Mascot Hexapod

Mascot Hexapod

School of Engineering and Information Technology, Murdoch University

The Mascot field robot is designed to demonstrate that six-legged locomotion can provide good speed, traction and stability in uneven or broken terrain. Initially, it will be a remotely teleoperated, fast, stable, mobile platform which can carry a pair of cameras anywhere outdoors, including off-roadways, up stairs, through the bush and in the rough, and send useful imagery back to a video recording station. But the goal of the project is to automate routine tasks of this kind to the extent that the machine could carry them out without a human operator. Such a machine could be used for maintenance photography and sensing in remote locations, such as the surface of Mars. Part of this work has been published in the Proceedings of the 12th Australian Mars Exploration Conference (AMEC2012).

To avoid the well-known problem of unreliability in complex, jointed leg systems, the mechanism has been reduced to its simplest form. Six simple passive spring legs, each mounted on an independent revolving axis (6 DoF in total) are driven by 18V 100W DC motors fitted with 150:1 planetary gearboxs. The motors are driven by six servo control boards connected to a 32-bit RS485 multidrop network controlled by an onboard subcompact laptop.

The machine is 590mm long, 570mm wide at the middle legs and 700mm from the ground to the top of the camera mast. It weighs approximately 14kg. Imitating the gait of an insect, the machine moves by “tripod walking”: at any instant three legs are on the ground, and these alternate between the sides of the robot. The machine is steered by altering the phase relationship between the tripods on either side. The main power supply for the motors consists of two 18 volt, 5.0 Ah Lithium-Ion battery packs with built in voltage regulators and thermal shutdown circuitry. A 11.1v 1Ah Lithium Ion battery supplies logic power.

It is at present remotely controlled by a six-channel, 900Mhz RC controller for leg speeds and a 2.4Ghz analog video/audio link from the mast camera/microphone to the control station.

An early video of the machine walking can be seen at http://www.youtube.com/watch?v=OskuPsk9DRI