Patent Application
20190061918
This application relates to a system which is relatively lightweight, but provides reliable control for an actuation system of a safety critical system such as on aircraft.
Aircraft applications are becoming increasingly complex. Also, demands on reducing the weight for such systems are becoming more and more important.
One such actuation system is for changing an angle of incidence of variable vanes in a compressor section. As known, variable vanes in a compressor section for a gas turbine engine can be moved between various angles during different flight conditions.
In the prior art, the system has been generally fully mechanical. A constant pressure hydraulic pump has provided hydraulic fluid through hydraulic lines and electric valves. There are disadvantages to a fully mechanical actuation system.
One disadvantage is that the hydraulic pump continuously draws engine power and must be sized for worst case scenario. Also, the actuator's performance is tied to the pump speed and limits performance at engine idle. A single pump providing a common fluid source for all actuators increases a risk of leaks and contamination.
Feedback signals are remote from an engine controller, which is undesirable. The thermal load on the actuation system is additive from all of the actuators to the fluid. An actuator's health and prognostic is limited by the bandwidth of the engine controller.
Traditionally, the actuator controls are centralized. As an example, the actuator controls may be contained in a full authority digital electronic controller (“FADEC”) on an associated gas turbine engine. The FADEC performs numerous critical functions, which limits the processor bandwidth for the actuator control computation.
One possible solution would be to provide electric driven pumps for each actuator. However, such a system can result in a great increase in weight.
An actuation system for a component has a plurality of cylinders. A piston is in operable communication with each of the cylinders and is configured to move at least a portion of the component to a desired position. A plurality of pumps are in fluidic communication with the plurality of cylinders, and are each driven by electric motors. The number of pumps is less than a number of cylinders.
These and other features may be best understood from the following drawings and specification.
A system 20 which may benefit from this disclosure is illustrated in
The synchronization ring 24 may include a cam groove 25. As the cam groove 25 moves axially, it cams a portion of the variable vanes 22, such that they turn. A plurality of actuators 26 moves the cam ring 24.
As shown, fluid lines 40 and 42 communicate the pump 31 to the cylinder 36. Secondary fluid lines, or hydraulic rails, 50 and 52 communicate the pump 31 to a second actuator cylinder 46 driving a piston 45, which is also connected to drive the sync ring 24.
In the prior art systems, a pump displacement is typically directly proportional to an engine speed. Most of this flow is typically bypassed and sent to coolers and returned to a tank. This is all wasted energy. The fluid that is supplied to the actuators is modulated by servo valves to achieve a desired position.
The instant disclosure improved on this prior system, in that no valves are required, and the motor and pump combination provides the flow regulator function. If no movement of the sync ring is desired, there will be no flow, and the motor simply holds pressure.
Another benefit of the
A second system 60 which is effectively identical to the system 30 disclosed with regard to pump 31 is also included.
The benefits of the electric controlled system are achieved without the requirement of having individual pumps/motors/electronics for each actuator cylinder 34/46 in the systems 30, 46. That is, there are at least two pumps, and more cylinders than pumps. Thus, weight and cost benefits are achieved.
In addition, while still providing redundant pumps and motors, a safety aspect is achieved in that even if one of the pumps fails, there is at least one other pump/motor combination which can serve to move the variable vanes to a safer position should a failure occur.
Should there be a failure of pump 76, then a controller can switch to operation of the pump 72, which also communicates with the rails 90 and 92 (not illustrated, but built into this schematic).
Also, pump 72 can be used to assist transient conditions, allowing reduction of the power draw by only using pump 72 to high load conditions.
The duty cycle between the pumps can also be shared. Each of the motor and pump units can be sized for half of a maximum flow and pressure, and thus half the power. This decreases weight, yet maintains safety margins.
The disclosure thus results in a system which is relatively lightweight, yet provides redundant control to ensure that the safety critical operation of the system, such as the position of the variable vane in a compressor section for a gas turbine engine, will be achieved.
With the disclosed “local” or distributed control architecture, there is a dedicated controller local to the actuator. In addition, the added weight of running wires to communicate to the FADEC, as described in the prior art, is reduced.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
