Latest Papers

ASME Journal of Mechanisms and Robotics

  • Mechanical Characterization of Supernumerary Robotic Tails for Human Balance Augmentation
    on August 31, 2023 at 12:00 am

    AbstractHumans are intrinsically unstable in quiet stance from a rigid body system viewpoint; however, they maintain balance, thanks to neuro-muscular sensory control properties. With increasing levels of balance related incidents in industrial and ageing populations globally each year, the development of assistive mechanisms to augment human balance is paramount. This work investigates the mechanical characteristics of kinematically dissimilar one and two degrees-of-freedom (DoF) supernumerary robotic tails for balance augmentation. Through dynamic simulations and manipulability assessments, the importance of variable coupling inertia in creating a sufficient reaction torque is highlighted. It is shown that two-DoF tails with solely revolute joints are best suited to address the balance augmentation issue. Within the two-DoF options, the characteristics of open versus closed loop tails are investigated, with the ultimate design selection requiring trade-offs between environmental workspace, biomechanical factors, and manufacturing ease to be made.

Experimental Verification of Kinematics and Kinetics in a Biomimetic Bipedal Robot


This article presents experimental test results for joints used in a biomimetic bipedal robot. In this work, magnetic resonance imaging (MRI) and computed tomography (CT) scans are utilized to inform the design of joints of similar size and function to the biological counterparts. Three lower body joints, to be actuated by artificial muscles, were designed and constructed. Then the range of motion and passive stiffness were tested. The knee joint consists of a four-bar mechanism that provides increased extensor moment arm as the joint becomes more flexed, a “screw home” locking mechanism analog, and large contact surfaces for force distribution. The hip, ankle, and foot are hybrid hard-soft joints, consisting of a ball and socket held together with an outer, inflatable sleeve made from a braided pneumatic actuator (BPA) material. These joints provide a novel way for real-time stiffness adjustments and energy storage during the gait cycle. Results show that the physical knee prototype matches the previous simulation of joint movement (Steele, A., Hunt, A., and Etoundi, A., 2018, “Biomimetic Knee Design to Improve Joint Torque and Life for Bipedal Robotics,” Bristol, UK.). A linear relationship exists between the increase in angle and the force required to bend the hybrid joints. First, this article documents a process that others may use to develop their own joints. Second, the range of motion and passive forces in the hybrid hard-soft joints is characterized, which will enable improved control of the joints and inform other researchers to whether a hybrid joint design is appropriate for their applications. This process has several applications in prosthetic designs and robotics.

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