Data logging and telemetry: tools for performance optimization Francesco Meschia
I ﬂy gliders • Since 2000 • Slope soaring since 2003 • FAI F3J since 2006 • Team manager for the F3J Italian team in 2007, 2008, 2011 • Team pilot for the F3J Italian team in 2009 • FAI F5J since 2011
F3J launch • Man-on-man competition (6-15 pilots) • No winches! • Two-men tow with monoﬁlament line (500 ft) • Incredible amount of energy!
F3J launch tenets • You don’t launch high, you lose • You don’t launch fast, you lose • You don’t launch strong, you lose your friends – towmen, that is
F3J Launch Optimization: why? • “We’ve been watching the German guys closely, our planes don’t launch nearly as strong as theirs do – we need to understand why, quick!” (G.Gallizia, 2008, after the F3J Eurotour France contest)
F3J Launch Optimization: what? • Three simple things we can play with – launch camber – elevator preset – towhook position • Can’t be that hard, huh? – well, it turns out it is…
F3J launch optimization: how? • Need to set a goal • Need to measure the outcome • Need to analyze how the parameters inﬂuence the outcome • Need to ﬁnd a path to improve
Measure to know • Optimization goal is to extract maximum energy in the shortest time – time is easy to measure – how to measure energy? • Energy at the end of the launch comes in two forms: – gravitational potential energy (i.e. “how high”) – kinetic energy (i.e. “how fast”)
Tools of the trade: data recorder From top le*, clockwise: www.eagletreesystems.com, www.sm-‐modellbau.de, www.rc-‐electronics.org
Data reduction and analysis • Just altitude and airspeed – ok for end state only • Need something more if we want to understand what’s going on • How does energy “ﬂow” from towing system to plane? – towmen pull line, line pulls plane – wait! the line!
The importance of the towline • Energy goes into line and from line into model • Line stretches with tension – it is essentially a spring – it is the main “mode” of energy transfer • We need a way to measure line tension!
Line tension transducer • Suitable load cell manufactured by a French modeler (www.xerivision.com) • Attaches to the towline, hooks onto the towhook – cable brings analog signal to data logger, disconnects upon release
…to answer old questions almost no “ringing” Only one “hump” Towhook moved 5 mm a*
Other optimization: the zoom airspeed 50 m/s altude gain 55 m… yield is 43% only!
Optimizing zoom with snap ﬂap same airspeed, 50 m/s Altude gain now 90 m! yield 70%
Wait! all this is not telemetry • True, but… – data collection comes ﬁrst • Real-time telemetry is a useful addition – potentially, another game changer – not allowed by FAI rules, except for safety • Good for training – the pilot should not be looking at a display – audio or buddy relay is to be preferred • Great for team training!
UniLog and telemetry • Available for Graupner, Multiplex, Jeti • Of course I ﬂy Futaba • Needed to invent something myself – well, almost: the actual inventor is W. Korosec • 2.4 GHz, Bluetooth protocol radio link from UniLog to UniDisplay
Telemetry as a team project • 3 complete units were built • Used in team training sessions • Data are received directly into PC • Real-time or deferred analysis possible – real time: ﬁnding best “ﬂoat” – deferred: launch setup
Finding minimum sink setup too steep… trim up… beOer trim maybe down… too perfect! slow…
Further possibilities • Angular position sensors available – allow AoA and sideslip measurement • Direct servo/receiver current draw measurement • In electric sailplanes/models – current, voltage, input power – RPM, output power, efﬁciency – climb performance (m/(s*W)), (m/mAh) • Live onboard video feed?
Radio gear current draw Altude Current draw Pull-‐up
Electric motor logging Voltage Current Eﬃciency Altude RPM
Wrapping up • Real-time, deferred analysis, all is good • Measuring and collecting data over time is key – a way to compare, understand, improve – sharing within a team is equally important – real improvement is possible • New radios are arriving with telemetry – integrated display of telemetry data – sound and speech synthesis (readout, vario, alarms)