Window mechanism

by Roberto Lot

> restart: mylib :="C:/LIBS": libname := mylib,libname: with(MBSymba_r5):

Warning, Non-Linear Modeling option has been choosen

points definition

> A := make_POINT(ground,0,0,0): show(A); ##frame pin joint

> B := make_POINT(ground,xB,yB,0): show(B);

> C := make_POINT(ground,xC,yC,0): show(C);

> E := make_POINT(ground, 0,yE,0): show(E); ##slider

> F := make_POINT(ground,xF,yF,0): show(F);

variables set

> q := {xB,yB,xC,yC,yE,xF,yF}; nq := nops(q);

Since the single-degree-of-freedom mechanism is described by means of 7 variables, 6 constraint equations must be written.

distance between A and C

> AC := make_VECTOR(A,C): phi[1] := dot_prod(AC,AC)-lAC^2;

AB is linearly dependent of AC

> AB := make_VECTOR(A,B):
AA := 1/lAB*AB-1/lAC*AC: show(AA);
phi[2] := simplify(lAC*lAB*Xcomp(AA));
phi[3] := simplify(lAC*lAB*Ycomp(AA));

distance between E and F

> EF := make_VECTOR(E,F): phi[4] := dot_prod(EF,EF)-lEF^2;

distance between B and E

> BE := make_VECTOR(B,E): phi[5] := dot_prod(BE,BE)-lBE^2;

distance between C and F

> CF := make_VECTOR(C,F): phi[6] := dot_prod(CF,CF)-lCF^2;

assembly constraints

> constraints := convert(phi,list):

Numerical solution (Newton-Rapson algorithm)

mechanims characteristics

> geometric_data := lAB=0.30, lBE=0.40, lEF=0.08, lAC=0.40:

> geometric_data := geometric_data , subs(geometric_data, lCF = lAB+lBE+lEF-lAC);

numerical equations

> eqns := convert(subs(geometric_data,constraints),set);

definition of the independent variable and unknowns variables

> yE;
unks := q minus {%};

numerical solution

> np:=15: solz:=array[np]:
for i from 1 to np do
x := 0.69999-0.15*(i-1)/(np-1):
solz[i] := {yE=x} union fsolve(subs(yE=x,eqns),unks, {xF=0..1} )
end do:

tabbed results

1 | +0.002 +0.300 | +0.002 +0.400 | +0.000 +0.700 | +0.001 +0.780 |

2 | +0.060 +0.294 | +0.081 +0.392 | +0.000 +0.689 | +0.019 +0.767 |

3 | +0.085 +0.288 | +0.113 +0.384 | +0.000 +0.679 | +0.027 +0.754 |

4 | +0.104 +0.282 | +0.138 +0.375 | +0.000 +0.668 | +0.033 +0.741 |

5 | +0.119 +0.275 | +0.159 +0.367 | +0.000 +0.657 | +0.038 +0.727 |

6 | +0.133 +0.269 | +0.177 +0.359 | +0.000 +0.646 | +0.043 +0.714 |

7 | +0.145 +0.263 | +0.193 +0.350 | +0.000 +0.636 | +0.046 +0.701 |

8 | +0.156 +0.256 | +0.207 +0.342 | +0.000 +0.625 | +0.050 +0.688 |

9 | +0.166 +0.250 | +0.221 +0.334 | +0.000 +0.614 | +0.053 +0.674 |

10 | +0.175 +0.244 | +0.233 +0.325 | +0.000 +0.604 | +0.056 +0.661 |

11 | +0.183 +0.237 | +0.245 +0.317 | +0.000 +0.593 | +0.058 +0.648 |

12 | +0.191 +0.231 | +0.255 +0.308 | +0.000 +0.582 | +0.061 +0.634 |

13 | +0.199 +0.224 | +0.265 +0.299 | +0.000 +0.571 | +0.063 +0.621 |

14 | +0.206 +0.218 | +0.275 +0.291 | +0.000 +0.561 | +0.065 +0.607 |

15 | +0.213 +0.211 | +0.284 +0.282 | +0.000 +0.550 | +0.067 +0.594 |

mechanism drawing

> with(plots): with(plottools):

> draw_mechanism := proc(q)
local revj_A,revj_B,revj_C,revj_E,revj_F, AC,BE,EF,slider,window:
revj_A := disk([ 0, 0], 0.02, color=yellow);
revj_B := disk(subs(q,[xB,yB]), 0.02, color=yellow);
revj_C := disk(subs(q,[xC,yC]), 0.02, color=yellow);
revj_E := disk(subs(q,[ 0,yE]), 0.02, color=yellow);
revj_F := disk(subs(q,[xF,yF]), 0.02, color=yellow);
AC := line( [ 0, 0] ,subs(q,[xC,yC]), color=red, thickness=5);
BE := line( subs(q,[xB,yB]),subs(q,[ 0,yE]), color=blue, thickness=5);
EF := line( subs(q,[ 0,yE]),subs(q,[xF,yF]), color=red, thickness=5);
slider := rectangle( subs(q,[-0.03, yE+0.05]), subs(q,[+0.03, yE-0.05]), color=grey ):
window := line( subs(q,[xF,yF]),subs(q,[xC+1.3*(xC-xF),yC+1.3*(yC-yF)]), color=black, thickness=5);

display( revj_A,revj_B,revj_C,revj_E,revj_F, AC,BE,EF,slider,window, scaling=constrained);
end:

display a single configuration

> draw_mechanism(solz[8]);

animation

> display([seq(display(draw_mechanism(solz[i])),i=1..np)], insequence=true, scaling=constrained);

Numerical solution (Newton-Rapson algorithm)

Window mechanism

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