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Autonomous Systems > Lecture 7 - Manipulation and Sensors > Flashcards

Lecture 7 - Manipulation and Sensors Flashcards

1
Q

Manipulation

A

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

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2
Q

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

How can manipulator joints be controlled?

A

Independently

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4
Q

What has to be avoided during movement (2)?

A
  1. Overextention of joints (joint limits) and other body parts
  2. Obstacles in environment
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5
Q

Free space / Workspace

A

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

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6
Q

2 Types of Joints

1. Rotary (revolute) joint

A

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

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7
Q

2 Types of Joints

2. Prismatic joint

A

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

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8
Q
  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?
A
  1. Yes, normally one cDoF. For each additional one, a seperate actuator is needed
  2. Many cDoF require many actuators.
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9
Q

“Human like in shape”

A

Anthropomorphic

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10
Q

Characteristics of a anthropomorphic hand (3)

A
  1. Large number of joints
  2. Large number of DoF
  3. Compact design
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11
Q

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

A

Its kinematics

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12
Q

Kinematics

A

The correspondence between actuator motion and the resulting effector motion

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13
Q

(3) Examples teleoperated robots

A
  1. robot-assisted surgery
  2. Space robots
  3. Rescue robots/operations
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14
Q

(3) Challenges teleoperated robots

A
  1. Complexity of manipulator (DoF’s)
  2. Constraints of the interface
  3. Limitations of sensing
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15
Q

Teleoperation can be combined with…

A

Autonomy! A system that is not continuously controlled

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16
Q

Forward Kinematics

A

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

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17
Q

Inverse Kinematics

A

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

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18
Q

Forward Kinematics - Formula

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

A

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

19
Q

Forward Kinematics - Formula

2. Equation for x1 & y1

A

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)

20
Q

Forward Kinematics - Formula

3. Equation for xe & ye

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

xe & ye = position of endeffector

21
Q

Simple Kinematic Model

1. Linear Velocity

A
  1. Denoted as V, means speed (forwards, backwards)
22
Q

Simple Kinematic Model

2. Angular velocity

A
  1. Denoted as weird W, speed of turn (sideways)
23
Q

Simple Kinematic Model

Velocity of robot’s center (linear) formula

A

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

24
Q

Simple Kinematic Model

Angular Velocity formula

A 
W = R/d (Vl-Vr)
d = distance between wheels
r = wheel radius
25
Q

What does Manipulation involve (3)?

A
  1. Trajectory planning
  2. Kinematics
  3. Dynamics (properties of motion and energy of a moving object)
26
Q

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?
A
  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)
27
Q

Sensor Classification

1. Proprioceptive sensors

A

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

28
Q

Sensor Classification

2. Exteroceptive sensors

A

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

29
Q

Sensor Classification

3. Passive sensors

A

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

30
Q

Sensor Classification

4. Active sensors

A

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

31
Q

What are sensor and what can they measure?

A

They are physical devices that measure physical quantities

32
Q

Uncertainty in Robotics

1. Definition

A
  1. Inability to be certain about the state of the robot
33
Q

Uncertainty in Robotics

2. (4) sources

A
  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
34
Q

Properties of Sensors
1. Dynamic range
+ example

A
  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

35
Q

Properties of Sensors

2. Resolution

A

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

36
Q

Properties of Sensors

3. Linearity

A

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

37
Q

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

A

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

38
Q

Sensor information

Signal-to-Symbol problem + solution

A

The sensor output has to be translated to useful information

-> sensor processing is needed

39
Q

Simple Sensors

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

A
  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
40
Q

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

A 
1. They are photocells
2.
(1) Light intensity
(2) Differential intensity (between sensors)
(3) Break in continuity (break beam)
41
Q 
Simple Sensors
Reflective Optosensors
1. Parts (2)
2. Reflectance sensors
3. Break beam sensors
A
  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
42
Q

2 Types of joints

A
  1. Rotary joint

2. Prismatic joint

43
Q 
Simple Sensors
(3) switches
A
  1. Contact sensor
  2. Limit sensor
  3. Shaft encoders
44
Q

Thing that emits and senses light

+ two different kinds

A

Reflective Optosensor

  1. Reflectance sensor
  2. Break-beam sensor

Autonomous Systems (10 decks)

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