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TAS > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

What are the three problems encountered in System Theory?

A
  1. Simulation
  2. Control
  3. System Identification
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2
Q

What is system identification?

A

System identification is the determination, on the basis of observation of input and output, of a system within a specified class of systems to which the system under test is equivalent.

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3
Q

What are the must haves of data gathering for system identification?

A
  • Minimum sampling rate given by Nyquist frequency (twice the frequency of interest)
  • A signal-to-noise ratio of significantly higher than 1 (literature: 10:1)
  • Time-tagging of measurement channels
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4
Q

What are the types of sensors / measurements for an Aircraft? (6)

A
  • Basic Aircraft Sensors
  • Inertial Sensors
  • GNSS
  • Air Data Sensors
  • Control Surface Deflections
  • Pilot Forces
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5
Q

What are three important inertial sensors?

A
  • Accelerometers
  • Gyroscopes
  • Angular Accelerometers
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6
Q

What is the difference between integrating and non-integrating sensors?

A

Non-Integrating sensors measure rates,

Integrating sensors measure increments

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7
Q

Where should accelerometers be installed?

A

Near the center of gravity

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8
Q

What are the components of a mechanical accelerometer? How does it work?

A
  • proof mass
  • suspension for mass
  • pickoff providing signal related to the acceleration

Measures acceleration by measuring deflection of proof mass from initial position while also accounting for gravitational force

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9
Q

What are the three main types of gyroscopes and what physical effect do they use?

A
  1. Spinning mass : Gyroscopic moment
  2. Optical Laser Ring (RLG) / Fiber Optic (FOG) : Sagnac
  3. Micro Electro Mechanical Sensor (MEMS) : vibratory
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10
Q

What are the advantages and disadvantages of spinning mass gyros?

A

Advantages:
- Wide performance range of 0.0001 to >100 degree /h

  • Low noise

Disadvantages:
- High cost
- Long warmup
- Fragile

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11
Q

What are the advantages and disadvantages of RLG/FOG gyros?

A

Advantages:
- Rapid reaction and turn on <1s

  • No moving parts

Disadvantages:
- Performance increases with size

  • High Voltage device
  • Temperature sensitive
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12
Q

What are the advantages and disadvantages of MEMS gyros?

A

Advantages:
- Small
- No moving parts
- Low cost

Disadvantages:
- Higher precision to be developed

  • Limited performance range
  • Bias stability
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13
Q

What are the Air Data systems and what info do they provide?

A
  • Air data systems (ADS) provide calibrated measurements of atmospheric conditions and the aircraft’s aerodynamic state:
  • Static Pressure, pressure altitude, rate of climb
  • Total Pressure, dynamic pressure
  • Mach Number, calibrated and equivalent air speed
  • AOA
  • Angle of sideslip
  • True airspeed, air density, temperature
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14
Q

What are pitot static probes?

A
  • Probes that measure total pressure at the stagnation point, static pressure in cavities. Are different from pitot probes as they also give differential pressure
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15
Q

How are pilot forces meausred?

A

Strain gauges on control rods

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16
Q

What are the three types of Sensor errors?

A
  1. Systematic Errors
  2. Random Errors
  3. Sensor Dynamics
17
Q

What is hysteresis error?

A

Different output for increasing and decreasing input

18
Q

What is Bias instability?

A

Random medium to long-term bias variation

19
Q

What is dead band error?

A

Small area around null where input is not detected

20
Q

What is resolution / quantization error?

A

Minimum measurable input/floating point representation

21
Q

What is turn on bias?

A

Variation of scale factor and bias from day-to-day

22
Q

What are the error sources for GNSS? (6)

A
  1. Ephemeris Range error:
    Difference between true and broadcast satellite position
  2. Atmospheric Range Error: Speed of signal affected by atmosphere
  3. Multipath range error:
    Due to reflected signals from surfaces near receiver
  4. Receiver Clock Error:
  5. Satellite clock error:
  6. Receiver Noise
23
Q

What does the integration of errors produce?

A

Large deviations

24
Q

What are some values used in linear regression and what do they mean? (7)

A
  1. Independent variables x: Influence the output
  2. Regressors: Functions of the independent variables included in the model
  3. Regressor matrix X: All regressors in one matrix
  4. Dependent variable y
  5. Measurements z: Observation of output including error
  6. Parameters \theta
  7. Error r
25
Q

What is the problem statement and Solution of the least squares method?

A

For an over-determined system z=x\theta the number of parameters is less than the number of equations so there doesn’t exist a solution that satisfies all equations

We find an approximate solution that minimizes the Euclidian-Norm of the vector x\theta - z

26
Q

What are the assumptions for ordinary least square?

A
  • Model is linear in parameters
  • Regressors are deterministic
  • White zero mean measurement noise with constant variance
27
Q

What are some measures of accuracy for ordinary least squares?

A

Parameter Covariance and Correlation Matrix

Noise Covariance and Fit Error

Coefficient of Determination

28
Q

What are the sum of squares for ordinary least squares?

A

Measure deviation from Model

  • Total sum of Square
  • Regression Sum of Square
  • Residual Sum of Square
29
Q

What is the coefficient of determination?

A

Ratio of Explained info to total info

30
Q

What are some properties of ordinary least square estimators?

A
  • Unbiased
  • Minimum Variance
  • Consistent
  • Maximum Likelihood
31
Q

What is the residual?

A

Shows model deficiencies and departure from the underlying assumptions

32
Q

What are tests of residual analysis?

A
  1. Whiteness Test
  2. Graphical Analysis
  3. Tests for Normality
33
Q

What are four additional least square methods?

A
  • Multidimensional
  • Generalized
  • Total
  • Recursive
34
Q

What are regressors?

A

Regressors are explanatory functions, built from the independent variables, in order to explain the dependent variable

TAS (12 decks)

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