This paper introduces the body weight support gait training system known as the AIRGAIT exoskeleton and delves into the design and evaluation of its leg orthosis control algorithm. The implementation of the mono- and biarticular pneumatic muscle actuators (PMAs) as the actuation system was initiated to generate more power and precisely control the leg orthosis. This research proposes a simple paradigm for controlling the mono- and bi-articular actuator movements cocontractively by introducing a cocontraction model. Three tests were performed. The first test involved control of the orthosis with monoarticular actuators alone without a subject (WO/S); the second involved control of the orthosis with mono- and bi-articular actuators tested WO/S; and the third test involved control of the orthosis with mono- and bi-articular actuators tested with a subject (W/S). Full body weight support (BWS) was implemented in this study during the test W/S as the load supported by the orthosis was at its maximum capacity. This assessment will optimize the control system strategy so that the system operates to its full capacity. The results revealed that the proposed control strategy was able to co-contractively actuate the mono- and bi-articular actuators simultaneously and increase stiffness at both hip and knee joints. 1. Introduction Considerable assistive gait rehabilitation training methods for the neurologically impaired (including stroke and spinal cord injury (SCI) patients) have been developed using a variety of actuation systems to generate the necessary force to operate the leg orthosis. One of the best examples of gait rehabilitation orthosis is the LOKOMAT (Hocoma AG, Volketswill, Switzerland) or driven gait orthosis (DGO) which is commercially available and extensively researched in many rehabilitation centres [1–3]. This orthosis uses a DC motor for the actuation power to control trajectory at the hip and knee joints. Initially, this DGO implemented the position controller for the control system. However, with further research, this method was improved with the addition of the adaptive and impedance controllers. Emphasis is placed on providing adequate afferent input to stimulate the locomotor function of the spinal cord and activate leg muscles that have lost the capacity to actuate voluntary movement. On the other hand, The Lower Extremity Powered Exoskeleton (LOPES) is a gait rehabilitation orthosis that employs the Bowden-cable driven series elastic actuator (SEA) with the servomotors as the actuation system to implement low-weight (pure) force sources
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