Link operation apparatus

Abstract

To provide a link operation apparatus capable of improving positioning accuracy even during direct teaching.SOLUTION: A control device 70 of a link operation apparatus 7 includes posture calculation means 74, actuator position calculation means 75, and teaching data storage means 76. When teaching of a distal link hub 13 is performed through direct teaching, the posture calculation means 74 calculates the posture of the distal link hub 13 by forward transformation from a position of an actuator 10 in a state where no preload is applied to a parallel link mechanism 9. The actuator position calculation means 75 calculates, by inverse transformation, the position of the actuator 10 in a state where the preload is applied to the parallel link mechanism 9, on the basis of the posture of the distal link hub 13. The teaching data storage means 76 stores, as teaching data, a set of the posture of the distal link hub 13 and the position of the actuator 10 calculated by the inverse transformation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a link actuator that requires a precise and wide operating range, such as for medical equipment or industrial equipment, and to a technique for improving positioning accuracy by direct teaching. [Background technology]

[0002] As shown in FIG. 1, a link actuator 7, which is one aspect of a parallel mechanism, has been proposed.

[0003] Patent Document 1 proposes a technology for improving the positioning accuracy of a mechanical body having a link mechanism, in which a position where a force (preload) is applied to shift the play that occurs in each rotational pair or mechanism part of the mechanical body to one side is set as the origin position.

[0004] A specific operation method of Patent Document 1 will be described below. As shown in Figure 2, consider a case where the attitude of the tip side link hub 13 is at the origin position (θ0, φ0) and the rotation angle of the base side end link member 15 corresponding to the attitude of this tip side link hub 13 is (β10, β20, β30).

[0005] At this time, as shown in Table 1, the actuator rotation position (M10, M20, M30) corresponding to the rotation angle of the base end side end link member 15 when there is no preload is added with the offset amount for the preload (Preload1, Preload2, Preload3), and the result (M10+Preload1, M20+Preload2, M30+Preload3) is set as the origin position of the actuator rotation position.

[0006] [Table 1] Thereafter, by performing positioning operations based on this origin position, the offset amount for the preload is always taken into account, which results in the backlash of the mechanical body being shifted to one side, thereby improving the positioning accuracy of the mechanical body. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5951224 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when manually moving a mechanical body during direct teaching, it is necessary to release electrical and mechanical constraints by turning off the actuator positioning control (and releasing the brake), or by setting the torque output value to a lower value than during positioning control. In this case, the preload disappears, and if the actuator rotation positions (M1n, M2n, M3n) obtained when the preload has disappeared are set as teaching data as is, the positioning accuracy of the mechanical body will be worse than when there is a preload.

[0009] An object of the present invention is to provide a link actuator that can improve positioning accuracy even during direct teaching. [Means for solving the problem]

[0010] The link actuation device of the present invention is a link actuation device comprising: a parallel mechanism 9 in which a tip side link hub 13 is connected to a base side link hub 12 via a link mechanism 14 so as to be able to change its posture; an actuator 10 that changes the posture of the tip side link hub 13; and a control device 70 that controls the actuator 10, The control device 70 a posture calculation means (74) for calculating the posture of the tip side link hub (13) by forward transformation from the position of the actuator (10) when teaching the tip side link hub (13) by direct teaching, with no preload applied to the parallel mechanism (9); an actuator position calculation means (75) that calculates the position of the actuator (10) in a state where a preload is applied to the parallel mechanism (9) by inverse transformation based on the calculated attitude of the tip side link hub (13); a teaching data storage means (76) for storing the attitude of the tip-end link hub (13) and the position of the actuator (10) calculated by inverse transformation as a set of teaching data; It has. The "direct teaching" means that the tip side link hub 13 is manually moved to the teaching position.

[0011] With this configuration, when teaching the tip side link hub 13 by direct teaching, the actuator positions (M1n+Preload1, M2n+Preload2, M3n+Preload3) corresponding to the rotation angle of the base side end link member 15 in a preloaded state are calculated by inverse transformation (inverse kinematics) based on the attitude (θn, φn) of the tip side link hub 13 calculated by forward transformation (forward kinematics) from the position of the actuator 10 (M1n, M2n, M3n) relative to the rotation angle (β1n, β2n, β3n) of the base side end link member 15 in an unpreloaded state at a taught position n selected by the operator. Furthermore, the attitude (θn, φn) of the tip side link hub 13 and the actuator positions (M1n+Preload1, M2n+Preload2, M3n+Preload3) are stored as teaching data. Therefore, the position of the actuator 10, which eliminates the influence of backlash occurring in each revolute pair and mechanism, can be stored as teaching data, making it possible to perform highly accurate positioning control even during direct teaching.

[0012] The control device 70 may control the positioning of the actuator 10 based on the teaching data stored in the teaching data storage means 76. After the teaching by direct teaching is completed, the control device 70 shifts to positioning control of the actuator 10 based on the stored teaching data, thereby improving the positioning control.

[0013] The parallel mechanism 9 connects the distal end link hub 13 to the proximal end link hub 12 via three or more sets of the link mechanisms 14 in a manner that allows the position of the distal end link hub 13 to be changed. Each link mechanism 14 includes base-side and tip-side end link members 15, 16, one end of which is rotatably connected to the base-side link hub 12 and the tip-side link hub 13, and a central link member 17, both ends of which are rotatably connected to the other ends of the base-side and tip-side end link members 15, 16, respectively. The actuator 10 may be provided in all of the three or more sets of link mechanisms 14 .

[0014] With this configuration, the base end link hub 12, the tip end link hub 13, and three or more sets of link mechanisms 14 form a two-degree-of-freedom mechanism in which the tip end link hub 13 can rotate freely relative to the base end link hub 12 about two orthogonal axes. In other words, the tip end link hub 13 has two degrees of freedom of rotation relative to the base end link hub 12, allowing for free attitude change. This two-degree-of-freedom mechanism is compact, yet provides a wide range of movement for the tip end link hub 13 relative to the base end link hub 12. Because the actuator 10 is provided in all three or more sets of link mechanisms 14, the positioning of the tip end link hub 13 can be controlled with higher precision than if actuators were provided in only two of the three sets of link mechanisms 14.

[0015] The actuator 10 may be a motor installed in the base end link hub 12, and the control device 70 may drive the motor to control the bending angle and pivot angle of the tip end link hub 13. In this case, the control device 70 may control each motor to change the attitude of the tip end link hub 13 relative to the base end link hub 12 from the current attitude to a target link attitude (θ, φ).

[0016] The motor may be capable of positioning control and torque control. For example, when direct teaching is used to teach the distal link hub 13 to a desired position, the control device 70 controls the torque of the servo motor or stepping motor. After teaching is complete, the control device 70 can control the positioning of the servo motor or stepping motor.

[0017] The control device 70 may limit the output of the motor when teaching the tip side link hub 13 by direct teaching. Limiting the motor output also includes reducing the motor output to zero. In this case, direct teaching can be used to prevent resistance when the distal end link hub 13 is manually moved.

[0018] The attitude of the tip side link hub 13 calculated by the attitude calculation means 74 through forward transformation may be the bending angle and pivot angle of the tip side link hub 13. In this case, a link actuator can be provided that is compact in configuration but can operate over a wide operating range.

[0019] A preload may be applied to the parallel mechanism 9 by applying a force to move the backlash of the parallel mechanism 9 to one side using the torque of the motor. In this case, the preload can be easily applied using an existing motor without providing a separate member for applying the preload.

[0020] The force that shifts the backlash of the parallel mechanism 9 to one side may be a force that compresses the parallel mechanism 9 in a predetermined direction. The determined direction is determined appropriately depending on the installation state of the link actuator 7. For example, when the link actuator 7 is installed so that the central axis of the base-side link hub 12 faces the vertical direction, the predetermined direction is the vertical direction. When the link actuator 7 is installed so that the central axis of the base-side link hub 12 faces the horizontal direction, the predetermined direction is the horizontal direction. By compressing the parallel mechanism 9 in a predetermined direction, the moment of inertia of the parallel mechanism 9 can be reduced, the rigidity can be increased, and the positioning accuracy of the parallel mechanism 9 can be improved.

[0021] The inverse transformation value, which is the position of the actuator 10 calculated by inverse transformation, is the output value of an absolute encoder 55 that detects the rotational position of the motor, and may represent the amount of movement from the origin position of the tip side link hub 13, which has been previously given a force that moves the parallel mechanism 9 to one side. By using an absolute encoder 55 that detects the rotational position of the motor as an absolute angle, even if the power to the link actuator 7 is turned off and then on again, it is not necessary to perform initial settings again, and it becomes possible to easily return to the origin.

[0022] The teaching data may be stored in at least one of an internal storage area 81 of the controller 71 for the link actuator, an external storage device 78 that is removably installed in the controller 71 or connected to the controller 71 via communication, and an external device 73. In this case, the storage area for storing the teaching data can be selected according to the user's system configuration.

[0023] The torque of the motor that applies a force in a direction that pulls the parallel mechanism 9 to one side may be set from an input device 72 or other external device 73 that is electrically connected to the link actuator controller 71. In this case, the torque of the motor that applies a force in a direction that pulls the parallel mechanism 9 to one side can be easily set according to the user's system configuration. [Effects of the Invention]

[0024] The link actuation device of the present invention includes a parallel mechanism in which a tip link hub is connected to a base link hub via a link mechanism so that its attitude can be changed, an actuator that changes the attitude of the tip link hub, and a control device that controls the actuator. When teaching the tip link hub by direct teaching, the control device includes: an attitude calculation means that calculates the attitude of the tip link hub by forward transformation from the position of the actuator when no preload is applied to the parallel mechanism; an actuator position calculation means that calculates the position of the actuator by inverse transformation based on the calculated attitude of the tip link hub when a preload is applied to the parallel mechanism; and a teaching data storage means that stores the attitude of the tip link hub and the position of the actuator calculated by inverse transformation as teaching data. This improves positioning accuracy even during direct teaching. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a perspective view of a link actuator according to a first embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a front view showing one axis of a link mechanism that constitutes the link actuation device. [Figure 3] FIG. 3 is a partial cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 2 is a diagram showing one link mechanism of the link actuator device in a straight line. [Figure 5] FIG. 2 is a perspective view of an actuator of the link actuator device. [Figure 6] FIG. 10 is a conceptual diagram illustrating direct teaching of the link actuator. [Figure 7] FIG. 2 is a diagram showing the configuration of a positioning control system using the link actuator. [Figure 8] FIG. 2 is a diagram showing the internal configuration of a controller of the link actuator. [Figure 9] FIG. 10 is a diagram showing a conversion flow when teaching the link actuator by direct teaching. [Figure 10] 10 is a flowchart showing a process for teaching the link actuator by direct teaching in a step-by-step manner. [Figure 11] FIG. 10 is a front view of a parallel mechanism of a link actuator according to a second embodiment of the present invention. [Figure 12] FIG. 12 is a view taken along the arrow AA in FIG. [Figure 13] FIG. 12 is a view taken along the arrow BB in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] [First embodiment] A link actuation device according to an embodiment of the present invention will be described with reference to Figures 1 to 10. This link actuation device is used, for example, in medical equipment or industrial equipment. As shown in Figure 1, the link actuation device 7 includes a parallel link mechanism 9, which is a parallel mechanism, an actuator 10, and a control device 70.

[0027] <Parallel link mechanism> The parallel link mechanism 9 has a base end link hub 12 and a tip end link hub 13 connected to it via three sets of link mechanisms 14 so that the position can be changed. The number of sets of link mechanisms 14 may be four or more. In FIG. 2, only one set of link mechanisms 14 is shown, with the remaining two link mechanisms being omitted. A working body that performs work on a workpiece, or the workpiece itself, is attached to the tip end link hub 13 (a tip member 40 described later). When a working body is attached to the tip end link hub 13, the workpiece is provided on the side of another device. When a workpiece is attached to the tip end link hub 13, the workpiece is provided on the side of another device.

[0028] Each link mechanism 14 has an end link member 15 on the base end side, an end link member 16 on the tip end side, and a central link member 17, and forms a three-bar chain link mechanism consisting of four revolute pairs. 1, the proximal and distal end link members 15, 16 are substantially L-shaped, with one end rotatably connected to the proximal end link hub 12 and the distal end link hub 13, respectively. As shown in FIG. 2, the central link member 17 has the other ends of the proximal and distal end link members 15, 16 rotatably connected to both ends, respectively.

[0029] The parallel link mechanism 9 has a structure in which two spherical link mechanisms are combined. The central axes of the revolute pairs between the base-end link hub 12 and the base-end end link member 15, and the revolute pairs between the base-end end link member 15 and the central link member 17, intersect at the base-end spherical link center PA. Similarly, the central axes of the revolute pairs between the tip-end link hub 13 and the tip-end end link member 16, and the revolute pairs between the tip-end end link member 16 and the central link member 17, intersect at the tip-end spherical link center PB.

[0030] The distance from the center of each revolute pair between the base end link hub 12 and each base end end link member 15 to the base end spherical link center PA is the same. The distance from the center of each revolute pair between each base end end link member 15 and each central link member 17 to the base end spherical link center PA is the same. Similarly, the distance from the center of each revolute pair between the tip end link hub 13 and each tip end link member 16 to the tip end spherical link center PB is the same. The distance from the center of each revolute pair between each tip end link member 16 and each central link member 17 to the tip end spherical link center PB is the same.

[0031] The central axes of the rotation pairs of the base end and tip end link members 15, 16 and the central link member 17 may have a certain cross angle γ or may be parallel to each other. The arm angle, which is the angle formed by the central axis of each rotation pair between the base end link hub 12 and the base end end link member 15 and the central axis of each rotation pair between the base end end link member 15 and the central link member 17, is specified to a predetermined angle.

[0032] The three link mechanisms 14 have geometrically identical shapes. "Geometrically identical shapes" refers to a geometric model in which each link member 15, 16, and 17 is represented by straight lines, i.e., a model represented by each rotation pair and the lines connecting these rotation pairs, in which the base end and tip end portions are symmetrical with respect to the center of the central link member 17, regardless of the posture of the model, as shown in FIG. 4. FIG. 4 is a diagram showing one link mechanism 14 represented by straight lines. The parallel link mechanism 9 of this embodiment is a rotationally symmetric type, and the positional relationship between the base end link hub 12 and the base end end link member 15 and the tip end link hub 13 and the tip end end link member 16 is rotationally symmetric with respect to the center line C of the central link member 17. The centers of each central link member 17 are located on a common orbital circle.

[0033] The base end link hub 12, the tip end link hub 13, and the three link mechanisms 14 constitute a two-degree-of-freedom mechanism in which the tip end link hub 13 can rotate freely around two perpendicular axes relative to the base end link hub 12. In other words, the tip end link hub 13 has two degrees of freedom of rotation relative to the base end link hub 12, allowing for free posture change. This two-degree-of-freedom mechanism is compact, yet allows for a wide range of movement of the tip end link hub 13 relative to the base end link hub 12.

[0034] For example, if the straight line passing through the base-end and tip-end spherical link centers PA and PB and intersecting at right angles with the central axis O1 (FIG. 1) of each rotation pair of the base-end and tip-end link hubs 12 and 13 and the base-end and tip-end end link members 15 and 16 is defined as the central axis QA and QB of the base-end and tip-end link hubs 12 and 13, the maximum bending angle θ between the central axis QA of the base-end link hub 12 (base-end central axis) and the central axis QB of the tip-end link hub 13 is maxcan be set to approximately 90°. The pivot angle φ of the tip side link hub 13 relative to the base side link hub 12 can be set in the range of 0° to 360°. The bending angle θ is the vertical angle at which the central axis QB of the tip side link hub 13 is inclined relative to the central axis QA of the base side link hub 12. On the other hand, the pivot angle φ is the horizontal angle at which the central axis QB of the tip side link hub 13 is inclined relative to the central axis QA of the base side link hub 12. The maximum bending angle θ max may be 90° or more.

[0035] The position of the tip side link hub 13 relative to the base side link hub 12 is changed around the intersection O of the center axis QA of the base side link hub 12 and the center axis QB of the tip side link hub 13 as the center of rotation. Figure 4 shows a state in which the center axis QB of the tip side link hub 13 forms a certain operating angle (bend angle) with respect to the center axis QA of the base side link hub 12. Even if the position of the tip side link hub 13 relative to the base side link hub 12 changes, the distance L between the base side and tip side spherical link centers PA and PB does not change.

[0036] In this parallel link mechanism 9, when all of the following conditions 1 to 5 are satisfied, due to geometric symmetry, the base end link hub 12 and base end end link member 15, and the tip end link hub 13 and tip end end link member 16 move in the same way. Therefore, when transmitting rotation from the base end to the tip end, the parallel link mechanism 9 functions as a constant velocity universal joint in which the base end and tip end sides rotate at a constant speed with the same rotation angle.

[0037] Condition 1: As shown in Figures 3 and 4, the angle α between the central axes O1 and O2 of the rotation pairs of the base-end and tip-end link hubs 12 and 13 and the base-end and tip-end end link members 15 and 16 in each link mechanism 14, and the lengths from the base-end and tip-end spherical link centers PA and PB are equal to each other.

[0038] Condition 2: The central axes of the rotation pairs between the base-end and tip-end link hubs 12, 13 of each link mechanism 14 and the base-end and tip-end end link members 15, 16, and the central axes of the rotation pairs between the base-end and tip-end end link members 15, 16 and the central link member 17 intersect with the base-end and tip-end spherical link centers PA, PB at the base-end and tip-end sides.

[0039] Condition 3: The geometric shapes of the end link member 15 on the base end side and the end link member 16 on the tip end side are the same. Condition 4: The geometric shapes of the base end portion and the tip end portion of the central link member 17 are the same. Condition 5: The angular positional relationship between the central link member 17 and the end link members 15, 16 on the base end side and the tip end side with respect to the symmetry plane of the central link member 17 is the same on the base end side and the tip end side.

[0040] As shown in Figure 1, the base-side link hub 12 has a flat base member 6 and three rotary shaft connecting members 21 that are integral with the base member 6. The three rotary shaft connecting members 21 are circumferentially arranged at equal intervals on one surface of the base member 6. Each rotary shaft connecting member 21 is rotatably connected to a rotary shaft 22 (shown in Figure 3) whose axis intersects with the central axis QA (Figure 4) of the base-side link hub 12. One end of the base-side end link member 15 is connected to this rotary shaft 22.

[0041] As shown in FIG. 1 , the tip side link hub 13 has a flat tip member 40 and three rotating shaft connecting members 41 circumferentially equidistantly arranged on the bottom surface of the tip side member 40. The center of the circumference on which each rotating shaft connecting member 41 is arranged is located on the central axis QB ( FIG. 4 ) of the tip side link hub 13. A rotating shaft 43, whose axis intersects with the central axis QB ( FIG. 4 ) of the tip side link hub 13, is rotatably connected to each rotating shaft connecting member 41. One end of the tip side end link member 16 is connected to this rotating shaft 43. The other end of the tip side end link member 16 is connected to a rotating shaft 45, which is rotatably connected to the other end of the central link member 17. Here, the central axis or tip of a working body or workpiece (workpiece) provided on the tip side link hub 13 (tip side member 40) may be configured to coincide with or intersect with the central axis QB of the tip side link hub 13.

[0042] <Actuator> As shown in FIG. 5, the actuator 10 that changes the position of the distal link hub 13 is a brake-equipped rotary motor (motor) equipped with a reducer 52 that changes the position of the distal link hub 13 (FIG. 1), and an output shaft 54 ​​protrudes from the motor body via the reducer 52. The motor is a servo motor or stepping motor capable of positioning control and torque control. The motor is equipped with an absolute encoder 55 that detects the rotational position (absolute angle) of the motor. As shown in FIG. 1, the motor is installed coaxially with the rotation shaft 22 (FIG. 3) on one plane of the base end member 6 of the proximal link hub 12. The motor body and reducer 52 are integrally provided, and the reducer 52 is fixed to the base end member 6 by a motor fixing member 53.

[0043] In this example, all three link mechanisms 14 are provided with actuators 10. If at least two of the three link mechanisms 14 are provided with actuators 10 for posture control, the posture of the distal link hub 13 relative to the proximal link hub 12 can be determined. The three actuators 10 are arranged so that their rotation axes 22 (Figure 3) are perpendicular to the central axis QA (Figure 4) of the base-end link hub 12, and the central position, which is the intersection of the rotation axes 22 (Figure 3) of these actuators 10, is on the central axis QA (Figure 4) of the base-end link hub 12.

[0044] The link actuation device 7 rotates and drives each actuator 10, thereby actuating the parallel link mechanism 9. More specifically, when an actuator 10 is rotated, the rotation is reduced in speed via a reducer 52 and transmitted to the rotation shaft 22 (FIG. 3). This changes the angle of the base-side end link member 15 relative to the base-side link hub 12, and the attitude of the tip-side link hub 13 relative to the base-side link hub 12 can be changed as desired. An unillustrated working body (end effector) is attached to the tip member 40 of the tip-side link hub 13. Examples of the end effector include a hand including a grip, a cleaning nozzle, a dispenser, a welding torch, and an image processing device including a camera.

[0045] <Control device> The control device 70 controls the actuator 10. The control device 70 drives the motor that is the actuator 10, enabling positioning control of the bending angle and rotation angle of the tip-side link hub 13. The control device 70 is configured to be able to switch between the positioning control and torque control. The control device 70 applies a preload to the parallel link mechanism 9, which is a parallel mechanism, by applying a force that shifts the play of the parallel link mechanism 9 to one side using the torque of the motor. The force that shifts the play of the parallel link mechanism 9 to one side is a force that compresses the parallel link mechanism 9 in a specified direction. The torque of the motor that applies a force in the direction that shifts the parallel link mechanism 9 to one side can be set from an input device 72 electrically connected to a link actuator controller 71 or from a personal computer (abbreviated as PC) 73, which is another external device, as shown in FIG. 7. By rotating each motor provided in each actuator 10 in the same direction (clockwise or counterclockwise) with the same torque, a force is applied in a direction that moves the parallel link mechanism 9 to one side, and the backlash can be moved to one side, i.e., the backlash of each rotational pair and mechanism part can be reduced.

[0046] As shown in FIG. 1, the control device 70 of the link actuation device includes, among other things, an attitude calculation means 74, an actuator position calculation means 75, and a teaching data storage means 76. As shown in FIG. 6, when teaching the tip-end link hub 13 by direct teaching using a finger or the like, the control device 70 limits the output of the motor and transitions to torque control. When teaching the tip-end link hub 13 by direct teaching manually or the like, highly accurate positioning control can be achieved by performing direct teaching with a working body or workpiece (work) attached to the tip member 40. Furthermore, when attaching a working body to the tip member 40, direct teaching is performed with the workpiece (workpiece) attached to another device, and when attaching a workpiece (workpiece) to the tip member 40, direct teaching is performed with the working body attached to another device.

[0047] 1 and 9, when teaching the tip side link hub 13 by direct teaching, the attitude calculation means 74 calculates the attitude of the tip side link hub 13 by forward transformation from the position of the actuator 10 with no preload applied to the parallel mechanism. The attitude of the tip side link hub 13 calculated by the attitude calculation means 74 through forward transformation is the bending angle and rotation angle of the tip side link hub 13.

[0048] The actuator position calculation means 75 calculates, by inverse transformation, the rotational position (position) of the actuator 10 in a state where a preload is applied to the parallel mechanism, based on the calculated attitude of the tip side link hub 13. The inverse transformation value, which is the position of the actuator 10 calculated by inverse transformation, is the output value of the absolute type encoder 55 (FIG. 5) that detects the rotational position of the motor, and represents the amount of movement from the origin attitude position of the tip side link hub 13, which has been given a force in advance to move the parallel mechanism to one side.

[0049] The teaching data storage means 76 in FIG. 1 stores the attitude of the tip side link hub 13 and the position of the actuator 10 calculated by inverse transformation as a set, as teaching data. The control device 70 controls the positioning of the actuator 10 based on the teaching data stored in the teaching data storage means 76 .

[0050] The posture calculation means 74 calculates the posture (θn, φn) of the tip side link hub 13 by forward transformation (forward kinematics) from the actuator rotational position (M1n, M2n, M3n) relative to the rotational angle (β1n, β2n, β3n) of the base end side end link member 15 in an unpreloaded state at the teaching position n (position n in Table 1) selected by the operator during direct teaching.

[0051] Specifically, the attitude (θn, φn) of the tip side link hub 13 is calculated by performing a forward transformation on the following relational expression (1). Here, ε0 in equation (1) is calculated using equation (2). The rotation angle and the actuator rotation position are associated in advance by a relationship setting means such as a map or a relational expression. Note that the teaching position n selected during direct teaching may be only one final attitude of the tip side link hub 13, or may include multiple attitudes of the tip side link hub 13 ranging from any attitude to the final attitude.

[0052]

number

[0053] however, γ: the angle (crossing angle) formed between the connecting end shaft of the central link member 17 rotatably connected to the end link member 15 on the base end side and the connecting end shaft of the central link member 17 rotatably connected to the end link member 16 on the tip end side α: Angle between the connecting end axis of the central link member 17 rotatably connected to the base end side and tip end side end link members 15, 16 and the connecting end axis of the base end side and tip end side link hubs 12, 13 rotatably connected to the base end side and tip end side end link members 15, 16 δn (n=1, 2, 3, . . . ): circumferential separation angle of each base end link member 15 relative to the base end link member 15 that serves as the reference εn (n=1, 2, 3, ...): The circumferential separation angle of each rotation pair relative to the reference phase on the circumference through which the rotation pairs of the base end link member 15 and the central link member 17 pass.

[0054] The actuator position calculation means 75 calculates the actuator rotational position (M1n+Preload1, M2n+Preload2, M3n+Preload3) corresponding to the rotational angle of the base-end side end link member 15 in a preloaded state by inverse transformation (inverse kinematics) based on the calculated attitude (θn, φn) of the tip-end side link hub 13. Specifically, by inversely transforming the following relational expression (1), the rotational angle βn of the base-end side end link member 15 is calculated, and the actuator rotational position (M1n+Preload1, M2n+Preload2, M3n+Preload3) corresponding to this rotational angle βn is calculated. The rotational angle βn and the actuator rotational position are associated in advance by a relationship setting means such as a map or a relational expression.

[0055]

number

[0056] The teaching data storage means 76 stores the attitude (θn, φn) of the tip side link hub 13 and the actuator rotational position (M1n+Preload1, M2n+Preload2, M3n+Preload3) as teaching data, enabling highly accurate positioning control.

[0057] 7 is a diagram showing the configuration of a positioning control system using a link actuator 7. The control device 70 includes, for example, a controller 71 for the link actuator, drivers 77a, 77b, and 77c for each actuator, a storage device (external storage device) 78, and an input device 72. The control device 70 is electrically connected to, for example, a personal computer 73 which is an external device, and a host PLC (Programmable Logic Controller) 79 which is a host control device. The host PLC 79 controls, for example, a linear actuator (not shown) in synchronization with the link actuator 7.

[0058] As shown in FIG. 8, the controller 71 has a CPU 80, an internal memory area 81, a slot 82 for an external memory device, a general-purpose communication interface 83, a display 84, a LAN interface 85, a field network interface 86, an input / output interface I / O, and a power supply unit.

[0059] 1 and 8, the CPU 80 of the controller 71 stores the above-mentioned attitude calculation means 74 and actuator position calculation means 75. A teaching data storage means 76 (FIG. 1) is stored in an internal storage area 81 of the controller 71 or in a storage device 78 of FIG. 7, which is an external storage device. As shown in FIGS. 7 and 8, the storage device 78 is removably installed in an external storage device slot 82 of the controller 71, or is connected by communication via a general-purpose communication interface 83 of the controller 71. The teaching data is stored in at least one of the internal storage area 81 of the controller 71, the storage device 78, and the personal computer 73, which is an external device.

[0060] <Direct teaching flow chart> Figure 10 is a flowchart showing the steps of the process when teaching the link actuator by direct teaching. The explanation will also refer to Figures 1 and 7 as appropriate. After starting this process, the controller 71 determines whether or not teaching by direct teaching is selected (step S1). When the operator operates the operation key 72a of the input device 72, which indicates the start of direct teaching (step S1: YES), the control shifts from positioning control to torque control of the actuator 10 (step S2).

[0061] In step S2, the controller 71 switches off the positioning control of the actuator 10, releases the brake, or limits the output torque value of the actuator 10 and transitions to torque control. Thereafter, when the distal end link hub 13 is moved to an arbitrary posture (bend angle, swivel angle) by manual operation (step S3), the process transitions to step S4. In step S4, the posture calculation means 74 calculates the current posture (bend angle θn, swivel angle φn) of the distal end link hub 13 by forward transformation (forward kinematics) from the current rotational position (M1n, M2n, M3n) of the actuator 10 relative to the rotation angle of the base end end link member 15.

[0062] The actuator position calculation means 75 calculates the actuator rotational positions (M1n+Preload1, M2n+Preload2, M3n+Preload3) corresponding to the rotational angle of the base-end end link member 15, taking into account the force that shifts the backlash of the parallel link mechanism 9 to one side, by inverse transformation (inverse kinematics) based on the calculated current attitude (bend angle θn, pivot angle φn) of the tip-side link hub 13 (step S5). Next, the teaching data storage means 76 stores the attitude (bend angle θn, pivot angle φn) of the tip-side link hub 13 and the actuator rotational positions (M1n+Preload1, M2n+Preload2, M3n+Preload3) as teaching data (step S6).

[0063] Next, the controller 71 determines whether or not teaching by direct teaching has ended (step S7). When the operator operates the operation key 72a of the input device 72, which indicates the end of direct teaching (step S7: YES), the actuator 10 is shifted to positioning control (step S8), and this process ends. If it is determined that teaching has not ended (step S7: NO), the process returns to step S3. After shifting to positioning control, the controller 71 performs feedback control using the output value of the encoder 55 (FIG. 5) so that the rotation angle βn becomes the control target value, thereby improving positioning control.

[0064] <Action and effect> 1 described above, when direct teaching is performed, the actuator position when a preload is applied to the parallel link mechanism 9 and the attitude of the tip-side link hub 13 are stored as a set of teaching data. Therefore, the position of the actuator 10 that eliminates the effects of backlash that occurs in each revolute pair and mechanism part can be stored as teaching data, enabling precise positioning control even during direct teaching.

[0065] According to the link actuator 7, the distal link hub 13 has two degrees of freedom of rotation relative to the proximal link hub 12, allowing for free posture change. This two-degree-of-freedom mechanism is compact, yet allows for a wide range of movement of the distal link hub 13 relative to the proximal link hub 12. Because the actuator 10 is provided in all three or more link mechanisms 14, the distal link hub 13 can be positioned and controlled with higher precision than if actuators were provided in only two of the three link mechanisms 14.

[0066] <Other embodiments> In the following description, parts corresponding to matters previously described in each embodiment are given the same reference numerals, and duplicated description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those in the previously described embodiment unless otherwise specified. The same configuration produces the same effects. It is possible to combine not only the parts specifically described in each embodiment, but also partially combine embodiments as long as there is no particular problem with the combination.

[0067] [Second embodiment: Figs. 11 to 13] As shown in Fig. 11, the parallel link mechanism 9 may have an asymmetric structure between the base end side and the tip end side. As shown in Fig. 12 and Fig. 13, the distances L1A, L1B (hereinafter referred to as "link lengths") from the respective spherical link centers PA, PB to the respective rotation pair center points C1A, C1B of the end link members 15, 16 and the central link member 17 are the same on the base end side and the tip end side.

[0068] In contrast, the distances (hereinafter referred to as "arm lengths") L2A, L2B from the respective spherical link centers PA, PB to the respective rotation pair center points C2A, C2B of the link hubs 2, 3 and the end link members 5, 6 are different on the base end side and the tip end side. In the second embodiment, the arm length L2A on the base end side is longer than the arm length L2B on the tip end side.

[0069] Here, the rotation pair center points C1A, C1B, C2A, and C2B refer to the center points in the width direction of the end link members 15 and 16 along the rotation pair axes O1A, O1B, O2A, and O2B of the respective rotation pairs. Even if the arm lengths L2A, L2B are different between the base end and the tip end, as long as the link lengths L1A, L1B are the same between the base end and the tip end, the three sets of link mechanisms 14 (Figure 11) will have the same geometric shape between the base end and the tip end regardless of the posture of the parallel link mechanism 9.

[0070] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0071] 7...Link actuator, 9...Parallel link mechanism (parallel mechanism), 10...Actuator, 12...Base end link hub, 13...Tip end link hub, 14...Link mechanism, 15...Base end link member, 16...Tip end link member, 17...Central link member, 55...Absolute type encoder, 70...Control device, 71...Controller, 72...Input device, 73...External device, 74...Attitude calculation means, 75...Actuator position calculation means, 76...Teaching data storage means, 78...External storage device, 81...Internal storage area

Claims

1. A link actuation device comprising: a parallel mechanism in which a tip-side link hub is connected to a base-side link hub via a link mechanism so as to be able to change its position; an actuator that changes the position of the tip-side link hub; and a control device that controls the actuator, The control device an attitude calculation means for calculating an attitude of the tip side link hub by forward transformation from the position of the actuator when teaching the tip side link hub by direct teaching, with no preload applied to the parallel mechanism; an actuator position calculation means for calculating the position of the actuator in a state where a preload is applied to the parallel mechanism by inverse transformation based on the calculated attitude of the tip side link hub; a teaching data storage means for storing the attitude of the tip end side link hub and the position of the actuator calculated by inverse transformation as a set of teaching data; A link actuator having:

2. 2. The link actuation device according to claim 1, wherein said control device controls the positioning of said actuator based on the teaching data stored in said teaching data storage means.

3. 3. The link actuation device according to claim 1, wherein the parallel mechanism connects the tip-end link hub to the base-end link hub via three or more sets of the link mechanisms in a manner that allows the position of the tip-end link hub to be changed. Each of the link mechanisms includes a base-end side and a tip-end side end link member, one end of which is rotatably connected to the base-end side link hub and the tip-end side link hub, and a central link member, both ends of which are rotatably connected to the other ends of the base-end side and tip-end side end link members, A link actuation device including the actuator in each of the three or more sets of link mechanisms.

4. 4. The link actuation device according to claim 3, wherein the actuator is a motor installed in the base-end link hub, and the control device drives the motor to control the bending angle and pivot angle of the tip-end link hub.

5. 5. The link actuation device according to claim 4, wherein the motor is capable of positioning control and torque control.

6. 5. The link actuation device according to claim 4, wherein the control device limits the output of the motor when teaching of the tip side link hub is performed by direct teaching.

7. 3. The link actuation device according to claim 1, wherein the attitude of the tip-side link hub calculated by the attitude calculation means through forward transformation is a bending angle and a turning angle of the tip-side link hub.

8. 5. The link actuation device according to claim 4, wherein a preload is applied to the parallel mechanism by applying a force to bias the backlash of the parallel mechanism to one side by the torque of the motor.

9. 5. The link actuation device according to claim 4, wherein the force that shifts the backlash of the parallel mechanism to one side is a force that compresses the parallel mechanism in a predetermined direction.

10. 5. The link actuation device according to claim 4, wherein an inverse transformation value, which is the position of the actuator calculated by inverse transformation, is an output value of an absolute encoder that detects the rotational position of the motor, and represents an amount of movement from an origin posture position of the tip-side link hub to which a force has been applied in advance to bias the parallel mechanism to one side.

11. 3. The link actuation device according to claim 1, wherein the teaching data is stored in at least one of an internal storage area of ​​a controller for the link actuation device, an external storage device that is removably installed in the controller or connected to the controller by communication, and an external device.

12. 5. The link actuation device according to claim 4, wherein the torque of the motor that applies a force in a direction that pulls the parallel mechanism to one side can be set from an input device or other external device that is electrically connected to a controller for the link actuation device.

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