The electrification, agglomeration, and levitation of particles in a strong electric field were analyzed experimentally and theoretically. Particle layers of glass, alumina, and ferrite were formed on a plate electrode and an external voltage was applied. Microscopic observations of the agglomerates levitated from the particle layers revealed that the number of primary particles constituting an agglomerate is affected by particle diameter and electrical resistance, but not by the applied electric field. The electric field distributions in the system were calculated by considering the charges and geometries of the agglomerates formed on the particle layers. The charges of the agglomerates were obtained experimentally. All forces acting on the agglomerates (i.e., gravitational forces, Coulomb forces, interaction forces between polarized particles, image forces, and gradient forces) were analyzed under different conditions, including various electric field distributions and charges of agglomerates. Furthermore, the critical conditions for the levitation of the agglomerates were evaluated using a force balance.

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This paper presents a numerical approach to solve the Hamilton-Jacobi-Bellman (HJB) equation, which arises in nonlinear optimal control. In this approach, we first use the successive approximation to reduce the HJB equation, a nonlinear partial differential equation (PDE), to a sequence of linear PDEs called a generalized-Hamilton-Jacobi-Bellman (GHJB) equation. Secondly, the solution of the GHJB equation is decomposed by basis functions whose coefficients are obtained by the collocation method. This step is conducted by solving quadratic programming under the constraints which reflect the conditions that the value function must satisfy. This approach enables us to obtain a stabilizing solution of problems with strong nonlinearity. The application to swing up and stabilization control of an inverted pendulum illustrates the effectiveness of the proposed approach.