Robotics Antarctic Meteorite Search April 2nd, Group Meeting Notes General comments: -Nomad goes to the field today to test new GPS setting, measure torque on the wheels and show it to Keith.  -Reid interested in when testing NAV.  -Alex and Liam have proper material to send abstracts to SPIE  -Reid: Rattler worked by having two defined days a week to field testing. Sign up sheet to inform about what each person would like to do to organize field tests.  -Reid introduces Keith, from Nasa ames visiting us.  Mike presentation: Solar power for Meteorobot Solar power: theoretical solar constant 1353 W/m2 on Earth Factors that modify this: angle of incidence, location, weather (unpredictable), atmosphere (thickness)  1000 W/m2 maximum at sea level, sun overhead, is standard metric for evaluation (uncommon, more like that 800-900 W/m2)  Stewart: we got at most 110 W/m2 in antarctica  Orientation of the collector  -radiation total = radiation * cos angle  -angles at patriot hills: Nov. 01 to Feb. 01 7 to 33 degrees  -panel elev. angle: optimize for direct radiation  intensity vs. optimize for total radiation intensity (direct, diffuse, reflected energy) Discussion: how close can we get to Patriot hills given its shadow, how do we include the shadow effect in the rover planning  Basic stuff about solar cells, solar experiment were rated 10W (which is max. peak output)  Different efficiencies for solar cells: 10-25% Red: new development with higher efficiency with certain particular frequencies (if you know the freq., you get 60%) Another idea is using crystals that diffract the solar light and use this selective cells underneath. another is working with nasa to do the right request and get the fancier staff.  Current uses: satellites, comms.. relays (on earth), solar racers (specification, performance) 10 m2 of solar panels (get 1000W) top speed 130 mph, sojourner rover  Antarctica results: cold increase efficiency, 4 Siemens 10W solar panels (0,4 m2)  Discussion on the panel angle, that might be important to have more reflected light in to consideration. So conditions in Antarctica are interesting and we can maximize this in the design  Load makes a difference in the efficiency of solar panels. high resistance doesn't get max. so proper load management makes a difference in the total power output. how to change load to have power transference?  Panel configurations: tracking panel vs fixed panels, panels to use at most 1m3 volume  1. tracking panel: total area 1.4 m2, peak output 126 m2  2. multiple panel: tot area: 4 m2, peak 140W  3. cylinder panel: 3.14m2, peak 132W  Reid: peak does not matter, average is what we really care  Meteorobot: 1.5 m x 1.5 m x1.5 m fits twin otter  total solar area 4.7m2, peak power output 200W  average speed 15 cm/s, weight 200 kg  Hybrid power system: solar cells and batteries  energy storage:   lead acid 45 W-h/kg 250 W/kg   Lithium 130 Wh/kg 800 W/kg   AgZn 160 Wh/Kg 210 W/kg  Discussion about batteries and power management. What is optimal: do we use batteries or not: they help to provide power to climb, they provide ballast to prevent tipping over because of wind.  Mass and power comparison between different vehicles (nomad, Rattler, solar racers, sojourner)  Conclusions: solar power is feasible.  Target: 200 W continuos  Do preliminary research on Nomad and refine later to mount on solar machine  Power management: distribution (locomotion, computing, science)  Operational Modes: high speed, general area research, inspection of sample, comms. to sat)  Comparison with the moon: moon still has reflectance, panel degradation (example in Mars, high rate of degradation), no diffusion.  Meeting is over. Reid's presentation on autonomy is delayed.