Introduction 2
Automated Guided Vehicle (AGV) 3
Operation of an AGV 3
Advantages of AGV systems 8
Disadvantages of AGV systems 9
Robotics 9
Elements of a Robotic system 10
Advantages of Robots 12
Disadvantages of robots 12
Conclusion 12
Works Cited 13
Introduction
During manufacturing and production processes, material handling is key in realizing high throughputs. Most industries however still use manual techniques such as trucks, conveyor belts, and roller chains despite the discovery of automated and advanced systems which could make transportation easier. This is because of cost-related issues. In the long run however, cutting on overhead costs, reliability and flexibility in the sense that it’s possible to integrate to different environments, are realized in the long run among many other advantages. Automating some of these manual systems like trucks gave birth to Automated Guided Vehicles (AGV) which are operated by a computer software to carry out transportation of materials and goods inexpensively.
Automated Guided Vehicle (AGV)
An AGV is a vehicle that is controlled automatically by a computer system as its driving element used to move materials and goods. They find application in industries to transport raw materials and finished goods, in the military, in risky environments like deep seas and nuclear reaction processes, moving physically handicapped people, and in space exploration .They are powered by means of batteries or through inductive charging. Movement is with the help of stored computer instructions that define the destination, select routes, track movement and position the vehicle. Where many vehicles are being used, navigation by use of lasers aid to move goods according to priority and select routes with less traffic to avoid deadlocks and collisions. AGVs have been found flexible and reliable as compared to manual transportation methods.
Operation of an AGV
Various stations have their own paths, but once in a while, different stations can have a common path. Once an AGV sets off to a particular station, it follows a path that has already been selected by the control system. This is possible with a combination of sensors, lasers, Electric and RF signals that assist in navigation, communication with the controller and give feedback on distance, speed and location.
There are three types of AGVs : towing AGVs, load lifters for floor applications and AGVs for lifting loads to shelves or racks.
There are different AGV guidance methods which depend on cost, future needs, and transportation needs. They include;
Laser guidance: this method is considered flexible because it does not require lines or tracks to move the vehicle. The routes can be adjusted by making modifications in the software. It is suitable for both indoor and outdoor applications.
Wire guidance: most sure system because the vehicle path follows wire that is already installed on the ground. Information is relayed through this wire back to the computer.
Tape guidance: the vehicle moves along a line or tape on the ground by use of cameras. Information exchange is done only through radio and is only suitable for use indoors.
The sensor does its work of collecting information and sending it to the controller to drive the motors in the desired path. There are two ways of controlling movement of an AGV namely; closed and open path systems which are factors of size, cost and application
Close path system is where there is a line buried on the ground or embedded and the AGV has a sensor on its bottom that detects the line and moves along that line. There can be two types of lines; colourful line and magnetic line. The magnetic line is embedded while the colourful line is buried. Since the lines are fixed in these systems it makes them inflexible in case there’s need to adopt change.
The open path system sought to solve the problem of inflexibility encountered in the closed path system since the paths are not predetermined. This means that while the system remains the same, it is possible to change the path to suit changing needs. This achieved by having rows of crisscrossing laser lines where the AGV is controlled to move in any of the paths making the system highly flexible and accurate. This method is however costly as compared to the closed path one.
Functional Parts of an AGV
Figure1: Functional Parts of an AGV 1
The Part names are identified as below
DC Motor operated by PLC
Components of PLC ,
Battery system
Front wheel
Back wheel
Sensors
Photo sensors
Robotic arm
Load to be moved
Material holding area
General AGV system component functions are explained below:
An on-board controller which is used to initiate procedures for start and shutting down, and functions in between like braking, propulsion, error monitoring and detection.
Management system responsible for controlling traffic, routing and dispatch, ensuring the vehicle is optimally utilized and material tracking.
Communication system- by means of wireless communication where the base station and vehicle exchange information such as position and path information. The vehicle is able to give feedback to the base station
A navigation system used to guide the AGV around its area of operation. This is based on either fixed route approach where the AGV can only follow a predetermined path or by free-ranging which is flexible and enables the operator to modify trajectories to suit changing needs.
Chassis –made up of base and supports, motor plates electric stand which are responsible for supporting the load, cushioning against unforeseen collisions and as holding places for other kits and devices.
DC motor-it is the driving system for the AGV
Power Transfer system- made of gears, belts and shafts required to transfer power from the motor to the gears and propel the AGV forward with minimal friction.
Electrical components- consisting of batteries for energy supply to the various units and the main kit unit which is the backbone of the AGV and controls all its functions. The sensor board, switch and monitor are also located here.
Covers- both front and back cover which are meant to protect inner components of the AGV and hold the switch and antenna in place.
A load transfer system- which is used to load and offload the truck and can be a part of the truck or be permanently positioned at the station
The following figure represents an overall overview of an AGV system
Figure1: Components of an AGV System 1
Stationary control system is responsible for issuing out orders for transportation, scheduling and communicating with the central controller. It also manages interactions with customers and provides interface for analysis.
Peripheral system components are used to connect to other vehicle counterparts such as loading batteries and mechanisms for transfer.
On-site system components include structures at the facility where the vehicle is being used such as lifts, floor and entry points.
Graph 1: The number of AGVs put into operation world-wide
Advantages of AGV systems
Accountability- products are tracked while on transit via AGV therefore less chances of getting lost
Flexibility- in the sense that it is possible to adjust paths to suit changing needs of the industry
Reduced cost of operations- Tasks like battery changing can be automated. The wear and tear of conveyor systems can be reduced by use of control systems. The result is a reduced overall cost.
Minimal product damage- products are handled gently reducing chances of damage.
Safety- since there are predefined paths there is no loss of goods as AGVs follow on this paths that are monitored.
Scalability-It is possible to increase vehicles to suit increased demand thereby increasing throughput.
Scheduling- AGVs operate on schedule thereby making planning easy and overall efficiency is increased.
Disadvantages of AGV systems
Cost – these systems require high initial and overall cost as compared to manual systems.
They are driven along fixed paths only making it inflexible and expensive to design and accommodate new paths in the workplace
Interaction between workplaces and AGVs is also limited since they only transport loads to and from workstations.
Robotics
Robots have become part of the modern day life processes appearing in various forms to perform a wide range of tasks. A robot is an intelligent device that runs and is controlled by a computer program which acts like the brain to move and carry out tasks that are otherwise done by human beings. They offer a cheaper, reliable and accurate means of labour as compared to human beings. Jobs considered dirty, boring or dangerous can be done by robots. They find application in manufacturing and production industries, space exploration, surgery, laboratory and many other places. Most robots emulate human body parts and therefore perform functions done by such parts. The most widely used is the robot arm which can perform simple motions like picking components from a machine, painting, moving and packaging goods, and welding among others. Future industrial applications seek to include more robots in their processes to increase productivity.
For easy navigation of robots, the following things are required to localize it:
Prior analysis and evaluation of the operating environment
Comparison means of the present past gathered information
A means of estimating location of the robot from the reference point.
Elements of a Robotic system
Figure2: Elements of an Industrial Robot system
The hardware subsystem for a robot can be collectively summarized as follows
Locomotion- means of movement in its area of operation
Sensing –sensors are attached at different points of the robot to detect any changes in their environments to avoid any collisions therefore ensuring their safety.
Reasoning-to interpret instructions into appropriate actions
Communication- as a means for communication with the operator
The various component operations are summarized below
Operation of a robotic system 1
Dynamic System -Required for movement around the operation area mostly the robotic arm. It consists of axes which determine the scope of freedom for arm movement, the greater the number of axes the better the ability to move. There are three driving mechanisms namely: electric, pneumatic and hydraulic systems.
End-of-arm tools -They are used to install hooks, clamps, electromagnets whose function is to hold together components of the robot.
Computerized digital controller whose function is to control operations by use of programs.
Actuators-To control axes and uphold direction of movement.
Feedback system-used to measure speed, position and acceleration of the robot.
Sensors – to evaluate position and change in patterns that can cause failure.
Advantages of Robots
Robots can perform human tasks in a more effective way since they can do several shifts in a day, do not grow weary or strike thereby increasing overall output.
Since they run on a computer programs, the instructions can be adjusted to suit changing needs.
In the case of a robotic arm, the joints are driven by electric or hydraulic motors which are more powerful than human beings.
Minimizing on cost -achieved because robots work longer hours and more effectively reducing overall operating costs
Disadvantages of robots
There is need for qualified people to supervise the robots
Unemployment – robots took up jobs that were previously done by human beings
Consume a lot of time to assemble and make programs to run robots.
Require a large working area to avoid collisions and accidents.
Conclusion
Robots and AGVs are both automated systems aimed at making work easier. They find applications in industries and production sites to make processes easier, faster and efficient. The overall effect is increased productivity, reduced costs and time saving. Modern and future industries aim to increase investment in these systems to increase productivity.
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