Automatic guided vehicle
In this project our robot will sense wall according to sensor it will take action.
We design this vehicle for future automation. Assume that if any small robot is moving on the table then can it is possible robot can not fall from the table, when robot move to the end of table then robot sense the depth and at that time depth sense provide a signal to the microprocessor to stop the vehicle . It is also possible to reverse the robot on the table by using reversing the motor. When we reverse the motor then again we require a one more depth sensor on the back side of the robot.
For the depth sensing we use inra red rays . one photodiode and one infra red is connected in pair with the vehicle. We design the circuit so that when any car move on the track then both infra red sensor, front and back reflect the rays and circuit sense the track. If the track is okay then circuit sense the rays and move the motor forward. When the vehicle move forward then if the track is going to the depth region then infra red rays are not reflected from the surface and due to that processor get a signal and . vehicle move backward automatically.
In this project we use ic 89c2051 microcontroller as a main processor. IC 89c2051 is a 20 pin microcontroller. This ic is a 20 pin version of 40 pin main atmel ic 89c51 microcontroller. We program this ic with the help of computer. Software is written in the assembley language and then transfer into the blank ic with the help of programmer kit.
In addition with the anti falling concept we use auto collosion concept.
In this project we show that how we design a future vehicle for automation. By using this automation we design the vehicle for auto path finding. We use this concept for remote area. Where we control the robot from remote are . Or we send the machine in any small tunnel. If we fit a wireless camera with this robot then it is possible for us to capture the all detail of facing area.
In this project we use two sensor. These sensor are reflective type sensor. When infra red rays reflective from any surface then we sense this reflective signal and pass to the microcontroller circuit. Microcontroller circuit sense the input signal and compare this signal with the other eye signal and then change the direction of one motor. When there is no deflection from any sensor then there is no signal from the sensor and at that time both the motor of the vehicle run smoothly to the forward direction.
In this vehicle we use total two motor for the forward and reverse direction. When one motor stop then vehicle change its direction for a short second and then again came to the origional position.
Main circuit is based on the microcontroller. Here in this project we use 89c2051 microcontroller as a main processor. Motor’s control by a H bridge circuit. For two motor we use two H bridge circuit. Here in this project we use two slow speed dc gear motor .
In this project we use ic 89c2051 is a main processor. IC 89c2051 is a family member of 8051 micrcontroller. Pin no 20 is connected to the positive supply. Pin no 10 is connected to the negative supply. Pin no 1 is act as a reset pin. On this pin we use one capacitor and resistor network. Two infra red sensor is connected as a collosion sensor. We using two infra red sensor and infra red sensor for a anti falling concept. These sensors are connected to the port p3.0, p3.3 and port p3.4. On this pin we directly connect a photodiode as a receiver sensor. In fra red led is directly connected with the 5 volt supply through 100 ohm resistor. Port p1.0 , p1.1 and port p1.2 and port p1.3 is output pin. IN this controller we use negative input and negative output circuit. Output of the microcontroller is connected to the four different optocoupler connectivity. Output of the optocoupler is inverted by the inverter circuit. Output of the inverter circuit is connected to the H bridge circuit. Here we use H bridge circuit to control the direction of the motor. IN this project we use two slow speed motor so with the help of dc motor we move forward and reverse the robot.. when we insert the battery then robot move to forward. If there is any obstruction on one sensor then one photodiode is get a signal and so that negative signal is applied to the photodiode . Photodiode receive the signal and so on microcontroller stop one motor and so that robot move to another direction. Now if the robot sense a bit then depth sensor active and stop both the motor. Now when both motor stop and with small delay motor reverse back to few step . after taking back few step robot changes its direction to right and again move forward. So when robot falling any depth then takes back few step and changes its direction and again go forward
P1.0 and p1.1 is connected to the one motor. When both the pins are high logic then motor stop. At the same time when both the pins are 0 then again motor stop. To move a motor forward and reverse we provide a high logic on one pin and 0 logic on second pin. If we change the logic 0 and 1 then we change the direction of motor
BASIC OF ROBOTICS
A mechanical device that sometimes resembles a human and is capable of performing a variety of often complex human tasks on command or by being programmed in advance is defined as a ROBOT
A Robot never becomes fulfill until it can take decisions. We can’t go for computers for the computation & intelligence. But we can use single chip microcontrollers for controlling. This robot is not going to do any big tasks there will only be predefined tasks. The robot’s full control is embedded into one chip which is otherwise known as embedded systems designing.
To make a robot we must surely know to at least use a single microcontroller. So let us see about Embedded System thru 8051.
What is Open SYSTEM?
An open system is the normal desktop computer where you can use it for any tasks. If you want to process text documents you can install Ms-word if you want to send mail you can use outlook express and counts on.
What is Embedded System ?
An embedded system is the system where you can use it for a specific task.
A microcontroller (often abbreviated MCU) is a single computer chip that executes a user program, normally for the purpose of controlling some device hence the name microcontroller.
A microcontroller is differed from microprocessor in many ways. Basically microprocessors are the devices which can process huge amount of data. A microprocessor can’t do anything on it own. Even to light a led a microprocessor needs minimum of a ROM, RAM, Latch, Address decoders, PORT controllers. But for the same application if you take a microcontroller you barely need a crystal and some capacitors.
So from this you can understand how versatile the microcontroller is.
It is always good to know the market scenario before learning any thing. The following will explain the whole scenario of the embedded industry. This will make you to choose the best one for you.
Different microcontrollers in market.
- PIC One of the famous microcontrollers used in the industries. It is based on RISC Architecture which makes the microcontroller process faster than other microcontroller.
- INTEL These are the first to manufacture microcontrollers. These are not as sophisticated other microcontrollers but still the easiest one to learn.
- ATMEL Atmel’s AVR microcontrollers are one of the most powerful in the embedded industry. This is the only microcontroller having 1kb of ram even the entry stage. But it is unfortunate that in India we are unable to find this kind of microcontroller.
The H-Bridge Circuit
This circuit known as the H-bridge (named for its topological similarity to the letter “H”) is commonly used to drive motors. In this circuit two of four transistors are selectively enabled to control current flow through a motor.
opposite pair of transistors (Transistor One and Transistor Three) is enabled, allowing current to flow through the motor. The other pair is disabled, and can be thought of as out of the circuit.
By determining which pair of transistors is enabled, current can be made to flow in either of the two directions through the motor. Because permanent-magnet motors reverse their direction of turn when the current flow is reversed, this circuit allows bidirectional control of the motor.
The H-Bridge with Enable Circuitry
It should be clear that one would never want to enable Transistors One and Two or Transistors Three and Four simultaneously. This would cause current to flow from Power + to Power – through the transistors, and not the motors, at the maximum current-handling capacity of either the power supply or the transistors. This usually results in failure of the H-Bridge. To prevent the possibility of this failure, enable circuitry as depicted in Figure is typically used.
In this circuit, the internal inverters ensure that the vertical pairs of transistors are never enabled simultaneously. The Enable input determines whether or not the whole circuit is operational. If this input is false, then none of the transistors are enabled, and the motor is free to coast to a stop.
By turning on the Enable input and controlling the two Direction inputs, the motor can be made to turn in either direction.
Note that if both direction inputs are the same state (either true or false) and the circuit is enabled, both terminals will be brought to the same voltage (Power + or Power – , respectively). This operation will actively brake the motor, due to a property of motors known as back emf, in which a motor that is turning generates a voltage counter to its rotation. When both terminals of the motor are brought to the same electrical potential, the back emf causes resistance to the motor’s rotation.
Stepper motors are special kind of heavy duty motors having 2 or 4 coils. The motors will be stepping each time when it get the pulse. As there are many coils in the motors we need to energize the coils in a specific sequence for the rotation of the motor. These motors are mostly used in heavy machines. The figure shown below consists of a 4 coil stepper motor and the arrow mark will rotate when the coils are energized in the sequence.
Unlike DC motors stepper motors can be turned accurately for the given degrees.
Servo motors unlike the stepper motor it has to be controlled by the timing signal. This motor has only one coil. It is mostly used in robots for its lightweight and low power consumption. The servo motors can also be accurately rotated by the making the control signal of the servo motor high for a specific time period. Actually the servo motor will be having 3 wires where 2 are for power supply and another one is for the control signal. Driving the servomotors is so simple that you need to make the control signal high for the specific amount of time. The width of the pulse determines the output position of the shaft
Detecting objects without whiskers doesn’t require anything as sophisticated as machine vision. Some robots use RADAR or SONAR (sometimes called SODAR when used in air instead of water). An even simpler system is to use infrared light to illuminate the robot’s path and determine when the light reflects off an object.The IR illuminators and detectors are readily available and inexpensive.
Infrared As Headlights
The infrared object detection system we’ll build on the Bot is like a car’s headlights in several respects. When the light from a car’s headlights reflects off obstacles, your eyes detect the obstacles and your brain processes them and makes your body guide the car accordingly. We will be using infrared LEDs for headlights. They emit infrared, and in some cases, the infrared reflects off objects and bounces back in the direction of the Bot. The eyes of the Bot are the infrared detectors. The infrared detectors send signals to the Microcontroller indicating whether or not they detect infrared reflected off an object. The brain of the Bot, the microcontroller makesdecisions and operates the motors based on this sensor input.
More about IR – Detector
The IR detectors have built-in optical filters that allow very little light except the 980 nm infrared that we want to detect onto its internal photodiode sensor. The infrared detector also has an electronic filter that only allows signals around 38.5 kHz to pass through. In other words, the detector is only looking for infrared that’s flashing on and off 38,500 times per second.
This prevents common IR interference sources such as sunlight and indoor lighting. Sunlight is DC interference (0 Hz), and indoor lighting tends to flash on and off at either 100 or 120 Hz, depending on the main power source in the region where you reside. Since 120 Hz is way outside the electronic filter’s 38.5 kHz band pass frequency, it is, for all practical purposes, completely ignored by the IR detectors.
As the receivers detects only modulated signals we need to have our IR LEDs modulated in 36 KHz to 40 KHz. We can use 555 timer to make this 40 KHz pulse. The simple circuit is given below.
555 timer 40khz IR:
|U1||555 Timer IC|
|R1||47 ohm resistor|
|R2||470 ohm resistor|
|R3||5k variable resistor|
|C1||0.0047uf ceramic capacitor|
This circuit oscillates two infrared LED’s at 40 khz. We can use this as our transmitter.
Pin 1 is ground
Pin 2 is Vcc
Pin 3 is Data Data Pin gives logic 0 when ever it detects IR Pulse.
MOTORS FOR LOCOMOTION.
Your car needs an engine to run, Even your can opener probly has a little motor inside to spin the can around. Your robot also needs something to make it run.
An actuator activated a mechanical device and is basically anything that causes movement on your robot. Motors, such as the motors that drive a robot, are the most common type of actuator. Motors come in several varieties such as the gear motor and the servo motor.Motors vary in power, speed , accuracy and power consumption. Some motors have shaft that rotate continuosly ; other types turn less than a complete rotation.
Motors can add a lot of weight to a robot. Lightweight aluminium motors or even plastic motors might save your robot a lot of power in the long run.
DC GEAR MOTOR.
The two types of motor’s that you are likely to use in robotic adventure are DC motors and RC servo motors. The most common motor for robotics is the DC gear motor, which works by gearing down a fast Dc motor to make the motor turn at a slower speed and give the motor a higher torque suitable for robot locomotion.
A dc gear motor is basically a regular DC motor with a special gear box attached to the output shaft . Your robot electrical drive circuitary can control the dc gear motor to rotate the wheels of your robot for locomotion.
You can get a DC motor without a gear head, but generally these are too fast ( around 15,000 RPM). For a robot to move at a reasonable rate you have to gear down a DC motor to about 30 to 80 RPM . When you gear down a DC motor, you get a slower speed and plenty of torque.
H BRIDGE CIRCUIT.
One of the most popular motor controller circuits is an H bridge circuit. An H bridge circuit turns a motor on and off, allows a computer or processor to control a motor’s direction and regulate speed, and may even provide a breaking mechanism . A dc gear motor’s rotation direction is usually controlled with an H bridge circuit.
A processor can not control a motor directly for a several reasons. First, a computer doesnot output enough power to drive a motor. Second, a computer cannot control direction because it has only outputs. Third, motors are noisy electrically speaking, and would quickly damage a computer . essentially, the computer sends, signals to the H bridge to tell it to go forward, reverse, brake or add speed. The H bridge then steps up the voltage and power for the motor. The H bridge circuits also isolates the computer or processor from destrutive voltage spikes and noise, which arise maily from motors. In addition to using an H bridge circuit, you might want to have two sets of batteries: one for your electronics and another for your motors.