I have already used MPLAB to create a 40khz signal from the transmitters and the signal recieved back was better than anyone expected as it could recieve the signal from over 4 metres and we only need it to go 1m (2m if u include it bouncing back up ) The problem i am having is making the code for the helicopter rising to 1m, going forward for 10 seconds, and then land again. I know that you would probably use delay commands in the code but i aint really experienced at it :-) Does anyone know who to write these part of the code? ------------------------------------------------------------------------------------------------------------------------------------------------ >From: "Sean H. Breheny" >Reply-To: pic microcontroller discussion list >To: PICLIST@MITVMA.MIT.EDU >Subject: Re: helicopter simulation programs PIC16C74A >Date: Sat, 13 Apr 2002 23:27:42 -0400 > >Hi Phillip, > >While I agree that the requirement to use ultrasonics seems very arbitrary >and unwarranted, there are some reasons why gyros alone are not adequate. >The type of gyros that are available cheaply (less than the 1000s of >dollars) are piezo rate gyros. These do not tell you your orientation. >Rather, they tell you the rate at which your orientation is changing. This >is useful if all you need to do is make something stable (i.e., prevent the >helicopter from starting to roll wildly), but it can not hold a given >orientation (let alone position) for very long. > >This is because of bias drift. The output of the gyro has some constant >level even when you are not rotating. You need to subtract this out to get >an accurate reading, but the level is dependent on temperature, often >heavily (1deg/sec per deg C). Even if you add decent temperature >compensation, you will be lucky to keep the thing from rolling more than 1 >deg/sec. The addition of the ultrasonics (which are an absolute sensor, >i.e., they directly tell you orientation) can allow you to cancel out the >drift. Roughly speaking, you can low pass filter the output of the >ultrasonic orientation system (to get rid of the noise caused by the rotor >downwash), and add it to a high pass filtered version of the gyro data (to >get rid of its shifting DC offset), to give you a good estimate of your >orientation with very certain error bounds. > >Of course, it is possible to do this with other types of sensors (besides >ultrasonics), and they might work better for this application. > >Sean > > > >At 08:24 PM 4/13/02 -0400, you wrote: >>Can you mount the ultrasonics on outriggers? This would accomplish two >>things. 1) get them out of the downwash into some (relatively) stable air, >>and 2) amplify the differences in their distance from the ground. >> >>Personally, I would tell the instructor to shove it and use gyros. They're >>proven technology for this job. But, then again, instructors don't like me >>very much. >> >>Phillip >> >>-----Original Message----- >>From: pic microcontroller discussion list >>[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of David Wilson >>Sent: Saturday, April 13, 2002 7:17 PM >>To: PICLIST@MITVMA.MIT.EDU >>Subject: Re: helicopter simulation programs PIC16C74A >> >> >>Everything you said before was correct apart one one small thing, the >>helicopter will mov forward for 10 seconds not hover, sorry for not >>clarifying it too much when i described it. Answering other peoples >>questions the helicopter will be tested outdoors on a level surface. The >>reason we have to use ultrasonic sensors is that we have no choice because >>our college lecturer insists we use them :-(. The main problem that we >>have >>is that we are not really good at the code for the PIC cause we have only >>had 12 about 8 weeks experience at it (about.... 30hrs) and he says we can >>get any outside help apart from himself. >> Thanks >> David >> >>----------------------------------------------------------------------- >>On Mon, 8 Apr 2002, David Wilson wrote: >> >> >Hi my name is David and i have been having trouble trying to create an >> >auto-pilot based helicopter program. The problem i am having (basically >>all >> >of it really) is that there is 4 ultrasonic transmitters/receivers >>situated >> >on a cradle below the helicopter. These are used seperately to find out >>the >> >time taken for the waves to be transmitted and then received, the times >>are >> >then used to calculate if the helicopter is level. >> > The other part of the program is that the helicopter must take off >>to a >> >height of around 1 to 2 metres fly level for around 10 seconds and then >> >land >> >again without blowing up! >> > I would be grateful if anyone could help me try and complete >> >this >> >program, no matter how small information given will be gratefully >> >appreciated and would help me a lot. thank you >> > David >> >> >>_________________________________________________________________ >>Get your FREE download of MSN Explorer at >>http://explorer.msn.com/intl.asp. >> >>-- >>http://www.piclist.com hint: The list server can filter out subtopics >>(like ads or off topics) for you. 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