1 | #LyX 2.0 created this file. For more info see http://www.lyx.org/ |
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2 | \lyxformat 413 |
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3 | \begin_document |
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4 | \begin_header |
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5 | \textclass article |
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41 | \index Index |
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42 | \shortcut idx |
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43 | \color #008000 |
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44 | \end_index |
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45 | \secnumdepth 3 |
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46 | \tocdepth 3 |
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47 | \paragraph_separation indent |
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48 | \paragraph_indentation default |
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49 | \quotes_language english |
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58 | \end_header |
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59 | |
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60 | \begin_body |
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61 | |
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62 | \begin_layout Standard |
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63 | System |
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64 | \begin_inset Formula |
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65 | \[ |
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66 | y_{t}=y_{t-1}+bu_{t}+e_{t} |
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67 | \] |
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68 | |
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69 | \end_inset |
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70 | |
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71 | is assumed to fullfill causality, i.e. |
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72 | |
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73 | \begin_inset Formula $y_{t-1}\rightarrow u_{t}\rightarrow y_{t}$ |
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74 | \end_inset |
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75 | |
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76 | |
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77 | \end_layout |
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78 | |
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79 | \begin_layout Standard |
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80 | with change in notation, i.e. |
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81 | |
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82 | \begin_inset Formula $y_{t-1}\rightarrow u_{t-1}\rightarrow y_{t}$ |
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83 | \end_inset |
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84 | |
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85 | the same system is: |
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86 | \begin_inset Formula |
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87 | \[ |
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88 | y_{t}=y_{t-1}+bu_{t-1}+e_{t} |
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89 | \] |
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90 | |
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91 | \end_inset |
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92 | |
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93 | and can be transformed as |
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94 | \begin_inset Formula |
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95 | \begin{eqnarray*} |
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96 | x_{t+1} & = & x_{t}+bu_{t}+e_{t}\\ |
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97 | y_{t} & = & x_{t} |
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98 | \end{eqnarray*} |
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99 | |
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100 | \end_inset |
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101 | |
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102 | Morale: |
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103 | \end_layout |
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104 | |
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105 | \begin_layout Itemize |
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106 | for transcription from ARX to State-Space, the state is one time-step shorter |
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107 | than the regressor in ARX! |
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108 | \end_layout |
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109 | |
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110 | \begin_layout Subsection* |
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111 | Delays in |
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112 | \begin_inset Formula $u$ |
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113 | \end_inset |
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114 | |
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115 | : |
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116 | \end_layout |
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117 | |
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118 | \begin_layout Standard |
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119 | System |
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120 | \begin_inset Formula |
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121 | \[ |
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122 | y_{t}=y_{t-1}+bu_{t}+cu_{t-1}+e_{t} |
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123 | \] |
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124 | |
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125 | \end_inset |
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126 | |
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127 | is |
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128 | \begin_inset Formula |
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129 | \begin{eqnarray*} |
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130 | \left[\begin{array}{c} |
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131 | x_{t+1}\\ |
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132 | u_{t} |
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133 | \end{array}\right] & =\left[\begin{array}{cc} |
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134 | 1 & c\\ |
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135 | 0 & 0 |
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136 | \end{array}\right] & \left[\begin{array}{c} |
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137 | x_{t}\\ |
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138 | u_{t-1} |
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139 | \end{array}\right]+\left[\begin{array}{c} |
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140 | b\\ |
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141 | 1 |
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142 | \end{array}\right]u_{t}+e_{t}\\ |
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143 | y_{t} & = & x_{t} |
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144 | \end{eqnarray*} |
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145 | |
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146 | \end_inset |
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147 | |
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148 | |
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149 | \end_layout |
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150 | |
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151 | \begin_layout Standard |
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152 | System #2: |
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153 | \begin_inset Formula |
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154 | \[ |
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155 | y_{t}=ay_{t-1}+a_{2}y_{t-2}+bu_{t-1}+cu_{t-2}+e_{t} |
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156 | \] |
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157 | |
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158 | \end_inset |
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159 | |
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160 | is |
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161 | \begin_inset Formula |
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162 | \begin{eqnarray*} |
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163 | \left[\begin{array}{c} |
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164 | x_{t+1}\\ |
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165 | x_{t}\\ |
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166 | u_{t} |
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167 | \end{array}\right] & =\left[\begin{array}{ccc} |
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168 | a_{1} & a_{2} & c\\ |
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169 | 1 & 0 & 0\\ |
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170 | 0 & 0 & 0 |
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171 | \end{array}\right] & \left[\begin{array}{c} |
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172 | x_{t}\\ |
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173 | x_{t-1}\\ |
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174 | u_{t-1} |
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175 | \end{array}\right]+\left[\begin{array}{c} |
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176 | b\\ |
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177 | \\ |
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178 | 1 |
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179 | \end{array}\right]u_{t}+e_{t}\\ |
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180 | y_{t} & = & x_{t} |
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181 | \end{eqnarray*} |
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182 | |
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183 | \end_inset |
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184 | |
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185 | |
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186 | \end_layout |
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187 | |
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188 | \begin_layout Standard |
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189 | Notation in BDM: |
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190 | \end_layout |
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191 | |
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192 | \begin_layout Standard |
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193 | xrv = [y{0}, u{-1}] |
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194 | \end_layout |
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195 | |
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196 | \begin_layout Subsection* |
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197 | Constant term |
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198 | \end_layout |
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199 | |
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200 | \begin_layout Standard |
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201 | System |
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202 | \begin_inset Formula |
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203 | \[ |
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204 | y_{t}=y_{t-1}+bu_{t-1}+g+e_{t} |
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205 | \] |
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206 | |
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207 | \end_inset |
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208 | |
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209 | must be modelled as |
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210 | \begin_inset Formula |
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211 | \[ |
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212 | \left[\begin{array}{c} |
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213 | x_{t+1}\\ |
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214 | one |
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215 | \end{array}\right]=\left[\begin{array}{cc} |
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216 | 1 & c\\ |
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217 | 0 & 0 |
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218 | \end{array}\right]\left[\begin{array}{c} |
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219 | x_{t}\\ |
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220 | one |
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221 | \end{array}\right]+\left[\begin{array}{c} |
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222 | b\\ |
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223 | 1 |
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224 | \end{array}\right]u_{t}+e_{t} |
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225 | \] |
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226 | |
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227 | \end_inset |
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228 | |
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229 | where one is an extra state variable. |
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230 | \end_layout |
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231 | |
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232 | \end_body |
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233 | \end_document |
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