There are definitely freelance jobs that don't involve the web - I know folks who have them, doing e.g. optics design - but they're rarer, just because the potential customer base is so much smaller. And obviously in robotics systems it will be harder to telecommute.

The usual advice is to specialize in something that's specific but in demand. For example, you could get really good at setting up a particularly common type of robotics system, or setting up systems for a particular type of problem. Perhaps try approaching the sales folks for a robot company and seeing if their customers are often looking for experienced freelancers: If so, would they be willing to recommend you? (Of course, if the robotics company has its own consulting division you might not have much luck with this plan…)