Category:Outer convexification

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For time-dependent and space- independent integer controls often another formulation is beneficial, e.g., [1]. For every element vi of Ω a binary control function \omega_i(\cdot) is introduced.

The general equation

0 = F[x,u,v(t)]

can then be written as


0 = \sum_{i=1}^{n_{\omega}} F[x,u,v^i] \; \omega_i (t),  \;\;\;\; t \in [0, t_f].

If we impose the special ordered set type one condition


\sum_{i=1}^{n_{\omega}} \omega_i (t) = 1,  \;\;\;\; t \in [0, t_f],

there is a bijection between every feasible integer function v(\cdot) \in \Omega and an appropriately chosen binary function \omega(\cdot) \in \{0,1\}^{n_{\omega}}, compare [2]. The relaxation of \omega(t) \in \{0,1\}^{n_{\omega}} is given by \omega(t) \in [0,1]^{n_{\omega}}. We will refer to the two constraints as outer convexification [3] of the original model.

References

  1. Kirches, C., Sager, S., Bock, H. G., & Schlöder, J. P. (2010). Time-optimal control of automobile test drives with gear shifts. Optimal Control Applications and Methods, 31(2), 137. Bib
  2. Sager, S., Reinelt, G., & Bock, H. G. (2009). Direct Methods With Maximal Lower Bound for Mixed-Integer Optimal Control Problems. Mathematical Programming, 118(1), 109. Bib
  3. Sager, S. (2005). Numerical methods for mixed–integer optimal control problems. Tönning, Lübeck, Marburg: Der andere Verlag. Bib

Pages in category "Outer convexification"

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