Agenda: OLPC -ML Summit - Monday, March 5th Location: One Cambridge Center 9: :00 a.m. Breakfast 10:00 -11:00 a.m. Presentations from OLPC on Current Status 11:00-12:00 p.m. Presentations from ML on XO projects Cynthia Brazeal (Center for Virtual Life) Henry Holtzman (MAS One Laptop Per Child) Benj "Mako" Hill Polychronis Ypodimatopoulos (Networked XO apps + Viral Comm on XO) Matt Adcock (Distributed wikis/wikipedia on XO) Sanjoy Mahajan Alex Wigner-Gross - Wikiosity Barry Vercoe Mihir Sarkar (TablaNet) Ned Twigg Noon-1 p.m. Lunch (Topic: OLPC Summer of Code / Planning for May Event/ Opportunities for ML/MIT student involvement in laptop deployment) 1 p.m. - 2p.m. Peripherals For Laptop ($10 Mindstorm.Scratch, Medical Peripherals, Sensors etc.). Mitch Resnick ($10 Mindstorm.Scratch) Scott Manalis (USB HIV Test) Ed Boyden Joe Paradiso Marko Popovic (H2.0) 2 p.m. - 3p.m. Laptop Entrepreneurship - Joost Bonsen 3 p.m. - 4p.m. Gen 3.0 and beyond ($50 Laptops)

Experimental study on the energetics of the crank generator and the pull-cord device Marko Popovic*, Colin Bulthaup** Hugh Herr* * MIT ML Biomechatronics Group, ** Potenco

Overview 10 test subjects (age 8-12 years) Generator devices attached to solid base. Mechanical properties linked to the circuit parameters. Three experimental conditions: –Crank generator, max power 1 minute –Pull-cord device, max power 1 minute –Pull-cord device & oxygen mask, comfortable pace 3 minutes 5.1 W 12.8 W 3.9 W (Steady metabolic consumption 4.4 W ) Average Electric Power

LabView view on power generation Crank 1 minute Max power

LabView view on power generation Yo-Yo 1 minute Max power

LabView view on power generation Yo-Yo 3 minutes Moderate pace

Power Generated over 60secs Crank Yo-Yo

Metabolic Study The energy cost estimated from O2 consumption and CO2 production (with respiratory exchange ratio, V(CO2)/V(O2) less than one) K4 telemetric system consists of silicon mask with flow-rate turbine and O2, CO2 analyzer Resting values of O2, CO2 were subtracted from values obtained during the trials with pull-cord device

Rate of Net Metabolic Consumption

Efficiency Efficiency defined as ratio of generated electric power and rate of metabolic energy cost SEXAGEMASS (kg)HEIGHT(m)P1*(W)P3**(W)RMC***(W)Efficiency (%) F F F F M F M M F N/A10±235 ± ± ±2.94.4±1.887 ± ± 1.7 * P1=average generated electric power during 1 minute pull cord trial ** P3=average generated electric power during steady metabolic consumption period during 3 minute pull-cord trial *** RMC=rate of metabolic cost during steady metabolic consumption during 3 minute pull-cord trial

Questionnaire How did you like the hand-crank generator? How did you like the pull-string generator? Were you comfortable wearing the face mask? -The hand-crank was uncomfortable but it could possibly work better if the handle was a little bigger. -It was OK. Hands and arms became a little tired. -I dont like it. It hurts my knuckles. -I felt this was much more comfortable than the hand-crank generator and I produced more power with it. -I preferred the pull-string generator over the hand crank. It was easier to gain speed to generate power. -I loved this. It didnt hurt like the hand-crank and felt like it didnt take as much energy as the hand crank. -It was perfectly comfortable wearing the face mask. -Yes – no problems -The face mask feels weird.

Discussion & Summary Max power generation during 1 minute trials strongly in favor of the pull-cord device with average output ~ 13 W; for the crank generator average output is ~ 5 W Comfortable pace power generation with the pull-cord device during 3 minutes trials resulted in a moderate average generated power, ~ 4.5 W, and moderate efficiency, ~ 5.5 %. Net efficiency equals product of bio, transmission & motor efficiencies (back of the envelope estimate ~0.25, ~0.7, ~0.6)

Discussion & Summary Results strongly dependant on the experimental setup. Results dependant on posture and specific movement strategy. Realistically, presented numbers should be thought as a lower bounds on both generated power and efficiency. According to filled questionnaires kids were typically more satisfied with the pull-cord device.

References C. Hausswirth, A.X. Bigard and J.M. Lechevelier, The Cosmed K4 telemetry system as an accurate device for oxygen uptake measurement during exercise, Int. J. of Sports Medicine 18 (1997) J.M. Brockway, Derivation of formulae used to calculate energy expenditure in man, Human Nutrition: Clinical Nutrition 41 (1987)