Systems with independent metering offer a high potential for increasing the functionality and efficiency of valve-controlled hydraulic drives. But nowadays there are only a few prototypical applications. One reason for that are the so far insufficient safety investigations. Besides the structural investigations carried out at the research institute, this contribution deals with a fault detection by means of limit checking of the applied pressure sensors. A detection algorithm is derived from several software-in-the-loop simulations of the independent metering system applied at an excavator arm. The functionality and limits of the fault detection will be shown by means of measurements. As a result, all safety-critical faults can be detected which leads to a Diagnostic Coverage of DC = 99% and thus allows the use of independent metering up to a Performance Level PL = e.
Keywords: Hydraulic systems, independent metering, machine safety, ISO 13849, fault detection