ACCIDENT PROTECTION SYSTEM USING ELECTROMAGNETIC ABS BRAKING SYSTEM
Ultrasonic car braking system includes an ultrasonic wave emitter provided in a front parts of an automatic braking car producing and expend ultrasonic surge front side in a calculated distance in front of the car. A equipment which will receive and also generate in a front portion of the car operatively receiving a reflective ultrasonic wave signal as reflected by obstacles positioned within the calculated distance in front of the automatic braking car. The reflected surge was determine to get the distance between the vehicle and the obstruction. Then controller is used to control servo motor based on find pulse information to push pedal brake to brake the car many time for automatically braking the car for a safe braking purpose.
An original ultrasonic accident Alert system is a new system that can help drivers while car is braking. It is consist of ultrasonic surge emitter and receiver that can producing and receiving the ultrasonic surge to check the distance between car and obstacle. But it is not good enough for the safety of cars, in this paper, we are meant to design a system that can help drivers stop the car automatically, an electronic circuit was constructed. According to this circuit we design, a signal was produced to the braking system of car based on the distance between car and obstacle for a safe braking purpose. Error is also discussed and during the experiment, the improvement for the original system has also achieved.
This project work describes in detail, the project work undertaken by us during the final semester. The contents of this report includes a brief description of the Electro-Magnetic Disk Breaking System, supplemented by a good numbers of necessary and descriptive figures which makes this projects report very easy to understand.
In addition to these, the report also contains the detail regarding how electro-magnets do works. Above all, this report gives a detailed description of Electro-Magnetic Disk Breaking System. This description is empowered with the experimental analysis of the system and electro-magnets. This report will be of help for those who wish to understand about the basic working of electromagnetic disk braking system, especially those who wish to study electromagnetic disk braking system.
Driving is a compulsory activity for most people. People use their car to move from one place to other place. The number of vehicle is increasing day by day. It is produced tacked tightly and risk to accident. Nowadays, the numbers of accident is so high and uncertainly. Accident will occurs every time and everywhere and cause worst damage, serious injury and dead. These accidents are mostly cause by delay of the driver to hit the brake.
This project is designed to develop a new system that can solve this problem where drivers may not brake manually but the vehicles can stop automatically due to obstacles. This project is about a system that can control braking system for safety. Using ultrasonic as a ranging sensor, its function based on ultrasonic wave. After transmit by transmitter, the wave can reflect when obstacle detected and receive by receiver. The main target for this project is, car cans automatically braking due to obstacles when the sensor senses the obstacles. The braking circuit function is to brake the car automatically after received signal from the sensor.
This project report deals in depth with our project electromagnetic disk braking system”. In this project we have designed and establishment and Electromagnetic disk braking system so as to have a future alternative to traditional breaking systems. Electromagnetic disk braking system slows an objects by creating an eddy current through electromagnetic induction which create resistance. When electromagnetic are used, control of the breaking action is made possible by varying the strength of the magnetic field of the electromagnets creates eddy currents in the discs. These eddy currents generate an opposing magnetic field (Lenz\'s law), which then resists the rotation of the discs, providing braking force. The net result is to convert the motion of the rotors into heat in the rotors
The objectives of this project are;
To develop a safety car braking system using ultrasonic sensor
To design a vehicle with less human attention to the driving
SCOPE OF PROJECT
To develop an ultrasonic sensor to detect the obstacle
To process the output from the ultrasonic sensor to drive the servo motor as an actuator.
Before transmit the ultrasonic wave, there is a part which is ultrasonic wave generator that function to generate ultrasonic wave. In that part, there is timing instruction means for generating an instruction signal for intermittently providing ultrasonic waves. This signal will send to an ultrasonic wave generator for generating ultrasonic waves based on the instruction signal from said timing instruction means (transform electrical energy into sound wave). After ultrasonic wave was produced, ultrasonic transmitter transmits the ultrasonic waves toward a road surface to find out the obstacle. The range that obstacle detected is depends on the range of ultrasonic sensors that used.
If the ultrasonic wave detect the obstacle, its will produce a reflected wave. An ultrasonic receiver is used for receiving the ultrasonic waves reflected from the road surface to generate a reception signal. There is ultrasonic transducer that will transform back the sound wave to electrical energy. This signal amplified by an amplifier. The amplified signal is compared with reference signal to detect components in the amplified signal due to obstacles on the road surface. The magnitude of the reference signal or the amplification factor of the amplifier is controlled to maintain a constant ratio between the average of the reference signal and the average of the amplified signal.
The processed signal will be send to the braking circuit. At the braking circuit, there is a controller that can process the signal and give the instruction to the output based on condition of the signal. For this project, controller that used is microcontroller use the high language and easy to do the programming. above is shown about Flow Chart of Development of this project. Once, the title of this project Ultrasonic Car Braking System is selected. The identifying and understanding process was done. In this process, I found out all notes and information related to the project. The process was divided into two main groups which are software and hardware development. For the software development, the controller that prefers is microcontroller (8-bit microcontroller). Therefore all programming must suitable and match with this controller. The process of software development is continuously done until get the perfect resulted.
This chapter reviews some of the work related to the study of the ultrasonic car braking system. The main reviews are about sensor, ultrasonic sensor, microcontroller and motor. Sensor is an electrical device that maps an environmental attribute to a quantitative measurement. It is created to collect information about the world. Each sensor is based on a transduction principle which is conversion of energy from one form to another form
SUN Jingting,SHI Shicai,CHEN Hong,LIU Hong (State Key Laboratory of Robotics and System, Harbin Institute of Technology,Harbin 150080,China):
Temperature rise optimization design of space manipulator electromagnetic brake coil is done; using a new method which combines genetic algorithm with penalty function.Firstly, optimization model of space manipulator electromagnetic brake coil is obtained with the objective of temperature rise, which considers the restrictions such as electromagnetic force, current and magnetic density. Then, a method combining penalty function with genetic algorithm is proposed to solve the nonlinearity of constraint conditions in optimization model. The method is suitable for global optimization, and guarantees that the solution is always feasible in whole calculation process. The optimization result demonstrates that temperature rise is reduced remarkably. Finally, the brake is put into thermal vacuum environment simulation equipment and temperature rise curve is drawn. The temperature rise measured in the experiment closely meets the objective obtained by the optimization calculation, and this experimental result verifies the correctness of the method and the design.
G.L. Anantha Krishna, K.M. Sathish Kumar, \"Investigation on Eddy Current Braking Systems – A Review\", Applied Mechanics and Materials, Vols 592-594, pp. 1089-1093, Jul. 2014:
The changing magnetic field will induce eddy currents in the conductor. These currents will dissipate energy in the conductor and generate drag force. It is found that Aluminum is the best material as conductor compared to Copper and Zinc. Also, it is found that the larger thickness of disc, more number of turns of electromagnet and higher electrical conductivity of conductor influences the generation of greater braking torque. Conventional braking system relies on adhesion force between rail and wheel. It is found that a brake built up from permanent magnet pieces that combine both magnetic rail Brake and eddy current brake permits the most profitable braking action through the whole range of acceptable speeds.
Permanent magnet eddy current brake uses Neodymium - Iron - Boron (NdFeB) magnets. The analysis of permanent magnet eddy current shows that the parallel magnetized eddy current topology has the superior braking torque capability. In electrically controlled eddy current braking system subjected to time varying fields in different wave forms, the triangular wave field application resulted in highest braking torque. Electromagnetic brakes were found to interfere with the signaling and train control system. Permanent magnet eddy current brakes are a simple and reliable alternative to mechanical or electromagnetic brakes in transportation applications. Greater the speed greater is the eddy current braking efficiency. Hence, author intends to work on the development and investigation of permanent magnet eddy current braking system.
Mrs Mi Azian Ab. Karim: [24 Jun 2013]
Brake is one of crucial components in almost every vehicle. The need of brake performances is much based on what kind of applications or transportations that particular vehicle is meant to be. Racing car or motorcycle brakes are often made with different kind of material and different characteristics compared to conventional vehicle brakes. Formula Varsity (FV) car that being built has no motor on it yet, so, the brake design is made based on the weight and reference speed targeted on that car. Based on the result of surveys, designing House of Quality methods is used to determine crucial factors of the brake characteristic to be carried out on further designing method using CAD software. The design of the brake disc rotor is decided to be using conventional Perodua Kancil‟s disc brake with some customization made on it such as lathe to flatten it and drilling to match the mounting holes on it. Moreover, a pedal box assemble is being designed using CATIA V5 software with two designs and choosing one of those designs using design scoring method which is Weighted Decision Method. The design „B‟ is chosen. Some calculation is being made to determine any crucial parameter such as clamping force, which is 607.95N per disc and the torque required to stopping the car per disc brake is 741Nm. The analysis is done by using ANSYS software for both disc brake and pedal box assembly. For disc brake analysis, the clamping force is 700N and 789.34 Nm of torque acted on it. The result shows 0.00048699mm of deformation, 11.211Mpa of Von-Misses stress, 6.4637Mpa of shear stress along the disc neck and the safety factor turn out to be more than enough to withstand the clamping force which is more than 10 safety factor based on the software results. For pedal box analysis, there are two sections of force acting and the other parts are fixed. Section A is put 100N of force and section B is300N of force. The bearing is fixed. The results are 0.070922mm of deformation on the end region of pedal, 33.269Mpa of Von- Misses, 5.8817Mpa of shear stress and the safety factor is shown minimum of 2.591. Based on the results, it shows that both designed part and assembly is meet all the requirements based on the calculations.
The behavior of electromagnetic braking using eddy current was studied. Started with preliminary study investigating 3 different materials of aluminum, copper and zinc to choose the best material as brake disc. It also looks on effects of increasing current induced into electromagnet. Aluminum performs better copper and zinc, and then the study continues using two different series of aluminum which are Al6061 and Al7075. A few parameters been varied such as Air-gap, brake disc thickness, number of electromagnet turns and voltage supplied to DC motor. For the purpose of recording speed (rpm) and time (s), an optical tachometer connected to PULSE Analyzer been used. Graphs presented to show the behavior and reaction of parameters involved, including the calculation of braking torque that been generated using previous study equation. From this study, it can be concluded that Al6061 have greater performance than Al7075 as the Brake disc material. It also founded that the thicker the disc, small air-gap, large number of Electromagnet turns and increasing the current induced will increase the performance of this Electromagnetic braking. All parameters that been studied show significant effects to be considered in developing electromagnetic braking to replace the conventional braking system.
The scope of this project allowed for no test or simulation of the actual performance of current generation automatic emergency braking systems (AEBS). The project has aimed to assess systems based on: Review of scientific literature; Gathering information from industry; Analysis of accident data; Simulation of potential implications of reduced accident severity on congestion costs; Cost benefit analysis. An extensive review of literature was carried out. This included marketing and promotional information from manufacturers on AEBS and other active safety systems that they sold or were developing as well as scientific papers on the technical behaviour and development of such systems and technical standards, regulations and guidelines and research papers on the effectiveness of systems. The project has been carried out in an open manner with industry involvement at several stages. Representatives of the automotive industry and other interested stakeholders were invited to the three main project meetings at inception, mid-point and final. In addition to input provided at these meetings, attendees were asked to complete two separate surveys. The first requested detailed information about the technical characteristics and performance of AEBS systems that were either in production or under development. The respondents included vehicle manufacturers and tier one suppliers and was widely distributed via the relevant trade bodies (e.g. ACEA, JAMA, CLEPA). The second survey was sent to the same respondents in a similar manner and asked for comments on a proposal for generic characteristics of systems to be tested against accident data to estimate benefits and to request information concerning the cost of the systems for use in the cost benefit analysis. In addition to the scientific research identified that assessed AEBS in terms of effectiveness and accidents, specific studies of accident data were carried out. This involved the use of the UK STATS 19, On-the-Spot (OTS), and Heavy Vehicle Crash Injury Study (HVCIS) databases. The work was necessarily focussed on the use of UK databases for the in-depth analysis because these are the only data sources with sufficient level of detail for the assessment to which TRL has access. Estimates of the effect across Europe were, therefore, made via the assumption that the detailed effect in other countries would be the same as in the UK and that the high level differences in accident types and numbers would be accounted for by using the EU CARE database. Most analyses of the costs and benefits of vehicle safety systems rely on accidents as the principal benefit. However, congestion is becoming an increasing problem and it is widely recognised that accidents contribute substantially to congestion problems and that this congestion also represents a cost to European business and society. For this reason, a preliminary investigation of the potential reduction in congestion that might arise from reducing the severity of accidents was carried out, based on the principle that accidents of lesser severity may, typically, have shorter durations in terms of road and lane closures and the obstruction of other traffic. This analysis was carried out based principally on UK data derived for separate research for the UK Highways Agency and the use of a congestion cost model known as INCA
FORWARD COLLISION WARNING/BRAKE ASSIST
Bosch has developed a suite of Predictive Safety Systems (PSS), the aim of which is to warn drivers of an impending emergency situation, support them and intervene to reduce the consequences of an accident . The description provided in the manufacturer\'s literature states that the radar sensor used for Adaptive Cruise Control (ACC) monitors a distance of up to 200m ahead of the vehicle to detect vehicles in the same lane and calculate their distance and speed. When a dangerous situation is recognised in the area in front of the vehicle safety measures are introduced in three stages as soon as an accident is likely. If an accident risk is detected an emergency stop is considered by the system to be probable and the manufacturer then describes the following actions that can be taken: The first stage, the Predictive Brake Assistant (PBA), prepares the braking system for an emergency stop by pre-filling the circuit with fluid such that the linings are just in contact with the discs. The tripping threshold of the Hydraulic Brake Assist (HBA) system is also lowered. In this way Bosch claim that as soon as the driver initiates braking, full braking performance is available, around 30ms earlier than without the system, significantly shortening braking distances. Bosch suggest that this will offer substantial safety benefits because only one-third of drivers react to an emergency braking situation with a full brake application and also state that “most drivers are so hesitant that hydraulic brake assist is not activated”. Predictive Collision Warning (PCW) is the second module warning the driver of critical situations by applying a short burst of braking, a brief tug on the seatbelt and visual and acoustic signals to warn of imminent danger. Bosch claimed that a study by the Association of German Insurers shows that almost half of all drivers involved in accidents did not brake at all, prior to the crash. Early warning allows drivers to react faster to the danger of a collision by taking corrective action and/or braking to reduce the impact speed, significantly contributing to avoiding many accidents and reducing the severity of collisions. The Nissan Brake Assist system with Preview Function (BAP) utilises information provided by Adaptive Cruise Control (ACC) ensors to judge when emergency braking application may be required based on the distance to the followed vehicle and the relative velocity (Tamura et al, 2001). Figure 1 is extracted from the paper by Tamura et al (2001) and shows that when an impending collision is detected a small braking force is applied to minimise the separation between the brake pad and rotor to reduce the brake response time. The small braking force is activated when the target deceleration for stopping without colliding with the vehicle ahead exceeds 5.88m/s² (0.6g).
shows the results of experiments conducted by Tamura et al (2001) with the prototype vehicle. It shows that the delay time from the operation of the brake pedal to the rise of the brake pressure was shortened by 100ms with BAP.
Tamura et al (2001) claim that the improved reaction time would translate into a 5km/h reduction in impact speed in a typical accident scenario where a driver travelling at 50km/h becomes aware of an obstacle at a forward distance of 20m. The impact speed of a BAP-equipped vehicle would be 17km/h, or 5km/h less than the 22km/h impact speed of a vehicle without this system.
The available literature suggests that Adaptive Cruise Control (ACC) technology is used to monitor the road ahead, the millimetre-wave radar detects vehicles within a range of 4-100m in a horizontal detection area of 16° and a vertical detection area of 4°. The control ECU judges the risk of a collision approximately every 0.02s based on the location of the vehicle ahead and the relative speed between vehicles. When the closing rate to the vehicle in front increases to a point where a collision is likely to occur, CMBS operates in the following manner: A primary warning, comprising an audible warning and a visual ‘BRAKE' warning on the dash display, is given when the space between the vehicles becomes closer than the set safety distance for ‘normal avoidance' or ‘normal cruising'. This warning is given at approximately three seconds time to collision. Depending on the situation at the time, a collision can be avoided with correct braking. At this stage brake assist will not be activated with light braking because the accident may be avoided with a normal brake application. Examples of when the collision may not be avoided at this stage include when the relative speed between vehicles is high, the grip available is low or if the driver's braking is insufficient. If the distance between the two vehicles continues to diminish, CMBS applies light braking and the driver\'s seatbelt pre-tensioner is activated by an electric motor which retracts the seatbelt gently two or three times, providing the driver with a tactile warning. The audible and visual warnings are also repeated. The secondary warning is given at approximately two seconds time to collision. At this stage the brake assist activation parameters are altered such that it is easily activated to provide maximum deceleration. Depending on the situation the collision may be avoided if the driver brakes appropriately, however in the case of high relative speed or low grip there are cases where the collision may not be avoided. If, after issuing the primary and secondary warnings, the system determines that a collision is unavoidable, the pre-tensioner retracts the driver\'s and front passenger\'s seatbelts and
activates the brakes forcefully to reduce the speed of impact and mitigate the effects of the collision. At this stage, depending on the situation, it would be difficult for the driver to avoid the collision with last minute braking. The literature claims that the Honda CMBS is effective at detecting, large vehicles, cars, larger motorcycles in the centre of the lane, parked vehicles, and roadside furniture. However, there are some limitations as described belo: The sensor system is unable to accurately identify relative speeds less than 15km/h. Pedestrians cannot be detected Smaller motorcycles and two wheeled vehicles travelling in the edge of the road, diagonally parked vehicles and small objects such as fallen rocks may not be detected. The system will not function when the distance between vehicles is very short or when the conflict is very sudden such as at junctions The system may not function in adverse weather conditionsof a collision with the vehicle in front and the driver must take avoidance action immediately the system sounds a warning to prompt action by the driver to help avoid a rear-end collision. When a rear-end collision cannot be avoided by the driver\'s action the system activates the brakes to decelerate the vehicle at a maximum deceleration of 0.5g, thereby helping to reduce occupant injuries resulting from the collision.
The 2006 Mercedes-Benz S-Class is equipped with Brake Assist PLUS (BAS PLUS) and PRE-SAFE Brake . The available information suggests that both systems utilize a single 77GHz radar sensor capable of monitoring a typical three lane motorway environment in front of the vehicle with a narrow field of view angle of nine degrees up to a distance of 150m. Two additional 24GHz radar sensors with an 80° field of view monitor the area immediately in front of the vehicle up to a distance of 30m. DISTRONIC PLUS is claimed to be an additional driver assistance system which also relies upon the radar sensors to provide adaptive cruise control at speeds between 0 and 200km/h, maintaining headway to the vehicle in front by automatically braking the vehicle to a standstill if required and then accelerating the vehicle as soon as the traffic situation allows. Depending on the speed, automatic deceleration of up to 4m/s2 is possible. Should heavier braking be required an audible warning is given telling the driver to watch the traffic situation and apply the brakes if necessary, and a warning light illuminates on the instrument cluster. Daimler Chrysler claim that Brake Assist PLUS (BAS PLUS) expands BAS into an anticipatory system which registers the distance from the vehicle in front, provides an audible and visual warning to the driver when the gap is too small and calculates the deceleration necessary to avert a collision. The appropriate deceleration, which may not necessarily imply full ABS braking, will then be automatically applied as soon as the driver presses the brake. The fact that the system only provides the deceleration necessary to avoid a collision, rather than full ABS braking that might have been activated by a standard BAS, is claimed to give drivers behind the vehicle more time to react. According to the manufacturers literature, PRE-SAFE Brake is a supplement to BAS PLUS. Should the driver fail to react to the warning proved by BAS PLUS, PRE-SAFE Brake intervenes by autonomously braking the vehicle with a deceleration of up to 4m/s2 if there is acute danger of an accident. Figure 4 shows a timeline representing a typical rear-end collision situation and the warnings provided.
PRINCIPLES OF BRAKE SYSTEM
In the diagram below we have a rotating metal disc that is free to rotate on an axle. If we lower the disc into the poles of the horseshoe magnet shown it will stop quickly. Why?
Look at the diagram below.
A simple disc about to be stopped quickly by eddy currents
As the disc enters the magnetic field a series of eddy currents will be produced (as explained by Lenz's law). This produces a magnetic field that will oppose the change brought about by the rotating disc. If the magnetic field of the horseshoe magnet is coming out of the page then the induced magnetic field will be into the page. The induced current will be in a clockwise direction to produce this field. This will bring the disc to a halt very quickly and will result in a small amount of heat being produced by the eddy currents.
The diagram below shows the same disc from a view side on with the magnetic field coming out of the page. In (a), the disc has just started to rotate in a uniform magnetic field and no eddy currents have formed. In (b), the disc is shown a short time later when eddy currents have been formed. These currents will oppose the motion of the disc, slowing it down and finally stopping it.
The effect of placing a rotating disc in a magnetic field
ABOUT OUR PROJECT
As the above information we are constructing foot control electromagnetic braking system. In this project we are operating our project in two modes:
1. Foot pad mode
2. Infrared Sensor based auto stop mode
In first mode, we are using one manual foot pad with scaling positioning sensor. These sensors give input to controlling circuit. This controlling circuit control provides current to electromagnet for applying brake to the rotating dice.
In second mode, we are Appling instant brake with the help of infrared sensor to avoid short distance accident, in this mode controlling unit take self decision for short distance brake to avoid accident.
Current brake systems fall into two types: drum brakes and disk brake. Both have distinctive strengths and weaknesses.
Drum brake has been used in automobiles for a long time. Its reliability and excellent braking performance have accounted for the popularity today. In drum brake, two semi-circular brake pads are inserted onto the inner wheel ring and slow or stop the car via friction between pads and wheels following the principle of leverage theory. Drum brake is mostly applied to big-tonnage cars (and mostly used in the rear wheels). Here's the working principle: with two semi-circular brake pads in the inner ring of wheels, The drive stomps on the brake, hydraulic piston rods connected to the brake pad will put the motionless pads in contact with wheels in speedy motion and create a tremendous amount of friction force, Thus reducing wheels' rotation speed or stopping the car. Its strengths include great force of braking force and the function of automatic tightening-braking. The processing and composition of parts are relatively simple and easy to handle. Another strength is its low production cost. Its weaknesses: in the case of successive brake, the pads will be overheated by the inner wheel ring and heat-fade if such case lasts long. This will compromise the brake effect. It's also plagued by slow response of the brake system and not suitable for high-frequency braking actions. The large number of parts in drum brake system makes it a big trouble to debut and maintain the brake system.
As the disk brake has its pads exposed to air in the outer ring of the wheel, heat can be well dissipated and pads won't heat-fade with successive braking actions. So, the disk brake has a higher level of safety and becomes the major trend (mostly used in front-wheel-driven cars). Many disk brakes also have ABS(Anti-lock Braking System) to improve its level of safety ( refers to that an air sac inside the valve body, creates friction between the wheel and brake pad owing to its instant pressure on brake oil. The air sac then retracts and continues to apply pressure on the brake oil. The process will go on and on. Each second may see 8-30 Hai Wang & Ronghong Xiao Automatic Car Braking System 18 occurrences of such process. This system can prevent instant wheel locking in braking and cars sideslipping or turning over caused by inertia.) Disk brake works via two brake pads located on both sides of a wheel. When the driver stomps on the brake, two pads will get closer, clamp the moving wheels and apply friction to stall the car. Strengths of this brake system include: its dissipation effect is better than that of the drum brake; in the case of successive brakes, there won't be heat-fading; it lasts long; brake response speed is fast and suitable for high-frequency braking cases. The structure of the disk brake system is easier than that of the drum disk, thus facilitating debugging and maintenance. The weaknesses of the disk brake include: its braking force isn't as strong as that of the drum brake; it's hard to mount a disk brake; moreover, the cost of disk brake is higher than that of drum brake.
DESIGN OF ELECTROMAGNETIC DISK BRAKE
• Dc motor (as engine)
Centre distance between the pulleys= 32cm Diameter of the driving pulley = 4.4cm=d Diameter of the driven pulley = 5.5cm=D Speed of the driving pulley = 100 rpm=N1
12 volts DC motor (1)
Timing chain, L = 86cm 12 volts (1), 24 volts (1) 26cm dia. Aluminum, Alloy
A. Determination of speed of the driven pulley
B. Checking for centre distance:
“The centre distance between the two pulleys must be greater than the average value of the diameters of both the pulleys.”, is 4.95 cm,
C. Arc of Contact:
With Disc gear=188
With Motor gear=172
D. Length of the chain = 86c
Figure 3A Wheel Figure 3B Disk
Figure 3C Electromagnets
Figure 3D Aluminum bars
Figure 3E Wooden Base
Figure 3F: (3D) modeling
• Dc motor (as engine)
• ultrasonic sensor
Dc motor is an electric motor converts electrical energy into mechanical motion. The reverse task that of converting mechanical motion into electrical energy, is accomplished by a generator or dynamo. In many cases the two devices are identical except for their application and minor construction details. DC motors are used when there is positioning requirement and also changes in load and torque. DC motors can be conveniently interfaced to Bipolar DAC, or MPUs can generate PWMs to control them.
The classic DC motor has a rotating legature in the form of an electromagnet. A rotary switch called a commutator reverses the direction of the electric current twice every cycle, to flow through the armature so that the poles of the electromagnet push and against the permanent magnets on the outside of the motor. As the poles of the armature electromagnet pass the poles of the permanent magnets, the commutator reverses the polarity of the armature electromagnet. During that instant of switching polarity, inertia keeps the classical motor going in the proper direction. (See the diagrams below.)
Simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.
The armature continues to rotate.
When the armature becomes horizontally aligned, the commentator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats Wound field DC motor
The permanent magnets on the outside (stator) of a DC motor may be replaced by electromagnets. By varying the field current it is possible to alter the speed/torque ratio the motor. Typically the field winding will be placed in series (series wound) with the armature winding to get a high torque low speed motor, in parallel (shunt wound) the armature to get a high speed low torque motor, or to have a winding partly in parallel, and partly in series (compound wound) for a balance that gives steady speed over a range of loads. Further reductions in field current are possible to gain even higher speed but correspondingly lower torque, called \"weak field\" operation.
A chain drive is a mechanism for transferring mechanical power between two places, and is a common means of locomotion in bicycles and motorcycles. It is also a motive source for many different types of machinery. Chain drives have existed as a technology since the third century BC and have remained much the same in their basic design since that time.
Typically, a chain drive works by having a power source, usually a motor or pedal system, rotate a toothed wheel known as a sprocket, around which a specially designed chain is looped. As the sprocket spins, its teeth catch slots in the chain drive, causing it to rotate around the sprocket. At the other end is a second gear that transforms the mechanical energy delivered by the drive chain into the desired force.
In a bicycle or motorcycle, for instance, the second hub is attached to a shaft which houses a series of gears that power the rear wheel. Depending on the gear, the power is applied in varying capacities. Gears with different numbers of teeth are used to generate propulsion along a wide range of speeds, and the relationship between these gears is known as gear ratio. Typical gear ratio progressions feature multiple sprocket revolutions per single output revolution at the low end. These often then progress to a single revolution of the drive sprocket, causing multiple revolutions of the secondary hub at higher gears.
While simple chain drives are looped designs containing two gears, more complicated shapes can be created by adding additional gears into the design. These additional intermediary gears are known as idler gears, and do not affect the overall ratio of the drive. Only the first and last gears, and specifically the difference in number of their teeth, impact the gear ratio in a chain drive.
Chain drives are typically constructed of metal, and aside from bikes and motorcycles can been seen in machines ranging from commercial toasters to tanks. They are used on a large scale in mining operations, functioning as a conveyor hauling material from one place to another by a series of buckets connected to the chain. The chain drive was a popular drive train in automobiles during the first half of the 20th century, but by the late 1950s had been abandoned altogether in favor of the much more durable, though heavier, driveshaft mechanism. The chain drive is not altogether absent from modern automobiles, however, and is still a popular option to power the timing chain associated with an engine\'s camshaft.
Today there is a very wide range of chain products available. Some of these are special low-volume products, for example, nuclear-waste-handling chain. Motorcycle chain and other high-volume products are an offshoot of one of the key groups shown below. At the top level of the chain groups, conveyor chain is perhaps the most difficult to compartmentalize, since most types of chain can be used to convey. There is, however, arrange of so-called conveyor chain products typified by their long pitch, large roller diameter, and emphasis on tensile strength rather than fatigue life.
Offset link chain, like conveyor chain, is intended to run only at low speeds, since the presence of an offset link plate will reduce fatigue life. This chain tends to be used in conveying applications where harsh environmental conditions prevail, in mineral excavation, for example.
Leaf chain is similar in construction to the old Galle chain, except that plates are interleaved in various configurations right across the width of the pin.
Ultrasonic Ranging Module HC - SR04
Ultrasonic ranging module HC - SR04 provides 2cm - 400cm non-contact measurement function, the ranging accuracy can reach to 3mm. The modules includes ultrasonic transmitters, receiver and control circuit. The basic principle of work:
(1) Using IO trigger for at least 10us high level signal,
(2) The Module automatically sends eight 40 kHz and detect whether there is a pulse signal back.
(3) IF the signal back, through high level , time of high output IO duration is the time from sending ultrasonic to returning. Test distance = (high level time×velocity of sound (340M/S) /
Wire connecting direct as following:
• 5V Supply
• Trigger Pulse Input
• Echo Pulse Output
• 0V Ground
Working Voltage DC 5 V
Working Current 15mA
Working Frequency 40Hz
Max Range 4m
Min Range 2cm
MeasuringAngle 15 degree
Trigger Input Signal 10uS TTL pulse
Echo Output Signal Input TTL lever signal and the range in proportion
The Timing diagram is shown below. You only need to supply a short 10uS pulse to the rigger input to start the ranging, and then the module will send out an 8 cycle burst of ultrasound at 40 kHz and raise its echo. The Echo is a distance object that is pulse width and the range in proportion .You can calculate the range through the time interval between sending trigger signal and receiving echo signal. Formula: uS / 58 = centimeters or uS / 148 =inch; or: the range = high level time * velocity (340M/S) / 2; we suggest to use over 60ms measurement cycle, in order to prevent trigger signal to the echo signal.
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