CN111360828B - Three-dimensional space rolling target envelope capture method based on multi-finger mechanism - Google Patents

Three-dimensional space rolling target envelope capture method based on multi-finger mechanism Download PDF

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CN111360828B
CN111360828B CN202010157734.6A CN202010157734A CN111360828B CN 111360828 B CN111360828 B CN 111360828B CN 202010157734 A CN202010157734 A CN 202010157734A CN 111360828 B CN111360828 B CN 111360828B
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finger
envelope
finger mechanism
dimensional space
space rolling
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CN111360828A (en
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孙冲
万文娅
袁源
宋金丰
宋硕
张震
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Northwestern Polytechnical University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1612—Programme controls characterised by the hand, wrist, grip control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G4/00—Tools specially adapted for use in space
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G4/00—Tools specially adapted for use in space
    • B64G2004/005—Robotic manipulator systems for use in space

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Abstract

The invention discloses a three-dimensional space rolling target enveloping capturing method based on a multi-finger mechanism, which comprises the following steps: s100, establishing a structure description model of the multi-finger mechanism according to the relative position relation among the base joints of the fingers 4 of the multi-finger mechanism and the configuration description of the fingers 4, and S200, deducing effective envelope conditions of the multi-finger mechanism according to conditions which should be met between the multi-finger mechanism and a three-dimensional space rolling target when the multi-finger mechanism can restrain the three-dimensional space rolling target from moving; and S300, finding out an effective multi-finger mechanism configuration meeting the envelope condition according to a multi-finger mechanism envelope algorithm. When the method catches a space rolling target, the method has the advantages of no need of catching points, no need of accurate target information, better compatibility to the geometric shape of the target and capability of realizing the motion constraint of the target only through simple position control.

Description

Three-dimensional space rolling target envelope capture method based on multi-finger mechanism
Technical Field
The invention belongs to the field of aerospace, relates to a capture scheme for a three-dimensional space rolling target, and particularly relates to a three-dimensional space rolling target enveloping capture method based on a multi-finger mechanism.
Background
Along with the continuous exploration and utilization of space resources by human beings, a large amount of space garbage caused by various reasons such as failed satellites, various explosions and fragments not only occupies valuable orbital resources, but also poses serious threats to the safety of the normally on-orbit running spacecraft. Most space debris are non-cooperative targets, and as the targets lose posture adjustment capability and run in an out-of-control state for a long time, the targets are influenced by shooting moments such as sunlight pressure and gravity gradient and residual angular momentum before failure, complex rotary motion often occurs and even tend to freely roll, so that the capturing of the targets is very challenging. Furthermore, such targets often do not have docking and cooperative measuring devices or the like dedicated to capture the connection, which undoubtedly further increases the difficulty of space tumbling targets.
Disclosure of Invention
The invention aims to provide a three-dimensional space rolling target envelope capture method based on a multi-finger mechanism, aiming at the problems in the prior art. When the method catches a space rolling target, the method has the advantages of no need of catching points, no need of accurate target information, better compatibility to the geometric shape of the target and capability of realizing the motion constraint of the target only through simple position control.
In order to achieve the above object, the present invention provides the following technical solutions.
A three-dimensional space rolling target envelope capture method based on a multi-finger mechanism comprises the following steps:
s100, establishing a structural description model of the multi-finger mechanism according to the relative position relationship among the base joints of each finger of the multi-finger mechanism and the configuration description of each finger,
s200, deducing effective envelope conditions of the multi-finger mechanism according to conditions which should be met between the multi-finger mechanism and the three-dimensional space rolling target when the multi-finger mechanism can restrain the three-dimensional space rolling target from moving;
s300, searching an effective multi-finger mechanism configuration meeting an envelope condition according to a multi-finger mechanism envelope algorithm;
the multi-finger mechanism envelope algorithm specifically comprises the following steps:
s301, dividing fingers of the multi-finger mechanism into a main finger and the remaining auxiliary fingers;
s302, controlling the main finger base joint to track the envelope point to realize motion synchronization;
s303, matching the configuration of the main finger with the envelope edge by adjusting the joint angle value of the main finger;
s304, determining the configuration of the slave finger by using the structural description model of the multi-finger mechanism in the S100;
and S305, determining the effective envelope configuration by using the effective envelope conditions of the multi-finger mechanism in the S200.
As a further improvement of the present invention, in S100, the multi-finger mechanism is connected to a service satellite through a robot arm; the multi-finger mechanism comprises a palm and n fingers, wherein each finger consists of m connecting rods and m single-degree-of-freedom rotary joints.
As a further improvement of the invention, the base joint finger position P of the ith fingerb_iAnd base joint finger position P of j-th fingerb_jSatisfies the following relationship:
Pb_j＝Pb_i+δij(j≠i,i≤n,j≤n) (2)
wherein, deltaijIs the base joint finger position P of the ith finger determined by the self structure of the multi-finger mechanismb_iAnd base joint finger position P of j-th fingerb_jRelative vector relationship between them.
As a further improvement of the present invention, in S100, the positions of other finger base joints are determined according to the spatial position of any given finger base joint and by combining the relative position relationship between the base joints; and determining the possible configuration of each finger according to the joint angle range of each finger, and further determining the possible configuration of the whole multi-finger mechanism.
As a further improvement of the present invention, in S200, the effective envelope condition of the multi-finger mechanism is represented as:
g(Θ):＝max(di,i→i+1,di,k→k+1,{di,j})-lcl<0
wherein i, j is 1,2, …, n; i is not equal to j; k is 1,2, …, m-1; wherein d isi→i+1,kRepresents a line segment Ji,kJi,k+1And line segment Ji+1,kJi+1,k+1The distance between them; di,k→k+1Represents a line segment Ji,kJi+1,kAnd line segment Ji,k+1Ji+1,k+1The distance between them.
As a further improvement of the present invention, in S300, the envelope point is selected as a point which is within a certain distance range near the three-dimensional space rolling target and is stationary with respect to the space rolling target; the envelope edge is selected as a line on one face of the three-dimensional space rolling object.
As a further improvement of the invention, the tracking envelope point of the main finger base joint in S300 is realized by model predictive control.
As a further improvement of the invention, in the step S300, the main finger configuration is matched with the envelope edge by searching for the main finger joint angle which enables the one-way distance between the main finger configuration and the envelope edge to be minimum through a fast search random tree algorithm.
Compared with the prior art, the invention has the following beneficial effects:
the method utilizes the characteristics of envelope capture itself-motion constraint on the target is achieved only through position control and mechanical characteristics such as contact do not need to be considered. On one hand, the 'master-slave' type multi-finger mechanism envelope algorithm has the capability of processing the dynamic property of a three-dimensional space rolling target, and also simplifies the degree of freedom of the system so as to improve the calculation efficiency; on the other hand, the method has the advantages of no need of a capture point, no need of accurate target information, better compatibility on target geometric shape and capability of realizing target motion constraint only through simple position control. When the space rolling target is caught, the method has the advantages of no need of catching points, no need of accurate target information, better compatibility on the geometric shape of the target and capability of realizing the motion constraint of the target only through simple position control.
Drawings
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In addition, the shapes, the proportional sizes, and the like of the respective members in the drawings are merely schematic for facilitating the understanding of the present invention, and do not specifically limit the shapes, the proportional sizes, and the like of the respective members of the present invention. Those skilled in the art, having the benefit of the teachings of this invention, may choose from the various possible shapes and proportional sizes to implement the invention as a matter of case. In the drawings:
FIG. 1 is a schematic view of a multi-fingered mechanism of the present invention;
FIG. 2 is a schematic diagram of a possible situation of a multi-finger mechanism enveloping a three-dimensional space rolling object;
FIG. 3 is an illustration of a multi-fingered hand with adjacent finger and fingertip distance calculations;
FIG. 4 is an illustration of a possible configuration of a primary finger;
FIG. 5 is an envelope edge matching algorithm;
FIG. 6 is a diagram of the positional relationship of the base joints of the multi-fingered mechanism;
FIG. 7 is a graph of the primary finger base joint tracking envelope point results;
FIG. 8 is a graph of the results of a master finger matching an envelope edge;
FIG. 9 is a diagram showing an effective configuration of a multi-finger mechanism.
Wherein, 1, service satellite (base); 2. a mechanical arm; 3. a palm; 4. a finger; 5. a joint; 6. a connecting rod; 7. multiple finger joints.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The invention relates to a three-dimensional space rolling target envelope capture method based on a multi-finger mechanism, which comprises the following steps of:
s100, establishing a structural description model of the multi-finger mechanism;
once the space position of any one finger base joint is given, the positions of other finger base joints can be determined according to the relative position relation between the base joints; then, according to the joint angle range of each finger, the possible configuration of each finger can be determined, and further the possible configuration of the whole multi-finger mechanism can be determined.
S200, deducing effective envelope conditions of the multi-finger mechanism;
the effective envelope condition of the multi-finger mechanism refers to a condition which is required to be met between the multi-finger mechanism and the three-dimensional space rolling target when the multi-finger mechanism can restrain the three-dimensional space rolling target from moving.
S300, designing a 'master-slave' type multi-finger mechanism envelope algorithm, and finding out an effective multi-finger mechanism configuration meeting envelope conditions.
The structural description model of the multi-finger mechanism gives the relative position relationship among the base joints of each finger of the multi-finger mechanism and the configuration description of each finger.
The basic idea of the multi-finger mechanism envelope algorithm of the 'master-slave' type is as follows: considering the high degree of freedom problem of the multi-finger mechanism and the relative motion between the multi-finger mechanism and the three-dimensional space rolling object, firstly, dividing fingers of the multi-finger mechanism into a main finger and a residual slave finger; secondly, controlling the main finger base joint to track the envelope point to realize motion synchronization; then, the configuration of the main finger is matched with the enveloping side by adjusting the joint angle value of the main finger; then, determining the configuration of the slave finger by using the structural description model of the multi-finger mechanism in S100; and finally, determining the effective envelope configuration by using the effective envelope conditions of the multi-finger mechanism in the S200.
Further, the selection of the main finger in S300 is random, and the envelope point is selected as a point within a certain distance range near the three-dimensional space rolling object and stationary with respect to the space rolling object. The tracking envelope point of the joint of the main finger base is realized by model predictive control. The envelope edge is selected as a line on one face of the three-dimensional space rolling object. The matching of the main finger configuration and the envelope edge is to search for the main finger joint angle which enables the one-way distance between the main finger configuration and the envelope edge to be minimum through a fast search random tree algorithm.
The invention is described in detail below with reference to the figures and the specific embodiments.
Examples
A three-dimensional space rolling target envelope capture method based on a multi-finger mechanism comprises the following specific steps:
and S100, establishing a structural description model of the multi-finger mechanism.
First, the relative positions between the base joints of the respective fingers 4 of the multi-finger mechanism are determined. As shown in fig. 1, the multi-fingered mechanism is connected to a service satellite through a robotic arm 2. The multi-finger mechanism consists of a palm 3 and n fingers 4, wherein each finger 4 also consists of m connecting rods 6 and m single-degree-of-freedom rotary joints 5. Subject to the mechanical constraint of the multi-finger mechanism, the base joint finger position P of the ith finger 4b_iAnd the base joint finger position P of the j-th finger 4b_jSatisfies the following relationship:
Pb_j＝Pb_i+δij(j≠i,i≤n,j≤n) (3)
wherein, deltaijIs the base joint finger position P of the ith finger 4 determined by the structure of the multi-finger mechanismb_iAnd the base joint finger position P of the j-th finger 4b_jRelative vector relationship between them.
Then, the possible configurations of the individual fingers 4 themselves are determined. Configuration S for the i-th (i-1, 2, …, n) finger 4iIt is determined by the joint angle theta of the fingeri＝[θi,1,θi,2,…,θi,m]TDetermining:
Si＝f(θi)＝f(θi,1,θi,2,…,θi,m)(i＝1,2,…,n) (4)
wherein, f (theta)i) Denotes SiAnd thetaiFunctional relationship between them.
Therefore, once the space position of the base joint of any one finger 4 is given, the positions of the base joints of other fingers can be determined according to the relative position relationship among the base joints; then, according to the joint angle range of each finger 4, the possible configuration of each finger 4 can be determined, and further the possible configuration of the whole multi-finger mechanism can be determined.
Further, the range of joint angular rotation of the fingers is limited, provided that
Figure BDA0002404684620000061
Here, the
Figure BDA0002404684620000062
And
Figure BDA0002404684620000063
the kth joint of the ith finger 4 can be rotated to the upper and lower limits of the range.
And S200, deducing the effective envelope condition of the multi-finger mechanism. The fact that the multi-finger mechanism effectively envelops the three-dimensional space rolling target means that the three-dimensional space rolling target cannot escape from the constraint of the multi-finger mechanism. Specifically, the finger cannot escape from the gap between adjacent fingers of the multi-finger mechanism and the gap between the tips of the fingers 4.
Further, the three-dimensional space tumbling object is in a free floating state, which means that the multi-finger mechanism can envelop the three-dimensional space tumbling object from any direction, as shown in fig. 2. When different envelope directions are adopted, the relative postures of the three-dimensional space rolling target and the multi-finger mechanism are greatly different, which causes complexity and high difficulty in effective envelope condition derivation. Not in general, we assume that the palm 3 of the multi-fingered mechanism is always parallel to one plane of the three-dimensional space scrolling object (fig. (c)) during the enveloping process, which can be achieved by adjusting the pose of the multi-fingered mechanism.
First, the gap between the ith finger 4 and the (i +1) th finger 4 link 6 is calculated, and as shown in fig. 3 (a), the graph formed by the ith finger 4 and the kth link 6 of the (i +1) th finger 4 is a space quadrangle Ji,kJi,k+1Ji+1,k+1Ji+1,k(i-1, 2, …, n; n + 1-1; k-1, 2, …, m; m + 1-E, E representing a fingertip). If J isi,kJi,k+1Ji+1,k+1Ji+1,kThe distance between the opposite sides is less than the corresponding characteristic length l of the three-dimensional space rolling targetclThen the three-dimensional space scrolling object cannot be selected from the ith finger 4 and the (i +1) th fingerEscape in the gap of the finger 4:
Figure BDA0002404684620000071
wherein d isi→i+1,kRepresents a line segment Ji,kJi,k+1And line segment Ji+1,kJi+1,k+1The distance between them; di,k→k+1Represents a line segment Ji,kJi+1,kAnd line segment Ji,k+1Ji+1,k+1The distance between them.
Next, the distance between the fingertips of the respective fingers 4 is calculated. As shown in FIG. 3(b), the tip of each finger 4 of the multi-finger mechanism forms a space n-polygon, and the tip E of the ith finger 4iAnd the tip E of the jth finger 4j(i, j ≠ j) of 1,2, …, n ≠ j)i,jComprises the following steps:
Figure BDA0002404684620000072
where d (·,) represents a function for calculating the distance between any two points in space, and in this patent, euclidean distance is used, where p ═ 2. In order to ensure that the three-dimensional space tumbling object does not escape from the gap between the fingertips, the following relationship should be satisfied:
Figure BDA0002404684620000073
further, in conjunction with equations (5) and (7), the effective envelope condition of the multi-fingered mechanism can be expressed as:
Figure BDA0002404684620000074
the formula (8) provides conditions which are required to be met by each joint angle of the fingers of the multi-finger mechanism when the multi-finger mechanism can effectively envelop a three-dimensional space rolling target.
S300, designing a 'master-slave' type multi-finger mechanism envelope algorithm, and finding out an effective multi-finger mechanism configuration meeting envelope conditions. Considering the high degree of freedom problem of the multi-finger mechanism and the relative motion between the multi-finger mechanism and the three-dimensional space rolling object, the fingers of the multi-finger mechanism are divided into two types of a main finger and the remaining slave fingers, and a 'main-slave' type multi-finger mechanism envelope algorithm is provided. Wherein the selection of the master finger is random.
Firstly, based on model predictive control, the motion synchronization of the base joint and the envelope point of the main finger is realized. The envelope point is selected as a point which is within a certain distance range near the three-dimensional space rolling target and is static relative to the space rolling target. Serving any point on a spacecraft
Figure BDA0002404684620000081
And any point on the three-dimensional space rolling target
Figure BDA0002404684620000082
The equation of relative motion between discrete forms with a sampling period T can be expressed as:
X(k+1)＝ATX(k)+BTU(k)+CTγ(k) (9)
wherein X (k) and U (k) respectively represent sampling time k ∈ Z+State of time and control vector;
Figure BDA0002404684620000083
γ (k) is a disturbance variable.
Further, the output variable
Figure BDA0002404684620000084
Can be expressed as:
Figure BDA0002404684620000085
order to
Figure BDA0002404684620000086
And
Figure BDA00024046846200000810
respectively representing a state variable set, an output variable set, a control input set and a constant vector set, wherein the expressions are as follows:
Figure BDA0002404684620000088
wherein N ispAnd NcRespectively representing a prediction time domain and a control time domain; x (k + j | k) is a state quantity at time k + j predicted based on X (k).
Further, based on equations (9) and (10), there are
Figure BDA0002404684620000089
Wherein A iss、Bs、CsAnd DsIs defined as follows:
Figure BDA0002404684620000091
further, in deriving the discrete form of the equation of relative motion, an assumption is made that both the control torque and the external disturbance torque are 0. In addition, assume that the serving spacecraft has the capability to achieve synchronization with the attitude motion of the three-dimensional space tumbling object, i.e., the relative angular velocity ω ═ ω between the serving spacecraft and the three-dimensional space tumbling objectx,ωy,ωz]T→ 0 and angular acceleration
Figure BDA0002404684620000092
Further, in order to ensure the safety of tracking the envelope point by the main finger base joint, a collision avoidance constraint, a control input saturation constraint and a speed constraint are modeled and expressed:
GsUs(k)≤gs (14)
wherein G issAnd gsIs as shown inThe following:
Figure BDA0002404684620000093
Figure BDA0002404684620000101
wherein the content of the first and second substances,
Figure BDA0002404684620000102
coordinates representing envelope points; r isplRepresents a safe radius; u. ofupperAn upper bound representing a control input; vupperA boundary value vector representing a velocity; i denotes an identity matrix.
Further, the main finger base joint tracking envelope point problem can be expressed as a quadratic programming problem as follows:
Figure BDA0002404684620000103
wherein Π (k) is the objective function shown in equation (16); rhoij_dIs the desired relative position vector between the primary finger base joint and the envelope point;
Figure BDA0002404684620000104
and
Figure BDA0002404684620000105
respectively representing a positive definite state weight matrix and a positive definite control weight matrix;
Figure BDA0002404684620000106
Figure BDA0002404684620000107
Figure BDA0002404684620000108
Figure BDA0002404684620000109
further, when the main finger joints are in position
Figure BDA00024046846200001010
And envelope point position Pl＝Pt jAnd meanwhile, the motion synchronization of the base joint and the envelope point of the main finger can be realized.
And then, the configuration of the main finger is matched with the envelope edge by adjusting the joint angle value of the main finger. Wherein the envelope edge is selected as a line (red line in fig. 4) on a certain face of the three-dimensional space rolling object. In theory, the primary finger may have many possible configurations in order for the primary finger L to bel＝{Jl,1,Jl,2,...,Jl,m,ElAnd the envelope edge elMatching as much as possible, introducing a one-way distance Dowd(Ll,el) To measure the similarity of the two shapes:
Figure BDA0002404684620000111
wherein, | | Ll| represents the total length of the master finger link 6; LS (least squares)l＝{Ll,1～2,Ll,2～3,…,Ll,m-1～m,Ll,m～m+1}(Ll,m～m+1＝(Jl,m,El) ) represents the main finger LlAll the links 6 (each link 6 is simplified to a line segment); dowd(Ll,i～i+1,el) Showing the connecting rod 6Ll,i～i+1To the envelope edge elThe one-way distance of (c) can be calculated by equation (18).
Figure BDA0002404684620000112
Wherein D ispoint(p,el) Showing the connecting rod 6Ll,i～i+1From any point p on to the envelope edge elThe shortest distance of：
Figure BDA0002404684620000113
Further, the Euclidean distance DEuclid(p,q)＝||p-q||2。
Further, a main finger joint angle value theta which enables the one-way distance between the main finger configuration and the enveloping side to be minimum is found through a fast search random tree algorithmoptThe specific algorithm is shown in fig. 5. Wherein, thetanewWhether the effect is effective or not is judged by detecting whether the main finger collides with the three-dimensional space rolling object or not.
Then, using the structure description model of the multi-finger mechanism in S100, the slave finger configuration is determined. First, according to any one of the slave fingers Li(i ═ 1,2, …, n; i ≠ L) base joint and master finger LlPosition vector delta between base jointsilDetermining LiBase joint position P ofb_i：
Pb_i＝Pb_l+δil(i≠l,1≤i≤n,1≤l≤n) (22)
Then according to LiIs determined by the allowable range of joint angular rotation ofiPossible configurations of (a):
Figure BDA0002404684620000121
wherein the content of the first and second substances,
Figure BDA0002404684620000122
and
Figure BDA0002404684620000123
respectively represent LiThe lower and upper limits of the allowable range of joint angular rotation of (1);
Figure BDA0002404684620000124
represents LiObject O incapable of rolling with three-dimensional spacetThe restraint requirements for a collision.
And finally, determining the effective envelope configuration by using the effective envelope conditions of the multi-finger mechanism in the S200. First, a set C of possible configurations of the multi-fingered mechanism can be determinedmf_possible：
Cmf_possible＝{Ll，{Li}}(i≠l,1≤i≤n,1≤l≤n) (24)
Then, using the effective envelope condition, from Cmf_possibleRandomly selecting an effective envelope configuration.
Simulation example
The present invention is further described with reference to the specific embodiment shown in fig. 1, wherein the object in fig. 4 is enveloped by a 4-finger 3-joint multi-finger mechanism:
let each connecting rod 6 be d in lengthlThe joint angle ranges are all theta at 0.25mi∈[-90°,90°](ii) a All joint angles of the multi-finger mechanism have initial values of theta i0 °; the number of the main finger is 1; the positional relationship between the proximal joints of the multi-fingered mechanism is shown in fig. 6. The length, width and height of the three-dimensional space rolling target are 1.2m, 0.6m and 0.4m respectively; the track radius was 7100 km. Initial time t0When the coordinate is 0s, the coordinate of the envelope point is [0, -0.225, -0.31%]Tm; the coordinate of the base joint of the main finger is Pb_l＝[0.5,-0.5,0.5]Tm; the relative position vector is ρij(t0)＝[-9,16,18]Tm；
Figure BDA0002404684620000125
Further, let T be 0.1 s; n is a radical ofc＝20；Np＝20；
Figure BDA0002404684620000126
uupper＝1(m/s2)；
Figure BDA0002404684620000127
rpl1 m. At a given desired time tcThe tracking of the envelope is completed within 40s, as shown in fig. 7.
FIG. 8 shows the matching result of the main finger with the envelope edge, where Dowd(Ll,el) Converge to 0.02974 thetaopt＝[-90,-2.35,-5.16]T°。
Fig. 9 shows an effective multi-fingered mechanism configuration: pb_1＝[0m,-0.225m,-0.31m]T，θ1＝[-90°,-2.35°,-5.16°]T；Pb_2＝[-0.7m,0.025m,-0.31m]T，θ2＝[90°,10°,8°]T；Pb_3＝[0m,0.275m,-0.31m]T，θ3＝[90°,8°,6°]T；Pb_4＝[0.7m,0.025m,-0.31m]T，θ4＝[-90°,-10°,-8°]T. In addition, the distance between the fingertips of the finger 1 and the finger 3 is 0.3619m, which is smaller than the characteristic length in the direction of-0.4 m; the distance between the tips of the fingers 2 and 4 is 1.1587m, which is smaller than the characteristic length in this direction-0.6 m.
It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and many applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the present teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are hereby incorporated by reference for all purposes. The omission in the foregoing claims of any aspect of subject matter that is disclosed herein is not intended to forego such subject matter, nor should the applicant consider that such subject matter is not considered part of the disclosed subject matter.

Claims (7)

1. A three-dimensional space rolling target envelope capture method based on a multi-finger mechanism is characterized by comprising the following steps:
s100, establishing a structural description model of the multi-finger mechanism according to the relative position relationship among the base joints of each finger of the multi-finger mechanism and the configuration description of each finger,
s200, deducing effective envelope conditions of the multi-finger mechanism according to conditions which should be met between the multi-finger mechanism and the three-dimensional space rolling target when the multi-finger mechanism can restrain the three-dimensional space rolling target from moving;
s300, searching an effective multi-finger mechanism configuration meeting an envelope condition according to a multi-finger mechanism envelope algorithm;
the multi-finger mechanism envelope algorithm specifically comprises the following steps:
s301, dividing fingers of the multi-finger mechanism into a main finger and the remaining auxiliary fingers;
s302, controlling the main finger base joint to track the envelope point to realize motion synchronization;
s303, matching the configuration of the main finger with the envelope edge by adjusting the joint angle value of the main finger;
s304, determining the configuration of the slave finger by using the structural description model of the multi-finger mechanism in the S100;
s305, determining an effective envelope configuration by using the effective envelope condition of the multi-finger mechanism in the S200;
s303, adjusting the joint angle value of the main finger to enable the configuration of the main finger to be matched with the enveloping edge specifically comprises the following steps:
the envelope edge is selected as a line on a certain plane of the three-dimensional space rolling target, and a one-way distance D is introducedowd(Ll,el) To measure the main finger Ll＝{Jl,1,Jl,2,...,Jl,m,ElAnd the envelope edge elSimilarity of both shapes:
Figure FDA0003324278960000011
wherein, | | Ll| represents the total length of the master finger link; LS (least squares)l＝{Ll,1～2,Ll,2～3,…,Ll,m-1～m,Ll,m～m+1}(Ll,m～m+1＝(Jl,m,El) ) represents the main finger LlEach connecting rod is simplified into a line segment; dowd(Ll,i～i+1,el) Indicating the connecting rod Ll,i～i+1To the envelope edge elIs not only a sheetThe directional distance is calculated by the following equation;
Figure FDA0003324278960000012
wherein D ispoint(p,el) Indicating the connecting rod Ll,i～i+1From any point p on to the envelope edge elThe shortest distance of (c):
Figure FDA0003324278960000021
further, the Euclidean distance DEuclid(p,q)＝||p-q||2；
Further, a main finger joint angle value theta which enables the one-way distance between the main finger configuration and the enveloping side to be minimum is found through a fast search random tree algorithmopt。
2. The three-dimensional space rolling target envelope capture method based on the multi-finger mechanism according to claim 1, characterized in that: in S100, the multi-finger mechanism is connected with a service satellite through a mechanical arm; the multi-finger mechanism comprises a palm and n fingers, wherein each finger consists of m connecting rods and m single-degree-of-freedom rotary joints.
3. The three-dimensional space rolling target envelope capture method based on the multi-finger mechanism according to claim 2, characterized in that: base joint finger position P of ith fingerb_iAnd base joint finger position P of j-th fingerb_jSatisfies the following relationship:
Pb_j＝Pb_i+δij(j≠i,i≤n,j≤n)
wherein, deltaijIs the base joint finger position P of the ith finger determined by the self structure of the multi-finger mechanismb_iAnd base joint finger position P of j-th fingerb_jRelative vector relationship between them.
4. The three-dimensional space rolling target envelope capture method based on the multi-finger mechanism according to claim 1, characterized in that: in S100, determining the positions of other finger base joints according to the space position of any given finger base joint and the relative position relation between the base joints; and determining the possible configuration of each finger according to the joint angle range of each finger, and further determining the possible configuration of the whole multi-finger mechanism.
5. The three-dimensional space rolling target envelope capture method based on the multi-finger mechanism according to claim 1, characterized in that: in S200, the effective envelope condition of the multi-finger mechanism is represented as:
g(Θ):＝max(di,i→i+1,di,k→k+1,{di,j})-lcl＜0
wherein i, j is 1,2, …, n; i is not equal to j; k is 1,2, …, m-1; di→i+1,kRepresents a line segment Ji,kJi,k+1And line segment Ji+1, kJi+1,k+1The distance between them; di,k→k+1Represents a line segment Ji,kJi+1,kAnd line segment Ji,k+1Ji+1,k+1The distance between them.
6. The three-dimensional space rolling target envelope capture method based on the multi-finger mechanism according to claim 1, characterized in that: in S300, the enveloping point is selected as a point which is within a certain distance range near the three-dimensional space rolling object and is static relative to the space rolling object.
7. The three-dimensional space rolling target envelope capture method based on the multi-finger mechanism according to claim 1, characterized in that: in S300, tracking the envelope point of the main finger base joint is realized through model prediction control.
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