Applied Mechanics and Materials Vols. 268-270

Abstract: The impact that distance between thermal wires and nozzle on flow distribution of fluidic gyroscope with three different cavity structures was researched. Using the Finite element method we calculated the two-dimensional flow distribution of fluidic gyroscope with rectangular cavity and two streamlined cavity structures when the distance d between thermal wires and nozzle is different. The results show that: flow velocity at the outlet in two streamlined cavities is larger than that in rectangular cavity, which is 28.87% and 28.91% of flow velocity at the nozzle respectively; the velocity in the three cavities decrease with d, the velocity in streamlined cavity 1 is always larger than that in streamlined cavity 2. When d = 16mm and 17mm, there are a larger velocity and a smaller x-axial velocity of the fluidic beam center in streamlined cavity 1, and velocity difference of two thermal wires increase, so the resolution of fluidic gyroscope can have an improvement.

Abstract: A PWM controller is designed for the active suspension without external energy supply (ASWEES) using the LQG control method. Based on the quarter-vehicle ASWEES model, Energy flow equation between the suspension and the accumulator with a 2 kW load was deduced and a PWM controller was designed. When 200Hz solenoid valves were adopted, the carrier frequency and series value of the carrier signal were set as 40 and 5 respectively. Simulation results show the suspension quadratic performance index of ASWEES decreases 24.97% than that of the passive suspension. The passive suspension consumes 2.211kW power, but ASWEES reclaims energy of 2 kW.

Abstract: This article takes the optimization of general parameters of low-orbit spacecraft as object. Three subsystems of attitude and orbit control subsystem, power subsystem and structure subsystem were researched. Coupling relations between subsystems and system were described. Analysis models of the subsystems were provided. Meanwhile, optimization models of the researched problem were established based on collaborative optimization (CO). Sequential quadratic programming (NLPQL) was selected as search strategy of CO subsystem optimizer. While NLPQL, adaptive simulated annealing algorithm (ASA) and multi-island genetic algorithm (MIGA) were respectively selected as the search strategy of CO system-level optimizer to search. Furthermore, multidisciplinary feasible method (MDF) was used to optimize the same problem. NLPQL, ASA, MIGA were respectively selected as the search strategy of MDF system-level optimizer. The optimization result of CO was compared to the optimization result of MDF shows that using CO can get the result which close to the optimal result. That proves CO can be effectively applied to multidisciplinary design optimization of the general parameters of the low-orbit spacecraft.

Abstract: Traditionally, guide dogs are used as a travel aid for blind people. But they cannot be popularized because the training cost for guide dogs is quite high. This paper presents an intelligent guide vehicle prototype for blind people. The system is developed by using ARM as a controller and processor, via integration of ultrasonic detection and photoelectric detection technology, aiming at automatically navigation for blind people. This system mainly consists of four modules, which are ultrasonic detection module, photoelectric detection module, voice prompt module and automatic control module. The signal reflected by roadblock on the road can be detected by ultrasonic detection module which can work out distance between roadblock and guide vehicle. The aim of photoelectric detection module is to realize the function of road recognition and tracking. Voice prompt module can provide information of distance of roadblock. Strategies of obstacle avoidance were taken to the blind when the guide vehicle is going to avoid roadblock. If the roadblock is less than 50cm away, the automatic control module will automatically set the guide vehicle to avoid obstacles. Preliminary experimental results show that users can control and navigate with the intelligent guide vehicle.

Abstract: Stable and reliable automatic control system of Vacuum Consumable Arc Remelting (VAR) furnace with thyristor power supply is the key to smelt successfully special alloy metal and high temperature alloy metal, which is related to special properties of remelting ingot directly, however, it is key problem to test the drop pulse for thyristor supply. This paper makes a deep study for drop short pulse testing system on AVR with thyristor power supply, and digital signal processing is used to obtain drop short pulse value with different frequency ranges. According to the specification of thyristor power supply, firstly, basic theory analysis of drop short pulse measuring is researched. Secondly, high-speed digital signal processing technology is adopted to sample furnace voltage signal real-timely, trap filter group is designed to remove the multiple order harmonic, and band pass filter group is designed directly to process and calculate the amount of drop short pulses in different frequency ranges, finally, the material parameters which impact on drop short frequency. Field experiment results show the effectiveness of the whole drop short pulse testing system.

Abstract: Based on the failure data of the CNC system in two years, the failure positions, failure modes, failure causes, failure sources of the CNC system hardware and software were analyzed. The more failure positions were analyzed further by FMECA method, proposing content, key point and method which should be paid attention to while using and maintaining the CNC system. The weak parts and its correlative components were also pointed out, so as to provide the basis for improving the reliability of the CNC system hardware and software.

Abstract: The model of magnetic bearing and vibration producing mechanism were analyzed. A new adaptive law was developed to eliminate the rotor vibration. The adaptive control system for stabilization of the rotor geometric center to the origin was designed by varying magnetic stiffness through excitation of the bias currents. Finally, the simulation results validated the effectiveness of the proposed algorithm

Abstract: The purpose of this work is to develop an experiment applied to milling process cutting parameters optimization based on data collection from the factory shop floor. The cutting parameters to be optimized were cutting speed, feed rate and depth of cut. Hardened steel dies currently used for forging process were milled to generate data to be used during the experiments. The optimization focus was to minimize the milling process cost or to increase it’s the productivity. Two stages had been used: one based in Design of Experiment (DOE) technique and another based on a deterministic method. Both were used to optimize cutting condition parameters to be applied instead of that being used before the experiments. It was possible to conclude, following DOE method results that were recommended to use the smaller cutting speed, the smaller feed rate and the greatest depth of cut, considering the cutting parameters tested. These results were considered by the authors as initial values to apply a deterministic method. The greatest depth of cut and the smaller feed rate were compatible with the machining conditions of the part, considering the initial blank and surface finish required respectively. So, deterministic method was used only to optimize cutting speed. As final result, the authors conclude that minimum cost cutting speed, greatest around 10% to that one found by DOE method was much more convenient to be applied in shop floor, because the smaller cost involved. Finally, this work allowed also concluding that both DOE and deterministic methods can be used to optimize cutting process parameters taking a small number of results collected from factory shop floor during the process evolution.

Abstract: The logistics and loading machinery is the typical hydromechatronics integrated system. How to solve the reasonable power match in the driving and lifting process of the logistics and loading machinery, we need to establish the mathematical model of the driving and lifting system, and analyze their control characteristics. Aiming at the load requirements for different operating conditions, this paper studies respectively the dynamic characteristics of the driving and lifting system. Through simulation and computation, the control methods and strategies based on the best performance are proposed. That lays the foundation for the optimization design of the logistics and loading machinery.

Abstract: The measures of eliminating system oscillation by using parameters were put forward in semi-closed loop and closed loop control. The setup procedures of parameters were introduced, which included position loop gain, bi-position feedback, mechanical speed feedback. The setting of the parameters such as acceleration of backlash, compensation for static friction, feed forward and look-ahead feed forward of servo were also proposed, for purpose of improving the position accuracy and interpolation accuracy. The application of the system parameters is significant for improving the machining accuracy and ability of CNC machine tools.