SUBSUMPTION ARCHITECTURE
In a seminal paper in AI which introduced a the paradigm of 'Subsumption Architecture', 'Robust Layered Control System for a Mobile Robot' by Rodney Brooks; Brooks argues that a mobile robot should be equipped with multiple sensors as that adds to the robustness of the control of the robot. The robot can respond efficiently to a dynamic environment thus the behaviours are apparently more 'smoother'.
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| Fig.1 Control schematics for multiple sensors, from Brooks |
To come up with examples to illustrate Brook's theory led me to this simple experiment in Player-Stage.
I. A robot with sonars, STUCK !
II. Introducing lasers, VOILA it is unstuck and on its way
WHAT IS HAPPENING ?
Here the simulation starts off with a robot equipped with long-ranged sonars, the robot is stuck.
Introducing a short-ranged laser (SICK LASER) unstuck the robot.
Obviously, other solutions can be by modifying the code (sonarobstacleavoid.cc) or changing the geometry of the placement of the sonars. However, the idea of this demonstration is to illustrate the robustness gained by the use of two sensors.
REFERENCES
(2) 6 Architectures
Using the speech.cc file found in player installation files at player-3.0.0/examples/libplayerc++/speech.cc, modifying that file so slightly ! 
Using this script while WALL-E is set to 'wander' (Stage Controller) creates a fair animation, nicely combining the 2 behaviours; wandering and speech. 
