ELECTRONICALLY MANAGED SUSPENSION introduction system overview sensors and control mechanisms checking procedures tmc

ELECTRONICALLY MANAGED SUSPENSION Introduction The purpose of any suspension system is to ease the shock of the road surface. To improve riding comfort and stability. To help the tyres hold the road. Before we talk about active type suspension systems, lets think about some basic 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 generated by friction between road and wheels to the vehicles body. Transports body on axles and maintains proper relationship between body and wheels.

ELECTRONICALLY MANAGED SUSPENSION Shock Absorbers - Purpose To improve ride handling and comfort by quickly damping oscillations of the springs (up and down movement). Help tyres hold the road better. A M P L I T U D E With shock absorbers. Without shock absorbers. TIME

ELECTRONICALLY MANAGED SUSPENSION Action of the shock absorber and springs.

ELECTRONICALLY MANAGED SUSPENSION On electronic systems shock absorbers must reconcile 2 requirements. 1 = passenger comfort, for which dampening should be soft (85% of use). 2 = performance dampening that should be hard.

ELECTRONICALLY MANAGED SUSPENSION

ELECTRONICALLY MANAGED SUSPENSION Upper Wishbone Shock Absorber Spring Lower Wishbone

ELECTRONICALLY MANAGED SUSPENSION Shock Absorbers - Types Single action shock absorber. Damping only occurs when the shock absorber is extended. When the shock absorber is compressed no damping force is generated.

ELECTRONICALLY MANAGED SUSPENSION Orifice Valve Fluid

ELECTRONICALLY MANAGED SUSPENSION Valve is now open, fluid flows from the lower chamber through the now open valve and the orifice. The flow resistance of the fluid moving through the orifice creates a damping force.

ELECTRONICALLY MANAGED SUSPENSION Multi action shock absorbers. Damping occurs when the shock absorber is extended and when it is compressed.

ELECTRONICALLY MANAGED SUSPENSION Twin tube shock absorbers. Cylinder divided by pressure tube and outer tube into working chamber (inner cylinder) and reservoir chamber (inner chamber). When the piston is forced down, oil which is incompressible flows through a check valve and damps the descent of the piston. This process is reversed during rebound. As the plunger enters the cylinder an equivalent amount of oil enters the reservoir between the jacket and the cylinder.

ELECTRONICALLY MANAGED SUSPENSION Gas filled shock absorbers: Charged with mainly Nitrogen gas. There are 2 main types: Low pressure - 142 to 213 psi. High pressure - 284 to 427 psi. The smaller the check valves the stiffer the shock absorber. The larger the valves the softer the shock absorber.

ELECTRONICALLY MANAGED SUSPENSION Normal

ELECTRONICALLY MANAGED SUSPENSION Dive - braking

ELECTRONICALLY MANAGED SUSPENSION Pitch - acceleration

ELECTRONICALLY MANAGED SUSPENSION Pitching can also occur when the vehicle has gone over a hump or obstacle in the road and continues to oscillate.

ELECTRONICALLY MANAGED SUSPENSION The roll caused by an evasive manoeuvre or rapid lane changing.

ELECTRONICALLY MANAGED SUSPENSION Dive - braking Normal Pitch - acceleration Pitching Roll

ELECTRONICALLY MANAGED SUSPENSION Due to the fact that the check valves size, will determine the stiffness of the suspension conventional systems have to either have a balance between the two or be one or the other. Electronically controlled systems have the major advantage of being able to deliver both. It can alter the stiffness of the shock absorbers in a fraction of a second depending upon driving style and road profile.

ELECTRONICALLY 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.

ELECTRONICALLY MANAGED SUSPENSION Actuator, rotates clockwise and anti clockwise. Channel closed damping is heavy. SPORT position.

ELECTRONICALLY MANAGED SUSPENSION Actuator, rotates clockwise and anti clockwise. Channel open damping is soft. COMFORT position.

Drivers selector switch ELECTRONICALLY MANAGED SUSPENSION Inputs for system requirements. Outputs from the control unit. Steering angle sensor Damper motor n/s/f Yaw / pitch sensor Electronic Control Unit Damper motor o/s/f Brake pressure switch Damper motor n/s/r Pedal potentiometer Damper motor o/s/r Vehicle speed sensor Drivers selector switch

ELECTRONICALLY MANAGED SUSPENSION The speed sensor is an inductive device. PERMANENT MAGNET SOFT IRON CORE WINDING It is a tiny alternator that produces an AC waveform.

ELECTRONICALLY MANAGED SUSPENSION The steering wheel sensor. This is mounted on the steering column and informs the ECU of conditions that could induce roll.

ELECTRONICALLY MANAGED SUSPENSION The steering wheel sensor. This measures the steering wheel angle and the speed in which it is rotated. It consists of a Phonic wheel fitted to the steering column. The sensor itself consists of 2 LED’s and 2 photo transistors. The phonic wheel turns with the steering wheel and blocks or allows the light through to the transistors.

ELECTRONICALLY MANAGED SUSPENSION Yaw /pitch sensor - this measures suspension movement that may induce pitching or yawing movement. Its mounted on the front sub - frame and connected by a link to the anti - sway bar. During suspension travel the anti sway bar actuates the link. The link drives a notched phonic wheel that blocks or allows through light from 4 LED’s. The trim height is calculated from the succession of signals. SBY - LED’s

ELECTRONICALLY MANAGED SUSPENSION Yaw / Pitch sensor. The trim height is calculated from the succession of signals. SBY - LED’s

ELECTRONICALLY MANAGED SUSPENSION Pedal potentiometer. This evaluates the risk of front end lift or dive. It delivers 2 types of information: The rate which the pedal is being operated. The amplitude of any acceleration or deceleration.

ELECTRONICALLY MANAGED SUSPENSION The brake pressure sensor limits dive. It consist of a switch that when the pressure exceeds 15 bars it opens the circuit. What does the ECU do with this information? The ECU has basic maps programmed into it’s memory with reference points for all the sensors.

ELECTRONICALLY MANAGED SUSPENSION What does the ECU do with this information? Steering Angle Angular Velocity of the Steering Wheel O/S O KM/H KM/H

ELECTRONICALLY MANAGED SUSPENSION Body Height Amplitude of acceleration H 5 4 3 O/S KM/H KM/H

ELECTRONICALLY MANAGED SUSPENSION Amplitude and rate of deceleration Braking pressure O/S Bar 15 KM/H KM/H

ELECTRONICALLY MANAGED SUSPENSION Consider the reference point for the steering wheel angle. It defines 2 zones a green zone and a blue zone. Steering Angle The vehicle is travelling at the same speed but now enters a sharp bend with a steering angle of 15°. It is now in the blue zone. Sport position. O The vehicle enters a large radius bend at 90km/h and a steering angle of 90°. The point P is in the green zone normal ride dampening. 15 5 15 5 P P 90 90 KM/H

ELECTRONICALLY MANAGED SUSPENSION The ECU sends a signal 150 m/s long to the shock absorbers when point P is in the blue zone. The valves of the 4 shock absorbers close changing to the sport position.

ELECTRONICALLY MANAGED SUSPENSION When the ECU senses a stable condition for at least 2 seconds it sends a signal 300 m/s long which closes the actuators in the shocks. These valves remain closed for as long as point P stays in the blue zone. If a fault is detected in the systems the ECU forces all the valves closed - sport position.