W.A.L.T.E.R. Returns as a 2WD/4WD

Lynxmotion Rovers, Sumo, and Tracked
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Yes, W.A.L.T.E.R. will be returning to the lime light soon, and I just ordered a few additional parts for him. I think W.A.L.T.E.R. is truely an SES robot now. You just have to look at all the SES holes there are on his new decks (that Alan painstakenly drilled, even while protesting). :slight_smile: :slight_smile: I did give in on the long slots I had in the original deck designs and the four large round holes work almost as well for wire feed through, even though they don’t have quite as high of a coolness factor IMO. :slight_smile:

I’m even seriously considering putting him on one of the newer version 2.0 A4WD1 rover bases, but I don’t know if three of his current decks, associated batteries, and the custom 6DOF SES arm (includes 2DOF gripper) would be too much for it or not. I know the A4WD1 is very sturdy though, and this may be the ideal way to go. The A4WD1 base would also be a great platform for experimentation with just arms. Going with four wheels would certainly remove all my problems of finding proper casters and getting the stability I want.

I really don’t want to deal with putting four wheels together, but know I can handle the rest of the A4WD1 assembly just fine. I do not get along well at all with glues and am allergic to many of them.

I just don’t think two wheels is going to be stable enough, although the current deck size is perfect for what I want to do. If I end up going with the A4WD1 approach, I’d want to have two of the motors (the rear ones, most likely) with encoders. I’m not sure that would work, or maybe not well enough to be usable.

I’m not sure W.A.L.T.E.R. will really be W.A.L.T.E.R. on four wheels though. I have not been able to find appropriate stock casters for him so far. I’m affraid I will have to go with a custom caster design, if I stay with the current two wheel setup, to get the stability I want. If I stay with a two wheel setup, I may want to convert to 12V motors instead of the current 7.2V setup I have now, but may not really gain anything from doing this change.

I already have the arm mostly assembled, including servos, and just have to add the gripper to complete that. I have all the parts to do that now. This arm can bend fully forward and backwards, thanks to a double joint in the center of it. I’m going to complete the arm and get it all connected to one of my SSC-32’s so I can start testing that out. It is already mounted on W.A.L.T.E.R. and I am still deciding whether to add another DOF to provide arm rotation. My original idea was to allow him to provide the arm rotation as he rotates, but this may not be desirable even though I believe I can get the accuracy I want using various sensors. I am also getting two pair of the newer ASB-24B brackets so I can experiment with other possible joint combinations - these look very interesting and should provide additional possibilities.

As always, I am open to constructive suggestions and feedback. :slight_smile:

I also have to get a new webcam that is supported by Windows Vista (which dropped support for my current one), so I can take the required pictures and videos as I progress. I’d like to be able to take pictures and videos with better resolution anyway. :slight_smile:

8-Dale

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Hi Dale,

Glad to hear Walter is getting attention. Wish you had pics! Looking forward to seeing him.

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Maybe I can take a few with my camera phone to at least show what I have got done so far, especially with the arm. The quality will be a little bit better than my current webcam. I’ll see what I can do about getting some pictures after I wire a few things up on W.A.L.T.E.R. :slight_smile:

Right now, I don’t have anything wired up, so that will be my first task so he’ll be ready for the addition of a new “brain” board. I may even revisit the Atom Pro, since I have one here and it’s real easy to program. I really need to end up with something that can multitask well though, since it’s a bit hard to program true subsumption code without it.

Do you think three 11 1/2" diameter decks with associated batteries (2x 7.2V 2800 mAH) and a 6 joint arm would be reasonable to put on an A4WD1 chassis if I decide to go that way?

8-Dale

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As far as weight goes it’s probably not a problem. You are asking about adding decks and an arm. Depends on what sort of arm and if it needs to be at the top of the stack of decks. :wink:

Xan has made a killer Atom Pro rover plus arm program that works very well.

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Currently the arm is attached to the front of the top deck, with a total of 6DOF SES (2DOF is the little grip). If I put W.A.L.T.E.R. on an A4WD1 base, I can see relocating the arm to a lower deck, or maybe even to the front part of the base. I would probably want his “body” mounted as close to the center of the chassis as possible for the best stability.

I didn’t think the weight would really be a problem because I know the A4WD1 base is sturdy. I just don’t want to destabilize everything, which is why I am considering a 4 wheeled base. I also know the A4WD1 motors are plenty powerful enough since I am using two similar motors on W.A.L.T.E.R. now. I had to cut the speed back considerably on those, to prevent him from hitting walls before the sensors could be processed.

I will have to take a look at that, whether I go back to using an Atom Pro or switch to something else. I can always convert the algorithms to any other language - been there, done that many times. :slight_smile:

8-Dale

6

I’ve done it! I finally decided on and ordered the first of several controllers that will be controlling W.A.L.T.E.R. v2.0 - An AXON by Society of Robots. It has plenty of program flash, lots of serial ports (3 available plus USB console for programming), and lots of I/O including up to 16 analog channels. On top of all that, it’s 100% Open Source! :smiley: I’ll put an SSC-32 on one of those serial ports for servo and motor control.

I also ordered two ball casters to see if I can make them work, at least for starting out. I just have to see if I can make standard standoffs work for the distance from the bottom deck to the floor. Hopefully they will work fine, for at least awhile, and I can get back to doing what I enjoy most soon - writing robot control software for W.A.L.T.E.R. :smiley:

8-Dale

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I’ve confirmed that I can connect all the electronics the way I need to, thanks to Jim. I missed the name of the VL=VS1 jumper, thinking it was just VL=VS. I hate when that happens! :wink:

My current power plan for W.A.L.T.E.R. is to power all the electronics, including motor controller and motors, from a 7.2V@2800mAH NiMH pack (connected to VL) and get a 6V@2800mAH NiMH pack (to be connected to VS2) just for servo power. This should give me reasonable runtime for everything.

On the SSC-32, I’ll have the VS=VS1 jumper installed and the VS1=VS2 jumper removed.

The new casters look like they will work, although they are quite a bit larger than I anticipated, which could be a good thing. I may not even have to add a shim between the bottom deck and the caster. I’m thinking about just letting W.A.L.T.E.R. tilt a bit to put which ever caster needs to be on the ground down and letting the other caster ride above ground level. Actually, when I get the new slightly smaller wheels, this may not even happen since there isn’t much of a difference right now.

8-Dale

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Right now, WALTER is in many pieces. I disassembled him yesterday, because I need to rewire him and change the distance between the bottom and second deck to handle the new front pan/tilt for two sensors (PING and Sharp IR) that I have built. I want to be sure everything can be retracted completely within his body as much as possible.

I need some additional spacers to get enough clearance (about 4.5") between bottom and second decks, so I put in a small order to McMaster yesterday.

I’ve also got the 3D CAD done for new bottom and main decks, to replace the models I lost. The decks are slightly different from what Alan made for me though, and I am sticking to having long slots instead of the four large holes to pass wiring between decks. I am just finding the feed through holes a bit too inconvenient. This time, I put in SES holes for motor mounts so I can use the MMT-03 instead of MMT-02. When I get new decks made, I am thinking about having them made out of light aluminum.

I am not sure when I will have new pictures, but probably not for awhile. I want to get a new web cam first, hopefully in November. I’ll have a good 3D CAD model before then though. I want to document this build better than I did for WALTER v1.x and do better videos this time around. More people are getting interested in WALTER’s development now, and I think there is some potential to win an award or two. :slight_smile:

I’ve also decided to put both WiFi-G and ZigBee on WALTER. The same wireless setup will also go on ASTRID. :slight_smile:

8-Dale

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After thinking about what I am trying to do with WALTER, and robotics in general, I’ve decided to remove the pan/tilt from the bottom deck and remove the arm from the top deck. I think I’ve been trying to do way too much with WALTER, and am going to orient him only to three specific areas now. Doing this will allow me to use both of the nice ball casters I recently purchased for him and solve the last mechanical problem I’ve been working on. I’ve been real unhappy with the placement of the new casters on the bottom deck due to the location of the pan/tilt.

From now on, I will orient WALTER completely for line following, maze solving, sensor experimentation, swarm research (with ASTRID), and behavior based robotics. With the AXON controller, I have the processing power and potential to do some really cool and interesting stuff in these areas. I think this will be the perfect fit for WALTER. :slight_smile: I’m getting a Tracker sensor that I’ll mount at the front of the bottom deck for line following.

This will be the last complete rebuild I do with WALTER.

8-Dale

10

I’ve been doing a lot of thinking on which direction I want to take W.A.L.T.E.R. I’ve decided I definitely want to go with four wheels instead of two, but with a twist inspired by Scarab. Since the current hybrid wheeled leg is just too heavy for the HS-645 servos I have to lift/move, I am going to cut it back to just two joints plus a third servo for steering the wheel. All four wheels will be independently controlled using two Sabertooth 2x5 motor controllers and will also be independently steerable. Using this configuration, I believe I can make it work using just three HS-645 servos per hybrid leg. I’ll start out attaching these to just a single deck and see if I can get everything working that way before adding more weight on top of that. Hopefully a single deck with all the electronics and batteries will not be too heavy for the HS-645 servos. This should not make W.A.L.T.E.R. any heavier than a small quadrapod robot.

Now I just have to disassemble the existing hybrid leg, remove two joints, and attach the remaining parts together. There will be one joint for horizontal motion, one for vertical lift, and the last for steering the wheel with motor. In this configuration, there will not be any requirement for the entire leg to be lifted as in the last configuration, so hopefully everything will come together this time around. I’ve been facinated by Scarab and am hoping to build some of these features into a four wheeled W.A.L.T.E.R.

My plans for the new brain of W.A.L.T.E.R. will consist of a BeagleBoard controlling an SSC-32. I’m starting development on the software setup for the BeagleBoard now. If all goes well, I will be able to get a full web interface, irc chat interface, and full robot control integrated using Python as the control language. I’m testing out a new image build for the BeagleBoard now, which will include the base required software as well as a native development environment so I will have the capability of building software right on the board. This has been one problem with getting some of the software I want for W.A.L.T.E.R. onto an embedded Linux board. The BeagleBoard has the memory (256 MB) and storage (bootable SD/MMC card) necessary to do what I want and so far things are looking pretty good. I may end up using a Gumstix Overo (same processor as the BeagleBoard) as the final master controller for W.A.L.T.E.R. just because it has built in wifi and bluetooth, but will also be experimenting with adding wifi using one of my USB wifi dongles.

I also finally bought a new webcam, so will be getting ready to take some pictures of everything I have built now.

8-Dale

11

Hi everyone!

It’s been quite awhile since I did anything on WALTER, but I have not been well. I’m starting to feel better now. :slight_smile: I can still only work on technical stuff for a limited period of time though, due to still continuing health issues which I am working on getting taken care of.

I am starting to look at ways to convert WALTER to a 4WD setup instead of 2WD. I want a self leveling setup so WALTER can adapt to different terrains and situations. I am hoping to eventually end up with a hybrid design that can walk or roll as needed. I believe I can accomplish this with a 3DOF design, which will include wheel steering. I’m about to CAD up the design and will follow with pictures. :slight_smile:

I’ll use existing sensors each side of center and front. Eventually I want to replace the front sensors with a small black and white camera on a pan/tilt for object and terrain recognition. I will also incorporate XBee wireless (and eventually PS2 wireless) for untethered computer or manual control.

8-Dale

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Sorry to hear you have not been well. Hope you continue to feel better. :slight_smile:

Hope you continue to make improvements to Walter. :smiley:

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I’ve been doing a lot of thinking about the leveling system for WALTER and believe I have a setup that will work. I’ll be ordering the rest of the parts I need to assemble the brackets and tubes for 4 complete 2DOF levelers with motor mounts next month. Each leveler will be mounted on the points each side of front and rear center. I also think I have worked out a proper sequence for changing height on the levelers, which will actually make use of some of the ideas used for quadrapods.

I’m debating whether I should just jump in and go for a horizontal motion joint as well, because this would really make new things possible and interesting - but wait, that would turn WALTER into a real hybrid robot with walking ability as well. Hmmmmmm…

I also want to find a source of one piece (solid) wheels. I need something in the 2" to 2.5" diameter range that would be compatible with a 6mm hub. I’m hoping to find a wheel that would be good on carpet as well as wood or tile/linoleum type floors. Ideally, I think this would use a tiny knobby type of tread pattern.

This will truely take WALTER to v2.0! :smiley:

8-Dale

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Where are those W.A.L.T.E.R. pics?

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I won’t post any pictures until I have assembled the brackets for all four stuts/legs - that will be early next month after I have the rest of the parts.

I’m also still debating whether to go all the way to 3DOF or not and the added cost of servos to do that. I do have the brackets to add the extra DOF, so that is not an issue.

I also have not chosen wheels yet - still looking for what I want, but it may not be available. I may have to find some sort of reasonable compromise on the wheels/treads. I do like the idea of the ARW-01 wheels, but they are not as wide as I would like and I don’t know which hubs go with them.

8-Dale

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I did a bit of tinkering with strut configurations last night and decided to jump right in and go with a 3DOF plus steering setup. :slight_smile: I’m going to try a dual ASB-11 setup between the “knee” and “tibia” joints rather than using “C” brackets there or a “C” and ASB-11 setup. Next week, I should have the rest of the brackets and tubing to complete construction of two of these hybrid legs. I think I have enough servos to fill two of these assemblies, and at present am planning to use HS-645’s in the two heavy lifting joints and HS-475’s for horizontal movement and wheel steering.

If this all comes together the way I hope, WALTER will be in a two wheel plus caster setup. In this setup, the strut/legs will be added on the chassis points each side of rear center and the caster will be on the front center point. I also have an HS-475 installed on the front center point for a pan/tilt sensor platform with a Sharp IR and PING sensor.

As for motor controllers, I am planning to try out two of the RoboClaw 2x5A controllers which can be operated from a single UART and has dual quadrature motor decoders built in. Hopefully I will be able to get two of these next month. In the meantime, just to get things running, I’ll fall back to my Sabertooth 2x5 just for motion and possibly use the Webbot routines for quadrature decoding.

I just have not chosen the wheels and hubs yet, but am hoping to start out with the ARW-01 wheels and an appropriate hub.

As for controllers, I will bring my Society of Robotics AXON (Atmega640 based) into service. It has 3 additional UARTs in addition to one dedicated to USB. I will use one UART for an SSC-32, one for motor controllers, and one for XBee wireless. It’s too bad the AXON has all but 16 I/Os wired for direct battery power. Only 16 I/Os (analog and digitial capable) are wired for 5V use. :frowning: For now, the AXON has the I/O and memory (64K flash) I need to do what I want to do with WALTER. I’ve already got the AXON working with Sharp IR and PING sensors and, thanks to the Webbot library, things are quite easy to do.

8-Dale

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OK, I have done it! I just put in an order for all the brackets and tubing I will need to construct all four leg/struts (3DOF plus steering for each wheel) and some wheels (2 78" diameter x 0.8" wide orange banebot) and hubs. Assuming for now that I have at least 4 good HS-645 and 6 good HS-475 servos, everything should come together nicely as far as hardware goes. Next week I will have all the parts to build two complete strut/leg assemblies with motors, encoders, and wheels. Shortly after I have all the parts and assemble everything, I will be able to take and post some pictures after I’ve done mechanical calibration and selected the appropriate center points for each joint. :slight_smile:

WALTER will be a two deck robot to start out, using the original two wheel bottom deck with front pan servo and caster already installed. As with earlier versions of WALTER, there will be a 7.2V @ 2800 mAH pack for the motors. I’ll temporarily be using a 6V @ 1600 mAH pack for servos and electronics, but may use a separate supply for the electroncs. Motors will be temporarily controlled by my trusty Sabertooth 2x5.

Time to take inventory on my servos and select the ones to be used! :slight_smile:

8-Dale

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Well, it turns out that I do not have enough servos to fill even just two of the struts/legs I want to put on WALTER. However, I can still get him two wheeling (rear wheel positions instead of centered), and then four wheeling. This only requires four ASB-24 brackets mounted on the points left and right of rear and center. I should be able to use HS-475 servos for steering the wheels. QME-01 Encoders will be on the rear wheels and eventually on the front wheels also.

I figure a four wheeled rover with all wheel drive and independent four wheel steering should be very interesting to work with. :slight_smile: I should also be able to tinker with code for routines to do motions inspired by another robot for ASTRID. This is what WALTER is all about - tinkering with new things and code. Speaking of code, I have a basic layout of code for WALTER that I believe will work from a basic two and four wheel setup all the way up to the 3DOF strut/leg and steerable wheel layout. If I do the coding right, I should not have to recode too much (if any at all) for the various configurations. I’ve also allowed for up to eight PING and 8 Sharp IR sensors.

I’ll have the new wheels and hubs this Friday (tomorrow) and the rest of the brackets I need next Tuesday. I already have the four ASB-24 brackets mounted for the steering servos now, and next is adding the second deck with enough space to allow for a dual sensor pan/tilt at the front point.

Yes, I will be taking and posting pictures as things progress with WALTER, now that I have a nice new Logitech webcam. :slight_smile: There should not be any complaints about my new pictures. :smiley:

8-Dale

19

I now have the new wheels/hubs and just received my latest box of goodies from Lynxmotion. :smiley:

I have all the steering servos (HS-475) installed now and have verified the new wheels will give the clearance I want. I am sure glad I did not order smaller wheels! I was a little disappointed that the new hubs are made of plastic, but they seem to be quite sturdy so should work just fine. Now I just have to get a 1/16" allen wrench so I can manipulate the tiny set screws. I much prefer the Lynxmotion hubs, but they won’t fit these Banebot wheels. It’s possible I should have ordered the narrower wheels, but will see how these 0.8" wide wheels work on various surfaces soon. I’m anxious to get the back wheels installed and working so I can start working on new locomotion code. :slight_smile:

My trusty Sabertooth 2x5 will control the rear motors. I’m going to try out the serial control modes of the Sabertooth, which I have never used. Since the Axon controller has three available serial ports, it makes sense to fully utilize them. Another reason for exploring the serial control modes (besides the fact I’ve never used this mode) is that the RoboClaw controller has built in quadrature decoders that can only be utilized in packet serial mode. I already have two motors with encoders installed for the rear wheels. I’ve already decided that the home position for the wheel steering will be with the motor shaft pointing directly out from end of the ASB-24, which will provide a full 180 degrees of steering motion.

I’m also assembling one full leg/strut (3DOF) to tinker with. I think I have enough servos left to fill one up, except maybe for the hip servo. I’m still playing with different ways to attach the hip to WALTER. Using an ASB-06 and an ASB-09 will probably provide the most strength.

Pictures soon! These new pictures are very clear, so all detail should be very visible. I’m very happy with this webcam. :smiley:

8-Dale

20

OK, here it goes finally - PICTURES! :smiley:

Here is the top view of WALTER with a side view of two of the four legs I am assembling to eventually turn WALTER into a hybrid quadrapod.

walter_top.jpg
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Front view of WALTER with the top view of the same two leg assemblies.
walter_front.jpg
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Side view of WALTER
walter_side.jpg
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More to come! Only three attachments are allowed per post. :frowning:

8-Dale