Control architecture of an antagonistically actuated wearable assistive device

Wearable assistive devices assist rehabilitation and recuperation; however, their development is impeded by traditional control paradigms. Presented is a novel control structure for a WAD, whose joints are antagonistically actuated by pneumatic McKibben actuators. Here, we discuss the actuators and controller´s two sub-sections: the joint torque controller and the differential pressure controller. The joint torque controller tracks a desired joint trajectory point and utilises the iterative Newton-Euler algorithm, via the simINEA Simulink library, to generate a desired torque. The differential pressure controller tracks the desired torque and, via the simDeltaP Simulink library, generates a desired PMA pressure. The simDeltaP´s pneumatic McKibben actuator model parameters have been experimentally determined and are presented. The discussed control architecture has been deployed to and executed in real-time on a 1GHz ARM-based Cortex-A8 computer running the Ubuntu 11.10 (Oneiric Ocelot) Linux distribution. Results of the real-time execution of the control structure on the remote target are given for desired trajectory points, where we present and discuss the joint torque and differential pressure controllers´ outputs.