Tag Archives: summer course

Lego Mindstorms Crocodile Robot

The objective of the AM36 2007 course was to build an animal-like robot, using Lego Mindstorms NXT, for the RobotsAtPlay Festival 2007. Specific requirements included: Not using wheels for propulsion, some form of interactivity available, and ready in two weeks.

Designing the Robot

The following drawings were made for the initial design of the robot.The head and body were implemented in the basic style sketched here,while several changes were made to the design of the legs. Additionally, some of the planned sensors were not used, and the activities linked to those sensors not implemented.


Head design and a first draft of possible design for legs.


Body seen from top. Approximate proportions, and sensor placement.

The following sections are the design document containing the original plans for interaction, software, use of sensors etc.


The Lego Crocodile is an interactive Lego model, resembling in outlook and behaviour a real crocodile. The model is capable of moving around, either because of activity in its proximity, as well as by its own will. The model will in general remain passive, seeking to obtain a position in the sun, as other animals in the reptile family. Occasionally it will become active, either seeking a better position in the sun, or scavenging for food in its vicinity. The model can also be activated by other animals or humans entering its proximity. Depending on a number of things, including the interval since last eating, the crocodile will attempt to either engage the disturbance, or move to another position to resume sun bathing.


To make the robot interactive, the robot processes sensory input simulating sound, sight and touch. The robot will also have additional behaviour patterns, which are driven by a schedule. Finally, a remote controller, using Bluetooth, can activate several functions of the robot.

Activity patterns

The robot will actively try to place it self in a lighted area, seeking sunlight as other animals in the reptile family. It will stay in the light for a period of time, unless disturbed, and occasionally seek out a better spot. The robot can be “stirred” by entering into its field of vision, and will then react according to several variables. Either moving towards the object in its vision, or trying to back away and finding a new place to rest. The robot will send out sounds, warning intruders of its mood. As well as vision, the robot will use hearing to react to objects coming close to it. If stirred by its hearing, the robot will try to move around, seeking to get the disturbance into its field of vision. The robot will seek out food thrown to it, if it’s hungry, and try to consume the food. Continue reading