PERANCANGAN SISTEM KONTROL VIBRASI PADA ROBOT SINGLE LINK FLEXIBLE JOINT MANIPULATOR DENGAN PID TUNING GENETIC ALGORITHM

Abstrak Single Link Flexible Joint Manipulator merupakan salah satu robot industri yang sering digunakan untuk berbagai macam produksi. Penggunaan dari Single Link Flexible Joint Manipulator sangat diperlukan karena memudahkan barang yang hendak didistribusikan ke beberapa tempat yang telah ditentukan. Umumnya flexible link memiliki beban yang lebih ringan untuk mencapai respon yang cepat dengan kebutuhan energi yang rendah serta hanya membutuhkan aktuator yang lebih kecil. Namun, sering terjadi masalah pada vibrasi pada manipulator sehingga terjadi kurang akurat pada titik akhir. Ketidakakuratan ini disebabkan karena adanya vibrasi dan defleksi statis pada interval waktu tertentu dengan gerakan bolak balik. Pada penelitian ini menggunakan PID tuning Genetic Algorithms untuk mengatasi masalah vibrasi pada manipulator. Setelah dilakukan penelitian, didapatkan parameter PID menggunakan metode Genetic Algorithm yaitu Kp = 4,728 ; Ki = 4,91 ; Kd = 0,857. Setelah menentukan parameter PID tersebut dan diterapkan pada sistem, didapatkan respon yang baik dengan tidak adanya overshoot pada sistem. Respon paling baik terdapat pada setpoint 5 dengan Time sampling (Ts) sebesar 0.7895s, Time delay (Td) sebesar 0.1858s, dan Time rise (Tr) sebesar 0,825s. Walaupun pada respon open loop memiliki Time sampling dan Time delay yang lebih baik, namun respon open loop masih memiliki overshoot sedangkan pada respon close loop tidak mengalami overshoot. Kata Kunci : Genetic Algorithm, Single Link Flexible Joint Manipulator, PID, Vibrasi. Abstract Single Link Flexible Joint Manipulator is one of the industrial robots that are often used for various kinds of production. The use of a Single Link Flexible Joint Manipulator is needed because it makes it easy to distribute goods from one place to another. Generally, flexible links have a lighter burden to achieve fast responses with low energy requirements and only requires smaller actuators. However, there is often a problem with vibrations in the manipulator so that it occurs less accurately at the end point. This inaccuracy is caused by static vibrations and deflections that are alternating movements within a certain time interval In this study using PID tuning Genetic Algorithms to overcome the problem of vibration in the manipulator. After doing research, PID parameters obtained using the Genetic Algorithm method, namely Kp = 4,728; Ki = 4.91; Kd = 0.857. After determining the PID parameters and applied to the system, a good response is obtained in the absence of overshoot on the system. The best response is at setpoint 5 with Time sampling (Ts) of 0.7895s, Time delay (Td) of 0.1858s, and Time rise (Tr) of 0.825s. Even though the open loop response has better Time sampling and Time delay, the open loop response still has overshoot while the close loop response does not experience overshoot. Keywords : Genetic Algorithm, PID, Single Link Flexible Joint Manipulator, Vibras

A Robust Controller Design Method for a Flexible Manipulator with a Large Time Varying Payload and Parameter Uncertainties

Abstract. A new robust controller design method is proposed to obtain a less conservative feedback controller and it is applied to a single-link flexible manipulator. The objective is to maximize the control performance guaranteeing the robust stability when regulating the tip position of the flexible manipulator in the presence of a large time-varying payload and parameter uncertainties such as stiffness and joint friction. A descriptor form representation, which allows separate treatment of payload uncertainty from other parametric uncertainties, is used to reduce the conservatism of the conventional robust control approaches. Uncertainty of the payload in the inertia matrix is represented by polytopic approach and the uncertain parameters in the damping and stiffness matrices are treated with descaling techniques. Using aforementioned techniques, the robust LQ controller design problem for a flexible manipulator based on the guaranteed cost approach is formulated. Then, the formulated problem is solved by LMIs

Modeling and control of a two-arm elastic robot in gravity

This thesis develops and experimentally verifies a model of a two arm robot with highly elastic arms. The model is later used in this research to evaluate control algorithms. The model includes the effects of gravity. The dimensions of the arms are chosen to maximize the coupling between the flexible and large scale motion of the robot. The model is then linearized and a new analytical solution is presented for the natural frequencies and mode shapes of the robot at given equilibrium positions. This analytical solution is then compared to the assumed mode shape solutions to determine the accuracy relative to the number of assumed modes included in the model. An experimental test rig is built and tests are conducted to verify the model. A number of different amounts of end mass and torsional stiffness at the joints are used during the validation. For 12 cases tested, the measured first four natural frequencies are within ±7% of the frequencies predicted by the model with an average error of only 2.89%. Finally, the model is used to design a control algorithm for end effector control of the robot using a torque input at each of the two joints. An optimal control algorithm developed using LQR with the prescribed degree of stability method results in effective end effector control with short response time and little overshoot

Dynamic modeling, property investigation, and adaptive controller design of serial robotic manipulators modeled with structural compliance

Research results on general serial robotic manipulators modeled with structural compliances are presented. Two compliant manipulator modeling approaches, distributed and lumped parameter models, are used in this study. System dynamic equations for both compliant models are derived by using the first and second order influence coefficients. Also, the properties of compliant manipulator system dynamics are investigated. One of the properties, which is defined as inaccessibility of vibratory modes, is shown to display a distinct character associated with compliant manipulators. This property indicates the impact of robot geometry on the control of structural oscillations. Example studies are provided to illustrate the physical interpretation of inaccessibility of vibratory modes. Two types of controllers are designed for compliant manipulators modeled by either lumped or distributed parameter techniques. In order to maintain the generality of the results, neither linearization is introduced. Example simulations are given to demonstrate the controller performance. The second type controller is also built for general serial robot arms and is adaptive in nature which can estimate uncertain payload parameters on-line and simultaneously maintain trajectory tracking properties. The relation between manipulator motion tracking capability and convergence of parameter estimation properties is discussed through example case studies. The effect of control input update delays on adaptive controller performance is also studied

Modelling and control of flexible manipulators

Structural flexibility is a characteristic of all robotic systems. Designing a high performance controller for a robot with a certain degree of link flexibility is not an easy task. This requires, not only a sound knowledge of the dynamics of the system to be controlled, but also a good characterization of the friction as well as an appropriate form of friction compensation. The presence of structural Vibrations in the system during and after high speed positioning makes the design of such a controller even more difficult. This thesis presents a method of modelling and controlling a single-link flexible manipulator for high speed precise end-point positioning. Several mathematicalmodels for a flexible robotic system are presented and described together with those for friction in the system. The parameters of the flexible system such as the natural frequencies, damping ratios and the parameters of friction, including Coulomb and Viscous friction coefficients, are identified offline, based on experimental data. Methods used for finding these parameters are described in detail. The objective of the control system is to move the flexible robot as fast as possible without producing vibrations at the end-point of the move. The position control of a single-link flexible robot is seen as a combination of two different problems namely trajectory planning and trajectory following. Two computational techniques, based on radial basis functions and the assumed-modes method, for planning the trajectories for a single-link flexible robot arm, are presented. These two techniques are compared with the aid of some numerical examples. In order to follow the derived trajectories, a combination of feedback and feedforward control along with a lead compensator is developed. The parameters of the compensator are found using an optimization process based on GeneticAlgorithms. Results of the experiments performed to verify the effectiveness of the proposed control strategy show that feedback control with feedforward compensation is more suitable than a simple feedback controller. Furthermore, these experiments also demonstrate the effectiveness of the trajectory planning process

From plain visualisation to vibration sensing: using a camera to control the flexibilities in the ITER remote handling equipment

Thermonuclear fusion is expected to play a key role in the energy market during the second half of this century, reaching 20% of the electricity generation by 2100. For many years, fusion scientists and engineers have been developing the various technologies required to build nuclear power stations allowing a sustained fusion reaction. To the maximum possible extent, maintenance operations in fusion reactors are performed manually by qualified workers in full accordance with the "as low as reasonably achievable" (ALARA) principle. However, the option of hands-on maintenance becomes impractical, difficult or simply impossible in many circumstances, such as high biological dose rates. In this case, maintenance tasks will be performed with remote handling (RH) techniques. The International Thermonuclear Experimental Reactor ITER, to be commissioned in southern France around 2025, will be the first fusion experiment producing more power from fusion than energy necessary to heat the plasma. Its main objective is “to demonstrate the scientific and technological feasibility of fusion power for peaceful purposes”. However ITER represents an unequalled challenge in terms of RH system design, since it will be much more demanding and complex than any other remote maintenance system previously designed. The introduction of man-in-the-loop capabilities in the robotic systems designed for ITER maintenance would provide useful assistance during inspection, i.e. by providing the operator the ability and flexibility to locate and examine unplanned targets, or during handling operations, i.e. by making peg-in-hole tasks easier. Unfortunately, most transmission technologies able to withstand the very specific and extreme environmental conditions existing inside a fusion reactor are based on gears, screws, cables and chains, which make the whole system very flexible and subject to vibrations. This effect is further increased as structural parts of the maintenance equipment are generally lightweight and slender structures due to the size and the arduous accessibility to the reactor. Several methodologies aiming at avoiding or limiting the effects of vibrations on RH system performance have been investigated over the past decade. These methods often rely on the use of vibration sensors such as accelerometers. However, reviewing market shows that there is no commercial off-the-shelf (COTS) accelerometer that meets the very specific requirements for vibration sensing in the ITER in-vessel RH equipment (resilience to high total integrated dose, high sensitivity). The customisation and qualification of existing products or investigation of new concepts might be considered. However, these options would inevitably involve high development costs. While an extensive amount of work has been published on the modelling and control of flexible manipulators in the 1980s and 1990s, the possibility to use vision devices to stabilise an oscillating robotic arm has only been considered very recently and this promising solution has not been discussed at length. In parallel, recent developments on machine vision systems in nuclear environment have been very encouraging. Although they do not deal directly with vibration sensing, they open up new prospects in the use of radiation tolerant cameras. This thesis aims to demonstrate that vibration control of remote maintenance equipment operating in harsh environments such as ITER can be achieved without considering any extra sensor besides the embarked rad-hardened cameras that will inevitably be used to provide real-time visual feedback to the operators. In other words it is proposed to consider the radiation-tolerant vision devices as full sensors providing quantitative data that can be processed by the control scheme and not only as plain video feedback providing qualitative information. The work conducted within the present thesis has confirmed that methods based on the tracking of visual features from an unknown environment are effective candidates for the real-time control of vibrations. Oscillations induced at the end effector are estimated by exploiting a simple physical model of the manipulator. Using a camera mounted in an eye-in-hand configuration, this model is adjusted using direct measurement of the tip oscillations with respect to the static environment. The primary contribution of this thesis consists of implementing a markerless tracker to determine the velocity of a tip-mounted camera in an untrimmed environment in order to stabilise an oscillating long-reach robotic arm. In particular, this method implies modifying an existing online interaction matrix estimator to make it self-adjustable and deriving a multimode dynamic model of a flexible rotating beam. An innovative vision-based method using sinusoidal regression to sense low-frequency oscillations is also proposed and tested. Finally, the problem of online estimation of the image capture delay for visual servoing applications with high dynamics is addressed and an original approach based on the concept of cross-correlation is presented and experimentally validated