Design Development and Performance Evaluation of Semi-Active Mono-suspension With Regular Swing Arm for Two Wheelers

Abstract

Suspension system is the main part of the vehicle which is used for comfort and for better ride through rough roads . It absorbs shocks and vibration by providing smooth functioning to the vehicle. Suspension is the system of springs, shock absorbers and linkages that which connects a vehicle to its wheels and allows relative motion between the two. Suspension systems serve a dual purpose- contributing to the vehicle's road holding/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. Isolation from the forces transmitted by external excitation is the fundamental task of any suspension system. The suspension has several important functions. So, currently there are different types of suspension in the market. Dual Suspension is the most widely used suspension in two wheeler vehicle. It transfer loads equally to the chassis of the vehicle. There is no any type of harm to this suspension if we increase load on the vehicle. It is widely prefer in the vehicle which is used in rough terrain vehicle. As in rough roads there is continuously changing loads on the vehicle ,so its suspension transfer the load properly to get better ride comfort. The adjustment of this suspension is difficult , Does not provide proper cornering , Ride is compromised at high speed. Traditionally telescopic suspension is used in two wheelers motorcycles with only one Shock Absorber and helical coil springs over it are called mono shock motorcycles. Telescopic forks are replaced by mono shock for better ride comfort, it provides better handling and steering of vehicle increasing life of suspension. Whereas in telescopic suspension there is unequal length distribution while taking turn. Mono shock suspension provides safety while breaking. Mono shock suspension also eliminate torque to the swing arm and provide more consistent handling and breaking. It is also a gas pressurized shock, the piston in the shock is also called as working piston and it moves in relative synchrony inside the pressure tube in response to changes in road smoothness. Length of mono shock absorber is more than the dual shock absorber. Mono shock absorber can be mounted in either way i.e. is does not have any directionality. It does not have any compression valve, whose role has been taken up by dividing piston and the gas in a mono tube shock is under high pressure which can actually help it to support some of the vehicle’s weight. At constant speed as load increases system transmissibility goes on decreasing gradually. Horizontal suspension displacement can be achieved by using a pivoted triangular section. Easier to adjust on the vehicle as there is only one shock to adjust The linkage used to connect the shock to the swing arm are frequently designed to give a rising rate of damping for the rear It has better cornering ability. Semi-active suspensions have been studied in four wheeled vehicles but have not been thoroughly studied in two-wheeled vehicle applications. These systems offer an attractive alternative in comparison to passive suspensions in applications where comfort, handling, or both are desired because of its relatively low cost, energy consumption and improved performance. They have been available in high-end vehicles . A swing arm, or "swinging arm", originally known as a swing fork or pivoted fork, is the main component of the rear suspension of most modern Motorcycles and ATV’s. It is used to hold the rear axle firmly, while pivoting vertically, to allow the suspension to absorb bumps in the road. consumer vehicles (i.e., Cadillac vehicles and Ducati motorbikes but are often underutilized in case of two wheelers It is underlined that the application of semi-active suspensions focused on competition performances has not been fully addressed in case of two wheeler automobiles.

Keywords

Introduction

Active or adaptive suspension is an automotive technology that controls the vertical movement of the wheels with an onboard system rather than the movement being determined entirely by the road surface. The system virtually eliminates body roll and pitch variation in many driving situations including cornering, accelerating, and braking.This technology allows car manufacturers to achieve a greater degree of ride quality and car handling by keeping the tires perpendicular to the road in corners, allowing better traction and control.

Methods of Active Suspension

Active suspensions can be generally divided into two main classes: pure active suspensions and semi-active suspensions.

Active: Active suspensions, the first to be introduced, use separate actuators which can exert an independent force on the suspension to improve the riding characteristics. The drawbacks of this design (at least today) are high cost, added complication/mass of the apparatus, and the need for rather frequent maintenance on some implementations. Maintenance can be problematic, since only a factory-authorized dealer will have the tools and mechanics with knowledge of the system, and some problems can be difficult to diagnose.

Hydraulic actuated: Hydraulically actuated suspensions are controlled with the use of hydraulic servomechanisms. The hydraulic pressure to the servos is supplied by a high pressure radial piston hydraulic pump. Sensors continually monitor body movement and vehicle ride level, constantly supplying the computer with new data.

As the computer receives and processes data, it operates the hydraulic servos, mounted beside each wheel. Almost instantly, the servo-regulated suspension generates counter forces to body lean, dive, and squat during driving manoeuvers.

In practice, the system has always incorporated the desirable self-levelling suspension and height adjustable suspension features, with the latter now tied to vehicle speed for improved aerodynamic performance, as the vehicle lowers itself at high speed.

Colin Chapman - the inventor and automotive engineer who founded Lotus Cars and the LotusFormula One racing team - developed the original concept of computer management of hydraulic suspension in the 1980s to improve cornering in racing cars. Lotus developed a version of its 1985 Excel model with electro-hydraulic active suspension, but this was never offered to the public.

Computer Active Technology Suspension (CATS) co-ordinates the best possible balance between ride and handling by analysing road conditions and making up to 3,000 adjustments every second to the suspension settings via electronically controlled dampers.

Electromagnetic recuperative

This type of active suspension uses linear electromagnetic motors attached to each wheel. It provides extremely fast response, and allows regeneration of power consumed by utilizing the motors as generators. This nearly surmounts the issues of slow response times and high-power consumption of hydraulic systems. It has only recently come to light as a proof of concept model from the Bose company, the founder of which has been working on exotic suspensions for many years while he worked as an MIT professor. Electronically controlled active suspension system (ECASS) technology was patented by the University of Texas Centre for Electro mechanics in the 1990s and has been developed by L-3 Electronic Systems for use on military vehicles. The ECASS-equipped HMMWV exceeded the performance specifications for all performance evaluations in terms of absorbed power to the vehicle operator, stability and handling.

Semi-active

Semi-active systems can only change the viscous damping coefficient of the shock absorber, and do not add energy to the suspension system. Though limited in their intervention (for example, the control force can never have different direction than that of the current speed of the suspension), semi-active suspensions are less expensive to design and consume far less energy. In recent times, research in semi-active suspensions has continued to advance with

respect to their capabilities, narrowing the gap between semi-active and fully active suspension systems.

Solenoid/valve actuated

This type is the most economic and basic type of semi-active suspensions. They consist of a solenoid valve which alters the flow of the hydraulic medium inside the shock absorber, therefore changing the damping characteristics of the suspension setup. The solenoids are wired to the controlling computer, which sends them commands depending on the control algorithm (usually the so called "Sky-Hook" technique). This type of system used in Cadillac's Computer Command Ride (CCR) suspension system.

Magneto rheological damper

Another fairly recent method incorporates magneto rheological dampers with a brand name MagneRide. It was initially developed by Delphi Corporation for GM and was standard, as many other new technologies, for Cadillac Seville STS (from model 2002), and on some other GM models from 2003. This was an upgrade for semi-active systems ("automatic road- sensing suspensions") used in upscale GM vehicles for decades. It allows, together with faster modern computers, changing the stiffness of all wheel suspensions independently. These dampers are finding increased usage in the US and already leases to some foreign brands, mostly in more expensive vehicles. In this system, being in development for 25 years, the damper fluid contains metallic particles. Through the onboard computer, the dampers' compliance characteristics are controlled by an electromagnet. Essentially, increasing the current flow into the damper raises the compression/rebound rates, while a decrease softens the effect of the dampers. Information from wheel sensors (about suspension extension), steering, acceleration sensors and some others is used to calculate the optimized stiffness. The fast reaction of the system allows, for instance, make softer passing by a single wheel over a bump in the road.

CONCLUSION:

The proposed research work will bring forward the significance and utility of the mono suspension in semi-active or active mode to improve the damping ability of the suspension system along with increase in ride comfort and vehicle stability.

The socio-economic aspect of the project outcome being , development of two wheeler suspension that is adaptable to all road conditions giving equal ride comfort on the city road as well as the village roads , and also the potential to employment growth through the commercial production of the newly developed system.

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