Patent Application
20110169439
This application relates to a control for an electromechanical actuator that ensures that the viscosity of an included lubricant will not become too high due to very low temperatures.
Electromechanical actuators are utilized to move any number of components in aircraft. As an example, flaps such as stabilizers, elevators, rudders, etc. are all positioned to precise location by electromechanical actuators. The electromechanical actuators typically include a drive motor, which drives a positioning element to in turn move the position of the aircraft component. A lubricant is typically included in the electromechanical actuator to ensure smooth operation of the actuator.
One challenge with the use of electromechanical actuators, especially in aircraft, is that the electromechanical actuator is exposed to extremely low temperatures. Further, during long cruise segments of a flight, the actuators may be rarely used, such that the actuator approaches those same very low temperatures.
At these very low temperatures, the viscosity of the actuator lubricant is high, resulting in increased friction losses and potentially degraded performance.
Currently, the electromechanical actuators are periodically moved during such long periods of non-use to address this concern.
A component intended for use in very low temperature situations has an electromechanical actuator with a control for an electric motor. The control receives a temperature signal indicative of a temperature being experienced by the electromechanical actuator. The control is operable to produce a current signal sent to the electric motor which will generate heat without significant torque.
A method of operating the electromechanical actuator is also disclosed.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
As shown in
A position regulator 38 sends a signal to the torque/current regulator, which takes a target position signal x* and an actual position signal x, and determines what command torque TFORCE* should be delivered as a signal to the torque/current regulator 36. Based on the commanded torque, motor current i, and motor position θ, the torque/current regulator 36 generates a commanded voltage v* to an inverter 37. In addition, the torque/current regulator can add non-torque producing current as previously described. An inverter 37 provides the power to drive the electromechanical actuator 24 to position the component 22. That is, the torque-current regulator 36 is operable to generally control the electric motor, and position the electric motor as desired, but is also operable to identify and/or generate a signal to be delivered to the inverter 37 that will provide the no-torque load at the electric motor 23.
Notably, the components 38, 32, 34, 36, 37 and 39 are all part of the control 28, as shown in
However, when the block 32 is “on,” then a signal is sent that an additional no-torque output is desired to heat the motor and, subsequently, the actuator. There are a number of ways in which a “no-torque” current can be sent to the inverter 32 to generate heat. The magnitude, frequency and form of the current depends on power quality, EMI requirements, allowable motor flux modulation, and desired level of power loss generated.
One simple way of control is to send current to the motor to maintain a minimum actuator temperature using a hysteresis temperature controller (block 32) as shown in
One simple method of providing a non-torque current is to provide a signal which is at a very high frequency, and above a frequency at which the motor can produce torque.
Another method, which may be particularly applicable to the use of a permanent magnet motor, is to provide the power signal in phase with permanent magnets. In this manner, the strength of the magnets will simply be increased or decreased, rather than any torque being produced.
Another method, which may be particularly applicable to the use of a switched reluctance motor, is to provide the a fluctuating current through one or more phases of the machine so that the net reluctance torque on the shaft is at or near zero.
In sum, if the temperature of an electromechanical actuator is found to be below a threshold temperature, a signal is created and sent to a motor within the electromechanical actuator to produce heat, without significant torque being produced. It should be understood that the term “no-torque” or “without significant torque” are somewhat functional statements, rather than absolute statements. It may be that some limited torque could be produced, however, without any significant movement of the component 22.
With both embodiments, the control can be iterative, and ongoing until the temperature again rises above the threshold (TLow or TMin*).
Although embodiments of this invention have 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.
