Robotic Gripper 2

pneumatic gripper

A gripper was designed for transplanting. The gripper seedlings
grasping is composed of a pneumatic piston which actuates
two parallel hinged jaws that perform a scissors type movement,
which cause the jaws to grasp the plant in between. The size
and shape of the gripper was adapted to fit trays with different
plant cells sizes.

http://old.agri.gov.il/AGEN/Reports/AgriculturalRobot.html




slider gripper

This is the first of six soft tissue grippers. The gripper, thanks to two
suction cups, can pick and place large portions of fabric.
The distance between the two suction cups can be adjusted to
better fit the fabric size.

dimec.unige.it/PMAR/pages/research/robot

The 3-Jaw Parallel Gripper


The 3-Jaw Parallel Gripper is ideal for applications requiring three
points of contact, positive pick and place, and the flexibility of stroke.
It offers self-centering of parts and a high clamping force for
rapid part transfer and part gripping during grinding or de-burring, etc

expo21xx.com/automation77/news/2057_robotic

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Schematic Objective of the project based on microcontroller 8051

Objective of the project (Humidity sensing and development of digital clock) based on micro controller 8051:-

This is very first post after the table of the contents in the last post. In this post we will try to communicate the objectives of doing this project. It is good practise to learn and find the objective of any project. It could be found if some one ask a very common question with himself that why i am doing something. In the same manner, we are doing this thing here.

The main and very important objective of this post to deliver knowledge of my skills and finding about micro controller to all my students. So that if any of my student is struggling , he /she may get his desired solution from my blog.

The project objective is very clear:

In this project we will learn following things:

1. What are the humidity sensors, What are the working principles of the humidity sensors, How the level of humidity is converted into the electrical signals. How the humidity transducers work?
2. What is the functionality of the humidity sensor we are using in this project.
3. How the Analog to digital converter works?
4. What is the working principle of ADC?
5. What are the features of adc0804?
6. How we calculate the resolution of the ADC0804 or any other ADC?
7. What are the DAC (Digital to Analog converters)?
8. How does the DAC work?
9. What are the methodologies of DAC?
10. Why we use DAC with Micro controllers?
11. How does LCD (Liquid crystal Displays) work?
12. What are the Different registers of LCD?
13. How the line and characters counting is implemented in LCD?
14. What is serial communication?
15. What is RS232 or MAX232?
16. What is the protocol of data transfer in serial communication?
17. What is DB9 connector?
18. What is null modem cable?
19. How the digital clock is implemented?
20. What are the time trigger applications?

The objective is to implement the different techniques at the grass root level which can be integrated to form the complex system for instance , Memory mapping, calibration of ADC and DACs, Serial or Parallel interfacing with PC and also to study different aspects of the LCD.

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Schematic Humidity Sensing and Digital Clock Employing Memory Mapping

Humidity Sensing and Digital Clock Employing Memory Mapping

As the name of the project shows, here we are going to discuss three things togerther,

1. Measuring Humidity, using Humidity sensors, Interfacing of Humidity sensor with microcontroller 8051
2. Developement of digital clock using microcontroller 8051
3. Understanding the memory Mapping of microcontroller 8051

So here is

Introduction of the Project:-

The main focus of this project is to implement the methods to obtain the data from the low voltage operated sensors and their digital interface to microcontroller or microprocessor, a part from this the technique of memory mapping is also implemented along with the serial interface for both transmission and reception with hyper terminal.


The input to this project is a time varying voltage from sensor calibrated by the ADC as +10 to –10 volts. The output is the actuation of the alarm after every 1 hour also it can be made to alarm when the humidity exceeds some threshold value.

The serial communication techniques are also a part of this project, when the system is booted the initial messages from the controller is transmitted to the PC, and can be viewed on the hyper terminal and then user update the system by sending time from the hyper terminal, hence we have implemented both transmission and reception.

Humidity Sensing and Digital Clock Employing Memory Mapping

Table of Contents

1 Objective of the project based on microcontroller 8051
2 Implementation Details of Humidity sensing project
2.1 Humidity Sensors
2.2 Humidity Transducers or Humidity Transmitters
2.3 Humidity Display and transducer consideration
2.4 Selection of Humidity Sensor
3 LCD Overview (Liquid crystal display)
3.1 Function Description of LCD
3.1.1 Registers of LCD
3.1.2 Busy Flag (BF) of LCD
3.1.3 Address Counter (AC) of LCD
3.1.4 Initializing by Internal Reset Circuit of LCD
3.1.5 Pin Assighnment of LCD
3.1.6 Data Write into LCD
3.1.7 Assembly Language program for LCD code
4  MAX 232 serial communication of microcontroller and PC
4.1 DB9 connector used for serial data communication and RS232 cable
4.2 Testing Circuit of humidity sensing project
5 ADC0804 introduction and features
5.1 Interfacing the ADC0804 to the AT89C51
6 DAC0800 introduction

7. 82C55 PROGRAMMABLE PERIPHERAL INTERFACE
8. Circuit Diagram
9. Code (program written in C51 for microcontroller 8051)

After going through this project or tutorial of 8051 you would be able to do following tasks.

1. You would have idea of hardware and software of the microcontroller 8051.
2. you will come to know the usuage of microcontroller ATMEL AT89c51 or AT89s51.
3. You will get information about the working of different general purpose components and their usuage along together to make some useful project or application based on microcontroller 8051.
4. The function and features of ADC0804, DAC0800 are discussed, you would come to know how these components can be interfaced with microcontroller.
5. LCD is discussed in detail so, after going through this project you would feel easy to work with LCD.
6. You would be able to interface the LCD with Microcontroller 8051.
7. Humidity sensors are also discussed here in some detail, so you would be able to handle these sensors with now fear.
digital humidity controller and sensor lesson on triacs ti 8051 microcontroller development solenoid lcd humidity transducer for high temp ovens how to program ir sensor in assembly language humidity sensing dsp embedded keil analog digita converter program affordable female pelvic ultrasound wiring humidity switch for motors application based on 8051 in industry

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Schematic Assembly Language code for Microcontroller 8051 project

This is the last post of pressure sensor project based on microcontroller 8051. The code is written in assembly language.Data Collection Analog to Digital Conversion and Communicating ,It uses an ADC0804 chip to convert from analog to digital and an AT89C2051 is interfaced with ADC and LCD.
Below is Assembly Language code for Microcontroller 8051 project; this code have all the features including, ADC interface with microcontroller 8051, getting data from ADC to microcontroller, controlling seven segment display with microcontroller, performing required calculation of pressure from measured voltages using formula described in previous post. And serial communication with microcontroller and PC through RS232 port.circuit diagram and assembly language program for interfacing of ADC Samples of 89c2051 interfacing with MAX 233/ ADC0804 an assembly language program and loading it into the microcontroller.
org 0000h
CALL INITILIZE_SERIAL
main: clr p3.7 ;this is for WR signal of ADC to give it a rising edge
call delay ;
setb p3.7 ;
call delay
call delay
clr p3.6 ; to clear the RD signal of ADC
mov a, p0 ; latches data at port A
setb p3.6 ; to set the RD of ADC
subb a,#50h ; received data is displaced by 80 so it is
mov r3, a
call TO_FORCE
call TO_PRESSURE
mov b,#10
div ab ; used to convert the two digit BCD to BINARY
mov r0,b
mov r1,a
mov dptr,#data_table ;to read the seven segment code against a Binary ;form the Code Memory
mov a, r0
movc a, @a+dptr
mov r0, a
mov a, r1
movc a, @a+dptr
mov r1, a
clr p3.5
clr p3.4
setb p3.4
mov p1,r0
call delay
clr p3.5
setb p3.5
mov p1,r1
call delay
clr p3.5
sjmp $
TO_FORCE: ; the pressure transducer having different parameters
mov r4, #1 ;1 is the spring constant (supposed)
mov b, r4
mul ab
ret
TO_PRESSURE: ; in this subroutine the pressure is calculated from the incoming data and using formula
mov r4, #1 ;1 is the Area of the cylinder ( supposed )
mov b, r4
div ab
ret
delay:
mov r0, #127
djnz r0, $
ret
data_table: db 7eh,30h,60h,79h,13h,5bh,5fh,70h,7fh,77h
INITILIZE_SERIAL:; In this subroutine the required initialization of the serial communication is done, ;different registers of microcontroller are initialized to get response from RS232
;intilize the timer 1 in auto reload mode
;and then set the baud rate 2400 in mode1 of
;serial port
MOV SCON,#01000000B; it is the serial control register of microcontroller 8051
MOV TMOD,#20H; timer mode of microcontroller 8051 is selected here
MOV TH1,#-12; upper byte of timer 1 is feed
SETB TR1
CLR RI
CLR TI
RET
SEND_TO_PC: This subroutine sends data to PC from Microcontroller 8051 using RS232 serial communication
MOV SBUF,A; serial buffer register SBUF is feed the data in register A
JNB TI,$
CLR TI
RET
end
 Tags:-
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Control Video Lecture Industrial Automation and Control - Signal Conditioning and Data Acquisition Systems

Lecture Series on Industrial Automation and Control by Prof. S. Mukhopadhyay, Department of Electrical Engineering, IIT Kharagpur.


Video Lecture Signal Conditioning



Video Lecture Signal Conditioning (Contd.)



Video Lecture Data Acquisition Systems

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Control Video Lecture Industrial Automation and Control -Sensor and Measurement

Lecture Series on Industrial Automation and Control by Prof. S. Mukhopadhyay, Dept.of Electrical Engineering, IIT Kharagpur.

Measurement Systems Characteristics Lecture Video



Temperature Measurement Lecture Video



Pressure, Force and Torque Sensors Lecture Video



Motion Sensing Lecture Video



Flow Measurement Lecture Video

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Control Interfacing Keypad and LCD Embedded Microprocessor

This is circuit for interfacing I/O keypad and LCD that can study in laboratory for student to experience interfacing basic I/O devices to the HCS12 microcontroller mounted on the CML12S-DP256 development board. The keypad that using in this circuit is a standard 4 X 4 matrix keypad with 4 rows and 4 columns. This is the figure of the interfacing of keypad.


The DCM-20434 LCD display is interfaced to the MCU’s SPI-0 serial port through a serial to parallel converter as shown in Figure 3. Figure 3 shows the interface connections between the SPI-0 serial port, the 74HC595 (serial to parallel converter) device, and the LCD-PORT. The DCM-20434 LCD should be configured in four bit mode as the schematic shows DB3 through DB0 connected to ground. This is the interface figure.


To interface the LCD display to the HCS12 MCU you must understand how the physical layer interface circuit is constructed (shown in Schematics for Development Board), how to configure and use the SPI serial port (SPI Serial Bus Document), and how to configure and use the LCD display (DMC-20434 LCD Specifications ).

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Schematic Binding things together in pressure sensing project

 Binding things together to complete the project or pressure monitoring using microcontroller 8051.
Let us see how these components work and how the things were titted together in order to complete the pressure sensing and monitoring projects, different components were purchased and soldered on PCB then the the circuit was tested using test points. Mean while the code or program for pressure monitoring was written for microcontroller at89s51 using assembly language. The code will be posted in the next post. All this work is described here in steps, so please click on links as much as possible to find valuable information regarding project.
Step 1:
The first step involved the testing of the pressure sensor manually. The pressure sensor was test by applying different pressures on the sensing element and displacement was watched. As we have discussed in the previous post about the construction of our developed sensor that it have cylinder which will move according to applied pressure. The movement of the cylinder is to be monitored and Microcontroller will calculate the pressure at the end.
Pressure is applied to the cylinder and the piston moves . motion of the piston is restricted by the damper.
Step 2:
As discussed in the first step that the movement of the piston is coupled with variable resistor. The movement of the piston in cylinder of pressure sensor will be checked with variable resistor. Displacement is measured by Voltage change detected across the in the linear variable resister.
Step 3:
The change in voltage due to change in resistance is the transducer in our case. This voltage is applied across the ADC. ADC converts this voltage to 1’s and 0’s form. And sent to the processing unit. The microcontroller will get digital form of these voltages for further processing.
Step 4:
In the code microcontroller 89s51, a formula is written which will convert these voltages into pressure. as we have derived this formula already and proved its working. Thus in microcontroller its calculation is not problem. The algorith to calculate the pressure from the voltages changed at the variable resistance is developed in the code. The microcontroller code will be available in the next post. Here only the calculation is discussed, that how micro-controller will do this.
Processor (Micro controller) takes output ‘x’of ADC as input and does the following calculation.
F=Ks * x
Ks is the spring constant .
P=F/A
Where A= phi *D*D/4
Where D is the diameter of the cylinder. P is the pressure that is applied on the cylinder.
Step 5:
This P is then conveyed to seven segment and computer. In this project serial communication with microcontroller a computer is done using rs232. The pressure calculated rather sensed or monitored is also transmitted to wards the computer for better processing of this parameter.
A database can also be attached to stored all monitored values and then a history graph can be draws to analysis the behaviour of the machine whose pressure is monitored here.
Tags:- How to develop pressure sensors,Pressure transducers, sensing element of pressure switch, industrial pressure sensors, home automation and control, Microcontroller 8051 based pressure sensing project, pressure monitoring based on microcontroller 8051, Algorithm to find pressure in a pipe, fluid pressure, fluid dynamics, flow sensor, interfacing of pressure transducers with microcontroller 8051, how can we measure pressure using microcontroller 8051. calculate pressure in the pipe, data logging and monitoring of pressure of pipe, computer aided pressure monitoring project, microcontroller and computer based data acquisition and control, industry automation using microcontroller, jigger machine pressure monitoring program, pressure jigger machine, how monitor high pressure with microcontroller, textile industry pressure monitoring project, cotton industry pressure monitoring project, microcontroller 8051 project to monitor pressure, velocity, flow rate height of fluid

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Control Video Lecture Series on Industrial Automation and Control 1

Lecture Series on Industrial Automation and Control by Prof. S. Mukhopadhyay, Dept.of Electrical Engineering, IIT Kharagpur.



Introduction Lecture Video - 1




Architecture of Industrial Automation Systems Lecture Video - 2

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Robotic Gripper 1

A parallel jaw gripper

A parallel jaw gripper A parallel jaw gripper was developed for the
robotic arm for pick and place operations. To maintain the jaws
of the gripper parallel to each other, they were connected through
a parallel mechanism of links. A linear actuator actuates the gripper.
A CAD model of the gripper mechanism is shown on the
right. The mechanism simulation was done in Idea8 mechanism
solver.

http://www.cs.cmu.edu/~amampett/pastProjects.html

Robotic Gripper Sizing

The force that a robotic gripper applies to a part is typically used by
engineers to select grippers. While gripper force is a first order
consideration, the torque that is experienced by the gripper is equally
as critical and, unfortunately, usually only addressed in a cursory
manner. In some cases the torque is addressed via the gripper
manufacturer supplying jaw length vs. force charts. These gripper
charts are helpful but are only useful in low G-force applications
and provide rough guidance at best. The result of this situation is
that “rookie” gripper application engineers end up with dropped
parts and “old hands” end up with grippers far larger and more
expensive than required. Before we start let's look at some of the
lore that is wrong!
http://www.grippers.com/size.htm

Rotational gripper

The 1 DoF gripper is the end effector of a parallel robot for
high speed assembly tasks. The gripper is mounted on a triangular
plate. The parallel architecture of the robot drives the plate
translation. An actuator rotates the whole robot (instead of the
plate itself) to allow the gripper rotation around an axis normal
to the plate; this solution minimizes the inertia of the end-effector.

dimec.unige.it/PMAR/pages/research/robot/grippers

Robotic Gripper Index

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Control AUTO-TUNING CONTROL SYSTEM

DESIGN AND EVALUATION OF AN AUTO-TUNING CONTROL SYSTEM
FOR AN ALTITUDE TEST FACILITY
Abstract
Simulated altitude testing of large aircraft engines is a
very expensive, but essential step in the development and
certification of gas turbines used by commercial airlines. A
significant contributor to the cost of this process is the
time-intensive task of manually tuning the facility control
system that regulates the simulated flight condition. Moreover,
control system tuning must be performed each time
the test conductor changes the flight condition. An adaptive
control system that automatically performs this task can
significantly reduce the costs associated with this type of
engine testing.

This paper examines the features of an auto-tuning
controller architecture that contains both disturbance feedforward
and PID feedback components in a two-input, twooutput
multivariable configuration. The paper reviews the
underlying concepts of an auto-tuning system and contrasts
its advantages/disadvantages with respect to other adaptive
control techniques. The algorithm used to automatically
tune the controller does not require a facility model. However,
a nonlinear facility model was developed and used to
substantiate a decoupled-loop design approach, to validate
the controller design concept, and to evaluate the resulting
adaptive control system design performance. This analysis
and other practical design issues that impact the auto-tuning
control system performance are addressed in the paper. The
paper also presents results that illustrate the automatic tuning
sequence and the disturbance rejection performance
exhibited by this system during large engine transients at
several key points in the flight envelope. The auto-tuning
controller described in the paper was implemented at a
Pratt & Whitney flight test facility used in the development
of large, high bypass ratio gas turbines.

Rationale for the Auto Tune Control Concept
Unlike the MRAC and STR concepts, the Auto-Tune adjustment
(adaptation) mechanism does not require any a
priori information about system dynamics to compute the
PID controller parameters. Moreover, an Auto-Tune system
only updates the controller on an operator-demand basis.
The MRAC and STR methods do not explicitly interact
with the system operator. These two characteristics of the
auto-tuning concept were the primary factors in selecting
this adaptive concept for the altitude test facility application.
This section examines the underlying features of the
Auto-Tune concept and motivates the rationale for selecting
a PID controller for this application.

The automatic tuning performed with this scheme can be
characterized as a crude, but robust method that identifies
two key parameters characterizing process dynamics. The
Auto-Tune adaptation algorithm approaches the control
design in a manner quite familiar to first-generation single
input/single output control system designers. The fundamental
idea centers on determining the gain and frequency
at which the system dynamics become conditionally stable
under pure proportional feedback control. These frequencydomain
characteristics of the system are designated as the
ultimate gain and ultimate frequency, respectively. Using
Ziegler-Nichols relationships, the PID controller parameters
can be determined from the ultimate gain and frequency
information. It is well known that PID control systems
designed with the Ziegler-Nichols method exhibit
very good disturbance rejection performance, but tend to
have significant overshoot when responding to set-point
changes (Astrom & Hagglund - 1995). Degraded set point
responses do not present a problem in the altitude test facility
application since the control problem focuses completely
on disturbance rejection performance. The chamber
pressure and plenum pressure set points remain at fixed
values throughout an engine transient test scenario.

As in most control system synthesis problems, both time
and frequency based methods exist for formulating an experiment
that produces the information required to compute
the Ziegler-Nichols gains. In most practical control applications,
a frequency-based experiment produces superior results
and was the method chosen in this application. The
central idea in the frequency-based approach relies on the
fact that most real systems produce stable limit-cycles under
relay feedback. The theoretical basis for this statement
was developed in Astrom - 1991. The method of harmonic
balance or describing function method (Gelb and VanderVelde
– 1968) provides the mathematical framework for
analyzing relay-induced limit-cycles and extracting the
ultimate gain and ultimate frequency from the experimental
data.

http://web.iac-online.com/images/Publications/35.pdf
On-line PID Controller Design via a Single Auto-tuning Neuron

Abstract:
A simple tuning strategy for PID controller design will be proposed in this paper. With the
use of single neural estimator (SNE), three control gains of PID controller are not fixed during the
control procedure, but will be adjusted on-line such that better output response can be achieved. In
this control strategy the exact model of plant will not need to be known and identified. Lastly, two
simulation results are provided to show the control performance by using the proposed adaptive PID controller.

1. Introduction
2. Preliminaries
2.1 Auto-tuning neuron
2.2 PID controller
3. Self-tuning Adaptive PID
Controller
3.1 MIT rule
3.2 Control structure and algorithm
3.2.1 A tuning algorithm for PID control gains
3.2.2 A tuning algorithm for the SNE
4. Illustrative Examples
5. Conclusions

http://www.kyu.edu.tw/93/95paper/v8/95-061.pdf

Auto-Tuning of PID Controllers via Extremum Seeking
Abstract—The proportional-integral-derivative (PID) controller
is widely used in the process industry, but to various
degrees of effectiveness because it is sometimes poorly tuned.
The goal of this work is to present a method using extremum
seeking (ES) to tune the PID parameters such that optimal
performance is achieved. ES is a non-model based method
which searches on-line for the parameters which minimize a
cost function; in this case the cost function is representative
of the controllers performance. Furthermore, this method has
the advantage that it can be applied to plants in which
there is no knowledge of the model. We demonstrate the
ES tuning method on a cross section of plants typical of
those found in industrial applications. The PID parameters
are tuned based on the results of step response simulations to
produce a response with minimal settling time and overshoot.
Additionally, we have compared these results to those found
using other tuning methods widely used in industry.

Overall ES PID tuning scheme.





http://www.nt.ntnu.no/users/skoge/prost/proceedings/acc05/PDFs/Papers/0401_ThA17_2.pdf

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Control Temperature Sensor Using ATmega8

This is design for temperature sensor that is based ATMega 8. LM35 is using for sensing the temperature. This IC is cheaper than the price of this component is also easy to be in the market. This is the figure of the circuit.


LM35 have 10mV voltage change per 1 degree centigrade. LM35, in principle, given the voltage + Vs and GND, the voltage Vout will issue of
Vout = surrounding temperature (centigrade) x 10mV.
on the # include “lcd.h” you can download click here.

This is source code from this project in AVR-GCC format.

#include
#include
#include
#include
#include “lcd.h” //header lcd
volatile unsigned char suhu; //variabel store adc
//deklarasi lcd to stdio
static int lcd_putchar(char c, FILE *stream); //prototype
static FILE mystdout = FDEV_SETUP_STREAM(lcd_putchar, NULL,_FDEV_SETUP_WRITE); static int lcd_putchar(char c, FILE *stream)
{
if (c == ‘\n’) lcd_putchar(’\r’, stream);
LCD_send_char(c);
return(0);
}
//fungsi delay mili sekon
void delay_ms(int ms)
{for(int i=0;i<=ms;i++){_delay_ms(1);};
}
void adc_init(void) //inisialisasi lcd
{ ADMUX =(1<<
|(1<
|(0<<<<
ADCSRA =(1<<<
|(1<<<
sei ();
}
ISR(ADC_vect)
{ suhu=ADCH;
LCD_send_command(0xc0); //cursor line2
printf(”sekarang:%3d c”,suhu);
return;
}
int main (void)
{ adc_init();
delay_ms(200);
LCD_init();
stdout = &mystdout;
LCD_send_command(LCD_CLR);
LCD_send_command(LCD_HOME);
LCD_send_command(0×80); //cursor line1
printf(”suhu ruangan ini”);
LCD_send_command(0xc0); //cursor line2
printf(”sekarang:%3d c “,suhu);
while(1){
ADCSRA|=(1<
delay_ms(500);
}
return(0);
}

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Control Audiometer Circuit Using Microcontroller AT89S51

This is a design for audiometer circuit. This audiometer is an instrument used for the diagnosis threshold of human hearing to give some particular audio frequency and also a certain level of intensity. Raised from the signal generator sinus and selected using a multiplexer 4051. Amplitude or intensity of sound can be arranged through the DAC. Use as bait with the audio signal. Voltage to references from the DAC, so the output can be set with accuracy Vref/255. This is the figure of the connection of the circuit.


Procedure for programming the audiometer circuit is initial view will display the form fields Name and Date patients now on the Character LCD screen, which can be entered via the keyboard. After the data in the content of the system will wait for the emphasis the Enter key when keyboard enter key is pressed the system will start working on procedures audiometer. Through the multiplexer 4051 then selected the most low frequency, 125 Hz and data on the issue with the DAC will be issued with the signal frequency and amplitude particular. Interruption through the system timer 0, mode with 16 bit then remove the signals that can be set to increase amplitude for every 10 seconds: 0:05 x 200 = 10 seconds if the patient does not press the button, when 10 patients amplitude still does not listen to the sound of the automatic frequency raised to a higher level and again at the lowest amplitude. By using an external system interruptions 0, then we can do so that interruptions can be patient when the system starts listening to a sound. When patients hear then press the button so that there will be a process data storage dB and Frequency at the time. When the process is completed the system will re-open the data-data that have been stored for the data storage process is done.

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Control Auto-Tuning Control Base on Ziegler-Nichols

Auto-Tuning Control Using Ziegler-Nichols
Automatic step testsOne of the earliest auto-tuning controllers still on the market is the 53MC5000 Process Control Station from MicroMod Automation. It uses the Easy-Tune algorithm originally developed at Fischer & Porter (now part of ABB) in the early 1980s. It automatically executes a step test similar to the open-loop Ziegler-Nichols method that forces the controller to make an abrupt change in its control effort while sensor feedback is disabled.

The amount by which the process variable subsequently changes and the time required
for it to reach 63.2% of its final value indicate the steady-state gain and time constant of the process, respectively. If the sensor in the loop happens to be located some distance from the actuator, the process’s response to such a step input may also demonstrate a deadtime between the instant that the step was applied and the instant that the process variable first began to react.

These three model parameters tell the Easy- Tune algorithm everything it needs to know about the behavior of a typical process, allowing it to predict how the process will react to any corrective effort, not just step inputs. That in
turn allows the Easy-Tune algorithm to compute tuning parameters to make the controller compatible with the process.



Closed loop tests
In 1984, Karl Åström and Tore Hägglund of the Lund (Sweden) Institute of Technology
published an improved version of Ziegler and Nichols’ closed-loop tuning method. Like the open-loop method, this technique excites the process to identify its behavior, but without disabling sensor feedback.

The Åström-Hägglund method works by forcing the process variable into a series of
sustained oscillations known as a limit cycle. The controller first applies a step input to the process and holds it at a user-defined value until the process variable passes the setpoint. It then applies a negative step and waits for the process variable to drop back below the setpoint. Repeating this procedure each time the process variable passes the setpoint in either direction forces the process variable to oscillate out of sync with the control effort, but at the same frequency. See the “Relay Test” graphic. The time required to complete a single oscillation is known as the process’s ultimate period (Tu), and the relative amplitude of the two oscillations multiplied by 4/π gives the ultimate gain (Pu). Ziegler and Nichols theorized that these two parameters could be used instead of the steady-state gain, time constant, and deadtime to compute suitable tuning parameters according to their famous tuning equations or tuning rules shown in the equation on the left.

They discovered empirically that these rules generally yield a controller that responds quickly to intentional changes in the setpoint as well as to random disturbances to the process variable. However, a controller thus tuned will also tend to cause overshoot and oscillations in the process variable, so most auto-tuning controllers offer several sets of alternative tuning rules that make the controller less aggressive to varying degrees. An operator typically only has to select the required speed of response (slow, medium, fast), and the controller chooses appropriate rules automatically.

http://www.das.ufsc.br/~aarc/ensino/posgraduacao/DAS6613/Auto-Tuning%20Control%20Using%20Ziegler-Nichols.pdf
REVISITING THE ZIEGLER-NICHOLS TUNING RULES
FOR PI CONTROL — PART II
THE FREQUENCY RESPONSE METHOD
ABSTRACT
This paper presents an analysis of the Ziegler-Nichols frequency response
method for tuning PI controllers, showing that this method has severe
limitations. The limitations can be overcome by a simple modification for
processes where the time delay is not too short. By a major modification it is
possible to obtain new tuning rules that also cover processes that are lag
dominated.

I. INTRODUCTION
II. TEST BATCH AND DESIGN METHOD
2.1 The MIGO design method
2.2 The test batch
2.3 The AMIGOs tuning rules
2.4 Parameterization
III. A FIRST ATTEMPT
3.1 Stable processes
3.2 Integrating processes
3.3 Tuning rules for balanced and
delay-dominated processes
3.4 Summary
IV. ANALYSIS
4.1 Modified tuning procedures
V. THE AMIGOF TUNING RULES
5.1 Other values of Ms
5.2 How to find the frequency ωφ?
5.3 Summary
VI. AN INTERPRETATION OF
THE RESULTS
VII. EXAMPLES
Example 1. LAG DOMINATED DYNAMICS
Example 2. BALANCED LAG AND DELAY
Example 3. DELAY DOMINATED DYNAMICS
VIII. CONCLUSION

http://www.ajc.org.tw/pages/PAPER/6.4PD/AC0604-P469-FR0371.pdf

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