proximity controlled cruising prototype (pccp)
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Proximity Controlled Cruising Prototype (PCCP)Literature Survey and Identification of Problem
The considerations kept in mind while deciding the problem for project work were: Problem chosen should be of field of interest It should be possible to complete the problem within the required time For analysis information should be available in the library, books, magazines, or other sources of information For investigation necessary equipment should be available in the labs or it may be possible to get the same in local markets For fabrication, suitable facilities should be available in the college workshop or in the local markets It should be possible to investigate the problem within the funds available. It should be possible to determine the technique for handling the problem.
Since the very beginning automobiles have always fascinated us and we have always kept in touch with the latest developments in this field. Being an avid reader of international publications like popular mechanics and other Indian journals like Indian Auto we came to know that the latest research in Mercedes benz is in the field of cruise control using proximity sensors so we logged on to their web site whose address is given below http://www.mercedes-benz.com/e/innovation/rd/forschung_feb97.htm#5 From the information available at the web site we were impressed and we decided to build a prototype of Proximity Controlled Cruising Prototype (PCCP) Cruise control concept The system measures the distance and speed relative to the car in front with the help of a radar sensor and powerful microcomputer, and maintains a safe distance. All the driver has to do is select the desired speed using the cruise control lever. The electronic cruise control does the rest. If the two cars get too close, the device automatically backs off the gas and
activates the brakes, if necessary. The system has already been tested successfully on a simulator and on the highway. Proximity-Controlled Cruising is relaxing and safe.The system has already been tested successfully on a simulator and on the highway. Test drivers have said driving with Proximity-Controlled Cruising is relaxing and safe. The system is currently in the development stage and should go into production in a few years. ABS, ASR, ETS, ESP - innovate technology has been making driving increasingly safer recently. With the advent of microelectronic technology, these systems have become reliable aids for the driver, helping him to master critical situations better
Electronic Copilot Mercedes engineers have shown that the dream of an electronic copilot to keep a safe distance isn't just Utopia. They tested an S-Class Mercedes, titling their project "ProximityControlled Cruising". The name alone reveals the secret behind this future-oriented technology. "It's the next logical step up from cruise control which is standard equipment on many of our models", says Walter Klinkner, head of the traffic control experiment at Mercedes-Benz. Cruise control maintains a speed preset by the driver and has proven to be an extra comfort on long trips.However, this holds true primarily when there is little traffic on the road.Once traffic gets heavy and the gap between cars diminishes however, the driver has to intervene, either selecting a new cruise speed or turning off the cruise control altogether. This will be a thing of the past. Mercedes-Benz engineers have combined cruise control with a radar sensor that keeps an eye on the road ahead. Together with a microcomputer, it makes sure that a safe distance is maintained at all times
Proximity Control: Radar Sensor Proximity-Controlled Cruising will be as easy to use as normal cruise control. Once the car has reached the desired speed, depressing the cruise control lever on the steering column is all that is needed to activate the electronic system. The small radar sensor mounted in the grill detects cars up ahead up to a distance of approximately 120 meters and calculates the
distance and the relative speeds of the two cars in a fraction of a second. Proximity Control works at speeds of between 35 and 150 Km/h. Bad-weather visibility is no longer a factor thanks to the use of radar beams. Because radar signals are emitted and returned in extremely short intervals, the system is able to register a sudden drop in speed of the car in front and applies the brakes accordingly. If the situation becomes too risky for the computer to handle alone, however, a warning signal also sounds, alerting the driver to apply the brakes. "Proximity-Controlled Cruising isn't an automatic emergency brake. It isn't supposed to eliminate the driver. He's still in charge and he still has to pay attention to traffic conditions and react in dangerous situations", says Mercedes engineer Walter Klinkner Simulator Tests This futuristic driver's aid already has many years of development and testing behind it. Engineers from Mercedes-Benz's Research Institute laid the groundwork as part of the European "Prometheus" project. The result was, among other things, a radar sensor suitable for mass production. The electronic brake booster which permits exact calibration of the extent to which the system influences braking, is based on the Braking Assistant, another technical innovation from Mercedes-Benz. Here too, development work is proceeding in high gear. Tests in the Mercedes-Benz simulator in Berlin rounded out development work on the various components, giving researchers an idea of the acceptance level among motorists for such a system
Testing Ground - The Autobahn The initial positive simulator results were confirmed by road tests carried out by Mercedes engineers and experts from Rhineland inspection authorities. A team of 30 drivers tested Proximity-Controlled Cruising on stretches of the German Autobahn between Cologne and Frankfurtand Cologne and Aachen at speeds of up to 145 KPH. The results are impressive:
Testers said that driving with Proximity-Controlled Cruising was relaxing, safe and less of a chore than driving without it. When Proximity-Controlled Cruising was engaged, stress on the driver was reduced considerably as measured against such criteria as pulse rate and the ability to maintain a lane. Drivers were able to concentrate better on other tasks thanks to Proximity-Controlled Cruising Less Stress at the Wheel Proximity-Controlled Cruising will be available on Mercedes models in just a few years. It will make an important contribution to driving comfort, an area that has been receiving increased attention from Mercedes-Benz recently. By driving comfort we mean the capacity of a car to keep a driver physically and mentally fit on long trips. An automatic assistance system such as Proximity-Controlled Cruising can do just that. Methodology After deciding on the problem of interest we started to device the strategy on the methodology to be followed. The problem boils down to the identification of proximity sensors and the control of steering wheel and the accelerator through motors. For the control of steering wheel the choice for motors was as below DC motors are inexpensive, small, and powerful motors that are widely used. Gear-train reductions are typically needed to reduce the speed and increase the torque output of the motor.
Servo motors are used for angular positioning, such as in radio control airplanes to control the position of wing flaps, or in RC cars to turn the wheels. The output shaft of a servo does not rotate freely as do the shafts of DC motors, but rather is made to seek a particular angular position under electronic control. In effect, a servo motor is a combination of a DC motor, a shaft position sensor, and a feedback circuit. A servo motor also usually includes a built-in gear-train and is capable of delivering high torques directly. No servo motors are included in the 1999 ELEC 201 kit. Stepper motors also called actuators, do not rotate continuously, but turn in fixed increments, and resist a change in their fixed positions. They require special driving circuits to apply the correct sequence of currents to their multiple coils. They are commonly used in robotics, particular in mechanisms that perform linear positioning, such as floppy and hard disk drive head motors and X-Y tables. DC Motors DC motors are widely used in robotics because of their small size and high energy output. They are excellent for powering the drive wheels of a mobile robot as well as powering other mechanical assemblies. Ratings and Specifications Several characteristics are important in selecting a DC motor. The first two are its input ratings that specify the electrical characteristics of the motor. Operating Voltage. If batteries are the source of power for the motor, low operating voltages are desirable because fewer cells are needed to obtain the specified voltage. However, the electronics to drive motors are typically more efficient at higher voltages. Typical DC motors may operate on as few as 1.5 Volts or up to 100 Volts or more. Roboticists often use motors that operate on 6, 12, or 24 volts because most robots are battery powered, and batteries are typically available with these values.
Operating Current. The ideal motor would produce a great deal of power while requiring a minimum of current. However, the current rating (in conjunction with the voltage rating) is usually a good indication of the power output capacity of a motor. The power input (current times voltage) is a good indicator of the mechanical power output. Also, a given motor draws more current as it delivers more output torque. Thus current ratings are often given when the motor is stalled. At this point it is drawing the maximum amount of current and applying maximum torque. A low voltage (e.g., 12 Volt or less) DC motor may draw from 100 mA to several amperes at stall, depending on its design. The next three ratings describe the motor's output characteristics: Speed. Usually this is specified as the speed in rotations per minute (RPM) of the motor when it is unloaded, or running freely, at its specified operating voltage. Typical DC motors run at speeds from one to twenty thousand RPM. Motor speed can be measured easily by mounting a disk or LEGO pulley wheel with one hole on the motor, and using a slotted optical switch and oscilloscope to measure the time between the switch openings. Torque. The torque of a motor is the rotary force produced on its output shaft. When a motor is stalled it is producing the maximum amount of torque that it can produce. Hence the torque rating is usually taken when the motor has stalled and is called the stall torque. The motor torque is measured in ounce-inches (in the English system) or Newton-meters (metric). The torque of small electric motors is often given in milli-Newton-meters (mN-m) or 1/1000 of a N-m. A rating of one ounce-inch means that the motor is exerting a tangential force of one ounce at a radius of one inch from the center of its shaft. Torque ratings may vary from less than one ounce-inch to several dozen ounce-inches for large motors. Power.
The power of a motor is the product of its speed and torque. The power output is greatest at about half way between the unloaded speed (maximum speed, no torque) and the stalled state (maximum torque, no speed). The output power in watts is about (torque) x (rpm) / 9.57. Measuring Motor Torque
A simple experiment can be performed to determine the torque rating of a motor. All that is needed is a motor to be measured, a power supply for the motor, a piece of thread, a mass of known weight, a table, and a ruler. The mass is attached to one end of the thread. The other end of the thread is attached to the motor shaft so that when the motor turns the thread will be wound around the motor shaft. The motor shaft must be long enough to wind the thread like a bobbin. The motor is put near the edge of a table with the mass hanging over the edge, as illustrated in Figure. When the motor is powered it will begin winding up the thread and lifting the mass. At first this will be an easy task because the moment arm required to lift the mass is small--the radius of the motor shaft. But soon, the thread will wind around the shaft,
increasing the radius at which the force is applied to lift the mass. Eventually, the motor will stall. At this point, the radius of the thread bobbin should be measured. The torque rating of the motor is this radius times amount of mass that caused the stall. Alternatively, a LEGO gear and long beam can be mounted on the motor shaft, and a small scale (such as a postage scale) calibrated in grams can be used to measure the force produced by the stalled motor at the end of the lever resting on the scale. The torque in mN-m is given by (force in grams) x (lever length in cm) x (0.09807). The stall current can be measured at the same time. The measurement must be made quickly (1 second) because the large current will heat the motor winding, increasing its resistance, and significantly lowering the current and torque. Figure below shows a relative comparison some of the motors considered.
Speed, Torque, and Gear Reduction
It was mentioned earlier that the power delivered by a motor is the product of its speed and the torque at which the speed is applied. If one measures this power over the full range of operating speeds -- from unloaded full speed to stall -- one gets a bell-shaped curve of motor power output. When unloaded, the motor is running at full speed, but at zero torque, thus producing zero power. Conversely, when stalled, the motor is producing its maximum torque output, but at zero speed -- also producing zero power! Hence the maximum power output must lie somewhere in between, at about one-half of the maximum speed and of the maximum torque. A typical DC motor operates at speeds that are far too high to be useful, and at torques that are far too low. Gear reduction is the standard method by which a motor is made useful. The motor shaft is fitted with a gear of small radius that meshes with a gear of large radius. The motor's gear must revolve several times into order to cause the large gear to revolve. The speed of rotation is thus decreased, but overall power is preserved (except for losses due to friction) and therefore the torque must increase. By ganging together several stages of this gear reduction, a strong torque can be produced at the final stage. The challenge when designing a high-performance gear reduction for a competitive robot is to determine the amount of reduction that will allow the motor to operate at highest efficiency. If the normal operating speed of a motor/gear-train assembly is faster than the peak efficiency point, the gear-train will be able to accelerate quickly, but will not be operating at peak efficiency once it has reached the maximum velocity. Remember that the wheel is part of the drive train and gearing, and its size, the velocity desired, the motor characteristics, and other factors all effect the optimum gear ratio.
Pulse Width Modulation
Pulse width modulation is a technique for reducing the amount of power delivered to a DC motor. Instead of reducing the voltage operating the motor (which would reduce its power), the motor's power supply is rapidly switched on and off. The percentage of time that the power is on determines the percentage of full operating power that is accomplished. This type of motor speed control is easier to implement with digital circuitry. It is typically used in mechanical systems that will not need to be operated at full power all of the time.
Figure illustrates this concept, showing pulse width modulation signals to operate a motor at 75%, 50%, and 25% of the full power potential. A PWM waveform consisting of eight bits, each of which may be on or off, is used to control the motor. Every 1/1000 of a second, a control bit determines whether the motor is enabled or disabled. Every 1/125 of second the waveform is repeated. Therefore, the
control bit make 8 checks per cycle, meaning the PWM waveform may be adjusted to eight power levels between off and full on. Servo Motors Servo motors incorporate several components into one device package: A small DC motor; A gear reduction drive for torque increase; An electronic shaft position sensing and control circuit. The output shaft of a servo motor does not rotate freely, but rather is commanded to move to a particular angular position. The electronic sensing and control circuitry -- the servo feedback control loop -- drives the motor to move the shaft to the commanded position. If the position is outside the range of movement of the shaft, or if the resisting torque on the shaft is too great, the motor will continue trying to attain the commanded position. Servo motors are used in model radio control airplanes and helicopters to control the position of wing flaps and other flight control mechanisms. Servo Motor Control A servo motor has three wires: power, ground, and control. The power and ground wires are simply connected to a power supply. Most servo motors operate from five volts. The control signal consists of a series of pulses that indicate the desired position of the shaft. Each pulse represents one position command. The length of a pulse in time corresponds to the angular position. Typical pulse times range from 0.7 to 2.0 milliseconds for the full range of travel of a servo shaft. Most servo shafts have a 180 degree range of rotation. The control pulse must repeat every 20 milliseconds. Stepper Motors The shaft of a stepper motor moves between discrete rotary positions typically separated by a few degrees. Because of this precise position controllability, stepper motors are excellent
for applications that require high positioning accuracy. Stepper motors are used in X-Y scanners, plotters, and machine tools, floppy and hard disk drive head positioning, computer printer head positioning, and numerous other applications. Stepper motors have several electromagnetic coils that must be powered sequentially to make the motor turn, or step, from one position, to the next. By reversing the order that the coils are powered, a stepper motor can be made to reverse direction. The rate at which the coils are respectively energized determines the velocity of the motor up to a physical limit. Typical stepper motors have two or four coils. Stepper Motor Control The stepper motors have two sets of three wires: power, and two control/ground lines. The power wire is simply connected to a power supply. The two control/ground signals are alternately grounded for a brief period. This series of pulses thus steps the motor to the desired position of the shaft. Each pulse pair represents one step command. The length of a pulse in time does not correspond to any angular position. The pulses must simply be long enough to cause the motor coil to actuate. CIRCUIT DESCRIPTION The ckt can be devided into following parts Power Supply The transformer converts the 220 volts AC into 12 volts AC. This AC is then rectified using full wave rectifier. The ripple of the DC current is smoothened using a filter capacitor 1000uF 25 V.
2. IR sensor
Port 1 has been used to sense the traffic using IR sensors. IR sensor is basically a reverse biased IR diode, whose conductivity increases as the IR light falls on its junction. This change in conductance pulls the end of 1K resistance to 5 volts thus sending a higher voltage to the microcontroller 3. Microcontroller card The logic for pulses is generated by 8951 microcontroller which determines the motion of the motor and the switching on of the alarm. The AT89C51 is a low-power, highperformance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is manufactured using Atmels high density nonvolatile memory technology and is compatible with the industry standard MCS51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a con-ventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly lexible and cost effective solution to many embedded control appli-cations. Features Compatible with MCS-51 Products 4K Bytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 128 x 8-Bit Internal RAM 32 Programmable I/O Lines Two 16-Bit Timer/Counters
Six Interrupt Sources Programmable Serial Channel Low Power Idle and Power Down Modes 4. Stepper motor driver. The outputs of the microcontroller stage are not enough to drive the stepper motor. Hence switching transistors are used to increase the current levels. They consist of darlington pairs of transistors, one for each winding coil of the stepper motor, which act as switches that give current to the windings so as to rotate the motor in the desired direction. The stepper motor consists of a magnet suspended in a field of 4 coils which are arranged around it in a circle. To move the motor in clockwise direction the pulses are given to the windings one after the other in the clockwise direction and vicaversa Choice of proximity Sensors For proximity sensor radar principle is used. The pulses of particular frequency are transmitted and the reflections are measured. Depending on the magnitude of the reflected pulses the proximity can be ascertained. Different choices are available ranging from microwave pulses to IR pulses. Since it is not possible to use microwave frequency range due to legal problems we have decided to use IR pulses. IR or infra red pulses are similar to the ones used in TV remote. Although technically this is not the best solution since sun rays also have some IR radiation which can interfere with the sensing system but due to legal issues IR will be used which can be substituted by microwave in the actual system.
IR PROXIMITY SENSOR
STEERING uC STEPPER MOTOR DRIVER STEPPER MOTOR FOR STEERING
ELECTRO MAGNETIC RELAY
SOLENOID FOR FUEL SUPPLY
; ; 8051 Disassembly of CRUISE.hex
mov mov acall acall acall acall acall
p1,#0 p2,#0 X0110 X0110 X0110 X0110 X0110
X0010:mov anl cjne mov acall acall
acc,p0 a,#1 a,#0,X0010 p2,#0ffh X0110 X0110
acall acall acall acall acall acall mov acall
X0110 X0110 X0110 X0110 X0110 X0110 p2,#0 X0110
X0030:mov anl cjne acall acall acall acall acall acall acall
acc,p0 a,#1 a,#0,X0030 X0080 X0080 X0080 X0080 X0110 X0110 X00a0
acall acall acall ajmp
X00a0 X00a0 X00a0 X0010
X0080:mov acall mov acall mov acall mov acall ret
p1,#1 X0110 p1,#2 X0110 p1,#4 X0110 p1,#8 X0110
X00a0: mov acall
mov acall mov acall mov acall ret
p1,#4 X0110 p1,#2 X0110 p1,#1 X0110
X0110:mov X0112:dec mov X0115:dec mov jnz mov jnz ret
r0,#0ffh r0 r1,#0ffh r1 a,r1 X0115 a,r0 X0112
DESIGN CONCEPTS INTRODUCTION Engineering can be defined as a profession in which a knowledge of the mathematical and physical sciences gained by study experience and practice is applied with judgement to develop ways to utilize economically the materials and forces of nature for the progressive well being of mankind. Design can be defined as an iterative decision making process to conceive and implement optimum systems to solve societies problems and needs. We have used a systematic methodology for designing. The Design Logic is as shown below
It is the act breaking the problem into pieces and extending the boundary of a design situation. It is the starting point and the initial brief is expected to evolved or remodeled. The aims at this stage are tentative and the objectives are unstable. The boundary is not properly defined and the evaluation is deferred. Typical divergence methods are Literature searching, Questionnaire, Strategy Switching, Matchetts fundamental design method, Synectics etc.
Transformation In this stage we use boundary shifting method, Functional innovation method, System transformation and Analysis of interconnected decision area. Convergence In this stage we use Ranking & weighting, Boundary searching, Quircks reliability index, Checklists, Systematic decision making, Man machine system designing in order to reach the desired goals in optimal way. In our project we have followed the same approach. We have first used the divergent approach and tried to think of as many possible solutions as we could using our creativity. SYSTEM DESIGN CYCLE
FEASIBILITY STUDY PRELIMINARY DESIGN DETAILED DESIGN
PLANNING ACHIEVEMENT OF GOALS
FEASIBILITY STUDY This stage involves Need Analysis, Problem Study, Problem Formulation with due regards to engineering scientific financial, social, political and similar relevant factors. PRELIMINARY DESIGN This stage involves main synthesis of the expected design, analysis of this design for realization and checking, Optimization of the accepted design and transformation from vaguely defined concepts to tentatively final design concepts. DETAILED DESIGN This stage involves detailing the parts components and their assembly, going into sufficient details of fabrication/ manufacture in implementing the design. PLANNING This stage involves evaluating and altering the design concepts to suit the requirements of production, distribution, consumption and product retirement. INFORMATION SOURCES For gathering information for our project we conducted a survey at various car dealerships and prospective customers Some more hard information was downloaded from the internet and collected from Mercedes benz web site. For design calculations various text books were consulted.
CREATIVITY We wanted to put in a lot of creativity so that the design is as innovative as possible. Various determinants of creativity are Knowledge Effort Aptitude Method Chance The various steps in a creative cycle are Preparation Concentration Withdrawal Insight or illumination Verification or follow through The various aids to creativity are Concentrated effort Liberally use questioning attitude Follow a systematic approach Try many alternatives Review historic information Try check lists Break mental set Brain storming Inversion Empathy
Analogy Avoid conservatism Avoid premature rejection Avoid premature satisfaction Fantasy Work in an atmosphere conducive to creative thought See existing solutions. ESTIMATION Estimation involves approximate answer to predict the results. This one can reach by observing the existing solutions and using ones own judgement to find an approximate result. CHECKING The checking of various estimations is done By logic By arithmetic or algebraic rules By higher mathematical rules By engineering sense Dimensionally correct Limiting values Trend values Sign check Relevant factors appear in the equation Symmetry checking By experimentation OPTIMIZATION
Methods Mental survey Appraisal of alternatives Differential calculus Graphic Numerical Method of steepest descent Using linear programming Use of dual variables Langrangian multipliers Newton Raphson approximation method
DECISION MAKING Source factors Finances R & D facilities R & D skills Materials Admn of R & D Prodn & Sales Resources for decision making Technical factors Dimensions size & Shape Weight Strength Identify weakest points Electrical effects Magnetic effects Temperature effects Corrosion Erosion Fluid flow effects drag Wear lubrication effects Power Input / Output Fatigue Creep Dynamics Thermal effects Inertia Effeciency Manufacturing effects
Chemical effects Mass production Noise Damping characterstics Human Factors Ethics Others views of alternative Aesthetic factors Resistance to change fear of new Personal tastes Decision maker Scientific method State the desired goal or objective Generate a number of alternatives List as many related factors as possible Use the list of related factors to remove the list of alternatives FEASIBILITY STUDY Input Primitive Needs COLLECT INFORMATION ANALYSE NEED & STUDY ENV. NEED STATEMENT IDENTIFY PROBLEM SYNTHESIS CONCEPTS QUANTITY INPUT & OUTPUT ANALYZE PROBLEM
TECHNICAL STATEMENT OF PROBLEM
Establishing need Study the nature of the need Establish the need reasonably well to the extent possible Make primitive statement of the need Do reconnoisance study Wrt qualitative aspects Wrt quantitave aspects Wrt. Overall validity Studying Environment Physical Technological Organisational Social & Customers acceptability Time consideration Estimation of competition Political environment Economic feasibility Financial feasibility Need Analysis For conducting analysis we asked ourselves the questions Who are the end users ? How it can be satisfied ? With the design chosen by us this need can be satisfied. Why the project is to be started ?
PRELIMINARY DESIGN The preliminary design stage involved Generation of several possible solutions Subdivision of system into sub-systems Generating solution of a sub system from Technical literature publications Kinematics & known constraints Methods already established Historical developments & patents Physical characterstics Assemby of sub-systems Selection of the most promising concepts from several solutions Formulation of a useful model preferably mathematical for this selected solution Analysis of the model formulated Sensitivity analysis Compatibility analysis Reliability analysis Stability analysis Optimization Prediction of performance Preparing layouts of the selected solutions and check its function
VARIOUS PROPOSED SOLUTIONS TO THE PROBLEM During our preliminary design stage we applied our creativity and took help of various information sources and thought of different designs using different types of motors and sensors. CONCLUSION As this project has been undertaken as a part of the compulsory requirement for fulfilling the condition for BE Engineering degree following points were kept in mind Problem chosen was of field of interest It should be possible to complete the problem within the required time For analysis information should be available in the library, books, magazines, or other sources of information For investigation necessary equipment should be available in the labs or it may be possible to get the same in local markets For fabrication, suitable facilities should be available in the college workshop or in the local markets It should be possible to investigate the problem within the funds available. It should be possible to determine the technique for handling the problem.
BIBLIOGRAPHY 1. An introduction to Systems Design - D.K. Agarwal, S.L. Singla 2. Machine Design P.C. Sharma, D.K. Agrarwal 3. Hydraulics Fluid Mechanics S. Ramamurtham 4. Machine design by Dr. R.S. Khurmi 5. Web Site www.eatons.com
1. Web Site www.vds.net 2. Web Site www.wesco.com 3. Web Site www.yahoo.com