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embedded system report

  1. 1. CHAPTER-1 Introduction to Robotics In practical usage, a Robot is a mechanical device which performs automated physical tasks, either according to direct human supervision, a pre-defined program, or a set of general guidelines using artificial intelligence techniques. Robots are typically used to do the tasks that are too dirty, dangerous, difficult, repetitive or dull for humans. This usually takes the form of industrial robots used in manufacturing lines. Other applications include toxic waste cleanup, underwater and space exploration, mining, search and rescue, and mine finding. Recently however, robots are finding their way into the consumer market with uses in entertainment, vacuum cleaning, and lawn mowing. A robot may include a feedback-driven connection between sense and action, not under direct human control, although it may have a human override function. The action may take the form of electro-magnetic motors or actuators (also called effectors) that move an arm, open and close grips, or propel the robot. The step by step control and feedback is provided by a computer program run on either an external or embedded computer or a microcontroller. By this definition, a robot may include nearly all automated devices. Ask a number of people to describe a robot and most of them will answer they look like a human. Interestingly a robot that looks like a human is probably the most difficult robot to make. It is usually a waste of time and not the most sensible thing to model a robot after a human being. A robot needs to be above all functional and designed with qualities that suit its primary tasks. It depends on the task at hand whether the robot is big, small, is able to move or nailed to the ground. Each and every task means different qualities, form and function; a robot needs to be designed with the task in mind. 1
  2. 2. 1.1 Types of robots Figure 1.1 mobile robots Mobile robots are able to move, usually they perform task such as search areas. A prime example is the Mars Explorer, specifically designed to roam the mars surface. Mobile robots are a great help to such collapsed building for survivors Mobile robots are used for task where people cannot go. Either because it is too dangerous of because people cannot reach the area that needs to be searched. Mobile robots can be divided in two categories: Figure 1.2 rolling robots 1. Rolling Robots: Rolling robots have wheels to move around. These are the type of robots that can quickly and easily search move around. However they are only useful in flat areas, rocky terrains give them a hard time. Flat terrains are their territory. 2
  3. 3. Figure 1.3 walking robots 2. Walking Robots: Robots on legs are usually brought in when the terrain is rocky and difficult to enter with wheels. Robots have a hard time shifting balance and keep them from tumbling. That’s why most robots with have at least 4 of them, usually they have 6 legs or more. Even when they lift one or more legs they still keep their balance. Development of legged robots is often modeled after insects or crawfish. 3
  4. 4. CHAPTER 2 INTRODUCTION TO LINE PATH FOLLOWER Line follower is a machine that can follow a path. The path can be visible like a black line on a white surface (or vice-versa) or it can be invisible like a magnetic field. Sensing a line and maneuvering the robot to stay on course, while constantly correcting wrong moves using feedback mechanism forms a simple yet effective closed loop system. As a programmer you get an opportunity to ‘teach’ the robot how to follow the line thus giving it a human-like property of responding to stimuli. Practical applications of a line follower: Automated cars running on roads with embedded magnets; guidance system for industrial robots moving on shop floor etc. In our minor project we had built a collision avoidance system in which we made a robot which could detect objects in its front and rear and could avoid a collision using infrared radiations. We have extended the same project as major making it a line path follower and a collision avoidance system altogether. In this our robot will be able to detect white line only leaving all other colors undetected and also it will be able to detect obstacles in its front making the robot turn 360 degrees and follow the white line again. For this we had to make certain changes in our circuit. Earlier 20 pin microcontroller was used in our project which is now changed to a 40 pin one. We also included LED-LDR sensors for color detection and we have attached a comparator IC for control of sensors. Two 9 volts motors have been used for which we added a motor driving IC also. 4
  5. 5. Figure 2.1: Basic Block Diagram of Line Path Follower The robot uses IR sensors to sense the line, an array of 8 IR LEDs (Tx) and sensors (Rx), facing the ground has been used in this setup. The output of the sensors is an analog signal which depends on the amount of light reflected back, this analog signal is given to the comparator to produce 0s and 1s which are then fed to the microcontroller. L4 L3 L2 L1 R1 R2 R3 R4 Left Center Right Sensor Array Starting from the center, the sensors on the left are named L1, L2, L3, L4 and those on the right are named R1, R2, R3, and R4. Let us assume that when a sensor is on the line it reads 0 and when it is off the line it reads 1. The microcontroller decides the next move according to the algorithm given below which tries to position the robot such that L1 and R1 reads 0 rest reads 1. L4 L3 L2 L1 R1 R2 R3 R4 5
  6. 6. 1 1 1 0 0 1 1 1 Left Center Right Desired State L1=R1=0, and Rest=1 Figure 2.2: circuit Diagram of Line Path Follower 6
  7. 7. CHAPTER 3 COMPONENT LIST Component Specifications Quantity Microcontroller AT89S51 1 Sensors LED-LDR 3 TSOP 1 Actuators DC motor 2 Motor driving IC IC L293D 1 Comparator IC IC LM324 1 Motor 100 rpm, 12 V 2 Crystal oscillator 11.054 MHz 1 Battery 6V 1 Regulator IC IC7805, IC7812 1 Resistors 10 Kohm 5 20 Kohm 6 1 Kohm 10 Capacitors 33pF 7 1uF 8 7
  8. 8. CHAPTER 4 SENSORS A sensor is a type of transducer. A sensor is a device that converts a physical phenomenon into an electrical signal. As such, sensors represent part of the interface between the physical world and the world of electrical devices, such as computers. The other part of this interface is represented by actuators, which convert electrical signals into physical phenomena. Sensors are used in everyday life. Applications include automobiles, machines, aerospace, medicine, industry and robotics. 4.1 Key Characteristics of Sensors There are a vast number of different sensors being used in robotics, applying different measurement techniques, and using different interfaces to a controller. What is important is to find the right sensor for a particular application. This involves the right measurement technique, the right size and weight, the right operating temperature range and power consumption, and of course the right price range. The key characteristics of sensors are as: S. No. KEY POINT CONSIDERATION 1. Range How far the object to be detected? 2. Environment How dirty or dark is the environment? 3. Accessibility What accessibility is there to both sides of the object to be detected? 4. Wiring Is wiring possible to one or both sides of the object? 5. Size What size is the object? 6. Consistency Is the object consists in size, shape, and reflectivity? 8
  9. 9. 7. Requirements What are mechanical and electrical requirements? 8. Output signal What kind of output is needed? 9. Logic functions Are logic function needed at the sensing point? 10. Integration Is the system required to be integrated? Table 4.1 key characteristics of sensors 4.2 Types of sensors Sensors are classified broadly in two types: 1. Energy detected. 2 Signal detection. 4.2.1 Energy detected Since there is a significant exchange of energy involved, on the basis of energy sensors are classified as: S.No. Energy Example 1. Thermal Thermometer, bolometer 2. Electromagnetic Multimeter, RADAR 3. Mechanical Pressure gauge, strain gauge 4. Chemical Oxygen sensors, pH glass 5. Optical radiation Photo detector, Fiber optics 6. Ionizing radiation Neutron detection 7. Acoustic Microphones, Ultrasonic Table 4.2 on the basis of energy sensors 9
  10. 10. There are much more examples & types of sensor e.g. Motion sensor, orientation sensor etc. 4.2.2 Signal detection Different sensors require different sensing strategies. There are three modes of signal detection used by sensors: 1. Through-beam detection 2. Reflex detection. 3. Proximity detection. Through beam detection method The through-beam method requires that the source and detector are positioned opposite each other and the light beam is sent directly from source to detector. When an object passes between the source and detectors, the beam is broken; signal shows the detection of an object. Through-beam detection generally provides the longest range of the three operating modes and provides high power at shorter range to penetrate steam, dirt, or other contaminants between the source and detector. Alignment of the source and detector must be accurate. Reflex detection method The reflex method requires that the source and detector are installed at the same side of the object to be detected. The light beam is transmitted from the source to a retro reflector that returns the light to the detector. When an object breaks a reflected beam, the object is detected. 10
  11. 11. The reflex method is widely used because it is flexible and easy to install and provides the best cost-performance ratio of the three methods. The object to be detected must be less reflective than retro reflector. Proximity detection method The proximity requires that the source and detector are installed on the same side of the object to be detected and aimed at a point in front of the sensor. When an object passes in front of source and detector, light from the source is reflected from the object’s surface back to the detector, and the object is detected. The only difference between reflex detection & proximity method is reflection of signal from retro reflector and from object to be detected. Each sensor type has a specific operating range. In general through-beam sensor offer the greatest range, followed by reflex sensors, then by proximity sensors. 4.2.3 Infrared Emitter Detector Figure 4.1 Infrared Emitter Detector Description: The infrared emitter detector pair act as an eye with a flashlight in the infrared spectrum. The detector (a transistor) detects all ambient infrared light. The emitter (a LED) emits infrared light into an otherwise dark (in the infrared spectrum) room. Availability: It is easily available anywhere, very cheap. Power: Low, Typical LED power requirements. 4.2.4 LED & LDR Sensor:- 11
  12. 12. Figure 4.2 LED & LDR Sensor We have used this sensor in our project as this is one of the cheapest sensors available in the market. FEATURES • Input common-mode voltage range • Includes ground • Large voltage gain: 100dB • very low supply current/amplitude : 375mA • Low input bias current: 20nA • Low input offset voltage: 5mV max. • Low input offset current: 2nA DESCRIPTION We have used this sensor in our project as LED & LDR sensor is one of the cheapest sensor used in mobile robotics. The major parts of this sensor are as: Light-dependent resistances (LDR): are cheap light sensors. The light dependent resistor (LDR) is a sensor whose resistance decreases when light impinges on it. The schematic symbol of LDR is as:- 12
  13. 13. Figure 4.3 symbol of LDR This kind of sensor is commonly used in light sensor circuits in open areas. LDR’s are made of semiconductors as light sensitive materials, on an isolating base. The most common semiconductors used in this system are cadmium sulphide, lead sulphide, germanium, silicon and gallium arsenide. The light falling on the brown zigzag lines on the sensor causes the resistance of the device to fall. This is known as a negative co-efficient. There are some LDRs that work in the opposite way i.e. their resistance increases with light called positive co- efficient. The resistance of the cell varies depending on the intensity of the light striking it. When no light strikes the cell, the device exhibits very high resistance, typically in the high 100 kilo ohms, or even mega ohms. Light reduces the resistance, usually significantly. An LDR may be connected either way round and no special precautions are required when soldering. Light-emitting diode (LED): is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward direction of the p-n junction. The color of the emitted light depends on the composition and condition of the semiconducting material used, and can be infrared, visible, or near ultraviolet. Figure 4.4 symbol of LED Precautions: • Don’t bother using this circuit outside, the sun will flood your IR detector and make it useless. 13
  14. 14. • Certain indoor lighting can also emit IR interference. • Only if you modulate the IR emitter and set the detector to only detect modulated IR can you use this outside. This is commonly done with Sharp IR rangefinders. • Tweaking is necessary to determine sensitivity of your circuit. Sensitivity will help increase range but also increase ambient interference. By using certain resistor values, your IR emitter detector can also detect color, such as for line tracking. Maximum Rating Table 4.3 Maximum Rating Like a normal diode, an LED consists of a chip of semi-conducting material impregnated, or doped, with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers electrons and holes flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon. The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction. This is photo of 5mm. white/white LED which is used. 14
  15. 15. LEDs are made from a variety of inorganic semiconductor materials. The most common color of led & materials used are as follows: S No Material Used Color 1. Aluminum gallium arsenide (AlGaAs) red and infrared 2. Aluminum gallium phosphide (AlGaP) green 3. Gallium phosphide (GaP) red, yellow and green 4. InGaN-GaN White Table 4.4 LED color material The accurate use of led depends on the polarity selected, the way to determine the polarity of an LED is to examine its datasheet, these methods are usually reliable: Sign + - Polarity Positive Negative Terminal Anode (A) Cathode (K) Leads Long Short Exterior Round Flat Interior Small Larger Table 4.5 Polarity datasheet 4.2.5 IR LED & PHOTO DIODE Sensor The major parts of this sensor are as follows: 1. IR LEDs are not any other special kind of led. These are just like any other simple led they are differ in only the material used for emitting the light. The emitted light is in the Infrared range which is not visible by nicked eyes. The symbol of IR LED is: 15
  16. 16. Figure 4.5 IR LED 2. Photodiode is a semiconductor diode that functions as a photo detector. Photodiodes are packaged with either a window or optical fiber connection, in order to let in the light to the sensitive part of the device. Most Photodiodes will look like similar to a Light Emitting Diode. A photodiode is a p-n junction or p-i-n structure. When a photon of sufficient energy strikes the diode, it excites an electron thereby creating a mobile electron and a positively charged electron hole. If the absorption occurs in the junction's depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in field of the depletion region, producing a photocurrent. Figure 4.6 photodiode Photodiodes can be used under either zero bias or reverse bias. In zero bias, light falling on the diode causes a current across the device, leading to forward bias which in turn induces "dark current" in the opposite direction to the photo current, this is called the photovoltaic effect. Reverse bias induces only little current known as saturation or back current along its direction. But a more important effect of reverse bias is widening of the depletion layer therefore expanding the reaction volume and strengthening the photocurrent, this is called the photoconductive effect. Circuits based on this effect are more sensitive to light than ones based on the photovoltaic effect. 4.2.6 Ultrasonic sensor 16
  17. 17. Ultrasonic sensing is an example of reflective sensing. The sensor usually consists of a transmitter and receiver pair and responds to variation in the amount of reflected energy detected by the receiver. The transmitter emits a high frequency sound wave, which reflects off the object and is detected by the receiver, where the Time-of-Flight (TOF) information can be calculated. The range of the object can be determined from the TOF data if the speed of the sound wave is a known constant. These sensors are accurate over distances of several meters, with their accuracy dependent on the span of the transmitted signal. Figure 4.7 ultrasonic sensor If the transmitted signal covers a large area, the likelihood of an obstacle being detected is higher than if a narrow span were used. The advantage of the narrow span is that the position of the obstacle relative to the device is known with more accuracy. Ultrasonic proximity sensor circuit has two parts: a transmitter and a receiver. The transmitter circuit works as follows: a stream of 40 kHz pulses are produced by a 555 timer wired up as an astable multi vibrator. The receiving transducer is positioned two or more inches away from the transmitter transducer. The use of foam piece between the two transducers eliminates direct interference. The signal from the receiving transducer needs to be amplified; an op-amp LM741 is used for amplification. The amplified output of the receiver transducer is directly connected to another 741 op- amp wired as a comparator. The ultrasonic receiver is sensitive only to sounds in about the 40 kHz range. The closer the ultrasonic sensor is to an object, the stronger the reflected sound will be. The output of the comparator will change between LOW 17
  18. 18. and HIGH as the sensor is moved closer to or farther away from an object. Depending on the quality of the transducers the range of this sensor is varies. Figure 4.8: Ultrasonic Proximity Sensor Transmitter Figure 4.9: Ultrasonic Proximity Sensor Receiver CHAPTER 5 Comparator IC LM324 18
  19. 19. The LM324 consist of four independent, high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide voltage range. The operational amplifier is used in open loop configuration. Figure 5.1 LM324 Figure 5.2 Op-Amp loop configuration Operational amplifier has two terminals positive terminal known as non-inverting terminal & negative terminal as inverting terminal. The input to non-inverting & inverting terminals are Vin1 & Vin2 respectively. The output voltage is: V0 = A (Vin1 – Vin2) Where, A is gain of amplifier. When input to inverting terminal is greater than non-inverting terminal output is low & when input to non-inverting terminal is greater than the inverting terminal output is high. 19
  20. 20. 5.1 Features • Wide gain bandwidth: 1.3MHz • Input common-mode voltage range • Includes ground • Large voltage gain: 100dB • very low supply current/amplitude : 375mA • Low input bias current: 20nA • Low input offset voltage: 5mV max. • Low input offset current: 2nA • Wide power supply range: single supply: +3V to +30V Dual supplies: ±1.5V to ±15V 5.2 Description These circuits consist of four independent, high gain, internally frequency compensated operational amplifiers .They operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage. 20
  21. 21. Figure 5.3 Pin Diagram for LM324 Figure 5.4: Schematic Diagram 21
  22. 22. CHAPTER 6 TSOP1738 & TIMER 555 Sensor 6.1 TSOP1738 The TSOP17XX – series are miniaturized receivers for infrared control systems. PIN diode and preamplifier are assembled on lead frame, the epoxy package is designed as IR filter. The demodulated output signal can directly be decoded by a microprocessor or microcontroller. Figure 6.1 TSOP1738 TSOP17XX consists a photo detector and preamplifier in a single package with internal filter for PCM frequency. It is an output active low device & TTL and CMOS compatible. It consumes very little power. The circuit of the TSOP17XX is designed in that way that unexpected output pulses due to noise or disturbance signals are avoided. The signal carrier frequency should be close to center frequency of the band- pass filter e.g. 38 kHz for TSOP1738. FEATURES • 600ma output current capability per channel. 22
  23. 23. • 1.2a peak output current (non repetitive) per channel. • Enable facility. • Over temperature protection • Logical”0” input voltage up to 1.5 V (high noise imm.) internal clamp diode. 6.2 TIMER555:- The 555 is a monolithic timing circuit that can produce accurate and highly stable time delays and oscillation. Timer 555 is reliable, easy to use, and economical with TTL compatibility. Timer 555 has many applications as: mono stable and astable multivibrator, voltage regulator & infrared transmitter etc. Figure 6.2 timer 555 DESCRIPTION: Figure 6.3 functional diagram of timer 23
  24. 24. As in timer 555 functional diagram there are two internal comparators with reference voltage 2/3 Vcc & 1/3 Vcc at C1 and C2 respectively. The frequency and duty cycle both are controlled by two external resistors and one capacitor. To use with TSOP1738 sensor timer 555 is used in astable multivibrator mode. Figure 6.4 Description of timer with TSOP Timer 555 as astable multivibrator to generate 38 kHz frequency at output. 24
  25. 25. The external resistors R1, R2 & capacitor C determine the output frequency f0 CHAPTER 7 25
  26. 26. The Motor Driving IC L293D 7.1 Features • 600ma output current capability per channel. • 1.2a peak output current (non repetitive) per channel. • Enable facility. • Over temperature protection • Logical”0” input voltage up to 1.5 V (high noise imm.) internal clamp diode. 7.2 Description The Device is a monolithic integrated high voltage, high current four channel driver designed to accept standard DTL or TTL logic levels and drive inductive loads (such as relays solenoids, DC and stepping motors) and switching power transistors. To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and internal clamp diodes are included. This device is suitable for use in switching applications at frequencies up to 5 kHz. The L293D is assembled in a 16 lead plastic package which has 4 center pins connected together and used for heat sinking The L293DD is assembled in a 20 lead surface mount which has 8 center pins connected together and used for heat sinking. 26
  27. 27. Figure 7.1. Block Diagram of L293D Fig.7.2 Pin Description of L293D 27
  28. 28. CHAPTER 8 Microcontroller – AT89S51 The AT89S51 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes 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 80C52 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 AT89S51 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications. The AT89S51 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 AT89S51 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 con-tents but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware reset. 8.1 Pin Configuration 28
  29. 29. Figure 8.1 pin diagram of microcontroller 8.2 Pin Description: VCC +5V GND -5V Port 0 Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-impedance inputs. Port 0 can also be configured to be the multiplexed low-order address/data bus during accesses to external program and data memory. In this mode, P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming and outputs the code bytes during program verification. External pull- ups are required during program verification. . Port 1 Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 29
  30. 30. external count input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown in the following table. Port 1 also receives the low-order address bytes during Flash programming and verification. Table 8.1 port 1 Port 2 Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2 output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (IIL) because of the internal pull-ups. Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses (MOVX @ DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit addresses (MOVX @ RI), Port 2 emits the contents of the P2 Special Function Register. Port 2 also receives the high-order address bits and some control signals during Flash programming. Port 3 Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3 output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled low will source current (IIL) because of the pull ups. Port 3 receives some control signals for Flash programming and verification. Port 3 also serves the functions of various special features of the AT89S52, as shown in the following table: 30
  31. 31. Table 8.2 port 3 RST Reset input. A high on this pin for two machine cycles while the oscillator is running resets the device. This pin drives high for 98 oscillator periods after the Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature is enabled. ALE/PROG Address Latch Enable (ALE) is an output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode. PSEN Program Store Enable (PSEN) is the read strobe to external program memory. When the AT89S51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. 31
  32. 32. EA/VPP External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset. EA should be strapped to VCC for internal program executions. This pin also receives the 12-volt programming enable voltage (VPP) during Flash programming. XTAL1 Input to the inverting oscillator amplifier and input to the internal clock operating circuit . XTAL2 Output from the inverting oscillator amplifier. 8.3 Block Diagram 32
  33. 33. Figure 8.2 block diagram 33
  34. 34. 8.4 Special Function Registers A map of the on-chip memory area called the Special Function Register (SFR) space. Timer 2 Registers: Control and status bits are contained in registers T2CON (shown in Table 5- 2) and T2MOD (shown in Table 10-2) for Timer 2. The register pair (RCAP2H, RCAP2L) are the Capture/Reload registers for Timer 2 in 16-bit capture mode or 16-bit auto-reload mode. 8.4.1 Interrupt Registers: The individual interrupt enable bits are in the IE register. Two priorities can be set for each of the six interrupt sources in the IP register. Table 8.3 Interrupt Registers 1 34
  35. 35. Table 8.4 Interrupt Registers 2 8.4.2 Dual Data Pointer Registers: To facilitate accessing both internal and external data memory, two banks of 16-bit Data Pointer Registers are provided: DP0 at SFR address locations 82H-83H and DP1 at 84H-85H. Bit DPS = 0 in SFR AUXR1 selects DP0 and DPS = 1 selects DP1. The user should always initialize the DPS bit to the appropriate value before accessing the respective Data Pointer Register. Power off Flag: The Power off Flag (POF) is located at bit 4 (PCON.4) in the PCON SFR. POF is set to “1” during power up. It can be set and rest under software control and is not affected by reset. 35
  36. 36. Table 8.5 Dual data pointer register 8.5 Absolute Maximum Ratings Table 8.6 Absolute Maximum Ratings 36
  37. 37. 8.6 DC Characteristics Table 8.7 DC Characteristics 37
  38. 38. CHAPTER 9 REGULATOR IC LM7812 9.1 General Description The LM78LXX series of three terminal positive regulators is available with several fixed output voltages making them useful in a wide range of applications. When used as a zener diode/resistor combination replacement, the LM78LXX usually results in an effective output impedance improvement of two orders of magnitude, and lower quiescent current. These regulators can provide local on card regulation, eliminating the distribution problems associated with single point regulation. The voltages available allow the LM78LXX to be used in logic systems, instrumentation, HiFi, and other solid state electronic equipment. Voltage regulator ICs are available with fixed (typically 5, 12 and 15V) or variable output voltages. They are also rated by the maximum current they can pass. Negative voltage regulators are available, mainly for use in dual supplies. Most regulators include some automatic protection from excessive current ('overload protection') and overheating ('thermal protection'). Figure 9.1 LM7812 regulator IC Many of the fixed voltage regulator ICs has 3 leads and look like power transistors, such as the 7805 +5V 1A regulator shown on the right. 38
  39. 39. 9.2 Features • Output voltage tolerances of g5% (LM78LXXAC) over the temperature range • Output current of 100 mA Y Internal thermal overload protection • Output transistor safe area protection • Internal short circuit current limit • Available in plastic TO-92 and metal TO-39 and plastic SO-8 low profile • Output voltages of 5.0V, 6.2V, 8.2V, 9.0V, 12V, 15V Figure 11.2 features 39
  40. 40. 9.3 Electrical Characteristics * Table 9.1 Electrical characteristics LM78L05ac 40
  41. 41. Table 9.2 Electrical characteristics LM78l05AC 41
  42. 42. CHAPTER 10 LINE PATH FOLLOWER I started with building a parallel port based robot which could be controlled manually by a keyboard. On the robot side was an arrangement of relays connected to parallel port pins via opto-couplers. The next version was a true computer controlled line follower. It had sensors connected to the status pins of the parallel port. A program running on the computer polled the status register of the parallel port hundreds of times every second and sent control signals accordingly through the data pins. The drawbacks of using a personal computer were soon clear – It’s difficult to control speed of motors. As cable length increases signal strength decreases and latency increases. A long multi core cable for parallel data transfer is expensive. The robot is not portable if you use a desktop PC. The obvious next step was to build an onboard control circuit; the options a hardwired logic circuit or a microcontroller. Since I had no knowledge of microcontroller at that time, I implemented a hardwired logic circuit using multiplexers. It basically mapped input from four sensors to four outputs for the motor driver according to a truth table. Though it worked fine, it could show no intelligence like coming back on line after losing it, or doing something special when say the line ended. To get around this problem and add some cool features, using a microcontroller was the best option. 10.1 Algorithm 1.L= leftmost sensor which reads 0; R= rightmost sensor which reads 0. If no sensor on Left (or Right) is 0 then L (or R) equals 0; 42
  43. 43. Ex: Left Center Right Here L=3 R=0 Left Center Right Here L=2 R=4 2. If all sensors read 1 go to step 3, else, If L>R Move Left If L<R Move Right If L=R Move Forward Goto step 4 3. Move clockwise if line was last seen on Right Counter Clockwise if line was last seen on Left Repeat step 3 till line is found. 4. Goto step 1. L4 L3 L2 L1 R1 R2 R3 R4 1 0 0 1 1 1 1 1 L4 L3 L2 L1 R1 R2 R3 R4 1 1 0 0 0 0 0 0 10.2 Sensor Circuit To get a good voltage swing, the value of R1 must be carefully chosen. If Rsensor = a when no light falls on it and Rsensor = b when light falls on it. The difference in the two potentials is: Vcc * {a/ (a+R1) - b/ (b+R1)} Relative voltage swing = Actual Voltage Swing / Vcc = Vcc * {a/ (a+R1) - b/ (b+R1)} / Vcc = a/ (a+R1) - b/ (b+R1) The resistance of the sensor decreases when IR light falls on it. A good sensor will have near zero resistance in presence of light and a very large resistance in absence of light. 43
  44. 44. We have used this property of the sensor to form a potential divider. The potential at point ‘2’ is Rsensor / (Rsensor + R1). Again, a good sensor circuit should give maximum change in potential at point ‘2’ for no-light and bright-light conditions. This is especially important if you plan to use an ADC in place of the comparator. Figure 10.1 sensor circuit 10.3 Diagrammatical representation of our robot For our final project, we decided to make a line-follower robot. This simple robot is designed to be able to follow a black line on the ground without getting off the line too much. The robot has two sensors installed underneath the front part of the body, and two DC motors drive wheels moving forward. A circuit inside takes an input signal from two sensors and controls the speed of wheels’ rotation. The control is done in such a way that when a sensor senses a black line, the motor slows down or even stops. Then the difference of rotation speed makes it possible to make turns. For instance, in the figure on the right, if the sensor somehow senses a black line, the wheel on that side slows down and the robot will make a right turn. 44
  45. 45. Figure 10.2 Diagrammatical representation of our robot 45
  46. 46. i) How to sense a black line The sensors used for the project are Reflective Object Sensors, 0PB710F that are already ready in the Electronic Lab. The single sensor consists of an infrared emitting diode and a NPN Darlington phototransistor. When a light emitted from the diode is reflected off an object and back into the phototransistor, output current is produced, depending on the amount of infrared light, which triggers the base current of the phototransistor. In my case, the amount of light reflected off a black line is much less than that of a white background, so we can detect the black line somehow by measuring the current. (This current is converted to voltage.) ii) How to control a DC motor Instead of applying a constant voltage across a DC motor, we repeat switching on and off the motor with a fixed voltage (Vcc) applied to the motor. This is done by sending a train of PWM (Pulse Width Modulation) pulses to a power MOSFET in order to turn it on and off. Then, the motor sees the average voltage while it depends on duty cycle of PWM pulses. The speed of rotation is proportion to this average voltage. By PWM method, it’s easier to control the DC motor than by directly controlling the voltage across it. All we have to do is to modulate pulse width, in order words, a duty cycle. Also, a power MOSFET consumes only negligible power in switching. iii) Circuit diagram My circuit consists of two parts: PWM (Pulse Width Modulation) part and a sensor part. First, we take a look at the sensor part. The photodiode turns on the phototransistor and then the output current is converted to output voltage through the first op-amp circuit. The R6 is a variable resistor, so that we can tune the scale of output voltage. The second op-amp circuit is added to change the polarity of voltage. (Positive CV is necessary later.) One thing we should know is that –Vcc to Vcc of voltage rail is needed, not from 0 to Vcc. In the circuit built-up, LM747 Dual Operational Amplifiers were used. Second, in the PWM section, two 555 timers (LM555) are used to produce a pulse-width modulated train of pulses. The timer on the left works in astable mode to generate regular square- 46
  47. 47. wave pulses. The frequency is fixed by the values of R1, R2 and C1 here. Then, this output Q1 is connected to the trigger pin of the second timer that works in monostable mode this time. As you can see in the diagram, at a falling edge of Q1, a pulse is triggered and stays high during some time. The time (width of a pulse) is purely determined by the value of R3 and C3 if CV (Control Voltage) pin is not connected at all. (Look at the pulse diagrams of Q1 and Q2 at the bottom of the circuit diagram.) CV plays a role of changing the threshold level of a timer. (Without CV, threshold = 2/3 * Vcc) CV just becomes triggering voltage level. Therefore, the higher the CV is, the longer it takes time until discharge. In this way, the duty cycle of output pulses Q2 can be controlled. Back to my circuit, the output voltage of the sensor part provides CV. 47
  48. 48. Figure 10.3 line follower path circuit diagram 48
  49. 49. Third, the PWM pulses are supplied to the gate of a power MOSFET (IRF520) to switch the DC motor on and off. Then, the DC motor only sees the average voltage proportional to the duty cycle of the pulses. When CV is high, so is the duty cycle and the motor turns fast. In my robot, the distance between sensors and the ground is fixed. So, when a sensor is off the black line (The sensor sees white paper.), CV keeps its maximum value and both motors keep turning in a constant speed. As soon as the sensor enters the black line part, CV drops down and thus duty cycle decreases, which means the slowdown of a wheel. * Component Values: R1=6K, R2=1K, R3=20K, R4=10, R5=82, R6=5K (variable), R7=1K C1=1μF, C2=0.1μF, C3=0.1μF, 49
  50. 50. Figure 10.4 line path follower robot Flow Chart: Figure 10.5 Figure Flow Diagram As per the flow diagram, the microcontroller receives signals from the sensors placed in front (SFront) and at the rear end (SRear) of the vehicle. Based on the signals the vehicle is moved forward and backward. 50 SENSORS CONTROL UNIT (µC) ACTUATORS (DC MOTOR) FORWARD REVERSE STOP IF SFRONT =1 IF SREAR =1 IF SFRONT =1 IF SREAR =1 REVERSE REVERSEFORWARD FORWARD STOP NO YES NO NO NO YES YES YES
  51. 51. If the signal from SFront is high (i.e. this sensor detects the object) then the microcontroller turns the direction of the motor to make the vehicle move in reverse direction, else the vehicle will continue moving in the forward direction. When signal from SFront is high and the vehicle starts moving back then, the signal from SRear is checked by the microcontroller. Now if SRear is high then the vehicle stops, otherwise the vehicle continues moving in reverse direction. This process takes place when initially the vehicle was moving in the forward direction. If initially the vehicle was moving in reverse direction then SRear is checked first and then SFront is analyzed for similar conditions as explained above. 51
  52. 52. CHAPTER- 11 INTRODUCTION OF COLLISION AVOIDANCE SYSTEM 11.1 What is a Collision Avoidance System? A Collision Avoidance System can be defined as a device that detects possible obstructions in the way of a host vehicle (i.e. the vehicle that has the system installed in it), and helps in evading a collision. 11.2 Why use a Collision avoidance System? Many systems and technologies are now being implemented to alert the driver of a vehicle of a potential hazard and assist him or her in taking action to avoid that hazard. Although object detection and collision avoidance systems may still be regarded as being in their infancy, their perceived value in enhancing safety and reducing accidents is high. Such systems provide special benefits for older systems: as drivers grow in age, they expect to continue to be able to drive safely, even though their reaction times are increasing and senses like sight and hearing are diminishing. Two categories of systems are currently available or under development: Passive collision warning systems and Active collision avoidance systems. A passive system detects a hazard and alerts the driver to risks, whereas an active system detects the hazard and then takes preventive action to avoid a collision, if possible. Both types of systems require object detection. The only difference in them is how a collision diverting event is actuated following object detection, by the driver or automatically. 52
  53. 53. Like other automotive safety systems, to be truly effective and influence safety statistics, these systems need to be widely adopted, and that in turn would require a low production cost. The technology impact is significant, as an improvement in sensing capability on the vehicle is necessary, and increased computing throughput is required. The challenge now faced by the suppliers of such systems is to find a balance between the perceiving value by the customers and the cost of producing such a system. The University of Michigan Transportation Research Institute has predicted that by 2007 passive systems will be implemented on 1% of North American vehicles and active systems will be implemented on further 10% vehicles. Development engineers are proceeding cautiously with active collision avoidance work. Any systems that control the brakes from the driver are potential sources of litigation. Standards and federal regulations will emerge during the next few years which will cover such systems. For example, today there are no universally accepted standards for false-alarm rates and the certainty of detecting a target for automotive object detection systems. In Europe and the United States (by the Federal Communications Commission), a frequency standard of 76 to 77 GHz has already been approved for vehicle frontal radar systems. In the United States, the National Highway Traffic Safety Administration (NHTSA) is establishing functional requirements for collision avoidance systems. These will cover parameters such as sensor range and sensitivity, system reliability, drive warning information and data architecture standards. Similarly, in Japan the Ministry of Transport is conducting an advanced safety program (ASV). The total cost of such systems may largely within existing vehicle costs, as there will be much reuse of existing electronic controllers. It is now commonplace for to have engine controllers, anti-lock braking systems, electronic steering control and audio systems. The collision warning and avoidance systems will use these existing systems control units for additional functions. 53
  54. 54. 11.3 Different Types of Systems There are different types of Collision Avoidance systems. Categories are based on different aspects viz. the functionality of the system, the location of the sensors in the vehicle, and the technology used to implement such a system. Based on functionality the systems are differentiated as Passive or Active systems. In a passive system when a situation arises, an alarm is generated for the driver to take further action. Whereas an active system itself takes control and performs the necessary action to prevent the accident. In case of system based on location of sensors the systems are of three types; Frontal system, Rear system and Side system. In a Frontal system the sensors are placed only in front of the vehicle to detect the object coming in the way when vehicle is moving in forward direction. Similarly in Rear and Side systems the sensors are located at the back and sides of the vehicle respectively. Third criterion is of the technologies or the type of sensors used. Based on this there are again two types one is the radar based systems and second is the Camera based systems. A radar based system may use Laser or Ultrasonic radars. While a camera based system uses a digital camera which gives images of the object in front of the vehicle and then it is decided by the microcontroller whether the object is static or moving and whether it is a threat to the host vehicle or not. The details of all the above mentioned systems along with the appropriate diagrams is given in the subsequent chapters 54
  55. 55. 11.4 Types of Systems based on Functionality 11.4.1 Active and Passive Safety Systems A passive collision warning safety system seeks to reduce the risk of a collision by warning the driver of an impending risk so that he or she can take action to avoid the hazard. For example – Parking assist type of systems that provide an audible alarm when parallel parking and approaching a stationary object such as another vehicle or wall. A passive collision warning system is shown in Figure 14.1 Figure 11.1 Passive Safety System Active safety systems take the Collision avoidance philosophy a stage further by interacting with the power train, braking, and even the steering systems. Advanced active collision avoidance systems use many clever techniques, over and above object event is facilitated safely and efficiently. 55 Driver Vehicle Passive System Audio Warning Visual Warning Driver Vehicle Passive System Audio Warning Visual Warning
  56. 56. Figure 11.2 Active Safety System 11.5 Types of systems based on their position in Vehicles There are types of systems categories of such safety systems for collision avoidance viz. Frontal Vehicle Systems Rear Vehicle systems Side Vehicle Systems. These categories are explained below. 11.5.1 Frontal Vehicle Systems For Frontal systems, long range and large azimuth resolution radars are required because of the high forward speed of the car and the need to determine objects in adjacent lanes. The forward range of these systems is usually about 100 to 200m, which gives about 3 to 6 seconds warning of a stationary hazard when the host car is traveling at 100Kmph. It is important that frontal systems distinguish when there is more than one car ahead, positioned very closely but in different lanes. Therefore frontal radars must operate at high frequency than rear systems, as better azimuth resolution is obtained at higher frequencies. A key difference between the object detection systems used in active and passive systems is that the active systems require more accurate object recognition, so as to 56 Driver Vehicle Active System Audio Warning Visual Warning + +/-
  57. 57. prevent collision avoidance maneuvers against objects like road signs. So in such systems road recognition is prime importance. The most challenging task here is to find whether which object is hazardous when there are many objects present. It may be possible to detect all obstacles but if a warning is generated for each of such circumstances then there will be a lot of false alarms which may irritate the driver. 11.5.2 Rear Vehicle Systems Rear warning systems can use short range, often non scanning sensors to provide close range sensing for parking assist capability. These systems are nowadays provided in many cars by different manufacturers. A rear system uses lower frequency radar system than a frontal system, as the azimuth resolution required is not as large. The operating range is also shorter. 11.5.3 Side vehicle Systems Side warning systems use radar sensors to detect objects in the traditional blind spots that are often responsible for causing accidents. These sensors would be mounted in the rear quarter area of the cars (usually rear doors) and detect objects in adjacent lanes. These systems enhance the car safety by complementing the use of the wing mirrors. The radars mounted on the sides of car are not just useful for blind spot warnings, but also aid in lane tracking, in order to determine corridor trajectory. 11.6 Technologies already in use or under consideration The key element in a collision warning and collision avoidance system is a sensor that sends information to the electronic control unit on distance between the host vehicle and a potentially hazardous object. The object could be another vehicle or even an inanimate object such as a road sign or tree. If the object is scanned as a horizontal line and its distance is known, it can be tracked as the movement of the target vehicle negotiates the curves in the road. A smart algorithm may also analyze the placing of 57
  58. 58. roadside identifiers such as reflectors. For these reasons, scanning radars are a popular solution in the industry. 11.6.1 Scanning Pulse Laser Radar The principal operation of the scanning radar is very straight forward. The time of flight of a pulse, which is proportional to range, is measured. The scanning device transmits a pulse of light in a horizontal line, back and forth. Distance is calculated easily, as the microcontroller timer can determine the time interval from the transmitting pulse and received pulse. The receiver looks for an echo pulse, hence the transmission is non-continuous. As transmission frequency is phase coherent from pulse to pulse, it is also possible to measure the Doppler Shift of the target. This information can in turn yield target motion, speed and direction. Doppler shift occurs when the frequency of the reflected waves becomes higher or lower, relative to the receiver, as the target moves closer or farther away. A simplified control circuit for this system is shown in the Figure 14.3. The circuit consists of a microcontroller which executes the control algorithm and generates output signals to control the laser diode. The laser diode signal is reflected via a system of mirrors and lenses, controlled by stepper motor. The motor is used to step through different positions and allows the deflected horizontally in a scanning motion. There are several different mechanisms that can scan the laser beam, the most popular being the galvanometer and a polygon mirror. Both have good accuracy and anti- vibration capabilities. 58
  59. 59. Figure 11.3 Block Diagram for Scanning Pulse Laser Radar System In each position, the laser beam echo will be reflected back to a complementarily located mirror, through a laser diode, and then back to the microcontroller. The microcontroller will then calculate distance to target or object using the formula D= c (t)/2, where D is distance, t is time and c is speed of light. The time value is measured using a counter which is enabled when the pulse is transmitted and read when the input is received from the signal amplifier. As the speed of light is 3 x 108 m/s, the microcontroller clock speed must be reasonably high in order to measure distance with acceptable resolution. A disadvantage of the pulse radar is the requirement of a narrow pulse. In order to achieve an acceptable resolution on range, a very high receiver bandwidth is required. This in turn means that a lot of noise is received with the echo pulse, so the transmitter must have a relatively high peak power. The radar will provide several hundred distance measurements and calculations per scan, and the algorithm executed by the microcontroller will average these data to obtain a higher degree of reliability in the result. 59
  60. 60. A photo diode is also used in the system to determine whether the optical port is clean and free from debris. If the port glass is dirty, the laser beam pulse may be scattered, and performance can be affected. Bad weather can also affect performance, although this may be overcome by increasing the output power of laser pulse. The addition of the photodiode to determine clarity of the optical port is necessary, as this type of frontal scanning pulse radar system is likely to be mounted at the front of car, where debris and dirt from the road are common place. One solution is a wiper system for optical port. An alternative for laser radar can be Ultrasonic radar. The same principle of sending a pulsed wave and measuring the time for an echo to return applies, except with ultrasonic sensors a sound wave is used instead of a pulse of light. Knowing the speed of sound the distance can be calculated. As speed of sound is relatively slow, ultrasonic sensors are only considered effective for use in low-speed type applications such as parking assistance. 11.7 WORKING OF COLLISION AVOIDANCE SYSTEM 11.7.1 Introduction The system here in consideration consists of five vehicles with two sensors each, one at the front end and the other at the rear end. The vehicles are initially kept at different coordinates and then turned on. Each vehicle moves in forward and reverse directions and the sensors check for obstructions in the front and rear of the vehicle. Based on the obstruction detected by any of the two sensors, the collision is avoided by moving the vehicle in appropriate direction. 11.7.2 Bock Diagram of the system The system mainly consists of three blocks viz. Sensors block, Control unit and Actuators, as shown in the figure below. 60
  61. 61. Figure 14.4 Block Diagram of the System Sensors Block This part of the system contains the sensors which perceive the signals reflected by the objects falling in the path of host vehicle. This is an important part of the system as based on the signals received the sensors the system is made to perform some scheduled tasks. There are different types of sensors that can be used for the purpose viz., IR sensors, Radars and even digital cameras. The system here, being just a prototype uses two IR sensors with a range of 1-3m. One sensor is placed in front of the vehicle and one at the rear end. Based on the signals from these sensors the vehicle will move. Control Unit The control unit consists of a microcontroller which receives signals from sensors, and decides what operation to be performed by the system. The microcontroller used here is 8051 core. 61 CONTROL UNIT (µC) ACTUATORS (DC MOTOR) SENSORS
  62. 62. The microcontroller here is interfaced with a DC motor whose motion is controlled on the basis of the signals received from the sensors at the front and rear of the vehicle. Actuators The actuator used in this system is a DC Motor. The motor is interfaced with the microcontroller using the motor driving IC L293D. This IC has an H-bridge built into it, which allows the motor to be run in both clockwise and anti-clockwise by changing the polarity. This motor is responsible for the movement of the vehicle. 62
  63. 63. CHAPTER-12 CONCLUSION Robotics systems is the collbaration of software & hardware through which most of the complicity reduces, even systems size & coast also reduced. Such human creation put us spell bound that why a topic of invention is taken Robotics design. The line path follower and collision avoidance system that we have created has been in practical use in various companies like in constuction companies and reasearch areas. This system can avoid collisions in traffic systems when used and will also be able to detect only a single colour light for usage in definite purpose areas. Limitations of the system The system carries only two sensors in front, hence the collision with any object lying in the sides (i.e. the left and the right sides) of the vehicle cannot be evaded. 1. IR Sensors have a short range so they cannot be widely used in real time applications. 2. The performance of IR Sensors is affected by day light and bad weather. Industrial Implementation of the System This type of system can be used in robotic vehicle that travel within a store or a factory compound. The work of such vehicles may be to carry certain things around the area from one point to the other. If such a system is installed in these vehicles then they can be left to travel without anyone bothering to be hit by them, because in this case the vehicles’ system will take care of any such collision. This basic idea can also be used in automotive systems with certain up gradations and enhancements. For instance if case of a car if the IR sensors and the LED LDR sensors are replaced by radars or cameras then it can be used to detect distant objects with a better resolution and hence can help in evading collisions and saving lives of the peo 63
  64. 64. FUTURE ASPECTS We humans are fortunate & we always inspired from the nature because it is only which is our beast friend in the universe. Robotics dreation is also inspired by the human body itself. The human body is, all things considered, a nearly perfect machine: it is (usually) intelligent, it can lift heavy loads, it can move itself around, and it has built-in protective mechanisms to feed itself when hungry or to run away when threatened. Robots are often modeled after humans, if not in form then at least in function. For decades, scientists and experimenters have tried to duplicate the human body, to create machines with intelligence, strength, mobility, and auto-sensory mechanisms. That goal has not yet been realized, but perhaps some day it will. Nature provides a striking model for robot experimenters to mimic, and it is up to us to take the challenge. Some, but by no means all, of nature’s mechanisms—human or otherwise— can be duplicated to some extent in the robot shop. Robots can be built with eyes to see, ears to hear, a mouth to speak, and appendages and locomotion systems of one kind or another to manipulate the environment and explore surroundings. Many futurists believe that robots will eventually and inevitably become more capable than humans, but some experts in artificial intelligence assert that machines will never be able to develop the consciousness and emotions needed for reasoning and creativity. Nonetheless, there are already commercially available robots that can live in our houses and do basic chores for us. Robots are very good at processing certain kinds of information, and they are ideally suited to answering the telephone and being controlled over the Internet. 64
  65. 65. REFERENCES [1] Ronald K Jurgen “Automotive Electronic Handbook”: New York: McGraw-Hill, 2nd ed., 1999, Part 7 Chapter 29. [2] Peter Seiler, Bong sob Song, J. Karl Hedrick “Development of a Collision Avoidance System”: 1998 Society of Automotive Engineers. [3] Toyota debuts Line Path Follower in Lexus [online], available: http://www.abrn.com [4] Mercedes Autonomous Braking Can Reduce Crash Severity [online], available: http://www.abrn.com/abrn/article/articleDetail.jsp?id=359127 [5] General Motors: “The Ultimate Crash Safety is Avoiding Crashes” [online], available: http://www.gm.com/company/careers/career_paths/rnd/nws_071800.html [6] Daimler-Chrysler: “Safety on the Interstate” [online], available: http://www.daimlerchrysler.com/dccom/0-5-7180-1-465281-1-0-0-0-0-0-8-7165-0-0- 0-0-0-0-0.html [7] Ford Motors: “Active Safety system turns vehicles into co-drivers” [online], available: http://media.ford.com/newsroom/feature_display.cfm?release=22037 [8] Volvo Cars: “City Safety: System for avoiding collisions at low speeds and line path follower” [online], available: http://media.ford.com/newsroom/feature_display.cfm?release=24310 [9] Douglas H. Williams “Line Follower”: New York: McGraw-Hill, 2003, Chapter 6, pg 107-pg114. [10] Datasheet of NE555 [11] Datasheet of TSOP1738 [12] Datasheet of TIP122 and TIP127 [13] www.alldatasheets.com 65