## 30 Reputation

8 years, 239 days

## Double Pendulum Linearization...

I'm confused by the state equations resulting from linearizing the DoublePendulum example model.

The state equations are:

diff(x[1](t),t) = x[2](t),

diff(x[2](t),t) = 0,

diff(x[3](t),t) = x[4](t),

diff(x[4](t),t) = 0

where:

x[1](t) = R1_theta(t),

x[2](t) = diff(R1_theta(t),t),

x[3](t) = R2_theta(t),

x[4](t) = diff(R2_theta(t),t)

Am I understanding correctly that the state equations say that the angular acceleration of both revolute joints is zero? This is clearly not the case when you simulate the model and view the plots for angular acceleration. Can someone explain to me what's going on? Model with worksheet attached.

## Error, `MapleSim` does not evaluate to a...

I have maplesim installed and I get the error "Error, `MapleSim` does not evaluate to a module" when I run A:=MapleSim:-LinkModel(); in a Maple worksheet.

Does anyone know how to solve this error?

## Flexible Beam State Variables ...

I'm trying to run c code generated from a simple MapleSim example (Spin Up Beam). To makes things even simpler, I set the input real expression to just time, and changed the input function in my c code to:

static void inpfn(double T, double *U)
{
U[0] = T;
}

I set all the state variables to 0 for the initial conditions. I ran the code and my output doesn't resemble the MapleSim output at all, and I'm getting errors. So my question is about the state variables, which I initially set to 0:

* State variable(s):
* x[ 0] = `Main.SpinUpBeam.FB3.uf1`(t)
* x[ 1] = diff(`Main.SpinUpBeam.FB3.uf1`(t),t)
* x[ 2] = `Main.SpinUpBeam.FB3.uf2`(t)
* x[ 3] = diff(`Main.SpinUpBeam.FB3.uf2`(t),t)
* x[ 4] = `Main.SpinUpBeam.FB3.vf1`(t)
* x[ 5] = diff(`Main.SpinUpBeam.FB3.vf1`(t),t)
* x[ 6] = `Main.SpinUpBeam.FB3.vf2`(t)
* x[ 7] = diff(`Main.SpinUpBeam.FB3.vf2`(t),t)

What do these represent for this flexible beam (FB3)? I.e. what is uf1, uf2, vf1, vf2? Should they be set to 0, or no?

Thanks.