Algorithmic | class-MOC | cp-MOC | ||
option | ||||
23 | 51 | 20 | 49 | |
10 | 9 | 8 | 8 | |
39 | 32 | 39 | 33 | |
12 | - | 12 | - | |
10 | - | 6 | - |
The paper proposes a Lyapunov theory-based method to compute inner estimates of the region of attraction (ROA) of stable limit cycles. The approach is based on a transformation of the system to transverse coordinates, defined on a moving orthonormal coordinate system (MOC) for which a novel construction is presented. The proposed center point MOC (cp-MOC) is associated with a user-defined center point and provides flexibility to the construction of the transverse coordinates. In particular, compared to the standard approach based on hyperplanes orthogonal to the flow, the new construction allows the analyst to obtain larger regions of the state space where the well-definedness property of the transformation is satisfied. This has important benefits when using transverse coordinates to compute inner estimates of the ROA. To demonstrate these improvements, a sum-of-squares optimization-based formulation is proposed for computing inner estimates of the ROA of limit cycles for polynomial dynamics described in transverse coordinates. Different algorithmic options are explored, taking into account computational and accuracy aspects. Results are shown for three different systems exhibiting increasing complexity. The presented algorithms are extensively compared, and the newly cp-MOC is shown to markedly outperform existing approaches.
Citation: |
Figure 2. Left plot: Illustration of the hyperplanes $ \mathcal{S}( \tau) $ given by the class-MOC for the limit cycle of the Van der Pol oscillator. Right plot: Illustration of the hyperplanes $ \mathcal{S}( \tau) $ given by the cp-MOC with $ x{}_c = [0,0]^ T $ for the limit cycle of the Van der Pol oscillator
Figure 10. Results showing the volume of $ \mathcal{R} $ on each of the $ 49 $ selected distinct hyperplanes $ \mathcal{S}( \tau_i), i = 1,...,49 $, obtained from the different algorithmic options in Section 4.2 and from both presented options of MOC in Section 2.3. A quadratic and a quartic (where applicable) Lyapunov function were used
Table 1. Comparison of iteration numbers obtained for the dual orbit example for each algorithmic option and MOC
Algorithmic | class-MOC | cp-MOC | ||
option | ||||
23 | 51 | 20 | 49 | |
10 | 9 | 8 | 8 | |
39 | 32 | 39 | 33 | |
12 | - | 12 | - | |
10 | - | 6 | - |
Table 2. Comparison of iteration numbers obtained for the deterministic kite example for each algorithmic option and MOC
Algorithmic | class-MOC | cp-MOC | ||
option | ||||
19 | 44 | 11 | 10 | |
10 | 18 | 15 | 19 | |
54 | 27 | 18 | 15 | |
8 | - | 12 | - | |
7 | - | 14 | - |
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Illustration of the orthogonal projection of a notional 3-dimensional periodic orbit with periodic solution
Left plot: Illustration of the hyperplanes
Comparison of
Illustration of the computed ROA estimates shown in Figure 3 for the Van der Pol oscillator (59). The results for the quartic Lyapunov function are overlaid with those for the quadratic. Left plot: ROA estimates for the class-MOC. Right plot: ROA estimates for the cp-MOC
Phase portrait of the dual-orbit system (60) in the neighborhood of the attractive and unstable LCs. The green lines show examples of converging trajectories while the red lines represent diverging ones
ROA estimates as a function of
ROA estimates as a function of
Illustration of selected ROA estimates shown in Figure 7 and Figure 6 for the dual-orbit system (60). The results for the quartic Lyapunov function are overlaid with those for the quadratic. Left plot: ROA estimates for the class-MOC. Right plot: ROA estimates for the cp-MOC
Illustration of the hyperplanes in the cp-MOC from two different angles. In the right plot, the red dashed line indicates the
Results showing the volume of
Results showing
Rotated view of the plots in Figure 11. Left plot: Results for the class-MOC. Right plot: Results for the cp-MOC