dots/config/Typora/draftsRecover/2026-3-19 README 105540.md
2026-06-05 13:11:08 +02:00

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---
Author: Antoine Foucault-Castelli
Date: 17/03/2026
Bibliography: @karmiFiabiliteOptimisationSystemes @ghorbelEffectBrakeLocation2020a @zhengAnalyticalApproachMesh2022
Version: 4.0
---
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# Gearbox simulation
## Structure
```
main.m
func.m
time_sampling
inertia
gearbox_geometry
mesh_stiffness
wind_excitation
mass_matrix
stiffness_matrix
stiffness_update
damping_matrix
forces_matrix
initialization
newmark
parameters.m
display.m
disp_xy(t,x,i)
speed_xy(t,v,i)
acc_xy(t,v,i)
disp_theta(t,x,i)
speed_theta(t,v,i)
acc_theta(t,a,i)
mesh_stiffness(t,k_var,k_mean,i)
taero(t,T_aero,i)
rms_on_x(x)
spectral_on_x(x,i,tf,dt)
plot_x(t,x,i)
only_display.m
display_update.m
```
`main.m` is the launcher for the full code compilation
`func` is the function class, containing every function used in the code
`parameters` is the model parameters document
`display` is the displayer for figures
`only_display` to skip non-needed full compilation
`display_update` to update a single graph if needed
## How does it work ?
**For Matlab under windows :**
open matlab and launch main.m
> [!WARNING]
> remove `graphics_toolkit("gnuplot")` which is only useful for Octave visualization
**For Octave/Linux :**
```bash
cd [path_to_cloned]/code/versions/[current_version]/
octave
>>> run main.m
>>>
```
## Informations
- [x] Verified code with base code and paper
- [x] Implemented wind excitation
- [x] Implemented Ghorbel parameters
- [~] Add varying output torque depending on number of tooth in contact ?
- [~] add brake ?
- [~] Variation of C ?
- [~] ODE45 ?
- [x] Displays from last version (in class)
- [x] New mesh stiffness variation model (trapezoidal)
- [x] Print in pdf
- [ ] Errors/defects implementation
- [ ] profile error
- [ ] assembly defect (change on gear stiffness)
- [ ] README
- [x] Maths
- [ ] Source(s)
- [ ] Random models implementation
- [x] Display
- [x] time response on a2
- [x] speed response
- [x] x movement (vs y movement ?)
- [x] RMS STD Kurtosis
- [ ] Tests
- [ ] different speed
- [ ] different blade radii
## Maths
The model is represented by two 4DDL shafts in a gear connection : $x$ and $y$ are free at the pinion, $\theta$ is free at both ends of the shaft (input/output is $\theta_{ii}$ and meshing rotation is $\theta_{ij}$).
### Parameters
### Energy equations
$$
\frac{\partial Ep}{\partial q_i}+
\frac{d}{dt}\left(\frac{Ec}{\dot{q}_i}\right)-
\frac{\partial Ec}{\partial q_i}+
\frac{\partial D}{\partial \dot{q}_i}
=\frac{W}{\partial q_i}
\\
Ec = \frac{1}{2}m_1*\dot{x}_1^2+
\frac{1}{2}m_1*\dot{y}_1^2+
\frac{1}{2}I_{11}\dot{\theta}_{11}^2+
\frac{1}{2}I_{12}\dot{\theta}_{12}^2+
\frac{1}{2}m_2*\dot{x_2}^2+
\frac{1}{2}m_2*\dot{y_2}^2+
\frac{1}{2}I_{22}\dot{\theta}_{22}^2+
\frac{1}{2}I_{21}\dot{\theta}_{21}^2
\\
Ep = \frac{1}{2}k_{x_1}x_{1}^2+
\frac{1}{2}k_{y_1}y_{1}^2+
\frac{1}{2}k_{\theta_1}(\theta_{11}-\theta_{12})^2+
\frac{1}{2}k_{x_2}x_{2}^2+
\frac{1}{2}k_{y_2}y_{2}^2+
\frac{1}{2}k_{\theta_2}(\theta_{21}-\theta_{22})^2+
\frac{1}{2}K_e(t)\delta_1^2(t)
$$
### Equations of movement
$Ep$ and $Ec$ are separated between the two shaft (1 and 2)
$$
\begin{cases}
&\frac{\partial Ep_1}{\partial x_1}+\frac{d}{dt}\left(\frac{\partial Ec_1}{\partial \dot{x}_1}\right)=m_1\ddot{x}_1+k_{x1}x_1+sin(\alpha)K_e(t)\delta _1(t)=0 \\
&\frac{\partial Ep_1}{\partial y_1}+\frac{d}{dt}\left(\frac{\partial Ec_1}{\partial \dot{y}_1}\right)=m_1\ddot{y}_1+k_{y1}y_1+cos(\alpha)K_e(t)\delta _1(t)=0 \\
&\frac{\partial Ep_1}{\partial \theta_{11}}+\frac{d}{dt}\left(\frac{\partial Ec_1}{\partial \dot{\theta}_{11}}\right)=I_{11}\ddot{\theta}_{11}+k_{\theta 1}(\theta_{11}-\theta_{12})=Cm \\
&\frac{\partial Ep_1}{\partial \theta_{12}}+\frac{d}{dt}\left(\frac{\partial Ec_1}{\partial \dot{\theta}_{12}}\right)=I_{12}\ddot{\theta}_{12}+k_{\theta 1}(\theta_{12}-\theta_{11})+K_e(t)r_{b12}\delta_1(t)=0 \\
&\frac{\partial Ep_1}{\partial x_2}+\frac{d}{dt}\left(\frac{\partial Ec_2}{\partial \dot{x}_2}\right)=m_2\ddot{x}_2+k_{x2}x_2-sin(\alpha)K_e(t)\delta _1(t)=0 \\
&\frac{\partial Ep_1}{\partial y_2}+\frac{d}{dt}\left(\frac{\partial Ec_2}{\partial \dot{y}_2}\right)=m_2\ddot{y}_2+k_{y2}y_2-cos(\alpha)K_e(t)\delta _1(t)=0 \\
&\frac{\partial Ep_1}{\partial \theta_{22}}+\frac{d}{dt}\left(\frac{\partial Ec_2}{\partial \dot{\theta}_{22}}\right)=I_{22}\ddot{\theta}_{22}-k_{\theta 2}(\theta_{21}-\theta_{22})=-Cr \\
&\frac{\partial Ep_1}{\partial \theta_{21}}+\frac{d}{dt}\left(\frac{\partial Ec_2}{\partial \dot{\theta}_{21}}\right)=I_{21}\ddot{\theta}_{21}-k_{\theta 2}(\theta_{21}-\theta_{22})+K_e(t)r_{b21}\delta_1(t)=0
\end{cases}
$$
With $\delta_i(t)=(x_1-x_2)sin(\alpha)+(y_1-y_2)cos(\alpha)+\theta_{12}r_{b1}+\theta_{21}r_{b2}$ and $r_{bij}$ the base radius of pinions, $K_e$ is the varying meshing stiffness, mass $m_i = \pi r^2_{i}\rho$ for both pinions, and $I_{ij} = \frac{1}{2}m_{ij}r_{ij}^2$ for pinions and input/output inertia.
### Matrices
**Equation to solve :**
$$
[M]\{\ddot{q}\}+C\{\dot{q}\}+([Ks]+[K(t)])\{q\}=\{F_0\} \\
\{q\}=\{x_1,y_1,\theta_{11},\theta_{12},x_2,y_2,\theta_{22},\theta_{21}\}
$$
**Mass matrix :**
$$
M =
\begin{bmatrix}
m_1 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & m_1 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & I_{11} & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & 0 & I_{12} & 0 & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & m_2 & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & m_2 & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & I_{22} & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & I_{21} \\
\end{bmatrix} \\
$$
With $m_1$ mass of shaft 1 and $m_2$ mass of shaft 2
**Variable mesh stiffness matrix**
$$
K(t)= K_e(t)
\begin{bmatrix}
sin(\alpha)^2 & sin(\alpha).cos(\alpha) & 0 & r_1.sin(\alpha) & -sin(\alpha)^2 & -sin(\alpha).cos(\alpha) & 0 & r_2.sin(\alpha) \\
sin(\alpha).cos(\alpha) & cos(\alpha)^2 & 0 & r_1.cos(\alpha) & -sin(\alpha).cos(\alpha) & -cos(\alpha)^2 & 0 & r_2.cos(\alpha) \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
r_1.sin(\alpha) & r_1.cos(\alpha) & 0 & r_1^2 & -r_1.sin(\alpha) & -r_1.cos(\alpha) & 0 & r_1.r_2 \\
-sin(\alpha)^2 & -sin(\alpha).cos(\alpha) & 0 & -r_1.sin(\alpha) & sin(\alpha)^2 & sin(\alpha).cos(\alpha) & 0 & -r_2.sin(\alpha) \\
-sin(\alpha).cos(\alpha) & -cos(\alpha)^2 & 0 & -r_1.cos(\alpha) & sin(\alpha).cos(\alpha) & cos(\alpha)^2 & 0 & -r_2.cos(\alpha) \\
0 & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
r_2.sin(\alpha) & r_2.cos(\alpha) & 0 & r_1.r_2 & -r_2.sin(\alpha) & -r_2.cos(\alpha) & 0 & r_2^2 \\
\end{bmatrix}
$$
> [!NOTE]
>
> In matlab, cos and sin terms will be noted as $s_i$, for visual simplification
**Constant stiffness matrix**
$$
Ks=
\begin{bmatrix}
k_{x1} & 0 & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & k_{y1} & 0 & 0 & 0 & 0 & 0 & 0 \\
0 & 0 & k_{\theta1}& -k_{\theta1} & 0 & 0 & 0 & 0 \\
0 & 0 & -k_{\theta1} & k_{\theta1} & 0 & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & k_{x1} & 0 & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & k_{y1} & 0 & 0 \\
0 & 0 & 0 & 0 & 0 & 0 & k_{\theta2} & -k_{\theta2} \\
0 & 0 & 0 & 0 & 0 & 0 & -k_{\theta2} & k_{\theta2} \\
\end{bmatrix}
$$
**Damping matrix**
$$
C = \eta M+\beta K_{mean}
$$
**Forces**
$$
F =
\begin{bmatrix}
0 \\ 0 \\ T_{in} \\ 0 \\ 0\\ 0\\ T_{out}\\ 0
\end{bmatrix}
$$
## TO FIX
> [!ATTENTION]
> ...
## Machine specifications
Example of computational time : `44sec for fs=2500` / `n_periods = 10`
```
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`+oooo: Host: 20EV000UFR ThinkPad E560
`+oooooo: Kernel: 6.19.8-arch1-1
-+oooooo+: Shell: zsh 5.9
`/:-:++oooo+: Terminal: kitty
`/++++/+++++++: CPU: Intel i5-6200U (4) @ 2.300GHz
`/++++++++++++++: GPU: Intel Skylake-U GT2 [HD Graphics 520]
`/+++ooooooooooooo/` Memory: 1703MiB / 3792MiB
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```