Journal of the Robotics Society of Japan

In order for humanoid robots to behave with soft contacts among humans, whole-body tactile sensing function is indispensable. For enclosing whole-body regions of a humanoid, softness and the stretchable property is necessary especially for the regions around joints. Although there are some studies to realize a whole-body enclosing-type tactile sensing exterior so far, most of them have difficulties to enclose the joint regions. Therefore, we propose the method to construct a soft stretchable enclosing type tactile sensing exterior using electro-conductive knitting structure and about 200% stretchable and pressure sensitive exterior can be realized. Furthermore cardigan type knit sensor exterior is developed and the feasibility of the proposed method is confirmed through behavior experiments by a humanoid wearing the developed cardigan knit sensor.

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We have developed safe, soft, and energy-saving actuators which have the elastic mechanism. Using proposed soft actuators, a robot with twelve joints has been developed. Due to the elasticity of the actuator, vibration of joints arises when usual joint control is adopted. In this paper, a new vibration suppression control based on Lie algebra is proposed. Rubustness for inertia fluctuation is evaluated by experiments. Finally, standing experiment by using the proposed control has been carried out.

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The problem of motor redundancy is well known as Bernstein's problem, named after the scientist who first posed the knotty problem in the early 1930s. At present, it is still a mystery how the central nervous system (CNS) solves the ill-posed problem of motor control. We recently made a discovery that links with influential hypotheses that the CNS may produce movements by combining units of motor output. This paper introduces the key concept we call the “A-A ratio,” which is the EMG ratio of agonist-antagonist muscle pairs. The statistical analysis based on the A-A ratio specifies that (1) human lower limb movement during walking is explained as the superposition of a few modular units, and that (2) decomposed modules encode the kinematic information of body movement. The results also clarifies that various hypotheses, such as the muscle synergy hypothesis, the population vector hypothesis, and the convergent force fields hypothesis, are different interpretations of a common equation derived from our analysis. The concept of an A-A ratio provides a beneficial suggestion to many studies on muscle-synergy extraction and gives an important clue to solving Bernstein's problem of redundant degrees of freedom.

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With the increase of the number of humanoid robots, the importance in developing a motion planning and synthesis tool that can easily be dealt by general users without a long training process have been growing for a wide range of applications. To this end, in this paper, we propose a novel user interface allowing whole-body motion planning and synthesis for humanoid robots. Our interface consists of two fundamental elements. The first element is a process for automatically constructing a 2D graphical interface from a variety of motion data by using a dimensionality reduction method so that all topological features of each motion and similarities among different motions are preserved. With the constructed interface, the user can synthesize a variety of whole-body motions by simply following the lines on the plane. The second element is a motion-interpolation process for the synthesized motions even if the user roughly indicates motions by the interface. These elements allow to synthesize smooth and naturally-looking whole body motions even by a general user. We developed a system composed of a tablet-type input device and a small humanoid robot for the validation of our method. Through experiments with human subjects, the effectiveness of the proposed approach was validated.

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