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- Ardeshiri, Tohid, 1980-, et al.
(författare)
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Convex Optimization Approach for Time-Optimal Path Tracking of Robots with Speed Dependent Constraints
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The task of generating time optimal trajectories for a six degrees of freedom industrial robot is discussed and an existing convex optimization formulation of the problem is extended to include new types of constraints. The new constraints are speed dependent and can be motivated from physical modeling of the motors and the drive system. It is shown how the speed dependent constraints should be added in order to keep the convexity of the overall problem. A method to, conservatively, approximate the linear speed dependent constraints by a convex constraint is also proposed. A numerical example proves versatility of the extension proposed in this paper.
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- Ardeshiri, Tohid, 1980-, et al.
(författare)
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Convex Optimization Approach for Time-Optimal Path Tracking of Robots with Speed Dependent Constraints
- 2011
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Ingår i: Proceedings of the 18th IFAC World Congress. - : IFAC. - 9783902661937 ; , s. 14648-14653
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Konferensbidrag (refereegranskat)abstract
- The task of generating time optimal trajectories for a six degrees of freedom industrial robot is discussed and an existing convex optimization formulation of the problem is extended to include new types of constraints. The new constraints are speed dependent and can be motivated from physical modeling of the motors and the drive system. It is shown how the speed dependent constraints should be added in order to keep the convexity of the overall problem. A method to, conservatively, approximate the linear speed dependent constraints by a convex constraint is also proposed. A numerical example proves versatility of the extension proposed in this paper.
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- Bakarac, Peter, et al.
(författare)
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Explicit MPC Based on Approximate Dynamic Programming
- 2018
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Ingår i: 2018 EUROPEAN CONTROL CONFERENCE (ECC). - 9783952426982 - 9781538653036
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Konferensbidrag (refereegranskat)abstract
- In this paper we show how to synthesize simple explicit MPC controllers based on approximate dynamic programming. Here, a given MPC optimization problem over a finite horizon is solved iteratively as a series of problems of size one. The optimal cost function of each subproblem is approximated by a quadratic function that serves as a cost-to-go function for the subsequent iteration. The approximation is designed in such a way that closed-loop stability and recursive feasibility is maintained. Specifically, we show how to employ sum-of-squares relaxations to enforce that the approximate cost-to-go function is bounded from below and from above for all points of its domain. By resorting to quadratic approximations, the complexity of the resulting explicit MPC controller is considerably reduced both in terms of memory as well as the on-line computations. The procedure is applied to control an inverted pendulum and experimental data are presented to demonstrate viability of such an approach.
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- Barbosa, Filipe Marques, et al.
(författare)
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Fast or Cheap: Time and Energy Optimal Control of Ship-to-Shore Cranes
- 2023
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Ingår i: Special issue: 22nd IFAC World Congress. - : ELSEVIER. ; , s. 3126-3131
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the trade-off between time and energy-efficiency for the problem of loading and unloading a ship. Container height constraints and energy consumption and regeneration are dealt with. We build upon a previous work that introduced a coordinate system suitable to deal with container avoidance constraints and incorporate the energy related modeling. In addition to changing the coordinate system, standard epigraph reformulations result in an optimal control problem with improved numerical properties. The trade-of is dealt with through the use of weighting of the total time and energy consumption in the cost function. An illustrative example is provided, demonstrating that the energy consumption can be substantially reduced while retaining approximately the same loading time.
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- Barbosa, Filipe Marques, et al.
(författare)
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Time-optimal control of cranes subject to container height constraints
- 2022
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Ingår i: Proceedings of 2022 American Control Conference (ACC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665451963 - 9781665451970 - 9781665494809 ; , s. 3558-3563
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The productivity and efficiency of port operations strongly depend on how fast a ship can be unloaded and loaded again. With this in mind, ship-to-shore cranes perform the critical task of transporting containers into and onto a ship and must do so as fast as possible. Though the problem of minimizing the time spent in moving the payload has been addressed in previous studies, the different heights of the container stacks have not been the focus. In this paper, we perform a change of variable and reformulate the optimization problem to deal with the constraints on the stack heights. As consequence, these constraints become trivial and easy to represent since they turn into bound constraints when the problem is discretized for the numerical solver. To validate the idea, we simulate a small-scale scenario where different stack heights are used. The results confirm our idea and the representation of the stack constraints become indeed trivial. This approach is promising to be applied in real crane operations and has the potential to enhance their automation.
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