Week 2

Question 1

What is a signal?

Answer 1

A time varying value

Question 2

What is a system?

Answer 2

Something that transforms signals (actions of the robot)

Question 3

What are perceptions?

Answer 3

Derived from input signals to the robot

Question 4

What is measurement range?

Answer 4

The set of values that can be measured using a measuring instrument.

Specified as a pair of numbers

Question 5

What is measurement resolution?

Answer 5

The smallest change in the measurement of a measuring device that can be observed

(typically a ‘small’ number)

Question 6

What is an outlier?

Answer 6

An experimental data point not following the underlying distribution of points.

Question 7

Define Sampling theorem

Answer 7

Provides a way of ensuring that the original signal can be “reconstructed” from a finite set of samples.

Question 8

Define Aliasing

Answer 8

High frequency changes appear as low frequencies.

Question 9

What is Sampling frequency?

Answer 9

Number of times per second a given sensor is read (v, measured in Hz)

Question 10

What is the Sampling period?

Answer 10

Time elapsed between two consecutive readings of one sensor (T, measured in seconds)

Question 11

Define Proprioceptive in relation to robotic sensors

Answer 11

Measures an internal robot variable; battery level, motor temperature, encoders

Question 12

Define Exteroceptive in terms of robotics sensors

Answer 12

Measure external (environmental) variables; distance sensors, compass, bumpers, cameras…

Question 13

What is an Active sensor?

Answer 13

These sensors measure the effect of something they put in the environment: laser scanner, encoders, Kinect…

Question 14

What is a Passive sensor

Answer 14

Measures some variable that is in the environment: compass, camera…

Question 15

What are Polar coordinates?

Answer 15

Measurement provided by the laser scanner are pairs (θ, r ), direction and distance to the obstacle

Question 16

What are Cartesian coordinates?

Answer 16

Coordinates represented as x and y, relative to the robot

x = r cos θ
y = r sin θ

Question 17

What are the steps to calibrate a laser scanner?

Answer 17

1. Ensure the robot and environment are static
2. Read the laser many times
3. Compute the mean for each reading
4. Compute the standard deviation for each reading

Question 18

What is the Split and Merge algorithm?

Answer 18

A recursive algorithm to extract line segments from points

Question 19

Define the Split part of the Split and Merge algorithm

Answer 19

Input: List of points (xi , yi ) i = 1, · · · , n.

Output: List of segments (pairs of points)

Parameters: Threshold distance dth

1. Build the line: first:i – last:j points
2. Find further point:k to the line (distance d )
3. If d > dth Split(i ,k); Split(k,j)
4. Return segment(i ,j)

Question 20

Define the Merge part of the Split and Merge algorithm

Answer 20

Input: List of segments (pairs of points)

Output: List of segments (pairs of points)

Parameters: Threshold angle θth

1. For all consecutive segments si and si +1
2. If the angle between si and si +1 is smaller than θth, join the two segments si , si +1.
3. End

Question 21

List some sensors that are used in robotics

Answer 21

GPS
Force sensors
Tactile sensors
Magnetic sensors
Pressure sensors