344 of rotor 342 relative to reference structure 310 a second degree of freedom can be defined as angle of rotation 345 of stator 323 relative to reference structure 310 output member 280 is coupled to rotors 322 342 therefore output member 280 rotates together with rotors 322 342 relative to reference structure 310 second portion of 310 b reference structure 310 has couplings 315 and 316 which respectively provide additional support in holding rotors 322 342 in rotary engagement with reference structure 310 output member 280 may be coupled to an object to be driven such as an aircraft control surface stator 323 and stator 343 are rotationally coupled together through coupling 360 coupling 360 causes stator 323 to rotate relative to reference structure 310 by an angle opposite to the rotation of stator 343 relative to reference structure 310 more specifically coupling 360 causes any change in angle 325 to cause an equal and opposite change in angle 345 in other words a degree of freedom between rotary actuator 320 and reference structure 310 is caused to be shared with one degree of freedom between rotary actuator 340 and reference structure 310 by coupling 360 coupling 360 is a link 360 a pivotally connected to drive arm portion 323 a of stator 323 and pivotally connected to drive arm portion 343 a of stator 343 however coupling 360 may alternatively be a gear coupling a belt coupling or other similar coupling rotor 322 and rotor 342 are both coupled to output member 280 through coupling 370 coupling 370 causes the rotation of both rotors 322 and 342 to be transmitted to the output member 280 such that.