【正文】 roaches for identifying spatial conflicts. The first approach detects collision between equipment workspaces and building structures. The other approach is a conventional approach that detects collision between pieces of equipment and building structures at every time step throughout the course of equipment motion. The time steps for detecting collision are determined by a time increment specified by the user. Later, these two approaches will be called workspacebased and time stepbased approaches, respectively.To assess the effectiveness of using equipment workspaces for spatial conflict detection, we created a construction scenario demonstrating installation of a set of steel beams. During the installation, a telescopicboom truck crane is used to lift one m WF 2462beam at a time from a laydown area, and then place it on existing building structures. We modeled the building ponents, the truck crane, and a sequence of geometric transformation of the truck crane during lifting operation, based on the information collected from an actual construction site. However, we modeled only the building ponents that are in close proximity with the crane to avoid excessive tests in spatial conflict detection. In the scene, a building is posed of fiftyfour ponents including floors, beams, and columns, which are totally represented by 2120 triangles. The truck crane modeled in this scene has eight parts. For simplicity, we modeled each part of the crane as a rectangular box. Since the operation of the truck crane involves both rotation and translation of equipment parts of the crane, the workspaces of the truck crane are posed of all types of the polyhedrons . Therefore, we can assess the effectiveness of different types of the representations of equipment workspaces in one construction scenario. In this assessment, we pared the time spent in detecting spatial conflicts and the accuracy of spatial conflicts detected by the approach discussed in this paper against those used by the time stepbased approach. The two spatial conflict detection approaches are based on the same type of a spatial data structure and use the same algorithms for performing intersection tests. Comparing the effectiveness of the two approaches using the same collision detection algorithms allows us to assess how well equipment workspaces can support identification of equipment related spatial conflicts.4. ConclusionsThis paper addresses the need for modeling equipment workspace requirements and identifying spatial conflicts related to mobile crane operations prior to the execution of the actual operations. The approach presented accounts for dynamic behavior of mobile cranes during their operation in representing and reasoning about their workspace requirements in 3D and over time. The equipment workspaces were geometrically represented by a set of polyhedrons, each of which encloses a space occupied by an equipment part or an attached material moving during an operation.Equipment workspaces provide a basis to identify possible spatial conflict without needing to define time increments for simulation. They enable the detection of spatial conflicts between a piece of equipment and existing building ponents only once during a given operation. This is different from current spatial conflict detection approaches in which the course of motion is subdivided into time steps and spatial conflicts between actual pieces of equipment and building ponents are identified at each time step.Generation of equipment workspace requirements involves (1) breaking down a piece of equipment into its parts according to the kinematics of the equipment and defining a sequence of geometric transformations of a piece of equipment, (2) creating workspace polyhedrons of each part and materials attached to a piece of equipment, and (3) aggregating the workspaces in a hierarchical spatial data structure based on geometric transformation for faster spatial conflict detection.Based on an implementation of the approach, the equipment workspaces generated can be used to identify spatial conflicts ac。以ZL50 裝載機液力變矩器為例，分析討論了裝載機的實用調速特性、發(fā)動機與液力變矩器共同工作的輸入、輸出特性，并對實際匹配曲線進行了分析討論，得出匹配合理的結論；針對實際需要，設計了動力換擋變速器，詳細討論了新的動力換擋變速器的傳動方案圖及擋位、速比、齒輪模數(shù)等主要參數(shù)的選擇和確定過程。(5)原傳動系變速器為前二后一三擋行星傳動變速器；新傳動系屬變速器前四后四八擋定軸式動力換擋變速器。新老傳動系的主要不同點如下：(1)原傳動系屬液力—機械串聯(lián)的復合傳動；新傳動系屬純液力傳動。但由于液力變矩器采用了雙渦輪，功率損失大，造成有效牽引功率、效率較低，高效區(qū)范圍較窄；超越離合器受力狀況和潤滑條件較差，可靠性差；尺寸鏈較長，不易保證，造成變速器噪音較大；結構復雜，零件加工制造困難，維修不方便。采用的雙渦輪變矩器，屬于將液力變矩器與機械傳動元件組合起來的功率內分流的力機械變矩器，在高速輕載工況下，自由輪機構脫開，第一渦輪空轉，動力自第二渦輪單獨傳遞；在低速重載工況下，自由輪機構鎖緊，兩個渦輪共同傳遞功率，從而使變矩系數(shù)加大，K0 =，最高效率高。而加上液力變矩器以后，無論是拋物線負載還是恒轉矩負載，在任何工況點都是穩(wěn)定的。比較柴油機加上液力變矩器的傳動特性與單獨使用(即不加變矩器)的動力特性，可得：①發(fā)動機加上液力變矩器后使其工作范圍大大地擴大了。η渦輪功率5（KW）渦輪扭矩（Nm）圖46 ZL50裝載機與YJ320液力變矩器共同工作輸出特性發(fā)動機一變矩器匹配的特征參數(shù)如下：最大輸出扭矩(Nm): 最大輸出功率(kw)/對應轉速(rpm)：最高效率工況輸出功率(kw)/對應轉速(rpm) ：平均輸出功率(kw) ： 由此可以看出，最大輸出功率工況對應的功率及轉速與變矩器最高效率工況對應功率及轉速，這兩個工況比較接近，說明發(fā)動機的功率得到充分利用，即匹配比較合理。相應的可在發(fā)動機外特性曲線圖上做出泵輪在不同傳動比下的轉矩曲線，如圖45所示。再根據(jù)公式MB=ρg若滿足，進行復選:若不滿足，則排除。對可透性的變矩器來說，因為λb隨i的變化較大，所以不同傳動比的負載拋物線相距就較遠，它們所包括的工況區(qū)就較寬。②發(fā)動機的外特性曲線。根據(jù)發(fā)動機的主要參數(shù)考慮采用第二種方法對發(fā)動機特性曲線進行擬合，采用MATLAB得到圖43所示發(fā)動機的扭矩擬合曲線:圖43 發(fā)動機扭矩曲線 液力變矩器與發(fā)動機共同工作的輸入輸出特性液力變矩器與發(fā)動機聯(lián)合進行工作后，牽引車使用性能的好壞，除與液力變矩器的特性有關外，更主要的則取決于兩者的合理配合。在變矩器與發(fā)動機匹配的計算中，通常使用發(fā)動機凈扭矩曲線，即扣除功率分流裝置消耗功率之后的凈扭矩特性曲線。如果己知特性曲線上的若干離散點(，Mei)(i=l，2，…)，采用分段最小二乘擬合，曲線方程如公式41：≤時: Me= a0+a1ne+a2ne2 ＞時: Me= b0+b1ne (41) 式中：Me, ne分別為發(fā)動機扭矩及其對應的轉速；為外特性曲線與調速特性交點對應的發(fā)動機的轉速；a0, al, a2, b0, b1分別為待定系數(shù)。在給定外特性實驗數(shù)據(jù)的情況，用數(shù)值方法進行匹配計算，需要將沒有函數(shù)關系的發(fā)動機扭矩特性曲線以擬合的方式用解析式表示，以便求解發(fā)動機凈外特性曲線與變矩器輸入特性曲線(有解析表達式)的交點，即二者共同工作點。要使發(fā)動機與液力變矩器有一個最佳、最合理的匹配，應滿足以下基本原則。ZL50裝載機發(fā)動機主要性能指標見表42。廣泛應用的萬有特性以轉速為橫坐標，以平均有效壓力為縱坐標，在圖上畫出許多等比燃油消耗量曲線和等功率曲線，等比燃油消耗量是根據(jù)不同轉速下的負荷特性曲線做出來的. 發(fā)動機典型工況及主要性能指標發(fā)動機最大功率工況： (額定功率), (額定轉速)。 發(fā)動機的特性 柴油機速度特性柴油機的速度特性是指當噴油泵的油量調節(jié)機構(油門拉桿或齒條)位置固定不動時，柴油機的輸出轉矩T、功率及比燃油消耗量等性能指標隨轉速變化而變化的關系。 MT=MT()，MB=MB()，η=η() 當渦輪轉速變化時，能保持泵輪轉矩MB不變或