Reporter: Associate Prof. Xuepeng Cao
Time & Day: 6:30-8:00 pm, Nov. 29,2019
Location: Lecture Hall on the fourth floor at School of Construction Machinery
Biography:
Xuepeng Cao is an associate professor at the department of mechatronic engineering, School of construction machinery, Chang’an University. He obtained his PhD degree at Southwest Jiaotong University in 2010. With the full-funding of China Scholarship Council (SCS), he went to Tampere University at Finland to research as a visiting scholar from 2st November, 2018 to 2st November, 2019. His research interests include machine automation, energy-efficiency of fluid power systems, and hydraulic system self-adpted to deepwaterenvironment.
In the lecture, he introduced Tampere University, intelligent hydraulic and automation (IHA), mainly study work, interest experiences during visiting days and Finnish life. The main lecture focused on the control and application of hydraulic series elastic actuators, and the specific contents are asfollows.
Lightweight arms with electrical servomotor drives have demonstrated outstanding performance and speed in exoskeletons, prosthesis, and legged robot applications. They all share a similarity in actuation, which is based on series elastic actuators (SEAs). In SEAs, the system benefits from known compliance in the actuation that improves the overall performance, especially in contact with an environment that can have an unknown stiffness in assembly tasks. In some of these cases, harmonic drives or gears on the power transmission lines create the robot’s compliance. For hydraulically actuated SEAs, the previous researches addressed the SEA challenges for lightweight hydraulic manipulators. However, this study focuses on the design and control architecture of SEAs in heavy-duty manipulation having hydraulic load dynamics with variable stiffness or damping of fluid flexibility. The system faces challenging issues of payload dynamics and compressibility of fluid with high order system. A hydraulic SEA concept is designed, and a fifth-order state space SEA model is feedback controlled in a free space motion to demonstrate load dynamics of hydraulic actuation. In addition, a P controller and a controller based on integral of time-weighted absolute error (ITAE) are designed. The simulation results show the latter has better performance in the spring deflection of the SEA. Finally, a mixed working condition that changes from a purely inertia payload to an inertia and elastic reaction force is designed to examine the switching smoothness for varying payloads, and the control adaptability of controllers in different workingconditions.