Atsushi Nakayama

Development of a Wearable Robot for Assisting Carpentry Workers

The work of fitting ceiling boards is one of the hardest in carpentry, as it requires large muscular power. Hence there is a need to develop assisting apparatus for such work. In order to use this apparatus anywhere a wearable robot is the most suitable. As the robot must be autonomous and lightweight, a design requiring low power is proposed. A semi-active control method has been developed using springs, which requires low energy but satisfies the requirements of compliance and assistive force. In this paper several aspects of design, control and experiments of the developed prototype is explained. The experimental results prove that the robot reduces the muscular fatigue of carpentry worker by providing suitable assistive force.

Hybrid Control of Powered Orthosis and Functional Neuromuscular Stimulation for Restoring Gait

The restoration of motor functions of patients with spinal cord injury (SCI) is one of important subjects for study. For this purpose, methods of functional neuromuscular stimulation (FNS) have been investigated in medical science and practice during these three decades. However, we have not achieved complete restoration of motor functions in SCI patients. On the other hand, we have achieved useful devices in human-scaled transportation by using power assist technology. Thus, applying power assist technology to the problem of restoring motor functions is one of possible solutions and sounds practical. In this paper, we propose a new hybrid system to combine power assist technology and FNS for restoring motor functions of lower extremity in SCI patients. Both powered orthosis and FNS are used to generate and control the joints moments of lower extremity in the proposed hybrid system. The main role of powered orthosis Vs is to compensate the joints moments generated by FNS and to enhance the controllability of FNS with the actuators. The proposed hybrid control system has been experimentally evaluated in gait motions by measuring the angle trajectories and generated moments around the knee and hip joints in the cases when only actuators are used and both FNS and actuators of the orthosis are used. The results prove that the control method for the hybrid system is useful to restore motor functions of lower extremity in SCI patients.

Real-time estimation of tongue movement based on suprahyoid muscle activity

In this study, we introduce a real-time method for tongue movement estimation based on the analysis of the surface electromyography (EMG) signals from the suprahyoid muscles, which usual function is to open the mouth and to control the position of the hyoid, the base of the tongue. Nine surface electrodes were affixed to the underside of the jaw and their signals were processed via multi-channel EMG system. The features of the EMG signals were extracted by using a root mean square (RMS) method. The dimension of the variables was reduced additionally from 108 to 10 by applying the Principal Component Analysis (PCA). The feature quantities of the reduced dimension set were associated with the tongue movements by using an artificial neural network. Results showed that the proposed method allows precise estimation of the tongue movements. For the test data set, the identification rate was greater than 97 % and the response time was less than 0.7 s. The proposed method could be implemented to facilitate novel approaches for alternative communication and control of assistive technology for supporting the independent living of people with severe quadriplegia.

Estimation of tongue movement based on suprahyoid muscle activity

With attention to voluntary tongue motion, which is capable of communicating the intentions of a person with a disability, we estimated the position and contact force of the tongue simultaneously using EMG signals of the underside of the jaw. We affixed a multi-channel electrode with nine electrodes to the underside of the jaw. Then, deriving many EMG signals using monopolar leads, we calculated 36 (= 9C2) channel EMG signals between any two of the nine electrodes. Associating these EMG signals and tongue movement using a neural network, we confirmed our ability to estimate the tongue position and contact force with precision, with a correlation coefficient greater than 0.9 and RMS error less than 10%. Furthermore, building a neural network estimating deglutition, yawning, and mouth opening, which are potential origins of false estimation, and introducing mask processing to reduce estimation error in voluntary tongue movement more than 95%, we suggest precise extraction of only the signal of that movement from EMG signals obtainable from the underside of the jaw.

Task based approach on trajectory planning with redundant manipulators, and its application to wheelchair propulsion

We introduce an optimization method for the trajectory planning of redundant manipulators which achieve a given task with high efficiency, and apply the method to a wheelchair propulsion problem. A GA is used to optimize the redundant variables of a manipulator. Additionally, the procedure of the method does not use any forward dynamics computation. The effectiveness of the proposed algorithm has been shown by applying the method to wheelchair propulsion.

Computer aided rehabilitation engineering (CARE) system with a walking model

This paper describes a computer simulation model of human walking that seeks to improve the practicability of the simulation method for application to rehabilitation. The musculo-skeletal system was represented by a three-dimensional, 14-rigid-link model and 60 muscle models. Muscular forces were controlled by a neuronal system model consisting of 16 pairs of the neural oscillators. This simulation model was applied to investigate biomechanical relationship between walking stability and body dynamics properties. Such simulation methods will provide us with a novel computational assessment tool of human movement that we call computer aided rehabilitation engineering (CARE) system.

Integrated Design of Airframe and Stabilizing Controller in Wing-in-Ground Effect Aircraft.

Wing in-Ground effect aircrafts have gained much attention during these thirty years because of their high efficiency. The aircrafts require active stabilizing controllers for safety maneuvering, which cause difficulties in designmg. In this paper, we apply simultaneous optimization technique to design Wing-in-Ground aircraft. It is shown that the simultaneous optimization on parameters of aerodynamics design and of stabilizing controller can give superior design to conventional methods. An example is given to illustrate the procedure of design and the effectiveness of simultaneous optimization.