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BETA
Freidovich, Leonid B.ORCID iD iconorcid.org/0000-0003-0730-9441
Alternative names
Biography [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.

Publications (10 of 113) Show all publications
Castillo, I. & Freidovich, L. B. (2020). Describing-function-based analysis to tune parameters of chattering reducing approximations of Sliding Mode controllers. Control Engineering Practice, 95, Article ID 104230.
Open this publication in new window or tab >>Describing-function-based analysis to tune parameters of chattering reducing approximations of Sliding Mode controllers
2020 (English)In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 95, article id 104230Article in journal (Refereed) Published
Abstract [en]

Sliding Mode Control (SMC) is a powerful feedback control design technique leading to insensitivity to certain types of disturbances under ideal conditions. Among these conditions, there are discontinuity in the generated control signal and absence of unmodeled dynamics. In many cases, the former maybe not implementable while the latter is often not holdable. Such non-ideal conditions typically excite high-frequency oscillations, known as chattering, not only in the input to the plant but also in the output, leading to a degradation of performance and losing the attractive insensitivity property. One of well-known and widely used approaches to achieve chattering reduction, caused by delays, parasitic dynamics, unmatched perturbations, etc., is implicitly or explicitly approximating the discontinuity. Theoretically, removing the discontinuities in the input to the plant, as well as in the internal controller dynamics, leads to loosing the insensitivity property under ideal conditions, but may insure better performance under more realistic conditions. This paper presents a Describing Function analysis in frequency domain of some SMC algorithms under presence of unmodeled (parasitic) dynamics, in the case when the discontinuous sign function is replaced or approximated by a saturation function. We are to concentrate here on a systematic procedure to tune parameters of the approximation.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Sliding Mode Control application, Chattering reduction, Describing functions, Frequency domain analysis
National Category
Control Engineering
Identifiers
urn:nbn:se:umu:diva-168337 (URN)10.1016/j.conengprac.2019.104230 (DOI)000510526900018 ()
Available from: 2020-02-24 Created: 2020-02-24 Last updated: 2020-02-24Bibliographically approved
Söderström, U., Freidovich, L. B., Nordström, T. & Kunert, K. (Eds.). (2020). Proceedings of the 18th Student Conference in Interaction Technology and Design and the 6th Student Conference in Electronics and Mechatronics. Paper presented at The 18th Student Conference in Interaction Technology and Design and the 6th Student Conference in Electronics and Mechatronics, Umeå, Sweden, January 16-17, 2020. Umeå University
Open this publication in new window or tab >>Proceedings of the 18th Student Conference in Interaction Technology and Design and the 6th Student Conference in Electronics and Mechatronics
2020 (English)Conference proceedings (editor) (Other academic)
Abstract [en]

The joint Student Conference in Interaction Technology and Design and Student Conference in Electronics and Mechatronics is the annual grand finale of the courses Current Topic in Interaction Technology and Design and Student Conference in Electronics and Mechatronics at the Department of Applied Physics and Electronics, Umeå  University. The idea and objective of the two courses are to give the students a forum, where they can actively participate in scientific research and development through their own ideas and interests. The course introduces students to independently finding and researching a topic of interest for them, using a foreign language orally and in writing, writing a scientific article, peer-reviewing and presenting their work at a conference. The conference format was chosen to provide a realistic environment for the presentation of the results. The work has been reviewed both by other participant on the course and members of the department. If the reviews are favorable, the paper is accepted as a full paper at the conference and included in the proceedings.

Place, publisher, year, edition, pages
Umeå University, 2020. p. 113
Series
Interaction and Media Technology Report Series ; 1/2020
National Category
Interaction Technologies Robotics Signal Processing Media and Communication Technology
Identifiers
urn:nbn:se:umu:diva-167502 (URN)
Conference
The 18th Student Conference in Interaction Technology and Design and the 6th Student Conference in Electronics and Mechatronics, Umeå, Sweden, January 16-17, 2020
Available from: 2020-01-23 Created: 2020-01-23 Last updated: 2020-01-24Bibliographically approved
Wang, Z., Freidovich, L. B. & Zhang, H. (2019). Almost periodic motion planning and control for double rotary pendulum with experimental validation. Asian journal of control
Open this publication in new window or tab >>Almost periodic motion planning and control for double rotary pendulum with experimental validation
2019 (English)In: Asian journal of control, ISSN 1561-8625, E-ISSN 1561-8625Article in journal (Refereed) Epub ahead of print
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.

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
double rotary pendulum, periodic motion planning, underactuated mechanical systems, virtual lonomic constraints
National Category
Control Engineering
Identifiers
urn:nbn:se:umu:diva-162005 (URN)10.1002/asjc.2154 (DOI)000476849300001 ()
Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-08-13
Wang, Z., Freidovich, L. B. & Zhang, H. (2019). Periodic Motion Planning and Control for Double Rotary Pendulum via Virtual Holonomic Constraints. IEEE/CAA Journal of Automatica Sinica, 6(1), 291-298
Open this publication in new window or tab >>Periodic Motion Planning and Control for Double Rotary Pendulum via Virtual Holonomic Constraints
2019 (English)In: IEEE/CAA Journal of Automatica Sinica, ISSN 2329-9266, Vol. 6, no 1, p. 291-298Article in journal (Refereed) Published
Abstract [en]

Periodic motion planning for an under-actuated system is rather difficult due to differential dynamic constraints imposed by passive dynamics, and it becomes more difficult for a system with higher underactuation degree, that is with a higher difference between the number of degrees of freedom and the number of independent control inputs. However, from another point of view, these constraints also mean some relation between state variables and could be used in the motion planning. We consider a double rotary pendulum, which has an underactuation degree 2. A novel periodic motion planning is presented based on an optimization search. A necessary condition for existence of the whole periodic trajectory is given because of the higher underactuation degree of the system. Moreover this condition is given to make virtual holonomic constraint (VHC) based control design feasible. Therefore, an initial guess for the optimization of planning a feasible periodic motion is based on this necessary condition. Then, VHCs are used for the system transformation and transverse linearization is used to design a static state feedback controller with periodic matrix function gain. The controller gain is found through another optimization procedure. The effectiveness of initial guess and performance of the closed-loop system are illustrated through numerical simulations.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2019
Keywords
Double rotary pendulum, periodic motion planning, under-actuated mechanical systems, virtual holonomic constraint (VHC)
National Category
Control Engineering Robotics
Identifiers
urn:nbn:se:umu:diva-155967 (URN)10.1109/JAS.2017.7510712 (DOI)000455705900027 ()
Available from: 2019-02-07 Created: 2019-02-07 Last updated: 2019-02-07Bibliographically approved
Söderström, U. & Freidovich, L. B. (Eds.). (2019). Proceedings of the 16th Student Conference in Interaction Technology and Design and the 5th Student Conference in Electronics and Mechatronics. Paper presented at The 16th Student Conference in Interaction Technology and Design and the 5th Student Conference in Electronics and Mechatronics, Umeå, Sweden, January 17, 2019. Umeå, Sweden: Umeå University
Open this publication in new window or tab >>Proceedings of the 16th Student Conference in Interaction Technology and Design and the 5th Student Conference in Electronics and Mechatronics
2019 (English)Conference proceedings (editor) (Refereed)
Abstract [en]

The joint Student Conference in Interaction Technology and Design and Student Conference in Electronics and Mechatronics is the annual grand finale of the courses Current Topic in Interaction Technology and Design and Student Conference in Electronics and Mechatronics at the Department of Applied Physics and Electronics, Umeå University. The idea and objective of the two courses are to give the students a forum where they can actively participate in scientific research and development through their own ideas and interests.  The course introduces students to independently researching an interesting topic, using a foreign language orally and in writing, writing a scientific article, peer-review and presenting their work at a conference. The conference format was chosen to provide a realistic environment for the presentation of the results. The work has been reviewed both by other participant on the course and members of the department. If the reviews are favorable, the paper is accepted as a full paper at the conference and included in the proceedings. Research that has an interesting topic and potential for future publication is presented as work-in-progress at the conference and the abstract is included in the conference proceedings. This year 10 full papers and 2 work-in-progress papers were accepted at the conference and all included in this proceedings as full papers and extended abstracts, respectively.

Place, publisher, year, edition, pages
Umeå, Sweden: Umeå University, 2019. p. 139
Series
Interaction and Media Technology Report Series ; 1/2019
National Category
Interaction Technologies Robotics Signal Processing Media and Communication Technology
Identifiers
urn:nbn:se:umu:diva-155594 (URN)
Conference
The 16th Student Conference in Interaction Technology and Design and the 5th Student Conference in Electronics and Mechatronics, Umeå, Sweden, January 17, 2019
Available from: 2019-01-24 Created: 2019-01-24 Last updated: 2019-01-25Bibliographically approved
Wang, Z., Freidovich, L. B. & Zhang, H. (2018). Periodic motion planning and control for underactuated mechanical systems. International Journal of Control, 91(6), 1350-1362
Open this publication in new window or tab >>Periodic motion planning and control for underactuated mechanical systems
2018 (English)In: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 91, no 6, p. 1350-1362Article in journal (Refereed) Published
Abstract [en]

We consider the problem of periodic motion planning and of designing stabilising feedback control laws for such motions in underactuated mechanical systems. A novel periodic motion planning method is proposed. Each state is parametrised by a truncated Fourier series. Then we use numerical optimisation to search for the parameters of the trigonometric polynomial exploiting the measure of discrepancy in satisfying the passive dynamics equations as a performance index. Thus an almost feasible periodic motion is found. Then a linear controller is designed and stability analysis is given to verify that solutions of the closed-loop system stay inside a tube around the planned approximately feasible periodic trajectory. Experimental results for a double rotary pendulum are shown, while numerical simulations are given for models of a spacecraft with liquid sloshing and of a chain of mass spring system.

Keywords
Periodic motion planning, underactuated mechanical systems, nonlinear systems, robotics, linear riodic systems
National Category
Control Engineering
Identifiers
urn:nbn:se:umu:diva-147486 (URN)10.1080/00207179.2017.1314022 (DOI)000430094800011 ()
Available from: 2018-05-07 Created: 2018-05-07 Last updated: 2018-06-09Bibliographically approved
Pchelkin, S. S., Shiriaev, A. S., Robertsson, A., Freidovich, L. B., Kolyubin, S. A., Paramonov, L. V. & Gusev, S. V. (2017). On Orbital Stabilization for Industrial Manipulators: Case Study in Evaluating Performances of Modified PD plus and Inverse Dynamics Controllers. IEEE Transactions on Control Systems Technology, 25(1), 101-117
Open this publication in new window or tab >>On Orbital Stabilization for Industrial Manipulators: Case Study in Evaluating Performances of Modified PD plus and Inverse Dynamics Controllers
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2017 (English)In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 25, no 1, p. 101-117Article in journal (Refereed) Published
Abstract [en]

Orbital stabilization is one of the available alternatives to the classical asymptotic stabilization, known as the reference tracking control, which is typically considered and implemented for controlling motions of industrial robot manipulators. Since asymptotic orbital stability means convergence of solutions of a closed-loop system to an orbit of a reference trajectory, instead of tracking it as a function of time, new feedback designs can potentially improve performance with respect to several key criteria for industrial manipulators such as absolute path accuracy for tool's motions and robustness to uncertainties in the model. The main outcomes of this paper are a new class of controllers that achieve asymptotic orbital stabilization of motions and a novel analytical method for analysis and redesign of system's dynamics using an excessive set of easy-to-compute transverse coordinates. The contributions have been validated in a series of experimental studies performed on a standard industrial robot ABB IRB 140 with the IRC5-system extended with an open control interface. The outcomes of the tests show that the proposed redesign allows achieving significantly reduced deviations of the actual trajectories from the desired ones at different ranges of speeds and for several different paths, often outperforming the state-of-the-art commercial implementations. A comprehensive discussion of one of such experiments is given.

Keywords
Industrial robotic manipulators, model-based feedback design, motion and trajectory planning, bital stabilization, path accuracy, transverse dynamics
National Category
Control Engineering
Identifiers
urn:nbn:se:umu:diva-132039 (URN)10.1109/TCST.2016.2554520 (DOI)000391498700010 ()
Available from: 2017-03-28 Created: 2017-03-28 Last updated: 2018-06-09Bibliographically approved
Ortega-Montiel, T., Villafuerte-Segura, R., Vázquez-Aguilera, C. & Freidovich, L. (2017). Proportional Retarded Controller to Stabilize Underactuated Systems with Measurement Delays: Furuta Pendulum Case Study. Mathematical problems in engineering (Print), Article ID 2505086.
Open this publication in new window or tab >>Proportional Retarded Controller to Stabilize Underactuated Systems with Measurement Delays: Furuta Pendulum Case Study
2017 (English)In: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, article id 2505086Article in journal (Refereed) Published
Abstract [en]

The design and tuning of a simple feedback strategy with delay to stabilize a class of underactuated mechanical systems with dead time are presented. A linear time-invariant (LTI) model with time delay of fourth order and a Proportional Retarded (PR) controller are considered. The PR controller is shown as an appealing alternative to the application of observer-based controllers. This paper gives a step forward to obtain a better understanding of the effect of output delays and related phenomena in mechatronic systems, making it possible to design resilient control laws under the presence of uncertain time delays in measurements and obtain an acceptable performance without using a derivative action. The Furuta pendulum is a standard two-degrees-of-freedom benchmark example from the class of underactuated mechanical systems. The configuration under study includes an inherent output delay due to wireless communication used to transmit measurements of the pendulum's angular position. Our approach offers a constructive design and a procedure based on a combination of root loci and Mikhailov methods for the analysis of stability. Experiments over a laboratory platform are reported and a comparison with a standard linear state feedback control law shows the advantages of the proposed scheme.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2017
National Category
Mathematics Control Engineering
Identifiers
urn:nbn:se:umu:diva-143956 (URN)10.1155/2017/2505086 (DOI)000418855900001 ()
Available from: 2018-01-15 Created: 2018-01-15 Last updated: 2018-06-09Bibliographically approved
Yung, I., Vázquez, C. & Freidovich, L. B. (2017). Robust position control design for a cylinder in mobile hydraulics applications. Control Engineering Practice, 69, 36-49
Open this publication in new window or tab >>Robust position control design for a cylinder in mobile hydraulics applications
2017 (English)In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 69, p. 36-49Article in journal (Refereed) Published
Abstract [en]

Automation of various agricultural tasks, which are nowadays routinely executed by operators of hydraulically actuated tractors equipped with front-end loaders, is an important open problem. The so-called self-leveling task is considered here, where the lifting and lowering motions of the loader are performed manually while the orientation of the tool must be adjusted automatically. The proposed controller is constituted by a proportional feedback, a disturbance compensator based on an observer and a relay controller. A model-based tuning procedure for the controller parameters is discussed and an implementation is validated experimentally on an industry-standard commercial set-up.

Keywords
Hydraulic cylinder, Self-leveling, Robust control, Disturbance compensation, Stability analysis, Tuning procedure
National Category
Control Engineering
Identifiers
urn:nbn:se:umu:diva-141963 (URN)10.1016/j.conengprac.2017.09.004 (DOI)000414109400004 ()
Available from: 2017-12-06 Created: 2017-12-06 Last updated: 2018-06-09Bibliographically approved
Pchelkin, S. S., Shiriaev, A. S., Mettin, U., Freidovich, L. B., Paramonov, L. V. & Gusev, S. V. (2016). Algorithms for finding gaits of locomotive mechanisms: case studies for Gorilla robot brachiation. Autonomous Robots, 40(5), 849-865
Open this publication in new window or tab >>Algorithms for finding gaits of locomotive mechanisms: case studies for Gorilla robot brachiation
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2016 (English)In: Autonomous Robots, ISSN 0929-5593, E-ISSN 1573-7527, Vol. 40, no 5, p. 849-865Article in journal (Refereed) Published
Abstract [en]

We consider a model of a 24-degree-of-freedom monkey robot that is supposed to perform a brachiation locomotion, i.e. to swing from one row of a horizontal ladder to the next one using the arms. The robot hand is constructed as a planar hook so that the contact point, about which the robot swings, is a passive hinge. We identify the 10 most relevant degrees of freedom for this underactuated mechanical system and formulate a tractable search procedure consisting on the following steps: (a) to introduce a parametrized family of coordination patterns to be enforced on the dynamics with respect to a path coordinate; (b) to formulate geometric equality constraints that are necessary to achieve a periodic locomotion; (c) to generate trajectories from integrable reduced dynamics associated with the passive hinge; (d) to evaluate the energetic cost of transport. Moreover, we observe that a linear approximation of the reduced dynamics can be used for trajectory generation, which allows us to incorporate computation of an approximate gradient of the cost function into the search algorithm significantly improving the computational efficiency.

Keywords
Dynamic robot locomotion, Underactuated robots, Trajectory generation, Virtual holonomic nstraints, Numerical optimization
National Category
Robotics
Identifiers
urn:nbn:se:umu:diva-120353 (URN)10.1007/s10514-015-9497-1 (DOI)000374253200005 ()
Available from: 2016-05-25 Created: 2016-05-16 Last updated: 2018-06-07Bibliographically approved
Projects
Observatörsdesign och stabilisering av periodiska rörelser i underactuated mekaniska system [2010-01692_VR]; Umeå UniversityAUTOMATION AV FRONTASTARE FÖR JORDBRUKSTRAKTORER [2012-04172_VR]; Umeå University
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ORCID iD: ORCID iD iconorcid.org/0000-0003-0730-9441

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