Cfl E3
`
`'3
`[Lil
`
`Museum
`
`APRIL 1985
`
`ABB Inc.
`
`EXHIBIT 1037
`
`Page 1 of 15
`
`

`
` Cormtuter
`Muscgum - .-
`
`
`
`
`René Martinelli
`
`
`
`Rene Martineiii was born
`near Grenoble, France and
`received a master of sci-
`ence degree from the Uni-
`versity ot Grenoble (1969)
`. and an electronic engineer-
`ing degree from the Univer-
`sity ofTouiouse (1971 ). His
`experience before coming
`to HP in 1973was in lCtest
`design. At HP he has been a production engineer
`on the HP 2100 and HP 21 MX series of computers,
`the supervisor of the local HP repair center, and an
`Ft&D engineer. He contributed to the design of the
`HP 307X family of terminals and was the project
`ieaderfor the analog design of the HP 2392ATer-
`minai. He lives with his wife and son in Eybens,
`France and likes amateur radio and skiing.
`
`25 : Intelligent Plotter
`
`Martin L Stone
`'
`.
`
`' Martin Stone received his
`BSME degreefrom the Uni-
`versity ofTexas at Austin in
`1973 and came to HP’s San
`Diego Division in the same
`year. He has been a man-
`ufacturing engineer and
`was an R&D engineer and
`33 project managerfor the HP
`5‘ 7550A Plotter. A native of
`--
`Dallas, Texas, he now lives in San Diego, California
`and enjoys backpacking, racquetball, golf, and
`playing his guitar.
`
`
`
`Todd L. Russell
`» "
`
`
`
`Todd Russell is an R&D
`engineerat HP’s San Diego
`Division. Since coming to
`HP in 1978 he has contrib-
`uted to the design of plotter
`products, including the HP
`7090A and the HP 7550A.
`Todd was born in Los
`Angeles, California and
`now lives in San Diego,
`L.
`California with his wife and son. He is a scoutmaster
`and commissioner for the Boy Scouts of America
`and is interested in camping, softball, tennis, and
`church activities.
`
`Peter L. Ma
`
`
`
`9 : Terminal VLSI Design
`
`Jean-Jacques Simon
`
`
`
`Born in Metz, France, Jean~
`Jacques Simon studied
`electronics at the University
`of Nice, from which he re-
`ceived masters and doc-
`toral degrees (1975 and
`1978). AtHP since 1977, he
`has contributed to
`‘ hardware and firmware de-
`velopment of a number of
`terminal products, including the HP 3075A, 3077A,
`and 2642A. He was also the project leader for IC
`development for the HP 2392A Terminal and is
`coauthor of a patent on the HP Human interface
`Loop. Jean-Jacques is married, has two children,
`and lives in Saint Egreve, France. He likes outdoor
`activities and rides his motorbike to work every day,
`even in the winter.
`
`16 Z Automated Production
`
`Christian-Marcel Dulphy
`Christian-Marcel Dulphy
`was born in Tonnay-
`Charente, France and
`graduated in 1966from the
`’ Ecole NationaieSupérieure
`d‘Electronique et de
`Radioélectricité de Gre-
`. noble. Before coming to HP
`in 1972 he served as a chief
`Ln petty officer in the French
`i-‘Q
`Navy and worked as an electronics technician and
`as an Ft&D engineer. His HP experience has cen-
`tered on engineering and management in produc-
`tion and manufacturing. He contributed to the de—
`velopment of the manufacturing process for the
`HP 2100 Computer and the HP 7905 Disc Drive.
`His professional interests include robotics and
`automation. Christian—Marcel is married, has three
`children, and lives in Saint-Egreve, France. When
`he is not involved in do—it-yourself projects, he
`enjoys cross-country skiing, hiking, gardening, and
`reading.
`
`
`
`18 1: Terminal Analog Design
`
`Authors
`
`April 1985
`
`4 : Low-Cost Terminal
`
`Jean-Louis Chapuis
`"
`
`v Jean-Louis Chapuis is a
`section manager at HP’s
`Grenoble Networks Divi-
`sion and has been at HP
`since 1978. He provided
`technical marketing sup-
`port forthe HP 263X family
`of printers and 264Xiamily
`V of terminals, was the de-
`
`signer of the HP 3074M
`..
`,
`Data Link Adapter, and was the project manager
`for the HP 2392A Terminal. Before coming to HP
`he was a researcher and teacher in an Ft&D iabfor
`the French Air Force. Jean-Louis is a native of
`Ftochefort, France and earned an electronic en-
`gineering degree from the Ecoie Superieure
`d’Eiectricite in 1977. He lives in Meylan, France with
`his wife and two daughters and likes skiing, bi-
`cycling, and reading.
`
`
`
`Michele Prieur
`'
`‘
`
` an
`
`Michele Prieurcameto HP
`‘ in1980,thesameyearshe
`earned a degree in elec-
`tronic engineeringfrom the
`EcoleSuperieure D’Eiectri-
`cite. She contributed to the
`development of the
`firmware for the HP 2392A
`and is now working on ter-
`minal emulation. She is in-
`terested in terminal firmware and application soft-
`ware for personal computers. Michele was born in
`Lyon, France and is a resident of Grenoble, France.
`She is married and enjoys horseback riding.
`
`Jean-Yves Chatron
`'
`
`"
`
`8:TerminaI Mechanical Design
`Michel Cauzid
`“ 3
`
`
`
`
` . ’ ‘"
`
`
`
`
`
`Jean-Yves Chatron joined
`Michel Cauzid was born in
`HP’s Grenoble Division in
`, 1973, where he has worked
`_ Vouziers, France and re-
`ceived his dipiomafromthe
`as a production engineer,
`a service engineer, and as
`Ecole Nationale Superieure
`de Mechanique et Micro-
`an R&D engineer. He con-
`techniques in 1970. Before
`tributedtothe development
`Peter Ma was born in Hong
`of the HP interface Busfor
`coming to HP in 1979, he
`“ Kong and educated at the
`the HP 3075ATerminal and
`taught mathematics in
`University of Washington
`Africa as an alternative to
`(BSEE, 1978) and at Stan-
`designedthe powersupply
`for the HP 2392A. A native of Nantes, France, he
`French military service and
`ford University (MSEE,
`worked in micromechanics. At HP he has been a
`received an engineering degree from the lnstitut
`1982). Hejoined HPin 1978
`mechanical designerforthe HP2333A Controller,
`Universitaire de Technologie (1972) and served in
`and designed the l/O pro-
`the HP 3092 Terminal, and the HP 2392A. Michel’s
`the Army as a radio communicator. He now lives
`cessor system for the HP
`near Grenoble, is married and is thefatherof two
`professional specialty is computer-aided design.
`731 0A Printerand the digi-
`Heis aresidentofBresson, France, is married, has
`sons and a daughter. Outside of work, he is in-
`talcircuits and gate arrays
`‘
`terested in audio electronics.
`four sons, and enjoys hiking.
`for the HP 7470A Plotter. He was the project leader
`
`APRIL 1985 HEWLETT-PACKARD JOURNAL 23
`
`Page 2 of 15
`
`Page 2 of 15
`
`

`
`
`
`for the electronic design of the HP 7550A and is
`now the section manager for manufacturing en-
`gineering. Peter lives in San Diego, California and
`is interested in tennis, skiing, water sports, and
`traveling. He is also an audio enthusiast.
`
`from Stanford University in 1982. He lives in San
`Diego, California with his wife and loves the ocean.
`He enjoys scuba diving, body surfing, and walking
`on the beach,
`
`Thomas J. Halpenny
`Author's biography appears elsewhere in this
`section.
`
`Kenneth A. Hegas
`
`Ken Regas was born in San
`Diego, California, served in
`the US. Navy, and re-
`‘_ ‘‘ ceived a BA degree in man-
`_. agement from Golden Gate
`K Universityin 1976. He also
`studied at San Jose State
`
`
`
`V
`-
`
`University (BSME, 1980)
`and at Stanford University
`through the HP fellowship
`.
`:
`»
`program(MSME, 1984). At HP since 1980, he con-
`tributed to the development of the HP 7550A and
`is now an R&D project leader. Ken is a resident of
`Poway, California, is married, has two children, and
`is interested in machine design and control.
`
`34: Plotter Firmware
`
`Thomas J. Halpenny
`
`Tom Halpenny came to HP
`in 1974 and has worked on
`rmware development for a
`umber of HP plotters, in-
`luding the HP 7245A, HP
`7221 8, HP 7220A, and HP
`7550A. He received his BS
`degree in engineering from
`_ Harvey Mudd College in
`1973and his MSEE degree
`.
`from Stanford University in 1974, and is interested
`in computer programming and firmware develop-
`ment. A native of San Diego, California, Tom now
`lives in Escondido, California, is married and has
`a young daughter. He likes bicycling, video en-
`gineering, and reading books to his daughter.
`
`
`
`Jeffery W. Groenke
`M
`
`
`
`A native of Minneapolis,
`Minnesota. Jeff Groenke at-
`tended the University of
`Minnesota (BSME, 1980)
`and San Diego State Uni-
`versity (MSME, 1983). He
`has been at HP since 1980
`and has worked as a man-
`ufacturing engineer and
`later as an R&D engineer
`for the HP 7550A. He is a member of the ASME and
`is continuing his engineering education at the Uni-
`versity of California at San Diego. Jeff is a resident
`of San Diego, is married, and has a son. His outside
`interests include skiing, bicycling, sports cars, and
`spending time with his family.
`
`29: Pen-Lift Mechanism
`
`Hatem E. Mostafa
`_
`
`
`
`Hatem Mostafa is an R&D
`project leader at HP’s San
`Diego Division. Afterjoining
`HP in 1979, he designed
`the power supplyforthe HP
`7580A Plotter. Later he de-
`signed the linear motor, the
`drive electronics, and the
`servo control system for the
`penliftforthe HP 7550A. He
`is the coauthor of a November, 1981 HP Journal
`article on the HP 7580A. Hatem was born in Cairo,
`Egypt and received his BSEE degree from the Uni-
`versity of Minnesota in 1979 and his MSEE degree
`
`Tammy V. Herr
`
`
`
`At HP’s San Diego Division
`since 1980, Tammy Herr
`has been a development
`engineer and mechanical
`designer. More recently
`she has worked as a reg-
`ional sales engineer and
`sales development en-
`” gineer. She is a native of
`San Diego, California and
`,
`,
`presently lives in Fallbrook, California with her hus-
`band. She likes skiing, bicycling, bodysurfing, sail-
`ing, and guitar playing.
`
`31 Z X-Y Servo
`
`David C. Tribolet
`
`
`
`Born in Tucson, Arizona,
`_ Dave Tribolet was edu-
`' cated at the University of
`Arizona (BSME, 1978) and
`Stanford University (MSME,
`1979 and MSEE, 1982).
`Since coming to HPin 1979
`he has been a mechanical
`designerforthe HP 7470A
`Graphics Plotter and a proj-
`ect leader for the HP 7550A Plotter. He is now an
`R&D project manager. He is the coauthorofan HP
`Journal article on the HP 7470A and is named as
`a coinventor on a patent on a bidirectional pen
`change mechanism. His work has also resulted in
`a patent application on a switchless pen sensor.
`Dave lives in San Diego, California, teaches a
`machine design course at the University ofCalifornia
`at San Diego, and enjoys basketball and bicycling.
`
`24 HEWLETT-PACKARD JOURNAL APRIL 1985
`
`Page 3 of 15
`
`Page 3 of 15
`
`

`
`
`An Intelligent Plotter for High-Throughput,
`
`Unattended Operation
`
`This p/otter quickly produces multiple copies of high-‘qua/ity
`graphics output for use in presentations and reports. Its high
`throughput and automatic cut-sheet feeder make it useful
`
`for unattended operation in shared environments.
`
`by Martin L. Stone, Peter L. Ma, Jeffery W. Groenke, and Todd L. Russell
`
`T HE EXPLOSION OF COMPUTER GRAPHICS in the
`
`business and technical environments has been inten-
`
`sified by the availability of products that generate
`hard-copy color graphics easily. Hewlett-Packard’sA pen
`plotters have made major contributions in this area, espe-
`cially with the advent of microgrip plotting technology.”
`The application of this technology made HP plotters excel-
`lent high-performance, high-quality, low-cost solutions for
`both environments. There were features, however, that
`plotter customers were demanding, but that did not yet
`exist. These consisted of much greater throughput, unat-
`tended operation, more intelligence, and drafting plotter
`capabilities in an A/B-media-size machine. The addition
`of these features at a very low price while retaining the
`highest quality was paramount in the design of the HP
`7550A Graphics Plotter [Fig. 1).
`The HP 7550A is an eight-pen, A/B-size plotter with high
`
`quality and performance. Its increased throughput was
`achieved by developing high-performance servos to drive
`the pen and paper axes and the pen-lift mechanism. Placing
`the HP 755OA’s microprocessor in all three servo loops,
`performing extensive servo modeling, and developing
`sophisticated control firmware were all key points in the
`resulting high-quality, high-performance, low-cost design.
`Plots done on the HP 7550A take less than half the time
`
`that they take on many other small-format plotters without
`sacrificing plot quality.
`The customer's need to minimize time in handling pens
`and paper is answered by the HP 755OA’s design. Thanks
`to the automatic cut-sheet feeder, the user no longer has
`to load plain paper or transparencies by hand, and the great
`inconvenience of tearing off sprocket holes or separating
`plots along perforations is eliminated. The design of the
`pen-lift mechanism contributes to lengthening the life of
`
`
`
`1. The HP 7550A 8-Pen
`Fig.
`Graphics P/otter is designed for
`high-throughput, unattended op-
`eration. These features allow the
`preparation of multiple copies of
`high—qua/ity computer graphics,
`automated output of single charts
`for process monitoring, or use as
`a central graphics server.
`
`APRIL 1985 HEWLETT-PACKARD JOURNAL 25
`
`Page 4 of 15
`
`Page 4 of 15
`
`

`
`the pen by carefully controlling the velocity of the pen as
`it hits the paper. These features make the HP 7550A an
`excellent choice as a central source of hard-copy graphics,
`or for automatic test and process control systems.
`Ease of use, or friendliness, comes from the extensive
`firmware features included in the HP 7550A. One key con-
`tribution is the internal, 12K-byte, user-definable graphics
`memory. This memory space can be allocated for five dif-
`ferent functions: I/O buffer, vector buffer, replot buffer,
`space for polygon fill definition, and downloadable charac-
`ter space.
`Two of the most powerful features are the replot and
`polygon fill capabilities. The replot buffer enables the user
`to store an entire plot in the HP 7550A and then reproduce
`it up to 99 times. Now the user can give a presentation
`using transparencies plotted by the HP 7550A and give the
`audience personal copies of the same information pro-
`duced quickly and easily on paper. The polygon (area) fill
`capability is a real time-saving benefit in user programming
`and plotting time. Instead of programming a plotter to move
`stroke by stroke (many, many instructions) to fill a complex
`solid or crosshatched area, all the user must do is invoke
`two or three HP-GL (Hewlett-Packard Graphics Language)
`commands to define a polygon and a fill type. From this
`information, the HP 7550A automatically figures out the
`required number and pattern of strokes.
`Another contribution is the32-character liquid-crystal
`display on the front panel. This display, coupled with the
`keyboard design, gives the user a simple menu-driven front
`panel that is easy to operate. Also, with the use of an inter-
`nal nonvolatile memory, the customer can completely con-
`figure the HP 7550A in an RS-232-C/V.24 or HP-IB (IEEE
`488) environment through the front panel, thus eliminating
`bothersome rear-panel switches.
`The final major customer need addressed by the HP
`7550A is for a plotter for the low-cost CAD/CAM systems
`available today. Users of these systems want a quality A/B-
`size drafting plotter with a price in agreement with the rest
`of their system. The HP 7550A is designed to use both
`polyester film and vellum paper, and liquid-ink as well as
`roller-ball pens. The high throughput of this plotter makes
`it a very good solution for producing check plots quickly,
`
`and its drafting-quality output produces excellent final
`drawings.
`
`Mechanical Design
`The mechanical design of the HP 7550A is characterized
`by the widespread use of plastic molded parts. This low-
`cost design approach was taken while still keeping quality
`and reliability as the top objectives. Many parts are de-
`signed to serve several purposes.
`I Pen carriage:
`D Actuates a cam that lifts the pinch wheels for paper
`loading.
`El Actuates a cam to uncap pens during pen picks.
`I Pen-lift mechanism:
`
`Cl Opens access door to platen surface to begin auto-
`matic paper-load sequence.
`D Senses paper during paper loading.
`I Carousel sensing pair:
`D Detects presence,
`carousel.
`
`type, and positions of pens in
`
`Cl Detects up/down position of plotter window.
`The key mechanical designs are highlighted in the articles
`on pages 29 and 31.
`
`Electronic Design
`The objective of the electronic design was to develop a
`cost-effective means of providing a high level of function-
`ality and many enhanced features. For instance, one main
`printed circuit board contains nearly all of the electronic
`circuits, leaving only a small portion on the servo motor’s
`optical encoder board and the pen-lift’s encoder board.
`More functions and higher performance can be found on
`the one main board than are on seven separate boards from
`an earlier HP plotter. Several design philosophies helped
`achieve this, such as replacing analog circuitry with digital
`circuitry whenever possible, using large-scale integration
`(LS1), eliminating the need for any adjustments, and per-
`forming many functions with the same components.
`The single 68000 microprocessor controls every move-
`ment in the servo motors and pen-lift mechanism from
`commands received through the HP-IB or RS-232-C inter-
`face. It services the front panel and rotates the carousel
`
`Pinch Wheel
`(Feed Position)
`
`Sheet Deflector
`(Feed Position)
`
`
`
`
`
`
`
`
`Corner
`Separator
`
`
`
`
`11111111111:
`Illlllllllll.
`‘r,
`iIIIiI35I
`\\
`5. \\\\\\\\\\\\§\\\\\\\\\\\\\‘§\\§\‘s
`—m
`
`
`Pressure
`Pressure
`Plate
`Spfing
`
`Idler
`Roller
`
`26 HEWLEFT-PACKARD JOURNAL APRIL 1985
`
`Fig. 2. The HP 7550A P/otter's
`sheet-feed mechanism is similar
`to that of a photocopier, but with
`much higher alignment accuracy.
`It can feed up to 150 sheets with-
`out reloading.
`
`Page 5 of 15
`
`Media
`Sheet
`Supply
`
`Relgggfble
`
`D-Shaped
`Feed Tire
`
`Page 5 of 15
`
`

`
`
`
`media. The system requirements were that it be able to
`remove individual sheets from a supply stack, deliver each
`to the writing area, and align each sheet with the pen axis
`within two-tenths of a degree. Also, it had to eject and
`stack completed plots automatically and provide capabili-
`ties for feeding ANSI A and B and ISO A3 and A4 papers.
`as well as A and A4 transparency film. The system had to
`be very reliable, yet provide easy access if a feed failure
`should occur. In addition, the ability to load single sheets
`manually was required.
`The cut-sheet feeding system for the HP 7550A uses a
`forward buckling technique for separating the top sheet
`from the supply stack (Fig. 2). This technique, commonly
`seen on inexpensive photocopiers, was selected because
`of its low cost and high reliability. The stack of sheets is
`first placed in a removable tray in which are mounted two
`corner separators, one at either side of the forward edge of
`the stack. These separators allow the feed tires to buckle
`an individual sheet off the top of the stack. The stack is
`pressed up against the feed rollers by two compression
`springs under a hinged plate, which is located in the tray
`directly beneath the stack. Two different trays are available.
`One comes with the instrument and can be adjusted easily
`for A or A4 media sizes. The other is an inexpensive option
`and can be adjusted easily for B or A3 media.
`A significant contribution of the sheet feeder is the design
`of the feed shaft system. Conventional feed systems use
`two rubber tires mounted to the feed shaft by one-way
`mechanical clutches and forced down on the stack, requir-
`ing an elaborate mechanism to relieve the tension springs
`when the user desires to insert or remove the tray. The HP _
`7550A uses a specially designed feed tire which has a flat
`cut on one side, giving it the shape of a D. When the flat
`side is lined up parallel with the surface of the top sheet,
`there is no contact, and the tray can be removed easily
`without the need for any complex release mechanisms. A
`key element of this system is that the HP 7550A's micropro-
`cessor must be able to determine the orientation of the feed
`shaft, so the flats can be positioned parallel to the media
`when a sheet is not being fed. To do this, a very simple
`encoder was designed, consisting of a molded plastic gear
`with a narrow slit and an LED emitter-detector pair. This
`gear runs off the same gear the step motor uses to drive
`the shaft. The gear is keyed to the shaft orientation and
`passes between the emitter-detector pair. When the slit
`passes in front of the emitter, the receiver generates a signal
`that indicates to the processor that the shaft is aligned, and
`the feed cycle is complete.
`Once the sheet has been pushed from the tray, it strikes
`
`Trailing
`Edge
`
`Fig. 3. Edge sensing. (a) A probe
`on the Z carriage bottoms on the
`media. (b) The Y carriage moves
`the probe overa hole in the platen.
`(c) As the trailing edge of the sheet
`passes, the probe drops into the
`hole.
`
`APRIL 1955 HEWLETT-PACKARD JOURNAL 27
`
`Page 6 of 15
`
`(3)
`
`(b)
`
`(*3)
`
`and paper-feed step motors. It also participates in measur-
`ing the unregulated power supply voltage for the servo
`motors by successive approximation. The task of continu-
`ously pulsing the LED (light-emitting diode] in the carousel
`detector is performed entirely by the microprocessor, rather
`than by a separate timer circuit.
`The digital electronics section is greatly simplified by
`the use of the 68000 microprocessor and two custom stan-
`dard-cell ICs manufactured at HP’s Cupertino Integrated
`Circuits Operation. The microprocessor’s strong output
`drive capabilities and the use of high-density ROMs and
`RAMs eliminate the need for any costly address or data
`bus buffering. The two custom 40-pin NMOS ICs contribute
`to significant cost savings by replacing more than 80 small-
`to-medium-scale ICs. Overall, the digital section is mostly
`made up of a handful of LSI components, reaping the bene-
`fits of increased reliability and reduced board space and
`power consumption.
`The power supply portion of the electronics offered some
`interesting challenges. The servo motors require a power
`supply with very high (greater than 300 watts] peak power
`capabilities to produce the desired accelerations and decel-
`erations. Since servo performance depends on the supply
`voltage, a costly regulated design would seem necessary.
`However, by not regulating the voltage, but instead measur-
`ing the value and compensating the servo operating param-
`eters in firmware by using the microprocessor, optimum
`performance can be maintained. To help keep the power
`supply simple, a single switching circuit provides three
`regulated voltages—a tightly controlled 5-volt output along
`with two adequately controlled 12-volt outputs. The
`switching circuit takes advantage of a sophisticated IC reg-
`ulator and employs a switching element that gives three
`outputs rather than just one. The result is a much reduced
`parts count and improved efficiency and reliability.
`
`Unattended Media Handling
`Unattended operation requires that a plotter be able to
`supply a new sheet of plotting media without user interven-
`tion. Most plotters that feature automatic media handling
`use a system that supplies the media from a rolled or fanfold
`format. It was decided early in its design that these formats
`were unacceptable for the HP 7550A’s intended market.
`These formats require special paper which is more expen-
`sive. To change the media type, the user must go through
`a time-consuming sequence of removing and changing the
`supply and getting the new media started in the feed system.
`Hence, the decision was made to design this new plotter
`with an integral system for feeding precut stacks of sheet
`Probe
`_
`Direction
`of
`
` Media
`
`Motion
`
`Move——->
`
`
`
`Sheet
`
`Probe Hole
`
`Page 6 of 15
`
`

`
`fore the trailing edge was detected.
`Once the entire sheet is on the platen, the alignment
`sequence starts by raising the right pinch wheel, leaving
`only the left pinch wheel engaged. The sheet is then driven
`back and forth twice. Initially the sheet is completely away
`from the left guide. As the first move begins, a mechanical
`couple is set up between the driving left grit wheel on one
`hand and the media’s friction against the platen surface
`(Fig. 4a] and its inertia on the other. This causes the sheet
`to rotate about the left grit wheel and swing in against the
`edge guide. A stop above this guide keeps the sheet from
`climbing up and over it. As the move continues, the media
`edge under the left pinch wheel approaches the edge guide
`(Fig. 4b]. The left grit wheel direction is then reversed,
`causing the trailing edge to move completely against the
`guide. After two more passes, the sheet is firmly aligned
`to the guide.
`The final tasks are to find the trailing edge accurately (it
`is roughly known already) and to determine whether ISO
`or ANSI standard media is being used. The trailing edge
`is found as before. To determine which standard is used,
`the sheet width must be measured. The position of the left
`edge is now known to be at the edge guide. Only the right
`edge need be found to calculate the sheet width. The pro-
`cedure is similar to that for finding the trailing edge. The
`Y carriage is moved to the right side of the platen over a
`slot (underneath and perpendicular to the right edge of the
`sheet] and inside the edge of an ANSI sheet, which is the
`narrower of the two (11 inches versus 297 mm]. The probe
`is lowered until it bottoms on the sheet. The Y carriage is
`then moved enough to the right to be beyond an ANSI sheet
`edge. If the probe drops into the slot, the size is known to
`be ANSI. Otherwise, it is assumed to be ISO. The plotting
`area is now set.
`
`After plotting, the sheet is unloaded on command by
`ejecting it past the grit wheels, stacking it in a catch tray
`placed behind the plotter. A new sheet is then automati-
`cally loaded, aligned, and ready for plotting.
`
`Acknowledgments
`The success of the HP 7550A was due to the great efforts
`of many people. Product design was done by Dick Kemplin
`and Lynn Palmer. The project benefited from the early
`leadership of Neal Martini, as well as continued support
`from Peggy Wyman and John Page. Bill Royce had the
`responsibility for the power supply and motor drive cir-
`cuits and for meeting product electromagnetic-compatibil-
`ity goals. Dave Ellement and John Wickeraad were involved
`in designing the custom ICs and the digital circuits.
`Special thanks to Wally Halliday for the initial sheet
`feeding mechanism, Mark Majette for the media drive axis,
`and Kevin Bockman for the unloading design.
`We could not have been successful without the extensive
`
`efforts of our manufacturing team: Juergen Przyllas, John
`Morton, Steve Lorenc, Rich Mandle, Marv Kozai, Otto Hirr,
`Dave Kelly, and Tim Holscher. And we give special thanks
`for the support and guidance of Norm Johnson.
`
`Page 7 of 15
`
`a ramped surface, which directs it upward into a deflector.
`This deflector can be rotated open by motion of the Z car-
`riage (pen-lift mechanism] to direct the sheet onto the pla-
`ten. The pinch wheels are raised by engaging the Y carriage
`(pen-holder carriage] with a rotating cam. The sheet is fed
`until the D-shaped feed tires have completed a full revolu-
`tion, passing the leading edge of the sheet under the raised
`pinch wheels. The Y carriage then disengages the cam,
`lowering the pinch wheels and grabbing the sheet between
`the pinch and grit wheels. Then, the sheet is ready to be
`pulled from the tray with the X-axis drive motor.
`Edge sensing is done with the Z carriage. The Y carriage
`is moved over the platen and the pen holder is lowered.
`Since there is no pen in the holder at this time, lowering
`continues until a probe bottoms on the sheet on the platen
`surface (Fig. 3a]. The position is read from the Z-carriage
`linear encoder and recorded. The platen height (including
`media thickness] is now known. The Y carriage then makes
`a short move, dragging the probe across the sheet until it
`is over a hole in the platen. Now the sheet is pulled from
`the tray (Fig. 3b]. As the trailing edge passes, the probe
`drops to the bottom of the hole, signaling the end of the
`sheet (Fig. 3c]. The paper length (A/A4 or B/A3] can be
`determined by reading how long the sheet was pulled be-
`
`Rotation
`K-
`Leading Edge
`
`
`
`Media Friction
`
`
`
`l Pinch Wheel Force
`Trailing Edge
`
`Guide
`
` Edge
`
`
`Direction of Move 1
`
`la)
`
`Reaction
`of
`Edge
`Guide
`
`l Drive
`
`I Friction
`
`(b)
`
`Direction ot Move 1
`
`Fig. 4. Sheet alignment. (a) As the first move begins, the
`sheet rotates about the left pinch/grit wheel combination and
`toward the edge guide. (b) As the move continues, the edge
`under the left pinch/grit wheel combination approaches the
`guide. Then a move in the reverse direction completes the
`alignment of the sheet against the guide.
`
`28 HEWLEITPACKARD JOURNAL APRIL 1955
`
`Page 7 of 15
`
`

`
`References
`1. W.D. Baron, et al, “Development of a High-Performance, Low-
`Mass, Low-Inertia Plotting Technology," Hewlett-Packard Journal,
`Vol. 32, no. 10, October 1981.
`2. M.L. Patterson and G.W. Lynch, “Development of a Large Draft-
`ing Plotter," Hewlett—Packard Iournal, Vol. 32, no. 11, November
`1981.
`
`
`
`Low-Mass, Low-Cost Pen-Lift Mechanism
`
`for High-Speed Plotting
`
`by Tammy V. Herr and Hatem E. Mostafa
`
`T HE PEN—LIFTMECHANISMintheHP 7550APlotter
`
`was designed to minimize manufacturing cost and
`to minimize the overall mass of the pen carriage
`assembly while meeting performance criteria of reducing
`cycle time (pen down and pen up) and providing variable
`writing forces for various pen types.
`
`Mechanics
`
`The pen-lift assembly (Fig. 1) consists largely of inexpen-
`sive injection-molded plastic parts. Every element of the
`vertically moving assembly attaches to a complex and
`highly critical part, the pen holder. The most severe operat-
`ing condition imposed on this holder is during pen ex-
`change, when several pounds of force are exerted on the
`pen pawl during sliding contact with the HP 7550A’s 8-pen
`carousel. To supply the strength and lubricity necessary
`to survive pen exchange, the pen holder is molded of
`polycarbonate filled with 30% glass and 15% Teflon.“
`Miniature radial ball bearings mounted on the pen holder
`constrain the assembly to the desired vertical motion.
`Dynamic modeling was performed to determine the opti-
`mal combination of bearing geometry and preload required
`to sustain the imposed loads while inducing no frictional
`forces greater than 3 gm.
`Actuation for vertical travel and pen-down force is pro-
`vided by a highly efficient linear motor. A coil-wound bob-
`bin is electromagnetically translated over a pole cap and
`magnet column located inside a voice-coil cup. Energizing
`this coil with an electric current produces a vertical force
`proportional to the input current. An inexpensive insula-
`tion-displacement connector terminates the bobbin coil
`wire, eliminating a soldering operation. This magnetic as-
`sembly weighs only 40 grams and delivers 122 grams of
`force per root watt of power dissipation.
`Because of the accumulation of tolerances, the distance
`between the pen nib and the platen surface can vary from
`1.5 to 4 mm. Therefore, the geometry of the voice-coil cup
`is optimized for minimizing leakage flux, thus providing
`a constant force over the entire 4-mm working range of the
`
`pen-lift assembly. An optical encoder senses the vertical
`position of the pen-lift assembly to within 0.05 mm. The
`use of digital feedback eliminates the offset and drift prob-
`lems inherent in traditional analog feedback systems.
`
`Control
`
`The pen-lift control system provides the minimum pen
`up/down cycle time while reducing pen impact momentum
`to maximize pen nib life. The control system’s complexity
`is reduced and its reliability is greatly enhanced by incor-
`porating the plotter’s microprocessor into it. For any given
`control mode, the microprocessor can determine the posi-
`tion and velocity of the pen by reading an encoder register.
`Using the proper algorithm, the processor outputs two
`pulse-width-modulated signals to the pen-lift driver (see
`Fig. 2). The front end of the pen-lift driver performs a
`differential digital-to-analog conversion on the two control
`
`
`
`Fig. 1. The pen-lift mechanism used In the HP 7550A P/otter
`is based on an electromagnetic voice-coil actuator and the
`use of the plotter’s microprocessor to control pen drop velocity.
`
`APRIL 1985 HEWLETF-PACKARD JOURNAL 29
`Page 8 of 15
`
`Page 8 of 15
`
`

`
`known pen height, the control system can execute a pen-
`down command very quickly. The pen-down move is ac-
`complished in this case by switching the control system
`from a position to a velocity servo and then commanding
`the pen to descend at a high velocity. Slightly before im-
`pact, the control system significantly decreases the pen’s
`downward velocity, thereby greatly reducing the impact
`momentum as the pen nib strikes the plotting media [see
`Fig. 3a]. The final impact velocity is selected by the micro-
`processor as a function of pen type. This dual velocity
`approach makes it possible to lower the pen at a high speed,
`while independently selecting the optimum impact veloc-
`ity for various pen and media combinations to reduce pen
`bounce and increase pen-nib life. The result is a pen-down
`delay of only 34 ms.
`If, on the other hand, a lateral move greater than 2.5 cm
`occurs while the control system is in fast-drop mode, no
`assumptions about the distance of the pen from