Elastic rotary actuator, particularly for robotics applications, and method for its control
This  invention  provides  a  rotary  actuator  featuring  small  size  and  high  compactness,  combined with active control of compliance in a wide range of values, suitable in particular for robotic applications, where size, weight and complexity are critical parameters.

This invention achieves a very compact structure by using a input drive unit on the shaft  of an electric motor-reduction gearbox, which is coupled to a three-spoke drive output via six helical springs, as shown  in the pictures; differential rotation between  input and output  provides  a  first,  fixed  degree  of  compliance  for  the  drive,  determined  by  the springs elastic constant. Moreover,  the  addition  of  rotary  encoders in both the input and the output sections of  the  actuator  gives  information  on  absolute position,  rotation  speed and applied  torque (via  relative  rotation),  which  allows  an active  control  unit  to  provide  an  effective compliance regulated over a wide range.

Small size  and  effective  compliance controlled over  an  ample  range  allow integration of this actuator  in many robotic systems with various degrees of complexity.  The compact  design  of  the  actuator  is  due to  the novel  compliant module mechanical implementation. The  miniaturization  of  the  high performance  unit  was  achieved  with a  use  of  a  novel  rotary  spring module realized by six linear springs arranged to constrain  the motion  of  a  three  spoke structure  which  rotates  relatively  to the reduction drive output and acts as a mounting basement for the output link. Despite  its  small  size,  the  actuator  still retains  high  level  of  performance  and it  is  a  potential  actuation  solution  for robotic systems when compliance is also desired. The  passive  compliance  of  this  unit  is  also  combined with  active  compliance  control based on velocity regulation allowing the compliance adjustment within a wide range. Industrial applications are in the field of industrial automation and robotics.

Patent  Application No. TO2009A000257
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