Simultaneous precision positioning and vibration suppression of reciprocating flexible manipulators

Ma, Kougen,Ghasemi-Nejhad, Mehrdad N. Techno-Press 2005 Smart Structures and Systems, An International Jou Vol.1 No.1

Simultaneous precision positioning and vibration suppression of a reciprocating flexible manipulator is investigated in this paper. The flexible manipulator is driven by a multifunctional active strut with fuzzy logic controllers. The multifunctional active strut is a combination of a motor assembly and a piezoelectric stack actuator to simultaneously provide precision positioning and wide frequency bandwidth vibration suppression capabilities. First, the multifunctional active strut and the flexible manipulator are introduced, and their dynamic models are derived. A control strategy is then proposed, which includes a position controller and a vibration controller to achieve simultaneous precision positioning and vibration suppression of the flexible manipulator. Next, fuzzy logic control approach is presented to design a fuzzy logic position controller and a fuzzy logic vibration controller. Finally, experiments are conducted for the fuzzy logic controllers and the experimental results are compared with those from a PID control scheme consisting of a PID position controller and a PID vibration control. The comparison indicates that the fuzzy logic controller can easily handle the non-linearity in the strut and provide higher position accuracy and better vibration reduction with less control power consumption.

Impedance Control of Flexible Base Mobile Manipulator Using Singular Perturbation Method and Sliding Mode Control Law

Mahdi Salehi,Gholamreza Vossoughi 대한전기학회 2008 International Journal of Control, Automation, and Vol.6 No.5

In this paper, the general problem of impedance control for a robotic manipulator with a moving flexible base is addressed. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base mobile manipulator is rather new and is being considered for first time using singular perturbation and new sliding mode control methods by authors. Initially slow and fast dynamics of robot are decoupled using singular perturbation method. Slow dynamics represents the dynamics of the manipulator with rigid base. Fast dynamics is the equivalent effect of the flexibility in the base. Then, using sliding mode control method, an impedance control law is derived for the slow dynamics. The asymptotic stability of the overall system is guaranteed using a combined control law comprising the impedance control law and a feedback control law for the fast dynamics. As first time, base flexibility was analyzed accurately in this paper for flexible base moving manipulator (FBMM). General dynamic decoupling, whole system stability guarantee and new composed robust control method were proposed. This proposed Sliding Mode Impedance Control Method (SMIC) was simulated for two FBMM models. First model is a simple FBMM composed of a 2 DOFs planar manipulator and a single DOF moving base with flexibility in between. Second FBMM model is a complete advanced 10 DOF FBMM composed of a 4 DOF manipulator and a 6 DOF moving base with flexibility. This controller provides desired position/force control accurately with satisfactory damped vibrations especially at the point of contact. This is the first time that SMIC was addressed for FBMM.

Design of the flexible switching controller for small PWR core power control with the multi-model

Zeng, Wenjie,Jiang, Qingfeng,Du, Shangmian,Hui, Tianyu,Liu, Yinuo,Li, Sha Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.3

Small PWR can be used for power generation and heating. Considering that small PWR has the characteristics of flexible operating conditions and complex operating environment, the controller designed based on single power level is difficult to achieve the ideal control of small PWR in the whole range of core power range. To solve this problem, a flexible switching controller based on fuzzy controller and LQG/LTR controller is designed. Firstly, a core fuzzy multi-model suitable for full power range is established. Then, T-S fuzzy rules are designed to realize the flexible switching between fuzzy controller and LQG/LTR controller. Finally, based on the core power feedback principle, the core flexible switching control system of small PWR is established and simulated. The results show that the flexible switching controller can effectively control the core power of small PWR and the control effect has the advantages of both fuzzy controller and LQG/LTR controller.

Experimental studies of control concepts for a parallel manipulator with flexible links

Markus Burkhardt,Robert Seifried,Peter Eberhard 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.7

Control of flexible multibody systems, such as flexible manipulators, is a challenging task. This is especially true if end-effector trajectorytracking is aspired. On the one hand, these systems require a large number of generalized coordinates to describe their dynamicalbehavior accurately. On the other hand, only a small subset of these values can be measured or reconstructed on-the-fly. Hence, it is difficult,if not nearly impossible, to use a state controller. In addition, flexible systems are underactuated, i.e. they possess less control inputsthan generalized coordinates. In case of a non-collocated output controller, which is the case for end-effector trajectory tracking, theclosed loop of the system might lose passivity and is non-minimum phase. In order to achieve end-effector trajectory tracking, exact andapproximate feed-forward controls can be applied. In this work, two different versions of such concepts are compared experimentally. These model-based concepts are computed off-line and they supply, next to the required input values, a C1-continuous solution of thecomplete state vector which can be used for feedback control. If the system is non-minimum phase, a two-sided boundary value problemhas to be solved and the solution includes a pre-actuation as well as a post-actuation phase. While the exact method incorporates all dynamicaleffects of the flexible multibody system, the approximate concepts neglect certain implications, for example the dynamical effectsdue to the flexibility. In addition to the presentation of the theoretical basics of the control approaches and the underlying models,this contribution addresses some of the crucial obstacles, which have to be overcome for the operation of the test bench, e.g., signal conditioning,state reconstruction and friction compensation. Since the installed sensors do not allow the direct measurement of the endeffectorposition, image tracking is used to judge the quality of the different control approaches.

Modified Bilateral Control by Using Intervention Impedance Based on Passivity of Flexible Master-Slave Manipulators and Its Design Methods

Takahiko Mori 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

Recently,study on a control of flexible manipulators have been receiving increasing attension in the domain of master-slave system. The master-slave system is a control system to operate a manipulator for objects in a remote environment which is at a distance from the presence of a human operator. In order to consider the influence by the elasticity of flexible manipulators, it is necessary to study on the control of vibration of flexible master-slave manipulators and the passivity. Thus in this paper, we discuss about a new modified bilateral controller considering the elasticity by using intervention impedance in basis on the passivity and a control performance of the system. This paper is organized in the following way : First, we introduce mechanical models of manipulators. Second, we propose bilateral controls by using intervention impedance based on passivity. Third, we transeform each models represented by time domain into models represented by s-plain, find the scattering matrix,and prove the passivity of system. Fourth, we propose a new modified controller controller for the purpose of realizaion. Lastly, we show some results of experiments in order to verify the usefulness of proposed controller.

The Influence of Structural Dynamics on Cascaded Joint Position Control of a Flexible Beam with a Compliant Gear

Tobias F. C. Berninger,Chenhong Huang,Marvin A. Ochsenius,Daniel J. Rixen 제어로봇시스템학회 2019 제어로봇시스템학회 국제학술대회 논문집 Vol.2019 No.10

The structural dynamics of a robot manipulator can have a large influence on its overall dynamic behavior. They can cause unwanted resonances, limit the control bandwidth and lead to instability. For this reason, a significant amount of research has focused on the development of advanced control methods which consider the structural dynamics of a robot. These techniques are, however, still rarely employed in practice due to their complex nature and reliance on accurate models. A popular decentralized control scheme for robot joints is cascaded position, velocity and current control of the motor. The goal of this paper is to visualize the influence of the structural dynamics of a flexible beam and flexible harmonic drive gear on this type of joint controller. The derived effects are explained by mainly relying on simulated and measured transfer functions, without the use of the typical equations. The difference between closing the control loop with position feedback from the motor side or on the joint side after the flexible gear is also investigated. The results are first generated using a flexible multibody simulation and later verified on a robot joint test rig.

전작권 전환 정상추진과 한미동맹의 비전

정경영 ( Kyung Young Chung ) 한국군사학회 2013 군사논단 Vol.74 No.-

The transition of wartime operational control and North Korea`s nuclear issue is an issue of national identity and survival. The idea to defer the transition of wartime operational control before North Korea`s nuclear issue is resolved seems like a strategy that guarantees South Korea`s national security. This opinion is similar to the logic that as long as the current North Korean regime exists, because North Korea will never abandon nuclear weapons for regime stability, securing of economic support, holding South Korea as hostage, and nuclear attack and threat, South Korea will never be able to accomplish the transition of wartime operational control. As long as wartime operational control isn`t normalized, South Korea will continue to be in a situation being dragged around by a dictatorship regime and a nuclear-armed North Korea. The transition of wartime operation control implies the following significance in terms of the fundamental changes in the national security of the Republic of Korea. First, exercising operational control over the ROK Armed Forces is essential for pursuing unification during both peacetime and wartime. Second, by recovering national identity and securing autonomous employment of military forces, South Korea will be able to deter North Korean military adventurism and promptly and decisively retaliate in the event of any provocation. The transition of wartime operational control provides a momentum for expanding South Korean diplomatic activity by demonstrating a more independent foreign policy. Those who oppose this transition insist that the implementation of the transition of wartime operation control by December 2015 will inevitably dismantle the ROK-US combined defense system and will have a severe impact on the security capability of the country. They also reason out that the implementation of the wartime operational control transition could induce US forces to pull out of the peninsula and eventually end the ROK-US Alliance. In particular, it will be more difficult for the US Government to deploy augmentation forces to the Korean Peninsula in the event of war because the transition turns the alliance into a mere cooperative relationship. Hence, there will no longer be automatic support and deployment in the event of war. Finally, the fact that the pre-planned war fighting capability project was not executed because of national defense budget constraints makes it more practical, they insist, to delay the implementation of the transition. It is for these intertwining reasons that some factions oppose the planned wartime operational control transition scheduled on December 1, 2015. However, the counter arguments to all of these are strong. The wartime operational control transition must be implemented as planned because the North Korean nuclear crisis and OPCON issues should be managed separately from each other. Moreover, the North is exploiting the South`s heavy dependence on the US. North Korea views the South as having no authority to command its own forces. Pyongyang therefore would rather push for a bilateral talk with Washington instead of dealing with Seoul. This is a vulnerability for South Korea and is continuously being exploited by Pyongyang. Furthermore, even though the transition pushes through as planned, the US will continue to have a presence on the Korean Peninsula because of the threat posed by China in the region. The US will want to exercise USFK strategic flexibility in dealing with potential Chinese threats. Also the US War Power Act enables the US President to mobilize forces to be deployed in the Korean theater without prior approval from the US Congress. Finally, the vulnerable ROK war-fighting capability could be integrated by the US bridging capabilities. The North Korean nuclear and missile threat that continues to be the reason why some people oppose the implementation of wartime operation control transition should be resolved by the US extended deterrence and South Korea`s own comprehensive strategies. During and after the Key Resolved Combined Exercise last Spring, the US has demonstrated its resolve and commitment to defend the Republic of Korea against the nuclear and missile threats posed by the North, mainly through power projection. The US power projection was exhibited through sending B52 and B2 bombers, as well as F22 fighter jets and a Nimitz Class Aircraft Carrier from Okinawa, Guam and even from as far as the continental United States. All of these should erase any doubt against the US commitment to the defense of the Republic of Korea. Meanwhile, South Korea should continue to develop preemptive action to prevent any disaster resulting from a nuclear attack. The Kill-Chain System as well as the Korean Air Missile Defense System should be established. Seoul needs to acquire Global Hawk and develop ballistic missiles to neutralize North Korea`s missile capability. Moreover, a diplomatic track should also be explored by institutionalizing the trilateral strategic talks among Seoul, Washington and Beijing in order to prevent further military provocations from Pyongyang. It could also be a venue to induce North Korea to become a responsible member of the community of nations in the region. Further, South Korea should actively join international consortium for Cross-border Regional Economic Development with China, North Korea and Russia as partners. Our two countries have made every effort for the preparation of the wartime operation control transition in accordance with Strategic Alliance 2015, such as the ROK-JCS Military Structure reorganization, reinforcement of ROK war fighting capability, and a joint war plan and strategic directives that will be applicable to ROK-US Combined Forces after the transition of wartime operation control. An evaluation team will report the results to the 2015 Security Consultative Meeting. Eventually, by the 1st of December 2015, the transition of wartime operation control will be executed. There were critical agreements and joint communiqu? between the two governments. First, the ROK Chairman of JCS and the USFK Commander signed a joint operation plan against North Korean provocation on March 22nd. Second, during Park Geun-hye`s visit to Washington, both presidents proclaimed a join communiqu? on the 60th Anniversary of the ROK-US Alliance. President Obama made it clear that the transition of wartime operation control should be implemented as planned. Third, the Defense Ministerial Talks between the US and ROK, which was held in Singapore on May 31, 2013 reconfirmed the preplanned implementation of the transition, including the review of ROK-US theater command to be commanded by the ROK Chairman of the JCS supported by USFK Commander as deputy commander. These imply a strong determination from both governments to implement the mutually agreed wartime operation control transition. Finally, the President of South Korea should initiate quarterly wartime operation control transition preparedness conference. This is to facilitate bipartisan and public support. A synchronized effort by the presidential leadership will enable South Korea to smoothly implement the transition of wartime operation control as planned by December 1, 2015. This historical epochal event, the transition of wartime operation control, indicates that South Korea is taking off as a strong and rich nation. This would deter the North from ever challenging the resolve of the country again through provocations. The ROK-US Alliance will be a great model by achieving industrialization and democratization, followed by self-reliant defense of the Republic of Korea.

Semi-Active Operation Assist Control Device for Manual Conveyance of Flexible Parts

Kensuke Yamaguchi,Michihiro Takeshige,Noritaka Sato,Yoshifumi Morita,Hiroyuki Ukai,Susumu Hara 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

This paper proposes an assist-handle for manual conveyance of flexible part and its semi-active operation assist control. The assist-handle consists of a handle, a variable damper and a mechanical spring. The variable damper and the mechanical spring are connected in parallel. The assist-handle can be attached to a general hand cart, through which a human operates the hand cart. In order to suppress the vibration of the flexible part, the operating force is shaped by changing the viscosity of variable damper. Then the shaped force is transmitted to the hand cart through the assist-handle. The controlled system, which consists of the assist-handle, a hand cart and a flexible part, is represented as a bilinear system. The semi-active operation assist control is designed by using the bilinear optimal control theory. The performance index of bilinear optimal control involves the vibration of the flexible part and the control input. The effectiveness of the assist-handle and the semi-active operation assist control is verified by simulations.

Active Vibration Isolator with Feed-forward Augmented Control Taking Account of Dynamics of Elastic Load

Junya HIJIOKA,Hazime SHIRAISHI,Toru WATANABE,Kazuto SETO 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-

This paper deals with control system design for active isolation table. If elastic loads are put on the isolation table, vibration modes of the table are changed. Therefore, the controllers for the active isolation table should be designed taking account of elastic loads. According to this fact, a dynamical model must be identified that takes the dynamics of elastic loads into consideration for such controllers. In this research, an experimental active isolation table with an elastic load is built. Its dynamical model is identified by using experimental modal analysis or FEM analysis. A controller is designed by using the model according to sub-optimal control theory, absolute velocity feed-back control theory and feed-forward control theory. Property of the obtained controller is qualified through computer simulations and control experiments.

A Comprehensive Survey of Optimal Placement and Coordinated Control Techniques of FACTS Controllers in Multi-Machine Power System Environments

Bindeshwar Singh,N. K. Sharma,A. N. Tiwari 대한전기학회 2010 Journal of Electrical Engineering & Technology Vol.5 No.1

This paper presents exhaustive review of various methods/techniques for coordinated control between FACTS controllers in multi-machine power systems. It also reviews various techniques/methods for optimal choice and allocation of FACTS controllers. Authors strongly believe that this survey article will be very much useful to the researchers for finding out the relevant references in the field of placement and coordination of FACTS Controllers.