Extend muscle to allow McKibben braided type

[samborambo]

I see there is a spherical type of muscle actuator available. Would it be difficult to extend this type to include muscles with braided tension fibres? An approximation for the contracted shape would be two hemispherical ends with a cylinder in the middle.

It's also possible for braided muscles to arc around a joint when expanded, especially for 1 DoF joints. This allows almost 360deg of joint rotation with opposed muscles. What would be needed to make this work in Webots?

I like hydraulic braided muscles because they're cheap and easy to make (braided cable sleeve, latex tube and some pipe fittings), very high power density, and lightweight. They can be a lot faster than piston-type hydraulics as they don't rely on high-viscosity fluids to stop leaks past the seals, because there are no seals. Water can be used instead of oil for less dynamic pressure drop and faster flow. Also, with opposed muscles around joints, you can dial-up the desired compliance of the joint with the collective pressure of the opposed muscles.

A hydraulic/pneumatic model would be very useful. Not a full CFD solver but basic, pragmatic fluid network computation. Much like solving an electronic circuit. Adding components such as pressure sensors, servo valves, solenoid vales, pressure reservoirs, fluid reservoirs, check valves, pressure regulators, flow sensors, pipes with dynamic pressure drop, elastic muscles, hydraulic motors, and pumps. Happy to help with the math behind all of it.