Posts Tagged walker
Code Progress is Still Progress
It’s been a long time since I’ve updated, and to those following my project I apologize, I know how annoying it is to see an interesting project on the net stall for years. (well, at least I hope my project the info I’m putting is useful/interesting/inspiring to others)
Long story short, I left my old job last December, moved cities and started a new job in a different industry. Needless to say, life has been busy, and I haven’t had as much time for my projects as I’d like, which may or may not be a good thing depending how you view it. Moving 1,154 km away from my Dad’s basement workshop hasn’t helped either. No more driving to my parents place to do machine work in my spare time. I’m left to slowly acquire my own tools now.
I haven’t forgotten about the quadruped, and have even managed to get some work done on it. I’ve powered up the motor drivers and haven’t found any major design errors yet, which is a good sign. Motors are spinning, and potentiometers are being sensed properly. I still need to do a bit of work to tap the 0-80 holes to mount the angle sensors, and machine the drive shafts a little bit to engage said angle sensors properly, before I can get the PID controller working properly to move the joint to the appropriate angle.
I’m also considering moving to brass gears, at least on the motor. I’m not overly concerned about the Delrin gears stripping, as there shouldn’t be a massive loads on them that cause outright concern, but I am having trouble mounting them securely to the motor shafts. As it ends up, Delrin is a bit flexible, enough so that it won’t hold a set screw securely, and even with a set screw the motor shafts end up spinning inside the gear. Moving to a brass screw should solve this problem, and is likely the easiest solution, albeit a little bit expensive.
On that note, you may have noticed I’ve put up ads. For the longest time I’ve been against ads on my personal website, but web hosting and robotics as a hobby does cost money. I haven’t really settled on whether or not I’ll keep the ads yet…
Quadruped Robot Introduction
Sometime in the mid to late 90s, I got the idea to build a quadrupedal walking robot. Ideas bounced around my head constantly since then, but school and work got in the way of “free time”. Over the years I gained more knowledge and experience in electronics and robotics design, and constantly refined the ideas I had in my head. In mid-October 08, with the local diving season comming to the time of year where it no longer takes up most of my free time, I finally began to get concrete design work done on the robot. The picture below is what I came up with.
Concept Sketch of Spyder (aka Bert) the Quadruped
An admittedly ambitious project, this Quadruped is to be named Bert and/or Spyder, I haven’t really decided yet. It will be powered by 3 PortEscap gear motors per leg (a sum total of 12), due to a lucky surplus find a couple of years back, at BG Micro. Each joint will have bearings for smoothness (another surplus find, care of the the Electronics Goldmine). The frame will be rough cut from from Aluminum by the Big Blue Saw. Although it’ll add a bit of cost, it will save me an imense ammount of time making some intricate parts and fancy shapes, so I decided it would be worth it. The rest of the machining to be completed on my Dad’s Sherline mill and lathe.
The brains will be a Gumstix computer I picked up a while back and have been playing with, and eventually I plan on creating a head to go in the center of the robot, however I haven’t quite decided how I want to go about this. The entire robot will be powered by some LiPo batteries, which hopefully should provide a good life time.
Waterjet Cut Parts
After a couple of months of design work, I finally sent the files off to have the core, and one leg water jet cut. I only ordered one leg to start with in order to make sure everything works out properly before committing to building the other four legs. Today I got the water jet cut parts back, and they look nice! All the parts came connected as one big piece, so some dremel work was required to seperate them without damaging the parts, and I’ll have to take care in filing the connecting bits flush to the part.
Another issue with water jet cutting is the kerf diameter, or diameter of the waterjet stream, in this case approximatley 1mm, so some corners that I had cut to that diameter will need to be filed into square points, but that’s no big deal.
Bunch o' Parts
To the left you can see some of the parts that will make up one leg of the robot. I’m still waiting on some small parts such as teflon washers to use in the joints, but that should be arriving any day now. You can see my H-Bridge in the mix, I’ll need 6 of those dual H-Bridge boards on the final robot.
All in all an exciting build!