Safety, compliance and human-friendliness are some of the trending keywords in robotics nowadays. The most significant reason for the increase in the popularity of these keywords is the continuous development of service robots interacting with its environment, including human beings. Following this trend, Series-elastic Actuators (SEAs) have received significant attention as a next-generation actuator in the robotics field. Consequently, numerous researchers have developed various SEA since its introduction in the 1990s. In spite of the development and applications of many SEAs, there are still some challenging problems such as backlash of the gear reducer, encoder resolution problem, spring non-linearity, limited working range, so forth, are needed to be solved.
To address the mentioned problem, Motion Control Lab is developing rotary-type Series Elastic Actuators (SEAs) with the following research topics.
1.Actuator transmission design
2.Elastic element design and analysis
3.The minimisation of nonlinear effect in SEAs such as backlash, friction and encoder resolution.
4.Development of performance criteria for SEAs
5.Force control and (link-side) position control
6.Interactive force (impedance) control with the environment
7.Human-robot interactive applications
A novel SEA mechanism called compact Planetary-geared Elastic Actuator (cPEA) has developed through this project.The proposed cPEA utilizes the planetary gear as the power transmission. The design is compact to minimize the backlash in SEA motions. Series elasticity is achieved by using torsional spring which is placed in the redundant space of mechanism.
Motion Control Lab aims to increase the performance of the proposed SEA system significantly. Following this objective, we have developed Harmonic-geared Elastic Actuator (HEA), a second generation rotary-type SEA that allows more compact design, precise movement, and torque measurement.
1.International journal: Residual-Based External Torque Estimation in Series Elastic Actuators Over a Wide Stiffness Range: Frequency Domain Approach, Jinoh Lee, Chan Lee, Nikolaos Tsagarakis and Sehoon Oh, IEEE Robotics and Automation Letters, vol. 3, no. 3, pp. 1442-1449, Jul. 2018. (Jinoh Lee and Chan Lee are co-first authors)
2.International journal: Development of Force Observer in Series Elastic Actuator for Dynamic Control, Yongsu Park, Nicholas Paine and Sehoon Oh, IEEE Transactions on Industrial Electronics, vol. 65, no. 3, pp. 2398-2407, Aug. 2017.
3.International journal: Generalization of a Series Elastic Actuator Configurations and Dynamic Behavior Comparison, Chan Lee, Suhui Kwak, Jihoo Kwak and Sehoon Oh, Actuators, vol. 6. no. 3, Aug. 2017.
4.International journal: High Precision Robust Force Control of a Series Elastic Actuator, Sehoon Oh and Kyoungchul Kong, IEEE/ASME Transactions on Mechatronics, vol. 22, no. 1, pp. 71-80, Feb. 2017.
5.International conference: Comparison of resonance ratio control and inner force control for series elastic actuator, Su-Hui Kwak and Sehoon Oh, pp. 7583-7588, Conf. of IECON, 2017
6.International conference: Robust assistive force control of leg rehabilitation robot, Chan Lee and Sehoon Oh, pp. 634-638, Conf. of AIM, 2017
7.International conference: Interactive force control of an elastically actuated bi-articular two-link manipulator, Chan Lee and Sehoon Oh, pp. 2917-2922, Conf. of ICRA, 2017
8.International conference: Wire-tension control using Compact Planetary geared Elastic Actuator, Jihoo Kwak, Chan Lee, Junyoung Kim, Shinyoon Kim and Sehoon Oh, pp. 3684-3689, Conf. of ICRA, 2017
9.International conference: Configuration and performance analysis of a compact planetary geared Elastic Actuator, Chan Lee, Sehoon Oh, pp. 6391 – 6396, Conf. of IECON, 2016
10.International conference: Maximum torque generation of SEA under velocity control, Lee Chan, Wiha Choi, and Sehoon Oh, pp. 16-23, Proc. of IEEE AMC, 2016
11.International conference: Force control and force observer design of series elastic actuator based on its dynamic characteristics, Sehoon Oh, Chan Lee and Kyounchul Kong, Proc. of IECON, 2015
12.US Patent: Elastically Actuating Device, 15-564091, Chan Lee and Sehoon Oh. (pending)
This work was supported by,
1.the Ministry of Trade, Industry and Energy of Korea(MOTIE) (NO. 10080355)
2.the National Research Foundation of Korea(NRF) grant(NRF-2016R1A2B4016163)
Global PH.D Fellowship Program funded by the Ministry of Education (NRF-2016H1A2A1907509).