Spoke type morphing mechanism and method of designing the same

Abstract

The present application relates to the field of shape fitting and the field of deformable rigid body mechanism, in particular to a spoke type deformable mechanism, the present application first converts a given picture contour into data points, then calculates the driving node distribution and spoke center position, determines the required length of the telescopic mechanism and the angle at which the rotating mechanism should be, and the motor drives the telescopic mechanism and the rotating mechanism to realize the required motion, the skin clamping device drives the skin to deform, so that the skin presents the required contour shape; the spoke type deformable mechanism of the present application can realize the transformation of multiple arbitrary smooth contours, the design and calculation process is relatively simple, the mechanism structure is simple, easy to install, high reliability, the skin material can be replaced, and can be suitable for various application scenarios.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of shape fitting and the field of deformable rigid body mechanism, in particular to a spoke type deformable mechanism. BACKGROUND

[0002] Many mechanical systems depend on their geometric shape for performance, so the ability to control deformation can make mechanical systems more efficient to adapt to a variety of working environments or perform a variety of tasks. Mechanical systems with deformation capability have a wide range of applications, such as cams, robots, aircraft wings, furniture, toys, etc. For example, a cam is a high-speed, high-precision mechanism, and a deformable mechanism can meet the needs of different shapes of the mechanism in different application scenarios. For another example, a reasonable deformable mechanism design can achieve high-speed movement of a robot on complex terrain without obstacles and meet the shape requirements of an aircraft wing in different situations. The deformable mechanism in the prior art can only achieve one deformation and reset through a pre-made mechanical structure, and the deformation mode is relatively single, which cannot realize the deformation of a complex structure. SUMMARY

[0003] The present application aims to solve the problems in the background art, and provides a spoke type deformable mechanism and a design method thereof, which can achieve a given shape of the outer contour of a designed mechanical device through at least two given two-dimensional closed contours.

[0004] The technical scheme of the present application is a design method of a spoke type deformable mechanism. The present application first converts a given picture contour into data points, then calculates the driving node distribution and spoke center position, determines the required length of the telescopic mechanism and the angle at which the rotating mechanism should be, drives the telescopic mechanism and the rotating mechanism to achieve the required movement by the motor, and makes the skin deformed by the skin clamping device, so that the skin presents the required contour shape.

[0005] The calculation part can be divided into three parts: input data, calculation of driving nodes, and calculation of spoke centers. First, different formats of contour curves are processed and converted into data point coordinates. Then, the relative angles of each data point on the contour are calculated, the data points with larger relative angles are selected as driving nodes, and the spoke center position that can make the driving telescopic mechanism and rotating mechanism work least when transforming between contours is calculated. The calculation part of the present application can be divided into the following steps.

[0006] Step 1: Process the target contour curve that the deformable mechanism is expected to reach into the form of two-dimensional data point coordinates.

[0007] Step 2: Connect every K (K is an integer greater than or equal to 0) points on the contour with a straight line segment, calculate the included angle between the two adjacent straight line segments formed by three points, and record it as the relative angle corresponding to the middle point.

[0008] Step 3, on each contour, screen out the points with larger relative angle by a set angle threshold, then merge the points with very close interval, get the driving node position on the contour. At this time, the number of driving nodes on each contour is , where the maximum number of driving nodes on a single contour is .

[0009] Step 4, according to the maximum number of driving nodes obtained in step 3 , the driving nodes on each contour are supplemented, that is, the number of driving nodes that need to be supplemented on each contour is The principle of supplement is to make all driving nodes as evenly distributed on the contour as possible. There are two methods for supplement: method one is to lower the threshold of screening relative angle on the contour, so as to obtain the required number of driving nodes; when method one cannot effectively screen, method two can be used, that is, according to the principle of making the driving nodes on the contour as evenly distributed as possible, determine the number of driving nodes that should be supplemented between the original driving nodes.

[0010] Step 5, according to the principle of the total work required for driving spoke type telescopic mechanism to rotate and telescope being the least, the position of the spoke center is calculated by the driving node positions calculated in steps 3 and 4.

[0011] A spoke type deformable mechanism, comprising a skin, a spoke type telescopic mechanism for driving the skin to deform, a rotating mechanism for driving the telescopic mechanism to rotate, and a center fixing part. The number of telescopic mechanisms is consistent with the number of driving nodes set in the calculation part, which can be increased or decreased according to the number of driving nodes set.

[0012] The telescopic mechanism is composed of an electric push rod, an F-shaped connecting piece, an outer skin clamping piece, and an inner skin clamping piece. The skin passes between the outer skin clamping piece and the inner skin clamping piece, which can ensure that the skin can slide freely therein. The outer skin clamping piece, the inner skin clamping piece, and the electric push rod are connected by a cylindrical pin. The electric push rod is connected to the T-shaped connecting piece through the cylindrical pin, and the T-shaped connecting piece is connected to the F-shaped connecting piece through a screw. The electric push rod performs telescopic motion and pushes the skin to the length of the driving center calculated by the calculation part. If the difference between the circumferences of the two contours is small, a rigid skin can be used. If the difference between the circumferences of the two contours is large, the skin needs to use honeycomb material or flexible material.

[0013] The rotating mechanism is composed of a motor, a T-shaped sleeve, a straight electric push rod, and a cylindrical pin. The motor uses a stepping motor, which is convenient for controlling the rotation angle. The motor is connected to the lower end of the T-shaped sleeve through a key, and the upper end is connected to the straight electric push rod through a cylindrical pin. The lower end of the motor is positioned with the center positioning pin of the center fixing part.

[0014] The main body part is an inner shell and an outer shell, and the coaxiality of the two shells is ensured by positioning pins. The inner shell and the outer shell do not rotate relative to each other, and the surface roughness thereof is required to be low.

[0015] Compared with the prior art, the present application has the following beneficial technical effects:

[0016] 1. In the calculation part, the driving node positions are arranged reasonably, and using the high-curvature points on the contour as the driving node positions is beneficial to improving the shape fitting accuracy, and the supplementary driving nodes are arranged as evenly as possible on the contour, which is beneficial to uniformly distributing the tension on the skin.

[0017] 2. In the mechanism design part, the mechanism design is simple, the connection is simple, the parts are easy to install, the module division is obvious, a larger rotation angle and elongation length can be provided, the limitation on the input closed contour is small, and the like, so that the deformation of a complex structure is realized. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a telescopic mechanism schematic diagram of the present application.

[0019] Figure 2 is a rotating mechanism schematic diagram of the present application.

[0020] Figure 3 is a center fixing part schematic diagram of the present application.

[0021] Figure 4 is a schematic diagram of the overall structure of the present application.

[0022] Figure 5 is an F-type connecting piece schematic diagram of the present application.

[0023] Figure 6 is a spoke force schematic diagram of the present application.

[0024] Reference signs: 1, outer skin clamping piece; 2, inner skin clamping piece; 3, electric push rod; 4, T-type connecting piece; 5, screw; 6, F-type connecting piece; 7, motor; 8, T-type sleeve; 9, straight electric push rod; 10, cylindrical pin; 11, positioning pin; 12, outer shell; 14, inner shell; 15, center fixing part; 16, rotating mechanism; 17, telescopic mechanism; 18, insertion hole. DETAILED DESCRIPTION Example 1

[0025] Since the change between multiple contours is the change from a previous contour to a target contour, and then the change from the target contour to a subsequent contour, two contours are taken as an example. The calculation part of the present application can be divided into the following steps:

[0026] Step 1, the input picture format data is converted into data points by MATLAB, tpsDig, ImageJ software, and input into the processing program. The input contour can be in the form of a picture, and the software and algorithm (such as the cscvn function of MATLAB) can directly convert the picture into a certain order of data points. Data points can also be directly inputted.

[0027] Step 2, the effect of burr is reduced by algorithm, and the relative angle of the adjacent three points after calculation is processed. The data points in step 1 are arranged in order, and the interval point number K is selected. One point is taken every K points to form a new set of data points, and the adjacent three points are selected by formula 1 to calculate the relative angle. The larger the value of K, the larger the value of the relative angle obtained by calculation. The interval point method can effectively highlight the characteristics of high curvature points.

[0028]

[0029] Step 3, find out the points with large relative angle by setting threshold value, segment the contour line, and fuse the points with very close relative angle. The threshold value is calculated by formula 2 , where is the maximum relative angle, is the minimum relative angle, is the threshold coefficient, and the value range is between 0 and 1.

[0030]

[0031] The threshold value is obtained , and the data greater than the threshold value in the relative angle array is arranged in order to form a screening array. If the threshold value is calculated, the threshold coefficient is a non-zero value set by yourself, which proves is 0, which can be judged as the same value, and the first point is directly selected and the remaining points are deleted. If the two driving points are very close, they are merged into one driving point, and the screening array is segmented; the interval sequence number J between adjacent driving points is introduced, and the interval value J is set. The larger the value, the fewer the number of segments obtained, and the smaller the number of points apart, the more the number of segments obtained. Assuming that the interval value J is set to 10, if the sequence number of the data points in the screening array is more than 10, the data points are divided into new segments, and the segmentation array is divided into segments. Find the point with the maximum relative angle in each segment, and if the number of continuous points around this point is greater than P, select this point as the driving point. If the number of continuous points around this point is less than P, take the second largest point, and so on. If all the points are found, there is no such point, and the segment is deleted.

[0032] Step 4, the driving nodes are supplemented according to the number of driving nodes required, so that they are evenly distributed around the profile. The total length of the profile is calculated to obtain the average length of the profile, and the segment whose adjacent driving point distance is greater than the average length is found, which is divided by less than the average length, is the number of driving points that need to be supplemented behind this driving point. The value of is increased until the condition is met, is the number of supplementary points needed to be inserted between the i-th point and the i+1-th point, and then the genetic algorithm is used to achieve uniform distribution on the curve profile.

[0033] Step 5, the driving nodes calculated in steps 3 and 4 are used to calculate the position of the spoke center of each profile according to the minimum work condition. The present application provides a solution method, MATLAB has a fminsearch function, provides an initial value, and after the target function and the loop exit condition are met, the optimal spoke center position can be found. Fermat point is the point with the smallest distance sum to the three endpoints of a triangle. In this case, the generalized form of Fermat point is used: find the point with the smallest distance sum to the remaining six points. This is used as the initial value of the function. According to the minimum work condition, the present application selects the work, which includes the work done by the moving part and the work done by the rotating part. The mechanism first rotates and then elongates. Since the force of the rotating motion is approximately proportional to the force of the elongation motion, the present application only considers the effect of distance on work, is the work coefficient obtained when the selected skin is rubber, is the length of the push rod that needs to be changed when profile one becomes profile two, is the length of the arc that needs to be rotated when profile one becomes profile two, and the target function is

[0034]

[0035] The calculation formula is

[0036] wherein is the distance from the i-th point of profile one to its driving center, is the distance from the j-th point of profile two to its driving center, is the length of the push rod that needs to be changed when profile one becomes profile two, and the arc length calculation formula is

[0037]

[0038] wherein r is the radius of profile one, is the angle of the i-th push rod of profile one when it is rotated to the position of the j-th push rod of profile two.

[0039] As Figure 1As shown, the moving mechanism is composed of electric push rod 3, F-shaped connector 6, outer skin clamping piece 1, inner skin clamping piece 2 and skin; the skin passes between the outer skin clamping piece 1 and the inner skin clamping piece 2, which can ensure the skin to slide freely, the outer skin clamping piece 1, the inner skin clamping piece 2 and the electric push rod 3 are connected by cylindrical pin, the electric push rod 3 is connected with T-shaped connector 4 by cylindrical pin, and the T-shaped connector 4 is connected with F-shaped connector 6 by screw 5. The electric push rod 3 performs extension and retraction movement, and pushes the skin to the length of the distance from the driving center calculated by the calculation part. If the difference between the circumferences of the two profiles is small, rigid skin can be used, and if the difference between the circumferences of the two profiles is large, the skin needs to use honeycomb material or flexible material.

[0040] As shown in Figure 2 , the rotating mechanism is composed of motor 7, T-shaped sleeve 8, straight electric push rod 9 and cylindrical pin 10; the motor is a stepping motor, which is convenient for controlling the rotation angle, the motor is connected with the lower end of the T-shaped sleeve 8 by key, and the upper end is connected with the straight electric push rod 9 by cylindrical pin 10. The lower end of the motor 7 is positioned by the positioning pin 11 of the center fixing piece.

[0041] As shown in Figure 3 , the shell includes inner shell 14 and outer shell 12, and the coaxiality of the two shells is ensured by positioning pin. The inner shell 14 and the outer shell 12 do not rotate relative to each other.

[0042] As shown in Figures 1-4 , the overall mechanism is composed of center fixing piece 15, rotating mechanism 16 and telescopic mechanism 17; the rotating mechanism 16 is positioned by positioning pin 11 and connected with the center fixing piece. The telescopic mechanism 17 is connected with the center fixing piece by F-shaped connector 6. The deformation process is that the telescopic mechanism 17 rotates to the corresponding position, the straight electric push rod 9 is elongated into the small hole of the F-shaped connector 6, at this time when the rotating mechanism 16 rotates, the telescopic mechanism 17 also rotates, according to the rotation parameters obtained by the calculation part, it rotates to the corresponding position, as shown in Figure 5 , the insertion hole 18 of the F-shaped part is inserted into the screw stop, the straight electric push rod 9 is retracted, and it is rotated to the next telescopic mechanism 17, and so on. After the telescopic mechanism 17 rotates to the set angle, the electric push rod 3 starts to elongate to the set length, the skin is clamped by the outer skin clamping piece 1 and the inner skin clamping piece 2, and starts to deform along with the elongation of the electric push rod 3, and the shape of the skin is the realized profile. The control of the deformation process of the mechanism can be realized by single-chip microcomputer. Example 2

[0043] As shown in Figure 6The force diagram of the spoke is shown; the six driving nodes are selected, and the data of the selected driving nodes are input into the spoke center program in sequence. The selection condition of the spoke center is to make the work of the mechanism as small as possible, including the work done by the extension mechanism 17 and the work done by the rotation mechanism 16. The mechanism is first rotated and then extended. For the design example, since the initial shape is the original shape, the work done by the rotation part is the work done to overcome the friction of the skin, and the work done by the extension part is the work done to overcome the force of the skin perpendicular to the shaft. Since the contour I is a circle, the work done by the rotation part is calculated as The formula is as follows, wherein is the circumferential force received by the spoke head, is the displacement along the tangent direction of the contour. The calculation formula is

[0044]

[0045] The calculation formula of

[0046]

[0047] is the friction coefficient of the skin material, is the axial force received by the spoke during rotation. The work done by the extension part of the moving pair is The calculation formula is

[0048] is the axial force received by the spoke during extension, is the displacement of the spoke in the linear extension part. The total work can be calculated as

[0049] The formula is integrated, and the following relationship is obtained by calculation

[0050] The work coefficient T is obtained, which is the percentage of the work done by the rotation part and the work done by the extension part in the total work,

[0051] In the embodiment, the selected material is rubber material, and the friction coefficient of the material is 0.9. Since is greater than ​​​Therefore, the value of the work coefficient T is less than 0.9. In the design calculation results, it is found that the position of the spoke center does not change when the work coefficient is between 0.68 and 0.9, the position of the spoke center changes when the work coefficient is less than 0.68, and the position of the spoke center changes slightly when the work coefficient is greater than 0.97. The spoke center is searched using fminsearch, the initial value x0 (where the selected xy coordinates of the profile one and the selected xy coordinates of the profile two are stored) is brought in, the length and are calculated, the situation is judged, and the next point is searched. Finally, the optimal driving centers of the two profiles and the corresponding relationship of the driving nodes of the two profiles are obtained.

[0052] The embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited thereto, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application.

Claims

1. A design method for a spoke-type deformable mechanism, characterized in that, The specific steps include the following: S1. Given at least two two-dimensional closed contours, convert them into data points; S2. Based on the obtained data points, calculate the distribution of drive nodes and the position of the spoke center; S2 includes the following steps: S21. Process the target contour curve that the deformable mechanism is expected to achieve into the form of two-dimensional data point coordinates. S22. Points at intervals of K on the contour are connected by straight line segments. Calculate the angle between two adjacent straight line segments formed by the three points and record it as the relative angle corresponding to the middle point. S23. On each contour, filter out the regions on the contour that are greater than or equal to T by setting an angle threshold T, and take the point with the largest relative angle in each region as the driving node position on the contour. Number of driving nodes on each contour The maximum number of driving nodes on a single contour is ; S24. Based on the maximum number of driving nodes obtained in S23 The number of driving nodes to be added to each contour is: ; S25. Based on the driving node positions calculated by S23 and S24, the position of the spoke center is calculated according to the principle of minimizing the total work required for the rotation and extension of the spoke-type telescopic mechanism. S3. Determine the required length of the telescopic mechanism and the angle at which the rotating mechanism should be positioned. S4. The motor drives the telescopic and rotating mechanisms to achieve the required motion; S5. The skin holder causes the skin to deform, so that the skin presents the desired contour shape.

2. The design method of the spoke-type deformable mechanism according to claim 1, characterized in that, Two-dimensional closed contours can be in the form of images, mathematical function equations, or data point coordinates.

3. The design method of a spoke-type deformable mechanism according to claim 1, characterized in that, K is an integer greater than or equal to 0.

4. The design method of a spoke-type deformable mechanism according to claim 1, characterized in that, Methods for supplementing driving nodes include: a) lowering the threshold of the relative angle of the screening on the contour to obtain the required number of driving nodes; b) determining the number of driving nodes to be supplemented between the original driving nodes according to the principle of making the driving nodes on the contour evenly distributed.

5. A spoke-type deformable mechanism, designed according to the design method of any one of claims 1-4, characterized in that, It includes a skin, a spoke-type telescopic mechanism that causes the skin to deform, a rotating mechanism that causes the telescopic mechanism to rotate, a central fixing component (15), and a housing for support; The telescopic mechanism (17) consists of an electric push rod (3), an F-type connector (6), an outer skin clamp (1), and an inner skin clamp (2); the skin passes between the outer skin clamp (1) and the inner skin clamp (2); The outer skin clamp (1) is connected to the inner skin clamp (2) and the electric push rod (3) by a cylindrical pin. The electric push rod (3) is connected to the T-type connector (4) by a cylindrical pin. The T-type connector (4) is connected to the F-type connector (6) by a screw (5). The electric push rod (3) performs telescopic movement to push the skin to the distance driven center calculated by the calculation part. The rotating mechanism (16) includes a motor (7), a T-shaped sleeve (8), a straight electric push rod (9), and a cylindrical pin (10); the motor (7) is connected to the lower end of the T-shaped sleeve (8) by a key, and the upper end of the T-shaped sleeve (8) is connected to the straight electric push rod (9) by the cylindrical pin (10); the lower end of the motor (7) is positioned with the central fixing part by the central positioning pin (11); The rotating mechanism (16) is positioned by a positioning pin and connected to the central fixing part (15); the telescopic mechanism (17) is connected to the central fixing part (15) by an F-type connector (6); The housing includes an inner shell (14) and an outer shell (12), and the coaxiality of the inner and outer shells is ensured by a locating pin; the inner shell (14) and the outer shell (12) do not rotate relative to each other.

6. The spoke-type deformable mechanism according to claim 5, characterized in that, The motor is a stepper motor.

7. The spoke-type deformable mechanism according to claim 5, characterized in that, The skin can be made of rigid skin, honeycomb material or flexible material.

8. A spoke-type deformable mechanism according to claim 5, characterized in that, The rotating mechanism (16) and the telescopic mechanism (17) are controlled by a microcontroller and can move simultaneously.

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