JP2022103185A - Electric linear actuator and electric brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric linear actuator which can perform stable control by properly switching position control and load control, and can reduce a cost, and an electric brake device.

SOLUTION: A control device 2 of this electric linear actuator DA comprises: a load estimation function part 20; a position estimation function part 21; a load control function part 22; a position control function part 23; and a control changeover function part 24. When the control changeover function part 24 is in a switched state switched to the position control function part 23, and when the control changeover function part exerts a load from a non-loaded state, and also when an estimated load exceeds a first threshold, the control device switches the control changeover function part to the load control function part 22 from the position control function part 23. In a state that the control changeover function part is switched to the load control function part 23, and when the load is reduced or set to zero, and also when the load is reduced below a second threshold which is larger than the first threshold, the control device switches the control changeover function part to the position control function part 23 from the load control function part 22.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to, for example, an electric linear actuator and an electric brake device mounted on a vehicle or the like, and relates to a technique capable of appropriately switching between position control and load control to perform stable control.

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

Japanese Unexamined Patent Publication No. 6-327190 Japanese Unexamined Patent Publication No. 2006-19435 Japanese Patent Publication No. 2001-507779 Japanese Unexamined Patent Publication No. 2014-88811

For example, in an electric linear actuator that applies a load to an object as in Patent Documents 1 to 3, when a load is applied, the load is controlled so that the estimated load follows a predetermined target value, and the load is applied. When is set to zero, it is generally known that the position is controlled 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 perform appropriate switching, especially with a relatively small load.

For example, in the case of using a load sensor that detects an axial load as in Patent Documents 3 and 4, the vehicle at the time when the application of the load is started and ended, especially when a relatively large load is exerted. The output indicating zero load may be offset due to changes in posture and friction of each part.
Further, due to the influence of friction of each part, the output of the load sensor may have hysteresis and do not change at the time of decompression, especially under a relatively small load state. In such a case, if a method of performing control switching with respect to a certain threshold value is adopted, appropriate control switching may not be possible due to an error of the load sensor or the like. When a highly accurate sensor is used as a countermeasure against this problem, high cost or the like may become a problem.

An object of the present invention is to provide an electric linear actuator and an electric brake device capable of appropriately switching 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 rotational motion of the electric motor 4 into linear motion of the linear motion unit 14, and a control device 2 that controls the electric motor 4. In an electric linear acting actuator equipped with
The control device 2 is
The load estimation function unit 20 for estimating the axial load of the linear motion mechanism 6 and the load estimation function unit 20
The position estimation function unit 21 that estimates the axial position of the linear motion unit 14 in the linear motion mechanism 6 and the position estimation function unit 21.
Based on the estimated load that is the estimation result of the load estimation function unit 20, the load control function unit 22 that controls the load of the linear motion mechanism 6 and the load control function unit 22
The 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 for switching to either the load control function unit 22 or the position control function unit 23 is provided.
The control switching function unit 24 is
It is a state in which the position control function unit 23 is switched to, and 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 exerted. When the first determination condition that the first threshold value is exceeded is satisfied, the position control function unit 23 is switched to the load control function unit 22.
It is in 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 set to zero, and the load is larger than the first threshold value. When the second determination condition of falling below the second threshold value is satisfied, the load control function unit 22 is switched to the position control function unit 23.
The first and second thresholds are thresholds arbitrarily determined by design and the like, and are determined by obtaining an appropriate threshold by, for example, one or both of a test and a simulation. However, the second threshold value is larger than the first threshold value.

According to this configuration, when the position control function unit 23 is switched to the position control function unit 23 by the control switching function unit 24, the position control function unit 23 is the axial position of the linear motion unit 14 of the linear motion mechanism 6 based on the estimated position. To control. When the first determination condition is satisfied, the control switching function unit 24 switches from the position control function unit 23 to the load control function unit 22. 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.

When the second determination condition is satisfied, the control switching function unit 24 switches from the load control function unit 22 to the position control function unit 23. Satisfying the second determination condition means satisfying all of the following three conditions 2-1, 2-2, and 2-3.
Condition 2-1: It is in a state of being switched to the load control function unit 22.
Condition 2-2: When the load is reduced or set to 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 has changed from the zero load state, so even if a relatively small threshold value is used as the first threshold value, an erroneous judgment is made. It can be expected that switching from position control to load control can be performed without any problem.
On the other hand, when the pressure is reduced from the state where the load is applied, the effect of the offset of the zero point due to the friction in the electric linear actuator is taken into consideration, and in order to prevent erroneous judgment, a comparison is made as a second threshold value. Set a large threshold.
Therefore, by setting the first judgment condition for switching from position control to load control and the second judgment condition for switching from load control to position control as different conditions, the load control accuracy is prevented while preventing erroneous judgment of control switching. Can be improved. Therefore, stable control can be performed by appropriately switching between position control and load control without using a high-precision load sensor.

The storage means 30 for storing the history of the estimated load estimated in the execution state of the load control function unit 22 from the state where the load was set to zero last time is provided, and the control switching function unit 24 stores in the storage means 30. As the maximum load in the estimated load is increased, the second threshold value may be larger than the first threshold value.
According to this configuration, when a relatively large load is applied, the zero point offset of the sensor output for estimating the axial load occurs due to the influence of minute friction in the electric linear actuator, for example. It may be easy. Therefore, by increasing the second threshold value as the maximum load in the stored estimated load increases, it is possible to prevent erroneous determination of control switching due to the offset.

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 and causes the load control function unit 22 to continue the execution state. When the load of the linear motion mechanism 6 is reduced in the execution state, the position control by the position control function unit 23 may be executed.
Even if the sensor output increases monotonically on the pressure boosting side with respect to a minute load, the sensor output may not decrease monotonically due to hysteresis due to the influence of friction or the like on the decompression side. 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, so that the electric linear motion actuator DA It is possible to prevent malfunction.

In a configuration in which the load is switched to the position control function unit 23 when the load is reduced, the control switching function unit is provided with a storage means 30 for storing an estimated load when the load control function unit 22 is switched to the position control function unit 23. 24 controls the position control function unit 23 until the estimated load stored in the storage means 30 is reached when the load of the linear motion mechanism 6 is increased while being switched to the position control function unit 23. After continuing and 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 due to the hysteresis is used. 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 the control by the position control function unit 23 is continued until the stored estimated load is reached, thereby being electrically operated. It is possible to prevent the linear actuator DA from malfunctioning.

The position estimation function unit 21 has a function of estimating a gap until the linear motion mechanism 6 can apply a load based on the estimated load and the estimated position, and the control switching function unit 24 has a function of estimating a gap until the load can be applied. May set the first threshold value larger as the estimated void becomes larger.
The gap is a gap between the linear motion mechanism 6 and an 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 actuator operation abnormality when the control is switched due to an erroneous determination. Therefore, the larger the estimated void (estimated void) is, the larger the first threshold value is set, so that erroneous determination of control switching can be prevented. By changing the first threshold value according to the estimated gap in this way, 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 can apply a load based on the estimated load and the estimated position, and the load estimation function unit 20 has a function of estimating a gap until the load can be applied. May estimate the load using the estimated load in a state where the estimated void is larger than the defined void as a reference corresponding to zero.
The defined void is a void arbitrarily determined by design or the like, and is determined by, for example, one or both of a test and a simulation to obtain an appropriate void.
According to this configuration, when the estimated void is larger than the defined void, the load of the linear motion mechanism 6 can be expected to be substantially zero. Therefore, when the estimated void satisfies a condition larger than the defined void, the load can be estimated using the estimated load as a reference corresponding to zero.

The position estimation function unit 21 has a function of estimating a gap until the linear motion mechanism 6 can apply a load based on the estimated load and the estimated position, and the position control function unit 21 has a function of estimating a gap until the load can be applied. However, when 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 load determined from information including the rigidity of the electric linear actuator DA. It has a function to execute tracking control to follow the estimated position with respect to the target position.
When a load is applied from the execution state of the position control function unit 23 in the no-load state, the control switching function unit 24 has the void smaller than the set value or zero in a state where the first determination condition is not satisfied. Or, when it is determined by the position control function unit 23 that the position control has been achieved based on the deviation between the target position and the estimated position, the first determination condition is satisfied. It may have a proximity control function for moving the linear motion portion 14 of the linear motion mechanism 6 in the load application direction.
The defined load is a load arbitrarily determined by design or the like, and is determined by obtaining an appropriate load by, for example, one or both of a test and a simulation.

According to this configuration, the position estimation function unit 21 estimates the void 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 load determined from information including the rigidity of the electric linear actuator DA. Then, the follow-up control for making the estimated position follow the target position is executed.

Due to the influence of volume fluctuation due to temperature change and backlash of the mechanical coupling portion, the load may not be generated even at the position of the linear motion portion 14 to which the load should be applied. Therefore, there is a case where the load is not actually applied to a particularly minute load command value only by the position control. According to this configuration, when the load is not actually applied to the minute load command value as described above, the load can be reliably applied by moving the linear motion unit 14 in the load application 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 larger than a predetermined angular acceleration. It may be larger than the reference value.
The defined angular acceleration and reference value are angular acceleration and reference value arbitrarily determined by design and the like, respectively, and are appropriate angular acceleration and reference by, for example, one or both of test and simulation. 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 the load is not actually generated. .. Therefore, according to this configuration, when the estimated angular acceleration is larger than the predetermined angular acceleration, the first threshold value is made larger than the reference value to prevent erroneous determination that a 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 obtain a target value and a feedback value. It is a position control for correcting either one or both, and the control switching function unit 24 is either the position control function unit 23 in which the correction amount in the position control is zero, or the load control function in which the correction amount is not zero. It may be switched to the unit 22. By switching whether or not the correction amount in the position control is set to zero in this way, either the position control function unit 23 or the load control function unit 22 can be selectively switched.

The electric brake device 1 of the present invention exerts a braking force by contact between the electric linear actuator DA according to any one of the above, the friction material 9 operated by the electric linear actuator DA, and the friction material 9. It includes a brake rotor 8 to generate the brake rotor 8. According to this electric brake device 1, since any of the electric linear actuator DAs is provided, it is possible to improve the load control accuracy while preventing erroneous determination of control switching.

The electric linear actuator of the present invention includes an electric motor, a linear motion mechanism that converts the rotational motion of the electric motor into a linear motion of a linear motion unit, and a control device that controls the electric motor. In the dynamic actuator, the control device includes 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, and the load. The load control function unit that controls the load of the linear motion mechanism based on the estimated load that is the estimation result of the estimation function unit, and the linear motion mechanism based on the estimated position that is the estimation result of the position estimation function unit. The control switching function unit includes a position control function unit that controls the axial position of the linear motion unit and a control switching function unit that switches between the load control function unit and the position control function unit. It is a state in which the position is switched to the position control function unit, and 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 first. When the first determination condition of exceeding the threshold value of is satisfied, the position control function unit is switched to the load control function unit, the load control function unit is switched to the load control function unit, and the linear motion is performed. The load is when the load of the mechanism is reduced or set to zero, and when the second determination condition that the load is lower than the second threshold value larger than the first threshold value is satisfied. The control function unit is switched to the position control function unit. Therefore, it is possible to appropriately switch between position control and load control to perform stable control and reduce costs.

The electric brake device of the present invention includes an electric linear acting actuator according to any one of the 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. , Therefore, it is possible to appropriately switch between position control and load control to perform stable control and reduce costs.

It is a figure which shows schematic the electric brake device which concerns on embodiment of this invention. It is a block diagram of the control system of the electric linear actuator of the electric brake device. It is a block diagram which shows the execution configuration example of the load control function part of the control system. It is a block diagram which shows the configuration example when the position control function part of the control system is executed. It is a flowchart which shows the execution example of a control switching function part step by step. It is a block diagram of the control switching function part of the electric linear actuator which concerns on other embodiment of this invention. It is a block diagram which shows the configuration example which switched to the position control function part by the control switching function part.

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

<Structure of electric linear actuator DA and friction brake BR>
As shown in FIGS. 1 and 2, the electric linear actuator DA includes an actuator main body AH, a power supply device 3, and a control device 2 described later. The actuator main body AH includes 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 comprises, for example, a permanent magnet type synchronous motor. When a permanent magnet type synchronous motor is applied as the electric motor 4, it is suitable because it saves space and has a high torque. For example, a DC motor using a brush, a reluctance motor not using a permanent magnet, an induction motor, or the like is applied. You can also.

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

The speed reduction mechanism 5 is a mechanism for reducing the 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 decelerates 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 the rotation to the tertiary gear 11 fixed to the end of the rotation shaft 10. It is possible.

The linear motion mechanism 6 is a mechanism that converts the rotary motion output by the deceleration mechanism 5 into a linear motion of the linear motion portion 14 by the feed screw mechanism, and causes the friction material 9 to abut and separate from the brake rotor 8. The linear motion portion 14 is detented and is movably supported in the axial direction indicated by the arrow A1. A friction material 9 is provided at the outboard side end of the linear motion portion 14. By transmitting the rotation of the electric motor 4 to the linear motion mechanism 6 via the reduction mechanism 5, the rotational motion is converted into a linear motion, which is converted into the pressing force of the friction material 9 to generate a braking force. .. With the electric brake device 1 mounted on the vehicle, the outside of the vehicle in the vehicle width direction is referred to as the outboard side, and the center side of the vehicle in the vehicle width direction is referred to as the inboard side.

As the actuator 16 of the parking brake mechanism 7, for example, a linear solenoid is applied. A parking lock state is achieved by advancing the lock member 15 by the actuator 16 and fitting it into a locking hole (not shown) formed in the intermediate gear 13 to lock the intermediate gear 13 and prohibiting the rotation of the intermediate gear 13. To. By disengaging the lock member 15 from the locking hole, the intermediate gear 13 is allowed to rotate and is unlocked.

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

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 the 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 may detect the load using another external sensor. As an external sensor, for example, in the electric brake device 1 (FIG. 1) using the electric linear 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 front-rear force of the vehicle. In addition, various sensors such as a thermistor may be provided as needed.

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

As the upper ECU 17, for example, an electric control unit that controls the entire vehicle is applied. The upper ECU 17 has an integrated control function for each control device 2. The upper ECU is also referred to as "VCU". The upper ECU 17 includes a command means 17a, and the command means 17a 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 operation amount of the brake operation means (not shown). Output each. The command means 17a can, for example, determine braking in an autonomous vehicle and output a brake force command value to each control device 2 without depending 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. The various control calculation function units are composed of, for example, a processor such as a microcomputer, a calculation 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 of the load control function unit 22 and the position control function unit 23 from the command signal input from the command means 17a, respectively. The command generation function unit 19 can output, for example, a load command value in consideration of the gain and range of the load sensor Sb to the load control function unit 22. The command generation function unit 19 determines, for example, a position command value capable of exerting a load determined by the rigidity of the electric linear actuator DA for the position control function unit 23, or when the load is set to zero. It is possible to output the position command value that becomes the gap (clearance) that has been created. 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 an amount that can correspond to a position such as a motor angle. Further, in a linear actuator that generally controls a load, when the load is set to zero, a predetermined gap is provided for an object to which the load is applied, so that the position estimation function unit 21 outputs the load sensor Sb or the like. It is preferable to provide a function of estimating the position where the load is zero from the above and estimating the void.

The load control function unit 22 operates the electric motor so that the estimated load, which is the estimation result calculated by the load estimation function unit 20, follows the target load command value given by the command generation function unit 19. Determine the amount. 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 by the command generation function unit 19. .. The position control function unit 23 derives an angle capable of exerting a predetermined load based on the actuator rigidity or the like for the input load command value, and the position estimation function unit 21 calculates the derived angle command value. The amount of operation of the electric motor may be determined so as to follow the feedback angle.

The control switching function unit 24 is either a load control function unit 22 or a 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 by the command means 17a. It has a function to switch to one side. The control changeover function unit 24 includes a control changeover function main body unit 25 and a changeover switch 26. The control switching function main body 25 includes first and second switching determination units 27 and 28, a switching threshold setting unit 29, and a 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. The second switching determination unit 28 determines switching from the load control state to the position control. The switching threshold value setting unit 29 is used for determination in the first and second switching determination units 27 and 28, respectively, by combining the load estimation function unit 20, the position estimation function unit 21, and the braking force command value. Set the second threshold value and so on as appropriate. The first and second threshold values are rewritably stored in the storage means 30.

When the first determination condition is satisfied, the first switching determination unit 27 gives a command to the changeover switch 26 to switch from the position control function unit 23 to the load control function unit 22. 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 second determination condition is satisfied, the second switching determination unit 28 gives a command to the changeover switch 26 to switch from the load control function unit 22 to the position control function unit 23. Satisfying the second determination condition means satisfying all of the following three conditions 2-1, 2-2, and 2-3.
Condition 2-1: It is in a state of being switched to the load control function unit 22.
Condition 2-2: When the load is reduced or set to zero.
Condition 2-3: The load is below the second threshold. However, the second threshold value is larger than the first threshold value.

The motor driver 18 controls the electric power supplied to the coil of the electric motor 4. The motor driver 18 constitutes, for example, a half-bridge circuit using a switch element such as a field effect transistor (abbreviated as FET), and PWM control in which the voltage applied to the motor is determined by the ON-OFF duty ratio of the switch element. If it is configured to perform the above, it will be inexpensive and have high performance. Alternatively, a transformer circuit or the like may be provided to perform PAM control. In addition, configurations of current sensors and the like (not shown) can be appropriately provided as needed. Further, each functional unit is provided as a block for convenience, and may be integrated or divided as necessary.

<About 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 a configuration example during execution of the load control function unit 22, whereas FIG. 4 shows a configuration example 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 body unit 25. As a component common to FIGS. 3 and 4, the 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 actuator DA (FIG. 2). Has.

Further, the load-to-angle converter 31 may be provided with a function of deriving an angle that can be a predetermined void, if necessary, when the load is zero, for example. If the rigidity of the electric linear actuator DA (FIG. 2) is measured in advance and implemented by a look-up table (abbreviated as LUT) or the like, the above-mentioned function can be processed at high speed by a calculator, which is suitable. It can also be implemented by an expression or the like.

The difference calculator 32 has a function of calculating the difference of the estimated angle (estimated position) for each predetermined sample step. Generally, the estimated angle overflows or underflows and wraps at a predetermined cycle such as the mechanical angle or the electric angle of the motor. Therefore, in deriving the total rotation angle of the motor, the estimated angle between predetermined samples is used as in this function. It is preferable to calculate the difference.
The angle calculator 33 has a function of integrating the difference of 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 the estimated load by the load → angle converter 34 from the information such as the rigidity of the electric linear actuator DA (FIG. 2). An example of implementing as a function of correcting the control amount of the position control system from the deviation between the position (angle) and the total rotation angle is shown. Although FIG. 3 shows an example of correcting the feedback angle (feedback value), an angle command value may be corrected instead of the example of correcting the feedback angle.

The position control shown in FIG. 4 is performed by switching the changeover switch 26 according to a command from the control changeover function main body 25 to set the angle correction amount to zero with respect to FIG. 3, which is an example of the running configuration of the load control function unit 22. The functional unit 23 may be executed.

According to the configuration examples of FIGS. 3 and 4, since the control calculation unit is only the angle controller 35, it is not necessary to initialize the control variables for each control switching, and this electric linear actuator DA (FIG. 3). Even if the rigidity 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 and the like shall be appropriately provided as necessary. Further, each functional unit is divided as a block for convenience, and may be integrated or divided as necessary.

<Example of control switching flow>
FIG. 5 is a flowchart showing an execution example of the control switching function unit step by step. Hereinafter, the description will be given with reference to FIGS. 1, 2 and the like as appropriate.
After the start of this process, the control switching function unit 24 determines whether the load control function unit 22 or 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 a predetermined value Bk or more (step). S11). The predetermined value Bk is set as a threshold value that can be strongly expected that the load of the linear motion mechanism 6 is sufficiently released. When the space is sufficient (step S11: yes), the load of the electric linear 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. It is determined that the void is not equal to or greater than the predetermined value Bk (step S11: no), and the process proceeds to step S2. In step S2, the position control function unit 23 determines whether or not a non-zero load command value is input from the command generation function unit 19, that is, a request for exerting a predetermined load is received. If there is no request to apply the load (step S2: no), the position control is continued (step S16). After that, this process ends.

When there is a request to apply a load (step S2: yes), the control switching function unit 24 determines whether the estimated load exceeds the predetermined first threshold value An and the estimated void is below the threshold value Bm (step). S3). When there is a request to apply a load, the electric linear actuator DA is driven in the direction of applying the load, so that the control switching function unit 24 loads the load when the estimated load exceeds the first threshold value An. Make a decision to switch to control. At that time, the larger the estimated void is, the less likely the load is to be generated, and conversely, the smaller the estimated void is, the more likely the load is to be generated.

Therefore, as in the present embodiment, if the generation of the load is determined from the estimated load and the estimated void, more accurate control switching can be performed. However, the control switching function unit 24 may determine the control switching only by the estimated load without considering the estimated void. Further, a plurality of threshold values or combinations may be set for either or both of the first threshold value An and the threshold value Bm to make a stepwise control switching determination, and the first threshold value An and the threshold value Bm may be linear. The control switching for the evaluation function may be determined by using the coupling function as the evaluation function.

When the condition of the switching threshold value is not satisfied in step S3 (step S3: no), it is determined whether the void has become zero (step S6). The determination of whether or not the void is zero may be determined by the position estimation function unit 21 whether or not the estimated void has become zero, and whether or not the position control tracking has been achieved by the position control function unit 23. You may judge. When it is determined that the void becomes zero (step S6: yes), the control switching function unit 24 performs a process of intentionally moving the linear motion mechanism 6 in the load application direction (step S7), and continues the position control. (Step S8).

Since the control device 2 has a proximity control function for intentionally moving the linear motion mechanism 6 in the load application direction as in step S7, for example, due to the influence of expansion and contraction due to temperature change and backlash of the mechanical coupling portion. It can solve the problem that the load is not generated due to the error between the estimated void and the actual void. In step S6, it is determined that the void is not zero (step S6: no), and the 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 the load control by the load control function unit 22 (step S4), and the load control function unit 22 performs the load control. Execute (step S5). After that, this process ends.

In the execution state of the load control function unit 22 (step S1: yes), the control switching function unit 24 obtains the maximum load exerted, that is, the maximum value of the load history from the history of the estimated load exerted during the execution of one load control. Acquire (step S13). The history of the estimated load is rewritably stored in the storage means 30. Here, "one-time load control" indicates the period from the state of zero load, which is a no-load state, to the time when the load is exerted and returns to zero load again, but if necessary, the history of a plurality of cycles is used. You may.

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

In step S9, the control switching function unit 24 determines whether the load has fallen below the second threshold value 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 equal to or greater than the second threshold value Ax. That is, it is separated from the no-load state to the state in which the load is generated or the state in which the pressure is reduced after the load has already been generated to some extent. In the former case, that is, in the case of a state due to the process in which a load is generated from the no-load state (step S22: no), the process proceeds to step S19. When the pressure is increased in step S19, the control switching function unit 24 continues load control (step S20), and when the pressure is reduced 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 turned to decompression and switched to the position control is stored in the storage means 30, and the control switching function unit 24 is the position control function unit. When the load of the linear motion mechanism 6 is increased in the state of being switched to 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 the execution of the position control in step S21 is temporary, the process does not shift to the position control in order to distinguish it from the flow after step S11.

In step S22, when the pressure is 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 The position control by 23 is executed (step S17). After that, this process ends.
The flow of this embodiment shows an example, and the execution order can be changed or a part of the flow can be omitted as necessary.

<Action effect>
According to the electric linear actuator DA described above, when the pressure is increased from the no-load state where no load is applied, it is only necessary to observe how much the estimated load has changed from the zero load state. Even if a relatively small threshold value is used as the threshold value, it can be expected that the position control can be switched to the load control without erroneous judgment.
On the other hand, when the pressure is reduced from the state where the load is applied, the effect of the offset of the zero point due to the friction in the electric linear actuator is taken into consideration, and in order to prevent erroneous judgment, a comparison is made as a second threshold value. Set a large threshold.

Therefore, by setting the first judgment condition for switching from position control to load control and the second judgment condition for switching from load control to position control as different conditions, the load control accuracy is prevented while preventing erroneous judgment of control switching. Can be improved. Therefore, stable control can be performed by appropriately switching between position control and load control without using a high-precision load sensor.

When a relatively large load is applied, the zero point offset of the sensor output of the load sensor Sb for estimating the axial load is likely to occur due to the influence of minute friction in the electric linear actuator. In some cases. Therefore, by increasing the second threshold value as the maximum load in the stored estimated load increases, it is possible to prevent erroneous determination of control switching due to the offset.

Even if the sensor output of the load sensor Sb increases monotonically on the boosting side with respect to a minute load, the sensor output of the load sensor Sb may not decrease monotonically due to hysteresis due to the influence of friction or the like on the depressurizing side. .. 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, so that the electric linear motion actuator DA malfunctions. Can be prevented.

The load sensor Sb for estimating the load due to the hysteresis even if the load is turned to increase again in the state of being switched to the position control function unit 23 when the load is reduced and in a minute load region. There may be an error in the sensor output of. 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 type is used. It is possible to prevent malfunction of the dynamic actuator DA.

The larger the gap, the lower the possibility that a load will be generated, and the greater the influence of the actuator operation abnormality when the control is switched due to an erroneous determination. Therefore, the control switching function unit 24 can prevent erroneous determination of control switching by setting the first threshold value larger as the estimated gap (estimated gap) is larger. By changing the first threshold value according to the estimated gap in this way, the risk of erroneous determination of control switching can be reduced.

<About other embodiments>
In the following description, the same reference numerals will be given to the parts corresponding to the matters described in advance in each embodiment, and duplicate description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described above unless otherwise specified. It has the same action and effect from the same configuration. Not only the combination of the parts specifically described in each embodiment, but also the combinations of the embodiments can be partially combined as long as the combination does not cause any trouble.

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 individually provided and switched. .. FIG. 7 shows a configuration example in which the position control function unit 23 is executed, while FIG. 6 is a configuration example in which the load control function unit 22 is being executed. In FIGS. 6 and 7, since the estimated load is used for direct control, it is advantageous in that it is easy to make the control system relatively robust against the model error. Adoption of any of the configurations of FIGS. 3, 4, 6, and 7 is appropriately determined according to the control requirements, or may be used in combination 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 value as a reference when the estimated angular acceleration is larger than the predetermined angular acceleration. May be greater than the value. The control device 2 can estimate the angular acceleration by differentiating the angular velocity obtained from the angle sensor Sa or the like.

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 or the like even when the load is not actually generated. Therefore, according to this configuration, when the estimated angular acceleration is larger than the predetermined angular acceleration, the first threshold value is made larger than the reference value to prevent erroneous determination that a load has been applied. be able to.

As the conversion mechanism portion of the linear motion mechanism 6, various screw mechanisms such as a planetary roller and a ball screw, a mechanism utilizing an inclination such as a ball lamp, and the like can be used.

Although the embodiments for carrying out the present invention have been described above based on the embodiments, the embodiments disclosed this time are exemplary in all respects and are not limiting. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

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

Claims (10)

In an electric linear actuator equipped with an electric motor, a linear motion mechanism that converts the rotational motion of the electric motor into a linear motion of a linear motion unit, 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, and
A position estimation function unit that estimates the axial position of the linear motion unit in the linear motion mechanism, and a position estimation function unit.
Based on the estimated load which is the estimation result of the load estimation function unit, the load control function unit that controls the load of the linear motion mechanism and the load control 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 estimation result of the position estimation function unit.
A control switching function unit for switching to either the load control function unit or the position control function unit is provided.
The control switching function unit is
It is a state in which the position control function unit is switched to, and a state in which 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 a state in which the load is zero. When the first determination condition that the estimated load exceeds the first threshold value sufficient for the load estimation function unit to determine that the state has changed to a non-zero state is satisfied, the position control function unit Switch to the load control function unit,
An electric linear actuator generated when the load is switched to the load control function unit, the load of the linear motion mechanism is reduced or reduced to zero, and the load is applied. The estimated load is lower than the second threshold value set to be larger than the offset amount of the zero point generated in the load estimation function unit due to the slight friction in and larger than the first threshold value. An electric linear actuator that switches from the load control function unit to the position control function unit when the determination condition of is satisfied. The electric linear actuator according to claim 1 is provided with a storage means for storing the history of the estimated load estimated in the execution state of the load control function unit from the state where the load was set to zero last time, and the control switching is performed. The functional unit is an electric linear actuator in which the second threshold value becomes larger than the first threshold value as the maximum load in the estimated load stored in the storage means increases. In the electric linear actuator according to claim 1 or 2, when the control device increases the load of the linear motion mechanism in the execution state of the load control function unit, the execution state of the load control function unit. An electric linear actuator that executes position control 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. The electric linear actuator according to claim 3 includes a storage means for storing an estimated load when switching from the load control function unit to the position control function unit, and the control device switches to the position control function unit. 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 the estimated load is reached, the position control function is performed. An electric linear actuator that switches from the unit to the load control function unit. In the electric linear actuator according to any one of claims 1 to 4, the position estimation function unit can apply a load to the position estimation function unit based on the estimated load and the estimated position. The control switching function unit has a function of estimating a gap until a state is reached, and the control switching function unit is an electric linear actuator that sets a larger first threshold value as the estimated gap becomes larger. In the electric linear actuator according to any one of claims 1 to 5, the position estimation function unit can apply a load to the position estimation function unit based on the estimated load and the estimated position. It has a function of estimating the void until the state is reached, and the load estimation function unit estimates the load using the estimated load in a state where the estimated void is larger than the defined void as a reference corresponding to zero. Electric linear acting actuator. In the electric linear actuator according to any one of claims 1 to 6, the position estimation function unit can apply a load to the position estimation function unit based on the estimated load and the estimated position. The position control function unit has a function of estimating a gap until a state is reached, and when the position control function unit is executed in a state where there is a request to apply a load, the position control function unit is the rigidity of the electric linear actuator. It has a function to derive a target position that can be a specified load from the information including, and execute a follow-up control to follow the estimated position to this target position.
When a load is applied from the execution state of the position control function unit in the no-load state, the control switching function unit determines that the void is smaller than the set value or zero in a state where the first determination condition is not satisfied. Or, when it is determined by the position control function unit that the position control has been achieved based on the deviation between the target position and the estimated position, the linear motion mechanism is satisfied until the first determination condition is satisfied. An electric linear actuator having a proximity control function for moving the linear moving portion in the load application direction. In the electric linear motion actuator according to any one of claims 1 to 7, the control device has a function of estimating the angular acceleration of the electric motor, and the control switching function unit is estimated. When the angular acceleration is larger than the specified angular acceleration, the first threshold value is made larger than the reference value. In the electric linear acting actuator according to any one of claims 1 to 8, the load control function unit is the linear moving unit calculated based on the estimated load and the rigidity of the electric linear acting actuator. It has 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. An electric linear actuator that switches to the position control function unit or the load control function unit whose correction amount is not zero. A brake rotor that generates a braking force by contact between the electric linear actuator according to any one of claims 1 to 9 and the friction material operated by the electric linear motion actuator, and the friction material. And, equipped with an electric brake device.

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