1. Robotics

2. Definition:
“A robot is a reprogrammable, multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.” (Robot Institute of America)
Alternate definition:
“A robot is a one-armed, blind idiot with limited memory
and which cannot speak, see, or hear.”

3. Ideal Tasks Tasks which are: Dangerous Space exploration
chemical spill cleanup
disarming bombs
disaster cleanup
Boring and/or repetitive
Welding car frames
part pick and place
manufacturing parts.
High precision or high speed
Electronics testing
Surgery
precision machining.

4. Automation vs. robots
Automation –Machinery designed to carry out a specific task
Bottling machine
Dishwasher
Paint sprayer
Robots – machinery designed
to carry out a variety of tasks
Pick and place arms
Mobile robots
Computer Numerical Control
machines

5. Types of robots Pick and place Moves items between points
Continuous path control
Moves along a programmable path
Sensory
Employs sensors for feedback

6. Pick and Place Moves items from one point to another
Does not need to follow a specific path between points
Uses include loading and unloading machines, placing components on circuit boards, and moving parts off conveyor belts.

7. Continuous path control
Moves along a specific path
Uses include welding, cutting, machining parts.

8. Sensory Uses sensors for feedback.
Closed-loop robots use sensors in conjunction with actuators to gain higher accuracy – servo motors.
Uses include mobile robotics, telepresence, search and rescue, pick and place with machine vision.

9. Measures of performance
Working volume
The space within which the robot operates.
Larger volume costs more but can increase the capabilities of a robot
Speed and acceleration
Faster speed often reduces resolution or increases cost
Varies depending on position, load.
Speed can be limited by the task the robot performs (welding, cutting)
Resolution
Often a speed tradeoff
The smallest step the robot can take

10. Performance (cont.) Accuracy
The difference between the actual position of the robot and the programmed position
Repeatability
Will the robot always return to the same point under the same control conditions?
Increased cost
Varies depending on position, load

11. Control Open loop, i.e., no feedback, deterministic
Closed loop, i.e., feedback, maybe a sense of
touch and/or vision

12. Kinematics and dynamics
Degrees of freedom—number of independent motions
Translation--3 independent directions
Rotation-- 3 independent axes
2D motion = 3 degrees of freedom: 2 translation, 1 rotation
3D motion = 6 degrees of freedom: 3 translation, 3 rotation

13. Kinematics and dynamics (cont.)
Actions
Simple joints
prismatic—sliding joint, e.g., square cylinder in square tube
revolute—hinge joint
Compound joints
ball and socket = 3 revolute joints
round cylinder in tube = 1 prismatic, 1 revolute
Mobility
Wheels
multipedal (multi-legged with a sequence of actions)

14. Kinematics and dynamics (cont.)
Work areas
rectangular (x,y,z)
cylindrical (r,,z)
spherical (r,,)
Coordinates
World coordinate frame
End effector frame
How to get from coordinate system x” to x’ to x x
x'' x'

15. Transformations
General coordinate transformation from x’ to x is x = Bx’ + p , where B is a rotation matrix and p is a translation vector
More conveniently, one can create an augmented matrix
  which allows the above equation to be expressed as x = A x’.
Coordinate transformations of multilink systems are represented as
x0 = A01 A12A A(n-1)(n)xn

16. Dynamics Velocity, acceleration of end actuator power transmission
solenoid –two positions , e.g., in, out
motor+gears, belts, screws, levers—continuum of positions
stepper motor—range of positions in discrete increments

17. A 2-D “binary” robot segment
Example of a 2D robotic link having three solenoids to determine geometry. All members are linked by pin joints; members A,B,C have two states—in, out—controlled by in-line solenoids. Note that the geometry of such a link can be represented in terms of three binary digits corresponding to the states of A,B,C, e.g., 010 represents A,C in, B out. Links can be chained together and controlled by sets of three bit codes. A C B A C B A C B A C B A C B A C B A C B A C B

18. Problems Joint play, compounded through N joints
Accelerating masses produce vibration, elastic deformations in links
Torques, stresses transmitted depending on end actuator loads

19. Control and programming
Position of end actuator
multiple solutions
Trajectory of end actuator: how to get from point A to B
programming for coordinated motion of each link
problem—sometimes no closed-form solution

20. Control and programming (cont.)
Example: end actuator (tip) problem with no closed solution.
Two-segment arm with arm lengths L1 = L2, and stepper -motor control of angles 1 and 2.
Problem: control 1 and 2 such that arm tip traverses its range at constant height y, or with no more variation than y.
Geometry is easy: position of arm tip
x = L1 (cos 1 + cos 2)
y = L1 (sin 1 + sin 2) 1 2 L1 L2 y

21. Control and programming (cont.)
Arm tip moves by changing 1 and 2 as a function of time.
Therefore
So, as 1 and 2 are changed, x and y are affected.
To satisfy y = constant, we must have
. So the rates at which 1 and 2 are changed depend on the values of 1 and 2.

22. Control and programming (cont.)
There is no closed-form solution to this problem. One must use approximations, and accept some minor variations in y. Moving the arm tip through its maximum range of x might have to be accomplished through a sequence of program steps that define different rates of changing 1 and 2.
Possible approaches:
Program the rates of change of 1 and 2 for y = const. for initial values of 1 and 2 . When arm tip exceeds y, reprogram for new values of 1 and 2.
Program the rates of change of 1 and 2 at the initial point and at some other point for y = const. Take the average of these two rates, and hope that y is not exceeded. If it is exceeded, reprogram for a shorter distance. Continue program segments until the arm tip has traversed its range.

23. Control and programming (cont.)
Program the rates of change of 1 and 2 at the initial point and at some other point for y = const. Take the average of these two rates, and hope that y is not exceeded. If it is exceeded, reprogram for a shorter distance. Continue program segments until the arm tip has traversed its range.
The rate of change of 1 and 2 can be changed in a programming segment, i.e., the rates of change need not be uniform over time. This programming strategy incorporates approaches 1) and 2). Start with rates of change for the initial values of 1 and 2 , then add an acceleration component so that y = const. will also be satisfied at a distant position.

24. Feedback control Rotation encoders Cameras Pressure sensors
Temperature sensors
Limit switches
Optical sensors
Sonar

25. New directions Haptics--tactile sensing Other kinematic mechanisms,
e.g. snake motion
Robots that can learn