In physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body. This force enables the object to float or at least seem lighter.
Archimedes' principle
It is named after Archimedes of Syracuse, who first discovered this law. According to Archimedes' principle, "Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object."
Vitruvius (De architectura IX.9–12) recounts the famous story of Archimedes making this discovery while in the bath. He was given the task of finding out if a goldsmith, who worked for the king, was carefully replacing the king's gold with silver.
While doing this Archimedes decided he should take a break so went to take a bath. While entering the bath he noticed that when he placed his legs in, water spilled over the edge. Struck by a moment of realization, he shouted "Eureka!" He informed the king that there was a way to positively tell if the smith was cheating him. Knowing that gold has a higher density than silver, he placed the king's crown and then a gold crown of equal weight into a pool.
The king's crown caused more water to overflow, showing that it had a greater volume for the same weight. It was, therefore, less dense than gold, and Archimedes concluded that it contained silver, causing the smith to be executed. The actual record of Archimedes' discoveries appears in his two-volume work, On Floating Bodies. The ancient Chinese child prodigy Cao Chong (196–208 AD) also applied the principle of buoyancy in order to accurately weigh an elephant, as described in the Sanguo Zhi, also known as the Records of Three Kingdoms.
Archimedes' principle does not consider the surface tension (capillarity) acting on the body.
The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). Thus, among completely submerged objects with equal masses, objects with greater volume have greater buoyancy.
Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk completely to the sea floor. It is generally easier to lift an object up through the water than it is to pull it out of the water.
Showing posts with label Mechanical Notes. Show all posts
Showing posts with label Mechanical Notes. Show all posts
Thursday, August 27, 2009
Boundary layer
In physics and fluid mechanics, a boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. In the Earth's atmosphere, the planetary boundary layer is the air layer near the ground affected by diurnal heat, moisture or momentum transfer to or from the surface. On an aircraft wing the boundary layer is the part of the flow close to the wing. The boundary layer effect occurs at the field region in which all changes occur in the flow pattern. The boundary layer distorts surrounding nonviscous flow. It is a phenomenon of viscous forces. This effect is related to the Reynolds number.
Laminar boundary layers come in various forms and can be loosely classified according to their structure and the circumstances under which they are created. The thin shear layer which develops on an oscillating body is an example of a Stokes boundary layer, whilst the Blasius boundary layer refers to the well-known similarity solution for the steady boundary layer attached to a flat plate held in an oncoming unidirectional flow.
When a fluid rotates, viscous forces may be balanced by the Coriolis effect, rather than convective inertia, leading to the formation of an Ekman layer. Thermal boundary layers also exist in heat transfer. Multiple types of boundary layers can coexist near a surface simultaneously.
The aerodynamic boundary layer was first defined by Ludwig Prandtl in a paper presented on August 12, 1904 at the third International Congress of Mathematicians in Heidelberg, Germany. It allows aerodynamicists to simplify the equations of fluid flow by dividing the flow field into two areas: one inside the boundary layer, where viscosity is dominant and the majority of the drag experienced by a body immersed in a fluid is created, and one outside the boundary layer where viscosity can be neglected without significant effects on the solution.
This allows a closed-form solution for the flow in both areas, which is a significant simplification over the solution of the full Navier–Stokes equations. The majority of the heat transfer to and from a body also takes place within the boundary layer, again allowing the equations to be simplified in the flow field outside the boundary layer.
The thickness of the velocity boundary layer is normally defined as the distance from the solid body at which the flow velocity is 99% of the freestream velocity, that is, the velocity that is calculated at the surface of the body in an inviscid flow solution. An alternative definition, the displacement thickness, recognises the fact that the boundary layer represents a deficit in mass flow compared to an inviscid case with slip at the wall. It is the distance by which the wall would have to be displaced in the inviscid case to give the same total mass flow as the viscous case.
The no-slip condition requires the flow velocity at the surface of a solid object be zero and the fluid temperature be equal to the temperature of the surface. The flow velocity will then increase rapidly within the boundary layer, governed by the boundary layer equations, below. The thermal boundary layer thickness is similarly the distance from the body at which the temperature is 99% of the temperature found from an inviscid solution. The ratio of the two thicknesses is governed by the Prandtl number.
If the Prandtl number is 1, the two boundary layers are the same thickness. If the Prandtl number is greater than 1, the thermal boundary layer is thinner than the velocity boundary layer. If the Prandtl number is less than 1, which is the case for air at standard conditions, the thermal boundary layer is thicker than the velocity boundary layer.
In high-performance designs, such as sailplanes and commercial transport aircraft, much attention is paid to controlling the behavior of the boundary layer to minimize drag. Two effects have to be considered. First, the boundary layer adds to the effective thickness of the body, through the displacement thickness, hence increasing the pressure drag. Secondly, the shear forces at the surface of the wing create skin friction drag.
At high Reynolds numbers, typical of full-sized aircraft, it is desirable to have a laminar boundary layer. This results in a lower skin friction due to the characteristic velocity profile of laminar flow. However, the boundary layer inevitably thickens and becomes less stable as the flow develops along the body, and eventually becomes turbulent, the process known as boundary layer transition. One way of dealing with this problem is to suck the boundary layer away through a porous surface (see Boundary layer suction).
This can result in a reduction in drag, but is usually impractical due to the mechanical complexity involved and the power required to move the air and dispose of it. Natural laminar flow is the name for techniques pushing the boundary layer transition aft by shaping of an aerofoil or a fuselage so that their thickest point is aft and less thick. This reduces the velocities in the leading part and the same Reynolds number is achieved with a greater length.
At lower Reynolds numbers, such as those seen with model aircraft, it is relatively easy to maintain laminar flow. This gives low skin friction, which is desirable. However, the same velocity profile which gives the laminar boundary layer its low skin friction also causes it to be badly affected by adverse pressure gradients. As the pressure begins to recover over the rear part of the wing chord, a laminar boundary layer will tend to separate from the surface. Such flow separation causes a large increase in the pressure drag, since it greatly increases the effective size of the wing section. In these cases, it can be advantageous to deliberately trip the boundary layer into turbulence at a point prior to the location of laminar separation, using a turbulator. The fuller velocity profile of the turbulent boundary layer allows it to sustain the adverse pressure gradient without separating.
Thus, although the skin friction is increased, overall drag is decreased. This is the principle behind the dimpling on golf balls, as well as vortex generators on aircraft. Special wing sections have also been designed which tailor the pressure recovery so laminar separation is reduced or even eliminated. This represents an optimum compromise between the pressure drag from flow separation and skin friction from induced turbulence.
Laminar boundary layers come in various forms and can be loosely classified according to their structure and the circumstances under which they are created. The thin shear layer which develops on an oscillating body is an example of a Stokes boundary layer, whilst the Blasius boundary layer refers to the well-known similarity solution for the steady boundary layer attached to a flat plate held in an oncoming unidirectional flow.
When a fluid rotates, viscous forces may be balanced by the Coriolis effect, rather than convective inertia, leading to the formation of an Ekman layer. Thermal boundary layers also exist in heat transfer. Multiple types of boundary layers can coexist near a surface simultaneously.
The aerodynamic boundary layer was first defined by Ludwig Prandtl in a paper presented on August 12, 1904 at the third International Congress of Mathematicians in Heidelberg, Germany. It allows aerodynamicists to simplify the equations of fluid flow by dividing the flow field into two areas: one inside the boundary layer, where viscosity is dominant and the majority of the drag experienced by a body immersed in a fluid is created, and one outside the boundary layer where viscosity can be neglected without significant effects on the solution.
This allows a closed-form solution for the flow in both areas, which is a significant simplification over the solution of the full Navier–Stokes equations. The majority of the heat transfer to and from a body also takes place within the boundary layer, again allowing the equations to be simplified in the flow field outside the boundary layer.
The thickness of the velocity boundary layer is normally defined as the distance from the solid body at which the flow velocity is 99% of the freestream velocity, that is, the velocity that is calculated at the surface of the body in an inviscid flow solution. An alternative definition, the displacement thickness, recognises the fact that the boundary layer represents a deficit in mass flow compared to an inviscid case with slip at the wall. It is the distance by which the wall would have to be displaced in the inviscid case to give the same total mass flow as the viscous case.
The no-slip condition requires the flow velocity at the surface of a solid object be zero and the fluid temperature be equal to the temperature of the surface. The flow velocity will then increase rapidly within the boundary layer, governed by the boundary layer equations, below. The thermal boundary layer thickness is similarly the distance from the body at which the temperature is 99% of the temperature found from an inviscid solution. The ratio of the two thicknesses is governed by the Prandtl number.
If the Prandtl number is 1, the two boundary layers are the same thickness. If the Prandtl number is greater than 1, the thermal boundary layer is thinner than the velocity boundary layer. If the Prandtl number is less than 1, which is the case for air at standard conditions, the thermal boundary layer is thicker than the velocity boundary layer.
In high-performance designs, such as sailplanes and commercial transport aircraft, much attention is paid to controlling the behavior of the boundary layer to minimize drag. Two effects have to be considered. First, the boundary layer adds to the effective thickness of the body, through the displacement thickness, hence increasing the pressure drag. Secondly, the shear forces at the surface of the wing create skin friction drag.
At high Reynolds numbers, typical of full-sized aircraft, it is desirable to have a laminar boundary layer. This results in a lower skin friction due to the characteristic velocity profile of laminar flow. However, the boundary layer inevitably thickens and becomes less stable as the flow develops along the body, and eventually becomes turbulent, the process known as boundary layer transition. One way of dealing with this problem is to suck the boundary layer away through a porous surface (see Boundary layer suction).
This can result in a reduction in drag, but is usually impractical due to the mechanical complexity involved and the power required to move the air and dispose of it. Natural laminar flow is the name for techniques pushing the boundary layer transition aft by shaping of an aerofoil or a fuselage so that their thickest point is aft and less thick. This reduces the velocities in the leading part and the same Reynolds number is achieved with a greater length.
At lower Reynolds numbers, such as those seen with model aircraft, it is relatively easy to maintain laminar flow. This gives low skin friction, which is desirable. However, the same velocity profile which gives the laminar boundary layer its low skin friction also causes it to be badly affected by adverse pressure gradients. As the pressure begins to recover over the rear part of the wing chord, a laminar boundary layer will tend to separate from the surface. Such flow separation causes a large increase in the pressure drag, since it greatly increases the effective size of the wing section. In these cases, it can be advantageous to deliberately trip the boundary layer into turbulence at a point prior to the location of laminar separation, using a turbulator. The fuller velocity profile of the turbulent boundary layer allows it to sustain the adverse pressure gradient without separating.
Thus, although the skin friction is increased, overall drag is decreased. This is the principle behind the dimpling on golf balls, as well as vortex generators on aircraft. Special wing sections have also been designed which tailor the pressure recovery so laminar separation is reduced or even eliminated. This represents an optimum compromise between the pressure drag from flow separation and skin friction from induced turbulence.
Friday, August 14, 2009
Bolt terminologies and working
Bolt terminologies and working
Introduction:
Bolts are the temporary fastening elements used for assembling of parts. There are 4 models of engines are producing. In these 4 models there are different application, about 40. Maximum torque of 120 Kg-m is required for torquing Main bearing cap bolts of 170 engine model and Connecting rod bolts, Cylinder head bolts, Damper and crank pulley, fly wheel etc. Conventional method of torquing the engine component bolts using manual torque wrench is more operator fatigue and precise control of applied torque is not possible. The difficulties involved in torquing for tightening engine component bolts are listed below.
No fool-proofing arrangementMeasurement of applied torque is not possibleConsuming more Torquing cycle time
Electric Nut Runner is newly emerged torque control fastener tightening tool that is usually powered by Electric power. Electric nut runner mainly consists of 3 components.
They are
1.Spindle
2.Controller
3.Cable
Spindle is equipped with brushless motor and it will tighten the bolt and the spindle is connected to the controller through a cable. Controller receives the feed back signal from the spindle and based on that signal it gives the controlling signal to the spindle. Cable is used to connect both the spindle and controller.
Objective
In the existing method, impact wrench and manual torque wrenches are using for torquing the Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts in engine assembly line. In this existing method of bolts torquing cycle time is more and also precise control of torque is not possible.
The objective of proposed work is to study the process requirements and Torquing sequence, mounting height details for Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts and propose the Electric Nut Runners spindle and Controller Specifications based on the studied process requirements and torquing sequence, mounting height details to the Manufacturer of Electric Nut Runners.
The Proposed work also includes Installation of 5 Electric Nut Runner in Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing stations and 10 pneumatic Nut runners at Selected points in Engine assembly line.
The proposed work also involves calculation of bolts torquing cycle time by Existing Manual Air guns and Pre-calibrated Torque wrench method and by using Proposed Electric and Pneumatic Nut runners Method and to determine how proposed methods are more economical compared to existing process.Finally we discuss here about the working of all the electrical nut runners, there procedure of operation, schematic diagram, and other supportive to nut runners lke PLC programming, Bosch programming.
Scope of the Work:
In six Engine assembly stages namely Main bearing cap bolts, Connecting rod bolts, Cylinder head bolts, Flywheel housing bolts, Flywheel bolts requires high torque with precise control (± 2%). In case of connecting rod bolts in addition to the above, the bolts are to be tightened i.e. “yield to torque”. In these cases number of bolts per engine assembly is ranging from 6 to 36 bolts. With the targeted increase in production levels to 1500 (during 2007-08) the present production practices need to be more reliable and free from operator dependencies.
With enhanced levels of production it is increasingly difficult and practically not possible to achieve a consistent torquing accuracy since the click-type torque wrenches used at present have an accuracy of +/-15%. In this industry, Present practice of pre-torquing using Pneumatic impact wrenches which is followed by manual torquing with pre-calibrated torque wrenches to ensure the final torque consumes lot of time, leave scope for improper torque application apart from need for extra operator to assist while tightening.
The objective of the company is to increase the capacity of the Assembly shop. Thus the primary option is to reduce the Torquing cycle time.Application of Electric and Pneumatic Nut Runners results in reduction in torquing cycle time required for the Assembling of Engine, thus solving the problem of the company.
Scope of project extends to the installation of the electrical nut runners, suitable for all the models, conducting trials to test the feasibility of the nut runners with all the models, check all the sequences, calibration of the nut runners, educating the supervisors, workers so the t they can easily use it.
Bolt Terminology
Helix: The curve formed on any cylinder by a straight line in a plane that is wrapped around the cylinder with a forward progression.
External thread: A thread on the outside of a member. An example is the thread of a bolt
Internal thread: A thread on the inside of a member. An example is the thread inside a nut.
Major diameter: The largest diameter of external or internal threads
Axis: The center line running lengthwise through a screw.
Crest: The surface of the thread corresponding to the major diameter of an external thread and the minor diameter of an internal thread.
Introduction:
Bolts are the temporary fastening elements used for assembling of parts. There are 4 models of engines are producing. In these 4 models there are different application, about 40. Maximum torque of 120 Kg-m is required for torquing Main bearing cap bolts of 170 engine model and Connecting rod bolts, Cylinder head bolts, Damper and crank pulley, fly wheel etc. Conventional method of torquing the engine component bolts using manual torque wrench is more operator fatigue and precise control of applied torque is not possible. The difficulties involved in torquing for tightening engine component bolts are listed below.
No fool-proofing arrangementMeasurement of applied torque is not possibleConsuming more Torquing cycle time
Electric Nut Runner is newly emerged torque control fastener tightening tool that is usually powered by Electric power. Electric nut runner mainly consists of 3 components.
They are
1.Spindle
2.Controller
3.Cable
Spindle is equipped with brushless motor and it will tighten the bolt and the spindle is connected to the controller through a cable. Controller receives the feed back signal from the spindle and based on that signal it gives the controlling signal to the spindle. Cable is used to connect both the spindle and controller.
Objective
In the existing method, impact wrench and manual torque wrenches are using for torquing the Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts in engine assembly line. In this existing method of bolts torquing cycle time is more and also precise control of torque is not possible.
The objective of proposed work is to study the process requirements and Torquing sequence, mounting height details for Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts and propose the Electric Nut Runners spindle and Controller Specifications based on the studied process requirements and torquing sequence, mounting height details to the Manufacturer of Electric Nut Runners.
The Proposed work also includes Installation of 5 Electric Nut Runner in Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing stations and 10 pneumatic Nut runners at Selected points in Engine assembly line.
The proposed work also involves calculation of bolts torquing cycle time by Existing Manual Air guns and Pre-calibrated Torque wrench method and by using Proposed Electric and Pneumatic Nut runners Method and to determine how proposed methods are more economical compared to existing process.Finally we discuss here about the working of all the electrical nut runners, there procedure of operation, schematic diagram, and other supportive to nut runners lke PLC programming, Bosch programming.
Scope of the Work:
In six Engine assembly stages namely Main bearing cap bolts, Connecting rod bolts, Cylinder head bolts, Flywheel housing bolts, Flywheel bolts requires high torque with precise control (± 2%). In case of connecting rod bolts in addition to the above, the bolts are to be tightened i.e. “yield to torque”. In these cases number of bolts per engine assembly is ranging from 6 to 36 bolts. With the targeted increase in production levels to 1500 (during 2007-08) the present production practices need to be more reliable and free from operator dependencies.
With enhanced levels of production it is increasingly difficult and practically not possible to achieve a consistent torquing accuracy since the click-type torque wrenches used at present have an accuracy of +/-15%. In this industry, Present practice of pre-torquing using Pneumatic impact wrenches which is followed by manual torquing with pre-calibrated torque wrenches to ensure the final torque consumes lot of time, leave scope for improper torque application apart from need for extra operator to assist while tightening.
The objective of the company is to increase the capacity of the Assembly shop. Thus the primary option is to reduce the Torquing cycle time.Application of Electric and Pneumatic Nut Runners results in reduction in torquing cycle time required for the Assembling of Engine, thus solving the problem of the company.
Scope of project extends to the installation of the electrical nut runners, suitable for all the models, conducting trials to test the feasibility of the nut runners with all the models, check all the sequences, calibration of the nut runners, educating the supervisors, workers so the t they can easily use it.
Bolt Terminology
Helix: The curve formed on any cylinder by a straight line in a plane that is wrapped around the cylinder with a forward progression.
External thread: A thread on the outside of a member. An example is the thread of a bolt
Internal thread: A thread on the inside of a member. An example is the thread inside a nut.
Major diameter: The largest diameter of external or internal threads
Axis: The center line running lengthwise through a screw.
Crest: The surface of the thread corresponding to the major diameter of an external thread and the minor diameter of an internal thread.
BY-WIRE-STEERED SYSTEM
BY-WIRE-STEERED SYSTEM
By-wire-steered system is integration of electronic devices and mechanical systems in order to improve the performance of the steering system.Recent advances in dependable embedded system technology, as well as continuing demand for improved handling and passive and active safety improvements, have led vehicle manufacturers and suppliers to actively pursue development programs in computer-controlled, by-wire subsystems. These subsystems include steer and brake-by-wire, and are composed of mechanically decoupled sets of actuators and controllers connected through multiplexed, in-vehicle computer networks.A steer-by-wire system replaces the traditional mechanical linkage between the steering wheel and the road wheel actuator (e.g., a rack and pinion steering system) with an electronic connection. This allows flexibility in the packaging and modularity of the design. Since it removes the direct Kinematic relationship between the steering and road wheels, it enables control algorithms to help enhance driver input.There is no mechanical link to the driver.
Steer- and brake-by-wire provide a number of packaging and assembly advantages over conventional subsystems. For instance, electromechanical brake-by-wire subsystems require no hydraulic fluid to store or load at the assembly plant and permit more modular assembly, thus reducing the number of parts to be handled during production. Steer-by-wire systems have no steering column and may also eliminate cross-car steering assemblies such as racks. Arguments for ‘by-Wire’ systems include production costs, packaging and traffic safety . The ‘by-Wire’ technology as in drive, brake and steer is gaining ground and is undoubtedly an automotive solution of the future.
The arguments to support such ‘by-Wire’ systems include reduced production costs and packaging advantages and improved traffic safety. Emerging drive-by- wire technologies offer new possibilities for designing the steering characteristics of road vehicles. When the mechanical link between the steering wheel and the front wheels is replaced by sensors, controllers and actuators, enormous flexibility is achieved in terms of the control device applied and in terms of the transfer function of the steering system. This offers new possibilities for optimizing the steering system for mass-produced vehicles. However, the flexibility is of even greater advantage in the area of car adjustment for drivers with physical disabilities.The transition to purely electrical steering systems will take place step by step via systems with mechanical or hydraulic backup. Development and production of the next generations of electrical steering systems up to purely electrical steering systems create high safety demands on components and systems. Reliable and safe electrical steering systems can be realized by using appropriate safety techniques for these new systems and their components combined with the know-how of safety relevant vehicle systems.
The main limitations of by-wire-steered system are the requirement of a 42 Volts car supply, high output alternator and new generation batteries.The steer-by-wire principle becomes absolutely necessary when Future innovative steering functions, such as vehicle dynamic interventions, collision avoidance, individual wheel steering, tracking assistance, automatic lateral guidance, and finally autonomous driving functions have to be implemented in a system compound of various vehicle systems.
INTRODUCTION
By-wire-steered system is an application of ‘MECHATRONICS’, which is the integration of electronic devices and mechanical systems in order to improve the performance of the system .Recent advances in dependable embedded system technology, as well as continuing demand for improved handling and passive and active safety improvements, have led vehicle manufacturers and suppliers to actively pursue development programs in computer-controlled, by-wire subsystems. These subsystems include steer and brake-by-wire, and are composed of mechanically decoupled sets of actuators and controllers connected through multiplexed, in-vehicle computer networks. There is no mechanical link to the driver.
Steer- and brake-by-wire provide a number of packaging and assembly advantages over conventional subsystems. For instance, electromechanical brake-by-wire subsystems require no hydraulic fluid to store or load at the assembly plant and permit more modular assembly, thus reducing the number of parts to be handled during production. Steer-by-wire systems have no steering column and may also eliminate cross-car steering assemblies such as racks. Arguments for ‘by-Wire’ systems include production costs, packaging and traffic safety.The ‘by-Wire’ technology as in drive, brake and steer is gaining ground and is undoubtedly an automotive solution of the future.
The arguments to support such ‘by-Wire’ systems include reduced production costs and packaging advantages and improved traffic safety (a boon for everybody involved). Emerging drive-by- wire technologies offer new possibilities for designing the steering characteristics of road vehicles. When the mechanical link between the steering wheel and the front wheels is replaced by sensors, controllers and actuators, enormous flexibility is achieved in terms of the control device applied and in terms of the transfer function of the steering system. This offers new possibilities for optimizing the steering system for mass-produced vehicles. However, the flexibility is of even greater advantage in the area of car adjustment for drivers with physical disabilities.
A steer-by-wire system replaces the traditional mechanical linkage between the steering wheel and the road wheel actuator (e.g., a rack and pinion steering system) with an electronic connection. This allows flexibility in the packaging and modularity of the design. Since it removes the directKinematic relationship between the steering and road wheels, it enables control algorithms to help enhance driver input.The transition to purely electrical steering systems will take place step by step via systems with mechanical or hydraulic backup. Development and production of the next generations of electrical steering systems up to purely electrical steering systems create high safety demands on components and systems.
Reliable and safe electrical steering systems can be realized by using appropriate safety techniques for these new systems and their components combined with the know-how of safety relevant vehicle systems.‘Steer-by-Wire’ (SbW) there exists a legislation obstacle as European regulations require a mechanical connection between the steering wheel and the wheels. The column electric power steering (C-EPS) in the Opel Astra is therefore only an electric
hybridization at steering level: the steering torque levels will increase when the car picks up speed. The “Dual drive” system in the Fiat Punto has an EPS with dual settings: the driver can activate the “city” mode and obtain gentler steering when parking. The main limitations of by-wire-steered system are the requirement of a 42 Volts car supply, high output alternator and new generation batteries.The steer-by-wire principle becomes absolutely necessary when Future innovative steering functions, such as vehicle dynamic interventions, collision avoidance, individual wheel steering, tracking assistance, automatic lateral guidance, and finally autonomous driving functions have to be implemented in a system compound of various vehicle systems
By-wire-steered system is integration of electronic devices and mechanical systems in order to improve the performance of the steering system.Recent advances in dependable embedded system technology, as well as continuing demand for improved handling and passive and active safety improvements, have led vehicle manufacturers and suppliers to actively pursue development programs in computer-controlled, by-wire subsystems. These subsystems include steer and brake-by-wire, and are composed of mechanically decoupled sets of actuators and controllers connected through multiplexed, in-vehicle computer networks.A steer-by-wire system replaces the traditional mechanical linkage between the steering wheel and the road wheel actuator (e.g., a rack and pinion steering system) with an electronic connection. This allows flexibility in the packaging and modularity of the design. Since it removes the direct Kinematic relationship between the steering and road wheels, it enables control algorithms to help enhance driver input.There is no mechanical link to the driver.
Steer- and brake-by-wire provide a number of packaging and assembly advantages over conventional subsystems. For instance, electromechanical brake-by-wire subsystems require no hydraulic fluid to store or load at the assembly plant and permit more modular assembly, thus reducing the number of parts to be handled during production. Steer-by-wire systems have no steering column and may also eliminate cross-car steering assemblies such as racks. Arguments for ‘by-Wire’ systems include production costs, packaging and traffic safety . The ‘by-Wire’ technology as in drive, brake and steer is gaining ground and is undoubtedly an automotive solution of the future.
The arguments to support such ‘by-Wire’ systems include reduced production costs and packaging advantages and improved traffic safety. Emerging drive-by- wire technologies offer new possibilities for designing the steering characteristics of road vehicles. When the mechanical link between the steering wheel and the front wheels is replaced by sensors, controllers and actuators, enormous flexibility is achieved in terms of the control device applied and in terms of the transfer function of the steering system. This offers new possibilities for optimizing the steering system for mass-produced vehicles. However, the flexibility is of even greater advantage in the area of car adjustment for drivers with physical disabilities.The transition to purely electrical steering systems will take place step by step via systems with mechanical or hydraulic backup. Development and production of the next generations of electrical steering systems up to purely electrical steering systems create high safety demands on components and systems. Reliable and safe electrical steering systems can be realized by using appropriate safety techniques for these new systems and their components combined with the know-how of safety relevant vehicle systems.
The main limitations of by-wire-steered system are the requirement of a 42 Volts car supply, high output alternator and new generation batteries.The steer-by-wire principle becomes absolutely necessary when Future innovative steering functions, such as vehicle dynamic interventions, collision avoidance, individual wheel steering, tracking assistance, automatic lateral guidance, and finally autonomous driving functions have to be implemented in a system compound of various vehicle systems.
INTRODUCTION
By-wire-steered system is an application of ‘MECHATRONICS’, which is the integration of electronic devices and mechanical systems in order to improve the performance of the system .Recent advances in dependable embedded system technology, as well as continuing demand for improved handling and passive and active safety improvements, have led vehicle manufacturers and suppliers to actively pursue development programs in computer-controlled, by-wire subsystems. These subsystems include steer and brake-by-wire, and are composed of mechanically decoupled sets of actuators and controllers connected through multiplexed, in-vehicle computer networks. There is no mechanical link to the driver.
Steer- and brake-by-wire provide a number of packaging and assembly advantages over conventional subsystems. For instance, electromechanical brake-by-wire subsystems require no hydraulic fluid to store or load at the assembly plant and permit more modular assembly, thus reducing the number of parts to be handled during production. Steer-by-wire systems have no steering column and may also eliminate cross-car steering assemblies such as racks. Arguments for ‘by-Wire’ systems include production costs, packaging and traffic safety.The ‘by-Wire’ technology as in drive, brake and steer is gaining ground and is undoubtedly an automotive solution of the future.
The arguments to support such ‘by-Wire’ systems include reduced production costs and packaging advantages and improved traffic safety (a boon for everybody involved). Emerging drive-by- wire technologies offer new possibilities for designing the steering characteristics of road vehicles. When the mechanical link between the steering wheel and the front wheels is replaced by sensors, controllers and actuators, enormous flexibility is achieved in terms of the control device applied and in terms of the transfer function of the steering system. This offers new possibilities for optimizing the steering system for mass-produced vehicles. However, the flexibility is of even greater advantage in the area of car adjustment for drivers with physical disabilities.
A steer-by-wire system replaces the traditional mechanical linkage between the steering wheel and the road wheel actuator (e.g., a rack and pinion steering system) with an electronic connection. This allows flexibility in the packaging and modularity of the design. Since it removes the directKinematic relationship between the steering and road wheels, it enables control algorithms to help enhance driver input.The transition to purely electrical steering systems will take place step by step via systems with mechanical or hydraulic backup. Development and production of the next generations of electrical steering systems up to purely electrical steering systems create high safety demands on components and systems.
Reliable and safe electrical steering systems can be realized by using appropriate safety techniques for these new systems and their components combined with the know-how of safety relevant vehicle systems.‘Steer-by-Wire’ (SbW) there exists a legislation obstacle as European regulations require a mechanical connection between the steering wheel and the wheels. The column electric power steering (C-EPS) in the Opel Astra is therefore only an electric
hybridization at steering level: the steering torque levels will increase when the car picks up speed. The “Dual drive” system in the Fiat Punto has an EPS with dual settings: the driver can activate the “city” mode and obtain gentler steering when parking. The main limitations of by-wire-steered system are the requirement of a 42 Volts car supply, high output alternator and new generation batteries.The steer-by-wire principle becomes absolutely necessary when Future innovative steering functions, such as vehicle dynamic interventions, collision avoidance, individual wheel steering, tracking assistance, automatic lateral guidance, and finally autonomous driving functions have to be implemented in a system compound of various vehicle systems
Tuesday, August 11, 2009
Amoeba Organization
Amoeba Organization
Introducing the concept of AMOEBA ORGANIZATION based on adaptability, which is the key to business success of modern days; but many organizations are too rigidly organized to adapt to constant change & seize new opportunities. Modern day organizations are lengthening their life span by reshaping internal systems for flexibility, modernizing their cultures & monitoring the ever-changing environments in which they operate.
Introducing the concept of AMOEBA ORGANIZATION based on adaptability, which is the key to business success of modern days; but many organizations are too rigidly organized to adapt to constant change & seize new opportunities. Modern day organizations are lengthening their life span by reshaping internal systems for flexibility, modernizing their cultures & monitoring the ever-changing environments in which they operate.
Adaptive cruise control System
Adaptive cruise control System
An automotive cruise control system that automatically slows down the car if it is moving too close to the vehicle in front of it. A radar or laser unit located behind the grille determines the speed and distance of the vehicle in front. When the distance is computed to be safe again, the system accelerates the car back to its last speed setting. Also called "active cruise control" and "intelligent cruise control.
Autonomous cruise control is an optional cruise control system appearing on some more upscale vehicles. The system goes under many different trade names according to the manufacture. These systems use either a radar or laser setup allowing the vehicle to slow when approaching another vehicle and accelerate again to the preset speed when traffic allows. ACC technology is widely regarded as a key component of any future generations of smart cars.
Types
Laser-based systems are significantly lower in cost than radar-based systems; however, laser-based ACC systems do not detect and track vehicles well in adverse weather conditions nor do they track extremely dirty (non-reflective) vehicles very well. Laser-based sensors must be exposed, the sensor (a fairly-large black box) is typically found in the lower grille offset to one side of the vehicle.
Radar-based sensors can be hidden behind plastic fascias; however, the fascias may look different from a vehicle without the feature. For example, Mercedes packages the radar behind the upper grille in the center; however, the Mercedes grille on such applications contains a solid plastic panel in front of the radar with painted slats to simulate the slats on the rest of the grille.
Radar-based systems are available on many luxury cars as an option for approx. 1000-3000 USD/euro. Laser-based systems are available on some near luxury and luxury cars as an option for approx. 400-600 USD/euro.
Cooperating systems
Radar-based ACC often feature a Precrash system, which warns the driver and/or provides brake support if there is a high risk of a collision. Also in certain cars it is incorporated with a lane maintaining system which provides power steering assist to reduce steering input burden in corners when the cruise control system is activated.
Examples of vehicles with adaptive cruise control
2005 Acura RLAudi A4 (see a demonstration on YouTube), A5, A6, A8, Q7BMW 7 Series, 5 series, 6 series, 3 series (Active Cruise Control)2004 Cadillac DTS, STS, XLR2007 Chrysler 300C2006 Ford Mondeo, Taurus, S-Max, Galaxy2003 Honda Inspire Accord, LegendHyundai Genesis (Smart Cruise Control, delayed)Infiniti M, Q45,QX56, G35, FX35/45/50 and G371999 Jaguar XK-R, S-Type, XJ, XF2000 Lexus LS430/460 (laser and radar), RX (laser and radar), GS, IS, ES 350, and LX 570Lincoln MKS, MKT1998 Nissan Cima, Nissan Primera T-Spec Models (Intelligent Cruise Control)1998 Mercedes-Benz S-Class, E-Class, CLS-Class, SL-Class, CL-Class, M-Class, GL-Class, CLK-Class (Distronic, removed in 2009 from certain US models)Range Rover SportRenault Vel SatisSubaru Legacy & Outback Japan-spec called SI-Cruise1997 Toyota Celsior, Sienna (XLE Limited Edition), Avalon, Sequoia (Platinum Edition), Prius, AvensisVolkswagen Passat, Phaeton, Touareg, 2009 GolfVolvo S80, V70, XC70, XC60
An automotive cruise control system that automatically slows down the car if it is moving too close to the vehicle in front of it. A radar or laser unit located behind the grille determines the speed and distance of the vehicle in front. When the distance is computed to be safe again, the system accelerates the car back to its last speed setting. Also called "active cruise control" and "intelligent cruise control.
Autonomous cruise control is an optional cruise control system appearing on some more upscale vehicles. The system goes under many different trade names according to the manufacture. These systems use either a radar or laser setup allowing the vehicle to slow when approaching another vehicle and accelerate again to the preset speed when traffic allows. ACC technology is widely regarded as a key component of any future generations of smart cars.
Types
Laser-based systems are significantly lower in cost than radar-based systems; however, laser-based ACC systems do not detect and track vehicles well in adverse weather conditions nor do they track extremely dirty (non-reflective) vehicles very well. Laser-based sensors must be exposed, the sensor (a fairly-large black box) is typically found in the lower grille offset to one side of the vehicle.
Radar-based sensors can be hidden behind plastic fascias; however, the fascias may look different from a vehicle without the feature. For example, Mercedes packages the radar behind the upper grille in the center; however, the Mercedes grille on such applications contains a solid plastic panel in front of the radar with painted slats to simulate the slats on the rest of the grille.
Radar-based systems are available on many luxury cars as an option for approx. 1000-3000 USD/euro. Laser-based systems are available on some near luxury and luxury cars as an option for approx. 400-600 USD/euro.
Cooperating systems
Radar-based ACC often feature a Precrash system, which warns the driver and/or provides brake support if there is a high risk of a collision. Also in certain cars it is incorporated with a lane maintaining system which provides power steering assist to reduce steering input burden in corners when the cruise control system is activated.
Examples of vehicles with adaptive cruise control
2005 Acura RLAudi A4 (see a demonstration on YouTube), A5, A6, A8, Q7BMW 7 Series, 5 series, 6 series, 3 series (Active Cruise Control)2004 Cadillac DTS, STS, XLR2007 Chrysler 300C2006 Ford Mondeo, Taurus, S-Max, Galaxy2003 Honda Inspire Accord, LegendHyundai Genesis (Smart Cruise Control, delayed)Infiniti M, Q45,QX56, G35, FX35/45/50 and G371999 Jaguar XK-R, S-Type, XJ, XF2000 Lexus LS430/460 (laser and radar), RX (laser and radar), GS, IS, ES 350, and LX 570Lincoln MKS, MKT1998 Nissan Cima, Nissan Primera T-Spec Models (Intelligent Cruise Control)1998 Mercedes-Benz S-Class, E-Class, CLS-Class, SL-Class, CL-Class, M-Class, GL-Class, CLK-Class (Distronic, removed in 2009 from certain US models)Range Rover SportRenault Vel SatisSubaru Legacy & Outback Japan-spec called SI-Cruise1997 Toyota Celsior, Sienna (XLE Limited Edition), Avalon, Sequoia (Platinum Edition), Prius, AvensisVolkswagen Passat, Phaeton, Touareg, 2009 GolfVolvo S80, V70, XC70, XC60
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