Not for walking robots, but for other projects:

I’ve used : https://www.firgellirobots.com

They have some that are PWM others need a motor driver that uses a PWM motor driver like the TREX

https://www.pololu.com/product/777

If any one is interested I can throw a video together on using these with EZB

I'm interested in using linear actuators. I'm also interested in the mechanical structure to move the robot hips, ankles, knees by linear actuators for walking. Has somebody experience about that ?

Hello @leonardo46

From my experience and research, using electric linear actuators will not be fast enough for allowing a humanoid robot to walk. Electric linear actuators are usually built as a worm gear assembly which by nature is slow in movement speed. This is why companies like Boston dynamics focus on hydraulic linear actuation and other companies like Festo use a pneumatic system.

With both hydraulic and pneumatic systems the problem becomes using a reservoir and miniature compressor. A reservoir represents a large cavity of space needed to be mounted onto the robot which is one problem. A miniature, high efficiency compressor is a technology that is hard to get access to, which is the biggest problem with using hydraulic/pneumatic systems. My hope is that miniature, high efficiency compressors become widely available in the near future and can be sold at a reasonable price.

Hi jeremie. Linear actuators may be fast enough if their motor has enough power, and the gear ratio between the motor shaft and the worm is properly selected. There is a wide range available. I have actuators with 25 lbs, at 2" per second. It's fast and powerful enough to move a large robot leg. I have experience in pneumatic actuators in player pianos. It's a century- old technology (bellows and vacuum pumps). The pressure is not very high and all can be done by simple devices. But it's not suited for feedback positioning. I'm looking for smart mechanical structures to make walking robots with linear actuators. James Bruton at Xrobots (UK) has developed something like that.

I was going to suggest James' videos. He replaces the gear motors with belts with linear actuators later in the series on his bipedal robot legs.

I’d also like to leave this link. Their fast linear actuators move like 9 inches a sec with force ipto 33 pounds. They have a lot to offer at good prices.

www.progressiveautomations.com

I stand corrected! I completely forgot about James and the work he was doing. For those of you who are curious (as I was) here's one of his videos:

good and cheap actuators, but without feedback pot and electronics.