With the increasing consumer demand, the mechanized shrimp productions become more and more popular for its high efficiency and much less bacterial infection. In particular, removal of shell and vein plays an important role to guarantee clean production in the shrimp processing. There are several kinds of machines which can achieve the required function worldwide up to now. Among these machines, the machine featured with a rotary plate has significant advantages if compared with others. Thus the structure and the development process about it were summarized in this paper. Through the summary, the advances of this machine were outlined in detail, and the future research direction of the industry of shrimp peeling machine was also indicated, that is, the mechanical structure need to be optimized and simplified. Meanwhile, if advanced electric automatic control system introduced, the labor occupation would be significantly reduced, and the production quality, productivity and efficiency accordingly be enhanced.
With the excellent damping performance, gas foil bearing (GFB) is becoming the promising hydrodynamic lubrication structure for high speed turbomachinery. To improve the performance of the conventional GFBs, a new double-layer gas foil bearing (PGFB) with double-layer protuberant strip as elastic support is developed. A 2D numerical model based on Reynolds equation and Kirchhoff equation is established to determine the gas film thickness, gas film pressure and foil deflection. Static performance and dynamic performance of three PGFBs with different elastic foil layers arrangement are presented and compared qualitative dues to the difficulties in measuring the practice eccentricity and load capacity with high speed rotor-bearing system. By applying in a turboexpander with ϕ25mm rotor diameter, the three PGFBs are tested. Because the three PGFBs share the same rotor structure and the same air supply pressure, the rotor drag torque and the bearing static load are almost the same in the tests. The experimental results show that all the PGFBs run well in turboexpander. Rotating speed, temperature and enthalpy differences and rotor synchronous vibration under the same turboexpander air supply pressure are compared. The numerical model predicted well the qualitative difference of the loading performance of the three PGFBs.
This paper proposes a constitution method for an adaptive PID control system that follows a non-stationary system. Because a PID controller has various practical benefits that are easy to implement, unnecessary of controlled model and highly robust, it is the most common control system in industrial world even today. However, its main drawback is that tuning is time consuming because each parameter is determined empirically based on trial-and-error, which is especially noticeable in a multi-input multi-output (MIMO) system composed of multiple PID controllers with interference between control input and controlled output. Other methods have been proposed, including the Ziegler-Nichols ultimate sensitivity method, but it cannot deal with a MIMO system. Additionally, methods using optimization exist, but they cannot provide online tuning for non-stationary systems during operations due to the numerous tuning parameters and repeated computations. In this study, we introduce a computationally efficient optimization method called the Simultaneous Perturbation Stochastic Approximation (SPSA) and investigate its performances when applied to a PID control system. We also propose an online parameter tuning method for the controller by improving the standard SPSA algorithm. The efficiency of proposed method is demonstrated by applying it to a MIMO system, which has some interference.
This paper deals with axial ultrasonic vibration-assisted machining with workpiece bending. It was proposed as a novel machining method for the reduction of the chippings at the machined holes during micro through-hole drilling of chemically strengthened glass. In micro through-hole drilling of chemically strengthened glass, machining accuracy and efficiency tend to be low because the material's high hardness and brittleness cause rapid tool wear and large chippings at the inlet and outlet of the machined holes. In order to machine small holes with high accuracy, the reduction of the tensile stress that causes large chippings at the outlet of the machined holes is an issue of primary importance that deserves investigation. In the proposed machining method, the glass plate is bent slightly to be convex upward through the application of a compressive stress at the posterior surface of chemically strengthened glass, with a specially designed jig. Using this proposed method that can reduce the tensile stress, the chipping size at the outlet of the machined holes was successfully reduced with applied compressive stress values of 38.9 MPa. In conclusion, it has been clear that the axial ultrasonic vibration-assisted machining with workpiece bending has the potential for achieving high-precision and high-efficiency machining for chemically strengthened glass.
In order to solve the welding formation defects of undercut and hump caused by the irrationality selection of parameters at a high welding speed more than 100cm/min in twin wire tandem co-pool submerged arc welding, a novel hybrid intelligent optimization model for twin wire tandem co-pool high speed submerged arc welding is proposed. This model combines local mean decomposition (LMD), energy entropy, back propagation neural network (BPNN) and particle swarm optimization algorithm (PSO). LMD is employed to decompose the collected welding current signal, excavate the underlying arc feature information related to the rationality of parameters and welding quality of welding seam formation appearance and sectional morphology. The energy entropy is used as the quantificational parameter to describe the rationality of parameters and welding quality. The relationship between the welding parameters and the energy entropy is established by BPNN, and the welding parameters are automatically obtained by the PSO. The application shows that the model is able to reliably achieve the optimization selection of welding parameters to guarantee welding quality.
Tire performances are strongly influenced by cross section profile, and equilibrium profile has been a focus of radial tire researches, however, how to use the profiles to design radial tires has been reported rarely due to reasons of secrecy. This paper describes a practical method of using equilibrium profile to design radial tires, which is based on the restricted dimensions by tire standards. Based on the membrane model and minimum energy principle, equations of equilibrium profiles of radial tires with flat and curved belts are obtained by using variational approach. A method of designing carcass contours by using these equations is developed, in contrast to earlier methods the proposed method makes the width rather than the height of the point with maximum width on the profiles as the input parameter, and the restriction lengths of carcass by the belt are also calculated at the same time. For 175R14 tire, this paper's results are compared with Akasaka's, the accuracy of this method is confirmed and the effects of belt radius on profiles are revealed. Four different designs of 295R22.5 tire are analyzed by finite element method to verify the benefits of this method. This method can be used to design both tires with larger and smaller aspect ratios, and it will offer a strong guide for designing radial tires.
This study proposes an online tuning method using a model-based controller with adaptive parameters in the controller to effectively maintain the control performance and stability due to characteristic variations in the structure. Although model-based control generally provides a highly controllable performance, its performance depends on the modeling accuracy of the controlled object. Typically modeling errors, characteristics that change over time, etc. cause the performance to deteriorate. Hence, tuning of the model-based controller's characteristics is proposed as a method to adapt to the errors between a real object and its model. The main idea of the tuning method proposed in this study is that tuning the poles of the controller greatly affects control performance and stability. The tuning algorithm in the proposed method employs the simultaneous perturbation stochastic approximation (SPSA), which is well suited for optimization problems with multiple design variables. To evaluate the effectiveness of the proposed tuning method, it is applied to vibration control simulations in which the model of the controlled object is perturbed to change its physical characteristics, and then the controller is tuned to adapt to these changes. Since SPSA is a stochastic optimization method, Monte Carlo simulations are also conducted to demonstrate the effectiveness of the proposed tuning method.