JP5216458B2 - Parallel link mechanism and manipulator with parallel link mechanism - Google Patents

Description

  The present invention relates to a parallel link mechanism and a manipulator including the parallel link mechanism.

  Conventionally, a manipulator having a serial link structure is known. However, in a manipulator having a serial link structure, there is a problem that, when an attempt is made to construct a manipulator similar to a human arm, the rigidity decreases as the degree of freedom increases. On the other hand, since a parallel link mechanism configured by connecting links in parallel realizes a plurality of degrees of freedom at the same time, the rigidity can be increased as compared with a structure in which links are connected in series for each degree of freedom.

  As a parallel link mechanism, a parallel link mechanism having six degrees of freedom in space is known (for example, see Patent Document 1 below). However, in a parallel link mechanism having six degrees of freedom, the degree of freedom becomes redundant when performing a four degree of freedom operation similar to a human forearm or upper arm. For this reason, the actuators, links, and the like increase uselessly by the amount of uselessness of freedom. Therefore, the weight increases and the configuration becomes complicated. There is also a problem that the control becomes complicated.

On the other hand, a parallel link mechanism having four degrees of freedom in space is also known (see Patent Document 2 below). In the parallel link mechanism disclosed in Patent Document 2, four linear motion actuators are connected via joints between the base plate and the end effector. The sum of the degrees of freedom at the joints at both ends of each linear actuator is 5 degrees of freedom or more. Moreover, one restraint link is connected between the base plate and the end effector via a joint. The sum of the degrees of freedom at each joint at both ends of the constraint link is 4 degrees of freedom or more. The four linear actuators are arranged so as to be twisted around the z axis passing through the joint of the constraint link. As a result, angular displacements about the x, y, and z axes in the xyz-axis orthogonal coordinate system are possible.
Japanese Patent Laid-Open No. 08-165673 (FIG. 3) Japanese Patent Laid-Open No. 08-011081

  As described above, in the parallel link mechanism having four degrees of freedom in the space disclosed in Patent Document 2, one constraining link is provided between the base plate and the end effector, and the four linear actuators are arranged around the z axis. By arranging them to be twisted in the same rotational direction, a so-called peculiar posture incapable of displacement is avoided, and angular displacement is enabled. However, in the parallel link mechanism, a force other than the axial direction, that is, a bending moment is generated in the constraining link. Therefore, the rigidity between the base plate and the end effector is lower than when no force other than the axial direction acts on the restraining link. In particular, when the distance between the base plate and the end effector, that is, the length of the constraining link is relatively long, the decrease in rigidity becomes more remarkable. In the parallel link mechanism, if the four actuators are arranged on a square centered on the restraining link, for example, even if the actuator is twisted in the same rotational direction around the z axis, a singular point is obtained in the reference posture. End up.

  The present invention has been made in view of such points, and an object of the present invention is to suppress a decrease in rigidity caused by a bending moment generated in a link in a manipulator having a parallel link mechanism having four degrees of freedom in space. There is to do.

  As shown in FIG. 9, the parallel link mechanism according to the present invention includes a first member, a second member spaced from the first member, and a joint whose one end can rotate with two or more degrees of freedom. Are connected to the first to fourth positions of the first member, respectively, and the other ends are connected to the fifth to eighth positions of the second member via joints capable of rotating with two or more degrees of freedom. Each of the one end and the other end can be rotated in a total of 5 degrees of freedom, and can be expanded and contracted by first to fourth movable links having expansion and contraction actuators, and one end having one or more degrees of freedom. It is connected to the ninth position of the first member via a rotatable joint, and the other end is connected to the tenth position of the second member via a joint capable of rotation with three or more degrees of freedom. The first fixed link that is not stretchable and a joint that is capable of rotating at one end with more than one degree of freedom. The tenth of the second member is connected to an eleventh position, which is different from the ninth position of the first member, and the other end is capable of rotating with more than three degrees of freedom. And a second fixed link that is not stretchable.

  A manipulator according to the present invention includes the parallel link mechanism.

  According to the manipulator, a force other than the axial direction does not act on each link including the fixed link. Therefore, no bending moment is generated in each link (the reason why the bending moment does not occur will be described in detail later). Accordingly, in the parallel link mechanism having four degrees of freedom in space, the rigidity between the base plate and the end effector can be improved. Therefore, a highly rigid manipulator can be realized.

  The manipulator may include an upper arm part and a forearm part connected to the upper arm part, and the forearm part may be constituted by the parallel link mechanism.

  This makes it possible to obtain a manipulator similar to a human arm that realizes three degrees of freedom of the wrist and one degree of freedom of the elbow.

  The manipulator may include an upper arm portion and a forearm portion connected to the upper arm portion, and the upper arm portion may be configured by the parallel link mechanism.

  This makes it possible to obtain a manipulator similar to a human arm that realizes three degrees of freedom of the shoulder and one degree of freedom of the elbow.

  The manipulator may include an upper arm part and a forearm part connected to the upper arm part, and the upper arm part and the forearm part may each be constituted by the parallel link mechanism.

  This makes it possible to obtain a manipulator similar to a human arm that achieves eight degrees of freedom comprising three degrees of freedom of the shoulder, three degrees of freedom of the wrist and two degrees of freedom of the elbow.

  The actuator may be an actuator driven by fluid pressure. The actuator may be an actuator having a motor and a ball screw. The actuator may be any actuator capable of linear motion, such as an actuator having a motor and a rack and pinion mechanism, or an actuator having a motor and a belt.

  In the manipulator, a perpendicular extending from the straight line connecting the ninth position and the eleventh position of the first member to the tenth position of the second member is the first member and When a posture when orthogonal to each of the second members is set as a reference posture, a straight line connecting the fifth position and the seventh position of the second member in the reference posture, and the sixth The moment generated by the extension of the first movable link and the third movable link is positive and negative with respect to an axis that passes through the intersection of the straight line connecting the position of the first position and the eighth position and is orthogonal to the second member. The first to fourth movable links are arranged so that the moment generated by the extension of the second movable link and the fourth movable link becomes the other value at any one of the values. Is preferred See Figure 10).

  With such an arrangement, it is possible to prevent a specific posture from being as wide as possible around the reference posture.

  According to the present invention, in a manipulator including a parallel link mechanism having four degrees of freedom in space, it is possible to suppress a decrease in rigidity due to a bending moment generated in the link.

(Parallel link mechanism)
As shown in FIG. 1, the parallel link mechanism 1 according to the present embodiment includes a base plate 2 and an end plate 3 spaced from the base plate 2. The base plate 2 and the end plate 3 include a first movable link 11, a second movable link 12, a third movable link 13, a fourth movable link 14, a first fixed link 21, and a second fixed link 22. It is connected through.

  One end 11a of the first movable link 11 is connected to the base plate 2 via a joint 31 capable of rotating with two or more degrees of freedom. The other end 11b of the first movable link 11 is connected to the end plate 3 via a joint 32 that can rotate with two or more degrees of freedom. In addition, the 1st movable link 11 can rotate 5 degrees of freedom in total with the one end 11a and the other end 11b. The first movable link 11 includes an actuator 10 for extending / contracting driving, and is extendable / contractable in the axial direction. The type of the actuator 10 is not particularly limited. For example, a fluid pressure cylinder such as an air cylinder, a hydraulic cylinder, and a hydraulic cylinder can be suitably used. Further, as the actuator 10, an actuator having a motor and a ball screw may be used.

  The second movable link 12, the third movable link 13, and the fourth movable link 14 have the same configuration as the first movable link 11. Further, the connection manner of the second movable link 12, the third movable link 13, and the fourth movable link 14 to the base plate 2 and the end plate 3 is the same as that of the first movable link 11. Therefore, description of the 2nd movable link 12, the 3rd movable link 13, and the 4th movable link 14 is abbreviate | omitted.

  The first fixed link 21 and the second fixed link 22 are non-extensible links. One end 21a of the first fixed link 21 and one end 22a of the second fixed link 22 are both connected to the base plate 2 via a joint 33 that can rotate by one degree of freedom or more. The one end 21 a of the first fixed link 21 and the one end 22 a of the second fixed link 22 are connected to different positions on the base plate 2. The other end 21b of the first fixed link 21 and the other end 22b of the second fixed link 22 are connected to the end plate 3 via a joint 34 that can rotate with three or more degrees of freedom. The other end 21 b of the first fixed link 21 and the other end 22 b of the second fixed link 22 are connected to the same joint 34. Therefore, the connection position of the other end 21 b of the first fixed link 21 with respect to the end plate 3 and the connection position of the other end 22 b of the second fixed link 22 with respect to the end plate 3 are the same position.

  In this embodiment, an intersection of a straight line connecting the fifth position and the seventh position of the second member and a straight line connecting the sixth position and the eighth position in the reference posture is set. As described above, with respect to an axis orthogonal to the second member, the moment generated by the extension of the first movable link and the third movable link is a positive or negative value, and the second movable link and The first to fourth movable links are arranged so that the moment generated by the extension of the fourth movable link becomes the other value. However, the first to fourth movable links may be arranged in other manners.

  In the present embodiment, with the above arrangement, it is possible to prevent a specific posture from being as wide as possible around the reference posture.

  When the Jacobian matrix related to the rotation of 4 degrees of freedom and the displacement of the movable link is not regular, it becomes a singular posture, but it is equivalent that the matrix is not regular and its determinant is 0. The following shows the data for examining which posture is unique by checking.

  The posture shown by the dotted line in FIGS. 11 and 12 is a posture where the determinant is 0, which is a unique posture. 11 and 12 show determinants of the Jacobian matrix of the link arrangement disclosed in Patent Document 1 and the link arrangement according to the present embodiment, respectively. In FIG. 11 and FIG. 12, the determinant of the Jacobian matrix when the θx and θy are swung around two axes passing through the tenth position of the second member and parallel to the second member with the reference posture as the center is used as contour lines. Represents.

(Reason why no bending moment is generated in each link)
Here, with reference to FIGS. 13 to 15, a mechanism in which a bending moment is not generated in each link by the configuration of the parallel link mechanism according to the present embodiment will be described.

  FIGS. 13A and 13B show a mechanism that realizes “rotation with 3 degrees of freedom on the second member side and rotation with 1 degree of freedom on the first member side”. FIG. FIG. 13B schematically shows the link mechanism according to this embodiment.

Here, when attention is paid to each of the fixed links, the joint between the fixed link and the first member is a rotary joint having one degree of freedom in the conventional link mechanism and three degrees of freedom in the link mechanism according to the present embodiment. The force and moment applied to the fixed link from the first member by the restraining force are respectively
Conventional link mechanism: X-axis direction force / Y-axis direction force / Z-axis direction force /
Moment about Y axis / Moment about Z axis Link mechanism of this embodiment: X-axis direction force / Y-axis direction force / Z-axis direction force (for fixed links 1 and 2 respectively)
It becomes.

Here, the fixed link balances against the force in the X-axis direction applied from the second member.

  As described above, in the conventional link mechanism, the shearing force F1 and the bending moment τ1 act on the fixed link, and in the link mechanism of the present embodiment, only the axial force of the fixed link acts. From the same consideration, in the balance with respect to the force in the Z-axis direction applied from the second member, only the axial force acts on both the conventional link mechanism and the link mechanism according to the present embodiment.

(manipulator)
Next, an example of a manipulator provided with the parallel link mechanism 1 will be described. The manipulator described below is a manipulator similar to a human arm and performs the same operation as the human arm.

  The manipulator 51 shown in FIG. 2 includes an upper arm portion 61 and a forearm portion 62, and the upper arm portion 61 is configured by the parallel link mechanism 1. In this manipulator 51, the base plate 2 corresponds to the elbow 72 and the end plate 3 corresponds to the shoulder 71. However, the base plate 2 and the end plate 3 can be interchanged. Reference numeral 63 represents a rotation axis of the forearm 62 with respect to the upper arm 61. That is, reference numeral 63 corresponds to the rotation axis of the elbow.

  The manipulator 52 shown in FIG. 3 also includes an upper arm portion 61 and a forearm portion 62, and the upper arm portion 61 is configured by the parallel link mechanism 1. Also in this manipulator 52, the base plate 2 corresponds to the elbow 72, and the end plate 3 corresponds to the shoulder 71. However, the base plate 2 and the end plate 3 may be interchanged. The manipulator 52 is different from the manipulator 51 in the direction of the rotation shaft 63 of the elbow.

  According to the manipulators 51 and 52, it is possible to obtain a manipulator similar to a human arm that realizes three degrees of freedom of the shoulder 71 and one degree of freedom of the elbow 72.

  The manipulator 53 shown in FIG. 4 includes an upper arm portion 61 and a forearm portion 62, and the forearm portion 62 is configured by the parallel link mechanism 1. In the manipulator 53, the base plate 2 corresponds to the elbow 72 and the end plate 3 corresponds to the wrist 73. However, the base plate 2 and the end plate 3 can be interchanged.

  The manipulator 54 shown in FIG. 5 also includes an upper arm portion 61 and a forearm portion 62, and the forearm portion 62 is configured by the parallel link mechanism 1. Also in this manipulator 54, the base plate 2 corresponds to the elbow 72, and the end plate 3 corresponds to the wrist 73. However, the base plate 2 and the end plate 3 can be interchanged.

  According to the manipulators 53 and 54, a manipulator similar to a human arm that realizes three degrees of freedom of the wrist 73 and one degree of freedom of the elbow 72 can be obtained.

  A manipulator 55 shown in FIG. 6 includes an upper arm portion 61 and a forearm portion 62, and each of the upper arm portion 61 and the forearm portion 62 is configured by the parallel link mechanism 1. In this manipulator 55, the base plate 2 of the parallel link mechanism 1 on the upper arm 61 side corresponds to the elbow 72, and the end plate 3 corresponds to the shoulder 71. Further, the base plate 2 of the parallel link mechanism 1 on the forearm portion 62 side corresponds to the elbow 72, and the end plate 3 corresponds to the wrist 73. In each parallel link mechanism 1 on the upper arm 61 side and the forearm 62 side, the base plate 2 and the end plate 3 can be interchanged.

  The manipulator 56 shown in FIG. 7 also includes an upper arm portion 61 and a forearm portion 62, and each of the upper arm portion 61 and the forearm portion 62 is configured by the parallel link mechanism 1. Also in this manipulator 55, the base plate 2 of the parallel link mechanism 1 on the upper arm portion 61 side corresponds to the elbow 72, and the end plate 3 corresponds to the shoulder 71. Further, the base plate 2 of the parallel link mechanism 1 on the forearm portion 62 side corresponds to the elbow 72, and the end plate 3 corresponds to the wrist 73. The base plate 2 and the end plate 3 may be interchanged in each parallel link mechanism 1 on the upper arm portion 61 side and the forearm portion 62 side. The manipulator 56 is different from the manipulator 55 in the direction of the rotation shaft 63 of the elbow.

  According to the manipulators 55 and 56, it is possible to obtain a manipulator similar to a human arm that realizes eight degrees of freedom including three degrees of freedom of the shoulder 71, three degrees of freedom of the wrist 73 and two degrees of freedom of the elbow 72. .

  FIG. 8 shows a manipulator 57 that uses the horizontal articulated mechanism 65 for the upper arm portion 61 and the parallel link mechanism 1 for the forearm portion 62. That is, the manipulator 57 employs a horizontal articulated mechanism 65 that mechanically easily withstands a force in the direction of gravity for the upper arm portion 61 to which a greater load is applied. According to the manipulator 57, the movement in the horizontal plane is mainly performed by the upper arm portion 61, and vertical lifting and wrist rotation are realized by the parallel link mechanism 1. As a result, the structural member up to the elbow and part of the weight of the actuator of the parallel link mechanism 1 are supported by the horizontal articulated mechanism 65, so that the required thrust of the actuator (not shown) of the upper arm portion 61 can be reduced. . Further, since the forearm portion 62 only needs to withstand a load about the weight of the hand portion 66 and the gripping object (not shown), the necessary thrust force of the actuator of the parallel link mechanism 1 can be kept relatively small.

(Effect of embodiment)
As described above, according to the present embodiment, a total of four degrees of freedom, such as one degree of freedom and three degrees of freedom, or three degrees of freedom and one degree of freedom, are provided between the base plate 2 side and the end plate 3 side of the parallel link mechanism 1. Since it is realizable, the mechanism corresponding to an elbow and a wrist and the mechanism corresponding to a shoulder and an elbow can be obtained. Therefore, a manipulator similar to a human arm can be realized.

  Further, according to the present embodiment, no force other than the axial direction is generated in each link 11, 12, 13, 14, 21, 22 of the parallel link mechanism 1. Therefore, no bending moment is generated in each of the links 11, 12, 13, 14, 21, 22, so that the rigidity between the base plate 2 and the end plate 3 can be increased. Therefore, a manipulator having a high strength can be realized. In addition, this effect becomes so remarkable that the length of each link 11, 12, 13, 14, 21, 22 becomes long.

  Further, according to the present embodiment, a manipulator similar to a human arm can be configured by the linear actuator 10 instead of the rotary actuator.

  According to this embodiment, higher rigidity can be obtained than a manipulator using a serial link mechanism.

  Further, since the actuators 10 are arranged in parallel, the weight of the actuator 10 can be received on the root side, and the inertia on the tip side can be suppressed to a small value.

  Compared to a case where a manipulator similar to a human forearm or upper arm is configured by a 6-degree-of-freedom parallel link mechanism, the manipulator can be configured with a smaller number of actuators 10, and thus costs can be reduced. In addition, since the entire arm can be configured to have 6 degrees of freedom, such as 4 degrees of freedom for the forearm and 2 degrees of freedom for the upper arm, when the manipulator of the present invention is used as a power assist manipulator, the space has 6 degrees of freedom. The manipulator can be operated in all six degrees of freedom by grasping the handle with the force sensor. This eliminates the need to operate the manipulator with more than 7 degrees of freedom by wearing a suit-like operation interface or by tying and fixing the operator's arm to the operation interface. It is easy to ensure the safety of the person.

  As described above, the present invention is useful for a manipulator having a parallel link mechanism.

It is a perspective view of a parallel link mechanism. It is a perspective view which shows an example of a manipulator. It is a perspective view which shows an example of a manipulator. It is a perspective view which shows an example of a manipulator. It is a perspective view which shows an example of a manipulator. It is a perspective view which shows an example of a manipulator. It is a perspective view which shows an example of a manipulator. It is a perspective view which shows an example of a manipulator. It is explanatory drawing of the parallel link mechanism which concerns on this invention. It is explanatory drawing of the parallel link mechanism which concerns on this invention. It is a figure for demonstrating the determinant of the Jacobian matrix in a well-known parallel link mechanism. It is a figure for demonstrating the determinant of the Jacobian matrix in the parallel link mechanism which concerns on embodiment. It is explanatory drawing for demonstrating the mechanism in which a bending moment does not generate | occur | produce in each link, (a) is a figure of the well-known parallel link mechanism, (b) is a figure of the parallel link mechanism which concerns on this embodiment. It is explanatory drawing for demonstrating the mechanism in which a bending moment does not generate | occur | produce in each link. It is explanatory drawing for demonstrating the mechanism in which a bending moment does not generate | occur | produce in each link.

Explanation of symbols

1 Parallel link mechanism 2 Base plate (first member)
3 End plate (second member)
DESCRIPTION OF SYMBOLS 10 Actuator 11 1st movable link 11a One end of 1st movable link 11b The other end of 1st movable link 12 2nd movable link 13 3rd movable link 14 4th movable link 21 1st fixed link 22 2nd fixed link 31, 32 , 33, 34 Joint 51, 52 Manipulator 61 Upper arm 62 Forearm 71 Shoulder 72 Elbow 73 Wrist

Claims (8)

A first member;
A second member spaced from the first member;
One end is connected to each of the first to fourth positions of the first member via a joint capable of rotating with two or more degrees of freedom, and the other end is connected via a joint capable of rotating with two or more degrees of freedom. The first member is connected to the fifth to eighth positions of the second member, and can be rotated by a total of five degrees of freedom at the one end and the other end, and can be expanded and contracted by first to fourth retractable actuators. A movable link of
One end is connected to the ninth position of the first member via a joint capable of rotating at least one degree of freedom, and the second member is connected to the ninth position of the first member via a joint capable of rotating at least three degrees of freedom. A first non-stretchable fixed link connected to the tenth position;
One end is connected to an eleventh position that is different from the ninth position in the first member via a joint capable of rotating with one degree of freedom or more, and the other end can be rotated with three degrees of freedom or more. A non-stretchable second fixed link connected to the tenth position of the second member via a flexible joint;
Parallel link mechanism consisting of   A manipulator comprising the parallel link mechanism according to claim 1. An upper arm, and a forearm connected to the upper arm,
The forearm is constituted by the parallel link mechanism;
The manipulator according to claim 2. An upper arm, and a forearm connected to the upper arm,
The upper arm is constituted by the parallel link mechanism;
The manipulator according to claim 2. An upper arm, and a forearm connected to the upper arm,
The upper arm part and the forearm part are each constituted by the parallel link mechanism,
The manipulator according to claim 2. The actuator is an actuator driven by fluid pressure,
The manipulator according to any one of claims 2 to 5. The actuator is an actuator having a motor and a ball screw.
The manipulator according to any one of claims 2 to 5. A perpendicular line extending from the straight line connecting the ninth position and the eleventh position of the first member to the tenth position of the second member is the first member and the second member. When the posture when orthogonal to each member is set as the reference posture, in this reference posture,
It passes through the intersection of a straight line connecting the fifth position and the seventh position of the second member and a straight line connecting the sixth position and the eighth position, and is orthogonal to the second member. With respect to the axis, the moment generated by the extension of the first movable link and the third movable link is a positive or negative value, and the extension of the second movable link and the fourth movable link The first to fourth movable links are arranged so that the generated moment is the other value.
The manipulator according to any one of claims 2 to 7.

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