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Applications of VSA-actuated System

Application I: Grasping object using a HVSA-actuated Gripper
  • Comparison between conventional gripper and HVSA-actuated gripper
    • Conventional gripper equipped with tactile sensor
      • Low impedance for the low-frequency range can be provided.
      • Low impedance for the high-frequency range converges the structural stiffness. 
    • Compliant gripper actuated by HVSA
      • Impact force can be absorbed when the contact occurs.
      • Contact force can be estimated by measuring passive elastic angle in the HVSA.
  • Features of HVSA-actuated gripper
    • 1 DOF compliant gripper actuated by hybrid type variable stiffness actuator (HVSA)
    • Two fingers are operated symmetrically by using 4 bar linkage mechanism.
    • Vertical motion can be achieved by using the elevation mechanism consisting of a screw-nut mechanism.
       < Two configurations of HVSA-actuated gripper >
    • Specifications of HVSA-actuated gripper
 Grasping range0 - 104 mm 
 Stiffness range0.87 - 27.3 N/mm
 Max. speed1 m/s 
    • Grasping fragile objects

  • Comparison between conventional gripper and compliant gripper
    • Grasping graphite lead
      • Thin and long object: Easy to bend
      • Brittle object: Easy to break
    • Conventional gripper
      • Low grasping speed: Success
      • High grasping speed: Fail (Even though the gripper detects the contact) 
    • Compliant gripper
      • Low grasping speed: Success (for all stiffness)
      • High grasping speed: Success (for low stiffness)

  • Tofu
    • Deformable object: Difficult to measure contact force
    • Slippery object: difficult to grasp
  • Conventional gripper
    • Easily failed to detect the contact by using tactile sensor at the finger tip
  • HVSA-actuated gripper
    • HVSA-actuated gripper can easily detect the contact with low stiffness (or high compliance).
    • A grasping force can be estimated even though a tofu is deformed by the grasping force.


Application II: Robotic assembly using a HVSA-actuated Manipulator
  • Comparison between conventional manipulator and a HVSA-actuated manipulator
    • Conventional manipulator equipped with a force/torque sensor
      • Low impedance for the low-frequency range can be provided.
      • Low impedance for the high-frequency range converges the structural stiffness. 
    • HVSA-actuated manipulator
      • Impact force can be absorbed when the contact occurs.
      • Contact force can be estimated by measuring passive elastic angle in the HVSA.
    • Features of HVSA-actuated manipulator
      • Two motors at the wrist of the manipulator are replaced with two HVSA.
      • Simultaneous control of position and stiffness can be achieved.

               < HVSA-actuated manipulator>
    • Position and stiffness control


  • Robotic assembly using HVSA-actuated manipulator
    • Square peg assembly
      • Assembly tolerance: 0.1 mm
      • Maximum assembly force: Less than 100 N
    • 6 DOF manipualtor with force/torque sensor
      • Maximum insertion speed: 30 mm/s
    • HVSA-actuated manipulator
      • Maximum insertion speed: 200 mm/s
      • Fast assembly while maintaining low contact force can be achieved.

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