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A TESTBED FOR STUDENT RESEARCH AND DESIGN OF CONTROL-MOMENT GYROSCOPES FOR ROBOTIC APPLICATIONS . Albert Soto, Daniel Brown, Mason Peck. ASEE Annual Conference & Exposition – Austin, Texas June 15, 2009. Space Systems Design Studio at Cornell University. Overview. Experimental Learning
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A TESTBED FOR STUDENT RESEARCH AND DESIGN OF CONTROL-MOMENT GYROSCOPES FOR ROBOTIC APPLICATIONS Albert Soto, Daniel Brown, Mason Peck ASEE Annual Conference & Exposition – Austin, Texas June 15, 2009 Space Systems Design Studio at Cornell University
Overview • Experimental Learning • Space-Robotics • Drive Design • Momentum Actuators • Reactionless Robotics • Specifications & Design • Student Benefits Space Systems Design Studio ASEE June 2009
Experimental Learning • Fundamentals of Professionals • Research Project-Oriented Learning • Teamwork • Self-confidence • Opportunity to apply coursework • Experience • Visualize professional career • Retention in engineering • Limiting Factors of Aerospace Research • Infrequent microgravity flight trips • Risks in spaceflight launch • Limited resources NASA Microgravity Research Aircraft Space Systems Design Studio ASEE June 2009
Space-Robotics • Robotic Arm Technology • Satellite assembly • Massive cargo relocation • Spacecraft repair Space Systems Design Studio ASEE June 2009
Actuator Design • What is a Drive Design? • Direct Drives • Conventional actuators for robotic arm joints • Control-Moment Gyroscopes (CMGs) • Traditional spacecraft attitude control • CMGs vs. Direct Drives • Reactionless actuation • Energy advantage? Space Systems Design Studio ASEE June 2009
Momentum Actuators • Control-Moment Gyroscope (CMG) • Constant-speed rotor • Gimbal the rotor about g-axis to change angular-momentum vector h • 100x less power than RWAs1,2 • CMGs produce greater torque for less energy tout h1 h2 • Comparison of CMGs to direct drive needed to bring CMGs into robotics Space Systems Design Studio ASEE June 2009 • Carpenter, Peck, 2008 • Van Riper, Liden, 1971
Reactionless Robotics • Actuator reaction torques • Inertial reaction forces • From D’Alembert’s principle • Benefits of CMGs • Reduce disturbances and low frequency vibrations • Isolate subsystems • Increased agility of robot • More power efficient than RWAs1,2 tCMG tj -tj -R1 R1 -R1 R1 • Carpenter, Peck, 2008 • Van Riper, Liden, 1971 Space Systems Design Studio ASEE June 2009 7
Reactionless Robotics in Space • Robotic manipulators • Space construction and repair • Pointing tasks • Independently orient cameras, sensors, transmitters, solar panels, etc. • Reduced propellant use in attitude control • Reduce launch mass • Extend mission life DARPA SUMO spacecraft & Cornell CMG team Efficient use of limited spacecraft power Space Systems Design Studio ASEE June 2009
Power Requirements • Power equations of output torques: • in terms of the joint torques and velocities Power equations do not equal! • CMG power has not previously been compared to direct drive for robotics Space Systems Design Studio ASEE June 2009
Testbed Specifications • Planar two-link robot • +/- 90 deg range • Dually actuated • CMGs from robot arm • DC motors at joints • Air bearing levitation • Wireless control/data acquisition • Expandable to 3-link robot • Removable base link Space Systems Design Studio ASEE June 2009
The Scissored-Pair CMG Configuration DC Motor Gear hr1+hr2 hr1 f -f tC2 tC1 CMG tC1+tC2 Space Systems Design Studio ASEE June 2009
Benefits • Student introduction to: • Reactionless robotics • Momentum actuators • Dynamics of CMGs • Research • Ground testing of space-systems • Mechanical design and fabrication • Advances faculty and graduate students • New experimental hardware • Design groups Experience for excellence in engineering Space Systems Design Studio ASEE June 2009
Future Possibilities • Additional Focuses: • Optimizing CMG size • Real-time data collection and analyses • Control laws for N-link robotic arm Single link Two links Space Systems Design Studio ASEE June 2009
Space Systems Design Studio ASEE June 2009
Acknowledgements • Cornell Leadership Alliance • Space Systems Design Studio • Dr. Michele Carpenter • Cornell 2007 CMG team • Mike Nagele • Nicole Monahan Space Systems Design Studio ASEE June 2009
Momentum Actuators • CMGs are part of a larger class of actuators • Internal momentum change provides output torque • A spinning body resists change • Magnitude or direction of spin • Reaction Wheel Assembly (RWA) • Rotor fixed to spacecraft • Vary rotor speed magnitude • Large energy change of rotor h2 h1 tout Space Systems Design Studio ASEE June 2009