Sterylite 6000

Part of the idea for Sterylite 6000 came from my desire to create a quadruped with greater ground clearance. As well as Fluffy works, it has less then a 0.5 inch of ground clearance, at least in autonomous modes. In general I think servo based walking robots have much worse ground clearance than people realize. You often see walking robots demonstrated on very smooth surfaces, or stepping up steps that are very predictably placed. Hexapods tend to have much better ground clearance autonomously than bipeds or quads, because of their inherent stability.

The other idea for Sterylite was to try and make a robot using fewer servo motors. From working with Fluffy I realized that with an eight servo system I was always using two motors to lift the body, and two motors to only lift the legs. I could see that I could do the same gaits with six motors instead of eight by using two lifting motors and four motors to propel the robot horizontally. Fewer motors is lighter, cheaper, and simpler. Also, because the lifting motors have to be very strong, it made sense to focus on two very strong motors for lifting and four smaller motors to propel the legs. That actually worked very well because I got a pair of very beefy servos to lift the robot up.

The six motor system actually works, but it never got very good ground clearance because of balance issues. A lot of this may be due to the poor design and construction of the chassis. You can read about the problems with the legs in my struggles in the walker challenge. Ultimately I decided that the easiest way to fix the balance problem was to add four servos to articulate the feet. This makes the robot quite mobile with good ground clearance.

Like Fluffy, Sterylite uses a Spin Studio card. This worked so well, I had to stick with it. I still feel I haven't approached the capability of the processor, and now I am starting to have some software to build off of.

Sterylite now walks pretty well, and I plan to continue to develop it. I want to tune it for the Walker Challenge next year, where I am pretty sure I can improve my performance. Also, since the robot is powerful, it has a good potential payload for sensors or other missions. One of the things I was thinking about doing was putting a model rocket launcher on top of it, to make a walking rocket launch pad. Silly, yes. But I know my kids would love it.

One problem with Sterylite is that it is two big and two heavy to run inside the house. It would scratch up the floor and the walls. Maybe if I can make it more graceful that won't be a problem. But I think this could be the direction I am heading, with future walkers that are not safe for the living room.

Here is Stery in action at the 2010 Robogames.