Project-1: Powertrain for aircraft in runways

Part A:

1. Search and list out the total weight of various types of aircrafts.

2. Is there any difference between ground speed and air speed?

3. Why is it not recommended to use aircraft engine power to move it on the ground at Airport?

4. How an aircraft is pushed to runway when its ready to take off?

5. Learn about take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing.

Part B:

6. A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.

B. Develop the model for the calculated force and power using Simulink.

7. A. Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of powertrain.

(Hint :DC7 Block)

B. Also, Design the parameters in excel sheet.

A.1 Types of aircrafts and its total weight:

Since 2020, there are four categories, based on maximum certificated take-off mass.

• Light (L) — aircraft types of 7,000 kg or less.
• Medium (M) — aircraft types more than 7,000 kg but less than 136,000 kg; and
• Heavy (H) — all aircraft types of 136,000 kg or more, with the exception of aircraft types in Super (J) category; and
• Super (J) — aircraft types specified as such in ICAO Doc 8643, Aircraft Type Designators.

Most are classified as Heavy. Not all aircraft variants of the same type have the same wake turbulence category. The narrow-bodied Boeing 707 - 100 is Medium but the 707-300 is Heavy.

A.2 Difference between ground speed and air speed:

Ground Speed

For a reference point picked on the ground, the aircraft moves relative to the reference point at the ground speed. Ground speed is also a vector quantity so a comparison of the ground speed to the wind speed must be done according to rules for vector comparisons.

Airspeed

The important quantity in the generation of lift is the relative velocity between the object and the air, which is called the airspeed. Airspeed cannot be directly measured from a ground position, but must be computed from the ground speed and the wind speed. Airspeed is the vector difference between the ground speed and the wind speed.

Airspeed = Ground Speed - Wind Speed

On a perfectly still day, the airspeed is equal to the ground speed. But if the wind is blowing in the same direction that the aircraft is moving, the airspeed will be less than the ground speed.

Examples

Suppose we had an airplane that could take off on a windless day at 100 mph (liftoff airspeed is 100 mph). We are at an airport with an east-west runway that is 1 mile long. The wind is blowing 20 mph towards the west and the airplane takes off going east. The wind is blowing towards the aircraft which we call a headwind. Since we have defined a positive velocity to be in the direction of the aircraft's motion, a headwind is a negative velocity. While the plane is sitting still on the runway, it has a ground speed of 0 and an airspeed of 20 mph:

Airspeed = Ground Speed (0) - Wind Speed (-20) = 20 mph

The airplane starts its take off roll and has a constant acceleration a. From Newton's second law of motion the ground speed V at any time t is:

V = a * t

and the distance d down the runway at any time is:

d = 1/2 * a * t^2

For a fixed length runway, this specifies the time to be used in the velocity equation. Let's assume that at 5000 feet down the runway, the velocity is 80 mph. Then the airspeed is given by

Airspeed = Ground Speed (80) - Wind Speed (-20) = 100 mph

and the airplane begins to fly. Now another pilot, with exactly the same airplane decides to take off to the west. The wind is now in the same direction as the motion and this is called a tailwind. The sign on the wind speed is now positive, not negative as with the headwind. The acceleration along the ground is the same, so at 5000 feet down the runway, the ground speed is again 80 mph. The airspeed is then given by:

Airspeed = Ground Speed (80) - Wind Speed (20) = 60 mph

This airplane doesn't have enough airspeed to fly. It runs off the end of the runway!

Significance of Understanding Relative Velocity

The importance of the relative velocity explains why airplanes take off and land on different runways on different days. Airplanes always try to take off and land into the wind. This requires a lower ground speed to become airborne, which means the plane can take off or land in the shortest distance traveled along the ground. Since runways have a fixed length, you want to get airborne as fast as possible on takeoff and stopped as soon as possible on landing. In the old days, a large "wind sock" was hung near the runway for pilots to see which way the wind was blowing to adjust their takeoff and landing directions. Now mechanical or electronic devices provide the information that is radioed to the cockpit.

The relationship between airspeed, wind speed, and ground speed explains why wind tunnel testing is possible and how kites fly.

• In the wind tunnel, the ground speed is zero because the model is fixed to the walls of the tunnel. The airspeed is then the negative of the wind speed that is generated in the tunnel. Whether the object moves through the air, or the air moves over the object, the forces are the same.
• A kite usually has no ground speed because a kite is held on the end of a string. But the kite still has an airspeed that is equal to the wind speed. You can fly a kite only with the wind at your back

A.3 Aircraft engine power is not recommended to move it on the ground at Airport:

Aircraft can move using their own engine power all the time on the airport apron and taxiways under their own power to go towards runways and after landing taxi to their assigned gate. But the thrust produced resulting jet blast might cause damage to the terminal building or equipment. Engines close to the ground may also blow sand and debris forward and then suck them into the engine, causing damage to the engine. A pushback is therefore the preferred method to move the aircraft away from the gate. And also it can reduce the cost for fuel. Taxiing can save money.

• Effectively a loss of control can happen, especially during high power engine running. Damage can occur to the aircraft itself, other aircraft nearby or to airside structures.
• There is a risk of injury to ground support personnel who may be in relatively close proximity to the aircraft.
• It is easier for truck driver to see the surroundings better than the pilot sitting in the cockpit with limited window. The pushback driver knows the airport better than the pilot.
• It also saves fuel virgin Atlantic had proposed a new system in which pushback truck will move the aircraft all the way to runway to save fuel and reduce impact of environment.
• The plane engines are very loud. When more than one plane will add up their sound, than it will not be pleasant for passengers and others near airport.

A.4 How an aircraft is pushed to runway when its ready to take off

Pushback is when an aircraft is pushed backwards away from the airport gate by vehicles called tugs or tractors.

Closer to departure, an aircraft tug will park right in front of the nose wheel.

The tug might be directly attached to the plane's nose gear with a tow bar, or could be a "wheel-lift" tug. These tugs cradle the nose gear, then lift it up before moving the plane. That gives the tug driver control over the plane's direction during pushback.

New taxi technologies are appearing, like pilot-controlled tugs, and electric motors mounted to the plane's landing gear. Both promise to save fuel, and reduce airport noise.

Takeoff is the phase of flight in which an aircraft goes through a transition from moving along the ground (taxiing) to flying in the air, usually starting on a runway. Usually the engines are run at full power during takeoff. Following the taxi motion, the aircraft stops at the starting line of the runway. Before takeoff, the engines, particularly piston engines, are routinely run up at high power to check for engine-related problems. This makes a considerable noise. When the pilot releases the brakes, the aircraft starts accelerating rapidly until the necessary speed for take-off is achieved.

The takeoff speed required varies with air density, aircraft weight, and aircraft configuration (flap and/or slat position, as applicable). Air density is affected by factors such as field elevation and air temperature.

Operations with transport category aircraft employ the concept of the takeoff V-Speeds, V1 and V2. These speeds are determined not only by the above factors affecting takeoff performance, but also by the length and slope of the runway. Below V1, in case of critical failures, the takeoff should be aborted; above V1 the pilot continues the takeoff and returns for landing. After the co-pilot calls V1, Then, V2 (the safe takeoff speed) is called. This speed must be maintained after an engine failure to meet performance targets for rate of climb and angle of climb.

The speeds needed for takeoff are relative to the motion of the air (indicated airspeed). A head wind will reduce the ground speed needed for takeoff, as there is a greater flow of air over the wings. This is why the aircrafts always take off against the wind. Side wind is not preferred as it would disturb the stability of the aircraft. Typical takeoff air speeds for jetliners are in the 130–155 knot range (150–180 mph, 240–285 km/h). For a given aircraft, the takeoff speed is usually directly proportional to the aircraft weight; the heavier the weight, the greater the speed needed. Some aircraft have difficulty generating enough lift at the low speeds encountered during takeoff. These are therefore fitted with high-lift devices, often including slats and usually flaps, which increase the camber of the wing, making it more effective at low speed, thus creating more lift. These have to be deployed from the wing before performing any maneuver.

At the beginning of the climb phase, the wheels are retracted into the aircraft and the undercarriage doors are closed. This operation is audible by the passengers as a noise coming from below the floor.

A.5 Take off power, tyre design, rolling resistance, tyre pressure, brake forces when landing

Take off power=>
Power Requirement to Keep a Jet Aircraft in the Air

The total energy of an aircraft flying in the atmosphere can be calculated using equation,
E = ½ m v2+ mgh

However, the engines mounted onto the wings of the plane are required to provide additional energy per time, power, in order to keep the aircraft flying at a constant altitude and speed. This extra power needed to overcome the drag acting on the airplane and is calculated using

P = (dh/dt) m g
where (dh/dt) is the decent speed required to keep the plane's speed constant if the engines fail.

Takeoff and Climb :

When ready for takeoff, and cleared by Air Trafic Control to proceed, the pilot or first officer of an aircraft releases the brakes and advances the throttle to increase engine power to accelerate down the runway.
Once aligned on the runway, steering the aircraft is normally accomplished by using foot pedals that manipulate the nose wheel until the speed is sufficient enough that wind rushing by the rudder on the aircraft tail makes nose wheel steering unnecessary.

As the aircraft gains speed, air passes faster and faster over its wings and lift is created. Instruments onboard the aircraft display this airspeed, which equals not only the speed of the plane relative to the ground, but also the speed of any wind that may be blowing toward the aircraft (aircraft normally take off headed into the wind). When the airspeed reaches a certain predetermined point known as rotation speed, the pilot manipulates panels on the tail of the aircraft to rotate the nose of the plane upward. This creates even stronger lift and the plane leaves the ground.

Rotation speed, abbreviated VR, is one of three important airspeed settings calculated before every flight.

The others are V1 - the speed beyond which a safe stop on a runway is no longer possible; and V2 - the minimum speed needed to keep a plane flying should an engine fail after the aircraft surpasses V1. Some of the factors affecting VR and V2 are the weight of the aircraft, the air temperature and the altitude of the airport. The heavier the aircraft, the more lift, and thus speed is needed to get it off the ground. Aircraft also need to go faster to y on a hot day than on a cool day. Hot air is less dense than cool air and less density produces less lift for the same speed.

Similarly, the higher the altitude, the less dense the air. Aircraft need more speed to leave the ground at a place like Denver than at a place like New York, with all other factors such as weight being equal. Some of these factors also are important in calculating V1, although the key factor is the length of the runway that is being used.

Most large jets leave the ground at about 160 miles per hour and initially climb at an angle in excess of 15 degrees. The angle of a plane's wings to the air owing around them is extremely important to maintaining lift. If the so-called angle of attack is too severe, the ow of air around the wings becomes disrupted and the plane loses lift.

To make an aircraft more aerodynamically effcient, the wheels on which an aircraft rolls when it is on the ground are retracted into a cavity in the belly of the plane after it is airborne. There is less drag (wind resistance), and an aircraft can fly faster when its landing gear is retracted.

Tyre design :=>

When it comes to safety tyres are one of the most important components of aircraft. They help to absorb the shock of landing and provide cushioning. It also provides the necessary traction for braking and stopping of an aircraft.

An aircraft tyre is designed to withstand extremely heavy loads while landing, take off, taxing and parking. The number of wheels required for aircraft increases with the weight of the aircraft, as the weight of the aeroplane needs to be distributed more evenly.

A Boeing 737NG & 737MAX uses 6 wheels, Boeing 787 uses 10 wheels, Boeing 777 uses 14 wheels and Airbus A380 uses 22 wheels. Aircraft tyres work under extreme conditions, carrying up to 340 tons and accelerating at over 250 km/hour at takeoff, in addition to enduring varied environmental stress when in flight and taxiing.

Design and Construction of Aircraft tyre

Carcass plies are used to form the tire. They are sometimes called casing plies. An aircraft tyre is constructed for the purpose it serves.

1. They support the weight of an aircraft while it is on the ground.
2. It also provides the necessary traction for braking and stopping of an aeroplane.
3. Tyre also helps to absorb the shock of landing and provide cushioning the roughness of takeoff, roll-out, and taxi operations.

Unlike an automobile or truck tyre, it does not have to carry a load for a long period of continuous operation. However, an aircraft tyre absorbs the high impact loads of landing and also it’s operating at high speeds for a short time when required.

Some technical aspects of the tyre :

Retreading – Retreading is methods of restoring a worn tyre by renewing the tread area or by renewing the tread area plus one or both sidewalls. Repairs are included in the tyre retreading process.

Load Rating – Load rating is the maximum permissible load at a specified inflation pressure.

Ply Rating – Ply Rating is used to identify the maximum recommended load rating and inflation pressure for a specified tyre. It is an index of tyre strength.

Speed Rating – The speed rating is the maximum takeoff speed to which the tyre has been tested.

Skid Depth – Skid depth is the distance between the tread surface and the deepest groove as measured in the mould.

Aircraft tyres must have an approved speed and load rating and have sufficient clearance when retracted through landing gear to allow for tyre growth. Tyre growth is the increase in the size of the tyre due to centrifugal forces at high speed.

Aircraft tyres may be Tube-type or Tubeless

Tubeless tyres are more advantageous over tube-type. There is no longer the use of tube-type tyre in recent aviation. Nowadays all airliners are using tubeless tyres. Tubeless that are meant to be used without a tube has the word TUBELESS on the sidewall of the tyre.

Aircraft tyres may be Radial or Bias

Almost all airliners are using Radial tyre. Bias is an older design, and it’s mainly used for road vehicles. Radial tyres have the word RADIAL on the sidewall. Radial tires are more expensive than bias-ply tyres. Radial tires are in demand because of their lower life cycle cost and long term value.

Radial tyre construction :

Radial tires are the most modern design of aircraft tyres. It is a design that is similar to that of car tyres. Typically, the radial tyre offers more landings per tread and lighter weight than a bias tyre; though sometimes at the expense of retread lives.

Radial tires are the most modern design of aircraft tyres. It is a design that is similar to that of car tyres. Typically, the radial tyre offers more landings per tread and lighter weight than a bias tyre; though sometimes at the expense of retread lives.

Radial aircraft tyres differ to bias aircraft tyres in that the plies all run radially from bead to bead at approximately 90° to the centre-line of the tyre. Angled belt plies are laid between the tread and the top casing ply, resulting in a flatter tread and adding strength to the tyre.

Bias ply tyre :

A bias-ply tyre has the fabric bias oriented with and across the direction of rotation and the sidewall. Since fabric can stretch on the bias, the tyre is flexible and can absorb loads. Tyre strength is obtained byadding plies.

Rolling resistance :=>

Rolling resistance is one of the forces that act to oppose the motion of a cyclist. It is caused mainly because of deformation of the tyre and can be understood by thinking about:
1. energy losses due to heat (hysteresis)
2. the forces pushing on the tyre.

Energy is lost as heat
As the tyre comes into contact with the road, it changes shape as it is compressed (pushed in a bit). This compression causes parts of the rubber tube and the casing of the tyre to heat up. It also causes the tread on the outside of the tyre to heat up as it comes into contact with the road. A tyre with knobby tread will have a lot more rolling resistance than a smooth tyre because there will be more rubber being compressed and so there will be more heat.

The tyre is a bit like a spring or a rubber band. Some of the energy is stored as the tyre becomes compressed (squeezed in). As the tyre comes back off the road, there is not as much of this stored energy returned because some of it has gone towards making the tyre heat up. This loss of available energy due to heating is called hysteresis. This means there will be less energy available to make the bike go faster.

If you feel the temperature of your tyres when you have been biking fast, you will notice this heat. If your tyres are not pumped up hard, there will be even more heat created.

The force of rolling resistance does not change at higher speeds. However, because there is a lot more heat being produced at higher speeds, the cyclist uses more power (energy per second) to work against rolling resistance.

Forces on the front part of the tyre are greater

Forces on a tyre

Rolling resistance happens because the force pushing backwards against the tyre as it comes into contact with the road is bigger than the force pushing forwards as it leaves.

As the front part of the tyre touches the road, it takes a lot of force to squeeze in the tyre. This causes a backwards force on the wheel. As the tyre comes back off the road, there is a force pushing forwards on the wheel, but this forwards force is not as great. This is because of internal friction in the tyre.

If you could design a tyre that didn’t have internal friction and didn’t heat up, the force at the front section of the tyre contacting the road would be the same size as the force on the back section. This would mean zero rolling resistance, assuming there was no energy loss due to compression of the road surface.

Some things that affect rolling resistance
Rolling resistance depends on the mass of the cyclist and the bike, cornering, the design of your tyres, tyre pressure and road surface.

Mass – more mass means more downwards force due to gravity onto the road. This results in more tyre compression so rolling resistance increases. Carrying things like extra water bottles increases your rolling resistance.

Cornering – going through corners causes track cyclists to slow down, partly because cornering results in a greater downwards force into the track, which increases rolling resistance. (Cornering also increases rolling resistance because the rubber is twisting sideways on the road a bit, and this twisting produces more friction and heat.)

Design of tyres – choosing materials and construction that don’t heat up as much will result in less rolling resistance. One way to do this is to make your tubes out of specialized latex rubber. Racing tyres are very smooth, narrow and pumped up hard. The casing is also designed to minimize heat loss as it deforms. With as little of the tyre being compressed in as possible, there will not be as much of this heating effect, so there will be more energy available for more speed. There are many options for cyclists to consider.

Road or track surface – wooden cycle tracks contribute to a very low rolling resistance. Rough sealed roads have more rolling resistance. Grass and soft dirt surfaces are much greater. If the surface can be deformed, this increases rolling resistance markedly.

Choosing tyre materials and construction that don’t heat up as much will result in less rolling resistance.

Calculating rolling resistance

This equation is used to calculate the force of rolling resistance from each tyre:
FRR = CRR x weight
FRR is the rolling resistance force.
CRR is the coefficient of rolling resistance (a number used to rate each tyre at a given pressure),
weight is the force due to gravity being exerted on each tyre (= mass (kilograms) x 9.8).
This equation shows that speed does not affect the force due to rolling resistance. The type of tyre and the mass of the bike plus rider are the only two variables.

Tyre pressure =>

An aircraft tire or tyre is designed to withstand extremely heavy loads for short durations. The number of tires required for aircraft increases with the weight of the aircraft, as the weight of the airplane needs to be distributed more evenly. Aircraft tire tread patterns are designed to facilitate stability in high crosswind conditions, to channel water away to prevent hydroplaning, and for braking effect.

Aircraft tires also include fusible plugs (which are assembled on the inside of the wheels), designed to melt at a certain temperature. Tires often overheat if maximum braking is applied during an aborted takeoff or an emergency landing. The fuses provide a safer failure mode that prevents tire explosions by deflating in a controlled manner, thus minimizing damage to aircraft and objects in the surrounding environment.

Inflation :
Each of the twelve Boeing 777-300ER main tires is inflated to 220 psi (15 bar; 1,500 kPa), weighs 120 kg (260 lb), has a diameter of 134 cm (53 in) and is changed every 300 cycles while the brakes are changed every 2000 cycles.

Aircraft tires generally operate at high pressures, Inflation up to 200 psi (14 bar; 1,400 kPa) for airliners, and even higher for business jets.

Tests of airliner aircraft tires have shown that they are able to sustain pressures of maximum 800 psi (55 bar; 5,500 kPa) before bursting.

Aircraft tires are usually inflated with nitrogen to minimize expansion and contraction from extreme changes in ambient temperature and pressure experienced during flight.

Brake forces and landing=>

Bringing at aircraft down to the runway from 37,000 feet is only part of the challenge. It’s not over until the aircraft is safely parked at its gate. In order to do this, pilots have a number of systems available to slow the aircraft down, even in a blizzard on a snow-covered runway.

The 787 braking system:
Stopping a 200-tonne aircraft landing at 180 mph requires a lot of braking force. To do this, the 787 has one brake unit on each of the eight wheels on the main gear assembly.

On other aircraft types, the brake units are powered by the hydraulics system. An electrical signal is sent from the flight deck to hydraulic actuators near the main landing gear. Here, hydraulic fluid at 3,000 pound per square inch is used to force the brake unit against the wheel, thus slowing it down.

That’s the case on the 787 Dreamliner. Designers did away with the use of the hydraulic system and all its associated architecture and instead used electricity to power the brakes. When the pilots press on the brake pedals, an electrical signal is sent to the brake unit on the wheel. Here, electrically powered actuators are used to press the carbon brake disc against the wheel, slowing it down.

Electric brakes
The brake system on the 787 Dreamliner is controlled by the pilots pressing the tops of the rudder pedals under their feet, demanding the rate of braking which they require. This sends an electronic signal to the Left and Right Brake System Control Units (BSCUs).

These then send signals to the four Electronic Brake Actuator Controllers (EBAC) which control the rate of braking on the wheels. Each wheel has four Electric Brake Actuators (EBA), a kind of piston which presses against the carbon brake discs.

The brake disks themselves are made up of two parts. Firstly, there are the rotors. These are connected to the wheel by drive tabs (in the video below they are the black rectangles on the rotor disks). As these drive tabs are in contact with the inside of the wheel, they spin at the same speed. Depending on the brake manufacturer, there are either four or five of these rotors on each brake assembly.

The second part of the disks are the stators. These sit around each rotor and are fixed in place and thus don’t move. As the wheel turns, the rotors spin round inside the stators.

When the brakes are applied, the four EBAs apply pressure to the first stator. This in turn squeezes the stationary stators up against the spinning rotors and it’s this friction which slows the wheel down.

Anti-skid protection
When landing on slippery runways, there’s a chance that the wheels may start to skid as the brakes are applied. To stop this from happening and to maintain maximum effective braking, each wheel has anti-skid protection.

Using a variety of sources to determine the aircraft speed, the brake units know how fast the wheels should be spinning. If that speed drops significantly, it’s because the current brake pressure on that wheel is too great and the wheel is just skidding over the surface.

In this situation, the anti-skid system automatically reduces the braking on that wheel to a point where the skid stops before reapplying the pressure. All this is done in a fraction of a second.

Autobrake
Pressing on the brakes is pretty straight forward when taxiing in a straight line at low speed. However, when we’re landing in strong winds, it can be a little tricky. We need to use our feet on the rudder pedals to line the nose of the aircraft up with the runway centerline at the last moment. Then, whilst holding that position, slide our feet up to press the toe brakes. Really not very easy when moving at 160 mph.
To help us get the braking underway as soon as we touch down, we have the autobrake system.This provides automatic braking at a preselected rate as soon as the aircraft senses that it is on the ground. It also provides full braking pressure in the case of a rejected takeoff if the speed is above 85 knots (98 mph).

Bottom line
Bringing an aircraft to a safe stop is the most important part of a flight. In order to do this, pilots have a number of facilities available to them.

The brakes bear the brunt of the hard work with the spoilers and reverse thrust lending a helping hand to ensure maximum efficiency. The autobrake system helps keep the deceleration nice and smooth whilst the anti-skid system reduces the distances needed to stop by modulating the brakes on individual wheels and stopping them from skidding.

Aircraft can also depart with part of the braking system not working. By carrying out a performance calculation before every takeoff and landing, we ensure that the aircraft will stop safely in the given conditions, even at maximum takeoff weight.

B.6.A. With necessary assumptions, calculate the force and power required to push / pull an aircraft by a towing vehicle.

Aircraft Calculations:

Mass of aircraft, mA = 575,000kg

Mass of pushback is 1000kg(assume)

Coefficient of rolling resistance (Cr) = 0.002

Rolling resistance (Fr) = Cr * m * g

For the Aircraft, Fr = 0.002*575,000*9.81

Fr = 11.2815kN

For the Towing Vehicle, Frt = 0.002*1000*9.81

Frt = 19.61N

As the towing vehicle resistance is very less compared to aircraft, since it is a heavy vehicle this resistance can be neglected.

Aerodynamic resistance, (Far)

Given

Drag coefficient Cd = 0.025

Air density ρ = 1.125kg/m^2

Frontal Area A = 150 m^2

Velocity v = 14.5kmph or 4m/s

Far = (1/2)*Cd*ρ*V^2

Far = (1/2)*0.025*1.125*150*(4)^2

Far = 33.75N

Total Force = 11281.5 + 33.75

= 11315.25 N

As the tow vehicle and plane moving at a low speed this force can be neglected

Hill Climbing resistance:

Runways are constructed flat so gradient force or hill climbing force is neglected.

Total Traction Force:

Ft = Fr

= 11281.5

Power required

P = Ft*v

= 11315.25*4

= 45.26kW

Since the minimum power required at the tow vehicle is 45.126kW to taxi a heavy aircraft at 4m/s.

B.6.B. Develop the model for the calculated force and power using Simulink.

7. A. Design an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application in Simulink. Estimate the duty cycle range to control the aircraft speed from zero to highest. Make all required assumptions. Prepare a table of assumed parameters. Draw a block diagram of powertrain.

(Hint :DC7 Block)

Assumption For Powertrain Design

The power required by the aircraft is 45.26kW. Consider a motor with following specifications

Voltage 400-800V

Peak Power 60-70kW

RPM 1500-4000

Torque 300Nm

Transmission

consider 60kW as peak power therefore voltage will be 400V.

Assume battery power to be 550V.

Now we can calculate the duty cycle

d=Vo/Vs

= 400/550 = 0.7272

Duty cycle is the 0.7272

Assume parameterss

Parameter value

Aircraft Mass (mA) = 575,000kg

Towing vehicle Mass =50,000kg(assume)

Rolling Resistance Co-efficient (Crr) = 0.002

Air density ρ = 1.125kg/m^2

Towing vehicle Drag coefficient Cd = 0.5

Aircraft Drag co-efficient =0.09

Fronatal Area A = 150 m^2

Inclination angle = 0 rad

Tyre Pressure = 203PSI/14 bar

Towing Velocity (V) = 14.5kmph or 4m/s

Towing Time(t) = 2 min

Radius of the towing vehicle wheel = 0.38

Block diagram of powertrain:

Simulink Model:

The above figure shows that powertrain arrangement of tow tractor for towing aircraft. The battery source is displayed at the left. The battery parameters are the maximum voltage value of selected motor. The motor characteristics is implemented as calculated above.

The 200 HP DC motor is separately excited with a constant 150 V DC field voltage source. The armature voltage is provided by an IGBT converter controlled by two PI regulators.

The converter is fed by a 515 V DC bus obtained by rectification of a 380 V AC 50 Hz voltage source. In order to limit the DC bus voltage during dynamic braking mode, a braking chopper has been added between the diode rectifier and the DC7 block.

The first regulator is a speed regulator, followed by a current regulator. The speed regulator outputs the armature current reference (in p.u.) used by the current controller in order to obtain the electromagnetic torque needed to reach the desired speed.

The speed reference change rate follows acceleration and deceleration ramps in order to avoid sudden reference changes that could cause armature over-current and destabilize the system.

The current regulator controls the armature current by computing the appropriate duty ratios of the 5 kHz pulses of the four IGBT devices (Pulse Width Modulation).

For proper system behavior, the instantaneous pulse values of IGBT devices 1 and 4 are opposite to those of IGBT devices 2 and 3. This generates the average armature voltage needed to obtain the desired armature current.

In order to limit the amplitude of the current oscillations, a smoothing inductance is placed in series with the armature circuit.

Output:

B. Also, Design the parameters in excel sheet

CONCLUSION :

With necessary assumptions, calculated the force and power required to push / pull an aircraft by a towing vehicle. Develop the model for the calculated force and power using Simulink. Designed an electric powertrain with type of motor, it’s power rating, and energy requirement to fulfill aircraft towing application in Simulink. Estimated the duty cycle range to control the aircraft speed from zero to highest. plotted necessary required graphs.