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New technologies in electrical drives and electrical distribution systems in future aircraft

Technology emerging power units and power distribution systems in future aircraft

u.sureshkumar *

* Professor in the Department of EEE

Mohamed sathak Enginnering College

Kilakkarai

E mail: uskrk@sify.com

 

 

 

 

 

Abstract:

It is hoped that in future aircraft, all power, except for propulsion, will be distributed and processed electrically. In other words, energy will be used for driving aircraft subsystems currently powered by using hydraulic, pneumatic or mechanical, including utility and flight control performance, the environment control system, lubrication and fuel pumps, and many other utility functions. These concepts are embraced as known as the plane of the initiative's electric (MEA). The MEA focuses on the use of electricity rather than hydraulic, pneumatic, and mechanical energy to optimize the aircraft performance and life cycle cost. It would eliminate the need for gearboxes and transmissions from the transmission of electricity rather than through mechanical, which reduces the weight of the aircraft and increasing fuel efficiency. Detailed analysis

the interaction between a electro mechanical actuator (EMA) connected to the system DC power distribution bus a plane of the next generation of transportation with driver bus is presented. Development of reliable power for wire drive systems in both aeronautics and space applications has recently been asked to remove the system hydraulics of the aircraft. Aircraft

Engineers have tested electrohydrostatic actuators (EHA), which combine electric and hydraulic, Hence the

development of the aircraft "more electric" concept. Efforts are made to replace

all hydropower schemes, leading to a new technology called "All Electric Aircraft".

Introduction:

Flight Control System

A flight control system consists of control surfaces for flight controls in the cockpit respective feeder links and operational cont4rol necessary mechanism for aircraft in flight.

Classification

Flight Control Systems (FCS) are classified as follows:

• FCS Mechanics
• Hydromechanical FCS (flight control units for motor (PFCU))
• Fly-by-wire FCS

FCS Mechanical:

FCS design is the most fundamental mechanics. Were used in early aircraft and currently in small aircraft aerodynamic forces are not excessive. The FCS uses a collection of mechanical parts such as rods, cables, pulleys and sometimes channels to transmit forces the cockpit controls to control surfaces.

Hydro mechanical FCS (Power Unit Flight Control (PFCU)):

The complexity and the weight of a mechanical FCS significantly increases the size and performance of the aircraft. Hydraulic overcomes these limitations

FCS has a hydraulic 2 parts:

• The mechanical circuit
• The hydraulic

The mechanical circuit links cockpit controls with hydraulic systems. As mechanical FCS, is made of rods, cables, pulleys and other chains. The hydraulic system has hydraulic pumps, piping, valves and actuators. The hydraulic pressure generated by pumps in power hydraulic actuators. The actuators convert hydraulic pressure of ground movements control. The servo valves that control the movement of cylinders. The checking system has a major drawback circuits containing heavy machinery, which increases the weight system. To overcome this drawback, a new technology "more electric TECHNOLOGY IN AIRCRAFT" has been developed. The plane in which this technology has been used is called "More Electric Aircraft (MEA).

In describing the MEA, the systems for flight control actuation can be considered the participation of two main areas of technology: fly-by-wire (electrical control) and power-by-wire (PBW). FBW technology includes the design, development and implementation of electronic flight control. The electronic control controls the theft and feature control valve out using centralized or distributed architectures. Distributed control systems reduce the processing load on the airborne equipment of centralized control, and offer greater flexibility in developing system architecture. Another advantage is weight reduction achieved by reducing the size of the game and the amount. In recent years, progress technological FBW focuses on the field as FBW control systems are now the norm in commercial and military aircraft today. Power-by-wire (PBW) is the next action breakthrough in the control of the aircraft. As the fly-by-wire control system of management has eliminated the need for mechanical interfaces, power-by-wire actuators eliminate the need for hydraulic power systems. Supply control system comes directly from the electrical device. This has several advantages. Hydraulic power systems are complicated and difficult to maintain. The elimination of these systems will significantly reduce the amount of support equipment and personnel needed to maintain and operate the current air and space vehicles. In addition, PBW actuators have the potential to be more efficient than their hydraulic counterparts. A hydraulic system must generate and maintain large hydraulic pressure (3,000 to 6000 pounds per square inch) at any time, regardless of demand. PBW actuators that use electricity if necessary. Finally, PBW drive systems can be more fault tolerant than those based on the central hydraulic supply. Once a hydraulic line is compromised, usually leads to loss of all hydraulic. Consequently, several hydraulic circuits are required to maintain a certain level of redundancy. With a system of PBW, an actuator can not be disabled simply by isolating the problem of a single surface.

The types of actuators PBW

There are several types of actuators PBW, including electrohydrostatic actuators (EHA) and electromechanical actuators (EMA). EHA Pumpmotor use a reversible drive electricity directly to the free piston hydraulic pump fluid. What determines the RAM in the same way as a standard hydraulic actuator (Figure 1 (a)). EMA no internal hydraulic fluid, using electric motors instead of driving directly to RAM through a mechanical gearbox (Figure 1 (b)). Compared to an EHA, the EMA has certain advantages. It is lighter, smaller and less complex than equivalent EHA because of the absence of a system internal hydraulic. Since no fluid in the load path, EMA tends to be stiffer than an equivalent EHA. The EMA tends to be more effective because there is no drift or loss of the inefficiency of the pump. Finally, since there is no risk of leakage with EMA, is more suitable for long term storage or space applications.

Electromechanical switching (EMA)

EMA uses a mechanical transmission for coupling an electric motor for flight control surface. This is achieved using a rotation of the gearbox, and the method necessary action may include some form of rotation for the linear conversion as a ball screw. Electric motors require power supply continuous are usually used, but the addition of step with a diode for rectification also allow them to operate from an AC power source. Speed motor direction, and directly translate into the speed, direction, and the load on the cylinder. Figure 1 shows a current EMA developed by TRW for an application top-flight of the butterfly. In its basic form, EMA is sensitive to certain faults alone can lead to a mechanical jam, and therefore presents complications for the flight certification in some areas. Additional features can be used to reduce this type of damage, but in doing so increased the complexity, cost and weight. For these reasons, the EMA-based applications is not suitable for primary flight control. However, the systems and drive systems wing could secondary EMA accommodate the technology.

EMA Design System

 

 

EMA great for high-Order Electric Flight

 

 

 

 

 

Baseline Power System Architecture

 

The proposed distribution system energy is built around a bus of 270V DC distribution. The typical architecture of power system for a base of new-generation aircraft is shown in Fig. 1. We can see that the major components that are able to control the bidirectional power converters (CAE). A controller provides a bus interface between the starter / generator and the distribution bus. Most loads, including the actuators are controlled using power converters for bi-directional control the power and status of the DC bus.

With the proliferation power converters and actuators developed at the bi-directional power distribution system, it is important to develop methods for analyzing the interaction between different subsystems. Due to the complexity of the supply base and many sub-systems, power distribution system of the samples, which takes advantage of the features key reference system, but not so complicated, is introduced. The power system of the sample is represented as an interconnection of a source and charging systems.

 

Example of power distribution system

The distribution system power samples are shown in Fig. 2. The source sub-system represented by the subsystem 1 is in an ideal three-phase voltage sources, three rectifiers propulsion phase to provide regulated DC 270V required by the DC bus. The load subsystem represented sub-system 2 is an electromechanical actuator used to control secondary flight control surfaces of aircraft. Other costs in the DC bus are modeled by a current source or a simple resistance.

 

 

The EMA model shown in Fig. 5 shows to include a DC motor with constant field, a ball screw transmission between the engine and control surface, and a model of the surface dynamics. The motor voltage is controlled by a bidirectional Buck converter with a PWM input filter. The EMA is controlled by a multi-loop controller, which includes a motor current, motor speed and position feedback loops.All spindle load bus is modeled by a resistor or current source.

 

 

 

 

Electro Hydrostatic Actuator (EHA)

 

1. In contrast to EMA, EHA (Figure 2) uses transmission fluid between the electric motor and the surface of the actuator. The hydraulic fluid provides a means of power transmission to the surface. In this engine, variable speed power (usually DC) is used to drive a fixed displacement hydraulic pump, which in turn, powers a conventional hydraulic cylinder piston. Change of address is obtained by a bi-directional motor. An important advantage of this approach is that the EHA mode of operation can be managed as a conventional hydraulic actuator. This approach is made by hydraulic bypass valve or standard buffer (Figure 3) and traditional active standby or active-active configurations actuator can be easily adopted. This feature makes the EHA more suited to applications of primary flight control of the EMA. Although the technology presented EHA new hydraulic components and fluid, is fully autonomous in the assembly of the actuator. In comparison the traditional hydraulic cylinder systems, the inconvenience of disconnecting the hydraulic equipment of aircraft and bleeding complications during transfer system are not met during the interview.

Electrohydrostatic Actuators (EHA)

EHA Grande

EHA Control Scheme

Advantages of electric actuators:

The potential benefits of level electric drive system are well known.

Electric drive can provide:

• Improving the maintainability of aircraft:
• Under the hydraulic components are necessary,
• Faster performance aircraft
• Less spare parts and tools are necessary,
• Improved through integrated problem solving in test (BIT).
  • Improved system availability and reliability:
  • Electricity distribution is the most convenient and provides system flexibility with respect to the reconfiguration of the ability to date Ñ difficult to obtain using the hydraulics
  • Improving mean time between failure (MTBF), deleting (from drive demand use of electromechanical or EMA) o-(trigger electrohydrostatic or EHA) of hydraulic components.
  • Ñ improved flight safety in the configuration of the MEA, improving safety system is achieved by different power supply and the avoidance of further actuator common mode failures.
  • Reducing the weight of the weighting system Ñ savings achieved by replacing the entire hydraulic system, including pumps, distribution systems (pipes and liquids), and the valve lock, for electrical systems.

The main advantage is the reduction of the costs of aircraft, for example, reducing fuel costs (due to weight reduction) and reduce maintenance costs (faster recovery). However, before these benefits can be done, additional work is needed to improve technology and provide appropriate application platforms to introduce this technology in use.

In addition, the aircraft maintenance industry must align their IT infrastructure so you can get the benefits of electric technologies.

Some of the additional benefits both the EMA and EHA actuators are:

• Under resting energy consumption during standby operation,
• Home rapid response
• It can be easily adapted for use with AC power sources or DC
• Unaffected frequency variation supply supplies electric motors.

EHA versus EMA?

An alternative the EHA are the "electromechanical actuators (EMAS), in which the torque is mechanically amplified and transmitted to the control surface with a string, screws or any mechanical transmitting device, can be seen as an alternative. Moreover, since the complexity, weight, reliability and maintenance obligation EMAS are potentially more attractive than EHA, at least for low power applications. In particular, all relevant issues of hydraulic technology are obviously EHA configuration withdrawn. However, in the following three areas EHA are always preferable to EMAS:

? Probability that the interference of a used EMA in a primary enforcement of flight is difficult to predict and justify the existence of a service experience. EHA Jamming probability can be evaluated directly from actual experience of slavery, and noted as "very unlikely" so convoluted. In contrast, the probability of interference from the experience of mechanical systems incorporating hundreds of teeth of gears and screw mechanisms is questionable and ongoing application of flight control school in May are not directly transferable to primary flight controls due to very different operating cycles, especially

The wear of the components of power transmission can result in control of the game free surface "or other nonlinearities, which can generate unacceptable limit cycles

? The introduction of the EHA, in parallel with slavery in addition regular supply basic architecture described above is easier than EMA. EHA is easily reversible standby mode, a device that can incorporate identical buffer those currently used for the protection of uncertainty, and that can be built with many elements in common with the adjacent servo as the piston, cylinder, coupled transducer position or the battery. In a move to diversify the obvious technical and financial risk, Airbus has engaged the talents several companies for the design, production and supply of many actuators on the giant aircraft. Specifically, Ala A380 and EHA elevator and rudder are purchased EBHAs Goodrich, while Messier-Bugatti will supply the pumps associated EHA. Meanwhile, the spoiler is EBHAs Liebherr, which provides its own bombs. Phil Hudson, Goodrich, vice president of engineering drive systems says: "The EHA electronic concept can also be designed to provide functionality that a simple motor control. It can serve as an actuator controller chip in its own right and being part of a distributed control system or control of a set of multiple actuators. Another advantage is that this technology is distributed to local intelligence elements of a command and control system can significantly reduce weight and improve game failure detection and isolation. "

Maintenance services are also considerable. Power-by-wire action units are line-removable EHA with only mechanical and electrical connections to the aircraft, eliminating the need for recharging or cleaning system of hydraulic fluid required a system central hydraulic. Since the power wire actuators are autonomous and remotely located on the surface, the surface is exposed to damage significantly reduced. Furthermore, the power wire actuators can be designed as a sensitive, meaning that the actuators provide only the flow and pressure needed to move and keep the trigger on a slide

position. The conventional hydraulic power systems are configured to produce a continuous pressure. The flow is measured at each actuator, which can lead to greater consumption of energy and generate unwanted heat. William Schley, Supervisor of R & D, Parker Aerospace Controls Division EHA Systems said only consume energy demand. Specifically, they consume energy in proportion to the power delivered to the load. In contrast, a feature servoactuators conventional hydropower EVSV consumed proportional to the speed of production, the allocation of load power output, if necessary, with the rest of the energy is dissipated by the pressure drop (heat) through the main control valve. While hydraulic actuators to be more efficient, are charged, the charges are usually lower during a flight. "Another important benefit of electric actuators is survival. Ballistic Damage or explosives to a distribution system or electric actuator causes no loss of function of this channel in its entirety, especially if the damage is peripheral. In a hydraulic system, according to its design, even a small leak can cause significant loss of function and / or fire. Although some contain actuators Electrical

hydraulic fluid, the system is still most often survival. For now, these advanced management functions currently provided good by the EHA and its variants. EHA combines the best of electric drive and hydraulic hybrid design classic approach, which is more tolerant to error than most Euro-Mediterranean Year. In addition, EHA is mechanically simple, without jamming gear train. The typical capacity for long term storage of EHA is 10.

 

 

— Next-Generation All-Electric Aircraft:

 

The all-electric aircraft "is a concept that emerged in the 1970s and has generated a great deal of research. An electric motor at all, which could replace existing gas turbine aerodynamics, that the unity of all electrical through a distribution network, motor / generator integrated into the motor windings. Expanding the role of motor / generator to include services such as active system of magnetic bearings could facilitate the extraction of oil. The all-electric concept thus offers considerable scope for both engines and the reconfiguration of the cell and operational improvements, with studies indicating the benefits of reduced total weight, greater reliability, easy maintenance, reduced operating costs (including reduced fuel consumption), and improved security.

Conclusion:

From the hypothesis of a single hydraulic power supply replaced by an electric, it is possible to establish relativity and scale of the necessary changes in the migration to all-electric "aircraft concept. In a small civilian aircraft, usually a minimum of five electric actuators would be required to provide a control channel electric primary flight control surfaces. If all hydraulic systems have made electricity more than 20 electric actuators would be necessary to ensure control Complete all primary flight controls and secondary surfaces. The resulting increase in electricity demand has significant implications for electricity production and distribution. Therefore, an amount Significant work is still needed to address the consequences of distributing many electrical drives around a plane, and the resulting top-up, steady state and peak demand power supplies required for aircraft.

It is clear that migration to electric control systems involving civil and military markets. As described above, replacing a system of substitution of a single hydraulic power is an important step in the transition to all electric technologies. It is clear that the statements made in aircraft generators and distribution architectures are increasing significantly to meet the needs of this migration. A company called TRW has developed products to meet the demands set by PBW and ongoing programs to ensure respond to future requests for all electric aircraft. Finally, it is expected that once operational, electrical actuators and system architectures Electrical improve commercial viability and reliability of service for cells that are installed. These improvements will undoubtedly drive the adoption levels future high power-operated plane.

References:

• J. Weimer A management and distribution of electricity for more aircraft, "Proceedings of the30thIntersocietyEnergyConversion Engineering Conference, vol. July 1, 1995, pp. 273-277

• Technology Review Journal – • Millennium number of fall / winter 2000

• ACTUATOR Development Overview

D. Tesar, UT Austin, Robotics Research Group April 1, 2006

About the Author

Gail Austin-Pinder, Red Cross, Trinidad & Tobago

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