Why is this code returning values of zero?

Im trying to use loop closure to analyze a mechanism. So I have equations that describe the motion, however when I try to solve the system of equations the returning values are just zero and I'm not sure why. If anyone could help I would greatly appreciate it!

clear;
clc;
% Known parameters
r1=0.15;
r2=0.125;
r3=0.15;
r4=0.054;
theta1=0.4811;
theta2=-0.1366;
theta3=pi; 
theta4=pi/2;
syms thetadot1 thetadot2 rdot4 theta1dd theta2dd r4dd
 
% Equations
L1post = r1*exp(1i*theta1)+ r2*exp(1i*theta2) + r3*exp(1i*theta3) +r4*exp(1i*theta4)==0;
L1vel = 1i*thetadot1*r1*exp(1i*theta1) + 1i*thetadot2*r2*exp(1i*theta2) + rdot4*exp(1i*theta4)==0;
L1accel = 1i*theta1dd*r1*exp(1i*theta1) - thetadot1^2*r1*exp(1i*theta1)+1i*theta2dd*r2*exp(1i*theta2)+r4dd*exp(1i*theta4)==0;
eqns=[L1post,L1vel,L1accel];
vars = [thetadot1 thetadot2 rdot4 theta1dd theta2dd r4dd];
y=solve(eqns,vars)
y.thetadot1
y.thetadot2
y.rdot4
y.theta1dd
y.theta2dd
y.r4dd

Answer 1

[John D'Errico]

Does zero for all variables trivially satisfy the equations? (Yes.)

Did you request a solution of the equations? (Yes.)

Do you know that non-trivial solutions exist? (Not at all clear. In fact, if I arbitrarily constrain one of the parameters to be strictly positive for example, no solution at all seems to be found. While that does not mean no non-trivial solution exists, it suggests the idea as something you should consider.)

[Shiva Amini]

Is there a way to get non trivial solution?