CN1285449C - Polygonal-target multi-finger grab planning method and apparatus - Google Patents
Polygonal-target multi-finger grab planning method and apparatus Download PDFInfo
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Abstract
The present invention relates to a method and a device for the multiple-finger grabbing plan of a skillful robot hand. The method has the grabbing planning steps that a target image is obtained by using a digital video camera by an image obtaining and processing device, and is converted into a three-dimensional solid figure which is convenient for a computer to express, and a polygon on a grabbing plane is finally output. Then, a grabbing planning device determines all practicable grabbing plans of a workpiece by a grabbing hand with four fingers, the optimum grabbing plan is determined and is output to a controlling and driving device to control and drive the multiple-finger grabbing hand, and the grabbing operation is realized. The device is composed of the image obtaining and processing device, the grabbing planning device, the controlling and driving device and the multiple-finger skillful hand. The multiple-finger grabbing plan of the present invention can make an anthropomorphic robot have the skillful operation and the accurate force and motion control capability for objects with various shapes, and the anthropomorphic behavior is realized.
Description
Technical Field
The invention relates to a multi-finger grabbing planning method and device, in particular to a multi-finger grabbing planning method and device for a polygonal object.
Background
In the research of intelligent robots, anthropomorphic robots are used as the highest level of robot research, and the realization of humanoid behaviors is always used as the target of sleepiness. The multi-finger dexterous hand which has fine manipulation capability and imitates a human hand in structure and function is the most complex and key research content in the field of robot research. At present, multi-finger dexterous hands are developed successfully all over the world, have position and strength sensing capabilities and can realize dexterous grasping and operation.
However, the control and manipulation of the finger movements of the multi-finger dexterous hand of the robot are still in the human-computer interaction stage, and usually, a user wears a data glove with a plurality of sensors and then remotely controls and operates the dexterous hand through the movement of the fingers in the data glove and by using a computer network. The current multi-finger dexterous hand is only the mechanical extension of a human hand and cannot be separated from a human body to independently complete the basic motion control and operation. Therefore, the multi-finger grabbing planning method of the multi-finger dexterous hand is very key to the application and research of the anthropomorphic robot, the multi-finger grabbing planning is also one of the landmark application fields of the artificial intelligence technology, and once the technology is broken through, the anthropomorphic robot can have dexterous operation and accurate force control and motion control capacity on objects in various shapes, so that humanoid behaviors are realized.
Disclosure of Invention
The invention aims to provide a polygonal object multi-finger grabbing area planning method and device, which can automatically determine that grabbing operation is carried out according to an optimal grabbing scheme when a multi-finger dexterous hand with four fingers grabs a polygonal object, and realize intelligent operation of grabbing a polygon by the multi-finger dexterous hand.
In the robot multi-finger grabbing plan, the shape sealing is a basic criterion for judging the reasonability of a robot multi-finger grabbing scheme, and the stability and balance of a grabbed object can be ensured at the contact position of fingers meeting the shape sealing requirements. In this arrangement, any external disturbing forces acting on the gripped object can be borne by the robot fingers in contact with the object. For the problem of frictionless gripping of planar objects, the form closure requirement is usually achieved only by a proper arrangement of four fingers.
The invention discloses a guaranteed-shape closed multi-finger grabbing planning method for a planar polygonal object, which is an automatic planning and control problem of distribution positions of fingers of a multi-finger dexterous hand with four fingers on a grabbing boundary of a workpiece. The grabbing object is a prismatic workpiece, namely the grabbing surface of the workpiece is a plane perpendicular to the grabbing plane, and all grabbing points of the workpiece are located on the same plane. According to the shape closure requirement, the friction force at the contact part of the finger and the grabbed object is not considered.
The conception of the invention is as follows: a new geometric explanation is made on the shape closure requirement by the instantaneous center triangle concept, namely, a method for representing the position relation between four fingers and a polygon meeting the shape closure requirement is established by using the instantaneous center triangle concept. And determining the contact areas of the four fingers on any polygonal object according to the representation method, wherein the contact area of each finger has independence, namely the independent movement of each finger in the area of the finger can ensure that the finger and the other three fingers form a closed grabbing scheme together.
The following introduces the relevant theory:
1. definition of instantaneous center triangle and its properties
The problem of contact with a point on a plan view can be described by the characteristics of the centrode triangle. The instantaneous center triangle is a triangle formed by the intersection points of the direction lines of the contact force of any three fingers of the multi-finger hand on the workpiece. The concept of the instant center is derived from planar kinematics, the instant center is the instantaneous same-speed point of two objects making relative motion, and if one of the objects is fixed, the instant center is the instantaneous rotation center of the other object. Three instant centers exist in the combination of every two of the three fingers. The centrode triangle has the following properties:
the sides of the centrode triangle have directionality, with the positive direction being the same as the direction of the contact force that the side is in.
The homodromous and heterodromous sides of the centrocentric triangle. If the two sides of the centrode triangle have the same direction to the moment of any point in the triangle, the two sides are called as the homodromous sides, and the other side is called as the heterodromous side.
The centrode triangle has two morphologies: the instantaneous triangle with three sides in the same direction and the instantaneous triangle with two sides in the same direction and one side in different direction.
For an instantaneous triangle with two homodromous sides, the positive direction of the opposite side must be within the sector area sandwiched by the positive directions of the two homodromous sides.
2. Determining the position range of the fourth finger meeting the shape closing requirement according to the property of the instantaneous center triangle
The position of the fourth finger contact point relative to the centrode triangle under the condition of ensuring the grabbing balance (meeting the shape closure requirement) can be determined by utilizing the centrode triangle without considering the friction between the fingers and the grabbed object. Two theorems are given below regarding the contact force direction and position condition of the fourth finger that satisfies the form closure condition.
Theorem 1: for the instantaneous triangle with two homodromous sides, the direction line position of the contact force of the fourth finger must intersect with the two homodromous sides of the instantaneous triangle, and the direction of the contact force must be in a fan shape enclosed by the negative directions of the two homodromous sides.
Theorem 2: for a centrode triangle with three sides in the same direction, the direction line position of the contact force of the fourth finger cannot intersect with any side of the centrode triangle. Direction condition of contact force of the fourth finger: the positive direction of the contact force must be opposite to the direction of the moment about a point inside the centrode triangle with respect to any side of the centrode triangle with respect to the same point.
In order to achieve the purpose, the invention adopts the following technical scheme:
a polygonal object multi-finger grabbing planning method is characterized in that the grabbing planning steps are as follows:
a. the image acquisition and processor captures the image of the prismatic workpiece, processes and converts the image into a three-dimensional solid figure which is convenient for computer representation, and finally outputs a polygon on a capture plane;
b. determining, by a gripping planner, all possible gripping scenarios of a four-finger dexterous hand with respect to a given workpiece, and determining an optimal gripping scenario;
c. and outputting a finger position signal of the optimal gripping scheme to a control and driver of the finger gripper by the gripping planner to carry out gripping work.
The step of determining the feasible grabbing scheme by the grabber planning comprises the following steps:
a. an instantaneous center triangle is formed by the intersection points of any three fingers in the dexterous multi-finger hand on the working contact force direction line of the workpiece;
b. and determining the position range of the fourth finger on the workpiece polygon meeting the shape closing requirement according to the instantaneous center triangle.
The step of determining the contact position range of the fourth finger on the polygon according to the polygon of the workpiece, which meets the requirement of shape closure, comprises the following steps:
a. judging whether a grabbing scheme meeting the shape sealing requirement exists in the boundary quadruple;
b. for 4 grabbing edges of a grabbing scheme meeting the shape sealing requirement, a feasible grabbing scheme is established, and the method comprises the following steps:
(a) determining a feasible grabbing section on the 4 th edge according to an instantaneous center triangle which is composed of the first three edges and the inner normals at the two end points and has two homodromous edges;
(b) determining a grabbing position section which meets the shape sealing requirement on a grabbing edge corresponding to one different-direction edge;
(c) determining the section of the grabbing position meeting the shape sealing requirement on the grabbing edges corresponding to the two parallel edges
c. And maintaining a balance condition according to the distribution condition of the space positions of the fingers and the magnitude of the contact force of the fingers, and determining the optimal grabbing positions on the four grabbing position sections meeting the shape sealing requirement.
The step of judging whether the boundary quadruple has the grabbing scheme meeting the shape sealing requirement is as follows:
a. selecting three grabbing sides, constructing 8 instantaneous center triangles with two homodromous sides by using the inner normal lines at two end points of each side, and if the instantaneous center triangles with the homodromous sides cannot be constructed, determining that a grabbing scheme meeting the shape sealing requirement does not exist in the boundary four-element group;
b. if the fourth edge satisfies the following two conditions, the fourth edge has a grabbing scheme satisfying the shape closure condition:
(a) the directional condition: the included angle between the inner normal of the fourth side and the positive direction of the anisotropic side of the instantaneous center triangle is more than 90 degrees;
(b) the positional conditions: if the intersection of the projection of the two homodromous sides of at least more than one of the 8 centroidal triangles on the fourth side is not null.
The method for determining the feasible grabbing section satisfying the shape closure requirement on the 4 th edge of the boundary quadruple comprises the following steps: the sum of the intersection of the projections of the two homodromous sides of all the instantaneous center triangles on the 4 th grabbing side is a feasible grabbing section which can ensure a closed condition on the 4 th side.
The step of determining the section of the grabbing position on the different-direction edge meeting the shape closing requirement comprises the following steps:
a. the grabbing sides are named first: for the boundary quadruple capable of forming the instantaneous center triangle, naming the polygon boundary where the anisotropic side of the instantaneous center triangle is located as E2, and the grabbing sides corresponding to the two homodromous sides as E1 and E3 respectively, specifically determining the positions of the intersection point of the internal normals of the two sides relative to the two homodromous sides of the instantaneous center triangle, if the intersection point is the starting point of the homodromous side, the grabbing side where the internal normal coincident with the homodromous side is located is E3, the other side is E1, otherwise, the other side is E, the other past side is E3, and the 4 th side is E4;
b. the method for determining the grabbing position section meeting the form closure requirement on the grabbing edge corresponding to the instantaneous center triangle anisotropic edge comprises the following steps:
(A) constructing an instantaneous center triangle by using the internal normals at the starting positions of E1, E2 and E3, obtaining intersection points J21 and J23 of the internal normal n2 at the starting position of E2 and the internal normals n1 and n3 at the starting positions of E1 and E3, and obtaining intersection point J42 of the internal normal n2 at the starting position of E2 and the internal normal n4 of E4;
(a) if the intersection points J21, J23 and the intersection point J31 are located on two sides of the n4, the E2 can form a feasible closed grabbing section from the starting position to the end position; j31 is the intersection of the E1 origin position normal n1 with the E3 origin position internal normal n 3;
(b) otherwise, moving the n2 in the forward direction of E2, so that the intersection points J21, J23 and J31 of the n2, the n1 and the n3 are respectively positioned at two sides of the n4, and then moving the n2 from the current position to the end point of the edge E2, wherein the section meets the first feasible section of the shape closure requirement; the feasible location of n4 is also the end point from the current location to edge E4;
(c) if the movement n2 cannot be made to enable J21, J23 and the intersection point J31 to be located at the two sides of n4, the instant center triangle containing the intersection point of the starting limit position does not exist; or;
(B) constructing an instantaneous center triangle by using the inner normals at the end positions of E1, E2 and E3, calculating the intersection points J21 'and J23' of the normals at the end position of E2 and the normals n1 and n3 at the end positions of E1 and E3, and calculating the intersection point J42 of the normals n2 at the starting position of E2 and the normals n4 at E4;
(a) if the intersection points J21 ', J23 ' and J31 ' are located on both sides of n4, respectively, then E2 is feasible from the end point to the start point as a closed grasping section; j31' is the intersection of normal n3 in the end position of E3 and normal n1 in the end position of E1;
(b) otherwise, moving n2 in the direction from the end point of E2 to the starting point, so that J21 ', J23 ' and the intersection point J31 ' are located right on both sides of n4, starting from the current position of n2 to the starting point of E2, the sections are all feasible grabbing sections of E2, which are the closed contact points;
(c) if the movement of n2 is not such that J21 ', J23 ' and the intersection point J31 ' are located just on both sides of n4, it is said that the centrode triangle containing the endpoint limit intersection point does not exist.
The method for determining the grabbing position section meeting the shape sealing requirement on the grabbing edge corresponding to the equidirectional edge comprises the following steps: perpendicular lines are drawn through point J42 for E1 and E3 to give corresponding feet P1, P3, with fold lines P1-J42-P3 possibly dividing E1 and E3 into two parts, and fold lines P1-J42 likewise dividing internal normals n2 and n4 on E2 and E4 into two parts, on both of which there are possible catch position segments:
a. the portion of the planar area taken along the fold line P1-J42-P3 containing E2: n3 feasible grasping segments in E3: the remaining part of E3 cut by the fold line P1-J42-P3; n1 feasible grasping segments in E1: p1 '-P1 ", wherein determination of the P1' position: for the inner normal n3 of any given contact point on E3, the position of P 'is the projection point of the intersection point of the current position of n3 and n4 on E1, and the position of P' is the end point of E1 or P1;
b. the portion of the planar area taken along the fold line P1-J42-P3 containing E1: n1 feasible grasping sector in E1: a portion cut from E1 by fold line P1-J42-P3;
n3 feasible grasping sector in E3: p3 '-P3 ", wherein determination of the P3' position: for the inner normal n1 of any given contact point position on E1, P3' is the projection point of the intersection point of the current position of n1 and n4 on E3; position P3 "is end point E3 or P3.
The above method for determining the optimal grabbing scheme is as follows: and (3) taking the wrist motion amplitude, the finger motion amplitude, the relative position of the finger contact point and the finger contact force as evaluation indexes, and finding out the optimal grabbing scheme from all feasible grabbing schemes.
A multi-finger grab planning method for polygonal object is composed of a control and driver for controlling and driving a multi-finger flexible hand, and features that an image acquisition and processor has its output connected to the input of a grab planner whose output is connected to the input of the control and driver.
Compared with the prior art, the invention has the following obvious outstanding characteristics and obvious advantages: the invention adopts an image acquisition and processor to take the image of the prismatic workpiece, and outputs the polygon on the grabbing plane to a grabbing planner after processing, and the grabbing planner carries out grabbing planning and determines the optimal grabbing scheme, thereby inputting the optimal grabbing scheme to a control and driver to control and drive the multi-finger dexterous hand, and realizing the intelligent operation of grabbing the polygonal object by the multi-finger dexterous fingers. The multi-finger grabbing plan of the invention can enable the anthropomorphic robot to have smart operation and accurate force control and motion control capability on objects with various shapes, thereby realizing humanoid behavior.
Drawings
Fig. 1 is a block diagram showing the structure of the apparatus of the present embodiment.
Fig. 2 is a diagram of the operational procedure of the grab planner of the example of fig. 1.
Figure 3 is a centrode triangle formed by three contact points.
FIG. 4 is a graph of the relationship between the instantaneous center triangle with two homodromous sides and the contact point positions of four fingers
FIG. 5 is a graph showing the relationship between the positions of the centrode triangle with three homodromous sides and the contact points of four fingers
FIG. 6 is a view of an instant center triangle formed by three grasping sides
FIG. 7 is a diagram of determining a fourth edge potential capture contact point segment
Fig. 8 is a solution diagram of determining possible grabbing contact point sections of the opposite sides, and establishing an instantaneous center triangle by normals in the starting point positions of the three grabbing sides.
Fig. 9 is a solution diagram of determining possible grabbing contact point sections of the opposite sides and establishing an instantaneous center triangle by normals in the end point positions of the three grabbing sides.
Fig. 10, 11, 12 and 13 are solving diagrams of possible grasping contact point sections for determining the homodromous edges.
Detailed Description
A preferred embodiment of the present invention is:
referring to fig. 1, the device of the multi-finger grasp planning method for polygonal objects comprises a control and driver 3 for controlling and driving a multi-finger dexterous hand 4, an image acquisition and processor 1 with an output connected with an input of a grasp planner 2, and an output of the grasp planner 2 connected with an input of the control and driver 3.
Referring to fig. 1, the method for multi-finger capture planning of the polygonal object includes: the image acquisition and processor 1 acquires the image of the target by using the digital camera, converts the image into a three-dimensional solid figure which is convenient for computer representation, and finally outputs a polygon on the grabbing plane. The grabbing planner generates grabbing schemes according to the specific geometric dimensions of the polygons and the multi-finger dexterous hand sent by the image acquisition and processor 1, inputs grabbing constraint, quality evaluation indexes and other information which embody the requirements of users by a keyboard, and finally outputs the optimal grabbing schemes to the control and driver 3 to control and drive the multi-finger grab 4.
To illustrate the operation of the gripping planner 2, a more detailed description of FIGS. 3-13 is provided:
fig. 3 illustrates a centrode triangle formed by three contact points, in which three small circles represent three fingers, a broken line represents a plane contour of a grasped object, a solid line represents a graspable boundary on the plane contour, an upper case A, B, C represents a contact position of the finger with a polygon, and lower case letters a, b, and c are centrode triangles formed by contact force direction lines of the three fingers with a workpiece (i.e., inner normal lines of the contact points of the fingers on the boundary of the workpiece).
Fig. 4 shows the relationship between the positions of the contact points of four fingers and the centrode triangle with two homodromous sides, which is a-b-c, and ab and bc respectively. According to theorem 1, the action line of the fourth contact force satisfying the shape closure must intersect with the two homodromous sides bc and ab of the centrode triangle, and according to the direction requirement of theorem 1, in the force-receiving direction of the contact force, the action line must first intersect with bc and then intersect with ab.
Fig. 5 shows a centrode triangle with three co-directional sides and the positional relationship of the contact points of four fingers. The three sides are all in the same direction with respect to the distance of a point inside the triangle. The large arrows in the figure indicate the possible location and direction of the fourth contact force.
The centrode triangle formed by the internal normals at the end points of the three grabbing sides in the figure 6 is characterized in that the internal normals are respectively made at the end points of the three sides of any given polygon, so that the internal normals of the workpiece are made at the two end points of the three sides and are called the internal normals of the extreme positions of the workpiece. The three sides have 6 inner normals at the extreme positions, one inner normal at the extreme positions is taken out from each of the three sides to form an instantaneous center triangle, and the 6 inner normals can form 8 instantaneous center triangles. The 8 instantaneous triangles are all instantaneous triangles with two homodromous sides or all instantaneous triangles with three homodromous sides. The figure shows two homodromous instantaneous triangles.
Fig. 7 judges whether the given four sides have the shape closed grabbing scheme, and determines the range of feasible contact points of the fourth side. In fig. 7, the intersection of the projections of two homodromous sides Q1Q2 and Q2Q4 of the instantaneous center triangle Q1-Q2Q4 to E4 is t1t2, and the angle between the inner normal n4 of the E4 and the inner normal n2 of the boundary E2 where the anisotropic side of the instantaneous center triangle is located is greater than 90 degrees, so that the 4 sides E1, E2, E3 and E4 of the polygonal object have a grabbing scheme meeting the requirements of shape closure.
FIG. 8 is a diagram illustrating a feasible region solution method for two equidirectional edges when the two equidirectional edges are located at the starting point of the grabbing edge.
FIG. 9 is a diagram for determining feasible finger contact sections of the different-direction edges, and a method for solving the feasible region of the different-direction edges when the two same-direction edges are located at the end positions of the grabbing edges.
FIG. 10 identifies the feasible finger contact section of the homodromous side, the part containing E2 in the area sectioned by the fold lines p1-J42-p3, n4 is close to E3, so that the position of n3 on E3 is used as an independent variable parameter, and the position range of n1 changes with the change of n 3.
FIG. 11 shows the possible finger contact section of the homodromous side, the part containing E2 in the area divided by the fold lines p1-J42-p3, and n4 is close to E1, so that the starting point of n1 on E1 is used as an independent variable parameter, and the position range of n3 changes with the change of n 1.
FIG. 12 shows the possible finger contact section of the homodromous side, the part containing E4 in the area divided by the fold lines p1-J42-p3, and n4 is close to E1, so that the starting point of n1 on E1 is used as an independent variable parameter, and the position range of n3 changes with the change of n 1.
FIG. 13 shows the possible finger contact section of the homodromous side, the part containing E4 in the area divided by the fold lines p1-J42-p3, and n4 is close to E3, so that the starting point of n3 on E3 is used as an independent variable parameter, and the position range of n1 changes with the change of n 3.
Figure 2 shows the working procedure of the grab planner.
The working steps of the grabbing planner are as follows:
1. grabbing scheme for judging whether given boundary quadruple exists and meets shape closure condition
Including the creation of boundary quadruples, i.e. finding four edges from a polygon, which is a combinatorial problem of choosing 4 edges from a polygon of n edges. The method for judging whether the boundary quadruple has the grabbing scheme comprises the following steps: 1) three sides are selected to construct 8 instantaneous center triangles with two homodromous sides; if the instantaneous center triangles with two same-direction edges cannot be constructed, the boundary quadruple does not have a grabbing scheme meeting the shape closure requirement. Otherwise, the next judgment is carried out. 2) If the 4 th edge satisfies the following two conditions, the 4 edges have a grasping scheme that satisfies the form closure requirement. Under two conditions:
the directional condition: the included angle between the direction of the inner normal of the fourth side and the direction of the opposite side of the instantaneous center triangle is larger than 90 degrees.
The position condition: if the intersection of the projection of two homodromous sides of at least more than one of the 8 centroidal triangles on the fourth grabbing side is not null.
In fig. 7, the intersection of the projections of two homodromous sides Q1Q2 and Q2Q4 of an instantaneous center triangle Q1-Q2-Q4 to the E4 is t1t2, and the included angle between the inner normal n4 of the E4 and the inner normal n2 of a polygon boundary side E2 where the instantaneous center triangle is located is larger than 90 degrees, so that the 4 sides E1, E2, E3 and E4 of the polygon have a grabbing scheme meeting the shape closure requirement.
2. Snatch edge naming
For a boundary quadruple capable of forming a centrode triangle, the first three edges are named as follows: the boundary where the anisotropic side of the centrode triangle is located is E2, and the 4 th side is E4. E1 and E3 are specified according to the position of the intersection point of the inner normals of the two sides relative to the two homodromous sides of the centrode triangle, if the intersection point is the starting point of the homodromous side, the grabbing side where the inner normal coincident with the homodromous side is located is E3, the other side is E1, and otherwise, the opposite is realized.
3 determining feasible grabbing sections of the fourth edge of the boundary four-tuple meeting the shape closed grabbing condition
The sum of the intersection of the projections of the two homodromous sides of all the instantaneous center triangles on the fourth side is the feasible interval for ensuring the shape-closed grabbing on the fourth side. In fig. 7, E4 is a feasible grabbing section in the full length range because the intersection of the projections of the two homodromous sides of the instant center triangle P1-Q2-P4 on the fourth grabbing side E4 completely covers E4.
And 4, determining a contact point possible grabbing section on the opposite side.
The sides of the three internal normals forming the instantaneous center triangle are E1, E2 and E3, wherein E2 is the grabbing side where the anisotropic side of the instantaneous center triangle is located. For any point on the position where the finger can be grasped on E4, the direction line of the finger contact force (i.e. the inner normal of E4) at the point is n4, and the two end points passing through E1 and E3 are respectively taken as the respective inner normals, so that 4 inner normals are total. There are four intersections of these 4 internal normals, and if the four intersections are on either side of n4, the graspable segment on E2 is composed of two parts, otherwise there is only one graspable segment on E2. The method for calculating the feasible grabbing position specifically comprises the following steps:
1) centro triangles were constructed with the internal normals at the start positions of E1, E2, and E3.
Intersection points J21 and J23 between the normal line in the starting point position of E2 and the normal lines n1 and n3 in the starting point positions of E1 and E3 are obtained, and intersection point J42 between the normal lines n2 and n4 in the starting point position of E2 is obtained.
If the intersection points J21, J23 and the intersection point J31 are located on both sides of n4, respectively, then E2 can form a closed gripping section from the starting position to the end position.
Otherwise, moving n2 in the forward direction of E2 so that the intersection points J21, J23 and J31 of n2 and n1 and n3 are located on both sides of n4, respectively, then n2 moves from the current position to the end point, which is the first feasible grabbing section where E2 satisfies the form closure grabbing. The feasible grabbing position of n4 is also the end point from the current position to the edge of E4.
If the movement of n2 is not such that J21, J23 and the intersection point J31 are located just on either side of n4, then the centrode triangle containing the origin limit intersection point is not present.
2) An centrode triangle is constructed with the internal normals at the end positions of E1, E2, and E3.
Intersection points J21 'and J23' between the end point limit position normal line of E2 and the end point normal lines n1 and n3 in the end points of E1 and E3 are determined, and intersection point J42 between the normal lines n2 and n4 in the start point position of E2 is determined.
If the intersection points J21 ', J23 ' and J31 ' are located on either side of n4, respectively. E2 is operable to form a closed gripping section from the end position to the start position.
Otherwise, starting from the end of E2, the movement is performed in the direction of the starting point position, so that J21 ', J23 ' and the intersection point J31 ' are located exactly on both sides of n4, and starting from the current position of n2 to the starting point position of E2, these areas are each a possible gripping section of E2, which forms a closed contact point. The feasible grabbing position of n4 is also from the start of the edge E4 to the current position.
If the movement of n2 is not such that J21 ', J23 ' and the intersection point J31 ' are located just on either side of n4, then the instant center triangle containing the endpoint limit intersection point is not present.
5 on the equidirectional side, a section of possible gripping contact points that satisfies a form closure condition.
After the potential grasping sections of E2 are determined, the potential grasping sections on the two co-directional sides E1 and E3 are determined based on the contact point positions on the given E2 and E4. After the feasible sections on the two same-direction edges are determined, namely the feasible sections on E1 are determined, the feasible sections on E3 are determined for a certain position of a given inner normal n1 on E1. According to the position relation between the intersection point J42 of n4 and n2 and the inner normal of the end point of the edge of E1 and E3, the feasible section on the equidirectional edge is probably composed of two parts, and the solving method of each part is as follows.
The corresponding vertical lines of E1 and E3 are drawn through point J42 to obtain p1 and p3, respectively. Depending on whether J42 is located within the inner normal limit section of E1, E3, it is possible to split E1 and E3 into two parts by the fold lines p1-J42-p3, and likewise the fold lines p1-J42-p3 split the inner normals n2 and n4 on E2 and E4 into two parts. There are feasible contact point segments on both of these parts, and the solution is as follows. As shown in fig. 13.
1) The first part (the part of the planar area taken by the fold line p1-J42-p3 containing E2) is solved as follows: if n4 is close to E3 in the region, so the position range of n1 changes with the change of the position of n3 by taking the position of n3 as an independent variable parameter, see FIG. 10. Otherwise, with the position of n1 as the argument, the position range of n3 varies with the position of n1, see fig. 11.
N3 feasible grasping segments in E3: the remaining part of E3 is cut by the fold line p1-J42-p 3.
The n1 graspable segment of E1 is P1' -P1 ". The solution of the position of P1 'is that, for the internal normal n3 of any given contact point position on E3, the position of P1' is the projection point of the intersection point of the current position of n3 and n4 on E1. The position of P1 "depends on the following conditions: assuming that the intersection point of n1 and n3 is J13, the intersection point of n3 and n4 is J34, and the intersection point of n3 and n2 is J32, the feasible region of n1 is to ensure that J34 is located between J13 and J32 on the internal normal n3, so that the position of P1 ″ is the end point of E1 or P1. As shown in fig. 8.
2) The second part (the part of the planar area taken by the fold line p1-J42-p3 containing E4) is solved as follows: if n4 is close to E3 in the region, so the position range of n1 varies with the position of n3, taking the position of n3 as an independent variable parameter, see FIG. 12. Otherwise, with the position of n1 as the argument, the position range of n3 varies with the position of n1, see fig. 13.
N1 feasible grasping sector in E1: the section cut from E1 by the fold line p1-J42-p 3.
N3 of E3, P3 '-P3 ", wherein P3' is determined by: for any given contact position on E1, p3 is the projection of the intersection of the current position of n1 and n4 at E3. The position of P3 "depends on the following conditions: and if the internal normal n1 is set, the intersection point of n1 and n3 is J13, the intersection point of n1 and n4 is J14, and the intersection point of n1 and n2 is J12, the feasible grabbing section of n3 is to ensure that J14 is located between J13 and J12 on the internal normal n1, so that the position of P3 ″ is the end point of E3 or P3. As shown in fig. 12
Fig. 12 and 13 are respectively the feasible contact position determination cases when n4 is close to E1 in the first region and n4 is close to E3 in the second region.
6 determining the optimal grabbing position
A feasible grabbing interval, namely an interval of finger contact positions which are guaranteed to be closed in shape on each edge, is obtained through the steps. The feasible interval on each edge changes along with the change of the position of n4, and the optimal grabbing position on the current 4 grabbing boundaries is determined according to the conditions of finger space position distribution condition, finger contact force keeping balance and the like.
7 determining the optimal grabbing scheme
When all the boundary quadruples of a given polygon object are processed, since there is a possibility that there exists a capture scheme for each boundary quadruple, an optimal capture scheme must be found from all the feasible schemes. The invention takes the factors of the wrist motion amplitude, the finger motion amplitude, the relative position of the finger contact point, the relative magnitude of the finger contact force and the like as evaluation indexes to evaluate all schemes and obtain the optimal grabbing scheme.
Claims (7)
1. A polygonal object multi-finger grabbing planning method is characterized in that the grabbing planning steps are as follows:
a. the image acquisition and processor acquires the image of the prismatic workpiece, processes and converts the image into a three-dimensional solid figure which is convenient for computer representation, and finally outputs a polygon on a grabbing plane;
b. determining all feasible gripping schemes of the grippers of the four fingers on the workpiece by using a gripping planner, and determining an optimal gripping scheme;
c. outputting a finger position signal of the optimal grabbing scheme to a control and driver of the finger gripper by the grabbing planner to carry out grabbing action;
the steps of the grabbing planner for determining the feasible grabbing scheme are as follows:
d. an instantaneous center triangle is formed by the intersection points of any three fingers in the dexterous multi-finger hand on the working contact force direction line of the workpiece;
e. and determining the position range of the fourth finger meeting the shape closing requirement according to the centrode triangle.
2. The multi-finger grasp planning method for polygonal objects according to claim 1, wherein the step of determining the contact position range of the fourth finger on the polygon satisfying the shape closure requirement according to the polygon shape of the workpiece comprises:
a. judging whether a grabbing scheme meeting the shape sealing requirement exists in the boundary quadruple;
b. for 4 grabbing edges of a grabbing scheme meeting the shape sealing requirement, a feasible grabbing scheme is established, and the method comprises the following steps:
(a) determining a feasible grabbing section on the 4 th side according to the first three sides and the instantaneous center triangle;
(b) determining a grabbing position section which meets the shape sealing requirement on one different-direction edge;
(c) determining the sections of the gripping positions on two parallel sides that satisfy the requirements of a form closure
c. And maintaining a balance condition according to the distribution condition of the space positions of the fingers and the magnitude of the contact force of the fingers, and determining the optimal grabbing positions on the four grabbing position sections meeting the shape sealing requirement.
3. The multi-finger grasp planning method for the polygonal object according to claim 2, wherein the step of judging whether the grasp scheme meeting the shape closure requirement exists in the boundary quadruple group comprises the steps of:
a. three edges are selected to construct 8 instantaneous center triangles with two homodromous edges, and if the instantaneous center triangles with two homodromous edges cannot be constructed, a grabbing scheme meeting the shape closing requirement does not exist in the boundary quadruplet;
b. if the fourth side meets the following two conditions, the fourth side has a grabbing scheme meeting the shape closure:
(a) the direction condition is as follows: the included angle between the inner normal of the fourth side and the direction of the anisotropic side of the instantaneous center triangle is necessarily larger than 90 degrees;
(b) position conditions: if the intersection of the projection of two homodromous sides of at least more than one of the 8 centroidal triangles on the 4 th side is not null.
4. The polygonal object multi-finger grasp planning method according to claim 2, wherein the sum of the intersections of the projections of the two homodromous sides of all centroidal triangles on the 4 th side is a feasible section on the 4 th side that can guarantee a shape-closed grasp.
5. The multi-finger grasp planning method for polygonal objects according to claim 2, wherein the step of determining the grasp location segment on the opposite side satisfying the shape closure requirement is:
a. firstly, naming a grabbing edge: for the boundary quadruple capable of forming the instantaneous center triangle, naming a polygonal boundary where an anisotropic side of the instantaneous center triangle is located as E2, and naming two homodromous sides as E1 and E3 respectively, specifically determining the positions of intersection points of internal normals of the two sides relative to the two homodromous sides of the instantaneous center triangle, if the intersection points are the starting points of the homodromous sides, a grabbing side where the internal normals coincident with the homodromous sides are located is E3, the other side is E1, otherwise, the other side is E1, the other side is E3, and the 4 th side is E4;
b. the method for determining the grabbing position section meeting the shape closing requirement on the different-direction edge comprises the following steps:
(A) constructing an instantaneous center triangle by using the internal normals at the starting positions of E1, E2 and E3, obtaining intersection points J21 and J23 of the internal normal n2 at the starting position of E2 and the internal normals n1 and n3 at the starting positions of E1 and E3, and obtaining intersection point J42 of the internal normal n2 at the starting position of E2 and the internal normal n4 of E4;
(a) if the intersection points J21, J23 and the intersection point J31 are located on two sides of the n4, the E2 can form a feasible closed grabbing section from the starting position to the end position; j31 is the intersection of normal n1 in the E1 starting position and normal n3 in the E3 starting position;
(b) otherwise, moving n2 in the forward direction of E2 to enable intersection points J21, J23 and J31 of n2 and n1 and n3 to be located on two sides of n4 respectively, and then moving n2 from the current position to the end point, wherein the section is the first feasible section meeting the shape closure grabbing; the feasible location of n4 is also the end point from the current location to edge E4;
(c) if such a normal does not exist, it indicates that a triangle containing the origin limit intersection does not exist;
or,
(B) constructing an instantaneous center triangle by using the inner normals at the end positions of E1, E2 and E3, calculating the intersection points J21 'and J23' of the normals at the end position of E2 and the normals n1 and n3 at the end positions of E1 and E3, and calculating the intersection point J42 of the normals n2 and n4 at the end position of E2 and the normal n 4;
(a) if the intersection points J21 ', J23 ' and J31 ' are located on two sides of the n4, respectively, the E2 is a feasible closed grabbing section from the end position to the starting point; j31' is the intersection of normal n3 in the end position of E3 and normal n1 in the end position of E1;
(b) otherwise, moving the n2 along the direction that the end point of the E2 points to the starting point position, so that the J21 ', the J23 ' and the intersection point J31 ' are just positioned at two sides of the n4, starting from the current position of the n2 to the starting point position of the E2, and the sections are all feasible grabbing sections of the E2, which form a closed contact point;
(c) if the movement of n2 is not such that J21 ', J23 ' and the intersection point J31 ' are located at the right sides of n4, it is said that the centrode triangle including the endpoint limit intersection point does not exist.
6. The multi-finger grasp planning method for polygonal objects according to claim 5, wherein the method for determining grasp location segments satisfying the shape closure requirement on the homodromous side comprises: perpendicular lines are drawn through point J42 for E1 and E3 to give corresponding feet P1, P3, with fold lines P1-J42-P3 possibly dividing E1 and E3 into two parts, and fold lines P1-J42 likewise dividing internal normals n2 and n4 on E2 and E4 into two parts, on both of which there are possible catch position segments:
a. the portion of the planar area taken along the fold line P1-J42-P3 containing E2:
n3 feasible grasping segments in E3: the remaining part of E3 cut by the fold line P1-J42-P3;
n1 feasible grasping segments in E1: p1 '-P1 ", wherein determination of the P1' position: inner normal n3 for any given contact point on E3; the position of P' is a projection point of the intersection point of the current position n3 and n4 on E1; p "is at the end point of E1 or P1;
b. the portion of the planar area taken along the fold line P1-J42-P3 containing E4:
n1 feasible grasping sector in E1: a portion cut from E1 by fold line P1-J42-P3;
n3 feasible grasping sector in E3: p3 '-P3 ", wherein determination of the P3' position: for the inner normal n1 of any given contact point position on E1, P3 'is the projection point of the intersection point of the current position of n1 and n4 on E3, and the position of P3' is the end point of E3 or P3.
7. The multi-finger grasp planning method for polygonal objects according to claim 1, wherein the method for determining the optimal grasp scheme is: and (3) taking the wrist motion amplitude, the finger motion amplitude, the relative position of the finger contact point and the finger contact force as evaluation indexes, and finding out the optimal grabbing scheme from all feasible grabbing schemes.
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| US8875460B2 (en) | 1999-11-05 | 2014-11-04 | Faus Group, Inc. | Direct laminated floor |
| US8209928B2 (en) | 1999-12-13 | 2012-07-03 | Faus Group | Embossed-in-registration flooring system |
| US7836648B2 (en) | 2002-05-03 | 2010-11-23 | Faus Group | Flooring system having complementary sub-panels |
| US7836649B2 (en) | 2002-05-03 | 2010-11-23 | Faus Group, Inc. | Flooring system having microbevels |
| US8099919B2 (en) | 2002-05-03 | 2012-01-24 | Faus Group | Flooring system having microbevels |
| US8112958B2 (en) | 2002-05-03 | 2012-02-14 | Faus Group | Flooring system having complementary sub-panels |
| US8181407B2 (en) | 2002-05-03 | 2012-05-22 | Faus Group | Flooring system having sub-panels |
| US8448400B2 (en) | 2002-05-03 | 2013-05-28 | Faus Group | Flooring system having complementary sub-panels |
| US8201377B2 (en) | 2004-11-05 | 2012-06-19 | Faus Group, Inc. | Flooring system having multiple alignment points |
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