Presentation on theme: "ELECTRONICALLY MANAGED SUSPENSION"— Presentation transcript:
1ELECTRONICALLY MANAGED SUSPENSION introductionsystem overviewsensors and control mechanismschecking procedurestmc
2ELECTRONICALLY MANAGED SUSPENSION IntroductionThe purpose of any suspension system is to ease the shock of the roadsurface.To improve riding comfort and stability.To help the tyres hold the road.Before we talk about active type suspension systems, lets think about somebasic systems. Functions:Connects the body of the vehicle to the wheel assembly.Absorbs and damps vibrations and shocks.Protects passengers and cargo.Transmits driving and braking forces generatedby friction between road and wheels to the vehiclesbody.Transports body on axles and maintains properrelationship between body and wheels.
3ELECTRONICALLY MANAGED SUSPENSION Shock Absorbers - PurposeTo improve ride handling and comfort by quicklydamping oscillations of the springs (up and downmovement).Help tyres hold the road better.AMPLITUDEWith shockabsorbers.Without shockabsorbers.TIME
4ELECTRONICALLY MANAGED SUSPENSION Action of the shockabsorber and springs.
5ELECTRONICALLY MANAGED SUSPENSION On electronic systems shock absorbers must reconcile 2 requirements.1 = passenger comfort, for whichdampening should be soft(85% of use).2 = performance dampening thatshould be hard.
8ELECTRONICALLY MANAGED SUSPENSION Shock Absorbers - TypesSingle action shock absorber. Dampingonly occurs when the shock absorberis extended. When the shock absorberis compressed no damping force isgenerated.
10ELECTRONICALLY MANAGED SUSPENSION Valve is now open, fluid flows from thelower chamber through the now openvalve and the orifice.The flow resistance of the fluid movingthrough the orifice creates a dampingforce.
11ELECTRONICALLY MANAGED SUSPENSION Multi action shock absorbers.Damping occurs when the shockabsorber is extended and whenit is compressed.
12ELECTRONICALLY MANAGED SUSPENSION Twin tube shockabsorbers.Cylinder divided bypressure tube and outertube into working chamber(inner cylinder) andreservoir chamber (innerchamber).When the piston is forceddown, oil which isincompressible flowsthrough a check valve anddamps the descent of thepiston. This process isreversed during rebound.As the plunger enters thecylinder an equivalentamount of oil enters thereservoir between the jacketand the cylinder.
13ELECTRONICALLY MANAGED SUSPENSION Gas filled shock absorbers:Charged with mainly Nitrogen gas.There are 2 main types:Low pressure to 213 psi.High pressure to 427 psi.The smaller the check valves thestiffer the shock absorber.The larger the valves the softerthe shock absorber.
20ELECTRONICALLY MANAGED SUSPENSION Due to the fact that the check valves size, willdetermine the stiffness of the suspensionconventional systems have to either have a balancebetween the two or be one or the other.Electronically controlled systems have the majoradvantage of being able to deliver both.It can alter the stiffness of the shock absorbers in afraction of a second depending upon driving styleand road profile.
21ELECTRONICALLY MANAGED SUSPENSION How does it work?The twin tube shock absorber contains the following:Hollow plunger.Actuator.16,000 rpm miniature electric motor.Reduction gear train, ratio 46 : 1.Torque limiter to cut power to the motor.Rotary valve.
23ELECTRONICALLY MANAGED SUSPENSION Actuator, rotates clockwise andanti clockwise.Channel open damping is soft.COMFORT position.
24Drivers selector switch ELECTRONICALLY MANAGED SUSPENSIONInputs for systemrequirements.Outputs from thecontrol unit.Steering angle sensorDamper motor n/s/fYaw / pitch sensorElectronicControlUnitDamper motor o/s/fBrake pressure switchDamper motor n/s/rPedal potentiometerDamper motor o/s/rVehicle speed sensorDrivers selector switch
25ELECTRONICALLY MANAGED SUSPENSION The speed sensor is an inductive device.PERMANENTMAGNETSOFT IRON COREWINDINGIt is a tiny alternator thatproduces an AC waveform.
26ELECTRONICALLY MANAGED SUSPENSION The steering wheel sensor.This is mounted on thesteering column and informsthe ECU of conditions that couldinduce roll.
27ELECTRONICALLY MANAGED SUSPENSION The steering wheel sensor. This measures the steering wheel angle andthe speed in which it is rotated.It consists of a Phonicwheel fitted to thesteering column.The sensor itself consistsof 2 LED’s and 2 phototransistors.The phonic wheelturns with thesteering wheel andblocks or allowsthe light through tothe transistors.
28ELECTRONICALLY MANAGED SUSPENSION Yaw /pitch sensor - this measures suspension movement that mayinduce pitching or yawing movement.Its mounted on the front sub - frame and connected by a link to the anti - swaybar.During suspension travel the anti sway bar actuates the link. The link drivesa notched phonic wheel that blocks or allows through light from 4 LED’s.The trim height iscalculated from thesuccession of signals.SBY - LED’s
29ELECTRONICALLY MANAGED SUSPENSION Yaw / Pitch sensor.The trim height iscalculated from thesuccession of signals.SBY - LED’s
30ELECTRONICALLY MANAGED SUSPENSION Pedal potentiometer.This evaluates the risk of front end lift ordive.It delivers 2 types of information:The rate which the pedal is being operated.The amplitude of any acceleration or deceleration.
31ELECTRONICALLY MANAGED SUSPENSION The brake pressure sensor limits dive.It consist of a switch that when the pressure exceeds 15 bars it opensthe circuit.What does the ECU do with this information?The ECU has basic maps programmedinto it’s memory with reference pointsfor all the sensors.
32ELECTRONICALLY MANAGED SUSPENSION What does the ECU do with this information?Steering Angle Angular Velocity of the Steering WheelO/SOKM/H KM/H
33ELECTRONICALLY MANAGED SUSPENSION Body Height Amplitude of accelerationH543O/SKM/H KM/H
34ELECTRONICALLY MANAGED SUSPENSION Amplitude and rate of deceleration Braking pressureO/SBar15KM/H KM/H
35ELECTRONICALLY MANAGED SUSPENSION Consider the reference point for the steering wheel angle. It defines2 zones a green zone and a blue zone.Steering AngleThe vehicle is travellingat the same speed but nowenters a sharp bend witha steering angle of 15°.It is now in the blue zone.Sport position.OThe vehicle enters a largeradius bend at 90km/h anda steering angle of 90°.The point P is in the green zonenormal ride dampening.155155PP9090KM/H
36ELECTRONICALLY MANAGED SUSPENSION The ECU sends asignal 150 m/s longto the shock absorberswhen point P is in theblue zone.The valves of the4 shock absorbersclose changingto the sport position.
37ELECTRONICALLY MANAGED SUSPENSION When the ECUsenses a stablecondition for atleast 2 seconds itsends a signal300 m/s long whichcloses the actuatorsin the shocks.These valves remainclosed for as long aspoint P stays in theblue zone.If a fault is detectedin the systems theECU forces all the valvesclosed - sport position.