Design, control and evaluation of educational devices with series elastic actuation

摘要

STEM is a curriculum targeted to be used in all educational levels to support the education of students in four speci c disciplines{science, technology, engineering and mathematics{in an interdisciplinary and applied approach. Recently, as computational thinking and strong foundation in computing have been identi ed as de ning features that are likely to strongly shape the future, major research and development e orts have been put together to also promote computing by programs like STEM+C, where \C" further emphasizes computing. STEM+C not only aims to make the topics concerning these elds more understandable and enjoyable, but also to make them more accessible and a ordable for every group in the society. STEM+C promotes active learning, in other words, direct involvement of the student in class instead of passively listening, as an essential feature of an ideal learning environment and advocates for the use of technology and hands-on experience for strengthening the understanding of fundamental concepts. We propose HandsOn-SEA, a low cost, single degree-of-freedom, force-controlled educational robot with series elastic actuation, to enable physical interactions with educational tools, helping solidify STEM+C concepts. The novelty of the proposed educational robot design is due to the deliberate introduction of a compliant cross- exure pivot between the actuator and the handle, whose de ections are measured to estimate interaction forces and to perform closed-loop force control. As an admittance-type robot, HandsOn-SEA relies on a force control loop to achieve the desired level of safety and transparency during physical interactions and complements the existing impedance-type force-feedback educational robot designs. HandsOn-SEA also serves as a building block of more complex, higher degrees of freedom force-feedback robot designs. HandsOn-SEA is e ective in the education of STEM+C concepts, as physical interaction with virtual educational environments not only ensures a higher level of student engagement by adding new bi-directional sensorimotor pathway for active student perception, but also improves student motivation by enabling more engaging and exciting learning experiences. Furthermore, HandsOn-SEA allows for quantitative measurements of student progress and enables visually impaired students to bene t from a larger range of educational tools, by replacing certain visual presentations with haptic feedback. Along these lines, we present the integration of HandsOn-SEA into STEM+C education, by providing guidelines for the use of the device for teaching fundamental concepts in physical human-robot interaction (pHRI) at the undergraduate level and for teaching algorithmic thinking at both the high school and undergraduate levels. For pHRI education, we provide a set of laboratory modules with HandsOn-SEA to demonstrate the synergistic nature of mechanical design and control of force feedback devices. In particular, we propose and evaluate e cacy of a set of laboratory assignments that allow students to experience the performance trade-o s inherent in force control systems due to the non-collocation between the force sensor and the actuator. These exercises require students to modify the mechanical design in addition to the controller of the educational device by assigning di erent levels of sti ness values to its compliant element, and characterize the e ects of these design choices on the closed-loop force control performance of the device. We have evaluated the e cacy of introducing HandsOn-SEA into engineering education by testing the device in a senior level robotics course and provide evidence that the device is e ective in providing experience on admittance control architectures for pHRI and instilling intuition about fundamental trade-o s in the design and control of force-feedback devices. To promote algorithmic thinking, we propose to use force-feedback educational robotic devices for hands-on teaching of algorit