| 1. |
- Gupta, Ankit, 1988, et al.
(författare)
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A Framework for Vehicle Lateral Motion Control With Guaranteed Tracking and Performance
- 2019
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Ingår i: 2019 IEEE Intelligent Transportation Systems Conference, ITSC 2019. ; , s. 3607-3612
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a framework to design a controller for the vehicle lateral dynamics, which guarantees to meet desired safety and performance requirement. Bounded lateral deviation from the reference trajectory is the strict safety requirement considered in this paper.The proposed control design relies on a mild assumption. That is, the trajectory planner generates a trajectory that is piece-wise clothoidal (PWC), with bounded curvature and curvature rate.Closed-loop simulations using a linear quadratic regulator (LQR) and a model predictive control (MPC) controller, developed based on the proposed framework, validates the proposed approach.
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| 2. |
- Gupta, Ankit, 1988, et al.
(författare)
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Computation of low-complexity control-invariant sets for systems with uncertain parameter dependence
- 2019
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 101, s. 330-337
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the problem of computing a low-complexity robust control-invariant (LC-RCI) set for uncertain systems, along with a static linear state-feedback law. The LC-RCI set, assumed to be symmetric around the origin and described by the same number of affine inequalities as twice the dimension of the state vector, is the result of an iterative procedure, where semi-definite programs (SDPs) are solved at each step. The SDPs are formulated to increase the LC-RCI volume at each step, subject to tractable reformulations of the system constraints as well as the invariance condition (in the form of standard or dilated LMIs), and a new approach to determinant maximization. The two proposed algorithms are applicable to systems with rational parameter dependence, which cannot be handled with the existing similar approaches without introducing additional conservatism.
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| 3. |
- Gupta, Ankit, 1988, et al.
(författare)
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Computation of Parameter Dependent Robust Invariant Sets for LPV Models with Guaranteed Performance
- 2023
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 151
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an iterative algorithm to compute a Robust Control Invariant (RCI) set, along with an invariance-inducing control law, for Linear Parameter-Varying (LPV) systems. As the real-time measurements of the scheduling parameters are typically available, in the presented formulation, we allow the RCI set description along with the invariance-inducing controller to be scheduling parameter dependent. The considered formulation thus leads to parameter-dependent conditions for the set invariance, which are replaced by sufficient Linear Matrix Inequality (LMI) conditions via Polya's relaxation. These LMI conditions are then combined with a novel volume maximization approach in a Semidefinite Programming (SDP) problem, which aims at computing the desirably large RCI set. In addition to ensuring invariance, it is also possible to guarantee performance within the RCI set by imposing a chosen quadratic performance level as an additional constraint in the SDP problem. The reported numerical example shows that the presented iterative algorithm can generate invariant sets which are larger than the maximal RCI sets computed without exploiting scheduling parameter information.
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| 4. |
- Gupta, Ankit, 1988, et al.
(författare)
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Computation of Robust Control Invariant Sets with Predefined Complexity for Uncertain Systems
- 2021
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Ingår i: International Journal of Robust and Nonlinear Control. - : Wiley. - 1099-1239 .- 1049-8923. ; 31:5, s. 1674-1688
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an algorithm that computes polytopic robust control-invariant (RCI) sets for rationally parameter-dependent systems with additive disturbances. By means of novel LMI feasibility conditions for invariance along with a newly developed method for volume maximization, an iterative algorithm is proposed for the computation of RCI sets with maximized volumes. The obtained RCI sets are symmetric around the origin by construction and have a user-defined level of complexity. Unlike many similar approaches, fixed state feedback structure is not imposed. In fact, a specific control input is obtained from the LMI problem for each extreme point of the RCI set. The outcomes of the proposed algorithm can be used to construct a piecewise-affine controller based on offline computations.
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| 5. |
- Gupta, Ankit, 1988
(författare)
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Control of Constrained Dynamical Systems with Performance Guarantees: With Application to Vehicle motion Control
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In control engineering, models of the system are commonly used for controller design. A standard control design problem consists of steering the given system output (or states) towards a predefined reference. Such a problem can be solved by employing feedback control strategies. By utilizing the knowledge of the model, these strategies compute the control inputs that shrink the error between the system outputs and their desired references over time. Usually, the control inputs must be computed such that the system output signals are kept in a desired region, possibly due to design or safety requirements. Also, the input signals should be within the physical limits of the actuators. Depending on the constraints, their violation might result in unacceptable system failures (e.g. deadly injury in the worst case). Thus, in safety-critical applications, a controller must be robust towards the modelling uncertainties and provide a priori guarantees for constraint satisfaction. A fundamental tool in constrained control application is the robust control invariant sets (RCI). For a controlled dynamical system, if initial states belong to RCI set, control inputs always exist that keep the future state trajectories restricted within the set. Hence, RCI sets can characterize a system that never violates constraints. These sets are the primary ingredient in the synthesis of the well-known constraint control strategies like model predictive control (MPC) and interpolation-based controller (IBC). Consequently, a large body of research has been devoted to the computation of these sets. In the thesis, we will focus on the computation of RCI sets and the method to generate control inputs that keep the system trajectories within RCI set. We specifically focus on the systems which have time-varying dynamics and polytopic constraints. Depending upon the nature of the time-varying element in the system description (i.e., if they are observable or not), we propose different sets of algorithms. The first group of algorithms apply to the system with time-varying, bounded uncertainties. To systematically handle the uncertainties and reduce conservatism, we exploit various tools from the robust control literature to derive novel conditions for invariance. The obtained conditions are then combined with a newly developed method for volume maximization and minimization in a convex optimization problem to compute desirably large and small RCI sets. In addition to ensuring invariance, it is also possible to guarantee desired closed-loop performance within the RCI set. Furthermore, developed algorithms can generate RCI sets with a predefined number of hyper-planes. This feature allows us to adjust the computational complexity of MPC and IBC controller when the sets are utilized in controller synthesis. Using numerical examples, we show that the proposed algorithms can outperform (volume-wise) many state-of-the-art methods when computing RCI sets. In the other case, we assume the time-varying parameters in system description to be observable. The developed algorithm has many similar characteristics as the earlier case, but now to utilize the parameter information, the control law and the RCI set are allowed to be parameter-dependent. We have numerically shown that the presented algorithm can generate invariant sets which are larger than the maximal RCI sets computed without exploiting parameter information. Lastly, we demonstrate how we can utilize some of these algorithms to construct a computationally efficient IBC controller for the vehicle motion control. The devised IBC controller guarantees to meet safety requirements mentioned in ISO 26262 and the ride comfort requirement by design.
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| 6. |
- Gupta, Ankit, 1988, et al.
(författare)
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Full-complexity characterization of control-invariant domains for systems with uncertain parameter dependence
- 2019
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 3:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- This letter proposes an algorithm to find a robust control invariant (RCI) set of desired complexity and the associated linear, state-feedback control law. The candidate RCI set is restricted to be symmetric around the origin. The algorithm is applicable to rational parameter dependent systems with bounded additive disturbance. The system constraints are framed as simple affine inequalities whereas the invariance condition as a set of sufficient LMI conditions. The proposed iterative algorithm is guaranteed to be recursively feasible and converge to some stationary point.
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| 7. |
- Gupta, Ankit, 1988, et al.
(författare)
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Low-Complexity Explicit MPC Controller for Vehicle Lateral Motion Control
- 2018
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Ingår i: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC. ; , s. 2839-2844
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of controlling the vehicle lateral motion in highway scenarios while guaranteeing safety. We propose a solution consisting of a Low-Complexity Explicit Model Predictive Controller (LC-EMPC), where the lateral deviation from the desired path is hard constrained according to prescribed bounds. The robust satisfaction of such safety constraints can be achieved by imposing the terminal state to enter a Robust Invariant Set (RIS), which is known to result into a potentially high number of additional constraints, thus increasing the computational complexity of the controller. Our controller, instead, relies on recent results on the calculation of low-complexity RIS to significantly reduce the number of constraints in the MPC controller. Simulation results show that the designed controller is able to meet the desired objectives with highly reduced complexity.
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| 8. |
- Gupta, Ankit, 1988, et al.
(författare)
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Restricted-Complexity Characterization of Control-Invariant Domains with Application to Lateral Vehicle Dynamics Control
- 2017
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Ingår i: IEEE Conference on Decision and Control. - 9781509028733 ; 2018-January, s. 4946-4951
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Konferensbidrag (refereegranskat)abstract
- This paper proposes two algorithms to find a restricted-complexity robust control invariant (RCI) set along with a state-feedback gain. These algorithms are applicable to a linear system with additive disturbances subject to found polytopic state and input constraints. The RCI set is a polytope with restricted complexity, symmetric around the origin. Using a state transformation, novel LMI conditions are derived for the system constraints and invariance condition. Moreover, a new approach is proposed to iteratively increase the volume of the computed RCI set. The effectiveness of the proposed algorithm is illustrated by using lateral vehicle dynamics control example.
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| 9. |
- Klintberg, Emil, 1989, et al.
(författare)
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A primal active-set minimal-representation algorithm for polytopes with application to invariant-set calculations
- 2018
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. ; 2018-December, s. 6862-6867
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Konferensbidrag (refereegranskat)abstract
- This paper provides a description of a practically efficient minimal-representation algorithm for polytopes. The algorithm is based on a primal active-set method that heavily exploits warm-starts and low-rank updates of matrix factorizations in order to reduce the required computational work. By using a primal active-set method, several nonredundant inequalities can be identified for each solved linear program. Implementation details are provided both for the minimalrepresentation algorithm and for the underlying active-set method.
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| 10. |
- Klintberg, Emil, 1989, et al.
(författare)
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Tree-Structured Polyhedral Invariant Set Calculations
- 2020
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Ingår i: IEEE Control Systems Letters. - 2475-1456. ; 4:2, s. 426-431
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Tidskriftsartikel (refereegranskat)abstract
- This letter provides a description of how hierarchical dependencies between inequalities can be exploited in order to efficiently calculate polyhedral approximations of maximal robust positive invariant sets using geometrically motivated methods. Due to the hierarchical dependencies, the calculations of preimage sets and minimal representations can be alleviated. It is also shown that as a byproduct from the calculations of minimal representations, a stopping criterion is obtained, which means that the commonly used subset test is superfluous.
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| 11. |
- Ni, Lei, et al.
(författare)
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Vehicle Lateral Motion Control with Performance and Safety Guarantees
- 2016
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 49:11, s. 285-290
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Konferensbidrag (refereegranskat)abstract
- This paper explores the use of Model Predictive Control (MPC) techniques to solve vehicle lateral motion control problem on highway scenarios. In particular, the problem of autonomously driving a vehicle along a desired path is formulated, where safety constraints and performance levels must be guaranteed for all possible road curvatures within a con [pact set. Safety constraints are translated into a maximum lateral deviation and orientation error w.r.t. a desired path, while performance requirements are formulated in terms of bounded lateral acceleration and velocity. Preliminary simulation results ahoy that the designed controller is capable of delivering acceptable performance at the cost of limited online computational costs. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
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| 12. |
- Nilsson, Magnus, et al.
(författare)
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Admissible sets for polytopic linear systems subject to slowly-varying unobservable disturbances
- 2020
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This note describes a method to calculate sets of safe initial conditions for polytopic linear systems subject to slowly-varying unobservable disturbances. Such sets are herein called admissible sets; invariant sets are admissible but admissible sets are not necessarily invariant. By examining conditions for admissible sets of this particular system class, we prove that admissible sets can be calculated by only considering a special property that we call \emph{the $\lambda$-proximal-contraction property} at the vertices of the set that bounds the slowly-varying disturbances. An academic example is used to illustrate how to apply the method, and a discussion follows that summarizes the main points.
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