The field of earth moving equipment is experiencing a transformation due to the introduction of more electronic control capability and advanced control concepts. Conventional hydraulic control systems are controlled by proportional directional spool valve. The construction of the spool valve is such that a given position of the spool determines the flow in and the flow out restriction sizes. Thus, metering in and metering out are dependent or coupled. A certain restriction size on the inlet corresponds to a certain restriction size on the outlet. Therefore, we have one degree of freedom. It can provide for good motion control but it cannot achieve energy saving potential at the same time. In this paper, the concept of ‘independent meter in / meter out’ will be emphasized. Decoupling of meter in from meter out provides for more controllability and potential for energy saving in overrunning load cases when compared with a conventional spool valve controlled hydraulic system. A four-valve configuration controlling a hydraulic cylinder will be stressed. The four-valve configuration can operate in several modes because each of the four valves is controlled separately from the others. Five of these metering modes will be pointed out; two conventional modes and three regenerative modes. An industry system supplier has introduced a novel distributed independent metering in/meter out hydraulic system with actuator force feedback. This control system is going to presented in brief. The distributed, actuator mounted implementation of this system maximizes the efficiency of the regeneration flow by minimizing the line losses associated with the recirculating fluid This control system can be used to control a multi-functional hydraulic device, e.g. excavators, tractor loader backhoes, etc... An experiment was done where a typical dig cycle was performed by a tractor loader backhoe equipped with this new technology. The data recorded from this experiment is used to perform an off-line optimization of metering modes selection for each function during the cycle. this off-line optimization can be used to maximize machine productivity or machine efficiency or a weighted combination of both. A general objective function will be presented and results will be given for maximizing machine productivity. Finally conclusions and future work suggestions are presented.

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