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Some things change, some things don't.

It began for us in 1962, as we read news wires, and listened on the radio about the 18th America's Cup held at Newport, R.I. The NYYC was the Defender and Winner against Australia's Royal Sydney Yacht Squadron. It was President John F. Kennedy's and his wife Jackie's first and last America's Cup. He would be assassinated just over a year later. Now we collect phrases in anticipation of digital dialogues with New Zealanders on the Internet, during the 36th America's Cup scheduled to run in Auckland in 2021 (e.g., Ka pai Aotearoa; Māori, "Good job, New Zealand"). An impeached American president sits tenuously in the Oval Office today, as a pandemic/plague ravages the world. And New Zealand defends the 35th Cup, while America still relies on the New York Yacht Club to challenge the Kiwis for its return. Some things change, some things don't.

CaptainGigi

CaptainGigi

 

On America's twilight…

@NYGovCuomo's recent focus on telehealth, remote learning, and broadband as key components of change in a post-coronavirus society are what other state and local leaders must also prioritize for the continuation of a re-engineered "brave new world." It's based on Network Theory that helps make sense of how society can move forward after the chaos of a raging plague diminishes to some degree. O wonder!
How many goodly creatures are there here!
How beauteous mankind is! O brave new world,
that has such people in't.
—William Shakespeare, "The Tempest," Act V, Scene I, ll  

CaptainGigi

CaptainGigi

 

(Updated 07.02.2020 2010PDT:) CoVid Plague/Pandemic

A plague, by any other name, is still a plague. __________ An Island of Graves in the Bronx, New York, the largest in the United States, perhaps the world “… A report published by 'The Intercept' on March 31 suggested that prisoners with convictions were being offered US$6 an hour to dig the graves. “The same report also outlined a response from New York City mayor Bill de Blasio, who confirmed that prisoners were burying people there, but maintained that it was not necessarily related to the state’s deadly COVID-19 emergency. Inmates have been digging graves on Hart Island for years, he said.” Source: “Hart Island burials COVID-19 pandemic,” Vincent Mingalone, narrator, former inmate of New York City’s Rikers Island prison, now a Manhattan florist arranger for funerals • © The Hart Island Project April 2, 2020 (via Storyful), in Jackie Vandinther (@JackVanD), "Drone video shows inmates digging mass burial graves on New York's Hart Island," CTVNews, April 8, 2020, https://www.ctvnews.ca/world/drone-video-shows-inmates-digging-mass-burial-graves-on-new-york-s-hart-island-1.4888134
__________
Mass graves in burial trenches on Hart Island, at the western end of Long Island Sound, in the northeastern Bronx, New York City (ca. April 8–12, 2020) • © John Minchillo + AP + Wikipedia

CaptainGigi

CaptainGigi

 

Elders are engaged in a war.

In the final analysis, we are only numbers. If you're young, you get first dibs on crisis medical care. If someone decides you may live only five years after crisis medical care, you go to the bottom of the list. We now look at the younger (18–59 years), Coronavirus 'super-spreaders' in our neighbourhood as enemies.
__________
"COVID-19 Addendum: Allocation of Scarce Resources in Acute Care Facilities: Recommended for Approval by State Disaster Medical Advisory Committee (SDMAC), June 12, 2020" • © “Arizona Crisis Standards of Care Plan,” 3rd edition, Arizona Department of Health Services  
 

“When the time is right…”

“… But for now, we listen. Papatūānuku (our earth mother) is breathing."  —Manawanui Maniapoto Mills  https://youtu.be/YKyekQ1njNQ Launch dates for the first AC75s Emirates Team New Zealand (NZL): September 6 American Magic (USA): September 10 (approx.) Luna Rossa (ITA): October 2 INEOS Team UK (GBR): October 4 _________ A`ohe hana nui ka alu`ia. (No task is too big, when done together by all.)
 

"It is the worst of times." —Charles Dickens

An IMF report Thursday warns that a 'disconnect' between financial markets and economic prospects has emerged ("IMF warns markets at risk of correction after run-up," Reuters, June 25, 2020). Or, the markets are not the economy, as the American president would have you believe. There can be no "momentum" in anything good happening in 2020, including the very real spectre of Trump's re-election. Or, grab the camping gear, fill up the gas tanks, and head for the hills, since you can't head "North to Alaska" anymore. But check the long-range forecast before you choose a hideout. Forest fires, you know. This summer is forecast to be one of the hottest on record in every which way.

Test Flight 2

Finally real success!  I got back out there this week with a fully waterproofed servo, an added lidar sensor and a major code overhaul based on Test Flight 1's test data.  Observations were: 1) Pitch control is now much better.  While I still think the control loops could be better tuned, I am now getting long runs with very good pitch stability and no more porposing as you get with the wand-based systems.  In lighter air, I suspect that the lack of paddle / wand drag will allow me to fly more easily as well.   2) Servo waterproofing worked great.  20 knots of wind and lots of spray and crashes and the servo never blinked.  This was a big victory and only involved some grease and spray urethane.   3) There is still some servo chatter / oscillation.  It is minor and doesn't affect performance much but it is bothering and inefficient.  I will comb through the data and see what code changes could be made to maintain the low latency reaction while smoothing the servo reaction.     Two and a half hours of good foiling and 5.5MB of data taken.  Great day out there and lots more data to pick through!  In another few flights it might be time to think about the follow on to this prototype.  Lighter, smaller, sleeker and more awesome!      

DerekF

DerekF

First Flight

I got out Monday for a first flight for my digital flight control system.  Overall it was a big success!  The one thing I cut corners on to get out there was fully waterproofing the servo.  I felt that the likelihood of a turtle capsize was low (my last one was months ago).  Of course, what did I do after 90 minutes out there?  Turtled the boat and killed the servo--HAHA!  But still a great day with lots of learning and successes:   1) Being able to "arm" the system at the press of a button was a major convenience.  When the system is "not armed" it is as if the wand is all the way up and in non-foiling mode.  In the armed state, the boat will try to fly at the desired altitude set point.  Sailing off the dock and around the marina where you really don't want to foil is super easy.  No more swimming out to the spirit to adjust ride height!  Furthermore, adjusting altitude and other parameters was easy with the key fob switch.  The LCD could have been easier to read, but it worked.   2) The electronics enclosure really is waterproof!  After a tough turtle recovery, the electronics survived DRY after 3-4 minutes submerged in about 12 inches of water! 3) The servo is NOT as waterproof.  After the same submersion the servo continued to work for another 5-10 minutes before water ingress fried the circuit board in the servo.  Thankfully these are $40 parts and available with 2-day shipping.  There are lots of tutorials on how to waterproof servos.  I plan on doing so prior to my next flight test. 4) Control loops need tuning.  Things worked out on the water but the control loops felt like they were always behind where they should have been.  I can see it in my data collected and it can be seen in the videos (below).  After an hour of tuning with the wireless key fob, I was starting to get close to the performance I wanted.  Thinking more about the wand if it were a PID controller (Proportional, Integral, Differential), it will have a P = infinity and I = D = 0 (yes, I know I'm ignoring the mode where the wand is just fluttering on top of the water, but let's keep this simple folks).  That leads me to believe, I will need to really crank up my P constant (currently set at 9.0).  I think the I and D constants will be helpful for improving performance beyond the wand, but I'd like to duplicate what I have first.   5) Epic data collection!  After 90 minutes of floating and foiling I have 5MB of CSV data on heel angle, pitch angle, altitude, smoothing params, PID params, acceleration in X, Y and Z axes, battery cell voltages, etc.  This data will help me tune control loops on shore.  My first guess at constants was made by watching our UFO videos frame-by-frame and estimating elevation and rise/sink rates.  My new data is at 20ms resolution and will give me a much better shot at getting things very close on shore before I head out next! 6) Battery life will NOT be an issue.  After 1.5 hours of foiling I had better than 85% of the battery left.  On prototype #2 I will definitely go with a smaller battery to cut costs and reduce size / weight).  Either way, I have hard numbers on cell voltages vs. time and will accurately be able to calculate how much battery capacity will give me how much time on the water.   7) I need a hard-reset switch on the boat.  The ultrasonic altimeter I am using is a cheap one from a car bumper.  Occasionally it gets noisy and needs a reset.  Having a way to do a full power cycle on the water short of taking the lid off the enclosure would make resetting the altimeter easier.  In the long run, I will be looking for a higher reliability part for prototype 2.         

DerekF

DerekF

Integration, Data Crunching, and Mechanical Integration

Another update from the land of digital flight control systems! Integration
I now have all sensors talking to the Grand Central board and the algorithms (PID loop, ultrasonic sensor filter and smoothing, etc.) performing as designed.  The wireless remote is also working and allowing the user to adjust PID Parameters, Altitude Setpoint, and Smoothing coefficients.  The LCD is putting out status messages and feedback when the user is changing parameters.  I am also collecting all the data from accelerometers, gyros, ultrasonic sensor, battery cell voltages, etc. and storing it to an SD card (sample data and charts below).  The data gathering ability will be a major feature in itself.  We will really get to be data-driven about what sorts of tunings make the boat go fast.  For example, comparing nose up vs. nose down pitch angle, fastest ride height for different points of sail, etc.  A simple battery management system is also now working indicating battery State of Charge as well as cutting off power to the servo when the battery gets too low to avoid damage to the cells. Last, the integrated PCB and battery have been installed into the waterproof housing and a gland has been installed to allow for a waterproof cable passthrough.   I am planning on doing some more testing of the integrated system in the “test tank” (aka my hot tub with the jets going).  I may throw my 5-year-old in there and tell him to do some cannonballs.  The goal is to ensure that the ultrasonic sensor is reading turbulent water well and that the default IIR smoothing filter settings are correct.  In particular, the smoothing needs to be set to smooth water ripple and wake without paying too bit a price in lag.  The smoothing coefficient is tunable using the wireless remote so the goal here is just to get the default setting close.  Final tuning can be done out on the water. A lot of progress for 6 weeks.       Data Analysis
The other fun side-project is analyzing data from all of the sensors and graphing things.  I am able to gather data every 10ms which gives very good granularity.  Currently I am collecting the following data fields: 1)    Raw ultrasonic range sensor altitude (cm)
2)    Filtered ultrasonic range sensor altitude (cm)
3)    Smoothed ultrasonic range sensor altitude (cm)
4)    Vertical acceleration (m / s*s)
5)    Heel Angle (degrees)
6)    Roll Angle (degrees)
7)    Commanded servo position (0-100%)*
8)    Battery cell 1 voltage (Volts)
9)    Battery cell 2 voltage (Volts) *Rotary servo position (0-180 degrees) is converted in software to linear servo position using the proper trigonometric functions.  In the code, the servo is commanded between zero- and one-hundred percent representing percent of total linear throw. I have attached some screenshots from excel where you can see the value of visualizing the data and how different filtering techniques and filter combinations affect altitude readings.  Great to see that the outlier rejection (orange line) and IIR smoothing (gray line) are doing what they are supposed to do! I am also curious as to how fast the battery drains during foiling and monitoring cell voltages should give me a good picture of battery life.   
Mounting Plate
I have also purchased Clickbond studs which will be bonded to the sprit.  The mounting plate will then be screwed on to the Clickbond studs.  The mounting plate still needs to be designed but it should be pretty straight forward.  It will hold the enclosure, and mount the waterproof servo and ultrasonic range sensor.  I am currently experimenting with perforated aluminum as it is strong and easy to work.   Linkage
My last step is designing the linkage to mate the servo to the existing flap control rod.  Thankfully, there is already a bell crank on the sprit.  I will not use the existing bell crank because it is not shaped correctly for my purposes, but I will use its pivot pin.  I have to do the calculations to determine the correct length of each side of the bell crank to ensure the mechanical advantage and throw are correct.  Additionally, I need to measure the total actuation length of the flap.  Time to get out the calipers.   Until next time, stay flying.....

DerekF

DerekF