【摘要】：機(jī)床夾具是在生產(chǎn)制造過程中被廣泛應(yīng)用的夾持裝備,用于工件在機(jī)床工作臺(tái)上的定位和夾緊。夾具定位元件的制造和安裝誤差以及工件定位穩(wěn)定性等因素會(huì)導(dǎo)致工件產(chǎn)生位姿偏差,即工件的實(shí)際位置與理論位置存在誤差,最終導(dǎo)致工件產(chǎn)生加工誤差。通過分析夾具定位布局對(duì)工件定位精度與穩(wěn)定度的影響,建立了多目標(biāo)夾具布局模型,可以準(zhǔn)確獲得由已知定位誤差所導(dǎo)致的工件位姿偏差,進(jìn)而對(duì)夾具進(jìn)行優(yōu)化設(shè)計(jì)以減小工件的位姿偏差。本文主要對(duì)夾具布局進(jìn)行研究,完成了以下工作:首先,分析了機(jī)床夾具的定位誤差與工件位姿偏差之間的關(guān)系,建立了描述工件位姿誤差與夾具各定位元件誤差之間的定位精度模型,求得由已知的夾具定位誤差引起的工件位姿誤差;分析了工件的定位穩(wěn)定性與定位點(diǎn)布局的整體幾何圖形之間的關(guān)系,建立了工件定位穩(wěn)定性模型。通過調(diào)整每個(gè)定位點(diǎn)的位置來調(diào)整夾具定位布局的的幾何分布,最終使得工件的定位最穩(wěn)定,從而在加工過程中減少工件的偏轉(zhuǎn)或位移,進(jìn)而使得工件的位姿偏差最小,提高工件的加工精度。其次,由于工件的位姿誤差模型與定位布局的幾何穩(wěn)定性模型都與夾具定位點(diǎn)位置相關(guān)。因此,將工件的位姿誤差模型與定位布局的幾何穩(wěn)定性模型聯(lián)立,組成最小化的多目標(biāo)夾具布局優(yōu)化模型。該模型綜合考慮了影響工件位姿偏移的穩(wěn)定性因素與定位點(diǎn)的誤差因素,在給定各個(gè)定位點(diǎn)的誤差時(shí),通過對(duì)目標(biāo)函數(shù)的優(yōu)化,使得工件位姿偏移量最小、工件定位更穩(wěn)定,最終提高工件的加工精度。最后,提出了一種基于Memetic Algorithms(MA)的多目標(biāo)夾具布局優(yōu)化的新方法。通過熵權(quán)法計(jì)算得出每個(gè)目標(biāo)函數(shù)的權(quán)系數(shù),再將各目標(biāo)函數(shù)的權(quán)系數(shù)乘以其對(duì)應(yīng)的目標(biāo)函數(shù),相加求和得到評(píng)價(jià)函數(shù)。之后再利用MA優(yōu)化計(jì)算出評(píng)價(jià)函數(shù)的最優(yōu)值,也就獲得了最優(yōu)夾具布局。通過與基于GA(遺傳算法)的單目標(biāo)優(yōu)化方法得出工件位姿偏移最小量的結(jié)果進(jìn)行對(duì)比驗(yàn)證多目標(biāo)夾具布局優(yōu)化模型的正確性;MA與GA的收斂性對(duì)比,驗(yàn)證文中所提出的多目標(biāo)優(yōu)化方案的有效性和可行性。
[Abstract]:The machine tool fixture is a kind of clamping equipment which is widely used in the production and manufacturing process, and is used for the positioning and clamping of the work piece on the working platform of the machine tool. The manufacturing and installation errors of the fixture positioning elements and the positioning stability of the work pieces can cause the workpiece to generate the pose deviation, that is, the actual position of the workpiece and the theoretical position are errors, and finally the work piece is caused to generate machining errors. By analyzing the influence of the fixture positioning layout on the positioning accuracy and stability of the workpiece, a multi-objective fixture layout model is established, and the position and pose deviation of the workpiece caused by the known positioning error can be accurately obtained, and then the clamp can be optimized and designed to reduce the pose deviation of the workpiece. In this paper, the fixture layout is studied, the following work is completed: firstly, the relation between the positioning error of the machine tool fixture and the position and position deviation of the workpiece is analyzed, the positioning accuracy model between the position and the position error of the workpiece and the error of each positioning element of the clamp is established, The position and pose error of the workpiece caused by the known fixture positioning error is obtained, the relation between the positioning stability of the workpiece and the whole geometric figure of the positioning point layout is analyzed, and the positioning stability model of the workpiece is established. And the position of each positioning point is adjusted to adjust the geometric distribution of the fixture positioning layout, and finally, the positioning of the workpiece is most stable, so that the deflection or displacement of the workpiece is reduced during the machining process, so that the pose deviation of the workpiece is minimized, and the machining accuracy of the workpiece is improved. Secondly, because the position and pose error model of the workpiece and the geometric stability model of the positioning layout are all related to the position of the positioning point of the fixture. Therefore, the pose error model of the workpiece and the geometric stability model of the positioning layout are combined to form a minimized multi-objective fixture layout optimization model. According to the model, the error factors of the stability factors and the positioning points of the workpiece pose deviation are comprehensively considered, and when the error of each positioning point is given, the position and position deviation of the workpiece is minimized by the optimization of the objective function, and the positioning of the workpiece is more stable, and the processing precision of the workpiece is finally improved. In the end, a new method of multi-target fixture layout optimization based on Metic Algorithm (MA) is presented. The weight coefficient of each objective function is calculated by the entropy method, then the weight coefficient of each objective function is multiplied by the corresponding objective function, and the sum is added and summed to obtain the evaluation function. Then, the optimal value of the evaluation function is calculated by MA optimization, and the optimal fixture layout is obtained. The validity and feasibility of the multi-objective optimization scheme proposed in this paper are verified by comparing the results of the method of single target optimization based on GA (Genetic Algorithm) to verify the correctness of the multi-objective fixture layout optimization model.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG75

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本文編號(hào)：2501795