Development of hybrid hydraulic–electric power units for field and service robots

Energetic autonomy of a hydraulic-based mobile robot requires a power source capable of both hydraulic and electrical power generation. The hydraulic power is used for locomotion, and the electric power is used for the control computer, sensors and other peripherals. In addition, the power source must be lightweight and quiet. This study presents several designs of internal combustion engine-based power units. Each power unit is evaluated with a Ragone plot which shows its performance over a wide range of operation times. Several hydraulic–electric power units (HEPUs) were built and successfully demonstrated on the Berkeley lower extremity exoskeleton (BLEEX). The best-performing design of the HEPUs, based upon the Ragone plot analysis, is described in detail. This HEPU produces constant pressure hydraulic power and constant voltage electric power. The pressure and voltage are controlled on board the power unit by a computer. A novel characteristic of this power unit is its cooling system in which hydraulic fluid is used to cool the engine cylinders. The prototype power unit weighs 27 kg and produces 2.3 kW (3.0 hp) hydraulic power at 6.9 MPa (1000 p.s.i.) and 220 W of electric power at 15 V DC.     

以太网现场总线的跨平台网络通信

核聚变装置EAST极向场电源控制系统由三层网络组成:WINDOWS监测层、QNX实时控制层、现场总线执行层。其中现场总线层负责采集大量现场设备的状态并将其传递给实时控制层和监测层。本文描述了以太网现场总线控制器与QNX和WINDOWS不同操作系统之间的一种跨平台网络通信。实践表明基于MODBUSTCP/IP协议,利用SocketAPI建立的套接字使现场总线同时与两种操作系统之间进行通信是完全可行的,而且是高效的。     

Comparison of four methods to evaluate flow fields in CSP casting mould

Abstract

Commercial flow analysis tools are widely used in industry, but their capacity, efficiency and accuracy to solve complex flows are not so clear. In the present paper, first, three-dimensional computations are performed to calculate the flow field in the mould region of compact strip production (CSP) casting using a conventional finite volume method program, CFX4, with laminar model, standard k–? model, renormalisation group k–? model and low Reynolds number k–? model with default model parameters for handling turbulence. Next, these were compared with the flow pattern in a 1 : 1 scale water model by other investigations and quantitative comparisons were made for the flow velocities. Finally, the four numerical simulation models were evaluated in detail. Each method has its own merits and disadvantages, so model verification is always necessary for a highly accurate numerical analysis of complex flows. Under the situation of lacking experimental data, the standard k–? may be a good choice to evaluate liquid steel in a CSP mould.     

CAPTURE EFFECT OF ELECTRORHEOLOGICAL SUSPENSIONS IN FLOW FIELD

According to the results of experiments and theoretical analysis,a phenomenon called “capture effect” is put forward,which could be used to describe the particles dynamic behavior of electrorheological (ER) suspensions. Then a “structure-force” mathematical model is established to explain this effect based on electrostatic energy density equation. The analysis results show that the dynamic coupling process of ER suspensions under an external electric filed is the function not only of the electric intensity,but also of the dielectric properties and the structure form.     

Mushy zone coarsening with fluid flow

Abstract

Cylindrical samples of a near-eutectic AlCu30 alloy are annealed applying constant axial temperature gradients to directionally molten samples in an aerogel furnace. During annealing with various times and gradients also a rotating magnetic field (RMF) of 6 mT was applied leading to azimuthal and meridional flows of well known magnitude. The specific surface area of the primary phase was measured on metallographic in section perpendicular to the sample axis with a fixed amount of fraction solid. The specific surface area varies as the inverse cube root of annealing time if no RMF is applied, but varies as an inverse forth root at 6 mT. The experimental procedure and results are presented in detail and compared to isothermal coarsening measurements of Voorhees and co-workers.     

Investigation of pitting potential of carbon steel using experimental design method

Abstract

The dependence of the pitting potential E_p of 1018 carbon steel on chloride concentration, pH and the temperature of the solution was studied by the potentiodynamic method in accordance with a statistical experimental design. The parameters of the empirical pitting potential model determined on the basis of Box-W ilson ex perimental design method were evaluated using the experimental data. Comparison of the predicted values from the model with the observed values showed that the model is a good fit. From the model equation the most noble pitting potential value of -225 mV (SCE) was obtained when the Cl^- ion concentration, temperature and pH of the solution were 205 ppm, 25°C, and 6·4, respectively. The Box-Wilson experimental design technique was proved to be applicable in modelling the pitting potential of carbon steel.     

Effect of exciting current of high frequency electromagnetic field on initial solidification of steel during electromagnetic continuous casting

Abstract

A three-dimensional finite element model of the electromagnetic field and temperature field of electromagnetic continuous casting (EMCC) process was developed. The aim was to investigate the effects of induction heat of high frequency electromagnetic field on the early solidification process of molten steel in mould under various conditions of exciting current parameters. The results show that the induction heat has significant effects on the early solidification process, which appear as increasing the billet surface temperature, thinning the initial solidified shell and lowering the starting point of the initial solidification. The increases in exciting current frequency and density make the effects of induction heat on solidification process increase remarkably. Especially, with the exciting current frequency increase, the early solidification process and shell growth become non-uniform in billet circumferential direction. Furthermore, if the exciting current density exceeds a certain value, there occurs a high temperature region in the top of molten steel column, and then the initial solidification rate is greatly decreased. As a conclusion, the effects of induction heat on initial solidification process must be considered when the exciting current frequency and density are adjusted during the electromagnetic continuous casting process.     

VFP通用字段中的信息导入SQL Server的实现方法

综合应用VFP、VB及ADO技术,实现了在VFP通用字段的信息中导入SQL Server数据库image字段,有效地解决了VFP数据库升迁到SQL Server上、通用（Gen）字段转为image字段后无法读取的问题。     

The Coupled FEM Analysis of the Transient Temperature Field During Inertia Friction Welding of GH4169 Alloy

The inertia friction welding process is a non-linear process because of the interaction between the temperature field and the material properties as well as the friction force. A thermo-mechanical coupled finite element model is established to simulate the temperature field of this process. The transient temperature distribution during the inertia friction welding process of two similar workpieces of GH4169 alloy is calculated. The region of the circular cross-section of the workpiece is divided into a number of four-nodded isoparametric elements. In this model, the temperature dependent thermal properties, time dependent heat inputs, contact condition of welding interface, and deformation of the flash were considered. At the same time, the convection and radiation heat losses at the surface of the workpieces were also considered. A temperature data acquisition system was developed. The temperature at some position near the welding interface was measured using this system. The calculated temperature agrees well with the experimental data. The deformation of the flash and the factor affecting the temperature distribution at the welding interface are also discussed.     

Hardware implementation of neuromodulated neural network for a CPU-less autonomous mobile robot

In order to construct truly autonomous mobile robots, the concept of 'packaging' is indispensable; in packaging, all parts such as controllers, power systems and batteries should be embedded inside a finite physical space, i.e., a robot's body. Therefore, implementing a controller on hardware is one of the most promising ways, since this contributes to low power consumption, miniaturization, etc. Another crucial requirement in the field of autonomous mobile robots is robustness, i.e., autonomous mobile robots have to cope with their unpredictably changing environment in real-time. In this study, to meet these requirements, the concept of a dynamically rearrangeable electrical circuit (DREC) is proposed and we implement this onto field progammable gate arrays as physical electronic circuits by borrowing the idea from neuromodulation widely observed in biological nervous systems through the diffusion-reaction mechanism of neuromodulators. We developed the DREC for the peg-pushing task as a practical example. We confirmed that the physical DREC can successfully regulate the behavior according to the situation encountered by changing its properties in real-time.