Biologically Inspired Nano-rovers: Innovative and Low Cost Technologies using Shape Memory Alloys

Paper number

IAC-09.A3.I.4

Author

Dr. Chakravarthini M. Saaj, Surrey Space Centre, University of Surrey, United Kingdom

Coauthor

Ms. Beatrice Smith, United Kingdom

Year

2009

Abstract

To date, all Martian exploration vehicles have been wheeled, such as the Mars Exploration Rover (MER) and the upcoming ExoMars mission. However, wheeled vehicles have low traction and usually cannot  adapt to difficult terrain and tracked vehicles tend to be slower and require more power than wheeled vehicles, although they have better traction. Conversely, legs can be lifted over rocks, or be used to climb over rocks and up steep slopes. Using legs, the attitude of the entire system can be adapted, from a ‘tiptoeing’ configuration to allow the rover to step over rocks in its path or get a better look at its surroundings, to a sprawled configuration for climbing slopes, inspecting small rocks, or avoiding Martian dust storms. Mass was identified as another important design factor; when planning a space mission the heavier a payload or structure is, the more expensive it will be to launch. Similarly, for the same cost of one large system, multiple copies of a smaller system can be launched at once, giving multiple redundancy and increasing the chances of mission success.  The smallest rover used to explore Mars so far has been the Sojourner microrover, which weighed 11kg. 

This paper presents an innovative nanorover for planetary surface missions. This research aims to develop a biologically inspired, small but manoeuvrable vehicle with a mean free path comparable to that of the Sojourner microrover. A working prototype of the proposed legged nanorover, weighing less than 5kg, using commercial off the shelf components is under development. In order to minimise mass, nitinol Shape Memory Alloy (SMA) actuators are used instead of conventional motors. This approach is novel as it is the first time shape memory alloy has been used as the primary actuator of a planetary exploration vehicle, although it has seen some use in deploying solar panels or experiments in missions such as the Hubble space telescope or the Sojourner rover. SMA wires were selected as they have a high ratio of force to mass, and do not have any moving parts. Being linear actuators they are ideal for a legged vehicle, as they can be used in a similar way to muscles in biological systems. This led to the vehicle being based on a stick insect, with six segmented legs actuated by SMA ‘muscles’.  The system design and performance of the proposed nanorover, based on experimental investigations will be presented in the final paper. 

Abstract document

IAC-09.A3.I.4.pdf

Manuscript document

IAC-09.A3.I.4.pdf (🔒 authorized access only).

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