Controller, control techniques and sensorless operation

May 14 • Notes • 1351 Views • 4 Comments on Controller, control techniques and sensorless operation

Controller

A controller can be defined as  a device  in the form of a chip, analogue electronic or as a computer which monitors and changes  the operating conditions of the system as per the conditions.

Types of controller

The modern control system of the dependent on computers for the industrial controller. I has various advantages like—it has become an easier task to implement complex control algorithm on a computer than using a mechanical system.

For feedback controllers

The input  to the feedback controller is what is to be controlled i.e. the  controlled variable is “fed back” into the controller.

Proportional controller.

The controller output i.e. control action is proportional to the error in the measured variable.

In feedback control,

the error us defined as  the difference between the desired value ds (t) and the current value d(t) .

The error is directly proportional to the control action,If the error is large  then the control action is large and vice verse.

Mathematically:

Uc(t) = Kc * e(t) + u0

Where,

uc (t ) —- the control action ( controller output ),

e(t) = ds(t) – d(t) —- the error,

Kc —-  controller’s gain

u0 —-  steady static control action necessary to maintain the variable as the steady state when there is no error.

.

Types of controllng system

There are two basic types of control.controller

1.feedback

The input  to the feedback controller is what is to be controlled i.e. the  controlled variable is “fed back” into the controller.

Feedback control are basically the outcome where the controlled variable is not at the desired set-point.

For example—some variables are taken into account  like if the temperature of the room is taken as the variable. with the cooler example if the door of the house was kept opened on the hot day the room will be heated up.After the temperature of the room rises above the considered temperature then the cooler will be turned  on. But it is to be noted that for some instance of the time the room was hotter than it was desired to be(It is considered to be its disadvantage as its takes time to respond)

2.Feed forward

This control action is to avoid the slow nature of the feed back control.Before the disturbances are accounted they are measured and  accounted.

If we consider the same example as above then the feedback system will account that the door is opened and it automatically turns on the heater before the temperature of the room could rise.

The disadvantage with this control is that disturbance should have to be predicted to the system before hand in order to be accounted and measured.If not then then it can’t measure those disturbances .For example if the windows of the room are kept opened it can’t account it and lets the room gets heated up..

Servo drive as controller

A servo drive is defined as a special type of the electronic amplifier which is used to power back the servomechanism.It basically monitors out the signals which are feedback from the servomechanism and similarly the the related adjustments are done.

Basic function

A servo drive gets the signal from the control system which is then amplified and then electric current is transmitted to the servo motor.This is done in order to produce equivalent  motion as the command signal.The command signal represents the torque.motor’s actual status back to the servo drive is is reported by the sensor attached to the servo motor.

SENSOR LESS OPERATION

Due to the inherent  control simplicity and the lower cost the stepper motors and the servo drives needs motion and position control applications.They are prone to generate the mechanical  resonance and hence generate audible noise.

Hence sensor less operation is required  which helps to operate the servo drives and the stepper motor to operate without the position sensors which as a result boosts up the performance at the same time maintaining the inherent simplicity of the stepper motor and the servo drives.

 

sensor less operation which doesn't use the conventional method of micro stepping

sensor less operation which doesn’t use the conventional method of micro stepping

The sensor less operation in the stepper motor if we take for the instance makes to operate  without the position sensors and it derives the position sensors from the sampling of the phase current and the back emf.It maintains the advantages of the stepper motor and improves the disadvantageous points.

For e.g. The audible noise of the stepper motor to reduced to almost 75% as compared to the non sensor less operation.

It increases the motor speed as compared to before.

It even eliminates the resonance effects of the machine.

At the full torque limit acceleration takes place.

The stepper motor the input digital pulses to the rotor output movement which is analog in the nature.

The noise is actually caused as the result of the discontinuous stepping and thus cause the resonance effects.

The use of the sensor less operation makes the stepper motor to operate in the flux-vector mode and the closed position loop.The motor is kept to operate in the continuous mode rather than the previously used method of the stepping mode.The audible noise which are generated due to the previously used method of the stepping.The drive system is not limited to the acceleration given by the system’s resonant frequency in the previously used methods of the stepper motor drive.

 

CONTROL TECHNIQUES 

1.FOR SERVO MOTOR

a)High performance brush less AC servomotor matched with the range for the use in the control techniques drives.

b) Modified electromagnetic construction with greater performance of the torque range.

c)Maximum torque density technique is to be used.Low inertia should be retained for its applications in high torque requirement either in the acceleration or deceleration

In the drives the control techniques  provided by

a)intelligence:modules for the programmable automation and the motion

b)communication: The communication option modules through the Ethernet and the field bus.

c)feedback:encoder and the decoder modules are present

d)input/output modules:The analog and digital input /output modules

.Related questions-answers

1. What do you mean by a controller.

A controller can be defined as  a device  in the form of a chip, analogue electronic or as a computer which monitors and changes  the operating conditions of the system as per the conditions.

2.Name the two types of the controlling techniques.

1.feed back

2.feed forward

3.Explain using the formula the concept of the feed back control.

In feedback control,the error us defined as  the difference between the desired value ds (t) and the current value d(t) .The error is directly proportional to the control action,If the error is large  then the control action is large and vice verse.

Mathematically:

Uc(t) = Kc * e(t) + u0

Where,uc (t ) —- the control action ( controller output ),

            e(t) = ds(t) – d(t) —- the error,

            Kc —-  controller’s gain

           u0 —-  steady static control action necessary to maintain the variable as the steady state   when there is no error.

4,Explain the concept of the feedback controller and the proportional controller.

 feedback controllers

The input  to the feedback controller is what is to be controlled i.e. the  controlled variable is “fed back” into the controller.

Proportional controller.

The controller output i.e. control action is proportional to the error in the measured variable.

5.what are the control techniques provided for the drives??

In the drives the control techniques  provided by

a)intelligence:modules for the programmable automation and the motion

b)communication: The communication option modules through the Ethernet and the field bus.

c)feedback:encoder and the decoder modules are present

d)input/output modules:The analog and digital input /output modules

6)what are the advantages a stepper motor gains in the sensor less operation

The audible noise of the stepper motor to reduced to almost 75% as compared to the non sensor less operation.

It increases the motor speed as compared to before.

It even eliminates the resonance effects of the machine.

At the full torque limit acceleration takes place.

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4 Responses to Controller, control techniques and sensorless operation

  1. Rachita Mishra says:

    Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems with inputs.This article describe controll theory and it’s type .good article.

  2. patlakshi Jha says:

    This post exlains about the control and its techniques . These controllers has become nowadays an integral part for the process and manufacturing system.

  3. Shilpa Ranjan says:

    This article explains about the controller and its types.how it works i.e. techniques used for control operation and sensor less operation.This article explains everything in detail with relevant pictures.Going through this post one can be able to understand it completely.Related expressions and formulas are explained with help of question answer section..

  4. Ritika Savita says:

    Controllers are part of evry electronic manufacturing or processing system. They provide supervision & have replaced the manual force. this article also explaines the various types of controllers.

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