CN211696245U - Video measuring instrument based on Tsai parallel mechanism - Google Patents
Video measuring instrument based on Tsai parallel mechanism Download PDFInfo
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- CN211696245U CN211696245U CN202020317527.8U CN202020317527U CN211696245U CN 211696245 U CN211696245 U CN 211696245U CN 202020317527 U CN202020317527 U CN 202020317527U CN 211696245 U CN211696245 U CN 211696245U
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Abstract
The utility model discloses a video measuring instrument based on a Tsai parallel mechanism, which belongs to the technical field of precision measurement, and comprises a bracket, a Tsai parallel motion module and a video sensor, wherein the bracket comprises a base, a stand column and a static platform, and the static platform is connected with the base through the stand column; the Tsai parallel motion module comprises a Tsai parallel mechanism, a driving motor, a revolute pair, a driving rod inclination angle sensor, a driven rod inclination angle sensor and a movable platform; the Tsai parallel mechanism, the driving motor and the rotating pair are fixedly connected with the static platform, and the video sensor is arranged on the movable platform; the Tsai parallel mechanism comprises three sets of connecting rod mechanisms, the three sets of connecting rod mechanisms are connected with the movable platform together, the driving rod inclination angle sensor is installed on the driving rod, and the driven rod inclination angle sensor is installed on the driven rod. The utility model discloses there is not accumulative error, mechanism response speed is fast, easily add, the precision is high, be applicable to the accurate transmission.
Description
Technical Field
The utility model belongs to the technical field of the precision measurement, more specifically relates to a video measuring apparatu based on Tsai parallel mechanism.
Background
The current video measurement technology is mature, can measure the geometric quantity in a larger range by means of an image processing technology and a precise displacement technology, has higher measurement precision, meets the measurement and analysis requirements of the fields of modern machining, microelectronics, semiconductors and the like, and is widely applied to scientific research institutions and industrial production.
At present, a common video measuring instrument mainly uses a Cartesian coordinate system and a spherical coordinate system, has strong universality, but has the defects of large series error, small rigidity and the like. If the precision requirement is higher, the traditional measuring instrument has high processing difficulty and high cost.
The parallel mechanism has the advantages of large rigidity, small motion inertia, error averaging effect and the like, is mature to be applied to parallel robots and parallel machine beds, but is not fully applied to the field of size detection.
The prior art discloses a precise video mapping analyzer, which adopts a cartesian coordinate system motion mechanism as a moving mechanism of a video measuring instrument, supports a vertical motion mechanism and a video sensor by using a gantry structure, controls the motion of the moving mechanism by a numerical control system, and performs video measurement on a measured workpiece by using precise displacement detection and image measurement technologies. The moving mechanism of the video measuring instrument adopts a Cartesian coordinate system structure, so that accumulated errors exist, and the response speed of the mechanism is low; meanwhile, the gantry structure is used for supporting the vertical displacement mechanism and the video sensor, so that the measuring range of the instrument is reduced.
The prior art discloses a three-coordinate measuring machine based on a Delta parallel mechanism and a measuring method, wherein the Delta parallel mechanism is used as a moving mechanism of a video measuring instrument. Compared with a traditional Cartesian three-coordinate moving mechanism, the Delta parallel mechanism is adopted, so that the dynamic response speed of the three-coordinate measuring machine is improved, and the rigidity of the mechanism is greatly improved. However, because the Delta parallel mechanism adopts the ball hinge joint, although the number of the mechanism parts is reduced and the installation is convenient, the ball hinge needs to precisely process the spherical surface, compared with the cylindrical surface, the processing difficulty is increased, and the precision is difficult to ensure, so the Delta parallel mechanism is only suitable for the occasions with lower precision requirements, but not suitable for precision transmission.
Therefore, the prior art has the technical problems of accumulated error, low mechanism response speed, high processing difficulty, difficulty in ensuring precision and inapplicability to precision transmission.
SUMMERY OF THE UTILITY MODEL
To the above defect of prior art or improve the demand, the utility model provides a video measuring apparatu based on Tsai parallel mechanism solves prior art from this and has accumulative error, and the mechanism response speed is slow, the processing degree of difficulty is big, the precision is difficult to guarantee, is not suitable for accurate driven technical problem.
In order to achieve the above object, the utility model provides a video measuring instrument based on Tsai parallel mechanism, include: a bracket, a Tsai parallel motion module and a video sensor,
the support comprises a base, an upright post and a static platform, and the static platform is connected with the base through the upright post;
the Tsai parallel motion module comprises a Tsai parallel mechanism, a driving motor, a revolute pair, a driving rod inclination angle sensor, a driven rod inclination angle sensor and a movable platform; the Tsai parallel mechanism, the driving motor and the rotating pair are fixedly connected with the static platform, and the video sensor is arranged on the movable platform;
the Tsai parallel mechanism comprises three sets of link mechanisms, the three sets of link mechanisms are jointly connected with the movable platform, each set of link mechanism comprises a driving rod, an upper connecting rod, a cylindrical pin, a driven rod, a lower connecting rod and a bearing, and the driving rod is connected with the upper connecting rod through the bearing; the upper connecting rod is hinged with the driven rod through a cylindrical pin, the driven rod is hinged with the lower connecting rod through a cylindrical pin, the driving rod inclination angle sensor is installed on the driving rod, and the driven rod inclination angle sensor is installed on the driven rod.
Further, three sets of connecting rods are evenly distributed in the space around the axis perpendicular to the center of the static platform in a circumferential mode.
Further, the lower connecting rod is connected with the movable platform through a bearing.
Furthermore, stand one end and base fixed connection, the other end and quiet platform fixed connection.
Furthermore, one end of the revolute pair is connected with the driving motor, and the other end of the revolute pair is connected with the driving rod.
Generally, through the utility model discloses above technical scheme who conceives compares with prior art, can gain following beneficial effect:
(1) compared with the traditional Cartesian coordinate system video measuring instrument, the utility model discloses a video measuring instrument based on Tsai parallel mechanism has that the dynamic response speed is fast, compact structure, and mechanism rigidity is high, and bearing capacity is big, does not have accumulative error, has characteristics such as better isotropy; meanwhile, compared with a ball hinge of a Delta parallel mechanism, the cylindrical hinge has small processing difficulty, the precision is easy to guarantee, and the measurement precision is high.
(2) The utility model discloses driving motor is connected to well revolute pair one end, and the driving lever is connected to the other end, and then just can guarantee through driving motor drive revolute pair that video sensor on the movable platform can carry out linear movement in the space.
Drawings
Fig. 1 is a schematic structural diagram of a video measuring instrument based on a Tsai parallel mechanism provided by the present invention;
fig. 2 is a left side view of a video measuring instrument based on the Tsai parallel mechanism provided by the present invention;
fig. 3 is a top view of a video measuring instrument based on the Tsai parallel mechanism provided by the present invention;
FIG. 4 is a schematic view of the joint connection between the driving rod and the driven rod provided by the present invention;
fig. 5 is a schematic view of the joint connection between the driven rod and the movable platform provided by the present invention;
fig. 6 (a) is a diagram of a measurement model of the Tsai parallel mechanism, and (b) is an enlarged detail view of the measurement model of the Tsai parallel mechanism;
FIG. 7 is a simplified block diagram of a Tsai parallel mechanism;
the same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
the device comprises a base 1, a stand column 2, a static platform 3, a driving motor 4, a revolute pair 5, a driving rod 6, a driving rod inclination angle sensor 7, a driven rod inclination angle sensor 8, an upper connecting rod 9, a cylindrical pin 10, a driven rod 11, a lower connecting rod 12, a video sensor 13, a workpiece to be measured 14, a movable platform 15 and a bearing 16.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in 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. Furthermore, the technical features mentioned in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
As shown in fig. 1, a video measuring instrument based on the Tsai parallel mechanism includes: the device comprises a support, a Tsai parallel motion module and a video sensor 13, wherein the support comprises a base 1, a stand column 2 and a static platform 3; stand 2 one end and base 1 fixed connection, the other end and quiet platform 3 fixed connection support quiet platform 3 through four stands 2.
The Tsai parallel motion module comprises three driving motors 4, three revolute pairs 5, a Tsai parallel mechanism, three driving rod inclination angle sensors 7, three driven rod inclination angle sensors 8 and a movable platform 15; one end of the revolute pair 5 is connected with the driving motor 4, the other end of the revolute pair is connected with the driving rod 6, and the movement of the Tsai parallel mechanism is controlled by controlling the rotation of the driving motor 4.
The Tsai parallel mechanism is composed of three sets of connecting rod mechanisms, each set of mechanism is composed of a driving rod 6, an upper connecting rod 9, a driven rod 11, a cylindrical pin 10, a bearing 15 and a lower connecting rod 12, and the three sets of connecting rods are connected with a movable platform 15 together.
As shown in fig. 2, the driving link inclination sensor 7 is mounted on the driving link 6, and the driven link inclination sensor 8 is mounted on the driven link 11. As shown in fig. 3, the three sets of links are spatially evenly distributed circumferentially about an axis perpendicular to the center of the stationary platform.
As shown in fig. 4, the driving link 6 is connected to the upper connecting link 9 via a bearing 16; the upper connecting rod 9 is hinged with a driven rod 11 through a cylindrical pin 10. As shown in fig. 5, the driven rod 11 is hinged with the lower connecting rod 12 through a cylindrical pin 10; the lower connecting rod 12 is connected with the movable platform 15 through a bearing 16.
A video sensor measuring instrument based on a Tsai parallel mechanism comprises the following steps of: and controlling the driving motor 4 to drive each revolute pair 5 to rotate, so that each driving rod 6 performs rotary motion, converting the rotary motion of the three driving rods 6 into spatial translation motion of the movable platform 15 through the Tsai parallel mechanism, translating the movable platform 15 to a required position and then stopping moving, aligning the lens of the video sensor 13 to the corresponding position of the surface of the workpiece 14 to be measured, performing video acquisition on the workpiece to be measured through the video sensor, and calculating the size of the workpiece to be measured in an image through image processing and analysis. Simultaneously reading angle measurement values of the driving rod inclination angle sensor 7 and the driven rod inclination angle sensor 8, calculating a spatial position coordinate of the center of the movable platform 15 relative to the center of the static platform 3 according to angle measurement data of the driving rod inclination angle sensor 7 and the driven rod inclination angle sensor 8 and part size data of the Tsai parallel mechanism, and obtaining a size measurement value of a measured workpiece 14 by combining the amplification factor and the focal length of the video sensor 13; combining the magnification factor, the focal length and the image processing result (the size of the measured workpiece in the image) of the video sensor 13 to obtain the spatial position coordinates of the measured workpiece 14 relative to the center of the video sensor 13; the spatial position coordinates of the center of the movable platform 15 relative to the center of the static platform 3, the spatial position coordinates of the workpiece 14 to be measured relative to the center of the video sensor 13 and the size measurement value of the workpiece 14 to be measured are combined, so that video measurement is realized.
As shown in (a) and (b) of fig. 6, a measurement model of a video sensor measuring instrument based on the Tsai parallel mechanism is as follows: a coordinate system O-XYZ is established on the static platform 3, the origin of coordinates O is positioned at the center of the static platform, the direction of a Z axis is vertical to the static platform and upwards, the positive direction of an X axis is that the point O is parallel to the static platform and points to the center of a revolute pair, and the right-hand rule determines the Y axis.
(1) And (3) calculating the Tsai parallel mechanism freedom degree F by using a space mechanism freedom degree calculation formula, wherein the formula is as follows:
wherein n is the number of components, g is the number of kinematic pairs of the mechanism,
mu is the sum of all kinematic pair degrees of freedom, and mu is an over-constraint number.
Analyzing the mechanism, the number of components is 17, the number of mechanism kinematic pairs is 21, all kinematic pair degrees of freedom 21 and over-constraint 21, and substituting the equations to obtain the Tsai parallel mechanism degrees of freedom.
F＝6×(17-21-1)+21+12＝3
Therefore, the Tsai parallel mechanism has 3 translational degrees of freedom, that is, the moving platform moves in translation in X, Y, Z three directions in the robot working space.
(2) Slightly modifying a Tsai parallel mechanism model, and adding 3 virtual rods between the middle points of the upper and lower sides of 3 4R closed-loop chains; a fixed coordinate system O-xyz and a moving coordinate system O '-x' y 'z' are respectively established on the static platform and the moving platform, the geometric center of the static platform is taken as an origin, and the axis of Ox and the axis of O 'x' are respectively parallel to A1A2And C1C2The Oy axis and the O 'y' axis are respectively perpendicular to A1A2And C1C2(ii) a The external circle radiuses of the static platform and the dynamic platform are R, r respectively, and the driving rod AiBiLength of laSide bar BiCiLength of lb，OAiα from the x-axisi，OAiTo AiBiThe angle of rotation being thetai。
For the convenience of analysis, the virtual bar B is usediCiRespectively along O' CiTranslating, crossing the geometric center of the movable platform, recording the point as P, and simultaneously driving a rod AiBiAlong O' CiTranslating to obtain a simplified model diagram as shown in FIG. 7, and simultaneously, using an active rod laAs a benchmark, dimensionless parametric analysis was performed.
(3) As shown in fig. 7, in the triangular pyramid P-Bo1Bo2Bo3In which E is Bo1Bo2Midpoint of the edge, H is △ Bo1Bo2Bo3The center of the circumscribed circle of (1), EH ⊥ Bo1Bo2And △ Bo1Bo2P is an isosceles triangle, then PE ⊥ Bo1Bo2Obtaining HP ⊥ B by the theorem of three perpendicular lines of solid geometryo1Bo2In the same way, HP ⊥ Bo2Bo3HP ⊥ bottom surface △ Bo1Bo2Bo3And HP is a perpendicular line to the bottom surface.
It was demonstrated above that the bottom foot H is the centroid of the bottom triangle.
The vector expression for the motion control point P is:
in the formula
in the formula
Is composed of
The length of (a) of (b),
is composed of
Syntropy unit vector, expressed as:
at the same time
In the formula
The method for calculating the radius of the ground circumscribed circle comprises the following steps:
in the formula (I), the compound is shown in the specification,
p＝(a+b+c)/2
in the formula, a, b and c are respectively the side length of three sides of delta BCD:
in the formula (I), the compound is shown in the specification,
is composed of
The length of (a) of (b),
is composed of
Unit vectors in the same direction.
From this, obtain
And obtaining the space coordinate point of the movable platform. And calculating the space position coordinate of the movable platform by reading the reading of the tilt angle sensor, and further measuring the workpiece to be measured.
The utility model provides a video measuring apparatu based on Tsai parallel mechanism, Tsai parallel mechanism simple structure, the cylinder hinge processing in the structure is made conveniently, and the joint precision is easily guaranteed, and processing is convenient, more is fit for and accurate transmission. Therefore, the utility model discloses can effectively improve video measuring apparatu's positioning accuracy, reduce its and make the degree of difficulty, the motion control of being convenient for.
It will be understood by those skilled in the art that the foregoing is merely a preferred embodiment of the present invention, and is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Claims (5)
1. A video measurement instrument based on a Tsai parallel mechanism, comprising: a bracket, a Tsai parallel motion module and a video sensor (13),
the support comprises a base (1), an upright post (2) and a static platform (3), wherein the static platform (3) is connected with the base (1) through the upright post (2);
the Tsai parallel motion module comprises a Tsai parallel mechanism, a driving motor (4), a revolute pair (5), a driving rod inclination angle sensor (7), a driven rod inclination angle sensor (8) and a moving platform (15); the Tsai parallel mechanism, the driving motor (4) and the revolute pair (5) are fixedly connected with the static platform (3), and the video sensor (13) is installed on the movable platform (15);
the Tsai parallel mechanism comprises three sets of link mechanisms, the three sets of link mechanisms are jointly connected with a movable platform (15), each set of link mechanism comprises a driving rod (6), an upper connecting rod (9), a cylindrical pin (10), a driven rod (11), a lower connecting rod (12) and a bearing (16), and the driving rod (6) is connected with the upper connecting rod (9) through the bearing (16); the upper connecting rod (9) is hinged to the driven rod (11) through a cylindrical pin (10), the driven rod (11) is hinged to the lower connecting rod (12) through the cylindrical pin (10), the driving rod inclination angle sensor (7) is installed on the driving rod (6), and the driven rod inclination angle sensor (8) is installed on the driven rod (11).
2. The Tsai parallel mechanism-based video measuring instrument according to claim 1, wherein the three sets of connecting rods are spatially and uniformly distributed circumferentially around an axis perpendicular to the center of the stationary platform (3).
3. The Tsai parallel mechanism-based video measuring instrument according to claim 1 or 2, wherein the lower connecting rod (12) is connected with the movable platform (15) through a bearing (16).
4. The Tsai parallel mechanism-based video measuring instrument as claimed in claim 1 or 2, wherein one end of the upright column (2) is fixedly connected with the base (1), and the other end is fixedly connected with the static platform (3).
5. The Tsai parallel mechanism-based video measuring instrument as claimed in claim 1 or 2, wherein one end of the revolute pair (5) is connected with the driving motor (4), and the other end is connected with the driving rod (6).
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111272072A (en) * | 2020-03-15 | 2020-06-12 | 华中科技大学 | Video measuring method and measuring instrument based on Tsai parallel mechanism |
| WO2023168967A1 (en) * | 2022-03-07 | 2023-09-14 | 诺创智能医疗科技(杭州)有限公司 | Robotic arm, robot, minimally invasive surgical robot system, method for determining pose of robotic arm, industrial production system, and method for controlling robot |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111272072A (en) * | 2020-03-15 | 2020-06-12 | 华中科技大学 | Video measuring method and measuring instrument based on Tsai parallel mechanism |
| WO2023168967A1 (en) * | 2022-03-07 | 2023-09-14 | 诺创智能医疗科技(杭州)有限公司 | Robotic arm, robot, minimally invasive surgical robot system, method for determining pose of robotic arm, industrial production system, and method for controlling robot |
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