Lecture 7 - Manipulation and Sensors

Question 1

Manipulation

Answer 1

A goal-driven movement of any type of manipulator (effector)

Question 2

Manipulators

1. What is the name of general components? How many does it have?
2. What are they connected by?
3. What is each end connected to (2 terms)?

Answer 2

1. Manipulator links, several
2. Manipulator links are connected by joints
3. Robots body and endeffector

Question 3

How can manipulator joints be controlled?

Answer 3

Independently

Question 4

What has to be avoided during movement (2)?

Answer 4

1. Overextention of joints (joint limits) and other body parts
2. Obstacles in environment

Question 5

Free space / Workspace

Answer 5

The space in which movement is possible and in which a path has to be searched.

Question 6

2 Types of Joints

1. Rotary (revolute) joint

Answer 6

Rotational movement around a fix axis (human/mammal joints)

Question 7

2 Types of Joints

2. Prismatic joint

Answer 7

Smaller round metal piece in bigger metal piece that can slide out (slider)

Question 8

1. Does a joint provide a DoF? If yes, which one and how many?
2. What does an endeffector with many (c)DoF’s need?

Answer 8

1. Yes, normally one cDoF. For each additional one, a seperate actuator is needed
2. Many cDoF require many actuators.

Question 9

“Human like in shape”

Answer 9

Anthropomorphic

Question 10

Characteristics of a anthropomorphic hand (3)

Answer 10

1. Large number of joints
2. Large number of DoF
3. Compact design

Question 11

What do we have to know to control a robot manipulator?

Answer 11

Its kinematics

Question 12

Kinematics

Answer 12

The correspondence between actuator motion and the resulting effector motion

Question 13

(3) Examples teleoperated robots

Answer 13

1. robot-assisted surgery
2. Space robots
3. Rescue robots/operations

Question 14

(3) Challenges teleoperated robots

Answer 14

1. Complexity of manipulator (DoF’s)
2. Constraints of the interface
3. Limitations of sensing

Question 15

Teleoperation can be combined with…

Answer 15

Autonomy! A system that is not continuously controlled

Question 16

Forward Kinematics

Answer 16

For a robot with n joints, what is the endeffector pose, given the joint angles (q)

Question 17

Inverse Kinematics

Answer 17

Which joint movements (q) are needed to achieve a particular robot endeffector pose?
-> move endeffector to a desired position

Question 18

Forward Kinematics - Formula

1. What is a1,2 / x1,y1 / xe, ye/ q1,2?

Answer 18

a1 & 2 = length of links
x1 & y 1 = position of moving joint (other one is at 0,0)
xe & ye = position of endeffector
q1 & 2 = angles of first and moving link

Question 19

Forward Kinematics - Formula

2. Equation for x1 & y1

Answer 19

x1 = a1cos(q1)
y1 = a1sin(q1)
q1 & 2 = angles of first and moving link
x1 & y 1 = position of moving joint (other one is at 0,0)

Question 20

Forward Kinematics - Formula

3. Equation for xe & ye

Answer 20

xe = x1 + a2*cos(q1+q2)
ye = y1 + a2*sin(q1+q2)

xe & ye = position of endeffector

Question 21

Simple Kinematic Model

1. Linear Velocity

Answer 21

1. Denoted as V, means speed (forwards, backwards)

Question 22

Simple Kinematic Model

2. Angular velocity

Answer 22

2. Denoted as weird W, speed of turn (sideways)

Question 23

Simple Kinematic Model

Velocity of robot’s center (linear) formula

Answer 23

V = r/2 (Vl + Vr)
r = wheels radius
Vl & Vr = velocity left/right wheel

Question 24

Simple Kinematic Model

Angular Velocity formula

Answer 24

W = R/d (Vl-Vr)
d = distance between wheels
r = wheel radius

Question 25

What does Manipulation involve (3)?

Answer 25

1. Trajectory planning 2. Kinematics 3. Dynamics (properties of motion and energy of a moving object)

Question 26

Matrix Muliplication 1. A(row column) or A(column row)? 2. When is MM possible? 3. What are the dimensions of the result of a MM?

Answer 26

1. A(rows columns) 2. MM is possible iff columns of A == rows of B 3. A(rA cA) * B(rB cB) = C(rA cB)

Question 27

Sensor Classification | 1. Proprioceptive sensors

Answer 27

Measures values internal to the system (odometer, motor speed, joint angles, battery voltages)

Question 28

Sensor Classification | 2. Exteroceptive sensors

Answer 28

Acquire information from the environment (distance, light intensity, sound amplitude)

Question 29

Sensor Classification | 3. Passive sensors

Answer 29

Measure ambient environmental energy entering the sensor (temperature, microphone)

Question 30

Sensor Classification | 4. Active sensors

Answer 30

Emit energy into the environment and measure the environmental reaction (encoders, laser range finders, ultrasonic sensors)

Question 31

What are sensor and what can they measure?

Answer 31

They are physical devices that measure physical quantities

Question 32

Uncertainty in Robotics | 1. Definition

Answer 32

1. Inability to be certain about the state of the robot

Question 33

Uncertainty in Robotics | 2. (4) sources

Answer 33

1. Sensor noise & errors 2. Sensor limitations 3. Effector and actuator noise and errors 4. Lack of knowledge about the environment or dynamic (changing) environment

Question 34

Properties of Sensors 1. Dynamic range + example

Answer 34

1. Ratio of the maximum input value to the minimum measurable input value In photography: ratio (one number) between the max and min measurable light intensities

Question 35

Properties of Sensors | 2. Resolution

Answer 35

Minimum difference between two measured values that can be detected by a sensor -> often the lower limit of the dynamic range

Question 36

Properties of Sensors | 3. Linearity

Answer 36

The plot of a sensor's input and output response is a straight line

Question 37

Properties of Sensors 4. Bandwidth of Frequency + in what is it expressed? + is higher better?

Answer 37

The number of measurements per second + expressed in Hertz + yes, always

Question 38

Sensor information | Signal-to-Symbol problem + solution

Answer 38

The sensor output has to be translated to useful information | -> sensor processing is needed

Question 39

Simple Sensors (3) switches 1. Contact sensor 2. Limit sensor 3. Shaft encoders

Answer 39

1. Detect contact with another object (grabbing object/hitting wall) 2. Detect when a mechanism has moved to the end of its range (when is grabber wide open?) 3. Detect times a motor shaft turns, by having a switch click every time the shaft turns

Question 40

Simple Sensors Light sensor 1. What are they? 2. What do they detect (3)?

Answer 40

``` 1. They are photocells 2. (1) Light intensity (2) Differential intensity (between sensors) (3) Break in continuity (break beam) ```

Question 41

``` Simple Sensors Reflective Optosensors 1. Parts (2) 2. Reflectance sensors 3. Break beam sensors ```

Answer 41

1. (1) Emitter (LED) and (2) Detector 2. Reflectance sensor detects presence of object when the light reflects 3. Break beam sensor detects presence of object when light is interrupted

Question 42

2 Types of joints

Answer 42

1. Rotary joint | 2. Prismatic joint

Question 43

``` Simple Sensors (3) switches ```

Answer 43

1. Contact sensor 2. Limit sensor 3. Shaft encoders

Question 44

Thing that emits and senses light | + two different kinds

Answer 44

Reflective Optosensor 1. Reflectance sensor 2. Break-beam sensor