Abstract
This paper describes further progress in the design of a low mass, biologically inspired nanorover suitable for Mars surface exploration and sample return missions. An advanced legged vehicle is presented, incorporating a hybrid DC motor and Shape Memory Alloy (SMA) actuation system to minimise mass and conserve power. Previous work demonstrated that an ultra low mass vehicle could be designed using composite materials. Innovations in this new design include hybrid lightweight DC motor / SMA technology for high power / mass ratio whilst minimising power use, and steps to achieve proportional control of both DC motors and SMA actuators, although work on this area continues in order to resolve problems with proportional control of SMA. Agility is improved using legs with increased angular displacement, which facilitates attitude control over steep and uneven landscapes and enables implementation of biologically- inspired locomotion techniques such as crawling and sideways walking, and adding a third degree of freedom which allows the rover to display an extensive array of gait and pose options. System control applies embedded systems technology running a Linux operating system, force sensors are installed on each leg to provide feedback of terrain interaction for gait management purposes, and power storage capacity and efficiency are improved, enabling the vehicle to carry sufficient power reserves for meaningful excursion durations. The vehicle incorporates an innovative lightweight sample collection arm which uses two servo motors and two SMA actuators. This allows it to collect approximately 2cm3 of sample. Mass is minimised by using a combination of aluminium and Carbon Fibre Reinforced Polymer (CFRP). Total system mass is less than 1 kg, offering the opportunity for a swarm of rovers to form part of the overall Mars mission. These vehicles would take advantage of their superior agility and ability to traverse difficult landscapes and complement the operation of a larger wheeled mother rover - the mother vehicle would carry larger scale science and navigation equipment, as well as on board power resources, whereas the smaller vehicle can be dispatched to climb through rocky and steep terrain or deep into fissures to retrieve samples from the most interesting locations, returning to the mother rover for power and to deposit the sample.