Study On Robustness Design Of Mechanical System Based On Uncertainties Of Planar Constraints

The planar closed-chain mechanism is a kind of type which has been applied in practical engineering widely, such as the planar linkage mechanism, the gear mechanism, the planet gear mechanism and so on. These mechanisms are based on the structure of planar constraint so that it can realize planar movements. The man-made planar constraint will result that the constraints of a planar closed-chain becomes indeterminate-statically, so the performance of mechanical system is very sensitive to error. According to a viewpoint of generalized constraints, since the run of a mechanical system is subjected to all kinds of action from internal and external constraints, such as geometry constraints, kinematic constraints, dynamic constraints, constraints from working environments and so on, in fact, it is hardly impossible to ensure accurate planar characteristics of these constraints. For example, manufacturing errors, especially errors of profile and position, assembly errors, nonplanar characteristics of dynamic parameters of components (such as the distribution of mass, inertia forces, etc.), deformation of components, external environments (such as the temperature, the field of the gravity), varying of the condition and so on, all that will disturb the planar constraints, and make it uncertain. For uncertainties of planar constraints, it will result that over-constraints becomes obstacle and influence smooth movement of a mechanical system, and bring about a series of seriously influences on the performance of the machines, especially on their dynamic behavior and the quality. The shortcoming mainly show as following aspects: 1) The obstacle and the characteristic of indeterminate resulted from over-constraints, will lead to compelled deformation of links and kinematic pairs in process of running, and make action forces in kinematic pairs increase sharply, so the mechanical efficiency decrease obviously. Meanwhile, the abrasion of kinematic pairs is rapidly, so it is low in the reliability, poor in precision, short in life. 2) Because the above-mentioned elastic deformation and additional load is periodicity or randomicity generally, in addition, the clearance of kinematic pairs is increasing, all that will be primarily reason resulted into vibration, shock and noise. Therefore, it will influence the stability of machine running, and cause the pollution to environments. 3) The obstacle of over-constraints also will lead to difficulty of assembly and disassembly, and is unfavorable to assemble and disassemble automatically. 4) In order to decrease uncertainties of planar constraints, eliminate andreduce effects of over-constraints, ensure planar movement constraints, it is necessary to promote manufacturing precision and rigidity of structure, so manufacturing difficulty and cost will increase greatly. 5) Uncertainties of planar constraint will resulted that forces in machine is unbalance, it is difficult to realize self-adjustability and compensability, all that influences machine in determinate-statically, dynamic stability, adaptability to external environment.Therefore, in order to meet requirements of developments of modern science and technology and competitions of market, aimed at above-mentioned problems, this paper on the basis of all kinds of uncertain system theory, takes machine products of high quality, low cost and strong robustness as targets, explores methods and basic theory for robustness design of mechanical system oriented from uncertainties. Its mainly research contents and innovations show as following:(1) The viewpoint of uncertainty is presented from "concept "in cognizing science, "set" in mathematic, "class" and "object" in object-oriented idea, and author makes some discuss on classification of all kinds of uncertainties, reasons and emergences. Uncertainties in geometry constraints, kinematic constraints and dynamic constraints, which are mentioned in today several mechanism books, are analyzed by uncertain system theory.(2) In this paper, author points out a shortcoming that traditi...