Resource-efficient ball screw by adaptive lubrication

在优先计划1551子项目的第一阶段中，已经说明了在恒定的运行条件下，通过自适应润滑可以显著提高滚珠丝杠的使用寿命和资源效率。目前的结果表明，寿命增加50%或更多是可能的。然而，在工业实践中，滚珠丝杠的操作的特征在于由于变化的条件而引起的热变化和摩擦变化的周期。这也导致滚珠丝杠摩擦扭矩和温度的变化，这被视为周期1中润滑剂需求的指标。由于这些影响的相互作用，在动态变化的运行参数下，仅监控这些指令变量以实现自适应润滑是不够的。项目第二阶段的目标是实现自适应润滑并延长使用寿命，这在静态运行条件下已经得到了证明，在动态变化的运行条件下，这种方法是从第1阶段开始对润滑算法进行增强。该算法的核心是滚珠丝杠副的摩擦模型。这将在项目的下一阶段得到加强，以便考虑对滚珠丝杠摩擦扭矩和与动态条件相关的温度的叠加影响。作为增强型滚珠丝杠摩擦模型的输入，使用数据库，其中记录并终身存储实际和先前的转速、负载和温度值。增强摩擦模型的输出变量是期望的摩擦扭矩和温度。在增强润滑算法中，对可能的润滑过程的决策分两步进行。在第一步中，将测量值与增强摩擦模型的计算值进行比较。如果在算法的第二步中测量值过多，则将根据滚珠丝杠润滑文件做出决定。在文档中，所有以前的润滑过程都记录了时间和数量信息。该项目的结果是一种增强的润滑算法，允许在动态修改操作参数的情况下自适应地润滑滚珠丝杠，从而提高了滚珠丝杠的资源效率，因为使用寿命显著延长，平均润滑剂需求减少，功率消耗降低。减少摩擦力的电力驱动。

In period 1 of the sub-project of the Priority Program 1551 it was illustrated, that the achievable lifetime and thus the resource efficiency of ball screws can be significantly increased by an adaptive lubrication, for constant operating conditions. Current results suggest that lifetime increases of 50% and more are possible. However, the operation of ball screws in industrial practice is characterized by periods of thermal and tribological changes because of varying conditions. This also leads to a change of ball screw friction torque and temperature, which were taken as indicators for a demand of lubricant in period 1. Due to the interaction of these effects, the exclusive monitoring of these command variables for an adaptive lubrication during operation with dynamically changing operating parameters is not sufficient.The aim of the second period of the project is now to enable an adaptive lubrication and the increase of lifetime, which was already proven for static operating conditions, in the case of dynamically changing operating conditions, too.The approach for this is the enhancement of the lubrication algorithm from period 1. Core of the algorithm is the ball screw friction model. This will be enhanced in the following period of the project, to enable the consideration of the superimposed effects on the ball screw`s friction torque and the temperature associated with the dynamic conditions. As input to the enhanced ball screw friction-model a database is used in which the actual and previous values of revolution, load and temperature were recorded and stored lifelong. The output variables of the enhanced friction model are the expected friction torque and temperature.In the enhanced lubrication algorithm the decision on a possible lubrication process is carried out in two steps. In the first step the measured values are compared to the calculated values by the enhanced friction-model. In case of excessive measured values in the second step of the algorithm the decision will be taken based on the ball screw lubrication documentation. In the documentation all previous lubrication processes were logged with information regarding time and quantity.The result of the project is an enhanced lubrication algorithm that allows an adaptive lubrication of ball screws in the case of dynamically modified operating parameters and thus the resource efficiency of ball screws is increased because of a significantly longer lifetime and a decrease in the average lubricant demand and lower power consumption of the electric drives by reduced friction.