# Obstacle Avoidance

Compute obstacle-free direction using range sensor data and target position

*Since R2021b*

**Libraries:**

UAV Toolbox /
Algorithms

## Description

The Obstacle Avoidance block computes an obstacle-free direction using range sensor data and target position.

## Examples

### UAV Obstacle Avoidance in Simulink

Simulate waypoint following mission with obstacles using the 3D VFH+ algorithm to compute obstacle-free direction.

## Ports

### Input

**Position** — Position of UAV

vector

Position of the UAV, specified as a vector of the form
`[`

. *x*; *y*;
*z*]

,
*x*

, and
*y*

define the xyz-position of the UAV in any
right-handed coordinate frame, such as NED and ENU. Units are in meters.*z*

**Example: **
`[1; 1; 1]`

**Data Types: **`double`

**Orientation** — Orientation of UAV

vector

Orientation of the UAV in any right-handed coordinate frame, such as NED and ENU,
specified as a quaternion vector of the form `[`

.*w*;
*x*; *y*;
*z*]

**Example: **`[1; 0; 0; 0]`

**Data Types: **`double`

**ObstaclePoints** — Positions of obstacles

matrix

Obstacle points locations, specified as an *N*-by-3 matrix with
rows of the form `[`

. *x*
*y*
*z*]

,
*x*

, and
*y*

define the xyz-position of the obstacle
point in the reference frame of the range sensor. *z**N* is the number
of obstacle points. Units are in meters.

You can obtain the obstacle points using sensors such as the UAV Scenario Lidar which outputs obstacle points as a point cloud data.

**Example: **`[1 1 1; 2 2 2]`

**Data Types: **`double`

**TargetPostion** — Position of target

vector

Position of the target, specified as a vector of the form
`[`

. *x*; *y*;
*z*]

,
*x*

, and
*y*

define the xyz- position of the target in
any right-handed coordinate frame, such as NED and ENU. Units are in meters.*z*

**Example: **`[2; 3; 4]`

**Data Types: **`double`

### Output

**DesiredDirection** — Desired direction

vector

Desired direction, returned as a unit vector of the form
`[`

. *x*; *y*;
*z*]

,
*x*

, and
*y*

define the desired direction in the
right-handed coordinate frame that you specified in the position input. Units are in
meters.*z*

**Data Types: **`double`

**DesiredYaw** — Desired yaw

scalar

Desired yaw in the right-handed coordinate frame that you specified in the
position input, returned as numeric scalar in radians in the range of ```
[-pi,
pi]
```

.

**Data Types: **`double`

**Status** — Status of obstacle-free direction

`0`

| `1`

| `2`

| `3`

Status of the obstacle-free direction, returned as `0`

,
`1`

, `2`

, or `3`

.

`0`

— An obstacle-free direction is found.`1`

— No obstacle-free direction is found.`2`

— An obstacle-free direction is found but is close to the obstacle.`3`

— No obstacle-free direction is found and is close to obstacle.

**Data Types: **`uint8`

## Parameters

**Main**

**Sensor range limits (m)** — Limits of range sensor

`[0.2 10]`

(default) | vector of form `[`*min*
*max*]

*min*

*max*]

Specify the minimum and maximum limits of the range sensor as a vector of the form
`[`

, with values in meters.*min*
*max*]

**Data Types: **`double`

**Sensor horizontal field of view (deg)** — Horizontal field of view limits of range sensor

`[-60 60]`

(default) | vector of form `[`*min*
*max*]

*min*

*max*]

Specify the minimum and maximum horizontal field of view limits of the range sensor
as a vector of the form `[`

, with values in degrees.*min*
*max*]

**Data Types: **`double`

**Sensor vertical field of view (deg)** — Vertical field of view limits of range sensor

`[-30 30]`

(default) | vector of form `[`*min*
*max*]

*min*

*max*]

Specify the minimum and maximum vertical field of view limits of the range sensor as
a vector of the form `[`

, with values in degrees.*min*
*max*]

**Data Types: **`double`

**Sensor location [X, Y, Z] (m)** — Sensor mounting location on UAV

`[0 0 0]`

(default) | vector of form `[`*x*
*y*
*z*]

*x*

*y*

*z*]

Specify the mounting location of the sensor on the UAV body frame as a vector of the
form `[`

, with values in meters.*x*
*y*
*z*]

The configuration of the UAV body frame orients the *x*-axis as forward-positive, the *y*-axis
as right-positive, and the *z*-axis
downward-positive.

**Data Types: **`double`

**Sensor orientation [Roll, Pitch, Yaw] (deg)** — Orientation of sensor mounted on UAV

`[0 0 0]`

(default) | vector of form `[`*roll*
*pitch*
*yaw*]

*roll*

*pitch*

*yaw*]

Specify the orientation of the sensor on the UAV body frame as a vector of the form
`[`

, with values in degrees.*roll*
*pitch*
*yaw*]

**Data Types: **`double`

**Vehicle radius (m)** — Radius of UAV

`1`

(default) | numeric scalar

This dimension defines the smallest circle that can circumscribe your vehicle, in meters. The vehicle radius is used to account for vehicle size when computing the obstacle-free direction.

**Data Types: **`double`

**Minimum distance to obstacle (m)** — Safety distance around UAV to obstacle

`1`

(default) | numeric scalar

The safety distance specifies, in meters, the space accounted for between the UAV and obstacles in addition to the vehicle radius. The vehicle radius and safety distance are used to compute the obstacle-free direction.

**Data Types: **`double`

**Simulate using** — Type of simulation to run

`Interpreted execution`

(default) | `Code generation`

Specify whether to simulate the model using `Interpreted execution`

or `Code generation`

.

`Interpreted execution`

— Simulate the model using the MATLAB^{®}interpreter. This option reduces startup time, but has a slower simulation speed than`Code generation`

. In this mode, you can debug the source code of the block.`Code generation`

— Simulate the model using generated C code. The first time you run a simulation, Simulink^{®}generates C code for this block. The C code is reused for subsequent simulations, as long as the model does not change. This option requires additional startup time, but the speed of subsequent simulations is faster than`Interpreted execution`

.

**Tunable: **No

**Histogram**

**Histogram resolution (deg)** — Histogram grid resolution

`5`

(default) | `1`

| `3`

| `6`

| `10`

| `15`

| `18`

| `30`

| `45`

| `60`

To change the histogram grid resolution, select a value from the list. All values are in degrees.

**Histogram window size** — Histogram window size

`1`

(default) | odd integer

The histogram window size determines the angular width of an obstacle-free opening in the azimuth and elevation directions. This value is unitless.

**Data Types: **`uint8`

**Histogram threshold** — Threshold for computing histogram

`1`

(default) | positive integer

The threshold for computing the histogram specifies the minimum number of obstacle points that should be in an histogram cell to be considered as obstacle. If a cell contains fewer than this number of obstacle points, the cell is considered as obstacle-free.

**Data Types: **`uint8`

**Maximum age of obstacle point** — Maximum age of remembered obstacle point

`0`

(default) | numeric scalar

Specifies the maximum age of a remembered obstacle point as a numeric scalar. This value specify the number of previous time steps for which the obstacle points from those time steps is remembered.

**Data Types: **`double`

**Cost**

**Target direction weight** — Cost function weight for target direction

`5`

(default) | numeric scalar

Specifies the function weight for moving toward the target direction. To follow a
target direction, set this weight to be greater than the sum of ```
Current direction
weight
```

and ```
Previous direction
weight
```

. To ignore the target direction cost, set this weight to
`0`

.

**Data Types: **`double`

**Current direction weight** — Cost function weight for current direction

`2`

(default) | numeric scalar

Specifies the function weight for moving the vehicle in the current heading
directions. Higher values of this weight produce more efficient paths. To ignore the
current direction cost, set this weight to `0`

.

**Data Types: **`double`

**Previous direction weight** — Cost function weight for previous direction

`2`

(default) | numeric scalar

Specifies the function weight for moving in the previously selected steering
direction. Higher values of this weight produce smoother paths. To ignore the previous
direction cost, set this weight to `0`

.

**Data Types: **`double`

## Extended Capabilities

### C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

## Version History

**Introduced in R2021b**

## See Also

## MATLAB Command

You clicked a link that corresponds to this MATLAB command:

Run the command by entering it in the MATLAB Command Window. Web browsers do not support MATLAB commands.

Select a Web Site

Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .

You can also select a web site from the following list:

## How to Get Best Site Performance

Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.

### Americas

- América Latina (Español)
- Canada (English)
- United States (English)

### Europe

- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)

- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)