Zhiyong Zhang

Modeling and calibration of pointing errors using a semi-parametric regression method with applications in inertially stabilized platforms

This article investigates modeling and calibration issues that are associated with inertially stabilized platforms to achieve accurate pointing. In modeling part, the Denavit–Hartenberg notation is used to perform an error analysis of the kinematics of inertially stabilized platforms. A physical model is then established to illustrate the effects of geometric errors that are caused by imprecision in the manufacturing and assembly processes on the pointing accuracy of inertially stabilized platforms. In the calibration part, an improved hybrid model denoted as the semi-parametric regression model is developed to compensate for remaining nonlinear errors. With applications to a two-degree-of-freedom miniature inertially stabilized platform, semi-parametric regression model is shown to outperform physical model substantially in all cases. The experimental results also indicate that the proposed semi-parametric regression model eliminates both the geometric and nonlinear errors, and that the pointing accuracy of miniature inertially stabilized platform significantly improves after compensation.

Improved Angular Velocity Estimation Using MEMS Sensors with Applications in Miniature Inertially Stabilized Platforms

Abstract The performance of any inertially stabilized platform (ISP) is strongly related to the bandwidth and accuracy of the angular velocity signals. This paper discusses the development of an optimal state estimator for sensing inertial velocity using low-cost micro-electro-mechanical systems (MEMS) sensors. A low-bandwidth gyroscope is used alone with two low-performance accelerometers to obtain the estimation. The gyroscope has its own limited dynamics and mainly contributes to the low-frequency components of the estimation. The accelerometers have inherent biases and mainly contribute to the high-frequency components of the estimation. Extensive experimental results show that the state estimator can achieve high-performance signals over a wide range of velocities without drifts in both the t - and s -domains. Furthermore, with applications in miniature inertially stabilized platforms, the control characteristic presents a significantly improvement over the existing methods. The method can be also applied to robotics, attitude estimation, and friction compensation.

Design Consideration for Precise Cable Drive

A brief overview of previously built Electro-Optical Tracking system reveals a trend toward smaller, more agile systems. Steel cable drive technology is an alternative to gearbox, belt and pulleys, chains and sprocket and other currently available transmission for several significant advantages, which includes backlash free, high stiffness, high efficiency, no lubrication etc.. As a new type of drive form, there were several key tradeoffs for the cable drive application, which will be developed and subjected in detail in this paper. Firstly Transmission principle and properties of cable drive is studied. Secondly, related design considerations of cable drive will be implemented and researched in detail, including the cable selection and capstan design, cable-groove matching strategy and cable tensioning design. Finally, actual application example of precise steel cable drive is presented for an Electro-Optical tracking gimbals, and performances tested validate the significant advantages of precise cable drive technology.

Transverse Stiffness and Guiding Characteristics Analysis of Compliant Linear Guided Mechanism

This paper presents a novel compliant linear guided mechanism (CLGM) to replace traditional spring and translation joint to transfer motion and force with its advanced guiding characteristics. In view of the incompatible relationship between axial stiffness and transverse stiffness of CLGM, eight kinds of CLGMs were developed by using building block approach based on fixed-guided flexure beam. The finite element analysis (FEA) models of eight CLGMs were built to complete numerical analysis on the force-displacement in axis and off-axis direction with same geometric sizes. The FEA results show that the structure configuration of Type 2-Type 8 can achieve a larger axial travel, Type 2 and Type4 have the advanced guiding characteristic with higher ratio of axial/transverse stiffness. Analysis indicates that the building block approach is an efficient method to complete the conceptual synthesis of compliant mechanism and FEA is effective on the structure optimization for the required compliance and stiffness in axial and transverse direction.

Design and modeling of a novel monolithic parallel XY stage with centimeters travel range

Since most of XY positioning stages with large travel range proposed by former researchers suffer from loose structure and low out-of-plane payload, this article presents a novel monolithic parallel XY stage based on spatial prismatic–prismatic joints with centimeters travel range, compact size, and high out-of-plane payload capacity. The novel parallel linear compliant mechanism of the stage is composed of four spatial prismatic–prismatic joints, which is two compound leaf spring parallelograms serially connected in cubical space to obtain large travel, compact size, and high out-of-plane payload capacity simultaneously. The theoretical static stiffness and resonant frequencies are obtained by matrix structural analysis. As a case study, a reified stage is presented and discussed in detail. Finally, theoretical models are comprehensively compared with finite element analysis models. It is shown that the stage in the case study has the following merits: large travel range up to 20u2009×u200920u2009mm2, high-area ratio of workspace to the outer dimension of the stage about 2.26%, well-constrained cross-axis coupling motion less than 1.5u2009μm at the full primary motion, acceptable resonant frequencies of the two translational axes about 34u2009Hz, and large out-of-plane payload capacity more than 24u2009kg.

Improved velocity estimation using low-performance position and torque sensors with applications in friction compensation control systems

Velocity computation based on simple numerical differentiation from a low-resolution position sensor or numerical integration from an imperfect torque sensor may be highly erroneous, especially in the low-velocity or high-acceleration regions. To resolve this problem, a novel approach to obtaining high-performance velocities in these regions is presented. The proposed estimator is based on the framework of the Kalman filter. A switching architecture is used to address the estimation problem, with the sensors functioning under different situations. Experimental results show that the proposed estimator significantly reduces velocity errors in estimation compared with an encoder or torque sensor. A dual-loop control structure is also developed with estimated velocity feedback for application in the friction compensation control system of an inertially stabilized platform. Experimental findings show that the control characteristic significantly improves because the proposed approach enables the rejection of non-linear friction.

Error Analysis and Calibration of Gyro-Stabilized Platform for Electro-Optical Pointing System

A novel method in the solution of the pointing problem for electro-optical pointing system (EOPS) is presented in this paper. Firstly, the error sources are analyzed in detail. And then, a linear model whose parameters have definitely physical meaning is developed to improve pointing accuracy. Extensive experiments have been carried out and the results show that the system errors can be eliminated by the model effectively and the pointing accuracy of the azimuth and elevation axes have been improved from 0.4541º and 0.2959º to 0.038º and 0.031º respectively.

Error Analysis of Mast Mounted Electro-Optical Stabilized Platform Based on Multi-body Kinematics Theory

Error analysis of target location for Mast Mounted Electro-Optical Stabilized Platform based on multi-body kinematics theory is presented in this paper. Firstly, a typical structure of OMS, which is mounted on the reconnaissance vehicle, is introduced briefly and Multi-body kinematics theory is used to illustrate the topology structure and coordinates relations. Accordingly, target location equations between target and OMS are derived. Secondly, the characteristics and compensation methods are discussed in detail for the error analysis, which influence the system target location accuracy, such as imaging sensors errors, stabilized platform errors and equipments errors. Finally, simulation results based on Monte Carlo and experiment results are presented, showing that axis zero bit, consistency, verticality errors and equipments alignment errors are the primary factors, which influence system target location accuracy. After the compensation, the accuracy has been improved 2 orders and reached 5m/0.060.

Exploration into the Innovative Mode of Combining Learning with Researching and Production

It is proposed that the integration of learning, researching and production provides a good solution to the problem that higher education fails to offer qualified graduates demanded by machinery manufacturing industry. This paper first analyses the weakness of enterprises in scientific research and creativity and inexperience of higher education institutes in transferring scientific achievements, then some advice is given as to how to improve the innovative integration mode followed by some successful cases. At last it goes deeper into the future tendency of this mode.

Design and Analysis of a Novel Micro-Angular Vibration Testbed Driven by Voice Coil Actuator

The construction and the operating principle of the novel micro-angular vibration testbed (MAVT) are presented, the MAVT is designed to complete the angular performance testing for the micro sensor and parts such as MEMS-gyro, angular accelerometer. A systemic design procedure of the optimized flexure hinge and general voice coil actuator (VCA) to fine single-axis MAVT actuator are introduced for fast and precision actuation. A method for measuring frequency response function by means of a displacement sensor electric eddy current sensor is designed. To verify the performance of the designed MAVT, frequency response of the system are performed, the differential equation of the pull-tilting motion is established according to the Lagranges equation, the formula of the natural frequency is derived, and the model analysis of the MAVT is also carried out with the help of limited element analysis. The static stiffness experiments show that the angular stroke of the MAVT is 1° and preliminary tests performed on the closed-loop control system indicate that angular resolution of 1 can be achieved. Model experiments performed on the prototype of MAVT are presented and the theoretic result fits with the result of experiment (250Hz). For fast and precision actuation performances, design parameters are selected based on the dynamic model of VCA and flexure hinge, and design process is completed. The model results can be provided for the construction design of the MAVT. Conventional platforms of angular performance testing are bulky and costly. Analysis and experiments results indicate that the novel MAVT is an efficient platform to complete the angular performance testing for micro sensor and parts.