Siddharth Sanan, Michael H. Ornstein, Christopher G. Atkesoncga/papers/EMBC2011_SananOrnsteinAtkeson.pdf · 2011. 11. 23. · Siddharth Sanan, Michael H. Ornstein, Christopher G
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Physical Human Interaction for an Inflatable Manipulator Siddharth Sanan, Michael H. Ornstein, Christopher G. Atkeson The Robotics Institute, Carnegie Mellon University, Pittsburgh, PA ABSTRACT The Inflatable Manipulator Schematic of the robot • Low weight, contact and structural compliance lead to inherently safe design • Impact force magnitude <10N, impact speed of 5m/s • Well below injury-causing levels • Multiple inflatable chambers to maximize payload capacity • 3 active degrees of freedom • 4 motors: 1 motor actuating link 1, 2 motors actuating link 2 via tendons, 1 motor actuating base • Payload capacity: 4N, Maximum internal pressure: 7psi Seams in top view Seams in cross-section (side view plane) Multiple chambers (A,C)-Link, (B)-Joint Contact forces during impact N 10 impact F INFLATABLE JOINT ANGLE ESTIMATION • Angle at joint 2 cannot be directly sensed due to the absence of a physical joint • Joint angle can be estimated using a joint pressure based model • Model is identified empirically ` APPLICATION TO HUMAN INTERACTION Contact forces during wiping The inflatable manipulator detecting contact and moving away from the subject during an unintended interaction Contact force with and without the contact detection scheme The inflatable manipulator detecting contact and wiping the subject during an intended interaction SAFETY UNDER IMPACTS MANIPULATOR DESIGN • In the absence of contact, the joint 2 angle can be computed using a kinematic model that includes tendon lengths: • Kinematic model prediction is compared with pressure model prediction to infer contact ) ( 2 2 m T T Pressure model and kinematic model angle estimate, and contact variable for a trial CONTACT DETECTION • Robots for safe physical human interaction are needed to provide assistance to humans • Intrinsic safety is key to enabling everyday human robot interaction • Contact detection and reaction for an inflatable manipulator is developed for compliant interaction with humans • Prior work to improve safety has focused largely on introducing joint compliance and soft coverings to conventional rigid robots [1][2] • Inflatable structures have been utilized and studied extensively for space and architectural applications [3] • Some examples of inflatable structures in robotics do exist, although these have not been specifically utilized for providing human assistance [4]. RELATED WORK [1] M. Zinn, O. Khatib, and B. Roth, “A new actuation approach for human friendly robot design,” in Proc. 2004 IEEE Int. Conf. Robot. Autom. (ICRA), vol. 1, April-1 May 2004, pp. 249–254 [2] T. Mukai, M. Onishi, T. Odashima, S. Hirano, and Z. Luo, “Development of the Tactile Sensor System of a Human-Interactive Robot RI-MAN,” IEEE. Trans. Robot., vol. 24, no. 2, pp. 505–512, April 2008 [3] S.L. Veldman. Design and analysis methodologies for inflated beams. 2005. [4] R. Baldur and W. Blach, “Inflatable manipulator,” Society of Manufacturing Engineers, 1985. • High level of safety for physical human interaction achieved as evidenced by the low contact forces for impacts and unintended interactions • Method for detecting contact of the inflatable manipulator’s distal link with an external agent developed • Two reaction strategies based on contact detection developed to handle both unintended and intended interactions CONCLUSIONS FUTURE WORK • Detection of out of plane contacts and contacts on the first link • Improved state estimation and control using a larger variety of sensors Joint pressure and joint angle measured data for joint 2, and the model fit to the data
