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Assessment and Future Directions of Nonlinear Model Predictive ...

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Hybrid MPC: Open-Minded but Not Easily Swayed 31Table 1. Simulations <strong>of</strong> system with differing decision line spacing <strong>and</strong> sampling timefor uniformly distributed measurement noise e ∈ [−0.8, 0.8]. Each datum is generatedby 50,000 runs starting at x(0) = −1.5 <strong>and</strong>y(0) normally distributed constrained to(−1, 1). “TC” is total number <strong>of</strong> crashes <strong>and</strong> “AS” is average number <strong>of</strong> switches.δ 0.1 0.06 0.03 0.01 0.006 0.003 0.001s(µ) TC AS TC AS TC AS TC AS TC AS TC AS TC AS0.00 5110 2.61 5444 4.36 5791 8.73 5927 26.1 5922 43.8 6107 88.3 6125 2630.25 3248 1.75 3716 2.88 3862 5.72 4197 17.2 4334 28.9 4375 57.3 4144 1690.50 1575 1.13 1875 1.76 2253 3.38 2549 10.0 2529 16.7 2625 33.2 2638 1010.75 428 0.70 609 1.01 863 1.80 1102 5.00 1140 8.26 1155 16.4 1189 48.61.00 47 0.46 51 0.57 110 0.86 241 2.05 274 3.21 276 6.14 298 17.71.25 1 0.34 2 0.39 1 0.48 6 0.73 9 0.94 8 1.55 17 3.921.50 0 0.25 0 0.29 0 0.35 0 0.42 0 0.45 0 0.48 0 0.54spacing for a given sampling time, there are fewer crashes, as expected, <strong>and</strong> thetrajectories contain fewer switches. The number <strong>of</strong> switches can be thought <strong>of</strong> asa measure <strong>of</strong> the sensitivity to measurement noise. As the sampling time is decreased,the system also becomes more sensitive to measurement noise due to thesmaller movements <strong>of</strong> the system making it difficult to escape the neighborhood<strong>of</strong> the horizontal axis.For this system, a crash-free bound on the measurement noise (that solelydepends on µ) can be calculated as follows.Claim. Suppose the MPC with logic controller is implemented with the costfunctions l 1 ,l 2 . If the buffer gain µ>1, the measurement ( noise ) is bounded bys(µ)2 , <strong>and</strong> the horizontal component <strong>of</strong> the state x0, <strong>and</strong> constrain the horizontaldisplacement to z ∈ [−1, 1]. The goal <strong>of</strong> the vehicle is to reach some target whileavoiding the obstacle whose goal is to reach the vehicle. Both <strong>of</strong> the agents areconsidered as single points in R 2 <strong>and</strong> run MPC to achieve their goals as follows.The stage cost <strong>of</strong> the vehicle puts a high penalty on the current location <strong>of</strong> the

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