CHAPTER 1
INTRODUCTION
1.1 History
A forklift (also called a lift truck, a high/low, a stacker-truck, trailer loader, side loader or a fork hoist) is a powered industrial truck used to lift and transport materials. The modern forklift was developed in the 1920s by various companies including the transmission manufacturing company Clark and the hoist company Yale & Towne Manufacturing. The forklift has since become an indispensable piece of equipment in manufacturing and warehousing operations.
The middle 19th century through the early 20th century saw the developments that led to today's modern forklifts. The Pennsylvania Railroad in 1906 introduced battery powered platform trucks for moving luggage at their Altoona, Pennsylvania train station. World War I saw the development of different types of material handling equipment in the United Kingdom by Ransomes, Sims and Jeffries of Ipswich. This was in part due to the labor shortages caused by the war. In 1917 Clark in the United States began developing and using powered tractor and powered lift tractors in their factories. In 1919 the Towmotor Company and Yale & Towne Manufacturing in 1920 entered the lift truck market in the United States.
Continuing development and expanded use of the forklift continued through the 1920s and 1930s. World War II, like World War I before, spurred the use of forklift trucks in the war effort. Following the war, more efficient methods for storing products in warehouses were being implemented. Warehouses needed more maneuverable forklift trucks that could reach greater heights. New forklift models were made that filled this need. In 1956 Toyota introduced its first lift truck model, the Model LA, in Japan and sold its first forklift in the United States in 1967.

1.2 Working Principle
In this project we have two line tracking sensors and those are connected like ground line looking position. The robot’s path should be in black line, because of the sensors can easily detect the black line. When the power is given to the circuit the controller will on the DC motors, which is connected to the fork lift wheel. So the fork lift will move in forward direction on the black line. When the right side sensor sense the black line means the controller will rotate the wheels in right side. When the left side sensor sense the black line means the controller will rotate the wheels in left side, so that the robot can follow the black line.
Our model consists of three motors. The first two motors are used to run the robot model. The third motor is in the front of the frame which is mounted with the lead screw arrangement. The fork lift arrangement is mounted on the lead screw such that it can be moved up and down. The third motor in model is used for up and down movement of the fork. The above all arrangements are used to lift a weight from one place and carry it to another place. The whole setup is operated through remote signaling device.

1.3 Target Users
The Automatic Forklift System (AFS) is designed to make the process of stocking efficient while decreasing unnecessary work related spending. A one-sixth scale model forklift is being used to demonstrate the feasibility of the project. An operator will control the system at a safe distance away from the forklift, such as in a separate control room, decreasing the risk of work related injuries with a handheld user interface.
The intended users of the AFS would be distributing centers, as well as any company with a large warehouse that uses forklifts to move pallets. The ideal environment for this system would be warehouses with little to no foot traffic that require a forklift to move pallets from trucks to their respective shelves, or stacks, etc.
Employers will benefit from this system by saving money in the long run. An initial investment in the AFS will reduce the cost of employing multiple forklift operators needed to keep up with the inflow and outflow of large quantities of product. With this system, only one operator would be needed to operate the AFS, and as a possible future enhancement, multiple systems. As you can see, employers stand to benefit from this system.
With the AFS, the risk of injury to employees involving forklifts will be reduced, because there will be no need for an operator on the forklift itself to steer it manually. Thus, the operator will no longer be put into dangerous situations. This lowers the cost of workers’ comp. The AFS eliminates the opportunity for human error that may have caused workplace accidents resulting in property damage and bodily harm. This system offers the benefit of safety to employees.

CHAPTER 2
LITERATURE REVIEW
2.1 Description of Project
This project, Automatic Forklift System, aims to create mechanical movements in a forklift as per command signals produced and passed through RF module designed remote. The controller chip generates the data code and transmitted as a modulated signal. The receiver on receiving the signal demodulates it and the output is given to a microcontroller unit assembled over the forklift. The controller controls the motors via the H-bridge as programmed.
The forklift designed in this project can move in all directions including reverse direction. In this project, a communication is set up between two points in space. The waves that are transmitted and received are radio waves.
2.2 Description of equipments
2.2.1 DC Motor

Figure 1: Side view of a DC motor
In any electric motor, operation is based on simple electromagnetism. A current-carrying conductor generates a magnetic field; when this is then placed in an external magnetic field, it will experience a force proportional to the current in the conductor, and to the strength of the external magnetic field. As you are well aware of from playing with magnets as a kid, opposite (North and South) polarities attract, while like polarities (North and North, South and South) repel. The internal configuration of a DC motor is designed to harness the magnetic interaction between a current-carrying conductor and an external magnetic field to generate rotational motion.

Figure 2: Cut Section View of a DC Motor
Every DC motor has six basic parts -- axle, rotor (armature), stator, commutator, field magnet(s), and brushes. In most common DC motors, the external magnetic field is produced by high-strength permanent magnets. The stator is the stationary part of the motor -- this includes the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotates with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator. The above diagram shows a common motor layout -- with the rotor inside the stator (field) magnets.
The geometry of the brushes, commutator contacts, and rotor windings are such that when power is applied, the polarities of the energized winding and the stator magnet(s) are misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets. As the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the next winding. Given our example two-pole motor, the rotation reverses the direction of current through the rotor winding, leading to a "flip" of the rotor's magnetic field, driving it to continue rotating.
In real life, though, DC motors will always have more than two poles (three is a very common number). In particular, this avoids "dead spots" in the commutator. You can imagine how with our example two-pole motor, if the rotor is exactly at the middle of its rotation (perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with a two-pole motor, there is a moment where the commutator shorts out the power supply. This would be bad for the power supply, waste energy, and damage motor components as well. Yet another disadvantage of such a simple motor is that it would exhibit a high amount of torque "ripple" (the amount of torque it could produce is cyclic with the position of the rotor)
A few things from this -- namely, one pole is fully energized at a time (but two others are "partially" energized). As each brush transitions from one commutator contact to the next, one coil's field will rapidly collapse, as the next coil's field will rapidly charge up (this occurs within a few microsecond). We'll see more about the effects of this later, but in the meantime you can see that this is a direct result of the coil windings' series wiring:
There's probably no better way to see how an average DC motor is put together, than by just opening one up. Unfortunately this is tedious work, as well as requiring the destruction of a perfectly good motor.
The use of an iron core armature is quite common, and has a number of advantages. First off, the iron core provides a strong, rigid support for the windings -- a particularly important consideration for high-torque motors. The core also conducts heat away from the rotor windings, allowing the motor to be driven harder than might otherwise be the case. Iron core construction is also relatively inexpensive compared with other construction types.
But iron core construction also has several disadvantages. The iron armature has a relatively high inertia which limits motor acceleration. This construction also results in high winding inductances which limit brush and commutator life.
In small motors, an alternative design is often used which features a 'coreless' armature winding. This design depends upon the coil wire itself for structural integrity. As a result, the armature is hollow, and the permanent magnet can be mounted inside the rotor coil. Coreless DC motors have much lower armature inductance than iron-core motors of comparable size, extending brush and commutator life.

Figure 3: Exploded View of a DC Motor

2.2.2 Battery
In our project we are using secondary type battery. It is rechargeable type. A battery is one or more electrochemical cells, which store chemical energy and make it available as electric current. There are two types of batteries, primary (disposable) and secondary (rechargeable), both of which converts chemical energy to electrical energy. Primary batteries can only be used once because they use up their chemicals in an irreversible reaction. Secondary batteries can be recharged because the chemical reactions they use are reversible; they are recharged by running a charging current through the battery, but in the opposite direction of the discharge current. Secondary, also called rechargeable batteries can be charged and discharged many times before wearing out. After wearing out some batteries can be recycled.
Batteries have gained popularity as they became portable and useful for many purposes. The use of batteries has created many environmental concerns, such as toxic metal pollution. A battery is a device that converts chemical energy directly to electrical energy it consists of one or more voltaic cells. Each voltaic cell consists of two half cells connected in series by a conductive electrolyte.
One half-cell is the positive electrode, and the other is the negative electrode. The electrodes do not touch each other but are electrically connected by the electrolyte, which can be either solid or liquid. A battery can be simply modeled as a perfect voltage source which has its own resistance, the resulting voltage across the load depends on the ratio of the battery's internal resistance to the resistance of the load.

Figure 4: Cut Section of a lead-acid Battery

When the battery is fresh, its internal resistance is low, so the voltage across the load is almost equal to that of the battery's internal voltage source. As the battery runs down and its internal resistance increases, the voltage drop across its internal resistance increases, so the voltage at its terminals decreases, and the battery's ability to deliver power to the load decreases.
2.2.3 Lead Screw
A lead screw also known as a power screw or translation screw, is a screw designed to translate radial motion into linear motion. Common applications are machine slides (such as in machine tools), vises, presses, and jacks.
A lead screw nut and screw mate with rubbing surfaces, and consequently they have a relatively high friction and stiction compared to mechanical parts which mate with rolling surfaces and bearings. Their efficiency is typically between 25 and 70%, with higher pitch screws tending to be more efficient. A higher performing, and more expensive, alternative is the ball screw.
The high internal friction means that leadscrew systems are not usually capable of continuous operation at high speed, as they will overheat. Due to inherently high stiction, the typical screw is self-locking (i.e. when stopped, a linear force on the nut will not apply a torque to the screw) and are often used in applications where backdriving is unacceptable, like holding vertical loads or in hand cranked machine tools.
Leadscrews are typically used well greased, but, with an appropriate nut, it may be run dry with somewhat higher friction. There is often a choice of nuts, and manufacturers will specify screw and nut combinations as a set.
The mechanical advantage of a leadscrew is determined by the screw pitch and lead. For multi-start screws the mechanical advantage is lower, but the traveling speed is better.
Backlash can be reduced with the use of a second nut to create a static loading force known as preload; alternately, the nut can be cut along a radius and preloaded by clamping that cut back together.
A lead screw will back drive. A leadscrew's tendency to backdrive depends on its thread helix angle, coefficient of friction of the interface of the components (screw/nut) and the included angle of the thread form. In general, a steel acme thread and bronze nut will back drive when the helix angle of the thread is greater than 20°.

ADVANTAGES & DISADVANTAGES
The advantages of a leadscrew are: * Large load carrying capability * Compact * Simple to design * Easy to manufacture; no specialized machinery is required * Large mechanical advantage * Precise and accurate linear motion * Smooth, quiet, and low maintenance * Minimal number of parts * Most are self-locking
The disadvantages of leadscrew are: * Due to the low efficiency they cannot be used in continuous power transmission * They also have a high degree for friction on the threads, which can wear the threads out quickly. * For square threads, the nut must be replaced; for trapezoidal threads, a split nut may be used to compensate for the wear.
2.2.4 Bearing
A bearing is a device to permit constrained relative motion between two parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation. Low friction bearings are often important for efficiency, to reduce wear and to facilitate high speeds. Essentially, a bearing can reduce friction by virtue of its shape, by its material, or by introducing and containing a fluid between surfaces. By shape, gains advantage usually by using spheres or rollers. By material, exploits the nature of the bearing material used. Sliding bearings, usually called bushes, bushings journal bearings sleeve bearings rifle bearings or plain bearings. rolling-element bearings such as ball bearings and roller bearings. Jewel bearings, in which the load is carried by rolling the axle slightly off-center. fluid bearings, in which the load is carried by a gas or liquid magnetic bearings, in which the load is carried by a magnetic field. Bearings vary greatly over the forces and speeds that they can support. Forces can be radial, axial (thrust bearings) or moments perpendicular to the main axis. Bearings very typically involve some degree of relative movement between surfaces, and different types have limits as to the maximum relative surface speeds they can handle, and this can be specified as a speed in ft/s or m/s.
The moving parts there is considerable overlap between capabilities, but plain bearings can generally handle the lowest speeds while rolling element bearings are faster, hydrostatic bearings faster still, followed by gas bearings and finally magnetic bearings which have no known upper speed limit.
2.2.4.1 Types of Bearing
2.2.4.1.1 Ball Bearing Figure 5: Cut Section of a Ball Bearing
Ball bearings, as shown in the above figure, are the most common type by far. They are found in everything from skate boards to washing machines to PC hard drives. These bearings are capable of taking both radial and thrust loads, and are usually found in applications where the load is light to medium and is constant in nature (ie not shock loading). The bearing shown here has the outer ring cut away revealing the balls and ball retainer.
2.2.4.1.2 Roller Bearing Figure 6: Cut Section of a Roller Bearing
Roller bearings like the one shown the figure above, are normally used in heavy duty applications such as conveyer belt rollers, where they must hold heavy radial loads. In these bearings the roller is a cylinder, so the contact between the inner and outer race is not a point (like the ball bearing above) but a line. This spreads the load out over a larger area, allowing the roller bearing to handle much greater loads than a ball bearing. However, this type of bearing cannot handle thrust loads to any significant degree. A variation of this bearing design is called the needle bearing. The needle roller bearing uses cylindrical rollers like those above but with a very small diameter. This allows the bearing to fit into tight places such as gear boxes that rotate at higher speeds.
2.2.4.1.3 Thrust Ball Bearing Figure 7: Thrust Ball Bearing
Ball thrust bearings like the one shown above, are mostly used for low-speed non precision applications. They cannot take much radial load and are usually found in lazy Susan turntables and low precision farm equipment.

2.2.4.1.4 Thrust Roller Bearing

Figure 8: Thrust Roller Bearing
Roller thrust bearings like the one illustrated above can support very large thrust loads. They are often found in gear sets like car transmissions between gear sprockets, and between the housing and the rotating shafts. The helical gears used in most transmissions have angled teeth, this can causes a high thrust load that must be supported by this type of bearing.
2.2.4.1.5 Taper Roller Bearing Figure 9: Cut Section of a Taper Roller Bearing
Tapered roller bearings are designed to support large radial and large thrust loads. These loads can take the form of constant loads or shock loads. Tapered roller bearings are used in many car hubs, where they are usually mounted in pairs facing opposite directions. This gives them the ability to take thrust loads in both directions. The cutaway taper roller on the left shows the specially designed tapered rollers and demonstrates their angular mounting which gives their dual load ability.

2.2.5 RF Transmitter with Encoder
2.2.5.1 Encoder
In this circuit HT 640 is used as encoder. The 318 encoders are a series of CMOS LSIs for remote control system application. They are capable of encoding 18 bits of information which consists of N address bit and 18-N data bits. Each address/data input is externally trinary programmable if bonded out. It is otherwise set floating internally. Various packages of the 318 encoders offer flexible combination of programmable address/data is transmitted together with the header bits via an RF or an infrared transmission medium upon receipt of a trigger signal. The capability to select a TE trigger type further enhances the application flexibility of the 318 series of encoders.
In this circuit the input signal to be encoded is given to AD7-AD0 input pins of encoder. Here the input signal may be from key board, parallel port, microcontroller or any interfacing device. The encoder output address pins are shorted so the output encoded signal is the combination of (A0-A9) address signal and (D0-D7) data signal. The output encoded signal is taken from 8th which is connected to RF transmitter section.

Figure 10: RF Transmitter with Encoder
2.2.5.2 RF Transmitter Whenever the high output pulse is given to base of the transistor BF 494, the transistor is conducting so tank circuit is oscillated. The tank circuit is consists of L2 and C4 generating 433 MHz carrier signal. Then the modulated signal is given LC filter section. After the filtration the RF modulated signal is transmitted through antenna.

2.2.6 Decoder with RF Receiver

Figure 11: RF Receiver with Decoder
2.2.6.1 RF Receiver
The RF receiver is used to receive the encoded data which is transmitted by the RF transmitter. Then the received data is given to transistor which acts as amplifier. Then the amplified signal is given to carrier demodulator section in which transistor Q1 is turn on and turn off conducting depends on the signal. Due to this the capacitor C14 is charged and discharged so carrier signal is removed and saw tooth signal is appears across the capacitor. Then this saw tooth signal is given to comparator. The comparator circuit is constructed by LM558. The comparator is used to convert the saw tooth signal to exact square pulse. Then the encoded signal is given to decoder in order to get the decoded original signal.
2.2.6.2 Decoder
I n this circuit HT648 is used as decoder. The 318 decoder are a series of CMOS LSIs for remote control system application. They are paired with 318 series of encoders. For proper operation a pair of encoder/decoder pair with the same number of address and data format should be selected. The 318 series of decoder receives serial address and data from that series of encoders that are transmitted by a carrier using an RF or an IR transmission medium. It then compares the serial input data twice continuously with its local address. If no errors or unmatched codes are encountered, the input data codes are decoded and then transferred to the output pins. The VT pin also goes high to indicate a valid transmission.
The 318 decoders are capable of decoding 18 bits of information that consists of N bits of address and 18-N bits of data. To meet various applications they are arranged to provide a number of data pins whose range is from 0 t08 and an address pin whose range is from 8 to 18. In addition, the 318 decoders provide various combinations of address/ data numbering different package.
In this circuit the received encoded signal is 9th pin of the decoder. Now the decoder separate the address (A0-A9) and data signal (D0-D7). Then the output data signal is given to microcontroller or any other interfacing device.
2.2.7 Infra Red Sensor
IR sensors use infra red light to sense objects in front of them and gauge their distance. The commonly used Sharp IR sensors have two black circles which used for this process, an emitter and a detector.
A pulse of infra red light is emitted from the emitter and spreads out in a large arc. If no object is detected then the IR light continues forever and no reading is recorded. However, if an object is nearby then the IR light will be reflected and some of it will hit the detector. This forms a simple triangle between the object, emitter and detector. The detector is able to detect the angle that the IR light arrived back at and thus can determine the distance to the object. This is remarkably accurate and although interference from sunlight is still a problem, these sensors are capable of detecting dark objects in sunlight now.

Figure 12: IR Sensor

Figure 13: IR Sensor Circuit

Features of IR sensor circuit board used in the project: * Power supply: +5V * Operating current: <10mA * Operating temperature range: 0°C ~ + 50°C * Output interface: 3-wire interface (1 - signal, 2 - power, 3 - power supply negative) * Output Level: TTL level (black line of low effective, high efficient white line) * Module Size: 10mm×35mm * Module Weight: About 1g 2.2.7.1 IR Sensor as a Line Follower

Figure 14: IR Sensor as a Line Follower

A line tracker mostly consists of an infrared light sensor and an infrared LED. It functions by illuminating a surface with infrared light; the sensor then picks up the reflected infrared radiation and, based on its intensity, determines the reflectivity of the surface in question. Lightly colored surfaces will reflect more light than dark surfaces; therefore, lightly colored surfaces will appear brighter to the sensor. This allows the sensor to detect a dark line on a pale surface, or a pale line on a dark surface.
The line tracker enables a robot to autonomously navigate a line-marked path. By drawing a line in front of a robot outfitted with a line tracker, one can dictate the robot’s patch by showing it where to go without using a remote controller. It can detect the white lines in black and black lines in white. The single line-tracking signals can provide a stable output signals TTL, so look for more accurate and more stable line. So based on these signal, a differential drive mechanism kind of actuation signal is given to the motors.
2.2.8 Signal Conditioning Unit
Signal conditioning means manipulating an analogue to manipulating an analogue signal in such a way that it meets the requirements of the next stage for further processing. The signal conditioning is the amplification necessary to bring the voltage level up to that required by the ADC. Signal conditioning stage is a processing stage carried out by an ADC and microcontroller.
2.2.9 Relay
A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off. So relays have two switch positions and they are double throw (changeover) switches. Relays allow one circuit to switch a second circuit which can be completely separate from the first. The link is magnetic and mechanical. The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can be as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot provide this current and a transistor is usually used to amplify the small IC current to the larger value required for the relay coil. The maximum output current for the popular 555 timer IC is 200mA so these devices can supply relay coils directly without amplification. Figure 15: Glass Type Relay
Relays are usually SPDT or DPDT but they can have many more sets of switch contacts, for example relays with 4 sets of changeover contacts are readily available. Most relays are designed for PCB mounting but you can solder wires directly to the pins providing you take care to avoid melting the plastic case of the relay. The animated picture shows a working relay with its coil and switch contacts. You can see a lever on the left being attracted by magnetism when the coil is switched on. This lever moves the switch contacts. There is one set of contacts (SPDT) in the foreground and another behind them, making the relay DPDT.
2.2.10 Microcontroller
Microcontrollers are destined to play an increasingly important role in revolutionizing various industries and influencing our day to day life more strongly than one can imagine. Since its emergence in the early 1980's the microcontroller has been recognized as a general purpose building block for intelligent digital systems. It is finding using diverse area, starting from simple children's toys to highly complex spacecraft. Because of its versatility and many advantages, the application domain has spread in all conceivable directions, making it ubiquitous. As a consequence, it has generate a great deal of interest and enthusiasm among students, teachers and practicing engineers, creating an acute education need for imparting the knowledge of microcontroller based system design and development. It identifies the vital features responsible for their tremendous impact; the acute educational need created by them and provides a glimpse of the major application area.
A microcontroller is a complete microprocessor system built on a single IC. Microcontrollers were developed to meet a need for microprocessors to be put into low cost products. Building a complete microprocessor system on a single chip substantially reduces the cost of building simple products, which use the microprocessor's power to implement their function, because the microprocessor is a natural way to implement many products. This means the idea of using a microprocessor for low cost products comes up often. But the typical 8-bit microprocessor based system, such as one using a Z80 and 8085 is expensive. Both 8085 and Z80 system need some additional circuits to make a microprocessor system. Each part carries costs of money. Even though a product design may requires only very simple system, the parts needed to make this system as a low cost product.
To solve this problem microprocessor system is implemented with a single chip microcontroller. This could be called microcomputer, as all the major parts are in the IC. Most frequently they are called microcontroller because they are used they are used to perform control functions.
The microcontroller contains full implementation of a standard MICROPROCESSOR, ROM, RAM, I/0, CLOCK, TIMERS, and also SERIAL PORTS. Microcontroller also called "system on a chip" or "single chip microprocessor system" or "computer on a chip".
A microcontroller is a Computer-On-A-Chip, or, if you prefer, a single-chip computer. Micro suggests that the device is small, and controller tells you that the device' might be used to control objects, processes, or events. Another term to describe a microcontroller is embedded controller, because the microcontroller and its support circuits are often built into, or embedded in, the devices they control.
Today microcontrollers are very commonly used in wide variety of intelligent products. For example most personal computers keyboards and implemented with a microcontroller. It replaces Scanning, Debounce, Matrix Decoding, and Serial transmission circuits. Many low cost products, such as Toys, Electric Drills, Microwave Ovens, VCR and a host of other consumer and industrial products are based on microcontrollers.
Microcontroller is a general purpose device, which integrates a number of the components of a microprocessor system on to single chip. It has inbuilt CPU, memory and peripherals to make it as a mini computer. A microcontroller combines on to the same microchip: * The CPU core * Memory(both ROM and RAM) * Some parallel digital i/o
Micro controllers will combine other devices such as: * A timer module to allow the micro controller to perform tasks for certain time periods. * A serial i/o port to allow data to flow between the controller and other devices such as a PIC or another micro controller. * An ADC to allow the micro controller to accept analogue input data for processing. Micro controllers are: * Smaller in size * Consumes less power * Inexpensive Micro controller is a stand-alone unit, which can perform functions on its own without any requirement for additional hardware like i/o ports and external memory. The heart of the microcontroller is the CPU core. In the past, this has traditionally been based on a 8-bit microprocessor unit. For example Motorola uses a basic 6800 microprocessor core in their 6805/6808 microcontroller devices.
2.10.1 Atmel AT89S52 Microcontroller
The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8KBytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.
The AT89S52 provides the following standard features: 8K bytes of flash, 256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware reset. Figure 16: Pin Configuration of AT89s52
2.10.2 Features of Atmel AT89s52
• Compatible with MCS-51® Products
• 8K Bytes of In-System Programmable (ISP) Flash Memory – Endurance: 1000 Write/Erase Cycles
• 4.0V to 5.5V Operating Range
• Fully Static Operation: 0 Hz to 33 MHz
• Three-level Program Memory Lock
• 256 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Three 16-bit Timer/Counters
• Eight Interrupt Sources
• Full Duplex UART Serial Channel
• Low-power Idle and Power-down Modes
• Interrupt Recovery from Power-down Mode
• Watchdog Timer
• Dual Data Pointer
• Power-off Flag

CHAPTER 3
HARDWARE DESIGN

3.1 Schematic of the Project

Figure 17: Schematic of the Project
A clear schematic representation of the project is as shown in the figure above. The two DC motors (03) at the rear drives the forklift forward and backward. In front, two castor vehicles are installed for support and giving direction. The battery (04) is the main power source to the forklift. The battery supplies power to the relay and the microcontroller via a switch. The forklift runs on a lead screw mechanism where the lead screw is supported on either ends with a ball bearing. The lead screw mechanism is powered by a DC motor. Six line sensors are attached in the AFS. Two IR sensors are used for object detection. One of them is used to detect the object to be picked and the other acts as the “home Position Sensor” which gives the AFS the signal that the AFS has reached the home and the object can be kept down. Two IR sensors are attached to detect white and black lines and other two are attached for emergency stop i.e. any obstruction to the forklift in the either sides of the AFS. So, in total, 6 IR sensors are installed in the AFS.
3.2 Block Diagram of the Project Figure 18: Block Diagram of the Project
A clear view of how the project runs is represented by the use of block diagram. The input is given by the user through the keypad using switch button. The input from the switch is encoded and sent to the RF transmitter. The RF transmitter transmits the signal in the form of radio waves. The RF receiver receives the code and decoder decodes it and sends it to the microcontroller. The microcontroller gets the signal and controls the AFS accordingly. There are two IR sensors used as line tracking sensors. The line tracking sensors make the AFS to follow a particular line path, follow a black path on white ground or follow a white path on a black ground. There are two relays provided for each motor. One of the relays is for forward or clockwise motion of the motor and the other is for reverse or the anti-clockwise motion. Another sensor is provided as the object sensor which detects the object to be picked and through which the forward motor used for moving the fork up and down is actuated. A reverse object sensor signals the microcontroller to lower the fork when the “home position” is reached.
3.3 Fabrication of the Forklift model
The physical model is as shown in figure 19. According to the initial design parameters, a model of 1.5’×1’×1’ was fabricated with normal DC motor in the rear. But after the testing was done, it was found out that the leadscrew based fork mechanism was to heavy for that model as the lift was not balancing properly without support and kept tilting forward due to the weight of the fork mechanism. Hence, we needed a bigger model.
Another problem we faced during the first testing was that the normal motors which we had installed initially for the locomotion of the AFS were not sufficient to carry the weight of the model which was easily around 5 to 6 Kilograms.

Figure 19: Side View of the AFS Figure 20: Top View of the AFS
So, a new bigger chassis was fabricated with high torque Magna motors with given dimensions. Material used for fabricating the model is Mild Steel as it was the cheapest and most easily machined material available in the market. Mild Steel square section rods are used as the support members of the chassis because of their high tensile and compressive strength

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3.3.1 Leadscrew Based Forklift Mechanism Figure 21: Forklift Mechanism
Lead screw is one of the most common mechanisms for converting rotator to linear motion. It is used when the high load is to be moved. A very good example of application of the lead screw mechanism is lathe machine.
Earlier design consisted of a rack and pinion mechanism, but we faced difficulty in getting the fabrication of the rack so we resorted to leadscrew. Other actuation mechanisms like pneumatic cylinders etc would not have been a good choice as the size of the project is not big enough to implement these mechanisms, however these mechanisms are cheaper when actual size forklifts are to be made.
The torque required to lift or lower a load can be calculated by "unwrapping" one revolution of a thread. This is most easily described for a square or buttress thread as the thread angle is 0 and has no bearing on the calculations. The unwrapped thread forms a right angle triangle where the base is long and the height is the lead (pictured to the right). The force of the load is directed downward, the normal force is perpendicular to the hypotenuse of the triangle, the frictional force is directed in the opposite direction of the direction of motion (perpendicular to the normal force or along the hypotenuse), and an imaginary "effort" force is acting horizontally in the direction opposite the direction of the frictional force. Using this free-body diagram the torque required to lift or lower a load can be calculated: Figure 22: Unwrapped screw thread

* T = torque * F = load on the screw * dm = mean diameter * = coefficient of friction (common values are found in the table to the right) * l = lead * = angle of friction * = lead angle

Coefficient of friction for leadscrew threads Screw material | Nut material | | Steel | Bronze | Brass | Cast iron | Steel, dry | 0.15–0.25 | 0.15–0.23 | 0.15–0.19 | 0.15–0.25 | Steel, machine oil | 0.11–0.17 | 0.10–0.16 | 0.10–0.15 | 0.11–0.17 | Bronze | 0.08–0.12 | 0.04–0.06 | - | 0.06–0.09 |

The specifications of the lead screw used in our project are:
F= 2 kg dm= 1.2 cms µ= 0.2 (From the table specified above, for screw material: steel & nut material: steel) l = 6 mm ø = 33 degrees
ƛ= 7.5 degrees
Then, according to formula specified above, the torque requirement for the leadscrew is:
T(raise)= 1.024 kg –cm
T(lower)= 0.572 kg-cm

3.4 Circuit Design
3.4.1 Transmitter side

Figure 23: Transmitter Circuit In this circuit HT 12E is used as encoder. In this circuit the input signal to be encoded is given to AD7-AD0 input pins of encoder. Here the input signal may be from key board, parallel port, microcontroller or any interfacing device. The encoder output address pins are shorted so the output encoded signal is the combination of (A0-A9) address signal and (D0-D7) data signal. The output encoded signal is taken from 8th which is connected to RF transmitter section.
Whenever the high output pulse is given to base of the transistor BF 494, the transistor is conducting so tank circuit is oscillated. After the filtration the RF modulated signal at 433 MHz is transmitted through antenna.

Figure 24: Power Supply to the Transmitter
While testing the AFS quite a few times, a lot of 9V batteries were consumed, so we decided to give it a permanent power supply using AC. The figure shown is the power supply to the transmitter of the AFS. It consists of a 230V-9V step-down transformer. The stepped down voltage is then converted into DC using a Wheatstone bridge rectifier circuit. A 1000µFd capacitor is provided to filter off any noises present in the input supply. A IC 7805 along with a 10mFd capacitor attached in parallel is then used to regulate the voltage to a constant 5V, which is then supplied to the transmitter.

3.4.2 Receiver Side
4
3
2
1

Figure 25: Receiver with encoder
An HT12D Receiver and decoder set are used in the circuit. Diode D3 is provided is the power on bulb, 10Kohm resisters are provided at AD0 to AD7 as buffer resisters. The data pins D8, D9, D10 and D11 are linked to the pins P1.0, P1.1, P1.2 and P1.3 of the microcontroller respectively.
3.4.2.1 The Microcontroller
The microcontroller used in the project is Atmel AT89s52. The major reason behind using this microcontroller is because it can be programmed using Embedded C, which in fact is the most easy programming language used for programming microcontrollers. However, the PIC microcontrollers are better than atmel in some fields, yet ease of programming of the atmel using Embedded C trumps it over other microcontrollers. The requirement of our project was sufficiently covered by atmel.

From Sensors
From Receiver

To actuator motors
AT89s52

Figure 26: AT89s52
Figure shown above is of the connection given externally to the AT89s52 microcontroller. Pins 1, 2, 3 and 4 are the input terminals wherein the inputs from the receiver is given as explained in section 3.4.2. Pins 6 and 7 are used for giving input from the IR sensors which are the Line Follower sensors. Pins 5 and 6 are also utilized to provide input from the object sensor and the “home position” sensor. Between pins 18 and 19, a quartz crystal of frequency 12 MHz is provided. Pins 21 to 26 are the output pins which are used to give the command signals to the three actuator motors (2 for locomotion, and 1 for forklift mechanism).
Pin 31 is the charging input pin required by the micro controller which is an input of 5V, supplied by a charging circuit. A charging circuit is nothing but a 5V regulated power supply as explained in section 3.4.1. Only difference is that, there is a 1 watt power resister and a fuse attached in series with the power supply, which ensures extra protection to the microcontroller in case of power surge and also checks the reverse flow of current from circuit to the battery. A switch is provided to power on and off the AFS. Figure 27: Charging Circuit for the Microcontroller
3.4.2.2 IR sensors
To pins 5,6,7,8 of microcontroller

Figure 28: IR sensor
Shown above is the circuit diagram of the IR sensor used in the project as the line following sensor and the object detector. An LED which emits infrared light is powered with a 5V supply as shown. The receiver receives the reflection of the light whenever there is white background and gives high output (i.e. gives a voltage of 5V). This output is then compared with the set reference voltage of 5V at terminal 3 of the op-amp comparator LM358. Whenever there is zero difference between the receiver output and the reference voltage, the comparator gives high output as a signal that it has sensed to the microcontroller. This high output also lights an LED which makes the user to understand the working of the sensor. As explained before, four of these sensors are used in the project as line tracker and as the object sensors. Hence, four sensors are used whose output is fed to the microcontroller at the pins 5 and 6 (object sensor), 7 and 8 (line sensor).
3.4.2.3 DC motor Forward/Reverse Control
Reverse control motor drive
Forward control motor drive
Input from the microcontroller

Figure 29: DC motor Forward/Reverse Control

The diagram shown above is the forward and the reverse control motor drive circuit. So, as shown in the figure above, two motor driving circuits are used. A motor driving circuit or simply a motor drive is nothing but a signal amplification unit, which amplifies the input coming from the microcontroller and switches on the relay. A relay is nothing but an electrical switch, which when on, supplies 12V DC supply to the motor.
Hence, two output signal lines are provided for each motor. When the motor is required to run in the forward direction, a high signal is given to the forward motor drive, and a low signal is given to the reverse motor drive, hence the reverse motor drive is blocked. Thus motor terminal 1 becomes positive and motor terminal 2 becomes ground or zero and the motor runs in the forward direction. Similarly, when the motor is required to run in the reverse direction, a high signal is given to the reverse motor drive, and a low signal is given to the forward motor drive, hence the forward motor drive is blocked. Thus motor terminal 2 becomes positive and motor terminal 1 becomes ground or zero and the motor runs in the reverse direction. Now, when a high signal is given to a motor drive, the NPN transistor BC547, in the common emitter configuration, amplifies the signal and switches on the relay and the 12V DC supply goes to the motor which makes it run.
Glass type relays are used for the locomotion motors as it helps better for proportional control, while the normal relays are used for fork motor as variation of speed is not required in that motor.

Figure 30: Circuit Diagram of the AFS CHAPTER 4
SOFTWARE DESIGN

The main idea behind using an atmel microcontroller is the ease of programming it using Embedded C. Use of Embedded C is driven by following advantages: * It is small and reasonably simpler to learn, understand, program and debug. * C Compilers are available for almost all embedded devices in use today, and there is a large pool of experienced C programmers. * Unlike assembly, C has advantage of processor-independence and is not specific to any particular microprocessor/ microcontroller or any system. This makes it convenient for a user to develop programs that can run on most of the systems. * As C combines functionality of assembly language and features of high level languages, C is treated as a ‘middle-level computer language’ or ‘high level assembly language’ * It is fairly efficient * It supports access to I/O and provides ease of management of large embedded projects.
In our project, we have six inputs to the microcontroller: * r1= input from left line sensor * r2= input from right line sensor * r3= input from front object sensor * r4= input from back object sensor or the “home position sensor” * lmt1= lower limit switch input * lmt2= upper limit switch input
The output are to the relay to switch on and off as per the requirement. The whole process goes as follows:
Input is given from the RF transmitter by pressing a button. The AFS moves forward following the black path. When the AFS moves out of the way in the left side, the left line tracking IR sensor detects the change and gives the signal to the microcontroller. The microcontroller then gives the proportional signal to the left motor to rotate faster than the right motor. Hence the AFS comes back on line. The vice versa of the process happens when the AFS moves right of the line. Then when the object to be picked is detected, the fork motor is directed to pick up the object. After picking up the object, the lift hits the upper limit switch which is the command for the AFS to go back following the line. Now, the back position sensor when senses the “home position”, instructs the AFS to stop there and rotate the fork motor in the opposite direction to keeps the object down. In the process, after keeping the object down, it presses the lower limit switch which stops the AFS and keeps it on standby.
4.1 Coding
#include<AT89x52.h>
#include "smcl_lcd8.h"
#define r1 P1_0
#define r2 P1_1
#define r3 P1_2
#define r4 P1_3
#define rly5 P1_4
#define rly6 P1_5
#define ir1 P1_6
#define ir2 P1_7
#define obj1 P3_2
#define obj2 P3_3
#define obj3 P3_4
#define obj4 P3_5
#define lmt1 P3_6
#define lmt2 P3_7
#define rf1 P2_0
#define rf2 P2_1
#define rf3 P2_2
#define rf4 P2_3 void start(); void load(); void main()
{
Lcd8_Init(); Lcd8_Display(0x80," Auto Forklift ",16); Lcd8_Display(0xC0," Robo ",16); r1=r2=r3=r4=rly5=rly6==1; rly5=0; while(lmt1); rly5=1; r1=0; r2=0; r3=0; r4=0; while(1) { Lcd8_Display(0x80," Auto Forklift ",16); Lcd8_Display(0xC0," Robo ",16); if(!rf1) { start(); } }
}
void start()
{
//r1=0; r2=0; r3=0; r4=0; while(rf2) { //Lcd8_Display(0x80," Line Follower ",16); if((!ir1)&&(!ir2)) { r1=1; r2=1; r3=0; r4=0; Lcd8_Display(0x80,"****FORWARD*****",16); } else if((ir1)&&(!ir2)) { r1=1; r2=0; r3=1; r4=0; Lcd8_Display(0x80,"****RIGHT*******",16); } else if((!ir1)&&(ir2)) { r1=0; r2=1; r3=0; r4=1; Lcd8_Display(0x80,"******LEFT******",16); } else if((ir1)&&(ir2)) { r1=r2=r3=r4=1; Lcd8_Display(0x80,"******STOP******",16); } if(obj1) { load(); r1=0; r2=0; r3=1; r4=1; Lcd8_Display(0x80,"****Reverse*****",16);
}
if(obj2) { load(); r1=0; r2=0; r3=1; r4=1; Lcd8_Display(0x80,"****Reverse*****",16); } if(obj3) { r1=r2=r3=r4=1; Lcd8_Display(0x80,"******STOP******",16); } if(obj4) { r1=r2=r3=r4=1; Lcd8_Display(0x80,"******STOP******",16); } } r1=r2=r3=r4=1; Lcd8_Display(0x80,"******STOP******",16);
}
void load()
{
r1=r2=r3=r4=1; Lcd8_Display(0x80,"******STOP******",16); rly6=0; rly5=1; Lcd8_Display(0xC0,"******load*******",16); while(lmt2); rly6=1; rly5=1; Delay(65000); Delay(65000); rly6=1; rly5=0; while(lmt1); rly6=1; rly5=1; Lcd8_Display(0xC0,"****Unload*******",16);
}

CHAPTER 5
CONCLUSION
The Automatic Forklift System is designed to make stocking in warehouses easier and more efficient. With the AFS, the risk of injury to employees involving forklifts reduces, because there will be no need for an operator on the forklift itself to steer it manually. Thus, the operator will no longer be put into dangerous situations. The IR sensors installed in the AFS are calibrated to give highest accuracy. Two magna motors were installed in the rear to balance the weight of the forklift. Two IR sensors detect black and white lines and the AFS moves along that path. Thus, The Automatic Forklift System is able to detect an object on a particular pathway with the help of an IR sensor located in front, pick it, and return to the home position along the same path way and place the object down with the help of a back IR sensor.

CHAPTER 6 FUTURE ENHANCEMENTS Many enhancements can be done in AFS to improve its efficiency and productivity. The AFS can be designed to follow multiple paths to pick and place objects. More complicated algorithms can be designed to make the AFS work in more complicated environment and more complicated scenarios. Wireless video camera can be attached to give feedback about the position of the AFS. Camera will allow the operator to monitor the position of the AFS through his/her cabin via laptop or any other remote device. Image sensing is also one of the valuable options that may detect the objects of various shapes and sizes and decide on whether which protocol is to be followed. A local GPS can also be installed to monitor the position. With advanced programming, AFS can be commanded to lift objects from different levels. Artificial Intelligence can be implemented where the AFS can follow an alternate path in case of obstruction or in other words take decisions according to the situation. Fuzzy logic and variable power actuators can be combined to achieve smart AFS which might be capable of doing various other kinds of job than just picking it up. A more advanced type of AFS can be made where two AFS can “talk” with each other and decide on which protocol is to be followed and also decide on load sharing among them. Hence the possibilities as we just saw are huge and smarter AFS will lead to faster, safer, more automatic with lesser human interference, and more efficient handling of the goods.

REFERENCES * R.S. Kurmi (2008) Strength of Materials. 4th Edition. S.Chand Publishing Co. * K. Mahadevan, K.Balveera Reddy.(2013) Design Data Handbook For Mechanical Engineers : In SI and Metric Units . 3rd Edition. CBS Publisher * D.Patranabis (2009) Sensors and Transducers. 2nd Edition. PHI Learning * The Adafruit Learning System.( 2011) Overview on IR Sensor. Website : http://learn.adafruit.com/ir-sensor/overview [ Online] * Engineers Garage (2012) Introduction to Embedded C. Website : http://www.engineersgarage.com/tutorials/emebedded-c-language [Online] * Thomson BSA (2000) Lead screws and Ball screws . Website : http://www.thomsonbsa.com/ , http://en.wikipedia.org/wiki/Leadscrew [Online]