Electric Linear Actuator

Abstract

To provide an electrically-driven type linear actuator which can drive an electric motor with high accuracy by taking discontinuous rigidity occurring on the basis of a change gear ratio in a transmission mechanism into consideration.SOLUTION: An electrically-driven type linear actuator comprises: an electric motor; a linear motion mechanism; a control device which controls a load which is applied to an object in such a manner that the electric motor is driven and the linear motion mechanism linearly moves; and a transmission mechanism having transmission function such that a correspondence relationship between an amount of linear motion and an amount of rotation of the electric motor changes with a prescribed load as a boundary. The control device has: an estimator for estimating the load applied by the linear motion mechanism; a load controller which calculates a motor driving amount by using control gain multiplied by deviation between an estimated value and a target value of the load for control calculation, and by using control gain that discontinuously changes for transition of at least one of the estimated value and the target value of the load at one or more locations in the state where the estimated value and so on of the load are not zero; and a control gain adjustment part which adjusts the control gain.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a method for controlling an electric linear motion actuator that converts the rotational motion of an electric motor into linear motion. [Background technology]

[0002] Electric linear actuators have been considered for use in, for example, electric brake devices, electric press devices, etc. As a conventional electric brake device, for example, Patent Document 1 has proposed an electric actuator with a speed change function that uses a planetary roller screw structure included in a planetary rolling element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-057681 A Summary of the Invention [Problem to be solved by the invention]

[0004] In general, in applications such as electric brakes using an electric linear actuator, precise control of the actuator is often required. In such cases, when an electric linear actuator with a speed change mechanism such as that described in Patent Document 1 is used, if the correlation between the drive amount (rotation amount, rotation speed) of the electric motor during driving and the operation amount (linear amount) of the linear motion of the linear actuator (i.e., equivalent lead corresponding to the linear amount of the linear motion relative to the rotation amount of the electric motor) is different from the expected state, problems such as reduced controllability and responsiveness may occur.

[0005] For example, the linear actuator with a speed change mechanism described in Patent Document 1 has a speed change function in which, when the reaction force when the actuator applies a load to an object exceeds the spring force that applies the frictional force that rotates the planetary rollers and the sun roller (or rotation input shaft) that is the rotation axis at the center of the planetary rollers as one unit, the planetary rollers rotate in the planetary reduction structure provided in the planetary roller screw structure, and a planetary reduction effect occurs in which a difference in rotation speed occurs between the planetary carrier that supports the planetary rollers and the sun roller, thereby reducing the equivalent lead. In this case, there is a discontinuity in the equivalent lead based on the speed change ratio (the change ratio of the equivalent lead) in the speed change function. If the linear actuator is provided with such a speed change function, it is preferable because the equivalent lead can be relatively large until the linear actuator comes into contact with the object to which the load is applied, such as the clearance between the friction material and the brake rotor in an electric brake device, and the responsiveness is improved, and after the load is applied, the equivalent lead becomes relatively small, allowing even a small motor with a small output torque to generate a large load. However, a structure that immediately changes the speed of the linear motion mechanism using the speed change function when the load is no longer zero must achieve the above-mentioned speed change operation using a very minute spring force and spring deformation amount, which is extremely difficult from a manufacturing standpoint, and in order to build a stable speed change mechanism, a structure that changes speed while a certain degree of load is applied may be necessary. However, when it is necessary to control a small actuator load, such as during light braking in an electric brake device, the above-mentioned speed change operation may make it difficult to control the actuator load with high precision.

[0006] In addition, for example, in the gear shifting operation in the structure described in Patent Document 1, due to the nonlinear hysteresis characteristics between the displacement caused by friction and the spring force, a problem may occur in which the gear shift occurs at different times, for example, when the load applied to the actuator is increased (pressure increase) and decreased (pressure decrease).

[0007] An object of the present invention is to solve the problems of the conventional art described above by providing an electric linear actuator capable of driving an electric motor with high precision by taking into account discontinuous stiffness that occurs based on the speed ratio in a speed change mechanism. [Means for solving the problem]

[0008] In order to achieve the above object, the electric linear actuator according to the present invention comprises: the electric motor; a linear motion mechanism that converts a rotational motion of the electric motor into a linear motion; a control device that drives the electric motor to control a load that the linear motion mechanism applies to an object by the linear motion; and a speed change mechanism having a speed change function that changes the correspondence relationship between the linear motion amount of the linear motion and the rotation amount of the electric motor at a predetermined load; The control device includes: An estimator that estimates a load applied by the linear motion mechanism; a load controller that uses a control gain for a control calculation in a process of deriving a drive amount of the electric motor, the control gain being multiplied by at least one or more of a deviation between the estimated value of the load and a target value of the load, an integral value of the deviation, and a differential value of the deviation, and calculates a motor drive amount using a control gain that discontinuously changes in response to a transition of at least one of the estimated value of the load and the target value at at least one point in a state in which at least one of the estimated value of the load and the target value is not zero; a control gain adjustment unit that adjusts a control gain used in the load controller in accordance with a load condition; has.

[0009] According to the above configuration, the electric linear actuator of the present invention is capable of driving the electric motor with high precision by setting the control gain in consideration of discontinuous stiffness that occurs based on the speed change ratio in the speed change mechanism under load conditions where a speed change occurs.

[0010] In the above configuration, the speed change mechanism has the speed change function including a first equivalent lead state in which the amount of linear motion has a predetermined correlation with the amount of rotation of the electric motor, and a second equivalent lead state in which the amount of linear motion has a smaller correlation with the amount of rotation of the electric motor compared to the first equivalent lead state, the shifting function has a nonlinearity in which, in a process in which the load applied by the linear motion mechanism increases, the shifting function switches from the first equivalent lead state to the second equivalent lead state when the load exceeds a first shift load, which is the predetermined load, and, in a process in which the load applied by the linear motion mechanism decreases, the shifting function switches from the second equivalent lead state to the first equivalent lead state when the load falls below a second shift load, which is the predetermined load different from the first shift load; the control gain includes a first discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the first discontinuous point is smaller than the control gain on a side where the load is larger than the first discontinuous point; The shift function having nonlinearity of the shift mechanism and the control gain may satisfy either of the following conditions i) and ii). i) the first shift load of the shift function is greater than the second shift load, and the first discontinuity point of the control gain is closer to the first shift load than to the second shift load. ii) the second shift load of the shift function is greater than the first shift load, and the first discontinuity point of the control gain is closer to the second shift load than to the first shift load. As a result, in a load region where it is unstable as to whether a gear shift will occur or not, if the motor is driven assuming that the equivalent lead is small even though the equivalent lead is large, the actuator load will change significantly, which can result in unstable operation. Therefore, by operating the motor as if the equivalent lead was large at least in the region where gear shifting is unstable, the above-mentioned unstable actuator operation can be prevented.

[0011] In the above configuration, the linear motion mechanism includes: a rotation input member, a planetary carrier supported concentrically with the rotation input member for free rotation, and a planetary rolling element supported rotatably on the planetary carrier; an elastic member which applies a fastening force by which the planetary rolling body does not rotate on its axis and the rotation input member and the planetary carrier rotate synchronously by an elastic force, and which causes the fastening force to be lost by a reaction force of a load applied by the linear motion mechanism, causing the planetary rolling body to rotate on its axis and generating a difference in the amount of rotation between the rotation input member and the planetary carrier; having the elastic member has a nonlinear deformation characteristic in which, in a process in which the load applied by the linear motion mechanism increases, the deformation of the elastic member is completed when the load exceeds a predetermined first deformation load, and, in a process in which the load applied by the linear motion mechanism decreases, the deformation of the elastic member begins when the load falls below a second deformation load different from the first deformation load; the control gain includes a second discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the second discontinuous point becomes larger than the control gain on a side where the load is larger than the second discontinuous point; The deformation characteristic and the control gain of the elastic member of the linear motion mechanism may satisfy either of the following conditions i) and ii): i) The first deformation load of the elastic member is greater than the second deformation load, and the second discontinuity of the control gain is closer to the second deformation load than to the first deformation load. ii) the second deformation load of the elastic member is greater than the first deformation load, and the second discontinuity of the control gain is closer to the first deformation load than to the second deformation load. As a result, in a load region where it is unstable as to whether or not spring deformation will occur in a gear shifting function using a spring elastic member, if the motor is driven assuming that the spring will deform when in fact it does not, the actuator load will change significantly, which can result in unstable operation. Therefore, by operating the motor as if the spring is not deforming at least in the region where spring deformation is unstable, it is possible to prevent the above-mentioned unstable actuator operation.

[0012] In the above configuration, the control gain adjustment unit includes a pressure increase control gain which is the control gain at the time of pressure increase when the load increases, a pressure decrease control gain which is the control gain at the time of pressure decrease when the load decreases, and a control gain switching unit which determines which of the pressure increase control gain or the pressure decrease control gain is to be referenced, The control gain switching unit may switch the control gain based on at least a transition in the motor angle so as to refer to a control gain for a pressure increase control gain when the motor is rotating toward the pressure increase side, and to refer to a control gain for a pressure decrease control gain when the motor is rotating toward the pressure decrease side. As a result, when a linear actuator mechanism is adopted that has nonlinear characteristics that differ between pressure increase and pressure decrease, such as the first and second shift loads and the first and second deformation loads, and that stably exhibits pressure increase characteristics when pressure is increased and exhibits pressure decrease characteristics when pressure is decreased in a load region between the first and second shift loads, or in a load region between the first and second deformation loads, the actuator can be operated with higher accuracy.

[0013] In the above configuration, the control gain adjustment unit has a control gain switch unit which switches between a first control gain, which is a control gain of the electric motor when an equivalent lead corresponding to a direct motion amount of the linear motion with respect to an amount of rotation of the electric motor, a second control gain, which is the control gain when the equivalent lead is small and the elastic member is deformed, and a third control gain, which is the control gain when the equivalent lead is small and the elastic member has reached a deformation limit, and which uses as a reference any one of the first to third control gains; The electric linear actuator further comprises: a change gradient calculation unit that derives a gradient of a change in either the motor angle or the estimated load relative to a change in the other; a change gradient comparison unit that stores the gradient of change derived by said change gradient calculation unit, compares the stored gradient of change with a gradient of change newly derived by said change gradient calculation unit after said storage, and determines that a discontinuity in control gain exists when the gradient has changed by a predetermined value or more; the control gain switching unit uses the first to third control gains, and when there are a plurality of discontinuous points, performs a control process according to at least one of the plurality of discontinuous points determined by the change gradient comparing unit, When the load is changed in a pressure increasing direction while the first control gain is being referenced, if it is determined that the discontinuous point has occurred, the second control gain is referenced; when the pressure is increased while the second control gain is being referenced, if it is determined that the discontinuity has occurred, the third control gain is referenced, and when the pressure is decreased while the pressure is reduced, if it is determined that the discontinuity has occurred, the first control gain is referenced; In a state where the third control gain is being referenced, if a change occurs in the direction of decreasing the pressure, and it is determined that the discontinuous point has occurred, the second control gain may be referenced. As a result, the actuator can be operated with higher accuracy by adopting an appropriate control gain even in a region where the actuator stiffness is unstable, such as a linear actuator mechanism having nonlinear characteristics that differ between when the pressure is increased and when the pressure is decreased, such as the first and second shift loads and the first and second deformation loads, and a load region between the first and second shift loads and the first and second deformation loads.

[0014] In the above configuration, the control device an estimator for estimating a rotation angle of the electric motor; a stiffness parameter storage unit that stores a history of changes in the rotation amount of the electric motor and the estimated load when a predetermined amount of change in the load occurs within a range that includes at least the load corresponding to a discontinuity point of the pre-stored control gain; The control device further comprises: The control system may further include a nonlinear stiffness estimator that estimates a discontinuity point of the control gain from the change history of the angle of the electric motor and the estimated load, and updates the control gain based on the estimated discontinuity point. As a result, for example, regarding characteristic fluctuations in the control gain that may occur due to changes in the contact state of each component of the electric linear actuator or wear of the components, by estimating at least the change in the discontinuity point from the correlation between the motor rotation amount and the load of the actual electric linear actuator and reflecting this result in the control gain, it becomes possible to control the electric linear actuator with higher accuracy at least from the next operation onwards (estimated by updating from log information).

[0015] In the above configuration, the control device an estimator for estimating a rotation angle of the electric motor; When a predetermined amount of change in the load or the amount of rotation of the electric motor occurs, an amount of change in either the load or the amount of rotation of the electric motor is estimated and stored; The control device further comprises: The stored amount of change may be compared with an amount of change newly estimated after the storage, and if these amounts of change are greater than a predetermined amount, it may be determined that a discontinuity has occurred in the control gain between the angle and load of the electric motor, and the control gain may be updated based on the determined point of discontinuity. As a result, for example, regarding characteristic fluctuations in the control gain that may occur due to changes in the contact state of each component part of the electric linear actuator or wear of parts, by estimating at least the change in the discontinuity point from the correlation between the motor rotation amount and the load of the actual electric linear actuator and reflecting this result in the control gain, it becomes possible to control the electric linear actuator with higher accuracy at least from the next operation onwards (real-time estimation). Effect of the Invention

[0016] The electric linear actuator according to the present invention allows for highly accurate driving of the electric motor by taking into consideration discontinuous stiffness that occurs based on the speed change ratio in the speed change mechanism. [Brief description of the drawings]

[0017] [Figure 1A] 1 is a block diagram showing a schematic configuration of an electric linear motion actuator according to one embodiment of the present invention. [Figure 1B] FIG. 13 is a block diagram showing a schematic configuration of an electric linear motion actuator according to another embodiment of the present invention. [Diagram 2] 3 is a schematic diagram of a linear motion mechanism having a speed change mechanism in each of the electric linear motion actuators described above. FIG. [Figure 3A] FIG. 4 is a block diagram of an example of a load controller included in the control device in each of the electric linear motion actuators described above. [Figure 3B] FIG. 11 is a block diagram of another example of the load controller included in the control device in each of the electric linear motion actuators described above. [Figure 4A] 5 is an example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. [Figure 4B] 11 is a characteristic diagram illustrating another example of a control gain of a control gain adjustment unit included in the load controller. [Figure 4C] 11 is yet another example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. [Figure 4D] 11 is yet another example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. [Figure 4E] 11 is yet another example of a characteristic diagram illustrating a control gain of a control gain adjustment unit included in the load controller. [Figure 5A] FIG. 3B is an example of a block diagram illustrating the load controller shown in FIG. 3A in more detail. [Figure 5B] 3B is another example of a block diagram illustrating the load controller shown in FIG. 3A in more detail. [Figure 6] 5 is a waveform diagram showing an example of operation when a load is generated in the electric linear actuator. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] <<Configuration of the electric brake device>> An electric brake device 1A to which an electric linear actuator 1 according to one embodiment of the present invention is applied will be described. Fig. 1A shows an example of the configuration of the electric brake device 1A including an electric brake control device 100A as an example of a control device 100, a brake actuator 500A as an example of an actuator 500 using a linear mechanism, and brake instruction means 300A such as a brake pedal as an example of instruction means 300. In this embodiment, the electric brake device 1A is used for braking a vehicle.

[0019] <<Configuration of brake actuator 500A>> The brake actuator 500A is composed of an electric motor 510, a linear motion mechanism 520 that converts the rotational motion of the electric motor 510 into linear motion (linear motion) of a friction material 560 described later, an angle sensor 530 that detects and outputs the amount of rotation (number of rotations) or rotation angle (hereinafter also referred to as motor angle) of the rotor of the electric motor 510, a brake rotor 570 that rotates integrally with the wheel and is an object of load, a friction material 560 that is pressed against the brake rotor 570 to apply a load (or linear load; in this embodiment, also referred to as brake load) to generate a braking force on the vehicle (wheel), a load sensor 540 that detects and outputs the brake load, a reducer 550 that reduces the number of rotations of the electric motor 510 and outputs it to the linear motion mechanism 520, and a speed change mechanism 580. Note that a configuration without the reducer 550 may be used depending on the performance requirements of the brake.

[0020] The electric motor 510 is, for example, a permanent magnet synchronous motor, which is considered to be suitable for space saving, high efficiency and high torque. However, the electric motor is not limited to this, and for example, a DC motor using brushes, a reluctance motor not using permanent magnets, an induction motor, etc. may also be applied. In addition, the electric motor may be a radial gap motor with magnetic poles provided in the direction of the rotation diameter, or an axial gap motor with magnetic poles in the direction of the rotation axis.

[0021] In this embodiment, the linear motion mechanism 520 is a linear motion mechanism incorporating a speed change mechanism 580 in which the equivalent lead changes depending on the linear load applied. In particular, it is preferable to apply a planetary roller screw structure in which the equivalent lead changes as the planetary carrier 524 and the multiple planetary rolling elements 523 are fastened or separated by the reaction force of the linear load as shown in Fig. 2 described later, because this structure is simple and space-saving. Alternatively, a linear motion mechanism can be used that combines the above-mentioned planetary reducer provided with a speed change mechanism with various mechanisms capable of converting rotational motion into linear motion, such as a ball screw or a ball ramp mechanism.

[0022] 2, which will be described later, and a stopper 583. Note that the transmission mechanism 580 is not limited to being built into the linear motion mechanism 520 as in the present embodiment, and may be, for example, in the reducer 550 outside the linear motion mechanism 520, or may be the reducer 550, or may be another mechanism capable of producing a transmission function.

[0023] 1A is, for example, a resolver or a magnetic encoder, which is considered to be suitable for high accuracy and high reliability. However, the present invention is not limited to these, and various sensors such as an optical encoder can also be used. Alternatively, as another configuration, an angle sensorless estimation can be applied in which the motor angle is estimated from the relationship between voltage and current in a control device described later, without using an angle sensor.

[0024] The load sensor 540 is, for example, a sensor that detects distortion or deformation in response to the load applied by an actuator, and its use is considered to be preferable because it is inexpensive and highly accurate. However, the load sensor is not limited to this, and a pressure-sensitive medium such as a piezoelectric element can also be used. Alternatively, a torque sensor that detects the braking torque of a brake rotor, or an acceleration sensor that detects the longitudinal deceleration of a vehicle in the case of an electric brake device for a vehicle, can also be used.

[0025] In addition, as elements not shown, the brake actuator 500A may be provided with a power supply device that supplies power to each unit, and various sensors such as a thermistor, depending on requirements. The brake actuator 500A can also be used as a parking brake actuator by providing a mechanism for locking a part to which the power of the actuator, such as the linear motion mechanism 520, is transmitted, using a solenoid, a DC motor, or the like.

[0026] <<Configuration of electric brake control device 100A>> The electric brake control device 100A is composed of a brake controller 110A that performs brake control calculations which is an example of a load controller 110 that performs load control calculations, a motion state estimator 120 that calculates the operating state of the motor, a brake force estimator 130A that estimates the brake force which is an example of a load force estimator 130 that estimates the load force, a motor controller 140 that controls the motor current flowing through the electric motor 510 to obtain a predetermined motor output, a motor driver 150 that supplies power to the motor, and a current sensor 160 that detects the motor current.

[0027] The motion state estimator 120 includes at least an angle estimator 121 that estimates the angle (motor angle) of the electric motor rotor, and an angular velocity estimator 123 that estimates the angular velocity of the motor angle. Alternatively, instead of having these estimators, the motion state estimator 120 may be provided with a function for estimating a predetermined differential and integral value such as an electric motor angular acceleration, and a function for estimating a disturbance. The motor angle may be, for example, an electrical angle phase used for current control, or a total rotation angle corrected for overlap and underlap of an angle sensor used for angle control, and the angle estimator 121 has a function for appropriately calculating a required physical quantity based on a control configuration. In addition, the motor angle and angular velocity may be, for example, a rotation angle (rotation speed) of a predetermined part of a reducer calculated based on a reduction ratio, or a position or speed calculated based on an equivalent lead of a screw mechanism, instead of the electric motor rotor. The configuration for estimating the physical quantity may use, for example, a configuration such as a state estimation observer, or may be a direct calculation such as a back calculation based on a differential or an inertia equation.

[0028] The current sensor 160 may be, for example, a sensor made of an amplifier that detects the voltage across a shunt resistor provided in the current path, or a non-contact sensor that detects magnetic flux around the current path. Alternatively, the current sensor 160 may be configured to detect the terminal voltage of an element that constitutes a motor driver. The current sensor 160 may be provided between the phases of the electric motor, or one or more current sensors may be provided on the low side or high side. Alternatively, a current value may be calculated based on motor characteristics such as inductance and resistance value, without providing a current sensor, and feedforward control may be performed.

[0029] The brake controller 110A has a function of calculating an operation amount for the brake actuator 500A to follow a predetermined command input (specifically, a brake force command value or a press force command value; in Figs. 3A and 3B, a load command value) and converting it into a motor drive signal. The brake controller 110A is provided with a brake force control unit 113A (an example of a load force control unit 113 for controlling a load force generated by conversion to a linear motion of the linear motion mechanism) for controlling a stroke position [or a (linear motion) stroke amount (corresponding to a movement amount of the friction material 560)] of a so-called rod of a component part that mainly performs linear motion of the linear motion mechanism 520 and for controlling a brake force generated by abutment between the friction material 560 and the brake rotor 570, and a control gain adjustment unit 115 for adjusting a control gain calculated in the brake force control unit 113A according to a load condition.

[0030] The braking force control unit 113A (i.e., the load force control unit 113) may have a function of determining the motor drive amount of the electric motor 510 so as to control the linear stroke amount of the linear motion mechanism 520 converted from the motor rotation amount (or motor angle) based on, for example, an equivalent lead when a screw mechanism is used, a reduction ratio when a reducer is provided, or various specifications of the actuator 500. Alternatively, the braking force control unit 113A may have a function of providing a stroke sensor (not shown) separately and performing feedback control to make the sensor signal follow a predetermined target value. In addition, the braking force control unit 113A may also have a function of setting the stroke amount so that a predetermined gap can exist between the friction material 560 and the brake rotor 570 so that they do not come into contact with each other as much as possible when the brake is released. The stroke amount that can become the predetermined gap can be set, for example, as a position where the motor is rotated a predetermined amount from the motor angle where the estimated braking force estimated by the braking force estimator 130A becomes a predetermined value, or a position where the motor is rotated a predetermined amount after the estimated braking force stops changing with the transition of the motor angle (or after the amount of change becomes smaller than a predetermined value).The braking force control unit 113A may also function to set the stroke state where the gap becomes close to zero or a value smaller than zero, for example, in order to control an extremely slight braking force that can be difficult to detect by, for example, a load sensor that detects the braking force or the above-mentioned torque sensor.

[0031] In this embodiment, specifically, the braking force control unit 113A has a function of determining the motor drive amount so as to control the braking force when the friction material 560 and the brake rotor 570 are brought into contact with each other to follow a predetermined target value. In this embodiment, an example is shown in which the pressing force between the friction material 560 and the brake rotor 570 is detected by the load sensor 540, and the braking force control unit 113A functions based on a braking force (estimated braking force) estimated by a braking force estimator 130A described below from the output of the load sensor 540, but the braking force control may also be performed using a torque sensor or the like that detects the braking torque of the brake rotor described above.

[0032] Control gain adjustment unit 115 has a function of adjusting the control gain applied when braking force control unit 113A calculates the operation amount to a control gain that takes into consideration the nonlinear characteristics caused mainly by speed change mechanism 580 present in the linear motion mechanism in this embodiment, using the motor rotation amount determined from the motor angle of electric motor 510 and a brake load, which is an example of an actuator load, etc. This nonlinear characteristic will be described next.

[0033] (1) In the linear motion mechanism 520 of this embodiment, the equivalent lead is relatively large in a state in which the planetary carrier 524 and the rotating shaft 521 in Fig. 2 are fastened and rotate together (referred to as an integral rotation state), and the equivalent lead is relatively small due to the planetary deceleration effect in a state in which the planetary carrier 524 and the rotating shaft 521 are separated and the planetary rolling body 523 rotates (referred to as a separated rotation state). In other words, when the state changes between the integral rotation state and the separated rotation state, the stiffness, which is the correlation between the motor rotation amount and the brake load, becomes a discontinuous stiffness at least according to the presence or absence of the planetary deceleration effect. In other words, the stiffness becomes such that the gradient of change in either the motor rotation amount or the brake load relative to the other changes discontinuously at least by the deceleration ratio due to the planetary deceleration effect.

[0034] (2) For example, when using an elastic member (in this embodiment, a spring member) 581 that deforms due to the reaction force of a linear load as a means for fastening or separating the planet carrier 524 and the planet rolling element 523 described above, the closer to zero the deformation amount of the spring member 581 is, the better in terms of performance, but the reality is that a structure that deforms only a predetermined amount is unavoidable due to manufacturing reasons such as dimensional tolerances. Therefore, while the spring member 581 is deforming, the rigidity of the spring member becomes discontinuous, especially when the deformation of the spring member 581 reaches its limit and it can no longer deform.

[0035] Additionally, in this embodiment, for example, a function may be provided to provide a predetermined clearance between friction material 560 and brake rotor 570 when the braking force is set to zero. Furthermore, in braking force control unit 113A, an arithmetic expression for deriving a motor angle or angular velocity based on a feedback deviation of the braking force is used as a motor driving amount for controlling the braking force to follow a desired target value, and a minor control loop for feeding back the motor angle or angular velocity may be separately provided.

[0036] The motor controller 140 has a function of controlling the motor current so as to conform to a predetermined motor drive signal output from the braking force controller 110A (load controller 110). For the motor current, in order to obtain a predetermined torque at a predetermined motor angular velocity, the motor controller 140 stores optimal current conditions in a look-up table (LUT) in advance, determines a target current value from the current motor angular velocity, and controls the motor current to the target current value, which is considered to be a preferable function for performing inexpensive and highly accurate control. However, the present invention is not limited to this, and the motor controller 140 may also have a function of calculating a relational expression between current, voltage, etc. for deriving the output of the electric motor 510 in real time.

[0037] The motor driver 150 is preferably configured to perform PWM (Pulse Width Modulation) control, which determines the motor application voltage based on a predetermined duty ratio (the ratio between the high time and the low time of the voltage applied to the motor), and is inexpensive and has high performance. Alternatively, the motor driver 150 may be provided with a transformer circuit or the like and configured to perform PAM (Pulse Amplitude Modulation) control.

[0038] The braking force estimator 130A, which is an example of the load force estimator 130, has a function of estimating the braking force generated by the contact between the brake rotor 570 and the friction material 560. Specifically, the braking force estimator 130A receives an input from the load sensor 540 and outputs an estimated braking force.

[0039] The brake instruction means 300A may use various types of operation means operable by the driver, such as a volume, a joystick, a switch, etc., instead of a brake pedal.

[0040] The vehicle motion control device 700 includes an automatic brake function unit (not shown) for preventing a collision of the vehicle or reducing the impact of the collision, a skid prevention function unit for preventing the vehicle from spinning or the like by braking when the vehicle is in a skid state, and an anti-skid control unit for preventing the wheels from locking due to the brakes and making the vehicle behavior unstable, and determines and outputs a brake operation amount to apply a predetermined amount of brakes to the vehicle. The vehicle motion control device 700 may be an integrated control device that integrates information from various on-board sensors such as a gravity sensor, an object sensor, and a GPS (Global Positioning System), not shown, and performs calculations required for the various functions. The brake operation amount determined by the vehicle motion control device 700 is also transmitted to the electric brake control device 100A as a target brake force or a part of the target brake force.

[0041] <<Other>> A power supply device may be provided as an element not shown in the figure. For example, in an electric brake device for an automobile, the power supply device may be a low-voltage battery or a step-down converter for stepping down a high-voltage battery. Alternatively, a high-capacity capacitor or the like may be used, or these may be used in parallel for redundancy. In addition, it is preferable that the motor driver and solenoid driver are directly supplied with power output, and a small step-down converter is applied to the various computing units and functional units in the electric brake control device 100A to step down the voltage. Alternatively, the power supply output may be directly supplied to the various computing units and functional units, and power may be supplied to either or both of the motor driver and the solenoid via a step-up converter.

[0042] In addition, it is considered that the above various computing units and functional units are preferably configured with electronic components such as a processor such as a programmable microcomputer, an FPGA (Field Programmable Gate Array), and an ASIC (Application Specific Integrated Circuit), which are inexpensive and have high performance. The functional blocks shown in this figure are provided only for convenience of description and do not restrict the designation of the hardware or software configuration or the division of functions, and the functions of each block may be integrated or divided as necessary. In addition, the specific configuration of the software and hardware may be configured arbitrarily as long as it does not interfere with the functions shown in this embodiment. It is also possible to add elements not shown in the figure as long as it does not interfere with the functions of this embodiment, and it is preferable to appropriately add safety mechanisms in case of failure of various functions or sensors based on system requirements.

[0043] The electric brake device 1A can be used as a brake device for a vehicle, and can also be used as a brake device for stopping an elevator, a power generating device, or an energy storage device such as a flywheel.

[0044] An electric press 1B to which an electric linear actuator 1 according to another embodiment of the present invention is applied will be described. FIG. 1B shows an example of the configuration of the electric press 1B including an electric press control device 100B as an example of the control device 100, a press actuator 500B as an example of an actuator 500 using a linear mechanism, and a press controller 300B as an example of an instruction means 300. The electric press 1B is different from the electric brake device 1A of the previous embodiment in that the object to which the load is applied is a press object 590 of the press actuator 500B instead of the brake rotor 570 of the brake actuator 500A. In the electric press 1B, the same reference numerals as those of the electric brake device 1A have the same functions in principle, so that the functions can be guessed and will not be described below.

[0045] The press controller 110B of the electric press control device 100B is an example of the load controller 110 that performs load control calculations, and performs calculations for press control, etc. The press load estimator 130B is an example of the load force estimator 130 that estimates a load force, and estimates the press force (or press load) from the drive mechanism 520 to the press object 590.

[0046] The press load control section 113B (an example of a load controller 113) of the press controller 110B is an example of a load force control section 113 for controlling the load force generated by conversion to linear motion of the linear motion mechanism. The press load control section 113B has a function of determining a motor drive amount so as to control the press force from the drive mechanism 520 to the press object 590 so as to follow a predetermined target value. In the press load control section 113B of this embodiment, an example is shown in which the press force is detected by a load sensor 540, and the press load control section 113B functions based on a press force (estimated press force) estimated by a press load estimator 130B from the output of the load sensor 540.

[0047] <<Structural example of linear motion mechanism 520>> 2(a) is a schematic diagram of a linear motion mechanism 520 having a speed change mechanism 580 in an unloaded (unloaded) state. A planetary carrier 524 supporting a plurality of planetary rolling elements 523 is pressed against a stopper 583 by a spring member 581, which is an elastic member, and is integrated with the rotation input shaft 521 so that the planetary rolling elements 523 do not rotate on their own axis, and the planetary carrier 524 and the rotation input shaft 521 rotate together (integral rotation state), resulting in the same operation as a typical sliding screw.

[0048] 2(b) is a schematic diagram of the linear motion mechanism 520 having the speed change mechanism 580 when a linear motion load of a predetermined value or more is applied. The spring member 581 is compressed by Δ due to a reaction force transmitted from the outer ring 525 to the force applied by converting the rotational force of the rotation input shaft 521 into a linear motion load via the planetary rolling elements 523. As a result, the pressing of the planetary carrier 524 against the stopper 583 is released, the integration of the planetary carrier 524 and the rotation input shaft 521 is released, the planetary rolling elements 523 begin to rotate (separated rotation state), and a planetary deceleration effect occurs in which a difference in rotational speed occurs between the rotation input shaft 521 and the planetary carrier 524, and the equivalent lead is reduced compared to the case of FIG. 2(a).

[0049] <<Configuration Example of Load Controller 110>> Fig. 3A shows an example of the configuration of a load controller 110 including the brake controller 110A of Fig. 1A and the press controller 110B of Fig. 1B. The load target value (command input) and estimated load in the figure become a brake force command value and an estimated brake force, respectively, when configuring the brake controller 110A, and become a press force command value and an estimated press force, respectively, when configuring the press controller 110B.

[0050] The load control unit 113 derives a motor drive amount for making the estimated load value of the actual machine follow the load target value. For example, it can calculate the deviation between the load target value and the load estimated value, and obtain an operation amount for making the deviation zero or within an allowable error range.

[0051] The control gain adjustment unit 115 has a function of acquiring a load target value, deriving a control gain setting value corresponding to the load target value, and updating the control gain of the load control unit 113 to the control gain setting value. This control gain setting value is a value that changes discontinuously in response to discontinuous nonlinear stiffness (for example, due to a speed change mechanism as shown in FIG. 2).

[0052] In the load control unit 113, for example, PID compensation (or PID control [Proportional Integral Differential Control]) is performed on the deviation between the estimated value of the load and the target value of the load. In this case, the control gain adjustment unit 115 may have a function of adjusting one steady-state gain related to all gains of the P control [Proportional Control], the I control [Integral Control], and the D control [Differential Control], or may have a function of individually adjusting the gains of each element of the P control, the I control, and the D control. Alternatively, for example, in the case where a state feedback controller having a predetermined feedback loop eigenvalue is applied in the load control unit 113, the control gain adjustment unit 115 may have a function of adjusting at least the time constant of the eigenvalue. These adjusted values ​​can be derived by a predetermined arithmetic expression, but it is preferable to store predetermined design values ​​according to the load in a LUT (Look Up Table) or the like in advance and refer to the LUT or the like, since this reduces the amount of calculation.

[0053] In this embodiment, the motor drive amount indicates a motor torque command value, which is considered preferable because it allows the controller to be designed based on a simple equation of motion. However, the present invention is not limited to this, and it is also possible to use a configuration in which, for example, a motor current command value or a voltage to be directly applied to the motor is derived.

[0054] Fig. 3B shows an example of a configuration for the control gain adjustment unit 115 in Fig. 3A, in which the control gain is determined by referring to an estimated load instead of the load target value as an input. Since the configuration is the same as Fig. 3A except for this difference, detailed description will be omitted. Note that the calculation of the control gain setting value can also use an intermediate value such as a weighted average value of the load target value and the estimated load by using, for example, the configurations in Fig. 3A and Fig. 3B in combination.

[0055] <<Control gain adjustment unit 115>> 4A to 4E show examples of nonlinear stiffness (pressure increase characteristics, pressure decrease characteristics) when linear motion mechanism 520 having speed change mechanism 580 in Fig. 2 is applied, and corresponding control gains (control gain setting values) calculated by control gain adjuster 115 in Fig. 3A and Fig. 3B (actuator load vs. motor rotation amount and control gain characteristics diagrams). In the upper diagrams of each diagram, the solid line shows the pressure increase characteristics during pressure increase, and the dashed line shows the pressure decrease characteristics during pressure decrease.

[0056] 4A to 4E show the control gain with respect to the actuator load (or linear load) in the lower diagram. If the point where the gradient of change in the motor rotation amount with respect to the actuator load (called the gradient of change in the motor rotation amount) or the reverse gradient of change in the actuator load with respect to the motor rotation amount changes discontinuously is defined as a discontinuous point, in this embodiment, there are two discontinuous points of stiffness in each of the pressure increase characteristic and the pressure decrease characteristic in the diagram, and the first point counting from the lowest actuator load is a discontinuous point where a speed change occurs in which the equivalent lead of the linear mechanism changes, and the second point is a discontinuous point due to deformation such as the deformation limit of the spring member (elastic member) of the speed change mechanism. Here, discontinuity includes the discontinuity when the gradient of change changes extremely sharply when viewed macroscopically in full scale, even if it shows a continuity that changes gradually when viewed microscopically. On the other hand, discontinuity between samples caused by discretization in discretized information such as LUT is not included in the discontinuity.

[0057] Here, for example, in a case where a structure is adopted in which the deformation amount of the spring member is extremely close to zero, or a spring member that does not reach its deformation limit even when the linear motion mechanism 520 applies a maximum load, a control gain may exist in which the second discontinuity does not exist.

[0058] In general, the nonlinear stiffness of a linear motion mechanism during pressure increase and pressure decrease has a nonlinearity that does not match when pressure is increased and decreased, mainly due to factors such as friction at the contact points of the members where deformation occurs (the hysteresis characteristic described above), and the tendency of the mismatch varies depending on the linear motion mechanism used. In addition, the nonlinearity may change due to aging or wear, and the nonlinearity may also change depending on the operation history, such as how much load was generated. In other words, at least in the region (intermediate region) where the characteristics of the pressure increase side and the pressure decrease side differ in the control gain for the actuator load shown in the figure, it is difficult to clearly grasp in advance what type of stiffness will be exhibited.

[0059] 4A, when pressure is increased, at a first predetermined actuator load F1a as viewed from the low actuator load side, a speed change occurs as the actuator changes from an integral rotation state to a separate rotation state, reducing the equivalent lead and generating a discontinuous point where the gradient of change in motor rotation amount with respect to the actuator load increases. In the characteristics when pressure is reduced, the equivalent lead is large and the gradient of change in motor rotation amount is relatively small at F1a compared to the characteristics when pressure is increased. In the characteristics when pressure is reduced, at an actuator load F2a larger than F1a, a speed change occurs again as the actuator changes from a separate rotation state to an integral rotation state, generating a characteristic where the first discontinuous point occurs as viewed from the low actuator load side.

[0060] At this time, the control gain in the control gain adjustment unit 115 transitions from a low state to a high state at the first discontinuity point when viewed from the low load side, and in the section from F1a to F2a, the control gain is in a low state, and the discontinuity point of F2a on the pressure reduction side is adopted. This is preferable because it can prevent deterioration of controllability such as the actuator overshooting significantly due to the motor being driven strongly assuming that the equivalent lead is small even though the equivalent lead is large. Note that the discontinuity point of the control gain may be a discontinuity point at a load sufficiently closer to F2a than F1a, or the discontinuity point may be set to a load slightly larger than F2a, taking into account the characteristic variations of each individual actuator and aging, etc.

[0061] In this embodiment, high and low control gains not only mean that the absolute values ​​of the coefficients actually multiplied are large and small, but also mean that the time constants of the eigenvalues ​​of the control loops that are configured are small (= fast) and large (= slow).

[0062] Also, at the second actuator load F3a when viewed from the low actuator load side during pressure increase, the spring member (elastic member) 581 of the speed change mechanism 580 reaches its deformation limit, and a discontinuous point occurs where the gradient of the change in the motor rotation amount with respect to the actuator load decreases. At the time of pressure reduction, a predetermined actuator load F4a smaller than the F3a becomes the second discontinuous point when viewed from the low actuator load side. At this time, the control gain in the control gain adjustment unit 115 transitions from a high control gain state to a low control gain state at the second discontinuous point when viewed from the low load side, and in the section from F4a to F3a, the control gain is in a low state, and the discontinuous point adopts a characteristic having a discontinuous point of F4a on the pressure reduction side. This is preferable because it can prevent deterioration in controllability such as the actuator overshooting significantly due to the motor being driven largely on the assumption that the equivalent lead is small even when the equivalent lead is large. The discontinuity point of the control gain may be set at a load that is sufficiently closer to F4a than to F3a, or may be set at a load slightly smaller than F4a, taking into account variations in the characteristics of individual actuators and changes over time.

[0063] In Fig. 4B, when the actuator load is increased, a discontinuous point occurs at the first specified actuator load F1b when viewed from the low actuator load side, where the equivalent lead decreases and the gradient of change in the motor rotation amount with respect to the actuator load increases, because a speed change occurs as the actuator changes from the rotating-against-rotating state to the rotating-against-rotating state. When the actuator load is decreased, a discontinuous point occurs at the first specified actuator load F2b, which is smaller than F1b, when the actuator load is decreased, where the motor changes from the rotating-against-rotating state to the rotating-against-rotating state again, whereby the gradient of change in the motor rotation amount with respect to the actuator load increases. In the characteristics when the actuator load is decreased, the gradient of change in the motor rotation amount is larger in the load region smaller than F1b, compared to the characteristics when the actuator load is increased.

[0064] At this time, preferably, in the section from F2b to F1b, the control gain is in a low state, and the discontinuity point is the discontinuity point of F1b on the pressure increase side. The discontinuity point of the control gain may be a discontinuity point at a load sufficiently closer to F1b than F2b, or may be set to a load slightly higher than F1b, taking into consideration the characteristic variations of individual actuators and aging. Note that the control gain in the section from F4b to F3b, where a discontinuity point occurs due to deformation of the spring member in the characteristics of the increase and decrease of pressure, may be set in the same manner as in the section from F4a to F3a in FIG. 4A.

[0065] 4C, when viewed from the low actuator load side during pressure increase, spring member (elastic member) 581 of speed change mechanism 580 reaches its deformation limit at a second predetermined actuator load F3c, and a discontinuous point occurs where the gradient of change in motor rotation amount with respect to the actuator load decreases. When pressure is reduced, a predetermined actuator load F4c larger than F3c becomes the second discontinuous point when viewed from the low actuator load side.

[0066] In this case, preferably, the control gain in the control gain adjustment unit 115 is in a low state in the section from F3c to F4c, and the discontinuity point is the discontinuity point of F3c on the pressure increase side. The discontinuity point of the control gain may be a discontinuity point at a load sufficiently closer to F3c than F4c, or may be set to a load slightly smaller than F3c, taking into consideration the characteristic variations of individual actuators and aging. The control gain in the section from F1c to F2c, where the discontinuity point occurs due to the change in the equivalent lead, may be set in the same manner as in the section from F1a to F2a in FIG. 4A.

[0067] With regard to Fig. 4D, the control gain can be determined between actuator loads F1d and F2d in the same manner as between F1b and F2b in Fig. 4B, and between actuator loads F3d and F4d in the same manner as between F3c and F4c in Fig. 4C. Fig. 4E shows an example of the control gain when the electric linear motion actuator 1 having the speed change mechanism 580 is applied to the electric brake device 1A. The pressure increase characteristic, pressure decrease characteristic, and control gain in Fig. 4A are closer to a curve than a straight line.

[0068] In general, an electric brake device has nonlinear stiffness due to the influence of the nonlinear stiffness of, for example, a friction material for the brake, and while the change is generally continuous, discontinuous change occurs when the linear motion mechanism 520 having the speed change mechanism 580 shown in FIG. 2 is applied. Therefore, as a control gain for that, a discontinuous point of the control gain corresponding to the discontinuous point of the stiffness due to the speed change mechanism 580 is provided, and the control gain can be made to change continuously in other regions. Note that the nonlinearity due to pressure increase / decrease is described as showing a trend similar to that of FIG. 4A, but when an actuator showing the trends of FIG. 4B to FIG. 4D is used, discontinuous points of the control gain can be set similar to those of FIG. 4B to FIG. 4D. Also, an example is shown in which the section excluding the discontinuous points of the control gain has continuous nonlinearity, but the controller may be designed to be robust to a certain extent and simplified to change at a constant gradient, or may be set to an approximately constant value.

[0069] <<Another Example of the Control Gain Adjustment Unit 115>> Fig. 5A shows an example in which the nonlinear stiffness and its discontinuity points are estimated from the motor angle and the estimated load, and the control gain of the control gain adjustment unit 115 is adjusted and updated based on the estimation result. In Fig. 5A, the control gain adjustment unit 115 has pressure increase control gain 115a in which the control gain at the time of pressure increase is stored, and pressure decrease control gain 115b in which the control gain at the time of pressure decrease is stored, and further has a control gain switching unit 115c that determines whether the control gain at the time of pressure increase control gain 115a or pressure decrease control gain 115b is to be referred to.

[0070] The control gain switching unit 115c can have a function of switching the control gain so that, for example, when it is determined from the transition of the motor angle that the motor is rotating toward the pressure-increasing side, the control gain of the pressure-increasing control gain 115a is referred to, and when it is determined that the motor is rotating toward the pressure-reducing side, the control gain of the pressure-reducing control gain 115b is referred to. Alternatively, the control gain switching unit 115c may determine whether the motor is rotating by a predetermined amount or more toward the pressure-increasing side, the motor is rotating by a predetermined amount or more toward the pressure-reducing side, or an intermediate state that does not correspond to either of these, and may refer to a control gain in which the control gains during pressure-increasing and pressure-reducing are combined at a predetermined ratio in the intermediate state. Alternatively, instead of the motor angle, a determination may be made as to whether the control gain is to be referred to from the pressure-increasing control gain 115a or the pressure-reducing control gain 115b from the transition of the estimated load.

[0071] 5A includes the control gain adjuster 115 and, in addition to the configuration of FIG. 3A, a stiffness parameter storage unit 117 and a nonlinear stiffness estimation unit 118. The stiffness parameter storage unit 117 stores a history of changes in the amount of rotation of the electric motor 510 and the estimated load when a predetermined amount of change in the load occurs within a range that includes at least a load corresponding to a discontinuity point of the pre-stored control gain. Specifically, the stiffness parameter storage unit 117 includes a pressure-increasing data storage unit 117a that stores the motor angle and the estimated load during pressure-increasing operation, and a pressure-reducing data storage unit 117b that stores the motor angle and the estimated load during pressure-reducing operation.

[0072] The nonlinear stiffness estimation unit 118 estimates a discontinuous point of the correlation between the motor angle and the load in the control gain from the change history of the angle of the electric motor 510 and the estimated load, and updates the control gain based on the estimated discontinuous point. Specifically, the nonlinear stiffness estimation unit 118 includes a convergence calculation unit 118a that performs parameter fitting to minimize an error for a predetermined function for estimating the discontinuous point and deriving the nonlinear stiffness, for the motor angle and the estimated load stored in the stiffness parameter storage unit 117, and a control gain calculation unit 118b that derives the nonlinear stiffness based on the result of the convergence calculation unit 118a. The parameter fitting in the convergence calculation unit 118a is performed at a stage when a sufficient range of data including at least the discontinuous points of stiffness is accumulated in the stiffness parameter storage unit 117.

[0073] In the convergence calculation unit 118a, the nonlinear stiffness for the motor angle θ and load F is derived as follows using a function g1(F) indicating the stiffness when the equivalent lead is large, a function g2(F) indicating the stiffness when the equivalent lead is small and the spring member deforms, a function g3(F) indicating the stiffness when the equivalent lead is small and the spring member does not deform (deformation limit, etc.), and a load Fnl1 where g1(F) and g2 coincide, and a load Fnl2 where g2(F) and g3(F) coincide, which correspond to two discontinuous points.

number

[0074] The convergence calculation unit 118a calculates, for each data sample θ1···θk and F1···Fk (k is the number of samples) in the stiffness parameter storage unit 117 during pressure increase and decrease, two discontinuous points Fnl1, Fnl2, and variables of the constant term Fc in the equation θ=f(F) that minimize the following error function J by using a convergence calculation algorithm such as Newton's method.

number

[0075] The control gain calculation unit 118b derives the control gains for increasing and decreasing pressure based on the calculation results of the convergence calculation unit 118a. After the derivation of the control gains is completed, the control gains of the control gain adjustment unit 115 are updated. The control gains can be derived as control gains that are determined for each function based on the derivation results of the stiffness functions g1, g2, and g3, and are combined so as to switch under load conditions corresponding to the discontinuous points Fnl1 and Fnl2. Alternatively, the derivation process may be simplified by using a control gain that is preset instead of the control gains for each function, and that is combined so as to switch under load conditions corresponding to the discontinuous points Fnl1 and Fnl2. In this case, the functions g1, g2, and g3 in the convergence calculation unit can also be fixed functions, resulting in a further simplified calculation process.

[0076] After the derivation of the control gains is completed, the discontinuity points of the control gains stored in the control gain adjustment unit are updated based on the derived discontinuity points of the control gains by control gain adjustment unit 115. At this time, the discontinuity points for the control gains during pressure increase and pressure decrease are determined according to the method described with reference to Figs. 4A to 4E.

[0077] The pressure increase control gain and the pressure decrease control gain may be updated simultaneously, or may be updated individually at any desired timing.

[0078] In addition to the above-mentioned operations, the control device 100 may estimate and store the amount of change in either the load or the rotation amount relative to the other when a predetermined amount of change in the load or the rotation amount of the electric motor 510 occurs. Furthermore, the control device 100 may compare this stored amount of change with an amount of change newly estimated after the storage, and when these amounts of change are greater than a predetermined amount, determine that a discontinuity has occurred between the angle of the electric motor 510 and the load in the control gain, and update the control gain based on the determined discontinuity.

[0079] In addition, as an element not shown, it is preferable to provide a function for appropriately resetting internal parameters so that unnecessary motor drive commands are not calculated by the load control unit 113 when, for example, the control gain is switched by the control gain switching unit 115c of the control gain adjustment unit 115, or when the control gains 115a, 115b for pressure increase and pressure decrease are updated.

[0080] In FIG. 5B, unlike FIG. 3A etc., the control gain adjustment unit 115 includes a first control gain 115d adjusted to a control gain when the equivalent lead of the linear motion mechanism is large, a second control gain 115e adjusted to a control gain when the equivalent lead is small and the spring member is deformed, and a third control gain 115f adjusted to a control gain when the equivalent lead is small and the spring member reaches its deformation limit. In FIG. 5B, instead of using the control gain in FIG. 3A etc., the first to third control gains are appropriately switched and referred to, thereby achieving the same effect as referring to a nonlinear control gain having two discontinuities as in FIG. 3A etc. (which may include the pressure increase control gain and pressure decrease control gain in FIG. 5A). Therefore, the control gain adjustment unit 115 in FIG. 5B further includes a control gain switching unit that switches to one of the first to third control gains and refers to it. Also, in FIG. 5B, a discontinuity estimation unit 119 is present. The first to third control gains may each be a constant value as shown in the figure, but may also each vary so as to continuously increase or decrease with respect to the load.

[0081] The discontinuity point estimation unit 119 includes a change gradient calculation unit 119a that derives the change gradient of the motor angle or the estimated load in response to a change in the other one, and a change gradient comparison unit 119b that compares an already stored change gradient with the derivation result of the change gradient calculation unit and newly stores the derivation result of the change gradient calculation unit.

[0082] The change gradient calculation unit 119a may have a function of evaluating the amount of change in either the motor angle or the estimated load when the other changes by a predetermined amount. For example, specifically, for the load change amount Fdelta when the motor angle changes by a predetermined θdelta, the change gradient may be Fdelta / θdelta. Alternatively, for the angle and load change over a predetermined time dt, the change gradient may be (F(t+dt)-F(t)) / (θ(t+dt)-θ(t).

[0083] The change gradient comparison unit 119b compares the change gradient already stored with the derived change gradient, and if the comparison result shows a change of a predetermined amount or more, it can determine that a discontinuity in stiffness has occurred. If a discontinuity is determined, information on the discontinuity is transmitted to the control gain adjustment unit 115.

[0084] For example, in the pressure increasing direction, when it is determined that a discontinuity has occurred while the control gain of the first control gain 115d is being referred to, the control gain switching unit 115c may transition to a state in which the control gain of the second control gain 115e is being referred to. Also, in the pressure increasing direction, when it is determined that a discontinuity has occurred while the control gain of the second control gain 115e is being referred to, the control gain switching unit 115c may transition to a state in which the control gain of the third control gain 115f is being referred to, and in the pressure decreasing direction, when it is determined that a discontinuity has occurred while the control gain of the second control gain 115e is being referred to, the control gain switching unit 115c may transition to a state in which the control gain of the first control gain 115d is referred to. In the pressure decreasing direction, when it is determined that a discontinuity has occurred while the control gain of the third control gain 115f is being referred to, the control gain switching unit 115c may transition to a state in which the control gain of the second control gain 115e is being referred to.

[0085] As an element not shown, when the control gain is switched by the control gain switching unit 115c of the control gain adjustment unit 115, it is preferable to provide a function for appropriately resetting internal parameters so that unnecessary motor drive commands are not calculated by the load control unit 113.

[0086] <<Operation example of electric brake device 1A>> FIG. 6 shows an example of operation in which a predetermined braking force is generated from an unloaded state in which a predetermined clearance is provided between the friction material 560 and the brake rotor 570. FIG. 6(a) shows an example of application of the electric linear actuator 1 described in the above embodiment to which the linear mechanism 520 having the speed change mechanism 580 described in FIG. 2 is applied. In FIG. 6(a), the braking force FF can be exerted without overshooting due to deterioration in controllability depending on the occurrence of nonlinear speed change operation, and since the equivalent lead of the linear mechanism can be changed, the braking force is generated at a relatively early time TT1 from the unloaded state. FIG. 6(b) shows an example of operation by a conventional electric linear actuator to which a linear mechanism without a speed change mechanism is applied. In FIG. 6(b), since the equivalent lead of the linear mechanism is constant, it takes a relatively long time from the unloaded state to the time TT2 at which the braking force is generated. FIG. 6(c) shows an example of operation by a conventional control method to which the linear mechanism 520 having the speed change mechanism 580 described in FIG. 2 is applied, but other than that. In FIG. 2(c), because the equivalent lead of the linear motion mechanism can be changed, braking force is generated at a relatively short time TT1 from the no-load state. However, due to the occurrence of nonlinear gear shifting operation, controllability deteriorates and a relatively large overshoot occurs before the braking force FF is exerted.

[0087] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0088] 1 Electric linear actuator 1A Electric brake device (electric linear actuator) 1B Electric press device (electric linear actuator) 100 Control device 100A Electric brake control device (control device) 100B Electric press control device (control device) 113 Load Controller 113A Brake force control unit (load controller) 113B Press load control unit (load controller) 115 Control gain adjustment section 115a Pressure boost control gain 115b Pressure reduction control gain 115c Control gain switching unit 115d First Control Gain 115e Second control gain 115f Third Control Gain 117 Stiffness parameter memory section 118 Nonlinear stiffness estimation part 119a Change gradient calculation unit 119b Change gradient comparison section 510 Electric Motor 520 Linear motion mechanism 523 Planetary Rolling Element 524 Planet Carrier 530 Angle sensor (Estimator for estimating the amount of rotation of an electric motor) 540 Load sensor (Estimator for estimating the load applied by the linear motion mechanism) 570 Brake rotor (object) 580 Transmission Mechanism 581 Spring members (elastic members) (transmission mechanism) 583 Stopper (transmission mechanism)

Claims

1. the electric motor; a linear motion mechanism that converts a rotational motion of the electric motor into a linear motion; a control device that drives the electric motor to control a load that the linear motion mechanism applies to an object by the linear motion; and a speed change mechanism having a speed change function that changes the correspondence relationship between the linear motion amount of the linear motion and the rotation amount of the electric motor at a predetermined load; The control device includes: An estimator that estimates a load applied by the linear motion mechanism; a load controller that uses a control gain for a control calculation in a process of deriving a drive amount of the electric motor, the control gain being multiplied by at least one or more of a deviation between the estimated value of the load and a target value of the load, an integral value of the deviation, and a differential value of the deviation, and calculates a motor drive amount using a control gain that discontinuously changes in response to a transition of at least one of the estimated value of the load and the target value at at least one point in a state in which at least one of the estimated value of the load and the target value is not zero; a control gain adjustment unit that adjusts a control gain used in the load controller in accordance with a load condition; having the speed change mechanism has the speed change function including a first equivalent lead state in which the amount of linear motion has a predetermined correlation with the amount of rotation of the electric motor, and a second equivalent lead state in which the amount of linear motion has a smaller correlation with the amount of rotation of the electric motor compared to the first equivalent lead state; the shifting function has a nonlinearity in which, in a process in which the load applied by the linear motion mechanism increases, the shifting function switches from the first equivalent lead state to the second equivalent lead state when the load exceeds a first shift load, which is the predetermined load, and, in a process in which the load applied by the linear motion mechanism decreases, the shifting function switches from the second equivalent lead state to the first equivalent lead state when the load falls below a second shift load, which is the predetermined load different from the first shift load; the control gain includes a first discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the first discontinuous point is smaller than the control gain on a side where the load is larger than the first discontinuous point; The shift function having nonlinearity of the shift mechanism and the control gain satisfy either of the following conditions i) and ii): Electric linear actuator. i) the first shift load of the shift function is greater than the second shift load, and the first discontinuity point of the control gain is closer to the first shift load than to the second shift load. ii) the second shift load of the shift function is greater than the first shift load, and the first discontinuity point of the control gain is closer to the second shift load than to the first shift load.

2. 2. The electric linear actuator according to claim 1, The linear motion mechanism includes: a rotation input member, a planetary carrier supported concentrically with the rotation input member for free rotation, and a planetary rolling element supported rotatably on the planetary carrier; an elastic member which applies a fastening force by which the planetary rolling body does not rotate on its axis and the rotation input member and the planetary carrier rotate synchronously by an elastic force, and which causes the fastening force to be lost by a reaction force of a load applied by the linear motion mechanism, causing the planetary rolling body to rotate on its axis and generating a difference in the amount of rotation between the rotation input member and the planetary carrier; having the elastic member has a nonlinear deformation characteristic in which, in a process in which the load applied by the linear motion mechanism increases, the deformation of the elastic member is completed when the load exceeds a predetermined first deformation load, and, in a process in which the load applied by the linear motion mechanism decreases, the deformation of the elastic member begins when the load falls below a second deformation load different from the first deformation load; the control gain includes a second discontinuous point where a transition of the control gain with respect to the transition of the load becomes discontinuous, and the control gain on a side where the load is smaller than the second discontinuous point becomes larger than the control gain on a side where the load is larger than the second discontinuous point; The deformation characteristic and the control gain of the elastic member of the linear motion mechanism satisfy either of the following conditions i) and ii): Electric linear actuator. i) The first deformation load of the elastic member is greater than the second deformation load, and the second discontinuity of the control gain is closer to the second deformation load than to the first deformation load. ii) The second deformation load of the elastic member is greater than the first deformation load, and the second discontinuity point of the control gain is closer to the first deformation load than to the second deformation load.

3. 3. The electric linear actuator according to claim 1, the control gain adjustment unit has a pressure increase control gain which is the control gain at the time of pressure increase when the load increases, a pressure decrease control gain which is the control gain at the time of pressure decrease when the load decreases, and a control gain switching unit which determines which of the pressure increase control gain or the pressure decrease control gain is to be referred to, the control gain switching unit switches the control gain so as to refer to a control gain for a pressure increase control gain when the motor is rotating toward a pressure increase side, and to refer to a control gain for a pressure decrease control gain when the motor is rotating toward a pressure decrease side, based on at least a transition of the motor angle. Electric linear actuator.

4. 3. The electric linear actuator according to claim 2, the control gain adjustment unit has a first control gain which is a control gain of the electric motor when an equivalent lead corresponding to a direct motion amount of the linear motion with respect to an amount of rotation of the electric motor is large, a second control gain which is the control gain when the equivalent lead is small and the elastic member is deformed, and a third control gain which is the control gain when the equivalent lead is small and the elastic member has reached a deformation limit, and a control gain switching unit which switches between any one of the first to third control gains and uses them as a reference; The electric linear actuator further comprises: a change gradient calculation unit that derives a gradient of a change in either the motor angle or the estimated load relative to a change in the other; a change gradient comparison unit that stores the gradient of change derived by said change gradient calculation unit, compares the stored gradient of change with a gradient of change newly derived by said change gradient calculation unit after said storage, and determines that a discontinuity in control gain exists when the gradient has changed by a predetermined value or more; the control gain switching unit uses the first to third control gains, and when there are a plurality of discontinuous points, performs a control according to at least one of the plurality of discontinuous points determined by the change gradient comparing unit, When the load is changed in a pressure increasing direction while the first control gain is being referenced, if it is determined that the discontinuous point has occurred, the second control gain is referenced; when the pressure is increased while the second control gain is being referenced, if it is determined that the discontinuity has occurred, the third control gain is referenced, and when the pressure is decreased while the pressure is reduced, if it is determined that the discontinuity has occurred, the first control gain is referenced; and when the pressure is reduced in a state where the third control gain is being referenced and it is determined that the discontinuous point has occurred, the second control gain is referenced. Electric linear actuator.

5. The electric linear actuator according to any one of claims 1 to 4, The control device includes: an estimator for estimating a rotation angle of the electric motor; a stiffness parameter storage unit that stores a history of changes in the rotation amount of the electric motor and the estimated load when a predetermined amount of change in the load occurs within a range that includes at least the load corresponding to a discontinuity point of the pre-stored control gain; The control device further comprises: a nonlinear stiffness estimator that estimates a discontinuity point of the control gain from the change history of the angle of the electric motor and the estimated load, and updates the control gain based on the estimated discontinuity point; Electric linear actuator.

6. The electric linear actuator according to any one of claims 1 to 4, The control device includes: an estimator for estimating a rotation angle of the electric motor; When a predetermined amount of change in the load or the amount of rotation of the electric motor occurs, an amount of change in either the load or the amount of rotation of the electric motor is estimated and stored; The control device further comprises: comparing the stored amount of change with an amount of change newly estimated after the storage, and determining, when these amounts of change are greater than a predetermined amount, that a discontinuity has occurred in the control gain between the angle and load of the electric motor, and updating the control gain based on the determined discontinuity; Electric linear actuator.

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