--: ABSTRACT :--
Mechatronics, a concept of Japanese origin was first introduced during the early 1970's to qualify the dual alliance of electronics and computer technology to practical control application in Mechanical Engg. system.
The Japanese were very quick to exploit the advantages of this integrated technology through their consumer products while other are yet adopting this concept to realize it's benefits.
The combination of Mechanical, electronics and information technology is optimized to take full advantage of the ability of microelectronics to reduce the demand of mechanical system of a product. High technology CNC m/c, Robots, automated manufacturing systems are truly mechatronics product.
Definition :-- "Mechatronics is an aynergitics combination of precision mechanical engg., electronics control and systems thinking in design of product and manufacturing process."
---- IEEE Spectrum ----
It represents the next generation machine robots and smart mechanism for carrying out work in variety of environments,- predominantly factory automation, office automation and home automation as shown in fig.1.1
Evolution of Mechatronics :--
Mechanical engg. Mechanization Electro Mechanical System
Electrical Tech Electronics IT & software
Fig. Evolution of Mechatronics.
Features : -
4. Computer Integrated Manufacturing
This concept of mechatronics is giving or representing the machines of next generation .
Â¢ Use of electronics in this field of mechanical is to provide high level of precision and reliability.
Â¢ Use of mechanical in this field of electronics is to provide new functions and capabilities.
What is it IS it a need or development
Itâ„¢s a need of todayâ„¢s world . There are few advantages of mechanical which will gives us the service but the extent of fulfillment will not be there . The precision will not be there . Hence mechanical is having some limit . The same is with others e.g. Electronics and computer field.
NEED OF INDUSTRILISTS :--
To gain much money with short time and fulfilling customers need is :
1. Low volume
2. More variety
3. High level of flexibility
4. Reduced lead time in production
5. Automation in office and work stations
In order to produce quality international standers , the industries must excel in this technology: MECHATRONICS. And training and basic knowledge of this is new to student and engg. field to get success.
Just in time [JIT] concept is one of the principle of this mechatronics. Low cost, high service, total transport is the goal of each company which will help in achieving high benefits from a product everyone related with it.
In general in each field to achieve automation three things are used :
1. SYSTEM : --System is defined as part of universe which is taken under study or application .
Fig: An example of system
2. MEASUREMENT:-- It has itâ„¢s I/p as the quantity being measured and output as measured.
Fig: Fig : an example of measurement. 3. CONTROL SYSTEM :-- It is a block which is used to control its output to me particular value or
Fig : Control system
An electronics measurement system consists of
1. Sensor: -- which responds to the quantity being measured by giving as output a signal which is deleted to quantity .
2. Signal Conditioner :-- Takes the signal from the sensor and manipulates it into a condition which is suitable for either display or in the exercise control.
Microprocessor based controller :--
Microprocessor is now rapidly replacing the mechanical cam operated controllers and being used in general to carry out control function . They have greatest advantage that a greater variety of programs become feasible. In many simple systems there might be just an embedded microcontroller, this being a microprocessor with memory all integrated on one cheep , which has been basically / specially programmed for the task concerned.
A more adoptable form is programmable logic controller. This is a microprocessor based controller which uses a programmable memory to store instruction and to implement functions such as logic, sequence, timing counting and arithmetic to control events and can be rapidly reprogrammed for other task.
B PLC Q
Fig: 1.3 shows logic controller basic structure.
Example of microprocessor based control system ::--
I.C. Engine mgmt using microprocessor::--
Electronic engine mgmt is a new technology which is a part of mechatronics for efficient operation of ËœSPARK IGNITION Ëœ particularly for four stroke passenger car. In this system many sensors are used to monitor various conditions of engine. These signals are feed to the microcontrollers of Electronics Control Unit [ECU] Through analog to digital controllers. This micro-controller uses from sensor to determine the engine momentary operating conditions. This information serves the basic for EUC command signal, which are amplified by power o/p stages before being transmitted to final control elements used in this system.
BASIC FUNCTIONS ::--
The control of ignition and fuel injection process is at the core of motronic system.
Â¢ Idle speed control
Â¢ Lambda oxygen control
Â¢ Control of evaporative emission control system.
Â¢ Knock system control
Â¢ Exhaust gas recirculation(E.G.R.) for reducing NOx emission
Â¢ Control of secondary air injection to reduce HC emission
The system can also be expanded to meet special demands from automobile manufacturing by including the following :-
Â¢ Open loop turbo charger controller as well as control of variable track intake manifold for increased power output.
Â¢ Vehicle high speed governing to protect vehicle
Fig. 1.4. shows schematic configuration of electronic engine management system. This can be employed to satisfy
Â¢ Stringent emission control unit
Â¢ The requirement for an Onboard diagnosis system
ELECTRONIC FUEL INJECTION SYSTEM FOR S.I.ENGINE
The function of the carburetor or fuel injection system is to supply with the optimum air fuel mixture for instantaneous operating conditions. But it has few drawbacks as mentioned below::-
1. Induction passage of carburetor is of unequal length and after different resistance to mix flow which varies mixture to cylinders in both quality and quantity.
2. Condensation in induction manifold.
3. They do not have free passage for mixture due to choke tube jet etc. parts causing loss of volumetric efficiency.
4. Freezing problem in low temperature.
5. Wearing parts affect efficiency.
6. Surging problem due to tilting, sometimes.
7. Problem of backfiring.
To eliminate these problems and to achieve reduced fuel consumption as well as reduction exhaust emission Fuel injection system presents the preferred method. It is a development accelerated by the advantages that inject in the fuel provides in the area of economy, performance, drivability and low exhaust emission.
Fuel injection can be applied for extremely precise metering, supplying exactly correct amount of fuel for given operating and load condition with minimum exhaust emission and fuel consumption.
-: ADVANTAGES OF FUEL INJECTION :-
1. Reduced fuel consumption
2. Improved performances
3. Immediate response of acceleration
4. Improved cold starting and warm up behavior
5. Low exhaust emission
System and configuration and general working : -
Fig. shows the electronic fuel injection system by Robert Booch Co.
The L-Jetronics package consists of mainly four units
1. Fuel induction system
2. Air induction system
3. Sensors and air flow control system
1. FUEL DELIVERY SYSTEM :--
The fuel delivery system consists of an electrically driven fuel pump which draws fuel from the fuel tank and forces it through a filter in to a pressure line at the end of which is situated a pressure regulator. The pressure regulator is connected to intake manifold . The pressure difference between the fuel pressure and manifold is kept constant so that the quantity of fuel injected is dependent on injector open time.
2. AIR INDUCTION SYSTEM :--
The incoming air flows from air filter past in air flow meter designed to generate a voltage signal which is dependent on air flow.
A cold start magnetic injection valve just behind the throttle valve to inject additional fuel for cold start of the cold start, injection valve is controlled by a thermo switch to insure cold starting up to -33 C. The fuel needed during warm up period is also supplied by this valve.
After cold start the extra air required for idling in additional to richer air fuel mixture is supplied by an auxiliary air valve which bypasses the throttle valve. The extra air needed to increase engine speed after cold start to acceptable idling speed. The opening of air valve varies as a function of engine temperature.
Attached to throttle valve is a throttle switch equipped with a set of contacts which generate a sequence of voltage signals during opening of throttle valve. The voltage signals results in injection of additional fuel required for acceleration.
ELECTRONIC CONTROL UNIT (E.C.U.)
The operating data are measured at different locations of the engine by sensors and then transmitted electrically to the ECU which computes the amount of fuel injected during each cycle.
Â¢ INJECTION TIME :--
The fuel is injected for every revolution of camshaft, each injection contributing half of fuel quantity required. For engine cycle such a system simplifies triggering of injectors because no co-ordination between angular position of camshaft and start of injection is needed. The injectors are opened simultaneously although, with reference to individual cylinders, at different phase of operating cycle.
Â¢ ELECTROMAGNETIC INJECTOR :--
The electromagnetic injector consists of a solenoid armature mounted on a valve needle and travels through precise motions within the valve. When the unit is at rest, a coil spring presses the valve needle against the seat to seal the flow of fuel through the outlet orifice and into the intake manifold. When the control transmits activation current to the solenoid winding in the valve housing the solenoid armature raises between 60-100 micron, lifting the valve needle in the process, the fuel can now flow through the calibrated orifice. The response time lies between 1.5-1.8 ms at a control frequency 3-125 Hz, depending upon the type of injection and momentary engine speed and load condition.
--: OPERATING DATA ACQUISITION :--
1. ENGINE LOAD :-- One of the most important variables used for determining injection quantity and ignition advance angle is the engine load state (Load Monitoring).
2. TYPES OF LOAD SENSORS :--
Â¢ Air flow sensor
Â¢ Hot film air mass sensor
Â¢ Hot wire air mass sensor
Â¢ Intake manifold pressure sensor
Â¢ Throttle valve sensor
3. AIR FLOW SENSOR :- -It is located between air filter and the throttle valve where it monitors volumetric flow rate(m3/hr) of the air being drawn into the engine.
4. AIR MASS METER ::- The hot wire, air mass meter are both thermal load sensors. They are installed between air filter and throttle valve.
1. Improved Quality .
2. Reduced cost in maintenance and working.
3. Reduced lead time.
4. Accuracy of high level.
5. Reliability in the work/production.
6. Increased productivity.
7. High degree of flexibility.
1. High capital cost.
2. Error due to sensors and electronic devices which are negligible.
3. Necessity of diagnosis system to prevent failure of this system during running condition as no standby system is available.(some exceptional design could be there)
An electrically heated element is mounted in the intake air stream, where it is cooled by the flow of incoming air at a constant level. A control modulates the flow of heating wire or film and the intake air constant level. The amount of heating current required to maintain the temp. thus provide an index to air mass flow.
Â¢ Intake manifold pressure sensor:--
A pneumatic passage connects the intake manifold to this
pressure sensor which monitors absolute pressure within the intake manifold.
In this a series of piezo resistive resistor element is in response to changes in mechanical tension . These resistors are deflection at the diaphragm will lead to a change in bridge balance. Bridge voltage thus provides indication of intake manifold.
Â¢ Throttle valve sensor:--
This sensor provides a secondary load condition based on the angle of part throttle valve . Dynamic functions like load range recognition idle, full or part throttle are manifold by this sensor.
A potentiometer evaluates the throttle valves deflection angle and transmits a voltage ratio to ECU via-resistance circuit.
Engine speed , Crank shaft and its position :-
The speed at which the crank shaft changes its position is the engine speed. The degree of piston travel , within the cylinder is employed as a measured variable for determining the firing point .A sensor at the crank shaft thus provides information on the location of the piston in the cylinder with the help of this sensor. We are able to select the required firing point. Also the right injection time.
The intake and exhaust valves opening and closing timing respectively, can not be determined by crank shaft position and hence in order to manage these activities CCP sensor is utilized. The position of the crankshaft must also be monitored in those systems where separate injection timing is used for each individual cylinder, as is care with sequential injection.
# MIXTURE COMPOSITION:--
Excess air factor :-- The oxygen sensor monitors the excess air factor , lambda defines the number for mixtures A/R ratio. The catalytic converter functions best at Lambda =1.
# Combustion Knock :-- The characteristics vibration patterns generated by combustion knock can be monitored by knock sensor for conversion into electrical signals, which are then transmitted to the electronics control unit.
# Engine and intake air temp:- The engine temp. sensor incorporates a temp. sensitive resistor which exchanges into the coolant cut whose temp. it monitors. A sensor in the intake tract registers the intake air temp. in the same fashion.
# Battery voltage :-- An electromagnetic injector opening and closing timing are affected by batteries voltage. ECU prevents response delay caused by voltage fluctuation buy adjusting the duration of infection process.
# Calculating injection timing:-
Basic injection timing :-The base injection timing is calculated directly from the load signal and from the injector constants and defines the relations between the duration of the activation signal and flow quantity at the injector. This constant thus varies according to injector design . When the injection duration is muplied by the injector constant the result will be a fuel mass corresponding to a particular air mass for stroke.
The base setting is selected for an excess air factor of Lambda =1.
This remains valid for as long as the pressure differential between fuel and manifold stays constant. When it varies a Lambda correction map compensates for the influence on injection times. Meanwhile, a battery voltage correct compensates for the effects that fluctuation in battery voltage have on the injection openings and closing time.
# Effective injection time:-- The effective injection time results when the corrective factors are included in the calculations . The correction factor are determined in corresponding special functions and provides adjustment data for varying engine operating ranges and conditions . The corrections factors a used both individually and as combinations according to applicable parameter. The process for calculatoing this injection time is illustrated in fig 1.3. The individual operating ranges and conditions will be explained in more detail in following chapter.
Once cylinder filling drops below a certain level, the mixture will cease to ignite . Restricting the injection time thus prevents. The information of unburned hydro-carbons in the exhaust gas.
For starting, the injection time is calculated separately using criteria independent of the load signals.
1. Special calculations are employed to determined injection quantity.
2. Provision for special injection quantity for starting.
3. As temp. increases this quantity is cut down accordingly.
Post start phase:-
1. Further reduction is supplementary injection quantity.
2. these reduction depends upon
a) engine in temperature
b) time elapsed since the end of the starting phase.
c) Injection advance is also adjusted to correspond
I) reduced injection quantity
ii) different operating condition
Post start phase terminates with a smooth transition to the warm up phase.
WARM UP PHASE :-- Two options to increase exhaust temperature:
1. retarding ignition timing.
2. to employ rich warm up mixture together with secondary air injection.
Decisive Criteria:- Drivability, exhaust emission and fuel economy.
Â¢ Both the above measures help the catalytic converter to begin effective operation sooner.
Â¢ Higher idle speeds are provided by a specially designed air injection unit and also result in shorter warm up times at the catalytic converter. This supplements the effects of adjustment to ignition angle and timing.
Â¢ Once the converter reaches operating temp. the injection is governed to Lambda=1. This is accompanied by a corresponding adjustment in ignition angle.
Activation speed varies according to parameter such as engine temp. and rpm dynamics.
CLOSED LOOP IDLE SPEED CONTROL :--
1. Fuel consumption at idle is largely determined by I)Engine ii)idle speed
2. Substantial portion of emission is detected at idle.
3. Idle speed should be as low as possible.
4. Idle should so far rough running stage occur, even under some additional loads e.g. Ac, auto transmission, electric equipment etc.
IDLE SPEED CONTROL :--
Idle speed control must maintain a balance between torque generation and engine speed in order to ensure a constant idle speed.
The load on the idling engine is a combination of numerous elements including the int. within engine crankshaft and valve train assemblies as well as ancillary drives (e.g. water pump) The idle speed control compensates for this load, which in turn changes the life of the engine. These loads are extremely sensitive to temp. External factors such as AC also the load on engine. The lad from these external factors is subject to substantial variation as ancillary devices are switched on and off.
INPUT VARIEBLES :--
1. Throttle position in order to get required information to recognize idle stage.
2. Engine temp. to allow advance compensation for the effect of temp.
Where present the external factors ( like AC auto Xâ„¢ mission) also facilities the correction process. An air mass in specified with reference to engine temp. and target idle speed, this speed is corrected in close loop operation .
# Actuator adjustment :--
There options are available for adjusting the idle speed by means of adjustment of final control elements:
1. Air Control
2. Adjustment to ignition advance angle
3. Mixture composition
# AIR CONTROL:-
The air flow sensors contains an adjustable bypass via which a small quantity of air can bypass the sensor flap.
The idle mixture adjusting screw in the bypass permits a basic setting of fuel ratio or mixture enrichment by varying the bypass cross section . In order to achieve smoother running even at idle, the idle speed control increases the idle speed. This also leads to a more rapid warm up of engine. Depending upon engine temp. an electrically heated auxiliary air device in the form of a bypass allows the engine to draw in more air.
This auxiliary air is measured by the air flow sensor, and lead to ECU providing the engine with more fuel.
Precise adaptation is by means of the electrical heating facility. The engine temp. then determines how much auxiliary air is fed in initially through the bypass, and the electrical heating is mainly responsible for subsequently reducing the auxiliary air as a function of time.
# Adaptation to air temp:--
Cold Start Enrichment :--
When the engine is started additional fuel is injected for a limited period depending upon temp. of the engine. This is carried out in order to compensation losses in the induced mixture and in order to facilitate starting the cold engine. This extra fuel is injected by the cold start valve into the intake manifold. The injection duration of the cold start valve is limited by a thermo time switch depending upon the engine temp. This process is known as cold start enrichment and results in richer fuel air mixture i.e. Lambda<1.
# ACCELERATION ENRICHMENT :--
During acceleration the ECU meters additional fuel to the engine. If throttle is opened abruptly, the air fuel mixture is momentarily learned off and a short period of mixture enrichment is needed to ensure good transitional response.
With this abrupt opening of throttle valve, the amount of air which enters the combustion chamber, plus the amount of air needed to bring the manifold pr. Up to the new level. How through the air flow sensor. This causes the sensor plate to Ëœ over swingâ„¢ part the wide open throttle point. This over swing results in more fuel being metered to the engine and ensures good acceleration response.
# FULL LOAD ENRICHMENT:--
The engine delivers its maxim torque at full condition , when air fuel mixture must be enriched compared to that at part load. This enrichment is programmed in ECU specific to the particular engine.
The information on load condition is supplied too the control unit by the throttle switch.
# Throttle valve switch:--
Throttle valve switch communicated the Ëœidleâ„¢ and Ëœfull loadâ„¢ throttle position to the control unit. It is mounted on the throttle body and actuated by the throttle valve shaft. A contoured switching closed the Ëœidleâ„¢ contact at one end of switch travel and the Ëœfull loadâ„¢ contact at the other.
- : ELECTRONICS CONTROL UNIT :-
The ECU is the computer and control center for the engine management system. It employs stored functions and algorithms ( processing programe) to process the input signals transmitted by the sensors. These signals serve as the basis for calculating the control signals to the actuators (e.g. ignition coil, injectors) which it manages directly via power output stages.
Â¢ The ECU is a metal housing containing a PCB with electronic componentry
Â¢ A multiple terminal plug connector provides link between ECU and sensors, actuators and power supply.
The amplifier and power output components for direct actuator control are installed on heat sink in the ECU.
The ECU must withstand temp. extremes , moisture and mechanical loads with absolutely no impairment of operation. Resistance to electromagnetic interference and the ability to suppress radiation of high frequency static , must also be of higher order. Operating range of ECU -30 C
to 60 C at 6v (starting) to 15 v. To get clear understanding of construction and working of a particular microprocessor we will take example of ECU designed by using 16 bit 8097 Controller .
The ECU hardware is modular in structure and comprises of following sections:-
I. Signal Conditioning Section:-
provision of excitation signal to passive sensor
noise filtering on analog and digital inputs
optical isolation between signals input and processing stage
The major sensors used are :--
1. Manifold Absolute Pressure [MAP] Sensor
2. Throttle Angle Position [TAP] Sensor
3. Engine Speed Sensor
4. Engine Coolant Temperature [ECT] Sensor
5. Air Charge Temperature [ACT] Sensor
6. Crank Reference [TRIG] Sensor
II. OUTPUT DRIVE SECTION:--
Different output devices like throttle body fuel injector, idle motor, ignition coil and fuel pump receive control signals from micro-controller. The output drives forms interface between digital circuit and actuators by giving proper optimum isolation, power amplification etc. The output stages are protected against short circuit to ground, irregularities in battery voltage and electrical overload that could destroy them.
III. POWER SUPPLY SECTION:--
The ECU receives its power from the vehicle battery. This section provides resulted power supplies for analog and power circuits.
-: INTERFACE TO OTHER SYSTEMS :-
Increased application of electronics control systems in vehicle areas such as:
Â¢ Transmission Control
Â¢ Antilock Breaking system (ABS)
Â¢ Traction Control (ASR)
Â¢ On Board Computer etc.
Â¢ Electronic Throttle Control (EMS,E-Gas drive by wire.
All this has made it necessary to combine the respective ECUâ„¢s in networks. Data communication between control system reduce the number of sensors and allow a better exploitation of the individual system potentials.
ECU SOFTWARE :--
Here also we will consider ECU control software developed using 8097 microprocessor assembly language. Low level language software development in order to have optimized code generation.
Softer is modular in structure giving full flexibility for future expansion. The flow chart of control system is shown in fig. This control software along with the engine mapping data in the form of look up tables is programmed into EPROM. For every half revolution of the engine, the software acquires data from sensors and processes it digitally. Using this process data the mode scheduler identifies the engine operating conditions such as cranking idling, cruising, acceleration etc.
Once the engine mode is identified, depending upon the control strategies built into the software, proper look up tables for output parameters like fuel injector, pulses width and ignition angle are accessed. Battery voltage and temp. corrections are applied. Finally control signals for actuator are given out.
In the increasingly computive environment by the mechatrioncs has become the key to industrial prosperity the rapid advancement in the field of industrial engineering information technology and system engg. have been responsible for evolving new concept aimed at developing highly sophisticated machine tools for enhanced productivity in such environment, a systematic programe to face this challenge becomes vital issue in any corporation sector. CNC, Robotics and this microprocessor based control systems in mechanical field is an outcome of MECHATRONICS has been employed of the maximum for higher productivity and flexibility in the industrial sector.
Thus in short mechatroincs revolutionalised the domain of Machine Tools and ultimately Mechanical Engg. Flexibility of software enables the engineers / machincs working on this system to add special conditions that are arised in their experience to improve the effectively of the system.
1. Mechatronics : [N. Ramanuja, Chairman & m.d. , HMT Ltd]
2. Mechatronics : By W. Bolton
3. Motroinc Engine Mgmt. : - Bosch Fuel Injection Series, Robert Bosch Corp.
4. Auto India : Aug.1999
5. I.C. Engine : Mathur, Sharma.