This paper discusses the actuator-level control of Valkyrie, a new humanoid robot designed by NASA’s Johnson Space Center in collaboration with several external partners. We focus on several topics pertaining to Valkyrie’s series elastic actuators including control architecture, controller design, and implementation in hardware. A decentralized approach is taken in controlling Valkyrie’s many s...

This paper deals with impedance control of a rotary Series Elastic Actuator designed to assist in flexion/extension of the knee joint during physical therapy. The device includes a DC motor, a worm gear and a customized torsion spring. Since the elastic element is the most important component in the actuator design, a finite element analysis is used to meet the specific requirements of knee ass...

The generalized plane quasistatic deformations of linear piezoelectric laminated plates are analyzed by the Eshelby–Stroh formalism. The laminate consists of homogeneous elastic or piezoelectric laminae of arbitrary thickness and width. The three-dimensional differential equations of equilibrium for a piezoelectric body are exactly satisŽ ed at every point in the body. The analytical solution i...

The majority of the commercial transtibial prostheses are purely passive devices. They store energy in an elastic element during the beginning of a step and release it at the end. A 75 kg human, however, produces on average 26 J of energy during one stride at the ankle joint when walking at normal cadence and stores/releases 9 J of energy, contributing to energy efficient locomotion. According ...

The behavior of an exponentially graded hybrid cylindrical shell subjected to an axisymmetric thermo-electro-mechanical loading placed in a constant magnetic field is investigated. The hybrid shell is consisted of a functionally graded host layer  embedded with pyroelectric layers as sensor and/or actuator  that can be imperfectly bonded to the inner and the outer surfaces of a shell. The shell...

The use of actuators with inherent compliance, such as series elastic actuators (SEAs), has become traditional for robotic systems working in close contact with humans. SEAs can reduce the energy consumption for a given task compared to rigid actuators, but this reduction is highly dependent on the design of the SEA's elastic element. This design is often based on natural dynamics or a paramete...

Most robot designers make the mechanical interface between an actuator and its load as stiff as possible[9][10]. This makes sense in traditional position-controlled systems, because high interface stiffness maximizes bandwidth and, for non-collocated control, reduces instability. However, lower interface stiffness has advantages as well, including greater shock tolerance, lower reflected inerti...

This paper presents the modeling of the light-weight BioRob robot arm with series elastic actuation for simulation and controller design. We describe the kinematic coupling introduced by the cable actuation and the robot arm dynamics including the elastic actuator and motor and gear model. We show how the inverse dynamics model derived from these equations can be used as a basis for a position ...

Joint stiffness of an elastic-joint robot can be changed according to joint requirements. A series elastic actuator (SEA) reduce the contact between body and environment or human, which further ensure interactive operation in a human–machine-compatible environment. However, introduction SEA improves complexity dynamics model. In this paper, we propose control schema based on link-side accelerat...