There is set forth herein an articulated arm, the articulated arm comprising a first rigid link assembly and a second rigid link assembly. The articulated arm can be configured so that the second rigid link assembly rotates in relation to the first link assembly about a rotary axis. The articulated arm can include an actuator for causing rotary movement of the second rigid link assembly in relation to the first rigid link assembly about the rotary axis. The actuator can include a first fluid chamber, and a second fluid chamber. The articulated arm can include a fluid supply assembly for moving fluid into and out of the first fluid chamber and the second fluid chamber.