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 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.