# Meeting with mark

@design time consider the effects of different internal stiffness on hand behavior wrt some set of object and tasks at run time adjust preloads and forces in underactuated hand to vary its behavior you're doing it in a hand where you don't have anything else. joint control vs hand grasp stiffness control cost arguments idea colntrolling underactuatidd behavior by controlling stiffess preload.

able to increase the range of stable grasps by changing the mix of forces. mathematical argument of the same argument if you have one more motor you can keep your finger in different state. design of stops - allows you to bring the hand into a configuration that's not necessarily part of its natural kinematic space.

# Previous Work

• Hirose soft gripper
• Sarah / Mars Hand
• Vincent's paper
• Pneumatic one

# Hand Design

• Underactuation
• Fewer actuators than degrees of freedom
• Springs are often used to balance unconstrained degrees of freedom, provide return forces
• Grasp Taxonomies
• Way to organize & classify grasps
• many are anthropomorphic
• derived from human studies
• Current hand design
• double stage mechanism for compactness
• designed to contact wide range of sizes

# Deriving Stability

• Generating Loop equations
• Transmission matrix
• This depends both on your transmission design and your actuator attachment locations.
• Underactuation matrix
• Basic Jacobian
• Contact matrix
• what type of contact are we assuming?
• normal forces

# Major Points

• Variable-stiffness underactuated fingers(2 motors/) have a wider range of stability than highly underactuated fingers (one motor)
• This doesn't necessarily come at the cost of another large motor, because your kinematics can be designed to allow small motors to keep certain configurations near a singularity.
• what type of stability are we talking about?
• finger stability
• positive normal forces in all phalanges.
• How can we prove this
• two finger designs, one underactuated with stiffness control, the other locked or fully underactuated?
• simulations and experiment?
• Mechanical stops provide another set of design parameters
• You can use mechanical stops to stay in configurations that wouldn't otherwise be stable
• Mechanical stops reduce your degrees of freedom.

# Necessary Calculations / Simulations / Graphics

• The basic finger design
• Changing stiffness changes finger wrapping
• pinch / wrap
• Stable regions of the workspace vs. finger stiffness.
• Picture and graphic of actual finger setup

# References

 S. Krut, "A force-isotropic underactuated finger," IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, IEEE; 1999, 2005, p. 2314. S. Tan, W. Zhang, Q. Chen, and D. Du, Design and analysis of underactuated humanoid robotic hand based on slip block-cam mechanism, IEEE, 2009. L. Birglen, "An introduction to the analysis of linkage-driven compliant underactuated fingers," Engineering Conference, 2006. T. Laliberté and C. Gosselin, "Simulation and design of underactuated mechanical hands," Mechanism and Machine Theory, vol. 33, 1998, p. 39–57. G. Kragten, A. Kool, and J. Herder, "Ability to hold grasped objects by underactuated hands: performance prediction and experiments," Proceedings of the 2009 IEEE international conference on Robotics and Automation, IEEE Press, 2009, p. 3027–3032. V. Bégoc, S. Krut, E. Dombre, C. Durand, and F. Pierrot, "Mechanical design of a new pneumatically driven underactuated hand," 2007 IEEE International Conference on Robotics and Automation, Roma, 2007, p. 927–933. L. Demers and C. Gosselin, "Kinematic design of an ejection-free underactuated anthropomorphic finger," Proceedings of the 2009 IEEE international conference on Robotics and Automation, Institute of Electrical and Electronics Engineers Inc., The, 2009, p. 776–781. L. Birglen and C. Gosselin, "Optimal design of 2-phalanx underactuated fingers," Proceedings of 2004 International Conference on Intelligent Manipulation and Grasping, 2004, p. 110–116. L. Birglen and C. Gosselin, "On the force capability of underactuated fingers," IEEE International Conference on Robotics and Automation, Citeseer, 2003, p. 1139–1145. A. Dollar and R. Howe, "Joint coupling design of underactuated grippers," Proceedings the 30th Annual ASME Mechanisms and Robotics Conference, Citeseer, 2006, p. 10–13. R. Ozawa, K. Hashirii, and H. Kobayashi, "Design and control of underactuated tendon-driven mechanisms," Proceedings of the 2009 IEEE international conference on Robotics and Automation, Institute of Electrical and Electronics Engineers Inc., The, 2009, p. 287–292. L. Birglen, T. Laliberté, and C. Gosselin, "Grasping vs. Manipulating," Underactuated Robotic Hands, Berlin, Heidelberg: Springer Berlin Heidelberg, 2008, pp. 7-31. L. Birglen, "Force Analysis of Connected Differential Mechanisms: Application to Grasping," The International Journal of Robotics Research, vol. 25, 2006, pp. 1033-1046. A. Dollar and R. Howe, "A robust compliant grasper via shape deposition manufacturing," IEEE/ASME Transactions on Mechatronics, vol. 11, 2006, p. 154–161. X. Zhe, T. Deyle, and C. Kemp, 1000 Trials: An empirically validated end effector that robustly grasps objects from the floor, IEEE, 2009. L. Birglen, T. Laliberté, and C. Gosselin, "Optimal Design of Underactuated Fingers," Underactuated Robotic Hands, Berlin, Heidelberg: Springer Berlin Heidelberg, 2008, pp. 117-138.

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