Juliang Xiao

Numerical Simulation for Hydraulic Characteristics of Cylindrical Valve in Runaway Protection Process

In the present paper, numerical simulation about the emergency shut-down water process of cylindrical valve is performed in order to study hydraulic characteristics of three dimensional unsteady flow during runaway protection of cylindrical valve. The curves of the pressure distribution, the axial force exerting on the valve are given with the time passing under various openings. In addition, the pressure fluctuation caused by the unsteady flow of vortex tape through Francis turbine is provided and analyzed, which provides the reference for the installation and maintenance of hydro-generator unit along with the design of multi-cylinder synchronous motion system.

Electro-Hydraulic Proportional Synchronous Control System of Ring Gate for Hydraulic Turbine

Based on the analysis of opening and closing control manner for ring gate of hydraulic turbine, the electro-hydraulic proportional control system for ring gate of hydraulic turbine was studied. A new control system, which combines mechanics, hydraulics and electrics, was presented. More particularly, the modules of speed control and multi-cylinder synchronous control for the movement of ring gate was designed. The modules include control valve group, flow dividing module consists of flow dividing motors, and oil distributing module. And the ring gate control system principle under different condition was also studied. By the engineering application in Yunnan Honghe Nansha hydropower plant, it was show that all functions and performances of the control system satisfied the designing requirements.

Collision detection algorithm for collaborative robots considering joint friction

This article proposes a collision detection algorithm without external sensors that can detect potential collisions in man–robot interaction. The algorithm is based on a modified first-order momentum deviation observer that also takes friction into account. The collision detection algorithm uses joint angles, angular velocities, and torques during the detection process, without any need to consider angular acceleration. The algorithm also uses an accurate friction model that is based on a Stribeck model with second-order Fourier series compensation. The friction model is applied in advance so that compensation can be made in real time during collision detection. Identification data are filtered through a first-order low-pass filter to reduce high-frequency noise. In order to verify the algorithm, a simulation and experiment were carried out using a collaborative robot experimental platform. The results confirmed that collisions can be detected by setting appropriate threshold values. Different possible responses can be implemented according to different response strategies, with the ultimate arbiter being that collision forces are kept strictly within ordinary human tolerances. This makes sure that safety can be preserved in man–robot interaction processes.