I know that some people, probably my wife included, will think that an article dedicated 100% to photos of robot feet is somewhat bizarre, if not down right weird, but I’m going to do it anyway. Most of the well known robot kits, including the Kondo KHR-1, Hitec Robonova-1, and others, have foot soles that are very smooth and often slippery. Wouldn't it be better to give the robot some soles to improve traction, or would it . . .?
Like a lot of topics in this infant hobby/robo-sport, the topic of robot foot soles doesn't have any easy answer. Everyone you talk to, and we’ve talked to a lot of the robot builders here in Japan, will give you a slightly different answer.
Some of them prefer to keep their robots feet exactly the way they came from the factory. They argue that although the foot surface is smooth, it also allows it to slide its feet and move more easily.
Others claim that one of the first things you should do is to add some sole material to your robots feet. The only trouble is that they swear-by (and often swear-at) a wide range of different materials. We've seen robots that use simple rubber and even felt pads that you would pickup in a pack of 4 or 10 at the local 100 yen (dollar) store.
The more dedicated, and perhaps obsessive, use pricier materials ranging all the way from modified mouse pads up to really expensive custom rubber/plastics that have to be special ordered.
However, there are a few things that they all can agree on. First, if you are going to enhance your robots soles, then you need to take it into consideration when you program your motions for the robot. We ran into this first hand a couple of weeks ago. We had Gulliver, our KHR-1 based robot, programmed with some pretty cool moves and thought he was doing extremely well. Then we added small pieces cut out of a mousepad to both of his feet. Attaching them with double sided tape was simple enough. But when we started to put him through his paces he started to stumble, fall, and sometimes jump around totally unexpectedly. The problem was that with his new soles his feet didn't leave the surface as easily as they had before the modifications. His new, improved traction was causing rather than solving problems. It took us quite a few hours to sort everything out and make adjustments to all the motions we had already created and tested so carefully.
Another major concern is that the increased traction also puts more of a load on the robots leg servos. If you're not careful it's easy to end up with too much traction which will force your robot to work hard just to overcome resistance.
The important thing is to realize up-front that changing the sole material is not a trivial undertaking. It's definitely not something that you want to leave until the last minute on the night before a major competition.