Modal Space Control of Manipulator Vibrational Motion
TL;DR: In this article, a modal approach is used for obtaining the reduced order mathematical model of the manipulator flexible motion which is sufficiently tractable to be utilized for control purposes for compensating manipulator flexibility effects to cope with the current requirements on better accuracy and higher performance of manipulator motion.
About: This article is published in IFAC Proceedings Volumes.The article was published on 1985-11-01. It has received 4 citations till now. The article focuses on the topics: Parallel manipulator & Modal analysis.
Citations
More filters
01 Apr 1986
TL;DR: The problem of modeling flexible robots is considered and the dynamic model is obtained by using a generalized Lagrangian approach and by expanding in a limited number of terms the function describing the exact shape of bended beams constituting the robot.
Abstract: The problem of modeling flexible robots is considered. The dynamic model is obtained by using a generalized Lagrangian approach and by expanding in a limited number of terms the function describing the exact shape of bended beams constituting the robot. General properties of the models, as controllability, are then investigated. To manipulate the cumbersome formulae the SAM language MACSYMA has been extensively used.
44 citations
TL;DR: Some methods for the mechanical modelling of flexible robot structures are discussed and compared and an overview of possible control methods and strategies for the dynamic behavior is given.
12 citations
TL;DR: In this article, the tracking order of consistent and lumped finite element models is derived and compared with the tracking ordering of the continuous model when there is no tip-mass, and the same results are obtained if superposition of modes rather than finite elements is used.
Abstract: The inverse dynamics problem for a single link flexible arm is considered. The tracking order of consistent and lumped finite element models is derived and compared with the tracking order of the continuous model when there is no tip-mass. These comparisons show that discrete models fail to identify the tracking order of a modelled continuous system. A frequency domain analysis shows that an increase in the model order extends the well-modelled low-frequency range and, at the same time, increases the inadequacy in the high-frequency range. As a result, inverse dynamics solutions computed with discrete models do not converge to the continuous solution as the model order increases. The use of high-frequency filters allows us to construct a convergent numerical procedure. A conjecture about the tracking order is presented when there is a tip mass. It is shown that the same results are obtained if superposition of modes rather than finite elements is used.
10 citations
01 Oct 1996
TL;DR: In this paper, a Spline Varying Optimal (SVO) controller is developed for the kinematic nonlinear system, in which the spline function approximates the system model, observer, and controller gain.
Abstract: Anaysis and synthesis tools are developed to improve the dynamic performance of reconfigurable nonminimum phase, nonstrictly positive real-time variant systems. A novel Spline Varying Optimal (SVO) controller is developed for the kinematic nonlinear system. There are several advantages to using the SVO controller, in which the spline function approximates the system model, observer, and controller gain. They are: The spline function approximation is simply connected, thus the SVO controller is more continuous than traditional gain scheduled controllers when implemented on a time varying plant; it is easier for real-time implementations in storage and computational effort; where system identification is required, the spline funtion requires fewer experiments, namely four experiments; and initial startup estimator transients are eleminated. The SVO compensator was evaluated on a high fidelity simulation of the Shuttle Remote Manipulator System. The SVO controller demonstrated significant improvement over the present arm performance: (1) Damping level was improved by a factor of 3: and (2) Peak joint torque was reduced by a factor of 2 following Shuttle thruster firings.
4 citations
Cites background from "Modal Space Control of Manipulator ..."
...In the papers of Balas (1978) and Karkkainen and Halme (1985) a modal approach to the problem of approximating a general flexible mechanical system is used....
[...]
References
More filters
TL;DR: In this paper, three types of linear feedback control schemes are considered: joint angle and velocity feedback with (GRC) and without (IJC) cross joint feedback, and feedback of flexible state variables (FFC).
Abstract: The control of the flexible motion in a plane of two pinned beams is addressed with application to remote manipulators. Three types of linear feedback control schemes are considered: joint angle and velocity feedback with (GRC) and without (IJC) cross joint feedback, and feedback of flexible state variables (FFC). Two models of the distributed flexibility are presented along with some results obtained from them. The relative merit of the three control schemes is discussed.
395 citations
TL;DR: In this article, the potential benefits of the ability to control more flexible mechanical arms are discussed and a new controller design procedure is developed to provide this capability using both a frequency domain representation and a state variable representation of the arm model.
Abstract: The potential benefits of the ability to control more flexible mechanical arms are discussed. A justification is made in terms of speed of movement. A new controller design procedure is then developed to provide this capability. It uses both a frequency domain representation and a state variable representation of the arm model. The frequency domain model is used to update the modal state variable model to insure decoupled states. The technique is applied to a simple example with encouraging results.
205 citations
TL;DR: In this paper, an electrical control method of absorbing arm vibrations of industrial robots is described, where dampers are composed as electric manners by utilizing arm acceleration feedback to actuators of an industrial robot Acceleration signals are fed back to the corresponding actuators passed through phase compensation circuits.
Abstract: This paper describes an electrical control method of absorbing arm vibrations of industrial robots Arm vibration problems are divided into two categories: resonance vibration phenomenon depending on actuator velocity and transient oscillations caused by acceleration change of actuators Because resonance frequency of an industrial robot changes more than double due to the arm posture, mechanical vibration absorbing methods may not be easily utilized The method applied in this paper is to compose dampers as electric manners by utilizing arm acceleration feedback to actuators of an industrial robot Acceleration sensors are attached on three axes which construct a robot arm Acceleration signals are fed back to the corresponding actuators passed through phase compensation circuits By experiments applied to an industrial robot, this method has been proved to be effective in eliminating both resonance and transient vibrations According to this control, a smart motion industrial robot which does not have resonance characteristics and operates speedily and smoothly has been realized
77 citations
TL;DR: The parameter-adaptive self-organizing control of linear discrete-time systems is considered by designing dynamic feedback controllers which depend on the estimates of the parameters provided by an appropriate identifier.
Abstract: The parameter-adaptive self-organizing control of linear discrete-time systems is considered by designing dynamic feedback controllers which depend on the estimates of the parameters provided by an appropriate identifier. Two stochastic approximation algorithms for consistent identification of feedback systems are investigated and a condition of identifiability is presented. Then two controllers, one based on "overall" and another based on "per-interval" optimization, both depending on the output of the identifier, are discussed and their evaluations relative to the optimal are compared in illustrative examples.
68 citations
TL;DR: In this article, an experimental setup consisting of a free-free uniform beam acted upon by four electromagnetic force actuators, with the motion being measured by nine displacement sensors, was designed to control the motion of a beam.
Abstract: This paper is concerned with an experiment conducted at the NASA Langley Research Center that was designed to control the motion of a beam. The experimental setup consists of a free-free uniform beam acted upon by four electromagnetic force actuators, with the motion being measured by nine displacement sensors. The entire assembly is linked to a digital computer permitting on-line real-time computation of the control forces. The control scheme is based on the independent modal-space control method in conjuction with a nonlinear, on-off control law for the modal forces. The actuator forces are then synthesized from the modal forces by means of a linear transformation, resulting in quantized forces. The sensors' data are processed by modal filters. It is observed that the independent controls are very effective in suppressing the motion of the beam, even though there is about a 50% difference between the actual and the analytically computed natural frequencies.
47 citations