Complex mechanical system with numerous design variables and constraints is difficult or impossible to obtain results by adopting traditional methods. Various decomposition-based methods applied in various engineering fields are analyzed, whose advantages and disadvantages are commented. Through illustrations, research on possibility and validity of utilizing decomposition-based multilevel method in design of complex mechanical system is conducted. Furthermore, solving methods for the key problems in this field is discussed.

QFD (Quality Function Deployment) provides an effective method for product concept design to meet requirements of customers. Design model of Computer Aided QFD Concept Design Expert System and key technologies of computer implementation are proposed. Research on gaining customers’ requirements information is conducted and topology structure of knowledge description of customers’ requirements is established. From the perspective of knowledge engineering, database-based knowledge description and reasoning principle are presented and knowledge reasoning process of expert system is designed. Finally, taking the concept design of former main bearing of high-speed special grinding machine as an example, this system is validated and the result is satisfactory.

Decision-making and evaluation are the key parts of process plan for complex stamping parts and are also the principal technical problems influencing the intelligent degree of process design.  According to process plan design procedure and experts’ experience of complex stamping parts, in virtue of multi-intelligent KBE, feasible process plan design of complex stamping parts is conducted. Furthermore, by applying VE and Plus Ratio Method, quantified evaluation model is combined into intelligent decision-making system, which implements the self-evaluation process plan design based on KBE.

Based on Kaleidocycles and threefold-symmetric Bricard linkages, a new type of retractable structure was developed. This structure took threefold-symmetric Bricard linkages, composed of six tetrahedrons, as fundament, and implemented retractability through tetrahedrons’ rotation around the adjacent hinges. The form and design principle of this structure was presented. On the basis of the geometric parameters of this structure, the shape and dimension of every tetrahedron were determined, and then the relationship between rings of tetrahedron and the corresponding threefold-symmetric Bricard linkages was established. Furthermore, taking the inclining direction of the rotating axes as general displacements, the input-output equation of the rotating variables was obtained, which demonstrated that the movement of this structure had one freedom degree.

In test of thermo-vibration combined environment with high-linear-acceleration, centrifuge is usually utilized to realize high-linear-acceleration, and vibration bed and temperature box installed on it are employed to implement combined environment. Since rotating speed of centrifuge and frequency of vibration bed change in a wide range, furthermore, natural characteristics of centrifuge changes with rotating speed, the likelihood of resonance between centrifuge arm and vibration bed is large, which generates great difficulty for design of centrifuge arm.  Dynamic characteristics are analyzed and changing regulation of different order natural frequency with modal vibration is gained. Finally, modal experiment is conducted on centrifuge, which demonstrates that the computation result is reliable. This result provides important reference for design of centrifuge and vibration table.

This study puts forward an auto-detecting method of detecting the precision of dial gauges based on traveling wave ultrasonic motor and FPGA. This dial gauges automatic tester adopt closed loop position servo system of USM. The design of the position servo system depends on micro-step control technique of traveling wave USM and fuzzy control technique. Moreover, EDA technique, USB technique, sensor technology and digital image-processing technique are used in this system. The novel controller design of traveling wave USM using fuzzy micro-step control technique is put forward. Experments proved that the novel control method can highly enhance precision of position of USM without using precise sensor. This dial gauges automatic tester using USM has features of high precision, efficiency, flexible and convenient in operation and it has broad prospect in application.

In designing and controlling a Stewart platform, accuracy is one of the most important factors to be considered. In order to improve the accuracy of Stewart platforms, an effective method for the kinematical calibration is presented that enables the full set of geometric errors to be identified by measuring poses of the mobile platform. The calibration model between poses and kinematical parameters of a Stewart platform is derived from the inverse kinematics solution, which indicates that the length errors of the 6 actuators and the position errors of the passive joints on the base and the mobile platform play an important role in accuracy reducing. The kinematical parameters of the platform are measured and identified by three-dimension coordinate measuring machine and iterative least square method. The kinematical calibration experiments are carried out with the Stewart platform developed in Harbin Institute of Technology. And the results show that the method can improve the accuracy of Stewart platform.

Continuously variable transmission (CVT) is an ideal transmission for automobile. A commonly used VDT hydraulic system of CVT is introduced, on the basis of which, a new type of DPC hydraulic system is designed. Safety in case of pressure breakdown and shifting speed performance of these two hydraulic systems are compared through simulation. The results of analysis indicate that safety in case of pressure breakdown of DPC hydraulic system is prior to VDT hydraulic system and the former still exceeds the latter in shifting speed performances.

Through FEA on the composite structure of reinforced concrete and steel scuttle, seeking destruction reasons by referring to practical destruction features, a beneficial conclusion for this type of structure design is proposed. Compare between two analysis results obtained respectively from two different FEA softwares is conducted. In addition, how to model and analyze accurately but concisely is discussed. Some suggestions with reference value for FEA are presented by comparing several different modeling methods.

Quantification method of colors is expounded and a new method to quantify colors by employing improved changeball algorithm is proposed. This method meets the requirements of keeping some special colors of the original pictures, which is required by process or design of designers in design of jacquard CAD. Starting from the perspective of adaptability of human vision, changeball algorithm guarantees the rationality of the selected representative colors and can improve the process of jacquard CAD. Moreover, changeball algorithm can fulfill the demands of process and design. Simulation results indicate that color quantification effect of this algorithm is good, while its error is small. During real production, error can be well controlled and veracity is well assured.

Previous surface trimming algorithms are usually based on general application field of surface trimming; while for special product design fields, such as garment design, toy design, super-lines and darts as special cutting lines were seldom treated.  A new treating method for super-lines and darts as special cutting lines was put forward. Its processes included: duplicating intersections between super-lines, darts and triangles; distinguishing original and duplicated intersections by utilizing continuity of line segment in one triangle during cutting a base region. Comparing to existing algorithms, this algorithm is more intelligent on processing super-lines and darts, and suitable for special and complex product design. This algorithm has high efficiency since merely geometric elements on base region are processed.

Quadrilateral partition on triangular meshes data is the primary process of composite surface modeling. A novel method of quadrilateral partition on cloudy manifold triangular meshes is presented, which is based on algorithms of mesh simplification and harmonic mapping. Simplification technology grounded in removing vertexes is adopted to simplify triangular mesh model; and then quadrilateral partition is gained by mapping the simplified mesh to 2D parameter domain through harmonic map. By inverse mapping the gained data to 3D space and geodesic technology, 3D quadrilateral topological partition, fitting composite curve modeling, is eventually implemented. This method is simple, practical and has high operation speed. Real illustrations demonstrate that it is effective and feasible.