ADJUSTABLE FLOW-CONTROL VALVE FOR THE SELF-ENERGISING ELECTRO-HYDRAULIC BRAKE
Keywords:
hydraulic brake, self-energising, brake torque control, leakage-free adjustable flow-control valve, flow-control valve, integrated valveAbstract
This paper presents the design and performance of an electrically adjustable flow control valve. It is designed specifically for the self-energising electro-hydraulic brake which requires small volume flows, a fail-safe open characteristic, a leakage tight closed position, simple control by just one solenoid, good dynamics, and repeatability. The valve concept is based on a conventional pressure compensator design usually found in flow-control valves. The measuring orifice used to sense the flow through the valve is typically constant. In the presented design it is made adjustable using a hydro-mechanical pilot servo mechanism. The pilot is actuated by a proportional solenoid. The paper explains static flow equations used to parameterise the design. Dynamic simulation is used to validate the design before manufacturing. Measurements of the prototype show a good match with the simulation. Measurements of the main characteristics of the valve are shown, specifically the dynamic response to a step input as well as the flow-signal tracking and load pressure disturbance rejection behaviour. The valve is also tested in its target application, the self-energising electro-hydraulic brake, where it proves its effectiveness in normalising the response time of the non-linear and the inherently unstable brake. As opposed to a non-linear or gain scheduling control, with the new valve the controller of the brake can be designed as a simple switching control. This is an advantage for the overall brake's safety evaluation and therefore helps to improve the prospects of using the self-energising brake in future applications such as rail vehicles.
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