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 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..