High-pressure pneumatic control valves have been widely investigated during last decades. The published literature includes experimental and analytical studies on both constant value on–off valve and pressure reducing valve, but rarely on servo valve. In this paper, a novel voice coil motor (VCM) direct drive high-pressure pneumatic servo valve (HPPSV) is proposed. The mathematical model of the HPPSV including electromechanical and fluid subsystem is presented. Furthermore, the hybrid control scheme consisting of a proportional integral differential (PID) controller with velocity/acceleration feed-forward and a disturbance observer is proposed to improve the control performance of the HPPSV, taking into account the factors such as compressibility of high-pressure gas, high nonlinearity of gas flow force and friction force. The experimental results show that the spool position control system based on the proposed control scheme has strong robustness and disturbance rejection capability, and the control accuracy of the valve spool position can be enhanced greatly compared with the conventional PID controller. The study has general implications in the development of high-pressure pneumatic servo valves and high-pressure pneumatic precision control field.

A gradual change of the pitch angle was observed for a glider in a sea trial in August 2014. It took place when the glider moved in both upward and downward glides between the sea surface and a depth of 1200 m and there was neither any internal mass movement nor buoyancy engine regulation in the steady glide. In this paper, this phenomenon is validated via a nonlinear dynamic model, which is restricted to the vertical plane. The model is based on Kirchhoff's equations of motion for a submerged rigid body and takes the seawater pressure, temperature, and density, and the deformation of the pressure hull of the glider into consideration. While the variations of aforementioned four parameters influence many physical parameters, including added mass, buoyancy, center of buoyancy (CB), hydrodynamic forces, and torques, their effects on glide velocity appear to be the primary cause for the gradual change of pitch angle observed. To minimize the gradual change of pitch angle, two effective approaches are proposed and validated, namely increasing the lift/drag ratio and decreasing the hydrodynamic torque coefficients.

In this paper, an observer-based adaptive fuzzy robust controller is proposed for trajectory tracking control of a bionic mechanical leg (BML) with unmeasured system states, dynamic uncertainties and external disturbances. A high gain observer (HGO) is constructed to estimate the unavailable joint velocities using the joint position feedback signals, while an adaptive fuzzy logic system (AFLS) is employed to address the lumped uncertainties. The nonlinear robust controller is then synthesized via backstepping method to improve the position tracking performance. The stability of the closed loop system is mathematically demonstrated via the Lyapunov’s stability theory. It is proven that under the proposed controller all the closed-loop signals are bounded and the trajectory tracking errors converge to a small neighborhood of the origin with appropriate design parameters. The effectiveness of the proposed control scheme is illustrated by simulation studies.