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Community Hexapod Project

#1

Hey Guys. Work here at EMT has been insane to say the least. And the further away from finding time for hobby robotics I get, the more I miss it.

I thought it would be fun to build a hexapod from scratch. Not as a product or for any monetary gain, but just for fun. We have all seen the limitless possibilities of working with the SES brackets so I want to design a Hexapod that uses both SES brackets and custom made parts.

Here are the limits:

  • Based roughly on the size and shape of the lynxmotion hexes.
  • Using commonly available parts and custom made parts.
  • Using a SSC-32, Bot board and Atoms.
  • Using inexpensive servos.
  • Using a camera and Roborealm to provide head tracking
  • Using Sensors to provide some sort of input for avoidance.
  • Sporting a head with articulating neck.
  • And based on an insect of some sort.
  • Covered in a pliable skin to make it look real.

We will make the size dependent on our servos and mechanics.

I’ll fund the project and built it, you guys provide the design input, software tweaking, and decision making.

I would like to end up with a realistic looking large insect and aim for lifelike movement.

We will vote on a name and I’ll post it up on my website as a community project giving credit to everyone that helped.

So the first thing we need to concentrate on are the primary decisions:

  1. What insect should we base it on?

  2. Should we aim for semi-sessile state to concentrate on realistic interaction, or full mobility?

  3. Should we keep it in the 3DOF leg design to work with currently available programs and software?

  4. Should we tether for power and communication ease, or wireless?

  5. What should we name it?

We will move on to other details after we clear these up. Hopefully a few of you guys will be interested.

Note: Let’s make our best effort to keep this thread on topic and directly related to the project. All voting and related topics about the project will have their own thread made with a reference to the project in the title.

Anyone with any drawings or ideas?

#2

I’m going to sell off some spare SES stuff that isn’t related to this project so I can pickup some more relevant brackets. I’m going to keep track of the costs so we have a idea of what we spent when we’re done. We’ll see how much we can accomplish on as little money as possible.

#3

:open_mouth: Wow, that sounds like an awesome project :slight_smile:

is anyone able to input into this project and add into it? cause this would be something i would love to participate in :smiley:

I think maybe some type of veetle would be an interesting project to do. maybe a type of weevil. they have long little stick necks that you could mount the camera on and would provide a good telescoping neck to view everything from

http://www.loe.org/thisweek/050211weevil.jpg

theres a picture of one

obviously it would be a good idea to lower the scale length of that nexk due to servos, i think that might be a good idea for a camera stalk

again, these are only suggestions if everyone is allowed to input on this project :slight_smile:

#4

I’d suggest starting with developing the inexpensive generic hex and then tweeking that to fit some insect much later. If this isn’t done, the thread will become 90% hanger flying about parts of the project that will have little relevance to actually getting the project moving.

#5

That’s basically what we are doing. Once the thread gets pretty long and we are ready to move onto a new topic, I’ll start a new thread (part 2) with a brief summary and we’ll go from there. Just to keep it organized. But we are going to start out custom designing the hex first. Not an insane variation of the generis types, just slight modifications to keep it looking like what we are shooting towards. Kind fo like how the phoenix hex looks alot different but is very much the same as the other lynx hexes.

That’s exactly what we are doing. It’s community based so anyone who wants to contribute or participate is more than welcome, and will get credit for their contribution.
I’ll cover the costs, materials, fabricating and building. Then we, as a group, will decide design aspects, appearance, programming and additions.

#6

I was looking around and thought it would be cool to build a scorpion with 2 small arms and claws on the front. But that would really be getting away from using available programs to control it. Since the arms and tail would require their own programming.

I like the beetle idea. Even a simple 6 legged beetle with an “over animated” head would be cool. It doesn’t have to necessarily follow the bug to every anatomic detail. We can make it a bit “fictional looking”

I’m thinking the 6 legs would be controlled via an ssc32/basic atom28 with an available program for ps2 control. Pretty simple.
Then the head pan/tilt/rotate could be on it’s own ssc-32 with roborealm providing the tracking from a wireless rs232 link. Or on it’s own SSC32/Atom28 with a program for using sensors on the head to move the head around.

Just my thoughts so far.

#7

thats wicked sick 8)

i like this, people who have the ideas, but maybe not the money, can still get their ideas out there and have it realized :smiley:

#8

If we are able to, i’d think devising a way to have the legs underneath the main body of the quad, it would be more realistic. In stead of having the servos and legs stick out of the sides, have the legs originate from below the “beetle” and you would only be able to see the hip servos if you were to looks below, you wouldn’t be able to see it from above

#9

I suggest that as much of the structural components as possible be made from thin inexpensive plywood. Cheap, easy to work, and probably will meet most strength requirements.

#10

I’m glad you like it. I’m hoping we end up with something cool. :slight_smile:
We’ll try to keep the budget as low as possible. I’m hoping under $1000.

To save money I have a few things that may be relevant to the project.
3 SSC-32’s,
2 botboards,
2 Atom Pro’s,
a handful of SES brackets,
1 sensor,
about 16 HS-322 servos,
some HS-645’s,
some HS-475,
alot of HS-805’s,
about 500 feet of servo wire,
more cameras than I know what to do with,
aluminum,
ABS,
Delrin,
Lexan,
hardware,
ps2 controllers,
R/C gear,
setup for molding RTV and rubber skins and shapes,
vacforming table,
plastic mold,
lathe,
mill,
bandsaw,
scroll saw,
drill press,
sheet bender and form bender.

If need be, we can use the CNC machines and bigger stuff at the shop.

The more of this stuff we can utilize, the better chance we have of staying on budget.

Great idea. I do have an endless supply of scrap Lexan, Delrin, ABS and aluminum though. Ironically, I would actually have to go buy some wood to use it. :slight_smile:

#11

So should we go with a Beetle? Maybe we can find a way to make a beetle look “cute”. :slight_smile:
LOL

The hip rotate servos could be relocated below the body easy enough. Or we could keep them inside the body and add a foam-core shell on top so it still looks realistic.

Are we thinking an inline hex then? Or should we go round?
An oval shape would require tweaking in the hex software, right?

#12

I think the simple fact of just desiring to ‘skin’ the bot will lead to some design decisions. For instance, it might be best to make as much use of indirect drive linkages as possible, so that we don’t have bulky ‘knee’ joints.

Personally, I think the “ant” picture that Jim has is a very cool design. Maybe make that indirect drive?

Of course, the scorpion sounds cool too!

I guess my only opinion as a new comer to the group, it might be disappointing to see the “same old” built as a community project.

#13

I think the ant looks cool too, I was thinking of an ant, with real skin it will look real cool.

But my favorite projet would be the scorpion!

This kind would be real nive, machine some new pieces and all, we could also make it… cuter (won’t be too hard :laughing: )

Thinking of that, you could probably have 2 bot boards, one master the other slave (well more of the atoms) . Then one controls the sensors and the other the movements. Then you probably don’t need anything else (well 1 SSC-32 will probably be way enough)

#14

I like the scorpion idea. An indirect knee would be best.

Delrin for the body is best I think, or lexan.

#15

I thin the scorpian would definatley be kick ass, but a simpler project might be better to start out with, aka, the beetle, it can always be modified to look like a scorpian fairly easily

claws can always added on later for coolness or wat not

yes, i belivee that an indirect drive might be a good idea as well, this way it will look better :slight_smile:, then again, you can always place a servo in one of the insiect joint, and cover up over it, like how it looks with real insects

wat else is there to answer?

i think a good idea might be for each of the participates to make their own drawing/CAD of what they think the “insect” should look like and submit it, andfrom there we can vote on a over design or combine the features of multiple drawings

#16

I’m definitely leaning towards the scorpion now. :slight_smile: I think it would be cool but it would put us over our budget. With the added weight of 2 front arms and claws with a tail, we would have to go with some decent servos, HS-645 or better. If we stick with the beetle, I think we might get away with HS-645’s.

My other concern with the scorpion is programming the arms. The tail could be a simple 2 joint mechanism with free swinging joints attached. But I’m not much of a programmer and I wouldn’t know how to program the Atom to use PS2 inputs to move the arms. Could someone else tackle this?

Feel free to submit CAD drawings. We can always do a vote.

And I suppose, as suggested, we could start out making the body and head of the scorpion, get it working, and then start adding the arms and tail. Scorpions are also 8 legged but we’ll pretend that we don’t know that. :slight_smile:

Here is the current Poll for beetle vs scorpion vs lynx hex vs other.
lynxmotion.net/viewtopic.php?t=3286

We’ll vote on designs after we decide which insect/animal.
Keep in mind that scorpions don’t have an articulating head. So just the Beetle could have the option of having an interactive head.

#17

Looking into our servos options, I’d like some feedback on power requirements of the hexes.

The 76oz HS475’s are standard and the HS -645 133 oz are an upgrade. How well does the inline hex perform with HS-475’s?

Going along with the suggestion of using indirect drive to keep the joints small, we could possibly use HS-805’s for the hip rotate and a link from another for the hip vertical. Then use an HS-645 servo for the knee.

The HS-805’s would provide loads enough torque for their joints but their weight alone might make the HS-645 insufficient for the knee.
They weight almost 3 times what an HS-645 does. They have almost 3 times the torque too but that doesn’t help the knee joint.

Hmmm…

I talked to my servo source and found I can get unbadged (nameless) Hitec HS-805’s for around $18 each. Plus I have alot of them kicking around here.
I can also get HS-645 clones for $20. That is all he can offer right now though. So I’d like to try and work with these servos if possible. I’ll get an exact count of what else I have here.

#18

Are the HS-805s the quarter scale servos from your giant hex?

Also, is anyone familiar with that wire they use on bicycles that triggers the brakes? Maybe we could use something like that to put all the servos in the body, and just wire the legs?

#19

They are the same kind as the ones I used in my Giant Hex. And if they worked there, they would provide endless power in something half the size.

Bicycle cables are simply thin aircraft cable inside a plastic tube. Using push/pull cables for the joints is a VERY interesting idea. Especially if you use big one that won’t allow as much flex and play as smaller cables. I have some monstrous pushrod cable setups laying around from some of my 1/4 scale planes. We can definitely play with the idea.

EDIT: Along the lines of this, neat link I found:
students.olin.edu/2009/tmichon/s … =mechanism

#20

Recently there was a photo of a hex (possibly a prototype) that had linkage operated legs for the up/down leg motion. The way the linkage operated allowed for minimum electrical load on the servo (near zero in the down weight bearing position). As most hex bots in this forum are designed for operating on flat level ground, it might be something to factor into the design.