Week 2 Flashcards
What is a signal?
A time varying value
What is a system?
Something that transforms signals (actions of the robot)
What are perceptions?
Derived from input signals to the robot
What is measurement range?
The set of values that can be measured using a measuring instrument.
Specified as a pair of numbers
What is measurement resolution?
The smallest change in the measurement of a measuring device that can be observed
(typically a ‘small’ number)
What is an outlier?
An experimental data point not following the underlying distribution of points.
Define Sampling theorem
Provides a way of ensuring that the original signal can be “reconstructed” from a finite set of samples.
Define Aliasing
High frequency changes appear as low frequencies.
What is Sampling frequency?
Number of times per second a given sensor is read (v, measured in Hz)
What is the Sampling period?
Time elapsed between two consecutive readings of one sensor (T, measured in seconds)
Define Proprioceptive in relation to robotic sensors
Measures an internal robot variable; battery level, motor temperature, encoders
Define Exteroceptive in terms of robotics sensors
Measure external (environmental) variables; distance sensors, compass, bumpers, cameras…
What is an Active sensor?
These sensors measure the effect of something they put in the environment: laser scanner, encoders, Kinect…
What is a Passive sensor
Measures some variable that is in the environment: compass, camera…
What are Polar coordinates?
Measurement provided by the laser scanner are pairs (θ, r ), direction and distance to the obstacle
What are Cartesian coordinates?
Coordinates represented as x and y, relative to the robot
x = r cos θ
y = r sin θ
What are the steps to calibrate a laser scanner?
- Ensure the robot and environment are static
- Read the laser many times
- Compute the mean for each reading
- Compute the standard deviation for each reading
What is the Split and Merge algorithm?
A recursive algorithm to extract line segments from points
Define the Split part of the Split and Merge algorithm
Input: List of points (xi , yi ) i = 1, · · · , n.
Output: List of segments (pairs of points)
Parameters: Threshold distance dth
- Build the line: first:i – last:j points
- Find further point:k to the line (distance d )
- If d > dth Split(i ,k); Split(k,j)
- Return segment(i ,j)
Define the Merge part of the Split and Merge algorithm
Input: List of segments (pairs of points)
Output: List of segments (pairs of points)
Parameters: Threshold angle θth
- For all consecutive segments si and si +1
- If the angle between si and si +1 is smaller than θth, join the two segments si , si +1.
- End
List some sensors that are used in robotics
GPS
Force sensors
Tactile sensors
Magnetic sensors
Pressure sensors
