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teamawesome
10-21-2008, 10:55 AM
http://farm4.static.flickr.com/3269/2950773032_3c112d01aa.jpg?v=0


Well i can not go into the specifics on the project's design however there are a series of basic operations that need to be done in order to make it function correctly. What i can say is that it is a flying device like no other and requires several key components to keep it a float, based on your input, the complexity will vary. The team and i (known as team awesome) are all senior mechanical engineers here at VCU with little experience in this field. We have found our way hear from a long train of links and site searching and are looking for some experts to help give this portion of the project a mind of its own. So anyways that is us now on to the project.

Like i said above the design is one now owned by VCU and specifics will be vague, but you shouldn't have to worry about specifics in order to comprehend what needs to happen. There are several mechanical interfaces that can control the device and each require a mechanical input. These, in our hopes, would be linear actuators. Also we will be treating this as a UAV device for the time being sense there is nothing yet to keep it managable and stop it from flying off with one of us on it. YES this is a full scale prototype that is in the order of 16 feet long and 7 feet wide. Therefore larger actuators and higher ampes will be used in the construction, I'm not sure how this effects the electronic design but to each of you it may bring up some questions.

What this set-up has to do for us right now is balance. It must be able to hold still for us so that other controls can be added to give it true flight capablities and possibly the subtraction of the UAV status. There will be a total of 4 actuators in strategic places in the simplest of designs to handle the roll and pitch of the device, again the complexity will vary. Yaw is not a huge concern for us at the moment. The distance off the ground, left/right and foward/reverse will be controlled by another interface that is outside the scope of this thread. We understand the dynamics of flight and what the device has to do in order to correct certain stability issues however we dont know the electronic link between the actuators and gyroscope (or what else will be needed by your specs). The frame work is complete and our first tethered test flight is approching very very quickly. Here are some basic questions.

Understandably the actuators require a different voltage than the electronic components, so what is the order of events that allow the gyroscope to interact with the actuators?

What to look for in purchasing components? we are on a budget.

Any good articles out there? I've tried googling but unfortunatly did not find the basic chat needed to really get anything out of it.

We will have many more as time progresses.

thanks

Paul (team awesome)

ScuD
10-21-2008, 11:48 AM
Here are some basic questions.

Understandably the actuators require a different voltage than the electronic components, so what is the order of events that allow the gyroscope to interact with the actuators?

What to look for in purchasing components? we are on a budget.

Any good articles out there? I've tried googling but unfortunatly did not find the basic chat needed to really get anything out of it.





Depends on what you want to do with the signals from the gyro. A simple interconnection between the gyro and actuators with nothing but a voltage / current amplifier could be as simple as a transistor or an opamp. However, if you want to be able to modify the gyro's signals or the way the actuator responds to the gyro's output, you may want to consider using microcontrollers or even DSP's to handle that. It's all up to what you're trying to accomplish.
Depends on the speed/torque you're looking for. Since it's a full sized build, I'm guessing a few hobby servo's won't do. Do you need the power of hydraulics? Then be prepared to double your budget, and still blow right through it.:happy: DC or AC servomotor systems might be up to the task if using correct transmission, or you may want to look in to servo linear actuators. Once again, not the cheapest, but cheaper than hydraulics.
Articles... this one's a bit hard. I'm guessing you could look into people building their own "flight simulator" cockpits, since they use a lot of linear motor systems, both electric, pneumatic and hydraulic. For some reason I think there was a thread somewhere around here a while back, but I can't remember... Lynn?

All in all, we can pitch in with our best ability, but the hardest part lies in your hands. Figuring out what exactly it is you need to suit your application.

jes1510
10-21-2008, 12:06 PM
I don't have much that may be of help but RCGroups has a forum dedicated to homebuilt UAV's. There is a tone of information in there.

http://www.rcgroups.com/uav-unmanned-aerial-vehicles-238/

Adrenalynn
10-21-2008, 12:14 PM
Lynn?

This one's all yours, ScuD!

The problem with not sharing project details [for me, at least] is that it doesn't spawn any emotional attachment to the outcome. If I can't get emotionally invested, than it feels like "work". And I have way to much of that to take on any more, especially when it doesn't pay. ;) Heck, I don't even take on "work" projects that I'm not emotionally charged about anymore...

Quantum
10-21-2008, 12:33 PM
I havnt seen to many balancing projects in this forum.

Sparkfun.com has a forum as well and they carry a large assortment of gyro's and accelemeters.
I have seen several projects there that use this from a balancing skateboard to two wheel robots.

First your most likley going to need a gryo and a accelemter on it as well.
You didnt mention this in your post so just throwing it in not sure if you guys know this or not.
ACC. will measure your angles but not how fast your drifting so both are a must to make a stable balancing platform.

I personally tried to make a balancing two wheel pendulum type robot witha acc alone and it worked at figuring out what angles. But I needed to include the gyro to tell how fast the stepper motors needed to rotate to regain balance.

You guys need to decide which actuators so you know the voltage first before going any farther.
Most likley your going to need to build a controller. Somthing with a processor that will take the data from your gyro and acc. unit that will return the data to the processor. Processor computes that data and makes the corrections to your actuators.
Voltage issues can be controlled with optoisolators so that you can have your lower voltages for the controller board and you higher voltages from the actuators.

Paul

teamawesome
10-21-2008, 12:51 PM
Reading threw the written responces super fast ill try to add more detail and maybe more specifics. I've got some cool pictures of the weekends work but ill talk to the group and see whats what. thanks for the replies we really appreciate it. I'm super excited about the project and hope to gather the excitement of others as well.

darkback2
10-21-2008, 12:59 PM
Welcome team awesome...

I think part of what some of us are getting at, is what are you bringing to the forum? If you just want to be able to ask questions and get answers for your project, then people here aren't going to be all that excited. Especially if it is a one way street.

In my opinion this forum is about giving aswell as taking.

If you can't do that because of confidentiality issues, then maybe a forum isn't the right place for you to be getting information.

Also, if this is for a uny and not DOD, then won't you have to publish your work anyway? Heck...even if it is for the DOD certain aspects can be published...especially your use of off the shelf products. (http://www.egr.vcu.edu/egr/news_events/egr-wins_auvsi_competition.html)
(http://www.egr.vcu.edu/egr/news_events/egr-wins_auvsi_competition.html)
Just a thought.

ScuD
10-21-2008, 01:08 PM
According to general consensus, I seem to have an acute lack of emotion. So that might be a problem with getting projects done.. :happy:

Regarding the gyro / accelerometer, I'm surprised actually. I haven't tried any of them yet, but I thought the accellerometers were used to detect the angle, whereas the gyro is used to determine the speed with which the change in angle is occuring.
Sounds logical enough though, being 'accellerometers'... but then, I thought the gyro acted on the principle of a spinning disk, the harder you pull it off it's axis, the harder the response (gyroscopic effect). If the angle remains constant, the spinning disk accepts the new axis as it's "normal", which I had gathered to be what's known as gyro drift.

Guess I should use Wikipedia some more, and stop thinking about things without the correct information..

jes1510
10-21-2008, 01:19 PM
I'll answer the bit about accelerometers. They are a class of device that measures acceleration. When the device is sitting still it will still sense a bit of acceleration due to earths gravity pulling on it around 1G. If you roll the device around then you can derive the angle in relation to earths gravitational field. Using the proper math you can use the same device to measure angles as well as amount of acceleration along a plane.

A device I recently used gave an acceleration reading in radians. I could then convert it to G's using the following formula: (asin(x)*180) / pi

darkback2
10-21-2008, 01:59 PM
I'll answer the bit about accelerometers. They are a class of device that measures acceleration. When the device is sitting still it will still sense a bit of acceleration due to earths gravity pulling on it around 1G. If you roll the device around then you can derive the angle in relation to earths gravitational field. Using the proper math you can use the same device to measure angles as well as amount of acceleration along a plane.

A device I recently used gave an acceleration reading in radians. I could then convert it to G's using the following formula: (asin(x)*180) / pi

If the UAV is a plane, then if it banks wouldn't that create centripital acceleration thus nulling the downward pull of gravity? think about a plane doing a loopdy loop...the giro would always read that down was down even when the plane was upside down?

I dunno...

DB

Quantum
10-21-2008, 04:49 PM
Yea I switched those around by mistake. I will correct the earlier post.

teamawesome
10-21-2008, 05:35 PM
ok talking with everyone ill post a few pictures up. The frame work and prop lay-out is nothing new. However what is suppose to be held with some confidentiality is the control system around the shroud and how we are trying to differenciate ourselves from the other series of VTOL crafts. This hopefully will give a good representation to the size of the device. What is pictured in front of you is 4 days of hard work, and yes you can call us crazy but we are going for the gold on this project.

http://farm4.static.flickr.com/3241/2950732348_e35e783885.jpg?v=0

This is the frame sitting on a large truck scale. The five of us are in the picture obviously. This is the first of two prototypes constructed out of metal, the second prototype is a full carbon fiber make-up that will be used for obvious reasons. The weight of the metal means there is no room for passenger on this model, so it stands as a UAV device. The second, we will see, but hopefully will be more in the lines of a "driveable" unit. We need to make up a "black box" full of the electronics that can be transported to the carbon fiber body with ease, besides tweeking a few numbers. Thats our intention anyways.

To answer questions on the output mechanical side, pneumatics are a possibly because of there responce time and the ability to be controlled with ease, anything using oil has a weight factor. However the easiest would be electric actuators we feel, but thats were we need some input.

As far as also giving back to the forums i kinda understand were your coming from to some degree. However we would like to purchase the components from Trossen Robotics and after emailing the customer support from some answers this is were it landed for us. I understand that most people on here are not working for Trossen Robotics however we also feel that there may be a little bit of need to keep some ideas to ourselves for now at least. sorry

Also what is involved if we went the microprocesser route?

Quantum
10-21-2008, 09:33 PM
That's cool.

You guys have a lot of work ahead of you. But its fun I remeber when we did our project a rc airplane modified to make it easier for pilot to land and take off. So they didnt have to worry about crashing it at landing.

You have no choice but to use some sort of computer with processing power. You need to give this thing a brain.
You need to control the balance. This is the most important thing in your project. I dont think you would be able to control this mechanicaly. A person's reflex most likly are way to slow.

Plus your fans are running counter to each other and your going to need to slow one down and speed up the other to turn. Unless you guys plan on making really wide turns.

I would look around at some sights to see what you guys are comfortable as a prgramming language.
And look at some sensors and at actuators. Some manufactures might have examples of hooking stuff with diferent mcu. Break it into tiny parts and go up from there.

The black box idea is the way to go. Just plug everything into it. Make a box with all the jacks you need to hook all the different gizmos and what not that is going to be used.

Just my thoughts I might be way off or over doing it.

Paul

teamawesome
10-21-2008, 09:51 PM
great responce. i have really no experience with programing but that is what this is about. again there is only 5 of us and we show case everything on april 24, giving us a compact schedule. Is there any examples out there? if i were to order parts i wouldn't know where to start. Like you said we were thinking human reaction but this became alittle bit of a scare not knowing how this craft will act. We were also thinking using a mechanical control on top of a electronic base to simplify everything, but again we really need an example to pull ideas from.

metaform3d
10-22-2008, 12:19 AM
I'd suggest starting with a simulation to see if what you want to do is even possible. I don't think anyone could hack together a fly-by-wire control system for something that (apparently) unstable without a lot of theory behind it. If you're thinking you can just connect the output of a gyro to the input of an actuator you will be very frustrated.

Since it's a flying device the differential equations are relatively simple, and Octave (http://www.gnu.org/software/octave/) is free.

4mem8
10-22-2008, 12:44 AM
Good to meet the team behind this project, thanks for posting it. Your project looks awesome and I wish you all good luck with this project. I will be watching closely what eventuates.

teamawesome
10-22-2008, 07:53 AM
I'd suggest starting with a simulation to see if what you want to do is even possible. I don't think anyone could hack together a fly-by-wire control system for something that (apparently) unstable without a lot of theory behind it. If you're thinking you can just connect the output of a gyro to the input of an actuator you will be very frustrated.

Since it's a flying device the differential equations are relatively simple, and Octave (http://www.gnu.org/software/octave/) is free.


Very true indeed. We are working on some very simple testing in order to obtain and workable solution to the unbalancing. Also note that the design may not be terriably unstable as if it were on its own, however something is going to be needed if we take it further to human input. The differential equations are simple when it comes to the development of a pure balancing device. However they are much more involved when a human input control system is implemented on top of that and then even greater when traveling, so we have found.

darkback2
10-22-2008, 08:11 AM
Very true indeed. We are working on some very simple testing in order to obtain and workable solution to the unbalancing. Also note that the design may not be terriably unstable as if it were on its own, however something is going to be needed if we take it further to human input. The differential equations are simple when it comes to the development of a pure balancing device. However they are much more involved when a human input control system is implemented on top of that and then even greater when traveling, so we have found.

have you thought about making an underwater version for testing? or at least a small scale model using foam, wood, and rc plane parts?

Rokon
10-22-2008, 08:53 AM
Looks like a cool project. Other flying platforms I've read about used pilot weight shift as part of the control system. No weight penalties with that. I would consider counter rotating props on both fan units, to nullify torque, and rpm differences as part of the controlling system.
You've got your handsfull!! Any rc/electric models given a consideration for flight testing???

Rokon

teamawesome
10-22-2008, 09:48 AM
Well being the such short time limit and how much we need to accomplish, an rc model is really just using up more time. We have thought about it but i do know from experience that rc can take awhile when when its not a kit and everything is from scratch. Yes the props are counter rotating and are powered hopefully (they have not come in yet) 2x 40 hp kohler motors. The frames weight is 320lbs right now, but we are well within our "calculated" limit.

here is a wright brothers take on the design

http://farm4.static.flickr.com/3239/2950730050_4e98371096.jpg?v=0

jes1510
10-22-2008, 10:00 AM
Your very first test flight is going to be full scale on production level hardware? Man talk about pucker factor!

teamawesome
10-22-2008, 10:20 AM
puckr factor - (a.) A term used to describe the tightness of your sphincter following a close call. Some as yet unidentified factors are high enough to cause discomfort as you must take an appreciable amount of time to remove from your butt that what you were sitting on. (b.) A term used in the early 1970's US Army Paratrooper School to describe the fear of jumping out of an airplane for the first time.
NOTE:A Pucker Factor of 10 can only be truly achieved upon death or dismemberment.

Yes we will be standing back alittle and it will be tethered

Rokon
10-22-2008, 10:56 AM
Just curious, whats the projected flying weight??? The empty wt of my 1932 Pietenpol homebuilt is 680lbs, with 55hp Model A. You seem fat for a bare frame..... Having a tether will keep the FAA away. Eventual Experimental status??? Your makin me drool.......

Rokon

teamawesome
10-22-2008, 11:29 AM
Well in short the weight of everything combined is about 650 lbs, thats just plain adding up material and known values. Our calculated lift is on the order of 800 lbs, while some will be directed towards controls which cannot be deemed as lift. As far as eventual experimental status of the project is have a full working CARBON FIBER model to lower the weight for obvious reasons. I like the idea mentioned before were a computer was mounted in order to provide the processing power and a easiness of the control, however having no skill in that area we will just have to see how far we obtain that goal.

Adrenalynn
10-22-2008, 12:20 PM
I think you'd have the first-ever flying machine that wasn't scale-built first - if you can pull it off.

teamawesome
10-22-2008, 01:18 PM
What is a manufacturer that will enable be to use a laptop as a control system? and does each manufacturer have a different language were all the components must understand?

I understand, if we go this route, that we can get a ampilfier for the output signal from the componets to interact them with the actuators, but how does responce time change? and is it still programable or standalone?

darkback2
10-22-2008, 01:52 PM
A couple of considerations, how fast do you need to move whatever it is you are moving? Are you adjusting the rotar blades to increase lift? or are you adjusting the speed? or the angle of the entire assembly? Are you moving a counterweight under a balanced system? How much load will you need to move the parts that you need to move? how great a distance will you need to move them? are you using comercial software or programming this bad boy from scratch?...

As for actuators, look into either a stepper motor controller setup, or a servo controller setup. an SSC-32 coupled with an electronic speed controller for DC motors or a stepper motor controller for working with steppers. Also, if you tell us which linear actuators your planning to use we could maybe figure out the best control method...

DB

teamawesome
10-22-2008, 02:33 PM
A couple of considerations, how fast do you need to move whatever it is you are moving? Are you adjusting the rotar blades to increase lift? or are you adjusting the speed? or the angle of the entire assembly? Are you moving a counterweight under a balanced system? How much load will you need to move the parts that you need to move? how great a distance will you need to move them? are you using comercial software or programming this bad boy from scratch?...

As for actuators, look into either a stepper motor controller setup, or a servo controller setup. an SSC-32 coupled with an electronic speed controller for DC motors or a stepper motor controller for working with steppers. Also, if you tell us which linear actuators your planning to use we could maybe figure out the best control method...

DB

The speed of the props are 2200 rpm +-300 rpm. The motors that control the system more than likely cannot bring a 6ft prop up to speed with the correct responce time. Therefore that rules out throttle control as a simple means of adding stablization in that direction. Changing the rotors angle of attack like a helicopter is an added expense that we did not make when ordering the prop. (about a 1k dollar difference, as well as there responce times were around 5 seconds and could not handle repeated use) there will not be a counter weight, nor will the props change direction upon a specified axis (they are fixed).

The easiest way to think the controls as if were a series of baffles under the prop that changes the direction of the thrust. However this is not exactly how we are doing it, it is close enough of a example make everything else we do relate. Therefore the size of the baffle changes the responce time needed, as well as leverage on the actuator. Therefore as an actuator, depending on the size of the baffle, can have extreme pressure on it, obviously increasing the size of the actuators from hobby definition. As far as specifies to actuators i have none, i can pick out some but in fear that it won't be completely correct. Commercial software is a huge plus, looking for as of a simple language and set-up as possible. Remember this is just a prototype. im guessing around 100lbs or so and at a stroke of about 8 to 10 inches, with a responce time of about 1-2 sec. All can be vague because how they are implemented can change to match there specs. However the link to them is what im concerned more about.

darkback2
10-22-2008, 02:54 PM
Awesome...then...if I were you I would look at using a servo controller hooked up to an electronic speed controller...attached to either a linear actuator or a piston/cam sort of set up. You can translate rotation into linear movement, and get the response times/motion you want. I would also use some sort of sensor probably a potentiometer to locate the position of the baffles...that way you have a sort of bootleg servo setup. This way depending on the resolution of your sensor you can farely accurately locate the baffles. As for the 100lbs...try using multiple actuators for every baffle...also consider where on the baffle you attach the actuator...closer to the fulcrum means more output for less input...think lever...but requires a stronger actuator. OK...enough.

DB

lnxfergy
10-22-2008, 02:58 PM
You will probably want to take a look at National Instruments Labview for your control structure. The software isn't cheap, but it is industrial/commercial quality and can use a drag and drop interface (no real programming). Additionally, it supports many common industrial controller boards.

I highly doubt many people here will have recommendations on linear actuators that offer 100lbs of force and 1-2sec transition over 8-10 inch stroke. That's very serious machinery... Something like this http://www.firgelliauto.com/product_info.php?cPath=109&products_id=165 would take 4-5seconds to go 8-10 inches, with 150lbs of force at a cost of $140. You would have to add a controller to it, capable of handling 12V @ 4A, as well as the potentiometer feedback.

If there isn't a software/electrical engineer in your group, it would be best to find a pre-canned commercial solution to the feedback handling. I can just imagine something that sized developing an oscillation in a control system.... ouch.

-Fergs

teamawesome
10-22-2008, 03:00 PM
Can you eleborate more on the servo controller and electronic speed controller? Im not too worried about how to implement the actuators once there moving correctly. Its getting them to move correctly is the hard part.

yeah i do understand the actuators needed are tough be it is what it is. there is no software or electrical engineer with us, but i do have contacts, and you guys of course, :)

darkback2
10-22-2008, 03:26 PM
A servo controller like the SSC-32 (http://www.trossenrobotics.com/store/p/3191-SSC-32-Servo-Controller.aspx)takes input from a host controller like a computer and outputs that to one of 32 ports. You can connect either a servo motor...which is a motor that can assume a specific position, or and electronic speed controller (http://www.robotmarketplace.com/products/VT-RDFR21.html). This is a device that takes the servo motor position signal from the SSC-32 and translates it into voltages that determine a DC motors direction of movement. This coupled with some sort of sensor (http://www.trossenrobotics.com/store/p/5341-InterfaceKit-8-8-8.aspx)for determining the position of the motor can be used as a sort of high power servo. The motor turns moving X a certain distance, and then the sensor sends a signal to stop the motor.

DB

teamawesome
10-22-2008, 03:42 PM
ah. Thats perfect thanks a million for that. Now your saying that this works for a servo on the small scale. What if i want to run that large actuator as mentioned before? Is there an amplifer on the market that can plug and play to a larger device? Understandably a op-amp would do it or a push and pull transistor series but looking for something that i dont have to hard wire up, just splice inplace. Also do all of the devices mentioned work with the same software? Is there a specific one i should be looking for because of the demands or is it all generic? How hard is the programing, i realize that this is a generic question but some sence is needed and i dont have anything to relate it too.

thanks again, this is exactly what i was looking for. here are our props as mentioned before

http://farm4.static.flickr.com/3048/2949902369_f3fcff84cf.jpg?v=0

darkback2
10-22-2008, 03:54 PM
The large application would be using an electronic speed controller coupled with a potentiometer for feedback. The ESP sends voltage signals to the actuator, and when the correct position is attained, turns it off. Some like the Vantek listed in the previous post have a brake signal, which can hold the DC motor in place to some degree once the required position is attained...one thing though is that you may with any feedback system get an oscilation going which with a flying device could result in catostrophic failure...just a thought.

DB

ScuD
10-22-2008, 04:59 PM
Given the size /scope of your project, I'd be inclined to look to more "industrial" applications for the actuators.

Here (http://www.exlar.com/prod_I_oview.html) they have some high-end linear actuators with DC servo motors, prolly not the cheapest but it's just to point out the principle.

Now, these systems don't have the feedback control built-in. Usually it's just a motor with an encoder, so you'll need something that can connect to this and translate it to something you can drive quite simply with a microcontroller.

The same company has these kind of drives, but there's lots of them.Gecko (http://www.geckodrive.com/) is one of the best known companies providing drives for home-built CNC machines, and they're not too expensive.

Once you get that, you have a step/direction input, then you take a microcontroller or single-board computer, attach a sensor and the servo driver, program like you've never programmed before, and be amazed at how fast a flying object can become a burrowing object :veryhappy:

Adrenalynn
10-22-2008, 05:34 PM
I just want to point-out here that they have something like ~5months, and that includes learning to fly it, if I'm not mistaken.

So in the advice phase, keep that in mind.

If you check the tutorial section, I have some sample C# code written that demonstrates sending a pulse to the SSC32 programatically. ESCs have notoriously large granularity, 256 positions tops. Hard to use that to make fine corrections in a system.

teamawesome
10-22-2008, 07:28 PM
The idea behind the project is to say that YES it is possible. Turning this into a grocery getter is completely different aspect. Its the concepts we are after. I have still a bunch of questions but im thinking maybe some research is a better option until then.

Rokon
10-22-2008, 10:45 PM
Concerning the actuation of your control baffle and the force needed to move it I have this to give some thought. You may have a source of free power assist. Consider that on full size aircraft control surfaces the trim tabs require little force to operate because of the way they act on the control surface. They move opposite to the direction the control surface moves. They create lift on one side or the other so the control surface actually moves itself. 1800lb homebuilts often use standard rc model servos to operate electric trims and can be tied to autopilots and wing levelers. You can completely fly and control a plane with just the trim controls. I'm picturing your baffle system like the swiveling nozzles on the space shuttles engines , if there is good airflow on both sides of the baffle I would think that a relatively small trim tab would exert alot of force aerodynamicly to the baffle.
You could mock this up pretty easy. Set it up in the back of a pickup truck and rip down the highway and see what kind of force you get. Baffles on pivots above the cab, spring scales to measure. Cheap windtunnel!!!!
I love flying stuff !!!!!!
Rokon

teamawesome
10-23-2008, 07:27 AM
this is an intresting concept and we have given it ALITTLE thought and here is our conlusion. When it comes to flight i would be prepared to say that our angle of attack on the baffles that will be needed to move in a simple 2-D motion would be too great for a little servo to handle. However you do make a good arguement when the simple task of balance and stability is an issue, mainly because the craft is theortically not going anywhere, all it has to do is coop with the changes in weight distribution due to the pilot, or make up a small amount of trust/rotation difference between props.

However there is another theory like this. With an aircraft wing i can only illustrate what you told me in a simple "stick your hand out the window of a moving car" example. If you stick your hand out with an angle of attack letting your arm rise and fall freely then yes it does not take much torque in your wrist. But if you hold your arm firm at shoulder height the torque on your wrist is greater because your not traveling up with the air. So back to the plane that you were talking about, my theory in a plane this concept works because the plane is changing position with the angle of attack, like your hand. Our baffles will be like holding you hand firm and the torque will be greater because they have no where to go, they are fixed. Correct me if im wrong in that thinking.

I guess the real questions are how much force do you need and how big of a servo can i put on the ECU?

thanks for the input.

Rokon
10-23-2008, 09:45 AM
I think you can mate any size servo you want to the ecu, the servo amp would be the interface and would be sized accordingly. The big question is how much force do you require and how do you figure out that number? Are your props running in a ducted fan mode? Straight baffles in the wash like a Scat hovercraft rudder set up? Or is this more like a ring suspended in the propwash that your gimbeling for control? The point I was making with the trim tab control is your using aerodynamic forces to work for you in moving the control surface rather than brute force to move the surface in the direction you want. Your going to have alot of airspeed all the time (propblast) and you can harness that. Conventional aircraft trim force is relative to airspeed over the surface, but yours would be nearly constant.
Vertical control may be a bear too. Vectoring for lateral control results in a loss of lift that you'll have to chase with throttle that will have slow response. Like flying a fixed collective rc chopper, it's easy to get behind it and have oscillation.
Are you running the props direct drive or thru a reduction?

I realize you came here for control help not aircraft design...I just know alot more about aircraft than robots........


Rokon

teamawesome
10-23-2008, 10:32 AM
no this conversation is good, im no expert just trying to relate examples and use this little thing inside my head.

We have the understanding that when traveling up or moving in a direction the "vectored" air is not for lift. Therefore if we can not use 100% capacity just for lift or we will need a seperate device for lateral control and balance. Again the responce time of the throttle is high, therefore we cannot use the engine to help us. Lastly what we have come up with is to use for example 80% of the lift for normal operation (just keeping it in the air) and conserve the 20% for control. The props will be at a constant 2200 rpm (max lift, and stepped down from the 3600rpm from the motor). The 2ft shroud gives us about 20-30% more lift, therefore if we take the effeciency away from the shroud and then added it back where needed at a appropiate responce time, wahla we have a control. Thats the plan anyways. But playing with the shroud is tricky because there isnt any linear relations and thats where software, electonics and you guys come into play.

Rokon
10-23-2008, 11:24 AM
To see increased effiency of a shroud, ducted fan, requires tight running clearances between the shroud and the prop tips. This extra thrust disappears quickly as the gap increases. It also doesn't show up in static thrust as much as when the aircraft is at high speed. I've seen this with my model electric ducted fan aircraft.
I'm not sure if the prop will like having its airflow disrupted from the intake side of the duct. If it starts clawing for air it begins to stall (its a wing) and the stall will progress towards the root of the blade.
If your altering thrust this way I can see the lateral/roll control between the powerplants but how is pitch control going to work?
I'm not sure if you can bleed off thrust to vectored nozzles, aka Harrier, with a ducted fan....
Maybe having the entire powerplant/ shroud assembly on a gimbal deserves some thought. You would only need a few degrees of movement to significantly change the thrust centerline in all directions and you would maintain the close running clearances for the prop/shroud......

Rokon

Rokon
10-23-2008, 11:55 AM
Are you familar with the Hiller Aviation "Pawnee" platform built in the early 50's? Similar in scope to what you are trying to do.
Rokon

Adrenalynn
10-23-2008, 12:23 PM
Chop the servo power wires out of the little harness. Run them straight to the battery appropriately sized (voltage and current). Run just your PWM signal/control wire to the servo controller. Voila.

Vantec makes a monster servo (http://www.vantec.com/ssps105.htm)- 27 FOOT/POUNDS, 0.9sec to 90degrees. 12v DC. They also have a 13ft/lb, 0.45sec-90deg servo as well.

That thing will twist your arm off. Somewhere in the 5200oz-in range when you run the numbers, right?

Oh, interestingly enough, their page says: "Originally designed for RPV/UAV "muscles". "

teamawesome
10-23-2008, 01:01 PM
Putting the entire assembly on a swivel is difficult at this stage in the design. The blade tips are in tight tolerence with the shroud therefore changing just portions of the shroud is doable. This will take care of the vertical height and stability when pitching and rolling the craft. Each shroud will be independent, therefore raising one side to control roll. The pitch can come adding the same technique to specific areas around the shroud. The second series of the controls (possibly manual for now) will most likely be a series of baffles on the underside, this will take care of all the yaw and forward commands.

Lastly if baffles are not used, trust direction will be changed via a large plyable material under the shroud. or if electrical the actuators will have the ablitiy to raise and lower sections independently creating another from of control for pitch. We have yet to work out the numbers for the most effective.

Adrenalynn- Thanks for the info on splicing in a servo, I didnt realize you could do that. make much more sence now. And yes you spotted a 600 dollar servo. ouch, but do the same apply to a actuator?

Adrenalynn
10-23-2008, 01:05 PM
High-power/High-speed linear actuators are even more expensive in my experience.

You're building a device that is generally built with multi-million (or even multi-billion) dollar budgets. Don't expect to cheap-out too much.

teamawesome
10-23-2008, 01:35 PM
Yeah your right. However is was being more specific to the wiring on the actuators. Do they follow the same protocol?

Adrenalynn
10-23-2008, 01:46 PM
Ahh. Depends upon the actuator. Is it PWM or not? If it's just a straight motor, no, you'll need an ESC as Darkback noted. And your granularity will likely only be 0-127 backward, 128-255 forward - which makes fine control a challenge.

A servo like that Vantec should be controllable in 1uS pulses, so over 180deg have a granularity of about 2000 steps, comparatively, which should be (180deg / 2000) about 0.09deg/step. Compare that step size to what an ESC would be delivering - 360deg / 128 = 2.815deg/step.

Of course, a really accurate stepper motor is another option.

That's why the best of the really accurate linear actuators are either PWM driven or based on stepper motors...

To some extent this limitation can be defeated with lower gearing, but that lowers speed. And my imagination tells me that controlling thrust vector is going to want some substantial speed of control adjustments - but it seems like Rokon has a better grasp of those requirements than I, so I bow to his input on that.

[edit: Please note - given that I'm being prepped for surgery on my back at the moment, I reserve the right to retract any and all math. In fact, anything from Friday to _TBD_ is vicodin-influenced and subject to later redaction. ;)]

Also note: I in no way support or encourage this project without it being built to scale first. If you guys lop-off fingers, toes, necks, etc - or crash into some regent's car and the survivors all flunk out of college - don't come crying to me. 'Cause I'll just point, laugh, and chant "Told you so!", like some petulant two year old... You've been warned.

darkback2
10-23-2008, 02:16 PM
[edit: Please note - given that I'm being prepped for surgery on my back at the moment, I reserve the right to retract any and all math. In fact, anything from Friday to _TBD_ is vicodin-influenced and subject to later redaction. ;)]

Also note: I in no way support or encourage this project without it being built to scale first. If you guys lop-off fingers, toes, necks, etc - or crash into some regent's car and the survivors all flunk out of college - don't come crying to me. 'Cause I'll just point, laugh, and chant "Told you so!", like some petulant two year old... You've been warned.

First off, good luck with the surgury Adren...Let us know if there is anything we can send crabfu over to help with...

As for the other point, modeling proves invaluable in this sort of project, I think teamawesome's point that their project does not have to work, only prove that it is possible could be just well served with models, which would provide the ability to learn from mistakes, as well as gain an understanding of concepts that they seam to not understand.

alright...enough preaching...

Maybe a couple of high quality servos...4 $600 2 per cowel...though more may be necessary would be a better spend of budgeted funds than several cheaper options that may not work. Perhaps you could simply warp the shape of the cowel to provide lift on one side or the other. If the cowel is on a gimble then it would swivel in the direction opposite to the direction of lift causeing thrust to move forward or backward... Maybe? I dunno.

Also there is a guy in this article (http://www.dailymail.co.uk/sciencetech/article-1039614/Pictured-The-50-000-jet-pack-lets-real-life-James-Bond.html) who made a similar device. Maybe you can contact him to figure out how he did it, and get help. Also invite him to join the forum...

DB

teamawesome
10-23-2008, 03:04 PM
To Adrenalynn:
First off good luck with surgery on your back. And yes we have been told we are alittle crazy but then again where is the R & D in not being alittle crazy. We are praying that we don't do anything too stupid to get anyone hurt however we do want a reaction out of the community. Also all preliminary testing is done on the farm pictured, so it will be in the middle of know where to help with the risk of running it into things, actually all the work is done in my families farm shop. Bet thats a first, hmm maybe not.

What does PWN stand for?

To darkback2:
Yes models are all well and good but again, there is nothing like the real thing. The group of guys that I'm with have used this same concept of blowing it out of proportion to every project given to us at VCU and so far so good. We are up to the task and feel that the ah factor is much greater with a full size model, understandably the challenges, money, and support may change with the size but thats the risk we are taking. Again we are not trying to redesign a better the car with this model, its just a understanding that it can be done.

Anyways truthfully its done, so now looking at the servos and reading your post it does make sence to have something that will get the job done. I will have to look into our budget for some insight there. Thank you for the listings of parts and your knowledge.

darkback2
10-23-2008, 03:39 PM
Well...good luck then, and I don't mean that in a sarcastic way. You are making a really cool project, and I guess we all just want to see it work out for you.

DB

darkback2
10-23-2008, 03:44 PM
PWM is pulse with modulation. It is how servos know what position to go to. The pulses range from about 500 - 2500 though most hobby servos operate safely between 750 and 2250

it has to do with sending pulses down the signal wire so many pulses a second = such and such a position. with the ssc-32 you send a message out of a computers serial port which is then translated into pulses sent down the signal wire to the servo. The servo then attains the position, and hopefully your flyithingie goes in the direction you want.:)

DB

teamawesome
10-23-2008, 03:49 PM
ok thanks, yeah im not trying to come across as defensive in anyway however i realize its hard to back up a project that you have put alot of time into for over the last few months and not be. Ive contacted a UAV professor here at VCU for some extra boost. I believe someone here pointed out the article about VCU and UAVs and i greatly thank you for that. Hopefully he will respond back. Going to have a meeting with the group here shortly to discuss the servo approach.

ScuD
10-23-2008, 04:41 PM
For some reason beyond me, I applaud the fact you're not using a model but building full-scale from the get-go.

It probably has to do with a love for giant killer robots and dangerous machinery, but other than that, no idea..

Seriously though, I can understand where you're coming from perfectly, but please take all necessary precautions to make sure no one gets injured too badly.

Best of luck to you guys, and let us know when she flies!

teamawesome
10-23-2008, 05:04 PM
Its funny how one aspect of this project has taken me on a loop. I now find myself sitting and watching videos on robotics, there controls and how the owner has had there influence placed on each aspect of the design. Like i said before i have no experience in automation, however i remember clearly in high school as a junior and senior i headed up the TSA club. At the time the only competion that i took advantage of was the "RC challenge". We placed 3rd the first year at states, then 10th at nationals. In my senior year we took 2nd at states and i never did attend the national competition. For some reason i had never looked back until now, and it is intresting to see how the programming and automation has changed the entire realim so much in just 5 years. Things are more affordable now and the capablities seem endless as to what some of you guys can do with a robot. I'm guessing these are derivations of jobs you all have or are the pure hobby?

teamawesome
10-29-2008, 09:04 AM
Well i havent posted in 5 days so i figured I would to keep the communication flowing. No updates since we did not work on anything this weekend and the meeting was cancelled. However and intresting homework assignment popped up on PWN controllers for mechatronics. I do understand the basics now, if i got it right at least.

teamawesome
12-04-2008, 11:42 AM
I must say that i am sorry for the delay in posts, we have had only one more work day and it was not productive. We are still semi on schedule, landing gear and motor mounts are up next. The motors arrived 3 weeks ago from kohler.

here are some renderings floating around for the skin and frame work. personally i think they need alittle revising in the cockpit, doesnt look too confortable, however the basics are there.


http://farm3.static.flickr.com/2111/2998068073_644c4b90d0.jpg?v=0


http://farm4.static.flickr.com/3270/3073002827_eda348bca7.jpg?v=0



http://farm4.static.flickr.com/3029/2976964942_d8001be604_m.jpg

Rokon
12-04-2008, 12:17 PM
Are those the engines mounted fore and aft of the seat? You'll want the belts as short as possible. and cooling may be of an issue if the powerplants aren't in the airstream. I would consider widening the gear stance and making them taller. FOD is a real problem with the props low. Plus take into account uneven terrrain, bushes and sticks. You'll b e blasting alot of debris on lift off and the props will hate ingesting anything.
Looks way cool......

Rokon

jes1510
12-04-2008, 12:37 PM
I would be really concerned about stability in the pitch axis. It looks like it will really want to tip.

teamawesome
12-04-2008, 01:12 PM
I would be really concerned about stability in the pitch axis. It looks like it will really want to tip.

understandably yes, you are correct. We have got alittle bit of a trick up our sleeve on that i hope.

The engines compared to pilot mounting positions are still in much question be the basic idea is there. Obviously there is NO way the pilot would be able to be seated in that position, these are purely illustrational. The real deal will be quite different, at least i would do it differently :wink:

jes1510
12-05-2008, 07:55 PM
I forgot to add that the thing looks awesome if nothing else. Nice models!