Damping Coefficients and Torque Calculations for the Joint's Stability of Lower Extremity Exoskeleton Robots

Abstract

Exoskeleton robots are wearable electromechanical structures which can work interacting with human limbs. Theserobotsareused as assistivelimbs, rehabilitationandpoweraugmentationpurposesforelderly or paralyzedpersons andhealthypersons respectively.Human body neuro-muscular system varies the stiffness and damping of the human joints regularly and thus provides flexible and stable movement capability with minimum energy consumption. Damping coefficients and torques in the joints needs to be adjusted with the change of stiffness to provide stable behavior during walking cycles. Magneto-rheological brake are the passive actuators that can adjust the damping torques in a very short response time. However, the maximum values of damping coefficients and torques are needed for the design of MR dampers to be used in the joints of exoskeleton robots. Shamaei et. al. (2013) derived a set of statistical equations to predict thejoint stiffnessin a gait cycle for the persons with different height and weights. In this paper, the maximum values of damping coefficients and torques are calculated for the design of MR dampers to provide stability in the joints of exoskeleton robots. The results can be used as initial design criteria of MR dampers which will be added to the biomimetic joints of exoskeleton robots, prostheses, ortheses and humanoid robots

Keywords

• Exoskeleton robot
• Orthesis
• Prosthesis
• Variable stiffness actuator
• Variable damping actuator
• Magneto-rheological brake
• Stability

Alt Uzuv Dış İskelet Robot Eklemlerinde Kararlılık İçin Sönümleme Katsayıları ve Momentlerinin Hesaplanması

Abstract

Dış iskelet robotlar, insan uzuvları ile etkileşim halinde çalışan, giyilebilir elektromekanik yapılardır. Bu robotlar, yürüme engeli olan ya da yaşlı kişilerde yardımcı uzuv, felçli kişilerde rehabilitasyon ve sağlıklı insanlarda güç artırımı amacı ile kullanılmaktadır. İnsan vücudunun sinir-kas sistemi, bağlı bulundukları eklemlerde sertlik ve sönümlemeyi devamlı değiştirerek minimum enerji sarfiyatı ile esnek ve kararlı bir hareket kabiliyeti sağlamaktadır. Yürüme sırasında eklemlerin sertliğinin değişmesi ile birlikte kararlı bir yürümenin gerçeklenebilmesi için eklemlerdeki sönümleme katsayılarının ve sönümleme momentlerinin eş zamanlı olarak değiştirilmesi gerekmektedir. Manyeto-reolojik (MR) frenler, bu farklı sönümleme momentlerini en hızlı şekilde ayarlayabilen pasif eyleyicilerdir. Ancak, dış iskelet robotların eklemlerinde kullanılacak MR fren tasarımları için istenen maksimum sönümleme katsayısı ve sönümleme momenti değerlerinin bilinmesi gerekmektedir. Shamaei ve arkadaşları (2013) biyomekanik bir çalışma gerçekleştirerek farklı boy ve kilolardaki kişiler için yürüme sırasında eklem sertlik katsayısı değişimini genel istatiksel formüller ile ifade etmişlerdir. Bu makalede; alt uzuv dış iskelet robotların eklemlerinde kararlı bir yürüme davranışını sağlayabilecek MR fren tasarımları için gerekli olan sönümleme katsayısı ve momentlerinin maksimum değerleri hesaplanmıştır. Elde edilen sonuçlar, dış iskelet robotların, ortezlerin, protezlerin ve insansı robotların biyomimetik eklemelerine yerleştirilecek MR frenlerin başlangıç tasarım kriteri olarak kulllanılabilecektir.

Keywords

• Dış iskelet robot
• Ortez
• Protez
• Sertliği değiştirilebilir eyleyici
• Sönümlemesi değiştirilebilir eyleyici
• Manyeto-reolojik fren
• Kararlılık

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