Patent ID: 8291788

Claim:
A rotary actuator assembly comprising: a generally circular support frame defining an axis; a motor mounted about the axis within the support frame; a gear drive rotatably connected to the motor and mounted within the support frame about the axis; a torsion spring having a spring input and a spring output, wherein the spring input is rotatably connected to an output of the gear drive and the torsion spring is mounted within the support frame; a joint output connected to the spring output; a first absolute position sensor having a first stationary portion and a first rotary portion; a second absolute position sensor having a second stationary portion and a second rotary portion; wherein the first stationary portion and the second stationary portion are secured to the support frame; wherein the first rotary portion is secured to the output of the gear drive to sense the rotational position of the gear drive output relative to the support frame; wherein the second rotary portion is secured to the spring output to sense the rotational position of the joint output relative to the support frame; and wherein the difference in the position of the first rotary portion and the second rotary portion is the amount of deflection of the torsion spring.