A control valve is the most heavy and expensive device in the pneumatic driving system for a soft mechanism. To realize a compact and inexpensive pneumatic driving system, the size, weight, and cost of the control valve must be reduced. In the previous study, a small-sized servo valve that can control the flow rate using a diaphragm and gate mechanism, driven by a low-cost RC servo motor, was proposed and tested. However, the previous servo valve using gate mechanism should adjust the relative positions of the rotating disk and gate mechanism to achieve the desired flow rate characteristics. In this study, to decrease assembling time for adjusting the valve characteristics, a slide-gate mechanism servo valve that can adjust the valve opening of gate based on the rotational angle of a rotational cam with slope is proposed and tested. Evidently, the adjustment time of the tested valve significantly decreases compared with the previous valve. Further, the flow rate characteristics of the valve can be easily changed by replacing the cam. Herein, the construction and operating principle of the tested valves, the analytical models for obtaining the desired flow rate characteristics of the tested valves, and its result are reported.

The three-transducer method using the wave propagation model is a promising method for estimating the instantaneous flow rate in a pipe that can reduce the influence of the half-wavelength spacing problem. This paper extends the correction equation to flow rate and deals with the optimizations of the correction coefficients and their verification by experiments. The error reduction mechanism of the original method is discussed based on the principle of the Method of Characteristics, and the correction equation is extended to flow rate. A numerical experiment for small amplitude waves in a pneumatic pipeline is conducted, and numerical optimizations assuming realistic pressure calibration errors were performed for a flow chirp. The optimization results showed that the coefficient of flow rate correction was almost unity, indicating the validity of introducing flow rate correction. A transient response experiment was carried out on an actual pneumatic pipeline, using a laminar flowmeter with a fast response as a flow rate measurement. Comparison with the flow rate measurements and the flow rate estimation utilizing the pressure measurements showed the difference in the trend of absolute errors depending on the coefficients. Considering robustness, the optimized coefficient under ideal conditions was the best. On the other hand, the optimized coefficient under realistic conditions was found to be the best for unsteady flow with no change in line pressure.

Approximately 20% of the electrical power consumed in various industries is spent on electric air compressors. To reduce greenhouse gases, the principal contributor to global warming and is currently a global challenge, and it is necessary for electric air compressors to reduce their power consumption. To achieve this, we considered the use of wind energy, which is a renewable energy source. Therefore, this research proposes a wind-powered air compressor in which the compressor is driven directly by a wind turbine. By developing a new reciprocating compressor with a linkage mechanism employing a hypocycloid motion, compressing air through ideal linear motion without swiveling, we produced a wind-powered air compressor that can operate even at low revolving speed under low wind speeds. The characteristics of the wind-powered air compressor were analyzed and the compressor design was based on the analysis results. The results indicated a maximum discharge pressure of 0.8 MPa and a maximum efficiency of 12% for an annual average wind speed of 3 m/s in Japan. The target efficiency of 20% may be achieved using a different type of wind turbine with higher efficiency, revealing the potential for the practical application of wind-powered air compressors.