VSAs @ IRL

Three types of Variable Stiffness Actuators @ IRL

• Research Background

  • Simultaneous control of position and stiffness is required for the dexterous manipulation.

  • Compliant motion is advantageous to contact motion as well as dynamic motion.

• Research Objectives

  • Development of an actuator unit capable of providing simultaneous control of position and stiffness

  • Development of a small and light-weight actuator unit for robotic applications

• Research Outcomes

• Related Documents

  • Jae-Bok Song and Byeong-Sang Kim, Three Types of Dual Actuator Units for Variable Impedance Actuation, Variable Impedance Actuation Workshop (VIA 2010) .

  • Jae-Bok Song, Variable Stiffness Actuation based on Dual Actuators Connected in Series and Parallel, Robotics Science and Systems Workshop (RSS2008).

Hybrid type  Variable Stiffness Actuators (HVSA)

• Researchers

  • Byeong-Sang Kim (Ph.D., lovidia@gmail.com)

• Research Period

  • 2009. 06. ~ Current.

• Research Outcomes

  • The adjustable moment arm mechanism is adopted for the stiffness variation.

  • The modified planetary gear train is used for the compact design of actuator unit.

  • Constant stiffness irrespective of passive deflection can be achieved.

• Control of Position and Stiffness

• Hitting Blocks

  • Fast retraction motion is required to avoid collapse of the stack of the blocks.

  • Using variable stiffness control is advantageous to dynamic motion.

• Playing Darts

  • From the conversion of potential energy to kinetic energy, the joint velocity can be increased faster than the motor velocity.

• Related Papers/Patents

  • • Paper 1. Byeong-Sang Kim and Jae-Bok Song, Design and Control of a Variable Stiffness Actuator based on Adjustable Moment Arm, IEEE Transactions on Robotics (Accepted as short paper)

    • Paper 2. Byeong-Sang Kim and Jae-Bok Song, Hybrid Dual Actuator Unit: A Design of a Variable Stiffness Actuator based on an Adjustable Moment Arm Mechanism, Proc. of IEEE Int. Conf. on Robotics and Automation (ICRA 2010), pp. 1655-1660, 2010. (ICRA2010 Best Automation Paper Finalist) 

• • Patent 1. Active Actuator Module (10-2010-0030725, Domestic)

Parallel type  Variable Stiffness Actuators (PVSA)

• Researchers

  • Ki-Hoon Nam (M.S., nkh135@korea.ac.kr), Byeong-Sang Kim (Ph.D., lovidia@gmail.com)

• Research Period

  • 2008. 03. ~ 2010. 02.

• Research Outcomes

  • Two actuators are antagonistically connected to control the position and stiffness simultaneously.

  • The linear characteristic of spring is converted to nonlinear via the cam-follower mechanism.

  • The dual cam-follower mechanism is used for the compact design of an actuator unit.

  • Collision safety is mechanically guaranteed when the external torque is larger than the user-specified force.

• Position and stiffness control

  • (a) → (b): Increase of joints stiffness while maintaining position

  • (a) → (c): Position while maintaining joint stiffness

  • (a) → (d): Simultaneous control of position and stiffness

• Collision Safety 

  • The features of collision safety can be obtained by designing the cam profile.

  • AAM: Antagonistic Actuation Mode for simultaneous control of position and stiffness.

  • CSM: Collision Safe Mode for collision safety.

• Demonstration

  • Hammering a Nail

    • High impact force can be obtained from the conversion of potential energy to kinetic energy. 

    • Damage of gear reducer and motor can be avoided since the passive element absorbs the impact force.

  • Cutting a Zucchini

    • High impact force can be obtained from the conversion of potential energy to kinetic energy.

    • Damage of gear reducer and motor can be avoided since the passive element absorbs the impact force.

• Related Papers/Patents

  • • Paper 1. Ki-Hoon Nam, Byeong-Sang Kim and Jae-Bok, Song, Compliant Actuation of Parallel-type Dual Actuator Unit based on Antagonistic Actuation, Journal of Mechanical Science and Technology (JMST), Vol. 24, No. 11, pp. 2315-2321, 2010. 

• • Patent 1. Active Actuator Module and Active Actuator System Having the Same (10-2009-0092786, Domestic)

Serial type  Variable Stiffness Actuators (SVSA)

• Researchers

  • Byeong-Sang Kim (Ph.D., lovidia@gmail.com), Jung-Jun Park (Ph. D, hantiboy@gmail.com)

• Research Period

  • 2004. 10. ~ 2008. 04.

• Research Outcomes

  • Two actuators are connected in series via the planetary gear train.

  • The positioning actuator (PA) has high gear ratio for high poisoning accuracy.

  • The stiffness actuator (SA) has low gear ratio for soft manipulation.

  • The joint stiffness can be adjusted by controlling the current of the SA.

  • Joint torque can be estimated by measuring the encoder information provided by two encoders.

• Internal motion of SVSA

• Environment Estimation

  • Stiffness estimation: Stiffness of the environment can be estimated by measuring the contact force and the displacement.

  • Surface estimation: The shape of the environment can be estimated while maintaining low contact force.

• Wall Following

  • Contact force can be modulated by using force estimation feature of SVSA.

  • With force estimation: The manipulator can follow an arbitrary shaped wall while maintaining a small variation of contact force.

  • Without force estimation: The contact force varies as the manipulator follows the wall.

• Related Papers/Patents

  • Paper 1. Byeong-Sang Kim, Jung-Jun Park, Jae-Bok Song, Serial-type Dual Actuator Unit with Planetary Gear Train: Basic Design and Applications, IEEE/ASME Transactions on Mechatronics (TMECH), Vol. 15, No. 1, pp. 108-116, 2010. 

• • Paper 2. Byeong-Sang Kim, Jae-Bok Song, Environment Estimation using Serial-type Dual Actuator Unit Capable of Force Estimation, Proc. of Int. Conf. on Ubiquitous Robots and Ambient Intelligence (URAI 2008), pp. 395-399, 2008.11. 

• • Paper 3. Byeong-Sang Kim, Jung-Jun Park, Jae-Bok Song, Double Actuator Unit with Planetary  Gear Train for a Safe Manipulator, Proc. of IEEE Int. Conf. on Robotics and Automation (ICRA 2007), pp. 1146-1151, 2007. 

• • Paper 4. Byeong-Sang Kim, Jung-Jun Park, Jae-Bok Song, Improved Manipulation Efficiency using a Serial-type Dual Actuator Unit, Proc. of Int. Conf. on Control, Automation and Systems (ICCAS 2007), pp. 30-35, 2007.10. 

• • Patent 1: Double Actuator Unit, Double Actuator Apparatus with the same and the method for controlling the Double Actuator Apparatus (10-0835908)

- Last updated: 2012. 5. 9