Control test of a wearable elbow orthosis with bi-muscular pneumatic servo-drive based on brain-computer interface

The paper presents a control tests of a wearable orthosis of elbow joint with a bi-muscular pneumatic servo-drive. Brain-computer interface (BCI) based control is a complex task, because it must contain a device for recording bioelectric signals (BESs) and translate them into control signals (CS) of the elbow orthosis. The authors analysed the impact of the induced brain activity and the muscular tension within the head of the participant on the BESs which can be used to control the pneumatic servo drive of the elbow joint orthosis. For controlling the elbow joint orthosis, a distributed control system (DCS) was developed that contains two control layers: a master layer connected to the BCI device and a direct layer contained in a wireless manner with the controller of the pneumatic servo-drive (PSD). In the programming of the PSD controller, a kinematic-dynamic model of the elbow joint orthosis, patterned after the biological model of human biceps-triceps, was used. A biomimetic dynamic model of the pneumatic muscle actuator (PMA) was used, in which the contraction force results from the adopted exponential static model of the pneumatic muscle (PM). Use of direct visual feedback (DVF) makes it possible for the participant to focus on the movement of the orthosis taking into account the motoric functions of the elbow.