Actuator and robot arm

Abstract

To provide an actuator etc., which can effectively attenuate vibration applied to a motor.SOLUTION: An actuator 10 includes: a motor 20; and a controller for controlling the motor 20. The controller can operate at a first control mode for applying a first control signal which rotationally drives the motor 20 and a second control signal which attenuates vibration applied to the motor 20 to the motor 20. The motor 20 includes: a stator to which the first control signal and the second control signal are applied at the first control mode and which generates a magnetic field; and a rotor 23 which can rotate relative to the stator according to the magnetic field. The stator includes a first stator 21 to which the first control signal is applied and a second stator 22 to which the second control signal is applied.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present disclosure relates to an actuator and the like.

Background Art

[0002] In industrial sites such as factories, logistics warehouses, construction sites, and hospitals, industrial robots that perform various operations instead of humans have been introduced. Many conventional industrial robots are large and have high power, and it was necessary to provide an isolated space where humans cannot enter for safety reasons. On the other hand, in recent years, the introduction of collaborative robots that work together with humans in the same space has also been progressing. Compared with conventional industrial robots, small collaborative robots can be installed in narrow spaces and have low power, so they do not require a large-scale system for ensuring safety. Patent Document 1 discloses a drive device applicable to the joints of collaborative robots.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In collaborative robots, flexibility is often imparted to movable parts such as joints in order to absorb impacts such as when a human working together collides, thereby improving safety. While such a "soft" joint is preferable in light of the original purpose of the collaborative robot, there is a problem that it is easily affected by vibrations from the outside (for example, other moving joints).

[0005] The present disclosure has been made in view of such circumstances, and an object thereof is to provide an actuator or the like that can effectively attenuate vibrations applied to a motor. Note that although a collaborative robot has been exemplified above, the present disclosure is applicable to general industrial robots not limited to collaborative robots, and generally to actuators in which vibrations applied to a motor are a problem.

Means for Solving the Problems

[0006] In order to solve the above problems, an actuator according to an aspect of the present disclosure is an actuator including a motor and a controller that controls the motor, and the controller is operable in a first control mode in which a first control signal for rotationally driving the motor and a second control signal for attenuating vibrations applied to the motor are applied to the motor.

[0007] According to this aspect, the motor can be rotated by the first control signal, and the vibrations applied to the motor can be effectively attenuated by the second control signal.

[0008] Another aspect of the present disclosure is a robot arm. This robot arm is a robot arm including a plurality of joints that are rotationally driven by motors, and a controller that controls the motors in at least one joint is operable in a first control mode in which a first control signal for rotationally driving the motor and a second control signal for attenuating vibrations applied to the joint are applied to the motor.

[0009] Note that any combination of the above components, or those obtained by converting these expressions into a method, apparatus, system, recording medium, computer program, etc., are also included in the present disclosure.

Effects of the Invention

[0010] According to the present disclosure, vibrations applied to a motor can be effectively attenuated.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments for implementing the present disclosure (hereinafter also referred to as embodiments) will be described in detail with reference to the drawings. In the description and / or drawings, the same reference numerals are given to the same or equivalent components, members, processes, etc., and redundant descriptions are omitted. The scales and shapes of the respective parts shown are set for convenience in order to simplify the description, and are not to be construed in a limited manner unless otherwise particularly noted. The embodiments are examples and do not limit the scope of the present disclosure in any way. All features presented in the embodiments and combinations thereof are not necessarily essential to the present disclosure. The embodiments are presented, for convenience, as being decomposed into components for each function and / or function group for realizing the same. However, one component in the embodiments may actually be realized by a combination of a plurality of components as separate entities, or a plurality of components in the embodiments may actually be realized by one integrated component. Also, a plurality of embodiments and modifications may be disclosed in parallel, but any components of each embodiment and / or each modification may be combined in any manner as long as they do not inhibit each other's functions.

[0013] FIG. 1 is a perspective view showing the appearance of a robot arm 1 as an example of a robot such as an industrial robot or a collaborative robot. This robot arm 1 is a vertically articulated robot arm with a serial link mechanism. The robot to which the present disclosure is applicable is not limited to a robot arm in the narrow sense, and may be a robot arm in the broad sense having joints (corresponding to joints in the human body) that connect a plurality of links (corresponding to bones in the human body) so as to be relatively movable, or any robot having at least one movable part. Also, instead of the serial link mechanism, a parallel link mechanism may be used, or instead of the vertically articulated type, a horizontally articulated type may be used.

[0014] The robot arm 1 has seven joints or axes, namely the first joint 110, the second joint 120, the third joint 130, the fourth joint 140, the fifth joint 150, the sixth joint 160, and the seventh joint 170, in order from the side closer to the pedestal 100. Each joint corresponds to each joint of the human body. Specifically, the first joint 110 corresponds to the waist, the second joint 120 corresponds to the shoulder, the third joint 130 corresponds to the upper arm (twist), the fourth joint 140 corresponds to the elbow, the fifth joint 150 corresponds to the forearm (twist), the sixth joint 160 corresponds to the wrist, and the seventh joint 170 corresponds to the fingertip (twist). Each rotatable joint 110 - 170 and each link connected via each joint 110 - 170 constitute the movable parts of the robot arm 1 respectively.

[0015] Note that the direction of each axis can be appropriately designed according to the purpose and use of the robot arm 1. In this embodiment, assuming that the pedestal 100 is placed on a horizontal plane, the first joint 110 is in the vertical direction (perpendicular to the pedestal 100 which is a horizontal plane), the second joint 120 is in the horizontal direction (parallel to the pedestal 100 which is a horizontal plane), the third joint 130 is in the direction perpendicular to the second joint 120, the fourth joint 140 is in the direction perpendicular to the third joint 130, the fifth joint 150 is in the direction perpendicular to the fourth joint 140, the sixth joint 160 is in the direction perpendicular to the fifth joint 150, and the seventh joint 170 may face in the direction perpendicular to the sixth joint 160.

[0016] An end effector or a robot hand as a working part having a shape and function corresponding to the working purpose is attached to the seventh joint 170 at the tip of the robot arm 1. For example, various end effectors such as a grapple shape for grasping an object, a shovel shape for scooping an object, a fork shape for supporting and transporting an object from below, a hook shape for hooking and transporting an object, and a crane shape for lifting and transporting an object can be used.

[0017] Figures 2 and 3 schematically show the configuration of the connecting device 30 that constitutes each joint 110-170 of the robotic arm 1. The connecting device 30 in Figure 2 is applicable to joints that perform "bending" operations such as the second joint 120, the fourth joint 140, and the sixth joint 160 in Figure 1. The connecting device 30 in Figure 3 is applicable to joints that perform "twisting" operations such as the first joint 110, the third joint 130, the fifth joint 150, and the seventh joint 170 in Figure 1.

[0018] In Figure 2, the connecting device 30 connects the first link 41 as the first member and the second link 42 as the second member so as to be relatively movable. The connecting device 30 corresponds to a joint in the human body, and the first link 41 and the second link 42 that are interconnected by the connecting device 30 correspond to bones in the human body.

[0019] The first link 41 and the second link 42 perform relative movements in various modes according to the connection mode by the connecting device 30. In this embodiment, an example is described in which the first link 41 and the second link 42 rotate relative to each other about the rotation axis A perpendicular to the extending direction of the first link 41 and the second link 42.

[0020] Note that the relative movement of the first link 41 and the second link 42 is not limited to rotational movement but may also be translational movement. For example, the first link 41 and the second link 42 may be configured to move relatively translationally in a direction perpendicular to the extending direction of the first link 41 and the second link (a direction perpendicular to the plane of the paper in Figure 2), or the first link 41 and the second link 42 may be configured to move relatively translationally in a direction parallel to the extending direction of the first link 41 and the second link (the vertical direction in Figure 2).

[0021] The connecting device 30 includes a housing 31, a control board 32, a motor 20, a speed reducer 34, an elastic member 35, and an output flange 36. The housing 31 has a shape that is rotationally symmetric about the rotation axis A, and houses the components 32 - 36 of the connecting device 30 inside. On the outer periphery of the housing 31, a first attachment portion 311 to which the first link 41 is attached and a second attachment portion 312 to which the second link 42 is attached are provided.

[0022] The first link 41 fixed to the housing 31 at the first attachment portion 311 is rotatable relative to the second link 42 about the rotation axis A integrally with the housing 31. The second attachment portion 312 is an opening on the bottom side (the left side in FIG. 2) that communicates with the internal space of the housing 31 housing the components 32 - 36. The second link 42 is attached to the connecting device 30 via the output flange 36 provided at this opening.

[0023] The control board 32 controls the connecting device 30 under the control of a central control device (not shown) that is responsible for controlling the entire robot arm 1. For example, generation of a drive command for the motor 20, adaptive control based on measurement data of an output shaft encoder (not shown), detection of torque based on the elastic deformation of the elastic member 35, adaptive control based on the detected torque, etc. are performed by the control board 32. The motor 20 constitutes an actuator that generates power to rotationally drive the second link 42 about the rotation axis A in response to a drive command from the control board 32 as a controller. The speed reducer 34 reduces the rotation speed of the motor 20 by gears or the like and generates torque proportional to the reduction ratio.

[0024] The elastic member 35 is provided in series between the motor 20 and the speed reducer 34 as a power source and the second link 42 as a load that is rotationally driven by the power, and constitutes a series elastic actuator (SEA) in the connecting device 30. Even if a human who works together with the robot arm 1 as a collaborative robot collides with the robot arm 1, the impact is absorbed by the elastic deformation of the elastic member 35, so the safety is improved. In addition, since the elastic member 35 can accumulate and release the power generated by the motor 20 and the speed reducer 34 and the external force applied to the second link 42 as elastic energy, efficient operation like that of human muscles can be realized.

[0025] The elastic member 35 is a member that imparts elasticity to the connecting device 30 and is formed of an arbitrary elastic body such as a spring or rubber, for example. In addition to or instead of the elastic member 35, a resistance-imparting member that imparts resistance to the relative rotation of the first link 41 and the second link 42 of the connecting device 30 may be provided. Examples of the resistance-imparting member include those that impart resistance by mechanical friction and those that impart resistance by the viscosity of a viscous fluid such as oil or grease. The elasticity of the elastic member 35 and the resistance imparted by the resistance-imparting member may be made variable by the control board 32.

[0026] Note that the elastic member 35 also functions as a torque sensor that detects torque due to an external force including vibration. That is, since the external force causes elastic deformation of the elastic member 35, the torque can be detected based on the amount of elastic deformation. In order to measure the amount of elastic deformation of the elastic member 35, various displacement sensors such as a magnetostrictive sensor, a strain gauge, a piezoelectric element, a polarizing element, and a capacitance sensor may be attached to the surface of the elastic member 35 or the like. The amount of elastic deformation measured by such a displacement sensor is converted into torque by an arithmetic device or the like mounted on the control board 32. Note that the connecting device 30 may be provided with a force sensor that detects the force applied to the connecting device 30 by the elastic member 35 and / or other members. Hereinafter, the force sensor and the torque sensor are also collectively referred to as a force sensor.

[0027] As described above, a force sensor capable of detecting an applied force and / or torque may be attached to the coupling device 30. Based on the force and / or torque applied to the coupling device 30 that constitutes each of the joints 110 to 170, the end effector or robot hand such as a holding tool or a gripping tool as a movable part provided at the tip of the robot arm 1 can calculate the force, torque, the weight of the workpiece, etc. received from the workpiece such as the object to be held, the object to be gripped, or the object to be worked on. That is, the force sensors provided in each of the coupling devices 30 indirectly detect the force, torque, the weight of the workpiece, etc. received by the end effector from the workpiece. In addition to or instead of these force sensors, by attaching a force sensor to the end effector itself, the force, torque, the weight of the workpiece, etc. received by the end effector from the workpiece may be directly detected.

[0028] In the above configuration, the speed reducer 34, the elastic member 35, and the resistance-imparting member each constitute a flexibility-imparting part that imparts flexibility to the coupling device 30 as a joint. Here, flexibility means the ease of bending of the joint, and it is said that there is flexibility when the joint bends by an external force. For example, since the speed reducer 34 generates torque proportional to the reduction ratio, by lowering the reduction ratio, a state with high flexibility in which the joint easily bends by an external force can be realized. Also, it can be said that the elastic member 35 and the resistance-imparting member impart flexibility to the joint because they generate an elastic force or resistance against the external force while allowing the joint to bend. Note that the flexibility-imparting part may be provided in at least one joint, and it is not necessary to provide the flexibility-imparting part in all of the seven joints 110 to 170 in FIG. 1.

[0029] The output shaft encoder (not shown) is a rotary encoder that measures the rotational position around the rotation axis A of the second link 42 with respect to the first link 41. The output flange 36 transmits the torque generated by the speed reducer 34 to the second link 42 via the elastic member 35 and rotates the second link 42 around the rotation axis A. A bearing 361 that smoothes the rotation of the second link 42 with respect to the housing 31 is provided around the output flange 36.

[0030]

[0030] In the connecting device 30 of FIG. 3, the first link 41 and the second link 42 rotate relative to each other about a rotation axis B parallel to their respective extending directions. The notch 37 provided on the second link 42 side of the housing 31 prevents the housing 31 from interfering with the rotation of the second link 42 about the rotation axis B by the motor 20.

[0031]

[0031] FIG. 4 schematically shows an actuator 10 according to the present embodiment that supplies single-phase or polyphase alternating current to the motor 20 at each of the joints 110 to 170. The actuator 10 includes a converter 11 that rectifies three-phase alternating current of R phase, S phase, and T phase supplied from a commercial power supply or the like into direct current (pulsating current), a smoothing capacitor 12 that smooths the direct current converted by the converter 11 to adjust the waveform, and an inverter 13 that converts the direct current smoothed by the smoothing capacitor 12 into alternating current. Part or all of the actuator 10 excluding the motor 20 may be mounted on the control board 32 described above. In particular, the inverter 13 is preferably mounted on the control board 32 and constitutes a controller that controls the motor 20.

[0032] The converter 11 includes diodes 111 to 116 that rectify three-phase (R, S, T) alternating current supplied from a commercial power supply or the like in a certain direction (the direction from the bottom to the top in the figure). The diode 111 conducts current when the alternating voltage of the R phase is positive, the diode 112 conducts current when the alternating voltage of the R phase is negative, the diode 113 conducts current when the alternating voltage of the S phase is positive, the diode 114 conducts current when the alternating voltage of the S phase is negative, the diode 115 conducts current when the alternating voltage of the T phase is positive, and the diode 116 conducts current when the alternating voltage of the T phase is negative. A pulsating current with a constant direction and a fluctuating magnitude appears between the output terminals of the converter 11 due to the diodes 111 to 116 connected in a bridge shape in this way. The smoothing capacitor 12 supplies the inverter 13 with direct current obtained by smoothing the pulsating current obtained by the converter 11.

[0033] Hereinafter, the DC voltage input between the high-potential input terminal 131 and the low-potential input terminal 132 of the inverter 13 via the converter 11 and the smoothing capacitor 12 is denoted as V DC . The potential of the high-potential line to which the high-potential input terminal 131 is connected is denoted as V dd , and the potential of the low-potential line to which the low-potential input terminal 132 is connected is denoted as V ss . Then, V DC = V dd - V ss .

[0034] The inverter 13 outputs three-phase alternating current by the switching operation of the three-phase transistor pairs of the U-phase, V-phase, and W-phase connected in parallel between the high-potential line supplying the DC high potential V dd and the low-potential line supplying the DC low potential V ss . In other words, the inverter 13 generates three-phase alternating current based on the DC voltage V DC input between the high-potential input terminal 131 and the low-potential input terminal 132. Specifically, a U-phase inverter 13U that generates U-phase alternating current based on the DC voltage V DC , a V-phase inverter 13V that generates V-phase alternating current based on the DC voltage V DC , and a W-phase inverter 13W that generates W-phase alternating current based on the DC voltage V DC are provided in parallel. Since the configurations of the inverters 13U, 13V, and 13W of each phase are common, hereinafter, they are collectively referred to as the inverter 13 and described together as appropriate.

[0035] The inverter 13 includes a high-potential input terminal 131 to which a high DC power supply potential V dd is input, a low-potential input terminal 132 to which a low DC power supply potential V ss is input, and is provided between the high-potential input terminal 131 and the low-potential input terminal 132, and V dd and V ssIt includes an AC output terminal 133 that outputs an AC voltage that varies between them. A high-potential-side transistor 134H as a high-potential-side switching element is connected between the high-potential line and the AC output terminal 133, and a low-potential-side transistor 134L as a low-potential-side switching element is connected between the low-potential line and the AC output terminal 133.

[0036] The high-potential-side transistor 134H performs a switching operation to switch the conduction state of the current path according to a pulse (high-potential-side control signal) supplied from a high-potential-side driver 135H as a driver connected to its control terminal. The low-potential-side transistor 134L performs a switching operation to switch the conduction state of the current path according to a pulse (low-potential-side control signal) supplied from a low-potential-side driver 135L as a driver connected to its control terminal. Hereinafter, the high-potential-side transistor 134H and the low-potential-side transistor 134L are collectively referred to as the transistor 134 or the transistor pair 134 as appropriate, and the high-potential-side driver 135H and the low-potential-side driver 135L are collectively referred to as the driver 135 or the driver pair 135 as appropriate. Also, in the following description, "H" meaning "high-potential side" and "L" meaning "low-potential side" are appropriately omitted, but in the drawings, "H" and "L" are attached to the end of the reference numerals as necessary.

[0037] The transistors 134H, 134L in the illustrated example are insulated gate bipolar transistors (IGBTs: Insulated Gate Bipolar Transistors) having gates 31H, 31L as control terminals, collectors 32H, 32L as high-potential-side terminals connected to the high-potential line side, and emitters 33H, 33L as low-potential-side terminals connected to the low-potential line side. However, the transistor 134 or the switching element may be a field effect transistor (FET: Field Effect Transistor) having a gate as a control terminal, a drain as a high-potential-side terminal, and a source as a low-potential-side terminal, or a bipolar transistor having a base as a control terminal, a collector as a high-potential-side terminal, and an emitter as a low-potential-side terminal.

[0038] In the high-potential-side transistor 134H, the gate 31H is connected to the high-potential-side driver 135H, the collector 32H is connected to the high-potential input terminal 131 or the high-potential line, and the emitter 33H is connected to the AC output terminal 133 and the collector 32L of the low-potential-side transistor 134L. In the low-potential-side transistor 134L, the gate 31L is connected to the low-potential-side driver 135L, the collector 32L is connected to the AC output terminal 133 and the emitter 33H of the high-potential-side transistor 134H, and the emitter 33L is connected to the low-potential input terminal 132 or the low-potential line. In the above configuration, the connection point between the emitter 33H of the high-potential-side transistor 134H and the collector 32L of the low-potential-side transistor 134L forms the AC output terminal 133.

[0039] In each of the transistors 134H and 134L, the current path or channel between the collector 32H, 32L and the emitter 33H, 33L is switched between the conducting state according to the pulses (control signals) applied from the respective drivers 135 to the gates 31H, 31L. In parallel with this current path or channel, protection diodes 34H, 34L as protection diode elements may be provided. The protection diodes 34H, 34L may be discrete elements separate from the transistors 134H, 134L, or may be formed integrally or monolithically with the transistors 134H, 134L in the semiconductor manufacturing process for manufacturing the transistors 134H, 134L. The protection diodes 34H, 34L are provided so as to allow current to flow only in the direction from the low-potential line side to the high-potential line side.

[0040] Drivers 135H and 135L, which may be configured as an integrated circuit (IC: Integrated Circuit), supply switching pulses as control signals for switching operations to gates 31H and 31L of transistors 134H and 134L. For example, drivers 135H and 135L apply pulses whose duty ratio or pulse width is controlled by PWM (Pulse Width Modulation) to gates 31H and 31L of transistors 134H and 134L. Transistors 134H and 134L perform a switching operation that switches between an on state and an off state according to the presence or absence of a pulse. Specifically, while a pulse is applied to gates 31H and 31L, transistors 134H and 134L are in the on state, and the channels between collectors 32H, 32L and emitters 33H, 33L are in a conductive state. Also, while no pulse is applied to gates 31H and 31L, transistors 134H and 134L are in the off state, and the channels between collectors 32H, 32L and emitters 33H, 33L are in a non-conductive state.

[0041] Each-phase driver 135 performs switching control to complementarily switch the conduction states of a pair of transistors composed of a high-potential-side transistor 134H and a low-potential-side transistor 134L under the control of a control unit (not shown) that constitutes a controller according to this embodiment together with the driver 135, thereby converting direct current into alternating current for each phase. Here, "complementarily switch" means to control so that the pairs of transistors for each phase do not simultaneously turn on. In other words, it means that when one transistor in each phase is in the on state, the other transistor in that phase is controlled to be in the off state. However, it is allowed for the pairs of transistors for each phase to simultaneously turn off. Also, the high-potential-side control signal for the high-potential-side transistor 134H and the low-potential-side control signal for the low-potential-side transistor 134L, which are in the above relationship, are expressed as "complementary" to each other.

[0042] Specifically for the U-phase, when the high-potential side transistor 134H is in the on state, the low-potential side transistor 134L is controlled to be in the off state, and when the low-potential side transistor 134L is in the on state, the high-potential side transistor 134H is controlled to be in the off state. Therefore, when the high-potential side transistor 134H is in the on state, a high potential V dd appears at the U-phase AC output terminal 133U, and when the low-potential side transistor 134L is in the on state, a low potential V ss appears at the U-phase AC output terminal 133U. By periodically repeating such switching control, a U-phase alternating current in which the high potential V dd and the low potential V ss alternately appear is generated at the U-phase AC output terminal 133U.

[0043] As described above, the three-phase alternating current generated by the inverter 13 is supplied to the motor 20 that generates rotational power. The motor 20 is, for example, a three-phase brushless motor including three-phase coils 20U, 20V, and 20W of the U-phase, V-phase, and W-phase. A U-phase current from the AC output terminal 133U of the U-phase inverter 13U flows through the U-phase coil 20U, a V-phase current from the AC output terminal 133V of the V-phase inverter 13V flows through the V-phase coil 20V, and a W-phase current from the AC output terminal 133W of the W-phase inverter 13W flows through the W-phase coil 20W. Each of the inverters 13U, 13V, and 13W of each phase generates a rotating magnetic field by applying three-phase alternating currents with different phases to the coils 20U, 20V, and 20W of each phase based on the rotational position of the rotor (not shown) detected by the hall elements H1, H2, and H3 of the motor 20. Desired rotational power is obtained from the rotor that rotates due to this rotating magnetic field. Note that the motor 20 may be another type of motor driven by alternating current. Also, the number of phases of the motor 20 is not limited to three and may be any natural number. Similarly, the number of phases of the alternating current input to the converter 11 is not limited to three and may be any natural number.

[0044] FIG. 5 shows the output voltage waveforms V U , V V , V Wis schematically shown together with the high - potential - side and low - potential - side control signals (pulses) applied by the high - potential - side driver 135H and the low - potential - side driver 135L of each of the U, V, and W phases to the gates 31H and 31L of the transistor pair 134. Each output terminal 133U, 133V, 133W outputs a sinusoidal AC voltage V dd that varies between a high potential V ss and a low potential V U , V V , V W . In three - phase AC, the phase of the AC voltage waveforms V U , V V , V W of each phase differs by 120 degrees or 2 / 3π. In the following description, the average value of the high potential V dd and the low potential V ss is conveniently set to "0".

[0045] During the period when each output terminal 133U, 133V, 133W outputs a positive voltage, the high - potential - side driver 135H applies a pulse (high - potential - side control signal) whose duty ratio changes step - by - step between "0" and "1" to the gate 31H of the high - potential - side transistor 134H, while the low - potential - side driver 135L does not apply a pulse (low - potential - side control signal) to the gate 31L of the low - potential - side transistor 134L (that is, the duty ratio or pulse width is "0"). In particular, when the high - potential - side driver 135H applies a pulse with a duty ratio of "1" to the gate 31H of the high - potential - side transistor 134H, the channel of the high - potential - side transistor 134H conducts almost completely with the high - potential line, so a high voltage approximately equal to V dd appears at the output terminal 133.

[0046] During the period when each of the output terminals 133U, 133V, and 133W outputs a negative voltage, the low-potential side driver 135L applies a pulse (low-potential side control signal) whose duty ratio changes stepwise between "0" and "1" to the gate 31L of the low-potential side transistor 134L, while the high-potential side driver 135H does not apply a pulse (high-potential side control signal) to the gate 31H of the high-potential side transistor 134H (that is, the duty ratio or pulse width is "0"). In particular, when the low-potential side driver 135L applies a pulse with a duty ratio of "1" to the gate 31L of the low-potential side transistor 134L, the channel of the low-potential side transistor 134L conducts almost completely with the low-potential line, so that a low voltage approximately equal to V ss appears at the output terminal 133.

[0047] As described above, during the normal operation in which the inverter 13 outputs three-phase alternating current, in each of the inverters 13U, 13V, and 13W of the UVW phases, a pulse with a stepwise changing duty ratio is applied only to one of the high-potential side transistor 134H and the low-potential side transistor 134L, and no pulse is applied to the other of the high-potential side transistor 134H and the low-potential side transistor 134L (the duty ratio is "0").

[0048] Also, in order to change the AC voltages V U , V V , V W smoothly in a sinusoidal wave shape with the maximum amplitude between V dd and V ss , it is preferable that the duty ratio of the pulses (control signals) applied to the gates 31H and 31L of the respective transistors 134H and 134L is controlled substantially continuously within the maximum range between the minimum value of "0" and the maximum value of "1". Specifically, during the period when each of the transistors 134H and 134L outputs a positive or negative voltage, the duty ratio of the pulses (control signals) applied to the gates 31H and 31L of the respective transistors 134H and 134L increases continuously or stepwise from the minimum value of "0" to the maximum value of "1" (as described above, when the duty ratio is "1", the output voltage is the maximum value V dd or the minimum value V ssIt preferably decreases continuously or stepwise again to the minimum value of "0".

[0049] FIG. 6 is a schematic cross-sectional view of the actuator 10. The actuator 10 includes the motor 20 as described above and the control board 32 on which the main part of the controller for controlling the motor 20 is mounted. The motor 20 includes one or a plurality of stators 21 and 22 to which various control signals described later are applied to generate a magnetic field, and a rotor 23 that is rotatable with respect to the stators 21 and 22 in response to the magnetic field. The rotor 23 includes a single rotation shaft 24 that is rotatable around the axial direction, which is the left-right direction in FIG. 6, and a magnet (not shown) that is fixed to the rotation shaft 24 and acts on the magnetic field generated by the outer peripheral stators 21 and 22.

[0050] On the load side (the left side in FIG. 6) of the motor 20, the above-described speed reducer 34 and a load-side cover 18 that covers the speed reducer 34 from the load side are connected. Hereinafter, the direction of the rotation center line C12 of the rotation shaft 24 is also represented as the axial direction X, and the circumferential direction and the radial direction of the circle centered on the rotation center line C12 are also represented as the circumferential direction and the radial direction, respectively.

[0051] The actuator 10 drives a driven object W (load) connected to the load side while being supported by a support member 200 provided on the outer side in the circumferential direction thereof. Examples of the driven object W include movable parts such as a conveyor, a wheel, a machine tool, and a robot. In the illustrated example, the support member 200 is fixed to a speed reducer housing 28 that houses the speed reducer 34, and the driven object W is fixed to the load-side cover 18. The support member 200 may be fixed to the load-side cover 18, and the driven object W may be fixed to the speed reducer housing 28.

[0052] The speed reducer 34 includes an input shaft 24A that rotates integrally with the rotation shaft 24, a speed reduction mechanism 26 that transmits the rotation input through the input shaft 24A, and a speed reducer housing 28 that houses the speed reduction mechanism 26.

[0053] The speed reduction mechanism 26 in this embodiment includes an external gear 300 and internal gears 32A and 32B that mesh with each other, and one of them (in the illustrated example, the external gear 300) is a flexure meshing type gear mechanism that serves as a flexure gear. When the rotation from the input shaft 24A is transmitted, this speed reduction mechanism 26 flexurally deforms the flexure gear so as to change the meshing position with other gears in the rotational direction of the input shaft 24A. Due to this flexural deformation of the flexure gear, one of the external gear 300 and the internal gears 32A and 32B (in the illustrated example, the external gear 300) rotates, and this rotational component is output to the driven object W as a rotational output.

[0054] The speed reduction mechanism 26 in the illustrated example is a well-known cylindrical flexure meshing type gear mechanism having a first internal gear 32A arranged on the anti-load side (the right side in FIG. 6) and a second internal gear 32B arranged on the load side. This speed reduction mechanism 26 outputs rotation to the driven object W via the load side cover 18. Note that rotation may be output to the driven object W via the speed reducer housing 28 instead of the load side cover 18. A gear bearing 24B that rotatably supports the external gear 300 is arranged between the input shaft 24A and the external gear 300.

[0055] The speed reducer housing 28 in the illustrated example includes a plurality of housing members 28a and 28b that are integrated with each other. The first housing member 28a also serves as the first internal gear 32A, and the second housing member 28b is arranged radially outside the second internal gear 32B. The speed reducer housing 28 is connected to the motor housing 66 that houses the motor 20 by bolts or the like. A main bearing 38 is arranged between the speed reducer housing 28 and the second internal gear 32B.

[0056] The load-side cover 18 covers the speed reduction mechanism 26 and the input shaft 24A from the load side as a part of the speed reducer 34. The load-side cover 18, which is generally cylindrical, functions as a synchronizing member capable of synchronizing with the rotating component of the external gear 300. The load-side cover 18 is fixed to the second internal gear 32B by bolts or the like (not shown) in a state overlapping with the first protruding portion 32Ba protruding from the second internal gear 32B toward the load side. The load-side cover 18 protrudes toward the non-load side and includes a second protruding portion 18a that is in an in-roll fit with the first protruding portion 32Ba of the second internal gear 32B. A load-side bearing 40 that rotatably supports the rotating shaft 24 is disposed on the second protruding portion 18a of the load-side cover 18.

[0057] The actuator 10 includes a pipe member 43 disposed in the hollow portion 12a of the rotating shaft 24. The pipe member 43 penetrates through the hollow portion 12a of the rotating shaft 24 along the axial direction X. The load-side portion of the pipe member 43 is fixed to the load-side cover 18 and can rotate integrally with the load-side cover 18. In the illustrated example, the load-side portion of the pipe member 43 is fixed to the load-side cover 18 by being press-fitted into a through hole 18b formed in the load-side cover 18. This fixing may be realized by bolts or the like. The non-load-side portion of the pipe member 43 is rotatably supported by the rotating shaft 24 via an internal bearing 44 disposed between the pipe member 43 and the rotating shaft 24.

[0058] The actuator 10 includes a first rotation detector 46A that detects the rotation of the rotary shaft 24, and a second rotation detector 46B that detects the rotation of the pipe member 43. The first rotation detector 46A includes a first detected portion 46Aa that can rotate integrally with the rotary shaft 24, and a first detection portion 46A that faces the first detected portion 46Aa. The second rotation detector 46B includes a second detected portion 46Ba that can rotate integrally with the pipe member 43, and a second detection portion 46Bb that faces the second detected portion 46Ba. The detected portions 46Aa and 46Ba are, for example, positioning scales such as an optical scale or a magnetic scale. The detection portions 46Ab and 46Bb are, for example, positioning sensors such as an optical sensor or a magnetic sensor. The detection portions 46Ab and 46Bb can detect the rotation of the rotating bodies (rotary shaft 24, pipe member 43) by detecting a change in a predetermined physical quantity (such as light or magnetism) accompanying the rotation of the detected portions 46Aa and 46Ba. The first detection portion 46Ab and the second detection portion 46Bb are mounted on a common sensor substrate 48. The sensor substrate 48 is mounted on a mount 50 fixed to the motor housing 66. The mount 50 is attached with the aforementioned control board 32 on which a driver IC (not shown) and the like used for controlling the motor 20 are mounted.

[0059] The motor 20 includes two stators 21 and 22 that rotationally drive the rotary shaft 24 in the rotor 23. The first stator 21 and the second stator 22 may be provided at different positions in the axial direction (however, as will be described later, the first stator 21 and the second stator 22 may be provided at the same position in the axial direction as substantially one integrated stator). In the illustrated example, the first stator 21 on the load side and the second stator 22 on the anti-load side are provided adjacent to each other in the axial direction.

[0060] The first stator 21 and the second stator 22 annularly surround a rotating shaft 24 or a rotor 23 that is a common rotation drive target from the outer peripheral side. As will be described later, on the inner peripheral side of each of the first stator 21 and the second stator 22, at least one-phase coil (for example, the three-phase coils 20U, 20V, 20W in FIG. 4) that generates a magnetic field according to an applied control signal is provided. Further, on the outer peripheral side of the rotating shaft 24, a magnet such as a permanent magnet that magnetically acts on the magnetic field generated by the coil and receives rotational power is provided. In this way, the rotating shaft 24 is rotationally driven by a rotating magnetic field generated by the first stator 21 and / or the second stator 22 according to a control signal applied to the coil.

[0061] In the illustrated example, the length in the axial direction or the size in an arbitrary direction of the first stator 21 is larger than the length in the axial direction or the size in an arbitrary direction of the second stator 22. For this reason, the first stator 21 can generate a larger torque than the second stator 22 with the rotor 23. Note that the lengths or sizes of the first stator 21 and the second stator 22 may be substantially the same so that the first stator 21 and the second stator 22 can generate substantially the same torque with the rotor 23.

[0062] The first stator 21 and the second stator 22 as described above are fixed to a single motor housing 66. Further, a single rotating shaft 24 rotationally driven by the first stator 21 and / or the second stator 22 is rotatable around the axial direction within the motor housing 66.

[0063] FIG. 7 is a schematic cross-sectional view of the first stator 21 and / or the second stator 22 in a cross-section perpendicular to the axial direction when provided with three-phase coils 20U, 20V, 20W. The stators 21, 22 annularly surround a rotating shaft 24 or a rotor 23 that is a rotation drive target from the outer peripheral side. On the inner peripheral side of the stators 21, 22, three-phase coils 20U, 20V, 20W are periodically provided.

[0064] On the outer peripheral side of the rotor 23 facing these coils 20U, 20V, and 20W, a plurality of permanent magnets 231 are periodically provided which are fixed to the rotating shaft 24 and magnetically interact with the magnetic fields generated by the coils 20U, 20V, and 20W to receive rotational power. The magnetic poles on the outer peripheral sides of adjacent permanent magnets 231 are opposite to each other. That is, along the circumferential direction of the rotor 23, the N poles and S poles of each permanent magnet 231 are alternately arranged. The rotor 23 rotates in the circumferential direction due to the magnetic interaction between the coils 20U, 20V, 20W and the permanent magnets 231. In FIG. 7, φ represents the rotational position or rotational angle of the rotor 23, and ψ represents the rotational speed of the rotor 23.

[0065] FIG. 8 is a schematic functional block diagram of the actuator 10 according to the present embodiment including two stators 21 and 22 as shown in FIG. 6. As described above, the first stator 21 and the second stator 22 commonly rotate a single rotor 23. However, the motor 20 may be interpreted as including two motors, a first motor constituted by the first stator 21 and the rotor 23, and a second motor constituted by the second stator 22 and the rotor 23. Note that the rotor 23 may also be divided into a first rotor rotated by the first stator 21 and a second rotor rotated by the second stator 22. However, in this case, the first rotor and the second rotor are configured such that their respective rotational powers can be transmitted to each other and they rotate in conjunction with each other.

[0066] The first inverter device 10A that applies a first control signal to the first stator 21 converts the power supplied from a DC or AC power supply P into an AC first control signal. The first inverter device 10A may be configured in the same manner as the actuator 10 (particularly, the inverter 13) in FIG. 4. The first motor control unit 61 as the first controller that controls the first inverter device 10A causes the drivers 135 of each phase in the inverter 13 of the first inverter device 10A to perform complementary switching control of the transistor pairs 134 of each phase as described above. As a result, for example, sinusoidal AC voltages V U , V V , V W as shown in FIG. 5 are applied to the coils of each phase of the first stator 21 including three-phase coils 20U, 20V, and 20W as in FIG. 7.

[0067] As will be described later, the first motor control unit 61, the first inverter device 10A, and the first stator 21 are exclusively used for driving the rotor 23 to rotate. For this reason, commands such as the rotational position, rotational speed, rotational torque, and motor current related to the rotational drive of the rotor 23 (hereinafter collectively referred to as rotational drive commands) are input to the first motor control unit 61 as target data or command data. In response to this target data, the first motor measurement unit 51 acquires measurement data or current data such as the current position, current speed, current torque, and current motor current of the rotor 23 from the first stator 21 and / or the rotor 23 and provides it to the first motor control unit 61. The first motor control unit 61 calculates the deviations between the input corresponding target data and each measurement data, and controls the drivers 135 of each phase in the first inverter device 10A so as to reduce each of these deviations.

[0068] A second inverter device 10B that applies a second control signal to a second stator 22 converts the power supplied from a DC or AC power supply P into a second control signal that is AC. The second inverter device 10B may be configured in the same manner as the actuator 10 (particularly, the inverter 13) in FIG. 4. However, as will be described later, since the second stator 22 may include a smaller number of phase coils, for example, a single-phase coil, than the first stator 21 that includes three-phase coils 20U, 20V, and 20W, the number of phases of the inverter 13 in the second inverter device 10B is also adjusted accordingly.

[0069] A second motor control unit 62 as a second controller that controls the second inverter device 10B causes the driver 135 of each phase in the inverter 13 of the second inverter device 10B to perform complementary switching control of the transistor pair 134 of each phase as described above. As a result, a sinusoidal AC voltage of each phase as shown in FIG. 5 is applied to each phase coil of the second stator 22 that includes at least one phase coil.

[0070] As will be described later, the second motor control unit 62, the second inverter device 10B, and the second stator 22 are used for different purposes according to the control mode applied by the control mode switching unit 70. For this reason, commands such as the target position, target speed, target torque, and target motor current of the rotor 23 according to the applied control mode are input to the second motor control unit 62 as target data or command data. Corresponding to this target data, the second motor measurement unit 52 acquires measurement data or current data such as the current position, current speed, current torque, and current motor current of the rotor 23 from the second stator 22 and / or the rotor 23 and provides it to the second motor control unit 62. The second motor control unit 62 calculates the deviations between the input corresponding target data and each measurement data, and controls the driver 135 of each phase in the second inverter device 10B so as to reduce each deviation.

[0071] The first motor control unit 61 and the second motor control unit 62 as described above cooperate to control the first stator 21 and the second stator 22 according to the control mode applied by a control mode switching unit 70 described later. For this reason, it is preferable that the first motor control unit 61 and the second motor control unit 62 are configured to be able to share their respective control states with each other. Alternatively, the first motor control unit 61 and the second motor control unit 62 may be configured as an integrated motor control unit for the first stator 21 and the second stator 22.

[0072] The control mode switching unit 70 switches the control mode or the operation mode of the actuator 10, particularly the second motor control unit 62, according to the rotational drive command provided to the first motor control unit 61. Examples of the control mode include a first control mode or a vibration damping mode in which a first control signal for rotationally driving the rotor 23 is applied to the first stator 21, and a second control signal for damping the vibration applied to the joint 110-170 of the motor 20 or the robot arm 1 provided therewith is applied to the second stator 22; a second control mode or a torque enhancement mode in which magnetic fields for rotationally driving the rotor 23 in the same direction are generated in the first stator 21 and the second stator 22; and a third control mode or a stationary state maintenance mode in which torques in opposite directions are generated in the first stator 21 and the second stator 22 to maintain the rotor 23 in a stationary state.

[0073] FIG. 9 schematically shows the torque over time generated by the first stator 21 and the second stator 22 with respect to the rotor 23 in the first control mode or the vibration damping mode.

[0074] In the first control mode, for example, a three-phase alternating voltage V in a sine wave shape as shown in FIG. 5 is applied to the three-phase coils 20U, 20V, and 20W of the first stator 21. U , V V , V W(The first control signal) is applied. As a result, as shown in FIG. 9, the first stator 21 generates a relatively large positive-direction first torque with the rotor 23. This positive-direction rotational drive torque follows the torque command (rotational drive command) given to the first motor control unit 61 in FIG. 8. When the torque command varies over time according to the operation to be performed on each joint 110 to 170 where each motor 20 is provided, the first torque generated by the first stator 21 with the rotor 23 also varies adaptively as shown in FIG. 9.

[0075] In the first control mode, a sinusoidal AC voltage (second control signal) is applied to, for example, one-phase coils of the second stator 22. Here, the second control signal generates a second torque (small in the negative direction) in the opposite direction that is smaller than the first torque (large in the positive direction) generated by the rotor 23 according to the first control signal applied to the first stator 21. As a result, as shown in FIG. 9, the second stator 22 generates a relatively small negative-direction second torque with the rotor 23.

[0076] This negative-direction second torque is applied to the rotor 23 to attenuate the vibration applied to the motor 20 or joints 110 to 170. For example, external vibrations or external forces are applied to joints 110 to 170 of the robot arm 1 from other moving joints 110 to 170 and the like, but by constantly applying a second torque in the direction opposite to the first torque for normal rotational drive, such undesirable external vibrations and the like can be effectively suppressed. The "soft" joints 110 to 170 where the flexibility imparting section as described above may be provided are easily affected by external vibrations and the like, so the vibration attenuation by the second torque is particularly effective in a collaborative robot.

[0077] As shown in FIG. 9, the magnitude of the second torque may be set to be constant over time. In this case, a negative torque command (vibration damping command) of a constant magnitude is given to the second motor control unit 62 in FIG. 8. Note that, based on the external force and external vibration detected by the force sensor provided together with the motor 20 at the joints 110 to 170 as described above, the magnitude of the torque command as a vibration damping command for damping it may be adaptively adjusted.

[0078] Note that, by applying the second torque in the negative direction, the net (total) torque in the positive direction for the rotational drive of the rotor 23 is offset (decreased) in the negative direction. In order to reduce this influence, the first torque for the rotational drive of the rotor 23 may be offset (increased) in the positive direction by the same amount (absolute value) as the second torque.

[0079] Also, since the magnitude (absolute value) of the second torque generated by the second stator 22 in the rotor 23 in the first control mode is smaller than the magnitude of the first torque generated by the first stator 21 in the rotor 23, the number of phases of the coils in the second stator 22 may be less than the number of phases of the coils in the first stator 21. For example, as shown in FIG. 7, when the number of phases of the coils in the first stator 21 is 3, the number of phases of the coils in the second stator 22 may be 1 or 2. However, in the second control mode and the third control mode described later, when it is desired to generate substantially the same magnitude of torque in the rotor 23 by the first stator 21 and the second stator 22, it is preferable that the number of phases of the coils in the first stator 21 and the second stator 22 be equal. For example, both the first stator 21 and the second stator 22 may be provided with three-phase coils 20U, 20V, and 20W as shown in FIG. 7.

[0080] FIG. 10 schematically shows the torque over time generated by the first stator 21 and the second stator 22 in the rotor 23 in the second control mode or the torque enhancement mode.

[0081] In the second control mode, three-phase AC voltages V, V, V of substantially the same phase in a sine wave shape as shown in FIG. 5 are applied to, for example, the three-phase coils 20U, 20V, 20W of both the first stator 21 and the second stator 22. For example, as shown in FIG. 10, the first stator 21 generates a relatively large positive first torque in the same manner as in FIG. 9 in the first control mode by the rotor 23. Further, in the second control mode, the second stator 22 generates a second torque in the same positive direction as the first torque by the rotor 23. U , V V , V W are applied. For example, as shown in FIG. 10, the first stator 21 generates a relatively large positive first torque in the same manner as in FIG. 9 in the first control mode by the rotor 23. Further, in the second control mode, the second stator 22 generates a second torque in the same positive direction as the first torque by the rotor 23.

[0082] When the second stator 22 has a driving ability equivalent to that of the first stator 21, as shown in FIG. 10, the rotor 23 may generate a second torque substantially equal to the first torque. On the other hand, when the second stator 22 has a lower driving ability than the first stator 21, the second torque becomes smaller than the first torque. In any case, since a second torque in the same direction as the first torque is additionally generated, the net (total) torque in the positive direction for the rotational driving of the rotor 23 is offset (increased) in the positive direction. Thus, in the second control mode, the torque generated by the rotor 23 is enhanced by the second stator 22.

[0083] In the example of FIG. 10, in order to obtain a substantially doubled total torque by substantially the same first torque and second torque, substantially the same torque commands (rotational driving commands) are given to the first motor control unit 61 and the second motor control unit 62 in FIG. 8. Each torque command causes a torque that is half of the desired total torque to be generated in each of the first stator 21 and the second stator 22.

[0084] FIG. 11 schematically shows the torque generated by the first stator 21 and the second stator 22 over time in the third control mode or the stationary state maintenance mode.

[0085] In the third control mode, the first torque generated by the first stator 21 in the rotor 23 and the second torque generated by the second stator 22 in the rotor 23 are in opposite directions and have substantially equal magnitudes (absolute values). In the example of FIG. 11, the first stator 21 generates a first torque with a constant magnitude in the positive direction in the rotor 23, and the second stator 22 generates a second torque with a magnitude equal to that of the first torque in the negative direction in the rotor 23. Since the magnitudes of the first torque and the second torque in opposite directions are equal, the net (total) torque generated in the rotor 23 is substantially 0. Therefore, the rotor 23 stops rotating and remains stationary.

[0086] Although the rotor 23 is in a stationary state in this way, in reality, since positive and negative torques that oppose each other are applied to the rotor 23, even if external vibrations or external forces from other moving joints 110 to 170 are applied to the rotor 23, the stationary state of the rotor 23 is surely maintained. "Soft" joints 110 to 170 where a flexibility imparting portion as described above may be provided are easily affected by external vibrations and the like. Therefore, maintaining the stationary state by the first torque and the second torque is particularly effective in a collaborative robot.

[0087] In the example of FIG. 11, in order to obtain a total torque of substantially 0 by the first torque and the second torque with substantially the same magnitude in opposite directions, the first motor control unit 61 and the second motor control unit 62 in FIG. 8 are given torque commands (stationary state maintenance commands) with substantially the same magnitude in opposite directions.

[0088] As shown in FIG. 11, the magnitudes of the first torque and the second torque may be set to be constant over time. In this case, torque commands with constant magnitudes are given to the first motor control unit 61 and the second motor control unit 62 in FIG. 8, respectively. Note that, based on the external force and external vibration detected by the force sensor provided in parallel with the motor 20 in the joints 110 to 170 as described above, the magnitude of the torque command as a stationary state maintenance command for resisting them may be adaptively adjusted.

[0089] FIG. 12 schematically shows an example in which the control mode switching unit 70 switches the second motor control unit 62 among the first to third control modes as described above in response to the rotational drive command provided to the first motor control unit 61. In this figure, the vertical axis represents the torque to be generated by the rotor 23 (for example, the sum of the first torque and the second torque), and the horizontal axis represents the speed at which the rotor 23 should rotate. When the torque command on the vertical axis is less than a predetermined torque threshold, the control mode switching unit 70 operates the second motor control unit 62 in the first control mode (vibration damping mode), and when the torque command is equal to or greater than the torque threshold, the control mode switching unit 70 operates the second motor control unit 62 in the second control mode (torque enhancement mode).

[0090] As described above, when the required torque at the rotor 23 is small, external vibrations and the like can be effectively suppressed by the second stator 22 under the first control mode (FIG. 9). On the other hand, when the required torque at the rotor 23 is large, torque for rotational drive can also be obtained from the second stator 22 under the second control mode (FIG. 10). Note that in the second control mode, the vibration damping effect by the second stator 22 as in the first control mode cannot be obtained, but since a large torque is applied to the rotor 23 in the second control mode, it is in a state where it is hardly affected by external vibrations and the like. In this way, the rotor 23 has resistance to external vibrations and the like through the first control mode with relatively small torque and the second control mode with relatively large torque.

[0091] When the torque command on the vertical axis and the speed command on the horizontal axis are substantially 0, the control mode switching unit 70 operates the second motor control unit 62 in the third control mode (stationary state maintenance mode). Typically, when the torque command and / or the speed command for which the first control mode was applied change from a state where they are not 0 to 0, the control mode switching unit 70 switches the second motor control unit 62 from the first control mode to the third control mode.

[0092] The above has been described based on embodiments. It is obvious to those skilled in the art that various modifications are possible for the combination of each component and each process in the exemplary embodiments, and such modifications are included in the scope of the present disclosure.

[0093] FIG. 13 shows a modification example of the stators 21 and 22 in FIG. 7. In the example of FIG. 7, the first stator 21 and the second stator 22 were each constituted by a three-phase coil as shown in FIG. 7. In contrast, in the example of FIG. 13, substantially one stator 2 is constituted by, for example, a six-phase coil. Among this six-phase coil, the three-phase coils 20U1, 20V1, 20W1 function as the three-phase coil in the first stator 21, and the three-phase coils 20U2, 20V2, 20W2 function as the three-phase coil in the second stator 22.

[0094] Similar to the example of FIG. 8, a control signal from the first inverter device 10A is applied to the three-phase coils 20U1, 20V1, 20W1 (the first stator 21) under the control of the first motor control unit 61, and a control signal from the second inverter device 10B is applied to the three-phase coils 20U2, 20V2, 20W2 (the second stator 22) under the control of the second motor control unit 62. As shown in the figure, the three-phase coils 20U1, 20V1, 20W1 equivalent to the first stator 21 and the three-phase coils 20U2, 20V2, 20W2 equivalent to the second stator 22 are preferably arranged alternately along the circumferential direction of the rotor 23. Thus, according to this modification example, the functions of the first stator 21 and the second stator 22 can be realized by a single stator 2.

[0095] As described above, the second stator 22 may be constituted by, for example, a single-phase coil. The single stator 2 in FIG. 13 corresponding to such a case is constituted by a four-phase coil including three-phase coils 20U1, 20V1, 20W1 equivalent to the first stator 21 and a single-phase coil (for example, 20U2) equivalent to the second stator 22. Further, the single stator 2 may be constituted by substantially three-phase coils 20U, 20V, 20W similar to those in FIG. 7. In this case, two control signals of corresponding phases (for example, U phase) in the first inverter device 10A and the second inverter device 10B in FIG. 8 are applied in a superimposed manner to the coils of each phase (for example, 20U) in the single stator 2. The AC voltage applied to the coil of each phase in this case may be distorted from a sine wave as shown in FIG. 5.

[0096] In the above description, the coils are provided on the stators 2, 21, 22, and the permanent magnet 231 is provided on the rotor 23. However, the permanent magnet 231 may be provided on the inner peripheral side of the stators 2, 21, 22, and the coils may be provided on the outer peripheral side of the rotor 23.

[0097] Note that the configurations, operations, and functions of the devices and methods described in the embodiments can be realized by hardware resources or software resources, or by the cooperation of hardware resources and software resources. As the hardware resources, for example, a processor, a ROM, a RAM, and various integrated circuits can be used. As the software resources, for example, programs such as an operating system and an application can be used.

Explanation of Reference Numerals

[0098] 1 Robot arm, 2 Stator, 10 Actuator, 13 Inverter, 20 Motor, 21 First stator, 22 Second stator, 23 Rotor, 24 Rotation axis, 30 Connecting device, 32 Control board, 34 Reducer, 51 First motor measurement unit, 52 Second motor measurement unit, 61 First motor control unit, 62 Second motor control unit, 66 Motor housing, 70 Control mode switching unit, 231 Permanent magnet.

Claims

1. An actuator comprising a motor and a controller for controlling the motor, The controller is operable in a first control mode to apply a first control signal for rotationally driving the motor and a second control signal for attenuating vibrations applied to the motor to the motor. Actuator.

2. The motor includes a stator that generates a magnetic field when the first control signal and the second control signal are applied in the first control mode, and a rotor that is rotatable with respect to the stator in response to the magnetic field. The stator includes a first stator to which the first control signal is applied and a second stator to which the second control signal is applied. The actuator according to claim 1.

3. The first stator includes at least three-phase coils. The second stator has at least one-phase coil and is below the first stator. The actuator according to claim 2.

4. In the first control mode, the controller generates, in the rotor, a second torque in the opposite direction that is smaller than a first torque generated in the rotor according to the first control signal, according to the second control signal. The actuator according to claim 2.

5. The controller is operable in a second control mode to generate a magnetic field for rotationally driving the rotor in the same direction in the first stator and the second stator. The actuator according to any one of claims 2 to 4.

6. The first stator and the second stator each include three-phase coils. The actuator according to claim 5.

7. When the torque to be generated by the rotor is less than a predetermined torque threshold, the controller operates in the first control mode, and when the torque to be generated by the rotor is greater than or equal to the torque threshold, the controller operates in the second control mode. The actuator according to claim 5.

8. The controller is operable in a third control mode to generate torques in opposite directions in the first stator and the second stator to maintain the rotor in a stationary state. The actuator according to any one of claims 2 to 4.

9. The first stator and the second stator are fixed to a single motor housing. The rotor includes a single rotating shaft rotatable around an axial direction within the motor housing, and a magnet that is fixed to the rotating shaft and acts on a magnetic field generated by the first stator and the second stator on the outer peripheral side. The actuator according to any one of claims 2 to 4.

10. In the axial direction, the length of the first stator is greater than the length of the second stator. The actuator according to claim 9.

11. The first stator and the second stator are provided at different positions in the axial direction. The actuator according to claim 9.

12. A robot arm including a plurality of joints rotationally driven by a motor, The controller for controlling the motor in at least one of the joints is operable in a first control mode to apply a first control signal for rotationally driving the motor and a second control signal for attenuating vibrations applied to the joint to the motor. Robot arm.

Images