convert the torque output by a motor (60) into direct force by a linear motion mechanism (85) and press against the corresponding wheels (91-94) to generate braking force, Based on the requested braking force commanded from an external source, the torque command value (Trq) of the motor is controlled. ＊ A torque command calculation unit (403) calculates the torque command value, and a current command value (I) that energizes the motor based on the torque command value. ＊ It includes a current command calculation unit (50) that calculates the current command, and a braking force control unit (400) that controls the braking force generated by each of the electric brakes, The electric brake is equipped with a load sensor (71) that detects the actual load (F), which is the braking load actually pressed against the wheel, or position sensors (72, 73) that detect the actual rotation angle of the motor or the actual position (θ, X), which is the actual stroke of the linear motion mechanism. The relationship between the torque of the motor and the braking force generated in the electric brake has a hysteresis characteristic in which, as the torque increases, the braking force increases along the positive efficiency curve; as the torque decreases from the turning point where it changes from increasing to decreasing to the holding critical value, the braking force is maintained at a constant level; and as the torque decreases from the holding critical value, the braking force decreases along the negative efficiency curve. If we define the operation of increasing the torque and braking force of the motor along the positive efficiency line as an increasing operation, the operation of maintaining the braking force at any operating point between the positive efficiency line and the negative efficiency line as a maintaining operation, and the operation of decreasing the torque and braking force of the motor along the negative efficiency line as a decreasing operation, then, The torque command calculation unit, A specific controller (48) calculates the torque command value so as to bring the actual load detected by the load sensor closer to the load command value, or so as to bring the actual position detected by the position sensor closer to the position command value, A control adjuster (473) adjusts the parameters of the control calculation on the input or output side of the specific controller during the increase operation, the decrease operation, or the transition between the increase operation and the decrease operation. It has, The torque command calculation unit, The device includes a dead zone setting device (43) that sets the predetermined range as a dead zone so that the load deviation, which is the difference between the load command value input to the specified controller and the actual load, or the position deviation, which is the difference between the position command value and the actual position, is within a predetermined range including zero, so that the load deviation or the position deviation is considered to be zero. The control regulator is a vehicle braking device that changes the dead zone with the increasing operation and the decreasing operation.

6. If the load deviation is defined as the value obtained by subtracting the actual load from the load command value, or if the position deviation is defined as the value obtained by subtracting the actual position from the position command value, The aforementioned control regulator is In the aforementioned increasing operation, a dead zone is set in which the upper limit is zero only in the negative region of the load deviation or the position deviation. The vehicle braking device according to claim 5, wherein in the reduction operation, the dead zone is set in which the lower limit value is zero only in the positive region of the load deviation or the position deviation.

7. The vehicle braking device according to claim 5 or 6, wherein the control regulator sets the absolute value of the upper or lower limit of the dead zone to be larger as the load command value or the position command value increases.

8. A vehicle braking system mounted on a vehicle (900) in which a plurality of electric brakes (81-84) are provided on each wheel, which convert the torque output by a motor (60) into direct force by a linear motion mechanism (85) and press against the corresponding wheels (91-94) to generate braking force, Based on the requested braking force commanded from an external source, the torque command value (Trq) of the motor is controlled. ＊ A torque command calculation unit (404) calculates the torque command value, and a current command value (I) that energizes the motor based on the torque command value. ＊ It includes a current command calculation unit (50) that calculates the current command, and a braking force control unit (400) that controls the braking force generated by each of the electric brakes, The electric brake is equipped with a load sensor (71) that detects the actual load (F), which is the braking load actually pressed against the wheel, or position sensors (72, 73) that detect the actual rotation angle of the motor or the actual position (θ, X), which is the actual stroke of the linear motion mechanism. The relationship between the torque of the motor and the braking force generated in the electric brake has a hysteresis characteristic in which, as the torque increases, the braking force increases along the positive efficiency curve; as the torque decreases from the turning point where it changes from increasing to decreasing to the holding critical value, the braking force is maintained at a constant level; and as the torque decreases from the holding critical value, the braking force decreases along the negative efficiency curve. The torque command calculation unit, A specific controller (48) calculates the torque command value so as to bring the actual load detected by the load sensor closer to the load command value, or so as to bring the actual position detected by the position sensor closer to the position command value, A dead zone setting device (43) sets the predetermined range as a dead zone so that the load deviation, which is the difference between the load command value input to the specified controller and the actual load, or the position deviation, which is the difference between the position command value and the actual position, is within a predetermined range including zero, so that the load deviation or the position deviation is considered to be zero. A vehicle braking system having [a specific feature / feature].

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