Elastic Actuator Design Based on Torsion of Prismatic Shafts for Robotic Applications

Öz

Actuators are the most critical components that determine the overall performance of any robotic system. For many years, the lack of suitable actuators has hampered the development of high-performance machines or robots that can compete with living organisms in terms of motion, safety, and energy efficiency. Adaptation properties of biological systems to environmental variables; for example, the control performance of biological muscle with variable stiffness properties exceeds the performance of mechanical devices. The variable stiffness characteristics of elastic actuators are quite different from the operating principle of conventional solid actuators that require accurate reference trajectory tracking used in industrial robots. Although there has been a lot of work on the design of elastic actuators in recent years, a low-cost and compact elastic actuator that can be used in place of standard rigid servo actuators is not yet available. In this study, a standard servo motor, which is widely used in robotic applications and hobby vehicles due to its low cost, has been transformed into an elastic actuator by an elastic coupling attached to the gear system. The elastic coupling consists of four small shafts with a prismatic cross section placed on the circular disk, and the stiffness of the actuator is adjusted by varying the clutch length of the prismatic shafts. In the study, this innovative design is explained, then the equations expressing the variation of the torsional stiffness of the prismatic shaft with the coupling length and solutions of these equations are given.

Anahtar Kelimeler

• elastic
• actuator
• robot
• servo
• clutch
• shaft

Robotik Uygulamalar İçin Prizmatik Kesitli Millerin Burulması Esasına Dayanan Elastik Eyleyici Tasarımı

Öz

Eyleyiciler herhangi bir robotik sistemin genel performansını belirleyen en önemli bileşenlerdir. Uzun yıllar boyunca, uygun eyleyicilerin eksikliği, hareket, güvenlik ve enerji verimliliği açısından canlı organizmalarla rekabet edebilecek yüksek performanslı makinelerin veya robotların gelişmesini engellemiştir. Biyolojik sistemlerin çevresel değişkenlere adaptasyon özellikleri; Örneğin, değişken sertlik özelliklerine sahip biyolojik kasın kontrol performansı, mekanik cihazların performansını aşmaktadır. Elastik eyleyicilerin değişken rijitlik özellikleri, endüstriyel robotlarda kullanılan konum hassasiyeti gerektiren geleneksel rijit eyleyicilerin çalışma prensibinden oldukça farklıdır. Son yıllarda elastik eyleyicilerin tasarımı üzerine çok sayıda çalışma yapılmış olmasına rağmen, yaygın olarak kullanılan basit rijit servo eyleyiciler yerini alabilecek düşük maliyetli ve kompakt bir elastik eyleyici henüz mevcut değildir. Bu çalışmada, düşük maliyetli olması nedeniyle robotik uygulamalarında ve hobi araçlarında çok yaygın olarak kullanılan standart bir servo motor, dişli sistemine eklenen elastik bir kavrama vasıtasıyla sertliği değiştirilebilir bir eyleyiciye dönüştürülmektedir. Elastik kavrama, silindirik diskin üzerine yerleştirilmiş prizmatik kesitli dört küçük yayrak yaydan oluşmakta ve eyleyicinin sertliği, prizmatik yayların (millerin) kavrama uzunluğunu değiştirerek ayarlanmaktadır. Çalışmada, bu yenilikçi tasarım tanıtılmış, ardından prizmatik milin burulma rijitliğinin kavrama uzunluğu ile değişimini ifade eden denklemler ve bu denklemlerin çözümleri verilmiştir.

Anahtar Kelimeler

• elastik
• eyleyici
• robot
• servo
• kavrama
• mil

Kaynakça

1. Catalano, M., Grioli, G., Garabini, M., Bonomo, F., Mancini, M., Tsagarakis, N., & Bicchi, A., (2011). Vsa-cubebot: a modular variable stiffness platform for multiple degrees of freedom robots, IEEE International Conference on Robotics and Automation, Shanghai, China, 5090-5095.
2. Hollander, K.W., Ilg R., Sugar, T.G., & Herring, D., (2006). An efficient robotic tendon for gait assistance, Journal of Biomechanical Engineering, 128(5), 788–791.
3. Hurst, J.V., Chestnutt, J., & Rizzi, A., (2004). An Actuator with Mechanically Adjustable Series Compliance, Carnegie Mellon University, USA, CMU-RI-TR- 04-24.
4. Jafari, A., Tsagarakis, N., Vanderborght, B., & Caldwell, D., (2010). A novel actuator with adjustable stiffness (AwAS). IEEE/RSJ International Conference on Intelligent Robots and Systems, Taipei, Taiwan, 4201–4206.
5. Jafari, A., Tsagarakis, N., & Caldwell, D.G., (2011). AwAS-II: A new actuator with adjustable stiffness based on the novel principle of adaptable pivot point and variable lever ratio, IEEE International Conference on Robotics and Automation, Shangai, China, 4638–4643.
6. Lee, C., Kwak, S., & Oh, S., (2017). Generalization of Series Elastic Actuator Configurations and Dynamic Behavior Comparison, MDPI Actuators Journal. 1-26. Migliore, S.A., Brown, E.A., & De Weerth, S.P., (2005). Biologically inspired joint stiffness control, IEEE International Conference on Robotics and Automation, Spain, 4519–4524.
7. Pratt G.A., & Williamson M., (1995). Series elastic actuators, IEEE International Workshop on Intelligent Robots and Systems, USA, 399–406.
8. Quy, H.V., Aryananda, L., Sheikh, F.I., Casanova F., & Pfeifer, R., (2011). A novel mechanism for varying stiffness via changing transmission angle, IEEE International Conference on Robotics and Automation, Shanghai, China, 5076-5081.

9. Tonietti, G., Schiavi, R., & Bicchi, A., (2005). Design and control of a variable stiffness actuator for safe and fast physical human/robot interaction. IEEE International Conference Robotics and Automation, Spain, 526–531.
10. Van Ham R., S. Thomas, B. Vanderborght, K. Hollander, & D. Lefeber, (2009). Compliant actuator designs: review of actuators with passive adjustable compliance/controllable stiffness for robotic applications, IEEE Robotics and Automation Magazine 16(3), 81–94.
11. Van Ham, R..,Vanderborght, B., Van Damme, M., Verrelst, B., & Lefeber, D., (2007). MACCEPA, the mechanically adjustable compliance and controllable equilibrium position actuator: Design and implementation in a biped robot. Robotics and Autonomous Systems, 55(10), 761–768.
12. Vanderborght, B., Albu-Schaeffer, A., Bicchi, A., Burdet, E., Caldwell, D., & Carloni, R., (2013). Variable impedance actuators: A review, Robotics and Autonomous Systems, 61(12), 1601–1614.
13. Vanderborght B., A. Albu-Schaeffer, A. Bicchi, E. Burdet, D. Caldwell, R. & Carloni, M. (2012), Variable Impedance Actuators: Moving the Robots of Tomorrow, IEEE/RSJ International Conference on Intelligent Robots and Systems, Algarve, Portugal, 5454-5455.
14. Wolf, S., Hirzinger, G., (2008). A new variable stiffness design: Matching requirements of the next robot generation. IEEE International Conference on Robotics and Automation, California, USA, 1741-1746.