Papers by Author: J. Liu

Abstract: Pneumatic measurement and genetic algorithm based approach for form tolerances, including the cylindricity error, circularity error and straightness error of axis, of inner hole in spool valve are studied in this paper. A differential pressure type of pneumatic comprehensive measurement approach is put forward, which applies the pneumatic nozzle scanning measurement principle. The minimum zone evaluation and calculation approach for form tolerances based on an improved genetic algorithm is presented considering the characteristics of the measuring point. Finally, the automatic measurement experiment is developed, which can simultaneously measure and evaluate the form tolerances of inner hole in one process.

Abstract: Electric steering engine was generally applied in arm systems such as carrier rocket and missile, its life period is very short, and the space and weight of its reducer were strictly restricted, so it is not fit to adopt the conventional rule of infinite life to design electric steering engine gear reducer. This paper carried out the optimum design for it based on the rule of finite life and space, provided and demonstrated a new design scheme, and realized the interior overall structure design of reducer. We used the UG plane to realize three-dimension module design and virtual assembly of gear reducer, elaborated the implementation method of three-dimension motion simulation by the parameter drive mechanism, and simulated the actual working procedure. Experimental results indicated that this gear reducer satisfied excellently the requirement of big drive ratio under the finite life and space.

Abstract: This paper adopted the photoelectric micro measurement system based on CCD which was independently developed by Laboratory of Process Automatic and Detection Harbin Institute of Technology to detect dimension of the small precise parts. Under the various focusing status, it was discovered that articulation of focusing has huge effect on the measurement of measurand. According to the characteristics of measurand, we adopted the entropy function as the evaluation function of automatic focusing, developed a special software to process entropy value of the picked images, and obtained the relationship of focusing evaluation function and measurement error through a large number of experiments. The experimental result effectively verified the effect of articulation of focusing on dimension measurement.

Abstract: Spool valve orifice flow characteristic of servo valve plays an important role in the spool valve overlap measurement and manufacturing quality analysis of servo valve. The liner segment of flow characteristic curve could be used to calculate the overlap, and the non-linear segment could be used to evaluate the manufacturing quality of servo valve. This paper analyzed the valve orifice characteristic measurement based on the pneumatic flow method in detail, developed an automatic pneumatic measurement apparatus for valve orifice characteristic and spool valve overlap based on the thermal mass flow sensor AWM2300, verified the measurement accuracy and non-repeated error of this apparatus, and adopted the overlap as investigated object to contrast the measurement results by pneumatic flow method with by pneumatic pressure method. The non-repeated error of overlap measurement by pneumatic flow method did not exceed ±0.5(m, and the experimental results indicated that the automatic pneumatic flow measurement can excellently satisfy the actual requirement in the production of servo valve.