A translational positioning mechanism and positioning method suitable for a parallel structure

Abstract

The application relates to a parallel structure suitable for a translational positioning mechanism and a positioning method, wherein an elastic feedback device is arranged on an existing parallelogram linkage, a strain detection sensor is arranged on the elastic feedback device, for an arbitrary position of a positioning point, linkage non-parallelism makes the strain detection sensor generate a reading, a positioning end deviation value is obtained, and a positioning point deviation value is obtained; additional rotation or translation errors of the parallel positioning device are calculated through data of the strain detection sensor, and the positioning precision of the parallel positioning device is improved through a precision compensation link.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of measuring machines, and particularly relates to a parallel motion positioning mechanism and positioning method suitable for a parallel structure. BACKGROUND

[0002] The parallelogram constraint mechanism is a commonly used constraint mechanism in parallel positioning devices, and some parallel positioning devices adopt the parallelogram constraint mechanism. The common feature of these parallel positioning devices is that three groups of parallelogram constraint mechanisms in different directions are used to constrain the terminal platform, and the effect of this constraint mode is to completely constrain the rotation angle freedom of the terminal platform around the xyz three axes, and only the parallel motion freedom in the xyz three directions is reserved, so that the control algorithm is greatly simplified.

[0003] However, in general cases, the parallelogram mechanism is difficult to be in an ideal parallel state, and the reasons for this are as follows: (1) the parallelogram mechanism has manufacturing and installation errors; (2) in some applications, a spring is used to pull the rod to eliminate the gap of the rotation pair, so that the parallelism is affected; and (3) elastic deformation under the conditions of statically indeterminate constraint or load influence.

[0004] When the parallelogram mechanism is not in an ideal parallel state, additional rotation or translation errors will be introduced to the terminal platform of the parallel positioning device, which limits the parallel positioning device in high-precision positioning applications. SUMMARY

[0005] In order to solve the problem of insufficient positioning precision of the parallel positioning device, the application designs a parallel motion positioning mechanism and positioning method suitable for a parallel structure, which can detect the non-parallelism of the parallelogram mechanism, calculate the additional rotation or translation errors of the parallel positioning device according to the non-parallelism of each group of parallelogram mechanisms, and then improve the positioning precision of the parallel positioning device through the precision compensation link.

[0006] A parallel motion positioning mechanism suitable for a parallel structure, comprising: a column, a connecting rod, a moving platform, a bottom platform and a measuring head; the column is arranged on the bottom platform; a sliding motor is arranged on the column; one end of the connecting rod is connected with the sliding motor, and the other end is connected with the moving platform; the bottom of the moving platform is provided with the measuring head; the connecting rod is a parallelogram connecting rod, and the column is 3; an elastic feedback device is arranged on the parallelogram connecting rod.

[0007] Both ends of the elastic feedback device are connected through a connecting piece and a clamp;

[0008] The clamp is sleeved on the connecting rod through a Dingqing rubber ring;

[0009] A strain detection sensor is arranged on the elastic feedback device.

[0010] Preferably, two elastic feedback devices are arranged on the connecting rod.

[0011] Preferably, the circuit of the strain detection sensor comprises four resistors R1, R2, R3 and R4.

[0012] The resistors R1 and R2 form one branch, and the resistors R3 and R4 form another branch, and an external voltage U is applied across the two branches.

[0013] The resistors R1 and R2 are replaced by strain detection sensors.

[0014] The potential difference U0 between the connection between the resistors R1 and R2 and the connection between the resistors R3 and R4 is taken.

[0015] Preferably, the calculation method of the circuit is as follows:

[0016]

[0017]

[0018] wherein μ is the Poisson ratio, λ is the piezoresistive coefficient, and E is the elastic modulus, and the two formulas can be combined to obtain

[0019]

[0020] A translational positioning method suitable for a parallel structure, comprising:

[0021] Step S1, measuring and reading the values of different values and , ; using the least squares method to fit the coefficients … ;

[0022] Step S2, measuring the positioning point deviation values at different positioning points , , and comparing them ; using the perturbation method to calculate the element terms … ;

[0023] Step S3, obtaining a function of the positioning point deviation values and the connecting rod positioning end deviation values according to step S2.

[0024] Step S4, calculating the positioning point deviation values , , , and compensating the positioning accuracy with the positioning point deviation values.

[0025] Preferably, the step S1 comprises:

[0026] Step S11, lay the parallelogram mechanism on the horizontal plane, fix the reference end and the parallel link A, and make them have a fixed included angle ;

[0027] Step S12, apply different direction forces on the parallel link B to change the contact state of the clearance between the rotating pairs in the parallelogram mechanism

[0028] Step S13, measure the errors of the three directions of the midpoint of the positioning end 、 、 , and record the values of the two displacement sensors and ;

[0029] Step S14, fit the functional relationship between 、 、 and 、 and by numerical method as follows:

[0030] ;

[0031] Step S15, read the values of the two strain sensors, and the below 、 、 and 、 ; rewrite the functional relationship between 、 、 and 、 as:

[0032]

[0033] Measure the values of each of the three values, and solve the equation, and at least measure 9 groups to improve accuracy, and then fit the coefficients by least square method … .

[0034] Preferably, the step S2 comprises:

[0035] Step S21, equivalent the sensor values of to 、 、 three deviations

[0036] Step S22, deviation of actual positioning point may be expressed as , , combination;

[0037] Step S23, using perturbation method to obtain element item in matrix … .

[0038] Preferably, in the step S3, the function of the positioning point deviation value and the connecting rod positioning end deviation value is:

[0039] .

[0040] The advantages and effects of the present application are as follows:

[0041] The parallel motion positioning mechanism and positioning method designed by the present application are suitable for parallel structure, an elastic feedback device is arranged on the existing parallelogram connecting rod, a strain detection sensor is arranged on the elastic feedback device, the additional rotation or translation error of the parallel positioning device is calculated through the data of the strain detection sensor, and the positioning precision of the parallel positioning device is improved through the precision compensation link.

[0042] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, so as to implement according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following will be described in detail with the preferred embodiments of the present application and the accompanying drawings.

[0043] According to the detailed description of the specific embodiments of the present application in the following text combined with the drawings, those skilled in the art will be more clear about the above and other purposes, advantages and characteristics of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual proportion.

[0045] Figure 1 The structural design drawing of the parallel motion positioning mechanism suitable for parallel structure designed by the present application is shown in the following figure:

[0046] Figure 2 A circuit design diagram of a parallel structure suitable for the translational positioning mechanism designed in the present application;

[0047] Figure 3 A flow chart of a parallel structure suitable for the translational positioning method designed in the present application;

[0048] Figure 4 An equivalent diagram of a parallel structure suitable for the translational positioning method designed in the present application. DETAILED DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. In the following description, specific details such as specific configurations and components are provided only to help the overall understanding of the embodiments of the present application. Therefore, those skilled in the art should clearly understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, in order to be clear and concise, the description of known functions and structures is omitted in the embodiments.

[0050] It should be understood that the "one embodiment" or "the embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "one embodiment" or "the embodiment" appearing throughout the specification does not necessarily mean the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner.

[0051] In addition, reference numerals and / or letters can be repeated in different examples in the present application. Such repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or arrangements discussed.

[0052] The term "and / or" herein is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can mean that there are three cases of A alone, B alone and A and B together. The term "and" herein is to describe another association relationship of the associated objects, which means that there can be two relationships, for example, A and B can mean that there are two cases of A alone and A and B together. In addition, the character " / " herein generally means that the associated objects before and after are in an "or" relationship.

[0053] The term "at least one" is merely used to describe a corresponding relationship of associated objects, and indicates that three relationships can exist, for example, at least one of A and B can indicate that A exists alone, A and B exist together, and B exists alone.

[0054] It should be further noted that, in this document, relationship terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion.

[0055] Embodiment 1: This embodiment mainly introduces a parallel mechanism suitable for parallel structure, which includes a reference end, a positioning end and two parallel connecting rods to form a parallelogram, so that the positioning end and the reference end always remain parallel under ideal conditions. Among them, the reference end is the connecting end of the sliding motor, and the positioning end is the connecting end of the bottom platform. However, in actual situations, due to the manufacturing and installation errors of the parallel connecting rods, and the existence of gaps in the rotating pairs, the reference end and the positioning end are not absolutely parallel, thereby introducing additional positioning errors.

[0056] Please refer to Figure 1 Therefore, in this application, a set of parallel elastic feedback devices are added between the parallel connecting rods of the parallelogram mechanism, which are provided with strain detection sensors. The elastic feedback device has two functions: eliminating the gap in the rotating pairs of the parallelogram mechanism by using elastic tension; and detecting the change in parallelism and compensating the accuracy of the parallel positioning device according to the strain sensor value in the elastic element feedback device.

[0057] Further, please refer to Figure 2 The circuit of the strain detection sensor includes four resistors R1, R2, R3 and R4. The resistors R1 and R2 form one branch, and the resistors R3 and R4 form another branch. An external voltage U is applied across the two branches.

[0058] The resistors R1 and R2 are replaced by strain detection sensors.

[0059] The potential difference U0 between the connection between the resistors R1 and R2 and the connection between the resistors R3 and R4 is taken. When the parallelism of the parallelogram changes, the values of the resistors R1 and R2 will change, which will cause the change of the potential difference U0. Therefore, by detecting the potential difference U0, the change in parallelism of the parallelogram can be detected.

[0060] Through the above design, the application can obtain the relationship between the non-parallelism of each connecting rod and the stress sensor reading through the bridge circuit.

[0061] That is, connect the strain sensor on the elastic feedback device to R1 in the bridge circuit shown in the figure above, and connect the strain gauge with the same parameters to R2 and attach it to the adjacent position of the connecting rod that does not deform to compensate for the influence of temperature changes. The resistance values of other resistors in the bridge circuit are the same as the initial value of the strain gauge, and

[0062]

[0063]

[0064] Where μ is the Poisson ratio, λ is the piezoresistive coefficient, E is the elastic modulus, and the two formulas can be obtained by combining

[0065]

[0066] Example 2, based on example 1, please refer to Figure 3 This embodiment mainly introduces a translational positioning method suitable for parallel structure, including:

[0067] Step S1, measure, read different values of and , ; use the least squares method to fit the coefficient … ;

[0068] Step S2, measure the positioning point deviation value under different positioning points , , and ; use the perturbation method to calculate the element term … ;

[0069] Step S3, according to step S2, obtain the function of the positioning point deviation value and the connecting rod positioning end deviation value;

[0070] Step S4, calculate the positioning point deviation value , , , and compensate the positioning accuracy with the positioning point deviation value.

[0071] Further, the step S1 includes:

[0072] Step S11, place the parallelogram mechanism on the horizontal plane, fix the reference end and the parallel connecting rod A, and make a fixed included angle between them;

[0073] Step S12, apply different direction forces to the parallel connecting rod B to change the contact state of the clearance between the rotating pairs in the parallelogram mechanism;

[0074] Step S13, measure the error of the three directions of the midpoint of the positioning end 、 、 , and record the values of the two displacement sensors and ;

[0075] Step S14, fit the function relationship between 、 、 and 、 and by numerical method as follows:

[0076] ;

[0077] Step S15, as shown in the figure, there is a unique X, Y, Z position coordinate value corresponding to , the theoretical coordinate value can be calculated, and the deviation between the actual position and the theoretical position is measured by using the micrometer, and the values of the two strain sensors are read, so that the below 、 、 and 、 can be obtained. The function relationship between 、 、 and 、 is rewritten as:

[0078]

[0079] The values of each value under the three values can be solved by the equation, at least 9 groups are measured to improve the accuracy, and the coefficients … are fitted by the least square method.

[0080] Further, please refer to Figure 4 , the step S2 comprises:

[0081] Step S21, the sensor values of are equivalent to the three deviations of 、 、 ;

[0082] Step S22, the deviation of the actual positioning point can be expressed as , 、 the combination of

[0083] Step S23, the perturbation method is used to obtain the element in the matrix … .

[0084] Further, Figure 4 is the actual structure and the equivalent structure of the mechanism, the equivalent structure is equivalent to a driving rod for each set of parallelogram mechanism of the actual structure, and sensor values of 、 、 Three deviations, the deviation of the actual positioning point Can be expressed as 、 、 The combination, as shown in the following formula, wherein the element in the matrix … The perturbation method can be used to obtain. In the step S3, the function of the positioning point deviation value and the connecting rod positioning end deviation value is:

[0085] .

[0086] The parallel structure of the parallel structure and the positioning method designed by the application, the elastic feedback device is arranged on the existing parallelogram connecting rod, the strain detection sensor is arranged on the elastic feedback device, for any position of the positioning point, the non-parallel degree of the connecting rod makes the stress sensor produce reading, the positioning end deviation value is obtained, and then the positioning point deviation value is obtained; the additional rotation or translation error of the parallel positioning device is calculated through the data of the strain detection sensor, and the positioning accuracy of the parallel positioning device is improved through the accuracy compensation link.

[0087] The above only describes the preferred embodiments of the present application, and does not limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and variations. Any change, modification, replacement, integration and parameter change of these embodiments within the spirit and principles of the present application, which can realize the same function without departing from the principles and spirit of the present application, falls within the protection scope of the present application.

Claims

1. A translational positioning mechanism suitable for parallel structures, comprising: The system comprises a column, a connecting rod, a moving platform, a base platform, and a measuring head; the column is mounted on the base platform; a sliding motor is mounted on the column; one end of the connecting rod is connected to the sliding motor, and the other end is connected to the moving platform; a measuring head is mounted on the bottom of the moving platform; the connecting rod is a parallelogram-shaped connecting rod, and there are three columns; characterized in that an elastic feedback device is mounted on the parallelogram-shaped connecting rod. The two ends of the elastic feedback device are connected by a connector and a clamp, respectively. The clamp and the connecting rod are connected; The elastic feedback device is equipped with a strain detection sensor; The connecting rod is equipped with two elastic feedback devices.

2. The translational positioning mechanism suitable for parallel structures according to claim 1, characterized in that, The circuit of the strain detection sensor includes four resistors: R1, R2, R3, and R4. Resistors R1 and R2 form one branch, and resistors R3 and R4 form the other branch. A voltage U is applied across both branches. Both resistors R1 and R2 are replaced with strain detection sensors; The potential difference U0 between the connection points of resistors R1 and R2 and resistors R3 and R4 is taken. When the parallelism of the parallelogram changes, the values ​​of resistors R1 and R2 will change accordingly, which will cause a change in the potential difference U0. Therefore, by detecting the potential difference U0, the change in the parallelism of the parallelogram can be detected.

3. A translational positioning mechanism suitable for parallel structures according to claim 2, characterized in that, The calculation method for the circuit is as follows: Where μ is Poisson's ratio, λ is the piezoresistive coefficient, and E is the elastic modulus, the two equations can be combined to obtain 。 4. The translational positioning method for a translational positioning mechanism applicable to a parallel structure according to claim 3, characterized in that, include: Step S1: Measure and read different... Value and , The coefficients were fitted using the least squares method. … ;in, These are the measured deviation values ​​of the i-th test positioning point in the X, Y, and Z directions, respectively. , These are the measured strain values ​​from two displacement sensors, respectively. Step S2: Measure the positioning point deviation at different positioning points. , , and Comparison; calculate the element terms using the perturbation method … ; Step S3: Obtain the positioning point deviation value and the connecting rod positioning end deviation value according to step S2; Step S4: Calculate the positioning point deviation value , , The positioning accuracy is compensated by the deviation value of the positioning point.

5. A translational positioning method for a translational positioning mechanism suitable for a parallel structure according to claim 4, characterized in that, Step S1 includes: Step S11: Place the parallelogram mechanism flat on a horizontal surface, fix the reference end and parallel link A, and make them form a fixed angle. ; Step S12: Apply forces in different directions to the parallel link B to change the contact state of the revolute joint clearance in the parallelogram mechanism; Step S13: Measure the error in three directions at the midpoint of the positioning end. , , And record the values ​​from the two displacement sensors. and ; Step S14: Fitting using numerical methods , , ,and , and The functional relationship between them is as follows: ； Step S15: Read the values ​​from the two strain sensors to obtain the result. Down , , and , ;Bundle , , and , The functional relationship between them can be rewritten as: Measure three The equation can be solved by taking values ​​under each condition. To improve accuracy, at least 9 sets of measurements should be taken, and then the coefficients should be fitted using least squares. … .

6. A translational positioning method for a translational positioning mechanism applicable to a parallel structure according to claim 5, characterized in that, Step S2 includes: Step S21, The sensor values ​​are equivalent to , , Three deviations; Step S22: Adjust the deviation of the actual positioning point It can be represented as , , The combination; Step S23: Use the perturbation method to find the elements in the matrix. … .

7. A translational positioning method for a translational positioning mechanism applicable to a parallel structure according to claim 6, characterized in that, In step S3, the function of the positioning point deviation value and the connecting rod positioning end deviation value is: 。

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