The Role of Sensors in Robotics . Review: Why is robotics hard? . sensors are: limited inaccurate noisy effectors are: limited crude the state (internal and external, but mostly external) of the robot is partially-observable , at best the environment :
Simple and Complex Sensors
"given the sensory reading I am getting, what was the world like to make the sensor give me this reading."
New and Better Approaches to Perception