Difference between revisions of "HamsterPython"

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{{DISPLAYTITLE:Hamster Python API}}
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[[Category:Hamster]]
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=== Python setup ===
 
=== Python setup ===
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* Note you are on the HamsterNet
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* Note you are connected to the hamster_net (wifi / router)
  
 
<syntaxhighlight lang="bash" line='line'>
 
<syntaxhighlight lang="bash" line='line'>
Line 10: Line 13:
 
</syntaxhighlight>
 
</syntaxhighlight>
  
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* If the Hamster is powered and your terminal is well configured you should be able to
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See all data streams
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<syntaxhighlight lang="bash" line='line'>
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$ rostopic list
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</syntaxhighlight>
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See imagery from the robot
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<syntaxhighlight lang="bash" line='line'>
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$ rqt_image_view
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</syntaxhighlight>
  
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=== Python Example 1 ===
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* Install dependencies
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* Receive laser scan from robot to decide if free
 
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<syntaxhighlight lang="python" line='line'>
 
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#!/usr/bin/env python
 
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import rospy
 
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from sensor_msgs.msg import Imu
 
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def is_free(ranges ,start_index, end_index ,min_distance):
 
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#sub array from angle to angle
 
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s_ranges = ranges[start_index:end_index]
 
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#filter the array
 
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b_ranges = filter(lambda x: x <= min_distance, s_ranges)
 
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return len(b_ranges) == 0
 
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def callback(msg):    
 
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if is_free(msg.ranges,160,200,0.2): print "FREE"
 
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else: print "BLOCKED"
 
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rospy.init_node('scan_values')
 
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#Put your Hamster number instead of agent<number>
 
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#The agent number is printed on the Hamster cover
 
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sub = rospy.Subscriber('/agent14/scan', LaserScan, callback)
 
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rospy.spin()
 
  
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<syntaxhighlight lang="bash" line='line'>
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sudo apt-get install ros-kinetic-desktop ros-kinetic-ackermann-*
 
</syntaxhighlight>
 
</syntaxhighlight>
  
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=== Python Example 2 ===
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=== Beginner tutorials ===
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Detect right/left turn from IMU
 
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* IMU angles are represented in Quaternions [[https://en.wikipedia.org/wiki/Quaternion]] hence translated to RPY (roll pitch yaw)
 
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* RPY are in radians, translated to degrees
 
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<syntaxhighlight lang="python" line='line'>
 
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#!/usr/bin/env python
 
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import rospy
 
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import math
 
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from sensor_msgs.msg import Imu
 
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from tf.transformations import euler_from_quaternion, quaternion_from_euler
 
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def calculate_robot_angle(orientation):
 
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quaternion = (
 
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    orientation.x,
 
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    orientation.y,
 
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    orientation.z,
 
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    orientation.w)
 
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euler = euler_from_quaternion(quaternion)
 
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roll = euler[0]
 
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pitch = euler[1]
 
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yaw = euler[2]
 
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return math.degrees(yaw)
 
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prev_angle = 0
 
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def callback(msg):
 
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global prev_angle    
 
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curr_angle = calculate_robot_angle(msg.orientation)
 
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if curr_angle > prev_angle :
 
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print "TURINING LEFT"
 
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else:
 
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print "TURINIGN RIGHT"
 
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prev_angle = curr_angle
 
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−
 
 
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rospy.init_node('imu_values')
 
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last_angle = 0
 
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#Put your Hamster number instead of agent<number>
 
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#The agent number is printed on the Hamster cover
 
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sub = rospy.Subscriber('/agent14/imu', Imu, callback)
 
−
 
 
−
 
 
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rospy.spin()
 
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</syntaxhighlight>
 
  
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=== Example 3 ===
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* Exercise 1 - [https://wiki.cogni.io/index.php/HamsterPythonExample1 | Process laser Scan ]
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* Exercise 2 - [https://wiki.cogni.io/index.php/HamsterPythonExample2 | Process inertial measurement unit (IMU) ]
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* Exercise 3 - [https://wiki.cogni.io/index.php/HamsterPythonExample3 | Move until collision ]

Latest revision as of 09:21, 24 March 2019


Python setup

  • Note you are connected to the hamster_net (wifi / router)

<syntaxhighlight lang="bash" line='line'> 

$ export ROS_IP=<your IP>

</syntaxhighlight>

<syntaxhighlight lang="bash" line='line'> 

$ export ROS_MASTER_URI=http://10.0.2.<HAMSTER AGENT Number>:11311

</syntaxhighlight>

  • If the Hamster is powered and your terminal is well configured you should be able to

See all data streams <syntaxhighlight lang="bash" line='line'> 

$ rostopic list

</syntaxhighlight> See imagery from the robot <syntaxhighlight lang="bash" line='line'> 

$ rqt_image_view

</syntaxhighlight>

  • Install dependencies

<syntaxhighlight lang="bash" line='line'> sudo apt-get install ros-kinetic-desktop ros-kinetic-ackermann-* </syntaxhighlight>

Beginner tutorials

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