Sliding model control for a flexible robot arm

The purpose of this study is to control simultaneously, motion and vibration of flexible 2-link robot arms. For this purpose, we had used modeling method called an 'extended reduced-order physical model (extended model)' to make a model of one-link flexible robot arm. The model of the flexible 2-link robot arms is made of a combination of the model of each link that is regarded as one link flexible robot arm. To connect each link, the constraint addition method is used. This is creating method of an equation of motion in multi-body systems. It is verified that the results of the simulation are effective for control of flexible 2-link robot arms.

This paper discusses the open loop control problem of a flexible joint robot that is oriented in the vertical plane. This orientation of the robot arm introduces gravity constraints and imposes undesirable nonlinear behavior. Friction is also added at the joints to increase the accuracy of the model. Including these dynamics to the robot arm amplifies the open loop control problem. Differential flatness is used to propose a feed-forward control that compensates for these nonlinearities and is able to smoothly steer the robot from rest to rest positions. The proposed control is achieved without solving any differential equations which makes the approach computationally attractive. Simulations show the effectiveness of the open loop control design on a single link flexible joint robot arm.

This paper studies the effectiveness of various controller design approaches on a flexible robot arm. The robot arm model used is that of Cannon-Schmitz flexible one-link robot. It is shown that the conventional PI controller cannot stabilize the closed-loop system. The idea of controller design using the stable factorization approach is explored. The controller design procedures, both with and without constraints on the actuator torque are discussed. The simulation results shows better system performance can be achieved by using these controllers instead of conventional LQG controller. The conclusion of this paper is that the stable factorizatlon approach has great potential in the area of flexible robot arm control.

This paper describes the investigation of a flexible robotic arm with Degree of Freedom (DOF) through Linear Quadratic Gaussian (LQG) regulator under the influence of noise signals with using diagrams below. The derived model is based on the Euler-Lagrange approach while LQG mode is proposed as a modern control method. A flexible robotic arm that is test in the modern regulator is essential for applications. This is even more interesting while these arms have joints that work independently of each other, but they still ensure a tight connection between the joints. Testing the stability characteristics of the system through this regulator helps readers determine the output signals of a system exactly. From here, the author came up with strategies the match the requirements. Although the initial stage of the operating cycle is not stable with the use of LQG regulator, most of later stages of this process of closed systems of robotic systems gradually become stable. In particular, adjusting LQG for flexible joint robot gives satisfactory simulation results. This promises a positive result of other joint robot. Neural networks applied in this paper have proven its effectiveness in information security issues. It is also very useful for tight control of possible situations such as a large scale attack on network systems, automated control systems. The main contributions of this paper have been clearly demonstrated through two strategies that need to be addressed: LQG, neural networks for the data of LQG regulator.The methods described above have not been previously published for this model. Therefore, this article was born to outline the above objectives and the plans have been satisfactorily implemented. These studies are important because they serve as a necessary database in the selection of control strategies according to the requirements. Simulation results are done by Matlab. The purpose of the study of this paper: the author has searched for a stability of the system through the above methods. The applied method is a thorough study of the structure of the system as well as the construction of algorithms to form the regulator. The result ia a reliable simulation of events after the system is controlled by these regulators.

Materials with special appearance properties such as goniochromatic materials require complex bidirectional measurements to properly characterise their colour and gloss. Normally, these measurements are performed by goniospectrophotometers which are expensive and not commonly available. In this paper a flexible imaging system composed of a snapshot multispectral camera and a light source attached to a robotic arm, is used to obtain HDR BRDF measurements of patinas commonly used in cultural heritage objects. The system is evaluated by comparing the results to those of a commercially available goniospectrophotometer. It is found that with a known uncertainty, the system is capable of producing accurate measurements of samples with a roughness equal or lower than 6.19 μm. For roughnesses higher that 12.48 μm, the accuracy of the system decreases. Moreover, it is found that the size and orientation of the region of interest plays a great influence on the precision of the imaging system.

Flexible hydraulic robotic arm is a complicated system which coupled by mechanics and hydraulics. It is widely applied in all kinds of large engineering equipments, such as concrete pump truck, bridge monitor truck, arm frame of crane, etc. The arm system of the hydraulic robotic arm is a multi-body system with redundant freedom, strong nonlinear, coupled with rigid and flexible characters. So it is of great theoretic value and real engineering significance to study the arm system of the robotic arm. In this theme, the movement of flexible hydraulic robotic arm and hydraulic cylinders are seperately analyzed with flexible multi-body dynamics, and the mechanical hydraulic dynamic model of the driving system and the arm system is built with Lagrange Equation and Virtual Work Theory. And the dynamic differential equation is built with the driving force of the hydraulic cylinder as the main force. With the track programming and the optimization method, the dynamic converse problem of the arm end track is researched, so as to get the optimized rotation angle when the arm end reaches the expected point. By using the PD control theory, without decoupling and rank-decreasing, only with feed back from the hydraulic system to realize the close loop control of the arm end position, pose and movement, the relationship between the hydraulic system and the end position & pose is studied, so that the flexible distortion is reduced and the libration is restrained. What’s more, the simulation model of the mechanical arms is built by the dynamic simulation software. The simulation result prove that the movement equation built by this way can clearly describe each dynamic character of the mechanical arms.

Improved Takagi–Sugeno fuzzy model-based control of flexible joint robot via Hybrid-Taguchi genetic algorithm

A flexible robot arm is designed to realize high-speed motion as a result of the lightness of its links. However, vibration of the arm caused by high-speed motion remains after motion. In this paper, a deadbeat control scheme for a flexible arm is studied in order to speed up the motion of the arm and minimize the residual vibration at the end of the motion. First, the characteristics of the deadbeat controller for the system with single input, single rigid DOF and single elastic DOF are investigated and a switching deadbeat control scheme is proposed. The response of the system with this control is compared with that when time optimal control is used. Next, this control is applied to the flexible arm with two joints and two elastic links, and several implementation problems are discussed. Finally the effectiveness of this control is confirmed by experiment.

Force control becomes important in order to be the environmental realization where a robot and human being coexist. In such an environment, it is thought that the flexible arm is effective to weaken the force when the arm contacts human. In this study, the equation of motion of a flexible robot arm is assumed to be 2 link rigid body model. The equation of motion is driven by Lagrage's equation. However, by assuming that it is 2 link rigid body model, a modeling error arises. H_∞ Control is well known as the robust control method for a modeling error, disturbance, etc. This study shows the design method of vibration and force control for a flexible robot arm using H_∞ control theory.

Automation of agriculture is one of important characteristics of modern agriculture. Sprinkler irrigating equipment plays a necessary role in automation agriculture by spinning the facet and operating with timer, which has no enough DoFs to meet the demands of precise and intelligent irrigation. A flexible robotic arm using hydraulic driven bellows gives potential of multiple DoFs manipulation for precise irrigation and makes it possible for energy saving by using an underactuator configuration. A hydraulic driven bellow mechanism is a core part of a flexible robotic arm, which dynamic response is one of critical performances to system designer especially for situations when multiple flexible robotic arms operate coordination in precise irrigation. The essential operating modes of the arm are discussed deliberately to explain the reasonable hypothesis on modelling of the hydraulic driven bellow mechanism and its mathematic model for dynamic analysis is given. Parametric influences on dynamic response are discussed subsequently using MATLAB which may supply a fundamental contribution to engineers for designing a precise and intelligent irrigating system using a flexible robotic arm based on the hydraulic driven bellow mechanism.

: The program involved a series of individual projects coordinated to develop controls for a flexible light weight robot arm. A hydraulically actuated 3-link robot arm was installed on a PRAB hydraulic base, and was designed of tubular steel. A PERT program chart was prepared (appendix B) on which various interrelated project milestones were projected.

In this paper, we develop a novel approach for the stability of T-S fuzzy systems using the Lie algebra generated by the linear subsystems used in the T-S model. The theory is illustrated on the T-S fuzzy model of a flexible joint robot arm. We use our approach to design a controller satisfying our Lie algebra based stability criteria and demonstrate its performance on the robotic system.

In this chapter, a planar two-bar space robot is taken as the research object, and the dynamics equations of fully rigid and joint flexible space robot systems are derived by using momentum conservation and Lagrange equation of the second kind. Aiming at flexible joint space robot system, the system is decomposed into fast and slow subsystems based on singular perturbation. Considering the friction characteristics of joints, a robust controller based on the friction upper bound was designed to offset the influence of friction torque and improve the flat roof phenomenon in joint trajectory tracking control. For flexible joint space robot system, a fast variable subsystem controller is designed using moment differential to actively suppress flexible vibration. The controller of slow subsystem is designed by robust method and a bounded friction compensation term is introduced to offset the influence of joint friction torque. The effectiveness of the proposed manipulator control scheme is verified by numerical simulation experiments.

A Flexible Robot Control System with Both Task-Level Language and Visual Monitoring

This thesis addresses stable inversion based output tracking control and its applications to robotic systems. It considers the non-causal invertibility (stable inversion) problem of control systems in its various aspects including properties of stable inverses and algorithms for constructing stable inverses. Then, the stable inversion approach is applied to solve a control problem of long-standing interest: output tracking control for non-minimum phase nonlinear systems. A minimum energy property of stable inverses is firstly established. The property claims that given any desired output trajectory, out of infinitely many possible inverse solutions, the one provided by the stable inversion process is the only one that has finite energy. Based on this property, a numerical procedure is developed to provide an efficient approach to construct stable inverses. Secondly, a new output tracking control design is developed. The design incorporates stable inverses and assumes a controller structure of feed-forward plus feedback. It achieves high precision tracking together with closed-loop stability. Furthermore, when system uncertainties are considered and assumed to satisfy the so-called matching conditions, a modified controller structure is presented and the corresponding robust tracking performance is discussed. Finally, the stable inversion based tracking control design is applied to three flexible robotic systems. The first study is output tracking control of a flexible-joint robot. The application demonstrates how the new design deals with the undesirable non-minimum phase property and achieves desired output tracking. The second application is tip trajectory tracking for a two-flexible-link manipulator. This thesis, for the first time, addresses the problem of stable tip trajectory tracking without any transient or steady-state errors for such non-minimum phase systems. In the third application, a new optimal motion control strategy for a flexible space robot is presented. The space robot system is assumed to consist of a two-link flexible manipulator attached to rigid space-craft. Optimality is in the sense that a performance index measured by maneuvering time, control effort, and structural vibrations is minimized while the interference from the manipulator to spacecraft is kept satisfactorily small. Studies on three applications demonstrate that the stable inversion based control design is very effective on output tracking for various robotic systems. This approach is expected to perform equivalently well for many other realistic non-minimum phase nonlinear systems.