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Active Suspension System full report




Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose contributing to the car's roadholding /handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations,etc. These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different.

During cornering the car s tires produce so-called slip forces in lateral direction
These forces, displayed as horizontal arrows in Figure .1, result in an unfavorable deformation of the contact patch and a counter clockwise torque around a horizontal axis through the car s centre of gravity. Additional vertical reaction forces, the vertical arrows in Figure 2, counteract the torque and prevent the car from rolling over. In case of a passive suspension system, these reaction forces will cause the springs on the left side of the car to further compress and on the right side of the car to expand which causes some roll of the car s body. Depending on the geometry of the suspension links, the orientation of the wheels with respect to the car s body will change during suspension travel.
In case of a trailing arm geometry, the single suspension page link connecting each wheel to the chassis rotates along a lateral axis with respect to the chassis. During cornering the tires will therefore take over the angle of the car s body, which also results in a deformation of the contact patch. This combination leads to an undesirable contact patch, with a smaller area and a non-homogeneous pressure distribution.
The trailing arm suspension will force the camber angle of the tires to take over the roll angle of the vehicle s body. This characteristic is described by the value 1 /
(1 camber/ body roll). In case of cornering, it would be desirable to have a suspension system that provides so-called counter-camber (camber<0) during cornering: -1 / . The negative camber angle will result in a favorable deformation of the contact patch, which in combination with the unfavorable deformation due to the slip forces will lead to a desirable contact patch.
Most of today s suspension systems vary between 0 / (rigid axle) and 1 / (trailing arm). Examples are the double wishbone, the multi-link and the McPherson suspension system. The absence of counter-camber suspension systems can be explained by the fact that such a suspension system will result in extreme camber and therefore extreme tire wear in case of encountering a bump in the road or an extremely loaded car.
Usually, all suspension systems other than 1 / -systems will carry out a small lateral movement during suspension travel because the links in the system describe a circular arc. The lateral movement, displayed in Figure 6, causes the tire to deform and results in extra tire wear. This is prevented in case of 1 / -systems like a trailing arm suspension



The spring rate is a component in setting the vehicle's ride height or its location in the suspension stroke. Vehicles which carry heavy loads will often have heavier springs to compensate for the additional weight that would otherwise collapse a vehicle to the bottom of its travel (stroke). Heavier springs are also used in performance applications where the loading conditions experienced are more extreme.

Mathematics of the spring rate
Spring rate is a ratio used to measure how resistant a spring is to being compressed or expanded during the spring's deflection. The magnitude of the spring force increases as deflection increases according to Hooke's Law. Briefly, this can be stated as

F is the force the spring exerts
k is the spring rate of the spring.
x is the displacement from equilibrium length i.e. the length at which the spring is neither compressed or stretched.
The spring rate of a coil spring may be calculated by a simple algebraic equation or it may be measured in a spring testing machine. The spring constant k can be calculated as follows:

where d is the wire diameter, G is the spring's shear modulus (e.g., about 12,000,000 lbf/in or 80 GPa for steel), and N is the number of wraps and D is the diameter of the coil.


Wheel rate is the effective spring rate when measured at the wheel. This is as opposed to simply measuring the spring rate alone.Wheel rate is usually equal to or considerably less than the spring rate. Commonly, springs are mounted on control arms, swing arms or some other pivoting suspension member.


Roll couple percentage is the effective wheel rate, in roll, of each axle of the vehicle as a ratio of the vehicle's total roll rate. Roll couple percentage is critical in accurately balancing the handling of a vehicle. It is commonly adjusted through the use of anti-roll bars, but can also be changed through the use of different springs.


Weight transfer during cornering, acceleration or braking is usually calculated per individual wheel and compared with the static weights for the same wheels.
The total amount of weight transfer is only affected by four factors: the distance between wheel centers the height of the center of gravity, the mass of the vehicle, and the amount of acceleration experienced.
Unsprung weight transfer-Unsprung weight transfer is calculated based on the weight of the vehicle's components that are not supported by the springs. This includes tires, wheels, brakes, spindles, half the control arm's weight and other components.
Sprung weight transfer-Sprung weight transfer is the weight transferred by only the weight of the vehicle resting on the springs, not the total vehicle weight..


Jacking forces are the sum of the vertical force components experienced by the suspension links. The resultant force acts to lift the sprung mass if the roll center is above ground, or compress it if underground. Generally, the higher the roll center, the more jacking force is experienced.


Travel is the measure of distance from the bottom of the suspension stroke to the top of the suspension stroke . Bottoming or lifting a wheel can cause serious control problems or directly cause damage. "Bottoming" can be caused by the suspension, tires, fenders, etc. running out of space to move or the body or other components of the car hitting the road.


Damping is the control of motion or oscillation, as seen with the use of hydraulic gates and valves in a vehicles shock absorber. This may also vary, intentionally or unintentionally. Like spring rate, the optimal damping for comfort may be less than for control.


Camber changes is due to wheel travel, body roll and suspension system deflection or compliance. In general, a tire wears and brakes best at -1 to -2 of camber from vertical. Too much camber will result in the decrease of braking performance due to a reduced contact patch size through excessive camber variation in the suspension geometry. The amount of camber change in bump is determined by the instantaneous front view swing arm (FVSA) length of the suspension geometry, or in other words, the tendency of the tire to camber inward when compressed in bump.


This is important to body roll and to front to rear roll stiffness distribution. However, the roll stiffness distribution in most cars is set more by the antiroll bars than the RCH. The height of the roll center is related to the amount of jacking forces experienced.

Anti-dive and anti-squat are expressed in terms of percentage and refer to the front diving under braking and the rear squatting under acceleration. They can be thought of as the counterparts for braking and acceleration as jacking forces are to cornering. The main reason for the difference is due to the different design goals between front and rear suspension, whereas suspension is usually symmetrical between the left and right of the vehicle.


For most purposes, the weight of the suspension components is unimportant, but at high frequencies, caused by road surface roughness, the parts isolated by rubber bushings act as a multistage filter to suppress noise and vibration better than can be done with only the tires and springs. (The springs work mainly in the vertical direction.)

Certain modern vehicles have height adjustable suspension in order to improve aerodynamics and fuel efficiency. And modern formula cars, that have exposed wheels and suspension, typically use streamlined tubing rather than simple round tubing for their suspension arms to reduce drag..


During the design of a suspension system, a number of conflicting requirements has to be met. The suspension setup has to ensure a comfortable ride and good cornering characteristics at the same time. Also, optimal contact between wheels and road surface is needed in various driving conditions in order to maximize safety. Instead of a passive suspension, present in most of today s cars, an active suspension can be used in order to better resolve the trade-off between these conflicts. However, this is generally accompanied by considerable energy consumption. An active suspension is capable of leveling the car during cornering theoretically without consuming energy. Simulations using a full-car model show that this maximizes the car s cornering velocity. As extreme cornering may be required to remain on the road or to avoid an obstacle, implementing the active suspension system improves safety.

As the active part of the suspension takes care of realizing good cornering behaviour and of static load variations, the primary suspension springs can be tuned purely for optimizing comfort and road holding. Simulations show that the required energy for leveling the car during cornering is negligible, so it can be concluded that the active suspension system is able to economically level the car. The active suspension s potential for improving comfort is examined using a quarter-car model in combination with the skyhook damping principle. Performing simulations with an unrestricted actuator shows that comfort can slightly be improved with little actuator action and without deteriorating road holding and suspension travel. Further improving the comfort level requires more actuator action and results in considerable degradation of road holding and suspension travel


The major components of an active suspension system are a linear actuator, a microcontroller, and a sensor system that will allow us to monitor the displacement, velocity, and acceleration An input wave will be sent into the system, via the microcontroller, and the platform will move according to the type of wave entered. The wave entered will be asingle step, a square wave, or a sine wave with different options available for the user to control. This actuator will be controlled using a microcontroller . Thedisplay will show the maximum distance the platform moves, the maximum velocity and acceleration of the actuator, and the type of motion the it is undergoing (i.e. up or down).Sensors will permit monitoring and recording of the platform motion.



In this section, a controller will be designed which regulates the adjustable arm s angle and therefore the force produced by the active suspension. The control of the suspension system takes place in two stages. In the first stage a performance improvement controller determines the force that has to be produced by the active suspension for leveling the car, comfort improvement, wheel load variation reduction,
suspension travel reduction or a combination of these improvements. The required force functions as input for the actuator controller.In the second stage an actuator controller makes sure that the required force is produced as precise as possible. The actuator is capable of producing a force within certain limits. Therefore, a saturation filter first warrants that the force stays within these limits. Using the mathematical model, this limited required force is converted to an angle at which theactuator actually produces this force. This angle is called the reference angle . Hereafter, the actuator controller drives the adjustable arm, via a moment applied by an electric actuator, to the reference angle using a PD-controller with a correction for the estimated disturbance. This disturbance is caused by the reaction moment and can be predicted by the mathematical model. The actuator controller components are visualized


Improves driver control, safety and stability, with or without a load .
Eliminates sway and reduces roll on corners
Reduces axle wrap
Maximum safety
Absorbs load, rather than resisting it, thereby ensuring a much more comfortable ride
Eliminates the need for fitting extra blades which harden the ride
Better handling and control in windy and rough road conditions
Minimize wear on tires, shocks, shackles and leaf springs


Usually the suspension consists of passive force elements which are designed to optimize the trade-off between ride comfort, suspension travel and wheel load variations. Also, the geometry design of the suspension links is a trade off between optimal orientation of the wheels in case of bumps in the road or during cornering. Furthermore, the springs should be stiff enough to avoid exaggerate body roll or pitch during cornering, accelerating and braking. Modern suspension systems provide possibilities for optimizing the trade-offs, but will never be able to eliminate the conflicts. Moreover, they are complex and space consuming. The additional elements of an active suspension system are able to produce forces when required and therefore the trade-off between ride comfort, suspension travel and wheel load variations can be better resolved. Furthermore, an active suspension system can be used in order to eliminate body roll during cornering. As a result, the complicated and space consuming suspension links can be replaced with a compact and simple trailing arm suspension. Also, static load variations can be taken care of by adjusting the stiffness of the suspension. It can be adjusted to the driving situation and to individualize the handling characteristics and comfort level of the vehicle.

Active suspension system

The suspension system must support the vehicle, provide directional control during handling manoeuvres and provide effective isolation of passengers/payload from road disturbances [Wright 84]. Good ride comfort requires a soft suspension, whereas insensitivity to applied loads requires stiff suspension. Good handling requires a suspension setting somewhere between the two.
Due to these conflicting demands, suspension design has had to be something of a compromise, largely determined by the type of use for which the vehicle was designed. Active suspensions are considered to be a way of increasing the freedom one has to specify independently the characteristics of load carrying, handling and ride quality.
A passive suspension system has the ability to store energy via a spring and to dissipate it via a damper. Its parameters are generally fixed, being chosen to achieve a certain level of compromise between road holding, load carrying and comfort.
An active suspension system has the ability to store, dissipate and to introduce energy to the system. It may vary its parameters depending upon operating conditions and can have knowledge other than the strut deflection the passive system is limited to.
High bandwidth systems
In a high bandwidth (or fully active'') suspension system we generally consider an actuator connected between the sprung and unsprung masses of the vehicle. A fully active system aims to control the suspension over the full bandwidth of the system. In particular this means that we aim to improve the suspension response around both the rattle-space'' frequency (10-12 Hz) and tyre-hop'' frequency (3-4Hz). The terms rattle-space and tyre-hop may be regarded as resonant frequencies of the system. A fully active system will consume a significant amount of power and will require actuators with a relatively wide bandwidth. These have been successfully implemented in Formula One cars and by, for example, Lotus [Wright 84]
Low bandwidth systems
Also known as slow-active or band-limited systems. In this class the actuator will be placed in series with a road spring and/or a damper. A low bandwidth system aims to control the suspension over the lower frequency range, and specifically around the rattle space frequency. At higher frequencies the actuator effectively locks-up and hence the wheel-hop motion is controlled passively. With these systems we can achieve a significant reduction in body roll and pitch during manoeuvres such as cornering and braking, with lower energy consumption than a high bandwidth system.
Preview Systems
These aim to increase the bandwidth of a band-limited system by using feed-forward or knowledge of future road inputs. Some systems [Foag 89] aim to measure road disturbances ahead of the car (using perhaps a laser system [Prem 87]), and then use both standard feedback control and feed-forward from the sensor to achieve a superior response. Others eg. [Crolla 91] aim to use the information available from the front strut deflection to improve the performance of the rear suspension.
Current Technology and Applications
Active suspension systems that have been successfully implemented include the high profile examples found on Formula One racing cars. Most major motor manufacturers are researching there own systems and some are near to fruition. These include Jaguar [Williams 94], Mercedes Benz [Acker 91], and Toyota [Hayakawa 93] to name but three.
Formula one cars represent the extreme of active suspension implementation, being fully active systems using high bandwidth aerospace specification components [Wright 84]. For wide spread commercial use much cheaper actuators and control valves must be used, and so semi-active or low bandwidth systems are the norm here. The oleo-pneumatic actuator is a popular choice [Williams 94], giving both a low frequency active element and a high frequency passive element in one unit.


Suspension system

Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels

Serve a dual purpose contributing to the car's handling and braking.

Keeps vehicle occupants comfortable and well isolated from road noise, bumps, and vibrations,etc

Need of suspension system

Prevent the road shocks from being transmitted to the vehicle parts
To keep the vehicle stable while in motion.
Provides safe vehicle control and free of irritating vibrations and reduce wear and tear.

Suspension Parts

Suspension system
Steering system

Fundamental components of any suspension


Conventional suspension system

Active suspension system

Parameters that can be improved by ACTIVE SUSPENSION
Ride Control

Height Control

Roll Control


An electronic control unit (ECU)



Adjustable shocks and springs


Motion Module
Calculation Module
Interaction Module

Functions of Active Suspension
Improves driver control, safety and stability.
Eliminates sway and reduces roll on corners
Reduces axle wrap
Maximum safety
Absorbs load, rather than resisting it, thereby ensuring a much more comfortable ride
Eliminates the need for fitting extra blades which harden the ride
Better handling and control in windy and rough road conditions
Minimize wear on tires, shocks, springs

Benefits of Bose Suspension System
Superior comfort
Superior control
Reduces body roll during turns
Reduces need for camber roll during turns
Requires only 1/3 of the power needed by the AC
Wider damping range than Magneto-Rheological systems

System high end luxury vehicles such as Lotus, Infiniti, and Mercedes-Benz
Used in F1 cars
The same technology has been applied in Military applications.

Among the various Automobile technologies one of biggest boon has been in the suspension systems. The earlier suspension systems consisting of a combination of leaf springs, coil springs, special suspension mountings or replaced now by the new Active Suspension Systems' which has improved the driving comfort and vehicle stability tremendously. This also maintained the vehicle height at a known level. In addition to this vehicle height is lowered at high speeds for greater stability. The driver can vary the spring settings through switches according to the road conditions. This has helped the automobiles to be run faster, safer even under the worst road conditions giving greater comfort than ever before. As one of the important components of a vehicle, a suspension system plays a crucial role in handling performance and ride comfort characteristics of a vehicle. In a conventional passive suspension system which comprises of only springs and dampers, it is difficult to build a trade-off to resolve the conflicting requirements of ride comfort and good handling performance. Active or adaptive suspension is an automotive technology that controls the vertical movement of the wheels via an onboard system rather than the movement being determined entirely by the surface on which the car is driving. The system therefore virtually eliminates body roll and pitch variation in many driving situations including cornering, accelerating and braking. This seminar deals with general information of Active suspension System, Autonomous Adaptive Control (AAC) method and other systems, applications, future design advancements. Different advantages and disadvantages of the mechanism are also discussed here. Active control suspensions offer a wider range of comfort and control than most current suspension systems. Offers unmatched vehicle handling performance. They may eventually find their way into more common production vehicles

Active Suspension System


A Computer or an electronic control unit (ECU)


Actuator or Servo

Adjustable shocks and springs

Functions of Active Suspension

Improves driver control, safety and stability, with or without a load .
Eliminates sway and reduces roll on corners
Reduces axle wrap
Maximum safety
Absorbs load, rather than resisting it, thereby ensuring a much more comfortable ride
Eliminates the need for fitting extra blades which harden the ride
Better handling and control in windy and rough road conditions
Minimize wear on tires, shocks, shackles and leaf springs


In the case of active suspension system, as in any other innovations of automotive technology, today's innovation is tomorrow's standard feature. Inspite of its high initial cost, let us expect to see them in the Indian roads soon. The trickle-down effect will take some time, but it'll happen and when such a time comes we can expect much lesser accidents, less fatalities and more comfort in driving the roads.
to get information about the topic Active electrically controlled suspension full report ,ppt and related topic refer the page link bellow
Hi friend you can refer this page for more details on Active Suspension System full report
Hey bro.. Thnx for the ppt's n seminar reports of active suspension. Al ur efforts someone else's ease. Take pride for being noble. Thnx Wink
Sorry we don't have a full report on 'Active Suspension System' in the form of document right now. we will update it as soon as possible.
Hey please can you upload the full seminar report (doc)? Or mail it to me at [email protected]

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