Observer-based fractional-order dynamic terminal sliding mode control of active shock absorbing prostheses for lower limb amputees.

Recent biomedical engineering developments have empowered prosthetic devices to evolve from purely mechanical devices to more sophisticated controlled devices, allowing amputees to perform advanced locomotion modes such as passing stairs and walking on sloped surfaces. However, the strongly coupled nonlinear system dynamics make it difficult for the lower-limb prosthesis (LLP) to adapt to complex tasks and isolate the vibrations and acceleration from the residual limb soft tissue. In this regard, realizing the potential of active LLPs to increase user mobility and efficiency requires reliable, stable, and intuitive control strategies to provide a comfortable gait quality.

Soft variable structure control of linear fractional-order systems with actuators saturation.

In this paper, a new method of soft variable structure control for Fractional-Order System (FOS) is proposed to achieve faster response while the control signal is continuous and satisfies actuators' constraints. Our proposed method, by describing a desired commensurate FOS, with the help of a pole placement algorithm and applying an optimization routine, in the form of a procedure, leads the system to the desired character. The routine is done by solving an optimization problem subject to a control signal constraint qua we obtain the fastest response possible in the sense of stability region.