From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=unavailable autolearn_force=no version=3.4.4 Path: border1.nntp.dca3.giganews.com!backlog3.nntp.dca3.giganews.com!border3.nntp.dca.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!news.glorb.com!peer02.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!post02.iad.highwinds-media.com!news.flashnewsgroups.com-b7.4zTQh5tI3A!not-for-mail From: Stephen Leake Newsgroups: comp.lang.ada Subject: Re: Raspberry Pi, Real-Time and Ada References: <5e8fad3a-94e6-4517-af54-db8b4146803e@googlegroups.com> <858uto3cj3.fsf@stephe-leake.org> <85d2iz1g48.fsf@stephe-leake.org> <854n4a1004.fsf@stephe-leake.org> Date: Thu, 13 Feb 2014 09:23:12 -0600 Message-ID: <85iosjxcin.fsf@stephe-leake.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (windows-nt) Cancel-Lock: sha1:J5dk3jPzKw5C6XCEu4FPVm9Z30o= MIME-Version: 1.0 Content-Type: text/plain X-Complaints-To: abuse@flashnewsgroups.com Organization: FlashNewsgroups.com X-Trace: 13b8052fce366eef2f4a325494 X-Received-Bytes: 2928 X-Received-Body-CRC: 3900698612 X-Original-Bytes: 3169 Xref: number.nntp.dca.giganews.com comp.lang.ada:184823 Date: 2014-02-13T09:23:12-06:00 List-Id: "Rego, P." writes: >> For spacecraft, this is based on a stability and pointing accuracy >> analysis; if the control cycle were slower, the spacecraft would not be >> stable, or would not point accurately enough. 10 Hz is usually adequate. >> What does the control cycle in a drone do? I suspect the plane is >> basically stable by the design of the wings and tail, and the control >> system is just running the steering. >> Based on what analysis? > > Actually it depends highly on your design. Yes it does; that was my main point. >My perception is that as > smaller is the drone, faster you should be able to control it. For > example, wonder a quadcopter 10m high, falling down, maybe because you > (controller) lost communication. An autonomous recover-to-ground > algorithm should in 1s: 1) identify communication is lost; Assume no communications in 3 cycles = lost; that leaves 7 cycles. >2) assume > override; 3) read sensors (as always); 4) calculate the best landing; That all takes less than 1 cycle. > 4) command devices and land. No problem; each of the 7 remaining cycles keeps the quadcopter level, and moves it one step closer to the ground. > Using a complete model you would need to solve some conditions for a > 12-dimensions model. If that takes longer than 100 ms, you need a faster on-board computer. > With 10Hz I would have only 100 iterations in 1s. 10 iterations; 10 Hz = 10 cycles per second = 100 ms per cycle. >And all this should happen before the > human sense realizes (so 1s is quite fast for us). Right. So 10 Hz is adequate. 5 Hz is probably ok as well, if your computer can only manage that. This is a quad-copter, which is stabilized solely by controlling the rotor blades, and thus needs active control. I was talking earlier about a wing-and-tail design, which requires no active stabilization; paper airplanes manage to fly :). -- -- Stephe