CN112580167A - Stewart parallel mechanism construction method, system and computer storage medium - Google Patents

Abstract

The invention discloses a construction method of a Stewart parallel mechanism, which comprises the steps of firstly establishing a dynamic three-dimensional model and a kinematic inverse solution model of the Stewart parallel mechanism; and reversely solving the speeds of the electric cylinders through a kinematics inverse solution model and directly inputting the speeds into a dynamics three-dimensional model for interactive simulation. The invention also provides a Stewart parallel mechanism construction system and a computer readable medium for storing software. According to the invention, the inverse solution result can be directly input into the dynamic model by inputting the motion index of the upper platform, and the electric cylinder or motor parameter is output, so that a Stewart parallel mechanism can be directly built in an experiment, and the repeated modeling process is avoided.

Description

Stewart parallel mechanism construction method, system and computer storage medium

technical field

The invention belongs to the field of digital simulation, and in particular relates to a Stewart parallel mechanism construction method, system and computer storage medium.

Background technique

Stewart platform is a six-degree-of-freedom parallel mechanism. Compared with the series mechanism, it has the characteristics of high precision, high rigidity, stable structure and strong load capacity. It has a wide range of applications in aerospace, automotive engineering, biomedicine and other fields. Works where the working range is not large but the load is large. In the study of Stewart parallel mechanism, dynamic analysis is a very important aspect, which is the basis of the whole system design and control. Compared with the tandem mechanism, the Stewart platform is a spatial multi-loop closed motion system with passive joints, and the corresponding kinematic constraints need to be met during the motion process, so its dynamic analysis process is much more difficult than that of the tandem mechanism.

Virtual prototyping technology is based on kinematics, dynamics and control methods. Through virtual prototyping technology, simulation experiments that are difficult to complete with actual physical models can be quickly completed, and corresponding simulation results can be output, which can greatly reduce development costs and shorten development cycles. The application of prototype technology in the dynamic analysis of Stewart parallel mechanism is of great significance.

The main method at present is to import the 3D model of the Stewart platform in the Adams/View module, and add kinematic pairs between the parts according to the actual situation. According to the motion indicators of different working conditions, the upper platform is driven by point driving, and the change curve between the telescopic amount of each electric cylinder is reversely solved, and then the data is fitted by the function of Adams, and the power is imported again as the driving condition. The output of each electric cylinder and the power of the motor are calculated by the scientific model. The modeling of this method is based on the three-dimensional model of the part, and the shape is consistent with the actual structure; the simulation process has the function of animation demonstration, which can grasp the motion state of the mechanism in real time; it can analyze the interference and gap between the parts.

In the simulation process, due to the large number of motion conditions of the platform, it is necessary to inversely solve each condition, and then rebuild the dynamic model. The parameters of the electric cylinder or motor cannot be directly obtained through the input of the motion index of the upper platform. The modeling process It is cumbersome and takes a lot of time.

SUMMARY OF THE INVENTION

Purpose of the invention: Aiming at the problems existing in the prior art, the present invention proposes a Stewart parallel mechanism construction method that can directly give the electric cylinder selection parameters according to the motion of the working conditions.

Technical solution: In order to achieve the above purpose, a method for constructing a Stewart parallel mechanism is provided, which includes the following steps:

Establish the dynamic 3D model of Stewart parallel mechanism;

Build a kinematic inverse solution model; the kinematic inverse solution model includes a coordinate transformation module and an electric cylinder telescopic speed acquisition module; the coordinate transformation module obtains each hinge of the upper platform after transformation through the input displacement or angle variable of the upper platform The new coordinates of the point; the electric cylinder telescopic speed acquisition module calculates the real-time length of each electric cylinder in the dynamic three-dimensional model of the Stewart parallel mechanism according to the new coordinates of each hinge point of the upper platform obtained by the coordinate change module, and each The real-time length of the electric cylinder is subtracted from the initial length of the electric cylinder to obtain the telescopic amount of each electric cylinder, and the telescopic speed of each electric cylinder is calculated according to the telescopic amount of each electric cylinder;

The telescopic speed of each electric cylinder obtained by the inverse kinematics model is input into the established Stewart parallel mechanism dynamics model, and the output force of each electric cylinder is obtained;

Multiply the output force of each electric cylinder with the corresponding telescopic speed to obtain the power value of each electric cylinder.

Wherein, the method for establishing the dynamic three-dimensional model of the Stewart parallel mechanism is:

Step 101: Establish upper hinge point hard points (p1, p2, p3, p4, p5, p6) and lower hinge point hard points (b1, b2, b3, b4, b5, b6) in sequence;

Step 102: Using p1 as the starting point, along the direction of the straight line from p1 to b1, use the cylindrical geometry module to establish the geometric model of the push rod 1 according to the length of the push rod 1; with p2 as the starting point, along the two points from p2 to b2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second push rod according to the length of the second push rod; with p3 as the starting point, along the direction of the two points from p3 to b3, use the cylindrical geometry module, according to the length of the third push rod. Build the geometric model of the putter 3; take p4 as the starting point, along the direction of the line from p4 to b4, use the cylinder geometry module to build the geometric model of the putter 4 according to the length of the putter 4; take p5 as the starting point, along the In the direction of the straight line from p5 to b5, use the cylindrical geometry module to build the geometric model of the push rod five according to the length of the push rod five; take p6 as the starting point, along the direction of the two points from p6 to b6, use the cylindrical geometry module, according to The length of the putter six establishes the geometric model of the putter six;

Step 103: Using b1 as the starting point, along the direction of the straight line from b1 to p1, use the cylindrical geometry module to establish the geometric model of cylinder 1 according to the length of cylinder 1; starting from b2, follow the two points from b2 to p2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second cylinder according to the length of the second cylinder; with b3 as the starting point, along the direction of the two straight lines from b3 to p3, use the cylindrical geometry module, according to the length of the third cylinder Build the geometric model of cylinder 3; take b4 as the starting point, along the direction of the straight line from b4 to p4, use the cylindrical geometry module to establish the geometric model of cylinder 4 according to the length of cylinder 4; In the direction of the line from b5 to p5, use the cylindrical geometry module to establish the geometric model of cylinder five according to the length of cylinder five; take b6 as the starting point, along the direction of the line from b6 to p6, use the cylindrical geometry module, according to The length of cylinder 6 establishes the geometric model of cylinder 6;

Step 104: Taking p1, p2, p3, p4, p5, and p6 as vertices, use the slab geometry module to build the upper platform geometric model; taking b1, b2, b3, b4, b5, b6 as the vertices, use the slab geometry module to build the base geometry Model;

Step 105: respectively set the motion pair between the upper platform and each push rod; the motion pair between each push rod and its corresponding cylinder, the motion pair between each cylinder and the base; and set each part the weight of.

Further, the motion pair between the upper platform and each push rod adopts a Hooke hinge pair.

Further, the moving pair used between each push rod and its corresponding cylinder.

Further, the motion pair between each cylinder and the base adopts a ball pair.

The invention also provides a Stewart parallel mechanism construction system, including a three-dimensional model establishment unit, a dynamic inverse solution unit and an electric cylinder signal selection unit; wherein,

The three-dimensional model building unit is used to build a dynamic three-dimensional model of the Stewart parallel mechanism;

The kinematic inverse solution unit includes a coordinate transformation module and an electric cylinder telescopic speed acquisition module; wherein, the coordinate transformation module obtains the new coordinates of each hinge point of the upper platform after the transformation through the input displacement or angle variable of the upper platform; The electric cylinder telescopic speed acquisition module calculates the real-time length of each electric cylinder in the dynamic three-dimensional model of the Stewart parallel mechanism according to the new coordinates of each hinge point of the upper platform obtained by the coordinate change module, and compares the real-time length of each electric cylinder with the real-time length of each electric cylinder. The telescopic amount of each electric cylinder is obtained by subtracting the initial length of the electric cylinder, and the telescopic speed of each electric cylinder is calculated according to the telescopic amount of each electric cylinder; and the obtained telescopic speed of each electric cylinder is input into the 3D model establishment unit , the output force of each electric cylinder is obtained;

The electric cylinder signal selection unit multiplies the output force of each electric cylinder and the corresponding telescopic speed to obtain the power value of each electric cylinder and outputs it.

Wherein, the method for establishing the dynamic three-dimensional model of the Stewart parallel mechanism by the three-dimensional model establishment unit is:

Step 101: Establish upper hinge point hard points (p1, p2, p3, p4, p5, p6) and lower hinge point hard points (b1, b2, b3, b4, b5, b6) in sequence;

Step 102: Using p1 as the starting point, along the direction of the straight line from p1 to b1, use the cylindrical geometry module to establish the geometric model of the push rod 1 according to the length of the push rod 1; with p2 as the starting point, along the two points from p2 to b2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second push rod according to the length of the second push rod; with p3 as the starting point, along the direction of the two points from p3 to b3, use the cylindrical geometry module, according to the length of the third push rod. Build the geometric model of the putter 3; take p4 as the starting point, along the direction of the line from p4 to b4, use the cylinder geometry module to build the geometric model of the putter 4 according to the length of the putter 4; take p5 as the starting point, along the In the direction of the straight line from p5 to b5, use the cylindrical geometry module to build the geometric model of the push rod five according to the length of the push rod five; take p6 as the starting point, along the direction of the two points from p6 to b6, use the cylindrical geometry module, according to The length of the putter six establishes the geometric model of the putter six;

Step 103: Using b1 as the starting point, along the direction of the straight line from b1 to p1, use the cylindrical geometry module to establish the geometric model of cylinder 1 according to the length of cylinder 1; starting from b2, follow the two points from b2 to p2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second cylinder according to the length of the second cylinder; with b3 as the starting point, along the direction of the two straight lines from b3 to p3, use the cylindrical geometry module, according to the length of the third cylinder Build the geometric model of cylinder 3; take b4 as the starting point, along the direction of the straight line from b4 to p4, use the cylindrical geometry module to establish the geometric model of cylinder 4 according to the length of cylinder 4; In the direction of the line from b5 to p5, use the cylindrical geometry module to establish the geometric model of cylinder five according to the length of cylinder five; take b6 as the starting point, along the direction of the line from b6 to p6, use the cylindrical geometry module, according to The length of the cylinder tube six establishes the geometric model of the cylinder tube six;

Step 104: Taking p1, p2, p3, p4, p5, and p6 as vertices, use the slab geometry module to build the upper platform geometric model; taking b1, b2, b3, b4, b5, b6 as the vertices, use the slab geometry module to build the base geometry Model;

Step 105: respectively set the motion pair between the upper platform and each push rod; the motion pair between each push rod and its corresponding cylinder, the motion pair between each cylinder and the base; and set each part the weight of.

The present invention also provides a computer-readable medium storing software comprising instructions executable by one or more computers, the instructions, by such execution, cause the one or more computers to perform operations, the The operation includes the flow of the Stewart parallel mechanism construction method according to any one of claims 1-5.

Working principle: The present invention establishes the kinematic model of the Stewart platform through Simulink, inversely solves the speed of each electric cylinder, and directly inputs the dynamic module derived from Adams for interactive simulation. This method can directly input the inverse solution results into the dynamic model by inputting the motion index of the upper platform, and output the electric cylinder or motor parameters, avoiding the repeated modeling process.

Beneficial effects: Compared with the prior art, the present invention can directly output dynamic parameters such as electric cylinder output or motor power under the condition of inputting the motion index of the upper platform, and has the advantages of animation demonstration function and analysis of interference between parts.

Description of drawings

Fig. 1 is the schematic diagram of Stewart parallel mechanism;

Fig. 2 is the schematic diagram of electric cylinder thrust after the method provided by the present invention simulates the pitching condition;

3 is a schematic diagram of electric cylinder power after the method provided by the present invention simulates pitching conditions;

4 is a schematic diagram of the thrust of the electric cylinder after the method provided by the present invention simulates the rolling condition;

5 is a schematic diagram of the electric cylinder power after the method provided by the present invention simulates the rolling condition;

6 is a schematic diagram of the thrust of the electric cylinder after the method provided by the present invention simulates the side-shifting condition;

FIG. 7 is a schematic diagram of the power of the electric cylinder after simulating the side-shifting working condition by the method provided by the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the examples of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

This embodiment provides a Stewart parallel mechanism construction system, which mainly includes a three-dimensional model establishment unit, a dynamic inverse solution unit, and an electric cylinder signal selection unit; wherein, the three-dimensional model establishment unit and the electric cylinder signal selection unit pass through the modules in the Adams software. Completed, the kinetic inverse solution unit is built through the Matlab/Simulink module, which includes the following steps:

Step 1: Build the dynamic 3D model of the Stewart parallel mechanism:

Step 101: In the Adams/view module, create upper hinge point hard points (p1, p2, p3, p4, p5, p6) and lower hinge point hard points (b1, b2, b3, b4, b5, b6).

Step 102: Using p1 as the starting point, along the direction of the straight line from p1 to b1, use the Geometry-Cylinder module (cylindrical geometry module, hereinafter referred to as the Geometry-Cylinder module) in the Adams software, according to the push rod of the electric cylinder one used The actual length of the putter 1 is established by the geometric model, and the position of the reference point of the putter together is set to (LOC_RELATIVE_TO({0,0,0},p1)). This setting uses the Location option in the Adams software, which means The relative distances in the x, y, and z directions between the reference point and the p1 point are all 0. In this way, the established putter joint point can change with the modification of the hard point p1 position, and then set its reference point direction to (ORI_ALONG_AXIS(p1,b1,"Z")), this setting uses the Adams software in the The Orientation option indicates that the Z direction of the reference point at the first point of the putter is the same as the direction of the line from p1 to b1, so that the established putter one direction always follows the direction of the line from p1 to b1. By analogy, the models of putter two, putter three, putter four, putter five and putter six are established respectively.

Step 103: Using b1 as the starting point, along the direction of the straight line from b1 to p1, use the Geometry-Cylinder module in the Adams software to establish the geometric model of the cylinder tube 1 according to the actual length of the cylinder tube of the electric cylinder and the cylinder tube 1. The position of the reference point of the first point of the cylinder is set to (LOC_RELATIVE_TO({0,0,0},b1)), which uses the Location option in the Adams software, which means that the x, y, z between the reference point and the b1 point The relative distances of the directions are all 0, so that the starting point of the established cylinder 1 can be changed together with the modification of the position of the hard point b1, and then set the direction of its reference point to (ORI_ALONG_AXIS(b1,p1,"Z" )), this setting uses the Orientation option in the Adams software, indicating that the reference point Z direction of the first point of the cylinder is the same as the direction of the line from b1 to p1, so that the established direction of the cylinder can always be along the direction of b1 to p1. The direction of the line where p1 is located. And so on to establish the second cylinder, the third cylinder, the fourth cylinder, the fifth cylinder and the sixth cylinder.

Step 104: Using p1, p2, p3, p4, p5, and p6 as vertices, use the Geometry-plate module (plate geometry module, hereinafter referred to as Geometry-plate module) in the Adams software to establish a geometric model of the upper platform; there are 6 upper platforms The modeling reference points are set to their positions as (LOC_RELATIVE_TO({0,0,0},p1)), (LOC_RELATIVE_TO({0,0,0},p2)), (LOC_RELATIVE_TO({0,0,0}) ,p3)), (LOC_RELATIVE_TO({0,0,0},p4)), (LOC_RELATIVE_TO({0,0,0},p5)), (LOC_RELATIVE_TO({0,0,0},p6)), This setting uses the Location option in the Adams software, which allows the established upper platform to always change with the modification of the upper platform hinge point location. And build the base geometry model in the same way. The load position is added with the height of the actual center of gravity of the load. Here, the shape of the load can be ignored and replaced by a sphere. Pay attention to the position of the center of gravity, mass and moment of inertia of the load, and adjust the height of the center of mass by modifying the reference coordinate position of the sphere according to the actual situation, and manually Input method Input the load mass and the moment of inertia of the load.

Step 105: respectively set the motion pair between the upper platform and each push rod; the motion pair between each push rod and its corresponding cylinder, the motion pair between each cylinder and the base; and set each part the weight of.

Among them, materials are added to each part according to the actual situation. The main material used is steel. In order to ensure that the quality of the parts is consistent with the actual situation, the density of the material can be directly input to ensure that the quality of the parts is consistent with the actual situation.

Create constraints between parts:

(1) The connection between the upper platform 1 and the push rod one 2 adopts the Hook hinge pair, and the reference position of the connection point of the hook hinge pair is set to (LOC_RELATIVE_TO({0,0,0},p1)), which can make the established The Hook hinge pair always changes along with the modification of the position of the hard point p1. In the same way, set up the Hooke hinge pair between the upper platform 2 and the push rod 2 3, the push rod 3 4, the push rod 4 5, the push rod 5 6, and the push rod 6 7.

(2) A moving pair is set between the push rod one 2 and the cylinder one 8, and the reference position of the connection point of the moving pair is set as (LOC_RELATIVE_TO({0,0,0}, link1.cm)), where link.cm is The coordinates of the center of mass of the push rod-2, which are automatically generated after the push rod geometric model is built and the material is set. The direction is set to (ORI_ALONG_AXIS(b1,p1,"Z")), which means that the connection point of the moving pair refers to the Z direction and b1 The direction to the straight line where p1 is located is the same, so that the established moving pair is always located in the center of the putter, and the moving pair direction is always consistent with the putter. In the same way, push rod two 3 and cylinder two 9, push rod three 4 and cylinder three 10, push rod four 5 and cylinder four 11, push rod five 6 and cylinder five 12, push rod six 7 and A moving pair is arranged between the six cylinders 13 .

(3) A ball pair is set between the base 14 and the cylinder 1 8, and the reference position of the connection point of the ball pair is set to (LOC_RELATIVE_TO({0,0,0},b1)), so that the established ball pair can always follow the It changes together with the modification of the position of the hard point b1. In the same way, a ball pair is arranged between the base 15 and the second cylinder 10 , the third cylinder 11 , the fourth cylinder 12 , the fifth cylinder 13 , and the sixth cylinder 14 .

(4) A fixed pair is set between the load 15 and the upper platform 1, and the position of the fixed pair is set to (LOC_RELATIVE_TO({0,0,0},platform.cm)), where platform_base.cm is the center of mass coordinate of the upper platform 1, It will be automatically generated after the geometric model of the upper platform 1 is established and the material setting is completed, so that the fixed pair changes with the change of the position of the center of mass of the upper platform.

(5) A fixed pair is set between the base 14 and the ground, and the position of the fixed pair is set to (LOC_RELATIVE_TO({0,0,0}, base.cm)), where base.cm is the coordinate of the center of mass of the base, which will It is automatically generated after the foundation geometric model is established and the material setting is completed, so that the fixed pair changes with the change of the position of the center of mass of the foundation.

A displacement drive is added to the moving pair between each push rod and the cylinder. There are six displacement drives in total, namely, drive one (Motion_1), drive two (Motion_2), drive three (Motion_3), drive four (Motion_4), drive Five (Motion_5), drive six (Motion_6).

Step 2: Build the kinematic inverse solution model

The inverse kinematics model is built in the Matlab/Simulink module. The inverse kinematics model mainly includes a coordinate transformation module and an electric cylinder telescopic speed acquisition module.

Among them, the coordinate transformation module obtains the new coordinates of each hinge point of the upper platform after the transformation through the input displacement variable or angle variable of the upper platform, and the Fcn module mainly adds the transformation formula corresponding to each element of the rotation matrix to form a rotation containing 9 elements. array, and then convert the 9-element rotation array into a 3×3 rotation matrix through the Reshape module. Among them, the rotation matrix R is:

表示上平台1相对于底座14在x轴方向上的旋转角度。然后，旋转矩阵R与上铰接点的初始坐标相乘，得到旋转变换后的坐标矩阵，其中上铰接点的初始坐标即为步骤1中在Adams/view模块中依次建立上铰接点硬点时生成的坐标。再将输入的位移变量通过Matrix Concatenate模块转换为每行上元素相同的3×6移动矩阵，并与旋转变换后的坐标矩阵相加得到上平台每个铰接点的新坐标矩阵；其中移动矩阵中每一行的六个元素相同，其中第一行的每个元素值为位移变量在x轴方向上的位移目标量，第二行的每个元素值为位移变量在y轴方向上的位移目标量，第三行的每个元素值为位移变量在y轴方向上的位移目标量。Among them, ψ represents the rotation angle of the upper platform 1 relative to the base 14 in the z-axis direction, θ represents the rotation angle of the upper platform 1 relative to the base 14 in the y-axis direction,

Indicates the rotation angle of the upper platform 1 relative to the base 14 in the x-axis direction. Then, the rotation matrix R is multiplied by the initial coordinates of the upper hinge point to obtain the coordinate matrix after the rotation transformation, wherein the initial coordinates of the upper hinge point are generated when the hard points of the upper hinge point are successively established in the Adams/view module in step 1. coordinate of. Then, the input displacement variable is converted into a 3 × 6 movement matrix with the same elements on each row through the Matrix Concatenate module, and is added to the coordinate matrix after the rotation transformation to obtain a new coordinate matrix for each hinge point of the upper platform; The six elements in each row are the same, where each element in the first row is the displacement target amount of the displacement variable in the x-axis direction, and each element in the second row is the displacement target amount of the displacement variable in the y-axis direction , the value of each element in the third row is the displacement target amount of the displacement variable in the y-axis direction.

Thirdly, the electric cylinder telescopic speed acquisition module takes the coordinates of the lower hinge point after initialization of each electric cylinder as the starting point, and the new coordinates of the upper hinge point after transformation as the end point, respectively establishes the vector of each electric cylinder, and selects elements from the matrix mainly through the Selector module. , extract the vector where each electric cylinder is located. Take the modulo of the vector where each electric cylinder is located to obtain the real-time length of each electric cylinder. Subtract the real-time length of the electric cylinder from the initial length of the electric cylinder to obtain the telescopic amount of each electric cylinder, and then derive the telescopic amount of the electric cylinder to obtain the telescopic speed of each electric cylinder.

Step 3: Input the telescopic speed of each electric cylinder obtained from the dynamic inverse solution model into the established dynamic three-dimensional model of the Stewart parallel mechanism to obtain the output force of each electric cylinder; Multiply the telescopic speed to get the power value of each electric cylinder.

First, the measurements of each driving force are created in Adams software. The specific method is to right-click Motion_1, select the Measure function in the Adams software to measure the resultant force of drive one, and rename it to Measure_M_1, and so on to create the resultant force of the other five drives. Create input/output variables in Adams, and click "Element-System Element-Create State Variable" to create input/output variables. The input variables that need to be created include the speed of drive one (V_motion_1) and the speed of drive two (V_motion_2 ), the speed of drive three (V_motion_3), the speed of drive four (V_motion_4), the speed of drive five (V_motion_5), the speed of drive six (V_motion_6); the output variables to be created include the force of drive one (F_motion_1), the speed of drive two Force (F_motion_2), Force Three (F_motion_3), Force Four (F_motion_4), Force Five (F_motion_5), Force Six (F_motion_6).

Then, associate the input variable with the displacement drive through the VARVAL() function, set the drive function of drive 1 to VARVAL(V_motion_1), and so on to complete the association of the other five drive functions with the speed variable. In this embodiment, Velocity should be selected as the drive type, that is, velocity drive is used. If the displacement type (displacement drive) is used, the final simulation result will be wrong. In addition, it is necessary to associate the resultant force of each drive to the corresponding output variable, and set the function of the output variable F_motion_1 to Measure_M_1, which is the name of the resultant force of the drive. By analogy, complete the association between the resultant force of the other five drives and the output variable. Load the Adams/Control module to export the interaction file. Select the corresponding input/output variables through "Plugins-Controls-Plant Export" in Adams, and Target Software selects Matlab to export the kinetic interaction file.

Next, enter the name of the interaction file generated in Adams in the matlab command window to display the input/output variable names of all dynamic models, and then enter the adams_sys command to generate the adams_sub module in the Simulink module. Open the inverse kinematics model, copy the adams_sub module to the inverse kinematics model, and connect it.

Finally, multiply each output force of each electric cylinder by the corresponding driving speed to obtain the corresponding driving power value of each electric cylinder.

The present invention also provides a computer-readable medium storing software comprising instructions executable by one or more computers, the instructions, by such execution, cause the one or more computers to perform operations, the Operations include the flow of the Stewart Parallel Mechanism Construction Method as previously described.

The effects of the present invention will be described below with specific examples.

Taking a six-degree-of-freedom platform as an example, the platform is loaded with a spherical object with a mass of 2t, and the moment of inertia in all directions of the load is 1.805E+08kg·mm ² . The center of mass of the load is 0.5m away from the upper platform. According to the motion index of the upper platform, the output of the electric cylinder and the power of the motor under each working condition are calculated, which is convenient for the subsequent selection of the motor. Motion indicators of the upper platform: (1) Pitch condition (rotational motion around the x-axis), the platform performs sinusoidal pitching motion with 22.5° as the amplitude and 1s as the motion period; (2) Rolling condition (rotational motion around the y-axis) , the platform takes 22.5° as the amplitude, and 1s is the motion period to do a sinusoidal rolling motion; (3) in the lateral movement condition (moving along the x-axis), the platform takes 15mm as the amplitude, and 1s is the motion period to do a sinusoidal lateral motion. .

The first step is to enter the coordinates of the upper and lower hinge points in Adams to complete the creation of the rigid body 3D model.

The second step is to add constraints, drives and gravity to complete the establishment of the dynamic model.

The third step is to set the speed of the electric cylinder displacement drive as the input variable, the electric cylinder thrust as the output variable, and export the interactive file.

The fourth step is to open the interactive file generated in the third step in Matlab, and generate the adams_sub module.

The fifth step, open the inverse solution module and connect the adams_sub module in the fourth step with it.

The sixth step, add the sine wave module as input to the x rotation angle module, the amplitude is pi/8, and the frequency is 2*pi.

The seventh step is to set the simulation time and step size to simulate.

The eighth step, after the simulation is over, output the simulation results to obtain the magnitude and power of the output force and power of each electric cylinder that completes the motion in the pitching condition, as shown in Figures 2 and 3.

The ninth step, modify the sine wave module in the sixth step to Constant constant module and modify the value to 0, add the sine wave module as input to the y rotation angle module, the amplitude is pi/8, and the frequency is 2*pi.

The tenth step is to set the simulation time and step size to simulate.

The eleventh step, after the simulation is over, output the simulation results to obtain the magnitude and power of the output force and power of each electric cylinder that completes the motion under the rolling condition, as shown in Figure 4 and Figure 5.

The twelfth step, modify the sine wave module in the ninth step to Constant constant module and modify the value to 0, add the sine wave module as input in the x movement module, the amplitude is 15, and the frequency is 2*pi.

The thirteenth step is to set the simulation time and step size to simulate.

The fourteenth step, after the simulation is over, output the simulation results to obtain the magnitude and power of the output force of each electric cylinder that completes the movement under the sideshift condition, as shown in Figure 6 and Figure 7.

Table 1: Coordinates of the upper and lower hinge points of the platform.

If only Adams is used for simulation, it is necessary to first establish a 3D model, add constraints, add materials, and add point drives to inversely solve the telescopic amount of each electric cylinder in pitch attitude over time, and use the AKISPL function in the post-processing interface to calculate the telescopic amount of the electric cylinder. - The time change curve is imported back to the Data Elements of the Adams/View module, and then the point driver module in the kinematic model is deleted, and a translation driver is added to each moving pair, and each SPLINE line in the Data Elements is imported into the corresponding translation driver , the output of each electric cylinder and the motor power of the pitch attitude are calculated through dynamic simulation. Due to the large number of motion conditions of the upper platform (9 common conditions), it is necessary to perform the kinematic inverse solution for each condition according to the motion index, and then re-import the inverse solution results into the drive to rebuild the dynamic model. The input of the platform motion index directly obtains the parameters of the electric cylinder, and it takes a lot of time to model repeatedly.

In the present invention, the output of the electric cylinder and the power of the motor can be quickly solved for multiple working conditions only by modifying the input parameters for different motion indexes, and no repeated modeling is required.

Claims (8)

1. a Stewart parallel mechanism construction method, is characterized in that: comprise the following steps: Establish the dynamic 3D model of Stewart parallel mechanism; Build a kinematic inverse solution model; the kinematic inverse solution model includes a coordinate transformation module and an electric cylinder telescopic speed acquisition module; the coordinate transformation module obtains each hinge of the upper platform after transformation through the input displacement or angle variable of the upper platform The new coordinates of the point; the electric cylinder telescopic speed acquisition module calculates the real-time length of each electric cylinder in the dynamic three-dimensional model of the Stewart parallel mechanism according to the new coordinates of each hinge point of the upper platform obtained by the coordinate change module, and each The real-time length of the electric cylinder is subtracted from the initial length of the electric cylinder to obtain the telescopic amount of each electric cylinder, and the telescopic speed of each electric cylinder is calculated according to the telescopic amount of each electric cylinder; The telescopic speed of each electric cylinder obtained by the inverse kinematics model is input into the established Stewart parallel mechanism dynamics model, and the output force of each electric cylinder is obtained; Multiply the output force of each electric cylinder with the corresponding telescopic speed to obtain the power value of each electric cylinder. 2. Stewart parallel mechanism construction method according to claim 1, is characterized in that: the method for the described establishment of the dynamic three-dimensional model of Stewart parallel mechanism is: Step 101: Establish upper hinge point hard points (p1, p2, p3, p4, p5, p6) and lower hinge point hard points (b1, b2, b3, b4, b5, b6) in sequence; Step 102: Using p1 as the starting point, along the direction of the straight line from p1 to b1, use the cylindrical geometry module to establish the geometric model of the push rod 1 according to the length of the push rod 1; with p2 as the starting point, along the two points from p2 to b2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second push rod according to the length of the second push rod; with p3 as the starting point, along the direction of the two points from p3 to b3, use the cylindrical geometry module, according to the length of the third push rod. Build the geometric model of the putter 3; take p4 as the starting point, along the direction of the line from p4 to b4, use the cylinder geometry module to build the geometric model of the putter 4 according to the length of the putter 4; take p5 as the starting point, along the In the direction of the straight line from p5 to b5, use the cylindrical geometry module to build the geometric model of the push rod five according to the length of the push rod five; take p6 as the starting point, along the direction of the two points from p6 to b6, use the cylindrical geometry module, according to The length of the putter six establishes the geometric model of the putter six; Step 103: Using b1 as the starting point, along the direction of the straight line from b1 to p1, use the cylindrical geometry module to establish the geometric model of cylinder 1 according to the length of cylinder 1; starting from b2, follow the two points from b2 to p2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second cylinder according to the length of the second cylinder; with b3 as the starting point, along the direction of the two straight lines from b3 to p3, use the cylindrical geometry module, according to the length of the third cylinder Build the geometric model of cylinder 3; take b4 as the starting point, along the direction of the straight line from b4 to p4, use the cylindrical geometry module to establish the geometric model of cylinder 4 according to the length of cylinder 4; In the direction of the line from b5 to p5, use the cylindrical geometry module to establish the geometric model of cylinder five according to the length of cylinder five; take b6 as the starting point, along the direction of the line from b6 to p6, use the cylindrical geometry module, according to The length of cylinder 6 establishes the geometric model of cylinder 6; Step 104: Taking p1, p2, p3, p4, p5, and p6 as vertices, use the slab geometry module to build the upper platform geometric model; taking b1, b2, b3, b4, b5, b6 as the vertices, use the slab geometry module to build the base geometry Model; Step 105: respectively set the motion pair between the upper platform and each push rod; the motion pair between each push rod and its corresponding cylinder, the motion pair between each cylinder and the base; and set each part the weight of. 3. The method for constructing a Stewart parallel mechanism according to claim 2, wherein the motion pair between the upper platform and each push rod adopts a Hooke hinge pair. 4. The method for constructing a Stewart parallel mechanism according to claim 2, characterized in that: a moving pair is used between each push rod and its corresponding cylinder. 5 . The method for constructing a Stewart parallel mechanism according to claim 2 , wherein the motion pair between each cylinder and the base adopts a ball pair. 6 . 6. A Stewart parallel mechanism building system, characterized in that: comprising a three-dimensional model building unit, a dynamic inverse solution unit and an electric cylinder signal selection unit; wherein, The three-dimensional model building unit is used to build a dynamic three-dimensional model of the Stewart parallel mechanism; The kinematic inverse solution unit includes a coordinate transformation module and an electric cylinder telescopic speed acquisition module; wherein, the coordinate transformation module obtains the new coordinates of each hinge point of the upper platform after the transformation through the input displacement or angle variable of the upper platform; The electric cylinder telescopic speed acquisition module calculates the real-time length of each electric cylinder in the dynamic three-dimensional model of the Stewart parallel mechanism according to the new coordinates of each hinge point of the upper platform obtained by the coordinate change module, and compares the real-time length of each electric cylinder with the real-time length of each electric cylinder. The telescopic amount of each electric cylinder is obtained by subtracting the initial length of the electric cylinder, and the telescopic speed of each electric cylinder is calculated according to the telescopic amount of each electric cylinder; and the obtained telescopic speed of each electric cylinder is input into the 3D model establishment unit , get the output force of each electric cylinder; The electric cylinder signal selection unit multiplies the output force of each electric cylinder and the corresponding telescopic speed to obtain the power value of each electric cylinder and outputs it. 7. Stewart parallel mechanism building system according to claim 6, is characterized in that: the method that described three-dimensional model building unit builds the dynamic three-dimensional model of Stewart parallel mechanism is: Step 101: Establish upper hinge point hard points (p1, p2, p3, p4, p5, p6) and lower hinge point hard points (b1, b2, b3, b4, b5, b6) in sequence; Step 102: Using p1 as the starting point, along the direction of the straight line from p1 to b1, use the cylindrical geometry module to establish the geometric model of push rod 1 according to the length of push rod 1; starting from p2, along the two points from p2 to b2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second push rod according to the length of the second push rod; with p3 as the starting point, along the direction of the two points from p3 to b3, use the cylindrical geometry module, according to the length of the third push rod. Build the geometric model of putter 3; take p4 as the starting point, along the direction of the line from p4 to b4, use the cylinder geometry module to build the geometric model of putter 4 according to the length of putter 4; take p5 as the starting point, along the In the direction of the line from p5 to b5, use the cylindrical geometry module to build the geometric model of the push rod five according to the length of the push rod five; take p6 as the starting point, along the direction of the two points from p6 to b6, use the cylindrical geometry module, according to The length of the putter six establishes the geometric model of the putter six; Step 103: Using b1 as the starting point, along the direction of the straight line from b1 to p1, use the cylindrical geometry module to establish the geometric model of cylinder 1 according to the length of cylinder 1; starting from b2, follow the two points from b2 to p2 In the direction of the straight line, use the cylindrical geometry module to establish the geometric model of the second cylinder according to the length of the second cylinder; with b3 as the starting point, along the direction of the two straight lines from b3 to p3, use the cylindrical geometry module, according to the length of the third cylinder Build the geometric model of cylinder 3; take b4 as the starting point, along the direction of the straight line from b4 to p4, use the cylindrical geometry module to establish the geometric model of cylinder 4 according to the length of cylinder 4; In the direction of the line from b5 to p5, use the cylindrical geometry module to build the geometric model of cylinder five according to the length of cylinder five; take b6 as the starting point, along the direction of the line from b6 to p6, use the cylindrical geometry module, according to The length of cylinder 6 establishes the geometric model of cylinder 6; Step 104: Taking p1, p2, p3, p4, p5, and p6 as vertices, use the slab geometry module to build the upper platform geometric model; taking b1, b2, b3, b4, b5, b6 as the vertices, use the slab geometry module to build the base geometry Model; Step 105: respectively set the motion pair between the upper platform and each push rod; the motion pair between each push rod and its corresponding cylinder, the motion pair between each cylinder and the base; and set each part the weight of. 8. A computer-readable medium storing software comprising instructions executable by one or more computers that, by such execution, cause the one or more computers to perform operations, thereby The operation includes the flow of the Stewart parallel mechanism construction method according to any one of claims 1-5.

Images