Automated Material Management and Handling in Construction Projects
The automated material management is a part of computer integrated construction (CIC). It involves automated material identification system and the automated material handling systems.
Automated Material Management
The construction materials are identified at the unloading area as soon as these materials arrive the CIC job site. Then the job site inventory database in updated. A tight control is demanded by the CIC on the inventories and on the integrated operation of the equipment used in construction.
From the time the equipment starts working to the time it finishes the facility, all the construction materials will be tracked as per CIC.
The tracking of construction materials can be done either directly or indirectly. In the case of direct tracking, there exist a code over the surface of the equipment. These codes are used to identify the equipment by direct means.
In indirect tracking system, a code will be on the material handling equipment. For bulk material tracking like paints etc., these methods of indirect tracking can be employed.
Different automatic identification systems used for construction materials are described below:
- Bar Coding
- Voice Recognition
- Vision System
The bar coding system was initially implemented by the U.S Department of Defense (DOD). The barcode symbols helps in conveying information through the placement of narrow or wide dark bars.
The two-main technology used to read the bar codes are laser beams and magnetic foil code. For those bar codes that move easily, the laser beams will let to read easily. The most reliable identification system are the magnetic code readers.
This technology uses the computers to recognize the spoken words. These words are grasped and converted then to strings and sent to the central processing unit (CPU) of the computer unit. The handling of input patterns and classification of the same to words and phrases are the main objective of the computer voice recognition technology.
There are mainly two steps that are involved in the same:
Step 1: Analyzing of the voice signal. This will help in the extraction of the features and the characteristics of the voice. This is grasped sequentially with time.
Step 2: Comparison of the phrases with the computer language. After the comparison, the transcription of the spoken command is made.
In the vision system, a two-dimensional picture is obtained by means of vector or matrix method. The picture obtained is divided into several grid elements and these are called as pixels. The binary information needed for determining the picture parameter is obtained from the gray scale of the pixels. This is the main method through which the system recognizes the objects.
A high picture resolution from the current cameras is obtained by employing the vector method. In Vector method, the picture vectors of the scanned objects are taken. These are later stored in regular intervals. After the completion of an entire cycle, the picture information is evaluated by the pre-processor. From this, the parameter of interest is extracted.
Automated Material Handling System
The automated material handling system have an important position in computer integrated construction. Like for the handling of precast or prefabricated components. The construction work is made easier and fast by employing a material handling system with a material identification system.
Some of the important units in automated material handling systems are:
- Under hang cranes
- Inverted power and free conveyor systems
- Power and free conveyor systems
- Track and drive tube conveyors
- Automatic Vertical Transport systems
- Autonomous Dump truck system
- Automatic guided vehicles
This consist of a powered chain which will enable the movement of other carriers to the assigned destinations. Sophisticated computer electronic techniques are used to control the towlines. This works efficiently with other handling systems.
The towline system works very better with the automated material identification system. To read the bar-coded information and the relay signals, photoelectric readers or optical scanners can be used. The cart is routed to the destination by the control system.
Under Hang Cranes
Motor driven under hang cranes are of two types:
- Single bridge overhead cranes
- Double bridge overhead cranes
The motor driven crane consists if track, bridge girders, the control package, the end trucks, drive wheels, drive assembly, a traveling pushbutton control, cross-bridge electrification and the runway.
Inverted power and free conveyor systems
This system has an upside-down configuration. This comprises a power and free conveyor system. For complete access, the load is supported on the pedestal -type carrier.
Autonomous Dump Truck system
The figure below shows the autonomous dump truck system. This system helps in the driverless hauling operations. This help in the hauling of the earth and the aggregates by the dump trucks that are common in construction site.
Fig: An Autonomous Dump Truck System
The main two functions of autonomous dump truck system are:
- Advanced measurement function
- Autonomous driving function
The encoder sensors are attached to the tires of the truck to determine the driving distance and the velocity of the vehicle. A fiber-optic gyroscope is used to detect the vehicle’s direction in the construction site. The data from the encoder sensors and the fiber-optic gyroscope will let us know about the position of the vehicles in the site.
In the left side of the test vehicle bears a laser receiver or a laser transmitter. The reflectors are installed along the driving route of the vehicles throughout the site. These reflectors are kept at interval of 50m.
The long-distance driving can result in the error accumulation. These are corrected through the feedback information that is given by the transmitter or the receiver placed in the vehicles.
To check whether the workers are wearing helmets, an autonomous vehicle system is used. This uses a colour image processer to check whether they are wearing it or not.
Automatic Vertical Transport system (AVTS)
This is a system used to deliver the material throughout the job site. The material is automatically loaded with the help of an automated elevator system. This hoists the material to the designated floor. The system will automatically unload the lifts.
The hoisting of carriers between the crane runways that are adjacently placed is facilitated by the interlocks. This helps in maximizing the area covered by the overhead material handling system. The interlock system helps in duplicate handling.
Power and free conveyor systems
These systems allow the precast or the prefabricated component to be carried with the help of trolley or multiple trolley. These trolleys are carried either by conveyor or by gravity. These systems provide high weight capacities that are more common in construction.
Track and drive tube conveyors
The transport of components for prefabrication is carried out with the help of track and the drive tube conveyors. This system has a spinning tube which is mounted between the two rails.
By varying the angle of the drive school, the speed of the moving component can be controlled. The carrier remains stationary when the drive wheel is in 0-degree position. With the increase in the angle, the carrier starts to accelerate.
Automatic guided vehicles
The AGV s are the most flexible equipment among all the automatic material handling system. These are controlled with the help of on-board microprocessors, a central computer, and programmable controllers.
The automatic guided vehicle can be considered as construction robots as they are not dependent on the manual guidance and man intervention. The AGVs have their own motive power that moves them. A signal emanating from a buried wire will control the steering system.
Material Handling Equipment