Drive system, control method, and control program

Abstract

To provide a drive system including an actuator capable of easily performing a control logic construction, a simulation for equipment design, and the like.SOLUTION: A drive system includes: an actuator to be driven by a motor to generate a displacement; a driver that drives the motor; and a controller that supplies the driver with a control command. The controller includes: a model construction unit which constructs a physical model on the basis of a displacement generated when an external load is applied to the actuator; a first command generation unit which generates a control command for the motor in such a way that the actuator generates a displacement according to the physical model; a determination unit for determining a spring constant; a second command generation unit for generating a control command for the motor in such a way as to create a driving force calculated on the basis of the product of the spring constant and the displacement generated in the actuator; and a selection unit for selecting which of the control command from the first command generation unit and the control command from the second command generation unit is to be enabled.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drive system, a control method for the drive system, and a control program for controlling the drive system. [Background technology]

[0002] Various mechanisms have been proposed and put into practical use to attenuate or control the kinetic energy generated when objects come into contact with each other, including elastic bodies such as springs and rubber, dampers (e.g., oil dampers), air cylinders, etc. There are also mechanisms that employ control using sensing results from various sensors.

[0003] The ability of mechanisms that use springs or rubber to attenuate kinetic energy is determined by the physical properties of the springs or rubber used. The ability of dampers to attenuate kinetic energy is determined by factors such as size and orifice diameter. The ability of air cylinders to attenuate kinetic energy is determined by factors such as size and air pressure. These mechanical configurations have issues such as the inability to control forces below their own weight, the need for designs and mechanisms tailored to the target, and low positional accuracy.

[0004] There is also a configuration in which an actuator (for example, a cylinder) driven by air or a motor is controlled based on the sensing results of a sensor. The following prior art is an example of such an electrical configuration.

[0005] For example, Japanese Patent Application Publication No. 2006-074987 (Patent Document 1) discloses a path-wise, typically linear, controllable force source for actively absorbing energy from or applying energy to a vehicle wheel support assembly moving over a rough surface to facilitate significantly reducing the force transmitted to a vehicle body supported on the wheel support assembly.

[0006] Japanese Patent Application Publication No. 2006-125633 (Patent Document 2) discloses a method for actively suspending a real plant in a vehicle, which includes modifying a control signal based on a difference between the characteristics of the real plant, as indicated by the response of the real plant to the control signal, and the characteristics of a reference plant.

[0007] Japanese Patent Publication No. 2013-521443 (Patent Document 3) discloses an active vibration suppression device configured to control the position of a body relative to a reference frame. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-074987 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-125633 [Patent Document 3] Special Publication No. 2013-521443 Summary of the Invention [Problem to be solved by the invention]

[0009] The electrical actuators described above can have complex configurations for control logic, etc. For example, the control logic must be configured taking into account the characteristics of the object that comes into mechanical contact with the actuator, and if the control logic includes a large number of parameters, tuning it can be time-consuming.

[0010] One object of the present invention is to provide a drive system including an actuator that allows easy configuration of control logic and simulation for facility design. [Means for solving the problem]

[0011] A drive system according to one example of the present invention includes an actuator driven by a motor to generate a displacement, a driver that drives the motor, and a controller that issues a control command to the driver. The controller includes a model configuration unit that configures a physical model based on a displacement generated by an external load being applied to the actuator, a first command generation unit that generates a control command to the motor so that the actuator generates a displacement that conforms to the physical model, a determination unit that determines a spring constant, a second command generation unit that generates a control command to the motor so that the actuator generates a drive force calculated based on the product of the spring constant and the displacement generated in the actuator, and a selection unit that selects which of the first command generation unit and the second command generation unit to activate.

[0012] With this configuration, it is possible to selectively perform a behavior that appropriately receives external loads and alleviates excessive loads that occur when objects come into contact with each other, or that suppresses the occurrence of point loads, and a behavior that generates loads from the actuator that follow the behavior of an ideal spring.

[0013] The selector may be configured to enable the control command from the second command generator when a predetermined switching condition is satisfied while the control command from the first command generator is enabled. With this configuration, it is possible to realize an operation such as generating a predetermined load from the actuator after performing an operation to relieve a load applied to the actuator in accordance with the control command from the first command generator.

[0014] The switching condition may be based on the elapsed time since an external load was applied to the actuator. With this configuration, for example, control can be achieved to switch the behavior when a predetermined time has elapsed since the actuator started operating.

[0015] The switching condition may be based on the displacement occurring in the actuator. With this configuration, for example, control can be achieved such that the behavior is switched when the actuator contracts by a predetermined amount.

[0016] The first command generating unit may output a position command that specifies a target position of the motor as a control command, and the second command generating unit may output a torque command that specifies a torque to be generated by the motor as a control command. With this configuration, the first command generating unit controls the position of the actuator, thereby realizing ideal spring behavior. Furthermore, the second command generating unit controls the torque to be generated by the motor, thereby controlling the load generated by the actuator in accordance with the ideal spring behavior.

[0017] The model constructing unit may construct a physical model when a predetermined load is applied to the actuator from the outside. With this configuration, the actuator can maintain a stationary state until the predetermined load is applied from the outside, and can start behaving as a spring when the predetermined load is applied from the outside.

[0018] The determination unit may set the spring constant for each control cycle. With this configuration, an optimum spring constant can be set for each control cycle depending on the purpose and situation.

[0019] According to another example of the present invention, there is provided a control method for an actuator driven by a motor to generate a displacement, the control method including the steps of: configuring a physical model based on a displacement generated when an external load is applied to the actuator, determining a spring constant, controlling the motor so that the actuator generates a displacement in accordance with the physical model, and, when a predetermined switching condition is satisfied while the motor is being controlled so that the actuator generates a displacement in accordance with the physical model, switching control of the motor so that a driving force calculated based on the product of the spring constant and the displacement generated in the actuator is generated.

[0020] According to yet another example of the present invention, there is provided a control program for controlling an actuator driven by a motor to generate a displacement. The control program causes a computer to execute the following steps: constructing a physical model based on a displacement generated when an external load is applied to the actuator, determining a spring constant, controlling the motor so that the actuator generates a displacement in accordance with the physical model, and, when a predetermined switching condition is satisfied while the actuator is being controlled to generate a displacement in accordance with the physical model, switching control of the motor so that a driving force calculated based on the product of the spring constant and the displacement generated in the actuator is generated. [Effects of the Invention]

[0021] According to one aspect of the present invention, it is possible to realize a drive system including an actuator that allows for easy configuration of control logic and simulation for facility design. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram showing a main part of a drive system according to an embodiment of the present invention; [Figure 2] FIG. 10 is a schematic diagram showing the main parts of a modified example of the drive system according to the present embodiment. [Figure 3] 3A and 3B are diagrams for explaining the behavior of an actuator that configures the drive system according to the present embodiment. [Figure 4] FIG. 2 is a schematic diagram illustrating an example of the hardware configuration of a controller that configures the drive system according to the present embodiment. [Figure 5] 1 is a schematic diagram of a workpiece conveying system in which an actuator according to an embodiment of the present invention performs a shock absorbing operation. [Figure 6] 10A and 10B are diagrams for explaining behavior from a physical point of view regarding the impact absorbing operation of the actuator according to the present embodiment. [Figure 7] 1 is a schematic diagram showing a main functional configuration for realizing a shock absorbing operation by an actuator according to the present embodiment. FIG. [Figure 8] This is a diagram for explaining the elastic force generation operation of the actuator according to the present embodiment. [Figure 9] This is a schematic diagram showing the main functional configuration for realizing the elastic force generation operation by the actuator according to the present embodiment. [Figure 10] This is a diagram for explaining the process for suppressing the generation of impact force due to contact between objects using the actuator according to the present embodiment. [Figure 11] This is a schematic diagram showing the main functional configuration for realizing the shock mitigation operation and the elastic force generation operation by the actuator according to the present embodiment. [Figure 12] This is a flowchart showing an example of the processing procedure related to the shock mitigation operation and the elastic force generation operation by the actuator according to the present embodiment. [Figure 13] This is a schematic diagram showing an example of a one-degree-of-freedom stage mechanism including a plurality of actuators according to the present embodiment. [Figure 14] This is a schematic diagram showing the main functional configuration for realizing the elastic force generation operation by the stage mechanism shown in FIG. 13(A). [Figure 15] This is a schematic diagram showing an example of a multi-degree-of-freedom stage mechanism including a plurality of actuators according to the present embodiment. [Figure 16] This is a schematic diagram showing an example of an application using the actuator according to the present embodiment. [Figure 17] This is a flowchart showing the processing procedure in the assembly apparatus shown in FIG. 16.

Embodiments for Carrying Out the Invention

[0023] Embodiments of the present invention will be described in detail with reference to the drawings. For the same or corresponding parts in the drawings, the same reference numerals are given and their descriptions will not be repeated.

[0024] <A. Application Examples> First, an example of a scene to which the present invention is applied will be described.

[0025] 1 is a schematic diagram showing a main part of a drive system 1 according to the present embodiment. Referring to FIG. 1, the drive system 1 includes an actuator 2 and a drive device 4.

[0026] The actuator 2 is driven by a motor 18 to generate displacement (in the example shown in FIG. 1, displacement in the vertical direction on the page). Any configuration that can be driven by a motor may be used as the actuator 2, and for example, a ball screw or a linear actuator may be used. In the following explanation, as an example, a case where the actuator 2 is mainly composed of a ball screw will be explained.

[0027] More specifically, the actuator 2 includes a main body 10 having an internal space, a rod 12 that engages with a thread formed inside the main body 10, a tip 14 provided at the tip of the rod 12, a connecting member 16 that mechanically connects the rod 12 and a motor 18, and an encoder 20 that detects the number of rotations or rotation angle of the motor 18. The encoder 20 is mechanically connected to the motor 18 to detect the displacement of the actuator 2.

[0028] The driving device 4 includes a driver 42 that supplies power to the motor 18 to drive it, and a controller 40 that receives a detection signal from the encoder 20 and issues a control command to the driver 42.

[0029] Although FIG. 1 shows an example of a drive system 1 including one actuator 2, a configuration including multiple actuators 2 can also be realized.

[0030] Fig. 2 is a schematic diagram showing the main components of a modified example of the drive system 1 according to the present embodiment. Referring to Fig. 2, the drive system 1 has three actuators 2. The drive device 4 includes three drivers 42 corresponding to the respective actuators 2, and a controller 40 that controls the three actuators 2 in an integrated manner.

[0031] There is no particular limit to the number of actuators 2 included in the drive system 1, and an appropriate number may be set depending on the application to which it is applied. For example, if any workpiece can be supported by a single actuator 2, one actuator 2 is sufficient. Furthermore, for large workpieces, the member for supporting the workpiece may be configured to be driven by multiple actuators 2.

[0032] For convenience of explanation, the controller 40 and the driver 42 are depicted as independent components, but the controller 40 and the driver 42 may be implemented as independent devices, or the two may be implemented as an integrated device.

[0033] 3 is a diagram for explaining the behavior of actuator 2 constituting drive system 1 according to this embodiment. Referring to FIG. 3, in drive system 1 according to this embodiment, actuator 2 is controlled so that the spring behaves ideally. The ideal behavior of the spring is assumed to be, for example, a spring having a natural length X0 in the state where no external force is applied, as shown in FIG. 3(A).

[0034] When this spring is stretched to a length X1 (= X0 + ΔX1), a restoring force F1 is generated in the direction of returning it to its original natural length X0. The restoring force F1 is proportional to the amount of stretch ΔX1 from the original natural length X0. On the other hand, when this spring is shortened to a length X2 (= X0 - ΔX2), a restoring force F2 is generated in the direction of returning it to its original natural length X0. The restoring force F2 is proportional to the amount of shortening ΔX2 from the original natural length X0.

[0035] In this way, in the drive system 1 according to the present embodiment, a physical spring is realized by controlling the motor 18. The realized spring exhibits substantially ideal behavior (behavior according to a physical formula), so it is easy to configure control logic using a simple physical model and perform simulations for facility design.

[0036] A more detailed example of the operation of the actuator 2 according to this embodiment will be described later. <Example of the hardware configuration of the controller 40> Next, an example of the hardware configuration of the controller 40 that constitutes the drive system 1 according to the present embodiment will be described.

[0037] FIG. 4 is a schematic diagram showing an example of the hardware configuration of the controller 40 that constitutes the drive system 1 according to the present embodiment. Referring to FIG. 4, the controller 40 is a kind of computer and includes, as main hardware components, a processor 402, a main memory 404, an input / output unit 406, and a storage 408.

[0038] The processor 402 is typically composed of a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), etc., reads out the system program 410 and the control program 412 stored in the storage 408, expands them in the main memory 404, and executes them to realize control operations for controlling the behavior of the actuator 2 as described later.

[0039] The input / output unit 406 is responsible for transmitting and receiving signals between the controller 40 and an external device. In the example shown in FIG. 4, the input / output unit 406 receives a detection signal from the encoder 20 and transmits a control command to the driver 42.

[0040] The storage 408 is typically composed of an SSD (Solid State Disk), a flash memory, etc., and stores the system program 410 and the control program 412 for realizing basic processing.

[0041] FIG. 4 shows an example of a configuration in which the necessary processing is provided by the processor 402 executing a program. However, some or all of these provided processes may be implemented using a dedicated hardware circuit (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array), etc.).

[0042] <C. Shock Absorption Operation> Next, the shock absorption operation of the actuator 2 according to the present embodiment will be described. In the shock absorption operation, the actuator 2 operates passively according to the applied load.

[0043] FIG. 5 is a schematic diagram of a work transfer system 100 in which the actuator 2 according to the present embodiment performs a shock absorption operation. Referring to FIG. 5, as an example, a case where a work W adsorbed by an end effector 122 provided at the tip of a robot 120 is placed on a stage mechanism 110 is shown. The stage mechanism 110 includes a base portion 112 and a plate 114. Between the base portion 112 and the plate 114, they are mechanically connected via the actuator 2 according to the present embodiment. Note that, in FIG. 5, for ease of understanding, the actuator 2 is depicted as a spring.

[0044] In the work transfer system 100 as shown in FIG. 5, when the work W is placed, if the stage mechanism 110 that receives the work W does not move, the work W will collide with the plate 114 and stop, so to speak. That is, since the moving speed of the work W changes greatly before and after the collision, a large load (impact force) is applied to the work W from the stage mechanism 110 due to the change in acceleration accompanying the change in the moving speed.

[0045] Also, even if the stage mechanism 110 moves along the work W, if the contact area between the work W and the plate 114 is small, a large load will be applied to the contact portion of the work W. Such a phenomenon is also referred to as point loading or load concentration.

[0046] As shown in FIG. 5, in order to mitigate the excessive load (impact force) generated when an object contacts another object or to suppress the occurrence of point loading, the actuator 2 according to the present embodiment performs a shock absorption operation.

[0047] In shock absorption, the behavior of a spring when subjected to an external force, that is, the spring contracts or expands to a position (i.e., an equilibrium position) corresponding to the displacement at which a restoring force corresponding to the external force is generated. Such contraction or expansion behavior follows a physical model, which is a substantially ideal physical behavior.

[0048] 6 is a diagram for explaining the behavior of the shock absorbing operation of the actuator 2 according to this embodiment from a physical perspective. Referring to FIG. 6, when the actuator 2 behaves as a spring and is not being loaded (natural length state 50), the plate 114 is attached, and the mass M1 of the plate 114 is applied to the actuator 2. The actuator 2 receives the load of the mass M1 of the plate 114 and reaches an equilibrium state (balanced state 52) at a position (balanced position) where it is shortened by a predetermined length ΔXb. At this time, the length of the actuator 2 is assumed to be Xb.

[0049] In this embodiment, the behavior of the spring is calculated based on the equilibrium position. For example, when a load F is applied to the actuator 2, the actuator 2 reaches an equilibrium state (load equilibrium state 54) at a position (the position when the load F is generated) that is a predetermined length Xb shorter than the equilibrium position. At this time, the length of the actuator 2 is assumed to be X.

[0050] The behavior of the spring is determined depending on the deviation from the balanced state 52. For ease of explanation, a simple harmonic motion model is assumed as the simplest physical model. Considering the behavior of the spring with the balanced position as the reference, if the spring constant of actuator 2 is K (which can be set arbitrarily in advance), then the period of the simple harmonic motion of the spring is T = 2π√(M1 / K). Furthermore, the angular frequency ω = 2π / T = √(K / M1).

[0051] That is, when a load F is applied to the actuator 2, the actuator 2 starts to vibrate in a simple harmonic motion with an amplitude A1 that corresponds to the magnitude of the applied load F. The values related to the simple harmonic motion of the actuator 2 are as follows:

[0052] Displacement ΔX=A1×sin(ωt) Speed V=A1×ω×cos(ωt) Acceleration a=A1×ω 2 ×sin(ωt)=-ω 2 ΔX As will be described later, a physical model and the like are determined based on the displacement ΔX with respect to the state in which the object is attached to the actuator 2 (balanced state 52).

[0053] In the drive system 1 according to this embodiment, a physical model representing the behavior of the spring is used to reproduce the behavior of the spring in the actuator 2. The physical model may be the simple harmonic motion model described above, a model including a mass element representing the mass M1 of the plate 114, or a model including a damping element. These physical models may be determined according to an equation of motion for the spring (F=K×X+M×V, etc.).

[0054] 7 is a schematic diagram showing a main functional configuration for realizing an impact absorbing operation by actuator 2 according to the present embodiment. Referring to FIG. 7, controller 40 includes a physical model 420, a characteristic estimating unit 422, an angular frequency setting unit 424, and a position command generating unit 426.

[0055] The physical model 420 is a model for realizing behavior as a spring. As an example, a simple harmonic motion model is shown in Figure 7. In this case, the physical model 420 calculates the displacement at any time t according to the displacement ΔX(t) = A1 × sin(ωt).

[0056] The characteristic estimation unit 422 corresponds to a model construction unit that constructs the physical model 420 based on a displacement caused by an external load being applied to the actuator 2. More specifically, the characteristic estimation unit 422 estimates a parameter (amplitude A1 in the example shown in FIG. 7) included in the physical model 420 based on a detection signal from the encoder 20. The estimated parameter is reflected in the physical model 420. The characteristics (parameters) of the physical model 420 are determined based on a change caused by an arbitrary load F being applied to the actuator 2.

[0057] For example, if the physical model 420 is a simple harmonic motion model, the amplitude A1 of the physical model 420 can be calculated based on the position change (velocity) immediately after an arbitrary load F is applied to the actuator 2.

[0058] In this way, characteristic estimation unit 422 estimates the parameters of physical model 420 based on the change over time in the displacement of actuator 2 (speed, acceleration, jerk, etc.). The estimated parameters are determined appropriately depending on physical model 420. For example, a spring constant or a damping constant may be determined. In this way, the parameters of the physical model are estimated when a significant displacement occurs in actuator 2, and therefore physical model 420 has characteristics corresponding to a predetermined external load on actuator 2.

[0059] The angular frequency setting unit 424 sets the angular frequency ω of the physical model 420 based on the mass M1 of the object attached to the actuator 2 (the plate 114 in the example shown in FIGS. 1 and 2) and a preset spring constant K. More specifically, the angular frequency setting unit 424 sets the angular frequency ω based on the preset spring constant K and the known mass M1. As described above, the angular frequency ω is calculated as ω=2π / T=√(K / M1).

[0060] The position command generator 426 generates a control command so that the actuator 2 generates a displacement in accordance with the physical model 420. More specifically, the position command generator 426 generates a control command (position command or displacement command) for each control cycle based on the displacement ΔX calculated in accordance with the physical model 420, and outputs the control command to the driver 42. That is, the position command generator 426 may output a position command that specifies a target position of the motor 18 as a control command.

[0061] The above-described processing procedure estimates the parameters that define the physical model 420. Then, the behavior of the actuator 2 is determined according to the physical model 420 that includes the estimated parameters.

[0062] When the actuator 2 rotates in simple harmonic motion, the actuator 2 responds to the load F from the workpiece W by a =K×X+M1×V. That is, the load F a reflects the moment generated by the movement of the plate 114 (mass M1).

[0063] As described above, in the shock absorbing operation according to this embodiment, a physical spring (which acts as a damper) is realized by controlling the motor 18. Because control is performed based on the equilibrium position, behavior that follows a physical formula can be realized even when the applied load is small. Because behavior follows a physical formula, advance calculations and simulations when designing a control system become easier, and deviations from the advance design are reduced when an actual device is configured.

[0064] Typically, mechanisms consisting of multiple parts have resistance between the parts, and the magnitude of this resistance varies depending on the surrounding environment, usage history, and other factors, making it difficult to calculate in advance. In contrast, the shock absorbing operation according to this embodiment can achieve behavior that follows a physical formula, regardless of the magnitude of the resistance between the parts. Furthermore, because the actuator 2 according to this embodiment is driven by a motor 18, a spring with improved responsiveness and flexibility can be achieved.

[0065] <D. Elastic force generation operation> Next, the elastic force generation operation of the actuator 2 according to the present embodiment will be described. In the elastic force generation operation, a load calculated according to Hooke's law (F a = spring constant K × displacement ΔX) is generated. In the present embodiment, by varying the spring constant K, the target load (elastic force) can be applied to the work W or the like.

[0066] FIG. 8 is a diagram for explaining the elastic force generation operation of the actuator 2 according to the present embodiment. Referring to FIG. 8(A), assume a case where the actuator 2 generates displacement according to a physical model. As an example, when the actuator 2 changes from a contracted state to an extended state, a temporal change in displacement as shown in FIG. 8(B) is shown.

[0067] If the spring constant K is constant, a load F a proportional to the displacement ΔX (the change from the natural length) will be generated. However, by changing the spring constant K temporally, the magnitude of the generated load F a can be adjusted.

[0068] For example, as shown in FIG. 8(C), by changing the spring constant K temporally, the magnitude of the load F a changes as shown in FIG. 8(D). In the example shown in FIG. 8(D), by increasing the spring constant K along with the passage of time, the fluctuation of the generated load F a is suppressed.

[0069] Also, when the required load F a is preset, the spring constant K corresponding to the displacement ΔX may be calculated in each control cycle.

[0070] FIG. 9 is a schematic diagram showing the main functional configuration for realizing the elastic force generation operation by the actuator 2 according to the present embodiment. Referring to FIG. 9, the controller 40 includes a load command generation unit 428, a spring constant change unit 430, and a displacement calculation unit 432.

[0071] The spring constant changing unit 430 corresponds to a determining unit that determines the spring constant K. The spring constant changing unit 430 may set the spring constant K for each arbitrary section, or may set the spring constant K for each control cycle. As an example, the spring constant changing unit 430 sets the spring constant K(t) for each control cycle according to a predetermined pattern.

[0072] The spring constant changing unit 430 may have a pattern for outputting the spring constant K(t) as shown in Fig. 8(C). If there are multiple types of workpieces W, multiple patterns of spring constants may be stored in the spring constant changing unit 430. In that case, one of the multiple patterns may be selected depending on the setting mode.

[0073] The displacement calculation unit 432 calculates the displacement ΔX occurring in the actuator 2 based on the detection signal from the encoder 20. The displacement ΔX calculated by the displacement calculation unit 432 is calculated based on a state in which an object (plate 114 in the example shown in FIGS. 1 and 2) is attached to the actuator 2 as a reference.

[0074] The load command generating unit 428 generates a control command to generate a driving force calculated based on the product of the spring constant K and the displacement ΔX occurring in the actuator 2. More specifically, the load command generating unit 428 calculates the load F to be generated in each control cycle based on the displacement ΔX calculated by the displacement calculating unit 432 and the spring constant K(t) from the spring constant changing unit 430. a (=K(t)×ΔX) and calculate the calculated load F a That is, the load command generating unit 428 may output a torque command that specifies the torque that the motor 18 should generate as the control command.

[0075] By the above processing procedure, the load F according to the displacement ΔX and the spring constant K is calculated. aIt can be generated from the actuator 2. In actuality, since the moment generated by the movement of the plate 114 (mass M1) is reflected, the actuator 2 generates a load F a =K×X + M1×V.

[0076] When adopting a physical model including an attenuation (damping) element, in addition to the spring constant K, or instead of the spring constant K, the damping constant may be changed over time.

[0077] As described above, in the elastic force generation operation according to this embodiment, a physical spring (operating as a damper) is realized by the control of the motor 18. Since it exhibits behavior according to physical formulas, it facilitates pre-calculation and simulation when designing the control system, and also reduces the deviation from the pre-design when actually constructing the device.

[0078] Also, in the elastic force generation operation according to this embodiment, since a load is generated in proportion to the displacement occurring in the actuator, sensors for measuring an external force (load from the outside) etc. become unnecessary. Therefore, even for a manufacturing device with high rigidity or a manufacturing device having non-negligible internal resistance, the generated load can be precisely controlled.

[0079] Also, in the elastic force generation operation according to this embodiment, since the spring constant can be changed, it is possible to generate the target load according to the application while following the physical formula of generating a load in proportion to the displacement occurring in the actuator.

[0080] <E. Shock Mitigation Operation and Elastic Force Generation Operation> By switching the above-described shock mitigation operation and elastic force generation operation, it is possible to prevent a large load (impact force) from being generated when the work W comes into contact etc.

[0081] 10 is a diagram illustrating a process for suppressing the generation of an impact force due to contact between objects using the actuator 2 according to this embodiment. Referring to FIG. 10, the impact absorbing operation is performed first, and when a load is applied, the actuator 2 operates passively in response to the applied load. Thereafter, under a predetermined switching condition, the operation switches to an elastic force generating operation, and generates a load calculated based on the spring constant defined by the displacement that has occurred and the pattern.

[0082] In the shock absorption operation, no displacement occurs in the actuator 2 unless an external force (external load) is applied. When an external force is applied, parameters corresponding to the applied external force are calculated, and the displacement of the actuator 2 is controlled by a physical model having the calculated parameters.

[0083] The switching conditions for switching between the impact absorbing operation and the elastic force generating operation may be based on the elapsed time since an external load was applied to the actuator 2, the displacement (current position) occurring in the actuator 2, a trigger from an external device, etc.

[0084] 11 is a schematic diagram showing the main functional configuration for realizing the impact absorbing operation and elastic force generating operation by actuator 2 according to the present embodiment. Referring to FIG. 11, controller 40 includes a physical model 420, a characteristic estimating unit 422, an angular frequency setting unit 424, a position command generating unit 426, a load command generating unit 428, a spring constant changing unit 430, a displacement calculating unit 432, and a selecting unit 434.

[0085] The functional configuration shown in Fig. 11 corresponds to a combination of the functional configuration for realizing the impact absorbing operation shown in Fig. 7 and the functional configuration for realizing the elastic force generating operation shown in Fig. 9, to which a selection unit 434 is added. That is, the selection unit 434 selects which control command to activate from the control command for realizing the impact absorbing operation output from the position command generation unit 426 and the control command for realizing the elastic force generating operation output from the load command generation unit 428.

[0086] The selection unit 434 has a switching condition 436, and selects and outputs one of the control command output from the position command generation unit 426 and the control command output from the load command generation unit 428 based on whether the switching condition 436 is satisfied. Typically, when the control command from the position command generation unit 426 is being validated, the selection unit 434 validates the control command from the load command generation unit 428 if the switching condition 436 is satisfied.

[0087] Fig. 12 is a flowchart showing an example of a processing procedure for the impact absorbing operation and elastic force generating operation by the actuator 2 according to this embodiment. The steps shown in Fig. 12 are typically implemented by the processor 402 of the controller 40 executing the control program 412. When the processor 402 executes the control program 412, a library provided by the system program 410 may be used for part of the processing.

[0088] Of the processing shown in FIG. 12, steps S2 to S14 correspond to processing relating to the impact absorbing operation, and steps S20 to S28 correspond to processing relating to the elastic force generating operation.

[0089] That is, the controller 40 first executes processing related to the impact absorbing operation. More specifically, the controller 40 determines whether or not a load exceeding a predetermined value has been applied to the actuator 2 based on the detection signal from the encoder 20 (step S2). If a load exceeding the predetermined value has not been applied to the actuator 2 (NO in step S2), the processing from step S2 onwards is repeated.

[0090] When a load exceeding a predetermined value is applied to the actuator 2 (YES in step S2), the controller 40 calculates the velocity of the actuator 2 based on the detection signal from the encoder 20 (step S4), and estimates parameters of a physical model based on the calculated velocity (step S6). Then, the controller 40 constructs a physical model including the estimated parameters (step S8). In this way, the controller 40 constructs a physical model based on the displacement caused by the application of an external load to the actuator 2.

[0091] The controller 40 inputs the time that has elapsed since a load exceeding a predetermined value was applied to the actuator 2 into the physical model, calculates a control command (position command or displacement command) for the current control cycle (step S10), and outputs the calculated control command to the driver 42 (step S12). That is, the controller 40 controls the motor 18 so that the actuator 2 generates a displacement that conforms to the physical model.

[0092] Then, the controller 40 determines whether or not the condition for switching to the elastic force generating operation (switching condition 436) is satisfied (step S14). If the condition for switching to the elastic force generating operation is not satisfied (NO in step S14), the processing from step S10 onwards is repeated.

[0093] If the conditions for switching to the elastic force generating operation are met (YES in step S14), the controller 40 executes the following processing related to the elastic force generating operation. More specifically, the controller 40 determines the spring constant K in the current control cycle by referring to a preset pattern (step S20). In this way, the controller 40 determines the spring constant K.

[0094] Subsequently, the controller 40 acquires the current displacement of the actuator 2 (step S22), and calculates the load that the actuator 2 should generate based on the spring constant K and the current displacement of the actuator 2 (step S24). Then, the controller 40 calculates a control command (position command or displacement command) corresponding to the load to be generated (step S26), and outputs the calculated control command to the driver 42 (step S28). Thus, the controller 40 controls the motor 18 so as to generate a driving force calculated based on the product of the spring constant K and the displacement ΔX occurring in the actuator 2.

[0095] Thus, when a predetermined switching condition is satisfied while the actuator 2 is in the shock mitigation operation (when the motor is controlled to generate a displacement according to the physical model), the controller 40 switches the control of the motor 18 so as to generate a driving force calculated based on the product of the spring constant K and the displacement ΔX occurring in the actuator 2.

[0096] Then, the controller 40 determines whether or not the end condition of the elastic force generation operation is satisfied (step S30). If the end condition of the elastic force generation operation is not satisfied (NO in step S30), the processes below step S20 are repeated.

[0097] If the end condition of the elastic force generation operation is satisfied (YES in step S30), the process ends.

[0098] Note that FIG. 12 shows an example of a combined process of the shock mitigation operation and the elastic force generation operation by the actuator 2 according to the present embodiment, but only the shock mitigation operation or only the elastic force generation operation may be performed. An appropriate operation will be selected according to the application using the actuator 2.

[0099] <F. Example of drive mechanism> For convenience of explanation, the configuration including a single actuator 2 has been exemplified, but it is also possible to realize a mechanism including a plurality of actuators 2. An example of a drive mechanism including an actuator 2 will be described below.

[0100] (f1:1 degree of freedom stage mechanism) 13 is a schematic diagram showing an example of a one-degree-of-freedom stage mechanism including a plurality of actuators 2 according to this embodiment. Figures 13(A) and 13(B) show a configuration example of a stage mechanism in which a plate 114 is supported by three actuators 2-1, 2-2, and 2-3. In the stage mechanism shown in Figures 13(A) and 13(B), the plurality of actuators 2 are mechanically connected to the plate 114, which is a common member.

[0101] 13(A), the controller 40 controls the actuators 2-1, 2-2, and 2-3 in synchronization, thereby controlling the entire surface of the plate 114. At this time, the controller 40 generates control commands for the actuators 2-1, 2-2, and 2-3, respectively, so that the target load is generated from the plate 114, which is a common member.

[0102] 13(B), controllers 40-1, 40-2, and 40-3 control actuators 2-1, 2-2, and 2-3, respectively. By independently controlling the actuators 2-1, 2-2, and 2-3, even when a local load is applied to the plate 114, the plate 114 can behave in accordance with the local load.

[0103] Fig. 14 is a schematic diagram showing the main functional configuration for realizing the elastic force generating operation by the stage mechanism shown in Fig. 13(A). Referring to Fig. 14, actuators 2-1, 2-2, and 2-3 are driven by drivers 42-1, 42-2, and 42-3, respectively, and displacements are detected by encoders 20-1, 20-2, and 20-3.

[0104] The controller 40 includes load command generating units 428-1, 428-2, and 428-3, spring constant changing units 430-1, 430-2, and 430-3, and displacement calculating units 432-1, 432-2, and 432-3 to control the actuators 2-1, 2-2, and 2-3, respectively.

[0105] The timing of changing or updating the spring constants of the spring constant changing units 430-1, 430-2, and 430-3 is controlled to control the load generated across the entire surface of the plate 114. The spring constants may be changed gradually and synchronized, or the spring constants may be adjusted to compensate for variations in displacement.

[0106] By employing such control logic, the load generated by the plate 114 can be controlled over the entire surface.

[0107] Also, for the shock absorbing operation, by synchronizing the physical models corresponding to the respective actuators with each other, the load acting on the plate 114 can be controlled over the entire surface.

[0108] (f2: multi-degree-of-freedom stage mechanism) FIG. 15 is a schematic diagram showing an example of a multi-degree-of-freedom stage mechanism 110A including a plurality of actuators 2 according to this embodiment.

[0109] 15, stage mechanism 110A is a Zθ stage with two degrees of freedom. More specifically, stage mechanism 110A includes a rotation member 118 configured to rotate in the θ-axis direction, and three actuators 2-1, 2-2, and 2-3 that extend in the Z-axis direction.

[0110] By using a stage mechanism 110A as shown in FIG. 15, it becomes possible to use it in a variety of applications.

[0111] (f3:Other) As described above, the actuator 2 according to the present embodiment can be used alone as the actuator 2, or can be used as a stage incorporating the actuator 2. Further, it can also be used as a manufacturing apparatus including the stage.

[0112] <G. Application Example> An example of an application using the actuator 2 according to the present embodiment will be described.

[0113] FIG. 16 is a schematic diagram showing an example of an application using the actuator 2 according to the present embodiment. FIG. 16 shows an application in which two workpieces W1 and W2 are overlapped in order to attach them.

[0114] Referring to FIG. 16(A), an assembling apparatus 200 in which two workpieces are overlapped includes a stage mechanism 110A, a transfer mechanism 150, and a controller 40. The workpiece W1 is disposed on the plate 114 of the stage mechanism 110A. The workpiece W2 to be overlapped with the workpiece W1 is transferred by the transfer mechanism 150 from above the stage mechanism 110A. The controller 40 gives a control command to the stage mechanism 110A to control the stage mechanism 110A.

[0115] The stage mechanism 110A includes one or a plurality of actuators 2 that are driven by a motor 18 to cause displacement in a first direction (Z-axis direction). Since the configuration of the stage mechanism 110A has been described with reference to FIG. 15, a detailed description will not be repeated.

[0116] The transfer mechanism 150 includes a support column 152 and a plate 154. The plate 154 is connected to the support column 152 and can move in the vertical direction of gravity by a drive mechanism (not shown).

[0117] Suction holes are formed on the surface of the plate 154. The workpiece W2 is transferred while being adsorbed on the surface of the plate 154 by a suction mechanism (not shown).

[0118] Next, the processing procedure in the assembling apparatus 200 will be described with reference to FIG. First, the displacements of the actuators 2-1, 2-2, and 2-3 of the stage mechanism 110A are adjusted so that the workpieces W1 and W2 are parallel to each other ((1) parallelism maintenance operation). That is, the controller 40 issues a control command to the stage mechanism 110A in accordance with the workpiece W2 that is superimposed on the workpiece W1 so that the workpieces W1 and W2 are parallel to each other.

[0119] The parallelism maintaining operation may be realized by feedback control based on a detection signal from a sensor (not shown) provided in the transport mechanism 150. In the parallelism maintaining operation, a predetermined distance margin is provided between the workpieces by adjusting the orientation so that the workpieces W1 and W2 do not collide with each other.

[0120] After the workpieces W1 and W2 have been adjusted to be parallel by the parallelism maintaining operation, the distance between the workpieces W1 and W2 is reduced, i.e., control is performed to stack the workpiece W2 on top of the workpiece W1 ((2) Work Approaching Operation). In the workpiece approaching operation, the transport mechanism 150 brings the workpiece W2 closer to the workpiece W1, and adjusts the displacement of the actuators 2-1, 2-2, and 2-3 of the stage mechanism 110A to maintain the workpieces W1 and W2 in a parallel relationship.

[0121] Just before the workpieces W1 and W2 come into contact with each other, the impact mitigation operation is initiated ((3) Impact mitigation operation). That is, the controller 40 configures a physical model for the actuator 2 based on the displacement caused by the workpiece W2 coming into contact with the workpiece W1. The controller 40 then generates a control command that causes the actuator 2 to produce a displacement in accordance with the physical model. In this way, when the workpiece W2 comes into contact with the workpiece W1 and a load is applied to the actuator 2, the actuator 2 behaves like a spring in accordance with the physical model described above. The impact mitigation operation makes it possible to avoid excessive loads and point loads that occur when the workpieces W1 and W2 come into contact with each other.

[0122] Thereafter, when a predetermined switching condition is satisfied, an elastic force generating operation is initiated ((4) Elastic force generating operation). That is, a control command is generated to generate a driving force calculated based on the product of the spring constant K and the displacement ΔX occurring in the actuator 2. The elastic force generating operation generates a pressing force between the workpieces W1 and W2, completing the bonding of the workpieces W1 and W2.

[0123] Fig. 17 is a flowchart showing the processing procedure in the assembly apparatus 200 shown in Fig. 16. Each step shown in Fig. 17 is typically realized by the processor 402 of the controller 40 executing the control program 412. When the processor 402 executes the control program 412, a library provided by the system program 410 may be used for part of the processing.

[0124] 17, when an instruction to start processing is given (YES in step S100), the controller 40 outputs an instruction to place the workpiece W1 on the stage mechanism 110A and an instruction to adsorb the workpiece W2 to the transport mechanism 150 (step S102). Then, the controller 40 outputs an instruction to move the workpiece W2 adsorbed to the transport mechanism 150 closer to the workpiece W1 (step S104), and starts the parallelism maintaining operation.

[0125] More specifically, the controller 40 adjusts the displacement of the actuators 2-1, 2-2, and 2-3 of the stage mechanism 110A so that the workpieces W1 and W2 are parallel to each other based on the inclination of the workpiece W2 attracted to the transport mechanism 150 (step S106). In this way, the controller 40 issues a control command to the stage mechanism 110A in accordance with the workpiece W2 that is superimposed on the workpiece W1 so that the workpieces W1 and W2 are parallel to each other.

[0126] Then, the controller 40 determines whether or not a switching condition for switching to the workpiece approaching operation is satisfied based on the degree of parallelism between the workpieces W1 and W2 (step S108). If the switching condition is not satisfied (NO in step S108), the processing from step S106 onwards is repeated.

[0127] If the switching condition is satisfied (YES in step S108), the controller 40 adjusts the displacement of the actuators 2-1, 2-2, and 2-3 of the stage mechanism 110A so that the workpieces W1 and W2 are maintained parallel (step S110). Then, the controller 40 determines whether the switching condition for switching to the impact absorbing operation is satisfied based on the distance between the workpieces W1 and W2 (step S112). If the switching condition is not satisfied (NO in step S112), the processing from step S110 onwards is repeated.

[0128] If the switching condition is satisfied (YES in step S110), the controller 40 starts the impact absorbing operation (step S114). In the impact absorbing operation, the processes of steps S2 to S14 in FIG. 12 are executed.

[0129] Then, when the condition for switching from the impact absorbing operation to the elastic force generating operation is satisfied, the controller 40 starts the elastic force generating operation (step S116). In the elastic force generating operation, the processing relating to steps S20 to S28 in FIG.

[0130] When the overlapping of the workpiece W1 and the workpiece W2 is completed, the controller 40 outputs an instruction to transport the overlapped workpiece W1 and the workpiece W2 to the next process (step S118). This completes one processing cycle.

[0131] As described above, by a series of controls including the shock mitigation operation and the elastic force generation operation according to the present embodiment, it is possible to mitigate the shock generated between workpieces, reduce the damage caused to the workpieces, and uniformly apply the surface pressure between the workpieces while pressing them. As a result, the occurrence of defective products can be reduced, and higher-quality workpieces can be manufactured.

[0132] <H. Other Embodiments> As described above, the control of the actuator 2 according to the present embodiment (shock mitigation operation and / or elastic force generation operation) is applicable to any application including contact between objects, such as conveyance, superposition, lamination, and insertion.

[0133] In addition, the shock mitigation operation of the actuator 2 according to the present embodiment can be applied alone to spring mechanisms, tensioners, etc. for vibration damping and vibration suppression.

[0134] In addition, the elastic force generation operation of the actuator 2 according to the present embodiment can be applied alone to any mechanism that generates an arbitrary load, such as a press device.

[0135] <I. Advantages> According to the present embodiment, since the actuator behaves according to a physical formula, it is possible to easily perform simulations for the configuration of the control logic and the facility design. Also, when actually constructing the device, the deviation from the pre-design is reduced.

[0136] Note that, as an example of the technology for controlling the load and the position, there are impedance control and admittance control.

[0137] Impedance control is a technique for adjusting the characteristics (softness) of an actuator so that it stays at the target position when a load is applied to the actuator with the target position and impedance preset. Therefore, it does not achieve control such as mitigating impact force like the impact mitigation operation according to this embodiment, but rather, a larger impact force may be generated. Also, in impedance control, since the target position is given, it is not possible to control the generated load as in the elastic force generation operation according to this embodiment.

[0138] Admittance control is such that when a load is applied to the actuator with the impedance preset, the operating speed (position in each control cycle) is controlled based on the impedance. Therefore, it can only behave based on the preset impedance, and thus it is not possible to change its behavior according to the impact force like the impact mitigation operation according to this embodiment. Also, admittance control determines its behavior when a load is applied to the actuator, so it is not possible to control the generated load as in the elastic force generation operation according to this embodiment.

[0139] As described above, the impact mitigation operation and elastic force generation operation according to this embodiment are completely different controls from impedance control and admittance control.

[0140] <J. Appendix> The present embodiment as described above includes the following technical ideas.

[0141] [Configuration 1] An actuator (2) driven by a motor (18) to generate displacement, A driver (42) for driving the motor, And a controller (40) for giving a control command to the driver, The controller Based on the displacement generated when an external load is applied to the actuator, a model configuration unit (422) that constitutes a physical model, a first command generator (426) that generates a control command to the motor so that the actuator generates a displacement according to the physical model; A determination unit (430) that determines a spring constant; a second command generator (428) that generates a control command to the motor so as to generate a driving force calculated based on the product of the spring constant and the displacement occurring in the actuator; a selection unit (436) that selects which of the first command generation unit and the second command generation unit will activate a control command from.

[0142] [Configuration 2] The drive system according to configuration 1, wherein the selection unit enables the control command from the second command generation unit when a predetermined switching condition is satisfied while the control command from the first command generation unit is enabled.

[0143] [Configuration 3] 3. The drive system according to configuration 2, wherein the switching condition is based on an elapsed time since an external load is applied to the actuator.

[0144] [Configuration 4] 3. The drive system of claim 2, wherein the switching condition is based on a displacement occurring in the actuator.

[0145] [Configuration 5] the first command generation unit outputs a position command that specifies a target position of the motor as the control command; 5. The drive system according to any one of configurations 1 to 4, wherein the second command generating unit outputs, as the control command, a torque command that specifies a torque to be generated by the motor.

[0146] [Configuration 6] 6. The drive system according to any one of configurations 1 to 5, wherein the model constructing section constructs the physical model when a predetermined load is applied to the actuator from the outside.

[0147] [Configuration 7] 7. The drive system according to any one of configurations 1 to 6, wherein the determination unit sets the spring constant for each control cycle.

[0148] [Configuration 8] A method for controlling an actuator (2) that is driven by a motor (18) to generate a displacement, comprising: Steps (S4, S6, S8) of constructing a physical model based on a displacement caused by an external load being applied to the actuator; A step (S20) of determining a spring constant; Steps (S10, S12) of controlling the motor so that the actuator produces a displacement according to the physical model; a control method comprising steps (S22, S24, S26, S28) of switching control of the motor so as to generate a driving force calculated based on the product of the spring constant and the displacement generated in the actuator when a predetermined switching condition is satisfied while the motor is being controlled so that the actuator generates a displacement in accordance with the physical model.

[0149] [Configuration 9] A control program (412) for controlling an actuator (2) driven by a motor (18) to generate a displacement, the control program including: Steps (S4, S6, S8) of constructing a physical model based on a displacement caused by an external load being applied to the actuator; A step (S20) of determining a spring constant; Steps (S10, S12) of controlling the motor so that the actuator produces a displacement according to the physical model; a control program that, when a predetermined switching condition is satisfied while controlling the motor so that the actuator generates a displacement in accordance with the physical model, executes steps (S22, S24, S26, S28) of switching control of the motor so that a driving force calculated based on the product of the spring constant and the displacement generated in the actuator is generated.

[0150] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0151] 1 drive system, 2 actuator, 4 drive device, 10 main body, 12 rod, 14 tip, 16 connecting member, 18 motor, 20 encoder, 40 controller, 42 driver, 50 natural length state, 52 balanced state, 54 load balanced state, 100 work transport system, 110, 110A stage mechanism, 112 base, 114, 154 plate, 118 rotating member, 120 robot, 122 end effector, 150 transport mechanism, 152 support column, 200 assembly device, 402 processor, 404 main memory, 406 input / output unit, 408 storage, 410 system program, 412 control program, 420 physical model, 422 characteristic estimation unit, 424 angular frequency setting unit, 426 position command generation unit, 428 load command generation unit, 430 Spring constant change section, 432 displacement calculation section, 434 selection section, 436 switching conditions, W, W1, W2 workpieces.

Claims

1. an actuator driven by a motor to generate a displacement; a driver that drives the motor; a controller that issues a control command to the driver, The controller a model constructing unit that constructs a physical model based on a displacement caused by an external load being applied to the actuator; a first command generator that generates a control command to the motor so that the actuator generates a displacement in accordance with the physical model; a determination unit that determines a spring constant; a second command generator that generates a control command to the motor so as to generate a driving force proportional to the product of the spring constant and the displacement occurring in the actuator; a selection unit that selects whether a control command from the first command generation unit or the second command generation unit is to be given to the driver.

2. 2. The drive system according to claim 1, wherein the selection unit provides the driver with the control command from the second command generation unit when a predetermined switching condition is satisfied while the control command from the first command generation unit is being provided to the driver.

3. The drive system according to claim 2 , wherein the switching condition is based on an elapsed time since an external load is applied to the actuator.

4. The drive system of claim 2 , wherein the switching condition is based on a displacement occurring in the actuator.

5. the first command generation unit outputs a position command that specifies a target position of the motor as the control command; 5. The drive system according to claim 1, wherein the second command generating unit outputs, as the control command, a torque command that specifies a torque to be generated by the motor.

6. 6. The drive system according to claim 1, wherein the model constructing section constructs the physical model when a predetermined load is applied to the actuator from the outside.

7. 7. The drive system according to claim 1, wherein the determination unit sets the spring constant for each control cycle.

8. A method for controlling an actuator that is driven by a motor to generate a displacement, comprising: constructing a physical model based on a displacement caused by an external load being applied to the actuator; determining a spring constant; controlling the motor so that the actuator produces a displacement according to the physical model; a step of switching control of the motor so as to generate a driving force proportional to the product of the spring constant and the displacement generated in the actuator when a predetermined switching condition is satisfied while the motor is being controlled so that the actuator generates a displacement in accordance with the physical model.

9. A control program for controlling an actuator that is driven by a motor to generate a displacement, the control program being programmed into a computer to: constructing a physical model based on a displacement caused by an external load being applied to the actuator; determining a spring constant; controlling the motor so that the actuator produces a displacement according to the physical model; and when a predetermined switching condition is satisfied while the motor is being controlled so that the actuator generates a displacement in accordance with the physical model, switching control of the motor so that a driving force proportional to the product of the spring constant and the displacement generated in the actuator is generated.

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