Intelligent Robotics I: Servo Control

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Intelligent Robotics I Servo Control

• Overview and example of robot control
• Jeff Allen

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Robot Recipe

• Sensors
• Artificial (sonar, cameras, temp, light,
  water,.......you get the point)
• Human (From a controller perceiving a worthy
  input)
• Intelligence
• Artificial (computational, search, genetic, NN,
  cellular automata, too name a few)
• Human (a controller intelligence varies in
  extremes, and is both time and subject variant)
• Actuators
• Artificial (this is a requirement)

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Robotic System The world and the boxes

• Sensors
• Can exist solely in either domain
• Can exist in mix of both
• Intelligence
• Can exist solely in either domain
• Can exist in mix
• Robot State
• Internal conditions used to represent actions
• Actuators
• The method the robot interacts, injects its will
  onto the real world

Robo world
Sensors Input
Intelligence
Robot HW/SW State
Actuators Output
Outside World Part of your system feedback
mechanism hopefully!?
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Robotic System simplification

• Input to Intelligence
• Ignore all outside possibility as it is not in
  the system
• Intelligence to Robot State to Output
• Imply state as part of the connection

Robo world
Sensors Input
Intelligence
Robot HW/SW State
Actuators Output
Outside World Part of your system feedback
mechanism hopefully!?
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An Abridged Robotic SystemTransistions and
related factors

• Input to Intelligence
• Complexity of sensor input
• Must travel in robot world even if remote
  controlled.
• Intelligence to Actuators
• Must travel in robot world

Robo world
Sensors Input
Intelligence
Actuators Output
Outside World Part of your system feedback
mechanism hopefully!?
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Sensor Information Complexity (Artificial)

• Simple
• Touch
• Sonar
• IR
• Light
• Temp
• Engine and systems feedback
• Radio signal
• etc
• Middle to Upper Complexity
• Sonar Arrays/Radar Arrays
• LIDAR
• Camera(s)
• GPS Positioning
• Etc

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Consequences of increased sensor information
complexity

• Information size
• Processing difficulty
• Usefulness of data may require many different
  processes
• Yet another etc.
• All ultimately lead in one way or another to
  increased requirements of the robot system.
  Which usually means !

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Information Traveling in the Robot World

• Information and its communication must happen.
• If nothing is communicated how can it be a
  robot?
• We all know how it is done.
• Electrical signals and representations sent to
  devices program to respond accordingly.

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Some robot system methodologies

• Single autonomous unit
• All onboard system intelligence is onboard. With
  remote communications generally limited to system
  reprogramming or goal adjustments. Not direct
  actuator control.
• Remotely controlled units
• The controlling unit, human or artificial, is
  located at another location controlling the unit.
• Mixed units
• Remotely controlled units with certain automated
  subsumbtive responses controlled directly.
  Example robotic overrides, like your brakes

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More about robot system methodologies

• Single autonomous unit
• Varying complexities based on onboard
  computational and sensing abilities as well as
  actuator device complexities.
• Complexity increases are expensive and can create
  extremely difficult systems in situations where
  onboard requirements are stretched to limits
• Excellent response times are possible
• Remotely controlled units
• Onboard equipment requirements are lessened with
  respect to computational devices. (less
  expensive)
• Complexity increases due to sensors now increase
  bandwidth requirements, but are otherwise less
  expensive.
• Natural lag in response related to communicated
  distance as well as bandwidth
• Mixed units (see all above)

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PC remote controlled systemsTodays example

• Inexpensive.
• PC (look at a Frys ad)
• Servo controller board (10 - 200 on average)
• Potentially Powerful
• Information communicated can be communicated
  along multiple channels usb, serial, firewire,
  etc..
• Numerous programming languages to choose from.
• Why do we use them? Look above

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Review Traveling in the Robot World. what
did we say?

• Information and its communication must happen.
  If nothing is communicated how can it be a robot?
• We all know how it is done. In theory.
  Practically?

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A communicating exampleA PC controlled robot
Communication Channel PC to Control In this
case RS232 Our development environment Visual
Studio VB 6.0
Input to PC Predefined movement scripts /
Sensors
Actuator Control ASC 16 Board
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Communication channelPC to RS232 piece

• MS Visual studio provides the MSComm object
  capable of
• Transmitting/ receiving / open / close to a comm
  port using rs232. The requirement is only that
  the data be presented in the format it is to be
  sent according to receiving device.
• ASC 16 has specific commands for each servo
  device.
• Each servo is capable of 180 degrees of movement
  with a precision of 180/4000 degrees/point, .045
  Deg/point
• The ASC16 is capable of simple position commands
  ,small loop programs as well as positional
  feedback (not in this example)
• Commands are given in 1,2, and 3 byte packages

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Example goal

• We need something to convert commands from the PC
  to appropriate ASC16 commands, a translator.

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Requirements

• Each servo device will have a different range of
  motion and rarely will move all 180 degree.
• Each device is a separate entity, interrelations
  can be calculated but otherwise do not exist

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ASC16 Commands

• ac (81-96 DEC) (51-60 HEX)
• Acceleration
• am (250 DEC) (FA HEX)
• Abort All Motion
• at (249 DEC) (F9 HEX)
• Abort Triggers
• bt (124 DEC) (7C HEX)
• Base Time
• en (121 DEC) (79 HEX)
• Enable Module
• f (251 DEC) (FB HEX)
• Freeze Motion
• f- (252 DEC) (FC HEX)
• Freeze Motion Off

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ASC16 Commands (cont.)

• fp (21-36 DEC) (15-24 HEX)
• Flyby Position
• iv (112 DEC) (70 HEX)
• Invert Servo Coordinates
• la (242 DEC) (F2 HEX)
• Load All
• ld (123 DEC) (7B HEX)
• Load Default Position
• lm (253 DEC) (FD HEX)
• Loop Marker
• lp (254 DEC) (FE HEX)
• Loop
• mk (221-228 DEC) (DD-E4 HEX)
• Marker

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ASC16 Commands (cont.)

• mr (41-56 DEC) (29-38 HEX)
• Move Relative
• mk (221-228 DEC) (DD-E4 HEX)
• Marker
• mr (41-56 DEC) (29-38 HEX)
• Move Relative
• mv (1-16 DEC) (01-0F HEX)
• Move servo absolute
• no (0 DEC) (00 HEX)
• No Operation
• no no no (0,0,0 DEC) (00,00,00 HEX)
• Terminate
• nv (113 DEC) (71 HEX)
• Non-invert Servo Positions

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ASC16 Commands (cont.)

• op (110 DEC) (6E HEX)
• Output
• pg (120 DEC) (78 HEX)
• Program Module address
• ra (141-148 DEC) (8D-94 HEX)
• Read Input as Analog
• rd (179 DEC) (63 HEX)
• Read Inputs as digital
• rp (116 DEC) (74 HEX)
• Report Position
• rs (117 DEC) (75 HEX)
• Report Speed
• s (245 DEC) (F5 HEX)
• Servos On

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ASC16 Commands (cont.)

• s- (246 DEC) (F6 HEX)
• Servos Off
• sa (241 DEC) (F1 HEX)
• Save All
• sp (61-76 DEC) (3D-4C HEX)
• Speed
• st (151- 168 DEC) (97 - A8 HEX)
• Stop
• sv (122 DEC) (7A HEX)
• Save Default Servo Position
• tl (119 DEC) (77 HEX)
• Trigger Level
• tm (181-196 DEC) (65-C4 HEX)
• Trigger on Motion Completion
• tp (201-216 DEC) (C9-D8 HEX)
• Trigger on Servo Position

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ASC16 InformationCommand Set Example

• mv (1-16 DEC) (01-0F HEX) Move servo absolute
• Format mv position mv 1-16 for servo 1(mv1)
  to 16 (mv16)
• position 0-4000
• Description Moves a servo to a new absolute
  position at the speed and acceleration rate set
  for the specified servo.
• Example
• Mnemonic Numeric
• mv2 1500 Move servo 2 to position 1500 2, 5, 220
• mv10 200 Move servo 10 to position 200 10, 0,
  200

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Translator specs

• Class (single instance for each servo)
• Provides separate initialization data to exist
  within each object
• Separate variable data such as position and rates
  are stored with each object
• Functions compute output string based on object
  data
• - Normalized control

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Class local Variable

• 'local variable(s) to hold property value(s)
• Private mvarminRange As Integer 'local copy
• Private mvarmaxRange As Integer 'local copy
• Private mvarmultiplier As Single 'local copy
• Private mvarmark As Integer 'local copy
• Private mvarservo As Integer 'local copy
• Private mvarposition As Integer 'local copy
• Private mvarreverse As Boolean 'local copy
• Public outputstring As String
• Public value As Integer
• Private mvargood As Boolean 'local copy

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Why private?

• Private can help guarantee values are within
  appropriate ranges. This helps make sure the
  system doesnt get bad information.
• Provides protection to data from outside.
• It just means a function is must be called to
  write data.

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ASC16 InformationCommand Set Example

• ac (81-96 DEC) (51-60 HEX)
• Acceleration
• Format ac accel ac 81-96 for servo 1 (ac1)
  to 16 (ac16)
• accel 1-255
• Example
• mnemonic Numeric
• tl 2 set trigger level to suspend processing
  119, 2
• ac1 5 set acceleration rate for servo 1 to
  5cnts/20mS2 81, 0, 5

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Accel command for servo object

• Public Function Accel(ByVal rate As Integer) As
  String
• Dim locservo
• locservo mvarservo 80
• Accel Chr(locserver) Chr(rate)
• End Function

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ASC16 InformationCommand Set Example

• mv (1-16 DEC) (01-0F HEX) Move servo absolute
• Format mv position mv 1-16 for servo 1(mv1)
  to 16 (mv16)
• position 0-4000
• Description Moves a servo to a new absolute
  position at the speed and acceleration rate set
  for the specified servo.
• Example
• Mnemonic Numeric
• mv2 1500 Move servo 2 to position 1500 2, 5, 220
• mv10 200 Move servo 10 to position 200 10, 0,
  200

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Servo Movement as seen by PC

• Movement are absolute otherwise
• Increased chance of leaving initialized range
• Must poll often to stay up to date, therefore
  increasing communication

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Move command

• Public Function Move(ByVal pos As Integer) As
  String
• Dim bigmove As Integer
• Dim litmove As Integer
• Dim overall As Integer
• If pos gt 0 And pos lt 255 Then
• If mvargood Then
• If mvarreverse Then
• overall mvarminRange - (pos
  mvarmultiplier)
• litmove (overall Mod 256)
• bigmove ((overall - litmove) / 256)
• Else
• overall mvarminRange (pos
  mvarmultiplier)
• litmove overall Mod 256
• bigmove ((overall - (litmove)) /
  256)
• End If
• mvarposition pos
• Move Chr(mvarservo) Chr(bigmove)
  Chr(litmove)

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Initialization function

• Public Sub makenew()
• 'this is surely ugly as but since cannot use new
  like .NET
• 'this will do.
• If (mvarservo gt 1) And (mvarservo lt 16) And
  (mvarmaxRange lt 4000) And (mvarminRange lt 4000)
  And _
• (mvarmaxRange gt 0) And (mvarminRange
  gt 0) Then
• mvargood True
• If mvarmaxRange gt mvarminRange Then
• mvarreverse False
• mvarmultiplier (mvarmaxRange -
  mvarminRange) / 256
• Else
• mvarreverse True
• mvarmultiplier (mvarminRange -
  mvarmaxRange) / 256
• End If
• End If
• mvarposition 127
• End Sub

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Using objects

• Create instantiate an object for each servo
  device
• Dim eyeLr As New asc16stringbuilder
• Dim eyeDu As New asc16stringbuilder
• Dim neckLR As New asc16stringbuilder
• Dim neckDU As New asc16stringbuilder
• Dim mouth As New asc16stringbuilder
• Initialize
• eyeLr.servo 1
• eyeLr.minRange 1390
• eyeLr.maxRange 2810
• eyeLr.makenew
• Use
• MSComm.Output eyeLr.Move(value) value range
  0 255

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A trivial use example

• Random eye movement
• Public Sub LRAnimEye()
• Dim randomx As Integer
• randomx Int(10 Rnd) - 5
• randomx randomx 15
• MSComm.Output eyeLr.Move(randomx 127)
• End Sub

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Questions Discussion

• ??