SOLERO
The Solar-Powered Exploration Rover (SOLERO) activity had the objective to develop a system design for a Martian regional exploration rover including breadboarding for demonstration of locomotion capabilities, payload accommodation, power provision, and control.
The most prominent feature of SOLERO is its ability to operate relying on just-generated solar power, i.e. with minimal use of batteries (only for contingency or peak power demands). On Earth there are a number of solar-powered vehicles operating in this mode. However as Mars is further from the sun than Earth, the power available from sunlight is significantly reduced and thus to design a working and reliable system is much more difficult.
The work has been carried out by Swiss Federal Institute of Technology, Lausanne (EPFL) (CH), von Hoerner & Sulger GmbH (D) under ESA TRP contract.
SOLERO Locomotion System
The first challenge is to implement a very efficient locomotion system. The SOLERO passive mechanical design is simple, reliable and offers low power consumption. Based on EPFL’s Shrimp chassis, it has one wheel mounted on a fork at the front, one at the back and two bogies on either side. The parallel architecture of the bogies and spring suspended fork provide high ground clearance whilst keeping all 6 motorized wheels on the ground. As a result, SOLERO has not only an efficient locomotion but also excellent climbing capabilities over obstacles three times higher than the wheel diameter.
Power generation and storage
The second challenge has been in the optimisation of the power generation and storage system. Calculations for power demand have been based on results obtained from ground testing of the breadboard model. Accurate models of the Martian environment were also considered (i.e. reduced gravity, reduced intensity of sunlight and angles during climbs, temperatures and terrain surface, dust contamination on the solar arrays). It was found that the rover should incorporate energy storage for peak demand and contingency situations only, allowing the solar array to be sized for smaller loads and resulting in a lighter, smaller and reliable rover system.
SOLERO characteristics
| Size | 880x600x450 mm |
|---|---|
| Mass | 12 Kg |
| Payload Mass | 1.5 Kg |
| Payload Size | 170x95x100 mm |
| Wheels | 6 driving wheels; two of them are alos steering wheels |
| Solar Panel | 0.3 m2 |
| Maximal Speed | 0.5 m/s |
| Wheel diameter | 150 mm |
| Ground clearance | 208 mm |
| Maximal slope | 30 deg |
| Maximal step height | 230 mm |
| Power consumption | 4 + 2.5 W on flat terrain |
| Solar cells output | 30 W (outdoor) |
Current usage
The SOLERO rover has been upgraded to include all-aluminium groused wheels and is currently used in the Planetary Utilisation Testbed at ESTEC.
REFERENCES
- SOLERO: Solar-Powered Exploration Rover, S.Michaud, A. Schneider, R.Bertrand, P.Lamon, R.Siegwart, M. Van Winnendael, A. Schiele, 7th ESA Workshop on Advanced Space Technologies for Robotics and Automation 'ASTRA 2002' ESTEC, Noordwijk, The Netherlands, November 19 - 21, 200
- The SOLERO Rover for Regional Exploration of Planetary Surfaces, R. Bertrand, P. Lamon, S. Michaud, A. Schiele, R. Siegwart, European Geophysical Society, Geophysical Research Abstracts, Vol. 5, 11850, 2003