Linear Control of a Nonlinear Equipment Mounting Link

The linear control of a nonlinear response is investigated in this paper, and a nonlinear model of the system is developed and validated. The design of the control system has been constrained based on a suggested application, wherein mass and expense are parameters to be kept to a minimum. Through these restrictions, the array of potential applications for the control system is widened. The structure is envisioned as a robot manipulator link, and the control system utilises piezoelectric elements as both sensors and actuators. A nonlinear response is induced in the structure, and the control system is employed to attenuate these vibrations which would be considered a nuisance in practical applications. The nonlinear model is developed based on Euler–Bernoulli beam theory, where unknown parameters are obtained through optimisation based on a comparison with experimentally obtained data. This updated nonlinear model is then compared with the experimental results as a method of empirical validation. This research offers both a solution to unwanted nonlinear vibrations in a system, where weight and cost are driving design factors, and a method to model the response of a flexible link under conditions which yield a nonlinear response.

Genetic Optimization of a Manipulator: Comparison between Straight, Rounded, and Curved Mechanism Links

There are several ubiquitous kinematic structures that are used in industrial robots, with the most prominent being a six-axis angular structure. However, researchers are experimenting with task-based mechanism synthesis that could provide higher efficiency with custom optimized manipulators. Many studies have focused on finding the most efficient optimization algorithm for task-based robot manipulators. These manipulators, however, are usually optimized from simple modular joints and links, without exploring more elaborate modules. Here, we show that link modules defined by small numbers of parameters have better performance than more complicated ones. We compare four different manipulator link types, namely basic predefined links with fixed dimensions, straight links that can be optimized for different lengths, rounded links, and links with a curvature defined by a Hermite spline. Manipulators are then built from these modules using a genetic algorithm and are optimized for three different tasks. The results demonstrate that manipulators built from simple links not only converge faster, which is expected given the fewer optimized parameters, but also converge on lower cost values.

Approach to Positioning Links of the Manipulator Using Neural Networks

This paper considers development of positioning systems for manipulator links to solve the forward kinematics problem (FKP) and inverse kinematics problem (IKP). Here we study a robotic manipulator with four degrees of freedom. It should be noted, that one of the relevant research problems of modern modular robotic devices consists in the lack of the universal algorithms, that would ensure kinematics problem recalculations in the cases of reconfigurations of the whole system. Challenges, the researchers are facing with when solving this problem, have to do with geometrical and non-linear equations (trigonometric equations), finding of inverse matrix of the Denavit—Hartenberg presentation, as well with other problems, such as multiple solutions when using the analytical approach. Common mathematical solutions of the inverse kinematics problem, such as geometric, iterative and algebraic ones, may not always lead to physically appropriate solutions. It’s also noteworthy, that, trying to introduce physical solutions for the manipulator, we need to take into account, that the number of calculation formulas increases, what, in turn, causes further computing power consumption increase. If the manipulator acquires additional degrees of freedom, analytical modeling becomes virtually impossible. One of relevant inverse kinematics solution methods consists in implementation of neural networks to that end. To solve this problem various sources were analyzed, considering alternative ways of target point discovery. Considering the analyzed papers, we propose to use a perceptron. Before training the network, we compose an algorithm, calculating the Denavit—Hartman presentation matrix and check for correctness of target point reach by the terminal manipulator link. We did calculations for a thousand positions of manipulator and object in the environment, fed to the neural network. When solving FKP we obtain object coordinates as network output, whereas in the case of IKP — manipulator link angles. We present kinematic scheme testing results, as well a control scheme for a manipulator with four degrees of freedom.

Parameter Identification for Model-Based Control of Hydraulically Actuated Open-Chain Manipulators

In this paper, a nonlinear model-based controller with parameter identification is designed for a rigid open-chain manipulator arm actuated by servovalve-controlled hydraulic cylinders. The arising problem in adopting model-based controllers is how to acquire accurate estimates of system parameters, with limited available information about either the hydraulic actuator parameters or manipulator link inertial parameters. The objective of this study is to identify both the rigid-body parameters of the links and the hydraulic actuator parameters from collected cylinder chamber pressure and joint angle data, while no a priori knowledge of these parameters is available. Same physical plant models are used for control design as well as for parameter identification. Experimental results show that the proposed nonlinear model-based control scheme results in acceptable Cartesian position tracking performance in free-space motion when using the identified parameters.

ANALYSIS OF AIR-SPRING FOR A LINK OF HYPER-REDUNDANT MANIPULATOR

Urgency of the research. This research paper deals with a designing and analyzing of link for hyper-redundant manipulator/mechanism. The paper investigates 6-DOF manipulator link, consisting of pneumatic as well as electromagnetic actuators. A motion of upper platform of the link is reached by pneumatic actuators, namely air-springs. The main focus of this research is analysis of air-spring and its properties. From this reason FEM analysis is done in software SolidWorks. In the conclusion the results are discussed. Pneumatic actuators can play interesting role in order to be possible to change the mechanical properties of the manipulators. Target setting. Analysis of air-spring actuator for hyper-redundant manipulator. Actual scientific researches and issues analysis. Most of robotic arms consist of electrical actuators. Using pneumatic actuators the manipulator gets new properties like changing stiffness. Uninvestigated parts of general matters defining. Air-springs are still in the process of investigation from the view of mechanisms actuator. The research objective. In the paper simulations and analysis of the air-spring are done. The statement of basic materials. This paper investigates the area of modeling in software SolidWorks. At first CAD model of new segment for hyperredundant manipulator is introduced and its basic parts are described. Then, in the preprocessing phase, the detailed steps of its setup SolidWorks computation core were described. The second half of the article is to focus on the calculation and assessment of simulation results. Conclusions. The paper introduces new kind of manipulator link. The link is analyzed and tested by simulation.

A SIMULATION STUDY OF ENERGY UTILISATION IN A VARIABLE LINK LENGTH 3 DOF REVOLUTE ARTICULATED MANIPULATOR

Determination of manipulator link lengths is one of the important criteria in robotic design. The purpose of this study is to find the minimum energy utilization for a 3 DOF revolute articulated manipulator to perform certain point-to-point task by varying the link lengths of the manipulator. The lengths of the second and third link of the developed manipulator can be varied accordingly. The investigation of energy for different link length combinations is carried out theoretically. In the simulation, the work-energy method is constituted in order to determine the average mechanical energy of the manipulator. The simulation shows that, different trajectory of motions results in different link length combinations that could give optimum average energy utilization. Results of the simulations shows that, improvement of mechanical energy utilization could be achieved by having variable link length of manipulator rather than having fixed length of manipulator’s arms.

SHORTEST PATH PLANNING FOR SINGLE MANIPULATOR IN 2D ENVIRONMENT OF DEFORMABLE OBJECTS

A heuristic algorithm to perform path planning for single manipulator in 2D environment containing deformable objects is presented. The environment is partitioned into a quadtree hierarchy for both sampling and space navigation use before combination of artificial potential field and heuristic reasoning are applied iteratively to generate feasible path for the manipulator. The algorithm specifically targets for the shortest path without damaging any objects due to deep collision depth between manipulator link and object. Resulting path is in turn to be used in generating micro-instruction controlling the manipulator. Implementation results show feasibility to solve problems involving simple object and manipulator configuration.