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Advanced techniques for warehouse automation
Advancedtechniques forwarehouse automation by HUGO KARLSTROM
T
he most basic requirements of a sophisticated warehouse control system can be itemized as fol-
lows:
the control and coordination of different automatic materials handling equipment recording individual pallet loads and locations optimizing crane and truck movements for maximum throughput stock rotation The whole operation hinges on the free flow of information between the central administrative computer and the warehouse computer. Both keep constantly updated stock level records, but the warehouse computer also holds information on the contents of each individual pallet in the store at any one time. Goods inward information is fed from the warehouse computer to the administrative computer, and this in turn feeds back output orders to the warehouse system. The warehouse computer selects pallets to meet these orders on a ‘first in, first out’ (FIFO) basis. To avoid the whole system Abstract: The characteristicsof a computerizedwarehouse controlsystemare described. Particular attentionis paid to recording individualpallet loads and locations,optimizingcrane and truck movementsformaximum throughput and stockrotation. Kqwords: data processing, warehouse, stock control. Hugo Karlstrom is sales manager in the materials handling division of SattControl Ltd.
UK
38
0
0011-684W83/080038-03$03.00
A typical automated warehouse with AGVs.
breaking down in the event of stock losses or other shortfalls, the warehouse computer constantly updates the administrative system with actual output data. Communication between the two computers is carried out in different ways, according to system types, and depending whether data is required via an online link, or with a batch communication link. SattStore is a typical computerbased system for automatic control of materials handling in a variety of configurations. The system is driven by a PDP 1 l/44 minicomputer utilizing distributed processing for local control. Functions of a warehouse control system can be grouped into four separate categories: l l l l
inventory control crane control automated guided conveyor control
vehicle control
Inventory control
l l l
location file order file order line file
The Article file contains all the data on the article in the warehouse, both fixed information and current information showing the present status of the article. Fixed information, such as article number and name, can be complemented by information such as: storage zone for the article; weight per unit; number of units per full pallet; and supplier’s article number. Example of variable article data include: l
l
l
total quantity of this article in the warehouse total quantity of this article per crane aisle oldest and youngest pallet
Every load carrier in the warehouse generally a pallet - has a dedicated unique number under which the system stores information. This number is generated when a pallet is due to enter the warehouse. For each pallet current information is stored about the goods on the pallet, such as quantity, storage date, pallet weight etc. This data is stored in the Pallet file.
The administrative part of a warehouse system should keep a record of all articles in the warehouse, whether they are on shelves, on pallets in racks, being transported or handled in any other way. This information, which can be simply configured to suit the size and nature of the warehouse, is stored in the system database. The basic system has the following database files:
The Locationfile stores data about each location in the warehouse. A location file record contains information about whether a location is free, occupied by a certain pallet, or blocked. The record also provides information on the type of storage location.
article file 0 pallet file
orders
The Order file contains
l
1983 Buttetworth
& Co (Publishers)
Ltd.
entered,
which
all output are to be ful-
data processing
Winchester
disc
IZIMB
12iMB
Wtnchester
disc
~
6
terminal
Corsoi
Colsoi terminal --
3270
llnk to mainframe ‘I
Pallet control station 7.*nc 5 To local PBS io weight station Alarm
Message printer
~~i._en 8 picn stotlons
4 automatic
RPC
,,,.
I, _--A
iPallet control stction zone 6 1
cranes
with transfercars
L---Y
8 AGVs Y
Zone 5, auto VNA store
Wmzatzc hagram of the aut~te~
Input to store In order to input goods to the automatic warehouse the goods must be piaced on a load carrier, generally a pallet. The pallet will be checked with regard to size and condition and its stock contents entered into the computer. The pallet check is carried out at a special station which automatically checks the profile of the palletized goods, the pallet’s condition, the pallet height, and if desired the weight of the pallet. The check information is sent to the computer system and combined
october 1983
;_ye__
AGV system
8 semi outomattc Zone 6, manual
crones _-__.._
__-.A
VNG store
warebuse system at L&and Trucks, Ck~ley, UK.
filled by the system. Each order consists of one or more order lines, which in turn contain information about the required article number and quantity.
vol25 no 8
,:
VDU
c-3
Pick area
printer
there with the information entered in used as a complement to the manual the pallet identification. Pallet iden- method. A laser scanner reads the paltification takes place after the pallet let number from a barcoded label on check and can be carried out both the pallet. The goods on the pallet have manually and automatically. been reported earlier by what is In the cases of manual pallet iden- termed batch ident~cation. tification a VDU terminal is used and At batch identification of incoming all the information from the pallet palletized goods algroup of pallets is check is presented to the operator on identified against transport documents the screen. When certain information or other documents available at the has been given, the system replies with goods receiving check. Batch idenexplanatory data to help the operator tification can be done either via a VDU work correctly. For example, if the terminal or via a hand-held terminal. When using a hand-held terminal, article number has been given, the computer replies by stating the article the batch identification can be carried name. out locally at the goods receiving bay. about all pallets in When an ident~cation dialogue is When notation completed, the pallet is ready to be the batch has been entered, the handheld terminal is co~nnected to the contransported into the warehouse. Automatic pallet identification is trol system and the information is
39
applications transferred to the computer. After a batch identification the system prints pallet labels with the pallet number in barcode format for each identified pallet. Using the pallet weight, the computer can ensure that the down loading per rack section does not become greater than stipulated by constraints such as rack design or floor strength. By controlling the section weight the racking could be constructed for the average weight instead of the maximum weight of the pallets. It is also possible to locate heavy pallets on the lower part of the racking. Slow or fast moving articles can be placed in different zones of the warehouse. When this is the case the computer contains information about the move frequency for each article.
Output from store Goods out orders can be entered into the system either via a VDU terminal or by communication with another (mainframe) computer. An order is entered with an order number and a number of orders lines, each with the required article number and quantity. Output can be made both by whole pallet loads or by order picking. Normally the FIFO (first in, first out) principle is used, i.e. the oldest pallet holding the required article is chosen for output. Order picking can be done in different ways - either the operator travels to the goods or the goods are transported to the operator. In the first instance a picking store with semiautomatic pick cranes (or pick trucks) can be used. In the second instance pick stations are used. In a picking store, with semiautomatic pick cranes, order lines are presented one by one in location order for the crane operators. By using barcode reader pens in the cranes, the system can check that the picks are done from the correct pallets. After each completed order line the operator confirms the actual picks done to the system via a terminal in the crane.
40
When a manual picking store or an open picking area is used, a pick list is printed in location order. Each pick completed has later to be reported to the system. When pick stations are used, pallets are transported from the store to the pick stations. When the picks have been completed the operators confirm to the system via terminals at the pick stations. The pallets are then returned to the store. When an order has been completed for despatch, despatch notes and invoices are printed. These documents are then always based on the actual output from the stores.
Printouts It should be possible to obtain a variety of printouts from the computer which provide comprehensive information about the store contents. Examples of printouts are: all information on pallets with a certain article number; all recorded orders; all blocked pallets in the warehouse; and all pallets older than a given date.
Crane control
l
Input of a pallet Output of a pallet another aisle.
AGV control The Automatic Guided Vehicle (AGV) control system is divided into three control levels: task, traffic and truck. The task control is carried out in the central computer, and gives transport orders to the AGVs. A transport order is to transport a pallet from a pick up position to a deposit position within the AGV route layout. The task control checks that all transport orders are carried out and that empty AGV movements are limited. The current storage situation is updated and errors are reported by the task control. The traffic control is done by decentralized microcomputers in the AGV route layout. These micros direct the AGV through the route layout towards the destination and they ensure that the AGVs do not collide. The truck control is carried out by onboard microcomputers in the AGVs, which control steering, speed, lift devices etc.
Conveyor control
The central computer communicates with the microcomputers onboard the automatic cranes and gives them transport orders. Such a transport order can be one or any combination of the following:
l
crane can then pick up and/or deposit etc., even if the central computer is down.
or transfer
to
The microcomputer in the crane controls all the movements of the crane in the aisle and reports all events to the central computer. On completion of a transport order the movements carried out are acknowledged. If the transport order has not been performed as intended, the crane reports the error. As a reserve function it is also possible to connect a terminal directly to the microcomputer and run in automatic mode from the crane platform. The
Start, stop, interlocks, monitoring and other logical activities are controlled in this section of the system. The control unit also acts as an interface, for example, for external sensors. The central computer is responsible for the overall materials flow.
Data protection The extensive database associated with a storage system requires protection against faults which could compromise the integrity of this valuable information. Various techniques, e.g. double disc updates andor transaction logging, can be implemented to give maximum protection against power failure, disc faults, system failure, misuse etc. System restart should be simple 0 and rapid SattCantrol UK Ltd, 13 Holder Road, Aldershot, Ham GUlZ 4RH, UK. Tel: (0252) 331651.
data processing
T
he most basic requirements of a sophisticated warehouse control system can be itemized as fol-
lows:
the control and coordination of different automatic materials handling equipment recording individual pallet loads and locations optimizing crane and truck movements for maximum throughput stock rotation The whole operation hinges on the free flow of information between the central administrative computer and the warehouse computer. Both keep constantly updated stock level records, but the warehouse computer also holds information on the contents of each individual pallet in the store at any one time. Goods inward information is fed from the warehouse computer to the administrative computer, and this in turn feeds back output orders to the warehouse system. The warehouse computer selects pallets to meet these orders on a ‘first in, first out’ (FIFO) basis. To avoid the whole system Abstract: The characteristicsof a computerizedwarehouse controlsystemare described. Particular attentionis paid to recording individualpallet loads and locations,optimizingcrane and truck movementsformaximum throughput and stockrotation. Kqwords: data processing, warehouse, stock control. Hugo Karlstrom is sales manager in the materials handling division of SattControl Ltd.
UK
38
0
0011-684W83/080038-03$03.00
A typical automated warehouse with AGVs.
breaking down in the event of stock losses or other shortfalls, the warehouse computer constantly updates the administrative system with actual output data. Communication between the two computers is carried out in different ways, according to system types, and depending whether data is required via an online link, or with a batch communication link. SattStore is a typical computerbased system for automatic control of materials handling in a variety of configurations. The system is driven by a PDP 1 l/44 minicomputer utilizing distributed processing for local control. Functions of a warehouse control system can be grouped into four separate categories: l l l l
inventory control crane control automated guided conveyor control
vehicle control
Inventory control
l l l
location file order file order line file
The Article file contains all the data on the article in the warehouse, both fixed information and current information showing the present status of the article. Fixed information, such as article number and name, can be complemented by information such as: storage zone for the article; weight per unit; number of units per full pallet; and supplier’s article number. Example of variable article data include: l
l
l
total quantity of this article in the warehouse total quantity of this article per crane aisle oldest and youngest pallet
Every load carrier in the warehouse generally a pallet - has a dedicated unique number under which the system stores information. This number is generated when a pallet is due to enter the warehouse. For each pallet current information is stored about the goods on the pallet, such as quantity, storage date, pallet weight etc. This data is stored in the Pallet file.
The administrative part of a warehouse system should keep a record of all articles in the warehouse, whether they are on shelves, on pallets in racks, being transported or handled in any other way. This information, which can be simply configured to suit the size and nature of the warehouse, is stored in the system database. The basic system has the following database files:
The Locationfile stores data about each location in the warehouse. A location file record contains information about whether a location is free, occupied by a certain pallet, or blocked. The record also provides information on the type of storage location.
article file 0 pallet file
orders
The Order file contains
l
1983 Buttetworth
& Co (Publishers)
Ltd.
entered,
which
all output are to be ful-
data processing
Winchester
disc
IZIMB
12iMB
Wtnchester
disc
~
6
terminal
Corsoi
Colsoi terminal --
3270
llnk to mainframe ‘I
Pallet control station 7.*nc 5 To local PBS io weight station Alarm
Message printer
~~i._en 8 picn stotlons
4 automatic
RPC
,,,.
I, _--A
iPallet control stction zone 6 1
cranes
with transfercars
L---Y
8 AGVs Y
Zone 5, auto VNA store
Wmzatzc hagram of the aut~te~
Input to store In order to input goods to the automatic warehouse the goods must be piaced on a load carrier, generally a pallet. The pallet will be checked with regard to size and condition and its stock contents entered into the computer. The pallet check is carried out at a special station which automatically checks the profile of the palletized goods, the pallet’s condition, the pallet height, and if desired the weight of the pallet. The check information is sent to the computer system and combined
october 1983
;_ye__
AGV system
8 semi outomattc Zone 6, manual
crones _-__.._
__-.A
VNG store
warebuse system at L&and Trucks, Ck~ley, UK.
filled by the system. Each order consists of one or more order lines, which in turn contain information about the required article number and quantity.
vol25 no 8
,:
VDU
c-3
Pick area
printer
there with the information entered in used as a complement to the manual the pallet identification. Pallet iden- method. A laser scanner reads the paltification takes place after the pallet let number from a barcoded label on check and can be carried out both the pallet. The goods on the pallet have manually and automatically. been reported earlier by what is In the cases of manual pallet iden- termed batch ident~cation. tification a VDU terminal is used and At batch identification of incoming all the information from the pallet palletized goods algroup of pallets is check is presented to the operator on identified against transport documents the screen. When certain information or other documents available at the has been given, the system replies with goods receiving check. Batch idenexplanatory data to help the operator tification can be done either via a VDU work correctly. For example, if the terminal or via a hand-held terminal. When using a hand-held terminal, article number has been given, the computer replies by stating the article the batch identification can be carried name. out locally at the goods receiving bay. about all pallets in When an ident~cation dialogue is When notation completed, the pallet is ready to be the batch has been entered, the handheld terminal is co~nnected to the contransported into the warehouse. Automatic pallet identification is trol system and the information is
39
applications transferred to the computer. After a batch identification the system prints pallet labels with the pallet number in barcode format for each identified pallet. Using the pallet weight, the computer can ensure that the down loading per rack section does not become greater than stipulated by constraints such as rack design or floor strength. By controlling the section weight the racking could be constructed for the average weight instead of the maximum weight of the pallets. It is also possible to locate heavy pallets on the lower part of the racking. Slow or fast moving articles can be placed in different zones of the warehouse. When this is the case the computer contains information about the move frequency for each article.
Output from store Goods out orders can be entered into the system either via a VDU terminal or by communication with another (mainframe) computer. An order is entered with an order number and a number of orders lines, each with the required article number and quantity. Output can be made both by whole pallet loads or by order picking. Normally the FIFO (first in, first out) principle is used, i.e. the oldest pallet holding the required article is chosen for output. Order picking can be done in different ways - either the operator travels to the goods or the goods are transported to the operator. In the first instance a picking store with semiautomatic pick cranes (or pick trucks) can be used. In the second instance pick stations are used. In a picking store, with semiautomatic pick cranes, order lines are presented one by one in location order for the crane operators. By using barcode reader pens in the cranes, the system can check that the picks are done from the correct pallets. After each completed order line the operator confirms the actual picks done to the system via a terminal in the crane.
40
When a manual picking store or an open picking area is used, a pick list is printed in location order. Each pick completed has later to be reported to the system. When pick stations are used, pallets are transported from the store to the pick stations. When the picks have been completed the operators confirm to the system via terminals at the pick stations. The pallets are then returned to the store. When an order has been completed for despatch, despatch notes and invoices are printed. These documents are then always based on the actual output from the stores.
Printouts It should be possible to obtain a variety of printouts from the computer which provide comprehensive information about the store contents. Examples of printouts are: all information on pallets with a certain article number; all recorded orders; all blocked pallets in the warehouse; and all pallets older than a given date.
Crane control
l
Input of a pallet Output of a pallet another aisle.
AGV control The Automatic Guided Vehicle (AGV) control system is divided into three control levels: task, traffic and truck. The task control is carried out in the central computer, and gives transport orders to the AGVs. A transport order is to transport a pallet from a pick up position to a deposit position within the AGV route layout. The task control checks that all transport orders are carried out and that empty AGV movements are limited. The current storage situation is updated and errors are reported by the task control. The traffic control is done by decentralized microcomputers in the AGV route layout. These micros direct the AGV through the route layout towards the destination and they ensure that the AGVs do not collide. The truck control is carried out by onboard microcomputers in the AGVs, which control steering, speed, lift devices etc.
Conveyor control
The central computer communicates with the microcomputers onboard the automatic cranes and gives them transport orders. Such a transport order can be one or any combination of the following:
l
crane can then pick up and/or deposit etc., even if the central computer is down.
or transfer
to
The microcomputer in the crane controls all the movements of the crane in the aisle and reports all events to the central computer. On completion of a transport order the movements carried out are acknowledged. If the transport order has not been performed as intended, the crane reports the error. As a reserve function it is also possible to connect a terminal directly to the microcomputer and run in automatic mode from the crane platform. The
Start, stop, interlocks, monitoring and other logical activities are controlled in this section of the system. The control unit also acts as an interface, for example, for external sensors. The central computer is responsible for the overall materials flow.
Data protection The extensive database associated with a storage system requires protection against faults which could compromise the integrity of this valuable information. Various techniques, e.g. double disc updates andor transaction logging, can be implemented to give maximum protection against power failure, disc faults, system failure, misuse etc. System restart should be simple 0 and rapid SattCantrol UK Ltd, 13 Holder Road, Aldershot, Ham GUlZ 4RH, UK. Tel: (0252) 331651.
data processing