A parameter identification method for robot dynamic models using a balancing mechanism

Robotica ◽  
1989 ◽  
Vol 7 (4) ◽  
pp. 327-337 ◽  
Author(s):  
T. G. Lim ◽  
H. S. Cho ◽  
W. K. Chung

SUMMARYAccurate modeling of robot dynamics is a prerequisite for the design of model-based control schemes and enhancement of the performance of the robot. The dynamic parameters associated with a pseudo-inertia matrix are often difficult to identify accurately because the inertia torques are small in comparison to gravity loadings, thus creating signal processing problem. The identification method presented in this paper utilizes a balancing mechanism which increases the estimation accuracy of the dynamic parameters. The balancing mechanism has the effect of amplifying the inertia-related torque signal by eliminating gravity loadings acting on the robot joints. A series of motion data were experimentally obtained through sequential test steps. By incorporating the measured information about joint torques, angular positions, velocities and accelerations the least square algorithm was used to identify the dynamic parameters. The estimated values were converted to those of the original robot model to obtain its dynamic model parameters. The identified robot dynamic model was shown to be accurate enough to predict the actual robot motions.

Author(s):  
Yi Liu ◽  
Dragan Djurdjanovic

It has been demonstrated in the previous research that the node connectivity in the graph encoding the topological neighborhood relationships between local models in a piecewise dynamic model may significantly affect the cooperative learning process. It was shown that a graph with a larger connectivity leads to a quicker learning adaption due to more rapidly decaying transients of the estimation of local model parameters. In the same time, it was shown that the accuracy could be degraded by a larger bias in the asymptotic portion of the estimations of local model parameters. The efforts in topology optimization should therefore strive towards a high accuracy of the asymptotic portion of the estimator of local model parameters while simultaneously accelerating the decay of the estimation transients. In this paper, we pursue minimization of the residual sum of squares of a piecewise dynamic model after a predetermined number of training steps. The optimization of inter-model topology is implemented via a genetic algorithm that manipulates adjacency matrices of the graph underlying the piecewise dynamic model. An example of applying the topology optimization procedure on a peicewise linear model of a highly nonlinear dynamic system is provided to show the efficacy of the new method.


Author(s):  
Louis-Francis Y. Tremblay ◽  
Marc Arsenault ◽  
Meysar Zeinali

A model-based approach to control the automation of hydraulic excavators and rockbreakers necessitates an adequate dynamic model to increase the robustness of the controller and improve its performance (e.g., reduce tracking error). Most previous efforts in developing dynamic models for excavators have assumed planar motion while neglecting the dynamic effects of hydraulically driven prismatic actuators. In this paper, a dynamic model of the mechanical subsystem of a hydraulic rockbreaker is developed using the Euler–Lagrange formulation. The model considers the contributions of the hydraulic actuators and does not assume planar motion. Potential simplifications to the dynamic model are then introduced to facilitate the model’s parameterization for developing an adaptive control algorithm. To evaluate their level of accuracy, these simplified dynamic models are then evaluated based on the required joint torques for specified trajectories. It is shown that the proposed simplifications reduce the complexity of the dynamic model while preserving its accuracy, which is attractive for real-time control applications.


2009 ◽  
Vol 06 (04) ◽  
pp. 225-238 ◽  
Author(s):  
K. S. HATAMLEH ◽  
O. MA ◽  
R. PAZ

Dynamics modeling of Unmanned Aerial Vehicles (UAVs) is an essential step for design and evaluation of an UAV system. Many advanced control strategies for nonlinear dynamical or robotic systems which are applicable to UAVs depend upon known dynamics models. The accuracy of a model depends not only on the mathematical formulae or computational algorithm of the model but also on the values of model parameters. Many model parameters are very difficult to measure for a given UAV. This paper presents the results of a simulation based study of an in-flight model parameter identification method. Assuming the motion state of a flying UAV is directly or indirectly measureable, the method can identify the unknown inertia parameters of the UAV. Using the recursive least-square technique, the method is capable of updating the model parameters of the UAV while the vehicle is in flight. A scheme of estimating an upper bound of the identification error in terms of the input data errors (or sensor errors) is also discussed.


2001 ◽  
Vol 124 (1) ◽  
pp. 62-66 ◽  
Author(s):  
Pei-Sun Zung ◽  
Ming-Hwei Perng

This paper presents a handy nonlinear dynamic model for the design of a two stage pilot pressure relief servo-valve. Previous surveys indicate that the performance of existing control valves has been limited by the lack of an accurate dynamic model. However, most of the existing dynamic models of pressure relief valves are developed for the selection of a suitable valve for a hydraulic system, and assume model parameters which are not directly controllable during the manufacturing process. As a result, such models are less useful for a manufacturer eager to improve the performance of a pressure valve. In contrast, model parameters in the present approach have been limited to dimensions measurable from the blue prints of the valve such that a specific design can be evaluated by simulation before actually manufacturing the valve. Moreover, the resultant model shows excellent agreement with experiments in a wide range of operating conditions.


Author(s):  
Xiaowen Yu ◽  
Cong Wang ◽  
Yu Zhao ◽  
Masayoshi Tomizuka

This paper presents the dynamics modeling and dynamic identification of a dual-blade wafer handling robot. An explicit form dynamic model for this 8-link parallel robot is proposed. The dynamic model is transformed into a decoupled form to enable dynamic parameters identification with least-square regression. A well conditioned trajectory is chosen for identification experiment. Both viscous friction and Coulomb friction are considered to make the model more reliable. Model has been validated by experiments.


Electronics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 836 ◽  
Author(s):  
Pengcheng Li ◽  
Ahmad Ghasemi ◽  
Wenfang Xie ◽  
Wei Tian

Parallel robots present outstanding advantages compared with their serial counterparts; they have both a higher force-to-weight ratio and better stiffness. However, the existence of closed-chain mechanism yields difficulties in designing control system for practical applications, due to its highly coupled dynamics. This paper focuses on the dynamic model identification of the 6-DOF parallel robots for advanced model-based visual servoing control design purposes. A visual closed-loop output-error identification method based on an optical coordinate-measuring-machine (CMM) sensor for parallel robots is proposed. The main advantage, compared with the conventional identification method, is that the joint torque measurement and the exact knowledge of the built-in robot controllers are not needed. The time-consuming forward kinematics calculation, which is employed in the conventional identification method of the parallel robot, can be avoided due to the adoption of optical CMM sensor for real time pose estimation. A case study on a 6-DOF RSS parallel robot is carried out in this paper. The dynamic model of the parallel robot is derived based on the virtual work principle, and the built dynamic model is verified through Matlab/SimMechanics. By using an outer loop visual servoing controller to stabilize both the parallel robot and the simulated model, a visual closed-loop output-error identification method is proposed and the model parameters are identified by using a nonlinear optimization technique. The effectiveness of the proposed identification algorithm is validated by experimental tests.


Author(s):  
Pin Lyu ◽  
Sheng Bao ◽  
Jizhou Lai ◽  
Shichao Liu ◽  
Zang Chen

The dynamic model parameter identification is important for unmanned aerial vehicle modeling and control. The unmanned aerial vehicle model parameters are usually identified through wind tunnel experiments, which are complex. In this paper, a model parameter identification method is proposed using the flight data for quadrotors. The parameters of the thrust, drag force, torque, rolling moment and pitching moment are estimated through Kalman filter. Global positioning system and inertial sensors are used as measurements. The observabilities of the model parameters and their degrees of observability are analyzed. Flight experiments are carried out to verify the proposed method. It is shown that the model parameters estimated by the proposed method have good accuracies, demonstrating the validity of the proposed method.


Author(s):  
Wenjie Wang ◽  
Lingtao Yu ◽  
Jing Yang

This paper proposes a novel cable-driven micromanipulator for surgical robots. A single-joint principle prototype for surgical robot micromanipulator was manufactured to test the proposed design. Elasticity and friction were assessed to establish a joint angle estimator; estimator parameters were obtained by a combination of least square method and genetic algorithm. Angle closed-loop control was performed by considering the joint angle estimator output as the feedback signal. A nonlinear dynamic model was established in the state-space and described as a linear parameter variant model. The dynamic model parameters were determined via nonlinear modeling method, linear time invariant interpolator, and genetic algorithm. The angle estimator performs well and the linear parameter variant model efficiently estimates the micromanipulator’s behavior. The results presented here provide a workable foundation for surgical robot micromanipulator force estimation and control.


Author(s):  
С.А. Мамаев ◽  
В.М. Дорофеев ◽  
А.С. Мамаев

Представлены результаты исследований, направленных на создание динамических моделей сооружений, пригодных для расчета на сейсмостойкость. Рассмотрен метод определения параметров моделей на основе инженерно-сейсмометрической информации. Приведены примеры определения динамических параметров одномассовой модели для детерминированного и статистического случаев. Динамические нагрузки на сооружения характеризуются изменением динамических характеристик сооружения, возникающие колебаниями при землетрясениях и взрывах, при ударах массивных тел и т.д. Колебательный характер имеют не только перемещения точек сооружения, но и внутренние усилия и напряжения в его элементах. Определение ожидаемых амплитуд перемещений, внутренних усилий и напряжений в сооружении при его колебаниях под действием динамической нагрузки, т.е. при вынужденных колебаниях и сравнение их с допустимыми значениями составляют основное содержание динамического расчёта сооружения. Допустимые значения амплитуд внутренних усилий обусловлены требованиями прочности и долговечности строительных конструкций, а значения амплитуд скоростей и ускорений колебаний зданий и сооружений, в которых находятся люди или помещение производства с точной технологией, требованиями безвредного влияния колебаний на здоровье людей и на качество выпускаемой продукции Савович, 2005. По записям сейсмометрических приборов, установленных на покрытии здания, приблизительно определяются собственные периоды колебаний сооружений. В основном эти измерения соответствуют действительному периоду собственного колебания сооружения (основному тону собственных колебаний) лишь при небольших сейсмических воздействиях, микросейсмах или специально возбуждаемых для подобных исследований искусственных колебаний, т.к. при достаточно сильных сейсмических воздействиях выделение видимого периода значительно осложнено. Для определения динамических параметров зданий и возможности использования методов расчета сооружений с применением импульсных передаточных функций разработаны статистические методы решения обратных задач по восстановлению подобных передаточных функций на базе инженерно-сейсмометрической информации. Анализ зарегистрированных на инженерно-сейсмометрических станциях процессов входа и (основание, фундамент) и выхода (покрытие, перекрытия) позволяет определять импульсные передаточные функции, после чего решить приведенные интегральные уравнения Дейч, 1979 Denisov et al., 1986. The results of studies aimed at creating dynamic models of structures suitable for calculating earthquake resistance are presented. A method for determining model parameters based on engineering-seismometric information is considered. Examples of determining the dynamic parameters of a single-mass model for deterministic and statistical cases are given. Dynamic loads on structures are characterized by a change in the dynamic characteristics of the structure, arising from vibrations during earthquakes and explosions, when massive bodies are struck, etc. Not only the movement of the points of the structure, but also the internal forces and stresses in its elements are oscillatory. Determination of the expected amplitudes of displacements, internal forces and stresses in the structure during its oscillations under the action of dynamic load, i.e. in case of forced vibrations and their comparison with acceptable values are the main content of the dynamic calculation of the structure. The permissible values of the amplitudes of internal forces are determined by the requirements of strength and durability of building structures, and the amplitudes of the velocities and accelerations of vibrations of buildings and structures in which people or a production room with precise technology are located, by the requirements of the harmless effect of fluctuations on peoples health and on the quality of products Savovich, 2005. According to the records of seismometric instruments installed on the buildings cover, their own periods of oscillation of the structures are approximately determined. Basically, these measurements correspond to the actual period of the buildings own vibration (the fundamental tone of natural vibrations) only with small seismic effects, microseisms or artificial vibrations specially excited for such studies, because with sufficiently strong seismic effects, the selection of the visible period is significantly complicated. To determine the dynamic parameters of buildings and the possibility of using methods for calculating structures using pulsed transfer functions, statistical methods have been developed for solving inverse problems to restore such transfer functions on the basis of engineering-seismometric information. An analysis of the input and (base, foundation) and output (cover, overlap) processes recorded at the engineering-seismometric stations allows determining the impulse transfer functions, and then solving the given integral equations Deutsch, 1979 Denisov et al., 1986.


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