Mechatronics Vol. 1, No. 4, pp. 447-455, 1991
0957-4158/91 $3.00+0.00 © 1991 Pergamon Press pie
Printed in Great Britain
CASH DISPENSING M O D U L E HAMISH McLEAN Consultant Engineer, Advanced Manufacturing Systems, NCR (Manufacturing) Ltd., Kingsway West, Dundee DD2 3XX, U.K.
(Received 20 March 1991; accepted 25 April 199.1) Abstract--NCR (Manufacturing) Ltd., in Dundee, develops and produces automatic teller machines (ATM) for worldwide markets. It is the world leader in ATM quality and reliability. This article deals with, in the main, the cash dispensing module located within an ATM. This is a classic mechatronics example with the mechanical conveyor system for note movement controlled by a microprocessor, PROM, RAM, digital and analogue circuits. These in turn are controlled by the main ATM processor, running under an RMX operating system. The money movement and control mechansims will be addressed, as will the software procedures to ensure accurate note dispensing. To appreciate the manufacturing process discussion of the testing philosophy, the automated assembly line and robotic cell used to assemble the money cassettes is also included.
INTRODUCTION N C R (Manufacturing) Ltd. was established in Dundee in 1947 as the first overseas manufacturing facility of the Dayton, Ohio company. They produced, initially, cash registers for the British and European markets. This was augmented by the production of accounting machines and subsequently electromechanical products. Divergence into computer systems and related products followed during the 1960s, In the late 1970s the facility was granted the charter to design and manufacture self service terminals, since then the factory has become the undisputed world leader in A T M systems. The products are individually configured to meet customer requirements. They are shipped around the world to more than 80 countries. N C R are dedicated to continuous improvement in all aspects of the product. To that end a variety of manufacturing techniques are used to improve the business. These encompass just-in-time management, design for manufacturing, and a quality improvement program of get-it-right-first-time ( G R I T ) . The involvement of the workforce in achieving quality objectives is of prime importance.
NCR P R O D U C T OFFERINGS N C R provides a wide range of self service financial terminal products suitable for use with all types of financial institution from banks to building societies. (In this article the 'financial institution' will be referred to as the 'bank'.) The current production consists of three basic types of A T M , these are 'throughthe-wall', in-lobby and free standing products. The internal construction of each is 447
modular so that a very high degree of flexibility is available to satisfy any particular customer requirement. These modules are controlled by an integrated software system, the top level of which is accessible to the bank. This allows the bank to customise the product and make it appear unique to its customers. The lower layers are concerned with the module interface and the data transfer mechanism associated with them. Security features are a great concern at this level and include both software and hardware tamper-indicating features. The cash dispensing module and money cassettes are the subjects of this paper.
General description The function of the cash dispenser is to take notes from the money cassettes and deliver them to the customer in a neat and orderly bundle. The dispenser is made up of one to four money cassettes and related pick modules, a presenter and a purge bin. These are controlled by the microprocessor and associated circuits located on the module control board.
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Fig. 1. Cash dispenser--rear view.
Cash dispensing module The notes, contained in the money cassettes, are removed by the pick modules transported to the presenter for delivery to the customer. In the case of a dispense or the transaction being cancelled, they are conveyed to the purge bin. The control board houses the processing elements needed to interface commands issued from the main A T M computer to the dispenser hardware. It detects note movement and examines the sensors for correct dispensing of required quantity of notes prior to presenting them to the customer.
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Cassette Pick Transport
Fig. 2. Note movement. The m o n e y cassette
This is the reloadable mechanism which contains the notes for issuing to the customer. It is a sealed rectangular container which is opened automatically on insertion into the cash dispenser. It allows transportation of the notes from the bank's premises to the A T M in a secure and orderly manner. Internal adjustments can be made for the required note sizes and sensors can be set to distinguish the differing note denominations.
Fig. 3. Money cassette.
It is filled by opening the top entry lid and inserting the notes upright against the pusher plate. This plate is spring loaded to ensure that the notes are pressed against the front door. On insertion into the dispenser this door is opened and the notes are accessible to the pick module. The spring mechanism is triggered on closing the lid. The front roller door is opened by two tangs as the cassette is pushed into the dispenser. The notes are then available for the pick module to lift them off the stack, the pusher plate keeping an even pressure as notes are removed.
Pick module The pick mechanism provides the mechanics for lifting a note from the front of the cassette and passing it to the transport rollers on the way to the presenter and subsequently to the customer. Notes are picked on c o m m a n d from the dispenser onboard processor. When this c o m m a n d is issued two events commence; firstly, the transport m o t o r starts, which allows the vacuum p u m p to cycle, then a signal is sent to action the pick solenoid. This solenoid, when activated, blocks the air intake to the p u m p allowing the vacuum to be applied to the suction cup. The cup is in contact with the first note on the cassette stack. This note is then held on to the cup, while the pick arm rotates to feed the note into the transport rollers. Control is then taken over by the transport roller machanism. Located on the body of the pick unit are means of detecting the note denomination sensors. This allows any cassette to be inserted into any pick position, the control software taking care of the position/note value interrelationship. The second sensor associated with the pick unit is a money low sensor. This is actuated when the pusher plate moves towards the front of the cassette and interrupts the sensor. This position is reached when only 50 notes are left in the cassette. It is the early warning for the sofware to report a ' m o n e y low' status to the application and hence to the bank. By far the most important sensor is that which is actioned when the note leaves the cassette for the transport. This is a filament bulb photodiode pair and is used to detect the opacity of the note. Note opacity (a measure of the light transmission through the note), is used to ensure that only a single note is picked at a time. Each denomination of note has a unique value p r o g r a m m e d into the software. The sensor output is fed via an analogue to digital converter circuit to the control software. This opacity value is compared with the p r e p r o g r a m m e d value and if it is out with specification then an error will be noted. This sensor is also used to evaluate the time taken for the note to pass, thus giving a measure of the width of the note. If the width is outside the expected value this can be indicative of two notes being picked but overlapping. As can be seen, if more than a single note is picked or two overlapping notes are picked then the sensor will detect this and the note stack will be subsequently transported to the purge bin. The intensity of the bulb is also controlled by a network fed from this sensor in its inactive state. This compensates for any degradation of the lamp due to dust from the notes or variations in the sensor circuits.
Cash dispensing module
PICK MECHANISM MODES
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Pick sensor Fig. 4. Pick mode.
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Pick sensor Fig. 5. Feed mode.
Transport section This is the m e c h a n i s m u s e d to get the n o t e s f r o m the p i c k units to the p r e s e n t e r . It is a series o f r o l l e r s d r i v e n b y the t r a n s p o r t m o t o r . T h e s e allow single n o t e s to b e fed, in a serial m a n n e r , up to the p r e s e n t e r m o d u l e . A p i c k unit sucks a n o t e f r o m the c a s s e t t e , the pick a r m with the n o t e a t t a c h e d to its cup is t h e n r o t a t e d , as can be seen in Fig. 5, to a p o s i t i o n to let the n o t e rest on the ' D ' w h e e l flat. T h e v a c u u m is n o w
released and rotation of the ' D ' wheel feeds the note into the transport rollers. This action takes place sequentially for each note needed for the transaction.
Presenter module This, the last of the note m o v e m e n t modules, accepts notes from the transport, collects them and delivers them to the customer in a neat bundle. It checks that the correct n u m b e r of notes are received and provides means of ensuring that incorrect dispenses do not get to the customer. Notes received from the transport are fed into a stacker wheel to transfer the notes from a linear stream through 90 ° to stack onto the clamp plate. When all notes have been dispensed and the checks of the dispense function are finalised, the capture c o m m a n d to the clamp m o t o r is given. This causes the note stack to be gripped in the presenter and the whole mechanism is swung round to either present the notes to the customer or transport them to the purge bin. When in the correct position the feed is turned on to move the notes out of the presenter. This module also has the security shutter and exit sensor fitted to it. The security shutter is opened just prior to delivering the notes and closed when the bunch is taken. The exit sensor ensures that notes are taken by the customer or if not, after a time delay they are retracted and sent to the purge bin.
Present Give to customer
Fig. 6. Presenter modes.
The purge bin This is a container located under the presenter module and is used to receive notes which have been incorrectly dispensed or the transaction cancelled and cannot be given to the customer. This bin is closed and sealed as it is removed from the dispenser.
Control software The hierarchal control system consists of the bank's application program, the A T M operating system, and the module control software. The A T M operating system
Cash dispensing module
directs commands to the appropriate module software for actioning by the onboard firmware. This interrogates the command and provides the hardware with the signals needed to perform the actions required. It also receives the outputs from sensors--the status of the hardware. These are encoded into bytes and returned to the firmware which passes them on to the Module software. Here the appropriate action is determined: 'good'--continue with next command; ' b a d ' - - i n f o r m the application and await the next instruction.
Module Control Software
Cash Dispenser Module Firmware
Fig. 7. Software block diagram.
Dispenser operation The hardware associated with this module is contained on the control board mounted to the side of the presenter module. The processing element is an eight-bit 8049 LSI microprocessor with internal 2k R O M and 128 byte RAM. The firmware program is stored in an 8k E P R O M and uses a 2k R A M for a variable storage area. An I/O expander makes connection to the sensor elements and the control circuits. Also contained within the E P R O M is a diagnostic program to enable the dispenser to be tested off-line from the controlling ATM, the results being displayed on a set of LEDs. When the application issues a dispense command for a given amount, the module control software decides which notes to dispense. To do this a note mix algorithm is used; the inputs to the equation are the note values loaded in the money cassettes and the amount required; the outputs are the quantity of notes needed from each cassette. The bank's application software can select alternative note mix bias parameters for dispensing multiple denominations. This algorithm is re-accessed during a dispense operation if a cassette is emptied.
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Fig. 8. Hardware block diagram.
Once the module control software issues a dispense command, together with the amount to dispense, the onboard firmware takes over the task of providing the requirement. It issues an interrupt to the software when the operation is completed with a code as to its status. The firmware starts up the transport motor, checks that it is running then, having determined the pick units to enable, issues the c o m m a n d to the respective solenoids. It checks the values from the opacity sensors to ensure that the notes picked are correct. A count of the notes entering the presenter is made and, when the last pick is completed, it is checked against the required value. If this is correct and no rejected notes were detected at the pick exit then a c o m m a n d is issued to allow the presenter to give the note stack to the customer. Various checks are made throughout the dispense cycle to determine the state of the hardware. A timing wheel on the transporter drive mechanism is interrogated to ensure that the positioning of the presenter and its associated links are correct prior to note arrival. Retry facilities are actioned if a faulty pick takes place. If a cassette is empty and the required note value can be made up from other available note values then these are picked. After the completion of a good operation the whole mechanics are actuated with a zero note quantity to ensure that the note transport is clear and functional for the next dispense operation. When the money cassettes are loaded into the A T M the bank's application program forces the person replenishing the A T M to enter on the keyboard the quantity of notes in each cassette. These values are stored in nonvolatile m e m o r y locations. During the whole process of dispensing a total is kept of the amount of notes at each location within the module and also the amount taken by the customer. When removing empty or partly empty cassettes the bank staff, by printing out the values at initial load, and those dispensed, purged and remaining in the cassettes, can reconcile their totals with the actual notes still in the cassettes.
Cash dispensing module
Test operation Test of the final module takes place within a dedicated area of the assembly line. The philosophy behind the tests being carried out is one of running the module under more rigorous conditions than that expected on the A T M assembly line. The actual tests are actioned by specially written software taking the place of the bank's application program. This is intended to exceed the expected workload for the dispenser when it is in the A T M carrying out normal customer transactions. All aspects of the modules capability are carried out. These include single note dispensing from each cassette, double note detection, cassette low, note denomination sensing, present, purge and clear operations. After this a period of running the total dispense operation is performed to ensure that no mechanical tightness problems are experienced.
Production Various innovative techniques are employed to ensure a timely and quality module is produced. The manufacture of the cash dispenser module takes place on a carousel roller conveyer system which is controlled by a dedicated PC. The movement of the product along the rollers is controlled by gates and shutters. These feed the part assemblies to the area required for each operation. The control system ensures that the correct pick modules are available to assemble to the presenter for each order received. The completed module is then routed to the test area prior to moving to the A T M assembly build stages. Two robotic assembly stages are used within the dispenser assembly area, these are a simple robot used to assemble shafts, and a complex system used to construct the money cassettes. The shaft assembly consists of rubber rollers attached to a steel shaft. The robot is hopper fed with rubber rollers. It fits the rollers into the assembly jig then lifts the shaft from a container and inserts it through the rollers. Finally it places the finished assembly into the shipping container. The money cassette is constructed mainly from parts produced in thermoplastic. Simultaneous engineering was used to ensure that it was suitable for robotic assembly. The material for the assembly cell is fed from a conveyor and a hopper system. The robot arm lifts these as required. The assembly is complex and intricate. This necessitates various actuators to be available for the arm. These are fitted automatically as required. The completed module is fed to a conveyer system for transport to the stores area.
SUMMARY As this module is the main workhorse of an ATM, it has been designed to be manufactured as part of a quality product. All the engineering expertise has been employed to ensure that the strategies for manufacturing excellence have been adhered to throughout the design and assembly processes. The performance of this module, and the overall A T M product, in the marketplace, has been recognised by numerous awards for quality and export achievement from both the NCR Corporation and other business sources.