Manipulator Inertia Research Articles

Компьютерное моделирование момента инерции плоского манипулятора

Компьютерное моделирование момента инерции плоского манипулятора

A Safe and Energy Efficient Robotic System for Industrial Automatic Tests on Domestic Appliances: Problem Statement and Proof of Concept

In this paper, the design and the development of a robotic platform conceived to perform accelerated life tests on a newly manufactured domestic appliances is presented. The proposed system aims at improving the safety of human operators that share the workspace with the robotic platform which is a common scenario of test laboratories. A deep learning algorithm is used for the human detection and pose estimation, while the integration between a conventional motion planning algorithm with a fast 3D collision checker has been implemented as a global planner plugin for the ROS navigation stack. With the twofold objective of improving safety and saving energy in the battery-powered mobile manipulator used in this project, the problem of minimizing the overall kinetic energy is addressed through a properly designed task priority controller, in which the manipulator inertia matrix is used to weight the joint speeds while satisfying multiple robotic tasks according to a hierarchy designed to interact with the appliances while preserving the safety of the human operators. Simulations are carried out to evaluate the overall control architecture and preliminary results indicate the effectiveness of the developed system in the test laboratory floors.

Optimal Motion Planning for Fast Pointing Tasks With Spherical Parallel Manipulators

Spherical parallel manipulators can be effectively used for the execution of pointing tasks provided that their functional redundancy is well exploited. The present letter shows how the dynamic behavior of parallel wrists can be enhanced by optimizing their posture through suitable performance indexes; the indexes used in this letter are based on the manipulator inertia matrix reduced to the mobile platform, which can be readily worked out from the total kinetic energy of the wrist. First, the redundancy is solved by finding, for each pointing direction, the posture leading to the best dynamic manipulation capacity. Then, a path is planned on the surface of a sphere by means of Bezier curves; in this case, the performance function of the optimization problem drives the platform through the spherical attitudes that grant the maximum angular accelerations along a useful direction. The theoretical results are verified in simulation for the three-CPU manipulator by means of inverse dynamic analyses performed in a multibody software environment; however, the developed methodology is of general use and this letter is aimed at showing how it can be applied to a whole class of spherical parallel robots.

Introducing validity into self-organizing fuzzy neural network applied to impedance force control

In this paper, a novel self-organizing fuzzy neural network is proposed that constructed by an input–output mapping and monitored by a hierarchy of validity degrees. We define new operators called validification and devalidification to propagate validity into the six layers of proposed architecture. Self-organizing in structure learning is accomplished through a new measure that depends on error, the number of rules, and validity degrees. Additionally, a parameter learning condition is derived through studying the stability of proposed approach. To evaluate the proposed approach, an impedance controller is designed facing three challenges: different kinds of uncertainty, partial truth, and real-time realization. In the proposed controller, considering the challenge of partial truth, we assume that the manipulator's inertia is known according to first-principle knowledge while other parts are uncertain. Simulation results show the effectiveness of the proposed approach in the presence of disturbance. The proposed approach emerges as a promising approach by involving self-organizing property and possibility (fuzzy) and validity aspects of information.

DETERMINING DYNAMIC ACCURACY INDICATORS OF MULTICOORDINATE WORKING MACHINES IN THE FORM OF ROD STRUCTURES FOR FUZZY INERTIA AND DISSIPATION PARAMETERS

<p>The paper considers<strong> </strong>a manipulator design and its dynamic model developed by the authors. On the basis of this dynamic model a mathematical model of the manipulator has been created, which enables its spatial motion investigation. The mathematical model takes into account the manipulator inertia tensor with fuzzy components. The developed computation procedure makes it possible to determine cross-angular displacements of the manipulator for impact and sinusoidal laws of torque variation. During random variations of the moment of external forces, complex cross-angular displacements of the manipulator occur. The displacement trajectory includes an elliptical region that corresponds to the ellipse of the manipulator elastic system stiffness. The range of the manipulator upper-end displacement trajectory is maximal in the direction close to that of minimal cross-angular stiffness of the manipulator elastic system.</p>

Load Equivalent Simulation Method of Ultra-large Moment of Inertia of Space Station Redocking Manipulator

In order to simulate ultra-large moment of inertia required by space station manipulator without mechanism interfere, a load equivalent rotational inertia simulation method based on parallel mechanism configuration and planet-gear increaser is proposed. According to the principle of equivalent dynamics theory, mathematic model of equivalent moment of inertia of shoulder joint and wrist joint is established. This method proves effective by mechanism and numerical simulation under different operating conditions, and relative simulation errors of inertia simulator meet allowable precision requirements with smaller mass and volume. Copyright © 2015 Binary Information Press.

On the Uniform Positive Definiteness of the Estimated Inertia for Robot Manipulators

AbstractThis paper is dedicated to seeking a projection algorithm that can guarantee the uniform positive definiteness of the manipulator estimated inertia during parameter adaptation. To achieve this objective, we first investigate the convexity property of the parameter space which corresponds to the inertia parameters of a single rigid body, extending the existing result to a more general case. Then we propose a new projection algorithm to avoid the escape of estimated parameters from the pre-specified parameter region, while this cannot be ensured by the conventional projection approach. The second part of this paper is on how to guarantee the uniform positive definiteness of the estimated manipulator inertia matrix. We show that if we can guarantee the uniform positive definiteness of each link's estimated inertia, the manipulator estimated inertia can be considered to be the inertia of a physically existing robot manipulator, and hence must be uniformly positive definite. Based on this idea and the proposed new projection algorithm, we can obtain a uniformly positive definite estimated robot inertia. Under the frame work of the recursive passivity-based controller, we illustrate the performance of the proposed approach using a six-DOF manipulator.

Control of impulsive contact force between mobile manipulator and environment using effective mass and damping controls

Recently, mobile manipulators are being widely employed for various service robots in human environments. Safety is the most important requirement for the operation of mobile robot in a human-populated environment. Indeed, safe human-machine interaction is one of grand challenges in robotics research. This paper proposes a novel control method to reduce impulsive compact force between a mobile manipulator and its environment by using optimized manipulator inertia and damping-based motion control. To find the optimized configuration through null space motion, the combined potential function method is proposed considering both the minimum effective mass and joint limit constraints. The results of this study show that the inertia optimization along with a damping controller significantly reduces the impulsive force upon collision and the contact force after collision.

11907 マニピュレータの見かけの慣性を利用したインパクト・マニピュレーション(OS7 ロボティックス・メカトロニクス(2),オーガナイズドセッション)

11907 マニピュレータの見かけの慣性を利用したインパクト・マニピュレーション(OS7 ロボティックス・メカトロニクス(2),オーガナイズドセッション)

A quasi-velocity-based nonlinear controller for rigid manipulators

The problem of position control in the operational space of a robot manipulator is addressed in the paper. The proposed controller is based on equations of motion expressed in terms of normalized generalized velocity components (NGVC) which result from decomposition of the manipulator inertia matrix. The sufficient conditions for global exponential stability of the system under the controller are given. It is shown that using the controller an further insight into the system dynamics is possible. The proposed control algorithm is tested via simulation on a spatial manipulator with three degrees of freedom.

A decomposition of the manipulator inertia matrix

A decomposition of the manipulator inertia matrix is essential, for example, in forward dynamics, where the joint accelerations are solved from the dynamical equations of motion. To do this, unlike a numerical algorithm, an analytical approach is suggested in this paper. The approach is based on the symbolic Gaussian elimination of the inertia matrix that reveal recursive relations among the elements of the resulting matrices. As a result, the decomposition can be done with the complexity of order n, O(n), where n being the degrees of freedom of the manipulator, as opposed to an O(n/sup 3/) scheme, required in the numerical approach. In turn, O(n) inverse and forward dynamics algorithms can be developed. As an illustration, an O(n) forward dynamics algorithm is presented.

Repetitive and adaptive control of robot manipulators with velocity estimation

This paper presents repetitive and adaptive motion control schemes for rigid-link robot manipulators, when the manipulator's joint velocities cannot be measured by the control system. The control objective consists in tracking a prescribed desired trajectory. In the case of repetitive control, the desired trajectory is periodic and it is required that the robot achieve the control objective through repeated learning trials. We assume that the robot inverse dynamics are totally unknown, except that they can be represented by an integral of the product of known differentiable kernel and an unknown influence function. In the case of adaptive control, it is assumed that only the manipulator inertia parameters are unknown and that the desired trajectory jerks are available to the control system. In both control schemes, a velocity observer, which is formulated based on the desired input/output relation of the manipulator, is used to estimate the manipulator joint velocities. A stability analysis of the repetitive and adaptive control schemes with velocity estimation is presented. Simulation and experimental results show that the proposed repetitive control algorithm is successful in achieving the control objective without direct measurement of the joint velocities.

BACKSTEPPING-BASED HYBRID ADAPTIVE CONTROL OF ROBOT MANIPULATORS INCORPORATING ACTUATOR DYNAMICS

By using the integrator backstepping technique, the control of rigid link, electrically driven robot manipulators is addressed in the presence of arbitrary uncertain manipulator inertia parameters and actuator parameters. The control scheme developed is computationally simple owing to the avoidance of the derivative computation of the regressor matrix. Semiglobal asymptotic stability of the controller is established in the Lyapunov sense. Simulation results are included to demonstrate the tracking performance. © 1997 by John Wiley & Sons, Ltd.

Vibration Control of Redundant Flexible-Joint Manipulators

Presented in this paper is a method for controlling vibrations of a redundant flexible-joint manipulator. The main idea behind this method is to utilize joint redundancy to minimize the change in the manipulator inertia, so that a simple gain-fixed control law can be used to control joint vibrations. For this purpose, two optimal joint trajectory generators are proposed; one is based on the extended Jacobian method and the other is based on an optimization technique. Numerical simulations are provided to demonstrate the effectiveness of the proposed control method.

Internal force-based impedance control for cooperating manipulators

An internal force-based impedance control scheme for cooperating manipulators is introduced which controls the motion of the objects being manipulated and the internal force on the objects. The controller enforces a relationship between the velocity of each manipulator and the internal force on the manipulated objects. Each manipulator is directly given the properties of an impedance by the controller; thus, eliminating the gain limitation inherent in the structure of previously proposed schemes. The controller uses the forces sensed at the robot end effectors to compensate for the effects of the objects' dynamics and to compute the internal force using only kinematic relationships. Thus, knowledge of the objects' dynamics is not required. Stability of the system is proven using Lyapunov theory and simulation results are presented validating the proposed concepts. The effect of computational delays in digital control implementations is analyzed vis-a-vis stability and a lower bound derived on the size of the desired manipulator inertia relative to the actual manipulator endpoint inertia. The bound is independent of the sample time.

A motion control strategy based on equivalent mass matrix in multidegree-of-freedom manipulator

This paper describes a decoupling motion control strategy based on an equivalent mass matrix in operational space. In the conventional approach, the equivalent mass matrix is defined as a function of Jacobian matrix and inertia of manipulator. Therefore, it is difficult to know the variation of the equivalent mass matrix precisely and to select it arbitrarily. This makes it difficult to realize the decoupling motion controller in the operational space. To improve the above problem, the authors introduce a robust control strategy based on a disturbance observer. In the observer-based approach, the equivalent mass matrix is determined arbitrarily independently of configuration and inertia variation of the manipulator. First, the equivalent mass matrix based on robust control is derived. Second, a simplification method of an operational space controller is discussed by using the equivalent mass matrix. Several experimental results are shown to confirm the validity of the proposed methods.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of a redundant free-flying spacecraft/manipulator system

An analysis of the momentum conservation equations of a redundant free-flying spacecraft/manipulator system acting in a zero-gravity environment is presented. In order to follow a predefined end-effector path, the inverse kinematics at velocity level is considered. The redundancy is solved alternatively in terms of pseudoinverses and null-space components of the manipulator inertia matrix, the manipulator Jacobian matrix, and the generalized Jacobian matrix. A general manipulation task is defined as end-effector continuous path tracking with simultaneous attitude control of the spacecraft. Three subtasks of the general task are considered. The case of manipulator motions that yield no spacecraft attitude disturbance is analyzed in more detail and a special 'fixed-attitude-restricted' (FAR) Jacobian is defined. Through singular-value decomposition of this Jacobian, corresponding FAR dexterity measures (FAR manipulability and FAR condition number) are derived. >

On the design of a direct drive 5-bar-linkage manipulator

SUMMARYThe 5-bar-linkage manipulator configuration is well suited to many industrial robotic applications. Aside from kinematic suitability, the dynamic equations are greatly simplified due to a decoupling of the manipulator inertia matrix. The design also lends itself to the use of direct drive motors. However, these motors must be capable of providing a high continuous torque to counter gravitational loading in the conventional manipulator design. In this paper, the static and dynamic design of the 5-bar-linkage manipulator is analysed. A technique is proposed whereby the motor torque requirements may be reduced to a fraction of those required in the conventional design, while simultaneously retaining the advantage of a decoupled inertia matrix. Details of a prototype manipulator and experimental results of its performance are presented.

Parallel Algorithms for Computation of the Manipulator Inertia Matrix

This article presents the development of an O( log2 N) parallel algorithm for the manipulator inertia matrix. It is based on an efficient serial algorithm that uses the composite rigid- body method. Recursive doubling is used to reformulate the linear recurrence equations that are required to compute the diagonal elements of the matrix. It results in O( log2 N) levels of computation. Computation of the off-diagonal ele ments involves N linear recurrences of varying size, and a new method, which avoids redundant computation of position and orientation transforms for the manipulator, is developed. The O( log2 N) algorithm is presented in both equation and graphic forms that clearly show the parallelism inherent in the algorithm. The relationship between the number of pro cessors required and the order of the computation is also given for several versions of parallel algorithms for the inertia matrix.

An adaptive variable structure model following control design for robot manipulators

An adaptive variable structure model-following control (AVSMFC) design is proposed for trajectory tracking in a nonlinear robot system which ensures the stability of the intersection of the surfaces without necessarily stabilizing each individual one. The approach avoids the difficulties linked to the strict positive realness requirement in traditional AMFC by taking advantage of the inherent positive definiteness of the manipulator's inertia matrix, and is easily extendible to a higher number of links. The controller does not require any knowledge of a nonlinear robotic system and does not necessarily need the occurrence of a sliding mode at each individually stable discontinuity surface. It thus greatly reduces the complexity of design. In the closed loop, the joint angles asymptotically converge to the reference trajectory with a prescribed transient response. Chattering is eliminated by restricting the state of the system to slide within a boundary layer rather than along the intersection of the surfaces.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>