SUB SYSTEM USED IN ROBOT 1

  •  SUBSYSTEM THAT ARE USED IN ROBOTICS(ACTUATORS)

As we know that to manufacture a robot there are some sub system are used.in extent their are following important subsystem that are mainly use in robotics technology.

SUB SYSTEM-:

1.Actuators

2.Transmission system

3.Mechanism

4.Power supply

5.Power storage system

6.sensors

7.Micro-controller & Micro-processors

8.Algorithms & software

 

FOLLOWING DEFINITION ARE THERE 

ACTUATORS-:

An actuator is device that is used to change the some kind of energy into the desired motion.these are also used to produce force.there are many types of actuators  like hydraulic fluid ,pneumatic ,electric actuators etc.these are controlled by energy sources like motors,batteries,cells,and many types of energy sources.
           actuators are essentially the prime movers providing both force and motion.example of an actuator is human muscles.because muscles are also used to produce a motion to hand and all the movable parts of our body like finger,feet.

TYPES OF ACTUATORS-:

1.Hydraulic actuator
2.Pneumatic actuator
3.Electric actuator
4.Mechanical actuator
5.Thermal or magnetic(Shape memory alloys)  actuators

HYDRAULIC ACTUATOR

hydraulic actuators are mainly consist of cylinder,piston, in-compressible working fluid,spring.
 a schematic is shown below for better understanding of hydraulic system.hydraulic ACTUATORS are used when there is requirement of large amount of force at high speed.the working principle hydraulic actuator pascal’s law according to this law the pressure applied at a point of fluid is transmitted to undiminished and equal throughout the fluid in all the direction.
Here we can see a schematic of hydraulic system which is used to operates the valve.a in-compressible fluid at high pressure  is enter through the hydraulic supply manifold.after passing through the manifold it reaches into the cylinder.in cylinder a piston is situated which is connected with a spring.during the initial position spring is in it’s natural length.as the high pressure hydraulic fluid enters into the cylinder it forced the piston to upward direction.due to this process spring being compressed and it stored energy in the form of compression force and valve is open.after sometime as the hydraulic is release from the cylinder then pressure applied over the piston become less and if the g is lower than the spring force then the spring help the piston to go downward and valve become close.this process being continued according to the requirement of valve controlling   
 
hydrau317cb1934b7a44372a1445d6b02471250 SUB SYSTEM  USED IN ROBOT 1

PNEUMATIC ACTUATORS-:

The working principle of the pneumatic actuators is air pressure.main working substance of this type of actuator is air.these type of actuators mainly used in brake controlling system ,valve controlling etc.pneumatic actuators mainly consist of a piston, a cylinder,and high pressurize gas.main concept of these types of actuators is that as a high pressurize gas enters through the inlet to the lower part of cylinder then due to high pressure of the compressed gas,piston goes upward direction and valve may open or close depending upon assembly of the actuators.

WHY WE GO PNEUMATICS WHY??

1.BECAUSE MASS OF THE CYLINDER IS MUCH LESSER THAN THE MOTOR
2.THESE ARE MUCH EASIER TO MOUNT RATHER THAN MOTOR
3.MORE DURABLE THAN THE RACK AND PINION ASSEMBLY
4.LARGE AMOUNT OF FORCE AND ELASTICITY 
5.MORE RELIABLE
6.NO LEAKAGE PROBLEM
7.NO BURNOUT
     
  

there are some type of pneumatic actuators  

1.diaphragm pneumatic actuators
2.pneumatic power cylinders 
3.gas-engine pneumatic actuators
4.jet-stream pneumatic actuators
5.pneumomuscles
6.combined pneumatic actuators

1.diaphragm pneumatic actuators

 

slide_8 SUB SYSTEM  USED IN ROBOT 1

To control the diaphragm type of valve we can use different type of actuators like hydraulic,electric,and pneumatic but mostly we use pneumatic type of actuator to control the diaphragm valve. in this of valve air pressure is applied through a pilot valve into the actuator which control the diaphragm up and down.during this at high pressure the diaphragm may become rise and open or close the valve.

2.pneumatic power cylinders

 

  images?q=tbn:ANd9GcS4ZIDOPj0zWauq3_KQklY5ZGyAP8Li5HO8qTrqL4JNw4wQjuuI SUB SYSTEM  USED IN ROBOT 1

images?q=tbn:ANd9GcThk_-90jGgZkCWH0J4zVzm8D5Xf7-QtkWrLHrufHL7uA66ytFMRQ SUB SYSTEM  USED IN ROBOT 1
in this type of pneumatic actuator a cylinder with piston and spring arrangement is shown in figure.pressure energy or potential energy of gas is converted into the linear motion of the piston.here you can see two types of arrangement in first figure a single inlet port is used to supply the pressurize air inside the cylinder and a piston attach  with spring is used as a backup assembly but in second diagram instead of one,two ports are used but here we do not use spring as a backup assembly because two way supply of the air responsible for backup of the piston to it’s initial position.
   

3.gas-engine pneumatic actuators  

main motive of using of these type of pneumatic actuators is to reduce the pollution because these are used in power engine of buses and trucks instead of air fuel mixture which is used to produce the power to rotate the crankshaft,we are using compressive gas engine in which only gas is used as working substance.working principle is similar as working of combustion engine.these are also known as compressed air engine.
 

But the Compressed Air Engine (C.A.E.) has some disadvantages, which are:
1. Less power output
2. High pressure of compressed air may lead to bursting of storage tank.
3. Probability of air leakage.

6.pneumomuscles

fGlnQ SUB SYSTEM  USED IN ROBOT 1

these type of actuators are also known as air muscle actuators.
these are an extraordinary actuators which is very small,soft and easily controllable and more powerful.it consist of a rubber tube which is covered with a tough plastic which has  netting structure 
these are short in length like a muscle of a human when inflated with compressed air at low pressure.these are more reliable than other.these are more powerful so the power to weight ratio is much higher than the DC motor power to weight ratio respectively about 400:1 for air muscle and 16:1 for DC motor

ADVANTAGE OF AIR MUSCLE OVER THE DC MOTOR

1.Light in weight
2.lower in cost 
3.more powerful
4.more reliable
5.flexible
6.smooth or immediate response than motor

ELECTRIC ACTUATORS -:

An Electric actuator is more precise than other actuators .in these types of actuators  the electrical energy which is produce by  battery converted into the mechanical torque. main assembly of the electrical actuators consist of  permanent magnet with copper winding  and armature.the working principle of  actuator is similar as the DC motor .in which as the battery supply is provided to the Motor terminal  a magnetic field is generated by  copper coil which results to rotate the armature.these are manly used in  robotic arm controlling .there are mainly types of electric actuators .it does not involve oil or fluid so it is most cleanest actuator than other.
 
1.servo motor 
2.stepper motor 

 SERVO MOTOR 

It is a device which is controlled by  pulse width modulation(PWM).it is basically a DC motor with micro controller chip.the electric signal which is transmitted from the transmitter to the chip receiver tells about the instruction and according to this instruction the motor rotates with specific angle.To increase the torque of the motor there is a gear arrangement which reduces the speed of the motor and increase the torque.servo motor has been used in many  application like toys,robot,remote controlled cars,and in many industries etc.
                          servo motor mainly consist of DC motor,potentiometer and a micro controller  and gear assembly also provided which connected to the control wheel  so as the motor rotates .the resistance of the potentiometer changes which results to regulate the  rotation of motor for specific angle.

how-servo-motors-work-fig3 SUB SYSTEM  USED IN ROBOT 1   

there are two types of servo motors AC and DC servo motors .AC servo motors are mainly used in industrial areas and it can controlled over high current .DC motor are light in weight and these are designed only for lower current controlling so these are used in toys,remote control car etc.
   
 PWM(PULSE WIDTH MODULATION) -:   
 

A pwm is a analog  signal which is generated by a digital source .To understand the behavior of the pwm there is mostly two important terms
1.duty cycle
2.frequency

1.duty cycle

it is the indication of   time during which the  a single become high with respect to the total time of  it takes to complete the one cycle.

total time = TH+TL
where TH is the time during which the signal remains high(1)
TL=it is the during which the signal remains low(0)
so duty cycle is equal to

=TH/(TH+TL)

2.frequency 

it describes that  how fast the cycle of PWM completed 

PWM signals are used for a wide variety of control applications. Their main use is for controlling DC motors but it can also be used to control valves, pumps, hydraulics, and other mechanical parts. The frequency that the PWM signal needs to be set at will be dependent on the application and the response time of the system that is being powered.

PWM%20Graph%201%20Modified SUB SYSTEM  USED IN ROBOT 1                                                                                      25% DUTY CYCLE

   PWM%20Graph%202%20Modified SUB SYSTEM  USED IN ROBOT 1                                             50%DUTY CYCLE

PWM%20Graph%203%20Modified SUB SYSTEM  USED IN ROBOT 1                                              75% DUTY CYCLE

here you can understand about the duty cycle with the help of  above schematics which helps to give you over view of the PWM  signal.

                                                                                                                                                                                                             

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