科创中国

Dual mechanical port machine(DMPM), as a novel electromechanical energy conversion device, has attracted widespread attention. DMPM with spoke type permanent magnet arrangements(STPM-DMPM), which is one of several types of DMPM, has been of interest recently. The unique coupling characteristics of STPM-DMPM are beneficial to improving system performance, but these same characteristics increase the difficulties of control. Now there has been little research about the control of STPM-DMPM, and this has hindered its practical application. Based on a mathematical model of STPM-DMPM, the coupling characteristics and the merits and demerits of such devices are analyzed as applied to a hybrid system. The control strategies for improving the disadvantages and for utilizing the advantage of coupling are researched. In order to weaken the interaction effect of torque outputs in the inner motor and the outer motor that results from coupling in STPM-DMPM, a decoupling control method based on equivalent current control is proposed, and independent torque control for the inner motor and outer motor is achieved. In order to solve address the problem of adequately utilization of coupling, minimizing the overall copper loss of the inner motor and the outer motor of STPM-DMPM is taken as the optimization objective for optimal control, and the purpose of utilizing the coupling adequately and reasonably is achieved. The verification tests of the proposed decoupling control and optimal control strategies are carried out on a prototype STPM-DMPM, and the experimental results show that the interaction effect of torque outputs in the inner motor and the outer motor can be markedly weakened through use of the control method. The overall copper loss of the inner motor and the outer motor can be markedly reduced through use of the optimal control method, while the power output remains unchanged. A breakthrough in the control problem of STPM-DMPM is accomplished by combining the control methods. Good performance in the control of STPM-DMPM will enhance its practicality, particularly as applied to hybrid systems.

As the popularization of dual ring fieldbus,the optimized dual ring synchronization methods are still in short.The current synchronization methods are generally established in traditional industrial fieldbus,in which transmission is commonly considered in single track,the two-way transmitting cannot take full effect,and would result in unwanted idle load on equipment lines.In stamp-transferring part,the synchronizing algorithm is not properly processed to diminish the latency,so the real-time performance of entire system cannot be ensured.To support the synchronization control of stations in the CNC system,a real-time time synchronization method for dual ring fieldbus in the CNC system is designed in this paper.In this method a synchronizing message transmission scheme based on dual ring architecture and the synchronization algorithm between master and secondary stations are integrated.In the scheme,the clock models of both master and secondary stations are optimized with corresponding modules and the stamp data transmission based on the dual ring fieldbus is devised exclusively,so the transmitting efficiency improves with less idle work.In the algorithm,all the secondary stations can accomplish the consistent state with master station by updating clock discrepancy information in one communication cycle,and it takes the advantage of two-way transmitting and makes the best use of dual ring structure,so the real-time performance of the system can be promoted while retaining the precision of synchronization.To evaluate the performance,the costs of the method and errors during synchronizing are noted and analyzed based on the actual running environment in the industrial fieldbus.The results show that it reduces communication cost and ensures the smoothness of the system with low lag effects under heavy load.The proposed time synchronization method optimizes the architecture of sync message transmission in dual ring fieldbus,and improves the efficiency of time synchronization in the stations of CNC system.

The mechanical properties and microstructure evolution of cold-deformed CrMnN austenitic stainless steel annealed in a temperature ranging from 50 ℃ to 650 ℃ for 90 min and at 550 ℃ for different time were investigated by tensile test, micro hardness test, and Transmission Electron Microscope (TEM). The steel was strengthened when it got annealed at temperatures ranging from 100 ℃ to 550 ℃, while it was softened when it got annealed at temperatures ranging from 550 ℃ to 650 ℃. Annealing temperature had stronger effect on mechanical properties than annealing time. TEM observations showed that nano-sized precipitates formed when the steel was annealed at 150 ℃ for 90 min, but the size and density of precipitates had no noticeable change with annealing temperature and time. Recrystallization occurred when the steel was annealed at temperatures above 550 ℃ for 90 min, and its scale increased with annealing temperature. Nano-sized annealing twins were observed. The mechanisms that controlled the mechanical behaviors of the steel were discussed.

The compliance modeling and rigidity performance evaluation for the lower mobility parallel manipulators are still to be remained as two overwhelming challenges in the stage of conceptual design due to their geometric complexities. By using the screw theory, this paper explores the compliance modeling and eigencompliance evaluation of a newly patented 1T2R spindle head whose topological architecture is a 3-RPS parallel mechanism. The kinematic definitions and inverse position analysis are briefly addressed in the first place to provide necessary information for compliance modeling. By considering the 3-RPS parallel kinematic machine(PKM) as a typical compliant parallel device, whose three limb assemblages have bending, extending and torsional deflections, an analytical compliance model for the spindle head is established with screw theory and the analytical stiffness matrix of the platform is formulated. Based on the eigenscrew decomposition, the eigencompliance and corresponding eigenscrews are analyzed and the platform's compliance properties are physically interpreted as the suspension of six screw springs. The distributions of stiffness constants of the six screw springs throughout the workspace are predicted in a quick manner with a piece-by-piece calculation algorithm. The numerical simulation reveals a strong dependency of platform's compliance on its configuration in that they are axially symmetric due to structural features. At the last stage, the effects of some design variables such as structural, configurational and dimensional parameters on system rigidity characteristics are investigated with the purpose of providing useful information for the structural design and performance improvement of the PKM. Compared with previous efforts in compliance analysis of PKMs, the present methodology is more intuitive and universal thus can be easily applied to evaluate the overall rigidity performance of other PKMs with high efficiency.

Parallel kinematic machines have drawn considerable attention and have been widely used in some special fields.However,high precision is still one of the challenges when they are used for advanced machine tools.One of the main reasons is that the kinematic chains of parallel kinematic machines are composed of elongated links that can easily suffer deformations,especially at high speeds and under heavy loads.A 3-RRR parallel kinematic machine is taken as a study object for investigating its accuracy with the consideration of the deformations of its links during the motion process.Based on the dynamic model constructed by the Newton-Euler method,all the inertia loads and constraint forces of the links are computed and their deformations are derived.Then the kinematic errors of the machine are derived with the consideration of the deformations of the links.Through further derivation,the accuracy of the machine is given in a simple explicit expression,which will be helpful to increase the calculating speed.The accuracy of this machine when following a selected circle path is simulated.The influences of magnitude of the maximum acceleration and external loads on the running accuracy of the machine are investigated.The results show that the external loads will deteriorate the accuracy of the machine tremendously when their direction coincides with the direction of the worst stiffness of the machine.The proposed method provides a solution for predicting the running accuracy of the parallel kinematic machines and can also be used in their design optimization as well as selection of suitable running parameters.

Hydrostatic mechanical face seals for reactor coolant pumps are very important for the safety and reliability of pressurized-water reactor power plants.More accurate models on the operating mechanism of the seals are needed to help improve their performance.The thermal fluid–solid interaction(TFSI)mechanism of the hydrostatic seal is investigated in this study.Numerical models of the flow field and seal assembly are developed.Based on the mechanism for the continuity condition of the physical quantities at the fluid–solid interface,an on-line numerical TFSI model for the hydrostatic mechanical seal is proposed using an iterative coupling method.Dynamic mesh technology is adopted to adapt to the changing boundary shape.Experiments were performed on a test rig using a full-size test seal to obtain the leakage rate as a function of the differential pressure.The effectiveness and accuracy of the TFSI model were verified by comparing the simulation results and experimental data.Using the TFSI model,the behavior of the seal is presented,including mechanical and thermal deformation,and the temperature field.The influences of the rotating speed and differential pressure of the sealing device on the temperature field,which occur widely in the actual use of the seal,are studied.This research proposes an on-line and assembly-based TFSI model for hydrostatic mechanical face seals,and the model is validated by full-sized experiments.

Current researches show that mechanical deformation of seal ring face makes fluid film clearance decrease at high pressure side, thus a divergent clearance is formed and face wear occurs more seriously at the high pressure side than that on the low pressure side. However, there is still lack of published experimental works enough to prove the theoretical results. In this paper, a spiral groove dry gas seal at high pressures is experimentally investigated so as to prove the face wear happened at the high pressure side of seal faces due to the face mechanical deformation, and the wear behavior affected by seal ring structure is also studied. The experimental results show that face wear would occur at the high pressure side of seal faces due to the deformation, thus the leakage and face temperature increase, which all satisfies the theoretical predictions. When sealed pressure is not less than 5 MPa, the pressure can provide enough opening force to separate the seal faces. The seal ring sizes have obvious influence on face wear. Face wear, leakage and face temperature of a dry gas seal with the smaller cross sectional area of seal ring are less than that of a dry gas seal with bigger one, and the difference of leakage rate between these two sizes of seal face width is in the range of 24%–25%. Compared with the effect of seal ring sizes, the effect of secondary O-ring seal position on face deformation and face wear is less. The differences between these two types of dry gas seals with different secondary O-ring seal positions are less than 5.9% when the rotational speed varies from 0 to 600 r/min. By linking face wear and sealing performance changes to the shift in mechanical deformation of seal ring, this research presents an important experimental method to study face deformation of a dry gas seal at high pressures.

Innovation is a process of taking an original idea and converting it into a business value, in which the engineers face some inventive problems which can be solved hardly by experience. TRIZ, as a new theory for companies in China, provides both conceptual and procedural knowledge for finding and solving inventive problems. Because the government plays a leading role in the diffusion of TRIZ, too many companies from different industries are waiting to be trained, but the quantity of the trainers mastering TRIZ is incompatible with that requirement. In this context, to improve the training effect, an interactive training model of TRIZ for the mechanical engineers in China is developed and the implementation in the form of training classes is carried out. The training process is divided into 6 phases as follows: selecting engineers, training stage-1, finding problems, training stage-2, finding solutions and summing up. The government, TRIZ institutions and companies to join the programs interact during the process. The government initiates and monitors a project in form of a training class of TRIZ and selects companies to join the programs. Each selected companies choose a few engineers to join the class and supervises the training result. The TRIZ institutions design the training courses and carry out training curriculum. With the beginning of the class, an effective communication channel is established by means of interview, discussion face to face, E-mail, QQ and so on. After two years training practices, the results show that innovative abilities of the engineers to join and pass the final examinations increased distinctly, and most of companies joined the training class have taken congnizance of the power of TRIZ for product innovation. This research proposes an interactive training model of TRIZ for mechanical engineers in China to expedite the knowledge diffusion of TRIZ.

The current development of precision plastic injection molding machines mainly focuses on how to save material and improve precision, but the two aims contradict each other. For a clamp unit, clamping precision improving depends on the design quality of the stationary platen. Compared with the parametric design of stationary platen, structural scheme design could obtain the optimization model with double objectives and multi-constraints. In this paper, a SE-160 precision plastic injection molding machine with 1600 kN clamping force is selected as the subject in the case study. During the motion of mold closing and opening, the stationary platen of SE-160 is subjected to a cyclic loading, which would cause the fatigue rupture of the tie bars in periodically long term operations. In order to reduce the deflection of the stationary platen, the FEA method is introduced to optimize the structure of the stationary platen. Firstly, an optimal topology model is established by variable density method. Then, structural topology optimizations of the stationary platen are done with the removable material from 50%, 60% to 70%. Secondly, the other two recommended optimization schemes are given and compared with the original structure. The result of performances comparison shows that the scheme II of the platen is the best one. By choosing the best alternative, the volume and the local maximal stress of the platen could be decreased, corresponding to cost-saving material and better mechanical properties. This paper proposes a structural optimization design scheme, which can save the material as well as improve the clamping precision of the precision plastic injection molding machine.