week 2

Question 1

what is a signal?

Answer 1

a time-varying value
actions of robots are signals

Question 2

what is a system in reference to robotics?

Answer 2

something which transforms signals

Question 3

what is measurement range?

Answer 3

the set of values that can be measured using a measuring instrument
specified as a pair of numbers(e.g. a-b, [a,b])

Question 4

what is measurement resolution

Answer 4

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

Question 5

what is measurement error?

Answer 5

sensors can provide values that have errors

when measuring an item using tape errors an come from:
-tape elasticity
- tape shifting while measuring
-temperature of the item being measured and the tape

Question 6

why are statistics needed in measurement?

Answer 6

measuring an item once is not enough, two values need to be presented
1. average
2. deviating from average(uncertainty)

Question 7

what is gaussian distribution?

Answer 7

normal distribution
a bell-shaped curve, and it is assumed that during any measurement values will follow a normal distribution with an equal number of measurements above and below the mean value.

Question 8

what is an outlier?

Answer 8

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

Question 9

what is the sampling theorem?

Answer 9

a way of ensuring that an original signal can be reconstructed from a finite set of samples

Question 10

what is Aliasing?

Answer 10

high frequency chances that appear as low frequencies

Question 11

what is sampling frequency?

Answer 11

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

Question 12

what is sampling period?

Answer 12

the time elapsed between 2 consecutive readings of one sensor
(T, measured in seconds)

Question 13

what is a proprioceptive robotic sensor?

Answer 13

measuring an internal robot variable; battery level, motor temp, encoders…

Question 14

what is a exteroceptive robot sensor

Answer 14

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

Question 15

what is an active robot sensor?

Answer 15

sensors that measure the effect of something they put in the environment; laser scanners, encoders, Kinect…

Question 16

what is a passive robot sensor?

Answer 16

measure some variable that is in the environment; compass, camera…

Question 17

what is a bump sensor?

Answer 17

-Passive sensors that detect contact with objects
-Binary sensors, generally switches with some electronics
-Contact ON / Non-contact OFF
-They are being substituted by touch sensors (pressure,
temperature. . . ).
-Not very elegant to rely on them (last resort) Robots usually are surrounded by these sensors

Question 18

what are the pros of bump sensors?

Answer 18

-cheap and small
-notify of crashes

Question 19

what are the cons of bump sensors

Answer 19

-short range
-on means the robot has crashed
-not directional

Question 20

what is an infra-red sensor?

Answer 20

an electronic device that measures and detects infrared radiation in its surrounding environment.

Question 21

what are the pros of infra-red sensors?

Answer 21

cheap and small
directional

Question 22

what are the cons of infra-red sensors?

Answer 22

-short-range
-read reflectance (need calibration)
-sensitive to colour
-sensitive to electronics tolerance

Question 23

what is a time of flight (ToF) sensor?

Answer 23

an active sensor that measures the time a sent-out wave takes to fly forth and back to the sensor after hitting an object

Question 24

what is an ultra-sound sensor (ToF)

Answer 24

-active sensors based on ultra-sound reflected from obstacles
-vibrating metal sheet & associated electronics
-emitter and detector are the same
-sound intensity decays with the distance

robots usually have rings of ultra-sound sensors

Question 25

what are the pros of ultra-sound sensors?

Answer 25

-cheap and small
-sound speed almost constant (= 340m/s)

Question 26

what are the cons of ultra sound sensors?

Answer 26

-low directionality and side lobes
-specular reflections
-multiple paths
-cross-talks (between sonars)
-animals are sensitive to them

Question 27

what is a laser scanner?

Answer 27

active sensors that use laser light to detect obstacles

Question 28

what are the 2 main types of laser scanners

Answer 28

-time of flight
-phase shift (modulated light pulses)

Question 29

what are the pros of laser scanners?

Answer 29

-very precise with high directionality
-provides relative obstacle positions
-up to 360° angular range
-high frequency readings (16 Hz)

Question 30

what are the cons of laser scanners?

Answer 30

-expensive
-affected by dust and fog
-problems detecting mirrors and glass
-high power consumption