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VSA-actuated System

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 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

  • Demonstration on grasping objects
    • Grasping graphite lead
      • 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)

    • Grasping tofu
      • 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 tofu is deformed by the grasping force.

  • Related Papers/Patents
    • Byeong-Sang Kim, Jae-Bok Song, Object Grasping Using a 1 DOF Variable Stiffness Gripper Actuated by a Hybrid Variable Stiffness Actuator, Proc. of IEEE Int. Conf. on Robotics and Automation, pp. 4620-4625, 2010. 

HVSA-actuated Manipulator
  • Comparison between conventional manipulator and a HVSA-actuated manipulator
    • Features of HVSA-actuated manipulator
      • Low impedance for the low-frequency range can be provided.
      • Low impedance for the high-frequency range converges the structural stiffness. 
      • Impact force can be absorbed when contact occurs.
      • Contact force can be estimated by measuring passive elastic angle in the HVSA.
      • 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 a 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.
  • Related Papers/Patents
    • Byeong-Sang Kim, Young-Loul Kim, Jae-Bok Song, Preliminary Experiments on Robotic Assembly using a Hybrid-type Variable Stiffness Actuator, IEEE/ASME International Conference on Advanced Intelligent Mechatronics, pp. 1076-1080, 2011..