massprop_muscles {AvInertia} R Documentation

## Muscle mass properties

### Description

Calculate the moment of inertia of a muscle modeled as a solid cylinder distributed along the bone length

### Usage

```massprop_muscles(m, rho, l, start, end)
```

### Arguments

 `m` Mass of muscle (kg). `rho` Density of muscle (kg/m^3). `l` Length of the muscle group (m). `start` a 1x3 vector (x,y,z) representing the 3D point where bone starts. Frame of reference: VRP | Origin: VRP. `end` a 1x3 vector (x,y,z) representing the 3D point where bone ends. Frame of reference: VRP | Origin: VRP.

### Value

This function returns a list that includes:

• Ia 3x3 matrix representing the moment of inertia tensor of a muscle modeled as a solid cylinder distributed along the bone length.

• CGa 1x3 vector representing the center of gravity position of a muscle modeled as a solid cylinder distributed along the bone length.

• ma double that returns the input muscle mass.

### Warning

Parallel axis theorem does not apply between two arbitrary points. One point must be the object's center of gravity.

Christina Harvey

### Examples

```# refer to the vignette
library(AvInertia)

data(dat_id_curr, package = "AvInertia")
data(dat_bird_curr, package = "AvInertia")
data(dat_feat_curr, package = "AvInertia")
data(dat_bone_curr, package = "AvInertia")
data(dat_mat, package = "AvInertia")
data(clean_pts, package = "AvInertia")

# 1. Determine the center of gravity of the bird's torso (including the legs)
dat_torsotail_out = massprop_restbody(dat_id_curr, dat_bird_curr)
# 2. Calculate the inertia of the flight feathers about the tip of the calamus
feather_inertia <- compute_feat_inertia(dat_mat, dat_feat_curr, dat_bird_curr)
# 3. Determine the center of gravity of one of the bird's wings
dat_wing_out      = massprop_birdwing(dat_id_curr, dat_bird_curr,
dat_bone_curr, dat_feat_curr, dat_mat, clean_pts,
feather_inertia, plot_var = 0)
# Visualize the center of gravity of each wing component in the x and y axis
dat_wing_out      = massprop_birdwing(dat_id_curr, dat_bird_curr,
dat_bone_curr, dat_feat_curr, dat_mat, clean_pts,
feather_inertia, plot_var = "yx")
# or the y and z axis
dat_wing_out      = massprop_birdwing(dat_id_curr, dat_bird_curr,
dat_bone_curr, dat_feat_curr, dat_mat, clean_pts,
feather_inertia, plot_var = "yz")
# 4. Combine all data and obtain the center of gravity, moment of inertia
# and principal axes of the bird
curr_full_bird      = combine_inertialprop(dat_torsotail_out,dat_wing_out,
dat_wing_out, dat_id_curr, dat_bird_curr, symmetric=TRUE)

```

[Package AvInertia version 0.0.1 Index]