12 research outputs found
Using an enhanced homotopy perturbation method in fractional differential equations via deforming the linear part
AbstractConvergence and stability are main issues when an asymptotical method like the Homotopy Perturbation Method (HPM) has been used to solve differential equations. In this paper, convergence of the solution of fractional differential equations is maintained. Meanwhile, an effective method is suggested to select the linear part in the HPM to keep the inherent stability of fractional equations. Riccati fractional differential equations as a case study are then solved, using the Enhanced Homotopy Perturbation Method (EHPM). Current results are compared with those derived from the established AdamsâBashforthâMoulton method, in order to verify the accuracy of the EHPM. It is shown that there is excellent agreement between the two sets of results. This finding confirms that the EHPM is powerful and efficient tool for solving nonlinear fractional differential equations
A powered lower limb orthosis to assist the gait of incomplete spinal cord injured patients
This paper addresses the mechanical design and control of a
new active stance-control knee-ankle-foot orthosis. The orthosis
is intended to provide gait assistance for incomplete spinal cord
injured patients with functional hip muscles, but partially
denervated knee and ankle muscles. This device consists of a
passive compliant joint that constrains ankle plantar flexion,
along with a powered knee unit that prevents knee flexion
during stance and controls flexion-extension during swing. For
this purpose, the knee joint incorporates a controllable
mechanical locking system and an electrical DC motor. Based
on human walking biomechanics, a hybrid control model is
proposed. This model takes into account the parameters of the
orthosis and the characteristics of the gait cycle, which is
divided in eight different phases. A fractional order controller is
designed following decision based control techniques.Postprint (published version
A powered lower limb orthosis to assist the gait of incomplete spinal cord injured patients
This paper addresses the mechanical design and control of a
new active stance-control knee-ankle-foot orthosis. The orthosis
is intended to provide gait assistance for incomplete spinal cord
injured patients with functional hip muscles, but partially
denervated knee and ankle muscles. This device consists of a
passive compliant joint that constrains ankle plantar flexion,
along with a powered knee unit that prevents knee flexion
during stance and controls flexion-extension during swing. For
this purpose, the knee joint incorporates a controllable
mechanical locking system and an electrical DC motor. Based
on human walking biomechanics, a hybrid control model is
proposed. This model takes into account the parameters of the
orthosis and the characteristics of the gait cycle, which is
divided in eight different phases. A fractional order controller is
designed following decision based control techniques