Papers by Author: Hao Bo Cheng

Abstract: Magnetorehological jet finishing (MJF) for optical materials is a promising technique, which characterized as polishing arbitrary surface patterns and correction plates, micro-channels, thin ultra-uniform thickness substrates and near perfect optical components. The process and the machine are complicated. This paper is concerned with the process optimization and tool design, and results obtained by FEA on the designed MJF tool.

Abstract: This paper proposes a novel wheel-shaped grinding/polishing tool, which is designed to be controlled on both the self-rotation around its axis and the co-rotation around vertical axis Z at the specified speeds respectively. Therefore, the surface material of the workpiece can be removed by virtue of self-rotating motion. On the other hand, the co-rotating motion will also change the manufacturing orbit continually. To analyze the characteristics of the tool, material removal in the manufacturing zone on the workpiece surface is first established through theoretical modeling. Subsequently, a good evaluating method, i.e. power spectral density, for analyzing the frequency spectrum features of material removal function in computer-controlled optical grinding and polishing is introduced in detail. By simulation, the power spectral density of the material removal function was cut into several parts, some frequency with low amplifies of material removal function were removed, and the modified material removal function reflected the actual processing status, which was helpful in removing some residual high frequency errors on the surface of the workpiece. Finally, the high amplitude such as at high frequency of 110mm-1 and 210mm-1 was reserved and some other low amplitude frequencies were removed.

Abstract: This paper describes a two-dimensional tool-path planning model for minimizing the regularly distributed errors or mid-frequency errors during computer controlled optical surfacing (CCOS) by optimally connecting different tool-path segments. The model was established based on a neuro-fuzzy algorithm, a path neighborhood function which is defined as a victorious output element calculated in a self-organization way, then, the optimum material removal function with a modified weight was derived. The material removal function was studied theoretically and the results of simulation present a Gaussian distribution feature. Discrete removal points and optimized tool-path grid were simulated. Finally, an experiment involving a parabolic mirror was performed for residual error removal and the two-dimensional tool-path planning algorithm was found to be valid.

Abstract: This paper presents the design and implementation of a robust motion control structure for linear servo units used in noncircular machining. Compared with ball/screw driven system, the controller of the linear motor driven system must provide a high level of disturbance rejection performance, as the system is more sensitive to force disturbances and parameter variations. Thus, in this paper, a robust feedback controller based on disturbance observer is applied to enhance the stiffness and robustness. A magnitude and phase regulating control scheme (MPRC) is proposed to improve the system tracking accuracy, and a simple error feedforward compensator (EFC) further reduces the feedforward control error that result from inaccurate frequency response data. The effectiveness of the proposed controller is demonstrated by experiments.