Drive device

Abstract

To provide a drive device capable of highly accurate collision detection.SOLUTION: A motor includes: a decelerator having a high deceleration ratio and having back drivability; an arm fixed to a spindle; and a control circuit that generates a current instruction value of the motor. The control circuit includes: a velocity instruction value generation part that generates an angular velocity instruction value with respect to the arm; and a speed control part that generates a current instruction value of the motor on the basis of the angular velocity instruction value; and a disturbance observer that estimates an estimate value of an external torque applied to the arm on the basis of the current instruction value, an angular velocity of the arm, and an angular velocity of the motor. If an estimate value τL_est of the external torque exceeds a predetermined threshold τL_th, the velocity instruction value generation part sets an angular velocity instruction value ωL_ref to zero.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a drive device. [Background technology]

[0002] For example, an actuator combining a reducer and a motor is used as a drive device that constitutes the joint drive system of an industrial robot. In such a drive device, a reducer with a high reduction ratio of about 50:1 to 200:1 is used to obtain the torque required for the joint operation of the robot.

[0003] In collaborative robot systems where humans and robots share a workspace, improving backdrivability (ability to drive joints by external forces) is desirable from the perspective of avoiding danger from contact with humans. Generally, a reducer with a high reduction ratio reduces backdrivability. As a result, the backdrivability of the drive device tends to decrease. Patent Document 1 listed below discloses a technology that quickly starts backdriving (reaction force reduction operation in response to external forces) without switching control modes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-49852 Summary of the Invention [Problem to be solved by the invention]

[0005] The above-described conventional technology is a configuration for improving backdrivability in a drive system with low backdrivability by torque feedback control using an estimated value of external torque and an estimated value of angular transmission error disturbance. In a configuration using a reducer with low backdrivability, if a threshold is set for the estimated value of external torque to detect a collision, an error may occur in the torque estimation value due to the low backdrivability efficiency of the reducer, which may reduce the accuracy of collision detection.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a drive device capable of detecting a collision with high accuracy. [Means for solving the problem]

[0007] In order to achieve the above object, a drive device according to one aspect of the present invention includes a motor, a reducer that reduces the rotational speed of the motor and outputs the reduced rotational speed to a spindle, an arm fixed to the spindle, and a control circuit that generates a current command value for the motor, wherein the control circuit includes a speed command value generation unit that generates an angular velocity command value for the arm, a speed control unit that generates the current command value based on the angular velocity command value, and a disturbance observer that estimates an external torque applied to the arm based on the current command value, the angular velocity of the arm, and the angular velocity of the motor, and the speed command value generation unit sets the angular velocity command value to zero when the estimated value of the external torque exceeds a predetermined threshold.

[0008] The above configuration enables highly accurate detection of a collision with the arm. Furthermore, when a collision occurs, the drive of the arm by the motor (forward drive) is stopped, ensuring safety.

[0009] As a desirable aspect of the drive device, it is preferable that the drive device comprises a motor angle detection unit that detects a rotation angle of the motor, and a main shaft angle detection unit that detects a rotation angle of the arm, and that the disturbance observer calculates the angular velocity of the arm by performing pseudo-differentiation on the rotation angle of the arm, and calculates the angular velocity of the motor by performing pseudo-differentiation on the rotation angle of the motor.

[0010] This avoids a sudden differential kick, improving controllability.

[0011] In a preferred embodiment of the driving device, the disturbance observer preferably compensates for a gravitational torque component of the arm when estimating the estimated value of the external torque.

[0012] This improves the accuracy of estimating the external torque.

[0013] In a preferred embodiment of the driving device, the disturbance observer preferably compensates for a friction torque component of the motor when estimating the estimated value of the external torque.

[0014] This improves the accuracy of estimating the external torque.

[0015] As a desirable aspect of the drive device, it is preferable that the reducer includes a plurality of first planetary gears each rotatable around a plurality of planetary axes that are arranged at equal intervals around the axis; a plurality of second planetary gears each rotatable around the planetary axes, each having a smaller diameter and fewer teeth than the first planetary gears, and formed integrally with the first planetary gears to rotate together; a sun gear centered on the axis and meshing with the first planetary gears radially inward of the planetary axes; a first internal gear ring-shaped about the axis and meshing with the first planetary gears radially outward of the planetary axes; and a second internal gear ring-shaped about the axis and meshing with the second planetary gear radially outward of the planetary axes.

[0016] This enables highly accurate detection of collisions with the arm due to the high power transmission efficiency (back drive efficiency) of the reducer. In addition, when a collision occurs, the arm drive (forward drive) by the motor stops, and the high back drivability (reverse driveability) of the reducer ensures safety. [Effects of the Invention]

[0017] According to the present invention, a drive device capable of detecting a collision with high accuracy can be obtained. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating an example of a schematic configuration of a drive device according to an embodiment. [Figure 2]FIG. 2 is a cross-sectional view illustrating an example of the configuration of the drive module. [Figure 3] FIG. 3 is a conceptual diagram showing the configuration of the drive module. [Figure 4] FIG. 4 is an exploded perspective view illustrating a configuration example of a reducer of a drive device according to an embodiment. [Figure 5] FIG. 5 is a diagram showing a specific example of an evaluation environment for a reducer. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a control circuit of a drive device according to an embodiment. [Figure 7] FIG. 7 is a diagram showing an example of a block diagram including a control circuit and a controlled object. [Figure 8] FIG. 8 is a flowchart showing a specific example of the process in the speed command value generating unit. [Figure 9A] FIG. 9A is a conceptual diagram showing a change in reaction torque when a collision occurs. [Figure 9B] FIG. 9B is a conceptual diagram showing a change in reaction torque when a collision occurs. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments. Furthermore, the components in the following embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the following embodiments can be combined as appropriate.

[0020] 1 is a diagram showing an example of the schematic configuration of a drive device according to an embodiment. The drive device 1 according to the embodiment is applied to devices such as collaborative robots, power-assisted suits, wheel drives for mobile robots, and haptic devices. In this embodiment, as an example, a configuration will be described in which a drive module 50 is fixed to a fixed member 21, and an arm (e.g., a robot arm) 22 provided on the drive module 50 is rotated and moved.

[0021] Fig. 2 is a cross-sectional view showing an example of the configuration of a drive module. Fig. 3 is a conceptual diagram showing the configuration of a drive module. As shown in Figs. 2 and 3, a drive module 50 includes a housing 2, a motor 3, a motor output shaft 4, a reducer 5, a reducer input shaft 6, a connecting unit 7, a main shaft 8, a motor angle detection unit 9, a main shaft angle detection unit 10, a braking unit 11, and a control board 12. The drive device 1 according to the embodiment is configured by fixing an arm 22 to the main shaft 8.

[0022] The housing 2 is composed of a housing main portion 2A and a cover portion 2B. The housing main portion 2A is formed in a generally cylindrical shape and accommodates therein the motor 3, a portion of the motor output shaft 4, the reducer 5, the reducer input shaft 6, the connecting portion 7, and a portion of the main shaft 8. In this embodiment, the housing main portion 2A is fixed to a fixing member 21. The cover portion 2B is fixed to the housing main portion 2A with a screw 13A so as to close one opening of the cylindrical shape of the housing main portion 2A. The cover portion 2B is formed in a generally cup shape and accommodates therein a portion of the motor output shaft 4, a portion of the main shaft 8, the motor angle detection portion 9, the main shaft angle detection portion 10, the braking portion 11, and the control board 12.

[0023] The motor 3 includes a motor case 3A, a rotor 3B, and a stator 3C.

[0024] The motor case 3A is fixed to the main housing portion 2A with screws 13B. The rotor 3B is made of a permanent magnet, and a motor output shaft 4 is attached to a support member 3Ba that supports the permanent magnet. The stator 3C has a coil (not shown) and is attached to the motor case 3A. Therefore, when current is applied to the coil of the stator 3C, the rotor 3B rotates, causing the motor output shaft 4 to rotate about the axis CL. In the example shown in FIG. 2, the motor 3 is an outer rotor type motor in which the permanent magnet of the rotor 3B is provided on the outer periphery of the stator 3C. In addition, in the example shown in FIG. 3, the motor 3 is an inner rotor type motor in which the permanent magnet of the rotor 3B is provided on the inner periphery of the stator 3C. The motor 3 used in the drive device 1 of the present disclosure may be an outer rotor type motor as shown in FIG. 2 or an inner rotor type motor as shown in FIG. 3.

[0025] The motor output shaft 4 is provided in the housing 2, extending along the axis CL so as to straddle the housing main portion 2A and the cover portion 2B. The motor output shaft 4 is centered on the axis CL. The motor output shaft 4 is formed in a hollow cylindrical shape with a through hole 4A provided along the axis CL.

[0026] 4 is an exploded perspective view showing an example of the configuration of a reducer of a drive device according to an embodiment. The reducer 5 reduces the rotational speed input via a reducer input shaft 6 and outputs the reduced rotational speed to a main shaft 8. In this embodiment, the reducer 5 constitutes a planetary gear mechanism. As shown in FIG. 4, the reducer 5 mainly includes a reducer case 5A, a carrier 5B, a first planetary gear 5C, a second planetary gear 5D, a sun gear 5E, a first internal gear 5F, a second internal gear 5G, and an output shaft portion 5H.

[0027] The reducer case 5A is fixed to the housing main portion 2A with screws 13C. The reducer case 5A includes a reducer case main portion 5Aa and a reducer case cover portion 5Ab. The reducer case main portion 5Aa is formed in a cylindrical shape and houses the carrier 5B, the first planetary gear 5C, the second planetary gear 5D, the sun gear 5E, the first internal gear 5F, the second internal gear 5G, and the output shaft portion 5H. The reducer case cover portion 5Ab is formed in a disk shape with a hole through its center and is provided in one opening of the cylindrical shape of the reducer case main portion 5Aa. The other opening of the cylindrical shape of the reducer case main portion 5Aa is provided so that the reducer input shaft 6 passes through it.

[0028] The carrier 5B is rotatably mounted on the reducer input shaft 6 via a bearing 5I around the axis CL. The carrier 5B has a support shaft 5Ba that rotatably supports the first planetary gear 5C and the second planetary gear 5D. The support shaft 5Ba defines a planetary axis C that is parallel to the axis CL. The support shaft 5Ba, the first planetary gear 5C, and the second planetary gear 5D are provided at multiple locations (e.g., three locations) at equal intervals around the axis CL.

[0029] The first planetary gear 5C and the second planetary gear 5D are rotatably mounted on a support shaft 5Ba of the carrier 5B via a bearing 5J around a planetary axis C. The first planetary gear 5C and the second planetary gear 5D are integrally mounted and rotate together. The first planetary gear 5C has a larger diameter and more teeth than the second planetary gear 5D.

[0030] The sun gear 5E is provided around the axis CL on the outer periphery of the reducer input shaft 6. The sun gear 5E meshes with the first planetary gear 5C on the radially inner side of the planetary axis C (the side closer to the axis CL).

[0031] The first internal gear 5F is provided in a ring shape around the axis CL on the inner periphery of the reducer case 5A (reduction gear case main part 5Aa). The first internal gear 5F meshes with the first planetary gear 5C on the radially outer side of the planet axis C (the side farther from the axis CL).

[0032] The second internal gear 5G is provided in a ring shape around the axis CL on the outer periphery of the output shaft portion 5H. The second internal gear 5G meshes with the second planetary gear 5D on the radially outer side of the planet axis C (the side farther from the axis CL).

[0033] The output shaft 5H is rotatably mounted on the reducer case 5A (reduction gear case cover 5Ab) about the axis CL via a bearing 5K. The output shaft 5H is also rotatably mounted on the carrier 5B about the axis CL via a bearing 5L. The main shaft 8 is fixed to the output shaft 5H with a screw 13D.

[0034] Therefore, the first rotation about the axis CL is input to the reducer 5 via the reducer input shaft 6. The first rotation is transmitted to the reducer 5 as a second rotation of the first planetary gear 5C about the planetary axis C due to the meshing of the sun gear 5E of the reducer input shaft 6 with the first planetary gear 5C. The first planetary gear 5C supports the second rotation by meshing with the first internal gear 5F. The reducer 5 transmits the second rotation to the second planetary gear 5D, which is integral with the first planetary gear 5C, as a third rotation. The reducer 5 transmits the third rotation to the output shaft 5H via the second internal gear 5G due to the meshing of the second planetary gear 5D with the second internal gear 5G. Because the first planetary gear 5C has a larger number of teeth than the second planetary gear 5D, the rotational speed of the fourth rotation transmitted from the output shaft 5H to the main shaft 8 is reduced compared to the first rotation.

[0035] 2, the reducer input shaft 6 is provided in the housing main portion 2A of the housing 2. The reducer input shaft 6 is provided with a central axis CL as its center. The reducer input shaft 6 is formed in a hollow cylindrical shape with a through hole 6A provided along the central axis CL.

[0036] As shown in FIGS. 2 and 3 , the connecting portion 7 connects the motor output shaft 4 and the reducer input shaft 6. In this embodiment, the connecting portion 7 is formed of a spline formed by meshing of gear-shaped concave and convex portions. In this embodiment, the connecting portion 7 is formed by a spline shaft formed on the motor output shaft 4 and a spline hole formed on the reducer input shaft 6. The connecting portion 7 may also be formed by a spline hole formed on the motor output shaft 4 and a spline shaft formed on the reducer input shaft 6. Preferably, the connecting portion 7 is formed by an involute spline, which is more accurate and capable of transmitting greater torque. The connecting portion 7 may also be formed by a key and a keyway. In this case, for example, the connecting portion 7 may be formed by a key formed on the motor output shaft 4 and a keyway formed on the reducer input shaft 6. Alternatively, the connecting portion 7 may be formed by a keyway formed on the motor output shaft 4 and a key formed on the reducer input shaft 6. In this way, the connecting portion 7 enables the motor output shaft 4 and the reducer input shaft 6 to be coupled or separated from each other. Therefore, the motor output shaft 4 and the reducer input shaft 6, which are connected by the connecting portion 7, are arranged coaxially with the axis CL. Note that the connecting portion 7 can also be configured to connect the motor output shaft 4 and the reducer input shaft 6 with screws.

[0037] Here, in the drive unit 1, when the coupling portion 7 is configured with a spline, an involute spline, or a key and key groove, the motor output shaft 4 and the reducer input shaft 6 can be coupled or separated by mutual movement in the direction along the axis CL (axial direction). However, since the coupling is released when the motor output shaft 4 and the reducer input shaft 6 are moved away from each other in the axial direction, in the drive unit 1 of the embodiment, the axial movement of the motor output shaft 4 is restricted by fixing the motor 3 to the housing main part 2A with screws 13B, and the axial movement of the reducer input shaft 6 is restricted by fixing the reducer 5 to the housing main part 2A with screws 13C, thereby maintaining the coupling of the coupling portion 7.

[0038] As shown in FIG. 2, the main shaft 8 is provided in the housing 2, extending along the axis CL so as to straddle the housing main portion 2A and the cover portion 2B. The main shaft 8 is inserted through the through hole 4A of the motor output shaft 4 and the through hole 6A of the reducer input shaft 6, and is provided coaxially with the motor output shaft 4 and the reducer input shaft 6, with the axis CL at its center. The main shaft 8 is formed into a hollow cylindrical shape with a through hole 8A provided along the axis CL. One end of the main shaft 8 is fixed to the output shaft portion 5H in the housing main portion 2A and rotatably supported together with the output shaft 5H via bearings 5K and 5L. A coupling 8B is detachably provided on the other end, and is rotatably supported in the cover portion 2B via a bearing 14A provided in a fixing member 14 arranged inside the cover portion 2B.

[0039] 2, motor angle detector 9 is provided on motor output shaft 4 and detects the rotation angle of motor output shaft 4. Motor angle detector 9 is provided on the portion of motor output shaft 4 that is housed in cover portion 2B, and is housed in cover portion 2B.

[0040] As shown in Fig. 2, the spindle angle detection unit 10 is provided on the spindle 8 and detects the rotation angle of the spindle 8. The spindle angle detection unit 10 is provided on the part of the spindle 8 that is housed in the cover portion 2B, and is housed in the cover portion 2B.

[0041] The brake unit 11 brakes the motor output shaft 4. As shown in FIG. 2, the brake unit 11 includes an actuator 11A and a brake disc 11B. The actuator 11A is attached to a fixing member 14 arranged inside the cover unit 2B and is housed in the cover unit 2B. The brake disc 11B is attached to the motor output shaft 4 extending inside the cover unit 2B and rotates together with the motor output shaft 4. When the actuator 11A operates, the brake unit 11 suppresses the rotation of the brake disc 11B and brakes the motor output shaft 4.

[0042] Control board 12 receives detection signals from motor angle detector 9 and main shaft angle detector 10, and also has a control circuit mounted thereon for driving motor 3 and braking unit 11. As shown in FIG. 2, control board 12 is attached to a fixing member 14 disposed inside cover 2B and is housed in cover 2B. A cable 15 connected to the outside of drive unit 1 is also connected to control board 12. Cable 15 is inserted through through hole 8A of main shaft 8 and drawn out to the outside of housing 2.

[0043] In the drive device 1 according to the first embodiment having the above-described configuration, the reducer 5 has a high reduction ratio (for example, about 100:1), and both the forward drive efficiency and the reverse drive efficiency are high (for example, 90% or more), resulting in high backdrivability (reverse driveability: driveability by external force). Here, the evaluation environment for the power transmission efficiency of the reducer will be described with reference to Fig. 5. Fig. 5 is a diagram showing a specific example of the evaluation environment for the reducer.

[0044] 5 , evaluation environment 1000 includes a measuring device 1100 configured with a data logger, a meter controller, a PC, etc., a motor 1011, a drive-side rotating shaft 1012, a drive-side encoder 1013, a drive-side torque sensor 1014, a load-side rotating shaft 1031, a load-side torque sensor 1032, a load-side encoder 1033, and a powder brake 1034. The motor 1011, the drive-side rotating shaft 1012, the drive-side encoder 1013, the drive-side torque sensor 1014, the load-side rotating shaft 1031, the load-side torque sensor 1032, the load-side encoder 1033, and the powder brake 1034 are provided on a base plate 1001.

[0045] When a motor 1011 rotates in the evaluation environment 1000 shown in FIG. 5, a drive-side rotating shaft 1012 is rotationally driven by torque from the motor 1011 and rotates at the same rotation angle as the motor 1011.

[0046] The drive-side rotating shaft 1012 transmits torque from the motor 1011 to the drive-side torque sensor 1014, the drive-side encoder 1013, and the drive-side gear of the reducer 1020 to be evaluated.

[0047] The torque transmitted from the motor 1011 to the drive-side rotating shaft 1012 causes the drive-side gear of the reducer 1020 under evaluation to rotate at the same rotation angle as the motor 1011 and the drive-side rotating shaft 1012. The drive-side torque sensor 1014 detects the torque at the drive-side rotating shaft 1012. The drive-side encoder 1013 detects the rotation angle of the drive-side rotating shaft 1012. The torque at the drive-side rotating shaft 1012 detected by the drive-side torque sensor 1014 corresponds to the drive-side torque of the reducer 1020 under evaluation. The rotation angle of the drive-side rotating shaft 1012 detected by the drive-side encoder 1013 corresponds to the drive-side rotation angle of the reducer 1020 under evaluation.

[0048] Torque is transmitted from the drive-side gear to the load-side gear of the reducer 1020 under evaluation, and the torque is then transmitted from the load-side gear of the reducer 1020 to the load-side rotating shaft 1031, causing the load-side rotating shaft 1031 to rotate. The torque is then transmitted from the load-side rotating shaft 1031 to the load-side torque sensor 1032 and the load-side encoder 1033. The load-side torque sensor 1032 detects the torque at the load-side rotating shaft 1031. The load-side encoder 1033 detects the rotation angle of the load-side rotating shaft 1031. The torque at the load-side rotating shaft 1031 detected by the load-side torque sensor 1032 corresponds to the load-side torque of the reducer 1020 under evaluation. The rotation angle of the load-side rotating shaft 1031 detected by the load-side encoder 1033 corresponds to the load-side rotation angle of the reducer 1020 under evaluation.

[0049] In the evaluation environment 1000 shown in Figure 5, the measuring device 1100 controls the motor 1011 and the powder brake 1034, and based on the detection values of the drive side encoder 1013, the drive side torque sensor 1014, the load side torque sensor 1032, and the load side encoder 1033, can evaluate the torque dependence and rotation speed dependence of the power transmission efficiency (forward driving efficiency, reverse driving efficiency) of the reducer 1020 under test.

[0050] Hereinafter, a description will be given of a control block configuration of the drive device 1 according to the embodiment, which controls the motor 3, the reducer 5, and the arm 22. Fig. 6 is a block diagram showing an example of the configuration of a control circuit of the drive device according to the embodiment.

[0051] As shown in FIG. 6, the control circuit 100 of the drive device 1 according to this embodiment includes a speed command value generating section 200, a speed control section 300, and a disturbance observer 400 as main components.

[0052] The control circuit 100 is configured by, for example, a microcomputer or a programmable logic controller (PLC), and is provided on a control board 12.

[0053] The velocity command value generator 200 generates an angular velocity command value ω L_ref The speed control unit 300 generates the angular speed command value ω L_ref and the angular velocity ω of arm 22 L The motor current command value I ref Generate.

[0054] The disturbance observer 400 estimates disturbance components acting on a controlled object 500 (plant) of the control circuit 100. Fig. 7 is a diagram showing an example of a block diagram including a control circuit and a controlled object. In the controlled object 500 (plant) and each node of the disturbance observer 400 in Fig. 7, "s" indicates differentiation and "1 / s" indicates integration.

[0055] Here, the parameters of the controlled object 500 (Plant) and each node of the disturbance observer 400 in FIG. 7 will be described.

[0056] In Figure 7, J m indicates the moment of inertia of the rotor 3B of the motor 3. K t indicates the torque coefficient of the motor 3. θ m indicates the rotation angle of motor 3. Dm indicates the viscosity coefficient of the motor 3. τ c indicates the Coulomb friction of the motor 3. The rotation angle θ of the motor 3 m is detected by a motor angle detector 9 provided on the motor output shaft 4.

[0057] In addition, in Fig. 7, r indicates the reduction ratio of the reducer 5. η f indicates the forward drive efficiency of the reducer 5. η r indicates the back drive efficiency of the reducer 5. K r indicates the torque coefficient of the reducer 5. τ r indicates the output torque of the reducer 5. b' indicates the backlash of the reducer 5. Each parameter of the reducer 5 is a value determined by various constraints such as state variables such as the number of teeth of each gear constituting the reducer 5 and the reduction ratio, and is evaluated and measured using the evaluation environment 1000 described above.

[0058] Also, in Figure 7, J L indicates the moment of inertia of the arm 22. M L indicates the mass of the arm 22. g indicates the gravitational acceleration. l g indicates the position of the center of gravity of the arm 22 relative to the axis CL. L indicates the rotation angle of the arm 22 (see FIGS. 2 and 3). L indicates the torque due to an external force applied to the arm 22 (hereinafter also referred to as "external torque"). The rotation angle θ of the arm 22 L is detected by a main shaft angle detection unit 10 provided on the main shaft 8.

[0059] The control circuit 100 holds the above-mentioned parameters in advance. These parameters are used in the respective nodes of the disturbance observer 400 shown in FIG.

[0060] In this disclosure, the disturbance observer 400 calculates the external torque τ applied to the arm 22. L (hereinafter referred to as "estimated external torque")τ L_estSpecifically, the disturbance observer 400 estimates the motor current command value I ref , the angular velocity ω of the arm 22 L , and the angular velocity ω of the motor output shaft 4 m Based on this, the external torque estimate τ L_est Estimate.

[0061] Angular velocity ω of arm 22 L is the rotation angle θ of the arm 22 L It can be obtained by applying a pseudo differentiator with the transfer characteristic shown in the following equation (1) to G vl indicates the gain of the pseudo differentiator shown in the following equation (1).

[0062] sG vl / (s+G vl )···(1)

[0063] Angular velocity ω of motor output shaft 4 m is the rotation angle θ of the motor output shaft 4 m It can be obtained by applying a pseudo differentiator with the transfer characteristic shown in the following equation (2) to G vm indicates the gain of the pseudo differentiator shown in the following equation (2).

[0064] sG vm / (s+G vm )···(2)

[0065] The disturbance observer 400 includes a first-order LPF (Low Pass Filter). The transfer characteristic of the LPF is expressed by the following equation (3): G fl indicates the gain of the LPF shown in the following equation (3).

[0066] G fl / (s+G fl )···(3)

[0067] In the LPF having the transfer characteristic shown in the above equation (3), it is possible to adjust the disturbance detection band in the disturbance observer 400. Specifically, by increasing the cutoff frequency, it is possible to widen the disturbance detection band to the high frequency side.

[0068] In Figure 7, M L gl g sinθ L indicates the gravitational torque component of the arm 22. Also, D m ω m +τ c indicates the friction torque component of the motor 3. In the present disclosure, the disturbance observer 400 calculates the external torque estimate τ L_est When estimating the gravitational torque component M of the arm 22, L gl g sinθ L and the friction torque component D of motor 3 m ω m +τ c is used as a compensation value. L_est This can improve the estimation accuracy.

[0069] The external torque estimate τ estimated by the disturbance observer 400 L_est is input to the speed command value generating unit 200. Fig. 8 is a flowchart showing a specific example of the processing in the speed command value generating unit.

[0070] The velocity command value generating unit 200 generates an angular velocity command value ω for the arm 22 based on, for example, an external control command. L_ref is generated (step S101).

[0071] In the present disclosure, the speed command value generating unit 200 calculates the external torque estimate τ L_est Threshold τ for L_th The speed command value generating unit 200 stores the external torque estimated value τ L_est is the threshold τ L_th It is determined whether the external torque estimated value τ L_est is the threshold τ L_th If it is equal to or less than this (step S102; Yes), the angular velocity command value ω generated in step S101 is L_ref is output to the speed control unit 300.

[0072] External torque estimate τ L_est is the threshold τ L_th (step S102; No), the velocity command value generating unit 200 calculates the angular velocity command value ω L_ref is set to "0" (step S103), and output to the speed control unit 300, and the process ends.

[0073] As a result, the driving (forward driving) of the arm 22 by the driving of the motor 3 stops, and safety is ensured by the high backdrivability (reverse driving ability) of the reducer 5 of the present disclosure.

[0074] Furthermore, high-accuracy collision detection is possible due to the high power transmission efficiency (reverse drive efficiency) of the reducer 5 of the present disclosure. Figures 9A and 9B are conceptual diagrams showing changes in reaction torque when a collision occurs.

[0075] In the example shown in FIG. 9A and FIG. 9B, at time t c A collision occurs with the arm at time t s 9A and 9B show an example in which the reaction torque due to the collision is saturated. The solid lines shown in Fig. 9A and 9B show the estimated external torque values estimated by the disturbance observer in a configuration that employs the reducer of the present disclosure, and the dashed lines show the estimated external torque values estimated by the disturbance observer in a configuration that employs a reducer with lower backdriving efficiency than the reducer of the present disclosure.

[0076] In Figures 9A and 9B, t d indicates the collision detection time in a configuration employing a reducer with lower reverse drive efficiency than the reducer of the present disclosure, and t d ' indicates the time of collision detection in a configuration employing the reducer of the present disclosure.

[0077] As shown in Figures 9A and 9B, when the reducer of the present disclosure is used, the reaction torque generated upon collision with the arm is larger than when a reducer with low reverse drive efficiency is used, and the external torque estimate value estimated by the disturbance observer rises more quickly.

[0078] FIG. 9A shows an example in which the same collision detection threshold is used in a configuration employing the reducer of the present disclosure and a configuration employing a reducer with lower reverse drive efficiency than the reducer of the present disclosure. In this example, the time lag (t d -t c ) than the time lag (t d '-t c ) can be shortened. In addition, the saturation time t s The clearance of the collision detection threshold for the external torque estimation value estimated thereafter (the area indicated by diagonal lines in Figure 9A) can be set large, thereby suppressing the occurrence of collision detection errors (failure to detect that a collision has occurred).

[0079] FIG. 9B shows an example in which the collision detection thresholds are set so that the time lag from the time of collision occurrence to the time of collision detection is the same for a configuration employing the reducer of the present disclosure and a configuration employing a reducer with lower reverse drive efficiency than the reducer of the present disclosure. Specifically, the collision detection threshold 2 in the configuration employing a reducer with lower reverse drive efficiency than the reducer of the present disclosure is set to a smaller value than the collision detection threshold 1 in the configuration employing the reducer of the present disclosure. In this example, the collision occurrence time t c The clearance of the collision detection threshold can be set large relative to the previous external torque estimate, in other words, the external torque estimate that is steadily estimated when no collision has occurred, thereby suppressing the occurrence of false collision detection (falsely detecting that a collision has occurred when no collision has occurred).

[0080] The estimated external torque τ L_est is the threshold τ L_th If it exceeds (step S102; No), the processing is L_ref is not limited to the process of setting "0". For example, the braking unit 11 may be driven to brake the rotational movement of the arm 22. [Explanation of symbols]

[0081] 1. Drive unit 2. Housing 3 motors 4 Motor output shaft 4A through hole 5 Reducer 6 Reducer input shaft 6A through hole 7 Connecting part 8 spindle 9 Motor angle detection unit 10 Main shaft angle detection unit 11 Braking part 12 Control board 22 Arm 50 Drive Module 100 control circuit 200 Speed command value generation unit 300 Speed control section 400 Disturbance Observer CL axis center

Claims

1. A motor; a reducer that reduces the rotational speed of the motor and outputs the reduced rotational speed to the spindle; an arm fixed to the main shaft; a control circuit that generates a current command value for the motor; Equipped with The control circuit a velocity command value generation unit that generates an angular velocity command value for the arm; a speed control unit that generates the current command value based on the angular velocity command value; a disturbance observer that estimates an estimated value of an external torque applied to the arm based on the current command value, the angular velocity of the arm, and the angular velocity of the motor; Equipped with The speed command value generation unit When the estimated value of the external torque exceeds a predetermined threshold, the angular velocity command value is set to zero. Drive unit.

2. a motor angle detection unit that detects a rotation angle of the motor; a main shaft angle detection unit that detects a rotation angle of the arm; Equipped with The disturbance observer calculating an angular velocity of the arm by pseudo-differentiating the rotation angle of the arm; calculating an angular velocity of the motor by performing pseudo-differentiation on the rotation angle of the motor; The drive device according to claim 1 .

3. The disturbance observer Compensating for a gravitational torque component of the arm when estimating the estimated value of the external torque. The drive device according to claim 2 .

4. The disturbance observer a friction torque component of the motor is compensated for when estimating the estimated value of the external torque; The drive device according to claim 2 .

5. The reducer is a plurality of first planetary gears rotatably provided about a plurality of planetary axes provided at equal intervals around the axis center; a plurality of second planetary gears each rotatable about the planetary axis center, each having a smaller diameter and fewer teeth than the first planetary gear, and integrally formed with the first planetary gear to rotate together; a sun gear that is provided around the axis center and that meshes with the first planetary gear radially inside the planetary axis center; a first internal gear that is ring-shaped and centered on the axis, and that meshes with the first planetary gear on the radially outer side of the planetary axis; a second internal gear that is ring-shaped and centered on the axis, and that meshes with the second planetary gear on the radially outer side of the planetary axis; Including, A drive device according to any one of claims 1 to 4.

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