Feedback linearization and equivalent-disturbance compensation control strategy for piezoelectric stage

Piezoelectric stages use piezoelectric actuators and flexure hinges as driving and amplifying mechanisms,respectively.These systems have high positioning accuracy and high-frequency responses,and they are widely used in various precision/ultra-precision positioning fields.However,the main challenge with these devices is the inherent hysteresis nonlinearity of piezoelectric actuators,which seriously affects the tracking accuracy of a piezoelectric stage.Inspired by this challenge,in this work,we developed a Hammerstein model to describe the hysteresis nonlinearity of a piezoelectric stage.In particular,in our proposed scheme,a feedback-linearization algorithm is used to eliminate the static hysteresis nonlinearity.In addition,a composite controller based on equivalent-disturbance compensation was designed to counteract model uncertainties and external disturbances.An analysis of the stability of a closed-loop system based on this feedback-linearization algorithm and composite controller was performed,and this was followed by extensive comparative experiments using a piezoelectric stage developed in the laboratory.The experimental results confirmed that the feedback-linearization algorithm and the composite controller offer improved linearization and trajectory-tracking performance.

Using Fractional-order PI^λD^μ Controller for Control of Aerodynamic Missile

A new type of PID controller is introduced and some properties are given. The novelty of the proposed controller consists in the extension of derivation and integration order from integer to non-integer order. The PIλDμ controller generally has three advantages when compared to the integerl-order controller: the first is that it has more degrees of freedom in the model; the second is that it has a memory in model,the memory insure the history and its impact to present and future,the third is it ensures the stability of missile. This approach provides a more flexible tuning strategy and therefore an easier achieving of control requirements. Flight dynamic model of an aerodynamic missile is taken into account in implementing the PIλDμ controller. Simulation results show that the PIλDμ controller is not sensitive to the changes of control parameters and the system parameters. Also,the controller has more flexible structure and stronger robustness.

Optimization Algorithm of UWB Positioning for Aircraft Assembly Workshop

Due to the complexity of strong metal interference and multiple occlusions in aircraft assembly workshop,the random "drift"phenomenon often happens in the ultra wide band (UWB)based positioning system.To solve this,a fusion positioning optimization algorithm is proposed based on median filtering,hidden Markov model (HMM)a nd Kalman filtering.Firstly,based on the three-dimensional (3D) median filtering,aqueue optimization method with weights is introduced to smooth the measurement data and eliminate the abnormal value.Secondly,taking Singer model as a reference,a single-dimension acceleration distribution model is designed.In order to further consider the spatial motion characteristics of objects in workshop,the distribution is extended from 1D to 3D,and discretized into the state quantity of HMM.Subsequently,the data obtained by the two methods are fused by taking Kalman filter as an iterator,and then the optimized location solution is obtained based on dynamic weights.Finally,an experiment is conducted in an aircraft assembly workshop.Results show that 99.3% of dynamic positioning errors are less than 15 cm after using the proposed algorithm.Even in the situation with large signal-fluctuation,there are 71.6% of positioning data whose errors are reduced.The random "drift"is greatly decreased.

A noise removal algorithm for DR Images based on adaptive estimation of threshold

When DR （Digital Radiography） images are filtered, it is necessary to preserve the edges and key details. But the existing methods may inevitably take fine details mistaken for noise to remove. In order to solve the problem an improved anisotropic diffu- sion filtering model is proposed. Firstly, a novel diffusion function is introduced based on Perona and Malik model, which well overcomes the high rate of convergence. Secondly, the gradient threshold is modified to an adaptive estimation function, so it is bet- ter at adaptive threshold regulations according to the pixels and iteration times. Finally, the edges are extracted from the restored im- ages and the results are evaluated quantificationally. It is shown from the experiments that the proposed method is effective not only in noise reduction but also in details preserved.

Program Design of Graphic Realism Displaying System Based on DXF Lathe Turning Rotational Parts

For virtually realizing the graphic realism display of DXF machine parts, in AutoCAD2007 graphic drawing environment, an interactive experimental method was taken to realize the display of graphic in DXF, which was taken as the data-exchanged interface and source. Based on depth analysis of DXF data structure, take one drawing of DXF lathe turning rotational part asthe test piece. By VC＋＋6.0 programming, part＇s geometry information could be obtained. Through data processing, 3D data of the test piece could be generated, which is based on 2D data of DXF test piece. Then, OpenGL graphic processing technologies （light, material, texture, map, et al.） were applied on the 3D display of test piece from DXF files or program modules. Finally based on the test report, results of the system functions were shared to prove the realization of system design, and the feasibility of algorithms used. In the developed software, Machine Designers could get a full view of machine parts, and do some proper modifications. The study content and results of our work have some theory and practical significance on the application of program design in the practical projects.

Multi-Deme Parallel FGAs-Based Algorithm for Multitarget Tracking

For data association in multisensor and multitarget tracking, a novel parallel algorithm is developed to improve the efficiency and real-time performance of FGAs-based algorithm. One Cluster of Workstation （COW） with Message Passing Interface （MPI） is built. The proposed Multi-Deme Parallel FGA （MDPFGA） is run on the platform. A serial of special MDPFGAs are used to determine the static and the dynamic solutions of generalized m-best S-D assignment problem respectively, as well as target states estimation in track management. Such an assignment-based parallel algorithm is demonstrated on simulated passive sensor track formation and maintenance problem. While illustrating the feasibility of the proposed algorithm in multisensor multitarget tracking, simulation results indicate that the MDPFGAs-based algorithm has greater efficiency and speed than the FGAs-based algorithm.

Program design of STL machine graphics realistic system

This topic is based on AutoCAD graphic input environment. It takes the STL format graphic files as the data exchange interface to do the research of STL interactive 3D realistic graphics displaying content. Through the analysis of the STL file format, in VC＋＋6.0 programming environment, class if stream in the standard IO library was used for object class definition. And get line functions in the string class were called to read and bind STL file line by line. In data processing module, draw triangles in OpenGL programming technology was applied to realize the visual display of the STL graphics, with the corresponding 3D entity data generated. OpenGL graphics processing technologies were applied to display 3D graphics from STL files input or realistic program module, which contain the graphic transformation, light, materials, et al. Test reports were shared based on the test of the application system. Finally the program design of STL graphics realistic display system was completed based on research work, which has certain theoretical and practical significance in the aspect of engineering application.

Intelligent Cost Modeling Based on Soft Computing for Avionics Systems

In parametric cost estimating, objections to using statistical Cost Estimating Relationships （CERs） and parametric models include problems of low statistical significance due to limited data points, biases in the underlying data, and lack of robustness. Soft Computing （SC） technologies are used for building intelligent cost models. The SC models are systemically evaluated based on their training and prediction of the historical cost data of airborne avionics systems. Results indicating the strengths and weakness of each model are presented. In general, the intelligent cost models have higher prediction precision, better data adaptability, and stronger self-learning capability than the regression CERs.

MOF-derived multi-interface carbon-based composites with enhanced polarization loss and efficient microwave absorption

Metal-organic framework materials(MOFs)have been widely stu-died because of their adjustable composition and controllable structure in the field of microwave absorption(MA).Therein,Prussian blue analogs(PBA)have attracted the attention of researchers with ultra-high metal content.However,the attenua-tion ability of microwave for PBA-based composites is still unsatis-factory up to now.Therefore,the NiFe/CoFe@C composites were prepared by carbonizing polymetallic PBA(NiCoFe PBA)materials in this work,and the influence of different metal alloy components on MA was explored by adjusting the ratio of metal ions(Ni^(2+)/Co^(2+)).Moreover,the NiFe/CoFe@C composites have rich interfaces and enhance the polarization loss due to the introduction of Ni and it has an optimal performance at 2.7 mm that is the reflection loss(RL)is−41.49 dB and an effective absorption bandwidth(EAB)is 7.12 GHz with 1/1(Ni^(2+)/Co^(2+)).The above data provides a research idea for obtaining light and efficient absorbers.