Drive device and robot including parallel link

Abstract

To restrict an amount of data and improve the position accuracy of a screw shaft, in a drive device.SOLUTION: A control device 1b of a drive device 1 corrects a target position by using a correction value corresponding to a target position of a screw shaft 14 moved by drive of a motor 12; calculates a current position of the screw shaft 14, based on a detection value of a linear encoder 25; performs feedback control for determining an amount of operation of the motor 12 so as to reduce a difference between the corrected target position and the current position; and calculates a correction values by using an approximation formula indicating a lead error of the screw shaft 14.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a robot including a drive unit and a parallel link. [Background technology]

[0002] The driving device disclosed in Patent Document 1 includes a correction unit, an actuator, and a position sensor. The actuator includes a nut connected to a movable part (rod), a ball screw shaft (screw shaft) to which the nut is screwed, and a pulse motor that rotates and drives the screw shaft. The correction unit has a correction amount map in which a position correction amount for calibrating a predictable error is mapped for each position of the movable part. The correction unit estimates an ideal movement position to which the movable part moves in response to a command signal, and determines a position correction amount corresponding to a current position detected by a position sensor by referring to the correction amount map. Then, a correction signal is generated by correcting the command signal so that the difference between a corrected current position obtained by correcting the current position with the position correction amount and the ideal movement position is small. This makes it possible to improve the position accuracy of the rod.

[0003] Patent Document 1 also discloses a robot including a parallel link equipped with a plurality of the above-mentioned drive devices. As disclosed in Patent Document 1, the rod may be a screw shaft that moves when a nut rotates. In this case, the position accuracy of the screw shaft can be improved by the correction unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7088440 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the correction amount map of the correction unit has a huge amount of data because the position correction amount for calibrating the lead error and the like is mapped for each position of the rod (or screw shaft). Also, in a robot including a parallel link equipped with multiple drive units, the amount of data increases in proportion to the number of drive units.

[0006] An aspect of the present disclosure aims to provide a robot including a drive device and a parallel link that reduces the amount of data and improves the positional accuracy of a screw shaft. [Means for solving the problem]

[0007] In an aspect of the present disclosure, a drive device includes an actuator and a control device that controls the actuator, the actuator includes a housing, a nut stored in the housing, a motor that rotates the nut, a screw shaft that engages with the nut and moves relative to the housing as the nut rotates, and a sensor that detects the amount of movement of the screw shaft, and the control device corrects the target position of the screw shaft using a correction value corresponding to the target position, calculates the current position of the screw shaft based on the detection value of the sensor, and performs feedback control to determine the operation amount of the motor so as to reduce the deviation between the corrected target position and the calculated current position of the screw shaft, and calculates the correction value using an approximation equation that indicates the lead error of the screw shaft.

[0008] According to the aspects of the present disclosure, the drive device calculates a correction value for correcting the target position of the screw shaft, thereby reducing the amount of data compared to a case where the lead error value is stored in the storage unit for each position of the screw shaft. Also, the position accuracy of the screw shaft can be improved by correcting the target position based on the correction value.

[0009] In addition, in an aspect of the present disclosure, the control device has a storage unit that stores the following formula (1) which corresponds to the approximation formula. R=A×sin(α×θ)+Ka×L×cos(α×θ) +B×cos(α×θ)+Kb×L×sin(α×θ) (1) R is the correction value, α is any one of integers from 1 to 3, θ is the rotation angle of the screw shaft corresponding to the position of the screw shaft, L is the distance from the supported position of the screw shaft corresponding to the position of the screw shaft to the tip, and A, Ka, B, and Kb are real numbers that minimize the difference between the lead error of the screw shaft and R.

[0010] According to the aspects of the present disclosure, the target position is corrected based on the formula (1), thereby making it possible to reliably improve the positional accuracy of the screw shaft.

[0011] In addition, in an embodiment of the present disclosure, the drive device further includes a storage unit in which the values ​​of α, A, Ka, B, and Kb in the above formula (1) are stored.

[0012] According to an aspect of the present disclosure, the formula (1) stored in the storage unit can be made the same for each actuator, thereby further reducing the amount of data in the control device.

[0013] In addition, in an aspect of the present disclosure, the storage unit has an image of a two-dimensional code into which the values ​​of α, A, Ka, B, and Kb in the formula (1) are converted.

[0014] According to an aspect of the present disclosure, the storage section can be configured to be easily attached to the drive device.

[0015] In addition, in an aspect of the present disclosure, a robot including a parallel link includes a plurality of actuators provided in the above-mentioned drive device, and also includes a control unit having a memory unit that stores the above formula (1), and one storage unit in which the values ​​of α, A, Ka, B, and Kb in the above formula (1) corresponding to each of the plurality of actuators are stored, and one actuator among the plurality of actuators and the other actuator are arranged with their respective reference axes parallel to each other.

[0016] According to an aspect of the present disclosure, in a robot including a parallel link, similar to the above-described drive device, it is possible to reduce the amount of data and improve the positional accuracy of the screw shaft. Effect of the Invention

[0017] According to an aspect of the present disclosure, in a robot including a drive unit and a parallel link, it is possible to reduce the amount of data and improve the positional accuracy of the screw shaft. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view of a drive device according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view of the actuator taken along a reference axis. [Diagram 3] FIG. 3 is a diagram showing the lead error of a screw shaft. [Figure 4] FIG. 4 is a control block diagram showing the feedback control executed by the control device. [Diagram 5] FIG. 5 is a diagram showing the lead error of the screw shaft when the target position is corrected. [Figure 6] FIG. 6 is a diagram showing a drive device according to a modified example of the embodiment of the present disclosure. [Figure 7] FIG. 7 is a perspective view of a robot including a parallel link according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a plan view of the robot including the parallel link shown in FIG. 7 as viewed from the +Z side. [Figure 9] FIG. 9 is a side view of the robot including the parallel link shown in FIG. 7 as viewed from the -X side. [Figure 10] FIG. 10 is a diagram showing a state in which the second arm unit is inclined with respect to the first arm unit from the reference state of the robot including the parallel link shown in FIG. [Figure 11] FIG. 11 is a side view of the robot including the parallel link shown in FIG. 7 as viewed from the -Y side. [Figure 12]FIG. 12 is a diagram showing a state in which the medical instrument has been moved by the third arm unit being driven from the reference state of the robot including the parallel link shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited thereto. The components of each embodiment and each modified example described below can be appropriately combined. In addition, some components may not be used.

[0020] <Driver 1> A drive device 1 according to an embodiment of the present disclosure will be described with reference to the drawings.

[0021] 1 is a perspective view of a drive device 1 according to an embodiment of the present disclosure. The drive device 1 includes an actuator 1a and a control device 1b. The actuator 1a and the control device 1b are electrically connected to each other via a wire or wirelessly.

[0022] 2 is a cross-sectional view of the actuator 1a taken along a reference axis SL. The reference axis SL is a reference axis of the actuator 1a. As shown in FIGS. 1 and 2, the actuator 1a includes a drive unit 10 and a guide unit 20.

[0023] The driving unit 10 includes a housing 11, a motor 12, a nut 13, and a screw shaft 14. The housing 11 has a hollow rectangular parallelepiped shape extending along a reference axis line SL.

[0024] The motor 12 is a stepping motor and includes a stator 12a and a rotor 12b. The stator 12a is fixed inside the housing 11. The rotor 12b passes through the stator 12a and is disposed in the housing 11 via a first bearing 15 so as to be rotatable relative to the housing 11.

[0025] The nut 13 is accommodated in the housing 11 via a second bearing 16 so as to be rotatable relative to the housing 11. The nut 13 is fixed to the rotor 12b and rotates integrally with the rotor 12b.

[0026] The nut 13 includes a plurality of balls (not shown). The inner circumferential surface of the nut 13 has a spiral groove (not shown) in which the plurality of balls can roll. The plurality of balls circulate within the nut 13 as the nut 13 rotates.

[0027] The screw shaft 14 is disposed with a first end portion disposed within the housing 11 and a second end portion exposed from the housing 11. The central axis CL1 of the screw shaft 14 is aligned so as to be parallel to the reference axis SL.

[0028] The screw shaft 14 is fitted into the nut 13 and passes through the rotor 12b. The outer circumferential surface of the screw shaft 14 has a helical thread groove into which a plurality of balls provided in the nut 13 are rollably fitted. The screw shaft 14 moves relative to the housing 11 as the nut 13 rotates.

[0029] The guide unit 20 guides the screw shaft 14 along a reference axis SL. The guide unit 20 includes a support 21, a slide member 22, two guide rails 23a and 23b, four linear guides 24a, 24b, 24c and 24d, and a linear encoder 25.

[0030] The support body 21 has a cylindrical shape that is rectangular in cross section and extends along the reference axis line SL, and is fixed to the housing 11.

[0031] The slide member 22 is L-shaped and integrally includes a fixed portion 22a and a rectangular parallelepiped portion 22b. A second end of the screw shaft 14 is fixed to the fixed portion 22a. Thus, the slide member 22 moves integrally with the screw shaft 14 relative to the housing 11. The rectangular parallelepiped portion 22b penetrates the support body 21 along the reference axis SL.

[0032] The two guide rails 23a, 23b extend along the reference axis SL, and are fixed to the rectangular parallelepiped portion 22b of the slide member 22 at positions opposite to each other.

[0033] The four linear guides 24a, 24b, 24c, and 24d are fixed inside the support 21 and guide the two guide rails 23a and 23b along the reference axis SL. Specifically, the two linear guides 24a and 24b are disposed apart from each other in the direction along the reference axis SL and guide the guide rail 23a. The two linear guides 24c and 24d are disposed apart from each other in the direction along the reference axis SL and guide the guide rail 23b.

[0034] As described above, the support 21 is fixed to the housing 11, and the guide rails 23a, 23b are disposed on the slide member 22. Therefore, the slide member 22 is movable along the reference axis SL relative to the housing 11 by the linear guides 24a, 24b, 24c, 24d. Also, as described above, the slide member 22 moves integrally with the screw shaft 14. Therefore, the guide portion 20 guides the screw shaft 14 along the reference axis SL.

[0035] The linear encoder 25 is an optical (for example, reflective) linear encoder. The linear encoder 25 is an incremental linear encoder. The linear encoder 25 may be an absolute linear encoder. The linear encoder 25 includes a scale 25a and a head 25b.

[0036] The scale 25a is disposed along the reference axis SL on the slide member 22. The scale 25a has a reference position G and a plurality of slits (not shown) aligned along the direction in which the scale 25a extends.

[0037] Head 25b is disposed on support 21 in a state facing scale 25a. Head 25b includes a light-emitting element (e.g., LED: not shown) and a light-receiving element (e.g., photodiode: not shown). The light-emitting element emits light toward scale 25a. The light-receiving element detects light reflected by scale 25a. Light is not reflected by the slits in scale 25a.

[0038] The linear encoder 25 detects the amount of movement of the scale 25a in the direction along the reference axis SL from the position where the head 25b detects the reference position G (hereinafter referred to as the origin position) based on the detection result of the light receiving element of the head 25b. The support 21 on which the head 25b is disposed is fixed to the housing 11 as described above. The scale 25a is disposed on the slide member 22 and moves integrally with the screw shaft 14 relative to the housing 11. Thus, the linear encoder 25 detects the amount of movement of the screw shaft 14 from the origin position in the direction along the reference axis SL. The detection value of the linear encoder 25 is transmitted to the control device 1b.

[0039] The control device 1b shown in Fig. 1 controls the actuator 1a. Specifically, the control device 1b performs feedback control to determine the operation amount of the motor 12 so that the position of the screw shaft 14 becomes a target position. The target position is input to the control device 1b by a user. In addition, the control device 1b performs correction in the feedback control to suppress the influence of a lead error of the screw shaft 14.

[0040] Fig. 3 is a diagram showing the lead error of the screw shaft 14. In Fig. 3, the vertical axis represents the lead error, and the horizontal axis represents the amount of movement of the screw shaft 14 from the origin position (i.e., the position of the screw shaft 14). The horizontal axis in Fig. 3 corresponds to the rotation angle of the nut 13 from the origin position, i.e., the rotation angle of the motor 12 from the origin position. The rotation angle of the motor 12 is expressed in general angles.

[0041] The lead error varies from actuator to actuator 1a. The lead error is actually measured and derived for each actuator 1a. The lead error shown in FIG. 3 is assumed to be that of the actuator 1a shown in FIG.

[0042] In order to suppress the influence of the lead error shown in FIG. 3, the storage unit 1b1 of the control device 1b shown in FIG. 1 stores a correction formula shown in the following formula (1).

[0043] R=A×sin(α×θ)+Ka×L×cos(α×θ) +B×cos(α×θ)+Kb×L×sin(α×θ) (1)

[0044] In formula (1), R is a correction value. α is any one of integers from 1 to 3. α is predetermined to any one of integers from 1 to 3 based on the circularity of the diameter of the screw shaft 14 (=(maximum diameter of the screw shaft 14-minimum diameter of the screw shaft 14) / 2), and is stored in the memory unit 1b1 as that one integer. The smaller the circularity of the diameter of the screw shaft 14, the closer the waveform of the lead error shown in FIG. 3 is to a sine wave. On the other hand, the greater the circularity of the diameter of the screw shaft 14, the greater the fluctuation of the lead error shown in FIG. 3. Therefore, the greater the circularity of the diameter of the screw shaft 14, the larger the integer α is set to.

[0045] Note that α may be determined by further considering the roundness of the inner and outer rings of the first bearing 15 and the second bearing 16. The roundness of the first bearing 15 and the second bearing 16 affects the degree of inclination and eccentricity of the screw shaft 14. The smaller the roundness of the first bearing 15 and the second bearing 16, the closer the waveform of the lead error shown in FIG. 3 is to a sine wave. On the other hand, the greater the roundness of the first bearing 15 and the second bearing 16, the greater the fluctuation of the lead error shown in FIG. 3. Therefore, the greater the roundness of the diameter of the screw shaft 14 and the roundness of the first bearing 15 and the second bearing 16, the greater the integer α is determined to be.

[0046] θ is the rotation angle of the screw shaft 14 corresponding to the position of the screw shaft 14. Specifically, θ is the rotation angle of the screw shaft 14 corresponding to the amount of movement of the screw shaft 14 from the origin position. θ is expressed as a general angle. The amount of movement of the screw shaft 14 is proportional to θ. This proportional relationship is stored in the memory unit 1b1.

[0047] 2, L is the distance from a supported position P1 of the screw shaft 14 corresponding to the position of the screw shaft 14 to the tip P2. The supported position P1 of the screw shaft 14 is a position supported by the nut 13, and is a position corresponding to the center of the nut 13. Specifically, L is the distance from the supported position P1 of the screw shaft 14 to the tip P2 of the screw shaft 14 in the direction along the central axis CL1 of the screw shaft 14. In other words, L changes with the movement of the screw shaft 14. Specifically, L can be expressed as an equation proportional to θ as shown in the following equation (2). Equation (2) is stored in memory unit 1b1.

[0048] L = L0 + Kc × θ (2)

[0049] In formula (2), L0 is the length L at the origin position. In formula (2), Kc is a proportionality coefficient that is determined based on the lead of screw shaft 14 and is stored in memory unit 1b1. The lead of screw shaft 14 differs for each actuator 1a. Therefore, Kc differs for each actuator 1a. That is, formula (2) differs for each actuator 1a. Kc may be calculated by the following formula (3). In this case, formula (3) is stored in memory unit 1b1.

[0050] Kc = θ × Le / 2π (3)

[0051] In the formula (3), Le is the lead of the screw shaft 14. Le is actually measured in advance and stored in the storage unit 1b1.

[0052] In formula (1), A, Ka, B, and Kb are real numbers that minimize the difference between the lead error of the screw shaft 14 and R. In other words, the above formula (1) corresponds to an approximation of the lead error. A and B are real numbers that correspond to the degree of eccentricity of the screw shaft 14. Ka and Kb are real numbers that correspond to the degree of inclination of the screw shaft 14.

[0053] A, Ka, B, and Kb are values ​​that minimize the difference between the lead error and R, for example, using a computer, and are stored in the storage unit 1b1. Specifically, A, Ka, B, and Kb are real numbers that minimize the average value of the difference between the lead error and R in the movable range of the screw shaft 14. Note that A, Ka, B, and Kb may be real numbers that minimize the maximum value of the difference between the lead error and R. As described above, the lead error has individual differences for each actuator 1a. Therefore, A, Ka, B, and Kb are different for each actuator 1a. That is, the formula (1) is different for each actuator 1a. Note that, for α, an integer that minimizes the difference between the lead error and R among integers 1 to 3 may be determined in advance, for example, using a computer, and stored in the storage unit 1b1.

[0054] 4 is a control block diagram showing the feedback control executed by the control device 1b. The control device 1b acquires a target position (Pt) of the screw shaft 14. The control device 1b also calculates a correction value (R) corresponding to the target position of the screw shaft 14 using the above formulas (1) and (2). Specifically, the control device 1b calculates θ corresponding to the target position of the screw shaft 14, and calculates L from this θ and formula (2). Furthermore, the control device 1b calculates R (correction value) from the calculated θ, L, and formula (1).

[0055] The control device 1b corrects the target position using the correction value. Specifically, the control device 1b subtracts the correction value from the target position. In this manner, the target position is corrected based on the lead error.

[0056] Furthermore, the control device 1b calculates the current position of the screw shaft 14 using the detection value of the linear encoder 25 (the amount of movement of the screw shaft 14 from the origin position). The current position of the screw shaft 14 is equal to the detection value of the linear encoder 25. Furthermore, the control device 1b determines the operation amount of the motor 12 so as to reduce the deviation between the corrected target position and the calculated current position of the screw shaft 14. The operation amount of the motor 12 is the rotation angle of the motor 12, which corresponds to the rotation angle of the nut 13. The screw shaft 14 moves in accordance with the rotation of the nut 13, so that the screw shaft 14 approaches the target position.

[0057] Fig. 5 is a diagram showing the lead error of the screw shaft 14 when the target position is corrected. The vertical and horizontal axes in Fig. 5 are the same as those in Fig. 3. In the movable range of the screw shaft 14, the average value of the lead error shown in Fig. 5 is smaller than the average value of the lead error shown in Fig. 3. In other words, the position accuracy of the screw shaft 14 is improved.

[0058] Moreover, the storage unit 1b1 stores the above formulas (1) and (2) and the values ​​of α, A, Ka, B, Kb, and Kc. Therefore, in this case, the amount of data can be reduced compared to the case where the lead error value for each position of the screw shaft 14 within the movable range of the screw shaft 14 is stored in the storage unit 1b1.

[0059] The storage unit 1b1 may store a formula that is mathematically equivalent to the above formulas (1), (2), and (3) (for example, a formula obtained by modifying formulas (1), (2), and (3)). For example, instead of formula (1), the storage unit 1b1 may store the following formula (4) obtained by modifying formula (1).

[0060] R=(α+β×L)×sin(θ+φ) ···(4)

[0061] In equation (4), α is the lead error caused by the eccentricity of the screw shaft 14. β is the lead error caused by the inclination of the screw shaft 14. φ is the rotation angle of the screw shaft 14 at which the runout of the screw shaft 14 is maximum.

[0062] In equation (1), A = α × cosφ, B = α × sinφ, Ka = β × cosφ, and Kb = β × sinφ. By replacing A, Ka, B, and Kb in equation (1) and transforming equation (1), equation (4) can be derived.

[0063] As described above, according to this embodiment, the drive device 1 includes the actuator 1a and the control device 1b that controls the actuator 1a. The actuator 1a includes the housing 11, the nut 13 housed in the housing 11, the motor 12 that rotates the nut 13, the screw shaft 14 that is fitted with the nut 13 and moves relative to the housing 11 as the nut 13 rotates, and the linear encoder 25 that detects the amount of movement of the screw shaft 14. The control device 1b corrects the target position using a correction value corresponding to the target position of the screw shaft 14, calculates the current position of the screw shaft 14 based on the detection value of the linear encoder 25, and performs feedback control to determine the operation amount of the motor 12 so as to reduce the deviation between the corrected target position and the calculated current position of the screw shaft 14, and calculates the correction value using an approximation equation that indicates the lead error of the screw shaft 14. According to this, by calculating a correction value for correcting the target position of the screw shaft 14, the driving device 1 can reduce the amount of data compared to the case where the value of the lead error for each position of the screw shaft 14 is stored in the memory unit 1b1. Also, by correcting the target position based on the correction value, the position accuracy of the screw shaft 14 can be improved. Furthermore, by reducing the amount of data, the processing efficiency can be increased in the control device 1b. Furthermore, the capacity and cost of the control device 1b can be reduced.

[0064] Moreover, the control device 1b has a storage unit 1b1 that stores the above formula (1) which corresponds to the approximation formula. According to this, the target position is corrected based on the formula (1), so that the positional accuracy of the screw shaft 14 can be reliably improved.

[0065] 6 is a diagram showing a drive device 1 according to a modified example of the embodiment of the present disclosure. Compared to the drive device 1 according to the above embodiment, the drive device 1 of this modified example further includes a storage section 1c.

[0066] The storage unit 1c stores the values ​​of α, A, Ka, B, Kb, and Kc in the above formulas (1) and (2). The storage unit 1c has an image 1c1 of a two-dimensional code into which the values ​​of α, A, Ka, B, Kb, and Kc are converted. In this modification, the storage unit 1c is a sticker on which the image 1c1 is printed, and is attached to the actuator 1a.

[0067] In this modified example, the control device 1b has a camera (not shown) and obtains the values ​​of α, A, Ka, B, Kb, and Kc by capturing an image 1c1 with the camera.

[0068] In this case, α, A, Ka, B, Kb, and Kc in the formulas (1) and (2) stored in the memory unit 1b1 are variables. That is, in this modified example, the formulas (1) and (2) are the same for each actuator 1a. The control device 1b substitutes the values ​​of A, Ka, B, Kb, and Kc acquired from the storage unit 1c for A, Ka, B, Kb, and Kc in the formulas (1) and (2) stored in the memory unit 1b1, calculates the correction value (R) as described above, and performs feedback control.

[0069] According to this modification, the drive device 1 further includes a storage unit 1c in which the values ​​of α, A, Ka, B, and Kb in the above formula (1) are stored. According to this, it is possible to make the formula (1) stored in the memory unit 1b1 the same for each actuator 1a. Therefore, it is possible to further reduce the amount of data in the control device 1b. Furthermore, the value of Kc in the above formula (2) is stored in the storage unit 1c. Therefore, it is possible to make the formula (2) stored in the memory unit 1b1 the same for each actuator 1a. Therefore, it is possible to further reduce the amount of data in the control device 1b. In addition, the actuator 1a may be replaced in the driving device 1 due to aging of the actuator 1a. In this case, even if the amount of operation by the doctor is the same, the position of the screw shaft 14 may differ before and after replacement due to individual differences in the actuator 1a, which may reduce the position accuracy of the screw shaft 14. Therefore, by providing the actuator 1a with the storage unit 1c, the control device 1b can easily obtain the values ​​of A, Ka, B, Kb, and Kc corresponding to the replaced actuator 1a. Therefore, even when the actuator 1a is replaced, the driving device 1 can reduce the amount of data and improve the position accuracy of the screw shaft 14.

[0070] Furthermore, the storage unit 1c has an image 1c1 of a two-dimensional code into which the values ​​of α, A, Ka, B, and Kb in the above formula (1) have been converted. According to this, the storage unit 1c can be configured to be easily attached to the drive device 1. Therefore, the storage unit 1c can be made smaller. Specifically, the storage unit 1c has an image 1c1 of a two-dimensional code into which the values ​​of A, Ka, B, Kb, and Kc are converted. Therefore, the storage unit 1c can be reliably made smaller.

[0071] The storage unit 1c may store an image of a one-dimensional code into which the values ​​of α, A, Ka, B, Kb, and Kc have been converted.

[0072] The storage unit 1c may be a beacon having a memory unit in which the values ​​of α, A, Ka, B, Kb, and Kc are stored, and a transmission unit that transmits the values ​​of α, A, Ka, B, Kb, and Kc. In this case, the control device 1b receives the values ​​of α, A, Ka, B, Kb, and Kc transmitted from the beacon.

[0073] <Robot with parallel link 2> A robot 2 including a parallel link according to an embodiment of the present disclosure will be described with reference to the drawings.

[0074] In the following description, the Z direction is the up-down direction, the direction perpendicular to the Z direction is the X direction, and the direction perpendicular to the Z direction and the X direction is the Y direction. Note that the X, Y, and Z directions are merely examples, and the present disclosure is not limited to these directions. Also, viewing the robot 2 including the parallel links along the Z direction from the +Z side or -Z side is referred to as a "planar view."

[0075] FIG. 7 is a perspective view of a robot 2 including a parallel link according to an embodiment of the present disclosure. The robot 2 including a parallel link is a medical robot arm used during surgery performed by a doctor. The robot 2 including a parallel link may be an industrial robot arm used in the production of industrial products. The robot 2 including a parallel link is electrically connected to a control unit 2a provided in the robot 2 including a parallel link by wire or wirelessly. A doctor operates the robot 2 including a parallel link by operating the control unit 2a.

[0076] The robot 2 including a parallel link includes a first arm unit 110, a first joint portion 120a, a second arm unit 130, a second joint portion 120b, and a third arm unit 140. A medical instrument 3 is fixed to the third arm unit 140 in a replaceable manner.

[0077] The medical instrument 3 is an instrument used for treatment. The medical instrument 3 of this embodiment has a needle-shaped needle portion 3a. A doctor performs treatment by, for example, inserting the needle portion 3a from the tip of the needle portion 3a into an affected area of ​​a patient. Note that FIG. 7 shows the robot 2 including the parallel link in a reference state H in which the tip of the needle portion 3a faces the -Z side and the needle portion 3a of the medical instrument 3 extends along the Z direction.

[0078] Fig. 8 is a plan view of the robot 2 including the parallel link shown in Fig. 7 as seen from the +Z side. Fig. 9 is a side view of the robot 2 including the parallel link shown in Fig. 7 as seen from the -X side. Note that Fig. 9 omits the illustration of a counterweight 113, which will be described later.

[0079] 7, 8, and 9 includes a first arm unit 111, a second arm 112, and a counterweight 113. In a reference state H of the robot 2 including a parallel link, the first arm 111 and the second arm 112 are arranged in parallel along the Z direction in a posture extending along the Y direction.

[0080] The first arm 111 and the second arm 112 are the actuators 1a described above. The first arm 111 and the second arm 112 are arranged with their respective reference axes SL parallel to each other. In the reference state H of the robot 2 including the parallel link, the reference axes SL of the first arm 111 and the second arm 112 are parallel to the Y direction. The counterweight 113 is attached to the slide member 22 of the first arm 111 (see FIG. 8).

[0081] The first joint portion 120a connects the first arm unit 110 and the second arm unit 130 so that the second arm unit 130 can be inclined relative to the first arm unit 110. As shown in Figures 8 and 9, the first joint portion 120a includes a first link 121a, a second link 122a, a cylindrical first shaft member 123a, a third link 124a, a fourth link 125a, and a cylindrical second shaft member 126a.

[0082] The first link 121a is fixed to the slide member 22 of the first arm portion 111. The second link 122a is connected to a planar first mounting surface 130b of the first mounting portion 130a of the second arm unit 130 via a linear guide 127a and a guide rail 130c. As a result, the second link 122a is connected to the first mounting surface 130b so as to be movable along the first mounting surface 130b.

[0083] The first link 121a and the second link 122a are connected via a first shaft member 123a so as to be relatively tiltable around a central axis CL2a of the first shaft member 123a. In a reference state H of the robot 2 including the parallel links, the central axis CL2a of the first shaft member 123a is aligned along the X direction.

[0084] A first end of the third link 124a is fixed to the slide member 22 of the second arm portion 112. The fourth link 125a is fixed to the first mounting surface 130b.

[0085] The third link 124a and the fourth link 125a are connected via a second shaft member 126a so as to be relatively tiltable about a central axis CL3a of the second shaft member 126a. The central axis CL3a of the second shaft member 126a is parallel to the central axis CL2a of the first shaft member 123a.

[0086] In this manner, by connecting the first attachment portion 130a of the second arm unit 130 and the first arm unit 110 via the first joint portion 120a, the first arm unit 110, the first joint portion 120a, and the first attachment portion 130a configure a so-called parallel link mechanism. As a result, the second arm unit 130 inclines and moves in translation relative to the first arm unit 110, as will be described next.

[0087] Fig. 10 is a diagram showing a state in which the second arm unit 130 is inclined with respect to the first arm unit 110 from the reference state H of the robot 2 including the parallel link shown in Fig. 9. When the screw shaft 14 in the first arm 111 moves from the reference state H of the robot 2 including the parallel link shown in Fig. 9 to the side where it protrudes from the housing 11, as shown in Fig. 10, the second link 122a inclines with respect to the first link 121a and the fourth link 125a inclines with respect to the third link 124a in the counterclockwise direction in Fig. 10, so that the second arm unit 130 inclines with respect to the first arm unit 110.

[0088] In addition, when the screw shaft 14 in the second arm 112 moves from the reference state H of the robot 2 including the parallel link shown in Figure 9 toward the side where it protrudes from the housing 11, the second link 122a tilts clockwise in Figure 10 relative to the first link 121a, and the fourth link 125a tilts relative to the third link 124a, causing the second arm unit 130 to tilt relative to the first arm unit 110.

[0089] Furthermore, from the reference state H of the robot 2 including the parallel link shown in Figure 9, when the screw shafts 14 in the first arm unit 111 and the second arm unit 112 move at equal speeds toward the side protruding from the housing 11, the second arm unit 130 moves translationally toward the +Y side relative to the first arm unit 110.

[0090] As shown in FIGS. 7, 8 and 9, the second arm unit 130 includes a first attachment portion 130a, a third arm portion 131 and a fourth arm portion 132.

[0091] As described above, the first attachment portion 130a has a first attachment surface 130b to which the second link 122a and the fourth link 125a of the first joint portion 120a are connected.

[0092] The third arm 131 and the fourth arm 132 are arranged in parallel along the Z direction in a posture extending along the X direction in a reference state H of the robot 2 including a parallel link.

[0093] The third arm 131 and the fourth arm 132 are the actuators 1a. The third arm 131 and the fourth arm 132 are arranged with their respective reference axes SL parallel to each other. In the reference state H of the robot 2 including the parallel link, the reference axes SL of the first arm 111 and the second arm 112 are parallel to the X direction.

[0094] The second joint portion 120b connects the second arm unit 130 and the third arm unit 140 so that the third arm unit 140 can be tilted relative to the second arm unit 130. The second joint portion 120b has the same configuration as the first joint portion 120a, and therefore a description of the second joint portion 120b will be omitted. However, the reference numerals of the components of the second joint portion 120b are the same as those of the components of the first joint portion 120a that correspond to the components of the second joint portion 120b, except that the suffix "a" is changed to "b".

[0095] As shown in FIG. 8, in the second joint portion 120b, the second link 122b is connected to a planar second mounting surface 140b of the second mounting portion 140a of the third arm unit 140 via a linear guide 127b and a guide rail 140c. As a result, the second link 122b is connected to the second mounting surface 140b so as to be movable along the second mounting surface 140b. In addition, in the reference state H of the robot 2 including the parallel link, the first shaft member 123b is disposed so that the central axis CL2b of the first shaft member 123b is aligned along the Y direction. The fourth link 125b shown in FIG. 7 is fixed to the second mounting surface 140b.

[0096] In this way, the second attachment portion 140a of the third arm unit 140 and the second arm unit 130 are connected via the second joint portion 120b, so that the second arm unit 130, the second joint portion 120b, and the second attachment portion 140a configure a so-called parallel link mechanism. Therefore, the third arm unit 140 inclines clockwise and counterclockwise relative to the second arm unit 130 in FIG. 11 (described later) and translates along the X direction, similar to the inclination and translation of the second arm unit 130 relative to the first arm unit 110 described above.

[0097] Fig. 11 is a side view of the robot 2 including the parallel link shown in Fig. 7 when viewed from the -Y side. As shown in Figs. 8 and 11, in the reference state H of the robot 2 including the parallel link, the reference axis SLa of the third arm unit 140 extends along the Z direction. The third arm unit 140 includes a drive unit 141 and an instrument guide unit 142.

[0098] The driving section 141 has the same configuration as the driving section 10 of the actuator 1a described above. The central axis CL1 of the screw shaft 14 of the driving section 141 is aligned so as to be parallel to the reference axis SLa.

[0099] The instrument guide portion 142 guides the medical instrument 3. The instrument guide portion 142 includes the above-mentioned second attachment portion 140a and a slide member 142a.

[0100] 8, the drive unit 141 is fixed to the second attachment portion 140a. The second attachment portion 140a has a second attachment surface 140b to which the second joint portion 120b is connected, and a guide surface 140d. As described above, the second link 122b and the fourth link 125b of the second joint portion 120b are connected to the second attachment surface 140b.

[0101] The guide surface 140d is a plane parallel to the second mounting surface 140b. A slide member 142a is attached to the guide surface 140d so as to be movable relative to the second mounting portion 140a. Specifically, a linear guide 142b is fixed to the slide member 142a, and a guide rail 140e that fits with the linear guide 142b is fixed to the guide surface 140d. The guide rail 140e extends along the reference axis SLa. Therefore, the slide member 142a moves along the reference axis SLa relative to the second mounting portion 140a.

[0102] 11, the slide member 142a is fixed to a second end of the screw shaft 14 of the drive unit 141 by a fixing nut 18. The central axis CL1 of the screw shaft 14 of the drive unit 141 is aligned with respect to the reference axis SLa. In addition, the medical instrument 3 is fixed to the slide member 142a. In other words, when the screw shaft 14 of the drive unit 141 moves, the slide member 142a and the medical instrument 3 move together along the reference axis SLa relative to the second attachment portion 140a.

[0103] Moreover, the third arm unit 140 further includes a linear encoder 143. The linear encoder 143 is configured similarly to the above-mentioned linear encoder 25. The linear encoder 143 includes a scale 143a and a head 143b.

[0104] The scale 143a is disposed on the second attachment portion 140a along the reference axis SLa. The scale 143a has a reference position G (see FIG. 12 described later) and a plurality of slits (not shown) aligned along the direction in which the scale 25a extends. The head 143b is disposed on a slide member 142a that moves together with the screw shaft 14 of the drive portion 141 in a state facing the scale 143a.

[0105] The linear encoder 143 detects the amount of movement of the head 143b from the reference position G in the direction along the reference axis SLa based on the detection result of the light receiving element of the head 143b. The housing 11 of the drive unit 141 is fixed to the second attachment portion 140a on which the scale 143a is arranged. The head 143b moves integrally with the screw shaft 14 relative to the housing 11 of the drive unit 141. Thus, the linear encoder 143 detects the amount of movement of the screw shaft 14 of the drive unit 141 from the reference position G in the direction along the reference axis SLa. The detection value of the linear encoder 143 is transmitted to the control unit 2a.

[0106] Fig. 12 is a diagram showing a state in which the medical instrument 3 has been moved by driving the third arm unit 140 from the reference state H of the robot 2 including the parallel link shown in Fig. 11. When the screw shaft 14 of the drive unit 141 moves from the reference state H of the robot 2 including the parallel link shown in Fig. 11 to the side where it protrudes from the housing 11, the medical instrument 3 moves to the -Z side along the reference axis line SLa as shown in Fig. 12. On the other hand, when the screw shaft 14 of the drive unit 141 moves from the state of the robot 2 including the parallel link shown in Fig. 12 toward the side where it fits into the housing 11, the medical instrument 3 moves to the +Z side along the reference axis line SLa as shown in Fig. 11.

[0107] In the robot 2 including the parallel link configured as described above, a doctor inputs the operation amount (movement direction and movement amount) of the medical instrument 3 to the control unit 2a. The control unit 2a adjusts the movement amount of each screw shaft 14 corresponding to the input operation amount of the medical instrument 3 based on the detection values ​​of each linear encoder 25, 143. As described above, each screw shaft 14 is guided by the slide members 22, 142a and moves with high precision along the reference axes SL, SLa.

[0108] This allows for precise adjustment of the attitude and position of second arm unit 130 and third arm unit 140 relative to first arm unit 110. Furthermore, the attitude and position of medical instrument 3 is precisely adjusted, and medical instrument 3 moves precisely.

[0109] The robot 2 including the parallel link further includes a storage unit 2b shown in FIG. 7. The storage unit 2b is disposed on a base 110a fixed to the first arm unit 110. The robot 2 including the parallel link includes one storage unit 2b. In the storage unit 2b, α, A, Ka, B, Kb, and Kc in the formulas (1) and (2) for suppressing the lead error of the screw shaft 14 of each of the drive units 10 and 141 of the first arm unit 111, the second arm unit 112, the third arm unit 131, the fourth arm unit 132, and the third arm unit 140 are stored for each of the drive units 10 and 141 of the first arm unit 111, the second arm unit 112, the third arm unit 131, the fourth arm unit 132, and the third arm unit 140.

[0110] The storage unit 2b is a sticker having an image 2b1 of a two-dimensional code obtained by converting the values ​​of α, A, Ka, B, Kb, and Kc in the formula (1) similar to the storage unit 1c of the drive unit 1 according to the modified example of the above embodiment. The storage unit 2b is attached to the base 110a.

[0111] The control unit 2a of the robot 2 including the parallel link acquires the values ​​of α, A, Ka, B, Kb, and Kc stored in the storage unit 2b by a camera or the like, in the same manner as the control device 1b of the drive unit 1 according to the modified embodiment of the above. In addition, the storage unit 2a1 of the control unit 2a of the robot 2 including the parallel link stores the above formulas (1) and (2), in the same manner as the storage unit 1b1 of the control device 1b according to the modified embodiment of the above. The control unit 2a calculates a correction value (R) corresponding to the target position of the screw shaft 14 for each of the drive units 10 and 141 of the first arm 111, the second arm 112, the third arm 131, the fourth arm 132, and the third arm unit 140 using the acquired values ​​of α, A, Ka, B, Kb, and Kc, and formulas (1) and (2), and performs feedback control in the same manner as the control device 1b of the above embodiment.

[0112] As described above, according to this embodiment, the robot 2 including the parallel link includes a plurality of actuators 1a, a control unit 2a having a storage unit 2a1 that stores the above formula (1), and one storage unit 2b in which the values ​​of α, A, Ka, B, and Kb in the above formula (1) corresponding to each of the plurality of actuators 1a are stored. The actuators 1a constituting the first arm 111 and the actuators 1a constituting the second arm 112 among the plurality of actuators 1a are arranged with their respective reference axes SL parallel to each other. Moreover, the actuators 1a constituting the third arm 131 and the actuators 1a constituting the fourth arm 132 among the plurality of actuators 1a are arranged with their respective reference axes SL parallel to each other. According to this, in the robot 2 including the parallel link, similarly to the above-mentioned driving device 1, the amount of data can be reduced and the positional accuracy of the screw shaft 14 can be improved.

[0113] The control device 1b and the control unit 2a are computers, and include, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an internal storage unit (corresponding to storage units 1b1 and 2a1), an input interface, and an output interface. The CPU, ROM, RAM, and internal storage unit are connected by an internal bus. Programs such as BIOS are stored in the ROM. The internal storage unit is, for example, a HDD (Hard disk drive) or a flash memory, and stores an operating system program and application programs. The CPU realizes various functions by executing programs stored in the ROM or the internal storage unit while using the RAM as a work area. [Explanation of symbols]

[0114] 1 Drive unit 1a Actuator 1b Control device 1b1,2a1 Storage section 1c,2b Storage area 1c1,2b1 Images 2 Robots with parallel links 2a Control section 10 Drive unit 11. Housing 12 Motor 13 Nut 14 Screw shaft 20 Guide section 25 Linear encoder (sensor) P1 Supported position of the screw shaft P2 Screw shaft tip SL reference axis

Claims

1. An actuator; A control device for controlling the actuator, The actuator comprises: Housing and A nut housed in the housing; A motor that rotates the nut; a screw shaft that is fitted with the nut and moves relative to the housing as the nut rotates; A sensor for detecting the amount of movement of the screw shaft, The control device includes: Correcting the target position using a correction value corresponding to the target position of the screw shaft; Calculating a current position of the screw shaft based on the detection value of the sensor; A feedback control is performed to determine an operation amount of the motor so as to reduce a deviation between the corrected target position and the calculated current position of the screw shaft, The correction value is calculated using an approximation formula indicating the lead error of the screw shaft. Drive unit.

2. The control device has a storage unit that stores the following formula (1) corresponding to the approximation formula: The drive device according to claim 1 . R=A×sin(α×θ)+Ka×L×cos(α×θ) + B × cos(α × θ) + Kb × L × sin(α × θ) ... (1) R is the correction value, α is any one of integers from 1 to 3, θ is the rotation angle of the screw shaft corresponding to the position of the screw shaft, L is the distance from the supported position of the screw shaft corresponding to the position of the screw shaft to the tip, and A, Ka, B, and Kb are real numbers that minimize the difference between the lead error of the screw shaft and R.

3. A storage unit storing the values ​​of α, A, Ka, B, and Kb in the formula (1), The drive device according to claim 2.

4. The storage unit has an image of a two-dimensional code into which the values ​​of α, A, Ka, B, and Kb in the formula (1) are converted. The drive device according to claim 3.

5. The drive device according to claim 2 includes a plurality of the actuators, A control unit having a storage unit that stores the formula (1); a storage unit in which values ​​of α, A, Ka, B, and Kb in the formula (1) corresponding to each of the actuators are stored; one of the actuators and the other of the actuators are arranged in a state in which their respective reference axes are parallel to each other; A robot that includes a parallel link.

Images