Mental workload is a neuroergonomic human factor, which is widely used in planning a system's safety and areas like brain–machine interface (BMI), neurofeedback, and assistive technologies. Robotic prosthetics methodologies are employed for assisting hemiplegic patients in performing routine activities. Assistive technologies' design and operation are required to have an easy interface with the brain with fewer protocols, in an attempt to optimize mobility and autonomy. The possible answer to these design questions may lie in neuroergonomics coupled with BMI systems. In this study, two human factors are addressed: designing a lightweight wearable robotic exoskeleton hand that is used to assist the potential stroke patients with an integrated portable brain interface using mental workload (MWL) signals acquired with portable functional near-infrared spectroscopy (fNIRS) system. The system may generate command signals for operating a wearable robotic exoskeleton hand using two-state MWL signals. The fNIRS system is used to record optical signals in the form of change in concentration of oxy and deoxygenated hemoglobin (HbO and HbR) from the pre-frontal cortex (PFC) region of the brain. Fifteen participants participated in this study and were given hand-grasping tasks. Two-state MWL signals acquired from the PFC region of the participant's brain are segregated using machine learning classifier—support vector machines (SVM) to utilize in operating a robotic exoskeleton hand. The maximum classification accuracy is 91.31%, using a combination of mean-slope features with an average information transfer rate (ITR) of 1.43. These results show the feasibility of a two-state MWL (fNIRS-based) robotic exoskeleton hand (BMI system) for hemiplegic patients assisting in the physical grasping tasks.

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Abstract. The fundamental aspect of designing a legged robot is constructing a leg design that is robust and presents a simple control problem. In this paper, we have successfully designed a robotic leg based on a unique four bar mechanism with only one motor per leg. The leg design parameters used in our platform are extracted from design principles used in biological systems, multiple iterations and previous research findings. These principles guide a robotic leg to have minimal mechanical passive impedance, low leg mass and inertia, a suitable foot trajectory utilizing a practical balance between leg kinematics and robot usage, and the resultant inherent mechanical stability. The designed platform also exhibits the key feature of self-locking. Theoretical tools and software iterations were used to derive these practical features and yield an intuitive sense of the required leg design parameters. IntroductionBiomimics is an emerging field of robotics which aims at mimicking the motions of naturally existing organism and to utilize these systems in real life applications. Majority of the mammals use legs for locomotion but wheeled robots have been preferred because of enhanced stability and easy control of actuators [1][2]. Undoubtedly, legged robots have certain advantages over wheeled robots in natural environment [3] but their lower stability limits their use in real life applications. In order to minimize the stability issues related to the legged platforms, number of legs can be increased. As a rule, more the number of legs, more is the stability; whereas, increasing the number of legs adds to the difficulty of control problem [4]. Thus, a trade off approach is required. Therefore, researchers are in a quest to develop stable legged robots for the future. In literature, some researchers have reported their work which can be used as basic criteria for the leg design. Lee has reported a compartmentalized leg structure inspired by nature [4]. A biped named Raptor (made by KAIST), reported to run at high speeds, has made use of a nine bar mechanism. Recently, Oak and Narwane have investigated the use of modified four bar mechanism (two DOF per leg) [5]. Seok et al have developed advanced legged robot mimicking the movement of a Cheetah [6]. A detailed literature review has revealed that in an attempt to ensure the stability of legged robots the researchers have depended heavily on sensory equipment and control algorithms rather than the mechanical design. Moreover, controlling a large number of actuators, simultaneously, is troublesome. Thus, we propose an efficient leg design based on a simple four-bar mechanism with only one motor per leg. This leg design would yield an inherently stable robot with an exciting feature of self-locking. The design of one DOF based leg requires iterative and complex steps; the first of which is the development of a sound mechanical system.Quadrupeds are a moderate choice with respect to the stability of the platform [4]. Thus, the present study focuses on the mechanical design ...

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