Jiazhong Xu

Fuzzy PID control for AC servo system based on Stribeck friction model

Friction is the key factor influencing high precision and super low-speed running performance of AC servo system. In order to factually simulate the influence of friction on AC servo system, three-loop nonlinear model of industry AC servo motor including measured Stribeck friction disturbance factors is established. The control performance of position loop is simulated and studied by adopting traditional PID and fuzzy PID. The results show that Stribeck friction can lead to “flat top” of position tracking and “dead zone” of speed tracking adopting traditional PID, while fuzzy PID decreases the influence of friction on servo system performance and improves tracking precision and robust performance of the system.

Simulation and optimization of mandrel-heating process for composite shells using internal heat-curing method:

Internal heat-curing is a new method involving heating a mandrel inside a composite shell with steam to make a composite cure. High-quality composite shells can be efficiently molded using this method. However, the mandrel temperature does not change as expected during heating, and the temperature difference on the mandrel is large. In order to analyze the reasons for these problems, a mandrel-heating process in which an internal heat-curing method is applied to the composite shell is studied. A numerical simulation of the mandrel-heating process for a slender cylinder-shaped pipe is carried out, and the mandrel structure is optimized according to the simulation results. Temperature tests on the mandrel show that the uniformity of the optimized mandrel temperature is improved. The research in this article provides a basis for the temperature control and structural design of mandrels and their inner channels. Heating at the expected temperature is achieved, ensuring the quality of the formed composite shell.

The Numerical Simulation Research of Internal Curing Process for Fiber Winding Composite Shell

Curing process has a great impact on molding quality of the fiber-winding composite shell. In order to improve its curing quality and efficiency, a new curing process employed the method of heating the internal metal mandrel with steam can be adopted, which is called internal curing process. This paper introduces the principle of internal curing process and establishes the mathematical models of internal curing process, adopts ANSYS and APDL to develop the 3-D transient numerical simulation program of internal curing to realize numerical simulation of temperature, curing degree and residual strain, and analyze the influence of shell thick, fiber volume fraction and film coefficient on the simulation results. Taking the cylinder shell as an example, numerical simulation and experiment are carried out. This research provides theory basis and analysis method for the design, simulation and parameter optimization of internal curing process.

Tension design of heated-mandrel winding process based on analytical algorithm

Resin matrix filament wound composite shells are widely applied in the fields of military, aerospace, energy transportation, pressure vessel, and civil engineering. The curing and winding are regarded as the necessary procedures during molding, and they are the key factors affecting the final performance of the composite shells. This paper discusses the application of a new molding process called the heated-mandrel winding process, to take the place of the traditional molding process, which has a two-step procedure. It is proved that the heated-mandrel winding process can not only improve the product quality and production efficiency, but can also reduce the labor cost, without moving the wound shell from the winding machine to the oven. In contrast to the traditional molding process, some properties of the composite formed with the heated-mandrel winding process, including the curing degree and elastic modulus, will be changed because of the heat conduction from the heated mandrel during winding. Therefore, the traditional winding tension system design method is no longer suitable for this new process. Taking the temperature changes into account, this paper uses a theoretical investigation and calculations to suggest a tension system model that describes the relationship between the changeable parameters and the winding tension and to calculate the appropriate tension values for winding, based on the heated-mandrel winding process. The accuracy of the model is verified using an experiment. This paper applies an analytical algorithm based on simple iterative steps to design the tension system. The calculation procedures are simplified, and fewer calculation cycles are required in the analytical algorithm proposed in this paper because it is easier to calculate a few simple linear equations rather than complex nonlinear differential equations under the condition that some initial parameters can be known. As seen during practical application, the model is suitable for a tension system design based on the heated-mandrel winding process and provides further quality improvement in the molding shells.

Axial temperature distribution optimization of mandrel for heated mandrel winding method

The heated mandrel winding method is a new process based on the internal heat-curing method. With the advantages of high production efficiency, good pressure resistance, and so on, the thermosetting fiber composite shell produced using the heated mandrel winding method has been used as a high-pressure shell. Because of the differences between the heated mandrel winding method and the internal heat-curing method, it is especially important to ensure that the axial temperature is distributed as expected. To this end, the structure of the mandrel is improved, wherein the distribution of the holes is rearranged. An experiment shows that the improved mandrel improves the heat transfer. Furthermore, the steam heating process for mandrels with core pipes of different diameters is numerically simulated using FLUENT. The distributions of the flow field and temperature field are compared, and the influence of the mandrel-to-core-pipe diameter ratio on the temperature distribution on the external surface is analyzed based on the flow field characteristics of steam in a cavity. The conclusions provide the theoretical basis for the optimization of the mandrel structure.

A kind of robust processing for Gaussian filtering mean line of surface profile

For the surface with grooves measurement, robust filtering is developing direction of traditional filtering, which is to try to minimize the distortion of mean line caused by the abnormal signal. This paper presents a new method for processing, which combines closely error theory with Gaussian filtering method. The abnormal signal is firstly judged« identified and corrected by 5σ criterion. Then Gaussian filter is implemented through moving average approximation method to obtain the mean line of surface profile. Finally, surface roughness is separated based on the original profile and mean line, and this method achieves robust filtering. It has simple algorithm, is easy to realize and can effectively restrain surface abnormal signal.

Heat transfer simulation and analysis of mandrel for heated-mandrel winding method of tapered shell

With the advantages of high production efficiency and good product quality, the heated-mandrel winding method has been widely used for high-pressure shells. Previous research results show that it is very important to ensure that the axial temperature is distributed as expected because the temperature distribution influences shell-forming qualities to a large extent. In contrast to cylindrical shells, tapered shells have not only a tapered mandrel but also uneven thickness of the shell, so the internal structure of currently used mandrels cannot achieve the desired temperature distribution. The finite element model of the temperature field and flow field of the steam inside the mandrel of tapered shell using the standard k-e formula and the steam-heating process for mandrels with tapered shells is simulated using FLUENT. The results of the numerical simulation show the temperature, velocity, and pressure of the model. According to this, the flow and heat transfer characteristics of steam are analyzed to reveal the influences of process parameters and runner structure on the internal temperature distribution of the mandrel. By considering the influences of inlet pressure, hole positions, and hole diameters, the relationship between the temperature distribution of the surface of the mandrel and the process and the mandrel structure parameters are discussed. The conclusions provide the theoretical basis for the optimization of the mandrel structural design and the heated-mandrel winding method.

Research of heated winding process for composite based on “birth and death” method

The process of heated winding process for composite in which winding and curing occur at the same time and influence mutually is complicated. The fields of inside the composite have effect on each other while the layers wound are influenced by curing reaction. In this paper, the two dimensional model is built layer by layer in ANSYS and the model is activated using elements “birth and death” method to simulate the heated winding process. We can know the distribution of temperature and curing during winding by the charts of temperature field and curing field. The centre nodes of first, fifth and tenth layer are observed to obtain curve of temperature and degree of cure, from which the change of temperature and curing in the layer above during winding is obtained.

Four-axis winding machine control system design based on the embedded motion controller

A four-axis winding machine control system based on embedded motion controller is designed in this paper. The mathematical model of the axisymmetric body is established, the law of geodesic winding is analysed by the theory of differential geometry, the motion trail of eye and the corner of mandrel is attained by specific constraint condition and the control way of electronic cam is adopted to solve the trajectory of the wire tip and the rotation angle of the mandrel. The host and slave structure of “industrial computer + embedded motion controller” is adopted to realize longitudinal and circumferential winding of the four-axis winding machine. The host and slave computer software system is developed by the VC and Trio Basic language respectively. The practical operation shows: embedded motion controller runs without the host computer, which improves the systems reliability and openness.

Calculation and accuracy analysis of center of gravity of payload rack

In order to measure center of gravity of payload rack, a method is put forward to solve this problem by theory of torque balance in rotating coordinate system. Forward computation is used to calculate the weight and center of gravity of payload rack. Then makes an accuracy analysis of this method by inverse computation which focuses on calculating sensor readings including maximum expected errors, and finally makes an accuracy comparison when the payload rack weight is 10000 N and 1000 N. The results show that: if the accuracy of the sensors is 0.01%, measured weight is within 0.3% of actual weight, each of measured center of gravity is within 3 mm of actual center of gravity, and higher accuracy could be achieved by further increasing the weight of the rack under the same condition.