Here is a freak of robotics for you to all enjoy, and it is my first fully complete design for a hybrid robot. It’s big, it’s bad, and it is definitly not a pretty sight, but it sure would be fun to build and play with. As shown, the legs are not even fully extended and they almost take the wheels off the ground.
Howver, I realize that I could probably not get enough battery power onto this beast to power it for any reasonable length of time. It’s also possoble it would not be able to lift its own weight if I could. This beast has a total of 36 servos - 24 for the eight legs and another 12 for the all steerable and retractable wheels.
Regardless of whether I can build this whole thing all together, I do plan to build each of the subsystems (Octapod and Rover) separately. They each have some very interesting features and abilities I want to experiment with.
I have been watching this grow and wanted to add some comments. To make this more realistic I would do the following…
switch from 8 legs to 6. This will reduce the number of servos from 36 to a more managable 30. (one SSC-32) The current configuration doesn’t allow much horizontal travel for the middle two leg pairs anyway, so it’s just added weight.
change the 6" tubes in the legs (hip to knee) with 3" or even 1.5" tubes. Then add load balancing springs to lessen the work of the servos.
this is difficult to explain but I wil try. On the rover wheel support system. The ASB-06 will not fit the way you have it on the servo that holds the wheel. It must be connected in the long dimention. So put the ASB-06 on the top of the ASB-04 and turn that servo over so it’s horn is closer to the bottom. Then connect the ASB-06 to the horizontal ASB-18. I’m still not excitied about this configuration, but it will be much stronger than the current setup.
Can you show it with the landing gear up? Mid stride maybe? How much is this going to weigh? If its strong enough you could tote around some of these Bi-peds…
I did make a modification to the legs, but not as you suggested. You pointed out something that had been bugging me about the middle legs also, but I had just not done anything about it. Those legs should be much more useful now, and there are times when this bot would have to walk as a hexapod - even with it having 8 legs.
The tubes are actually 4 1/2", and they need to be long enough such that the bot can take its wheels fully off the ground so they can be safely retracted when switching to walking mode.
I understand exactly what you mean. Is this good?? Heh heh! I am nto really excited about this necessary modification either, and it is one of two places I am not happy with my design so far. The other place is the offset brackets are not quite long enough in the offset direction and may not actually gi ve the legs enough clearance to move the way I want them to move.
I wish there were longer versions of the ASB-06 and ASB-11 brackets.
It will take a bit more of a modification to do this, as I have to change the wheel subassemblies, delete the existing ones from the master, and add the modified subassemblies. I will work on that tonight. The modification is an easy one, but requires more work to get done due to how I have to do it in Solid Edge.
I can’t just modify a subassembly in place. This is just one disadvantage of working with building blocks - I have many subassemblies I can put together pretty quickly to make new bots. I prefer the subassembly approach anyway though.
In the meantime, here are two new views with the modifications I have done so far.
Yes, I added more servos rather than removing some. There will be two more than actually shown here because I don’t have a model for the last component.
Unfortunately, after I add a subassembly to a larger assembly (legs and wheels), I have very limited movement even though the subassemblies do have movement when I look at the separately. I do not know if I have any control of this with Solid Edge. I can only move the legs horizontally and can’t move the wheels at all.
OK, I have redesigned the wheel tower assembly. In the process of fixing the problem you described, I also discovered a design flaw of my own - it could not be used to lower the height of the bot closer to the ground as I said. I believe this new wheel tower will do that as well as fix the problem you found. I still managed to keep the center of the wheel as close to centered under the steering servo as possible.
Now I just have to incorporate this new wheel tower design into the walk 'n roller. It’s possible I may be able to get rid of the ASB-18 bracket, even if I have to use a small shim bewtween the wheel and the servo horn.
OK, I did it. I designed up a wheeled hexapod using all my latest designs, including the newest wheel tower. I have not added any load balancing springs yet, since I am not quite sure where to put them for best effect. The legs are shorter - having a 6" reach instead of a 9" reach (3" tubes instead of 4 1/2" tubes).
This gives a total of 22 servos for the walker part and 12 servos total for the wheeled part. Total is now 34 servos, which should be a lot more manageable. I can run the walker from a single SSC-32 and can run the wheeled system direct from a microcontroller or another SSC-32. I would opt to use the second SSC-32 for the wheeled system, since the wheels also require a certain amount of synchronized servo motion like the walker does.
One real upside to the Hexapod is the IK has already been done for this type. Software development for this Hexapod will be every bit as interesting and fun as for the Octapod.
This robot has some awesome capabilities built into it and I am looking very much foward to developing the software for it. This Hexapod is just screaming for a Propeller chip to control it. With the independent steerable wheels and the ability to raise/lower them, this Hexapod could even be a low rider!
Oh wow, it has skates! This is really cool. Yes, it would save a lot of weight, and cut down on the number of required servos. Hmmmm, I will have to think about this. Thanks! An eight legged robot with skates would be an interesting sight to see.
Since my original design has the robot rolling on four wheels, having it rool on for legs would be the obvious way to go. If I put the wheel assemblies on the front and back legs, it could work - just pull the middle legs up for rolling around. It would complicated the two front legs a bit, with the grippers, but I think it is doable.
I was thinking more about overall stability and having the wheeled legs as far apart as possible. However, putting the wheels on the rear and front middle legs would be an acceptable way to go. Good thinking!
Why not go all out and put grippers on the back legs too? Then you will have secondary functions for all of the legs. The middle sets for skateing and the fore and aft sets for gripping/flinging/pokeing…
I want to be able to tell whether the robot is coming or going…
BTW, I got my first success with the Alibre Design CAD software today. I got the servo horn put on the servo and it rotates just as it should. I am having a bit of trouble with the auto-constraint thing for placement of parts in an assembly, but I will get it figured out.
I decided not to try porting any of my assemblies over from Solid Edge to Alibre Design and the STEP parts seem to be working a lot better. I finished importing and saving all the SES parts and hardware into Alibre Design.
Actually, the automatic functions in Alibre Design are quite nice. I just have to forget what I learned with Solid Edge, because the two programs work very differently.
I almost have my servo in a bracket (ASB-04) subassembly done. The servo just isn’t quite constrained right to the bracket yet.
This is my thought also. It will give me much more opportunity to become more proficient with the new software. I’m still not quite used to having to hold both mouse buttons to rotate the view around, but am getting there.
As shown, the legs are not even fully extended and they almost take the wheels off the ground.
The current configuration doesn’t allow much horizontal travel for the middle two leg pairs anyway, so it’s just added weight.
