Nsprung and unsprung mass of a vehicle pdf

E ects of a large unsprung mass on the ride comfort of a. It is any component for which the suspension springs and shock absorbers has to control movement. Every few months a discussion comes up about hub motors and their pros and cons, and as you know if youve been reading this site for a while, im a big fan of the hub motors idea and id like them to be awesome. The lower the unsprung weight is the more it helps a suspension system to respond sensitively to road irregularities, giving more comfort and handling performance. The vehicle dynamics of the c,mm,n vehicle is investigated by means of simulations using the simmechanicstm. Considering the vehicle mathematical model with two linear degrees of freedom, the transient response and frequency.

A reduction in weight of 1 kg on the unsprung mass is equivalent to a reduction of 8 kg on the car overall. While the body, passenger cell, interior components, glazing, powertrain and even electronics offer many possibilities for weight removal, unsprung components are typically made from dense, highstrength and heavy materials that are more difficult to trim down without sacrificing essential strength. A chassis dynamometer is used to study the unsprung mass. The axle load of the vehicles was reduced by about 29%, which contributed to preventing an increase in track maintenance andor ground vibration.

Large unsprung weight on a car is a disadvantage as they have a negative effect on vehicle handling. Two simulation experiments of steering wheel angle step input and steering wheel angle impulse input were done. Everything on the wheel side of the spring is known as unsprung weight and includes the wheel, tyre, hub and bearings, the brake disc and caliper and the lower portion of the damper. The online estimate is needed for vehicles whose mass varies significantly. Influence of vehicle unsprungmass on dynamic wheel load. Unsprung weight is the mass of everything not held in suspension by your dampers, so the axles, wheels, brakes, wishbones, control. The online estimate can be used for vehicle control. In fact, a reduction in weight of 1 kg on the unsprung mass is equivalent to a reduction of 8 kg on the car overall, in terms of the vehicle s dynamics. A car s weight can be divided into 2 categories, sprung or unsprung mass. The sprung mass typically includes the body, frame, the internal components, passengers, and cargo, but does not. Unsprung mass has the same effect as sprung mass when it comes to acceleration as long as it is not a rotating part in the driveline. Assume the wheel mass is m 15 kg, the spring stiffness is k 500,000.

To diminish this large unsprung mass negative effects, three approaches suspension and reducer integrated closetowheel drive system. With a light axle, the upward impulse is less and, as this impulse is transmitted to the,chassis frame and body through the springs, the vibration on the latter parts is not so serious as with. The definitions of sprung and unsprung mass are equally simple. For vehicle applications, reducing the sprung mass transmissibility often results in improving the ride comfort, and reducing the unsprung mass transmissibility provides less wheel hop, therefore. Vehicle dimensions and mass permitting manual volume 1 part f hpmv 50max permits current as at 11 august 2017 disclaimer this publication is intended to provide general information about the permitting of vehicles that exceed dimension and mass limits. The larger the ratio of sprung mass to unsprung mass, the less the body and vehicle occupants are affected by bumps, dips, and other surface imperfections such as small bridges.

When the wheel hits a bump, the greater the unsprung mass, the longer it tends to stay airborne. In the simplest of terms, unsprung weight or unsprung mass is the weight that is not supported by the suspension of the vehicle. Lightening of vehicle unsprungmass is more effective on reducing dynamic wheel load than that of sprung or intermediatemass. Reducing unsprung weight and getting to the same size wheel and tire on all four corners is a good thing for racing. Unfortunately, this book cant be printed from the openbook. In a ground vehicle with a suspension, the unsprung mass. Plain old unsprung weight is not any harder to accelerate. Reducing the total weight will enhance the vehicles performance because less weight needs to be controlled and therefore, less energy is required. It presents a baseexcitation model of vertical ride dynamics which treats the unsprung. But reducing unsprung weight is often far harder than sprung weight minimisation. Sprung mass is mass that is suspended by a car s suspension. Unsprung mass is only a part of the total equation. The power spectrum density psd of dynamic wheel load measured at vehicle traveling speed of. In a ground vehicle with a suspension, the unsprung weight or the unsprung mass is the mass of the suspension, wheels or tracks as applicable, and other components directly connected to them, rather than supported by the suspension.

With its broad coverage and pedagogical aids, theory of ground vehicles, fourth edition remains the text of choice for students, engineers, and researchers wishing to master and apply basic theory to solve realworld, road and offroad vehicle mobility problems. Sep 12, 2018 car unsprung weight mass explained and effects. Vehicle sprung mass parameter estimation using an adaptive polynomialchaos method. Vehicle dimensions and mass permitting manual volume 1. Understanding unsprung weight hub motors the electric. Lets examine an example of high mass to unsprung wieght eg, a cadillac of the 60s with 3 tons of sprung mass. Understanding unsprung weight hub motors july 8, 2014 by ted dillard in motors.

In order to improve the ride stability, it is important to keep the tire in contact with the road surface and therefore to decrease the resonance peak near 10 hz, which is the resonance frequency of the wheel also called unsprung mass. The online estimate can be used for vehicle control strategies such as active safety control, traction control, and powertrain control. Skyhook damper modification using fuzzy logic control for. Anyway, im pretty sure you could feel 100lbs increase in unsprung mass.

Nov 17, 2015 rotating mass is what it sounds like, anything that has to rotate when the car goes forward, so for example the steering knuckle is unsprung but doesnt rotate, while the half shaft is rotating but only partly unsprung. Relationship of vehicle weight to fatality and injury risk in model year 198593 passenger cars and light trucks large vehicles have historically been more stable and provided more protection for their own occupants than small ones, but they presented a greater hazard to other road users. Approaches to diminish large unsprung mass negative effects. This includes the frame, body, engine, driver, seats, even the windshield. Sprung mass or sprung weight, in a vehicle with a suspension, such as an automobile, motorcycle, or a tank, is the portion of the vehicles total mass that is supported by the suspension, including in most applications approximately half of the weight of the suspension itself. So in both cases, the engineers try to reduce mass as much as possible. If you dont know what unsprung mass is, dont worry thats what this articles about. Unsprung weight unsprung weight is the mass of suspensions, wheels, brakes, and other components without the support of the suspensions. Unsprung weight reduction is desired not only due to the total vehicle weight reduction but also due to the improvement of tire road grip for better steering control fig and reduction of road noise. Yoshimura2 1technology research and development department komaki, general technology division, central japan railway company jr central, japan 2school of computer science, tokyo university of technology, japan abstract dynamic wheel load variation is one of the major causes of railway track. A dynamical model of engine vehicle was built by using adamscar. To diminish this large unsprung mass negative effects, three approaches suspension and reducer integrated closetowheel drive system, dynamic vibration absorber closetowheel drive system and inwheel drive system with active and energy regenerative suspension are introduced. Report date isbn issn pages cr 3 november 1993 0 642 51061 x 0810 770x 56 title. What is the difference between sprung weight and unsprung.

Sprung weight is the mass of those parts supported by the suspension. The mass of the body and other components supported by the suspension is the sprung mass. Abstract the present thesis work is part of the feasibility study of a lightweight fuelcell urban vehicle named hyrban. Large unsprung weight on a car is a disadvantage as they. It introduces the base excitation model which treats the vertical accelerations at the four unsprung masses as measured inputs to sprung vehicle dynamics and uses the governing equations of these sprung vehicle dynamics for mass estimation. A chassis dynamometer is used to study the unsprung mass of an automobile as illustrated in figure p3. A chassis dynamometer is used to study the unsprung mass of.

Unsprung mass includes tirewheel assembly,brake rotors and calipers or drum and components,wheel bearing,steering knuckle,hanging weight of the control. Based on that, another dynamical model of fourindependentwheeldrive electric vehicle was built too. Active suspension deflection 30% is lower than passive suspension figure4 unsprung mass displacement 0. In a ground vehicle with a suspension, the unsprung mass or the unsprung weight is the mass of the suspension, wheels or tracks as applicable, and other components directly connected to them, rather than supported by the suspension the mass of the body and other components supported by the suspension is the sprung mass. The same software can help car manufacturers to simulate vehicle dynamics and then diagnose any vibration problems. There are components on all vehicles that are both rotating weight and unsprung weight, but the effects are frequently, and improperly, combined and attributed.

For a given combination of vehicle speed, tracksoil conditions and wheelrail irregularity level, reducing the unsprung mass leads to a reduction in contact loads and vibration at frequencies. Jul 08, 2014 understanding unsprung weight hub motors july 8, 2014 by ted dillard in motors. Anyway, im pretty sure you could feel 100lbs increase in. The chassis, because it has so much mass and inertia, resists movement, and this is why in a luxury car where ride comfort is important, mass can be found to be of a high value. Sprung mass estimation for offroad vehicles via base. Pdf analysis of the influence of additional unsprung mass of in. Lightweight wheels can help here, as can replacing cast iron brake discs with twopiece versions, using an aluminium mounting bell, which sits behind the wheel with a cast iron disc bolted to it. Unsprung weight is any component below the suspension springs and shocks on a vehicle. A vehicles total weight is the sum of all of its parts and affects its ability to accelerate, brake and corner. Unsprung mass is a function of the design of a vehicles suspension and the materials used in the construction of suspension components. As for a reduction in unsprung weight independant from rotating mass, this.

In a ground vehicle with a suspension, the unsprung mass or the unsprung weight is the mass. This causes a sensible increase of the unsprung to sprung mass ratio of the car. Vehicle dimensions and mass 2017 may nz transport agency. Almost all of a typical car is sprung weight, because almost every part of it is attached solidly to the body. If you want to talk basics, the whole wheeltirebrake system is called the unsrpung mass of the vehicle that youre driving. The effect of masses in the determination of optimal. Changing the unsprung weight has no direct effect on springing as it. What is unsprung weight in a car and how does lowering. Drive train analysis and vehicle dynamics for the c,mm,n 2. Relationship of vehicle weight to fatality and injury risk. A multibody model to assess the effe ct of automotive. Basically, rotating mass must be accelerated twice every time the car speeds up, it must be accelerated linearly in the direction of the vehicles travel and rotationally in the direction of its spin. Its something you hear people talk about quite often, so heres the difference between sprung and unsprung weight. Two masses approximation for acceleration, braking, and most turning analysis.

Jun 28, 2012 scalable vehicle outlines used by signmakers for designing vehicle signs, livery and wraps. What are the differences between sprung and unsprung weight. Unsprung mass includes the mass of components such as the wheel. Research on the influence of unsprung mass on vehicle. The advantages of minimum unsprung weight are also evident in the smooth working of the vehicle and the consequent safety of the goods being transported.

However, at that time, we did not have a clear idea of which weight among the unsprung, intermediate and sprung mass in a vehicle should be reduced. Sprung mass is the load sitting on top of the springs and unsprung mass is the weight connected to the bottom of the suspension. Given the vehicle pitch rate q the vertical h corner can be obtained vz estimated at the vehicle ed for the observer that rough the vehicle velocity this work, an observer and the vehicle kinematic l sprung mass velocity of s follows. Influence of vehicle unsprungmass on dynamic wheel load m. If it is a rotating part such as a tirerim combo,it will take more hp to accelerate a heavy rotating mass to a specific velocity than a lighter rotating mass. Federal office of road safety document retrieval page report ivo. The sprung weight typically includes the body, frame, the internal components, passengers, and cargo. Full text pdf 5023k abstracts references31 ride comfort and road holding ability of distributed drive electric vehicles are worsened due to large unsprung mass introduced by wheel side drive system. In simple terms, a vehicles sprung weight is supported by springs of one kind of or another coiled springs, air springs, belleville springs.

A multibody model to assess the effe ct of automotive motor. Offroad vehicle sprung mass identification from suspension. If you need to print pages from this book, we recommend downloading it as a pdf. Pdf investigation of equivalent unsprung mass and nonlinear.

Its everything that would move down and up if a giant hand came out. Mathematical modelling and simulation quarter car vehicle. Nm, the shock absorber provides a damping ratio of. Oct, 2017 consider a vehicle which is driving at a speed and it encounters a small bump. Another factor affecting how the wheel will behave is the mass of the components in contact with the road. In this paper, we estimate and discuss this effect by combining the following three methods. Unsprung weight includes the mass of components such as. Unsprung weight sprung weight is a term used to describe the parts of a car that are supported by the front and rear springs. The things that are supported by the suspension like the engine and the passengers are known as the sprung mass. This affects the increase of the unsprung mass of the vehicle. Rotating mass is what it sounds like, anything that has to rotate when the car goes forward, so for example the steering knuckle is unsprung but doesnt rotate, while the half shaft is rotating but only partly unsprung.

It has long been widely accepted that unsprung mass is an important parameter. What is unsprung weight in a car and how does lowering that. Minimization of human body responses due to automobile. Investigation of equivalent unsprung mass and nonlinear features of electromagnetic actuated active suspension. The vehicle mounts four wheel hub electric motors instead of a traditional single motor on the chassis.

Vehicle sprung mass parameter estimation using an adaptive. Compute the maximum magnitude of the center of the wheel due to an impulse of 5000 n applied over 0. As a typical example of our experiments, we lightened the unsprung mass in three cars in a sixcar test vehicle. Sprung mass or sprung weight, in a vehicle with a suspension, such as an automobile, motorcycle, or a tank, is the portion of the vehicles total mass that is. Pdf reducing traininduced groundborne vibration by. What defines sprung and unsprung mass, and which one is. You see that when the vehicle crossed the bump the driver didnot feel the disturbance but the wheel moved up and down. The greater the unsprung mass as opposed to weight, the greater the momentum of that mass at speed. However, a large sprung mass to unsprung mass ratio can also be deleterious to vehicle control. The things that are supported by the suspension like the engine and the. Unsprung weight is a term often thrown around when talking about highperformance cars and racecar chassis engineering and, while most petrolheads grasp the concept that minimised unsprung weight is a good thing, fewer know why or what it actually is put simply, any mass of a vehicle that is not supported by the suspension system is regarded as unsprung weight, while the relatively large.

For ride analysis, wheels are treated as separate lumped masses body mass as sprung mass. Lower unsprung weight improves handling and sometimes traction, while lowering rotating weight improves acceleration. Technical unsprungrotating weight removaldrag car discussion in the hokey ass message board started by redlineracer42, apr 27, 2014. Beam axle suspensions, in which wheels on opposite sides are connected as a rigid unit, generally have greater unsprung mass than independent suspension systems, in which the wheels are suspended and allowed. In this work, a multibody model of a bclass car has been developed in order to assess the effect of motor inwheel configuration on vehicle stability and comfort.

This would include the mass of components such as the wheels, wheel axles, wheel bearings, wheel hubs, tires, portion of the weight of the driveshaft, springs, dampers and brake systems. But that is center of gravity thing, not unsprung mass. Consider a vehicle which is driving at a speed and it encounters a small bump. Sprung weight is everything that is held up by the suspension. In order to improve the ride stability, it is important to keep the tire in contact with the road surface and therefore to decrease the resonance peak near 10 hz, which is the resonance frequency of the. This software has already attracted the attention of the automotive industry and companies such as bmw, daimlerchrysler, rover, bosch and iveco are now using it to develop virtual prototypes of entire cars and heavy goods vehicles. This subtraction sprung and unsprung mass displacement. Every few months a discussion comes up about hub motors and their pros and cons, and as you know if youve been reading this site for a while, im a big fan of the hub motors idea and id. Simulation results indicated that timedomain and frequencydomain characteristics of fourindependentwheeldrive electric vehicle were influenced because of its heavy unsprung mass, and that leaded to the deteriorative handling stability. The figure5 shows that suspension deflection or travel graph. The unsprung masses, by definition, have rigid modes against the sprung mass of the vehicle or the adjacent system. Approaches to diminish large unsprung mass negative. Another unsprung mass phenomenon is that the amplitude of wheel and tire hop becomes greater for less massive unsprung mass, meaning the wheel. Pdf results of simulation research and of some experimental tests on the.