CN111702753A - Redundant mechanical arm inverse priority impedance control system and control method - Google Patents

Redundant mechanical arm inverse priority impedance control system and control method Download PDF

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CN111702753A
CN111702753A CN202010369736.1A CN202010369736A CN111702753A CN 111702753 A CN111702753 A CN 111702753A CN 202010369736 A CN202010369736 A CN 202010369736A CN 111702753 A CN111702753 A CN 111702753A
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manipulator
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CN111702753B (en
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刘海燕
苏宇
李敏斯
林春兰
吴雪颖
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Guangxi University of Science and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
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Abstract

The invention discloses a redundant mechanical arm reverse priority impedance control system and a control method. The manipulator redundancy mechanical arm reverse priority impedance control device belongs to the technical field of manipulator redundancy mechanical arm reverse priority impedance control, and facilitates recognition of grabbed objects. The manipulator comprises a movable moving platform, a manipulator and a control console for controlling the manipulator; the manipulator comprises a mechanical arm, a mounting seat, a vertical column, an output gripper and a vertical cylinder; the mechanical arm comprises a vertical lifting moving platform, an arm section I, an arm section II, an arm section III and an arm section IV; a vertical rail is arranged on the left surface of the vertical column, and the vertical lifting mobile platform is vertically and slidably arranged on the vertical rail up and down; the lower end of the vertical column is fixedly connected to the upper surface of the mounting seat, the cylinder seat of the vertical cylinder is fixedly connected to the upper surface of the mounting seat positioned on the left side of the vertical track, and the upper end of the telescopic rod of the vertical cylinder is fixedly connected to the lower surface of the vertical lifting moving table; the mounting seat is fixed on the mobile platform. The front end of the manipulator is provided with a camera.

Description

Redundant mechanical arm inverse priority impedance control system and control method
Technical Field
The invention relates to the technical field of reverse priority impedance control of manipulator redundant manipulator, in particular to a reverse priority impedance control system and a reverse priority impedance control method for the redundant manipulator.
Background
The control method adopted by the industrial robot at present is that each joint on the manipulator is taken as an independent servo mechanism, namely each axis corresponds to a server, and each server is controlled by a bus and is uniformly controlled and coordinated by a controller;
the mechanical arm with six degrees of freedom is the mechanical arm with the minimum degree of freedom for finishing space positioning, and the mechanical arms with more than six degrees of freedom are collectively called as redundant mechanical arms;
the existing mechanical arm impedance control method of the mechanical arm cannot realize the expected impedance control task under different hierarchical structures, so that the method which can enable the redundant mechanical arm of the mechanical arm to realize the expected impedance control task under different hierarchical structures is very necessary.
Disclosure of Invention
The invention aims to overcome the defect that the expected impedance control task cannot be realized by the existing impedance control method of the mechanical arm under different hierarchical structures, and provides a method which can control the balance of a mechanical arm, is convenient for the mechanical arm to move and is convenient for identifying and grabbing objects; and the other is a redundant mechanical arm reverse priority impedance control system and a control method which can enable the redundant mechanical arm of the mechanical arm to realize the expected impedance control task under different hierarchical structures.
The technical problem is solved by the following technical scheme:
the redundant mechanical arm reverse priority impedance control system comprises a mechanical arm and a control console for controlling the mechanical arm; the device also comprises a movable moving platform; the manipulator comprises a mechanical arm, a mounting seat, a vertical column, an output gripper and a vertical cylinder; the mounting seat is fixed on the mobile platform;
the mechanical arm comprises a vertical lifting moving platform, an arm section I, an arm section II, an arm section III and an arm section IV;
a vertical rail is arranged on the left surface of the vertical column, and the vertical lifting mobile platform is vertically and slidably arranged on the vertical rail up and down; the lower end of the vertical column is fixedly connected to the upper surface of the mounting seat, the cylinder seat of the vertical cylinder is fixedly connected to the upper surface of the mounting seat positioned on the left side of the vertical track, the telescopic rod of the vertical cylinder is vertically arranged upwards, and the upper end of the telescopic rod of the vertical cylinder is fixedly connected to the lower surface of the vertical lifting mobile platform; the vertical lifting mobile platform can move up and down along a vertical track under the driving of a telescopic rod of a vertical cylinder to form a first degree of freedom;
the arm section I comprises an A1 section pipe and an A2 section pipe which is telescopically connected in a left pipe orifice of the A1 section pipe, a first cylinder with a telescopic rod horizontally arranged towards the left is fixedly arranged at the right end in the A1 section pipe, and the telescopic rod of the first cylinder is fixedly connected at the right end of the A2 section pipe;
the arm section II comprises a section B1 pipe and a section B2 pipe which is telescopically connected in a left pipe orifice of the section B1 pipe, a second cylinder with a telescopic rod horizontally arranged towards the left is fixedly arranged at the right end in the section B1 pipe, and the telescopic rod of the second cylinder is fixedly connected at the right end of the section B2 pipe;
the left end of the vertical lifting moving platform is provided with a first horizontal rotating shaft driven by a first speed reducing motor, and the right end of the A1 section pipe is fixedly connected to the first horizontal rotating shaft, so that the first arm section can horizontally rotate to form a second degree of freedom; a first electromagnetic brake capable of controlling the first horizontal rotating shaft to rotate is further arranged on the first horizontal rotating shaft;
the left end of the section A2 pipe is provided with a second horizontal rotating shaft driven by a second speed reducing motor, and the right end of the section B1 pipe is fixedly connected to the second horizontal rotating shaft, so that the arm section II can horizontally rotate to form a third degree of freedom; a second electromagnetic brake capable of controlling the second horizontal rotating shaft to rotate is further arranged on the second horizontal rotating shaft;
the left end of the section B2 pipe is provided with a third horizontal rotating shaft driven by a third speed reducing motor, and the right end of the arm section III is fixedly connected to the third horizontal rotating shaft, so that the arm section III can horizontally rotate to form a fourth degree of freedom; a third electromagnetic brake capable of controlling the third horizontal rotating shaft to rotate is further arranged on the third horizontal rotating shaft;
the left end of the arm section III is provided with a first transverse vertical rotating shaft which is driven by a fourth speed reducing motor and can rotate on the left vertical surface and the right vertical surface, and the right end of the arm section IV is fixedly connected to the first transverse vertical rotating shaft, so that the arm section IV can vertically rotate on the left vertical surface and the right vertical surface to form a fifth degree of freedom; a fourth electromagnetic brake capable of controlling the first transverse vertical rotating shaft to rotate is further arranged on the first transverse vertical rotating shaft;
the left end of the arm section four is provided with a first longitudinal vertical rotating shaft which is driven by a fifth speed reducing motor and can rotate on the front vertical surface and the rear vertical surface, and the right end of the output gripper is fixedly connected to the first longitudinal vertical rotating shaft, so that the right end of the output gripper can vertically rotate on the front vertical surface and the rear vertical surface to form a sixth degree of freedom; a fifth electromagnetic brake capable of controlling the first longitudinal vertical rotating shaft to rotate is further arranged on the first longitudinal vertical rotating shaft;
the section A2 of the pipe can be driven by the telescopic rod of the first cylinder to move in a telescopic manner from side to side in the section A1 of the pipe to form a seventh degree of freedom;
the B2 section of pipe can be driven by the telescopic rod of the second cylinder to move in the B1 section of pipe in a left-right telescopic manner to form an eighth degree of freedom;
the left end of a first horizontal pipe is horizontally and fixedly connected to the right surface of the vertical column, a balance adjusting block is arranged in the first horizontal pipe in a sliding mode from left to right, a balance adjusting cylinder with a telescopic rod facing right horizontally is fixedly connected to the left end of the first horizontal pipe, and the right end of the telescopic rod of the balance adjusting cylinder is fixedly connected to the balance adjusting block;
the control end of No. one electromagnetic brake, the control end of No. two electromagnetic brakes, the control end of No. three electromagnetic brakes, the control end of No. four electromagnetic brakes, the control end of No. five electromagnetic brakes, the control end of a gear motor, the control end of No. two gear motor, the control end of No. three gear motor, the control end of No. four gear motor, the control end of No. five gear motor, the control end of a cylinder, the control end of No. two cylinders, the control end of balance adjustment cylinder and the control end of vertical cylinder are respectively control connection on the control cabinet.
The outer surface of the first longitudinal vertical rotating shaft is fixedly sleeved with an annular ring, a first moving block which is driven by a surrounding motor and can move along the annular ring is arranged on the annular ring, and a camera is arranged on the first moving block; the control end of the camera and the control end of the surrounding motor are respectively connected with the console. Object convenient to recognize and grab
The balance adjusting cylinder controls the balance of the vertical column by moving the balance adjusting block left and right, and then the balance of the manipulator is controlled. The manipulator is convenient to move. Because some mechanical arms of the invention have eight degrees of freedom, the invention has good flexibility and high reliability and is easy to complete control tasks.
A redundant mechanical arm reverse priority impedance control method comprises the following steps:
step 1, establishing a kinematic model of the redundant mechanical arm, and giving a gradient direction strategy of a zero space vector of the redundant mechanical arm;
step 2, establishing a task priority solving strategy for obtaining a singularity elimination algorithm through a singular robust solution;
step 3, establishing a singular robust solution inverse kinematics analysis model;
step 4, establishing a reverse priority control strategy of the multi-task redundant mechanical arm;
step 5, simplifying a reverse control equation of the redundant mechanical arm with the main task and the secondary task;
step 6, establishing a reverse priority control strategy of the manipulator;
step 7, solving the relation between the external force and the joint acceleration in the reverse priority impedance control of the manipulator by adopting the joint speed, thereby obtaining the reverse priority impedance control guarantee of the manipulator;
and 8, expanding the reverse priority calculation of the position control space to the reverse priority calculation of the force control space, thereby obtaining the overall framework of the speed-level reverse priority impedance control of the manipulator.
The motion of the redundant mechanical arm in the joint space is derived according to the reverse order; then, the Cartesian impedance control is combined with the inverse priority impedance control, the inverse hierarchical impedance control problem is solved, and the Cartesian impedance control behavior is divided into high-priority impedance control and low-priority impedance control. The high-priority impedance control task does not interfere with the low-priority impedance control task, and the motion in the joint space is influenced in the reverse order and needs to work in a corresponding projection operator; and finally, a high-priority impedance control task is realized, and deformation caused by singularity possibly occurring in the low-priority impedance control task is avoided. Thus, the proposed inverse-priority impedance control method enables the redundant robotic arm to achieve the desired impedance control task at the appropriate hierarchical structure.
Preferably, a kinematic model of the redundant manipulator is established, and a gradient direction strategy implementation process of a zero space vector of the redundant manipulator is given as follows:
the pose and the speed of the end effector in the Cartesian space are defined as x,
Figure BDA0002476495740000031
The angular position and angular velocity of the joint space are q,
Figure BDA0002476495740000032
J is a Jacobian matrix of the n-degree-of-freedom robot, where x ∈ Rn，
Figure BDA0002476495740000033
Figure BDA0002476495740000034
J∈Rm-n(ii) a The positive kinematic equation for a redundant degree of freedom robotic arm can be described by:
x＝Jq (1)
equation (1) is also referred to as a robot arm kinematics velocity model;
considering the solution of the least squares method, the optimal problem can be listed as:
Figure BDA0002476495740000035
the solution of formula (1) can be optimized by finding the best
Figure BDA0002476495740000036
To solve the problem;
Figure BDA0002476495740000037
thus, the pseudo-inverse solution of equation (1) can be expressed as:
Figure BDA0002476495740000038
in the formula J+Pseudo-inverse of the Jacobian matrix
I-identity matrix
Figure BDA0002476495740000041
-arbitrary null space vector
Figure BDA0002476495740000042
Minimum norm solution, defining hand movements
Figure BDA0002476495740000043
Homogeneous solution, no action at the end
Equation (4) represents the position and attitude control of the end effector; adding any residual error into the formula (4) to obtain a general expression containing a null space; the multi-task optimization can be realized on a zero vector by using the equation;
however, the above equation ignores the ill-conditioned state of the jacobian matrix; the regularization equation may be modified by adding additional regularization values,
Figure BDA0002476495740000044
where λ ≧ 0 is the weighting matrix,
Figure BDA0002476495740000045
is a weighting coefficient, and satisfies
Figure BDA0002476495740000046
The solution to the above equation can be expressed as:
Figure BDA0002476495740000047
equation (7) is also referred to as a redundant manipulator kinematics model;
the joint limit function of the joint limit gradient direction of the position-dependent scalar index of the null-space vector of the redundant manipulator is as follows:
Figure BDA0002476495740000048
preferably, a task priority solving strategy for obtaining the singularity elimination algorithm through a singular robust solution is established as follows:
in the solution of the redundant mechanical arm of the Jacobian matrix, an optimization task is realized in a null space of a main task; the reverse task kinematics is established on the basis of the forward task kinematics:
Figure BDA0002476495740000049
wherein
Figure BDA00024764957400000410
And
Figure BDA00024764957400000411
representation task1 and task2
The inverse kinematics equation of the redundant manipulator is obtained from expression (5) as follows:
Figure BDA00024764957400000412
task1 as the main Task and Task2 as the auxiliary Task; that is to say that the position of the first electrode,
Figure BDA00024764957400000413
is that
Figure BDA00024764957400000414
Is implemented in the null space of (1); the final inverse kinematics expression for the redundant manipulator is as follows:
Figure BDA00024764957400000415
wherein
Figure BDA00024764957400000416
Figure BDA00024764957400000417
Is a projection matrix which gives the applicable range of the secondary task to the primary task;
Figure BDA00024764957400000418
and
Figure BDA00024764957400000419
is the desired commanded speed;
Figure BDA00024764957400000420
is the main task of the method, and the method comprises the following steps of,
Figure BDA00024764957400000421
is a secondary task;
if two related tasks are interdependent, then the corresponding Jacobian matrix is singular; if the task jacobian matrix is singular, the corresponding task is not satisfied; in this case, the jacobian correlation matrix will be singularities, defined as algorithmic singularities;
that is, if
Figure BDA0002476495740000051
Where ρ (·) is the rank of the matrix;
it is clear that the singularity of the algorithm is caused by task conflicts between the secondary tasks and the primary task; in addition, task priority based redundant robotic arm inverse kinematics aims to provide better control over the effectiveness of the primary tasks;
therefore, the position control direction is used as a main task, so that the position ensures the accuracy of the control direction task; then, establishing a task priority solving strategy equation for obtaining a singularity elimination algorithm through singular robust solution:
Figure BDA0002476495740000052
preferably, the singular robust solution inverse kinematics analysis model is established as follows:
the motion singularity can occur based on the Jacobian pseudo-inverse solution, which is caused by the secondary matrix; for the motion singularity problem, a DLS (damped least squares) solution should also be given;
the cost function for the DLS solution can be modified to:
Figure BDA0002476495740000053
thus, the singular robust pseudo-inverse solution of the above equation can be expressed as:
Figure BDA0002476495740000054
equation (15) is a singular robust solution inverse kinematics analysis model, where λ is η2I, the DLS solution is equivalent to an additional regularization solution, and the scalar value η balances the task precision and singularity;
for the calculation of the pseudo-inverse solution of the Jacobian matrix, the singular value SVD decomposition form of the Jacobian matrix can be given
J＝U∑VT(16)
Wherein U ∈ Rm×n，V∈Rm×n，∑∈Rm×nU is a column vector UiA unitary matrix of V is formed by column vectors ViThe constituent unary matrix, ∑, is a block matrix of m × n diagonal matrices containing the singular values σ of JiMore than or equal to 0 contains n-m zero column vectors in descending order;
Figure BDA0002476495740000055
wherein r is less than or equal to m is the rank of the matrix J;
for motion singularity, with reference to the singular value decomposition SVD required to compute the pseudo-inverse solution, the large resulting joint velocity is due to the smallest singular value rapidly approaching 0, as follows:
Figure BDA0002476495740000056
factor lambda0Singularities of each influence, λ0The higher the value is, the larger the damping is, and the closer the joint velocity is to the singular point; in addition, the strategy for defining the variable damping factor is also different; we can get
Figure BDA0002476495740000061
From the above equation, we can see that the parameter > 0 monitors the smallest singular value.
Preferably, establishing a reverse priority control strategy of the multitask redundant mechanical arm as follows;
introducing an inverse-priority projection matrix
Figure BDA0002476495740000062
The matrix comprises a null space of corresponding elements of the lowest priority l-k-1 task independent of the kth task, so derived
Figure BDA0002476495740000063
Wherein Ji，jIs a jacobian matrix associated with all components of the i-th task that are linearly independent of the j-th task;
therefore, the priority derivation formula is as follows:
Figure BDA0002476495740000064
in the above derivation, k ═ l, l-1, …, 1; initial value
Figure BDA0002476495740000065
To give a general form of computation of the linear independent Jacobian matrix J, the inverse augmented Jacobian matrix is defined as:
Figure BDA0002476495740000066
have therein
Figure BDA0002476495740000067
Wherein
Figure BDA0002476495740000068
To represent
Figure BDA0002476495740000069
A row of (2);
therefore, the method is not to be taken,
Figure BDA00024764957400000610
the pseudo-inverse solution of (a) can be expressed as:
Figure BDA00024764957400000611
and
Figure BDA00024764957400000612
wherein, TkRepresentation matrix
Figure BDA00024764957400000613
Expansion of (2);
the final inverse priority projection can be written as:
Figure BDA00024764957400000614
thus, we can derive the expression of the pseudo-inverse solution:
Figure BDA0002476495740000071
the reverse priority control strategy equation of the multi-task redundant mechanical arm is established as follows:
Figure BDA0002476495740000072
preferably, the inverse control equations for a redundant robotic arm having a primary task and a secondary task are simplified as follows:
for a six-degree-of-freedom or seven-degree-of-freedom redundant manipulator, there are not enough six-degree-of-freedom DOF to complete multiple levels of tasks; it is necessary to carry out a dual task priority control; that is, the motion control of the manipulator is a primary task and a secondary task;
the equations for the inverse control of a redundant robotic arm having primary and secondary tasks are as follows
Figure BDA0002476495740000073
The above formula is very different from the previous expression (11), but the algorithmic framework is similar; in the above-mentioned equations, the process of the present invention,
Figure BDA0002476495740000074
is a secondary task that is to be performed,
Figure BDA0002476495740000075
is the main task; the main task is realized in a designated null space of the main task; the core point of reverse priority being a projection matrix
Figure BDA0002476495740000076
Calculating (1);
Figure BDA0002476495740000077
is expressed as formula (30):
Figure BDA0002476495740000078
using similar guides as in previous equations (22) - (28), a simplified inverse control equation for a redundant robotic arm having a primary task and a secondary task can be obtained:
Figure BDA0002476495740000079
preferably, the reverse priority control strategy for the manipulator is established as follows:
the dynamics of the manipulator in force control space can be written as:
Figure BDA00024764957400000710
where X is the position in Cartesian space, M (X) is an inertial matrix,
Figure BDA00024764957400000711
non-linear force, F input control force, FeIs the contact force;
furthermore, the input joint moments are obtained on the basis of a conversion of the Jacobian matrix
τ＝JT(q)F (33)
The desired equation of motion of the manipulator in force control space may be defined as follows:
Figure BDA00024764957400000712
wherein M isdAnd BdIs an inertia and damping matrix; fdIs a command force, FeIs the contact force;
thus, the relationship between the environment and the manipulator response can be written as
Figure BDA00024764957400000713
The combination of the above two equations is as follows
Figure BDA00024764957400000714
As can be seen from the above equation, if M ise、BeAnd KeKnown, then MdAnd BdWill affect the system response;
force control enables the manipulator to interact with the environment or human; in addition, in some cases, it is not necessary to implement omnidirectional force control and guarantee omnidirectional force control, that is, sometimes we only want to guarantee the force tracking control accuracy in a certain direction;
it is therefore necessary to perform a hierarchical force control of the manipulator; that is, it is necessary to provide a new hierarchical force control framework; from the above equation we can derive the desired hierarchical force control relationship as follows
Figure BDA0002476495740000081
Figure BDA0002476495740000082
The integral of these two equations can be written as
Figure BDA0002476495740000083
Figure BDA0002476495740000084
If the robot end effector is able to track the desired cartesian velocity of
Figure BDA0002476495740000085
And
Figure BDA0002476495740000086
accurate force control of the manipulator can be achieved; the relationship between Cartesian velocity and joint velocity should be borrowedCarrying out reverse discrimination priority control; thus, the equation for the inverse priority control strategy for the manipulator can be derived:
Figure BDA0002476495740000087
the joint velocity required by the above equation will ensure force control of the manipulator; it is worth mentioning that the force control law is only a speed step control law, which relies on an inner speed loop control; if the internal position control effect is good, accurate force control can be realized; because the inner speed ring control can realize low-frequency position tracking, the outer force ring can realize low-frequency force tracking.
Preferably, the relationship between the external force and the joint acceleration in the inverse-priority impedance control of the manipulator is solved by using the joint velocity, so that the inverse-priority impedance control of the manipulator is ensured in the following manner:
when the manipulator implements force control, the manipulator functions as an initiator to some extent, that is, the manipulator is ready to respond to the external environment; when the mechanical arm
When the robot arm works as an impedance control model, the robot arm passively responds to an external force;
the corresponding impedance relationship between the external force and the joint acceleration can be expressed as
Figure BDA0002476495740000088
Figure BDA0002476495740000089
The reference speed can be expressed as
Figure BDA00024764957400000810
Figure BDA0002476495740000091
Therefore, the inverse priority impedance control of the manipulator guarantees the expression:
Figure BDA0002476495740000092
preferably, the overall framework implementation of extending the inverse-priority computation of the position control space to the inverse-priority computation of the force control space to obtain the manipulator velocity-level inverse-priority impedance control is as follows:
hybrid impedance applications are a combination of the two strategies mentioned above, i.e. the cartesian task can be divided into two cases: the first is a position control subspace, in which the impedance control is implemented; the second is a force control subspace in which force control is implemented;
thus selecting a selection matrix; the relationship between the external force and the position response is as follows
Figure BDA0002476495740000093
Figure BDA0002476495740000094
So a simplified form of the desired speed can be expressed as
Figure BDA0002476495740000095
Figure BDA0002476495740000096
Then we get a solution based on reverse priority
Figure BDA0002476495740000097
Considering n-layer tasks, the corresponding impedance control task also belongs to n-layer framework, therefore, the overall framework expression of the manipulator speed level inverse priority impedance control is as follows
Figure BDA0002476495740000098
The expression (52) solves the problem that the reverse priority calculation of the position control space is expanded to the manipulator reverse priority mixed impedance control of the reverse priority calculation of the force control space, so that the redundant manipulator of the manipulator can realize the expected impedance control task under different hierarchical structures.
The invention can achieve the following effects:
the invention can control the balance of the manipulator, the manipulator is convenient to move and recognize and grab objects, and the redundant manipulator of the manipulator can realize expected impedance control tasks under different hierarchical structures.
Drawings
FIG. 1 is a schematic representation of the dynamics of force control of the present invention.
FIG. 2 is a schematic diagram of the dynamics of the impedance control of the present invention.
FIG. 3 is a schematic diagram of the dynamics of the hybrid impedance control of the present invention.
Fig. 4 is a schematic diagram of a seven-degree-of-freedom robot connection structure according to an embodiment of the present invention.
Fig. 5 is a schematic block diagram of a circuit principle connection structure according to an embodiment of the present invention.
Detailed Description
The invention is further described with reference to the following figures and examples.
An embodiment, a redundant robotic arm inverse priority impedance control system, see fig. 4, 5, includes a manipulator and a console S31 for controlling the manipulator; also includes a movable moving platform S41; the manipulator comprises a mechanical arm, a mounting seat S1, a vertical column S2, an output gripper S12 and a vertical cylinder S23; the mounting seat is fixed on the mobile platform;
the mechanical arm comprises a vertical lifting mobile platform S3, a first arm section S6, a second arm section S7, a third arm section S8 and a fourth arm section S10;
a vertical rail S24 is arranged on the left surface of the vertical column, and the vertical lifting mobile platform is vertically arranged on the vertical rail in a sliding manner; the lower end of the vertical column is fixedly connected to the upper surface of the mounting seat, the cylinder seat S21 of the vertical cylinder is fixedly connected to the upper surface of the mounting seat positioned on the left side of the vertical track, the telescopic rod S22 of the vertical cylinder is vertically arranged upwards, and the upper end of the telescopic rod of the vertical cylinder is fixedly connected to the lower surface of the vertical lifting mobile platform; the vertical lifting mobile platform can move up and down along a vertical track under the driving of a telescopic rod of a vertical cylinder to form a first degree of freedom;
the first arm section comprises an A1 section pipe S13 and an A2 section pipe S14 which is telescopically connected in a left pipe orifice of the A1 section pipe, a first air cylinder S25 with a telescopic rod horizontally arranged towards the left is fixedly arranged at the right end in the A1 section pipe, and the telescopic rod of the first air cylinder is fixedly connected at the right end of the A2 section pipe;
the arm section II comprises a section B1 of pipe S16 and a section B2 of pipe S17 which is telescopically connected into a left pipe orifice of a section B1 of pipe, a second cylinder 37 with a telescopic rod horizontally arranged towards the left is fixedly arranged at the right end in the section B1 of pipe, and the telescopic rod of the second cylinder is fixedly connected to the right end of the section B2 of pipe;
the left end of the vertical lifting moving platform is provided with a first horizontal rotating shaft S4 driven by a first speed reducing motor S26, and the right end of the A1 section of pipe is fixedly connected to the first horizontal rotating shaft, so that the first arm section can horizontally rotate to form a second degree of freedom; a first electromagnetic brake S32 capable of controlling the rotation of the first horizontal rotating shaft is also arranged on the first horizontal rotating shaft;
the left end of the section A2 of the tube is provided with a second horizontal rotating shaft S15 driven by a second speed reducing motor S27, and the right end of the section B1 of the tube is fixedly connected to the second horizontal rotating shaft, so that the arm section II can horizontally rotate to form a third degree of freedom; a second electromagnetic brake S33 capable of controlling the second horizontal rotating shaft to rotate is also arranged on the second horizontal rotating shaft;
the left end of the B2 section pipe is provided with a third horizontal rotating shaft S18 driven by a third speed reducing motor S28, and the right end of the arm section III is fixedly connected to the third horizontal rotating shaft, so that the arm section III can horizontally rotate to form a fourth degree of freedom; a third electromagnetic brake S34 capable of controlling the third horizontal rotating shaft to rotate is also arranged on the third horizontal rotating shaft:
a first transverse vertical rotating shaft S9 which is driven by a fourth speed reducing motor S29 and can rotate on the left vertical surface and the right vertical surface is arranged at the left end of the arm section III, and the right end of the arm section IV is fixedly connected to the first transverse vertical rotating shaft, so that the arm section IV can vertically rotate on the left vertical surface and the right vertical surface to form a fifth degree of freedom; a fourth electromagnetic brake S35 capable of controlling the first transverse vertical rotating shaft to rotate is further arranged on the first transverse vertical rotating shaft;
a first longitudinal vertical rotating shaft S11 which is driven by a fifth speed reducing motor S30 and can rotate on the front vertical surface and the rear vertical surface is arranged at the left end of the arm section four, and the right end of the output gripper is fixedly connected to the first longitudinal vertical rotating shaft, so that the right end of the output gripper can vertically rotate on the front vertical surface and the rear vertical surface to form a sixth degree of freedom; a fifth electromagnetic brake S36 capable of controlling the first vertical rotating shaft to rotate is further arranged on the first vertical rotating shaft;
the section A2 of the pipe can be driven by the telescopic rod of the first cylinder to move in a telescopic manner from side to side in the section A1 of the pipe to form a seventh degree of freedom;
the B2 section of pipe can be driven by the telescopic rod of the second cylinder to move in the B1 section of pipe in a left-right telescopic manner to form an eighth degree of freedom;
the left end of a first horizontal pipe S39 is horizontally and fixedly connected to the right surface of the vertical column, a balance adjusting block S40 is arranged in the first horizontal pipe in a left-right sliding mode, a balance adjusting cylinder S38 with a telescopic rod facing horizontally is fixedly connected to the left end of the first horizontal pipe, and the right end of the telescopic rod of the balance adjusting cylinder is fixedly connected to the balance adjusting block;
the control end of No. one electromagnetic brake, the control end of No. two electromagnetic brakes, the control end of No. three electromagnetic brakes, the control end of No. four electromagnetic brakes, the control end of No. five electromagnetic brakes, the control end of a gear motor, the control end of No. two gear motor, the control end of No. three gear motor, the control end of No. four gear motor, the control end of No. five gear motor, the control end of a cylinder, the control end of No. two cylinders, the control end of balance adjustment cylinder and the control end of vertical cylinder are respectively control connection on the control cabinet.
An annular ring S42 is fixedly sleeved on the outer surface of the first vertical rotating shaft, a first moving block S44 which is driven by a surrounding motor S43 and can move along the annular ring is arranged on the annular ring, and a camera S45 is arranged on the first moving block; the control end of the camera and the control end of the surrounding motor are respectively connected with the console.
The camera can rotate along the output tongs, is convenient for snatch the object.
The seventh degree of freedom can enable the mechanical arm to extend freely, and the eighth degree of freedom can enable the mechanical arm to extend freely, so that the operation range and flexibility are greatly increased.
The balance adjusting cylinder controls the balance of the vertical column by moving the balance adjusting block left and right, and then the balance of the manipulator is controlled. The manipulator is convenient to move. The mobile platform comprises an automobile.
Because some mechanical arms of the invention have eight degrees of freedom, the invention has good flexibility and high reliability and is easy to complete control tasks.
A redundant robotic arm inverse priority impedance control method, as shown in figures 1-3. The method comprises the following steps:
step 1, establishing a redundant mechanical arm kinematics model, and giving a gradient direction strategy implementation process of a redundant mechanical arm zero space vector as follows:
the pose and the speed of the end effector in the Cartesian space are defined as x,
Figure BDA0002476495740000111
The angular position and angular velocity of the joint space are q,
Figure BDA0002476495740000112
J is a Jacobian matrix of the n-degree-of-freedom robot, where x ∈ Rn，
Figure BDA0002476495740000113
Figure BDA0002476495740000114
J∈Rm-n(ii) a The positive kinematic equation for a redundant degree of freedom robotic arm can be described by:
Figure BDA0002476495740000121
equation (1) is also referred to as a robot arm kinematics velocity model;
considering the solution of the least squares method, the optimal problem can be listed as:
Figure BDA0002476495740000122
the solution of formula (1) can be optimized by finding the best
Figure BDA0002476495740000123
To solve the problem;
Figure BDA0002476495740000124
thus, the pseudo-inverse solution of equation (1) can be expressed as:
Figure BDA0002476495740000125
in the formula J+Pseudo-inverse of the Jacobian matrix
I-identity matrix
Figure BDA0002476495740000126
-arbitrary null space vector
Figure BDA0002476495740000127
Minimum norm solution, defining hand movements
Figure BDA0002476495740000128
Homogeneous solution, no action at the end
Equation (4) represents the position and attitude control of the end effector; adding any residual error into the formula (4) to obtain a general expression containing a null space; the multi-task optimization can be realized on a zero vector by using the equation;
however, the above equation ignores the ill-conditioned state of the jacobian matrix; the regularization equation may be modified by adding additional regularization values,
Figure BDA0002476495740000129
where λ ≧ 0 is the weighting matrix,
Figure BDA00024764957400001210
is a weighting coefficient, and satisfies
Figure BDA00024764957400001211
The solution to the above equation can be expressed as:
Figure BDA00024764957400001212
equation (7) is also referred to as a redundant manipulator kinematics model;
the joint limit function of the joint limit gradient direction of the position-dependent scalar index of the null-space vector of the redundant manipulator is as follows:
Figure BDA00024764957400001213
step 2, establishing a task priority solving strategy for obtaining a singularity elimination algorithm through a singular robust solution as follows:
in the solution of the redundant mechanical arm of the Jacobian matrix, an optimization task is realized in a null space of a main task; the reverse task kinematics is established on the basis of the forward task kinematics:
Figure BDA00024764957400001214
wherein
Figure BDA00024764957400001215
And
Figure BDA00024764957400001216
representation task1 and task2
The inverse kinematics equation of the redundant manipulator is obtained from expression (5) as follows:
Figure BDA0002476495740000131
task1 as the main Task and Task2 as the auxiliary Task; that is to say that the position of the first electrode,
Figure BDA0002476495740000132
is that
Figure BDA0002476495740000133
Is implemented in the null space of (1); the final inverse kinematics expression for the redundant manipulator is as follows:
Figure BDA0002476495740000134
wherein
Figure BDA0002476495740000135
Figure BDA0002476495740000136
Is a projection matrix which gives the applicable range of the secondary task to the primary task;
Figure BDA0002476495740000137
and
Figure BDA0002476495740000138
is the desired commanded speed;
Figure BDA0002476495740000139
is the main task of the method, and the method comprises the following steps of,
Figure BDA00024764957400001310
is a secondary task;
if two related tasks are interdependent, then the corresponding Jacobian matrix is singular; if the task jacobian matrix is singular, the corresponding task is not satisfied; in this case, the jacobian correlation matrix will be singularities, defined as algorithmic singularities;
that is, if
Figure BDA00024764957400001311
Where ρ (·) is the rank of the matrix;
it is clear that the singularity of the algorithm is caused by task conflicts between the secondary tasks and the primary task; in addition, task priority based redundant robotic arm inverse kinematics aims to provide better control over the effectiveness of the primary tasks;
therefore, the position control direction is used as a main task, so that the position ensures the accuracy of the control direction task; then, establishing a task priority solving strategy equation for obtaining a singularity elimination algorithm through singular robust solution:
Figure BDA00024764957400001312
step 3, establishing a singular robust solution inverse kinematics analysis model as follows:
the motion singularity can occur based on the Jacobian pseudo-inverse solution, which is caused by the secondary matrix; for the motion singularity problem, a DLS (damped least squares) solution should also be given;
the cost function for the DLS solution can be modified to:
Figure BDA00024764957400001313
thus, the singular robust pseudo-inverse solution of the above equation can be expressed as:
Figure BDA00024764957400001314
equation (15) is QiluInverse kinematics analysis model with bar solution, let λ be η2I, the DLS solution is equivalent to an additional regularization solution, and the scalar value η balances the task precision and singularity;
for the calculation of the pseudo-inverse solution of the Jacobian matrix, the singular value SVD decomposition form of the Jacobian matrix can be given
J＝U∑VT(16)
Wherein U ∈ Rm×n，V∈Rm×n，∑∈Rm×nU is a column vector UiA unitary matrix of V is formed by column vectors ViThe constituent unary matrix, ∑, is a block matrix of m × n diagonal matrices containing the singular values σ of JiMore than or equal to 0 contains n-m zero column vectors in descending order;
Figure BDA0002476495740000141
wherein r is less than or equal to m is the rank of the matrix J;
for motion singularity, with reference to the singular value decomposition SVD required to compute the pseudo-inverse solution, the large resulting joint velocity is due to the smallest singular value rapidly approaching 0, as follows:
Figure BDA0002476495740000142
factor lambda0Singularities of each influence, λ0The higher the value is, the larger the damping is, and the closer the joint velocity is to the singular point; in addition, the strategy for defining the variable damping factor is also different; we can get
Figure BDA0002476495740000143
From the above equation, we can see that the parameter > 0 monitors the smallest singular value.
Step 4, establishing a reverse priority control strategy of the multi-task redundant mechanical arm as follows;
introducing an inverse-priority projection matrix
Figure BDA0002476495740000144
The matrix comprises a null space of corresponding elements of the lowest priority l-k-1 task independent of the kth task, so derived
Figure BDA0002476495740000145
Wherein Ji，jIs a jacobian matrix associated with all components of the i-th task that are linearly independent of the j-th task;
therefore, the priority derivation formula is as follows:
Figure BDA0002476495740000146
in the above derivation, k ═ l, l-1, …, 1; initial value
Figure BDA0002476495740000147
To give a general form of computation of the linear independent Jacobian matrix J, the inverse augmented Jacobian matrix is defined as:
Figure BDA0002476495740000148
have therein
Figure BDA0002476495740000149
Wherein
Figure BDA00024764957400001410
To represent
Figure BDA00024764957400001411
A row of (2);
therefore, the method is not to be taken,
Figure BDA0002476495740000151
the pseudo-inverse solution of (a) can be expressed as:
Figure BDA0002476495740000152
and
Figure BDA0002476495740000153
wherein, TkRepresentation matrix
Figure BDA0002476495740000154
Expansion of (2);
the final inverse priority projection can be written as:
Figure BDA0002476495740000155
thus, we can derive the expression of the pseudo-inverse solution:
Figure BDA0002476495740000156
the reverse priority control strategy equation of the multi-task redundant mechanical arm is established as follows:
Figure BDA0002476495740000157
and 5, simplifying the reverse control equation of the redundant mechanical arm with the primary task and the secondary task as follows:
for a six-degree-of-freedom or seven-degree-of-freedom redundant manipulator, there are not enough six-degree-of-freedom DOF to complete multiple levels of tasks; it is necessary to carry out a dual task priority control; that is, the motion control of the manipulator is a primary task and a secondary task;
the equations for the inverse control of a redundant robotic arm having primary and secondary tasks are as follows
Figure BDA0002476495740000158
The above formula is very different from the above expression (11), but it is calculatedThe normal framework is similar; in the above-mentioned equations, the process of the present invention,
Figure BDA0002476495740000159
is a secondary task that is to be performed,
Figure BDA00024764957400001510
is the main task; the main task is realized in a designated null space of the main task; the core point of reverse priority being a projection matrix
Figure BDA00024764957400001511
Calculating (1);
Figure BDA00024764957400001512
is expressed as formula (30):
Figure BDA00024764957400001513
using similar guides as in previous equations (22) - (28), a simplified inverse control equation for a redundant robotic arm having a primary task and a secondary task can be obtained:
Figure BDA00024764957400001514
and 6, establishing a reverse priority control strategy of the manipulator as follows:
the dynamics of the manipulator in force control space can be written as:
Figure BDA00024764957400001515
where X is the position in Cartesian space, M (X) is an inertial matrix,
Figure BDA00024764957400001516
non-linear force, F input control force, FeIs the contact force;
furthermore, the input joint moments are obtained on the basis of a conversion of the Jacobian matrix
τ＝JT(q)F(33)
The desired equation of motion of the manipulator in force control space may be defined as follows:
Figure BDA0002476495740000161
wherein M isdAnd BdIs an inertia and damping matrix; fdIs a command force, FeIs the contact force;
the kinetic profile of force control is shown in FIG. 1;
thus, the relationship between the environment and the manipulator response can be written as
Figure BDA0002476495740000162
The combination of the above two equations is as follows
Figure BDA0002476495740000163
As can be seen from the above equation, if M ise、BeAnd KeKnown, then MdAnd BdWill affect the system response;
force control enables the manipulator to interact with the environment or human; in addition, in some cases, it is not necessary to implement omnidirectional force control and guarantee omnidirectional force control, that is, sometimes we only want to guarantee the force tracking control accuracy in a certain direction;
for example, when the manipulator interacts with the planer, only precise force tracking control needs to be maintained in the vertical direction, while precise force tracking control is not needed in the other direction; in other cases, position direction force control is more important than attitude direction force control;
it is therefore necessary to perform a hierarchical force control of the manipulator; that is, it is necessary to provide a new hierarchical force control framework; from the above equation we can derive the desired hierarchical force control relationship as follows
Figure BDA0002476495740000164
Figure BDA0002476495740000165
The integral of these two equations can be written as
Figure BDA0002476495740000166
Figure BDA0002476495740000167
If the robot end effector is able to track the desired cartesian velocity of
Figure BDA0002476495740000168
And
Figure BDA0002476495740000169
accurate force control of the manipulator can be achieved; the relation between the Cartesian velocity and the joint velocity should be based on inverse priority control; thus, the equation for the inverse priority control strategy for the manipulator can be derived:
Figure BDA00024764957400001610
the joint velocity required by the above equation will ensure force control of the manipulator; it is worth mentioning that the force control law is only a speed step control law, which relies on an inner speed loop control; if the internal position control effect is good, accurate force control can be realized; because the inner speed ring control can realize low-frequency position tracking, the outer force ring can realize low-frequency force tracking.
And 7, solving the relation between the external force and the joint acceleration in the reverse priority impedance control of the manipulator by adopting the joint speed, so as to obtain the realization mode of ensuring the reverse priority impedance control of the manipulator, wherein the realization mode comprises the following steps:
when the manipulator implements force control, the manipulator functions as an initiator to some extent, that is, the manipulator is ready to respond to the external environment; when the mechanical arm
When the robot arm works as an impedance control model, the robot arm passively responds to an external force; the kinetic scheme of impedance control is shown in fig. 2;
the corresponding impedance relationship between the external force and the joint acceleration can be expressed as
Figure BDA0002476495740000171
Figure BDA0002476495740000172
The reference speed can be expressed as
Figure BDA0002476495740000173
Figure BDA0002476495740000174
Therefore, the inverse priority impedance control of the manipulator guarantees the expression:
Figure BDA0002476495740000175
and 8, expanding the reverse priority calculation of the position control space to the reverse priority calculation of the force control space, so as to obtain the overall framework implementation mode of the manipulator speed-level reverse priority impedance control, wherein the overall framework implementation mode comprises the following steps:
hybrid impedance applications are a combination of the two strategies mentioned above, i.e. the cartesian task can be divided into two cases: the first is a position control subspace, in which the impedance control is implemented; the second is a force control subspace in which force control is implemented;
thus selecting a selection matrix; the relationship between the external force and the position response is as follows
Figure BDA0002476495740000176
Figure BDA0002476495740000177
So a simplified form of the desired speed can be expressed as
Figure BDA0002476495740000178
Figure BDA0002476495740000179
Then we get a solution based on reverse priority
Figure BDA0002476495740000181
The kinetic scheme of the hybrid impedance control is shown in FIG. 3;
considering n-layer tasks, the corresponding impedance control task also belongs to n-layer framework, therefore, the overall framework expression of the manipulator speed level inverse priority impedance control is as follows
Figure BDA0002476495740000182
Expression (52) solves the problem of extending the reverse-priority computation of the position control space into manipulator reverse-priority hybrid impedance control of the reverse-priority computation of the force control space; the redundant mechanical arm of the manipulator can realize the expected impedance control task under different hierarchical structures.

Claims (10)

1. A redundant robot arm inverse priority impedance control system including a robot and a console (S31) controlling the robot; characterized in that the device also comprises a movable moving platform (S41); the robot includes a robot arm, a mounting seat (S1), a vertical column (S2), an output gripper (S12), and a vertical cylinder (S23); the mounting seat is fixed on the mobile platform;
the mechanical arm comprises a vertical lifting mobile platform (S3), a first arm section (S6), a second arm section (S7), a third arm section (S8) and a fourth arm section (S10);
a vertical rail (S24) is arranged on the left surface of the vertical column, and the vertical lifting mobile platform is vertically arranged on the vertical rail in a sliding manner; the lower end of the vertical column is fixedly connected to the upper surface of the mounting seat, a cylinder seat (S21) of the vertical cylinder is fixedly connected to the upper surface of the mounting seat positioned on the left side of the vertical track, a telescopic rod (S22) of the vertical cylinder is vertically arranged upwards, and the upper end of the telescopic rod of the vertical cylinder is fixedly connected to the lower surface of the vertical lifting mobile platform; the vertical lifting mobile platform can move up and down along a vertical track under the driving of a telescopic rod of a vertical cylinder to form a first degree of freedom;
the first arm section comprises an A1 section of pipe (S13) and an A2 section of pipe (S14) which is telescopically connected in a left pipe orifice of the A1 section of pipe, a first air cylinder (S25) with a telescopic rod horizontally arranged towards the left is fixedly arranged at the right end in the A1 section of pipe, and the telescopic rod of the first air cylinder is fixedly connected at the right end of the A2 section of pipe;
the arm section II comprises a section B1 pipe (S16) and a section B2 pipe (S17) which is telescopically connected in a left pipe orifice of the section B1 pipe, a second cylinder (37) with a telescopic rod horizontally arranged towards the left is fixedly arranged at the right end in the section B1 pipe, and the telescopic rod of the second cylinder is fixedly connected at the right end of the section B2 pipe;
the left end of the vertical lifting mobile platform is provided with a first horizontal rotating shaft (S4) driven by a first speed reducing motor (S26), and the right end of the A1 section of pipe is fixedly connected to the first horizontal rotating shaft, so that the first arm section can horizontally rotate to form a second degree of freedom; a first electromagnetic brake (S32) capable of controlling the rotation of the first horizontal rotating shaft is also arranged on the first horizontal rotating shaft;
the left end of the A2 section of pipe is provided with a second horizontal rotating shaft (S15) driven by a second speed reducing motor (S27), and the right end of the B1 section of pipe is fixedly connected to the second horizontal rotating shaft, so that the second arm section can horizontally rotate to form a third degree of freedom; a second electromagnetic brake (S33) capable of controlling the second horizontal rotating shaft to rotate is also arranged on the second horizontal rotating shaft;
the left end of the B2 section pipe is provided with a third horizontal rotating shaft (S18) driven by a third speed reducing motor (S28), and the right end of the arm section III is fixedly connected to the third horizontal rotating shaft, so that the arm section III can horizontally rotate to form a fourth degree of freedom; a third electromagnetic brake (S34) capable of controlling the third horizontal rotating shaft to rotate is also arranged on the third horizontal rotating shaft;
a first transverse vertical rotating shaft (S9) which is driven by a fourth speed reducing motor (S29) and can rotate on the left vertical surface and the right vertical surface is arranged at the left end of the arm section III, and the right end of the arm section IV is fixedly connected to the first transverse vertical rotating shaft, so that the arm section IV can vertically rotate on the left vertical surface and the right vertical surface to form a fifth degree of freedom; a fourth electromagnetic brake (S35) capable of controlling the first transverse vertical rotating shaft to rotate is further arranged on the first transverse vertical rotating shaft;
a first longitudinal vertical rotating shaft (S11) which is driven by a fifth speed reducing motor (S30) and can rotate on the front vertical surface and the rear vertical surface is arranged at the left end of the arm section four, and the right end of the output gripper is fixedly connected to the first longitudinal vertical rotating shaft, so that the right end of the output gripper can vertically rotate on the front vertical surface and the rear vertical surface to form a sixth degree of freedom; a fifth electromagnetic brake (S36) capable of controlling the first vertical rotating shaft to rotate is further arranged on the first vertical rotating shaft;
the section A2 of the pipe can be driven by the telescopic rod of the first cylinder to move in a telescopic manner from side to side in the section A1 of the pipe to form a seventh degree of freedom;
the B2 section of pipe can be driven by the telescopic rod of the second cylinder to move in the B1 section of pipe in a left-right telescopic manner to form an eighth degree of freedom;
the left end of a first horizontal pipe (S39) is horizontally and fixedly connected to the right surface of the vertical column, a balance adjusting block (S40) is arranged in the first horizontal pipe in a sliding mode from left to right, a balance adjusting cylinder (S38) with a telescopic rod facing horizontally is fixedly connected to the left end of the first horizontal pipe, and the right end of the telescopic rod of the balance adjusting cylinder is fixedly connected to the balance adjusting block;
the control end of the first electromagnetic brake, the control end of the second electromagnetic brake, the control end of the third electromagnetic brake, the control end of the fourth electromagnetic brake, the control end of the fifth electromagnetic brake, the control end of the first speed reducing motor, the control end of the second speed reducing motor, the control end of the third speed reducing motor, the control end of the fourth speed reducing motor, the control end of the fifth speed reducing motor, the control end of the first air cylinder, the control end of the second air cylinder, the control end of the balance adjusting air cylinder and the control end of the vertical air cylinder are respectively connected to a control console in a control mode;
an annular ring (S42) is fixedly sleeved on the outer surface of the first longitudinal vertical rotating shaft, a first moving block (S44) which is driven by a surrounding motor (S43) and can move along the annular ring is arranged on the annular ring, and a camera (S45) is arranged on the first moving block; the control end of the camera and the control end of the surrounding motor are respectively connected with the console.
2. A redundant manipulator inverse priority impedance control method is characterized by comprising the following steps:
step 1, establishing a kinematic model of the redundant mechanical arm, and giving a gradient direction strategy of a zero space vector of the redundant mechanical arm;
step 2, establishing a task priority solving strategy for obtaining a singularity elimination algorithm through a singular robust solution;
step 3, establishing a singular robust solution inverse kinematics analysis model;
step 4, establishing a reverse priority control strategy of the multi-task redundant mechanical arm;
step 5, simplifying a reverse control equation of the redundant mechanical arm with the main task and the secondary task;
step 6, establishing a reverse priority control strategy of the manipulator;
step 7, solving the relation between the external force and the joint acceleration in the reverse priority impedance control of the manipulator by adopting the joint speed, thereby obtaining the reverse priority impedance control guarantee of the manipulator;
and 8, expanding the reverse priority calculation of the position control space to the reverse priority calculation of the force control space, thereby obtaining the overall framework of the speed-level reverse priority impedance control of the manipulator.
3. The inverse priority impedance control method of claim 2, wherein the kinematics model of the redundant manipulator is established, and the gradient direction strategy implementation process of the null-space vector of the redundant manipulator is given as follows:
the pose and the speed of the end effector in the Cartesian space are defined as x,
Figure FDA0002476495730000041
The angular position and angular velocity of the joint space are q,
Figure FDA0002476495730000042
J is a Jacobian matrix of the n-degree-of-freedom robot, where x ∈ Rn，
Figure FDA0002476495730000047
J∈Rm-n(ii) a The positive kinematic equation for a redundant degree of freedom robotic arm can be described by:
Figure FDA0002476495730000043
equation (1) is also referred to as a robot arm kinematics velocity model;
considering the solution of the least squares method, the optimal problem can be listed as:
Figure FDA0002476495730000044
the solution of formula (1) can be optimized by finding the best
Figure FDA0002476495730000045
To solve the problem;
Figure FDA0002476495730000046
thus, the pseudo-inverse solution of equation (1) can be expressed as:
Figure FDA0002476495730000051
in the formula J+Pseudo-inverse of the Jacobian matrix
I-identity matrix
Figure FDA0002476495730000052
-arbitrary null space vector
Figure FDA0002476495730000053
Minimum norm solution, defining hand movements
Figure FDA0002476495730000054
Homogeneous solution, no action at the end
Equation (4) represents the position and attitude control of the end effector; adding any residual error into the formula (4) to obtain a general expression containing a null space; the multi-task optimization can be realized on a zero vector by using the equation;
however, the above equation ignores the ill-conditioned state of the jacobian matrix; the regularization equation may be modified by adding additional regularization values,
Figure FDA0002476495730000055
where λ ≧ 0 is the weighting matrix,
Figure FDA0002476495730000056
is a weighting coefficient, and satisfies
Figure FDA0002476495730000057
The solution to the above equation can be expressed as:
Figure FDA0002476495730000058
equation (7) is also referred to as a redundant manipulator kinematics model;
the joint limit function of the joint limit gradient direction of the position-dependent scalar index of the null-space vector of the redundant manipulator is as follows:
Figure FDA0002476495730000059
4. the inverse priority impedance control method of the redundant manipulator according to claim 3, wherein a task priority solving strategy for solving the singularity elimination algorithm by a singular robust solution is established as follows:
in the solution of the redundant mechanical arm of the Jacobian matrix, an optimization task is realized in a null space of a main task; the reverse task kinematics is established on the basis of the forward task kinematics:
Figure FDA0002476495730000061
wherein
Figure FDA0002476495730000062
And
Figure FDA0002476495730000063
representation task1 and task2
The inverse kinematics equation of the redundant manipulator is obtained from expression (5) as follows:
Figure FDA0002476495730000064
task1 as the main Task and Task2 as the auxiliary Task; that is, task2
Figure FDA0002476495730000065
Is at task1
Figure FDA0002476495730000066
In the null space ofOf (1); the final inverse kinematics expression for the redundant manipulator is as follows:
Figure FDA0002476495730000067
wherein
Figure FDA0002476495730000068
Figure FDA0002476495730000069
Is a projection matrix which gives the applicable range of the secondary task to the primary task;
Figure FDA00024764957300000610
and
Figure FDA00024764957300000611
is the desired commanded speed;
Figure FDA00024764957300000612
is the main task of the method, and the method comprises the following steps of,
Figure FDA00024764957300000613
is a secondary task;
if two related tasks are interdependent, then the corresponding Jacobian matrix is singular; if the task jacobian matrix is singular, the corresponding task is not satisfied; in this case, the jacobian correlation matrix will be singularities, defined as algorithmic singularities;
that is, if
Figure FDA00024764957300000614
Where ρ (·) is the rank of the matrix;
it is clear that the singularity of the algorithm is caused by task conflicts between the secondary tasks and the primary task; in addition, task priority based redundant robotic arm inverse kinematics aims to provide better control over the effectiveness of the primary tasks;
therefore, the position control direction is used as a main task, so that the position ensures the accuracy of the control direction task; then, establishing a task priority solving strategy equation for obtaining a singularity elimination algorithm through singular robust solution:
Figure FDA0002476495730000071
5. the inverse priority impedance control method of the redundant manipulator according to claim 4, wherein a singular robust solution inverse kinematics analysis model is established as follows:
the motion singularity can occur based on the Jacobian pseudo-inverse solution, which is caused by the secondary matrix; for the motion singularity problem, a DLS (damped least squares) solution should also be given;
the cost function for the DLS solution can be modified to:
Figure FDA0002476495730000072
thus, the singular robust pseudo-inverse solution of the above equation can be expressed as:
Figure FDA0002476495730000073
equation (15) is a singular robust solution inverse kinematics analysis model, where λ is η2I, the DLS solution is equivalent to an additional regularization solution, and the scalar value η balances the task precision and singularity;
for the calculation of the pseudo-inverse solution of the Jacobian matrix, the singular value SVD decomposition form of the Jacobian matrix can be given
J＝U∑VT(16)
Wherein U ∈ Rm×m，V∈Rn×n，∑∈Rm×nU is a column vector UiA unitary matrix of V is formed by column vectors ViThe constituent unary matrix, ∑, is a block matrix of m × n diagonal matrices containing the singular values σ of JiMore than or equal to 0 contains n-m zero column vectors in descending order;
Figure FDA0002476495730000081
wherein r is less than or equal to m is the rank of the matrix J;
for motion singularity, with reference to the singular value decomposition SVD required to compute the pseudo-inverse solution, the large resulting joint velocity is due to the smallest singular value rapidly approaching 0, as follows:
Figure FDA0002476495730000082
factor lambda0Will affect the singularity, λ0The higher the value is, the larger the damping is, and the closer the joint velocity is to the singular point; in addition, the strategy for defining the variable damping factor is also different; we can get
Figure FDA0002476495730000083
From the above equation, we can see that the parameter > 0 monitors the smallest singular value.
6. The inverse priority impedance control method of the redundant manipulator according to claim 5, wherein the inverse priority control strategy of the multitasking redundant manipulator is established as follows;
introducing an inverse-priority projection matrix
Figure FDA0002476495730000084
The matrix comprises a null space of corresponding elements of the lowest priority l-k-1 task independent of the kth task, so derived
Figure FDA0002476495730000085
Figure FDA0002476495730000086
Wherein Ji|jIs a jacobian matrix associated with all components of the i-th task that are linearly independent of the j-th task;
therefore, the priority derivation formula is as follows:
Figure FDA0002476495730000091
in the above derivation, k ═ l, l-1, …, 1; initial value
Figure FDA0002476495730000092
To give a general form of computation of the linear independent Jacobian matrix J, the inverse augmented Jacobian matrix is defined as:
Figure FDA0002476495730000093
have therein
Figure FDA0002476495730000094
Wherein
Figure FDA0002476495730000095
To represent
Figure FDA0002476495730000096
A row of (2);
therefore, the method is not to be taken,
Figure FDA0002476495730000097
the pseudo-inverse solution of (a) can be expressed as:
Figure FDA0002476495730000098
and
Figure FDA0002476495730000099
wherein, TkRepresentation matrix
Figure FDA00024764957300000910
Expansion of (2);
the final inverse priority projection can be written as:
Figure FDA00024764957300000911
thus, we can derive the expression of the pseudo-inverse solution:
Figure FDA00024764957300000912
the reverse priority control strategy equation of the multi-task redundant mechanical arm is established as follows:
Figure FDA0002476495730000101
7. the inverse priority impedance control method of claim 6, wherein the inverse control equation of the redundant robot arm having the primary task and the secondary task is simplified as follows:
for a six-degree-of-freedom or seven-degree-of-freedom redundant manipulator, there are not enough six-degree-of-freedom DOF to complete multiple levels of tasks; it is necessary to carry out a dual task priority control; that is, the motion control of the manipulator is a primary task and a secondary task;
the equations for the inverse control of a redundant robotic arm having primary and secondary tasks are as follows
Figure FDA0002476495730000102
The above formula is very different from the previous expression (11), but the algorithmic framework is similar; in the above-mentioned equations, the process of the present invention,
Figure FDA0002476495730000103
is a secondary task that is to be performed,
Figure FDA0002476495730000104
is the main task; the main task is realized in a designated null space of the main task; the core point of reverse priority being a projection matrix
Figure FDA0002476495730000105
Calculating (1);
Figure FDA0002476495730000106
is expressed as formula (30):
Figure FDA0002476495730000107
using similar guides as in previous equations (22) - (28), a simplified inverse control equation for a redundant robotic arm having a primary task and a secondary task can be obtained:
Figure FDA0002476495730000108
8. the redundant manipulator reverse priority impedance control method of claim 7, wherein the manipulator reverse priority control strategy is established as follows:
the dynamics of the manipulator in force control space can be written as:
Figure FDA0002476495730000109
where X is the position in Cartesian space, M (X) is an inertial matrix,
Figure FDA0002476495730000111
non-linear force, F input control force, FeIs the contact force;
furthermore, the input joint moments are obtained on the basis of a conversion of the Jacobian matrix
τ＝JT(q)F (33)
The desired equation of motion of the manipulator in force control space may be defined as follows:
Figure FDA0002476495730000112
wherein M isdAnd BdIs an inertia and damping matrix; fdIs a command force, FeIs the contact force;
thus, the relationship between the environment and the manipulator response can be written as
Figure FDA0002476495730000113
The combination of the above two equations is as follows
Figure FDA0002476495730000114
As can be seen from the above equation, if M ise、BeAnd KeKnown, then MdAnd BdWill affect the system response;
force control enables the manipulator to interact with the environment or human; in addition, in some cases, it is not necessary to implement omnidirectional force control and guarantee omnidirectional force control, that is, sometimes we only want to guarantee the force tracking control accuracy in a certain direction;
it is therefore necessary to perform a hierarchical force control of the manipulator; that is, it is necessary to provide a new hierarchical force control framework; from the above equation we can derive the desired hierarchical force control relationship as follows
Figure FDA0002476495730000115
Figure FDA0002476495730000116
The integral of these two equations can be written as
Figure FDA0002476495730000121
Figure FDA0002476495730000122
If the robot end effector is able to track the desired cartesian velocity of
Figure FDA0002476495730000123
And
Figure FDA0002476495730000124
accurate force control of the manipulator can be achieved; the relation between the Cartesian velocity and the joint velocity should be based on inverse priority control; thus, the equation for the inverse priority control strategy for the manipulator can be derived:
Figure FDA0002476495730000125
the joint velocity required by the above equation will ensure force control of the manipulator; it is worth mentioning that the force control law is only a speed step control law, which relies on an inner speed loop control; if the internal position control effect is good, accurate force control can be realized; because the inner speed ring control can realize low-frequency position tracking, the outer force ring can realize low-frequency force tracking.
9. The method for controlling reverse priority impedance of a manipulator of claim 8, wherein the relationship between external force and joint acceleration in the reverse priority impedance control of the manipulator is solved by using joint velocity, so as to obtain the reverse priority impedance control guarantee of the manipulator, and the method is implemented as follows:
when the manipulator implements force control, the manipulator functions as an initiator to some extent, that is, the manipulator is ready to respond to the external environment; when the mechanical arm works as an impedance control model, the mechanical arm passively responds to an external force;
the corresponding impedance relationship between the external force and the joint acceleration can be expressed as
Figure FDA0002476495730000126
Figure FDA0002476495730000127
The reference speed can be expressed as
Figure FDA0002476495730000131
Figure FDA0002476495730000132
Therefore, the inverse priority impedance control of the manipulator guarantees the expression:
Figure FDA0002476495730000133
10. the redundant manipulator reverse priority impedance control method according to claim 9, wherein the overall framework implementation of extending the reverse priority computation of the position control space to the reverse priority computation of the force control space to obtain manipulator velocity reverse priority impedance control is as follows:
hybrid impedance applications are a combination of the two strategies mentioned above, i.e. the cartesian task can be divided into two cases: the first is a position control subspace, in which the impedance control is implemented; the second is a force control subspace in which force control is implemented;
thus selecting a selection matrix; the relationship between the external force and the position response is as follows
Figure FDA0002476495730000134
Figure FDA0002476495730000135
So a simplified form of the desired speed can be expressed as
Figure FDA0002476495730000136
Figure FDA0002476495730000137
Then we get a solution based on reverse priority
Figure FDA0002476495730000141
Considering n-layer tasks, the corresponding impedance control task also belongs to n-layer framework, therefore, the overall framework expression of the manipulator speed level inverse priority impedance control is as follows
Figure FDA0002476495730000142
Expression (52) solves the problem of extending the reverse-priority computation of the position control space into manipulator reverse-priority hybrid impedance control of the reverse-priority computation of the force control space; the redundant mechanical arm of the manipulator can realize the expected impedance control task under different hierarchical structures.
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