[dljsjr]

Lots of simulators for robotics use ODE or Bullet, actually, and they're quite good for lots of things that you might want to simulate. But there are some people who would argue that they aren't the best for it, especially for simulating legged locomotion, because of the way physical constraints such as joint limits are enforced (via Lagrange multipliers). A popular alternative formulation is Featherstone's Method[1], which is becoming more widely available and goes by other names sometimes; for example, Rust's `rapier` physics engine refers to this type of dynamics model as "reduced coordinates" (they don't yet support it, but it's on their roadmap). Featherstone's method is becoming more popular but it's still not widely used in a lot of physics engines because most physics engines are targeting games and Featherstone's doesn't always have the best performance characteristics, instead favoring physical fidelity. Bullet can run using Featherstone's Method, by the way. One of the few FOSS engines I know of that supports it out of the box.

Additionally, there are people in robotics who like to say that simulators are like lightsabers, you haven't become a true Jedi until you've built your own, so there's a lot of home grown physics simulators in robotics.

[1]: https://en.wikipedia.org/wiki/Featherstone%27s_algorithm