Parallel robot pose calibration device and method based on self-resetting linear displacement sensor

Abstract

The present application relates to the field of robot measurement technology, and in particular to a parallel robot pose calibration device and method based on a self-resetting linear displacement sensor, comprising a self-resetting linear displacement sensor, a platform adapter plate and a spherical hinge, the pose of a coordinate system {M} in a coordinate system {B} is calculated through data measured by N self-resetting linear displacement sensors, and the position and attitude of the upper platform of the parallel robot relative to the lower platform of the parallel robot are calculated in combination with coordinate system conversion matrices H1 and H2; the pose calibration realized by the self-resetting linear sensor has a simple device structure and a low price, can be applied to any parallel robot system, and the pose calibration device can be installed inside a six-degree-of-freedom parallel robot, does not affect the movement of the six-degree-of-freedom parallel robot, and can cover the entire movement space of the six-degree-of-freedom parallel robot.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of robot measurement technology, in particular to a parallel robot pose calibration device and method based on a self-resetting linear displacement sensor. BACKGROUND

[0002] With the continuous breakthrough and development of robot technology, serial industrial robots are widely used in welding, handling and other fields due to their good flexibility. However, serial industrial robots also have certain structural defects, such as low positioning accuracy and poor load capacity. On the contrary, parallel industrial robots have high positioning accuracy and load capacity.

[0003] The typical structure of an N-degree-of-freedom parallel industrial robot is a Stewart parallel robot. The robot mainly connects the upper platform and the lower platform through N telescopic connecting rods, and the controller drives the N connecting rods to perform telescopic movement to make the moving platform reach different poses. The connecting rods can be driven in three ways: pneumatically, hydraulically or electrically. However, the control system is still a semi-closed loop control system, i.e. the position control accuracy of each connecting rod is only concerned in the motion controller of the Stewart parallel robot. There is also a lack of corresponding sensor system in the current hardware system of the Stewart parallel robot for detecting the end pose of the parallel robot. The pose calculation of the Stewart parallel robot mainly relies on the length of the connecting rod. However, the machining and assembly errors of the upper and lower platforms of the parallel robot cannot be reflected through the length feedback of the connecting rod, thereby affecting the accuracy performance of the parallel robot.

[0004] If the pose measurement of the parallel robot is to be realized, the current method is mainly based on external measurement equipment, such as a laser tracker and a stereo vision measurement system. Such measurement systems need to install some external measurement devices on the upper platform of the parallel robot, such as target balls for laser trackers and vision targets for stereo vision measurement systems. The measurement range of such devices is affected by the measurement range of the measurement target, and cannot cover the full motion range of the parallel robot. Currently, some pull wire sensors, inclinometers and inertial sensors are used to detect part of the pose information, but cannot obtain complete and accurate attitude data. SUMMARY

[0005] The first aspect of the present application proposes a technical solution, a parallel robot pose calibration device based on a self-resetting linear displacement sensor, characterized by comprising:

[0006] N self-resetting linear displacement sensors, which are centrally symmetrically distributed around the central axis of the parallel robot and parallel to the central axis of the parallel robot;

[0007] A platform adapter plate, comprising an upper platform adapter plate and a lower platform adapter plate, the upper platform adapter plate and the lower platform adapter plate are respectively fixed at the middle position of the bottom of the upper parallel robot platform and the middle position of the top of the lower parallel robot platform;

[0008] 2N spherical hinges are respectively fixed at the two ends of the N self-resetting linear displacement sensors and are respectively fixedly connected with the upper platform adapter plate and the lower platform adapter plate;

[0009] Wherein, the definitions are as follows:

[0010] The plane coordinate system in which the upper platform adapter plate is located is a measurement coordinate system {M1}, and the plane coordinate system in which the lower platform adapter plate is located is a base coordinate system {B1};

[0011] The plane in which the centers of the N spherical hinges connected with the upper platform adapter plate are located is an upper platform spherical hinge plane, and the coordinate system thereof is {M}, and the origin of the coordinate system is at the center of symmetry of the centers of the N spherical hinges;

[0012] The plane in which the centers of the N spherical hinges connected with the lower platform adapter plate are located is a lower platform spherical hinge plane, and the coordinate system thereof is {B}, and the origin of the coordinate system is at the center of symmetry of the centers of the N spherical hinges;

[0013] The conversion matrix between the measurement coordinate system {M1} and the coordinate system {M} is defined as H1;

[0014] The conversion matrix between the base coordinate system {B1} and the coordinate system {B} is defined as H2;

[0015] The pose matrix T of the coordinate system {M} relative to the coordinate system {B} is obtained according to the data measured by the N self-resetting linear displacement sensors;

[0016] The pose conversion matrix T1 of the measurement coordinate system {M1} relative to the base coordinate system {B1} is H1·T·H2.

[0017] Preferably, the upper platform adapter plate can follow the synchronous motion of the upper parallel robot platform, and when the upper parallel robot platform moves, the 2N spherical hinges follow the motion position and attitude of the upper parallel robot platform, and the angles and lengths of the N self-resetting linear displacement sensors follow the changes of the motion position and attitude of the upper parallel robot platform.

[0018] Preferably, the self-resetting linear displacement sensors are six in number, and the spherical hinges are twelve in number.

[0019] Preferably, the spherical hinge comprises a first connecting rod, a second connecting rod and a spherical hinge joint, the first connecting rod and the second connecting rod are hinged through the spherical hinge joint, and the deflection angle between the first connecting rod and the second connecting rod is greater than the inclination angle of the line connecting the center point of the upper platform of the parallel robot and the center point of the lower platform of the parallel robot.

[0020] Preferably, twelve first connecting rods are respectively and perpendicularly fixedly connected with the upper platform adapter plate and the lower platform adapter plate, and twelve second connecting rods are respectively fixedly connected with two ends of six self-resetting linear displacement sensors.

[0021] Preferably, for the pose calculation of the coordinate system {M} in the coordinate system {B}, the following definitions are made:

[0022] r i =[ B r xi B r yi B r zi ] T Bi is the position vector of the spherical hinge center of the i-th spherical hinge in the lower platform spherical hinge plane in the coordinate system {B};

[0023] P i =[ M P xi M P yi M P zi ] T Mi is the position vector of the spherical hinge center of the i-th spherical hinge in the upper platform spherical hinge plane in the coordinate system {M};

[0024] X j =[ B x j B y j B z j ] T X is the position vector of the origin of the coordinate system {M} in the coordinate system {B} when the upper platform spherical hinge plane is in the j-th pose;

[0025] L ij =[ B l xij B l yij B l zij ] T L is the position vector of the self-resetting linear displacement sensor in the lower platform spherical hinge plane coordinate system {B};

[0026] Vector r i , P i , X j , L ij constitutes a closed space vector ring;

[0027] When the upper platform of the parallel robot moves to a set position, the upper platform spherical hinge plane reaches the jth pose, and the vector ring formed by the N self-resetting linear displacement sensors respectively can be expressed as:

[0028] L ij =R j P i +X j -r i (1)

[0029] In formula (1), R j is the rotation transformation matrix of the coordinate system {M j} relative to the coordinate system {B} when the upper platform spherical hinge plane reaches the jth pose, and the expression of the transformation matrix is:

[0030]

[0031] In formula (2), C j =[α β γ] T represents an Euler angle vector, wherein α is the rotation angle around the Z axis, β is the rotation angle around the new Y axis, and γ is the rotation angle around the new X axis;

[0032] The length of the ith self-resetting linear displacement sensor at the jth pose is:

[0033]

[0034] By measuring the lengths of the N self-resetting linear displacement sensors l=[l1 l2 l3 l4 l5 l6] T , an equation for solving the pose P=[x y z α β γ] T of the upper platform spherical hinge plane is established.

[0035] According to the kinematic model of the pose calibration device established above, the nonlinear equation group shown in formula (4) can be derived from formulas (1), (2), and (3):

[0036]

[0037] By inputting the lengths of the N self-resetting linear displacement sensors, the corresponding pose P=[x y z α β γ] T can be obtained by solving the nonlinear equation group of formula (4).

[0038] Preferably, the upper platform adapter plate and the lower platform adapter plate are arranged as circular plates, and the upper platform adapter plate and the lower platform adapter plate are centrally symmetrically distributed along the center line of the upper platform and the lower platform of the parallel robot.

[0039] Preferably, the upper platform adapter plate and the lower platform adapter plate are arranged as circular plates, and the upper platform adapter plate and the lower platform adapter plate are centrally symmetrically distributed along the center line of the upper platform and the lower platform of the parallel robot.

[0040] The second aspect of the present application provides a technical solution, a parallel robot pose calibration method based on a self-resetting linear displacement sensor, which applies the parallel robot pose calibration device based on the self-resetting linear displacement sensor described above, and includes the following steps:

[0041] Step 1, define the pose matrix of the pose calibration device, and calculate the kinematics model based on the Stewart parallel robot;

[0042] Step 2, calculate the pose of the upper platform spherical hinge plane coordinate system in the lower platform spherical hinge plane coordinate system:

[0043] Definition: the plane where the centers of the six spherical hinges connected with the upper platform adapter plate are the upper platform spherical hinge plane, and the coordinate system is {M}, and the origin of the coordinate system is at the center of symmetry of the six spherical hinge centers;

[0044] The plane where the centers of the six spherical hinges connected with the lower platform adapter plate are the lower platform spherical hinge plane, and the coordinate system is {B}, and the origin of the coordinate system is at the center of symmetry of the six spherical hinge centers;

[0045] The lengths of the six self-resetting linear displacement sensors can be measured as l = [l1 l2 l3 l4 l5 l6] T , and the equation for solving the pose P = [x y z a b g] of the upper platform spherical hinge plane is established; T

[0046] Step 3, calculate the pose of the upper platform of the parallel robot in the base coordinate system of the parallel robot:

[0047] Definition: the transformation matrix between the coordinate system {M1} and the coordinate system {M} is defined as H1;

[0048] The transformation matrix between the coordinate system {B1} and the coordinate system {B} is defined as H2;

[0049] According to the data measured by the N self-resetting linear displacement sensors in step 2, the pose matrix T of the coordinate system {M} relative to the coordinate system {B} is obtained;

[0050] ​The pose conversion matrix T1 of the measurement coordinate system {M1} relative to the base coordinate system {B1} is: H1·T·H2.

[0051] Preferably, in step 2, the pose P of the upper platform spherical hinge plane is determined by solving the following equations: T Solving the equations:

[0052] Define r i = B r xi B r yi B r zi ] T , (i = 1, … 6) is the position vector of the i-th spherical hinge center Bi in the lower platform spherical hinge plane in the coordinate system {B};

[0053] P i = M P xi M P yi M P zi ] T , (i = 1, … 6) is the position vector of the i-th spherical hinge center Mi in the upper platform spherical hinge plane in the coordinate system {M};

[0054] X j = B x j B y j B z j ] T is the position vector of the origin of the coordinate system {M} in the coordinate system {B} when the upper platform spherical hinge plane is at the j-th pose;

[0055] L ij = B l xij B l yij B l zij ] T is the position vector of the self-resetting linear displacement sensor in the lower platform spherical hinge plane coordinate system {B};

[0056] The vectors r i , P i , X j , L ij form a closed spatial vector ring;

[0057] When the upper platform of the parallel robot moves to a set position, the upper platform spherical hinge plane reaches the jth pose, and a vector ring formed by the N self-resetting linear displacement sensors can be expressed as:

[0058] L ij = R j P i + X j -r i (1)

[0059] In formula (1), R j is a rotation transformation matrix of the coordinate system {M j} relative to the coordinate system {B} when the upper platform spherical hinge plane reaches the jth pose, and the expression of the transformation matrix is:

[0060]

[0061] In formula (2), C j = [alpha beta gamma] T represents an Euler angle vector, wherein alpha is a rotation angle around the Z axis, beta is a rotation angle around the new Y axis, and gamma is a rotation angle around the new X axis;

[0062] The length of the ith self-resetting linear displacement sensor at the jth pose is:

[0063]

[0064] Six measurable self-resetting linear displacement sensor lengths l = [l1 l2 l3 l4 l5 l6] T are used to establish an equation for solving the pose P = [x y z alpha beta gamma] T of the upper platform spherical hinge plane.

[0065] According to the kinematic model of the pose calibration device established above, the nonlinear equation group shown in formula (4) can be derived from formulas (1), (2) and (3):

[0066]

[0067] By inputting the lengths of the six self-resetting linear displacement sensors (1), the corresponding pose P = [x y z alpha beta gamma] T can be obtained by solving the nonlinear equation group of formula (4).

[0068] Compared with the prior art, the advantages of the present application are:

[0069] The parallel robot pose calibration device provided by the application is simple in structure, low in price, and can be applied to any parallel robot system, and the pose calibration device can be installed in the interior of the six-degree-of-freedom parallel robot, which does not affect the movement of the six-degree-of-freedom parallel robot and can cover the whole movement space of the six-degree-of-freedom parallel robot. BRIEF DESCRIPTION OF DRAWINGS

[0070] The accompanying drawings are not intended to be drawn to scale. In the drawings, each same or approximately same component shown in each drawing can be denoted by the same reference numeral. For the sake of clarity, not every component is labeled in each drawing. Embodiments of various aspects of the present application will now be described, by way of example only, with reference to the accompanying drawings in which:

[0071] Figure 1 is a mounting structure schematic view of the parallel robot pose calibration device based on the self-resetting linear displacement sensor shown in the embodiment of the application;

[0072] Figure 2 is a front view structure schematic view of Figure 1 ;

[0073] Figure 3 is a three-dimensional structure schematic view of the parallel robot pose calibration device based on the self-resetting linear displacement sensor shown in the embodiment of the application from a first perspective;

[0074] Figure 4 is a three-dimensional structure schematic view of the parallel robot pose calibration device based on the self-resetting linear displacement sensor shown in the embodiment of the application from a second perspective;

[0075] Figure 5 is a coordinate system relative relationship schematic view of the parallel robot pose calibration device based on the self-resetting linear displacement sensor shown in the embodiment of the application. DETAILED DESCRIPTION

[0076] In order to better understand the technical content of the application, specific embodiments are described below with reference to the accompanying drawings.

[0077]

Parallel robot pose calibration device based on self-resetting linear displacement sensor

[0078] In combination with Figure 1 and Figure 2As shown, the first aspect of the present application provides a technical solution, a parallel robot pose calibration device based on self-resetting linear displacement sensor, self-resetting linear displacement sensor 1, platform adapter plate 3 and spherical hinge 2, wherein the parallel robot 100 has a parallel robot 100 upper platform and a parallel robot 100 lower platform, and six electric cylinders are arranged between the parallel robot 100 upper platform and the parallel robot 100 lower platform. Generally, the parallel robot 100 lower platform is fixed on the ground, and by the extension and retraction of the six electric cylinders, the parallel robot 100 upper platform can be tilted at a preset angle relative to the parallel robot 100 lower platform.

[0079] The purpose of the present application is to accurately measure the pose of the parallel robot 100 upper platform, wherein N self-resetting linear displacement sensors 1 are arranged between the parallel robot 100 upper platform and the parallel robot 100 lower platform, the N self-resetting linear displacement sensors 1 are centrally symmetrically distributed around the central axis of the parallel robot 100 and parallel to the central axis of the parallel robot 100, and the platform adapter plate 3 includes an upper platform adapter plate 31 and a lower platform adapter plate 32. The upper platform adapter plate 31 and the lower platform adapter plate 32 are respectively fixed at the middle position of the bottom of the parallel robot 100 upper platform and the middle position of the top of the parallel robot 100 lower platform.

[0080] Further, N spherical hinges 2 are arranged between the upper platform adapter plate 31 and the self-resetting linear displacement sensor 1, and N spherical hinges 2 are also arranged between the lower platform adapter plate 32 and the self-resetting linear displacement sensor 1. The two ends of the spherical hinge 2 are respectively fixedly connected with the self-resetting linear displacement sensor 1, the upper platform adapter plate 31 and the lower platform adapter plate 32.

[0081] In this way, when the parallel robot 100 upper platform is driven to move, the upper platform adapter plate 31 can follow the synchronous movement of the parallel robot 100 upper platform, and when the parallel robot 100 upper platform moves, the 2N spherical hinges 2 follow the movement position and attitude of the parallel robot 100 upper platform, and the angle and length of the N self-resetting linear displacement sensors 1 follow the change of the movement position and attitude of the parallel robot 100 upper platform.

[0082] In combination Figure 3 and Figure 4 As shown in the preferred embodiment, the self-resetting linear displacement sensor 1 is arranged as six, and the spherical hinge 2 is arranged as twelve.

[0083] Further, the upper platform adapter plate 31 and the lower platform adapter plate 32 are both arranged as circular plates, and the upper platform adapter plate 31 and the lower platform adapter plate 32 are centrally symmetrically distributed along the central line of the parallel robot 100 upper platform and lower platform.

[0084] The spherical hinge 2 comprises a first connecting rod 21, a second connecting rod 22 and a spherical hinge joint 23, and the first connecting rod 21 and the second connecting rod 22 are hinged through the spherical hinge joint 23.

[0085] Specifically, the twelve first connecting rods 21 are respectively fixedly connected with the upper platform adapter plate 31 and the lower platform adapter plate 32 perpendicularly, the twelve second connecting rods 22 are respectively fixedly connected with two ends of the six self-resetting linear displacement sensors 1, the peripheral edges of the upper platform adapter plate 31 and the lower platform adapter plate 32 are respectively and uniformly provided with six spherical hinges 2, and the twelve spherical hinges 2 are centrally symmetrically distributed along the center line of the upper platform and the lower platform of the parallel robot 100.

[0086] Preferably, in order to ensure that the calibration device does not affect the movement of the parallel robot 100 when the parallel robot 100 performs multi-angle posture movement, the deflection angle between the first connecting rod 21 and the second connecting rod 22 is greater than the inclination angle of the center line connecting the center point of the upper platform of the parallel robot 100 and the center point of the lower platform of the parallel robot 100.

[0087] Further, the plane coordinate system in which the upper platform adapter plate 31 is located is defined as a measurement coordinate system {M1}, the plane coordinate system in which the lower platform adapter plate 32 is located is defined as a base coordinate system {B1}, the plane in which the centers of the N spherical hinges 2 connected with the upper platform adapter plate 31 are located is defined as an upper platform spherical hinge plane, and the coordinate system is defined as {M}, and the origin of the coordinate system is at the symmetry center of the N spherical hinge centers; the plane in which the centers of the N spherical hinges 2 connected with the lower platform adapter plate 32 are located is defined as a lower platform spherical hinge plane, and the coordinate system is defined as {B}, and the origin of the coordinate system is at the symmetry center of the N spherical hinge centers.

[0088] Further, the distance between the upper platform adapter plate 31 and the upper platform spherical hinge plane is the length of the known first connecting rod 21 and the thickness of the upper platform adapter plate 31, and is h1, and thus the coordinate system conversion matrix between the plane coordinate system {M1} in which the upper platform adapter plate 31 is located and the plane coordinate system {M} in which the upper platform spherical hinge plane is located is defined as H1.

[0089] The distance between the lower platform adapter plate 32 and the lower platform spherical hinge plane is the length of the known first connecting rod 21 and the thickness of the lower platform adapter plate 32, and is h2, and thus the coordinate system conversion matrix between the plane coordinate system {B1} in which the lower platform adapter plate 32 is located and the plane coordinate system {B} in which the lower platform spherical hinge plane is located is defined as H2.

[0090] Thus, for the pose calculation of the coordinate system {M} in the coordinate system {B}, the following definitions are made:

[0091] r i = B r xi B r yi B rzi ] T (i = 1, ..., 6) is the position vector of the center Bi of the i-th ball joint 2 in the lower platform ball joint plane in the coordinate system {B};

[0092] P i =[ M P xi M P yi M P zi ] T (i = 1, ..., 6) is the position vector of the center Mi of the i-th ball joint 2 on the upper platform ball joint plane in the coordinate system {M};

[0093] X j =[ B x j B y j B z j ] T Let {m} be the position vector of the origin of coordinate system {M} in coordinate system {B} when the upper platform ball joint plane is in the j-th pose;

[0094] L ij =[ B l xij B l yij B l zij ] T The position vector of the self-resetting linear displacement sensor 1 in the lower platform ball joint plane coordinate system {B};

[0095] Vector r i P i X j L ij This forms a closed spatial vector ring;

[0096] When the parallel robot moves to the set position on the platform, the ball joint plane of the platform reaches the j-th pose. The vector loops formed by the six self-resetting linear displacement sensors 1 can be represented as:

[0097] L ij =R j P i +X j -r i (1)

[0098] In equation (1), R j When the upper platform ball joint plane reaches the j-th pose, the coordinate system {M} j The transformation matrix relative to coordinate system {B} is expressed as follows:

[0099]

[0100] In formula (2), C j =[α β γ] T represents an Euler angle vector, wherein α is an angle of rotation around the Z axis, β is an angle of rotation around the new Y axis, and γ is an angle of rotation around the new X axis;

[0101] The length of the ith self-resetting linear displacement sensor in the jth pose is:

[0102]

[0103] The lengths l of the N self-resetting linear displacement sensors 1 that can be measured are: T , and an equation for solving the pose P of the upper platform spherical hinge plane is established. T ;

[0104] According to the kinematic model of the pose calibration device established above, the nonlinear equation group shown in formula (4) can be derived from formula (1), (2) and (3):

[0105]

[0106] By inputting the lengths of the N self-resetting linear displacement sensors 1, the corresponding pose P of the upper platform spherical hinge plane can be obtained by solving the nonlinear equation group of formula (4). T .

[0107] The pose of the coordinate system {M} in the coordinate system {B} is calculated through the data measured by the N self-resetting linear displacement sensors 1, and the position and attitude of the upper platform of the parallel robot 100 relative to the lower platform of the parallel robot 100 are calculated in combination with the coordinate system conversion matrices H1 and H2.

[0108] The second aspect of the present application provides a technical solution, a parallel robot pose calibration method based on a self-resetting linear displacement sensor, which applies the parallel robot pose calibration device based on the self-resetting linear displacement sensor described above, and includes the following steps:

[0109] Step one, define the pose matrix of the pose calibration device, and calculate the kinematic model based on the Stewart parallel robot;

[0110] Step two, calculate the pose of the upper platform spherical hinge plane coordinate system in the lower platform spherical hinge plane coordinate system:

[0111] Definition: The plane coordinate system in which the upper platform adapter plate 31 is located is the measurement coordinate system {M1}, and the plane coordinate system in which the lower platform adapter plate 32 is located is the base coordinate system {B1};

[0112] The plane in which the centers of the six spherical hinges 2 connected with the upper platform adapter plate 31 are located is the upper platform spherical hinge plane, and the coordinate system is {M}, with the origin of the coordinate system at the center of symmetry of the six spherical hinge centers;

[0113] The plane in which the centers of the six spherical hinges 2 connected with the lower platform adapter plate 32 are located is the lower platform spherical hinge plane, and the coordinate system is {B}, with the origin of the coordinate system at the center of symmetry of the six spherical hinge centers;

[0114] The lengths l = [l1 l2 l3 l4 l5 l6] of the six self-resetting linear displacement sensors 1 that can be measured are obtained; T The equation for solving the pose P = [x y z a b g] of the upper platform spherical hinge plane is established; T

[0115] Step three, calculate the pose of the upper platform of the parallel robot 100 in the base coordinate system of the parallel robot 100:

[0116] Definition:

[0117] The transformation matrix between the coordinate system {M1} and the coordinate system {M} is defined as H1;

[0118] The transformation matrix between the coordinate system {B1} and the coordinate system {B} is defined as H2;

[0119] According to the data measured by the N self-resetting linear displacement sensors in step 2, the pose matrix T of the coordinate system {M} relative to the coordinate system {B} is obtained;

[0120] The pose transformation matrix T1 of the measurement coordinate system {M1} relative to the base coordinate system {B1} is H1·T·H2.

[0121] Specifically, in step 2, for the upper platform spherical hinge plane pose P = [x y z a b g] T The equation is solved:

[0122] Define r i = B r xi B r yi B r zi ] T , (i = 1, …, 6) as the position vector of the i-th spherical hinge (2) in the lower platform spherical hinge plane Bi in the coordinate system {B};

[0123] P​i =[ M P xi M P yi M P zi ] T , (i = 1, ... 6) is the position vector of the center Mi of the i-th ball joint (2) of the upper platform ball joint plane in the coordinate system {M};

[0124] X j =[ B x j B y j B z j ] T Let {m} be the position vector of the origin of coordinate system {M} in coordinate system {B} when the upper platform ball joint plane is in the j-th pose.

[0125] L ij =[ B l xij B l yij B l zij ] T The position vector of the self-resetting linear displacement sensor in the lower platform ball joint plane coordinate system {B};

[0126] Vector r i P i X j L ij This forms a closed spatial vector ring;

[0127] When the parallel robot 100 moves to the set position on the upper platform, the ball joint plane of the upper platform reaches the j-th pose. The vector loops formed by the N self-resetting linear displacement sensors 1 can be represented as:

[0128] L ij =R j P i +X j -r i (1)

[0129] In equation (1), R j When the upper platform ball joint plane reaches the j-th pose, the coordinate system {M} j The transformation matrix relative to coordinate system {B} is expressed as follows:

[0130]

[0131] In equation (2), C j=[α β γ] T represents Euler angle vector, wherein alpha is the rotation angle around the Z axis, beta is the rotation angle around the new Y axis, and gamma is the rotation angle around the new X axis;

[0132] The length of the i-th self-resetting linear displacement sensor 1 in the j-th pose is:

[0133]

[0134] The six measurable lengths of the self-resetting linear displacement sensors (1) are l=[l1 l2 l3 l4 l5 l6] T , and an equation for solving the pose P=[x y z α β γ] of the upper platform spherical hinge is established; T

[0135] According to the kinematic model of the pose calibration device established above, the nonlinear equation group shown in formula (4) can be derived from formula (1), (2) and (3):

[0136]

[0137] By inputting the lengths of the six self-resetting linear displacement sensors 1, the corresponding pose P=[x y z α β γ] can be obtained by solving the nonlinear equation group of formula (4). T

[0138] In combination with the above embodiments, the parallel robot pose calibration device provided by the application can realize the calibration of the pose by the self-resetting linear displacement sensor 1, has simple structure and low price, and can be applied to any parallel robot system. Meanwhile, the pose calibration device can be installed inside the six-degree-of-freedom parallel robot, does not affect the movement of the six-degree-of-freedom parallel robot, and can cover the entire movement space of the six-degree-of-freedom parallel robot.

[0139] Although the application has been disclosed as above with reference to the preferred embodiments, it is not intended to limit the application. Those skilled in the art can make various modifications and improvements without departing from the spirit and scope of the application. Therefore, the protection scope of the application shall be subject to the scope defined by the claims.​​

Claims

1. A parallel robot pose calibration device based on self-resetting linear displacement sensor, characterized in that, The device comprises: N self-resetting linear displacement sensors, which are symmetrically distributed around the central axis of the parallel robot and are parallel to the central axis of the parallel robot; a platform adapter plate, which comprises an upper platform adapter plate and a lower platform adapter plate, and the upper platform adapter plate and the lower platform adapter plate are respectively fixed at the middle bottom of the upper platform of the parallel robot and the middle top of the lower platform of the parallel robot; 2N spherical hinges, which are respectively fixed at the two ends of the N self-resetting linear displacement sensors and are respectively fixedly connected with the upper platform adapter plate and the lower platform adapter plate; wherein a coordinate system of the plane where the upper platform adapter plate is located is defined as a measurement coordinate system {M1}, and a coordinate system of the plane where the lower platform adapter plate is located is defined as a base coordinate system {B1}; a plane where the centers of the N spherical hinges connected with the upper platform adapter plate are located is an upper platform spherical hinge plane, and a coordinate system thereof is {M}, and the origin of the coordinate system is at the center of symmetry of the centers of the N spherical hinges; a plane where the centers of the N spherical hinges connected with the lower platform adapter plate are located is a lower platform spherical hinge plane, and a coordinate system thereof is {B}, and the origin of the coordinate system is at the center of symmetry of the centers of the N spherical hinges; a conversion matrix between the measurement coordinate system {M1} and the coordinate system {M} is defined as H1; a conversion matrix between the base coordinate system {B1} and the coordinate system {B} is defined as H2; a pose matrix T of the coordinate system {M} relative to the coordinate system {B} is obtained according to the data measured by the N self-resetting linear displacement sensors; a pose conversion matrix T1 of the measurement coordinate system {M1} relative to the base coordinate system {B1} is H1·T·H2.

2. The self-resetting linear displacement sensor based parallel robot pose calibration apparatus according to claim 1, wherein, The upper platform adapter plate can follow the synchronous movement of the upper platform of the parallel robot, and when the upper platform of the parallel robot moves, the 2N spherical hinges follow the movement position and attitude of the upper platform of the parallel robot, and the angle and length of the N self-resetting linear displacement sensors change with the movement position and attitude of the upper platform of the parallel robot.

3. The self-resetting linear displacement sensor based parallel robot pose calibration apparatus according to claim 2, wherein, The self-resetting linear displacement sensors are six in number, and the spherical hinges are twelve in number.

4. The self-resetting linear displacement sensor based parallel robot pose calibration apparatus according to claim 3, wherein, The spherical hinge comprises a first connecting rod, a second connecting rod and a spherical hinge joint, the first connecting rod and the second connecting rod are hingedly connected through the spherical hinge joint, and the deflection angle between the first connecting rod and the second connecting rod is greater than the inclination angle of the line connecting the center point of the upper platform of the parallel robot and the center point of the lower platform of the parallel robot.

5. The self-resetting linear displacement sensor based parallel robot pose calibration apparatus according to claim 4, wherein, Twelve first connecting rods are respectively fixedly connected with the upper platform adapter plate and the lower platform adapter plate, and twelve second connecting rods are respectively fixedly connected with the two ends of the six self-resetting linear displacement sensors.

6. The self-resetting linear displacement sensor based parallel robot pose calibration apparatus according to claim 2, wherein, For the pose calculation of the coordinate system {M} in the coordinate system {B}, it is defined that: r i = [ B r xi B r yi B r zi ] T Bi(i = 1,..., 6) is the position vector of the ball joint center Bi of the i-th ball joint in the lower platform ball joint plane in the coordinate system {B}; P i = [ M P xi M P yi M P zi ] T Mi is the position vector of the ball joint center Mi of the ith ball joint of the upper platform ball joint plane in the coordinate system {M}. X j = [ B x j B y j B z j ] T is the position vector of the origin of the coordinate system {M} in the coordinate system {B} at the jth pose of the upper platform spherical hinge plane; L ij = [ B l xij B l yij B l zij ] T is the position vector of the self-resetting linear displacement sensor in the lower platform spherical hinge plane coordinate system {B}; Vector r i , P i , X j , L ij constitutes a closed space vector ring; when the upper platform of the parallel robot moves to a set position, the upper platform spherical hinge plane reaches the jth pose, and the vector ring formed by the N self-resetting linear displacement sensors can be expressed as: L ij = R j P i + X j - r i (1) In formula (1), R j is the rotation transformation matrix of the coordinate system {M j} relative to the coordinate system {B} when the upper platform spherical hinge plane reaches the jth pose, and the expression of the transformation matrix is: In formula (2), C j = [a b g] T denotes an Euler angle vector, where a is the angle of rotation about the Z axis, b is the angle of rotation about the new Y axis, and g is the angle of rotation about the new X axis. the length of the ith self-resetting linear displacement sensor at the jth pose is: The lengths l = [l1 l2 l3 l4 l5 l6] of N self-resetting linear displacement sensors are measurable T Equations are established to solve the pose P = [x y z a b g] of the upper platform spherical hinge plane T ​ According to the kinematic model of the pose calibration device established above, the nonlinear equation group shown in the formula can be derived from formulas (1), (2) and (3). Input the length of N self-resetting linear displacement sensors, and the corresponding pose P = [x y z a b g] can be obtained by solving the nonlinear equations of formula (4). T .

7. The self-resetting linear displacement sensor based parallel robot pose calibration apparatus according to claim 3, wherein, The upper platform adapter plate and the lower platform adapter plate are arranged as circular plates, and the upper platform adapter plate and the lower platform adapter plate are centrally symmetrically distributed along the center line of the upper platform and the lower platform of the parallel robot.

8. The self-resetting linear displacement sensor based parallel robot pose calibration apparatus according to claim 7, wherein, The circumferential edges of the upper platform adapter plate and the lower platform adapter plate are respectively uniformly provided with six ball hinges, and twelve ball hinges are centrally symmetrically distributed along the center line of the upper platform and the lower platform of the parallel robot.

9. A parallel robot pose calibration method based on a self-resetting linear displacement sensor, characterized by, The parallel robot pose calibration device based on the self-resetting linear displacement sensor of claim 3 comprises the following steps: Step one, define the pose matrix calculation of the pose calibration device based on the kinematic model of the Stewart parallel robot; Step two, calculate the pose of the upper platform ball hinge plane coordinate system in the lower platform ball hinge plane coordinate system: Definition: the plane coordinate system in which the upper platform adapter plate is located is the measurement coordinate system {M1}, and the plane coordinate system in which the lower platform adapter plate is located is the base coordinate system {B1}; The plane in which the centers of the six ball hinges connected with the upper platform adapter plate are located is the upper platform ball hinge plane, and the coordinate system is {M}, and the origin of the coordinate system is at the symmetry center of the six ball hinge centers; The plane in which the centers of the six ball hinges connected with the lower platform adapter plate are located is the lower platform ball hinge plane, and the coordinate system is {B}, and the origin of the coordinate system is at the symmetry center of the six ball hinge centers; The lengths l = [l1 l2 l3 l4 l5 l6] of the six self-resetting linear displacement sensors are measured. T Equations are established to solve the pose P = [x y z a b g] of the upper platform spherical hinge plane. T Equations are established to solve the pose P = [x y z a b g] of the upper platform spherical hinge plane. Step three, calculate the pose of the upper platform of the parallel robot in the base coordinate system of the parallel robot: Definition: the transformation matrix between the coordinate system {M1} and the coordinate system {M} is defined as H1; The transformation matrix between the coordinate system {B1} and the coordinate system {B} is defined as H2; According to the data measured by the N self-resetting linear displacement sensors, the pose matrix T of the coordinate system {M} relative to the coordinate system {B} is obtained; The pose transformation matrix T1 of the measurement coordinate system {M1} relative to the base coordinate system {B1} is H1·T·H2.

10. The self-resetting linear displacement sensor based parallel robot pose calibration method according to claim 9, wherein, In step 2, the upper platform spherical hinge plane pose P = [x y z a b g] is solved for T Solution of the equations: Definition of r i = [ B r xi B r yi B r zi ] T Bi(i = 1,..., 6) is the position vector of the ball joint center Bi of the i-th ball joint in the lower platform ball joint plane in the coordinate system {B}; P i = [ M P xi M P yi M P zi ] T Mi(i = 1,..., 6) is the position vector of the ball joint center Mi of the i-th ball joint of the upper platform ball joint plane in the coordinate system {M}; X j = [ B x j B y j B z j ] T is the position vector of the origin of the coordinate system {M} in the coordinate system {B} at the j-th pose of the upper platform spherical hinge plane; L ij = [ B l xij B l yij B l zij ] T is the position vector of the self-resetting linear displacement sensor in the lower platform spherical hinge planar coordinate system {B}; Vector r i , P i , X j , L ij constitutes a closed space vector ring; When the upper platform of the parallel robot moves to a set position, the upper platform ball hinge plane reaches the jth pose, and the vector ring formed by the N self-resetting linear displacement sensors can be represented as: L ij = R j P i + X j - r i (1) In formula (1), R j is the rotation transformation matrix of the coordinate system {M j} relative to the coordinate system {B} when the upper platform spherical hinge plane reaches the jth pose, and the expression of the transformation matrix is: In formula (2), C j = [a β γ] T denotes an Euler angle vector, where a is the angle of rotation about the Z axis, β is the angle of rotation about the new Y axis, and γ is the angle of rotation about the new X axis. The length of the ith self-resetting linear displacement sensor at the jth pose is: The lengths l = [l1 l2 l3 l4 l5 l6] of the six self-resetting linear displacement sensors are measured. T Equations are established to solve the pose P = [x y z a b g] of the upper platform spherical hinge plane. T Equations are established to solve the pose P = [x y z a b g] of the upper platform spherical hinge plane. According to the kinematic model of the pose calibration device established above, the nonlinear equation group shown in formula (1), (2), (3) can be derived from formula (1), (2), (3): Input the length of six self-resetting linear displacement sensors (1), and the corresponding pose P = [x y z a b g] can be obtained by solving the nonlinear equations of formula (4). T .

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