DESIGN, CONTROL and EVALUATION of EDUCATIONAL DEVICES
with SERIES ELASTIC ACTUATION
Mechatronics Engineering, MSc. Thesis, 2017
Assoc. Prof. Volkan Patoglu (Thesis Advisor)
Assoc. Prof. Ahmet Onat
Prof. Çağatay Başdoğan
Date & Time: 27th, 2017 – 2:00 PM
Place: FENS G015
Keywords : physical human robot interaction, series elastic actuation, educational
robots, force control achitectures
STEM is a curriculum targeted to be used in all educational levels to support the education of students in four specific disciplines(science, technology, engineering and mathematics) with an interdisciplinary and applied approach. Recently, as computational thinking and strong foundation in computing have been identified as defining features that are likely to strongly shape the future, major research and development efforts 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 fields more understandable and enjoyable, but also to make them more accessible and affordable 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-flexure pivot between the actuator and the handle, whose deflections 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 effective 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 benefit 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 efficacy of a set of laboratory assignments that allow students to experience the performance trade-offs 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 different levels of stiffness values to its compliant element, and characterize the effects of these design choices on the closed-loop force control performance of the device. We have evaluated the efficacy of introducing HandsOn-SEA into engineering education by testing the device in a senior level robotics course and providing evidence that the device is effective in providing experience on admittance control architectures for pHRI and instilling intuition about fundamental trade-offs 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 algorithms and present an interactive tool for teaching several sorting and search algorithms with such educational devices. The addition of haptic feedback to teach algorithmic thinking is advantageous as haptic feedback enables an effective means of enforcing pairwise comparisons while ensuring data hiding, a key component in explaining several core concepts while teaching several sorting and search algorithms. Furthermore, physical interactions with virtual learning environments paves the way for more flexible, engaging and exciting learning experiences, surpassing what can be achieved by basic physical elements or applications based on pure visualization. We have evaluated the efficacy of introducing haptic feedback into teaching algorithmic thinking by testing the proposed force-feedback application with several student groups and provide evidence that the approach is effective in instilling the core principle of formulating a precise sequence of instructions for performing sorting tasks, in a technology independent manner.