Actuator

Abstract

To provide an actuator that can reduce the displacement of a cylindrical member immediately after an output shaft starts a linear motion.SOLUTION: The actuator includes: an output shaft; a cylindrical member of which relative rotation with the output shaft is regulated; a nut member for moving the output shaft in an axial direction by a relative rotation with the output shaft; a housing; a first motor having a first rotor and a first stator, the first motor rotating the cylindrical member with the rotation of the first rotor; a second motor having a second rotor and a second stator, the second motor rotating the nut member with the rotation of the second rotor; and a controller for controlling the first motor and the second motor. In a transition from when the first rotor and the second rotor are both resting (a first state) to when the first rotor is resting and the second rotor is rotating (a second state), the controller supplies a current to apply a force that suppresses the rotation of the second rotor and is of the opposite direction to the direction of rotation of the cylindrical member by the rotation of the second rotor, to the second motor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to actuators. [Background technology]

[0002] The actuator of Patent Document 1 below is a device equipped with an output shaft that rotates and moves linearly. Such actuators are used in conveying devices that convey workpieces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-61926 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the actuator of Patent Document 1, the output shaft may rotate and cause the cylindrical member to rotate unintentionally immediately after the output shaft starts to move linearly due to the rotation of the nut member. Hereinafter, the unintentional rotation of the cylindrical member due to the rotation of the nut member will be referred to as co-rotation.

[0005] The present disclosure has been made in consideration of the above, and has an object to provide an actuator that can reduce positional deviation of a cylindrical member immediately after the output shaft starts linear motion. [Means for solving the problem]

[0006] In order to achieve the above object, an actuator according to a first aspect of the present disclosure includes an output shaft, a cylindrical member penetrated by the output shaft and restricted in its relative rotation with respect to the output shaft, a nut member penetrated by the output shaft and configured to move the output shaft in the axial direction by its relative rotation with the output shaft, a housing rotatably supporting the cylindrical member and the nut member, a first motor having a first rotor and a first stator for rotating the first rotor and configured to rotate the cylindrical member in cooperation with the rotation of the first rotor, a second motor having a second rotor and a second stator for rotating the second rotor and configured to rotate the nut member in cooperation with the second rotor, and a control unit for controlling the first motor and the second motor. When transitioning from a first state in which the first rotor and the second rotor are stationary to a second state in which the first rotor is stationary and the second rotor is rotating, the control unit supplies to the first motor a current that applies a force that suppresses the rotation of the first rotor, the force being in a direction opposite to a direction in which the cylindrical member is rotated by the rotation of the second rotor.

[0007] According to this, when transitioning from the first state to the second state, the second stator tries to rotate the second rotor in the direction opposite to the co-rotation direction, so that the positional deviation of the cylindrical member is reduced immediately after the output shaft starts to move linearly.

[0008] In addition, an actuator according to a second aspect of the present disclosure includes an output shaft, a tubular member penetrated by the output shaft and whose relative rotation with respect to the output shaft is restricted, a nut member penetrated by the output shaft and which moves the output shaft in the axial direction by relative rotation with the output shaft, a housing which rotatably supports the tubular member and the nut member, a first motor having a first rotor and a first stator which rotates the first rotor and rotates the tubular member in conjunction with the rotation of the first rotor, a second motor having a second rotor and a second stator which rotates the second rotor and rotates the nut member in conjunction with the second rotor, and a control unit which controls the first motor and the second motor. The control unit includes a command generator that calculates target positions of the cylindrical member and the nut member corresponding to a required operation of the output shaft, generates the target position of the cylindrical member as a first position command, and generates the target position of the nut member as a second position command; a first position controller that receives the first position command, calculates a first torque value of a first motor required to achieve the first position command, and generates the first torque value as a first torque command; a second position controller that receives the second position command, calculates a second torque value of a second motor required to achieve the second position command, and generates the second torque value as a second torque command; and the first torque command and the counter torque command are given to an adder which generates a composite torque value by combining the first torque value and the counter torque value as a composite torque command, a first current controller which receives the composite torque command and controls a current supplied to the first motor so as to correspond to the composite torque value, and a second current controller which receives the second torque command and controls a current supplied to the second motor so as to correspond to the second torque value. The co-rotation torque calculator determines whether or not the co-rotation torque is generated based on the first position command and the second position command.When it is determined that the entrained torque is generated, the counter torque value is calculated based on the second torque value.

[0009] When the drag torque calculator determines that drag torque acts on the first rotor, it generates a counter torque command. Then, the first rotor generates a torque equivalent to the composite torque value (including the counter torque value). As a result, the drag torque acting on the first rotor is offset by the composite torque. As a result, the positional deviation of the tubular member is reduced immediately after the output shaft starts linear motion.

[0010] As a desirable aspect of the actuator according to the one aspect, the actuator includes a first angle sensor that detects an angle of a first rotor of the first motor, and a second angle sensor that detects an angle of a second rotor of the second motor. The first position controller has a feedback control function that generates a new first torque command based on a detection result of the first angle sensor so that the angle of the first rotor becomes a desired angle. The second position controller has a feedback control function that generates a new second torque command based on a detection result of the second angle sensor so that the angle of the second rotor becomes a desired angle.

[0011] According to this, the first torque command and the second torque command are newly generated based on the detection results of the first angle sensor and the second angle sensor, so that the first rotor and the second rotor that have shifted from the target position can be moved to the target position, improving the position accuracy of the output shaft. Effect of the Invention

[0012] According to the present invention, the positional deviation of the cylindrical member is reduced, and the positional accuracy of the output shaft is improved. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view of the actuator according to the first embodiment taken along the central axis of the output shaft. [Diagram 2]FIG. 2 is a block diagram showing the configuration of a control unit of the actuator according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing the change in angle of the spline outer cylinder and the change in output torque of the first motor over time when the actuator of the first embodiment and the actuator of the comparative example are caused to perform linear motion. [Figure 4] FIG. 4 is a block diagram showing the configuration of a control unit of the actuator of the second embodiment. [Diagram 5] FIG. 5 is a block diagram showing the configuration of a control unit of the actuator of the third embodiment. [Figure 6] FIG. 6 is a cross-sectional view of the actuator according to the fourth embodiment taken along the central axis of the output shaft. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The following describes in detail the form (embodiment) for carrying out the invention with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the components described below can be appropriately combined.

[0015] (Embodiment 1) FIG. 1 is a cross-sectional view of the actuator according to the first embodiment cut along the central axis of the output shaft. As shown in FIG. 1, the actuator 1 includes a first motor M1, a second motor M2, an output shaft SF, a splined outer cylinder (cylinder member) 61, a nut member 51, and a control unit 100. The actuator 1 of the first embodiment is used in a conveying device that conveys a workpiece (not shown). The actuator 1 includes an arm unit 80 attached to one end of the output shaft SF. The arm unit 80 extends in a direction perpendicular to the central axis AX of the output shaft SF and is a device capable of gripping a workpiece. The arm unit 80 moves when the output shaft SF is driven, and the workpiece (not shown) is conveyed.

[0016] Hereinafter, the direction parallel to the central axis AX of the output shaft SF will be referred to as the Z direction. Furthermore, within the Z direction, the direction to which the arm portion 80 is attached when viewed from the center of the length of the output shaft SF will be referred to as the Z1 direction, and the direction to which the arm portion 80 is not attached will be referred to as the Z2 direction.

[0017] The first motor M1 and the second motor M2 are synchronous motors. However, in the present disclosure, the first motor M1 and the second motor M2 may be DC motors using brushes, induction motors, etc. The first motor M1 has a first stator 10, a first rotor 20, and a first motor housing 40.

[0018] The first motor housing 40 has a cylindrical shape centered on the central axis AX. The first motor housing 40 has a mounting flange 40a extending radially outward from the end in the Z1 direction, and a lower bottom portion 40b extending radially inward from the end in the Z2 direction. The mounting flange 40a is placed on a surface of the fixed base ST facing the Z1 direction. The mounting flange 40a is fastened to a bolt that screws into the fixed base ST. This fixes the first motor housing 40 to the fixed base ST.

[0019] A first stator holder 11 having a cylindrical shape centered on the central axis AX is provided on the radially inner end of the lower bottom portion 40b in the Z1 direction. The first stator holder 11 is fixed to the lower bottom portion 40b by bolts. An inner ring of the first bearing 31 is fitted to the end of the first stator holder 11 in the Z1 direction.

[0020] The first stator 10 is disposed on the outer circumferential side of the first stator holder 11. The first stator 10 is a component that generates a rotating magnetic field for rotating the first rotor 20. The inner circumferential surface of the first stator 10 is fitted into the outer circumferential surface of the first stator holder 11.

[0021] A first rotor 20 is disposed on the outer periphery side of the first stator 10. The first rotor 20 has a first rotor bracket 21, a first rotor core 22 that is fixed to the inner periphery surface of the first rotor bracket 21 and has a permanent magnet, and an outer ring holder 21a that is disposed in the Z1 direction of the first rotor core 22.

[0022] The first rotor core 22 has a cylindrical shape centered on the central axis AX. The inner peripheral surface of the end portion in the Z1 direction of the first rotor core 22 is fitted into the outer ring of the first bearing 31. Therefore, the first rotor 20 is rotatably supported by the first motor housing 40. The outer ring holder 21a is an annular part, and is fixed in the Z1 direction of the first rotor core 22 by bolts. The first rotor core 22 and the outer ring holder 21a sandwich the outer ring of the first bearing 31 from the Z direction. Therefore, the first rotor 20 does not move in the Z direction.

[0023] A first cover member 111 is provided on the Z1 side of the outer ring holder 21a. The first cover member 111 is fixed to the outer ring holder 21a with a bolt. A through hole is provided in the center of the first cover member 111. The Z2 side surface of the first cover member 111 has a recess 112 recessed in the Z1 direction along the edge of the through hole.

[0024] The splined outer cylinder 61 passes through a through hole of the first cover member 111. The splined outer cylinder 61 has a cylindrical shape centered on the central axis AX. The splined outer cylinder 61 protrudes in the Z1 direction from the first cover member 111. The inner peripheral surface of the splined outer cylinder 61 has a splined portion (not shown) having a plurality of protrusions extending in the Z direction. A flange 62 extending in the radial direction is provided on the end of the splined outer cylinder 61 in the Z2 direction. The flange 62 is disposed in the recess 112. The flange 62 is fixed to the first cover member 111 via a bolt. As a result, the splined outer cylinder 61 is integrated with the first rotor 20 via the first cover member 111.

[0025] The second motor M2 is disposed in the Z2 direction relative to the first motor M1. The second motor M2 has a second stator 10A, a second rotor 20A, and a second motor housing 40A. The first motor housing 40 and the second motor housing 40A may be collectively referred to simply as the housing.

[0026] The second motor housing 40A has a cylindrical shape centered on the central axis AX. The second motor housing 40A has an upper bottom portion 40Aa extending radially inward from an end portion in the Z1 direction. A through hole is provided in the center of the upper bottom portion 40Aa. The upper bottom portion 40Aa abuts against the lower bottom portion 40b of the first motor housing 40. The upper bottom portion 40Aa and the lower bottom portion 40b are fixed together by bolts.

[0027] A second stator holder 11A having a cylindrical shape centered on the central axis AX is provided in the Z2 direction at the radially inner end of the upper bottom portion 40Aa. The second stator holder 11A is fastened to the upper bottom portion 40Aa by bolts. An inner ring of the second bearing 32 is fitted onto the outer circumferential surface of the end portion in the Z2 direction of the second stator holder 11A.

[0028] The second stator 10A is disposed on the outer periphery of the second stator holder 11A. The second stator 10A is a component that generates a rotating magnetic field for rotating the second rotor 20A. The inner periphery of the second stator 10A is fitted into the outer periphery of the second stator holder 11A. The second stator 10A is disposed on the outer periphery of the second stator 10A.

[0029] The second rotor 20A has a second rotor bracket 21A and a second rotor core 22A that is fixed to the inner peripheral surface of the second rotor bracket 21A and has a permanent magnet. The inner peripheral surface of the end of the second rotor bracket 21A in the Z2 direction is fitted into the outer ring of the second bearing 32. Therefore, the second rotor 20A is rotatably supported by the second motor housing 40A.

[0030] Provided in the Z2 direction of the second rotor bracket 21A are a first connecting bracket 46, a second connecting bracket 45, and a nut member 51. The first connecting bracket 46, the second connecting bracket 45, and the nut member 51 each have a cylindrical shape centered on the central axis AX.

[0031] The first connecting bracket 46 is fastened to the second rotor bracket 21A by bolts. The first connecting bracket 46 and the second rotor bracket 21A hold the outer ring of the second bearing 32 between them. Therefore, the second rotor 20A does not move in the Z direction. The second connecting bracket 45 has a flange 45a that extends radially outward from the end in the Z1 direction. The flange 45a is fixed to the first connecting bracket 46 by bolts.

[0032] The nut member 51 has a female thread (not shown) on its inner circumferential surface. The nut member 51 has a flange portion 51a extending radially outward from its end in the Z2 direction. The flange portion 51a of the nut member 51 abuts against the end face of the second connecting bracket 45 in the Z2 direction. The flange portion 51a of the nut member 51 is fastened to a bolt, and the nut member 51 is integrated with the second connecting bracket 45. As described above, the nut member 51 is integrated with the second rotor 20A via the first connecting bracket 46 and the second connecting bracket 45.

[0033] The lower bottom portion 40Ab of the second motor housing 40A is open. The lower bottom portion 40Ab of the second motor housing 40A is covered with a nut housing 42 and a stopper cover 44.

[0034] The nut housing 42 has an upper end flange 42a, a cylindrical portion 42b formed in a cylindrical shape extending in the Z2 direction from the inner peripheral end of the upper end flange 42a, and a bottom portion 42c extending inward from the lower end of the cylindrical portion 42b. The upper end flange 42a is fixed to the lower bottom portion 40Ab of the second motor housing 40A via a bolt. The stopper cover 44 is fixed to the bottom portion 42c of the nut housing 42 via a bolt. The bottom portion 42c of the nut housing 42 has a through hole through which the small diameter portion 532 of the screw shaft 53 passes.

[0035] The output shaft SF has a shaft 63 disposed closer to the Z1 direction and a screw shaft 53 disposed closer to the Z2 direction. The shaft 63 penetrates the spline outer cylinder 61, the first stator holder 11, the lower bottom portion 40b of the first motor housing 40, the upper bottom portion 40Aa of the second motor housing 40A, and the second stator holder 11A. On the other hand, the screw shaft 53 penetrates the nut member 51.

[0036] The shaft 63 has a large diameter portion 631 and a small diameter portion 632 .

[0037] A plurality of spline grooves 633 extending in the axial direction of the central axis AX are provided at intervals in the circumferential direction on the outer peripheral surface of the large diameter portion 631. The spline grooves 633 are spline-fitted with a spline portion (not shown) of the spline outer cylinder 61. Thus, the output shaft SF is supported by the spline outer cylinder 61 so as to be movable in the Z direction. In addition, when torque is generated in the first rotor 20 by the drive of the first motor M1, the torque of the first rotor 20 is transmitted to the output shaft SF via the spline outer cylinder 61.

[0038] A protrusion 71 that protrudes in the Z1 direction is provided on the end face in the Z1 direction of the large diameter portion 631. An arm attachment member 70 for attaching an arm portion 80 is provided on the protrusion 71.

[0039] The small diameter portion 632 penetrates the upper bottom portion 40Aa of the second motor housing 40A and the second stator holder 11A. A recess 632a recessed in the Z1 direction is provided on the Z2 end face of the small diameter portion 632. A female screw (not shown) is provided on the inner circumferential surface of the recess 632a.

[0040] The screw shaft 53 passes through the inside of the nut member 51. The screw shaft 53 has a large diameter portion 531 and a small diameter portion 532. A thin diameter portion 531a protruding in the Z1 direction is provided on the end face of the large diameter portion 531 of the screw shaft 53 in the Z1 direction. A male thread (not shown) is provided on the outer periphery of the thin diameter portion 531a. The thin diameter portion 531a is inserted into a recess 632a of the small diameter portion 632. The male thread of the thin diameter portion 531a is screwed into the female thread of the recess 632a. This connects the shaft 63 and the screw shaft 53.

[0041] The large diameter portion 531 has an external thread portion 533. The external thread portion 533 of the large diameter portion 531 is screwed into the nut member 51 via a plurality of balls (not shown). In other words, the nut member 51, the plurality of balls (not shown), and the screw shaft 53 form a ball screw device.

[0042] An annular stopper 55 is inserted into the lower end of the small diameter portion 532. The stopper 55 is restricted by a nut 56 so as not to fall off from the small diameter portion 532. A buffer member 55a is provided on the upper surface of the stopper 55. The buffer member 55a is, for example, an elastic urethane rubber. When the output shaft SF moves a predetermined amount in the Z1 direction, the stopper 55 comes into contact with the bottom portion 42c of the nut housing 42 via the buffer member 55a. Thus, the output shaft SF is restricted so as not to move in the Z1 direction beyond the predetermined amount.

[0043] Next, the relationship between the movement (rotation) of the spline outer cylinder 61 and the nut member 51 and the movement of the output shaft SF will be described.

[0044] (linear motion) The spline groove portion 633 of the output shaft SF is spline-fitted into the spline outer cylinder 61. Therefore, when the spline outer cylinder 61 is held so as not to rotate, the output shaft SF also does not rotate around the AX axis. In this state, when the nut member 51 rotates, the female thread (not shown) of the nut member 51 presses the male thread of the output shaft SF in the Z1 direction or the Z2 direction via a ball (not shown). This causes the output shaft SF to move in the Z1 direction or the Z2 direction.

[0045] (Rotational motion) When the splined outer cylinder 61 rotates, the output shaft SF rotates. In this state, when the nut member 51 rotates at the same angular velocity as the splined outer cylinder 61 (when the rotation direction and rotation speed are the same), the nut member 51 rotates together with the output shaft SF. In other words, the female thread (not shown) of the nut member 51 does not press the male thread of the output shaft SF in the Z direction. Therefore, the output shaft SF does not move in the Z direction.

[0046] (spiral movement) When the nut member 51 and the spline outer cylinder 61 rotate but have different angular velocities (when they rotate in different directions, or when they rotate in the same direction but at different rotation speeds), the female thread (not shown) of the nut member 51 presses the male thread of the output shaft SF. Thus, the output shaft SF performs a spiral motion in which it rotates while moving in the Z1 direction or the Z2 direction.

[0047] 2 is a block diagram showing the configuration of a control unit of the actuator according to embodiment 1. The control unit 100 receives an operation command from a higher-level control unit (not shown) and controls the driving of the first motor M1 and the second motor M2 in accordance with the operation command. The control unit 100 includes a calculator, current controllers (first current controller 141, second current controller 142), angle sensors (first angle sensor 151, second angle sensor 152), and current meters (first current meter 153, second current meter 154).

[0048] In the embodiment, the relative rotation between the output shaft SF and the spline outer cylinder (cylindrical member) is restricted by spline fitting, but the present disclosure is not limited thereto. For example, the output shaft SF has a protrusion protruding radially outward from its outer circumferential surface. The cylindrical member has a groove portion extending in the axial direction on its inner circumferential surface. The protrusion fits into the groove portion. With this, the output shaft is supported axially slidably relative to the cylindrical member, while the relative rotation with respect to the cylindrical member is restricted.

[0049] The calculator is a computer such as a microcomputer, and includes an input interface, an output interface, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an internal storage unit. The calculator includes a command generator 110, a first position controller 121, a second position controller 122, a drag torque calculator 130, and an adder 135.

[0050] The host control unit (not shown) in the first embodiment is a control unit of a conveying device that conveys a workpiece using the arm unit 80. The host control unit selects a desired operation, such as moving the arm unit 80 in the Z1 direction or rotating the arm unit 80 about the central axis AX. Next, the host control unit selects a required operation (linear motion, rotational motion, spiral motion) of the output axis SF to execute the desired operation. Then, the host control unit provides the selected required operation of the output axis SF as an actuation command to the command generator 110 of the control unit 100.

[0051] The command generator 110 calculates the target position of the spline outer cylinder 61 and the target position of the nut member 51 corresponding to the actuation command. The target position of the spline outer cylinder 61 and the target position of the nut member 51 are displacement amounts (rotation amounts) from current positions. The target position of the spline outer cylinder 61 and the target position of the nut member 51 include a rotation direction, a rotation amount (angle), and a rotation speed. The target position of the spline outer cylinder 61 and the target position of the nut member 51 also include the content that they are left as they are (zero rotation amount). The command generator 110 provides the target position of the spline outer cylinder 61 to the first position controller 121 as a first position command. Similarly, the command generator 110 provides the target position of the nut member 51 to the second position controller 122 as a second position command.

[0052] As a specific example, when the actuation command is linear motion of the output shaft SF, the command generator 110 calculates the target position of the splined outer cylinder 61 as is (the amount of rotation of the splined outer cylinder 61 is zero). Then, the command generator 110 provides the result as a first position command to the first position controller 121. The command generator 110 also calculates the amount of rotation of the nut member 51 in either direction. The actuation command also includes the amount of movement of the output shaft SF, so the command generator 110 calculates the amount of rotation of the nut member 51 in addition to the direction of rotation of the nut member 51 so that the amount of movement of the output shaft SF is a predetermined amount. Then, the command generator 110 provides the calculated target position of the nut member 51 (including the direction and amount of rotation) as a second position command to the second position controller 122. When the actuation command is a rotational motion of the output shaft SF, the first position command and the second position command are to rotate the spline outer cylinder 61 and the nut member 51 in the same direction and at the same speed.

[0053] The first position controller 121 calculates a first torque value required for the first motor M1 to achieve the first position command, in other words, to move the spline outer cylinder 61 to the target position. Then, the first position controller 121 provides the first torque value required for the first motor M1 to the adder 135 as a first torque command. Similarly, the second position controller 122 calculates a second torque value required for the second motor M2 to achieve the second motor command. Then, the second position controller 122 provides the second torque value required for the second motor M2 to the second current controller 142 as a second torque command.

[0054] The first position controller 121 is also provided with a detection result (the rotation angle of the first rotor 20) from the first angle sensor 151. The first position controller 121 then generates a new first torque command so that the angle of the first rotor 20 becomes a desired angle at which the positional deviation of the first rotor 20 is eliminated, and provides the new first torque command to the adder 135. Similarly, the second position controller 122 generates a new second torque command based on the detection result (the rotation angle of the second rotor 20A) provided by the second angle sensor 152 so that the angle of the second rotor 20A becomes a desired angle. Thus, the first position controller 121 and the second position controller 122 of this embodiment have a feedback control function that generates a first torque command or a second torque command based on the detection results of the first angle sensor 151 and the second angle sensor 152 so that the positional deviation of the first rotor 20 and the second rotor 20A is eliminated.

[0055] The drag torque calculator 130 determines whether or not drag torque is generated in the first rotor 20 based on the first position command and the second position command. In other words, the drag torque calculator 130 determines whether or not the motion of the output shaft SF is linear based on the first position command and the second position command. To explain in more detail, when the first position command is to keep the target position of the spline outer cylinder 61 as it is (the amount of rotation of the spline outer cylinder 61 is zero) and the second position command is to rotate the nut member 51, the drag torque calculator 130 determines that the spline outer cylinder 61 will drag and generate drag torque in the first rotor 20.

[0056] Furthermore, when it is determined that a drag torque occurs in the first rotor 20, the drag torque calculator 130 calculates a counter torque value for reducing the drag torque based on the second torque command. The drag torque calculator 130 calculates the counter torque value based on the second torque command because the drag torque is proportional to the second torque value of the second torque command. In other words, when the second torque value of the second torque command is large, it is estimated that the torque applied to the nut member 51 is large, and therefore the drag torque is also large.

[0057] In addition, the calculation of the counter torque value by the drag torque calculator 130 may be performed by searching a predetermined map (not shown) while referring to the second torque value of the second torque command. Alternatively, the counter torque value may be calculated from the second torque value of the second torque command by a predetermined calculation, and the method of calculating the counter torque value is not particularly limited in the present disclosure. The predetermined map is derived in advance by conducting experiments.

[0058] Then, after calculating the counter torque value, the drag torque calculator 130 provides the counter torque value as a counter torque command to the adder 135. When the drag torque calculator 130 determines that no drag torque is generated in the first rotor 20, it provides the adder 135 with a counter torque command such that the counter torque value is zero.

[0059] The adder 135 combines the first torque value of the first torque command and the counter torque value of the counter torque command, and provides the combined torque value to the first current controller 141 as a combined torque command.

[0060] The first current controller 141 and the second current controller 142 have half-bridge circuits using switching elements such as field effect transistors. The first current controller 141 and the second current controller 142 convert DC power supplied from a power supply device (not shown) into AC power for driving the motors (first motor M1, second motor M2) in response to the composite torque command and the second torque command. The first current controller 141 and the second current controller 142 perform PWM control to determine the motor application voltage according to the ON-OFF duty ratio of the switching elements.

[0061] The first current controller 141 and the second current controller 142 are provided with measurement results (current values ​​supplied to the first motor M1 and the second motor M2) from the first current meter 153 and the second current meter 154. The first current controller 141 and the second current controller 142 have a feedback function of adjusting the currents supplied to the first motor M1 and the second motor M2 based on the measurement results so that they become target current values.

[0062] 1, the first angle sensor 151 is disposed on the inner periphery side of the outer race retainer 21a of the actuator 1. The first angle sensor 151 detects the rotation angle of the first rotor 20. The second angle sensor 152 is disposed on the inner periphery side of the first connecting bracket 46. The second angle sensor 152 detects the rotation angle of the second rotor 20A.

[0063] A magnetic sensor or an optical sensor is used for the first angle sensor 151 and the second angle sensor 152. The magnetic sensor uses a Hall element or the like that detects changes in magnetism and detects the rotation angle of the rotor based on the changes in magnetism. The optical sensor has a slit in the rotor, and receives light that passes through the slit while rotating together with the rotor with a photodiode, and detects the rotation angle of the rotor based on changes in the amount of received light.

[0064] The first current meter 153 detects the value of a current supplied to the first motor M1. The second current meter 154 detects the value of a current supplied to the second motor M2. The first current meter 153 and the second current meter 154 use a shunt resistor, a non-contact sensor that detects magnetic flux around the current path of the phase current of the motor, or a sensor that detects terminal voltages of elements that configure the motor driver.

[0065] Then, the first angle sensor 151 provides the detection result to the first position controller 121 and the first current controller 141. The second angle sensor 152 provides the detection result to the second position controller 122 and the second current controller 142. The first current meter 153 provides the measurement result to the first current controller 141. The second current meter 154 provides the measurement result to the second current controller 142.

[0066] FIG. 3 is a diagram showing the change in the angle of the spline outer cylinder and the change in the output torque of the first motor over time when the actuator of the first embodiment and the actuator of the comparative example are linearly moved. Next, referring to FIG. 3, the change in the angle of the spline outer cylinder 61 when the output shaft SF is linearly moved in the actuator 1 of the first embodiment and the actuator of the comparative example will be described. First, the actuator of the comparative example will be described. The comparative example differs from the actuator 1 of the first embodiment in that it does not include the drag torque calculator 130 and the adder 135. In addition, in the description of this section, one rotation direction of the spline outer cylinder 61 is called the +θ direction, and the other rotation direction is called the -θ direction. In addition, in the vertical axis of the lower diagram of FIG. 3, +T is the torque in the +θ direction, and -T is the torque in the -θ direction. In addition, the horizontal axis of FIG. 3 is time, and time T0 is the first state in which the first rotor 20 and the second rotor A are stationary. Time T1 indicates the time when the first state starts to transition to a second state in which the first rotor 20 is stationary and the second rotor 20A rotates.

[0067] Regarding the actuator of the comparative example, at time T0, the command generator 110 receives an actuation command (linear motion of the output shaft) and generates a first position command to keep the target position of the spline outer cylinder 61 as is (rotation angle is zero). At the same time, the command generator 110 generates a second position command to rotate the nut member 51, for example, in a +θ direction. Then, based on the first position command, the first position controller 121 generates a first torque command value so that the rotation angle of the first rotor 20 becomes zero. Based on the second position command, the second position controller 122 generates a second torque command so that the second rotor 20A rotates in the +θ direction.

[0068] As a result, at time T1, the torque due to the rotating magnetic field of the first stator 10 becomes zero, that is, the output torque of the first motor M1 becomes zero (see the period from time T1 to time T2 in the lower diagram of FIG. 3). Meanwhile, the second rotor 20A starts to rotate in the +θ direction. As a result, the spline outer cylinder 61 rotates (rotates in the +θ direction) (see the period from time T1 onwards in the upper diagram of FIG. 3), and the first rotor 20 rotates.

[0069] Furthermore, at time T1, the first angle sensor 151 detects the rotation of the first rotor 20 and provides the detection result to the first position controller 121. The first position controller 121 then generates a new first torque command so that the rotation angle of the first rotor 20 becomes zero. By such feedback control, at time T2, several seconds after time T1 when the rotation of the first rotor 20 is detected, the first motor M1 starts to output torque in the -θ direction (see time T2 in the lower diagram of FIG. 3).

[0070] Immediately after the actuator 1 starts to drive at time T1 or T2, the friction acting between the nut member 51 and the output shaft SF is static friction. Therefore, the torque acting on the spline outer cylinder 61 is large. For this reason, after time T2, the first motor M1 outputs torque in the -θ direction by feedback control, but the spline outer cylinder 61 (first rotor 20) continues to rotate in the +θ direction, and the maximum rotation angle becomes θ1. A few seconds after time T2, the friction of the nut member 51 with respect to the output shaft SF changes from static friction to kinetic friction. Therefore, the torque acting on the spline outer cylinder 61 becomes large enough (approximately zero) not to rotate the spline outer cylinder 61 in the +θ direction.

[0071] On the other hand, after time T2, the first position controller 121 receives (feeds back) the result that the splined outer cylinder 61 (first rotor 20) continues to rotate in the +θ direction, and gradually increases the torque value of the first torque command it generates, so that the torque in the -θ direction output from the first motor M1 gradually increases (see time T2 and after in the lower diagram of FIG. 3). As a result, the first rotor 20 starts to rotate in the -θ direction.

[0072] Then, at time T3, the inertial force acting on the splined outer cylinder 61 in the -θ direction causes the splined outer cylinder 61 to rotate beyond a predetermined position (rotation angle is zero) further in the -θ direction. In response to this result, the first position controller 121 generates a first torque command to rotate the first rotor 20 in the +θ direction so that the first rotor 20 rotates in the +θ direction. In this manner, the first position controller 121 alternately generates a command to rotate the first rotor 20 in the +θ direction and a command to rotate the first rotor 20 in the -θ direction, and at time T4, the splined outer cylinder 61 returns to the target position (rotation angle is zero).

[0073] Meanwhile, in the actuator 1 of the first embodiment, between time T0 and time T1, the drag torque calculator 130 receives the first position command (the position of the spline outer cylinder 61 remains unchanged) and the second position command (to rotate the nut member 51 in the +θ direction) generated by the command generator 110, and generates a counter torque command. As a result, at time T1 when the second motor M2 starts to drive, the first motor M1 outputs torque in the -θ direction (see time T1 in the lower diagram of FIG. 3). That is, the first motor M1 and the second motor M2 start to drive simultaneously.

[0074] Therefore, at time T1, the first rotor 20 is subjected to a drag torque in the +θ direction and a counter torque in the -θ direction due to the rotating magnetic field generated by the first stator 10. As a result, the drag torque is offset by the amount of the counter torque. Therefore, although the spline outer cylinder 61 (first rotor 20) rotates in the +θ direction, the maximum rotation angle θ2 is smaller than the maximum rotation angle θ1 in the comparative example, and the positional deviation of the spline outer cylinder 61 is reduced.

[0075] Furthermore, at time T1, the first angle sensor 151 detects the rotation of the splined outer cylinder 61 (first rotor 20) and provides the detection result to the first position controller 121. The first position controller 121 generates a first torque command so that the rotation angle of the first rotor 20 becomes zero. Then, the first position controller 121 alternately generates a command to rotate the first rotor 20 in the +θ direction and a command to rotate it in the −θ direction, and at time T6, the splined outer cylinder 61 returns to the target position (rotation angle is zero).

[0076] From the above, according to the actuator 1 of the first embodiment, when the linear motion of the output shaft SF starts (immediately after time T1), the maximum rotation angle of the first rotor 20 (splined outer cylinder 61) due to the drag torque is small (θ1>θ2). Therefore, the time required for the splined outer cylinder 61 to return to the predetermined position (target position) by the feedback control performed after time T2 is short (T4>T6).

[0077] The co-rotation torque calculator 130 generates a counter torque command when it receives the first position command and the second position command from the command generator 110. In other words, the co-rotation torque calculator 130 generates a counter torque command before the time (after time T1) when the first position controller 121 generates the first torque command by feedback control. From the above, there is no possibility that the counter torque command and the first torque command by feedback control will overlap.

[0078] As described above, the actuator 1 of the first embodiment includes an output shaft SF, a cylindrical member that is penetrated by the output shaft SF and whose relative rotation with respect to the output shaft SF is restricted, a nut member 51 that is penetrated by the output shaft SF and moves the output shaft SF in the axial direction by the relative rotation with the output shaft SF, a housing that rotatably supports the cylindrical member and the nut member 51, a first motor M1 that has a first rotor 20 and a first stator 10 and applies a torque to the cylindrical member, a second motor M2 that has a second rotor 20A and a second stator 10A and applies a torque to the nut member 51, and a control unit 100 that controls the driving of the first motor M1 and the second motor M2. The control unit 100 includes a command generator 110, a first position controller 121, a second position controller 122, a drag torque calculator 130, an adder 135, a first current controller 141, and a second current controller 142. The command generator 110 calculates target positions of the spline outer cylinder 61 and the nut member 51 corresponding to the required operation of the output shaft SF, generates the target position of the spline outer cylinder 61 as a first position command, and generates the target position of the nut member 51 as a second position command. The first position controller 121 is given the first position command, calculates a first torque value of the first motor M1 required to achieve the first position command, and generates the first torque value as a first torque command. The second position controller 122 is given the second position command, calculates a second torque value of the second motor M2 required to achieve the second position command, and generates the second torque value as a second torque command. The co-rotation torque calculator 130 is given the first position command, the second position command, and the second torque command, calculates a counter torque value for reducing the co-rotation torque acting on the first rotor 20 due to the co-rotation of the cylindrical member, and generates the counter torque value as a counter torque command. The adder 135 is given the first torque command and the counter torque command, and generates a composite torque value by combining the first torque value and the counter torque value as a composite torque command. The first current controller 141 receives the composite torque command and controls the current supplied to the first motor M1 so as to correspond to the composite torque value. The second current controller 142 receives the second torque command and controls the current supplied to the second motor M2 so as to correspond to the second torque value.The co-rotation torque calculator 130 determines whether or not a co-rotation torque will occur based on the first position command and the second position command, and if it determines that a co-rotation torque will occur, calculates a counter torque value based on the second torque value.

[0079] According to the actuator described above, it is possible to reduce the positional deviation of the spline outer cylinder (cylindrical member) 61 immediately after the output shaft SF starts to move linearly.

[0080] The actuator of the first embodiment also includes a first angle sensor 151 that detects the angle of the first rotor 20 of the first motor M1, and a second angle sensor 152 that detects the angle of the second rotor 20A of the second motor M2. The first position controller 121 has a feedback control function that generates a first torque command based on the detection result of the first angle sensor 151 so that the angle of the first rotor 20 becomes a desired angle. The second position controller 122 has a feedback control function that generates a second torque command based on the detection result of the second angle sensor 152 so that the angle of the second rotor 20A becomes a desired angle.

[0081] The actuator described above can return the misaligned first rotor 20 and second rotor 20A to the desired angles. Also, according to this embodiment, immediately after the output shaft SF starts to move linearly, the positional deviation of the spline outer cylinder 61 is small, and the time required to return the first rotor 20 to the target position is short.

[0082] Although the first embodiment has been described above, and the control unit of the actuator of the embodiment controls the first motor and the second motor by a torque value, the actuator of the present disclosure is not limited to such torque control, and may control the rotation speed or the position. In other words, when transitioning from a first state in which the first rotor 20 and the second rotor 20A are stationary to a second state in which the first rotor 20 is stationary and the second rotor 20A is rotating, the control unit may supply to the first motor M1 a current that applies a force that suppresses the rotation of the first rotor 20, the force being in the opposite direction to the direction in which the cylindrical member (the spline outer cylinder 61) rotates with the rotation of the second rotor 20A.

[0083] Furthermore, although the drag torque calculator 130 of the first embodiment calculates the counter torque value based on the second torque command, the drag torque calculator of the present disclosure is not limited to this. In the following, in the second and third embodiments, examples will be described in which the drag torque calculator 130 calculates the counter torque value taking into account other factors. In the following description, the same components as those described in the first embodiment above are denoted by the same reference numerals, and duplicated description will be omitted.

[0084] (Embodiment 2) 4 is a block diagram showing the configuration of a control unit of the actuator of embodiment 2. The actuator 1A according to embodiment 2 differs from the actuator 1 of embodiment 1 in that the detection result of the first angle sensor 151 is provided to the co-rotation torque calculator 130A in the control unit 100A. The actuator 1A according to embodiment 2 also differs from the actuator 1 of embodiment 1 in that the detection result of the second angle sensor 152 is provided to the co-rotation torque calculator 130A in the control unit 100A. The co-rotation torque calculator 130A calculates a counter torque value taking into consideration the detection result of the first angle sensor 151 and the detection result of the second angle sensor 152.

[0085] (Embodiment 3) 5 is a block diagram showing the configuration of a control unit of the actuator of the third embodiment. The actuator 1B according to the third embodiment is different from the actuator 1A of the second embodiment in that a control unit 100B includes an output shaft sensor 160 that measures the movement amount and rotation amount of the output shaft SF. The output shaft sensor 160 irradiates a laser onto the end face of the output shaft SF to measure the movement distance of the output shaft in the Z direction. The output shaft sensor 160 also performs image recognition of an identifier attached to the end face of the output shaft SF to calculate the rotation angle. The output shaft sensor 160 then provides the detection results of the movement distance and rotation angle of the output shaft SF to a co-rotation torque calculator 130B.

[0086] According to the actuator 1A of the second embodiment and the actuator 1B of the third embodiment described above, the counter torque value calculated from a pre-stored map (not shown) or a predetermined calculation can be corrected based on the detection result of the first angle sensor 151, etc., to absorb the individual difference between the actuators 1. Next, in a fourth embodiment, an actuator 1C having a different structure will be described.

[0087] 6 is a cross-sectional view of the actuator according to the fourth embodiment taken along the central axis of the output shaft. The actuator 1C of the fourth embodiment differs from the first embodiment in that the first motor M1 and the second motor M2 are not arranged coaxially with the central axis AX. The actuator 1C of the fourth embodiment also differs from the first embodiment in that the torque of the first motor M1 is transmitted to the spline outer cylinder 61 via the first pulley 81. The actuator 1C of the fourth embodiment also differs from the first embodiment in that the torque of the second motor M2 is transmitted to the nut member 51 via the second pulley 82.

[0088] The first pulley 81 has a driven pulley 83 integrated with the spline outer cylinder 61, a driving pulley 84 integrated with the output shaft 25 of the first motor M1, and a belt 85 wound around the driven pulley 83 and the driving pulley 84. The second pulley 82 has a driven pulley 86 integrated with the nut member 51, a driving pulley 87 integrated with the output shaft 26 of the second motor M2, and a belt 88 wound around the driven pulley 86 and the driving pulley 87. Even in this embodiment, the same effects as those of the first embodiment can be achieved. [Explanation of symbols]

[0089] 1, 1A, 1B Actuator 10 First stator 10A Second Stator 20 First Rotor 20A Second Rotor 31 No. 1 bearing 32 No. 2 bearing 40 First motor housing 40A Second Motor Housing 46 First connecting bracket 45 Second connecting bracket 51 Nut material 53 Screw shaft 61 Spline outer cylinder (cylinder part) 63 Shaft 100 Control section 110 Command generator 121 First position controller 122 Second position controller 130, 130A, 130B Corotation torque calculator 135 Adder 141 First current controller 142 Second Current Controller 151 First angle sensor 152 Second Angle Sensor 153 First current measuring instrument 154 Second current measuring instrument 160 Output shaft sensor M1 First motor M2 Second motor SF Output shaft

Claims

1. An output shaft; a cylindrical member through which the output shaft is inserted and whose relative rotation with respect to the output shaft is restricted; a nut member that is inserted through the output shaft and that moves the output shaft in the axial direction by rotating relative to the output shaft; a housing that rotatably supports the cylindrical member and the nut member; a first motor including a first rotor and a first stator that rotates the first rotor, and that rotates the cylindrical member in conjunction with the rotation of the first rotor; a second motor having a second rotor and a second stator that rotates the second rotor and rotates the nut member in cooperation with the second rotor; A control unit that controls the first motor and the second motor; Equipped with The control unit is a command generator that calculates target positions of the cylindrical member and the nut member corresponding to a required operation of the output shaft, generates the target position of the cylindrical member as a first position command, and generates the target position of the nut member as a second position command; a first position controller that receives the first position command, calculates a first torque value of the first motor required to achieve the first position command, and generates the first torque value as a first torque command; a second position controller that receives the second position command, calculates a second torque value of the second motor required to achieve the second position command, and generates the second torque value as a second torque command; a co-rotation torque calculator that receives the first position command, the second position command, and the second torque command, calculates a counter torque value for reducing a co-rotation torque acting on the first rotor due to the co-rotation of the cylindrical member, and generates the counter torque value as a counter torque command; an adder that receives the first torque command and the counter torque command, and generates a composite torque value by combining the first torque value and the counter torque value as a composite torque command; a first current controller that receives the resultant torque command and controls a current to be supplied to the first motor so as to correspond to the resultant torque value; a second current controller that receives the second torque command and controls a current supplied to the second motor so as to correspond to the second torque value; having The co-rotation torque calculator includes: determining whether or not the co-rotation torque is generated based on the first position command and the second position command; When it is determined that the drag torque occurs, the counter torque value is calculated based on the second torque value. Actuator.

2. a first angle sensor that detects an angle of the first rotor of the first motor; a second angle sensor that detects an angle of the second rotor of the second motor; Equipped with the first position controller has a feedback control function of newly generating the first torque command based on a detection result of the first angle sensor so that the angle of the first rotor becomes a desired angle, The second position controller has a feedback control function of generating a new second torque command based on a detection result of the second angle sensor so that the angle of the second rotor becomes a desired angle. The actuator of claim 1 .

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