1. Robotics & Vision Analysis, systems, Applications

2. Robot::Body Typically defined as a graph of links and joints:
A link is a part, a shape with physical properties.
A joint is a constraint on the spatial relations of two or more links.

3. Link
Link n
q n+1
a n
q n
Joint n+1
Joint n
z n
x n
x n+1
z n+1
A link is considered as a rigid body which defines the relationship between two neighboring joint axes of a manipulator.

4. Link Length and Twist Axis i Axis i-1 ai-1 i-1
The distance between two axes in 3-space is measured along a line which is mutually perpendicular to both axes.
Link twist: If we imagine a plane whose normal is the mutually perpendicular line just constructed, we can project both axes I-1, I onto this plane and measure the angle between them. The angle is measured from i-1 to I by Right-Hand-Rule about the common normal.
Note: If the axes intersect, then a is zero, and  is still measured from axis i-1 to axis i.

5. Link and Joint Parameters
Axis i-1
Axis i ai di i
For kinematical studies we only need two more quantities to completely define the relative position of two neighboring links.
The Distance between the two common normals “di” at joint-i. This distance is called the “Link-Offset” (.
Angle of rotation about their common axis-i, between one link and its neighbor, “i”. This angleis called the “Joint-Angle” (“i” is the angle between ai-1 and ai about axis-i).
ai-1
i-1

6. Affixing Frames to Links
Link n-1
Link n
zn-1
yn-1
xn-1 zn xn yn
zn+1
xn+1
yn+1 dn an
Joint n+1
Joint n-1
Joint n
an-1
In the case of ai=0 Xi is normal to plane of Zi and Zi+1
This convention does not result in a unique attachment of frames to links…

7. Example: Puma 560

8. The Kinematics Model
The robot can now be kinematically modeled by using the link transforms ie:
Where
0nT is the pose of the end-effector relative to base;
Ti is the link transform for the ith joint;
and
n is the number of links.

9. General Transformation Between Two Bodies
In D-H convention, a general transformation between two bodies is defined as the product of four basic transformations:
A translation along the initial z axis by d,
A rotation about the initial z axis by q,
A translation along the new x axis by a, and.
A rotation about the new x axis by a.

10. A General Transformation in D-H Convention
D-H transformation for adjacent coordinate frames:

11. Robot Joints Prismatic Joint: Linear, No rotation involved.
(Hydraulic or pneumatic cylinder)
Revolute Joint: Rotary, (electrically driven with stepper motor, servo motor)

12. Robot Coordinates
Fig. 1.4
 Cartesian/rectangular/gantry (3P) : 3 cylinders joint
 Cylindrical (R2P) : 2 Prismatic joint and 1 revolute joint
 Spherical (2RP) : 1 Prismatic joint and 2 revolute joint
 Articulated/anthropomorphic (3R) : All revolute(Human arm)
 Selective Compliance Assembly Robot Arm (SCARA):
2 paralleled revolute joint and 1 additional prismatic joint

13. Robot Workspace
Fig. 1.7 Typical workspaces for common robot configurations

14. Actuators
Hardware devices that convert a controller command signal into a change in a physical parameter
The change is usually mechanical (e.g., position or velocity)
An actuator is also a transducer because it changes one type of physical quantity into some alternative form
An actuator is usually activated by a low-level command signal, so an amplifier may be required to provide sufficient power to drive the actuator

15. Actuators Signal Processing & Amplification Mechanism Electric
Hydraulic
Pneumatic
Final Actuation
Element
Actuator
Sensor
Logical
Signal

16. Types of Actuators Electrical actuators Hydraulic actuators
Electric motors
DC servomotors
AC motors
Stepper motors
Solenoids
Hydraulic actuators
Use hydraulic fluid to amplify the controller command signal
Pneumatic actuators
Use compressed air as the driving force

17. Stepper motor and Servomotor

18. DC Motors Most common and cheapest Powered with two wires from source
Draws large amounts of current
Cannot be wired straight from a PIC
Does not offer accuracy or speed control

19. Stepper Motors Stepper has many electromagnets
Stepper controlled by sequential turning on and off of
magnets
Each pulse moves another step, providing a step angle
Example shows a step angle of 90°
Poor control with a large angle
Better step angle achieved with the toothed disc

20. Stepper Motors
Step angle is given by: : where ns is the number of steps for the stepper motor (integer) Total angle through which the motor rotates (Am) is given by: where np = number of pulses received by the motor. Angular velocity is given by: where fp = pulse frequency Speed of rotation is given by:

21. Stepper motor operation

22. Stepper motor operation

23. Stepper motor operation

24. Stepper motor operation

25. Example
A stepper motor has a step angle = 3.6. (1) How many pulses are required for the motor to rotate through ten complete revolutions? (2) What pulse frequency is required for the motor to rotate at a speed of 100 rev/min?

26. Solution
(1) 3.6 = 360 / ns; 3.6 (ns) = 360; ns = 360 / 3.6 = 100 step angles (2) Ten complete revolutions: 10(360) = 3600 = Am Therefore np = 3600 / 3.6 = 1000 pulses Where N = 100 rev/min: 100 = 60 fp / ,000 = 60 fp fp = 10,000 / 60 = = 167 Hz

27. Servo Motor

28. NXT Mindstorms - Servo Motor

29. Motor Controllers
The POSYS® 3004 (Designed & Made in Germany) is a PC/104 form factor board dedicated to high performance motion control applications with extensive interpolation functionality. The POSYS® 3004 is designed to control up to 4 axes of servo and stepper motors and provides hardware linear, circular, Bit Pattern and continuous interpolation which allow to perform the most complex motion profiles. Update rates per axis do not exist as each axis runs in absolute real-time mode simultaneously which makes these boards to one of the best performing motion controllers for up to 4 axes in the market.

30. Servo motors Servo offers smoothest control Rotate to a specific point
Offer good torque and control
Ideal for powering robot arms etc.
However:
Degree of revolution is limited
Not suitable for applications which require
continuous rotation

31. Servo motors Operation
Pulse Width Modulation (0.75ms to 2.25ms)
Pulse Width takes servo from 0° to 150° rotation
Continuous stream every 20ms
On programming block, pulse width and output pin must be set.
Pulse width can also be expressed as a variable

32. Controller (The brain) Issues instructions to the robot.
Controls peripheral devices.
Interfaces with robot.
Interfaces with humans.

33. Robot Control Systems
Limited sequence control – pick-and-place operations using mechanical stops to set positions
Playback with point-to-point control – records work cycle as a sequence of points, then plays back the sequence during program execution
Playback with continuous path control – greater memory capacity and/or interpolation capability to execute paths (in addition to points)
Intelligent control – exhibits behavior that makes it seem intelligent, e.g., responds to sensor inputs, makes decisions, communicates with humans

34. Robot Control System Cell Supervisor Controller & Program Joint 1
Level 2
Controller
& Program
Level 1
Joint 1
Joint 2
Joint 3
Joint 4
Joint 5
Joint 6
Sensors
Level 0

35. The Hand of a Robot: End-Effector
The end-effector (commonly known as robot hand) mounted on the wrist enables the robot to perform specified tasks. Various types of end-effectors are designed for the same robot to make it more flexible and versatile. End-effectors are categorized into two major types: grippers and tools.

36. The Hand of a Robot: End-Effector

37. The Hand of a Robot: End-Effector
Grippers are generally used to grasp and hold an object and place it at a desired location.
mechanical grippers
vacuum or suction cups
magnetic grippers
adhesive grippers
hooks, scoops, and so forth

38. End Effectors (The hand) Spray paint attachments Welding attachments
Vacuum heads
Hands
Grippers

39. Robot Movement and Precision
Speed of response and stability are two important characteristics of robot movement.
Speed defines how quickly the robot arm moves from one point to another.
Stability refers to robot motion with the least amount of oscillation. A good robot is one that is fast enough but at the same time has good stability.

40. End Effectors
The special tooling for a robot that enables it to perform a specific task
Two types:
Grippers – to grasp and manipulate objects (e.g., parts) during work cycle
Tools – to perform a process, e.g., spot welding, spray painting

41. Grippers: mechanical, magnetic and pneumatic.
End Effectors
Tools: Tools are used where a specific operation needs to be carried out such as welding, painting drilling etc. - the tool is attached to the mounting plate.
Grippers: mechanical, magnetic and pneumatic.

42. Two fingered most common, also multi-fingered available
End Effectors
Mechanical:
Two fingered most common, also multi-fingered available
Applies force that causes enough friction between object to allow for it to be lifted
Not suitable for some objects which may be delicate / brittle

43. Magnetic:
Ferrous materials required
Electro and permanent magnets used
Pneumatic:
Suction cups from plastic or rubber
Smooth even surface required
Weight & size of object determines size and number of cups

45. Grippers and Tools

46. Power Sources for Robots
An important element of a robot is the drive system. The drive system supplies the power, which enable the robot to move.
The dynamic performance of a robot mainly depends on the type of power source.

47. Power Source
(The food)
Electric
Pneumatic
Hydraulic

48. There are basically three types of power sources for robots:
1. Hydraulic drive
Provide fast movements
Preferred for moving heavy parts
Preferred to be used in explosive environments
Occupy large space area
There is a danger of oil leak to the shop floor

49. 2. Electric drive
Slower movement compare to the hydraulic robots
Good for small and medium size robots
Better positioning accuracy and repeatability
stepper motor drive: open loop control
DC motor drive: closed loop control
Cleaner environment
The most used type of drive in industry

50. 3. Pneumatic drive
Preferred for smaller robots
Less expensive than electric or hydraulic robots
Suitable for relatively less degrees of freedom design
Suitable for simple pick and place application
Relatively cheaper

51. Sensors For Robotics

52. What makes a machine a robot?

53. Resistive Light Sensor
Gas Sensor
Accelerometer
Gyro
Metal Detector
Pendulum Resistive
Tilt Sensors
Piezo Bend Sensor
Gieger-Muller
Radiation Sensor
Pyroelectric Detector
UV Detector
Resistive Bend Sensors
CDS Cell
Resistive Light Sensor
Digital Infrared Ranging
Pressure Switch
Miniature Polaroid Sensor
Limit Switch
Touch Switch
Mechanical Tilt Sensors
IR Pin
Diode
IR Sensor w/lens
Thyristor
Magnetic Sensor
Polaroid Sensor Board
Hall Effect
Magnetic Field
Sensors
IR Reflection
Sensor
Magnetic Reed Switch
IR Amplifier Sensor
IRDA Transceiver
IR Modulator
Receiver
Lite-On IR
Remote Receiver
Radio Shack
Remote Receiver
Solar Cell
Compass
Compass
Piezo Ultrasonic Transducers

54. Why do robots need sensors?

55. What Is a Sensor? Anything that detects the state of the environment.
Collect information about the world
Sensor - an electrical/mechanical/chemical device that maps an environmental attribute to a quantitative measurement
Each sensor is based on a transduction principle - conversion of energy from one form to another

56. What you (and the robot) can do without sensors?
Close your eyes. Plug your ears. Hold your nose. Tie your hands behind your back.
Shut your mouth. Tie your shoelaces together. Spin yourself around a few times.
Now walk. How does it feel? That's exactly what your robot feels: nothing - without sensors.
You have been given many types of sensors that can be used in a variety of ways to give your robot information about the world around it.
We will explain each of the sensors you can find in the lab, how it works, what it's good for, and how to build it.

57. The simplest possible use of sensors
The diagram serves to illustrate the general case of sensing a specific phenomenon.
In this case it is the presence or absence of light.
The sensor in this case is a photo-resistor.
When sufficient light strikes it, its internal resistance is reduced to several hundred Ohms.
When no light strikes it its resistance is typically several million Ohms.
light

58. Simple and Complex Sensors
Sensors range from simple to complex in the amount of information they provide:
a switch is a simple on/off sensor
a human retina is a complex sensor consisting of more than a hundred million photosensitive elements (rods and cones)
Sensors provide raw information, which can be treaded in various ways,
For example, we can simply react to the sensor output:

59. For example, how would you detect people? Some options include:
How to detect people?
For example, how would you detect people? Some options include:
temperature: pyroelectric sensors detect special temperature ranges
movement: if everything else is static
shape: now you need to do complex vision processing
color: if people are unique colored in your environment

60. How to detect people?
Let's think about something even more simple: how would you measure distance:
ultrasound sensors give you distance directly (time of flight)
infra red through return signal intensity
two cameras (i.e., stereo) can give you distance/depth
a camera can compute it from perspective
use a laser and a fixed camera, triangulate
structured light; overlying grid patterns on the world
frequency and phase modulation interferometry

61. Biological Analogs
All of the sensors we describe in this lecture exist in biological systems
Touch/contact sensors with much more precision and complexity in all species (spiders?)
Polarized light sensors in insects and birds
Bend/resistance receptors in muscles
and many more...

62. You have to understand sensors
we need to make one point very clear:
Sensors are not magical boxes.
All information you get from sensors must be decoded by you, the human builder and programmer.
Sensors convert information about the environment into a form that can be used by the computer.
The sensors that are on the robot can be related to sensors found in humans.

63. You have to understand sensors
These sensors convert information about the environment into neural code that your brain can understand:
Touch sensors embedded in your skin,
visual sensors in your retina,
and hair cells in your ears
Your brain needs to understand the neural code before you can react.
Since you will be programming the robot, you will need to understand the output of the sensors before you can program your robot to react to different stimuli.

64. Types of Sensors Active Passive
send signal into environment and measure interaction of signal w/ environment
e.g. radar, sonar
Passive
record signals already present in environment
e.g. video cameras

65. Types of Sensors Classification by medium used
based on electromagnetic radiation of various wavelengths
vibrations in a medium
concentration of chemicals in environment
by physical contact

66. Types of Sensors Exteroceptive: deal w/ external world
where is something ?
how does is look ? (camera, laser rangefinder)
Proprioceptive: deal w/ self
where are my hands ? (encoders, stretch receptors)
am I balanced ? (gyroscopes, INS)

67. Types of Sensors Interoceptive
what is my thirst level ? (biochemical)
what is my battery charge ? (voltmeter)
For the most part we’ll ignore these in this class

68. Analog versus Digital Sensors
In all our robotics kits the sensors are digital or analog.
For instance, in HandyBoard, analog sensors can be plugged into the analog sensor ports, which return values between 0 and 255.
Digital sensors can be plugged into either the digital ports or the analog ports, but will always return either 0 or 1.
ANALOG 0 =< x =< 255
DIGITAL 0 or 1

69. Analog Sensors and Thresholding
Analog sensors, such as photo-resistors, can tell you:
how far the sensor has bent,
or how much light is hitting the sensor.
They answer questions with more detail.
Analog sensors, however can be converted to digital sensors using thresholding.
Instead of asking the question “How much is the sensor bent?” you can ask the question: “Is the sensor bent more than half way?”
The threshold can be determined by playing around with the specific sensor.

70. Touch sensors

71. Resistive Position Sensors: bending
We said earlier that a photocell is a resistive device, i.e., it senses resistance in response to the light.
We can also sense resistance in response to other physical properties, such as bending.
These bend sensors were originally developed for video game control
They are generally quite useful:
Video game accessories are in general useful for robotics and virtual reality and very cheap.

72. Bend Sensors Useful for contact sensing and wall-tracking
You can remove it from Nintendo gloves
Useful for contact sensing and wall-tracking
The bend sensor is a simple resistance
As the plastic strip is bent (with the silver rectangles facing outward), the resistance increases

73. Bend sensor

74. Applications of Resistive Analog Sensors
Measure bend of a joint
Wall Following/Collision Detection
Weight Sensor
Sensors
Sensor

75. Inputs for Resistive Sensors
Voltage divider:
You have two resisters, one
is fixed and the other varies,
as well as a constant voltage
V1 – V2 * (R2/R1+R2) = V R1 V
Analog to Digital
(pull down) R2 V2
micro
Known unknown
measure
micro +
Binary
Threshold
Single Pin
Resistance
Measurement -
Comparator: if
voltage at + is greater
than at -, high value out

77. Potentiometer

78. Potentiometer: the main ideas
Potentiometers are very common for manual tuning; you know them from some controls (such as volume and tone on stereos).
Typically called pots, they allow the user to manually adjust the resistance.
The general idea is that the device consists of a movable tap along two fixed ends.
As the tap is moved, the resistance changes.
As you can imagine, the resistance between the two ends is fixed, but the resistance between the movable part and either end varies as the part is moved.
In robotics, pots are commonly used to sense and tune position for sliding and rotating mechanisms.

79. Potentiometers Mechanical varieties:
Linear and rotational styles - make position sensors for both sliding mechanisms and rotating shafts
Resistance between the end taps is fixed, but the resistance between either end tap and the center swipe varies based on the position of the swipe
Electrical varieties:
Linear taper - linear relationship between position and resistance. Turn the pot 1/4 way, the resistance between the nearer end and the center is 1/4 of end-to-end resistance
Audio taper - logarithmic relationship between position and resistance. At one end, 1/4 turn would swipe over a small bit of total resistance range, while at the other end, 1/4 turn would be most of the range

80. Potentiometer Assemblies
Kits contain several sizes of potentiometers, also known as variable resistors.
Potentiometers should be wired with Vcc and ground on the two outside pins, and the signal wire on the center tap.
This will, in effect, place the resistance of the potentiometer in parallel with the 47K pull-up on the expansion board and is more stable than just using one side and the center tab to make a plain variable resistor

81. Various uses of Potentiometers
Potentiometers have a variety of uses:
In the past, they have been used for menuing programs
For angle measurement for various rotating limbs
For scanning beacons.
They can be used with a motor to mimic servos, but that's a difficult task.
It is important to notice that the pots are not designed to turn more than about 270 degrees.
Forcing them farther is likely to break them.

82. Linear Potentiometers and their use in HandyBoard
A linear potentiometer can be used to measure precise linear motion,
such as a gate closing,
or a cocking mechanism for ring balls or blocks.
Frob-knob
The frob knob is the small white dial on the lower left corner of the Expansion Board.
It returns values between 0 and 255 and provides a handy user input for adjusting parameters on the y or for menuing routines to select different programs.

83. Encoders Encoders measure rotational motion.
They can be used to measure the rotation of a wheel.
Servo motors: Used in conjunction with an electric motor to measure the motor’s position and, in turn, control its position.

84. Encoders

85. Encoder Incremental encoder Technology
usually requires 2 sensors to determine speed and direction
Technology
magnet + hall sensors (incremental)
optical sensors with black/white segments (incremental)

86. Encoder ⇒ This is done in parallel to normal calculations
• Encoder signal (2 lines) are connected to microcontroller like 2 binary sensors (digital input lines)
• Microcontrollers usually have special internal registers for pulse counting
⇒ This is done in parallel to normal calculations
Does not slow down the cpu

87. Sensors Based on Sound SONAR: Sound Navigation and Ranging
bounce sound off of something
measure time for reflection to be heard - gives a range measurement
measure change in frequency - gives the relative speed of the object (Doppler effect)
bats and dolphins use it with amazing results
robots use it w/ less than amazing results

88. Sonar and IR Proxmity

89. Odor Sensors
Detection of chemical compounds and their density in an area
spectroscopy - mostly lab restricted
fibre-optic techniques - recently developed
chemical detection - sniffers aand electronic noses via “wet chemistry on a chip”
No major penetration in robotics yet applications are vast (e.g. mine detection)

90. Temperature Sensor Options
Resistance Temperature Detectors (RTDs)
Platinum, Nickel, Copper metals are typically used
positive temperature coefficients
Thermistors (“thermally sensitive resistor”)
formed from semiconductor materials, not metals
often composite of a ceramic and a metallic oxide (Mn, Co, Cu or Fe)
typically have negative temperature coefficients
Thermocouples
based on the Seebeck effect: dissimilar metals at diff. temps.  signal