CN112518745B - Robot TCP rapid calibration method - Google Patents

Robot TCP rapid calibration method Download PDF

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CN112518745B
CN112518745B CN202011336145.0A CN202011336145A CN112518745B CN 112518745 B CN112518745 B CN 112518745B CN 202011336145 A CN202011336145 A CN 202011336145A CN 112518745 B CN112518745 B CN 112518745B
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robot
force
coordinate system
moment
sensor
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CN112518745A (en
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杨跞
王琰
李法设
张一楠
汪宇星
许楠
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Siasun Co Ltd
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1628—Programme controls characterised by the control loop
    • B25J9/1633—Programme controls characterised by the control loop compliant, force, torque control, e.g. combined with position control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1694—Programme controls characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion

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  • Engineering & Computer Science (AREA)
  • Robotics (AREA)
  • Mechanical Engineering (AREA)
  • Manipulator (AREA)

Abstract

A rapid calibration method for a robot TCP (transmission control protocol) is characterized in that the contact force and moment information of the tail end of the robot is utilized to estimate the TCP coordinate, the description of the force and moment borne by the TCP in a coordinate system of the tail end of the robot is measured, and then a constraint equation is solved to obtain the coordinate value of the TCP in the coordinate system of the tail end of the robot. The method can measure the TCP coordinate value only by one-time contact, thereby saving calibration time; the calibration can be automatically completed by the controller without manual alignment or calibration; there is no form and precision requirement for the fixed surface.

Description

Robot TCP rapid calibration method
Technical Field
The invention relates to the technical field of robot control, in particular to a rapid calibration method for a robot TCP.
Background
Patent 106502208A describes an industrial robot TCP calibration method, which needs to teach a robot to align TCP to the same fixed point under different postures, and then fit TCP coordinates by a least square method. Patent 105509671B describes a calibration method for TCP of a robot using a planar calibration plate, which requires the robot to contact TCP with the calibration plate more than 6 times at different postures. The TCP coordinates are then obtained by solving the constraint equations.
The prior art has the defects that:
(1) the robot needs to be taught for multiple times to coincide with a fixed point or a fixed surface in different postures, the calibration process is complicated, and the calibration precision is difficult to ensure because the robot is aligned in a manual mode; meanwhile, as the robot moves in a position control mode, a tool or a calibration plate can be damaged in the alignment process of the robot TCP;
(2) the precision requirement on the calibration tool is high, because the final TCP calibration precision is influenced;
(3) for a tool with certain flexibility, the deformation of the tool in the alignment process cannot be controlled, so that the calibration result is inaccurate.
Disclosure of Invention
The disclosure provides a robot TCP rapid calibration method, which can realize rapid calibration between TCP and a robot terminal coordinate system.
The invention provides a robot TCP quick calibration method, which comprises the following steps:
setting the magnitude of the calibration contact force according to the rigidity or hardness of the robot tool and the calibration surface;
adjusting the tail end attitude of the robot to ensure that the contact force vector cannot be positioned in the x-y, y-z and x-z planes of the force sensor coordinate system;
controlling the TCP to move to a position close to the calibration surface, and then switching the robot to a force control mode;
controlling the tail end of the robot to contact with the calibration surface, and keeping the contact force above and below a set value;
when the contact force of the tail end of the robot is detected to enter a set range, acquiring the contact force and the moment of the tail end of the robot within a period of time, and solving the average value of the force and the moment;
and obtaining the final TCP coordinate according to the average value of the force and the moment.
Alternatively, in the case where a six-dimensional force sensor is integrated at the end of the robot, i.e. the coordinate system of the sensor coincides with the end coordinate system of the robot, the contact force and moment at the end of the robot are directly obtained from the six-dimensional force sensor.
Alternatively, when a six-dimensional force sensor is additionally installed at the robot tip, that is, the coordinate system of the sensor does not coincide with the tip coordinate system of the robot, the contact force and moment of the robot tip are obtained by the following methods:
Figure BDA0002797202790000021
wherein the content of the first and second substances,endFendindicating the contact force of the robot tip,endMendindicating the contact moment of the robot tip,
Figure BDA0002797202790000022
a rotation transformation matrix representing the force sensor coordinate system to the robot tip coordinate system,endPsensorindicating robot end coordinatesThe coordinates of the system origin in the force sensor coordinate system,sensorFsensorwhich is indicative of the force to which the force sensor is subjected,sensorMsensorrepresenting the moment experienced by the force sensor.
Alternatively, in the case where the robot is equipped with a joint torque sensor, the contact force and torque of the robot tip are calculated from the joint torque of the robot by the following formula, that is
Fend＝J·(τsensor-τrobot)
Wherein, FendRepresenting forces and moments (6-dimensional vectors) at the end of the robot, J representing the Jacobian matrix of the robot, τsensorRepresenting the moment, τ, received by a joint moment sensor of the robotrobotRepresenting the moment acting on the joint moment sensor due to the dynamics of the robot itself, which can be derived from the newton-euler method.
Alternatively, in the case where a six-dimensional force sensor is installed at a robot base, the contact force and moment of the robot tip are calculated by the following formulas:
Figure BDA0002797202790000031
wherein the content of the first and second substances,endFendindicating the contact force of the robot tip,endMendthe contact moment of the robot tip is represented,
Figure BDA0002797202790000032
a rotation transformation matrix representing the base coordinate system to the end coordinate system of the robot,endPbaserepresenting the coordinates of the origin of the coordinate system of the robot end in the base coordinate system,sensorFsensorindicating the forces to which the robot base is subjected,sensorMsensorthe moment applied to the robot base is shown,baseFbaserepresenting the forces acting on the base force sensor due to the dynamics of the robot itself,baseMbaseindicating characteristics of dynamics due to the robot itselfMoment of force acting on the base force sensor, saidbaseFbaseAndbaseMbasethe values of (c) can be derived from the newton-euler equation.
Optionally, the coordinates of TCP in the robot end coordinate system are calculated according to the following formula:
Figure BDA0002797202790000033
wherein r is a coordinate of a force action point in a robot terminal coordinate system and a 3-dimensional vector; m is the contact moment of the tail end of the robot, and is a 3-dimensional vector; f is the contact force of the robot tip, a 3-dimensional vector,
Figure BDA0002797202790000034
according to the TCP quick calibration method provided by the disclosure, the TCP coordinates are calibrated by utilizing the contact force and moment information of the tail end of the robot, and as long as the description of the force and moment borne by the TCP in the coordinate system of the tail end of the robot can be measured, the coordinate values of the TCP in the coordinate system of the tail end of the robot can be obtained by solving a constraint equation. Compared with the prior art, the beneficial effect of this disclosure is: firstly, the contact force and moment information of the tail end of the robot is adopted to calculate the TCP coordinate, the TCP coordinate value can be measured only by one-time contact, and the calibration time is saved; secondly, the calibration can be automatically completed by the controller without manual point alignment or calibration, and meanwhile, no form and precision requirements are required on the fixed surface; and thirdly, for a tool with certain flexibility, the TCP calibration precision can be ensured through a force control mode.
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The foregoing and other objects, features and advantages of the disclosure will be apparent from the following more particular descriptions of exemplary embodiments of the disclosure as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the disclosure.
Fig. 1 shows a flowchart of a robot TCP fast calibration method according to an exemplary embodiment.
Detailed Description
Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
Fig. 1 shows a flowchart of a robot TCP fast calibration method according to an exemplary embodiment, including the following steps:
s101: and setting the value of the calibration contact force according to the rigidity or hardness of the robot tool and the calibration surface.
S102: and adjusting the tail end attitude of the robot to meet the calibration requirement, namely ensuring that the contact force vector cannot be positioned in the x-y, y-z and x-z planes of the coordinate system of the force sensor.
S103: the control robot TCP is moved to a position close to the calibration surface and then the control mode of the robot is switched to the force control mode.
S104: and starting calibration, controlling the robot to move towards the calibration surface until the tail end of the robot is contacted with the calibration surface, and keeping the contact force above and below a set value, namely maintaining the contact force.
S105: when the contact force of the tail end of the robot is detected to enter a certain range above and below a set value, the contact force and the moment of the tail end of the robot in a period of time are collected.
Optionally: (1) in case the robot tip is integrated with a six-dimensional force sensor, i.e. the coordinate system of the sensor coincides with the tip coordinate system of the robot, the contact forces and moments of said robot tip are directly obtained from the six-dimensional force sensor.
(2) When a six-dimensional force sensor is additionally installed at the tail end of the robot, namely, when a coordinate system of the sensor does not coincide with a tail end coordinate system of the robot, the contact force and the moment of the tail end of the robot are obtained by the following methods:
Figure BDA0002797202790000051
wherein the content of the first and second substances,endFendindicating the contact force of the robot tip,endMendindicating the contact moment of the robot tip,
Figure BDA0002797202790000052
a rotation transformation matrix representing the force sensor coordinate system to the robot tip coordinate system,endPsensorrepresenting the coordinates of the robot end coordinate system origin in the force sensor coordinate system,sensorFsensorwhich is indicative of the force to which the force sensor is subjected,sensorMsensorrepresenting the moment experienced by the force sensor.
(3) For the condition that the robot is provided with a joint moment sensor, the contact force and moment of the tail end of the robot are calculated by the joint moment of the robot through the Jacobian matrix of the robot, namely
Fend＝J·(τsensor-τrobot)
Wherein, FendRepresenting forces and moments (6-dimensional vectors) at the end of the robot, J representing the Jacobian matrix of the robot, τsensorRepresenting the moment, τ, received by a joint moment sensor of the robotrobotRepresenting the moment acting on the joint moment sensor due to the dynamics of the robot itself, which can be derived from the newton-euler method.
(4) For the case where a six-dimensional force sensor is installed at a robot base, the contact force and moment of the robot tip are calculated by the following formulas:
Figure BDA0002797202790000053
wherein the content of the first and second substances,endFendindicating the contact force of the robot tip,endMendindicating the contact moment of the robot tip,
Figure BDA0002797202790000054
a rotation transformation matrix representing a base coordinate system to an end coordinate system of the robot,endPbaserepresenting the coordinates of the origin of the coordinate system of the robot end in the base coordinate system,sensorFsensorindicating the forces to which the robot base is subjected,sensorMsensorthe moment applied to the robot base is shown,baseFbaserepresenting the forces acting on the base force sensor due to the dynamics of the robot itself,baseMbaserepresenting the moment acting on the base force sensor due to the dynamics of the robot itself,baseFbaseandbaseMbasethe values of (c) can be derived from the newton-euler equation.
S106: from each set of force and moment values, an average of the force and moment is calculated.
S107: according to the force and moment average value obtained by calculation, the final TCP coordinate is obtained
After the mean values of the robot terminal force and the moment are obtained, the coordinates of the TCP in the robot terminal coordinate system can be calculated according to the following formula:
Figure BDA0002797202790000061
wherein r is the coordinate (3-dimensional vector) of the action point of the force in the robot terminal coordinate system, M is the contact moment (3-dimensional vector) of the robot terminal, F is the contact force (3-dimensional vector) of the robot terminal,
Figure BDA0002797202790000062
because the robot runs in a force control mode in the process that the TCP is in contact with the fixed surface, the method can ensure that the contact force is within a certain threshold value range. Thus, for tools with some flexibility, the present method can still be employed.
According to the rapid calibration method for the TCP of the robot, the description of the force and the moment applied to the TCP in the terminal coordinate system of the robot is measured, and then the coordinate value of the TCP in the terminal coordinate system of the robot is obtained by solving a constraint equation. Compared with the prior art, the beneficial effect of this disclosure is:
the TCP coordinate is calculated by adopting the tail end force and moment information, and the TCP coordinate value can be measured only by one-time contact, so that the calibration time is saved. And calibration can be automatically finished by the controller without manual point alignment or calibration. Meanwhile, no form and precision requirements are required on the fixed surface. And thirdly, for a tool with certain flexibility, the TCP calibration precision can be ensured through a force control mode.
The foregoing is illustrative of the present invention and various modifications and changes in form or detail will readily occur to those skilled in the art based upon the teachings herein and the application of the principles and principles disclosed herein, which are to be regarded as illustrative rather than restrictive on the broad principles of the present invention.

Claims (6)

1. A robot TCP quick calibration method is characterized by comprising the following steps:
setting the magnitude of the calibration contact force according to the rigidity or hardness of the robot tool and the calibration surface;
adjusting the tail end attitude of the robot to ensure that the contact force vector cannot be positioned in the x-y, y-z and x-z planes of the force sensor coordinate system;
controlling the TCP to move to a position close to the calibration surface, and then switching the robot to a force control mode;
controlling the tail end of the robot to contact with the calibration surface, and keeping the contact force above and below a set value;
when the contact force of the tail end of the robot is detected to enter a set range, acquiring the contact force and the moment of the tail end of the robot within a period of time, and solving the average value of the force and the moment;
obtaining a final TCP coordinate according to the average value of the force and the moment;
wherein the contact force and moment acquisition means of the robot tip comprises: the tail end of the robot is integrated with a six-dimensional force sensor, or the tail end of the robot is additionally provided with the six-dimensional force sensor, or the robot is provided with a joint torque sensor, or a robot base is provided with the six-dimensional force sensor.
2. The robot TCP quick calibration method according to claim 1, wherein in the case that a six-dimensional force sensor is integrated at the end of the robot, that is, the coordinate system of the sensor coincides with the end coordinate system of the robot, the contact force and the moment at the end of the robot are directly obtained from the six-dimensional force sensor.
3. The robot TCP quick calibration method according to claim 1, characterized in that, when a six-dimensional force sensor is additionally installed at the tail end of the robot, that is, the coordinate system of the sensor does not coincide with the tail end coordinate system of the robot, the contact force and moment of the tail end of the robot are obtained by the following method:
Figure DEST_PATH_IMAGE001
wherein the content of the first and second substances,
Figure 417736DEST_PATH_IMAGE002
indicating the contact force of the robot tip,
Figure DEST_PATH_IMAGE003
indicating the contact moment of the robot tip,
Figure 688180DEST_PATH_IMAGE004
a rotation transformation matrix representing the force sensor coordinate system to the robot tip coordinate system,
Figure DEST_PATH_IMAGE005
representing the coordinates of the robot end coordinate system origin in the force sensor coordinate system,
Figure 454011DEST_PATH_IMAGE006
which is indicative of the force to which the force sensor is subjected,
Figure DEST_PATH_IMAGE007
representing the moment experienced by the force sensor.
4. The TCP quick calibration method for the robot according to claim 1, wherein for the case that the robot is installed with a joint torque sensor, the contact force and torque of the robot end are calculated from the joint torque of the robot by the following formula, that is, the contact force and torque are calculated
Figure 936945DEST_PATH_IMAGE008
Wherein the content of the first and second substances,
Figure DEST_PATH_IMAGE009
representing the forces and moments at the end of the robot, as 6-dimensional vectors,
Figure 740340DEST_PATH_IMAGE010
a Jacobian matrix representing the robot,
Figure DEST_PATH_IMAGE011
representing the torque received by the joint torque sensor of the robot,
Figure 181686DEST_PATH_IMAGE012
representing the moment acting on the joint moment sensor due to the dynamics of the robot itself, which can be derived from the newton-euler method.
5. The robot TCP quick calibration method according to claim 1, wherein for the case that a six-dimensional force sensor is installed on a robot base, the contact force and moment of the robot end are calculated by the following formulas:
Figure DEST_PATH_IMAGE013
wherein the content of the first and second substances,
Figure 169233DEST_PATH_IMAGE014
indicating the contact force of the robot tip,
Figure DEST_PATH_IMAGE015
indicating the contact moment of the robot tip,
Figure 721437DEST_PATH_IMAGE016
a rotation transformation matrix representing a base coordinate system to an end coordinate system of the robot,
Figure DEST_PATH_IMAGE017
representing the coordinates of the origin of the coordinate system of the robot end in the base coordinate system,
Figure 845251DEST_PATH_IMAGE018
indicating the forces to which the robot base is subjected,
Figure DEST_PATH_IMAGE019
the moment applied to the robot base is shown,
Figure 191919DEST_PATH_IMAGE020
representing the forces acting on the base force sensor due to the dynamics of the robot itself,
Figure DEST_PATH_IMAGE021
representing the moment acting on the base force sensor due to the dynamics of the robot itself, said
Figure 932342DEST_PATH_IMAGE022
And
Figure DEST_PATH_IMAGE023
the values of (c) can be derived from the newton-euler equation.
6. A robot TCP quick calibration method according to any one of claims 2-5, characterized by calculating the coordinates of TCP in the robot end coordinate system according to the following formula:
Figure 302885DEST_PATH_IMAGE024
wherein the content of the first and second substances,
Figure DEST_PATH_IMAGE025
the coordinate of the action point of the force in a robot terminal coordinate system is a 3-dimensional vector;
Figure 546785DEST_PATH_IMAGE026
the contact torque at the tail end of the robot is a 3-dimensional vector;
Figure DEST_PATH_IMAGE027
is the contact force at the end of the robot, a 3-dimensional vector,
Figure 798775DEST_PATH_IMAGE028
。
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