{"id":{"repo_id":"nus","oai_identifier":"oai:scholarbank.nus.edu.sg:10635/179141"},"canonical_url":"https://search.dev.ndltd.org/etd/nus/oai:scholarbank.nus.edu.sg:10635/179141","repository":{"repo_id":"nus","name":"National University of Singapore","base_url":"https://scholarbank.nus.edu.sg/oai/request"},"display":{"title":"DEVELOPMENT OF ADAPTIVE ROBUST SCHEMES FOR NONLINEAR UNCERTAIN SYSTEMS","abstract":"This thesis presents new developments in several different techniques to enhance the performance of control systems applicable to some classes of nonlinear uncertain systems. Associating the adaptive control techniques with other control methods, such as backstepping control method and variable structure control method, we propose new adaptive robust control schemes for nonlinear dynamical systems with both structured and unstructured system uncertainties. The adaptive robust methods are further applied to deal with various classes of uncertain systems and control problems, which are often encountered in engineering practice: • Cascaded control systems without parametric-pure feedback form; • Singular control systems; • Control systems with time-delay; • Non Minimum phase control systems; • Permanent Magnet Synchronous (PMS) motor control systems; • State estimation of control systems; • Derivative estimation problem. The thesis consists of five technical parts, each of which focuses on specific control problems. First an adaptive robust control method is presented for a class of nonlinear uncertain systems. A new update scheme, referred to as u-modification scheme, is proposed to clamp parameter adaptation in accordance with the adaptive robust control law. The novel property possessed by the new control scheme is that it guarantees the uniform boundedness of the system and at the same time, the tracking error enters an arbitrarily designated zone in a finite time. By using backstepping control method, the new control scheme is further extended to a class of cascaded nonlinear uncertain systems. The systems to be controlled are not required to be in the parametric-pure feedback form, which is usually necessary for the application of backstepping control scheme. The new adaptive robust control methods proposed above are applied in second technical part to deal with two classes of nonlinear uncertain systems: one is a class of uncertain dynamical systems with time-varying state delay, and the other is a class of nonlinear uncertain descriptor systems. The proposed controller for time-delayed systems is completely independent of the time-delay, thus the results are applicable to a class of dynamical systems with uncertain time delays. For uncertain descriptor systems, two adaptive robust control schemes are proposed. The first control scheme achieves asymptotic stability of the closed loop descriptor system. To avoid any potential problems such as parameter drift by unmodeled dynamics, in second control scheme, which guarantees the uniform boundedness of the system, the adaptation is \"damped\" when the control performance gets into the desirable region. In the third technical part, adaptive methods are incorporated into VSC scheme to design a continuum, integral variable structure controller (IVSC) for perturbed SISO systems. The proposed control strategy is further extended to non minimum-phase cases. It is well known that an extremely difficult task in VSC design is how to handle non minimum-phase plants, even if those unstable zeros are known a priori. The new IVSC method is also applied to a new class of uncertain systems in which the distribution matrix of system inputs is unknown. While focusing on adaptive robust control method design for uncertain dynamical systems in the previous parts, in the fourth technical part we put our research interest on system estimation in the presence of modeling uncertainties and system disturbances. By making use of interior point method [84], adaptive robust observer design for a class of nonlinear uncertain systems is first discussed. Then using variable structure system (VSS) and adaptive algorithms, a new derivative estimator is proposed. The new adaptive variable structure derivative estimator can adapt itself to possibly unpredictable parametric changes in system noise, and meanwhile significantly reduce the chattering to achieve much smooth derivative estimation in comparison with the existing variable structure derivative estimator. Finally, in the fifth technical part , a comparative study is made on control schemes suitable for PMS motors. Adaptive control, robust control, discontinuous adaptive robust control and continuous adaptive robust control methods are applied to address control problems for the same PMS model respectively. It is shown that the continuous adaptive robust controller is superior to other controllers in the sense that it achieves better tracking performance by combining the features of adaptive control with those of robust control, and at the same time significantly reduces the control input chattering associated with adaptive robust control using switching functions. In all these developments, the analytical properties of the overall systems are described, and the results are verified with simulation-based studies.","abstract_html":"This thesis presents new developments in several different techniques to enhance the performance of control systems applicable to some classes of nonlinear uncertain systems. Associating the adaptive control techniques with other control methods, such as backstepping control method and variable structure control method, we propose new adaptive robust control schemes for nonlinear dynamical systems with both structured and unstructured system uncertainties. The adaptive robust methods are further applied to deal with various classes of uncertain systems and control problems, which are often encountered in engineering practice: • Cascaded control systems without parametric-pure feedback form; • Singular control systems; • Control systems with time-delay; • Non Minimum phase control systems; • Permanent Magnet Synchronous (PMS) motor control systems; • State estimation of control systems; • Derivative estimation problem. The thesis consists of five technical parts, each of which focuses on specific control problems. First an adaptive robust control method is presented for a class of nonlinear uncertain systems. A new update scheme, referred to as u-modification scheme, is proposed to clamp parameter adaptation in accordance with the adaptive robust control law. The novel property possessed by the new control scheme is that it guarantees the uniform boundedness of the system and at the same time, the tracking error enters an arbitrarily designated zone in a finite time. By using backstepping control method, the new control scheme is further extended to a class of cascaded nonlinear uncertain systems. The systems to be controlled are not required to be in the parametric-pure feedback form, which is usually necessary for the application of backstepping control scheme. The new adaptive robust control methods proposed above are applied in second technical part to deal with two classes of nonlinear uncertain systems: one is a class of uncertain dynamical systems with time-varying state delay, and the other is a class of nonlinear uncertain descriptor systems. The proposed controller for time-delayed systems is completely independent of the time-delay, thus the results are applicable to a class of dynamical systems with uncertain time delays. For uncertain descriptor systems, two adaptive robust control schemes are proposed. The first control scheme achieves asymptotic stability of the closed loop descriptor system. To avoid any potential problems such as parameter drift by unmodeled dynamics, in second control scheme, which guarantees the uniform boundedness of the system, the adaptation is "damped" when the control performance gets into the desirable region. In the third technical part, adaptive methods are incorporated into VSC scheme to design a continuum, integral variable structure controller (IVSC) for perturbed SISO systems. The proposed control strategy is further extended to non minimum-phase cases. It is well known that an extremely difficult task in VSC design is how to handle non minimum-phase plants, even if those unstable zeros are known a priori. The new IVSC method is also applied to a new class of uncertain systems in which the distribution matrix of system inputs is unknown. While focusing on adaptive robust control method design for uncertain dynamical systems in the previous parts, in the fourth technical part we put our research interest on system estimation in the presence of modeling uncertainties and system disturbances. By making use of interior point method [84], adaptive robust observer design for a class of nonlinear uncertain systems is first discussed. Then using variable structure system (VSS) and adaptive algorithms, a new derivative estimator is proposed. The new adaptive variable structure derivative estimator can adapt itself to possibly unpredictable parametric changes in system noise, and meanwhile significantly reduce the chattering to achieve much smooth derivative estimation in comparison with the existing variable structure derivative estimator. Finally, in the fifth technical part , a comparative study is made on control schemes suitable for PMS motors. Adaptive control, robust control, discontinuous adaptive robust control and continuous adaptive robust control methods are applied to address control problems for the same PMS model respectively. It is shown that the continuous adaptive robust controller is superior to other controllers in the sense that it achieves better tracking performance by combining the features of adaptive control with those of robust control, and at the same time significantly reduces the control input chattering associated with adaptive robust control using switching functions. In all these developments, the analytical properties of the overall systems are described, and the results are verified with simulation-based studies.","abstract_has_math":false,"creators":["JIA QINGWEI"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1999,"date_issued":"1999","date_published":"1999","updated_at":"2026-07-24T03:33:34Z","subjects":[],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["JIA QINGWEI"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["1999"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://scholarbank.nus.edu.sg/handle/10635/179141"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://scholarbank.nus.edu.sg/bitstreams/b2fac6a1-89d7-4a50-bb9d-aa7856823279/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This thesis presents new developments in several different techniques to enhance the performance of control systems applicable to some classes of nonlinear uncertain systems. Associating the adaptive control techniques with other control methods, such as backstepping control method and variable structure control method, we propose new adaptive robust control schemes for nonlinear dynamical systems with both structured and unstructured system uncertainties. The adaptive robust methods are further applied to deal with various classes of uncertain systems and control problems, which are often encountered in engineering practice: • Cascaded control systems without parametric-pure feedback form; • Singular control systems; • Control systems with time-delay; • Non Minimum phase control systems; • Permanent Magnet Synchronous (PMS) motor control systems; • State estimation of control systems; • Derivative estimation problem. The thesis consists of five technical parts, each of which focuses on specific control problems. First an adaptive robust control method is presented for a class of nonlinear uncertain systems. A new update scheme, referred to as u-modification scheme, is proposed to clamp parameter adaptation in accordance with the adaptive robust control law. The novel property possessed by the new control scheme is that it guarantees the uniform boundedness of the system and at the same time, the tracking error enters an arbitrarily designated zone in a finite time. By using backstepping control method, the new control scheme is further extended to a class of cascaded nonlinear uncertain systems. The systems to be controlled are not required to be in the parametric-pure feedback form, which is usually necessary for the application of backstepping control scheme. The new adaptive robust control methods proposed above are applied in second technical part to deal with two classes of nonlinear uncertain systems: one is a class of uncertain dynamical systems with time-varying state delay, and the other is a class of nonlinear uncertain descriptor systems. The proposed controller for time-delayed systems is completely independent of the time-delay, thus the results are applicable to a class of dynamical systems with uncertain time delays. For uncertain descriptor systems, two adaptive robust control schemes are proposed. The first control scheme achieves asymptotic stability of the closed loop descriptor system. To avoid any potential problems such as parameter drift by unmodeled dynamics, in second control scheme, which guarantees the uniform boundedness of the system, the adaptation is \"damped\" when the control performance gets into the desirable region. In the third technical part, adaptive methods are incorporated into VSC scheme to design a continuum, integral variable structure controller (IVSC) for perturbed SISO systems. The proposed control strategy is further extended to non minimum-phase cases. It is well known that an extremely difficult task in VSC design is how to handle non minimum-phase plants, even if those unstable zeros are known a priori. The new IVSC method is also applied to a new class of uncertain systems in which the distribution matrix of system inputs is unknown. While focusing on adaptive robust control method design for uncertain dynamical systems in the previous parts, in the fourth technical part we put our research interest on system estimation in the presence of modeling uncertainties and system disturbances. By making use of interior point method [84], adaptive robust observer design for a class of nonlinear uncertain systems is first discussed. Then using variable structure system (VSS) and adaptive algorithms, a new derivative estimator is proposed. The new adaptive variable structure derivative estimator can adapt itself to possibly unpredictable parametric changes in system noise, and meanwhile significantly reduce the chattering to achieve much smooth derivative estimation in comparison with the existing variable structure derivative estimator. Finally, in the fifth technical part , a comparative study is made on control schemes suitable for PMS motors. Adaptive control, robust control, discontinuous adaptive robust control and continuous adaptive robust control methods are applied to address control problems for the same PMS model respectively. It is shown that the continuous adaptive robust controller is superior to other controllers in the sense that it achieves better tracking performance by combining the features of adaptive control with those of robust control, and at the same time significantly reduces the control input chattering associated with adaptive robust control using switching functions. In all these developments, the analytical properties of the overall systems are described, and the results are verified with simulation-based studies."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["ce649c3ca766aec64373af5fb3c8f39a","a9dc85de836586710c83c7b7284c9f12"]},{"key":"dc:title","label":"Title","values":["DEVELOPMENT OF ADAPTIVE ROBUST SCHEMES FOR NONLINEAR UNCERTAIN SYSTEMS"]}]}],"canonical_facts":{"dc:creator":["JIA QINGWEI"],"dc:date.issued":["1999"],"dc:description.abstract":["This thesis presents new developments in several different techniques to enhance the performance of control systems applicable to some classes of nonlinear uncertain systems. Associating the adaptive control techniques with other control methods, such as backstepping control method and variable structure control method, we propose new adaptive robust control schemes for nonlinear dynamical systems with both structured and unstructured system uncertainties. The adaptive robust methods are further applied to deal with various classes of uncertain systems and control problems, which are often encountered in engineering practice: • Cascaded control systems without parametric-pure feedback form; • Singular control systems; • Control systems with time-delay; • Non Minimum phase control systems; • Permanent Magnet Synchronous (PMS) motor control systems; • State estimation of control systems; • Derivative estimation problem. The thesis consists of five technical parts, each of which focuses on specific control problems. First an adaptive robust control method is presented for a class of nonlinear uncertain systems. A new update scheme, referred to as u-modification scheme, is proposed to clamp parameter adaptation in accordance with the adaptive robust control law. The novel property possessed by the new control scheme is that it guarantees the uniform boundedness of the system and at the same time, the tracking error enters an arbitrarily designated zone in a finite time. By using backstepping control method, the new control scheme is further extended to a class of cascaded nonlinear uncertain systems. The systems to be controlled are not required to be in the parametric-pure feedback form, which is usually necessary for the application of backstepping control scheme. The new adaptive robust control methods proposed above are applied in second technical part to deal with two classes of nonlinear uncertain systems: one is a class of uncertain dynamical systems with time-varying state delay, and the other is a class of nonlinear uncertain descriptor systems. The proposed controller for time-delayed systems is completely independent of the time-delay, thus the results are applicable to a class of dynamical systems with uncertain time delays. For uncertain descriptor systems, two adaptive robust control schemes are proposed. The first control scheme achieves asymptotic stability of the closed loop descriptor system. To avoid any potential problems such as parameter drift by unmodeled dynamics, in second control scheme, which guarantees the uniform boundedness of the system, the adaptation is \"damped\" when the control performance gets into the desirable region. In the third technical part, adaptive methods are incorporated into VSC scheme to design a continuum, integral variable structure controller (IVSC) for perturbed SISO systems. The proposed control strategy is further extended to non minimum-phase cases. It is well known that an extremely difficult task in VSC design is how to handle non minimum-phase plants, even if those unstable zeros are known a priori. The new IVSC method is also applied to a new class of uncertain systems in which the distribution matrix of system inputs is unknown. While focusing on adaptive robust control method design for uncertain dynamical systems in the previous parts, in the fourth technical part we put our research interest on system estimation in the presence of modeling uncertainties and system disturbances. By making use of interior point method [84], adaptive robust observer design for a class of nonlinear uncertain systems is first discussed. Then using variable structure system (VSS) and adaptive algorithms, a new derivative estimator is proposed. The new adaptive variable structure derivative estimator can adapt itself to possibly unpredictable parametric changes in system noise, and meanwhile significantly reduce the chattering to achieve much smooth derivative estimation in comparison with the existing variable structure derivative estimator. Finally, in the fifth technical part , a comparative study is made on control schemes suitable for PMS motors. Adaptive control, robust control, discontinuous adaptive robust control and continuous adaptive robust control methods are applied to address control problems for the same PMS model respectively. It is shown that the continuous adaptive robust controller is superior to other controllers in the sense that it achieves better tracking performance by combining the features of adaptive control with those of robust control, and at the same time significantly reduces the control input chattering associated with adaptive robust control using switching functions. In all these developments, the analytical properties of the overall systems are described, and the results are verified with simulation-based studies."],"dc:format.checksum.md5":["ce649c3ca766aec64373af5fb3c8f39a","a9dc85de836586710c83c7b7284c9f12"],"dc:identifier.uri":["https://scholarbank.nus.edu.sg/bitstreams/b2fac6a1-89d7-4a50-bb9d-aa7856823279/download"],"dc:relation.isreferencedby":["https://scholarbank.nus.edu.sg/handle/10635/179141"],"dc:title":["DEVELOPMENT OF ADAPTIVE ROBUST SCHEMES FOR NONLINEAR UNCERTAIN SYSTEMS"],"dc:type":["Thesis"]},"updated_at":"2026-07-24T03:33:34Z"}