CN103869705A - Method for track planning and generating of parallel 6-degree-of-freedom driving rotary platform - Google Patents

Abstract

The invention provides a method for track planning and generating of a parallel 6-degree-of-freedom driving rotary platform. The method comprises: (1) inputting end point coordinates of a central point of an upper platform and rotation angles x<p>, y<p>, z<p>, alpha<p>, beta<p> and gamma<p> with respect to a lower platform of the rotary platform; (2) inputting starting point coordinates x<b>, y<b> and z<b> of the central point of the upper platform and rotation angles alpha<b>, beta<b> and gamma<b> with respect to the lower platform of the rotary platform; (3) calculating coordinates of each hinge point of the upper platform in a moving coordinate; (4) calculating coordinates of each hinge point of the upper platform in a fixed coordinate; (5) assigning initial values to a coordinate transformation matrix R; (6) calculating rod stretching values along x, y and z directions as well as D<x>, D<y>, D<z>, D<alpha>, D<beta> and D<gamma>; (7) assigning new values to the matrix R with D<x>, D<y>, D<z>, D<alpha>, D<beta> and D<gamma> as reference values; (8) calculating coordinates of each hinge point of the upper platform in a fixed coordinate from the matrix R; (9) calculating the stretching amount of the rod length of each one of six rods at an increasing part; and (10) determining whether an end point is reached. If the end point is reached, the method is ended; otherwise, the method returns to the step (7). Track planning of a rotary platform single-cylinder electro-hydraulic servo control system is better in dynamic characteristics, high in stable state precision, good in robustness, simple in structure and easy for design and adjustment.

Description

A kind of six degree of freedom in parallel drives the trajectory planning generation method of turntable

Technical field

What the present invention relates to is the Track Control Technology that a kind of six degree of freedom in parallel drives turntable, specially refers to a kind of trajectory planning generation method of turntable.

Background technology

Six Degree-of-Freedom Parallel Robot in parallel is the high-grade, precision and advanced experimental facilities with great economy value and defense strategy meaning.Space six-degree-of-freedom parallel robot is the earliest that nineteen sixty-five D. Stewart proposes and develops.6-SPS mechanism is famous Stewart platform mechanism.Compared with traditional tandem movement mechanism with multiple degrees of freedom, it is strong that it has load-bearing capacity, good rigidity, and without accumulated error, precision advantages of higher.The difference relatively distributing according to upper and lower each six ball pivots, this mechanism can be divided into polytype, and its kinematics existing many scholars be studied.At the beginning of the seventies, after parallel six degrees of freedom study of platform achievement has been announced in the research centres such as the NASA of the U.S., in succession there is being equipped with the flight simulator of 6-dof motion platform.Entered the eighties particularly since the nineties, 6-dof motion platform is more and more widely used in robot, parallel machine, space articulation meter art, aviation and navigation equipment, waves on simulation and recreational facilities.Up to now, parallel six degrees of freedom platform is not also used widely industrial, its main cause: kinematics problem, and particularly positive motion knowledge topic is not also well solved; Dynamics problem does not solve; Coupled interference between the each branch of platform is difficult to eliminate.

The Six Degree-of-Freedom Parallel Robot design level of China is still quite large with manufacture level gap compared with western developed country at present, and the work that the key subject in these fields of Six Degree-of-Freedom Parallel Robot control theory, control system and technical research is done is also very superficial.Therefore the key components of six degree of freedom are carried out to deep theoretical and experimental study, develop as early as possible the Six Degree-of-Freedom Parallel Robot of function admirable, improve the emulation technology level of China, there is great theory significance and actual application value.

Summary of the invention

The object of the present invention is to provide a kind of trajectory planning that drives turntable for improving six degree of freedom in parallel, make that trajectory planning dynamic perfromance is better, stable state accuracy is high, strong robustness, simple in structure, be convenient to design modifying.

The object of the present invention is achieved like this:

Specifically comprise following step:

(1) terminal point coordinate of input upper mounting plate central point and the corner x with respect to turntable lower platform _p, y _p, z _p, α _p, β _p, γ _p;

(2) the starting point coordinate x of input upper mounting plate central point _b, y _b, z _b, and with respect to the corner α of turntable lower platform _b, β _b, γ _b;

(3) calculate the coordinate of the each hinge of upper mounting plate under moving axes;

(4) calculate the coordinate of the each hinge of upper mounting plate under position fixing;

(5) give coordinate conversion matrix R initialize;

(6) obtain the flexible value of three steering yokes of x, y, z and D _x, D _y, D _z, D _α, D _β, D _γ;

(7) with D _x, D _y, D _z, D _α, D _β, D _γfor parameter is composed new value to R;

(8) obtain the coordinate of the each hinge of upper mounting plate under position fixing system by R;

(9) ask the long stroke of the each increment of 6 bar place bar;

(10) judging whether terminal, is to finish, otherwise returns to step (7).

The advantage of this technical scheme is:

(1) first simply introduced the structure of Six Degree-of-Freedom Parallel Robot in parallel, and forward kinematics solution to Six Degree-of-Freedom Parallel Robot in parallel, instead separated and dynamics solution has been carried out brief analysis.This is the basis of 6-dof parallel platform being carried out to Control System Design, Mechanism Optimization, mechanism simulation research.

(2) be mainly the design to control system.First relatively determine rational control method, then carried out the design effort of the overall control structure of Six Degree-of-Freedom Parallel Robot in parallel, finally one-lever control system each several part has been carried out the type simplification work of detailed design, modeling and control system mould.

(3) for valve control symmetry cylinder system, first realize control and the emulation of conventional PID, then attempt the Control System Design based on neural network.Comprising: the PID control method based on mononeuron neural network and the neural PID control algorithm based on BP neural network tuned proportion integration differentiation, and utilize Matlab software to carry out emulation to control situation, its simulation result and conventional pid control algorithm simulation result are compared, reach a conclusion.

Brief description of the drawings

Fig. 1 is position algorithm flow chart;

Fig. 2 is Six Degree-of-Freedom Parallel Robot exemplary block diagram in parallel;

Fig. 3 is quiet coordinate system and moving coordinate system position view;

Embodiment

In conjunction with Fig. 1, Fig. 2 and Fig. 3,, the terminal point coordinate of input upper mounting plate central point and the corner x with respect to turntable lower platform _p, y _p, z _p, α _p, β _p, γ _p; Starting point coordinate x _b, y _b, z _b, and with respect to the corner α of turntable lower platform _b, β _b, γ _b; Calculate the coordinate of the each hinge of upper mounting plate under moving axes; Calculate the coordinate of the each hinge of upper mounting plate under position fixing; Give coordinate conversion matrix R initialize; Obtain the flexible value of three steering yokes of x, y, z and D _x, D _y, D _z, D _α, D _β, D _γ; With D _x, D _y, D _z, D _α, D _β, D _γfor parameter is composed new value to R; Obtain the coordinate of the each hinge of upper mounting plate under position fixing system by R; Ask the long stroke of the each increment of bar place bar; Judging whether terminal, is to finish, otherwise returns to step (7).

Claims (3)

1. the trajectory planning generation method of a six degree of freedom driving turntable in parallel, is characterized in that specifically comprising following step:

(1) terminal point coordinate of input upper mounting plate central point and the corner x with respect to turntable lower platform _p, y _p, z _p, α _p, β _p, γ _p;

(2) the starting point coordinate x of input upper mounting plate central point _b, y _b, z _b, and with respect to the corner α of turntable lower platform _b, β _b, γ _b;

(3) calculate the coordinate of the each hinge of upper mounting plate under moving axes;

(4) calculate the coordinate of the each hinge of upper mounting plate under position fixing;

(5) give coordinate conversion matrix R initialize;

(6) obtain the flexible value of three steering yokes of x, y, z and D _x, D _y, D _z, D _α, D _β, D _γ;

(7) with D _x, D _y, D _z, D _α, D _β, D _γfor parameter is composed new value to R;

(8) obtain the coordinate of the each hinge of upper mounting plate under position fixing system by R;

(9) ask the long stroke of the each increment of 6 bar place bar;

(10) judging whether terminal, is to finish, otherwise returns to step (7).

2. while establishing setting in motion, turntable center is respectively a along the acceleration of three directions of x, y, z _x1, a _y1, a _z1negative acceleration while reaching home is a _x2, a _y2, a _z2; Maximal rate at the uniform velocity time is V _vx, V _vy, V _zy, like this according to physics equation of motion V _t-V ₀=at, tries to achieve turntable when motion T along three directions ₁moment value, in addition, V in the time of turntable setting in motion ₀=0, therefore there is V _t=at is also t=V _t/ a, has this turntable:

$\left\{\begin{array}{c}{T}_{x1}=V_{\mathrm{vx}}/a_{x1}\\ T_{y1}=V_{\mathrm{vy}}/a_{y1}\\ T_{z1}=V_{\mathrm{vz}}/a_{z1}\end{array}\right.$

Obtain below at T ₂time be carved into the terminal time used because turntable must have V while moving into place _t=0, and V ₀=at, and a is for subtracting accekeration, also has:

$\left\{\begin{array}{c}{T}_{x2}=V_{\mathrm{vx}}/a_{x2}\\ T_{y2}=V_{\mathrm{vy}}/a_{y2}\\ T_{z2}=V_{\mathrm{vz}}/a_{z2}\end{array}\right.$

At the uniform velocity the time used in stage can be tried to achieve by following formula:

Wherein: S _x, S _y, S _z, platform is along the collapsing length value of three steering yokes, so platform is at the T of three directions ₂value is:

$\left\{\begin{array}{c}{T}_{x2}=T_{x3}+T_{x1}\\ T_{y2}=T_{y3}+T_{y1}\\ T_{z2}=T_{z3}+T_{z1}\end{array}\right.$

At platform setting in motion to T ₁in the moment, the distance moving along three directions is respectively:

From setting in motion to moment T ₃the distance moving along three directions is respectively:

$\left\{\begin{array}{c}{S}_{x2}=S_{x1}+V_{\mathrm{vx}}{T}_{x3}\\ S_{y2}=S_{y1}+V_{\mathrm{vy}}{T}_{y3}\\ S_{z2}=S_{z1}+V_{\mathrm{vz}}{T}_{z3}\end{array}\right.$

In like manner, from T ₂time be carved into the distance moving location:

By pushing over and draw above:

$\left\{\begin{array}{c}{S}_x=S_{x2}+S_{x3}\\ S_y=S_{y2}+S_{y3}\\ S_z=S_{z2}+S_{z3}\end{array}\right.$

So far, completed the trajectory planning task of platform motion.

3. known the starting point coordinate x of upper mounting plate central point _b, y _b, z _b, and with respect to the corner α of turntable lower platform _b, β _b, γ _b, terminal point coordinate x _p, y _p, z _p, α _p, β _p, γ _pafterwards, the distance that turntable upper mounting plate central point moves along three directions of x, y, z is:

Corner is:

If try to achieve displacement in certain direction and be zero or corner in certain direction be zero, illustrate that this side up is mobile or do not rotate.

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