23 Jan 2003 motters   » (Master)

I've now got Rodney version 4 up and running, and have been working on his head and eye movements. The system which I've used is similar to the previous tracking system. It's still pretty simple and uses a "centre of gravity" type algorithm to calculate a target position for the eyes.

It took quite a long time to tune the feedback loop which controls the saccade movements of the eyes, but I've now got them moving fairly accurately. If I place any object within stereo vision range the robot quickly moves its eyes and orients its head/torso to focus on it. The head and torso movements are just slaved from the eye movements, such that if the eyes move towards the limits of their motion the head and body make compensating movements to bring the eyes back to a central position. This orientation behavior looks fairly natural, and fixation of a nearby target by the eyes is almost completely accurate.

A new feature which I've added is a visual attention system. This is based on a similar system used on the MIT Cog and Kismet robots. Rodney presently pays attention to both stereo and motion cues. Physical movement of the robot's head supresses attention to visual motion in a classical subsumption style.

There are a couple of things to work on next. Firstly Rodney's behavior at the moment is entired "bottom up". He is entirely driven by events in his immediate environment. I need to add some internal goals and motivations which help to structure the behavior in a rational manner (for example a desire to explore his surroundings, rather than just being obsessed by whatever object is closest to him). This leads on to the second thing which I'll have a go at, which is a 3D occupancy grid similar to those devised by Hans Moravec. Using some crude stereo methods and servo position feedback I may be able to have the robot build up a rough 3D model of his immediate surroundings.

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