perm filename DOC.M[1,VDS]1 blob sn#150174 filedate 1975-03-11 generic text, type C, neo UTF8
C00001 00001
C00002 00002	MIT arm prices
C00030 00005			INSTALLATION 
C00039 00008					ARM CONNECTOR
C00040 00009
C00042 00010			Digital P.C. Card Pin Assignments
C00059 ENDMK
MIT arm prices

Industry price
4500 arm without hand
1000 hand
1000 tachs on all 6 joints  
1200 electronics
Total $7700

University price
4000 arm without hand
700 tachs on all 6 joints
800 electronics
600 hand

Total $5500 (package price)-quoted to M.I.T.

			By:  Vic Scheinman

The arm electronics will include the following major systems:

	A power supply
	Seven D.C. Servo Amplifiers
	Seven Velocity Amplifiers
	Five brake drivers
	Seven motor temperature sensors
	Overcurrent protection circuitry
	FET switch enables for all seven power amplifiers
	Socket pins suitable for computer interfacing with flat cable
Here are the details of each system.

The Power Supply:
	The  entire electronics package will operate on 115 vac.  The
power amplifiers require about +and- 30 vdc,or just +30 vdc if bridge
power  amps  are  used,  at  8  amps  filtered  but  not  necessarily
regulated.   A power supply for the op amps and any  switching  logic
must  also  be  considered.   The  brake drivers use the same 30 volt
amplifier supply.    A 10 volt dc reference supply,  providing  about
200  ma  of  smooth,  well  regulated  and  stable  dc should also be
included for running the potentiometer  elements.All  these  supplies
should be designed with low cost and light weight in mind.

D.C. Servo Amps:
	There are six joints on the arm and one degree of freedom  in
the  hand  which  gives  a  total  of  seven  permanent  magnet  d.c.
motors.All of these motors have current limits  which  can  never  be
exceeded.  The  motors should be driven with current drivers (current
is commanded rather than voltage). The amplifiers can all be the same
with  provision  for  individually  setting  their current limit, and
current gain.  A maximum of 2.2 amps is required. The amplifiers  are
driven  either  from  a  computer  DAC  output, typically of 0 to -10
volts, or +-10 volts, or 0 to +10 volts, or they are  driven  from  a
manual control amplifier which may also have the same output, or more
typically +-14 volts or so if run on a 15 volt supply.  Provision for
setting  the  amplifier  input to match the computer output should be
included. Amplifier bandwidth must be at least 1 khz, Switching  from
computer  to  manual  mode should also be included- like by using FET
switches.   There is one amplifier which is different  from  all  the
others.   This is the hand driver.  It must be able to operate in two
modes.   The first mode is a conventional mode, where current  output
is proportional to signal input.  The second mode is what we can call
a pulse mode.  The amplifier must be capable of putting out +  and  -
current  pulses  of a controlled width.This mode can be done with the
computer, but a hardwaare alternative would make programming simpler.
As  a suggestion, a NE556 dual timer could poossible be used to drive
the amplifier with pulse width being controlled by  trim  pots.   FET
swithes  or  other  logic should be used to switch these two modes in
and out.

Velocity Amplifers:
	The early versions of the arm will not have tachometers. This
has been done for economy and design simplification. In lieu of these
tachs,  the  velocity  will  have  to be derived by electronic means.
This involves the use of an amplifier which looks at both  the  motor
current  and the voltage across the motor.   See reference data for a
derivation of the amplifier gain, and other necessary details of  the
required  network.  In  manual  control  mode, one will be commanding
velocity rather than current.  In  computer  mode,  these  amplifiers
will  be  connected directly to an A-D channel because the servo loop
is closed within the computer, and not in the electronics package.

Brake Drivers:
	Five  of  the  joints  have brakes.   These electromechanical
devices require about 100 ma at 28-32 vdc each.  They are  controlled
from  the  computer by a logic level change (TTL), and thus the brake
driver should be compatible with this output.  In manual mode, it can
be assumed that a switch from open to ground will control the brakes.
As the brakes  are  inductive  devices,  the  electronics  should  be
protected from inductive spike damage (diode protection is required)

Motor Temperature Sensors:
	If operated at full current for too long a  period  of  time,
the  servo motors will overheat and damage themselves.   Some sort of
protection must be included to prevent this from happening.  A simple
solution  is  to  place  a resistor in series with the motor and then
tape a thermocouple or thermistor to the resistor.  As the motor runs
and  heats  up,  so  does  the resistor.   A threshold temperature is
sensed but the thermistor and a warning light or sound comes on.   At
a  second level, current is either switched off to the motor or it is
reduced to a level low enough to prevent furthur heating.  The  motor
thermal  time  constant is matched in the resistor-thermistor package
by suitably wrapping the  components  in  heat  conductive  and  heat
insulative  material. Another way of doing this is to place a current
integrator in the circuit. This is an op amp. set up as an integrator
with  a controlled loss in the loop.  Current to the motor causes the
integrator to integrate with a potential dependent loss.    Thus  the
output  of  this  special  integrator would be an analog of the motor
temperature.  Unfortunately, switching the power supply off and  then
on  would restart the device at an initial position rather than where
it should be.  In any event, as the sensor will be a set  at  a  safe
value,  some  provision  can  be  included to prevent override of the

Overcurrent Protection:
	As  mentioned  in  the section on Servo Amps., the motors are
very overcurrent sensitive.  This means that if the armature  current
ever  rises  above  a  certain  level,  the  armature  magnetic field
strength will be large enough  to  demagnetize  the  field  permanent
magnets.   In this event, the motor will then produce less torque for
the same current, until the motor is removed and  the  field  magnets
recharged  on  a special magnetizing device.  In current command mode
this sort of thing should not happen, as full  command  should  equal
maximum  allowable  current.    True-  but accidents will happen, and
protection features should be  included.As  an  example  of  possible
overcurrent  modes.   If you remove one of the supplies from a 741 op
amp., it will latch up at full output.  Besides causing  a  potential
overcurrent mode, it can result in a wild and disasterous arm motion.
So, if amplifiers of this sort are used, some sort  of  power  supply
protection  circuitry  should  be  included.   By  the way, there are
amplifiers which don't do this bad  thing...  I'm  not  sure  of  the
device numbers.   Power supply protection means that the supplies are
controlled so that they come up and go away at at the same time or at
a  rate  so  that both sides are reasonably close to one another.  An
alternative is to use bridge circuits with only one supply,  but  the
increased  component  count  may  not  be  worth it.  Another mode of
overcurrent failure is latchup of a DAC output.  Most DACs use a  741
or  equivalent  as  the  output device.  They produce a 0- to 10 volt
swing, execpt if they loose one of their supplies, or else  they  fry
themselves,  in  which  case  they put out 15 volts.  Thus, a 10 volt
zener on the inputs can be used  to  protect  from  this  overcurrent
mode.   Another safety device is to have a device look at the inputs,
and if they ever exceed the allowed maximum, they will open  the  FET
switches  which  enable  the  power  amplifiers.   This way, an input
failure can be prevented from causing disasterous arm motion.

Switch Enables:
	The arm will operate in two modes.  One  is  manual  and  the
other  is computer.  In manual mode a manual control device will move
the arm in velocity mode.  I.E., direction and speed of the  arm  are
controlled  by  the  position  of  a  control  knob.   Only one joint
operates at a time in this mode. In computer mode, the servo loop  is
closed in the computer, and all joints can be controlled at one time.
Seven DAC outputs run the seven servo motors, and the computer  reads
the  potentiometers,  and electronic tach signals, plus whatever else
is fed back from the arm.  FET switches  provide  an  easy  means  of
switching   modes   with  high  reliability  and  minimum  mechanical
switching.  There are two kinds of FET  switches,  one  is  good  for
switching  signals  of  all  levels  and the other good for switching
signals which can allow the FET drain to remain at less than 200  mv.
The  latter  are  cheap and simple and are suitable for op- amp input
control.  The brake drivers must be wired up  so  that  they  can  be
enabled  either by the computer or by manual mode.  The override mode
should be brake off.  Both brake modes can be allowed to  operate  at
the same time, so switching of modes is not required in this case.

Socket Pins:
	The following signals come from the arm  to  the  electronics
box, all in a single 50 conductor 3-m flat cable.

	7 motor supply wires
	7 motor return wires-to current sense resistor
	5 brake supply wires
	1 brake common wire
	2 pot element wires- from precision 10 volt supply
	9 pot wiper wires
	11  wires  reserved  for  future  use with their possible use
allocation as follows:

		5 tach supply wires
		1 tach common wire
		5 wires for touch or force sensors,etc.

A single 26 conductor flat cable from the manual  controller  to  the
electronics box with the following signals:

		7 brake wires
		1 brake common
		7 joint select signals
		1 pot signal for joint velocity
		2 pot element signals
		1 computer select signal
		2 emergency stop signals
		1 signal common
		4 spares

A  single  50  conductor 3-m flat cable will run from the electronics
box to the computer.  This will carry the following signals.

	7 DAC motor command signals.
	5 I.O. Buss Brake signals.
	1 DAC ground
	9 pot signals to the A-D.
	2 pot reference and gnd. signals
	7 tach signals to A-D.
	19 spare wires for any  future  applications  such  as  touch
sensors, etc.

General Design Guidelines:
	The electronic package should be  designed  to  fit  entirely
into  a  single  enclosed  box.   Its typical location will be on the
floor below an arm, or on the table next to the  arm.  It  should  be
light  enough  to be moved around easily, yet designed to be reliable
and uncomplicated. Ideally, it should contain a minimum of wire  wrap
connections,  or  hand  soldered wires, and a maximum of p.c.  carded
components.  To keep costs down, the number of different cards should
be  minimized,  and  the  package  count should be kept low by use of
multiple element packages.   It should be designed to  be  preset  so
that components such as trimmer pots can be eliminated.


	The  manipulator  is  basically a  seven  degree  of  freedom
electromechanical  device.  Each  degree of freedom  is essentially a
separate complete  servo system.   For  convenience  in referring  to
these  different degrees  of  freedom,  they are  numbered  1 thru  7
starting with the degree of freedom in the base (the rotation about a
vertical axis) numbered "#1 JOINT". The last degree of freedom is the
hand which is labeled the "#7 JOINT".  

	Each  servo system  ,execpt  the hand,  consists  of a  D.C.  
permanent magnet type motor, two  stages of gear reduction (giving  a
reduction of 30-40/1),  a position potentiometer on the  output shaft
(the  joint axis), an  electromechanical brake which  is energized to
hold (execpt joints  6 and  7 which  have no brakes),  and an  analog
tachometer   to   measure  velocity.      Joints   1  thru   5   have
electromechanical tachometers, and joints 6 and 7 have an "electronic
tachometer" which  is  an electronic  circuit  which looks  at  motor
voltage and current to derive velocity. 

	Going over  the layout drawings you will  note that this type
of arm is characterized by the complete servo system being placed  at
or  near the  corresponding joint.    This results  in  a stiff,  low
response  time system.   The layout of  each joint is  such that each
joint  can  operate  independently   of  all  other  joints.     This
facilitates programming. 

	The motors  used are permanent  magnet d.c. motors  which are
characterized  by  high torques  at modest  power  levels.   The high
performance level is obtained by using premium grade magnet material,
and complex armature winding  patterns.  Although producing very high
torques for their size, these motors are sensitive to overcurrents to
the armature.  Thus never run the arm on just a plain D.C. supply, as
you run  the risk of exceeding the  maximum allowable current through
the motor.   If you  do, even  for 1 ms.,  you will  reduce the  peak
torque output of the motor, and reduce  the strength of the arm.  The
motor  magnets will have to be  recharged- a procedure which requires
removing the motor from the arm. 

	The gear trains generally  consist of two meshes  of hardened
stainless steel pinion gears on  aluminum spur gears.  In some cases,
you will note the the output spur gear is actually machined into  the
arm structure itself.  This produces a  more accurately located gear,
and saves on weight and space too. 

	All  the position sensing potentiomenters  used in this model
arm are special elements  custom tailored to each particular  joint. 
In most cases the potentiometer  element is assembled into the output
gear  or  member.   The dull  black surface  of  this element  is the
conductive plastic material of the pot itself.  Do not touch this, as
your finger  nails may scratch the  surface, or your  finger oils may
change the resistance.  

	The joint brakes are electromechanical devices which  attract
a rotor  to a stator  when energized.   This allows  the joint to  be
locked in any  position without the need for continuous motor current
which can cause  excessive motor heating. In  general the brakes  are
about as  strong as  the joint motor.   Thus if  a brakes  slips when
energized, it  probably means that you are trying to handle too heavy
a load.    At maximum  load, the  brakes  must be  used  as often  as
possible, as the motors  are not capable of continuous output torques
at these levels.   Refer to the specification  sheet for the  maximum
intermittent and continuous torque levels for each joint. 

	Tachometers are used on  each joint to give an  indication of
motor  or joint velocity, for  use in velocity servoing  and also for
damping in position servoing.  Joints 1 thru 5 have electromechanical
tachometers.  These  are either directly connected to  each motor, or
are  geared, as in the case  of joints 2 and 4.   Joints 6 and 7 have
electronic tachometers.  The  derivation of motor speed is  done with
circuitry located in the power supply.  

	The  hand is  interfaced to  the arm  with a  threaded ring.  
Unscrewing this  ring  and then  pulling  lightly on  the  hand  will
release the hand.   You will then see the printed  circuit borad type
of  connector which is the  electrical interface between  the arm and
hand.  The hand has a motor,  a set of internal keys, a screw  thread
drive  shaft and  driven nut,  and a  potentiometer element  position
sensor imbedded in the hand structure. 

	All  joints  on  the arm  are  wired the  same.    Inside the
shoulder there is  a p.c.   board connector  manifold with 6  sockets
corresponding to joints 2 thru  7.  The socket for joint 1 is located
in the underside of the base of  the arm.  Although not all the  pins
are used,  a 16  pin polarized  plug is  associated with each  joint.
Color coding and pin assignments are the same for each of these plugs
and sockets on  the master  manifold.  This  facilitates tracing  and
debugging.   To provide good  flex life,  very thin stranded  wire is
used  in the outer  sections of the  arm.  Use care  in handling this
wire.  You will also note the the wire is not  tightly cabled, and in
some areas it is actually just loosly laid in place.  This produces a
more felxible and adaptive bundle which flexes longer. 

	If you must open the arm,  do so with care, as the  structure
of the  main  links is  characterized by  a very  stiff complete  box
section  made up  of two  halves,  which are  very flexible  when not
screwed together. 


	The basic arm is delivered a three separate components.  The
arm and hand, the power supply, and the manual control unit.  In addition
there is a single 50 conductor cable which connects the arm to the power

	Carefully remove the arm from the shipping container and place it on
a table or other workspace.  The joints will all be limp, so be careful not
to catch the hand or wrist on anything while moving the arm around.  The arm 
is best held by the base and tubular main column.  C-clamp or screw the base to
the table or another solid board, at least 3 feet square.  

	Unpack the Power supply and manual controller.  Connect the 50 conductor
ribbon cable assembly between the arm and ARM socket on the fron of the power supply,
making sure to match up the color code defining connector orientation.
Connect the manual control cable to the power supply, also observing the correct
connector orientation.   

	Now make sure that the manual control select know is in one of the OFF
positions, and all the brake switches are in ON mode.
Plug in the power supply and flip on the ON-OFF switch.  The arm should now
become rigid as the brakes on joints 1 thru 5 are energized ON.  Joint 1 is
in the base, and joint 5 is in the wrist, with numbering sequentially outward.
Check for proper brake operation by turning a brake off and physically moving 
the appropriate joint.  
	Now trun the selector knob to a joint number.  This engages the
velocity servo for that particular joint.  Turning the speed control
knob will move the selected joint at a commanded velocity.  The spring 
centering and center dead band mean that releasing the speed knob centers it, 
thereby turning off the velocity servo and turning on the brake.  
	Check out all the joints, but remember that this is not a position
servo, and joints will bang into their stops if driven too far.  
	The hand (#7 joint] has two modes, a standard mode and an impact mode
to give it greater grasp force.  The impact mode is also used to enable release
should the hand jam during grasping of a rigid object.  Do not use the impact
mode more than necessary, as this only causes excessive force to be built up.

	Another note of caution- all joints on the arm are reversible with their
brakes off (#6 joint doesnt have a brake- thus no brake switch].  Thus the arm can be
manually placed in a desired position and held there with the brakes.  The motors
are NOT designed to hold a fully loaded arm in place for more than a few seconds,
so don't servo the loaded arm slowly as this can cause motor damage from overheating.
The possibility of this happening is greatest in manual mode when tinkering is
most likely, and there is no computer monitoring of the motor status.

	For debugging, if is desireable to place the 1 inch thick sheet of 
hard foam rubber supplied as part of the packing material around the arm
base.  This way, damage from accidental bumping into the table will be

		3M- Connector Pin Numbers

1	Pot +Voltage Common (+10 vdc max)
2	Ground common
3	Pot -Voltage Common (-10 vdc max)
4	Ground (common)
5	CC Reset (momentary gnd. to disable arm)
6	Ground (common)
7	CC Set (momentary gnd. to enable arm)
8	Gnd (common)
9	Pot #1 Wiper-output (P1)
10	Tach. #1 output (T1)
11	CC Motor #1 (+-10 v range) (M1)
12	CC Brake #1 (gnd. to enable) (B1)
13	Spare
14	Spare
15	P2
16	T2
17	CC M2
18	CC B2
19	Spare
20	Spare
21	P3
22	T3
23	CC M3
24	CC B3
25	Spare					NOTES
26	Spare				
27	P4- wiper A				CC= Computer Command
28	T4					P = Potentiometer Wiper
29	P4- wiper B				T = Tachometer
30	CC M4					B = Brake
31	CC B4					M = Motor
32	Spare
33	P5					All grounds are common
34	T5
35	CC M5
36	CC B5
37	Spare
38	Spare
39	P6- wiper A
40	T6- 
41	P6-wiper B
42	CC M6
43	CC B6
44	Spare
45	P7 
46	T7
47	CC M7
48	Spare
49	CC M7-hammer mode
50	JOINT HOT (overtemperature signal- high=hot)


	Throughout the arm the following color codes are used
Red-	 Potentiometer Element
Brown-	 Potentiometer Element
Violet-  Motor
White -  Motor
Yellow-  Tachometer
Black-   Tachometer Common
Grey-    Brake
Orange-  Brake Common
Green-   Pot. Wiper #1
Blue-	 Pot. Wiper #2


1	B1 (high=on)
2	B2
3	B3
4	B4
5	B5
6	Spare
7	Hand- impact mode
8	Brake Common
9	Spare
10	J1 (Joint #1 manual control)
11	J2
12	J3
13	J4
14	J5
15	J6
16	J7 (Hand manual control)
17	Spare
18	+15vdc (from power supply to hand control)
19	-15vdc
20	Pot Wiper (From manual velocity control pot)
21	Spare
22	Manual Control/Computer Control Select (high=hand control)
23	Gnd
24	Spare
25	Emergency Stop
26	Control Command Cround


	Pin assignments for 50 pin 3-M connector from power supply to arm

1	Potentiometer Element
2	Spare Buss 1
3	Potentiometer Element
4	Spare Buss 2
5	Brake Common
6	Spare Buss 3
7	Tach Common 
8	Spare Buss 4
9	P1 
10	T1
11	Spare
12	M1
13	M1
14	B1
15	P2
16	T2
17	Spare
18	M2
19	M2
20	B2
21	P3
22	T3
23	Spare
24	M3
25	M3
26	B3
27	P4 (wiper #1)
28	T4
29	P4 (wiper #2)
30	M4
31	M4
32	B4
33	P5
34	T5
35	Spare
36	M5
37	M5
38	B5
39	P6 (wiper #1)
40	Spare
41	P6 (wiper #2)
42	M6
43	M6
44	B6
45	P7
46	Spare
47	Spare
48	M7
49	M7
50 	Spare


1 	Gnd
2	NC
4	NC
6	NC
10	NC
11	-HCM2EN
12	CCM4
13	GND
14	CCM3
15	-CCM2EN
16	CCM2
17	GND
18	HC input
19	CT1
20	CCM1
21	T1
22	-HCM1EN
23	T2
24	-CCM1EN
25	CT2
26	RFBM3
27	CT4
28	RFBM2
29	T4
30	RFBM1
31	NC
32	QNM1B
33	NC
34	QNM2B
35	NC
36	QPM2B
37	NC
38	QPM1B
39	-15VDC
40	QNM3B
41	NC
42	QNM4B
43	NC
44	GND
45	NC
46	QPM4B
47	NC
48	QPM3B
49	NC
50	QNM5B
51	NC
52	QNM6B
53	+15VDC
54	QPM6B
55	NC
56	QPM5B
57	NC
58	QNM7B
59	NC
60	QPM7B
61	T3
62	+O.V.C.
63	CT3
64	-O.V.C.
65	T6
66	T7
67	T5
68	NC
69	CT6
70	RFBM7
71	CT5
72	RFBM6
73	CT7
74	RFBM5
75	NC
76	RFBM4
77	GND
78	NC
79	-CCM7EN
80	NC
81	GND
83	-HCM7EN
84	CCM6
85	-CCM6EN
86	CCM5
87	NC
88	NC
89	GND
90	NC
91	-HCM6EN
92	NC
93	-CCM5EN
94	NC
95	GMD
96	NC
97	-HCM5EN
98	NC
99	NC
100	NC

GND   Connect all grounds together
		Digital P.C. Card Pin Assignments

4	NC
9	-15VDC
10	NC
12	NC
13	NC
14	GND
16	NC
17	NC
18	NC
19	NC
20	NC
21	GND
22	NC
24	CC B7 EN
25	+15VDC
26	+5VDC
28	-15VDC
30	TH M7
31	-HC M7 EN
32	NC
33	INV 1 OUT
34	CC M6 EN
35	INV 1 IN
36	CC B5 EN
37	-CC M7 EN
38	-HC M6 EN
39	-CC M6 EN
40	-HC M5 EN
41	-B5 REL
44	+5VDC
45	+15VDC
46	-15VDC
47	-B4 REL
48	TH M6
49	INV 2 OUT
50	TH M5
51	INV 2 IN
52	NC
53	INV 3 OUT
54	CC B4 EN
55	INV 3 IN
56	CC B3 EN
57	-CC M5 EN
58	-HC M4 EN
59	-CC M4 EN
60 	-HC M3 EN
61	-B3 REL
64	+5VDC
65	+15VDC
66	-15VDC
67	-B2 REL
68	TH M4
69	-B1 REL
70	TH M3
71	INV 4 OUT
72	NC
73	INV 4 IN
74	CC B2 EN
75	INV 5 OUT
76	CC B1 EN
77	INV 5 IN
78	-HC M2 EN
79	+5VDC
80	-HC M1 EN
81	-CC M3 EN
83	-CC M2 EN
84	+5VDC
86	-15VDC
87	-CC M1 EN
88	TH M2
89	-CC EN
90	TH M1
91	B7
92	NC
93	B5
94	+15VDC
95	B3
96	B1
97	B2
98	B4
99	B6


	The arm package consists  of three units, the arm,  the power
supply, and the  manual controller.
	The  arm must  be  clamped or  screwed  to a  suitable  rigid
support such  as a table, large plate or  rigid bracket of some sort.
For debugging purposes it is wise to place some flexible polyurethane
foam  (like  that used  in  the  arm  shipping container)  over  hard
surfaces within  the range of the arm.  This will help prevent damage
in the event errors are made in initially  interfacing or programming
the arm.  

	The manual  controller plugs into  the power supply,  and the
arm connects to  the power supply thru the 50 conductor 3M flat cable
provided.   One  end plugs  into  the arm,  the  other into  the  ARM
connector on the power supply.  As one end of the cable is polarized,
it  is not possible to plug it in wrong  (so long as you don't try to
force things).  It is best to lead the cable out  of the power supply
underneath the  carrying handle and under  the supply.   This way the
power supply acts  as a  strain relief  should the  cable recieve  an
unintentional pull.  

	The manual controller permits computerless remote movement of
individual joints  of the arm.  It  also selects the operating mode. 
There are 5 brake switches on this control.  They control  the brakes
on joints 1  thru 5.  (joint 6  and the hand have no  brakes).  Joint
numbering  starts at the  base (#1) and  works out to  the hand (#7).
These switches absolutely turn their  proper brake off.  They  AND to
turn their  proper brake  on.  The  arm can be  physically positioned
using only the brake switches (MODE switch in any position, including
OFF is OK).   Just turn  a joint brake off  and move that  joint with
your hands (execpt the hand which must be electrically operated). 

	The MODE switch  selects the  function.  OFF  means only  the
brake switches function (Both OFF  positions are the same).  COMPUTER
means  that the  computer controls  the ARM.   The numbered  and HAND
positions refer to the manual control mode where turning the VEL knob
+ and -  makes the selected joint move + or -.   Turning the VEL knob
does two things.  It first turns off the selected joint brake and  at
the same time commands a joint velocity.   This commanded velocity is
proportional to the  knob displacement, but also dependent on gravity
and load torques on the particular joint.  To properly use this mode,
keep the brake  switches in ON position, as their  off position is an
absolute OFF. 

	There  are  two more  buttons on  this  controller.   The RED
button is the stop button  when operating in COMPUTER mode.   Pushing
it momentarily  will disable the arm.   This means the  arm will stop
where it is and the brakes will  turn on.  To re-enable the arm,  see
the section under computer  control.  The BLACK button  is the impact
mode  on the hand.   Pushing this button WHILE  turning the VEL knob,
with HAND mode selected will cause the hand to see a rectangualr wave
drive  signal   whose  duty  cycle   is  proportional  to   VEL  knob
displacement.   This will  cause the  hand to tighten  or release its
grip.  CAUTION- use this mode sparingly, as it heats the motor up and
also causes more rapid hand screw wear.  

	Some observations on the  manual operation of the arm.  Under
manual control, the maximum  speeds of the arm  are much slower  than
the  maximums  under  computer  control.    In  addition,  the  joint
strengths are slightly reduced.  Do not hold a joint against its stop
too long.   If no  motion is taking  place, let the  VEL knob  center
itself.   This reduces  motor heating.   The  power supply  has motor
temperature  sensors in  it.   If you  do keep  a joint on  too long,
especially at high current  levels, the overtemp sensor  will disable
the arm until the motor cools a bit.  The hot joint will be indicated
by its correspondingly numbered LED on  the power supply.  DON'T  run
the arm into its  stops too frequently.  The arm  stops are primarily
to keep the joints from winding up.  Properly operated the arm should
never run into its  stops.  Just like with  a person- its painful  to
move a joint to its limits of motion, expecially at high speed.  This
caution is  very important under computer control where maximum joint
velocity is much higher. 


	The other 50 pin 3M connector comming out of the power supply
is  for  connection  to  a  computer  interface,  or  other  external
hardware.  The accompanying pin  chart lists the pin assignments  for
this  connector.   A summary  follows.   Pot  voltage  means the  pot
reference supply  terminals.  Customer must  supply his own precision
supply.  This should  be compatible with the  A/D used.  Typically  a
+-10 vdc supply is used.   This supply should be capable of supplying
at least  250 ma.  Ground or Gnd.  or Ground Common terminals are all
tied together and  represent the  ground terminals.   CC refers to  a
Computer  Command  terminal.    These  are Motors  (M1,  etc)  Brakes
(B1,etc.), and Enable and  Disable.  The Motors  accept a +- 10  vdc.
signal range at  10 ma.  max.   This corresponds to full  scale motor
current.    The  power supply  contains  CURRENT  amplifiers.   These
amplifiers output a motor  current proportional to the voltage  input
from the  computer on the  CC M1 (etc.)  terminals.  The  BRAKE input
terminals  accept a high (can be TTL or  floating) or low (TTL low or
GND) at 1 ma.   to turn the brakes off  or on.  LOW means  the brakes
are ON.  There is also the CC SET and CC RESET leads.  These are used
to enable or disable the  arm (all joints at  a time).  Grounding  CC
SET enables the arm, while grounding CC RESET disables the arm.  This
can be done with TTL logic, and only requires a momentary pulse.  The
reset function is  ORed with the  RED button  on the manual  control.
It's a good idea to trun the brakes on with the computer before doing
your  first ENABLE or else the arm may  fall.  Also, its advisable to
have a timeout on the ENABLE so that if the program dies the arm will
stop.  Thus a 100 ms. timeout is a good thing.  The software can give
enables every 50-100 ms. and a hardware timer can be set to trigger a
RESET in 100 ms.  if no new RESET is recieved. 

	On the output side, The POT  Wiper terminals (P1,P2,ETC.) are
the  joint position signals comming  directly from the potentiometers
on each  joint.  Their  range will  be about  90% of  the pot  supply
voltage, execpt for the hand which is  only about 20% at present.  On
joints  1,2,3,and 5  this  corresponds to  about 340  degrees maximum
rotation.  On joints  4 and 6 there  are two wipers spaced  about 180
degrees apart.  This allows  for about 600 degrees of rotation as one
wiper is always in an active region on the pot element.  The computer
must  have an  algorithm  for selecting  the  proper wiper  to  use.  
Starting algorithms must also be carefully thought out if both wipers
are to be properly  used.  Of course, many  useful tasks can be  done
with the  more limited motion resolved  by just a single  wiper.  The
pots  are not highly  linear devices. This doesn't  matter if Unimate
type of  operation is desired,  but for  computer planned motions,  a
table lookup procedure must be stored in the computer. 

	Joints 1 thru 5 have electromechanical tachometers.  Joints 6
and 7 have electronic tachometers.  In all cases, the output  signals
have been amplified inside the power supply.  This scaling results in
larger than raw  output. Due to electronic circuitry constraints, the
tach readings will be affected by  turning the VEL knob even when  in
COMPUTER mode.  Thus, keep your  hands off this knob when reading the
tachs,  or running in computer mode.   Joints 6 and 7 have electronic
tachometers.  These  are electronic circuits  which measure the  back
EMF  of the  motor and  attempt to  cancel out  the  armature losses.
Unfortunately, this is not too accurate a process, but it does  serve
its purpose of providing a damping signal  for use in improving servo
stability.  The  output of these electronic tachometers is about +- 3
volts full scale.  The other tachs have 6-10 volt full scales.  

	The CC M7  HAMMER MODE terminal  refers to the input  for the
hand hammer mode.   The hammer mode duty cycle is proportional to the
signal sign  and  amplitude.   Actually,  it  is probably  better  to
operate the hammer mode from software  directly into the CC M7 input.
This way  the duty cycle AND frequency can be program changed easily.
One less output  channel is needed  too.  Remember,  take it easy  in
using this mode. 

	The JOINT HOT output  is normally low.  it will  go high when
the arm is hot  and has stopped because of a hot motor.  This is just
a status bit so the computer can keep track of what has happened.  As
with all other digital inputs, it is TTL compatible. 

	You now have enough information to enable you to start using
your manipulator.   Good luck.