Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: Gualalasmooth on October 15, 2010, 11:29:09 AM
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I have built a 150 lb robot base and want to have a telescoping camera mount for filming football games . I would like it to be tall enough to view through the goal post and be retractable so it can change locations during the game. also I would like it to be able to shoot video on the fly with maybe some sort of steady cam features. any ideas?
Thanks Tom
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Maybe 12 volt linear actuators will do the job with cables and pulleys Has anyone done this before I would like to have the ability to shoot video while moving with some stability and control Thanks Tom
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You could do something complex with accelerometers and compensate for motion but what most of the cheap steady cam options do is counterbalance the camera. So suspend it and then add weight to the back to balance it. This will reduce the pan tilt motor requirements and proved stability.
Honestly it would probably be cheaper to mount a dedicated camera for the goal post and have a mobile unit as well. Depends on how fancy a camera your using. I think the NFL uses some sort of pulley system suspended above the field. Not sure how they keep it from swaying but might be an alternative.
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Thanks steady cam counter balance is a great idea I plan To use an x10 cam with remote pan and zoom any more input on the retractable remote tower
Tom
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Hi,
I have built a 150 lb robot base and want to have a telescoping camera mount for filming football games . I would like it to be tall enough to view through the goal post
How tall is that?
Not because I absolutely hate football (which I do), but I'd guess that if you lift the cam free of the grass, it should be perfectly able to shoot through the goal post.
[...] and be retractable so it can change locations during the game.
If you plan to use broadcast class cameras, it needs to be quite sturdy.
A scissor lift would probably be easy to construct and that would give you a platform to mount whatever pan/tilt/pseudo-steady-cam functions you need.
To get pan/tilt/whatever motion as smooth as possible, you can a technique found in broadcast quality tripods and dollies - two discs, one on the stationary part, the other on the moving part and sliding against each other in a very high viscosity silicone grease. This gives a lot of controlled "friction", so takes a bit more from the motors to move, but you get very smooth motion this way.
Place any mikes a good distance away from the motors involved, or they'll be all you hear.
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I have plans to build my robot body out of steel reinforced fiberglass replica Riddell football
helmet about 28 " circle And the tower comes out from the back of the helmet
Tom
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I'm sure the goal post is 10' high at the crossbar. I would like to keep the base stack at about 4' in height I will provide a link to my site below and you can view the robot base at its present state I do not try to sell anything at my site I just like to share ideas with other robot builders Thanks Tom
http://www.squidoo.com/diy-robots- (http://www.squidoo.com/diy-robots-)
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Maybe this would work? Probably lots of money though.
http://www.geosystemsinc.com/sam8/sam8.htm (http://www.geosystemsinc.com/sam8/sam8.htm)
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Hi,
I'm sure the goal post is 10' high at the crossbar. I would like to keep the base stack at about 4' in height
Haha, told you I'm not a football guy ;D
Apparently, I have no idea what part of a goal is the "post", whether it's translucent (which it'll have to be to film through it I guess), or what this crossbar might be. Measures like 10' and 4' are more "real" to me.
Going from a collapsed less-than-4' to 10' shouldn't be that tough with a scissor lift, but the more "X"-es needed, the harder it is to get it smooth acting and stable at the same time, so the length of each link will matter. I wouldn't drive it around with a camera 10' up though, as it would probably sway some.
Another thing to note is the vertical shift in the center of gravity - if you place something heavy up there, make sure it won't topple before mounting the camera.
I assume here, that you know what a scissor lift is and its basic mode of operation, but otherwise, here's a piccie of one with 5 "X"-es:
(http://www.superdroidrobots.com/pictures/ATR/scissorlift_ext.jpg)
The longer each bar in the links are, the fewer links are needed of course and the better the stability.
Fully collapsed, the bars will be touching, so the total height will be: bar width x number of bars.
Extended, which shouldn't be very much more than 90° angles (i.e. the first bars 45° from the base), to get max. stability, but it will depend a lot on your skills in the mechanical construction.
I will provide a link to my site below and you can view the robot base at its present state
Besides your slightly Rube Goldbergesque affection for automotive relays driven by microswitches driven by servos, I didn't really get that much impression of the base - the helmet that you describe as "28" circle", is the 28" the circumference, the diameter or what?
Or, IOW, how long can each bar be?
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Hi,
I'm sure the goal post is 10' high at the crossbar. I would like to keep the base stack at about 4' in height
Haha, told you I'm not a football guy ;D
Apparently, I have no idea what part of a goal is the "post", whether it's translucent (which it'll have to be to film through it I guess), or what this crossbar might be. Measures like 10' and 4' are more "real" to me.
Going from a collapsed less-than-4' to 10' shouldn't be that tough with a scissor lift, but the more "X"-es needed, the harder it is to get it smooth acting and stable at the same time, so the length of each link will matter. I wouldn't drive it around with a camera 10' up though, as it would probably sway some.
Another thing to note is the vertical shift in the center of gravity - if you place something heavy up there, make sure it won't topple before mounting the camera.
Since his rig is 150lbs, the scissor lift crossbars could be 2 feet long which then when cranked to an angle of 45 degrees would provide 2.8 feet of vertical height. If he added four more "Xs" then it would go up to 11 feet. This should be stable enough for the camera and probably no problem for the robot due to its weight. He could always add out-riggers if necessary.
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Hi,
Since his rig is 150lbs, the scissor lift crossbars could be 2 feet long
You're mixing apples and oranges here I think.
We have to get a more precise description of the 28" circle before assuming anything about how long the could be - as I envision it (with the 28" being the circumference and the "cam coming out of the back", the bars couldn't be more than about 8" max.
which then when cranked to an angle of 45 degrees would provide 2.8 feet of vertical height. If he added four more "Xs" then it would go up to 11 feet. This should be stable enough for the camera and probably no problem for the robot due to its weight. He could always add out-riggers if necessary.
Outriggers would only throw the COG off more.
If we're talking real cams (as in broadcast equipment), we're talking heavy stuff - there's a reason the shoulder rest are heavily padded.
10..20 lbs on a 3' outrigger at 10' height... Add a mild breeze or a ray of sunshine and the 150 lbs base will seem like nothing - careful counterbalancing would be required.
Anyway... Before all data is in, all we can do is guess.
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No offense taken but You think my motor controls are Rube Goldbergesque I guess maybe
its all for the sake of robotic art but anyway 28 in diameter so I can get through a doorway
and in the living room as well as behind the goal post that big post looking thing at the end of the football field they have one at each end of the field most have a single post about 10' high with a horizontal pipe about 16' wide and 2 upright pipes pointing up about 10' on the outside of the horizontal pipe And sometimes the players of football kick through those uprights at various distances to score points I want my camera to be there in between those uprights.
you guys have some great ideas thanks I love It Tom
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No offense taken but You think my motor controls are Rube Goldbergesque...
The reason why they/we think that is because you use a mechanical actuator (servo) to flip an electronic switch (microswitch) to drive a mechanical switch (relay)... which is a little more complex than absolutely necessary (5v relays work too).
...anyway 28 in diameter so I can get through a doorway and in the living room as well as behind the goal post that big post looking thing at the end of the football field...
If you've got a 28" diameter across the robot, then you can pretty easily fit the aforementioned 2' (24") scissor-lift crossbars. You'll just need to figure out a mechanical method to lift the whole thing up. More seriously, we do need to know what kind of camera you are using. Like Soeren said already, professional broadcast-quality cameras weigh in the vicinity of 15ish pounds, and on a 10'+ elevation from the base, that's some significant leverage.
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Hi,
No offense taken but You think my motor controls are Rube Goldbergesque I guess maybe
its all for the sake of robotic art
None meant either, I like Rube contraptions (as long as it's not driven into the plain silly), but it does mean that you lack speed control (could still be done with relays to replace the H-bridge (http://That.Homepage.dk/PDF/PWM+Relay_4_Motor_Ctrl.pdf) ). A direct receiver to relay control is possible as well, eliminating a (relatively expensive) servo and while I understand your train of thought - what's visible and known is more safe - the more links in a chain, the more can go wrong.
I have seen more mechanical switches fail than I have seen transistors break down - even 2" long microswitches, which is more reliable than the ~3/4" variety, do fail from time to time.
Anyway, use what you feel comfortable with.
[...] but anyway 28 in diameter so I can get through a doorway
and in the living room as well as behind the goal post that big post looking thing at the end of the football field they have one at each end of the field most have a single post about 10' high with a horizontal pipe about 16' wide and 2 upright pipes pointing up about 10' on the outside of the horizontal pipe And sometimes the players of football kick through those uprights at various distances to score points I want my camera to be there in between those uprights.
Ahaaa yes, here in Denmark we're more accustomed to soccer (called fodbold which translates directly into football, which we call rugby), so I was thinkin of a different kind of goal. But I have seen these goals (like giant slingshots) in Jutland - and in the Panthers stadium in Charlot, NC - so now I got the picture ;D
A scissor lift could be driven by a screw like the one you use for the steering or one from a car jack.
Should balance become an issue with the cam up high, you could add (retractable) stabilizers extending from the sides, like in some mobile cranes.
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Soeren here in the USA football is huge and everyone knows the game but we do have a lot of people that are involved in soccer the kind where they use a round ball and kick it up and down the field with big basket like goals defended by a single goalie who is the only one who can touch the ball American football is winning the popularity contest between these 2 sports here with many soccer players making a transition to football. Although the sport of the game you call Rugby Is on the rise here and is much more respected than soccer by the American football fans because because it is a contact sport.
Anyway I am a football coach and use video to evaluate my teams performance usually we just use a sony handy cam from the press box to shoot video I think this kind of camera would be good enough for what we are trying to accomplish although I was thinking that maybe a telescope as apposed to a scissor lift Any ideas about that method? I also love the idea that Stabilizer legs will drop into place when the tower is deployed.
I love all of the feed back that you guys are giving me on this project
Thank you all Tom
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I'm trying to get myself out of the box you guys are the reason for that I like the scissor lift seems to be proven for weight with full stabilizers how much weight can I lift to 11 feet with my 28" helmet?
Tom
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I'm trying to get myself out of the box you guys are the reason for that I like the scissor lift seems to be proven for weight with full stabilizers how much weight can I lift to 11 feet with my 28" helmet?
Tom
Since you say your just going to be filming with a Sony Handycam, then the scissor lift will do just fine with a moderately strong gearmotor. The problem is stability, as you said the robot base will be based on a 28" helmet, you'll need to expand the base to something that is about 4 feet wide/long. Or you could try Soeren's idea with the retractable stabilizers as that would allow you to have the small base, but still keep the rig solid and stable.
The retractable stabilizers could be based of a Camera Tripod, were each leg is controlled by an internal steel wire that could be pull up or let down by a few gearmotors. A locking mechanism could be put on each leg to lock the leg in place.
Another idea with the stabilizers is to cut out notches into the tripod legs and turn the tripod legs into a gear rack:
(http://visual.merriam-webster.com/images/science/physics-mechanics/gearing-systems/rack-pinion-gear.jpg)
Each leg would then be controlled by its own gearmotor and locked into place by electrically braking the motors.
As far as weight is concerned you should use atleast 1/4" metal sheeting with crossbars underneath to help distribute the weight out to the scissor lift beams.
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whats up Soeren
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Hi,
whats up Soeren
Oh, I just had to research a bit on the telescope variant.
I don't think it's a very good solution for several reasons.
To keep it under 4' and with the overlap each segment need to make it reasonably stable, you'd need many segments. Each segment should be assembled with a glide bushing, preferably (custom made) PTFE (Teflon) bushings or something with similar properties.
It would (of course) be more narrow, the closer the top and since it would probably be round, it would sway with the lightest breeze.
The mechanism for raising it is not too easy either.
I think it would be a bitch to get even barely usable results that way.
The scissor lift is the same size, bottom to top and the grid-like structure is more sideways stable (and shouldn't brake the wind as much). It's easier to build, in that it's just repeating steps a lot of the way.
The lower segment could be built from slightly heavier stock, as the force needed to raise each segment is largest at the bottom and takes off gradually, to a much lower needed force at the top end.
How much weight it can lift depends on how you construct it and what materials you use, of course, but the main issue is the force needed to raise it. You have a "gearing" in it, since you only need to raise the middle of the lower "X" to ~0.7 x bar length.
Assuming for a second that the construction doesn't weigh in and you want to lift say 10 lbs to 132" (11')
With # of X'es ___ each bar, hole center to hole center ___Multiply weight by
7 ___ 26.7" ___ 14
8 ___ 23.3" ___ 16
9 ___ 20.7" ___ 18
10 ___ 18,7 ___ 20
So, if you have each bar 23.3" hole-hole, your actuator needs to be able to push 10 lbs x 16 = 160 lbs for a distance of 0.7 x 23.3 = 16.3" (and don't get any non-expendable bodyparts caught in the mechanism).
That's a minimum, since the weight of the construction will ad to it, but it will depend on choice of materials and dimensions, so hard to say presently exactly how much force is needed.
It can be a very low geared motor though, as the total expansion will happen when the middle of the lower X is raised just 16.3".
For the construction of support legs, I would lift the design from a construction crane or a similar rig - they've done the research and know how it's done best.
Have you considered how to frame your shots, panning and tilting?
You have to get at least a preview down to where you can see it (I know some Canons can do this by wireless transfer, but I don't think you can do that with a Sony).
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Thank you Soeren all of your ideas make a lot of sense to me I will most likely go with the scissor lift for stability as you suggest I was thinking about 1"x2" aluminum rec for starters
and what about electric linear actuator to power it I also have a vanguard x 10 camera
with remote pan and tilt features and its very light weight although it sounds like this unit will be able to handle some weight .
Thanks again Tom