Robot control
Devika Subramanian
Fall 2008
Comp 140
1
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Robot Control: Sensors, Actuators, and the Sense-Decide-Act Cycle - Prof. Devika Subramani, Study notes of Computer Science
This document, authored by devika subramanian in fall 2008 for comp 140, covers various aspects of robot control, including sensors (contact, internal, proximity, sonar, visual, and satellite-based), actuators (turn motors and forward/reverse motors), and the sense-decide-act cycle. The document also discusses the operation of sonars and their characteristics, as well as building sensor models and robot actuators.
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Robot control
Devika Subramanian
Fall 2008
Comp 140
15 September 2008 (c) Devika Subramanian, 2008
Robots
15 September 2008 (c) Devika Subramanian, 2008
Sensors for mobile robots
(^) Contact sensors (^) bumpers (^) Internal sensors
accelerometers
gyroscopes
compasses
(^) Proximity sensors
sonars
infra-red
laser range finders
(^) Visual sensors: cameras (^) Satellite-based sensors: GPS
15 September 2008 (c) Devika Subramanian, 2008
Sonars
40kHz sonar range finders
16 cm to 600 cm range
Ultrasonic SRF http://www.robot-electronics.co.uk/htm/srf02tech.htm has the tech specs http://www.robot-electronics.co.uk/htm/sonar_faq.htm has a cool FAQ on sonars
15 September 2008 (c) Devika Subramanian, 2008
Sonar characteristics
http://www.cs.brown.edu/~tld/courses/cs148/02/sonar.html
15 September 2008 (c) Devika Subramanian, 2008
Sonar characteristics
http://www.cs.brown.edu/~tld/courses/cs148/02/sonar.html
15 September 2008 (c) Devika Subramanian, 2008
Building sensor models
d 0 15 30
10cm
20cm
30cm
40cm
50cm
degree of inclination
15 September 2008 (c) Devika Subramanian, 2008
Compass
degrees (0-360)
0: north
90: west
180: south
270: east
Measurements in deci-degrees
4 significant digits in reading
0/ 90 180 270 South East West North http://www.robot-electronics.co.uk/htm/cmps3doc.shtml http://www.robot-electronics.co.uk/htm/cmpsqa.shtml
15 September 2008 (c) Devika Subramanian, 2008
Programming embedded systems Embedded systems interact with the external world, sense it, and take actions to change their world. As the system computes, the world underneath it is changing. Embedded systems work in a sense- decide-act loop.
15 September 2008 (c) Devika Subramanian, 2008
The inadequacy of fixed plans (^) In the maze world shown in the Markov decision processes example (^) move north by 2 (^) move east by 3 (^) .. is not a robust plan! (^) world responds in a stochastic way to robot’s actions (^) Yet, it is possible for the robot to succeed in the maze world with a policy that gets it to the goal state while avoiding the trap state.
15 September 2008 (c) Devika Subramanian, 2008
Get robot to within 50 cm of wall (^) Perfect actuation/sensing Let d = current distance to wall (in cm) move(d-50) open loop control
15 September 2008 (c) Devika Subramanian, 2008
Get robot to within 50 cm of wall Imperfect actuation/perfect sensing Let d = current distance to wall (in cm) while d > 50: move(1) closed loop control sense act Is this program guaranteed to succeed?
15 September 2008 (c) Devika Subramanian, 2008
Proportional control
Instead of moving by a fixed amount
each time, move proportional to the
remaining distance
Let d = current distance to wall (in cm)
while d > 50:
move(k*(d-50))
15 September 2008 (c) Devika Subramanian, 2008
Get robot to within 50 cm of wall Imperfect actuation/imperfect sensing Let d = current distance to wall (in cm) while Pr(d > 50)>epsilon: move(k*(d-50)) closed loop control sense act Is this program guaranteed to succeed?