JP7250191B2 - Electric linear actuator and electric brake device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric linear motion actuator and an electric brake device mounted on a vehicle or the like, for example, and to a technique capable of performing stable control by appropriately switching between position control and load control.

The following techniques have been proposed as electric linear motion actuators.
1. An electric brake actuator using an electric motor, a linear motion mechanism and a speed reducer (Patent Document 1).
2. An electric actuator using a planetary roller mechanism and an electric motor (Patent Document 2).
3. An electric brake that detects an axial load with a strain gauge (Patent Document 3).
4. An electric linear motion actuator that controls an electric motor based on a converted load in the vicinity of a boundary between a load applied region and a no-load region (Patent Document 4). The converted load is set to continuously change between a negative load and a positive load when the linear motion member moves across the load applied region and the no-load region.

JP-A-6-327190 JP 2006-194356 A Japanese Patent Publication No. 2001-507779 JP 2014-88911 A

For example, in an electric linear motion actuator that applies a load to an object, such as those disclosed in Patent Documents 1 to 3, when applying a load, load control is performed so that the estimated load follows a predetermined target value, and the load is set to zero, position control is generally performed so that the position of the actuator estimated from the motor angle or the like follows a predetermined target value.
When switching between the position control and the load control, it may be difficult to switch appropriately, especially with a relatively small load.

For example, in the case of using a load sensor that detects an axial load, such as those disclosed in Patent Documents 3 and 4, when a relatively large load is exerted, the vehicle at the time when the application of the load starts and ends The output indicating zero load may be offset due to changes in attitude and the effects of friction on each part.
In addition, due to the influence of friction of each part, the output of the load sensor may have hysteresis and not change when the pressure is reduced, especially when the load is relatively small. In such a case, if a method of switching control with respect to a certain threshold value is adopted, there are cases where appropriate control switching cannot be performed due to the error of the load sensor or the like. If a highly accurate sensor is used as a countermeasure for this problem, high cost may be a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric linear motion actuator and an electric brake device that can appropriately switch between position control and load control to perform stable control and reduce costs.

The electric linear motion actuator DA of the present invention includes an electric motor 4, a linear motion mechanism 6 that converts the rotary motion of the electric motor 4 into a linear motion of a linear motion portion 14, and a control device 2 that controls the electric motor 4. In an electric linear actuator comprising
The control device 2 is
a load estimation function unit 20 for estimating the axial load of the linear motion mechanism 6;
a position estimation function unit 21 for estimating the axial position of the linear motion unit 14 in the linear motion mechanism 6;
a load control function unit 22 that controls the load of the linear motion mechanism 6 based on the estimated load that is the result of estimation by the load estimation function unit 20;
a position control function unit 23 that controls the axial position of the linear motion unit 14 of the linear motion mechanism 6 based on the estimated position that is the estimation result of the position estimation function unit 21;
A control switching function unit 24 that switches to one of the load control function unit 22 and the position control function unit 23,
The control switching function unit 24 is
It is a state in which the position control function unit 23 is switched to, and when the load of the linear motion mechanism 6 is exerted from a no-load state in which the load of the linear motion mechanism 6 is not applied, and the estimated load. is greater than a first threshold, switching from the position control function unit 23 to the load control function unit 22,
It is a state of being switched to the load control function unit 23, and when the load of the linear motion mechanism 6 is reduced or made zero, and the load is greater than the first threshold value. The load control function unit 22 is switched to the position control function unit 23 when the second determination condition that the second threshold value is exceeded is satisfied.
The first and second thresholds are thresholds that are arbitrarily determined by design or the like, and are determined, for example, by obtaining appropriate thresholds through either one or both of tests and simulations. However, the second threshold is larger than the first threshold.

According to this configuration, when the control switching function unit 24 is switched to the position control function unit 23, the position control function unit 23 changes the axial position of the linear motion unit 14 of the linear motion mechanism 6 based on the estimated position. to control. The control switching function unit 24 switches from the position control function unit 23 to the load control function unit 22 when the first determination condition is satisfied. Satisfying the first determination condition means satisfying all of the following three conditions 1-1, 1-2, and 1-3.
Condition 1-1: The state is switched to the position control function unit 23 .
Condition 1-2: When the load is exerted from the no-load state.
Condition 1-3: The estimated load exceeds the first threshold.
When the control switching function unit 24 switches to the load control function unit 22, the load control function unit 22 controls the load of the linear motion mechanism 6 based on the estimated load.

The control switching function unit 24 switches from the load control function unit 22 to the position control function unit 23 when the second determination condition is satisfied. Satisfying the second determination condition means satisfying all of the following three conditions 2-1, 2-2, and 2-3.
Condition 2-1: The state is switched to the load control function unit 22 .
Condition 2-2: When the load is reduced or made zero.
Condition 2-3: the load is below the second threshold.

When increasing the pressure from a no-load state where no load is applied, it is sufficient to observe how much the estimated load changes from the state where the load is zero. It can be expected that the position control can be switched to the load control without any problems.
On the other hand, when depressurizing from a state where a load is applied, the second threshold is set as a comparison set a relatively large threshold.
Therefore, by setting the first determination condition for switching from position control to load control and the second determination condition for switching from load control to position control as different conditions, it is possible to prevent erroneous determination of control switching and improve load control accuracy. can be improved. Therefore, it is possible to perform stable control by appropriately switching between position control and load control without using a highly accurate load sensor.

A storage means 30 is provided for storing a history of the estimated load estimated in the execution state of the load control function section 22 from the state where the load was zero last time. The second threshold value may be larger than the first threshold value as the maximum load in the estimated load increases.
According to this configuration, when a relatively large load is applied, for example, the zero point offset of the sensor output for estimating the axial load occurs due to the influence of minute friction within the electric linear motion actuator. Sometimes it's easy. Therefore, by increasing the second threshold value as the maximum load in the stored estimated load increases, erroneous determination of control switching due to the offset can be prevented.

When the load of the linear motion mechanism 6 is increased in the execution state of the load control function unit 22, the control switching function unit 24 continues the execution state of the load control function unit 22, When the load of the linear motion mechanism 6 is reduced in the execution state, position control by the position control function unit 23 may be executed.
Even if the sensor output monotonously increases on the pressure increasing side, the sensor output on the pressure reducing side may not monotonically decrease due to hysteresis due to the influence of friction or the like. Therefore, when the load of the linear motion mechanism 6 is reduced in the execution state of the load control function unit 22, the position control function unit 23 performs position control without using the estimated load. Malfunction can be prevented.

In the configuration for switching to the position control function unit 23 when reducing the load, a storage unit 30 for storing an estimated load when switching from the load control function unit 22 to the position control function unit 23 is provided, and the control switching function unit 24, when increasing the load of the linear motion mechanism 6 with the position control function unit 23 switched to, controls the position control function unit 23 until the estimated load stored in the storage means 30 is reached. After reaching the estimated load, the position control function unit 23 may be switched to the load control function unit 22 .

Even if the load is switched to the position control function unit 23 when the load is reduced and the load is increased again in a minute load region, the sensor output for estimating the load will not be output due to the hysteresis. Errors may occur. Therefore, the estimated load when switching from the load control function unit 22 to the position control function unit 23 is stored, and control by the position control function unit 23 is continued until the stored estimated load is reached. Malfunction of the linear motion actuator DA can be prevented.

The position estimation function unit 21 has a function of estimating a gap until the linear motion mechanism 6 becomes ready to apply a load based on the estimated load and the estimated position. may set the first threshold larger as the estimated gap becomes larger.
The gap is a gap between the linear motion mechanism 6 and the object to which the linear motion mechanism 6 applies a load.
The larger the gap, the lower the possibility that a load will be generated, and the greater the influence of the malfunction of the actuator when the control is switched due to an erroneous determination. Therefore, by setting the first threshold value larger as the estimated air gap (estimated air gap) increases, erroneous determination of control switching can be prevented. By changing the first threshold in accordance with the estimated air gap in this manner, the risk of erroneous determination of control switching can be reduced.

The position estimation function unit 21 has a function of estimating a gap until the linear motion mechanism 6 becomes capable of applying a load based on the estimated load and the estimated position. may estimate the load using the estimated load in a state in which the estimated air gap is larger than the determined air gap as a reference corresponding to zero load.
The defined gap is a gap that is arbitrarily determined by design or the like, and is determined, for example, by finding an appropriate gap through either one or both of tests and simulations.
According to this configuration, when the estimated clearance is larger than the defined clearance, it can be expected that the load on the linear motion mechanism 6 is approximately zero. Therefore, when the estimated air gap satisfies the condition that the air gap is larger than the predetermined air gap, the load can be estimated using the estimated load as a reference equivalent to zero load.

The position estimation function unit 21 has a function of estimating a gap until the linear motion mechanism 6 becomes ready to apply a load based on the estimated load and the estimated position. is executed in a state where there is a request to apply a load, the position control function unit 23 derives a target position that can be a predetermined load from information including the rigidity of the electric linear motion actuator DA, and this having a function of executing follow-up control for causing the estimated position to follow a target position;
When the position control function unit 23 is applied with a load from the execution state of the position control function unit 23 in the no-load state, the control switching function unit 24 determines whether the gap is smaller than a set value or zero in a state in which the first determination condition is not satisfied. or when the position control function unit 23 determines that the position control has been achieved based on the deviation between the target position and the estimated position, until the first determination condition is satisfied, the It may have a proximity control function to move the linear motion part 14 of the linear motion mechanism 6 in the load application direction.
The predetermined load is a load that is arbitrarily determined by design or the like, and is determined, for example, by obtaining an appropriate load through either one or both of tests and simulations.

According to this configuration, the position estimation function unit 21 estimates the gap until the load can be applied based on the estimated load and the estimated position. When the position control function unit 23 is executed in a state where there is a request to apply a load, the position control function unit 23 derives a target position that can be a predetermined load from information including the rigidity of the electric linear motion actuator DA. Then, follow-up control is executed to cause the estimated position to follow the target position.

A load may not be generated even at the position of the direct acting portion 14 where the load should be applied due to volume fluctuations due to temperature change, backlash of the mechanical coupling portion, and the like. For this reason, there are cases in which a load is not actually applied to a very small load command value only by position control. According to this configuration, when a load is not actually applied to a very small load command value as described above, the load can be reliably applied by moving the direct acting portion 14 in the load applying direction.

The control device 2 has a function of estimating the angular acceleration of the electric motor 4, and the control switching function unit 24 sets a first threshold value when the estimated angular acceleration is greater than a predetermined angular acceleration. It may be larger than the reference value.
The predetermined angular acceleration and reference values are the angular acceleration and reference values that are arbitrarily determined by design, etc. For example, the angular acceleration and reference values that are appropriate by either or both of tests and simulations It is determined by finding the value that becomes

When the electric motor 4 is operated with a large angular acceleration, the sensor for estimating the load may react due to the influence of the inertia of the linear motion mechanism 6 even when no load is actually generated. . Therefore, according to this configuration, when the estimated angular acceleration is greater than the predetermined angular acceleration, the first threshold is made larger than the reference value, thereby preventing erroneous determination that the load has been applied. be able to.

The load control function unit 22 uses the deviation between the calculated position of the linear motion unit 14 calculated based on the estimated load and the rigidity of the electric linear motion actuator DA and the estimated position to determine the target value and the feedback value. It is a position control that corrects either one or both, and the control switching function unit 24 is the position control function unit 23 that sets the correction amount in the position control to zero, or the load control function that does not set the correction amount to zero. You may switch to the part 22. FIG. By switching whether or not to set the correction amount in the position control to zero in this manner, either one of the position control function unit 23 and the load control function unit 22 can be selectively switched.

An electric brake device 1 of the present invention includes any one of the electric linear motion actuators DA described above, a friction material 9 operated by the electric linear motion actuator DA, and a friction material 9 that contacts with each other to generate a braking force. and a brake rotor 8 to generate. According to the electric brake device 1, since it includes any of the electric linear motion actuators DA, it is possible to improve load control accuracy while preventing erroneous determination of control switching.

An electric linear motion actuator according to the present invention includes an electric motor, a linear motion mechanism that converts rotary motion of the electric motor into linear motion of a linear motion portion, and a control device that controls the electric motor. In the dynamic actuator, the control device includes a load estimating function unit that estimates an axial load of the linear motion mechanism, a position estimation function unit that estimates an axial position of the linear motion unit in the linear motion mechanism, and the load A load control function unit that controls the load of the linear motion mechanism based on the estimated load that is the result of estimation by the estimation function unit; a position control function unit that controls the axial position of the linear motion unit; and a control switching function unit that switches to one of the load control function unit and the position control function unit, wherein the control switching function unit It is a state in which the position control function unit is switched to, and when the load of the linear motion mechanism is exerted from a no-load state in which the load of the linear motion mechanism is not applied, and the estimated load is the first. When the first determination condition of exceeding the threshold value of the linear motion when the load of the mechanism is reduced or brought to zero, and the load satisfies a second criterion of being below a second threshold greater than the first threshold. Switch from the control function unit to the position control function unit. Therefore, the position control and the load control can be appropriately switched to perform stable control, and cost reduction can be achieved.

An electric brake device according to the present invention includes any one of the electric linear motion actuators described above, a friction material operated by the electric linear motion actuator, and a brake rotor that generates a braking force by contact with the friction material. , the position control and the load control can be appropriately switched to perform stable control, and cost reduction can be achieved.

1 is a diagram schematically showing an electric brake device according to an embodiment of the invention; FIG. It is a block diagram of the control system of the electric linear motion actuator of the electric brake device. It is a block diagram which shows the structural example during execution of the load control function part of the same control system. 4 is a block diagram showing a configuration example when executing a position control function unit of the same control system; FIG. 5 is a flowchart showing step by step an example of execution of a control switching function unit; FIG. 5 is a block diagram of a control switching function section and the like of an electric linear motion actuator according to another embodiment of the present invention; It is a block diagram which shows the structural example which switched to the position control function part by the same control switching function part.

An electric brake device according to an embodiment of the invention will be described with reference to FIGS. 1 to 6. FIG. This electric brake device is mounted on a vehicle, for example.
As shown in FIG. 1, this electric brake device 1 includes an electric linear motion actuator DA and a friction brake BR. First, the structures of the electric linear motion actuator DA and the friction brake BR will be described.

<Structures of Electric Linear Actuator DA and Friction Brake BR>
As shown in FIGS. 1 and 2, the electric linear motion actuator DA includes an actuator main body AH, a power supply device 3, and a control device 2, which will be described later. The actuator main body AH has an electric motor 4, a deceleration mechanism 5, a linear motion mechanism 6, a parking brake device 7, an angle sensor Sa, and a load sensor Sb.

As shown in FIG. 1, the electric motor 4 is, for example, a permanent magnet synchronous motor. If a permanent magnet synchronous motor is used as the electric motor 4, it is preferable to use a space-saving and high-torque motor. can also

The friction brake BR has a brake rotor 8 that rotates in conjunction with the wheel of the vehicle, and a friction material 9 that comes into contact with the brake rotor 8 and generates a braking force. This friction material 9 is operated by an electric linear motion actuator DA. A mechanism can be used in which the friction material 9 is pressed against the brake rotor 8 by operating the actuator main body AH of the electric linear actuator DA to generate a braking force by the frictional force.

The deceleration mechanism 5 is a mechanism that decelerates rotation of the electric motor 4 and includes a primary gear 12 , an intermediate gear 13 and a tertiary gear 11 . In this example, the reduction mechanism 5 reduces the rotation of the primary gear 12 attached to the rotor shaft 4a of the electric motor 4 by the intermediate gear 13 and transmits it to the tertiary gear 11 fixed to the end of the rotating shaft 10. It is possible.

The linear motion mechanism 6 is a mechanism that converts the rotary motion output by the reduction mechanism 5 into linear motion of the linear motion portion 14 by means of a feed screw mechanism, and causes the friction material 9 to contact and separate from the brake rotor 8 . The direct-acting portion 14 is detented and supported so as to be movable in the axial direction indicated by arrow A1. A friction material 9 is provided at the outboard side end of the direct acting portion 14 . By transmitting the rotation of the electric motor 4 to the linear motion mechanism 6 via the reduction mechanism 5, the rotary motion is converted into linear motion, which is converted into the pressing force of the friction material 9, thereby generating the braking force. . When the electric brake device 1 is mounted on the vehicle, the outer side of the vehicle in the vehicle width direction is called the outboard side, and the center side of the vehicle in the vehicle width direction is called the inboard side.

A linear solenoid, for example, is applied as the actuator 16 of the parking brake mechanism 7 . The locking member 15 is advanced by the actuator 16 and engaged by being fitted into a locking hole (not shown) formed in the intermediate gear 13, and by prohibiting the rotation of the intermediate gear 13, the parking lock state is established. to By removing the locking member 15 from the locking hole, the rotation of the intermediate gear 13 is permitted, and the unlocked state is established.

As shown in FIG. 2, the angle sensor Sa detects the rotation angle of the electric motor 4. As shown in FIG. For the angle sensor Sa, for example, a resolver, a magnetic encoder, or the like is preferably used because of its high performance and reliability, but various sensors such as an optical encoder can also be used. Instead of using the angle sensor Sa, angle sensorless estimation may be used in which the motor angle is estimated from the relationship between the voltage and the current of the electric motor 4 in the control device 2, which will be described later.

The load sensor Sb detects the axial load of the linear motion mechanism 6 . As the load sensor Sb, for example, a magnetic sensor, a strain sensor, a pressure sensor, or the like that detects displacement or deformation of a predetermined member on which the load of the linear motion mechanism 6 acts can be used. Instead of using the load sensor Sb, the control device 2 may detect the load from the motor current or the like based on the relationship between the motor current and the load, or the load may be detected using an external sensor. As an external sensor, for example, in the electric brake device 1 (FIG. 1) using the electric linear motion actuator DA according to the present embodiment, the wheel torque of the wheel on which the brake is mounted or the electric brake device (FIG. 1) is mounted. It is also possible to use a sensor or the like that detects the longitudinal force of the vehicle. In addition, various sensors such as a thermistor may be provided as required.

<Regarding the control system>
FIG. 2 is a block diagram of the control system of the electric linear motion actuator DA of this electric brake device. For example, a controller 2 and an actuator main body AH are provided for each wheel. Each control device 2 controls a corresponding electric motor 4 . Each control device 2 is connected to a DC power supply device 3 and a host ECU 17 which is a host control means of each control device 2 . The power supply device 3 supplies electric power to the electric motor 4 and the control device 2 . For the power supply device 3, for example, a low-voltage (for example, 12V) battery of a vehicle in which the electric brake device 1 (FIG. 1) is mounted can be applied.

As the higher-level ECU 17, for example, an electric control unit that controls the vehicle in general is applied. The high-level ECU 17 has an integrated control function for each control device 2 . A higher-level ECU is also referred to as a "VCU". The host ECU 17 includes a command means 17a, which outputs a brake force command value (command signal) to each control device 2 according to the output of a sensor that changes according to the amount of operation of a brake operation means (not shown). Output each. Note that the command means 17a can also output brake force command values to each control device 2, for example, by judging braking in an automatically driven vehicle without relying on the operation of the brake operation means.

Each control device 2 includes various control calculation function units that perform control calculations, and a motor driver 18 . Various control arithmetic function units are configured by, for example, a processor such as a microcomputer, or an arithmetic unit such as FPGA or ASIC, and peripheral circuits. The various control calculation function units include a command generation function unit 19 , a load estimation function unit 20 , a position estimation function unit 21 , a load control function unit 22 , a position control function unit 23 and a control switching function unit 24 .

The command generation function unit 19 has a function of generating command values for the load control function unit 22 and the position control function unit 23 from command signals input from the command means 17a. The command generation function unit 19 can output a load command value to the load control function unit 22, for example, considering the gain and range of the load sensor Sb. The command generation function unit 19 provides the position control function unit 23 with, for example, a position command value that can exert a load determined from the rigidity of the electric linear motion actuator DA, or a value determined when the load is zero. It is possible to output a position command value that becomes a clearance. The gap is a gap between the linear motion mechanism 6 and the brake rotor 8 (FIG. 1) to which the linear motion mechanism 6 applies a load.

The load estimation function unit 20 estimates the axial load of the linear motion mechanism 6 from the output of the load sensor Sb and the like. The position estimation function unit 21 estimates the axial position of the linear motion unit 14 (FIG. 1) in the linear motion mechanism 6 from the output of the angle sensor Sa and the like. Alternatively, the position estimation function unit 21 may estimate a quantity that can correspond to the position, such as the motor angle. In general, in a linear motion actuator that controls load, when the load is set to zero, a predetermined gap is provided with respect to the object to which the load is applied. It is preferable to provide a function of estimating the position where the load is zero and estimating the air gap.

The load control function unit 22 operates the electric motor so that the estimated load, which is the estimated result calculated by the load estimation function unit 20, follows the target load command value given from the command generation function unit 19. Determine quantity. The position control function unit 23 determines the electric motor operation amount so that the estimated position calculated by the position estimation function unit 21 follows the target position command value given from the command generation function unit 19 . . For the input load command value, the position control function unit 23 derives an angle at which a predetermined load can be exerted based on the actuator stiffness and the like, and the position estimation function unit 21 calculates the derived angle command value. The electric motor operation amount may be determined so as to follow the feedback angle provided.

The control switching function unit 24 selects either the load control function unit 22 or the position control function unit 23 based on the load estimation function unit 20, the position estimation function unit 21, and the braking force command value given from the command means 17a. It has a function to switch to one side. The control switching function section 24 includes a control switching function body section 25 and a changeover switch 26 . The control switching function main unit 25 has first and second switching determination units 27 and 28 , a switching threshold value setting unit 29 , and storage means 30 . The first switching determination unit 27 determines switching from the position control state by the position control function unit 23 to the load control by the load control function unit 22 . A second switching determination unit 28 determines switching from the load control state to the position control. The switching threshold value setting unit 29 selects the first and second switching determination units 27 and 28, which are used for the determination by the respective first and second switching determination units 27 and 28, depending on the combination of the load estimation function unit 20, the position estimation function unit 21, and the brake force command value. Set the second threshold, etc. as appropriate. The first and second thresholds are rewritably stored in the storage means 30 .

The first switching determination section 27 gives a command to the changeover switch 26 to switch from the position control function section 23 to the load control function section 22 when the first determination condition is satisfied. Satisfying the first determination condition means satisfying all of the following three conditions 1-1, 1-2, and 1-3.
Condition 1-1: The state is switched to the position control function unit 23 .
Condition 1-2: When the load is exerted from the no-load state.
Condition 1-3: The estimated load exceeds the first threshold.

The second switching determination section 28 gives a command to the changeover switch 26 to switch from the load control function section 22 to the position control function section 23 when the second determination condition is satisfied. Satisfying the second determination condition means satisfying all of the following three conditions 2-1, 2-2, and 2-3.
Condition 2-1: The state is switched to the load control function unit 22 .
Condition 2-2: When the load is reduced or made zero.
Condition 2-3: the load is below the second threshold. However, the second threshold is larger than the first threshold.

The motor driver 18 controls power supplied to the coils of the electric motor 4 . The motor driver 18, for example, constitutes a half-bridge circuit using switch elements such as field effect transistors (abbreviated as FET), and performs PWM control that determines the motor applied voltage according to the ON-OFF duty ratio of the switch elements. If it is configured to perform the above, it becomes inexpensive and high performance. Alternatively, a transformer circuit or the like may be provided to perform PAM control. In addition, configurations such as a current sensor (not shown) can be appropriately provided as necessary. Also, each functional unit is provided as a block for convenience, and may be integrated or divided as necessary.

<Regarding the configuration of the control switching function unit 24>
3 and 4 show a configuration example of the control switching function unit 24 that switches between the load control function unit 22 and the position control function unit 23. FIG. 3 shows an example of the configuration during execution of the load control function unit 22, while FIG. 4 shows an example of the configuration when the position control function unit 23 is executed. The load control function unit 22 and the position control function unit 23 can be switched by switching the changeover switch 26 according to a command from the control switching function main unit 25 . As a component common to FIGS. 3 and 4, a load-to-angle converter 31 has a function of deriving a motor angle capable of exerting a predetermined load based on the rigidity of the electric linear motion actuator DA (FIG. 2). have

Furthermore, the load-to-angle converter 31 can have a function of deriving an angle that can be a predetermined gap as required, for example, when the load is zero. It is preferable to measure the rigidity of the electric linear motion actuator DA (FIG. 2) in advance and implement it with a look-up table (abbreviated as LUT) or the like, because the function can be processed at high speed by a computing unit. It can also be implemented with a formula.

The difference calculator 32 has a function of calculating the difference between the estimated angles (estimated positions) for each predetermined sample step. In general, the estimated angle overflows or underflows and wraps at a predetermined cycle, such as the mechanical or electrical angle of the motor. It is preferable to calculate the difference.
The angle calculator 33 has a function of accumulating the difference between the estimated angles obtained by the difference calculator 32 and calculating the total rotation angle of the electric motor 4 (FIG. 2).

The configuration example shown in FIG. 3 has a position control function, and the load control function unit 22 is derived from information such as the rigidity of the electric linear motion actuator DA (FIG. 2) from the estimated load by the load → angle converter 34. An example of implementation as a function that corrects the control amount of the position control system from the deviation between the position (angle) and the total rotation angle is shown. FIG. 3 shows an example of correcting the feedback angle (feedback value), but instead of the example of correcting the feedback angle, it is also possible to correct the angle command value.

3, which is an example of the configuration during execution of the load control function unit 22, the position control shown in FIG. Functional unit 23 can be executed.

According to the configuration examples of FIGS. 3 and 4, since the control calculation unit is only the angle controller 35, there is no need to initialize the control variables each time the control is switched. Even if the stiffness of 2) is non-linear, it is advantageous in that it is easy to design the control characteristics to the desired characteristics. In addition, for example, components not shown, such as initialization of each controller, etc., are appropriately provided as necessary. Also, each functional unit is divided into blocks for convenience, and may be integrated or divided as necessary.

<Example of control switching flow>
FIG. 5 is a flow chart showing step by step an example of execution of this control switching function unit. Hereinafter, description will be made with reference to FIGS. 1, 2, etc. as appropriate.
After starting this process, the control switching function unit 24 determines which of the load control function unit 22 and the position control function unit 23 is being executed (step S1). Upon determining that the position control function unit 23 is in the execution state (step S1: no), the position estimation function unit 21 determines whether the gap between the linear motion mechanism 6 and the brake rotor 8 is equal to or greater than a predetermined value Bk (step S11). The predetermined value Bk is set as a threshold with which it can be strongly expected that the load of the linear motion mechanism 6 is sufficiently removed. If there is a sufficient gap (step S11: yes), the load on the electric linear motion actuator DA can be expected to be substantially zero, so the zero point of the estimated load is updated (step S12).

After that, the process proceeds to step S2. When it is determined that the gap is not equal to or greater than the predetermined value Bk (step S11: no), the process proceeds to step S2. In step S2, the position control function unit 23 determines whether or not it has received a non-zero load command value from the command generation function unit 19, that is, whether or not it has received a request to exert a predetermined load. If there is no request to apply a load (step S2: no), position control is continued (step S16). After that, this process is terminated.

If there is a request to apply a load (step S2: yes), the control switching function unit 24 determines whether the estimated load exceeds a predetermined first threshold An and the estimated gap is below the threshold Bm (step S3). When there is a request to apply a load, the electric linear motion actuator DA is driven in the direction of applying the load. Make a decision to switch to control. At this time, the larger the estimated air gap, the lower the possibility that the load will occur, and conversely, the smaller the estimated air gap, the higher the possibility that the load will occur.

For this reason, if generation of a load is determined from the estimated load and the estimated air gap as in this embodiment, more accurate control switching can be performed. However, the control switching function unit 24 may make the determination of control switching only based on the estimated load without considering the estimated air gap. Further, for either one or both of the first threshold An and the threshold Bm, a plurality of thresholds or a combination thereof may be set to determine stepwise control switching. A coupling function may be used as an evaluation function to determine control switching for the evaluation function.

If the condition for the switching threshold is not satisfied in step S3 (step S3: no), it is determined whether the gap has become zero (step S6). Whether or not the air gap is zero may be determined by the position estimation function unit 21 by determining whether or not the estimated air gap has become zero, and by the position control function unit 23 by determining whether or not follow-up of position control has been achieved. You can judge. If it is determined that the air gap has become zero (step S6: yes), the control switching function unit 24 performs a process of intentionally moving the linear motion mechanism 6 in the load applying direction (step S7), and continues position control. (step S8).

As in step S7, since the control device 2 has a proximity control function of intentionally moving the linear motion mechanism 6 in the direction of load application, for example, due to the effects of expansion and contraction due to temperature changes and backlash of mechanical joints, It can solve the problem of no load caused by the error between the estimated air gap and the actual air gap. In step S6, when it is determined that the gap is not zero (step S6: no), position control is continued (step S16).

When the condition of the switching threshold is satisfied in step S3 (step S3: yes), the control switching function unit 24 shifts to load control by the load control function unit 22 (step S4), and the load control function unit 22 performs load control. Execute (step S5). After that, this process is terminated.

In the execution state of the load control function unit 22 (step S1: yes), the control switching function unit 24 determines the maximum load exerted, that is, the maximum value of the load history, from the history of the estimated load exerted during execution of the load control once. acquire (step S13). The history of the estimated load is rewritably stored in the storage means 30 . Here, "one-time load control" refers to the period from the no-load state of zero load to the time when the load is exerted and the load returns to zero again. may

When the maximum load among the estimated loads exceeds the predetermined threshold Ak (step S14: yes), the control switching function unit 24 corrects the second threshold Ax for shifting from load control to position control (step S15). After step S15, the process proceeds to step S9. As a method of correcting the second threshold Ax, for example, the control switching function unit 24 corrects the second threshold Ax to a larger value than the first threshold An as the maximum load increases. The relationship between this maximum load and the second threshold Ax is stored in the storage means 30, for example. When the maximum load in the estimated load is equal to or less than the predetermined threshold Ak (step S14: no), the process proceeds to step S9 without correcting the second threshold Ax.

In step S9, the control switching function unit 24 determines whether the load has fallen below the second threshold Ax. When the load does not fall below the second threshold Ax (step S9: no), the load control is continued (step S18), and when the load falls below the second threshold Ax (step S9: yes), the process proceeds to step S22. do.

In step S22, the control switching function unit 24 determines whether the maximum value of the load history is greater than or equal to the second threshold Ax. That is, it is separated into a state in which a load is generated from a no-load state and a state in which pressure is reduced after a certain amount of load has already been generated. In the former case, that is, in the case of a state in which a load is generated from the no-load state (step S22: no), the process proceeds to step S19. When pressure is increased in step S19, the control switching function unit 24 continues load control (step S20), and when pressure is decreased in step S19, the control switching function unit 24 executes position control (step S21).

At this time, in steps S19 to S21, the estimated load when the load of the linear motion mechanism 6 is reduced and switched to the position control is stored in the storage means 30. 23, even if the position control function unit 23 continues the position control until the estimated load at the time of switching stored in the storage means 30 is reached. good. Further, the control switching function unit 24 may switch from position control to load control after the load reaches the estimated load. Since position control is executed in step S21 only temporarily, the process does not shift to position control in order to distinguish from the flow after step S11.

In step S22, if the pressure has been reduced after a certain amount of load has already been generated (step S22: yes), the control switching function unit 24 shifts from load control to position control (step S10), and the position control function unit 23 is executed (step S17). After that, this process is terminated.
The flow of this embodiment is an example, and the order of execution can be changed, or part of the flow can be omitted, etc., as necessary.

<Effect>
According to the electric linear motion actuator DA described above, when the pressure is increased from the no-load state where no load is applied, it is sufficient to observe how much the estimated load has changed from the state where the load is zero. Even if a relatively small threshold is used as the threshold, it can be expected that position control can be switched to load control without erroneous determination.
On the other hand, when depressurizing from a state where a load is applied, the second threshold is set as a comparison set a relatively large threshold.

Therefore, by setting the first determination condition for switching from position control to load control and the second determination condition for switching from load control to position control as different conditions, it is possible to prevent erroneous determination of control switching and improve load control accuracy. can be improved. Therefore, it is possible to perform stable control by appropriately switching between position control and load control without using a highly accurate load sensor.

When a relatively large load is applied, for example, the zero point of the sensor output of the load sensor Sb for estimating the axial load tends to be offset due to the influence of minute friction within the electric linear motion actuator. Sometimes. Therefore, by increasing the second threshold value as the maximum load in the stored estimated load increases, erroneous determination of control switching due to the offset can be prevented.

Even if the sensor output of the load sensor Sb monotonically increases on the pressure increasing side, the sensor output of the load sensor Sb on the pressure reducing side may not monotonously decrease due to hysteresis due to the influence of friction or the like. . Therefore, when the load of the linear motion mechanism 6 is reduced in the execution state of the load control function unit 22, the position control by the position control function unit 23 is performed without using the estimated load. can be prevented.

A load sensor Sb for estimating the load due to the hysteresis even if the load is increased again in a minute load region in a state where it is switched to the position control function unit 23 when reducing the load. sensor output error. Therefore, by storing the estimated load when switching from the load control function unit 22 to the position control function unit 23 and continuing the control by the position control function unit 23 until the stored estimated load is reached, the electric direct control unit 23 can be operated. Malfunction of the dynamic actuator DA can be prevented.

The larger the gap, the lower the possibility that a load will be generated, and the greater the influence of the malfunction of the actuator when the control is switched due to an erroneous determination. Therefore, the control switching function unit 24 sets the first threshold value larger as the estimated air gap (estimated air gap) increases, thereby preventing erroneous determination of control switching. By changing the first threshold in accordance with the estimated air gap in this manner, the risk of erroneous determination of control switching can be reduced.

<About other embodiments>
In the following description, the same reference numerals are given to the parts corresponding to the items previously described in each embodiment, and duplicate descriptions are omitted. When only a portion of the configuration is described, the other portions of the configuration are the same as those previously described unless otherwise specified. The same configuration has the same effect. It is possible not only to combine the parts specifically described in each embodiment, but also to partially combine the embodiments if there is no particular problem with the combination.

FIG. 6 shows an example in which a load control function unit 22 that directly controls the load and a position control function unit 23 that controls the motor angle, which is the axial position of the linear motion unit 14 (FIG. 1), are separately provided and switched. . FIG. 7 shows a configuration example for executing the position control function unit 23, as opposed to FIG. In FIGS. 6 and 7, the estimated load is used for direct control, which is advantageous in that the control system can easily be made relatively robust against model errors. 3, 4, 6, and 7 may be appropriately determined depending on the control requirements, or may be used together as necessary.

The control device 2 has a function of estimating the angular acceleration of the electric motor 4, and the control switching function unit 24 uses the first threshold as a reference when the estimated angular acceleration is greater than a predetermined angular acceleration. It can be larger than the value. The control device 2 can estimate the angular acceleration by, for example, differentiating the angular velocity obtained from the angle sensor Sa.

When the electric motor is operated with a large angular acceleration, the load sensor for estimating the load may react due to the influence of the inertia of the linear motion mechanism, etc. even when no load is actually generated. Therefore, according to this configuration, when the estimated angular acceleration is greater than the predetermined angular acceleration, the first threshold is made larger than the reference value, thereby preventing erroneous determination that the load has been applied. be able to.

As the conversion mechanism of the linear motion mechanism 6, various screw mechanisms such as planetary rollers and ball screws, mechanisms utilizing inclination such as ball ramps, and the like can be used.

As mentioned above, although the form for implementing this invention was demonstrated based on embodiment, embodiment disclosed this time is an illustration and is not restrictive at all points. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

DESCRIPTION OF SYMBOLS 1... Electric brake device 2... Control device 4... Electric motor 6... Linear motion mechanism 8... Brake rotor 9... Friction material 14... Linear motion part 20... Load estimation mechanism part 21... Position estimation mechanism part 22... Load control function part 23 Position control function unit 24 Control switching function unit 30 Storage means BR Electric brake device DA Electric linear motion actuator

Claims (10)

An electric linear motion actuator that includes an electric motor, a linear motion mechanism that converts the rotary motion of the electric motor into a linear motion of a linear motion portion, and a control device that controls the electric motor,
The control device is
a load estimation function unit that estimates the axial load of the linear motion mechanism;
a position estimation function unit that estimates the axial position of the linear motion unit in the linear motion mechanism;
a load control function unit that controls the load of the linear motion mechanism based on the estimated load that is the result of estimation by the load estimation function unit;
a position control function unit that controls the axial position of the linear motion unit of the linear motion mechanism based on the estimated position that is the result of estimation by the position estimation function unit;
a control switching function unit that switches to one of the load control function unit and the position control function unit,
The control switching function unit
It is a state of being switched to the position control function part, and when the load of the linear motion mechanism is exerted from a no-load state in which the load of the linear motion mechanism is not applied, and from a state of zero load. If a first determination condition is satisfied that the estimated load exceeds a first threshold sufficient for the load estimation function unit to determine that it has changed to a non-zero state, from the position control function unit Switching to the load control function unit,
A state in which the load control function unit is switched to, a time when the load of the linear motion mechanism is reduced or zero, and an electric linear motion actuator generated by the application of the load. The estimated load is less than a second threshold that is set to be larger than the zero point offset amount that occurs in the load estimation function unit due to slight friction in the load estimation function unit and is larger than the first threshold. An electric linear motion actuator that switches from the load control function unit to the position control function unit when the determination condition of (1) is satisfied. 2. The electric linear motion actuator according to claim 1, further comprising storage means for storing a history of the estimated load estimated in the execution state of the load control function unit from a state in which the load was previously set to zero, wherein the control switching The functional unit is an electric linear motion actuator in which the second threshold value increases with respect to the first threshold value as the maximum load in the estimated load stored in the storage means increases. 3. The electric linear motion actuator according to claim 1, wherein when the control device increases the load of the linear motion mechanism in the execution state of the load control function unit, the load control function unit is in the execution state. is continued, and the position control function is executed by the position control function unit when the load of the linear motion mechanism is reduced in the execution state of the load control function unit. 4. The electric linear motion actuator according to claim 3, further comprising storage means for storing an estimated load when switching from the load control function section to the position control function section, wherein the control device switches to the position control function section. When the load of the linear motion mechanism is increased in this state, the control by the position control function unit is continued until the estimated load stored in the storage means is reached, and after reaching the estimated load, the position control function a motorized linear actuator for switching from the load control function unit to the load control function unit. 5. The electric linear motion actuator according to any one of claims 1 to 4, wherein the position estimation function unit allows the linear motion mechanism to apply a load based on the estimated load and the estimated position. an electric linear motion actuator having a function of estimating a gap until a state is reached, wherein the control switching function unit sets the first threshold value larger as the estimated gap becomes larger. 6. The electric linear motion actuator according to any one of claims 1 to 5, wherein the position estimation function unit allows the linear motion mechanism to apply a load based on the estimated load and the estimated position. The load estimating function unit has a function of estimating the gap until the state is reached, and the load estimating function unit estimates the estimated load in a state where the estimated gap is larger than the predetermined gap, with the load as a reference corresponding to zero. electric linear actuator. 7. The electric linear motion actuator according to any one of claims 1 to 6, wherein the position estimation function unit allows the linear motion mechanism to apply a load based on the estimated load and the estimated position. The position control function unit has a function of estimating the air gap until the state is reached. Deriving a target position that can be a predetermined load from information including
The control switching function unit determines that the gap is smaller than a set value or zero in a state where the first determination condition is not satisfied when a load is applied from the execution state of the position control function unit in the no-load state. or, when the position control function unit determines that the position control has been achieved based on the deviation between the target position and the estimated position, the linear motion mechanism continues until the first determination condition is satisfied. An electric linear motion actuator having a proximity control function for moving the linear motion portion of the above in a load applying direction. 8. The electric linear motion actuator according to claim 1, wherein the control device has a function of estimating the angular acceleration of the electric motor, and the control switching function unit an electric linear motion actuator that makes a first threshold value greater than a reference value when the angular acceleration received is greater than a predetermined angular acceleration. 9. The electric linear motion actuator according to any one of claims 1 to 8, wherein the load control function unit controls the load of the linear motion unit calculated based on the estimated load and the rigidity of the electric linear motion actuator. a position control function that corrects one or both of the target value and the feedback value using the deviation between the calculated position and the estimated position, and the control switching function unit sets the correction amount in the position control function to zero; or the load control function unit that does not set the correction amount to zero. The electric linear motion actuator according to any one of claims 1 to 9, a friction material operated by the electric linear motion actuator, and a brake rotor that generates a braking force through contact with the friction material. and an electric braking device.

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