A New High Performance Roto-Translating Valve for Fault Tolerant Applications 2014-01-2403
The new X-by-Wire systems under study for commercial and heavy-duty vehicles, as well as for Agricultural Tractors, are increasingly real autonomous systems, capable to autonomously control a vehicle functionality, actuating the operator's commands, or managing in a complete autonomy a machine function. These application need an higher Performance Level from the functional safety point of view, due to the risk of a malfunction consequence. The paper deals with a new concept hydraulic spool valve that allow the design of new safer and more compacted hydraulic circuit architectures, ensuring higher safety performance levels. The architecture presents advantages both from performance (precision, fastness), both from operational point of view. The paper will focus in particular on safety and control topics. The new patented valve presents a secondary rotary type actuator connected to a sleeve interposed between the spool and the valve body, thus composing a roto-translating valve. The sleeve presents holes that can be moved and positioned partially or totally overlapped to the valve ports, thus allowing a secondary independent metering. The valve port area is then related to the movement of the spool, and to the rotary movement of the cylinder. The valve port area is the result of two actuators position, both controlled by a microcontroller based unit. Due to the valve structure, the metering control precision and valve speed are virtually quadratic in respect to the traditional valve spool position electronic control, due to the concurrency of two electronically controlled actuators. The valve can be configured to realize various control functions and, in terms of safety, it offers a fail operational characteristic, in reason of an operational redundancy and functional diversity.