Here is my heuristic algorithm for applying manifold topology to system dynamics, control engineering, and (I think) robotics in general.
For each "moving part" in the dynamical system, we have a copy of $SE(3) = \mathbb{R}^3 \rtimes SO(3) (= Q_{\text{free}}$ in Bullo and Lewis's notation$)$. For $N$ moving parts, we have $N$ copies of $SE(3)$, $SE(3)^N$. The process for creating this is somewhat automated by Denavit-Hartenberg tables:
(The graphic is from this video series https://www.youtube.com/watch?v=4Y1_y9DI_Hw&list=PLZaGkBteQK3HQFSWDM7-yRQWTd86DeDIY&index=1)
We then have interconnections between the moving parts, which leads to an $n$ dimensional submanifold of $SE(3)^N$, $Q^n$, called the configuration space of the dynamical system.
This configuration space has a Riemannian metric $g$ it inherits as a submanifold of $SE(3)^N$. The Riemannian metric, $g$, then has a canonical lift $\tilde{g}$ to the tangent bundle, $TQ$, of $Q$, as outlined in do Carmo, for instance. With this lift of the Riemannian metric, we have a musical isomorphism between $TQ$ and $T^*Q$, the co-tangent bundle. Now, the co-tangent bundle is naturally a symplectic manifold, with canonical symplectic from $\omega$. Corresponding to $\tilde{g}$ and $\omega$, we have a canonical almost complex structure $J$ on $TQ$ (and/or $T^*Q$?), completing the canonical compatible triple, $(\tilde{g}, \omega, J)$, on (say) $TQ$.
Next, in a coordinate patch on $TQ$, we have a Lagrangian function $L$. We may then have a non-conservative force field acting additionally on the mechanical system, which we model as a differential 1-form $\mathcal{F}$. This lead to the system of first-order differential equations $$\begin{cases} \frac{d}{dt}\left\{\frac{\partial L}{\partial \dot{q}_1}\right\} - \frac{\partial L}{\partial q_1} = \mathcal{F}_1 \\ \ldots \\ \frac{d}{dt}\left\{\frac{\partial L}{\partial \dot{q}_n}\right\} - \frac{\partial L}{\partial q_n} = \mathcal{F}_n \end{cases}$$ Now, this system may have a critical point $(q, \dot{q})$. At this critical point, we can take the Jacobian matrix $A$ of the Lagrangian vector field/differential 1-form. This then becomes the plant function for a control engineering problem. The matrix $A$ should have $2n$ eigenvalues; because of a hypertechnical consideration, we will suppose none of them are purely imaginary, so the Hartman-Groβman Theorem applies. We then place a control feedback loop with proportional control gain matrix $K$ given as in this diagram.
We then use the gain matrix $K$ to place $2n-2$ of the eigenvalues of the closed-loop system to have real part between, say, -5 and -10 in the complex plane, then place the remaining two eigenvalues -- called the dominant eigenvalues or the dominant poles of the closed-loop system -- to have real part between, say, -2 and 0 and to satisfy the design requirements of the control engineering problem specifications.
No comments:
Post a Comment