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General Design Principles

There were three guiding requirements that led to the heavily custom design of the first Critterbot platform:

The first was robustness, both in regard to the environment and to self inflicted damage. In order to inhabit the lab for an extended period of time the platform must be capable of surviving without damage daily interaction with people, getting accidentally kicked or stepped on, running into all manner of objects, and possibly even falling off of small steps. To address these issues the platform's structure comes from three aluminum plates, dividing the internal space into two main levels, and a core structure with solid support from the wheels straight up to the top cover. The peripheral skin and cover are made from polycarbonate to protect the electronics from impacts from large or small objects. The wheels wells are closed to help prevent dirt and carpet fiber from spreading into the robot. Layers of safety prevent the robot from trying to execute commands that might damage it, primarily a level of intelligent power limiting to the motors. The robot monitors motor state and adjusts commands accordingly if executing them could result in overheating a motor.

The second requirement was a friendly and flexible interface. As the critterbot is open to be used by many researchers on different topics, providing a simple and central control system that could provide optional off-site control was important. Complete log files of all commands and sensor data from the robot are kept and accessible. A key scenario for every-day use of the robot was envisioned as connecting an agent or control system to the robot, without having to turn on, calibrate, or adjust anything on the hardware, and run some experiments. Log files would be tagged with a label by the researcher and be immediately available to everyone.

The third requirement was longevity. To facilitate research battery life was targeted to run for most of a work day (6-8 hours), and the robot can charge itself over night. Depending on work cycles it may be possible for the robot to have a second run during the night and then start charging in time to be avaliable for work in the morning. Minimal maintenance should be required for normal use.