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 range | 0 - 104 mm | Stiffness range | 0.87 - 27.3 N/mm | Max. speed | 1 m/s |
- 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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