Mihotel

Basic operation of the Webot object

For any object, it is invisible originally. Only if we add a “shape” property to the children part, could the object become visible to us.
If the object need to interact with the environment (like a wheel), we need to modify the “bnoundingObject” part of the robot. The bounding and the visible shape of the object does not need to be the same.
As shown below, the position and the direction is characterized by three line shown as below: red, green, and blue arrow represents the x, y, z axis respectively. By modifying the “translation” and “rotation” property of the object, the position and the direction could be changed.
For a default type of distance sensor, the maximum distance that it could detect is 10cm, which is far from enough. By modifying “lookup Table” property, we could change the maximum distance it could detect. [x y z] represent the maximum distance, the maximum return value and the standard of noise respective.

Usage of the distance sensor

Firstly, add the “distancesensor” to the children part of the robot.
By modifying the “translation” and “rotation” property, we could change the relative position between the robot and the sensor. By modifying “rotation” property, we could change the direction towards which the sensor detect.
Noticing that, the sensor always detect along the positive direction of the x-axis.
Changing the “name” property of the sensor, and this will be the name that we will use in the ### python code.

The typical Python code that calls the distance sensor:

ds = []
dsNames = ['ds_right', 'ds_left']
for i in range(2):
  ds.append(robot.getDistanceSensor(dsNames[i]))
  ds[i].enable(TIME_STEP)
...
if ds[0].getValue() > 950.0:
...

where robot.getDistanceSensor(dsNames[i]) will call the sensor and ds[0].getValue() will give the distance that the sensor detect.

The range of the sensor could reach is 10cm. when the distance it detect is equal or above 10cm, .getValue() will return a float of 1000.0

Basic usage of camera

Firstly, add the “camera” to the children part of the robot.
The modifying process of the position and the direction is the same shown in above section.
The direction that the camera towards is the negative direction along the z-axis (opposite to the blue arrow).
the upper part of the camera is along the positive direction along the y-axis (towards the green arrow). The position of the camera that I select:

The typical Python code that calls the camera:

from controller import Robot,Camera
...
camera=Camera("test")
camera.enable(1)
...
image = camera.getImageArray()

We need to import the Camera package. and camera=Camera("camera") calls the camera with a name property of “test”.
Only after being .enable(x), could the camera start to work. where x means the camera will use x ms to take a picture.
By using .getImageArray(), we could get a “list” the represent the last picture that the camera get. The channel is RGB.
By applying the “Hight” and “Weight” property. we could get picture with different pixels

Usage of the Opencv package in the Webot

Firstly, simply import the package
```
import numpy as np
import cv2
```
Applying .getImageArray(), we could get a list that represent the picture.

By applying the next several line of code, the picture could be process by the build in function of opencv

image = np.array(camera.getImageArray(),dtype="uint8")
r,g,b=cv2.split(image)
image=cv2.merge((b,g,r))

The default type of the picture get by the Webot camera is int32, which could not be processed by the opencv. In that case, we need to set dtype="uint8" so that the opencv could process without error.
The channel need to be changed.

Basic Usage of the Compass Sensor

Add a compass as the children of the robot. Change it name to what you want or the default “compass”
in the controller.py code:
```
from controller import Compass
Compass1=Compass("compass")
Compass1.enable(1)
print(Compass1.getValues())
```
could directly return a list with shape=[3], dtype=float64. The return shows the direction where the z-axis points to.

Basic Usage of the Accelerometer Sensor

Add a Accelerometer as the children of the robot. Change it name to what you want or the default “accelerometer”
in the controller.py code:

from controller import Accelerometer
Accelerometer1=Accelerometer("accelerometer")
Accelerometer1.enable(1)
print(Accelerometer1.getValues())

could directly return a list with shape=[3], dtype=float64. The return shows the acceleration along each axis.

The return of y-axis is the real acceleration with a gravity, g, added

Usage of the GPS Sensor

Add a GPS as the children of the robot. Change it name to what you want or the default “gps”

In the controller.py code:

from controller import GPS
GPS1=GPS("gps")
GPS1.enable(1)
print(GPS1.getValues())

could directly return a list with shape=[3], dtype=float64. The return shows the absolute position of the sensor along each axis.

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