121,707 research outputs found
A Parallel Riccati Factorization Algorithm with Applications to Model Predictive Control
Model Predictive Control (MPC) is increasing in popularity in industry as
more efficient algorithms for solving the related optimization problem are
developed. The main computational bottle-neck in on-line MPC is often the
computation of the search step direction, i.e. the Newton step, which is often
done using generic sparsity exploiting algorithms or Riccati recursions.
However, as parallel hardware is becoming increasingly popular the demand for
efficient parallel algorithms for solving the Newton step is increasing. In
this paper a tailored, non-iterative parallel algorithm for computing the
Riccati factorization is presented. The algorithm exploits the special
structure in the MPC problem, and when sufficiently many processing units are
available, the complexity of the algorithm scales logarithmically in the
prediction horizon. Computing the Newton step is the main computational
bottle-neck in many MPC algorithms and the algorithm can significantly reduce
the computation cost for popular state-of-the-art MPC algorithms
Planning natural repointing manoeuvres for nano-spacecraft
In this paper the natural dynamics of a rigid body are exploited to plan attitude manoeuvres for a small spacecraft. By utilising the analytical solutions of the angular velocities and making use of Lax pair integration, the time evolution of the attitude of the spacecraft in a convenient quaternion form is derived. This enables repointing manoeuvres to be generated by optimising the free parameters of the analytical expressions, the initial angular velocities of the spacecraft, to match prescribed boundary conditions on the final attitude of the spacecraft. This produces reference motions which can be tracked using a simple proportional-derivative controller. The natural motions are compared in simulation to a conventional quaternion feedback controller and found to require lower accumulated torque. A simple obstacle avoidance algorithm, exploiting the analytic form of natural motions, is also described and implemented in simulation. The computational efficiency of the motion planning method is discussed
Planning natural repointing manoeuvres for nano-spacecraft
In this paper the natural dynamics of a rigid body are exploited to plan attitude manoeuvres for a small spacecraft. By utilising the analytical solutions of the angular velocities and making use of Lax pair integration, the time evolution of the attitude of the spacecraft in a convenient quaternion form is derived. This enables repointing manoeuvres to be generated by optimising the free parameters of the analytical expressions, the initial angular velocities of the spacecraft, to match prescribed boundary conditions on the final attitude of the spacecraft. This produces reference motions which can be tracked using a simple proportional-derivative controller. The natural motions are compared in simulation to a conventional quaternion feedback controller and found to require lower accumulated torque. A simple obstacle avoidance algorithm, exploiting the analytic form of natural motions, is also described and implemented in simulation. The computational efficiency of the motion planning method is discussed
Synchronization-Aware and Algorithm-Efficient Chance Constrained Optimal Power Flow
One of the most common control decisions faced by power system operators is
the question of how to dispatch generation to meet demand for power. This is a
complex optimization problem that includes many nonlinear, non convex
constraints as well as inherent uncertainties about future demand for power and
available generation. In this paper we develop convex formulations to
appropriately model crucial classes of nonlinearities and stochastic effects.
We focus on solving a nonlinear optimal power flow (OPF) problem that includes
loss of synchrony constraints and models wind-farm caused fluctuations. In
particular, we develop (a) a convex formulation of the deterministic
phase-difference nonlinear Optimum Power Flow (OPF) problem; and (b) a
probabilistic chance constrained OPF for angular stability, thermal overloads
and generation limits that is computationally tractable.Comment: 11 pages, 3 figure
- âŠ