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Freidovich, Leonid B., DocentORCID iD iconorcid.org/0000-0003-0730-9441
Alternativa namn
Biografi [eng]

My research background is within classical mechanics and mathematical theory of nonlinear control systems. Currently, I am mostly working within technology development for robotics and automation, both basic and applied research, with emphasis on using mathematically justified new algorithms for designing control systems for various industrial applications.

Publikasjoner (10 av 130) Visa alla publikasjoner
Rosales, A., Freidovich, L. B. & Castillo, I. (2023). Describing function-based analysis and design of approximated sliding-mode controllers with reduced chattering. In: Tiago Roux Oliveira; Leonid Fridman; Liu Hsu (Ed.), Sliding-mode control and variable-structure systems: The state of the art (pp. 357-381). Springer Science+Business Media B.V.
Åpne denne publikasjonen i ny fane eller vindu >>Describing function-based analysis and design of approximated sliding-mode controllers with reduced chattering
2023 (engelsk)Inngår i: Sliding-mode control and variable-structure systems: The state of the art / [ed] Tiago Roux Oliveira; Leonid Fridman; Liu Hsu, Springer Science+Business Media B.V., 2023, , s. 25s. 357-381Kapittel i bok, del av antologi (Fagfellevurdert)
Abstract [en]

Sliding-mode control (SMC) is a powerful robust control design technique that, when appropriately implemented, ensures insensitivity to the so-called matched bounded disturbances and finite-time convergence. However, the insensitivity requires an ideal implementation of discontinuous signals, often based on the sign function that, in practice, results in the presence of parasitic oscillations called chattering. Chattering is unavoidable in systems with SMC, including continuous and higher-order SMC (HOSM) approaches. One of the simplest and commonly used solutions to alleviate chattering is the approximation of the SMC by substituting the sign function with its approximation by a sigmoid function or a saturation function, although this obviously transforms the insensitivity property into a reduction of the influence of the disturbances. In fact, the accuracy of approximating discontinuity creates a trade-off between the reduction of the influence of the disturbances and the amount of chattering. Hence, the following question appears: Is it possible to systematically design a SMC-approximation avoiding a blind search requiring a huge number of numerical and/or hardware experiments? This chapter presents a method to design the boundary-layer parameter of the saturation function. The design is based on the describing function (DF) and harmonic balance (HB) techniques for estimating the parameters of chattering, i.e., frequency and amplitude of the parasitic oscillations.

sted, utgiver, år, opplag, sider
Springer Science+Business Media B.V., 2023. s. 25
Serie
Studies in Systems, Decision and Control, ISSN 21984182 ; 490
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-217022 (URN)10.1007/978-3-031-37089-2_14 (DOI)2-s2.0-85176562746 (Scopus ID)978-3-031-37088-5 (ISBN)978-3-031-37089-2 (ISBN)
Tilgjengelig fra: 2023-11-29 Laget: 2023-11-29 Sist oppdatert: 2023-11-29
Luan, S., Gu, Z., Saremi, A., Freidovich, L. B., Jiang, L. & Wan, S. (2023). Timing performance benchmarking of out-of-distribution detection algorithms. Journal of Signal Processing Systems, 95(12), 1355-1370
Åpne denne publikasjonen i ny fane eller vindu >>Timing performance benchmarking of out-of-distribution detection algorithms
Vise andre…
2023 (engelsk)Inngår i: Journal of Signal Processing Systems, ISSN 1939-8018, E-ISSN 1939-8115, Vol. 95, nr 12, s. 1355-1370Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In an open world with a long-tail distribution of input samples, Deep Neural Networks (DNNs) may make unpredictable mistakes for Out-of-Distribution (OOD) inputs at test time, despite high levels of accuracy obtained during model training. OOD detection can be an effective runtime assurance mechanism for safe deployment of machine learning algorithms in safety–critical applications such as medical imaging and autonomous driving. A large number of OOD detection algorithms have been proposed in recent years, with a wide range of performance metrics in terms of accuracy and execution time. For real-time safety–critical applications, e.g., autonomous driving, timing performance is of great importance in addition to accuracy. We perform a comprehensive and systematic benchmark study of multiple OOD detection algorithms in terms of both accuracy and execution time on different hardware platforms, including a powerful workstation and a resource-constrained embedded device, equipped with both CPU and GPU. We also profile and analyze the internal details of each algorithm to identify the performance bottlenecks and potential for GPU acceleration. This paper aims to provide a useful reference for the practical deployment of OOD detection algorithms for real-time safety–critical applications.

sted, utgiver, år, opplag, sider
Springer-Verlag New York, 2023
Emneord
Deep Learning, Embedded systems, Machine Learning, Out-of-Distribution detection, Real-time systems
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-206357 (URN)10.1007/s11265-023-01852-0 (DOI)000955519800001 ()2-s2.0-85150652364 (Scopus ID)
Tilgjengelig fra: 2023-04-26 Laget: 2023-04-26 Sist oppdatert: 2024-05-10bibliografisk kontrollert
Rosales, A. & Freidovich, L. B. (2022). Estimation of time-varying parameters defining contact of a planar manipulator with a surface. In: CDC 2022: conference on decision and control. Paper presented at 61st IEEE Conference on Decision and Control (CDC 2022), Cancún, Mexico, 6-9 december, 2022. (pp. 1392-1397). Institute of Electrical and Electronics Engineers (IEEE)
Åpne denne publikasjonen i ny fane eller vindu >>Estimation of time-varying parameters defining contact of a planar manipulator with a surface
2022 (engelsk)Inngår i: CDC 2022: conference on decision and control, Institute of Electrical and Electronics Engineers (IEEE), 2022, s. 1392-1397Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The knowledge of parameters, defining interaction of a robotic manipulator with environment, is crucial when robots execute contact-tasks involving tracking of trajectories while desired forces are applied on the environment. For contact tasks on planar surfaces, the inclination and stiffness of the surface are key parameters since the first one defines the direction of the desired force and trajectory, which are typically defined relative to a frame attached to the environment, and the second one is required to compute the control signal. There exist methods for estimation of inclination and stiffness, whenever they are constant. The estimation of time-varying stiffness and inclination is less studied. In this paper, we propose a method to estimate on-line the stiffness and inclination of the planar surface, when they are varying during the task execution. The method is based on adaptive observers that ensure asymptotic or finite-time convergence of the estimates to the real values of the parameters.

sted, utgiver, år, opplag, sider
Institute of Electrical and Electronics Engineers (IEEE), 2022
Serie
IEEE Conference on Decision and Control, ISSN 07431546, E-ISSN 25762370
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-204497 (URN)10.1109/CDC51059.2022.9992576 (DOI)000948128101031 ()2-s2.0-85147038473 (Scopus ID)9781665467612 (ISBN)
Konferanse
61st IEEE Conference on Decision and Control (CDC 2022), Cancún, Mexico, 6-9 december, 2022.
Tilgjengelig fra: 2023-02-08 Laget: 2023-02-08 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Verdés, R. I., Ferreira de Loza, A., Aguilar, L. T., Castillo, I. & Freidovich, L. B. (2021). Accurate Position Regulation of an Electro-Hydraulic Actuator via Uncertainty Compensation-Based Controller. In: Emerging Trends in Sliding Mode Control: Theory and Application (pp. 279-303). Springer
Åpne denne publikasjonen i ny fane eller vindu >>Accurate Position Regulation of an Electro-Hydraulic Actuator via Uncertainty Compensation-Based Controller
Vise andre…
2021 (engelsk)Inngår i: Emerging Trends in Sliding Mode Control: Theory and Application, Springer, 2021, , s. 25s. 279-303Kapittel i bok, del av antologi (Fagfellevurdert)
Abstract [en]

Electro-hydraulic actuators are complex systems with uncertainties in their parameters and disregarded dynamics due to its complexity. This paper presents a disturbance observer-based controller method for the accurate position regulation of an electro-hydraulic actuator. To this aim, a super-twisting algorithm-based observer identifies the plant uncertainties and neglected dynamics, theoretically, in finite-time. Thus, a compensation based controller is designed to counteract the uncertainty and neglected dynamics effects through feedback, improving the position regulation accuracy. The closed-loop analysis is carried out using Lyapunov theory. The feasibility of the controller is validated through high-fidelity simulations and experiments in a forestry crane.

sted, utgiver, år, opplag, sider
Springer, 2021. s. 25
Serie
Studies in Systems, Decision and Control, ISSN 2198-4182, E-ISSN 2198-4190 ; 318
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-186191 (URN)10.1007/978-981-15-8613-2_12 (DOI)2-s2.0-85098194141 (Scopus ID)978-981-15-8612-5 (ISBN)978-981-15-8613-2 (ISBN)
Tilgjengelig fra: 2021-07-16 Laget: 2021-07-16 Sist oppdatert: 2023-03-24bibliografisk kontrollert
Rosales, A., Castillo, I. & Freidovich, L. (2021). Analysis of Higher Order Sliding Mode Controllers with Boundary Layer Approximation. In: 2021 60th IEEE Conference on Decision and Control (CDC): . Paper presented at 60th IEEE Conference on Decision and Control, CDC 2021, Austin, TX, December 13-17, 2021. (pp. 7070-7075). IEEE, 2021-December
Åpne denne publikasjonen i ny fane eller vindu >>Analysis of Higher Order Sliding Mode Controllers with Boundary Layer Approximation
2021 (engelsk)Inngår i: 2021 60th IEEE Conference on Decision and Control (CDC), IEEE, 2021, Vol. 2021-December, s. 7070-7075Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The presence of chattering, i.e. high frequency oscillations with finite amplitude, is unavoidable in systems driven by conventional and higher order sliding mode (HOSM) control. A widely used technique to attenuate chattering is the boundary layer (BL) method; it is based on the approximation of discontinuous terms by a saturation function. However, sliding mode control (SMC) systems with BL approximation still presents chattering due to unmodeled dynamics. Amplitude and frequency of chattering can be estimated applying describing function (DF) and harmonic balance (HB) equation techniques. In this paper, HOSM controllers such as Twisting, Nested second order, and Super Twisting (ST) extension to relative degree two, with BL approximation, are analyzed. The effect of the BL value in the parameters of chattering is studied. When the BL value increments, chattering in systems driven by Twisting and Nested may decrease in amplitude, whereas in the case of ST-extension the variation in amplitude and frequency is minimum. Analysis for the case when the derivative in Twisting and ST-extension algorithms is computed via a linear differentiator is also included. Examples and simulations verifying the results are presented.

sted, utgiver, år, opplag, sider
IEEE, 2021
Serie
Proceedings of the IEEE Conference on Decision & Control, ISSN 0743-1546, E-ISSN 2576-2370
Emneord
Describing function, Frequency domain analysis, Sliding mode control
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-193178 (URN)10.1109/CDC45484.2021.9683424 (DOI)000781990306014 ()2-s2.0-85126050334 (Scopus ID)978-1-6654-3659-5 (ISBN)978-1-6654-3660-1 (ISBN)
Konferanse
60th IEEE Conference on Decision and Control, CDC 2021, Austin, TX, December 13-17, 2021.
Tilgjengelig fra: 2022-03-17 Laget: 2022-03-17 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Luan, S., Gu, Z., Freidovich, L. B., Jiang, L. & Zhao, Q. (2021). Out-of-Distribution Detection for Deep Neural Networks with Isolation Forest and Local Outlier Factor. IEEE Access, 9, 132980-132989
Åpne denne publikasjonen i ny fane eller vindu >>Out-of-Distribution Detection for Deep Neural Networks with Isolation Forest and Local Outlier Factor
Vise andre…
2021 (engelsk)Inngår i: IEEE Access, E-ISSN 2169-3536, Vol. 9, s. 132980-132989Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Deep Neural Networks (DNNs) are extensively deployed in today's safety-critical autonomous systems thanks to their excellent performance. However, they are known to make mistakes unpredictably, e.g., a DNN may misclassify an object if it is used for perception, or issue unsafe control commands if it is used for planning and control. One common cause for such unpredictable mistakes is Out-of-Distribution (OOD) input samples, i.e., samples that fall outside of the distribution of the training dataset. We present a framework for OOD detection based on outlier detection in one or more hidden layers of a DNN with a runtime monitor based on either Isolation Forest (IF) or Local Outlier Factor (LOF). Performance evaluation indicates that LOF is a promising method in terms of both the Machine Learning metrics of precision, recall, F1 score and accuracy, as well as computational efficiency during testing.

sted, utgiver, år, opplag, sider
Institute of Electrical and Electronics Engineers (IEEE), 2021
Emneord
deep neural networks, isolation forest, local outlier factor, Out-of-distribution, outlier detection, runtime monitoring
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-191334 (URN)10.1109/ACCESS.2021.3108451 (DOI)000702542000001 ()2-s2.0-85113855730 (Scopus ID)
Tilgjengelig fra: 2022-01-13 Laget: 2022-01-13 Sist oppdatert: 2023-09-12bibliografisk kontrollert
Mejtoft, T., Söderström, U., Norberg, O. & Freidovich, L. B. (Eds.). (2021). Proceedings of the 21st Student Conference in Interaction Technology and Design. Paper presented at Proceedings of the 21st Student Conference in Interaction Technology and Design, Umeå, Sweden, June 2, 2021. Umeå: Umeå University
Åpne denne publikasjonen i ny fane eller vindu >>Proceedings of the 21st Student Conference in Interaction Technology and Design
2021 (engelsk)Konferanseproceedings (Fagfellevurdert)
Abstract [en]

The Student Conference in Interaction Technology and Design is the annual grand finale of the course Current Topic in Interaction Technology and Design at the Department of Applied Physics and Electronics, Umeå University, Sweden. The main objective of the course is to give the participants a forum, where they can actively discuss scientific research and development through the implementation of their own ideas and interests. The course introduces students to independently finding and researching a topic of interest for them, finding related sources of information and related research publications, writing a scientific article, peer-reviewing, and presenting their work at a conference. The course is conducted in English which is a foreign language for most of the students. The final examination format is chosen as a conference to provide a realistic environment for the presentation of the results. The work of each student has been reviewed by other participants on the course and members of the department acting not only as teachers and consultants but also as program committee members. If the reviews are favorable, the paper is accepted as a full paper at the conference and included in the proceedings.

sted, utgiver, år, opplag, sider
Umeå: Umeå University, 2021. s. 146
Serie
Interaction and Media Technology Report Series ; 2 / 2021
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-185397 (URN)
Konferanse
Proceedings of the 21st Student Conference in Interaction Technology and Design, Umeå, Sweden, June 2, 2021
Tilgjengelig fra: 2021-06-29 Laget: 2021-06-29 Sist oppdatert: 2021-06-29bibliografisk kontrollert
Sætre, C. F., Shiriaev, A. S., Freidovich, L. B., Gusev, S. V. & Fridman, L. M. (2021). Robust orbital stabilization: A Floquet theory-based approach. International Journal of Robust and Nonlinear Control, 31(16), 8075-8108
Åpne denne publikasjonen i ny fane eller vindu >>Robust orbital stabilization: A Floquet theory-based approach
Vise andre…
2021 (engelsk)Inngår i: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 31, nr 16, s. 8075-8108Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The design of robust orbitally stabilizing feedback is considered. From a known orbitally stabilizing controller for a nominal, disturbance-free system, a robustifying feedback extension is designed utilizing the sliding-mode control (SMC) methodology. The main contribution of the article is to provide a constructive procedure for designing the time-invariant switching function used in the SMC synthesis. More specifically, its zero-level set (the sliding manifold) is designed using a real Floquet–Lyapunov transformation to locally correspond to an invariant subspace of the Monodromy matrix of a transverse linearization. This ensures asymptotic stability of the periodic orbit when the system is confined to the sliding manifold, despite any system uncertainties and external disturbances satisfying a matching condition. The challenging task of oscillation control of the underactuated cart–pendulum system subject to both matched- and unmatched disturbances/uncertainties demonstrates the efficacy of the proposed scheme.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2021
Emneord
orbital stabilization, robust nonlinear control, sliding mode control, underactuated mechanical systems
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-187289 (URN)10.1002/rnc.5738 (DOI)000693307400001 ()2-s2.0-85113977209 (Scopus ID)
Tilgjengelig fra: 2021-09-07 Laget: 2021-09-07 Sist oppdatert: 2022-01-11bibliografisk kontrollert
Wang, Z., Freidovich, L. B. & Zhang, H. (2020). Almost periodic motion planning and control for double rotary pendulum with experimental validation. Asian Journal of Control, 22(6), 2434-2443
Åpne denne publikasjonen i ny fane eller vindu >>Almost periodic motion planning and control for double rotary pendulum with experimental validation
2020 (engelsk)Inngår i: Asian Journal of Control, ISSN 1561-8625, E-ISSN 1934-6093, Vol. 22, nr 6, s. 2434-2443Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The aim is to develop a systematic procedure for planning feasible motions for a double rotary pendulum. This pendulum has one directly actuated horizontal link and two passive links, moving in a rotating vertical plane. We plan a nontrivial oscillatory motion for the passive links that is consistent with the horizontal link rotating at a given average speed and also design a stabilizing controller to approximately induce such a motion. For the motion planning, a numerical optimization procedure is proposed in the form of a sequence of three simpler problems to systematically derive initial guesses for the final optimization search. For the controller design, firstly the system is linearized along a nominal trajectory, and then a parametrized family of candidate stabilizing controllers is designed. For each set of parameters, a necessary and sufficient stability condition can be checked for the derived linear time varying periodic system. Therefore, a numerical optimization procedure is used to find the controller gain for the linear system based on the stability condition. The performance of the closed-loop system is illustrated via numerical simulations and verified via experiments with an educational platform produced by PendCon, demonstrating achieving oscillations with required characteristics. However, the formal proofs for convergence and even for existence of almost periodic solutions are left for future studies.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2020
Emneord
double rotary pendulum, periodic motion planning, underactuated mechanical systems, virtual lonomic constraints
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-162005 (URN)10.1002/asjc.2154 (DOI)000476849300001 ()2-s2.0-85068439850 (Scopus ID)
Tilgjengelig fra: 2019-08-13 Laget: 2019-08-13 Sist oppdatert: 2024-02-28bibliografisk kontrollert
Surov, M., Gusev, S. & Freidovich, L. B. (2020). Constructing Transverse Coordinates for Orbital Stabilization of Periodic Trajectories. In: 2020 American Control Conference (ACC): . Paper presented at American Control Conference (ACC), JUL 01-03, 2020, Denver, CO, USA (pp. 836-841). IEEE
Åpne denne publikasjonen i ny fane eller vindu >>Constructing Transverse Coordinates for Orbital Stabilization of Periodic Trajectories
2020 (engelsk)Inngår i: 2020 American Control Conference (ACC), IEEE, 2020, s. 836-841Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

An approach for introduction of transverse coordinates in a vicinity of a periodic trajectory is presented. The approach allows finding by numerical integration periodic normalized mutually-orthogonal vector-functions that form a continuously differentiable basis on moving Poincare sections for a given periodic solution of a nonlinear dynamical system. The found moving frame is used to define new local (transverse) coordinates for an associated affine nonlinear control system in a neighborhood of the trajectory, and to proceed with orbital stability analysis and/or synthesis of a stabilizing feedback control law. As a demonstrating example of the approach, the problem of orbital stabilization of a trajectory of a multibody car system is considered. The results of computer simulations of the system are presented.

sted, utgiver, år, opplag, sider
IEEE, 2020
Serie
Proceedings of the American Control Conference, ISSN 0743-1619, E-ISSN 2378-5861
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-187151 (URN)000618079800128 ()2-s2.0-85089594866 (Scopus ID)978-1-5386-8266-1 (ISBN)978-1-5386-8267-8 (ISBN)
Konferanse
American Control Conference (ACC), JUL 01-03, 2020, Denver, CO, USA
Tilgjengelig fra: 2021-09-13 Laget: 2021-09-13 Sist oppdatert: 2022-04-04bibliografisk kontrollert
Prosjekter
Inbjuden som gästforskare till prof Leonid M. Fridman, Universidad Nacional Autónoma de México, 7 juni - 7 juli 2010. [2010-01692_VR]; Umeå universitetAUTOMATION OF FRONT END LOADERS FOR AGRICULTURAL TRACTORS [2012-04172_VR]; Umeå universitet
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-0730-9441