CN114619437A - Flexible impedance control method for redundant multi-joint robot - Google Patents
Flexible impedance control method for redundant multi-joint robot Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/16—Programme controls
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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 relates to the fields of intelligent manufacturing, automatic control and flexible man-machine interaction, in particular to a flexible impedance control method of a redundant multi-joint robot; the invention determines the relation between the torque of an impedance controller at the tail end of a robot arm and the angle, speed and acceleration of each joint of the robot arm by detecting the torque of the impedance controller at the tail end of the robot arm so as to form an impedance model, compares the detected torque at the tail end of the robot arm with the torque at the tail end of the robot arm calculated in the impedance model, forms a working instruction, and executes the working instruction by an actuator at the tail end of the robot arm so as to control the servo motor of each joint of the robot arm to perform motion control, thereby driving the robot arm to perform coherent action; therefore, the end effector of the robot can realize the purposes of various functional motions and operation tasks by directly detecting the relationship between the moment information of the end of the robot and the joint angle, the speed and the acceleration of the robot.
Description
Technical Field
The invention relates to the fields of intelligent manufacturing, automatic control and flexible man-machine interaction, in particular to a flexible impedance control method for a redundant multi-joint robot.
Background
At present, the application of traditional industrial robots in the manufacturing field is widely popularized due to the rapid development of robot technology, and the traditional robots are visible anywhere such as automobile manufacturing, stacking and carrying, 3C assembly, wharf delivery and the like.
With the emergence of a new generation of multi-joint robots, the production mode of the traditional manufacturing industry is being overturned, and the repetitive teaching is gradually evolved into man-machine cooperation manufacturing. In order to safely interact with the surrounding environment, the traditional robot is provided with a joint torque sensor or an ATI force control sensor to ensure the safety of information interaction with the surrounding environment, and the force information of the information interaction of the surrounding environment is fed back to the robot, so that the safe cooperation function of a new-generation multi-joint robot is realized.
The existing new generation industrial robot uses a terminal force sensor to perform force and position hybrid control, although force control and safety protection can be performed, the main disadvantages are that: although the joint flexibility is increased to a certain extent by force and position hybrid control, the control algorithm is complex and the environmental adaptability is poor.
Disclosure of Invention
The invention mainly solves the technical problem of providing a flexible impedance control method of a redundant multi-joint robot, and finally achieves the purposes of various functional motions and operation tasks of an actuator at the tail end of the robot by directly detecting the relation between the information of the moment at the tail end of the robot and the joint angle, speed and acceleration of the robot.
In order to solve the technical problems, the invention adopts a technical scheme that: the method for controlling the flexible impedance of the redundant multi-joint robot is provided, and comprises the following steps:
step S1, determining the relation between the angle, speed and acceleration of each joint of the robot arm by detecting the moment of an impedance controller at the tail end of the robot arm, thereby forming an impedance model;
step S2, comparing the detected moment of the tail end of the robot arm with the moment of the tail end of the robot arm calculated in the impedance model, and then forming a working instruction;
and step S3, executing the working instruction by an actuator at the tail end of the robot arm, so as to control the servo motors of all joints of the robot arm to perform motion control, and further drive the robot arm to perform coherent motion.
As a modification of the present invention, in step S1, the robot arm includes arm joints with seven degrees of freedom, i.e., shoulder rotation, shoulder swing, shoulder lift, elbow rotation, elbow swing, hand rotation, and hand swing, and the impedance model performs a kinematic analysis to obtain position values of the joints.
As a further improvement of the present invention, in step S1, the arm joints with seven degrees of freedom of the robot arm establish a transfer transformation matrix equation according to the MDH coordinate relation table, thereby obtaining a kinematics positive solution relational expression.
As a further improvement of the present invention, in step S1, a matrix of the end poses of the robot arm is obtained by solving the relational expressions kinematically.
As a further improvement of the present invention, in step S1, the position values of the joints of the robot arm are calculated by using a newton iteration equation system, so as to obtain the relationship between the moment of the impedance controller at the end of the robot arm and the angles, the speeds and the accelerations of the joints of the robot arm, thereby forming the impedance model.
As a further improvement of the present invention, in step S2, the torque at the end of the robot arm may be detected by using a torque sensor detection method, a series dynamic elastic control detection method, or a current estimation detection method.
The invention has the beneficial effects that: compared with the prior art, the invention determines the relation between the angle, the speed and the acceleration of each joint of the robot arm by detecting the torque of the impedance controller at the tail end of the robot arm so as to form an impedance model, compares the detected torque at the tail end of the robot arm with the torque at the tail end of the robot arm calculated in the impedance model, forms a working instruction, and executes the working instruction by the actuator at the tail end of the robot arm so as to control the servo motor of each joint of the robot arm to perform motion control, thereby driving the robot arm to perform continuous motion; therefore, the end effector of the robot can finally realize the purposes of various functional motions and operation tasks by directly detecting the relationship between the information of the moment at the tail end of the robot and the joint angle, the speed and the acceleration of the robot.
Drawings
FIG. 1 is a block diagram of the steps of the present invention;
FIG. 2 is a schematic view of a robot joint of the present invention;
fig. 3 is a diagram of the redundant control coordinates of the robot of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1 to 3, a method for controlling flexible impedance of a redundant multi-joint robot according to the present invention includes the following steps:
step S1, determining the relation between the angle, speed and acceleration of each joint of the robot arm by detecting the moment of an impedance controller at the tail end of the robot arm, thereby forming an impedance model;
step S2, comparing the detected moment of the tail end of the robot arm with the moment of the tail end of the robot arm calculated in the impedance model, and then forming a working instruction;
and step S3, executing the working instruction by an actuator at the tail end of the robot arm, so as to control the servo motors of all joints of the robot arm to perform motion control, and further drive the robot arm to perform coherent motion.
The invention finally enables the actuator at the tail end of the robot to realize the purposes of various functional motions and operation tasks by directly detecting the relationship between the information of the moment at the tail end of the robot and the joint angle, the speed and the acceleration of the robot.
In step S1, the robot arm includes arm joints with seven degrees of freedom, i.e., shoulder turn, shoulder swing, shoulder lift, elbow turn, elbow swing, hand turn, and hand swing, and performs kinematic analysis in the impedance model to obtain position values of the joints.
Further, the arm joints with seven degrees of freedom of the robot arm establish a transfer transformation matrix equation according to the MDH coordinate relation table, and therefore a kinematics positive solution relation expression is obtained.
Further, in step S1, a matrix of the end poses of the robot arm is obtained by solving the relational expression kinematically.
Further, in step S1, the position values of the joints of the robot arm are calculated by using a newton iteration equation system, so as to obtain the relationship between the moment of the impedance controller at the end of the robot arm and the angles, the speeds and the accelerations of the joints of the robot arm, thereby forming the impedance model.
Specifically, as shown in fig. 2, the mobile robot is a multi-joint type robot arm, the operating arm of the mobile robot is a humanoid robot arm, and the structure of the arm with seven degrees of freedom including shoulder rotation, shoulder swinging, shoulder lifting, elbow rotating, elbow swinging, hand rotating and hand swinging establishes a transfer transformation matrix equation according to an MDH coordinate relation table, and obtains a kinematics positive solution relation expression by using a positive solution multiplication matrix product.
The robot has seven degrees of freedom, and the terminal pose matrix of the mechanical arm can be obtained through the motor rotation angle which can be solved through the kinematics forward solution problem of the robot. The final transformation matrix is:
the conclusion is that:
the first four-axis iterative solution analysis: the method comprises the following steps of calculating four joint position values by using a Newton iteration equation set, and solving the joint position values: the joint position value is calculated from a set of newton iteration equations. The iteration formula of the Newton method for the downhill method is as follows:
xn+1＝xn-ω(F'(xn))-1F(xn) (2)
F(X(k)) As a Jacobian matrix, i.e.
Solving a nonlinear system of equations in a normal case, where the equation number is equal to the unknown number, for a nonlinear system of equations
fi(x0,x1,...,xn-1)＝0i＝0,1,...,n-1
Then the k +1 th iteration value is calculated to obtain the Newton iteration format as
X(k+1)＝X(k)-F(X(k))-1f(X(k))
Wherein
F(X(k)) As a Jacobian matrix, i.e.
From this, a system of four equations can be established:
solving a Jacobian matrix J, and ensuring that the Jacobian matrix J is reversible all the time:
from this, the newton iteration format is:
J(k)-1＝JT(JJT)-1
and solving the other three axes at the tail end by adopting an analytical method, and finishing the forward and inverse kinematics solving process.
As shown in fig. 3, the kinematics of the redundant arm: standard equations for known spheres: x is the number of2+y2+z2＝R2。
The coordinates of the point D are as follows:
in known amounts.
The standard equation for the ball is therefore:
the center of the circle is:
the radius of the circle is:
the resulting redundancy equation is:
the radius of the circle is:
the redundancy parameter α equation is:
the simplification is as follows:
where a is a set amount and the others are known amounts.
In step S2, the torque at the end of the robot arm may be detected by a torque sensor, a series dynamic elastic control, or a current estimation; specifically, model-based control is classified into the following three types: 1. controlling a torque sensor; 2. controlling the series connection elasticity; 3. current estimation control; if there is a first one for estimating the torque based on the current or for the torque sensor; if it is based on a six-dimensional force sensor, the second one is used.
M, B, K is the behavior that the user desires the robot to behave and is not a characteristic of the robot itself; the smaller B is, the faster the tracking force is, the physical meaning of B is a damper, and the physical meaning of K is a spring;
and (3) force control flow: and detecting the force, calculating the increment by using an impedance formula, and sending the increment to the robot.
1、
2、
3、
(fe-fd) Force deviation,
fd0N → just contacted;
4、
k is a stiffness coefficient;
5、fd＝0
impedance pulling back to origin: x is the number ofdIs the point of expected regression, xdIs 0 and the acceleration is 0;
when the space is constrained: k is 0;
b. k is a behavior that the user desires the robot to exhibit, and has no relationship with the robot itself, and b may be 40 to 60, k may be 100, or,
The smaller the b (damper), the faster the tracking force; the physical meaning of k is a spring.
In the invention, the positive and negative kinematics of the robot are solved, and then a mapping relation between a position and a force can be adjusted by means of impedance control without depending on traditional force-position hybrid control. The impedance control aims at realizing a special expected dynamic relation between the robot motion and external torque, the impedance control does not directly control the contact force between the tail end of the mechanical arm and the environment, when the mechanical arm is in contact with the environment, the characteristics of the mechanical arm are described by using impedance, and the contact force/position relation between the tail end of the mechanical arm and the environment is adjusted by adjusting three parameters (inertia coefficient, damping coefficient and rigidity coefficient) of an impedance controller; the joint force control technology of the robot is carried out by establishing a flexible impedance model of the multi-joint robot and comparing the detected force and the calculated force with each other by adjusting an inertia coefficient, a damping coefficient and a rigidity coefficient.
The invention has the following beneficial effects:
(1) the forward and reverse kinematics of the redundant multi-joint robot is solved, the relational mapping between the motor angle joint value and the tail end attitude value of the robot can be solved, and the safety of motion control is guaranteed;
(2) based on the tail end force control torque detection, the precision of the joint integrated robot manual control technology is improved to some extent, and certain safety is met;
(3) the redundant control function not only relates to the kinematic constraint relation of the redundant multi-joint robot, but also relates to a control method when the redundant multi-joint robot works together, so that the safety of the robot is improved, and the working efficiency can be improved by cooperating with a human.
(4) The purpose of impedance control is to realize a special expected dynamic relation between robot motion and external torque, the impedance is used for describing the characteristics of the mechanical arm, and the relation of contact force/position between the tail end of the mechanical arm and the environment is adjusted by adjusting three parameters (inertia coefficient, damping coefficient and rigidity coefficient) of an impedance controller, so that the cost is saved.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (6)
1. A flexible impedance control method for a redundant multi-joint robot is characterized by comprising the following steps:
step S1, determining the relation between the angle, speed and acceleration of each joint of the robot arm by detecting the moment of an impedance controller at the tail end of the robot arm, thereby forming an impedance model;
step S2, comparing the detected moment of the tail end of the robot arm with the moment of the tail end of the robot arm calculated in the impedance model, and then forming a working instruction;
and step S3, executing the working instruction by an actuator at the tail end of the robot arm, so as to control the servo motors of all joints of the robot arm to perform motion control, and further drive the robot arm to perform coherent motion.
2. The method as claimed in claim 1, wherein in step S1, the robot arm includes arm joints with seven degrees of freedom, such as shoulder rotation, shoulder swing, shoulder lift, elbow rotation, elbow swing, hand rotation, and hand swing, and the impedance model is subjected to kinematic analysis to obtain the position values of the joints.
3. The method as claimed in claim 2, wherein in step S1, the arm joints with seven degrees of freedom of the robot arm establish a transfer transformation matrix equation according to the MDH coordinate relation table, so as to obtain a kinematic positive solution relational expression.
4. The flexible impedance control method for the redundant multi-joint robot according to claim 3, wherein in step S1, the terminal pose matrix of the robot arm is obtained by solving the relational expression through kinematics.
5. The flexible impedance control method of the redundant multi-joint robot according to claim 4, wherein in step S1, the position values of each joint of the robot arm are calculated by using a Newton iteration equation system, so as to obtain the relationship between the moment of the impedance controller at the end of the robot arm and the angle, speed and acceleration of each joint of the robot arm, thereby forming the impedance model.
6. The method as claimed in claim 1, wherein in step S2, the torque at the end of the robot arm is detected by a torque sensor or a series dynamic elastic control or a current estimation.
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Citations (5)
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|---|---|---|---|---|
| JP2012223829A (en) * | 2011-04-15 | 2012-11-15 | Seiko Epson Corp | Robot control device, robot, and robot control method |
| US20140107843A1 (en) * | 2012-05-23 | 2014-04-17 | Panasonic Corporation | Robot, robot control apparatus, robot control method, and robot control program |
| CN108638052A (en) * | 2018-03-29 | 2018-10-12 | 南京航空航天大学 | A kind of closed chain formula multi-arm robot Shared control method |
| CN108748147A (en) * | 2018-06-01 | 2018-11-06 | 清华大学深圳研究生院 | A kind of control system and method for ectoskeleton mechanical arm |
| CN110065070A (en) * | 2019-04-29 | 2019-07-30 | 华中科技大学 | A kind of robot adaptive impedance control system based on kinetic model |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012223829A (en) * | 2011-04-15 | 2012-11-15 | Seiko Epson Corp | Robot control device, robot, and robot control method |
| US20140107843A1 (en) * | 2012-05-23 | 2014-04-17 | Panasonic Corporation | Robot, robot control apparatus, robot control method, and robot control program |
| CN108638052A (en) * | 2018-03-29 | 2018-10-12 | 南京航空航天大学 | A kind of closed chain formula multi-arm robot Shared control method |
| CN108748147A (en) * | 2018-06-01 | 2018-11-06 | 清华大学深圳研究生院 | A kind of control system and method for ectoskeleton mechanical arm |
| CN110065070A (en) * | 2019-04-29 | 2019-07-30 | 华中科技大学 | A kind of robot adaptive impedance control system based on kinetic model |
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