The following code is not giving errors, but it does not solve the system of equations.

1 次查看（过去 30 天）
Mohamed Amine TAIB
Mohamed Amine TAIB 2021-12-13
评论： Walter Roberson 2021-12-14
syms X_1 X_2 X_3 X_4 X_5 X_6 X_7 X_8 X_9 X_10 X_11 X_12 X_12 X_13 X_14 X_15 X_16 X_17 X_18 X_19 X_20 X_21 X_22 X_23 X_24 X_25 X_26
eq1=X_2
eq2=(-225000*X_1+35000*X_17+49000*sin(X_19)-52500*sin(X_21)-1000*X_2+1000*X_18+1400*cos(X_19)*X_20-1500*cos(X_21)*X_22-3.35^(-4)*X_3)/59
eq3= (-1*X_3-4.515^13*3.35^(-4)*(X_18+1.4*X_20*cos(X_19)-1.5*X_22*cos(X_21)-X_2) +((10342500-(X_4/abs(X_4)*X_3))/abs(10342500-(X_4/abs(X_4)))*X_3) *1.545^9*sqrt(abs(10342500-(X_4/abs(X_4))*X_3))*X_4) -4.515^13*3.35^(-4)*(X_18 + 1.4*X_20*cos(X_19) - 1.5*X_22*cos(X_21) - X_2) -X_3 - X_2
eq4=-X_4/0.003
eq5=X_6
eq7= -X_7 + (-1*X_7-4.515^13*3.35^(-4)*(X_18+1.4*X_20*cos(X_19)+1.5*X_22*cos(X_21)-X_6)+((10342500-(X_8/abs(X_8)*X_7))/abs(10342500-(X_8/abs(X_8)))*X_7)*1.545*10^9*sqrt(abs(10342500-(X_8/abs(X_8))*X_7))*X_8)*X_8 + -4.515^13*3.35^(-4)*(X_18 +1.4*X_20*cos(X_19) + 1.5*X_22*cos(X_21) - X_6)
eq8= - X_8/0.003 + X_24/0.003
eq9=X_10
eq11= -X_11 + (-1*X_11 -4.515^13*3.35^(-4)*(X_18-1.7*X_20*cos(X_19)-1.5*X_22*cos(X_21)-X_10) +((10342500-(X_12/abs(X_12)*X_11))/abs(10342500-(X_12/abs(X_12)))*X_11) *1.545^9*sqrt(abs(10342500-(X_12/abs(X_12))*X_11))*X_12)*X_12 -4.515^13*3.35^(-4)*(X_18 - 1.7*X_20*cos(X_19) - 1.5*X_22*cos(X_21) - X_10)
eq12= -X_12/0.003 + X_25/0.003
eq13=X_14
eq15= -X_15 - 4.515^13*3.35^(-4)*(X_18 - 1.7*X_20*cos(X_19) + 1.5*X_22*cos(X_21) - X_14) + -1*X_11-4.515^13*3.35^(-4)*(X_18-1.7*X_20*cos(X_19)+1.5*X_22*cos(X_21)-X_14) +((10342500-(X_16/abs(X_16)*X_15))/abs(10342500-(X_16/abs(X_16)))*X_15)*X_15 -1.545^9*sqrt(abs(10342500-(X_16/abs(X_16))*X_15))*X_16
eq16=- X_16/0.003 + X_26/0.003
eq17=X_18
eq18=((35000*X_1 + 35000*X_5 + 38000*X_9 + 38000*X_13- 146000*X_17 -(-31200)*sin(X_19)+ 1000*X_2 +1000*X_6 +1100*X_10 + 1100*X_14- 4200*X_18- (-940)*cos(X_19)*X_20)/1500)+3.35^(-4)*(X_3+X_7+X_11+X_15)/1500 + 3.35^(-4)*(X_3 + X_7 + X_11 + X_15)/1500
eq19=X_19
eq20=cos(X_19)/2160*3.35^(-4)*(1.4*(X_3 + X_7) - 1.7*(X_11 + X_15))+(49000*X_1 + 49000*X_5 - 64600*X_9 - 64600*X_13-(-31200)*X_17-356840*sin(X_19)+ 1400*X_2 + 1400*X_6 - 1870*X_10 - 1870*X_14-940*X_18- 10278*cos(X_19)*X_20)
eq21=X_22
eq22=cos(X_21)/460*3.35^(-4)*(-1.5*(X_3 + X_11) +1.5*(X_7 + X_15))+(cos(X_21)*(-52500*X_1+ 52500*X_5 - 57000*X_9 + 57000*X_13-328500*sin(X_21) -2100 + 1500*X_14 -9450*cos(X_21)*X_22)/460)+cos(X_21)*3.35^(-4)*(-1.5*(X_3+X_11) + 1.5*(X_7 + X_15))/460
eqs = [eq1, eq2, eq3, eq4, eq5, eq7, eq8, eq9, eq11, eq12, eq13, eq15, eq16, eq17, eq18, eq19, eq20, eq21, eq22]
[X_1,X_2,X_3,X_4,X_5,X_6,X_7,X_8,X_9,X_10,X_11,X_12,X_13,X_14,X_15,X_16,X_17,X_18,X_19,X_20,X_21,X_22,X_23,X_24,X_25,X_26]=vpasolve(eqs,[X_1,X_2,X_3,X_4,X_5,X_6,X_7,X_8,X_9,X_10,X_11,X_12,X_13,X_14,X_15,X_16,X_17,X_18,X_19,X_20,X_21,X_22,X_23,X_24,X_25,X_26])
I get the output Empty sym: 0-by-1, i need the solve it to determine the equilibrium point which i will use to linearize the system.

请先登录，再回答此问题。

回答（1 个）

J Chen
J Chen 2021-12-13
In order to solve a system of equations, the number of equations needs to equal the number of variables. You also need ==0 for the equations.
  1 个评论
Walter Roberson
Walter Roberson 2021-12-14
solve() and vpasolve() do not need == 0 : both of them assume == 0 if there is no relation in an expression.
Reference: https://www.mathworks.com/help/symbolic/sym.vpasolve.html#bt5sqi5-1-eqn
Equation to solve, specified as a symbolic equation or symbolic expression. A symbolic equation is defined by the relation operator ==. If eqn is a symbolic expression (without the right side), the solver assumes that the right side is 0, and solves the equation eqn == 0.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Symbolic Math Toolbox 的更多信息

标签

产品


版本

R2015a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by