The Effects of the Manipulator Type on the Vibrational Excitation During Motion

1992 ◽  
Author(s):  
Q. Tu ◽  
Jahangir Rastegar
Keyword(s):  
Degrees Of Freedom ◽  
Robot Manipulator ◽  
Vibrational Excitation ◽  
Mechanical Systems ◽  
Average Energy ◽  
Structural Type ◽  
Higher Harmonics ◽  
Modes Of Vibration ◽  
Prismatic Joints ◽  
And Control

Abstract The relationship between the structural type of a manipulator and its susceptibility to motion induced vibrational excitation is examined. For manipulators of different type, the average potential resonant energy transfer to a robot manipulator system by the higher harmonics of the actuating torques (forces) necessary for tracking trajectories that are uniformly distributed within a representative task space are determined, and used as a measure of the potential for vibrational excitation during motion. The manipulators are kinematically and dynamically equivalent. From the vibration and control points of view, manipulator types that do not demand high frequency actuating torque harmonics are more desirable, since the natural modes of vibration of mechanical systems are most likely to be excited by the higher harmonics of the actuating torques, and because of practical dynamic response limitations of all mechanical systems. As examples, plane two and three degrees-of-freedom manipulators constructed with revolute and prismatic joints are studied. Numerical calculations of the aforementioned and the total expected (average) energy input and the corresponding variances are presented for the two degrees-of-freedom manipulators. A number of points of interest are discussed.

Design and Control of Supporting Arm for Reducing Factory Worker Load With Desired Support Force and Stiffness Characteristics

2016 ◽  
Author(s):  
Tetsuro Miyazaki ◽  
Takuya Iijima ◽  
Kazushi Sanada
Keyword(s):  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulator ◽  
Experimental System ◽  
Factory Worker ◽  
Target Weight ◽  
Support Force ◽  
Stiffness Characteristics ◽  
And Control ◽  
Pneumatic Cylinders

This paper proposes a design and control method of a supporting arm which reduces factory worker load. The supporting arm is a robot manipulator, which is driven by pneumatic cylinders, and is attached to the worker’s hip. In some situation, the factory worker is forced to work with an uncomfortable posture. By using the supporting arm, the worker leg loads are relaxed, and the worker posture is stabilized. To support 50 % weight of the worker, the link system of the supporting arm is designed, and the pneumatic cylinders for actuation are selected. There are two required specifications: (i) support force is sufficient for supporting target load, and (ii) desired stiffness characteristics in the hip height direction can be obtained. The support force is controlled by a two degrees of freedom control system to satisfy the required specifications. An experimental system of the supporting arm was developed, and its performance was evaluated by experiments. As a result, the experimental system shows capability of supporting the target weight and controllability of stiffness.

scholarly journals The Modeling of Redundantly Actuated Mechanical Systems

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Yaojun Wang ◽  
Bruno Belzile ◽  
Jorge Angeles ◽  
Qinchuan Li
Keyword(s):  
Degrees Of Freedom ◽  
Screw Theory ◽  
Mechanical Systems ◽  
Coefficient Matrix ◽  
Dynamics Modeling ◽  
Norm Minimization ◽  
Redundantly Actuated ◽  
The Right ◽  
And Control

Abstract Dynamics modeling is essential in the design and control of mechanical systems, the focus of the paper being redundantly actuated systems, which bring about special challenges. The authors resort to the natural orthogonal complement (NOC), based on an adaptation of screw theory, to derive the dynamics model. Benefiting from the elimination of the constraint wrenches, the NOC offers a simple, systematic alternative to the modeling of redundantly actuated mechanical systems. The optimum actuator-torque distribution is determined via Euclidean-norm minimization; then, by relying on the QR-decomposition, an efficient and robust method is produced to compute explicitly the right Moore–Penrose generalized inverse of the coefficient matrix. The methodology is illustrated via a case study involving a redundantly actuated parallel-kinematics machine with three degrees of freedom and four actuators.

Fundamental Exercises in Mechanical Systems Engineering Using Robot Manipulator

2011 ◽  
Author(s):  
Hideaki Takanobu
Keyword(s):  
Mechanical System ◽  
Linear Algebra ◽  
Systems Engineering ◽  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Engineering Students ◽  
Robot Manipulator ◽  
Mechanical Systems ◽  
Forward Kinematics ◽  
Basic Learning

A five degrees-of-freedom (5-DOF) robot manipulator is used for the basic learning of mechanical system engineering. Students learned the forward kinematics as concrete applications of the mathematics, especially linear algebra. After making a manipulator, baton relay contest was done to understand the inverse kinematics by controlling the manipulator using a manual controller having five levers.

On the Effects of the Operating Speed on the Dynamic Behavior of Manipulators With Rigid Links

1992 ◽  
Author(s):  
Q. Tu ◽  
Jahangir Rastegar
Keyword(s):  
Energy Transfer ◽  
Total Energy ◽  
Dynamic Behavior ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Vibrational Excitation ◽  
Operating Speed ◽  
Higher Harmonics ◽  
Resonant Energy ◽  
Resonant Energy Transfer

Abstract The effect of tile operating speed on the dynamic behavior of robot manipulators is determined by examining the potential resonant energy transfer to a robot manipulator system during its motion by the different harmonics of the actuating torques (forces). The potential resonant energy transfer (hereafter called the energy transfer), particularly by the higher harmonics present in the actuating torques, is of considerable interest since they represent one of the main sources of vibration and control problems in such systems. For a given trajectory pattern, the ratios of the total energy transfer by the non-trajectory and the “higher” harmonics of the actuating torques to the total energy input to the system are determined. Here, the higher harmonics refers to the harmonics with frequencies above the highest frequency of the trajectory harmonics. It is shown that in the absence of gravity, for the class of nonlinear dynamics systems represented by the rigid link robot manipulators, the ratios are independent of the speed of operation. For a given path geometry, the relative magnitude of the individual energy transfer is, however, dependent on the positioning of the path within the workspace of the manipulator and the pattern of motion. In the presence of gravity, as the operating speed is increased, the ratios tend to their no gravity values. The application of the developed method to manipulator synthesis and path and trajectory planning for minimal system susceptibility to vibrational excitation, and a number of related topics of interest are discussed.

Linearized Dynamic Models for Robot Manipulators With Varying Link Parameters

1991 ◽  
Author(s):  
Chang-Jin Li ◽  
T. S. Sankar ◽  
A. Hemami
Keyword(s):  
Computational Complexity ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Mechanical Systems ◽  
Computational Algorithms ◽  
Inverse Dynamic ◽  
Dynamic Link

Abstract In this paper, two fast computational algorithms are developed for effective formulation for the linearized dynamic robot models with varying (kinematic and dynamic) link parameters. The proposed algorithms can generate complete linearized (inverse) dynamic models for robot manipulators, taking variations (e.g., inexactness, inconstancy, or uncertainty) of the kinematic and dynamic link parameters into account. They can be applied to any robot manipulator with rotational and/or translational joints, and can be utilized, also, for sensivitity analysis of similar mechanical systems. The computational complexity of these algorithms is only of order O(n), where n is the number of degrees-of-freedom of the robot manipulator.

Understanding Damping in Acoustic and Mechanical Systems

2014 ◽  
Author(s):  
Hugh Goyder
Keyword(s):  
Linear System ◽  
Degrees Of Freedom ◽  
Mechanical Systems ◽  
Degree Of Freedom ◽  
Vibration Modes ◽  
Acoustic System ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Modes Of Vibration ◽  
Straightforward Extension

A system with damping is much more difficult to model than an undamped system. In particular, the effect of damping on a multi-degree-of-freedom system is not a straightforward extension of the damping found in a single-degree-of-freedom system. The complications of a multi-degree-of-freedom system are first examined by investigating the acoustic modes of a pipe with energy leaking from the boundaries. This system can be modelled exactly and identifies the complexities that need to be understood. Although this is a linear system it is found that in contradistinction to an undamped system it cannot be separated into individual modes of vibration. Modes which bear some similarity to undamped modes can be found but these are always coupled by damping effects which, to add more complications, may involve some modes being active and supplying energy to other modes. The original acoustic system is simplified to systems of finite and eventually two-degrees-of-freedom in an effort to understand the effects of damping. It is found that when damping is added to a system some damping ratios may decrease moving the system into an unfavourable state. Overall some general properties of damping, for example, the constancy of average damping, are deduced.

scholarly journals MATLAB-based Tools for Modelling and Control of Underactuated Mechanical Systems

2020 ◽  
Vol 6 (3) ◽  
Author(s):  
Slávka Jadlovská ◽  
Lukáš Koska ◽  
Matej Kentoš
Keyword(s):  
Degrees Of Freedom ◽  
Mechanical Systems ◽  
Underactuated Systems ◽  
Underactuated Mechanical Systems ◽  
Software Support ◽  
Nonlinear Mechanical ◽  
Inertia Wheel Pendulum ◽  
Nonlinear Mechanical Systems ◽  
And Control ◽  
Insight Into

Underactuated systems, defined as nonlinear mechanical systems with fewer control inputs than degrees of freedom, appear in a broad range of applications including robotics, aerospace, marine and locomotive systems. Studying the complex low-order nonlinear dynamics of appropriate benchmark underactuated systems often enables us to gain insight into the principles of modelling and control of advanced, higher-order underactuated systems. Such benchmarks include the Acrobot, Pendubot and the reaction (inertia) wheel pendulum. The aim of this paper is to introduce novel MATLAB-based tools which were developed to provide complex software support for modelling and control of these three benchmark systems. The presented tools include a Simulink block library, a set of demo simulation schemes and several innovative functions for mathematical and simulation model generation.

scholarly journals Design, construction and control of a SCARA manipulator with 6 degrees of freedom

2019 ◽  
Vol 17 (2) ◽  
Author(s):  
Claudio Urrea ◽  
Juan Cortés
Keyword(s):  
Control Systems ◽  
Degrees Of Freedom ◽  
Robot Manipulator ◽  
Matlab Simulink ◽  
Graphic Interface ◽  
Control Techniques ◽  
Design And Implementation ◽  
6 Degrees Of Freedom ◽  
And Control ◽  
Design Construction

The design and implementation of a robot manipulator with 6 Degrees Of Freedom (DOF), which constitutes a physical platform on which a variety of control techniques can be tested and studied, are presented. The robot has mechanical, electronic and control systems, and the intuitive graphic interface designed and implemented for it allows the user to easily command this robot and to generate trajectories for it . Materializing this work required the integration of knowledge in electronics, microcontroller programming, MatLab/Simulink programming, control systems, communication between PCs and microcontrollers, mechanics, assembly, etc.

Stabilization of Internal Dynamics of Underactuated Systems by Periodic Servo-Constraints

2017 ◽  
Vol 17 (05) ◽  
pp. 1740004 ◽  
Author(s):  
László Bencsik ◽  
László L. Kovács ◽  
Ambrus Zelei
Keyword(s):  
Stability Analysis ◽  
Dynamic Behavior ◽  
Multibody Systems ◽  
Degrees Of Freedom ◽  
Mechanical Systems ◽  
Underactuated Mechanical Systems ◽  
Algorithmic Approach ◽  
Servo Constraints ◽  
And Control ◽  
Dependent Coordinates

The model-based motion control of underactuated, multiple degree-of-freedom, complex multibody systems is in focus. Underactuated mechanical systems possess less number of independent control inputs than degrees-of-freedom. The main difficulty in their control is caused by the dynamics of the uncontrolled part of the system. The complexity of multibody systems makes the dynamical and control formulation difficult. The direct application of traditional control techniques available in the literature can lead to unstable dynamic behavior in many cases. In order to avoid instability, these general methods are usually adapted for specific problems in an intuitive way. Here, we present a direct, more algorithmic approach, and propose the use of periodic servo-constraints to overcome stability problems and enhance the dynamic behavior. An exact, stability analysis-based method is also proposed for tuning the control parameters. A stability analysis procedure is developed which is directly applicable for investigating the dynamics of mechanical systems described by dependent coordinates and mathematically formulated as a set of algebraic differential equations.

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