DRIVE BY WIRE SYSTEM

DRIVE BY WIREK Ganesh babuRoll No: 701413Research scholarCONTENTSIntroductionHistoryWorking principle of drive by wireDrive by wire sub-systemsAdvantages of drive by wireDisadvantages of drive by wireINTRODUCTIONEmerging technology in the automotive environmentReplaces the conventional mechanical control systems with electronic control systemsIntermediate shafts, pumps, hoses, belts, coolers and master cylinders are eliminated.System reduce the number of moving partsThe brain of Drive by wire or Hy-Wire is a central computer housed in the middle of the chassis. HISTORY OF DRIVE BY WIRE1995 BMW technic, began work on project Z22 to change carbon fiber structures to Drive by wire.12 Jan 1998 aircraft technology using computerized joystick.Jan 2002 - Hy-wire car from General Motors.16 Nov 2009 - Wire De-assault Systems Solid Works release.10 Feb 2010 Introduced sensor for pedal.WORKING PRINCIPLE OF DRIVE BY WIREairplanes have used systems called "fly-by-wire" since the 1990s. "fly-by-wire just like drive-by-wire, uses electrical wires to control the normal operations of a plane. How does drive-by-wire in a car work? How can drivers speed up, slow down and steer with just a network of wiresWorks by electro mechanical control system.Drive-by-Wire replaces mechanical connections push rods, rack & pinion, steering columns, overhead cams, cables by mechatronic connections sensors, actuators, embedded microprocessors, control softwareMain controlling system is Engine control module (ECM)Sensors Send signals to ECM and actuators actuatesECM controls the signals and sends the signals to the suitable sub systemsCont.ENGINE CONTROL MODULEEngine control module (ECM) is one of the Electronic control unit (ECU), it is the main control unit.ECM controls the actuators after receiving signals from sensors for doing required task.Engine control module is heart of the system.ECM must have quick response in emergency.

8Hand WheelECUAccelelatorPedalECUSteeringECUTractionECUControlECU(CommandConditioning,Vehiclemanagementunder faults)Steering CommandSteering ReferenceForce Feedback ReferenceSpeed CommandSpeed ReferenceSteering AngleVehicle SpeedDrive StatusSteering StatusFrom Dashboard ECUDRIVE BY WIRE CONTROL ARCHITECTURECOMPONENTS USED IN DRIVE BY WIRE

DRIVE BY WIRE SUB-SYSTEMS

DRIVE BY WIRE CONCEPTUALIZATION

DRIVE BY WIRE SUB-SYSTEMS12WORKING OF STEER BY WIRE No direct mechanical connection between the steering wheel and the wheels of the vehicleAngle of the steering rod is sensed by the sensorECM receives signal of sensorElectric motor that controls the steering angle of the wheelsEnvironmental sensors analyses environmental factors like Yaw, roll over positionUsing all these inputs tires are actuated using steering sensors and actuators.STEER BY WIRE BLOCK DIAGRAMTorque InputControl UnitDC MotorRack /pinion gearTire/wheel assembly

Steer By WireSteering Wheel SubsystemController SubsystemFront Wheel SubsystemSteering Wheel MotorTorque SensorSteering Angle SensorSteering Actuator (Motor)Rack / Pinion GearTire-Wheel subsystemSteering ColumnTie rodControl UnitReactive torqueControl PathCOMPARISON BETWEEN CONVENTIONAL AND SBW SYSTEM

SBW ADVANTAGESNo steering column Simplify the design of a cars interior, giving the driver more space as well as better safety in case of a crash (no intrusion of the steering column).The absence of steering shaft and gear reduction mechanism allows much better utilization of the engines compartment.Decreases the total weight of the car issuing better energy reduction effectiveness.Easier implementation of left or right-hand driving.No noise or vibration can reach the drivers hands.The most significant benefit is the ability to electronically augment the drivers steering input depending of drives conditions, also called active steering.

BLOCK DIAGRAM OF AN ETC OR THROTTLE BY WIRE

THROTTLE BY WIRE CONCEPTUALIZATION

WORKING OF THROTTLE BY WIREElectronic throttle control are also known as throttle-by-wire systemsThe Throttle is a butterfly valve, housed in a Throttle body.The Throttle body is located between the Air filter box and the intake manifold.In conventional throttle system, the valve is mechanically linked with the throttle pedal or lever. In Electronic throttle Control (ETC), the valve is electronically controlled that allows Engine Control Unit (ECU) to reduce air emissions

ContThrottle by wire is widely used on automotive vehicles todayReplaces the traditional throttle linkage by cablesAccelerator pedal sensor senses the position of the accelerator pedal.ECM actuates a servo-pump, which actuates the butterfly valve by electronically operated throttlePosition of the throttle is continuously monitored by ECMInformation is conveyed to the ECM using a feedback circuitTHROTTLE BODY LOCATION IN AN ENGINE

Intake manifoldElectronic Throttle bodyAir filter duct

Electronic Throttle bodyThrottle plate or Butterfly valve

Throttle or Butterfly valveCONVENTIONAL THROTTLE SYSTEMTHROTTLE BY WIRE Throttle by wire (TBW) systems is same as Electronic throttle control (ETC)

Basic components in ETC are A position sensor on the accelerator pedal that detects the driver requirements An electronically controlled throttle body with a small electric motor to open / close the throttle. An Engine Control Unit (ECU) determines and positions the air valve the appropriate position through the use of a motor

ECU I/P Pedal Sensor I/P

Throttle Feedback ETC COMPONENTS1. Accelerator Pedal Module A potentiometer or contact-free sensor registers the exact position of the accelerator pedal. A high degree of mechanical precision is guaranteed with very little pedal play & minimal tolerances.

Pedal Sensor2. Electronic Control Unit (ECU)This high power microcontroller controls the cylinder charge, the fuel injection & ignition. Sensors register the operating status, and all the relevant influencing variables. Any deviations are immediately detected by the integrated On-Board Diagnostics.

ECU circuit3. Electronic Throttle Body (ETB)Based on the position of the accelerator pedal, the ECU calculates the required throttle valve opening, the ignition angle and the quantity of fuel to be injected. A DC motor actuates the throttle valve shaft through gearing. The throttle position sensor monitors the valve position & thus permits the position to be precisely maintained

Electronic Throttle BodyETB (showing internal parts)

3.1 Throttle Position Sensor (TPS) TPS is a feedback device that informs the ECU about the rate of throttle opening and relative throttle position. It is mounted externally on the throttle shaft of ETB. TPS is a variable resistor that changes resistance as the throttle opens & signals the ECU which then richen up the fuel mixture to maintain the proper air / fuel ratio.

Throttle Position SensorExploded view of an ETB

DC MotorThrottle BoreThrottle PlateThrottle ShaftMain Throttle gearIdler gearThrottle gasketThrottle body or HousingReturn springPinion Spur gearAdjusting screwBore axis

Assembled view of an ETBGear trainThrottle plateDC Motor actuatorThrottle Body (or) HousingThrottle Position Sensor mountedon throttle shaft

ADVANTAGES OF THROTTLE BY WIREImproved performances, efficiency and lower emissionNo requirement of bypass valve.Eliminates vibrations.Flexibility in designDISADVANTAGES OF THROTTLE BY WIREHigh Vehicle cost.Malfunctioning of ECU might cause vehicle to stop.WORKING OF BRAKE BY WIRE Brake by wire eliminates traditional mechanical and hydraulic components.Replaces them with electronic sensors and actuators to control the brakes in vehiclesIt offers enhanced safety and comfort, cuts off cost associated with manufacturing and maintenance, and eliminates environmental concerns caused by hydraulic systemsConsists of a rheostat that senses the position of the brake pedal

BRAKE BY-WIRE CIRCUIT

CONVENTIONAL BRAKING SYSTEM

Design freedom Almost arbitrary cockpit design is possible with a comprehensive drive-by-wire system Inputs can be reduced to hand controls. Could be useful for disabled drivers

Adaptability Controls can be programmed to suit driver preferences. For example throttle/brake pressures, steering wheel angles Driver position does not need to be fixed. Controls could be designed to be easily moved to adapt to different countriesDRIVE BY WIRE ADVANTAGES The cost of Drive by Wire systems is often greater than conventional systems. The extra costs stem from greater complexity, development costs and the redundant elements needed to make the system safe. Failures in the control system could theoretically cause a runaway vehicle (although this is no different to the throttle return spring snapping on a traditional mechanical throttle vehicle). The vehicle could still be stopped by turning the ignition off if this is occurred. Manufacturers often reduce throttle sensitivity in the low-mid throttle range to make the car easier or safer to control - or to protect the drive train (gearbox, clutch, etc) from driver abuse. The feeling to the driver is that the throttle feels less responsive. DISADVANTAGES Considerable safety improvements are possible Conventional steering column and pedals are dangerous for the driver in the event of an accident Electro mechanical systems have potential to be more reliable than conventional hydraulic/mechanical systems Increased presence of control allows for the introduction of more safety systems, for example a collision avoidance systemSAFETY ASPECTS

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