Work manipulator and system comprising work manipulator

Abstract

Provided is a work manipulator capable of improving the stability of the position and orientation of an end effector as achieved by means of a parallel link mechanism.　A work manipulator 10 has a distal link 13 for supporting an end effector 12, and a parallel link mechanism 10A having six linkages for moving the distal link 13. The distal link 13 has six distal links 14 connected to the six linkages. The six distal links 14 are arranged around the central axis of the distal link 13. Six angles between distal links 14 that are adjacent as viewed from the central axis are alternatingly set to a prescribed large angle α and a prescribed small angle β along the periphery of the central axis.

Description

Work manipulator and system including work manipulator

[0001] The present invention relates to a work manipulator applicable to an automatic work machine such as a surgical robot or an industrial robot, and a system including the work manipulator.

[0002] Microsurgery, which involves performing surgery under a microscope on minute surgical targets, such as anastomosis of small blood vessels, nerves, and lymphatic vessels with a diameter of approximately 0.5 to 2 mm, in orthopedic and plastic surgery surgeries and reconstructive surgery for defective parts, requires extremely precise and accurate work due to the small size of the surgical targets, and the surgery requires great skill. Furthermore, due to the difficulty of the surgery, it tends to take a long time, and such long surgeries place a heavy burden on the surgeon. For these reasons, the number of surgeons capable of performing microsurgery is limited compared to the need for it, and it has not been possible to perform the surgery frequently.

[0003] If we consider the use of manipulators (robots), which have made great technological advances in recent years, master-slave manipulators are not only able to exactly replicate human movements, but are also capable of performing movements that are scaled down to human movements. If a manipulator with precise movements were to take over the movements involved in surgery, it would be possible to eliminate the effects of hand shake and other factors, ensure precision, reduce the burden on the surgeon, and expect to improve the efficiency of surgery.

[0004] Therefore, the present inventors have proposed a fine work support system that can efficiently support work by remotely controlling appropriate work-related movements and reduce the burden on the worker, as well as a fine work manipulator to be used therein (see Patent Document 1).

[0005] Japanese Patent Application Publication No. 2017-87322

[0006] The fine manipulation manipulator disclosed in Patent Document 1 operates an end effector at its distal end by a parallel link mechanism. However, there are cases where the control of the end effector by the parallel link mechanism becomes inappropriate.

[0007] One of the factors that causes such a situation is a singularity. That is, when at least a part of the linkage of the parallel link mechanism assumes a posture near a singularity, the stability of the control of the position and posture of the end effector decreases. In addition, the rigidity of the parallel link mechanism may decrease near a singularity.

[0008] Another factor is the twisting motion of the end effector. That is, when the end effector is twisted (rotated) using a parallel link mechanism, the multiple linkages have a twisted positional relationship. This reduces the rigidity of the parallel link mechanism, which poses a problem of reducing the stability of control of the position and orientation of the end effector.

[0009] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a working manipulator that can improve the stability of the position and posture of an end effector using a parallel link mechanism, and an apparatus equipped with such a manipulator.

[0010] A work manipulator according to one aspect of the present invention includes a parallel link mechanism including six linkages arranged in parallel, each of the six linkages including one proximal link and one intermediate link, a manipulator base supporting the proximal ends of the proximal links of the six linkages, distal links having six distal junctions connected to the distal ends of the intermediate links of the six linkages at the six distal junctions, an end effector supported by the distal links, and six proximal actuators that move the proximal links of the six linkages relative to the manipulator base, respectively, to move the six distal links and thereby move the end effector. The six distal junctions of the distal links are arranged around a first axis of the distal link. The six distal junctions are designated in order around the first axis as the first, second, third, fourth, fifth and sixth distal junctions, and when viewed from the first axis, the angle between the first and second distal junctions is designated as the first angle, the angle between the second and third distal junctions is designated as the second angle, the angle between the third and fourth distal junctions is designated as the third angle, the angle between the fourth and fifth distal junctions is designated as the fourth angle, the angle between the fifth and sixth distal junctions is designated as the fifth angle, and the angle between the sixth and first distal junction is designated as the sixth angle, the first, third and fifth angles are greater than the second, fourth and sixth angles.

[0011] According to another aspect of the present invention, a system for controlling the position and attitude of an end effector includes a work manipulator that moves the end effector and a control device that controls the work manipulator. The work manipulator has a parallel link mechanism and a rotational actuator. The parallel link mechanism includes a distal link that supports the end effector, multiple linkages arranged in parallel that move the distal link, and a linkage actuator that moves the multiple linkages. The rotational actuator is provided between the distal link and the end effector and controls the roll angle of the end effector.

[0012] In the above system, the control device receives a first control command related to the position and orientation of the end effector and extracts a first control component related to the roll angle of the end effector from the first control command. If the first control component does not exceed a preset threshold, the control device controls only the linkage actuator out of the linkage actuator and the rotational actuator in accordance with the first control command. If the first control component exceeds the threshold, the control device calculates a second control component related to the roll angle by removing the threshold from the first control component, and calculates the second control command by removing the second control component from the control command. The control device controls the rotational actuator in accordance with the second control component related to the roll angle, and controls the linkage actuator in accordance with the second control command.

[0013] Alternatively, the control device of the above system may operate as follows: if a first control command related to the position and attitude of the end effector does not include a control component related to the roll angle of the end effector, the control device controls only the linkage actuator of the linkage actuator and the rotational actuator in accordance with the first control command. On the other hand, if the first control command includes a control component related to the roll angle, the control device calculates a second control command by removing the control component related to the roll angle from the first control command. Then, the control device controls the rotational actuator in accordance with the control component related to the roll angle, and controls the linkage actuator in accordance with the second control command.

[0014] According to the present invention, it is possible to improve the stability of control of the position and attitude of the end effector.

[0015] 1 shows a perspective view showing a schematic configuration of a system according to an embodiment. FIG. 1 shows a perspective view showing a schematic configuration of a system according to an embodiment. FIG. 2 shows a schematic diagram for explaining the configuration of a work manipulator according to an embodiment. FIG. 3 shows a block diagram showing a schematic configuration of a control device of a system according to an embodiment. FIG. 4 shows a perspective view showing a work manipulator according to an embodiment. FIG. 5 shows a side view showing a work manipulator according to an embodiment. FIG. 6 shows a plan view showing a work manipulator according to an embodiment. FIG. 7 shows a front view of a parallel link mechanism of a work manipulator according to an embodiment. FIG. 8 shows a rear view of a distal link and six linkages of a parallel link mechanism of a work manipulator according to an embodiment. FIG. 9 shows a rear view of six linkages and six linear actuators of a parallel link mechanism of a work manipulator according to an embodiment. FIG. 10 shows a side view showing an example of a singular point posture of a work manipulator according to an embodiment. FIG. 11 shows a rear view of a distal link according to a comparative example. FIG. 12 shows a side view showing an example of a singular point posture of a work manipulator according to a comparative example. FIG. 13 shows a diagram showing the results of a simulation for examining control stability near a singular point. FIG. 14 shows a diagram showing the results of a simulation for examining control stability near a singular point. FIG. 15 shows a diagram for explaining a modified example of a work manipulator. FIG. 1 shows a side view illustrating the posture of a singular point in a modified example of the work manipulator. FIG. 2 shows a diagram illustrating the results of a simulation to examine control stability near a singular point in the modified example. FIG. 3 shows a diagram illustrating the results of a simulation to examine control stability near a singular point in the modified example. FIG. 4 shows a flowchart illustrating an example of the operation of a control device for a system according to an embodiment. FIG. 5 shows a flowchart illustrating an example of the operation of a control device for a system according to an embodiment. FIG. 6 shows a front view illustrating an example of the posture of six intermediate links when twisting (rolling) the work manipulator according to an embodiment. FIG. 7 shows a side view illustrating an example of the posture of six intermediate links when twisting (rolling) the work manipulator according to an embodiment.

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the scope of the invention as claimed, and not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the invention. Furthermore, the following description will be limited to an embodiment in which the present invention is applied to a surgical support robot, but the present invention can be applied not only to surgical support robots but also to a wide range of general industrial robots.

[0017] In the drawings illustrating the embodiments, parts having the same functions are denoted by the same reference numerals, and repeated explanations thereof will be omitted. Also, the dashed and dotted lines in the drawings do not represent the configuration of the present embodiment, but are virtual lines used to explain the present embodiment.

[0018] In this embodiment, as an example, a system 1 configured as a surgical operation support robot equipped with a working manipulator 10 compatible with microsurgery will be described.

[0019] 1 to 4, the system 1 according to this embodiment has a working manipulator 10, an arm mechanism 20 to which the working manipulator 10 is attached at its distal end, a robot base 30 that supports the arm mechanism 20, an imaging unit 40 that is also attached to the robot base 30 and captures images of the surgical target, a display unit (not shown) that displays images of the surgical target captured by the imaging unit 40 so that they can be seen by the user, a first control unit (master manipulator) 50 that receives input instructions operated by the user, and a second control unit 60 that controls the working manipulator 10 and the arm mechanism 20 in accordance with the input instructions of the first control unit 50. The control device including the first and second control units 50, 60 will be described in detail below.

[0020] The robot base 30 has a movement mechanism (not shown), and is configured to be movable on the floor of an operating room (not shown) together with the working manipulator 10, arm mechanism 20, and imaging unit 40 provided on this robot base 30. This enables the system 1 to approach and move away from the operating table 3 on which a patient 2, the subject of surgery shown in Figure 1, lies, and further enables at least the distal end of the working manipulator 10 to be positioned at the surgical site on the patient 2.

[0021] The imaging unit 40 captures images of the distal end (e.g., forceps) of the end effector 12 of the working manipulator 10 (described later) and the surgical target, and is disposed, for example, at a position that provides a bird's-eye view of at least the distal end of the working manipulator 10 and the surgical target. The imaging unit 40 is a known video camera that can capture high-resolution images that can be reproducibly even when enlarged to the same magnification as when viewed with a conventional microsurgery microscope.

[0022] The arm mechanism 20 is positioned between the robot base 30 and the work manipulator 10, and enables the position and orientation of the work manipulator 10 to be changed relative to the robot base 30. The arm mechanism 20, for example, has a plurality of arms 21 variably connected in series via a plurality of arm junctions 22. A wrist 23 that supports the work manipulator 10 is connected to the distal end of the arm mechanism 20. For example, the arm mechanism 20 is configured to have three degrees of freedom in rotation and one degree of freedom in translation in the radial direction, but is not limited to this. Furthermore, in the illustrated example, a pair of arm mechanisms 20 and work manipulators 10 are provided on the robot base 30, but there is no particular limit to the number of arm mechanisms 20 and work manipulators 10.

[0023] The first control unit 50 has, for example, an operation input unit (not shown) operated by the user, and a support mechanism unit (not shown) that supports the operation input unit. For example, the support mechanism unit movably supports the operation input unit with six degrees of freedom similar to a work manipulator, obtains information about the position and orientation of the operation input unit corresponding to the support mechanism unit, and passes this information to the second control unit 60 of the work robot. As a result, the work operation of the system 1 is performed when the user operates the operation input unit.

[0024] Next, the work manipulator 10 will be described with reference to Figure 3 and Figures 5 to 7. The work manipulator 10 has a manipulator base 11, a parallel link mechanism 10A, a rotary actuator 19, and an end effector 12. The manipulator base 11 is supported by an arm mechanism 20. The parallel link mechanism 10A is attached to the manipulator base 11. The end effector 12 is mounted on the distal end of the parallel link mechanism 10A via the rotary actuator 19. The parallel link mechanism 10A controls the position and attitude of the end effector 12. The rotary actuator 19 controls the twisting (= rolling) of the end effector 12.

[0025] The parallel link mechanism 10A has, for example, six linkages 10B arranged in parallel, one distal link 13, and six distal junctions 14 that connect each of the six linkages 10B to one common distal link 13. The proximal end of each of the six linkages 10B is supported by the manipulator base 11. Note that the number of linkages 10B included in the parallel link mechanism 10A may be any number other than six, but an example in which six linkages are included will be described below.

[0026] Each of the six linkages 10B includes a linear actuator 18 (an example of a linkage actuator), a proximal link 17, a proximal junction 16, and a middle link 15. The middle link 15 and the proximal link 17 have a generally rod-like shape that is highly rigid and resistant to deformation. The distal end of the middle link 15 is connected to the distal link 13 via the distal junction 14. The proximal end of the middle link 15 is connected to the distal end of the proximal link 17 via the proximal junction 16. The proximal end of the proximal link 17 is attached to the manipulator base 11 via the linear actuator 18. The middle link 15 extends, for example, in a direction parallel to the central axis C1 of the parallel link mechanism 10A. The linear actuator 18 can linearly reciprocate the middle link 15 in its longitudinal direction (the direction parallel to the central axis C1).

[0027] The proximal junction 16 is, for example, a universal junction having degrees of freedom for rotation about two mutually perpendicular axes, and connects the proximal link 17 to the intermediate link 15. The distal junction 14 is also, for example, a universal junction having degrees of freedom for rotation about two mutually perpendicular axes, and connects the intermediate link 15 to the distal link 13.

[0028] In addition, the intermediate link 15 is composed of two generally rod-shaped members connected to each other so as to be rotatable about their longitudinal axes, and a degree of freedom of mutual rotation about the longitudinal axis is imparted between the distal end and proximal end of the intermediate link 15. Note that the proximal junction 16 and the distal junction 14 may be ball joints which provide an even greater degree of rotational freedom.

[0029] Six linear actuators 18 are supported by the manipulator base 11 and move the six linkages 10B, respectively. Each linear actuator 18 is, for example, a linear motor including a stator and a mover (not shown). For example, each stator is fixed to the manipulator base 11, and each mover is fixed to a proximal end of a proximal link 17, and each mover is capable of linear reciprocating movement relative to the stator along the longitudinal direction of the proximal link 17. For example, the stator may be a permanent magnet, and the mover may be a coil that is slidable relative to the permanent magnet. This allows each of the multiple proximal links 17 to be linearly moved in its longitudinal direction (a direction parallel to the central axis C1) by the corresponding linear actuator 18.

[0030] Because the linear actuator 18 uses a linear motor, it is possible to reduce the number of mechanical moving parts compared to other linear motion mechanisms such as ball screws, and also to reduce the number of contact parts that involve sliding and rolling, thereby preventing backlash, improving the reliability of the mechanism and reducing frictional resistance and power consumption required for driving.

[0031] The distal ends of the six linkages 10B of the parallel link mechanism 10A (i.e., the distal ends of the six intermediate links 15) are connected to one common distal link 13 via six distal junctions 14, respectively.

[0032] 8 and 9, the distal link 13 has a main member located at its center, six fingers 13b extending radially from the main member 13a, and six distal junctions 14 provided on each of the six fingers 13b. The distal link 13 is connected to the distal end of the middle link 15 of each of the six linkages 10B via the distal junctions 14 of the six fingers 13b.

[0033] The distal link 13 supports the end effector 12. For example, a rotary actuator 19 is attached to the distal end of the distal link 13, and the end effector 12 is attached to the distal end of the rotary actuator 19.

[0034] As shown in FIG. 6, for example, when the positions and postures of the six linkages 10B of the parallel link mechanism 10A are the same (i.e., the movement amounts of the six linear actuators 18 are the same), the central axis C4 of the distal link 13 coincides with the central axis C1 of the parallel link mechanism 10A (and the manipulator base 11).

[0035] 6, the end effector 12 and the rotary actuator 19 share the same central axis C2, which is slightly inclined with respect to the central axis C4 of the distal link 13. The tip of the end effector 12 is disposed on the central axes C2 and C4. However, the arrangement of the rotary actuator 19 and the arrangement of the tip of the end effector 12 are not limited to this example.

[0036] The parallel link mechanism 10A gives the distal link 13 six degrees of freedom simply by linearly moving the multiple linkages 10B using the linear actuators 18, allowing the position and orientation of the distal link 13 and the end effector 12 relative to the manipulator base 11 to be changed quite freely.

[0037] In addition, by having the rotational actuator 19, the work manipulator 10 can accommodate various movements related to changes in the position and posture of the end effector 12 provided at the distal end relative to the manipulator base 11 with six degrees of freedom, consisting of three degrees of freedom of movement in three mutually perpendicular axial directions and three degrees of freedom of rotation around each of the three axes, just as when the end effector 12 is supported by a human hand.

[0038] In the following description, the six distal junctions 14 and six linkages 10B may be distinguished from one another by using the modifiers first, second, third, fourth, fifth, and sixth in the clockwise arrangement order around the central axis C4 of the distal link 13 in the rear view of the distal link 13 and its peripheral components shown in FIG. 9 . For example, the first middle link 15 of the first linkage 10B is connected to the first distal junction H1 (14). The second middle link 15 of the second linkage 10B is connected to the second distal junction H2 (14). The third middle link 15 of the third linkage 10B is connected to the third distal junction H3 (14). The fourth middle link 15 of the fourth linkage 10B is connected to the fourth distal junction H4 (14). The fifth intermediate link 15 of the fifth linkage 10B is connected to the fifth distal junction H5 (14). The sixth intermediate link 15 of the sixth linkage 10B is connected to the sixth distal junction H6 (14).

[0039] As shown in FIG. 9 , the six distal junctions 14 of the distal link 13 (which may also be referred to as the distal ends of the six middle links 15) are arranged on a single imaginary plane 70, for example, along a single circle centered on the central axis C4. When a certain middle link 15 assumes a position in which its longitudinal direction is parallel to the imaginary plane 70 (in other words, the middle link 15 lies on the imaginary plane 70), the ability of that middle link 15 to control the position of the distal link 13 deteriorates. This position of the middle link 15 can be referred to as a singular point of that middle link 15. If the position of some of the six middle links 15 approaches a singular point, the stability of the positional control of the distal link 13 by the parallel link mechanism 10A may be reduced. In this embodiment, as described below, measures are taken to reduce the effects of this singular point regarding the arrangement of the six distal junctions 14.

[0040] 9 , with respect to the arrangement of the six distal junctions as viewed from the central axis C4 of the distal link 13, the angle between the first and second distal junctions H1 and H2 will be referred to as the first angle, the angle between the second and third distal junctions H2 and H3 as the second angle, the angle between the third and fourth distal junctions H3 and H4 as the third angle, the angle between the fourth and fifth distal junctions H4 and H5 as the fourth angle, the angle between the fifth and sixth distal junctions H5 and H6 as the fifth angle, and the angle between the sixth and first distal junctions H6 and H1 as the sixth angle, with the central axis C4 as the intersection point. The first, third, and fifth angles are larger than the second, fourth, and sixth angles. That is, the first to sixth angles are set so that relatively large angles and relatively small angles alternate along one rotational direction (e.g., clockwise) about the central axis C4. Specifically, as shown in FIG. 9, the first, third, and fifth angles are set to the same angle α, the second, fourth, and sixth angles are set to the same angle β, and the angle α is greater than the angle β.

[0041] For example, the angle α is greater than 60 degrees and less than 120 degrees, the angle β is greater than 0 degrees and less than 60 degrees, and the sum of the angles α and β is 120 degrees. Preferably, the angle α is set to be greater than 80 degrees and less than 100 degrees, and the angle β is set to be greater than 20 degrees and less than 40 degrees. More preferably, the angle α is set to be greater than 85 degrees and less than 95 degrees, and the angle β is set to be greater than 25 degrees and less than 35 degrees.

[0042] The arrangement of the first to sixth distal junctions 14 described above can be explained as follows. Here, the distance between the first and second distal junctions H1 and H2 is referred to as the first distance, the distance between the second and third distal junctions H2 and H3 as the second distance, the distance between the third and fourth distal junctions H3 and H4 as the third distance, the distance between the fourth and fifth distal junctions H4 and H5 as the fourth distance, the distance between the fifth and sixth distal junctions H5 and H6 as the fifth distance, and the distance between the sixth and first distal junctions H6 and H1 as the sixth angle. The first, third, and fifth distances are longer than the second, fourth, and sixth distances. That is, the first to sixth distances are set so that relatively long distances and relatively short distances alternate along one rotational direction (e.g., clockwise) around the central axis C4. Specifically, as shown in FIG. 9, the first, third, and fifth distances are set to the same distance (the distance corresponding to angle α), the second, fourth, and sixth angles are set to the same distance (the distance corresponding to angle β), and the former distances are longer than the latter distances.

[0043] By arranging the six distal junctions 14 at unequal intervals around the central axis C4, the stability of the control of the position and attitude of the end effector 12 by the parallel link mechanism 10A can be improved even when some of the intermediate links 16 assume a posture near a singular point, as will be described later.

[0044] The six linkages 10B of the parallel link mechanism 10A are arranged around the central axis C1 of the parallel link mechanism 10A. For example, as shown in FIGS. 9 and 10 , the six proximal links 17 are arranged along a circle centered on the central axis C1. The diameter of this circle is larger than the diameter of the circle on which the distal junctions 14 are arranged. Therefore, in most cases, each linkage 10B is bent at the proximal junction 16, and the proximal link 17 and the middle link 15 are not aligned in a straight line (singular point posture).

[0045] Here, in the rear view shown in Figure 10, the six linkages 10B are referred to as the first, second, third, fourth, fifth, and sixth linkages in clockwise arrangement order around the central axis C1, and the six proximal links 17 that these first, second, third, fourth, fifth, and sixth linkages respectively have are referred to as the first, second, third, fourth, fifth, and sixth proximal links (L1, L2, L3, L4, L5, L6).

[0046] 10 , with the central axis C1 as the intersection point, the angle between the first and second proximal links L1 and L2 will be referred to as the seventh angle, the angle between the second and third proximal links L2 and L3 as the eighth angle, the angle between the third and fourth proximal links L3 and L4 as the ninth angle, the angle between the fourth and fifth proximal links L4 and L5 as the tenth angle, the angle between the fifth and sixth proximal links L5 and L6 as the eleventh angle, and the angle between the sixth and first proximal links L6 and L1 as the twelfth angle. The seventh, ninth, and eleventh angles are set smaller than the eighth, tenth, and twelfth angles. That is, the seventh to twelfth angles are set so that relatively small angles and relatively large angles alternate along one rotational direction (e.g., clockwise) about the central axis C1. Specifically, for example, as shown in FIG. 10 , the seventh, ninth, and eleventh angles are set to the same angle γ, and the eighth, tenth, and twelfth angles are set to the same angle δ, with angle γ being smaller than angle δ.

[0047] The arrangement of the first to sixth proximal links 17 described above can be explained from another aspect as follows. Here, the distance between the first and second proximal links L1, L2 will be referred to as the seventh distance, the distance between the second and third proximal links L2, L3 as the eighth distance, the distance between the third and fourth proximal links L3, L4 as the ninth distance, the distance between the fourth and fifth proximal links L4, L5 as the tenth angular distance, the distance between the fifth and sixth proximal links L5, L6 as the eleventh distance, and the distance between the sixth and first proximal links L6, L1 as the twelfth distance. The seventh, ninth, and eleventh distances are set shorter than the eighth, tenth, and twelfth distances. That is, the seventh to twelfth distances are set so that relatively short distances and relatively long distances alternate along one rotational direction (e.g., clockwise) about the central axis C1. Specifically, for example, as shown in FIG. 10 , the seventh, ninth, and eleventh distances are set to the same distance (the distance corresponding to the angle γ), and the eighth, tenth, and twelfth distances are set to the same distance (the distance corresponding to the angle δ), with the former distances being shorter than the latter distances.

[0048] The six proximal links 17 are arranged parallel to the central axis C1. Therefore, the relative positions of the six proximal junctions 16 are also the same as the relative positions of the six proximal links 17 described above.

[0049] As described above, by disposing the six proximal links 17 at unequal angles and distances from one another, the six intermediate links 15 are disposed as follows: That is, as shown in FIG. 9 , the first and second intermediate links M1, M2 are disposed at their proximal ends by a relatively small central angle γ (close spacing) and at their distal ends by a relatively large central angle α (far spacing). A similar arrangement exists between the third and fourth intermediate links M3, M4 and between the fifth and sixth intermediate links M5, M6. On the other hand, the second and third intermediate links M2, M3 are disposed at their proximal ends by a relatively large central angle θ (far spacing) and at their distal ends by a relatively small central angle β (close spacing). A similar arrangement exists between the fourth and fifth intermediate links M4, M5 and between the sixth and first intermediate links M6, M1.

[0050] By arranging the six intermediate links 15 in this manner, the intermediate links 15 are not parallel to one another, but are spaced at a fairly large angle from one another, which allows the parallel link mechanism 10A to more stably control the posture of the end effector 12.

[0051] 11 is a side view showing an example of a singularity posture of the work manipulator 10. In this example, two adjacent middle links 15, for example, the first and second middle links 15 (M1 and M2), of the six middle links 15, are in a singularity posture (i.e., a posture parallel to the virtual plane 70 of the distal link 13). In this example, the two middle links 15 (M1 and M2) in the singularity posture are positioned higher than the other middle links 15, and the central axis C4 of the distal link 13 is tilted upward by an angle A1 (pitch angle) with respect to the horizontal direction C3. In this example, the two middle links 15 (M1 and M2) in the singularity posture cannot control the pitch angle of the distal link 13.

[0052] In practice, the work manipulator 10 is controlled so that none of the six middle links 15 assumes a singular posture. However, there may be cases where the postures of some of the middle links 15 (for example, the first and second middle links 15 (M1, M2) as shown in FIG. 11 ) approach the singular posture, deteriorating the posture control capability of those middle links 15. In such cases, if the posture control capability of the other middle links 15 is sufficiently high, those other middle links 15 can stably control the posture of the distal link 13 (end effector 12). The posture control capability of those other middle links 15 is affected by the arrangement of the six middle links 15. 11 , when the second intermediate link 15 (M2) is near the singular point, the greater the distance D1 between the line of action of the third intermediate link 15 (M3) and the fourth distal junction 14 (H4), the greater the ability of the third and fourth intermediate links 15 (M3 and M4) to control the attitude. In FIG. 11 , if the distal link 13 is considered to be a lever and the second distal junction 14 (H3) is considered to be the point of action of the lever, the third distal junction 14 (H2) is the point of force, and the fourth distal junction 14 (H4) is the fulcrum, and the distance D1 can be considered to be the distance between the point of force and the fulcrum. The distance D1 is determined by the arrangement of the six distal junctions 14 of the distal link 13.

[0053] In this embodiment, as shown in FIG. 9 , six distal junctions 14 are arranged at different unequal angles α and β around the central axis C4 of the distal link 13. Here, as a comparative example, as shown in FIG. 12 , a distal link 93 is assumed in which all six distal junctions 14 are arranged at an equal angle α2 (=60 degrees) around the central axis C4. (Hereinafter, the distal links 13 according to this embodiment may be referred to as "unequally arranged distal links," and the distal links 93 of the comparative example may be referred to as "equally arranged distal links.") Next, as shown in FIG. 13 , a work manipulator 110 is assumed in which evenly arranged distal links 93 are used instead of the unevenly arranged distal links 13. In the work manipulator 10 according to this embodiment using the unevenly arranged distal links 13 shown in FIG. 11 , the distance D1 is greater than in the work manipulator 110 using the evenly arranged distal links 93 shown in FIG. 13 . Therefore, the work manipulator 10 according to this embodiment has more stable posture control of the end effector 12 than the comparative work manipulator 110. Note that in order to constantly enjoy the benefits of this posture control, when the posture of the end effector 12 is changed so greatly that two adjacent middle links 15 in the work manipulator 10 come close to a singular point, it is desirable to control the overall posture of the work manipulator 10 by the arm mechanism 20 so that the two adjacent middle links 15 are arranged at a relatively large angle α, such as the first and second middle links 15 (M1, M2).

[0054] The inventors performed a computer simulation to investigate the difference in control stability in the attitude near the singular point between this embodiment and the comparative example. The results are shown in Figures 14 and 15.

[0055] In this simulation, the larger central angle α between the six distal junctions 14 according to this embodiment shown in FIG. 9 was set to 88 degrees, and the smaller central angle β was set to 32 degrees. The central angle α1 between the distal junctions 14 according to the comparative example shown in FIG. 12 was set to 60 degrees. As shown in FIGS. 11 and 13 , for each of the work manipulators 10, 110 according to this embodiment and the comparative example, the first and second intermediate links 15 (M1, M2) were positioned at the highest positions, and a trapezoidal velocity control process was performed in which the pitch angle A1 of the distal links 13, 93 was accelerated, moved at a constant velocity, and decelerated from zero to 26 degrees, and the change in the pitch angle A1 during this process was measured. Here, the pitch angle corresponding to the singular point of the first and second intermediate links 15 (M1, M2) in the work manipulator 10 according to this embodiment was 26.05 degrees, while that of the work manipulator 110 according to the comparative example was 26.8 degrees, with no significant difference between the two. The goal pitch angle of 26 degrees in the above control process corresponds to the vicinity of the singular points of the work manipulators 10 and 110. As a result of this simulation, as shown in Figures 14 and 15, vibrations occurred in the work manipulator 110 of the comparative example, but no vibrations occurred in the work manipulator 10 of this embodiment.

[0056] Next, a modified example of the working manipulator 10 according to this embodiment will be described with reference to FIGS.

[0057] In the distal link 130 according to the modified example shown in FIG. 16 , the second, fourth, and sixth angles β between the distal junctions 14 described with reference to FIG. 9 are set to the smallest possible angles, and the first, third, and fifth angles α are set to the largest possible angles. For example, the angle β is substantially 0 degrees, and the angle α is substantially 120 degrees. Three fingers 130 b extend from the main member 130 a. Two distal junctions 14 arranged closely to each other at an angle β are integrated into each junction unit 140 provided on each finger 130 b. Hereinafter, such an arrangement of distal junctions 14 may be referred to as an integrated arrangement. In the work manipulator 101 according to the modified example shown in FIG. 17 , an integrated distal link 130 is used, and two adjacent intermediate links 15 (e.g., the second and third intermediate links 15 (M2, M3)) are connected to each junction unit 140 at a relatively large central angle δ. In reality, the angle β may be set to be greater than 0 degrees and less than 15 degrees, and the angle α may be set to be greater than 105 degrees and less than 120 degrees. As shown in Fig. 17, the distance D1 for stability of attitude control near the singular point may be larger than in the embodiment shown in Fig. 11.

[0058] The inventors performed a similar simulation to that described above for a work manipulator 101 according to a modified example shown in FIG. 17. In this simulation, the central angle α between the distal junctions 14 of the distal links 130 according to the modified example was set to the theoretical maximum limit of 120 degrees, and the central angle β was set to the theoretical minimum limit of 0 degrees. Since the pitch angle A1 value corresponding to the singular point was 23.27 degrees, trapezoidal velocity control was performed to accelerate, move at a constant velocity, and decelerate the pitch angle A1 from 0 degrees to 23 degrees near the singular point, and changes in the pitch angle A1 were examined. For comparison, trapezoidal velocity control was also performed to accelerate, move at a constant velocity, and decelerate the pitch angle A1 from 0 degrees to 23 degrees for the work manipulator 110 according to the comparative example shown in FIG. 13, and changes in the pitch angle A1 were examined.

[0059] The results of the above simulation are shown in Figures 18 and 19. Vibrations occurred in the work manipulator 110 of the comparative example, but no vibrations occurred in the work manipulator 101 according to the modified example of this embodiment.

[0060] Therefore, it was confirmed that the work manipulators 10, 101 according to this embodiment can provide better stability in attitude control near singular points compared to the work manipulator 110 according to the comparative example.

[0061] Next, a control device for the system 1 including the working manipulator 10 according to this embodiment will be described.

[0062] 4 is a block diagram showing the schematic configuration of a control device of the system 1 according to this embodiment. The control device 200 has a first control unit 50 and a second control unit 60. In the system 1 according to this embodiment configured as a surgical support robot, the first control unit 50 includes, for example, a master manipulator that is manually operated by a user. The first control unit 50 outputs control instructions corresponding to the manual operation of the master manipulator to the second control unit 60. The control instructions include, for example, operation commands related to the three-dimensional position and orientation of the tip of the end effector 12. The second control unit 60 controls the work manipulator 10 and the arm mechanism 20 based on the control instructions from the first control unit 50.

[0063] In the second control unit 60, the first calculation unit 61a receives control instructions from the first control unit 50, grasps operation commands related to the position and orientation of the tip of the end effector 12, and calculates operation commands related to the arm mechanism 20 and operation commands related to the work manipulator 10 based on these operation commands. The arm mechanism control unit 62 receives operation commands related to the arm mechanism 20 from the first calculation unit 61a, and calculates and outputs operation control values ​​for each element of the arm mechanism 20. The servo controller 64 receives the operation control values ​​for each element of the arm mechanism 20 and drives and controls each element of the arm mechanism 20.

[0064] The second calculation unit 61c calculates a movement command for the parallel link mechanism 10A and a movement command for the rotary actuator 19 based on the movement command for the work manipulator 10 from the first calculation unit 61a. The rotary actuator control unit 65 receives the movement command for the rotary actuator 19 from the second calculation unit 61c, calculates a movement control value for the rotary actuator 19, and outputs it to the servo controller 66. The servo controller 66 drives and controls the rotary actuator 19 based on the movement control value for the rotary actuator 19. The parallel link control unit 63 receives the movement command for the parallel link mechanism 10A from the second calculation unit 61c, and calculates movement control values ​​for the six linkages 10B (i.e., the six linear actuators 18). The six servo controllers 64 receive the movement control values ​​for the six linear actuators 18, respectively, and drive and control the six linear actuators 18. In response to this, each servo controller 64 drives the linear motor of each linkage.

[0065] 20 and 21 are flow charts showing an example of the operation of the control device 200 of this embodiment.

[0066] As shown in FIG. 20, the user manually operates the master manipulator of the first control unit 50 (step S10).

[0067] The first control unit 50 encodes the movement of the master manipulator and calculates the position and orientation of the master manipulator after operation (step S11).

[0068] The first control unit 50 subtracts the known values ​​of the position and orientation of the master manipulator before the operation from the values ​​of the position and orientation of the master manipulator after the operation (step S12), thereby calculating the amount of change in the position and orientation of the master manipulator due to the manual operation (step S13).

[0069] The first control unit 50 multiplies the change in the position and orientation of the master manipulator by a predetermined reduction rate (step S14), thereby calculating the control amount of the position and orientation of the end effector 12 (step S15).

[0070] The second control unit 60 receives the control amounts for the position and orientation of the end effector 12 from the first control unit 50, and adds the known values ​​for the current position and orientation of the end effector 12 to the control amounts (step S16). As a result, target values ​​for the position and orientation of the end effector 12 are calculated (step S17).

[0071] The second control unit 60 determines whether or not the target values ​​of the position and orientation of the end effector 12 described above exceed a predetermined range of movement of the end effector 12 by the working manipulator 10 alone (step S18).

[0072] If the result of the above determination is YES, the position and orientation of the end effector 12 cannot be brought to their respective target values ​​without using both the work manipulator 10 and the arm mechanism 20. In this case, the second control unit 60 calculates the control amounts of the multiple actuators of the arm mechanism 20 required to adjust the position and orientation of the work manipulator 10 after returning the work manipulator 10 to its neutral position (step S19). The arm mechanism 20 is driven and controlled based on these control amounts (step S20).

[0073] In addition, the second control unit 60 recalculates the control amounts of the position and orientation of the end effector 12 from the neutral position of the working manipulator 10, which are necessary to bring the position and orientation of the end effector 12 to their respective target values ​​(step S21). Then, the control by the second control unit 60 proceeds to the process shown in FIG.

[0074] On the other hand, if the determination result in step S18 above is NO, the position and orientation of the end effector 12 can be brought to their respective target values ​​using only the working manipulator 10. In this case, the second control unit 60 validates the position and orientation of the end effector 12 calculated in step S15 (step S22). Then, control by the second control unit 60 proceeds to the process shown in FIG. 21.

[0075] Fig. 21 shows a process for controlling the work manipulator 10 by the second control unit 60. The second control unit 60 extracts (step S32) a control amount component for the twist angle of the distal link 13 (i.e., the roll angle of the distal link 13 about the central axis C4) from the control amounts for the position and orientation of the end effector 12 obtained in step S22 or S23 in Fig. 20 (step S31).

[0076] The second control unit 60 determines whether the control amount component of the twist (roll) angle extracted in step S32 exceeds a preset twist (roll) angle threshold (step S33). The threshold is set to a small roll angle value that satisfies the condition that the decrease in control stability that may occur when twisting (rolling) the distal link 13 with the parallel link mechanism 10A is so slight that it is not a problem. For example, the threshold may be set to an angle value of 20 degrees or less, or 10 degrees or less. Alternatively, the threshold may be set to 0 degrees. A threshold of 0 degrees means that the operation of twisting (rolling) the distal link 13 is performed solely by the rotation actuator 19, not by the parallel link mechanism 10A.

[0077] If the determination result in step S33 is YES, the second control unit 60 calculates an angle value by subtracting the above threshold value from the control amount component of the twist (roll) angle described above, and sets this as the control amount of the rotation actuator 19 (step S36).

[0078] The second control unit 60 drives and controls the rotary actuator 19 based on the control amount calculated in step S36 (step S37).

[0079] In addition, the second control unit 60 determines the angle value corresponding to the threshold value as the control amount for the twisting (rolling) operation of the distal link 13 to be performed by the parallel link mechanism 10A (step S38). Then, the control by the second control unit 60 proceeds to step S35.

[0080] On the other hand, if the determination result in step S33 is NO, the second control unit 60 determines the control amount component of the twist (roll) angle as the control amount of the twist (roll) operation of the distal link 13 to be performed by the parallel link mechanism 10A (step S34).Then, the control by the second control unit 60 proceeds to step S35.

[0081] In step S35, the second control unit 60 replaces the control amount component of the twist angle extracted in step S32, among the control amounts of the position and attitude of the end effector obtained in step S31, with the control amount component of the twist angle calculated in step S34 or S38. Then, using the control amounts of the position and attitude of the end effector updated by this replacement, the second control unit 60 calculates the control amount of each of the six linear actuators 18 of the parallel link mechanism 10A (step S35).

[0082] The second control unit 60 drives and controls the six linear actuators 18 of the parallel link mechanism 10A based on the control amount calculated in step S35 (step S39).

[0083] 21, in the working manipulator 10 using the parallel link mechanism 10A according to this embodiment, the twisting (rolling) operation performed by the parallel link mechanism 10A can be restricted to an appropriately small angle range. This prevents deterioration in the control ability of the parallel link mechanism 10A due to the twisting operation, and maintains stable control of the position and attitude of the end effector 12.

[0084] That is, when the end effector 12 is twisted (rolled) significantly using the parallel link mechanism 10A, the adjacent middle links 15 cross each other in an X-shape, as illustrated in FIG. 22 , which may reduce the overall rigidity of those middle links 15. Furthermore, the pressure angle from each middle link 15 to the distal link 13 increases. As a result, the stability of the attitude control of the distal link 13 may deteriorate. Furthermore, for example, as illustrated in FIG. 23 , if an attempt is made to change the attitude of the end effector 12 other than the roll angle (e.g., pitch angle A1) when the end effector 12 is twisted (rolled) significantly using the parallel link mechanism 10A, the pitch angle A1 at which one of the middle links 15 becomes a singular point may become smaller than when there is no twist or when there is a small twist, which may narrow the movable range of the end effector 12.

[0085] These problems can be alleviated by the control shown in FIG.

[0086] Furthermore, when it is predicted that the control target values ​​for the position or orientation of the end effector 12 will exceed the movable range of the work manipulator 10 using the control shown in Figures 20 and 21, by linking the work manipulator 10 with the arm mechanism 20, it is possible to control the position and orientation of the end effector 12 to their respective target values ​​without causing the work manipulator 10 to perform operations that would worsen the stability of the control of the work manipulator 10.

[0087] Furthermore, with the arrangement of the six distal junctions 14 of the distal link 13 shown in FIG. 9 and the arrangement of the six proximal links 17 shown in FIG. 10, the six intermediate links 15 are not always parallel to each other, so that the stability of the position and posture of the end effector 12 can be maintained.

[0088] It should be noted that the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, some of the configurations of each example can be added to, deleted from, or replaced with other configurations.

[0089] In the above-described embodiment, the first control unit 50 has a master manipulator that is manually operated by a user and generates control commands in response to the manual operation. However, the first control unit 50 may also be configured to automatically generate control commands in accordance with a pre-prepared program.

[0090] Furthermore, the system 1 according to the above-described embodiment can control the position and orientation of the end effector 12 with six degrees of freedom using the parallel link mechanism 10A having six linkages 10B. In other words, the system 1 has approximately the same degree of freedom of shape as a human hand and arm.

[0091] The system 1 according to the above-described embodiment can be applied to a variety of applications, including not only surgical operations but also product assembly, disassembly, processing, and maintenance, and human care. The configuration or function of the system can be changed depending on the application without departing from the spirit of the invention. Examples of applications to which the system 1 can be applied are as follows:

[0092] 1) Applications requiring a small load on the tip of the end effector 12 and high tracking accuracy, such as surgical operation support robots (master-slave robots).

[0093] 2) 3D microchip assembly robots. 3D fine manipulation for research, such as assembling biological cells one by one in 3D on a 3D collagen structure. High-speed picking, for example, involves repeatedly moving heavy objects to a predetermined position at high speed in a short period of time.

[0094] 3) Coating machines that can handle free-form surfaces. Applications that require constant pressure without being affected by fluctuations, such as bonding prepreg to a mold. For these applications, if the shape of the target object is fixed, the linear actuator's motion curve (operation method) can be preset and the linear actuator can operate according to that motion curve. To track irregular fluctuations, the distance to the location where pressure is scheduled to be applied a certain time from now can be measured, for example, with a laser distance sensor. Based on that measurement data, a motion curve for the linear actuator can be generated in real time and the linear actuator can be operated. Alternatively, a six-axis force sensor can be attached to the end effector, and the reaction force direction sensed by that sensor can be used to determine the direction of the curved surface of the target object with which the end effector is in contact. The end effector can then be moved in real time to apply a constant pressure perpendicular to that surface.

[0095] 4) Robots for drilling curved surfaces. Robots for holding grinders for deburring. These applications require the end effector to be pushed with a large force and controlled with high precision. To meet these requirements, a parallel link mechanism with an integrally arranged distal link 130 can be used, as shown in Figures 16 and 17. Furthermore, as the linear actuator 18, for example, a hydraulic actuator to which servo valve control is applied can be used.

[0096] In the above embodiment, the linear actuator 18 is used to move each linkage 10B of the parallel link mechanism 10A. However, instead, an actuator having two or more degrees of freedom of movement may be used.

[0097] In the above-described embodiment, the work manipulator 10 is automatically returned to the neutral position in response to a control command from the first control unit 50. However, the work manipulator 10 may also be returned to the neutral position in response to a command from the user (for example, a foot switch operated by the user) when the user desires. In this case, even if the work manipulator 10 returns to its initial position, the arm mechanism 20 may operate automatically to correctly control the position and orientation of the end effector 12.

[0098] REFERENCE SIGNS LIST 1...System, 10, 101...Work manipulator, 10A...Parallel link mechanism, 10B...Linkage, 11...Manipulator base, 12...End effector, 13...Distal link, 14...Distal junction, 15...Middle link, 16...Proximal junction, 17...Proximal link, 18...Linear actuator, 19...Rotational actuator, 20...Arm mechanism, 23...Wrist, 21...Arm, 22...Arm junction, 30...Robot base, 50...First control unit, 60...Second control unit, 61a...First calculation unit, 61c...Second calculation unit, 62...Arm mechanism control unit, 63, 64...Servo controller, 65...Rotational actuator control unit, 66...Parallel link actuator control unit, 70...Virtual plane, C1...Central axis of work manipulator, C2...Central axis of end effector, C3: central axis of the distal link; H1-H6: first to sixth distal junctions; L1-L6: first to sixth proximal links; M1-M6: first to sixth middle links.

Claims

1. A work manipulator for performing work on a work object, comprising: a parallel link mechanism including six linkages arranged in parallel, each of the six linkages including one proximal link and one intermediate link; a manipulator base supporting proximal ends of the proximal links of the six linkages; a distal link having six distal junctions, each connected to a distal end of the intermediate link of the six linkages at the six distal junctions; an end effector supported on the distal link; and six proximal actuators for moving each of the proximal links of the six linkages relative to the manipulator base to move the six distal links, thereby moving the end effector; the six distal junctions of the distal link are arranged around a first axis of the distal link, a first angle between the first and second distal junctions, a second angle between the second and third distal junctions, a third angle between the third and fourth distal junctions, a fourth angle between the fourth and fifth distal junctions, a fifth angle between the fifth and sixth distal junctions, and a sixth angle between the sixth and first distal junctions, wherein the first, third and fifth angles are greater than the second, fourth and sixth angles, when viewed from the first axis; 2. A work manipulator as described in claim 1, wherein said first, third and fifth angles are angle α, and said second, fourth and sixth angles are angle β, said angle α being greater than said angle β.

3. The six linkages are arranged around a second axis in the parallel link mechanism, and if the six linkages are named, in order around the second axis, as a first, second, third, fourth, fifth and sixth linkages, a first proximal link of the first linkage is connected to the first distal junction, a second proximal link of the second linkage is connected to the second distal junction, a third proximal link of the third linkage is connected to the third distal junction, a fourth proximal link of the fourth linkage is connected to the fourth distal junction, a fifth proximal link of the fifth linkage is connected to the fifth distal junction and a sixth proximal link of the sixth linkage is connected to the sixth distal junction; 3. The work manipulator according to claim 2, wherein, when viewed from the second axis, an angle between the first and second proximal links is defined as a seventh angle, an angle between the second and third proximal links is defined as an eighth angle, an angle between the third and fourth proximal links is defined as a ninth angle, an angle between the fourth and fifth proximal links is defined as a tenth angle, an angle between the fifth and sixth proximal links is defined as an eleventh angle, and an angle between the sixth and first proximal links is defined as a twelfth angle, the seventh, ninth and eleventh angles are smaller than the eighth, tenth and twelfth angles.

4. A work manipulator according to claim 3, wherein the seventh, ninth and eleventh angles are angles γ, and the eighth, tenth and twelfth angles are angles θ, and the angle γ is smaller than the angle θ.

5. A working manipulator according to any one of claims 1 to 4, further comprising a rotary actuator between said distal link and said end effector for rotating said end effector about a third axis of said end effector.

6. A work manipulator as described in any one of claims 1 to 4, wherein the six proximal actuators are six linear actuators supported on the manipulator base, and the six linear actuators linearly move the proximal links of the six linkages to move the distal links, thereby moving the end effector.

7. A system for controlling the position and attitude of an end effector, comprising: a work manipulator for moving the end effector; and a control device for controlling the work manipulator, wherein the work manipulator has a parallel link mechanism and a rotation actuator, and the parallel link mechanism includes: a distal link supporting the end effector; a plurality of linkages arranged in parallel for moving the distal link; and a linkage actuator for moving the plurality of linkages, wherein the rotation actuator is provided between the link and the end effector and controls a roll angle of the end effector, and wherein the control device receives a first control command relating to the position and attitude of the end effector, extracts a first control component relating to the roll angle of the end effector from the first control command, and if the first control component does not exceed a preset threshold, controls only the linkage actuator of the linkage actuator and the rotation actuator in accordance with the first control command, a second control component for the roll angle is calculated by removing the threshold from the first control component when the first control component exceeds the threshold, and a second control command is calculated by removing the second control component from the control command; controlling the rotational actuator according to the second control component for the roll angle; and controlling the linkage actuator according to the second control command.

8. The system described in claim 7, further comprising an arm mechanism for moving the work manipulator, wherein the control device determines whether or not the first control command exceeds a movable range of the work manipulator, and if the first control command does not exceed the movable range, controls only the work manipulator of the work manipulator and the arm mechanism in accordance with the first control command, and if the first control command exceeds the movable range, controls both the work manipulator and the arm mechanism in accordance with the first control command.

9. A system for controlling a position and attitude of an end effector, comprising: a work manipulator that moves the end effector; and a control device that controls the work manipulator, wherein the work manipulator has a parallel link mechanism and a rotation actuator, and the parallel link mechanism includes: a distal link that supports the end effector, a plurality of linkages arranged in parallel that move the distal link, and a linkage actuator that moves the plurality of linkages, and a rotation actuator is provided between the link and the end effector and controls a roll angle of the end effector, wherein the control device receives a first control command related to the position and attitude of the end effector, and if the first control command does not include a control component related to the roll angle of the end effector, controls only the linkage actuator of the linkage actuator and the rotation actuator in accordance with the first control command, and if the first control command includes a control component related to the roll angle, calculates a second control command by removing the control component related to the roll angle from the first control command, and controls the rotation actuator in accordance with the control component related to the roll angle, controlling the linkage actuator according to the second control command.

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