 I am Mr. Nagesh R. Thambake, Assistant Professor, Mechanical Engineering Department, Gulchan Instruct Technology, Sholapur. Today, we will discuss automobile power steering system. At the end of this session, students will be able to explain power steering system of an automobile. In this particular session, we are going to discuss what is power steering system, components of power steering system and types of power steering system. Now, before going to this power steering system, we will see what is the need of power steering system. As we have already discussed in previous lectures, a steering system decreases with the steering efforts which is the need of a four-wheel automobile vehicle. So we need power steering due to the following reasons. First one is quick response. As the number of the vehicles on the road increasing day by day and today almost 60 percent families of the world are having a four-wheeler in their houses, with this increasing number of vehicles, the danger of accidents on the road is also increased. So to avoid this danger and to take quick turn required by the road conditions, a quick response steering system is required in a four-wheel vehicle. Next one, steering effort. If you drive old cars like Maruti Suzuki 800, it is found that the steering wheel of the car feels very hard to rotate. When the vehicle is going below 40 kilometer per hour, above that the steering feels less hard, which is found to cause fatigue to the driver while going on the long ride. So a vehicle should be equipped with power steering system so that the steering effort required to steer the front wheels can be reduced. Now next one is bump steer. As we know, bumps of the road is reduced by the suspension system. But as the steering system is directly attached to the wheels, we'll have some amount of bumps force is also transferred to the steering system, which in turns tries to steer the vehicle against the wheel of the driver, due to which a vehicle can lose its stability. Through the bump, the steer can be controlled mechanically by providing optimum scrub radius. As we have discussed what is scrub radius in the previous lecture, angle between the center line of the wheel and the kingpin inclination of the knuckle. But the power steering control it in a more effective manner. Last one, return ability. After taking a turn, it is found that the steering return automatically to the original position, which is in turn automatically straightens the moving vehicle. A vehicle equipped with a power steering system provides better return ability to the steering system. What are the types of power steering system? Here types of power steering system, first one is hydraulic power steering system, second one is electro hydraulic power steering system, third one is electronic power steering system. These are the types of power steering system. Now before going to the types of power steering system, first of all we'll understand what is power steering system. This is the steering system of a vehicle which is running with the help of hydraulic power, electrical power and which will reduce automatically the human efforts is called as power steering system. Now we will see the first that is power steering system that is the hydraulic power system and before going to this particular details of the hydraulic power steering system we will see in detail the components of the hydraulic power steering system. Now the important parts of the power steering systems are steering mechanism. Usually rack and pinion steering mechanism is used in power steering in which rotational motion of the steering wheel is converted into the transverse motion of this wheels by a set of constantly measured worm gears called as rack that provide transverse motion and a pinion that provides a rotational motion. Linkages they are the mechanical constraints that provide relative motion between two components. The type of linkages used in power steering is the tires that connects the rack to the knuckle of the wheels in order to transfer the transverse motion of the rack to the wheels. The next important part is the power device which is cylinder and the piston which contain as we have already discussed above a force multiplied device either hydraulic or hybrid or electric is used to multiply the steering wheel force in order to reduce a steering effect. This device is attached with the pinion of the rack and pinion mechanism. Last one that is the important part steering wheel. A round steering wheel is used inside a cockpit operated by the driver that provides the rotational steering input to the further steering device in order to steer the vehicle. Now we will see the working of hydraulic power steering system. In this type of power steering system as we discussed early the hydraulic force is used to multiply the steering input force in order to smoothen the steering of the front wheels. This hydraulic force is generated by a series of components that includes hydraulic cylinder, rotator, hydraulic pump, hydraulic lines, highly compressed hydraulic fluid and a coupling mechanism that can couple this hydraulic system with the rack of the steering system. When the driver provides input by rotating the steering wheel the hydraulic pump driven by the engine start pumping the highly compressed hydraulic fluid through lines. The hydraulic pressure produces by the pump enters the hydraulic cylinder which in turn applies pressure over the cylinder piston. This piston which is under high pressure start moving from one end to the another which is in turn pushes the further fluid through lines. With this moment of the piston the input force applied by the driver is multiplied several times. This high pressure fluid sent by the hydraulic cylinder then applies the pressure to the attached opinion through the coupling mechanism which is in turns applied high force to the rack gear and the steering action in the front wheels taken place. This is regarding a hydraulic steering system. Now we will see second type is hybrid or semi hydraulic power steering system. In this type of power steering system the hydraulic pump driven by the engine from the hydraulic power steering system is replaced with electric pump which makes it more reliable. This is the only modification made rest the working of the system is same as the hydraulic power steering system mentioned earlier. Now next one is that is electric power steering system. This system is the latest of all the steering system mentioned earlier. In this type of steering system as we have already discussed the force multiplication is the function of the electric motor instead of hydraulic fluid and the working of this system is like this. When the driver gives input through the steering wheel the electronic sensor attached to the steering column reads the input and sends them to the electric control unit of the vehicle. The issue that is electronic control unit of the vehicle analyzes these inputs and send the voltage signal to the electric motor placed at the end of the steering column whose gear is in constant mesh with the opinion gear. Due to these voltages signal sent by the electronic control unit the motor which is driven by the battery of the vehicle starts and provides the particular torque according to the value of the voltage signal received. After the motor start the gear which is in constant mesh with the opinion gear start transmitting the multiplied torque to the opinion gear which in turn applies this torque to the rack through which it is attached. With this torque applied by the opinion over rack rack moves which is which in turn steer the front wheels with the help of the tie rods attached as per the requirement. Quantages of power steering system preventing the wheels from transferring the loads to the steering column reduces reducing the driver fatigue low input torque and continuous steering function. Oil input directly proportional to the steering speed. Some of the limitations are there limitations of the power steering system design is complicated hence cost is increases. Due to hydraulic system the fluid leakage is there. These are the references. Thank you.