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00100	\\M1BDR25;\M2SIGN57;\M3NGR25;\M4NGR20;\F2\CVICARM
00200	\F3\C154 EAST DANA STREET
00300	\CMOUNTAIN VIEW, CA. 94041
00400	\F4\←L\-R\/'7;\+R\→.\→S   Telephone:
00500	\←S\→.415-965-0557
00600	\F1\CDecember 18,1973
00700	
00800	
00900	
01000	Mr. David Orin
01100	Department of Electrical Engineering
01200	Ohio State University
01300	Columbus, Ohio
01400	
01500	
01600	Dear David:
01700	
01800	\J	Enclosed you will find some of the drawings you requested.  I
01900	do not yet have any detailed drawing showing all the internal  parts.
02000	Nor  do  I  yet  have  a really good assembly drawing showing how you
02100	maintain the arm, and just how everything goes together  and  how  it
02200	all  works.  These I am working on, and expect to be able to send you
02300	copies of these drawings shortly.  In the meantime, I  hope  a  brief
02400	explaination will suffice.
02500	
02600		The arm is powered by permanent  magnet  type  d.c.  electric
02700	motors.  A two stage spur gear train connects the motor shaft to each
02800	of the six rotary joints.  The gear ratios are in the range of 30  to
02900	50/1, depending on the joint.  A brake on each of 5 joints allows the
03000	joint to be  locked  in  a  fixed  position  without  applying  motor
03100	current.  Joint  position  feedback  is  from  potentiometer elements
03200	mounted on each  joint,  directly  attached  to  the  joint  axis  of
03300	rotation. Velocity feedback is done electronically by measuring motor
03400	back EMF, or by optional tachometers mounted on each joint.  The full
03500	scale  drawings show just what the overall size of the arm is, and an
03600	idea of the useful working space can be  obtained  by  assuming  that
03700	each joint has a minimum of 300 degrees of rotational freedom.
03800	
03900			A  power  supply is included which contains the motor
04000	power amplifiers and the  manual  control  electronics.   The  manual
04100	controller  allows  the  arm to be positioned remotely by selecting a
04200	joint and then moving the joint at a slow speed. Only one joint at  a
04300	time  can be selected, as the manual controller is not intended to be
04400	a general purpose type of controller.  As all joints of the  arm  are
04500	"free",  meaning  that  they  can  be  moved around by hand merely by
04600	pushing on them, the arm can be manually positioned just by  grasping
04700	it and leading it to a desired position.
04800	
04900		The electronics package is designed such that  a  dac  signal
05000	from  the  computer  can  set  the  torque on each of the joints.  We
05100	normally use an 8 bit dac for each joint, but maybe you  can  get  by
05200	with  less.    The  a-d  interface  is not included.  We use a 12 bit
05300	interface here, with lots and lots of channels.  You need  a  minimum
05400	of  seven  channels  for the arm joints and the simple hand, plus, if
05500	you want to read motor back EMF, or the tachometer output, another  7
05600	channels  are  necessary.  Thus, a minimum of a 16 way multiplexer is
05700	required.  You can get by with less than 12 bits but resolution  will
05800	go  down,  unless  you read in multiple samples. The a-d range can be
05900	whatever you have, as the potentiometer power supply is not included.
06000	This is normally a precision supply of typically 10 vdc at 100ma. The
06100	required  precision  can  be  lessened  by  reading the actual supply
06200	voltage with a spare a-d channel, or else using this supply  as  some
06300	sort of reference.
06400	
06500			With  a  PDP-8,  I  think  you are going to have some
06600	trouble using the computer both for  the  servo  controller  and  the
06700	trajectory  programmer.   I have sold an arm to the Stanford Research
06800	Institute  (SRI-  an  independent  corporation  not  affiliated  with
06900	Stanford Univ. anymore, but still very close).  They are working on a
07000	hardware servo system which will take a lot of the  workload  off  of
07100	the  computer.  This way, the computer can do planning and trajectory
07200	calculation and the hardware  will  handle  much  of  the  real  time
07300	servoing.   The  fellows  at  SRI have promised to let me use all the
07400	designs they develop, and I hope to keep people like  you  posted  on
07500	their  progress as it is very closely related to your wants and those
07600	of many other  people.   Enclosed  is  Richard  Paul's  thesis  which
07700	describes  the  computer servo and planning programs we use- they are
07800	basically the same for any arm, only the constants change.
07900	
08000			The  basic  philosophy  of  the  arm  is  to  have  a
08100	relatively  low  cost  device  which  is  easily  moved about and can
08200	perform simple human type tasks.  Thus, the arm can be clamped to  an
08300	office  desk  top, or similar surface.   The electronics package is a
08400	small box which sits on the floor under the desk,  or  on  the  table
08500	near  the  arm.   A  single  3-m  flat cable runs to the computer i-o
08600	interface.
08700	
08800		As for the nitty-gritty.  I originally wanted  to  sell  this
08900	arm  at  cost,  for about $4000, but it now looks like the break even
09000	price is somewhere  around  $5000,  especially  since  everything  is
09100	inflating like crazy these days.  Thus, I must price the arm at $5000
09200	for the arm, with a simple hand,  power  supply,  amplifiers,  driver
09300	electronics,  and  a  simple manual controller.  Delivery is about 16
09400	weeks.
09500	
09600		I hope this answers some of your questions.  Let me know if I
09700	can be of help in any other way.  By the way, it looks like I will be
09800	visiting in Cincinatti around the middle of January.  I may have time
09900	to stop by- possibly with a completed arm.\.
10400	\←L\→S\←R\-L\/'2;\+L\→L
10500	
10600	Yours sincerely,
10700	
10800	
10900	
11000	Victor Scheinman
11100	    President
11200	
11300	\←S\→L
11400	VDS:pdp10