Applied Mechanics and Materials Vol. 203

Abstract: Aiming at the pressure control of hydraulic transformer (HT), the fractional order PID (FOPID) controller is proposed for the control of the position of the valve plate. The assignment system of the HT is carefully modeled. To optimally determine the parameters of the FOPID controller, a self-adapting differential evolution algorithm is employed. Numerical simulation is conducted to investigate the proposed control strategy. Both step response and sinusoidal command signal tracking of the servo system is assessed, and the results demonstrate that the proposed control strategy is obviously superior to the conventional PID, Fuzzy Logic Controller (FLC) and fuzzy-PID control strategy, and can afford precise tracking performances. It is suitable for the precise adjustment of the output pressure of the HT.

Abstract: The dynamical model of an omni-directional mobile robot is bulit based on the Newtonian mechanics. Correspondingly, a backstepping-based controller is then proposed with proven global stability by selecting a Lyapunov function and introducing a virtual control input for the built dynamical model. Simulation results show the effectiveness of the proposed controller.

Abstract: The design use the car simulate unmanned vehicles, it take voice identificate and Bluetooth technology to control unmanned vehicles, Through identificate the speech of control person, extract the valid instruction, and send the instructions to car via bluetooth. After the car identificating the command, it can automatically finish the basic functions of start, forward, backward, turn left, turn right, accelerate, decelerate, stop, turn on the lights, turn off the lights automatically avoid obstacles and tracing. The car model also install LCD, four infrared sensors and long-range ultrasonic ranging sensors, it have good scalability, the model have a good reference value for the real unmanned vehicle.

Abstract: The design uses 32 ARM processor S3C44B0X and Spartan™ -3E500 FPGA chip produced by Xinlinx company for setting up the hardware platform, and integrates the camera, GPS module, MiniGUI interface module. And realized bus vehicle mounted multimedia transmission control network control based on MOST. All of these are in the purpose of achieving a Predigest Project of vehicle-bone multimedia transmission and control network based on FPGA. The experiment indicated that, the transmission and control network system constructed by S3C44B0X and Spartan - 3E500 FPGA is low cast, simple and reliable.

Abstract: For acquiring the initial velocity of high-speed object, it needs data fitting to get the unknown parameters. Least squares method(LS) is usually uses to complete this work, but LS method takes no account of the errors in the observation matrix, not only may makes error in unknown parameters' fitting, but also do harm to the further analysis. Therefore, this paper lead total least squares method(TLS) into data fitting, it can at the same time in consideration of observation data and its error margin, and at last in actually measure data analysis to prove TLS compare to LS enjoy higher accuracy.

Abstract: This paper presents a method of using single depth map to locate the key points of frontal human body. Human motion capture is the premise of motion analysis and understanding, and it has widely application prospects. There are many problems on former way to capture the state of human motion. For example, it can’t initialize automatically, it can not recover from tracking failure, it can not solve the problem caused by occlusion, or there are many constraints on participant, and so on. This article uses Kinect, which from Microsoft, to get depth maps, and use a single map as input to locate the key points of human body. First, depth map can reflect the distance, so background segmentation can be done easily by the characteristic. Then, extract the skeleton of the body’s silhouette. Finally, using the inherent connectivity features of human body, the key points of the body can be determined on the skeleton. Locating the key points from single depth map solve the problem of automatic initialization and recovery directly. The depth map can reflect distance on grayscale, which makes it easy to split the body region from the background. In addition, depth map contains some useful information can be used to solve the problem of occlusion. Using depth map can remove some constraints on the human body, as well as to reduce the influence of clothing and surround lighting, and so on. The experiment shows that this method is very accurate in locating the key points of frontal stand human body, and can solve some problems of occlusion. It is ideal used in a motion tracking system for automatic initialization and self-recovery when tracking failed

Abstract: Loudspeaker is a strongly nonlinear system which is associated with several situations such as electronic, magnetic, mechanical and acoustic. Recently, most of the methods used to measure and analysis loudspeaker are based on the FFT. Unfortunately, traditional Fourier transform based signal analysis method usually causes meaningless results when it is used to analysis non-stationary and nonlinear signal. In this paper, we use Hilbert-Huang transform (HHT) to review the instantaneous frequency of loudspeaker output. Experiments demonstrate that the distortion of loudspeaker can be recognized as intrawave frequency modulation caused by wave profile deformation. Then a novel nonlinear distortion measurement method is proposed which can reveal more accurate and physical meaningful characteristic of loudspeaker.

Abstract: Due to shortcoming of traditional image matching for computing the fitness for every pixel in the searching space, a new bat algorithm with mutation (BAM) is proposed to solve image matching problem, and a modification is applied to mutate between bats during the process of the new solutions updating. This new approach can accelerate the global convergence speed while preserving the strong robustness of the basic BA. The realization procedure for this improved meta-heuristic approach BAM is also presented. To prove the performance of this proposed meta-heuristic method, BAM is compared with BA and other population-based optimization methods, DE and SGA. The experiment shows that the proposed approach is more effective and feasible in image matching than the other model.

Abstract: The driving force of a genetic algorithm is the fitness function. The traditional fitness function based on the error sum of squares has a poor effect when the number of difference between classes is huge. Furthermore, it often fails to get better clustering results due to the lack of the clustering effect evaluation. So, this paper proposes a new K-means clustering based on Genetic Algorithm. Firstly, we define the concept of difference density and uses it as the fitness function of the genetic algorithm. Secondly, we evaluate the quality of the clustering results by some indicators and find the best cluster centers by iteration. The comparison proves that our method achieves a better result than the traditional K-means clustering based on genetic algorithm.

Abstract: A system traceable to mass standard below 10-5N with high precision was proposed. An electrostatic force generator was adopted to produce micro force. The principle of the system was a cylindrical capacitor. The outer electrode served as the reference. A rectilinear flexure mechanism suspended and guided the inner electrode. The electrostatic force was generated by the voltage between electrodes so that mechanics quantity was linked to electrical capacity. The capacitor can be used in a balance mode to compare an electrostatic force with the calibrated nominal mass. The experiments show that the capacitance change gradient is 0.84pF/mm so as to realize the electrostatic force in the range of 10-6～10-9N.