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Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

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Chapter 3 / Sensors<br />

_ _<br />

( t ) : = ϕ ( N ( 0 , σ ) , 1,<br />

)<br />

y ω<br />

D 2L<br />

3.2-22<br />

SN<br />

GM2<br />

SN<br />

GM2<br />

Equation 3.2-24<br />

The SIMULINK conversion from the continuous to the discrete domain,<br />

c2dm<br />

[ SN _ NP , SN _ DP ]<br />

: =<br />

2<br />

[ 1,<br />

2 ⋅ ω ω ] ⎟<br />

⎞<br />

SN GM1<br />

, SN GM2<br />

, SN R<br />

⎠<br />

⎜<br />

⎛ 2<br />

SN ωGM2<br />

,<br />

ω<br />

⎝<br />

SN_R2NP(z)<br />

SN_R2DP(z)<br />

1/SN_SF<br />

1-z-1<br />

0<br />

SN_B_7<br />

Equation 3.2-25<br />

Figure 3-12 : 2 nd Order Gauss-Markov Motion<br />

The scale factor error is a combination of separately selectable constant,<br />

quadratic and asymmetric terms,<br />

ϕ<br />

SF<br />

( x ) : = ϕ ( x , σ ) + ϕ ( x , σ ) + ϕ ( x , σ )<br />

CS<br />

SN<br />

CS<br />

QS<br />

SN<br />

QS<br />

AS<br />

1<br />

SN<br />

AS<br />

Equation 3.2-26<br />

The scale factor coefficients are initialised using Gaussian distributions<br />

defined by appropriate standard deviations,<br />

x ⋅ N<br />

( x )<br />

( 0 , σ ) + ⋅ ⎜⎛<br />

⋅ ( σ ) + ( σ ) ⎟⎞ SN CS x x N 0 ,<br />

= SN QS N 0 ,<br />

t : 0<br />

t : = 0<br />

SN AS t : = 0 ⎠<br />

3.2.2.3 Analogue to Digital Conversion<br />

⎝<br />

ϕ<br />

SF<br />

: =<br />

Equation 3.2-27<br />

The reference input, dynamics and error models are processed at a<br />

frequency representative of their analogue equivalent. The error models<br />

arising from the conversion of the analogue measurements into digital form<br />

are shown in Figure 3-13 and comprise:<br />

• Anti-Aliasing filter ( bit 23 )<br />

• Range limiting (without word length wrapping) ( bit 24 )<br />

• Quantisation ( bit 25 )<br />

• Uniformly distributed “N” bit ADC noise ( bit 26 )

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