CN111390872A - Double-arm cooperative flexible dragging and butt joint inverse operation method for extravehicular robot - Google Patents
Double-arm cooperative flexible dragging and butt joint inverse operation method for extravehicular robot Download PDFInfo
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- CN111390872A CN111390872A CN202010197025.0A CN202010197025A CN111390872A CN 111390872 A CN111390872 A CN 111390872A CN 202010197025 A CN202010197025 A CN 202010197025A CN 111390872 A CN111390872 A CN 111390872A
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- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
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- B25J9/00—Programme-controlled manipulators
- B25J9/0084—Programme-controlled manipulators comprising a plurality of manipulators
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The invention discloses an extra-cabin robot double-arm cooperative flexible dragging and butt joint inverse operation method, which solves the problem that a mechanical arm drags a body to a target adapter position in a closed mode to complete butt joint operation of a body adapter and a target adapter.
Description
Technical Field
The invention relates to an extra-cabin robot double-arm cooperative flexible dragging and butt joint inverse operation method, and belongs to the technical field of space robots.
Background
The existing double-arm operation generally forms a closed chain by double arms, the double arms are operated by adopting a force compliance strategy, and the application scene generally refers to the double-arm operation of a ground fixed base or the capture of a target by the double arms on an orbit. The existing system intelligently distributes explosion elimination tasks for two mechanical arms in the explosion elimination process, and solves the problem of collision avoidance between the two arms or between the mechanical arm and an obstacle in the mechanical arm movement process, and the problem that the two arms pull a body to move and the body is flexibly assembled at a target position cannot be solved.
Disclosure of Invention
The technical problem solved by the invention is as follows: the defects of the prior art are overcome, the method for operating the outdoor robot in the mode of double-arm cooperative flexible dragging and butt joint in the reverse mode is provided, the outdoor robot is an application scene that the body of the outdoor robot is in butt joint through double arms, a strategy for operating the outdoor robot in the mode of double-arm cooperative flexible dragging and butt joint in the reverse mode is provided, and the strategy problem that the outdoor robot adopts double arms to grasp handrails to form a shape sealing state and a force sealing state and then installs a mechanical arm body on a target adapter through flexible dragging and butt joint is solved.
The technical scheme of the invention is as follows: a double-arm cooperative flexible dragging and butt joint inverse operation method for an extravehicular robot comprises the following steps:
step S1, initializing, namely setting the structural parameters (namely DH parameters) of the double arms of the robot, the expected path of the tail end of the robot, the path planning time and the time step; the two arms are respectively a driving arm and a driven arm;
step S2, planning a dragging and butt joint inverse operation path of the extravehicular robot according to the robot double-arm structure parameters (namely DH parameters) set in the step S1, the expected path of the tail end of the robot, path planning time and time step;
step S3, according to the double-arm structure parameters of the robot set in the step S1, solving forward kinematics and inverse kinematics of the extravehicular robot to obtain a forward kinematics solution and an inverse kinematics solution;
step S4, setting a compliance control mode of the main arm according to the planned dragging and butting inverse operation path of the extravehicular robot in the step S2 and the forward kinematics solution and the inverse kinematics solution in the step S3;
step S5, setting a passive arm zero force control mode;
s6, setting an alternating control mode of the driving arm and the driven arm to switch a compliance control mode of the driving arm and a zero-force control mode of the driven arm;
and S7, according to task requirements, adopting an alternative control mode of the driving arm and the driven arm of S6 to enable the extravehicular robot to approach the target first and then fix the extravehicular robot on the target, and realizing flexible dragging and butt joint of the extravehicular robot through the coordination of the two arms.
Preferably, step S1, initializing, that is, setting the structural parameters of the two arms of the robot (i.e., DH parameters), the expected path of the tail end of the robot, the path planning time, and the time step; the two arms are respectively a driving arm and a driven arm, and the two arms are specifically as follows:
the two-arm structural parameters of the robot are two-arm DH parameters, and the DH parameters of each arm can be defined as follows as shown in fig. 3:
torsion angle α of rodi: around xiAxis of rotation from zi-1Rotate to ziThe corner of (d);
length of rod member ai: along xiAxis from zi-1The axis moving to ziDistance of the shaft;
distance d between jointsi: along zi-1Axis from xi-1Move to xiThe distance of (d);
angle of rotation theta of jointi: around zi-1Rotation of the shaft from xi-1Rotate to xiThe angle of (c).
Establishing a D-H coordinate system according to the following rules:
1) establishing a base coordinate system: the positive direction of the motion axis of the joint 1 is z with the position of interest on the base as the origin0Axis, establishing a right-hand orthogonal coordinate system(x0,y0,z0) Wherein x is0And y0Axis and z0Vertical and optional direction;
2) for each i (i is 1, …, n-1), completing 3 to 6 steps;
3) establishing the z-axis (i.e., z) of the link i-coordinate systemiShaft) joint shaft: with the positive direction of the motion (rotation or movement) axis of the joint i +1 as ziA shaft;
4) establishing an origin O of a connecting rod i coordinate systemi: if z isiAnd zi-1The axes are crossed, and the crossing point of the two axes is taken as the original point; if z isiAnd zi-1The axes being out of plane or parallel, the common perpendicular to the two axes being ziThe intersection point of the axes is the origin;
5) establishing the x-axis (i.e., x) of the link i-coordinate systemiShaft): according to xi＝±(zi-1×zi)/||zi-1×ziI establishment of xiAxis, i.e. xiAxis and zi-1And ziThe axes are vertical at the same time; if z isi-1And ziThe axes are parallel, and the common perpendicular line of the axes is xiA shaft;
6) establishing the y-axis (i.e., y) of the link i-coordinate systemiShaft): according to x establishediAxis and ziAxis, establishing y according to the right-hand ruleiAxes, i.e. reams yi＝(zi×xi)/||zi×xi||。
Desired path x (t) at the end of the robot, t ═ 0, Δ t, 2 × Δ t, …, tfThe method refers to a three-dimensional lower position sequence of the expected mechanical arm tail end changing along with time, wherein each expected path point X (j × delta t) is 0, 1,2, …, ntThe coordinate value x of the robot arm tip in three-dimensional space at time j × Δ tj，yj，zjAnd attitude angles p about three coordinate axes, respectivelyj，qj，rj. The attitude angular direction is determined around the right-hand rule of each coordinate axis, as shown in fig. 2.
Time t for planning pathfThe method comprises the following steps: total time of the end of the arm to perform the end path, tf＝nt×Δt。
The time step Δ t, refers to: the time interval between adjacent path points at the end of the mechanical arm is generally a fixed value.
Number of programming cycles ntMeans at the time t of path planningfTotal number of time steps in.
Preferably, in step S2, according to the set robot double-arm structure parameters (that is, DH parameters), the expected path of the robot tail end, the path planning time, and the time step set in step S1, the extravehicular robot towing and docking inverse operation path is planned, which is specifically as follows:
after the left and right mechanical arms capture the target, the left and right grippers are as shown in fig. 4, the end manipulators of the left and right mechanical arms keep a fixed relative pose with the target, so that the body needs to move and becomes a moving end, the end manipulators become a fixed end, the path planning of the tail end of the mechanical arm relative to the body is mainly planned through the conventional mechanical arm path planning, and the task needs to plan the path of the body relative to the tail end of the mechanical arm and is a reverse operation.
The extravehicular robot body adapter needs to be in butt joint with the target adapter, a pose path of the extravehicular robot body adapter relative to the target adapter needs to be planned, and the starting pose X of the extravehicular robot body adapter relative to the target adapter is determined firstlya0(6 × 1 vector) and end position pose Xaf(6 × 1 vector), the time step is delta t, the pose of the tail end of the mechanical arm is planned by adopting conventional path planning functions such as cubic polynomial, quintic polynomial or parabolic mode, and the like, and the pose sequence X changing along with the time can be obtaineda(t) (6 × n matrix.) planning with a cubic polynomial is considered as follows:
pose sequence Xs(t) is described by a cubic polynomial of
Xa(t)＝a0+a1t+a2t2+a3t3
The velocity and acceleration equations for the joints are:
the cubic polynomial has the following constraints:
Xa(0)＝Xa0
Xa(tf)＝Xaf
substituting the above constraints into velocity and acceleration formulas can obtain:
Xa0＝a0
0＝a1
the following can be obtained:
a0＝Xa0
a1＝0
the pose sequence of the extravehicular robot body adapter relative to the target adapter is obtained as Xa(t) because the left arm base and the right arm base are both fixed to the body, the attitude angles of the pose sequences of the left arm base and the right arm base are both equal to XaPosture in (t)The attitude angles are the same, but the positions are offset matrixes, namely the attitude sequence X of the left arm base relative to the target adapterlb(t) is
Wherein A islb，3×3To be from the left arm base coordinate system olb-xlbylbzlbConversion to target adapter coordinate System oa-xayazaOf 3-dimensional transformation matrix, I3×3Is a 3-dimensional unit array.
The pose sequence X of the right arm relative to the target adapter can be obtained in the same wayrb(t) is
Wherein A isrb，3×3To be from the right arm base coordinate system orb-xrbyrbzrbConversion to target adapter coordinate System oa-xayazaOf 3-dimensional transformation matrix, I3×3Is a 3-dimensional unit array.
Preferably, in step S3, forward and inverse kinematics solutions of the extravehicular robot are performed according to the robot dual-arm structure parameters set in step S1, so as to obtain a forward kinematics solution and an inverse kinematics solution, which are specifically as follows:
determining starting pose X of tail end of mechanical arm0(for the end of the arm of the left or right arm, the initial pose is represented by Xlb0) And end point pose Xt(for the arm end of the left arm, the end position pose is denoted Xtf) And the time step is delta t, and the pose of the tail end of the mechanical arm is planned by adopting a conventional path planning function such as a cubic polynomial, a quintic polynomial or a parabolic mode, so that a pose sequence X (t) changing along with time can be obtained. (for the end of the arm of the left arm, denoted Xl(t), for the arm end of the left arm, denoted Xr(t))；
Solving forward kinematics and inverse kinematics of the extravehicular robot to obtain a forward kinematics solution and an inverse kinematics solution, wherein the preferable scheme is as follows:
3.1 positive kinematics: and (3) knowing the angular displacement of each joint and the geometric parameters of the connecting rod, and solving the posture and the position of the end effector of the mechanical arm relative to the base, namely the positive kinematics of the mechanical arm.
According to parameters of left and right mechanical arms DH of the outboard robot, transformation matrixes of joints of the left and right arms can be obtained, the transformation matrixes of the joints are multiplied in sequence, and a positive kinematic formula of the left arm or the right arm of the outboard robot is obtained, wherein the detailed process is as follows;
by transforming matrices by linksi-1TiTo describe the pose of the ith joint coordinate system in the (i-1) th joint coordinate system
Pose of tip in base.i-1TiThe method represents the transformation of a connecting rod i coordinate system relative to a connecting rod i-1 coordinate system, and is obtained by sequentially carrying out the following four sub-transformations on the connecting rod i coordinate system:
1) around xi-1Axle rotation αi-1An angle;
2) along xi-1Axial movement ai-1；
3) Around ziAxis of rotation thetaiAn angle;
4) along ziAxial movement di；
The above transformations are all described relative to a moving coordinate system, and the connecting rod transformation is obtained according to the principle of' from left to right
Of the general formula (II)
Wherein c represents cos and s represents sin;
change the individual connecting rodsi-1Ti(i is 1,2, …, n) to obtain a manipulator transformation matrix
0Tn＝0T1 1T2…n-1Tn
From the above formula0TnThe positive kinematics of the mechanical arm can be obtained by the function of n joint variables and representing the description of a terminal coordinate system relative to a base coordinate system; n represents the total number of joints on each arm
From the left arm DH parameters, a positive kinematic transformation matrix for the left arm can be obtained as0TnlFrom the right arm DH parameters, a positive kinematic transformation matrix for the left arm can be obtained as0Tnr。
3.2 set Jacobian matrix:
the Jacobian matrix J represents the relation between the terminal pose velocity and the joint angular velocity, can be used for solving inverse kinematics, and is transformed according to a plurality of connecting rodsi-1TiThe general formula product of (a) is solved, and the solving formula is as follows:
wherein the content of the first and second substances,0T(i-1)＝0T1 0T2…0T(i-1)the matrix is a 4 × 4 matrix,0T(i-1)(1:3,3) represents0T(i-1)Lines 1,2 and 3 intersect column 3, and other variables are similarly meant. When the value of i is 1, the value of i,0T(i-1)as a unit array, i.e.
3.3 inverse kinematics: and solving the joint angle of the mechanical arm according to the positive kinematics transformation matrix, namely obtaining the inverse kinematics. The inverse kinematics solution can map the terminal velocity to joint space by using a Jacobian matrix to obtain joint velocity, and then the joint velocity is integrated to obtain joint displacement. The method can be used for various mechanical arm configurations, has good adaptability, and has the following speed-level kinematics
ΔX(j+1)＝J(j)ΔΘ(j+1) (1)
ΔX(j)X (j +1) -X (j), the tip pose change amount at the j +1 th time point, that is, the tip speed, is represented, where j is 0, 1,2, …, nt. J (j) represents a Jacobian matrix of the robot arm at the j-th time, and Θ (j) represents n joint angles [ θ ] at the j-th time1，θ2，…，θi，…，θn]T(the right-hand symbol T indicates transposition), and Δ Θ (j +1) ═ Θ (j +1) - Θ (j), which indicates n joint angles [ θ ] at the j +1 th time point1，θ2，…，θi，…，θn]TThe amount of change, i.e., the joint angular velocity.
The joint angular velocity formula is obtained from the above formula
ΔΘ(j+1)＝J-1(j)×ΔX(j+1)
Pose sequence X of left arm base relative to target adapterlb(t) pose sequence X of right arm base with respect to body adapterrb(t) is the value of X (j + 1). The joint angle is obtained from the above formula
Θ(j+1)＝J-1(j)×ΔX(j+1)+Θ(j) (2)
According to the inverse kinematics solution method, Θ (j +1), that is, the inverse kinematics solution of the left arm is Θl(t), similarly, the inverse kinematics solution of the right arm is calculated as Θr(t)。
Preferably, in step S4, a compliance control mode of the main arm is set according to the planned extravehicular robot towing and docking inverse operation path in step S2 and the forward kinematics solution and the inverse kinematics solution in step S3, specifically as follows:
the active compliance control approach incorporates force and position into a unified control system, preferably expressed as the following equation:
the transfer function is a control dynamics equation and is independently carried out according to six degrees of freedom
M is equivalent mass, K is equivalent stiffness, and C is equivalent damping; feThe contact force between the end of the mechanical arm and the environment is measured by a six-dimensional force sensor.
And e is the difference between the actual pose and the expected pose of the tail end of the mechanical arm, wherein the expected pose is the pose when the tail end of the mechanical arm is matched with the target, and the matching represents the complete attachment, for example, the pose when the tail end of the mechanical arm is completely counted into a screw head is represented in a mechanical arm screw-screwing scene, or the pose when the tail end of the mechanical arm is accurately placed into an assembling position is represented in a mechanical arm automatic assembling scene. When the flexible control mode of the main driving arm is set, a position and posture sequence X in a dragging and butt joint inverse operation path of the robot outside the planning cabin is useda(t) parameter, set to Xaa(t) actual pose of end of arm, Xae(t) is the expected pose of the end of the arm, then Xaa(t)-XaeAnd (t) is a parameter e in the control dynamics equation of the step. According to the step, the difference between the actual pose of the tail end of the mechanical arm and the expected pose of the tail end of the mechanical arm can be obtained through the contact force, the actual pose of the tail end of the mechanical arm can be measured, and therefore the corrected expected pose of the tail end of the mechanical arm can be obtained, the pose is caused by external force when the tail end of the mechanical arm operates, and the compliance control mode of the main arm is used for providing compliance power for the operation of connecting the body adapter into the target adapter.
Preferably, in step S5, the passive arm zero force control mode is set, and the preferable scheme is specifically as follows:
the zero-force control mode of the driven arm is preferably characterized in that the mechanical arm is a soft arm, the tail end of the mechanical arm generates an external force through contact with a target or an environment, the mechanical arm can move along with the external force, if the external force is a pushing force, the tail end of the mechanical arm is in a yielding state, and if the external force is a pulling force, the mechanical arm is in a forward advancing state. The specific implementation method comprises the following steps: the robot outside the cabin is operated outside the cabin of the space station, so that the control moment does not need to consider the influence of gravity.
The passive arm zero force control mode preferably comprises the following steps: the passive arm zero-force control mode does not provide direct power for the operation of connecting the body adapter into the target adapter, the motion path of the body adapter is compliantly tracked, and the passive arm zero-force control mode mainly aims to switch the passive arm zero-force control mode into the active arm zero-force control mode when the body adapter and the target adapter are clamped under the active arm compliance control mode in step S4.
Preferably, in step S6, an active arm and passive arm alternating control mode is set, so that a compliance control mode of the active arm and a zero force control mode of the passive arm can be switched, and the preferred scheme is as follows:
and detecting the measured value of the six-dimensional force sensor between the adapter and the base in the dragging process, converting the force/torque under the coordinate system of the six-dimensional force sensor into the coordinate system of the adapter of the extravehicular robot body, reflecting the mechanical relationship between the adapter and the target adapter on the robot by the measured value of the six-dimensional force sensor under the coordinate system of the extravehicular robot adapter in the weightless environment, and performing the alternate control of the left arm and the right arm according to the measured value.
The method is characterized in that a double-arm alternating active and passive control mode is adopted, namely one arm is in active control, the other arm is in follow-up control, when the measured value of the six-dimensional force sensor reaches a switching threshold value (the switching threshold value can be selected according to experience or experiments), the situation that the mechanical arm is in a clamping position and cannot continuously drag the body forwards is detected, so that the butt joint of the extravehicular robot body adapter and a target adapter is achieved, the other arm is used as an active arm to control, the previous active arm is changed into a passive arm, the left arm and the right arm are in active and passive control alternately, and flexible dragging and butt joint under the state of forming shape sealing and force sealing are achieved through the. And (3) switching between left and right main passive arms by adopting a selection matrix, wherein when the selection matrix is [ 01 ], the left arm is an active arm, the right arm is a passive arm, and when the selection matrix is [ 10 ], the left arm is the passive arm and the right arm is the active arm.
The active arm and the passive arm are controlled alternately, preferably: and the active arm and the passive arm are alternately controlled to switch between the active arm and the passive arm according to a threshold value, the active arm can be changed into the passive arm, the passive arm is changed into the active arm, the body adapter is smoothly connected into the target adapter, and power for connecting the body adapter into the target adapter is alternately provided at the left side and the right side of the body adapter.
Preferably, step S7, according to the task requirement, an active arm and a passive arm alternating control mode of S6 is adopted, so that the extravehicular robot approaches the target first, and then fixes itself on the target, thereby realizing the extravehicular robot double-arm cooperative flexible dragging and docking, wherein the preferable scheme is as follows:
the invention relates to task requirements, in particular to an extra-cabin robot which is arranged on a target adapter for fixing, so that an extra-cabin robot body and a target can be relatively fixed, and other operation tasks can be carried out through a mechanical arm of the extra-cabin robot.
The extravehicular robot approaches the target first, and the specific process is that the extravehicular robot drags the body to the vicinity of the target through two arms and ensures the posture that the extravehicular robot body adapter can be accessed to the target adapter, as shown in fig. 5.
And then fixing the self on a target, wherein the specific process is to flexibly connect the extravehicular robot body adapter into the target adapter through the cooperative flexible dragging and butt joint operation of the extravehicular robot double arms, so that the extravehicular robot and the target are relatively fixed.
The robot outside the cabin has two arms cooperating with each other to flexibly drag and butt joint, specifically: the robot outside the cabin grips a gripper of a target through two arms, the body adapter is moved to the position near the target adapter through the active arm, and when the body adapter contacts the target adapter and starts to be introduced, the active arm and the passive arm alternately output power, so that the body adapter is connected into the target adapter.
Compared with the prior art, the invention has the advantages that:
(1) the double-arm inverse operation planning scheme has the technical advantage that the mechanical arm moves the body of the mechanical arm, namely, the arm moves as a leg.
(2) According to the invention, through the active-passive alternative control strategy scheme, the advantage of preventing the adapter from being blocked when the mechanical arm drags the body is embodied.
(3) According to the robot, flexible operation of the robot is realized through a double-arm inverse operation planning and active-passive alternative control mode, the body is automatically installed at a target position through double arms, and the robot has the technical advantages of intelligence, refinement and autonomy.
Drawings
FIG. 1 is a schematic view of an extravehicular robot provided by the present invention;
FIG. 2 is a flow chart of an extra-cabin robot double-arm cooperative flexible dragging and docking inverse operation strategy provided by the invention;
FIG. 3 is a schematic view of the parameters of a DH robot provided in accordance with the present invention;
FIG. 4 is a schematic illustration of the objectives provided by the present invention;
FIG. 5 is a schematic diagram of the reverse operation of towing and docking provided by the present invention.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
The robot body with large inertia and mass can be guided into the adapter of the target in a flexible mode in an active and passive alternative control mode before reaching the target position for fine operation (such as screw screwing, connector plugging and unplugging and laser cutting), and the operation cannot be finished by adopting a conventional flexible strategy or obstacle avoidance.
The invention discloses an extra-cabin robot double-arm cooperative flexible dragging and butt joint inverse operation method, which solves the problem that a mechanical arm drags a body to a target adapter position in a closed mode to complete butt joint operation of a body adapter and a target adapter.
The extravehicular robot, as shown in fig. 1, preferably includes: the robot comprises two arms, a robot tail end and a body, wherein the two arms are a left arm and a right arm, one arm of the two arms is a driving arm, and the other arm of the two arms is a driven arm; the body is a base of the extravehicular robot and is used for connecting two arms, an adapter (playing a role in butting an upper adapter of a target) and a six-dimensional force sensor are arranged right above the body and are used for being matched with the target adapter, and the tail end of the robot refers to a tail end manipulator of the two arms and is arranged on the last joint of the two arms;
the two arms are respectively arranged at the two sides of the body; each arm comprising: arm (also known as bar or link), joint, tip; a joint is arranged between every two adjacent arm rods, and the arm rod at the most proximal end is connected with the body; the arm rod at the farthest end is connected with the tail end through a joint; the body is provided with a six-dimensional force sensor.
The two arms comprise a left arm and a right arm, wherein in the left arm and the right arm of the two arms, the arm adopting the flexible control mode of the active arm in the step S4 is the active arm, the arm adopting the zero control mode of the passive arm in the step S5 is the passive arm, each arm is provided with a plurality of joints and arm rods, the number of the arm rods is 1 more than that of the joints, a joint is arranged between every two adjacent arm rods, and the arm rod at the most proximal end is directly connected with the body; the arm rod at the farthest end is directly connected with the tail end; the body is provided with a six-dimensional force sensor.
A coordinate system is set for the extravehicular robot, and the preferable scheme is as follows:
setting coordinate system o of extravehicular robota-xayazaAs shown in fig. 1, it is established on the body, specifically, the origin is at the geometric center of the body adapter contact surface (the contact surface with the target adapter), xaThe positive axial direction is perpendicular to the geometric center of the contact surface of the body adapter and points to the outer side of the body adapter, yaPositive axial direction is equal to xaThe axis is vertical and points to the left arm side of the robot, and the right hand rule determines zaA shaft;
the invention discloses an extra-cabin robot double-arm cooperative flexible dragging and butt joint inverse operation method, which comprises the following steps in sequence according to the preferable scheme as shown in figure 2:
step S1, initializing, namely setting the structural parameters (namely DH parameters) of the double arms of the robot, the expected path of the tail end of the robot, the path planning time and the time step; the two arms are respectively an active arm and a passive arm, and the preferred scheme is as follows:
the two-arm structure parameters of the robot, i.e. the DH parameters of the two arms, may be defined as follows as shown in fig. 3:
establishing a D-H coordinate system according to the following rules:
1) establishing a base coordinate system (both the left arm base coordinate system and the right arm base coordinate system can be established in the following way): with the position of interest on the base as the origin O0The positive direction of the axis of motion of the joint 1 (i.e., the joint closest to the body) is z0Axis, establishing a right-handed orthogonal coordinate system O0-x0y0z0Wherein x is0And y0Axis and z0Vertical and optional direction; the interested position is the intersection point of the left arm base and the body when the coordinate system of the left arm base is established; when a right arm base coordinate system is established, the interested position is the intersection point of the right arm base and the body;
2) 3 to 6 steps are completed for each connecting rod i (i is 1, …, n-1); the connecting rod 1 of the left arm is a left arm base; the connecting rod 1 of the right arm is a left arm base;
3) establishing a coordinate system for each connecting rod i; establishing the z-axis (i.e., z) of the coordinate system of link iiAxis) is a joint axis (the joint can only rotate around one axis): the positive direction of the motion (rotation) axis of the joint i +1 is taken as ziA shaft; (the serial numbers of the joints in the left arm or the right arm are sequentially added with 1 from the near end to the far end, the serial numbers of the joints are recorded from 1, the joint 1 of the left arm is a left arm base, and the joint 1 of the right arm is a right arm base);
4) establishing an origin O of a connecting rod i coordinate systemi: if z isiAnd zi-1The axes are crossed, and the crossing point of the two axes is taken as the original point; if z isiAnd zi-1The axes being out of plane or parallel, the common perpendicular to the two axes being ziThe intersection point of the axes is the origin;
5) establishing the x-axis (i.e., x) of the link i-coordinate systemiShaft): according to xi＝±(zi-1×zi)/||zi-1×ziI establishment of xiAxis, i.e. xiAxis and zi-1And ziThe axes are vertical at the same time; if z isi-1And ziThe axes are parallel, and the common perpendicular line of the axes is xiA shaft;
6) establishing the y-axis (i.e., y) of the link i-coordinate systemiShaft): according to x establishediAxis and ziAxis, establishing y according to the right-hand ruleiAxes, i.e. reams yi＝(zi×xi)/||zi×xi||。
Definition of torsion angle α of rodi: around xiAxis of rotation from zi-1Rotate to ziThe corner of (d);
length of rod member ai: along xiAxis from zi-1The axis moving to ziDistance of the shaft;
distance d between jointsi: along zi-1Axis from xi-1Move to xiThe distance of (d);
angle of rotation theta of jointi: around zi-1Rotation of the shaft from xi-1Rotate to xiThe angle of (c).
Desired path x (t) at the end of the robot, t ═ 0, Δ t, 2 × Δ t, …, tfThe method comprises the following steps: a sequence of three-dimensional spatial positions of the desired end of the robot arm over time, each desired path point x (j), j being 0, 1,2, …, nt，(nt×Δt＝tf) Showing the coordinate value x of the tail end of the mechanical arm under the base coordinate system at the moment of j × delta tj，yj，zj(j × Δ t ═ t) and three coordinate axes x respectively around the base coordinate system0、y0、z0Attitude angle (i.e. pitch angle, yaw angle, roll angle) p ofj，qj，rjAs shown in fig. 2.
Time t for planning pathfThe method comprises the following steps: total time, t, of the robot arm tip to execute the tip path (i.e., the desired path of the tip)f＝nt×Δt。
The time step delta t refers to the time interval between adjacent path points at the tail end of the mechanical arm, and the common time step is a fixed value, wherein the path points are the adjacent path points X (j × delta t) and the path points X ((j +1) × delta t);
number of programming cycles ntMeans at the time t of path planningfTotal number of time steps in.
Step S2, planning a dragging and docking inverse operation path of the extravehicular robot according to the set robot double-arm structure parameters (namely DH parameters), the expected path of the robot tail end, the path planning time and the time step set in step S1, wherein the preferred scheme is as follows:
the target is provided with a left gripper and a right gripper; the left hand grip and the right hand grip can be matched with the tail end of the mechanical arm;
after the left and right mechanical arms capture the target, the left and right grippers are as shown in fig. 4, the end manipulators of the left and right mechanical arms keep a fixed relative pose with the target, so that the body needs to move and becomes a moving end, the end manipulators become a fixed end, the path planning of the tail end of the mechanical arm relative to the body is mainly planned through the conventional mechanical arm path planning, and the task needs to plan the path of the body relative to the tail end of the mechanical arm and is a reverse operation.
The extravehicular robot body adapter needs to be in butt joint with a target adapter, a pose path of the extravehicular robot body adapter relative to the target adapter needs to be planned, and firstly, the extravehicular robot body adapter (hollow cylindrical) relative to the target adapter in an extravehicular robot coordinate system o is determineda-xayazaInitial pose at bottom Xa0(6 × 1 vector) and end position pose Xaf(6 × 1 vector), the time step is delta t, the pose of the tail end of the mechanical arm is planned by adopting conventional path planning functions such as cubic polynomial, quintic polynomial or parabolic mode, and the like, and the pose sequence X changing along with the time can be obtaineda(t)(6×ntMatrix) (i.e., pose sequence of left arm base or right arm base). Planning with a cubic polynomial is considered as follows:
pose sequence Xs(t) is described by a cubic polynomial of
Xa(t)＝a0+a1t+a2t2+a3t3
In the formula, a0、a1、a2、a3Polynomial parameters for the band solution;
pose sequence Xa(t)(6×ntMatrix) velocity of the object
And acceleration
The formula is as follows:
the cubic polynomial has the following constraints:
Xa(0)＝Xa0
Xa(tf)＝Xaf
substituting the above constraints into velocity and acceleration formulas can obtain:
Xa0＝a0
0＝a1
the following can be obtained:
a0＝Xa0
a1＝0
the pose sequence of the extravehicular robot body adapter relative to the target adapter is obtained as Xa(t) because the left arm base and the right arm base are both fixed to the body, the attitude angles of the pose sequences of the left arm base and the right arm base are both equal to Xa(t) the attitude angles are the same, but there is a matrix of offset left and right arm base positions, i.e., sequence of poses X of the left arm base relative to the body adapterlb(t) is
Wherein A islb，3×3To be from the left arm base coordinate system olb-xlbylbzlbConversion to the body adapter coordinate system oa-xayazaOf 3-dimensional transformation matrix, I3×3Is a 3-dimensional unit array. Left arm base coordinate system olb-xlbylbzlbThe origin of (a) is located at the intersection point of the left arm base (namely the arm lever at the nearest end of the left wall) and the body; z is a radical oflbThe axial direction is outward (far away from the body) along the arm rod at the most proximal end of the left wall; x is the number oflbWith the axis pointing from the center of the body toward the center of the body adapter (i.e., vertically upward as viewed in FIG. 1), and the right-hand rule determines ylbA shaft;
in the same way, the pose sequence X of the right arm base relative to the body adapter can be obtainedrb(t) is
The right arm base coordinate system corresponds to the left arm base coordinate system in a defined mode;
wherein A isrb，3×3To be from the right arm base coordinate system orb-xrbyrbzrbConversion to coordinate system o of extravehicular robota-xayazaOf 3-dimensional transformation matrix, I3×3Is a 3-dimensional unit array.
Step S3, solving positive kinematics, Jacobian matrix and inverse kinematics of the extravehicular robot according to the double-arm structure parameters of the robot set in the step S1, wherein the preferable scheme is as follows:
the optimal scheme specifically solves the following solutions of a positive kinematics solution, a Jacobian matrix and an inverse kinematics solution:
determining starting pose X of tail end of mechanical arm0(for the end of the arm of the left or right arm, the initial pose is represented by Xlb0) And end point pose Xt(for the arm end of the left arm, the end position pose is denoted Xtf) Step of time isΔAnd t, planning the pose of the tail end of the mechanical arm by adopting a conventional path planning function such as a cubic polynomial, a quintic polynomial or a parabolic mode and the like to obtain a pose sequence X (t) changing along with time. (for the end of the arm of the left arm, denoted Xl(t), for the arm end of the left arm, denoted Xr(t))
3.1 positive kinematics: and (3) knowing the angular displacement of each joint and the geometric parameters of the connecting rod, and solving the posture and the position of the end effector of the mechanical arm relative to the base, namely the positive kinematics of the mechanical arm.
According to parameters of left and right mechanical arms DH of the outboard robot, transformation matrixes of joints of the left and right arms can be obtained, the transformation matrixes of the joints are multiplied in sequence, and a positive kinematic formula of the left arm or the right arm of the outboard robot is obtained, wherein the optimal scheme is as follows;
by transforming matrices by linksi-1TiTo describe the pose of the ith joint coordinate system in the (i-1) th joint coordinate system
Pose of tip in base.i-1TiRepresenting the transformation of the coordinate system of the connecting rod i relative to the coordinate system of the connecting rod i-1, by the connecting rodThe i coordinate system is obtained by the following four sub-transformations in sequence:
1) around xi-1Axle rotation αi-1An angle;
2) along xi-1Axial movement ai-1；
3) Around ziAxis of rotation thetaiAn angle;
4) along ziAxial movement di；
The above transformations are all described relative to a moving coordinate system, and the connecting rod transformation is obtained according to the principle of' from left to right
Of the general formula (II)
Wherein c represents cos and s represents sin;
change the individual connecting rodsi-1Ti(i is 1,2, …, n) to obtain a manipulator transformation matrix
0Tn＝0T1 1T2…n-1Tn
From the above formula0TnThe positive kinematics of the mechanical arm can be obtained by the function of n joint variables and representing the description of a terminal coordinate system relative to a base coordinate system; n represents the total number of joints on each arm
From the left arm DH parameters, a positive kinematic transformation matrix for the left arm can be obtained as0TnlFrom the right arm DH parameters, a positive kinematic transformation matrix for the left arm can be obtained as0Tnr。
3.2 setting a Jacobian matrix, wherein the preferable scheme is as follows:
the Jacobian matrix J represents the relation between the terminal pose velocity and the joint angular velocity, can be used for solving inverse kinematics, and is transformed according to a plurality of connecting rodsi-1TiGeneral formula (II) ofSolving the following formula by product:
wherein the content of the first and second substances,0T(i-1)＝0T1 0T2…0T(i-1)the matrix is a 4 × 4 matrix,0T(i-1)(1:3,3) represents0T(i-1)Lines 1,2 and 3 intersect column 3, and other variables are similarly meant. When the value of i is 1, the value of i,0T(i-1)as a unit array, i.e.
3.3 inverse kinematics: and solving the joint angle of the mechanical arm according to the positive kinematics transformation matrix, namely obtaining the inverse kinematics. The inverse kinematics solution can map the terminal velocity to joint space by using a Jacobian matrix to obtain joint velocity, and then the joint velocity is integrated to obtain joint displacement. The method can be used for various mechanical arm configurations, has good adaptability, and has the following speed-level kinematics
ΔX(j+1)＝J(j)ΔΘ(j+1) (1)
Δ X (j) ═ X (j +1) -X (j), which indicates the amount of change in the end pose at the j +1 th time point, i.e., the end speed, where j is 0, 1,2, …, nt. J (j) represents a Jacobian matrix of the robot arm at the j-th time, and Θ (j) represents n joint angles [ θ ] at the j-th time1，θ2，…，θi，…，θn]T(the right-hand symbol T indicates transposition), and Δ Θ (j +1) ═ Θ (j +1) - Θ (j), which indicates n joint angles [ θ ] at the j +1 th time point1，θ2，…，θi，…，θn]TThe amount of change, i.e., the joint angular velocity.
The joint angular velocity formula is obtained from the above formula
ΔΘ(j+1)＝J-1(j)×ΔX(j+1)
Pose sequence X of left arm base relative to target adapterlb(t) or right arm base relative to body adapterPose sequence X ofrb(t) is the value of X (j + 1). The joint angle is obtained from the above formula
Θ(j+1)＝J-1(j)×ΔX(j+1)+Θ(j) (2)
According to the inverse kinematics solution method, Θ (j +1), that is, the inverse kinematics solution of the left arm is Θl(t), similarly, the inverse kinematics solution of the right arm is calculated as Θr(t)。
Step S4, setting a compliance control mode of the main arm according to the planned dragging and butt joint inverse operation path of the extravehicular robot in the step S2 and the positive kinematics solution and the inverse kinematics solution in the step S3, and solving a joint angle sequence of each joint according to the compliance control mode of the main arm; the preferred scheme is as follows:
the active compliance control approach incorporates force and position into a unified control system. The formula is as follows:
the transfer function is a control dynamics equation and is independently carried out according to six degrees of freedom
M is the equivalent mass of the contact between the adapter of the body and the adapter of the target, K is the equivalent rigidity of the contact between the adapter of the body and the adapter of the target, and C is the equivalent damping of the contact between the adapter of the body and the adapter of the target; feThe contact force between the end of the mechanical arm and the environment is measured by a six-dimensional force sensor.
And e is the difference between the actual pose and the expected pose of the tail end of the mechanical arm, wherein the expected pose is the pose when the tail end of the mechanical arm is matched with the target, and the matching represents the complete attachment, for example, the pose when the tail end of the mechanical arm completely enters a screw head is represented in a scene of screwing screws by the mechanical arm, or the pose when the tail end of the mechanical arm accurately puts the target into an assembling position is represented in an automatic assembling scene of the mechanical arm. When the flexible control mode (namely a control dynamic equation) of the main driving arm is set, a pose sequence X in the dragging and butt joint inverse operation path of the robot outside the planning cabin is useda(t) parameter, set to Xaa(t) actual pose of end of arm, Xae(t) is machineExpected pose of end of arm, Xaa(t)-XaeAnd (t) is a parameter e in the control dynamics equation of the step. The method for controlling the compliance of the main arm comprises the following steps of obtaining the difference between the actual pose of the tail end of the mechanical arm and the expected pose of the tail end of the mechanical arm through contact force, and obtaining the actual pose of the tail end of the mechanical arm through measurement, so that the corrected expected pose X of the tail end of the mechanical arm can be obtainedae(t) the posture XaeAnd (t) is caused by external force when the tail end of the mechanical arm is operated, and the active arm compliance control mode is used for providing compliance power for the operation of connecting the body adapter into the target adapter.
Subtracting X from X in step 3.3aeAfter (t), Θ (J) in step 3.3 is substituted, and Θ (J +1) ═ J is used-1(j) × delta X (j +1) + theta (j) to obtain theta (j +1), namely a joint angle sequence of each joint to form a mechanical arm control instruction;
step S5, setting a passive arm zero force control mode, wherein the preferred scheme is as follows:
the zero-force control mode of the driven arm is specifically represented by that the mechanical arm is a soft arm, the tail end of the mechanical arm generates an external force through contact with a target or an environment, the mechanical arm can move along with the external force, if the external force is a pushing force, the tail end of the mechanical arm is in a yielding state, and if the external force is a pulling force, the mechanical arm is in a forward advancing state. The specific implementation method comprises the following steps: the robot outside the cabin is operated outside the cabin of the space station, so that the control moment does not need to consider the influence of gravity.
The passive arm zero-force control mode does not provide direct power for the operation of connecting the body adapter into the target adapter, the motion path of the body adapter is compliantly tracked, and the passive arm zero-force control mode mainly aims to switch the passive arm zero-force control mode into the active arm zero-force control mode when the body adapter and the target adapter are clamped under the active arm compliance control mode in step S4.
Step S6, setting an active arm and passive arm alternating control mode, so that the active arm compliance control mode and the passive arm zero force control mode can be switched, wherein the preferred scheme is as follows:
and detecting the measured value of the six-dimensional force sensor between the adapter and the base in the dragging process, converting the force/torque under the coordinate system of the six-dimensional force sensor into the coordinate system of the adapter of the extravehicular robot body, reflecting the mechanical relationship between the adapter and the target adapter on the robot by the measured value of the six-dimensional force sensor under the coordinate system of the extravehicular robot adapter in the weightless environment, and performing the alternate control of the left arm and the right arm according to the measured value.
The method is characterized in that a double-arm alternating active and passive control mode is adopted, namely one arm is in active control, the other arm is in follow-up control, when the measured value of the six-dimensional force sensor reaches a switching threshold value (the switching threshold value can be selected according to experience or experiments), the situation that the mechanical arm is in a clamping position and cannot continuously drag the body forwards is detected, so that the butt joint of the extravehicular robot body adapter and a target adapter is achieved, the other arm is used as an active arm to control, the previous active arm is changed into a passive arm, the left arm and the right arm are in active and passive control alternately, and flexible dragging and butt joint under the state of forming shape sealing and force sealing are achieved through the. And (3) switching between left and right main passive arms by adopting a selection matrix, wherein when the selection matrix is [ 01 ], the left arm is an active arm, the right arm is a passive arm, and when the selection matrix is [ 10 ], the left arm is the passive arm and the right arm is the active arm.
And the active arm and the passive arm are alternately controlled, the active arm and the passive arm are switched according to a threshold value, the active arm can be changed into the passive arm, the passive arm is changed into the active arm, the body adapter is smoothly connected into the target adapter, and power for connecting the body adapter into the target adapter is alternately provided at the left side and the right side of the body adapter.
S7, according to task requirements, an active arm and a passive arm alternative control mode of S6 is adopted, so that the extravehicular robot approaches a target firstly, then the extravehicular robot is fixed on the target, and the extravehicular robot is dragged and butted in a double-arm cooperative flexible mode, wherein the preferable scheme is as follows:
the task requires that the extravehicular robot is installed on a target adapter for fixing, so that the extravehicular robot canThe invention solves the technical problem that the adapter of the extravehicular robot body is connected into the target adapter, and does not consider the operation task of the connected mechanical arm. At the time of path planning tfThe time step delta t in the time sequence is used for sending corresponding mechanical arm control instructions to the driving arm, and meanwhile, the driven arm executes a driven arm zero-force control mode to complete the following tasks;
the extravehicular robot approaches the target first, and the specific process is that the extravehicular robot drags the body to the vicinity of the target through two arms and ensures the posture that the extravehicular robot body adapter can be accessed to the target adapter, as shown in fig. 5.
And then fixing the self on a target, wherein the specific process is to flexibly connect the extravehicular robot body adapter into the target adapter through the cooperative flexible dragging and butt joint operation of the extravehicular robot double arms, so that the extravehicular robot and the target are relatively fixed.
The robot outside the cabin has two arms cooperating with each other to flexibly drag and butt joint, specifically: the robot outside the cabin grips a gripper of a target through two arms, the body adapter is moved to the position near the target adapter through the active arm, and when the body adapter contacts the target adapter and starts to be introduced, the active arm and the passive arm alternately output power, so that the body adapter is connected into the target adapter.
According to the scheme of double-arm reverse operation planning, the technical advantage that the mechanical arm moves the body of the mechanical arm, namely, the arm moves as a leg is achieved, the advantage that the adapter is prevented from being blocked when the mechanical arm drags the body to operate is reflected through the active and passive alternative control strategy scheme, flexible operation of the robot is achieved through the double-arm reverse operation planning and active and passive alternative control mode, the body is automatically installed at the target position through double arms, and the intelligent, fine and autonomous technical advantage is achieved.
Claims (10)
1. A double-arm cooperative flexible dragging and butt joint inverse operation method of an extravehicular robot is characterized by comprising the following steps:
step S1, initializing, namely setting the structural parameters of the double arms of the robot, the expected path of the tail end of the robot, the path planning time and the time step; the two arms are respectively a driving arm and a driven arm;
step S2, planning a dragging and butt joint inverse operation path of the extravehicular robot according to the double-arm structure parameters of the robot, the expected path of the tail end of the robot, the path planning time and the time step set in the step S1;
step S3, solving positive kinematics, Jacobian matrix and inverse kinematics of the extravehicular robot according to the double-arm structure parameters of the robot set in the step S1 to obtain a positive kinematics solution and an inverse kinematics solution;
step S4, setting a compliance control mode of the main arm according to the planned dragging and butting inverse operation path of the extravehicular robot in the step S2 and the forward kinematics solution and the inverse kinematics solution in the step S3;
step S5, setting a passive arm zero force control mode;
s6, setting an alternating control mode of the driving arm and the driven arm to switch a compliance control mode of the driving arm and a zero-force control mode of the driven arm;
and S7, according to task requirements, adopting an alternative control mode of the driving arm and the driven arm of S6 to enable the extravehicular robot to approach the target first and then fix the extravehicular robot on the target, and realizing flexible dragging and butt joint of the extravehicular robot through the coordination of the two arms.
2. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: step S1, initializing, namely setting the structural parameters of the double arms of the robot, the expected path of the tail end of the robot, the path planning time and the time step; the two arms are respectively a driving arm and a driven arm, and the two arms are specifically as follows:
a robot, comprising: both arms and a body; one arm of the two arms is a driving arm, and the other arm of the two arms is a driven arm; the two arms are respectively arranged at the two sides of the body; each arm comprising: an arm lever; arm, joint, end; a joint is arranged between every two adjacent arm rods, and the arm rod at the most proximal end is connected with the body; the arm rod at the farthest end is connected with the tail end through a joint; the body is provided with a six-dimensional force sensor, and the structural parameters of the two arms of the robot are DH parameters of the two arms.
3. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: step S2, planning a dragging and docking inverse operation path of the extravehicular robot according to the set robot double-arm structural parameters, the expected path of the robot tail end, the path planning time and the time step set in step S1, which is specifically as follows:
after the left mechanical arm and the right mechanical arm capture a target, the tail end operators of the left mechanical arm and the right mechanical arm keep a fixed relative pose with the target, so that the body needs to move to be a moving end, the tail end operators are fixed ends, the path planning of the tail end of the mechanical arm is mainly to plan the path of the tail end of the mechanical arm relative to the body, and the path planning of the body relative to the tail end of the mechanical arm is to be the inverse operation.
4. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: step S3, according to the robot double-arm structure parameters set in the step S1, solving forward kinematics and inverse kinematics of the extravehicular robot to obtain a forward kinematics solution and an inverse kinematics solution, which are specifically as follows:
determining starting pose X of tail end of mechanical arm0And end point pose XtAnd the time step is delta t, and the pose of the tail end of the mechanical arm is planned by adopting a conventional path planning function such as a cubic polynomial, a quintic polynomial or a parabolic mode, so that a pose sequence X (t) changing along with time can be obtained.
5. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: step S4, setting a compliance control mode of the main arm according to the planned dragging and docking inverse operation path of the extravehicular robot in the step S2 and the forward kinematics solution and the inverse kinematics solution in the step S3, which is specifically as follows:
the active compliance control mode brings force and position into a unified control system, the active arm compliance control mode can obtain the difference between the actual pose of the tail end of the mechanical arm and the expected pose of the tail end of the mechanical arm through contact force, the actual pose of the tail end of the mechanical arm can be measured, and therefore the corrected expected pose of the tail end of the mechanical arm can be obtained, the pose is caused by external force when the tail end of the mechanical arm operates, and the active arm compliance control mode is used for providing compliance power for the operation of the body adapter connected into the target adapter.
6. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: step S5, setting a passive arm zero force control mode, specifically as follows:
the zero-force control mode of the driven arm is specifically represented by that the mechanical arm is a soft arm, the tail end of the mechanical arm generates an external force through contact with a target or an environment, the mechanical arm can move along with the external force, when the external force is a pushing force, the tail end of the mechanical arm is in a yielding state, and when the external force is a pulling force, the mechanical arm is in a forward advancing state.
7. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: the method for realizing the passive arm zero force control mode specifically comprises the following steps: the robot outside the cabin is operated outside the cabin of the space station, so that the control moment does not need to consider the influence of gravity.
8. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that:
and a passive arm zero-force control mode, wherein no direct power is provided for the operation of connecting the body adapter into the target adapter, and the motion path of the body adapter is compliantly tracked, and the passive arm zero-force control mode mainly aims to switch the passive arm zero-force control mode into the active arm zero-force control mode when the body adapter and the target adapter are tightly clamped under the flexible control mode of the active arm in the step S4.
9. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: step S6, setting an active arm and passive arm alternating control mode, so that the active arm compliance control mode and the passive arm zero force control mode can be switched, which is specifically as follows:
and detecting the measured value of the six-dimensional force sensor between the adapter and the base in the dragging process, converting the force/torque under the coordinate system of the six-dimensional force sensor into the coordinate system of the adapter of the extravehicular robot body, reflecting the mechanical relationship between the adapter and the target adapter on the robot by the measured value of the six-dimensional force sensor under the coordinate system of the extravehicular robot adapter in the weightless environment, and performing the alternate control of the left arm and the right arm according to the measured value.
10. The method for the cooperative flexible dragging and butting inverse operation of the double arms of the extravehicular robot according to claim 1, is characterized in that: s7, according to task requirements, an active arm and a passive arm alternative control mode of S6 is adopted, so that the extravehicular robot approaches a target first, then the extravehicular robot is fixed on the target, and the extravehicular robot is dragged and butted flexibly by the double arms in a coordinated mode, specifically, the following steps are adopted:
the extravehicular robot approaches a target firstly, and the extravehicular robot drags a body to be close to the target through two arms and ensures the posture that an extravehicular robot body adapter can be connected to a target adapter;
then fixing the self on a target, wherein the specific process is that the extravehicular robot body adapter is flexibly connected into the target adapter through the cooperative flexible dragging and butt joint operation of the extravehicular robot double arms, so that the extravehicular robot and the target are relatively fixed;
the robot outside the cabin has two arms cooperating with each other to flexibly drag and butt joint, specifically: the robot outside the cabin grips a gripper of a target through two arms, the body adapter is moved to the position near the target adapter through the active arm, and when the body adapter contacts the target adapter and starts to be introduced, the active arm and the passive arm alternately output power, so that the body adapter is connected into the target adapter.
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