SEN 3445
- Thermal Sniffer Update
- Hatschek International Challenge this weekend, May 30-31
- More on energy limits
Thermal Sniffer Update
From : Can Tezcan
Dear Users of Thermal Sniffer,
We discovered that the Thermal Sniffer can freeze under certain conditions, especially in environments with strong radio-frequency interference. I have therefore reworked the radio communication software, and the system is now completely free of freezes.
I can update your devices in two ways:
* You can send the device directly to me, and I will reflash and return it to you.
* Or we can arrange to meet at one of the World Cups, where I can update your device on-site.
In all cases, the update is completely free of charge.
For users in the USA:
Someone will travel from the USA to Germany at the end of June. If you send your device before June 20th, this person can personally bring it to me and also take it back to the USA afterward.
In any case, please contact me via email:
Meanwhile, I have also been working on a new version of the Thermal Sniffer — an extended and improved Version 2.
New features include:
* Integrated LiPo battery and charger (no more external battery boxes)
* Improved temperature and pressure sensor sensitivity
* New tablet app features
* Real glider-style variometer telemetry for thermal indication
This new version will be more expensive than Version 1. However, existing customers can upgrade for 100€ or US$120
For the Version 2 upgrade, I will also need your current device, as some electronics need to be replaced and the integrated LiPo and charger need to be installed.
So you have two options:
1. Keep your current Version 1 device and receive the new freeze-free software update for free
2. Upgrade to Version 2 by returning your old device and receive a completely rebuilt new version for US$120 / 100€
Best regards,
Can Tezcan
Hatschek International Challenge this weekend, May 30-31
From Tom Juell
Guys,
The forecast for Saturday, May 30, is very windy, but it will calm down in the late afternoon before sunset. There will be NO FAI contest events flown on Saturday. I will arrive at Barron Field after 3:00 PM on Saturday.
Later, at 5:30 pm, we will have the club dinner at the Jolly Union. This leaves a late afternoon flying window for mini events.
ALL FLYING is moved to SUNDAY, May 31st, with lots of flexibility.
Hope to see you at the club dinner!
Aram
More on energy limits
From Roy E. Smith
I write to comment on Peter Martin’s argument on the matter of open and closed loop control systems – and the issue of using a limit on electrical energy dissipation as a means to ‘level the playing field’ for competition in the electric-powered categories. At the outset l would like to say that I agree completely with Peter’s conclusion, that an energy limit is an open-loop system, no different in any fundamental respect from many such systems that have been in successful use almost since aeromodelling began – even going back to the humble DT fuse.
Let us first look at the definitions of closed-loop and open-loop control systems.
A closed-loop control system (or feedback control system) is an automated system that uses sensors to continuously monitor its output. It compares this actual output to a desired target and automatically adjusts its operation to minimize errors and maintain the target state, all without human intervention.
An open-loop control system is an automated system where the output has no effect on the control action. The controller operates strictly based on predefined inputs and time delays. Because it lacks a feedback loop, it cannot self-correct if errors or outside disturbances occur.
What would examples of such systems be, in aeromodelling terms? The target for a powered free flight aircraft (rubber, IC engine, or electric) is to have it gain as much height as possible under power so as to increase the chance of a prolonged glide phase. If there was a control system on board that sensed the angle of climb and adjusted the flying surfaces so that this maintained the optimum upward angle and speed, in defiance of any external disturbances that might alter that, and then, once the power phase was over, re-adjusted the surfaces to set the aircraft into an optimum glide configuration, minimizing the rate of descent by the use of sensors, and then, if it could detect that the aircraft was feeling the effects of a thermal, redirect the flight path so as to maintain the aircraft within that thermal, any or all of these would be a closed-loop system and would be banned from competition. A similar aircraft that is launched with the flying surfaces set to maximize the climb attitude while under power, and with a timer that is rigged to end the power phase and set the flying surfaces to positions that are preset prior to flight and not variable either from the ground or from on-board sensors, is an open-loop system and is acceptable in certain free flight competitions.
A system that shuts off power irrevocably once a pre-determined amount of energy has been expended, not controlled from the ground, or from on-board aircraft performance sensors, is also clearly an open-loop system and thus should be as acceptable as the many other open-loop systems used to limit aircraft performance.
I will give a different argument for the point that Peter made about a Montreal stop being an open-loop system. The Montreal stop (and many other variations on the theme) are just a means to ensure that, when the rubber motor winds down, a propeller that is designed to fold once the torque on it reduces to near zero, will fold at a specific rotation position, ensuring that the fold will be complete and will not occur with one blade hanging down below the fuselage. The mechanism does not control torque, based on the sensing of extremely low torque. The mechanism irrevocably determines propeller stop position, based on the torque falling below a pre-set value – quite clearly not a closed-loop control system.
I can only suppose that, with an energy limit on electric aircraft there will be two lines of approach taken to maximize aircraft performance. The first is the obvious one of propeller efficiency. The second is the not-so-obvious one of programming output to provide the most advantageous power output profile – so that the maximum time of flight is obtained from the energy expended. Unlike the situation when the power is delivered for a pre-set time – where maximum climb rate is paramount – when energy is the limit, a slower climb rate, with longer motor run, might prove to be highly advantageous – using the energy to overcome gravity, not aerodynamic drag.
All of that said, although it is not very difficult to set an energy limit on electric aircraft – it would be much more difficult (but not impossible) to apply the same principle to IC engine-powered aircraft. The amount of energy expended can easily be calculated from the torque multiplied by the number of revolutions of the propeller. The calculation is easy – the accurate determination of the two values required is much more difficult, and extremely difficult to verify. I do hope that no-one gets it into their head to propose such a scheme.
Roy E. Smith
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From the Aeronut
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