CN112580167B - Stewart parallel mechanism construction method, system and computer storage medium - Google Patents
Stewart parallel mechanism construction method, system and computer storage medium Download PDFInfo
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Abstract
本发明公开了一种Stewart并联机构构建方法，本发明首先建立Stewart并联机构的动力学三维模型和运动学反解模型；通过运动学反解模型反解出各电缸速度并直接输入动力学三维模型进行交互仿真。本发明还提供了一种Stewart并联机构构建系统及存储软件的计算机可读介质。本发明可通过输入上平台运动指标，直接将反解结果输入至动力学模型中，输出电缸或电机参数，便于在实验中直接搭建Stewart并联机构，避免了反复建模过程。
The present invention discloses a method for constructing a Stewart parallel mechanism. The present invention first establishes a dynamic three-dimensional model and a kinematic inverse model of the Stewart parallel mechanism; the speed of each electric cylinder is inversely solved by the kinematic inverse model and directly input into the dynamic three-dimensional model for interactive simulation. The present invention also provides a computer-readable medium for constructing a Stewart parallel mechanism and storing software. The present invention can directly input the inverse result into the dynamic model by inputting the upper platform motion index, and output the electric cylinder or motor parameters, so as to facilitate the direct construction of the Stewart parallel mechanism in the experiment and avoid repeated modeling processes.
Description
Technical Field
The invention belongs to the field of digital simulation, and particularly relates to a method and a system for constructing a Stewart parallel mechanism and a computer storage medium.
Background
The Stewart platform is a six-degree-of-freedom parallel mechanism, has the characteristics of high precision, high rigidity, stable structure, high load capacity and the like compared with a serial mechanism, has wide application in the fields of aerospace, automobile engineering, biomedicine and the like, and is particularly suitable for working occasions with a small working range but a large load. In the Stewart parallel mechanism study, kinetic analysis is a very important aspect, which is the basis for overall system design and control. Compared with a serial mechanism, the Stewart platform is a space multi-ring closed type motion system, a passive joint exists, and corresponding kinematic constraint conditions need to be met in the motion process, so that the dynamics analysis process is more difficult than that of the serial mechanism.
The virtual prototype technology takes kinematics, dynamics and a control method as a core, can rapidly complete a simulation test which is difficult to complete by an actual physical model, outputs a corresponding simulation result, can greatly reduce development cost and shorten development period, and has important significance in dynamics analysis of a Stewart parallel mechanism.
The main method at present is to introduce a three-dimensional model of a Stewart platform into an Adams/View module, and add kinematic pairs between parts according to actual conditions. And driving the upper platform in a point driving mode according to the motion indexes of different working conditions, solving a change curve between the expansion and contraction amounts of all the electric cylinders, fitting data through Adams self-contained functions, and re-introducing the data into a dynamic model as driving conditions to calculate the output of all the electric cylinders and the power of the motor. Modeling according to a three-dimensional model of the part, wherein the shape of the model is consistent with the actual structure; the simulation process has the animation demonstration function, and the motion state of the mechanism can be mastered in real time; interference, clearance, etc. between parts can be analyzed.
In the simulation process, as the platform motion working conditions are more, each working condition needs to be reversely solved, then the dynamic model is built again, parameters of the electric cylinder or the motor cannot be directly obtained through the input of the motion index of the upper platform, the modeling process is complicated, and a large amount of time is needed to be consumed.
Disclosure of Invention
The invention aims to: aiming at the problems in the prior art, the invention provides a Stewart parallel mechanism construction method capable of directly giving out the selection parameters of the electric cylinders according to the movement conditions of working conditions.
The technical scheme is as follows: in order to achieve the above purpose, a method for constructing a Stewart parallel mechanism is provided, which comprises the following steps:
establishing a dynamic three-dimensional model of the Stewart parallel mechanism;
building a kinematic inverse model; the kinematic inverse model comprises a coordinate transformation module and an electric cylinder expansion speed acquisition module; the coordinate transformation module obtains new coordinates of each hinge point of the transformed upper platform through the input displacement or angle variable of the upper platform; the electric cylinder expansion 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 coordinate of each hinge point of the upper platform obtained by the coordinate change module, subtracts the real-time length of each electric cylinder from the initial length of the electric cylinder to obtain the expansion amount of each electric cylinder, and calculates the expansion speed of each electric cylinder according to the expansion amount of each electric cylinder;
The method comprises the steps of inputting the expansion speed of each electric cylinder obtained by a kinematic inverse model into an established Stewart parallel mechanism dynamics model to obtain the output force of each electric cylinder;
And multiplying the output force of each electric cylinder by the corresponding telescopic speed to obtain the power value of each electric cylinder.
The method for establishing the dynamic three-dimensional model of the Stewart parallel mechanism comprises the following steps:
Step 101: sequentially establishing upper hinge point hard points (p 1, p2, p3, p4, p5, p 6) and lower hinge point hard points (b 1, b2, b3, b4, b5, b 6);
Step 102: using p1 as a starting point, and using a cylindrical geometric module along the direction of the two straight lines of the points p1 and b1 to establish a geometric model of the first push rod according to the length of the first push rod; using p2 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p2 to b2 to establish a geometric model of the second push rod according to the length of the second push rod; using p3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p3 to b3 to build a geometric model of the push rod III according to the length of the push rod III; using p4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p4 to b4 to build a geometric model of the push rod IV according to the length of the push rod IV; using p5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p5 to b5 to build a geometric model of the push rod five according to the length of the push rod five; using p6 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p6 to b6 to build a geometric model of the push rod six according to the length of the push rod six;
Step 103: taking b1 as a starting point, and establishing a geometric model of the cylinder barrel I according to the length of the cylinder barrel I by using a cylindrical geometric module along the direction of the two points b1 to p 1; using b2 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b2 to p2 to establish a geometric model of the cylinder barrel II according to the length of the cylinder barrel II; using b3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b3 to p3 to build a geometric model of the cylinder barrel III according to the length of the cylinder barrel III; using b4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b4 to p4 to build a geometric model of the cylinder barrel IV according to the length of the cylinder barrel IV; using b5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b5 to p5 to build a geometric model of the cylinder barrel five according to the length of the cylinder barrel five; taking b6 as a starting point, and establishing a geometric model of the cylinder barrel six according to the length of the cylinder barrel six by using a cylindrical geometric module along the direction of the two points of b6 to p 6;
Step 104: using p1, p2, p3, p4, p5 and p6 as vertexes, and using a flat plate geometric module to build an upper platform geometric model; b1, b2, b3, b4, b5 and b6 are taken as vertexes, and a flat plate geometric model is used for establishing a base geometric model;
Step 105: a kinematic pair between the upper platform and each push rod is respectively arranged; a kinematic pair between each push rod and the corresponding cylinder barrel, and a kinematic pair between each cylinder barrel and the base; and sets the weight of each part.
Further, a Hooke hinge pair is adopted as a kinematic pair between the upper platform and each push rod.
Further, a shifting pair is adopted between each push rod and the corresponding cylinder barrel.
Further, a ball pair is adopted as a kinematic pair between each cylinder barrel and the base.
The invention also provides a Stewart parallel mechanism construction system, which comprises a three-dimensional model establishment unit, a dynamics inverse solution unit and an electric cylinder signal selection unit; wherein,
The three-dimensional model building unit is used for building a dynamic three-dimensional model of the Stewart parallel mechanism;
The kinematic inverse solution unit comprises a coordinate transformation module and an electric cylinder expansion speed acquisition module; the coordinate transformation module obtains new coordinates of each hinge point of the upper platform after transformation through input displacement or angle variable of the upper platform; the electric cylinder expansion 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 coordinate of each hinge point of the upper platform obtained by the coordinate change module, subtracts the real-time length of each electric cylinder from the initial length of the electric cylinder to obtain the expansion amount of each electric cylinder, and calculates the expansion speed of each electric cylinder according to the expansion amount of each electric cylinder; the obtained expansion speed of each electric cylinder is input into a three-dimensional model building unit, and the output force of each electric cylinder is obtained;
And multiplying the output force of each electric cylinder by the corresponding expansion speed by the electric cylinder signal selection unit to obtain the power value of each electric cylinder and outputting the power value.
The method for establishing the dynamic three-dimensional model of the Stewart parallel mechanism by the three-dimensional model establishing unit comprises the following steps:
Step 101: sequentially establishing upper hinge point hard points (p 1, p2, p3, p4, p5, p 6) and lower hinge point hard points (b 1, b2, b3, b4, b5, b 6);
Step 102: using p1 as a starting point, and using a cylindrical geometric module along the direction of the two straight lines of the points p1 and b1 to establish a geometric model of the first push rod according to the length of the first push rod; using p2 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p2 to b2 to establish a geometric model of the second push rod according to the length of the second push rod; using p3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p3 to b3 to build a geometric model of the push rod III according to the length of the push rod III; using p4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p4 to b4 to build a geometric model of the push rod IV according to the length of the push rod IV; using p5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p5 to b5 to build a geometric model of the push rod five according to the length of the push rod five; using p6 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p6 to b6 to build a geometric model of the push rod six according to the length of the push rod six;
Step 103: taking b1 as a starting point, and establishing a geometric model of the cylinder barrel I according to the length of the cylinder barrel I by using a cylindrical geometric module along the direction of the two points b1 to p 1; using b2 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b2 to p2 to establish a geometric model of the cylinder barrel II according to the length of the cylinder barrel II; using b3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b3 to p3 to build a geometric model of the cylinder barrel III according to the length of the cylinder barrel III; using b4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b4 to p4 to build a geometric model of the cylinder barrel IV according to the length of the cylinder barrel IV; using b5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b5 to p5 to build a geometric model of the cylinder barrel five according to the length of the cylinder barrel five; taking b6 as a starting point, and establishing a geometric model of the cylinder barrel six according to the length of the cylinder barrel six by using a cylindrical geometric module along the direction of the two points of b6 to p 6; ;
Step 104: using p1, p2, p3, p4, p5 and p6 as vertexes, and using a flat plate geometric module to build an upper platform geometric model; b1, b2, b3, b4, b5 and b6 are taken as vertexes, and a flat plate geometric model is used for establishing a base geometric model;
Step 105: a kinematic pair between the upper platform and each push rod is respectively arranged; a kinematic pair between each push rod and the corresponding cylinder barrel, and a kinematic pair between each cylinder barrel and the base; and sets the weight of each part.
The present invention also provides a computer readable medium storing software comprising instructions executable by one or more computers which, by such execution, cause the one or more computers to perform operations comprising the flow of the Stewart parallel mechanism building method of any one of claims 1-5.
Working principle: according to the invention, a kinematic model of a Stewart platform is established through Simulink, the speed of each electric cylinder is reversely solved, and the electric cylinder is directly input into a dynamics module derived from Adams for interactive simulation. According to the method, the inverse solution result can be directly input into the dynamic model through inputting the motion index of the upper platform, and the parameters of the electric cylinder or the motor are output, so that the repeated modeling process is avoided.
The beneficial effects are that: compared with the prior art, the invention can directly output dynamic parameters such as the output force of the electric cylinder or the power of the motor under the condition of inputting the motion index of the upper platform, and has the advantages of animation demonstration function, capability of analyzing the interference among parts and the like.
Drawings
FIG. 1 is a schematic diagram of a Stewart parallel mechanism;
FIG. 2 is a schematic diagram of cylinder thrust after simulation of pitch conditions by the method provided by the invention;
FIG. 3 is a schematic diagram of cylinder power after simulating a pitching condition by the method provided by the invention;
FIG. 4 is a schematic diagram of cylinder thrust after simulation of rolling conditions by the method provided by the invention;
FIG. 5 is a schematic diagram of the power of the cylinder after the method provided by the invention simulates the rolling working condition;
FIG. 6 is a schematic diagram of cylinder thrust after simulation of side-shifting conditions by the method provided by the invention;
FIG. 7 is a schematic diagram of cylinder power after a side-shifting condition is simulated by the method provided by the invention.
Detailed Description
The following description of the embodiments of the present invention will be made more clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment provides a Stewart parallel mechanism construction system, which mainly comprises a three-dimensional model establishment unit, a dynamics inverse solution unit and an electric cylinder signal selection unit; the three-dimensional model building unit and the electric cylinder signal selecting unit are completed through modules in Adams software, the dynamics inverse solution unit is built through a Matlab/Simulink module, and the method specifically comprises the following steps of:
Step 1: establishing a dynamic three-dimensional model of a Stewart parallel mechanism:
Step 101: upper hinge point hard points (p 1, p2, p3, p4, p5, p 6) and lower hinge point hard points (b 1, b2, b3, b4, b5, b 6) are established in the Adams/view module in sequence.
Step 102: using p1 as a starting point, along the direction of the straight line of the two points p1 TO b1, using a Geometry-Cylinder module (hereinafter referred TO as a Geometry-Cylinder module) in Adams software, building a geometric model of the first push rod according TO the actual length of the first push rod of the adopted electric Cylinder, setting the position of a reference point of the starting point of the first push rod as (LOC_RELATIVE_TO ({ 0,0}, p 1)), wherein the setting uses a Location option in Adams software, namely, the RELATIVE distances between the reference point and the point p1 in the x, y and z directions are all 0. This allows the established start point of the putter to be changed together with the modification of the position of the hard point p1, and then the direction of the reference point is set to (ori_along_axis (p 1, b1, "Z")), which uses the Orientation option in Adams software to indicate that the direction of the reference point Z of the start point of the putter is the same as the direction of the straight line of p1 to b1, so that the established direction of the putter can always be ALONG the direction of the straight line of p1 to b 1. And the second push rod, the third push rod, the fourth push rod, the fifth push rod and the sixth push rod are respectively built by analogy.
Step 103: taking b1 as a starting point, ALONG the direction of the straight line of two points b1 TO p1, using a Geometry-Cylinder module in Adams software TO establish a geometric model of the Cylinder one according TO the actual length of the Cylinder one which is actually adopted, setting the position of a reference point of the Cylinder one as (LOC_RELATIVE_TO ({ 0,0}, b 1)), using a Location option in Adams software, namely, representing the RELATIVE distances of x, y and Z directions between the reference point and the point b1, TO be 0, so that the established starting point of the Cylinder one can be changed together with the position of the hard point b1, and then setting the direction of the reference point as (ORI_ALONG_AXIS (b 1, p1 and Z ")), and using an Orientation option in Adams software TO represent the direction of the reference point Z of the Cylinder one as the straight line of b1 TO be the same, so that the established direction can be always ALONG the straight line of the Cylinder one TO be ALONG the direction of the point b1 TO p 1. And the second cylinder, the third cylinder, the fourth cylinder, the fifth cylinder and the sixth cylinder are established by analogy.
Step 104: using p1, p2, p3, p4, p5 and p6 as vertexes, and using a Geometry-plate module (a flat plate Geometry module) in Adams software to build an upper platform geometric model; the upper platform has 6 modeling reference points, the positions of the 6 modeling reference points are respectively set to (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)),, and the setting uses a Location option in Adams software, so that the established upper platform can always change along with the modification of the positions of hinge points of the upper platform. And the base geometric model is built in the same way. The load position is added by the actual gravity center height of the load, the shape of the load can be ignored, the ball is used for replacing the load, the gravity center position, the mass and the moment of inertia of the load are needed to be noted, the height of the mass center is adjusted by modifying the reference coordinate position of the ball according to the actual situation, and the load mass and the moment of inertia of the load are input by adopting a manual input mode.
Step 105: a kinematic pair between the upper platform and each push rod is respectively arranged; a kinematic pair between each push rod and the corresponding cylinder barrel, and a kinematic pair between each cylinder barrel and the base; and sets the weight of each part.
The materials are added to each part according to actual conditions, and the materials mainly used are steel, so that the quality of the parts is guaranteed to be consistent with the actual conditions, and the density of the materials can be directly input, so that the quality of the parts is guaranteed to be consistent with the actual conditions.
Establishing constraint among parts:
(1) The upper platform 1 and the push rod one 2 are connected by a Hooke hinge pair, and the reference position of the Hooke hinge pair connecting point is set TO be (LOC_RELATIVE_TO ({ 0,0}, p 1)), so that the established Hooke hinge pair can be always changed along with the modification of the position of the hard point p 1. A Hooke hinge pair is arranged between the upper platform 2 and the push rod II 3, the push rod III 4, the push rod IV 5, the push rod V6 and the push rod VI 7 by the same method.
(2) A moving pair is arranged between the push rod I2 and the cylinder barrel I8, the reference position of the connecting point of the moving pair is set as (LOC_RELATIVE_TO ({ 0,0}, link1. Cm)), wherein link.cm is the centroid coordinate of the push rod I2, which is automatically generated after the geometric model of the push rod is built and the materials are arranged, the direction is set as (ORI_ALONG_AXIS (b 1, p1, Z'), the reference Z direction of the connecting point of the moving pair is the same as the direction of the straight line of b1 TO p1, so that the built moving pair is always positioned in the center of the push rod, and the direction of the moving pair is always consistent with the push rod. In the same way, a moving pair is arranged between the second push rod 3 and the second cylinder barrel 9, between the third push rod 4 and the third cylinder barrel 10, between the fourth push rod 5 and the fourth cylinder barrel 11, between the fifth push rod 6 and the fifth cylinder barrel 12, and between the sixth push rod 7 and the sixth cylinder barrel 13.
(3) A ball pair is provided between the base 14 and the cylinder one 8, and the ball pair connection point reference position is set TO (loc_related_to ({ 0,0}, b 1)), so that the established ball pair can be always changed along with the modification of the position of the hard point b 1. In the same way, a ball pair is arranged between the base 15 and the cylinder two 10, the cylinder three 11, the cylinder four 12, the cylinder five 13 and the cylinder six 14.
(4) A fixed pair is arranged between the load 15 and the upper platform 1, and the position of the fixed pair is set as (loc_related_to ({ 0,0}, platform. Cm)), wherein platform_base.cm is the centroid coordinate of the upper platform 1, which is automatically generated after the establishment of the geometric model of the upper platform 1 and the completion of the material setting, so that the fixed pair changes along with the change of the centroid position of the upper platform.
(5) A fixed pair is disposed between the base 14 and the ground (ground), and the position of the fixed pair is set TO (loc_related_to ({ 0,0}, base.cm)), where base.cm is the base centroid coordinate, which is automatically generated after the base geometric model is built and the material is set, so that the fixed pair changes with the change of the base centroid position.
And a displacement drive is added on a moving pair between each push rod and the cylinder barrel, and six displacement drives are respectively a first drive (motion_1), a second drive (motion_2), a third drive (motion_3), a fourth drive (motion_4), a fifth drive (motion_5) and a sixth drive (motion_6).
Step 2: setting up a kinematic inverse model
The kinematic inverse model is built on a Matlab/Simulink module and mainly comprises a coordinate transformation module and an electric cylinder expansion speed acquisition module.
The coordinate transformation module obtains new coordinates of each hinge point of the transformed upper platform through input displacement variables or angle variables of the upper platform, a transformation formula corresponding to each element of the rotation matrix is added through the Fcn module to form a rotation array containing 9 elements, and the rotation array containing 9 elements is converted into a rotation matrix of 3 multiplied by 3 through the Reshape module. Wherein, the rotation matrix R is:
Where, ψ represents the rotation angle of the upper stage 1 with respect to the base 14 in the z-axis direction, θ represents the rotation angle of the upper stage 1 with respect to the base 14 in the y-axis direction, The rotation angle of the upper stage 1 with respect to the base 14 in the x-axis direction is shown. And then multiplying the rotation matrix R by the initial coordinates of the upper hinge point to obtain a coordinate matrix after rotation transformation, wherein the initial coordinates of the upper hinge point are generated when the upper hinge point hard point is sequentially established in the Adams/view module in the step 1. Converting the input displacement variable into a3 multiplied by 6 movement matrix with the same elements on each row through Matrix Concatenate modules, and adding the movement matrix with the coordinate matrix after rotation transformation to obtain a new coordinate matrix of each hinge point of the upper platform; the six elements of each row in the movement matrix are the same, wherein each element value of the first row is a displacement target amount of the displacement variable in the x-axis direction, each element value of the second row is a displacement target amount of the displacement variable in the y-axis direction, and each element value of the third row is a displacement target amount of the displacement variable in the y-axis direction.
And thirdly, the telescopic speed acquisition module of the electric cylinders respectively establishes vectors of each electric cylinder by taking the coordinates of a lower hinge point after the initialization of each electric cylinder as a starting point and the new coordinates of an upper hinge point after transformation as an end point, and mainly selects elements from a matrix through the Selector module to extract the vectors of each electric cylinder. And taking a model of the vector of each electric cylinder to obtain the real-time length of each electric cylinder. Subtracting the real-time length of the electric cylinder from the initial length of the electric cylinder to obtain the expansion and contraction amount of each electric cylinder, and further deriving the expansion and contraction amount of the electric cylinder to obtain the expansion and contraction speed of each electric cylinder.
Step 3: the dynamic inverse solution model is used for obtaining the expansion speed of each electric cylinder, and inputting the expansion speed of each electric cylinder into a dynamic three-dimensional model of the established Stewart parallel mechanism to obtain the output force of each electric cylinder; and multiplying the output force of each electric cylinder by the corresponding telescopic speed to obtain the power value of each electric cylinder.
First, a measurement of each driving force is created in Adams software. The specific practice is right click motion_1, select the Measure function in Adams software to Measure the resultant force of one driver, rename measure_m_1, and so on, create the resultant force of the other 5 drivers. Creating input/output variables in Adams, wherein the creation of the input/output variables is realized by clicking an Element-SYSTEM ELEMENT-CREATE STATE Variable, and the input variables to be created comprise a first speed (V_motion_1), a second speed (V_motion_2), a third speed (V_motion_3), a fourth speed (V_motion_4), a fifth speed (V_motion_5) and a sixth speed (V_motion_6); the output variables that need to be created include force one (f_motion_1), force two (f_motion_2), force three (f_motion_3), force four (f_motion_4), force five (f_motion_5), force six (f_motion_6).
Then, the input variable is correlated into the displacement drive through VARVAL () function, the drive function of drive one is set to VARVAL (v_motion_1), and the other 5 drive functions are correlated with the velocity variable. In this embodiment, the driving type is to select the speed, that is, the final simulation result of using the Displacement type will be wrong. In addition, each driving resultant force is also associated with a corresponding output variable, and the function of the output variable f_motion_1 is set to measure_m_1, i.e. the name of the driving resultant force. And the other 5 driving resultant forces are associated with the output variable in the similar way. And loading an Adams/Control module to export the interaction file. And selecting a corresponding input/output variable through 'Plugins-Controls-Plant Export' in Adams, selecting Matlab by Target Software, and deriving a dynamic interaction file.
Secondly, inputting names of interaction files generated in Adams in a matlab command window, displaying names of input/output variables of all dynamic models, and inputting adams_sys commands to generate adams_sub modules in a Simulink module. Opening the inverse kinematics model, and copying the adams_sub module into the inverse kinematics model and connecting the adams_sub module with the inverse kinematics model.
And finally, multiplying the 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, causing the one or more computers to perform operations comprising a process as the Stewart parallel mechanism building method described above.
The effects of the present invention are described below with specific examples.
Taking a six-degree-of-freedom platform as an example, the platform is loaded by a spherical object with the mass of 2t, and the moment of inertia of the load in all directions is 1.805E+08 kg.mm 2. The load centroid is 0.5m from the upper platform. And the output of the electric cylinder and the power of the motor under each working condition are calculated according to the motion index of the upper platform, so that the subsequent motor model selection is convenient. Upper platform motion index: (1) The pitching working condition (rotation motion around the x axis), the platform takes 22.5 degrees as amplitude and takes 1s as a motion period to perform sine pitching motion; (2) The platform performs sinusoidal rolling motion with 22.5 degrees as amplitude and 1s as motion period under the rolling working condition (rotating motion around the y axis); (3) And the platform moves in a sinusoidal side-shifting mode by taking 15mm as an amplitude and taking 1s as a movement period under the side-shifting working condition (moving along the x axis).
And firstly, inputting the coordinates of the upper hinge point and the lower hinge point in Adams to finish the creation of the rigid body three-dimensional model.
And secondly, adding constraint, driving and gravity to complete establishment of a dynamic model.
And thirdly, setting the speed of the displacement drive of the electric cylinder as an input variable, setting the thrust of the electric cylinder as an output variable, and deriving an interaction file.
And fourthly, opening the interaction file generated in the third step in Matlab, and generating an adams_sub module.
And fifthly, opening the inverse solution module, and connecting the adams_sub module in the fourth step with the inverse solution module.
And sixthly, adding a sine wave module as input to the x rotation angle module, wherein the amplitude is pi/8, and the frequency is 2 pi.
Seventh, setting simulation time and step length, and performing simulation.
And eighth step, after the simulation is finished, outputting a simulation result to obtain the output force and the output power of each electric cylinder which moves under the pitching working condition, as shown in fig. 2 and 3.
And ninth, modifying the sine wave module in the sixth step into a Constant module and modifying the numerical value into 0, and adding the sine wave module as input into the y rotation angle module, wherein the amplitude is pi/8 and the frequency is 2 pi.
And tenth, setting simulation time and step length, and performing simulation.
And eleventh step, after the simulation is finished, outputting a simulation result to obtain the output force and the output power of each electric cylinder which moves under the rolling working condition, as shown in fig. 4 and 5.
And twelfth, modifying the sine wave module in the ninth step into a Constant module and modifying the value into 0, and adding the sine wave module as input to the x-moving module, wherein the amplitude is 15 and the frequency is 2 pi.
Thirteenth step, setting simulation time and step length, and performing simulation.
And fourteenth step, after the simulation is finished, outputting a simulation result to obtain the output force and the output power of each electric cylinder for completing the side-moving working condition movement, as shown in fig. 6 and 7.
Table 1: and (5) the upper and lower hinge point coordinates of the platform.
If simulation is performed by using Adams, a three-dimensional model is required to be firstly established, constraint is added, materials are added and point driving is added to reversely solve the expansion and contraction amount of each electric cylinder in the pitching gesture along with time, a change curve of the expansion and contraction amount of each electric cylinder along with time is led back to DATA ELEMENTS of the Adams/View module through AKISPL functions in a post-processing interface, a point driving module in a kinematic model is deleted, translation driving is added on each moving pair, each SPLINE line in DATA ELEMENTS is led into corresponding translation driving, and output force and motor power of each electric cylinder in the pitching gesture are calculated through dynamic simulation. Because the motion working conditions of the upper platform are more (9 common working conditions), each working condition needs to be subjected to kinematic inverse solution according to the motion indexes, then the inverse solution result is reintroduced into the drive to build the dynamic model again, the parameters of the electric cylinder cannot be directly obtained through the input of the motion indexes of the upper platform, and a great amount of time is required for repeated modeling.
The invention can quickly solve the output and the motor power of the electric cylinders under a plurality of working conditions only by modifying the input parameters aiming at different motion indexes, and repeated modeling is not needed.
Claims (6)
1. A method for constructing a Stewart parallel mechanism is characterized by comprising the following steps: the method comprises the following steps:
establishing a dynamic three-dimensional model of the Stewart parallel mechanism;
building a kinematic inverse model; the kinematic inverse model comprises a coordinate transformation module and an electric cylinder expansion speed acquisition module; the coordinate transformation module obtains new coordinates of each hinge point of the transformed upper platform through the input displacement or angle variable of the upper platform; the electric cylinder expansion 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 coordinate of each hinge point of the upper platform obtained by the coordinate change module, subtracts the real-time length of each electric cylinder from the initial length of the electric cylinder to obtain the expansion amount of each electric cylinder, and calculates the expansion speed of each electric cylinder according to the expansion amount of each electric cylinder;
The method comprises the steps of inputting the expansion speed of each electric cylinder obtained by a kinematic inverse model into an established Stewart parallel mechanism dynamics model to obtain the output force of each electric cylinder;
multiplying the output force of each electric cylinder with the corresponding expansion speed to obtain the power value of each electric cylinder;
the method for establishing the dynamic three-dimensional model of the Stewart parallel mechanism comprises the following steps:
Step 101: sequentially establishing upper hinge point hard points (p 1, p2, p3, p4, p5, p 6) and lower hinge point hard points (b 1, b2, b3, b4, b5, b 6);
Step 102: using p1 as a starting point, and using a cylindrical geometric module along the direction of the two straight lines of the points p1 and b1 to establish a geometric model of the first push rod according to the length of the first push rod; using p2 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p2 to b2 to establish a geometric model of the second push rod according to the length of the second push rod; using p3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p3 to b3 to build a geometric model of the push rod III according to the length of the push rod III; using p4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p4 to b4 to build a geometric model of the push rod IV according to the length of the push rod IV; using p5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p5 to b5 to build a geometric model of the push rod five according to the length of the push rod five; using p6 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p6 to b6 to build a geometric model of the push rod six according to the length of the push rod six;
Step 103: taking b1 as a starting point, and establishing a geometric model of the cylinder barrel I according to the length of the cylinder barrel I by using a cylindrical geometric module along the direction of the two points b1 to p 1; using b2 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b2 to p2 to establish a geometric model of the cylinder barrel II according to the length of the cylinder barrel II; using b3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b3 to p3 to build a geometric model of the cylinder barrel III according to the length of the cylinder barrel III; using b4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b4 to p4 to build a geometric model of the cylinder barrel IV according to the length of the cylinder barrel IV; using b5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b5 to p5 to build a geometric model of the cylinder barrel five according to the length of the cylinder barrel five; taking b6 as a starting point, and establishing a geometric model of the cylinder barrel six according to the length of the cylinder barrel six by using a cylindrical geometric module along the direction of the two points of b6 to p 6;
Step 104: using p1, p2, p3, p4, p5 and p6 as vertexes, and using a flat plate geometric module to build an upper platform geometric model; b1, b2, b3, b4, b5 and b6 are taken as vertexes, and a flat plate geometric model is used for establishing a base geometric model;
Step 105: a kinematic pair between the upper platform and each push rod is respectively arranged; a kinematic pair between each push rod and the corresponding cylinder barrel, and a kinematic pair between each cylinder barrel and the base; and sets the weight of each part.
2. The method for constructing the Stewart parallel mechanism as claimed in claim 1, wherein: the kinematic pair between the upper platform and each push rod adopts a Hooke hinge pair.
3. The method for constructing the Stewart parallel mechanism as claimed in claim 1, wherein: and a moving pair is adopted between each push rod and the corresponding cylinder barrel.
4. The method for constructing the Stewart parallel mechanism as claimed in claim 1, wherein: the kinematic pair between each cylinder barrel and the base adopts a ball pair.
5. A Stewart parallel mechanism construction system, characterized in that: the system comprises a three-dimensional model building unit, a dynamics inverse solution unit and an electric cylinder signal selection unit; wherein,
The three-dimensional model building unit is used for building a dynamic three-dimensional model of the Stewart parallel mechanism;
The dynamic inverse solution unit comprises a coordinate transformation module and an electric cylinder expansion speed acquisition module; the coordinate transformation module obtains new coordinates of each hinge point of the upper platform after transformation through input displacement or angle variable of the upper platform; the electric cylinder expansion 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 coordinate of each hinge point of the upper platform obtained by the coordinate change module, subtracts the real-time length of each electric cylinder from the initial length of the electric cylinder to obtain the expansion amount of each electric cylinder, and calculates the expansion speed of each electric cylinder according to the expansion amount of each electric cylinder; the obtained expansion speed of each electric cylinder is input into a three-dimensional model building unit, and the output force of each electric cylinder is obtained;
The electric cylinder signal selection unit multiplies the output force of each electric cylinder by the corresponding telescopic speed to obtain the power value of each electric cylinder and outputs the power value;
the method for establishing the dynamic three-dimensional model of the Stewart parallel mechanism by the three-dimensional model establishing unit comprises the following steps:
Step 101: sequentially establishing upper hinge point hard points (p 1, p2, p3, p4, p5, p 6) and lower hinge point hard points (b 1, b2, b3, b4, b5, b 6);
Step 102: using p1 as a starting point, and using a cylindrical geometric module along the direction of the two straight lines of the points p1 and b1 to establish a geometric model of the first push rod according to the length of the first push rod; using p2 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p2 to b2 to establish a geometric model of the second push rod according to the length of the second push rod; using p3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p3 to b3 to build a geometric model of the push rod III according to the length of the push rod III; using p4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p4 to b4 to build a geometric model of the push rod IV according to the length of the push rod IV; using p5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points p5 to b5 to build a geometric model of the push rod five according to the length of the push rod five; using p6 as a starting point, and using a cylindrical geometric module along the direction of the two points of the straight line from p6 to b6 to build a geometric model of the push rod six according to the length of the push rod six;
Step 103: taking b1 as a starting point, and establishing a geometric model of the cylinder barrel I according to the length of the cylinder barrel I by using a cylindrical geometric module along the direction of the two points b1 to p 1; using b2 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b2 to p2 to establish a geometric model of the cylinder barrel II according to the length of the cylinder barrel II; using b3 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b3 to p3 to build a geometric model of the cylinder barrel III according to the length of the cylinder barrel III; using b4 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b4 to p4 to build a geometric model of the cylinder barrel IV according to the length of the cylinder barrel IV; using b5 as a starting point, and using a cylindrical geometric module along the direction of the straight line of the two points b5 to p5 to build a geometric model of the cylinder barrel five according to the length of the cylinder barrel five; taking b6 as a starting point, and establishing a geometric model of the cylinder barrel six according to the length of the cylinder barrel six by using a cylindrical geometric module along the direction of the two points of b6 to p 6;
Step 104: using p1, p2, p3, p4, p5 and p6 as vertexes, and using a flat plate geometric module to build an upper platform geometric model; b1, b2, b3, b4, b5 and b6 are taken as vertexes, and a flat plate geometric model is used for establishing a base geometric model;
Step 105: a kinematic pair between the upper platform and each push rod is respectively arranged; a kinematic pair between each push rod and the corresponding cylinder barrel, and a kinematic pair between each cylinder barrel and the base; and sets the weight of each part.
6. A computer readable medium storing software comprising instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising the flow of the Stewart parallel architecture construction method of any one of claims 1-4.
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