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Spinal reflexes greatly contribute to the control of fast physical interactions (e.g., catching a moving ball) without the influence of higher level control systems involved in human motor control. Therefore, to realize the interactions in robots, it is a useful approach to mimic the nervous system controlling spinal reflexes. To this end, as the starting point for creating spinal reflexes, sensors that measure and encode body movements similar to human proprioceptors are needed to generate signals for the spinal reflexes. In this study, we developed artificial muscle proprioceptors to reproduce spinal reflexes in robots. In particular, we focused on pneumatic artificial muscles and designed an artificial muscle spindle and an artificial Golgi tendon organ, which were integrated with a pneumatic artificial muscle. A compact local measuring system consisting of a microcomputer and amplifiers was developed to easily install and organize the sensors.

The influence of substitutional atoms (Mn, Cr, Si, P, and Al) on the solubility limit of C in body-centered cubic iron in equilibrium with cementite was investigated in low-carbon steels at a temperature of 700 °C. The C solubility limit was determined from internal friction measurements combined with infrared analysis of C using a high-frequency combustion technique. Experiments clarified that Mn, Cr and Al hardly change the C solubility limit, whereas P and Si increase it.

The influence of substitutional atoms (Mn, P, Si, Al, Cr, Co) on the C Snoek peak in b.c.c. iron was investigated. In the dilute range of the substitutes, the addition of Co, Mn, Cr, Si, P and Al resulted in the decreases in Snoek peak height in this ascending order. However, the addition of Mn to the Fe–C–P alloy hardly changes Snoek peak height. There is even a case that Snoek peak height is increased by further Mn addition to this alloy. They can be explained systematically by the proposed model wherein the solute carbon present in the influence region where the lattice distortion around the substitute is greater than the threshold value cannot contribute to the Snoek peak. The strain field generated by a substitutional atom due to the difference in atomic size is concluded to be the main reason for the reduction in Snoek peak height.