As the crown of the scholar’s four jewels, the brush has occupied a cherished position in the culture of traditional Chinese painting and calligraphy

This paper describes an innovative free-form modeling system, Virtual Clay Modeling System (VCMS), in which users can directly manipulate the shape of a virtual object like a clay model in real world. With this system, some disadvantages of interaction with computer aided industry design (CAID) systems can be resolved. In order to enhance the immersion feelings and improve the controlling abilities to cut, paste, and compensate of VCMS, we use Spaceball 5000 and PHANTOM Desktop to assign the set of interaction tasks. During the process of realizing 6 degree-of-freedom (DOF) haptic feedback modeling control, we developed and accomplished the device interfaces with Open Inventor and Qt application framework. VCMS provides us a good immersion of allowing for effective modeling in a virtual world.

The acoustic pressure signal generated by blades is one of the key indicators for condition monitoring and fault diagnosis in the field of turbines. Generally, the working conditions of the turbine are harsh, resulting in a large amount of interference and noise in the measured acoustic pressure signal. Therefore, denoising the acoustic pressure signal is the basis of the subsequent research. In this paper, a denoising method of micro-turbine acoustic pressure signal based on the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) and Variable step-size Normalized Least Mean Square (VSS-NLMS) algorithms is proposed. Firstly, the CEEMDAN algorithm is used to decompose the original signal into multiple intrinsic mode functions (IMFs), based on the cross-correlation coefficient and continuous mean square error (CMSE) criterion; the obtained IMFs are divided into clear IMFs, noise-dominated IMFs, and noise IMFs. Finally, the improved VSS-NLMS algorithm is adopted to denoise the noise-dominated IMFs and combined with the clear IMF for reconstruction to obtain the final denoised signal. Adopting the above principles, the acoustic pressure signals generated by a micro-turbine with different rotation speeds and different states (normal turbine and fractured turbine) are denoised, respectively, and the results are compared with the axial flow fan test (ideal interference-free signal). The results show that the denoising method proposed in this paper has a good denoising effect, and the denoised signal is smooth and the important features are well preserved, which is conducive to the extraction of acoustic pressure signal characteristics.

A novel variable stiffness 3D virtual brush model and haptic decoration technique suitable for the surface of the three-dimensional objects for the automobile industry are introduced based on real-time haptic feedback mechanism using a 6 DOFs input device, and the haptic behavior of an expressive virtual 3D brush with variable stiffness is studied in detail for the first time. First, the intrinsic mechanism between the deformation of real hair brush and the applied external forces (such as the bending moment) is analyzed and studied in detail by introducing a bending spring to express the basic mechanical behavior for the 3D hair brush. Based on this brush model, many important painting features can be simulated, such as the softer brush tip, brush flattening, and bristle spreading. And a useful algorithm (named the weighted-average distance) for dealing with collision checking among the two objects (3D clay and the 3D brush) is presented. As long as the brush head is close to the 3D object, within a tolerance range, the computational tactile sensation force will be emerged, and the interactive painting process is implemented actually on the outer surface of the virtual object. We then calculate the related bounding ball for deformed 3D brush using a fast ball-expanding search algorithm to determine the virtual projection plane. Based on the real-time deformation about the virtual brush head at a sampling point, the 2D painting footprints, which is produced between the brush head and virtual projection painting plane, is calculated and rendered. Next, the 3D painting footprint could be easily produced via mapping the 2D painting footprints onto the surface of the 3D model in real time. Finally, the 3D painting strokes are formed via controlling the exerted force and overlapping the virtual 3D painting footprints with different shape, size, and following the moving direction of the 3D brush. Experiment result shows that the adopted method can effectively enhance reality to users, with high performance.

Compared with the single direction depth element (DEXEL) model, the three direction DEXEL model could express a shape more precisely. This paper gives a dexelization algorithm of polyhedrons. This algorithm could transform a polyhedron into its three direction DEXEL model. Under the same three direction DEXEL space, by Boolean operations such as union, intersection, and subtraction, complex DEXEL model could be produced. This paper used the three direction DEXEL model in rapid prototyping simulation. The complex features of the shape are preserved well .Under Java2.0 and Java 3D, these algorithms are tested. A simulation example of a part is given.

In order to introduce force feedback effect to virtual clay modeling system, a new force feedback model based on material removal rate is presented in this paper. According to the material removal rate and the properties of material, the proposed method can calculate the sculpting haptic force. The force is not only proportional to the removed material volume (Voxel volume), but also to the physical properties of model's material. This haptic model is well suitable for calculating haptic feedback and sculpting virtual clay model with haptic device, Phantom Desktop. Experiment results demonstrate that the adopted method can add an effective haptics to users and can be used widely in computer-aided industrial design field.