Optimization of the Parameters of a Hydraulic Excavator Swinging Mechanism

The presented paper is focused to the optimization of the parameters of a hydraulic excavator swinging mechanism. A trapezoidal velocity profile is considered for rotation of the excavator platform to the predefined angle. Equations for the torque and power, needed to rotate the platform according to the prescribed trapezoidal trajectory are derived. The maximum values of the driving torque and power are optimized

Numerical study of the hydraulic excavator overturning stability during performing lifting operations

This article presents a numerical study of the stability of a hydraulic excavator during performing lifting operations. A planar dynamic model is developed with six degrees of freedom, which considers the base body elastic connection with the terrain, the front digging manipulator links, and the presence of the freely suspended payload. Differential equations describing the excavator dynamic behavior are obtained by using the Lagrange formalism. Numerical experiments are carried out to study the excavator dynamic stability under different operating conditions during the motion along a vertical straight-line trajectory. It is shown that the arising inertial loads during the movement of the links along the vertical trajectory, combined with the payload swinging and the motion of the base body, decreases the excavator stability. It was found that the excavator stability during following vertical straight-line trajectory decreases considerably in the lower part of the vertical trajectory. If the stability coefficient is close to 1, the payload swinging can cause the separation of a support from the terrain; nevertheless, the excavator stability can be restored. A method for tire stiffness and damping coefficients estimation is presented. The validation of the dynamical model is performed by the use of a small-scale elastically mounted manipulator.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Transient motion of an industrial mixer with elastically suspended work head

This paper investigates the transient behavior of a novel design of an industrial mixer incorporating additional work head movement. In contrast to conventional models, this mixer consists of an elastic torsion bar with its longitudinal axis oriented orthogonally to the main drive shaft axis. Using the elastic torsion bar to hang the workhead adds an additional degree of freedom, greatly improving the mixing of fluids or powders. The motion of the electro-mechanical device was simulated using a system of nonlinear differential equations that consider the dynamic characteristics of the driving electric motor, as derived from the theorem for the rate of change of angular momentum. A numerical analysis was carried out to study the transient processes in the system under different working conditions. Finally, a constrained multiobjective optimization was performed to identify the optimal design variable values that minimize the force and power characteristics of the mixer

Dynamical modelling of hydraulic excavator considered as a multibody system

This paper considers the development of a plane multibody mechanical model of a hydraulic excavator simultaneously containing an open kinematic chain and closed loops. The Lagrange multiplier technique is used for modelling of the constrained mechanical systems. This approach is used for working out the dynamic equations of excavator motion in the case of performing transportation and digging operations. The excavator is considered as a rigid body system and detailed governing equations of the mechanical and hydraulic systems are presented. The performed verification and a typical digging task simulation show the applicability of the model for study of the excavator motion simulation. Simulation results of the machine’s response are provided. It is shown that the digging process considerably influences the mechanical and hydraulic system parameters. Such models can be used for training simulators, sizing components and system design.DFG, 325093850, Open Access Publizieren 2017 - 2018 / Technische Universität Berli

A THEORETICAL-EXPERIMENTAL APPROACH FOR ELASTO-DAMPING PARAMETERS ESTIMATION OF CONE INERTIAL CRUSHER MOUNTING

The present paper deals with estimation of the elasto-damping parameters of a cone inertial crusher mounting. The numerical values of these parameters are crucial for accurate reproduction of the machine vibrational behavior and dynamical model adequacy. Due to the significant difficulties arising during the purely theoretical determination of the stiffness and damping parameters of the rubber vibroisolators it is well-suited to use a theoretical-experimental approach. The developed approach is based on the theoretical determination of the mounting stiffness parameters as a function of two experimentally measured natural frequencies of the mechanical system. The crusher is represented as a six degrees of freedom system with two planes of symmetry. By using the system characteristic polynomial, the theoretical derivation of mathematical relationships for the mechanical system natural frequencies as a function of stiffness, inertial and geometrical parameters is performed. A good agreement is shown when comparing the experimental and the theoretical results for the system kinematical characteristics

CLOUD-BASED EXPERT SYSTEM FOR SYNTHESIS AND EVOLUTIONARY OPTIMIZATION OF PLANAR LINKAGES

The present paper introduces a cloud-based expert system for synthesis and evolutionary optimization of planar linkages. The kinematic structure of the linkage is composed by the modular approach based on Assur’s groups. The dyads are represented as functional blocks with input and output variables. The applied approach for obtaining the geometrical relationships between the input and the output variables of the dyads is based on the use of homogeneous transformation matrices. The developed software system allows a dimensional synthesis of planar linkages by using genetic optimization algorithms. One feature is remote creation of the models of genetic algorithms as well as the receiving of the results by means of a user-friendly interface. By exploiting the application, the user can produce and edit the initial information about the synthesized or optimized linkage; thus he can receive the calculation results as a web page and/or as MS Excel file. An additional mutation of the best chromosome genes by scanning of every gene within its searching space improves the optimal solution. The analyzed numerical case studies show the applicability of the developed software system for mechanism analysis, synthesis and optimization. Because the number of genes is not limited, the linkages with a very big number of design variables can be synthesized by exploiting the developed approach

Dynamical modelling of hydraulic excavator considered as a multibody system

Rad se bavi razvojem mehaničkog modela hidrauličnog bagera od više tijela koji u isto vrijeme sadrži otvoreni kinematički lanac i zatvorene petlje. Za modeliranje ograničenih mehaničkih sustava primijenjena je tehnika Lagrangeova faktora. Taj se pristup primjenjuje za dobivanje dinamičkih jednadžbi kretanja bagera kod obavljanja prijenosa i operacija kopanja. Bager se smatra sustavom krutog tijela i predstavljaju se detaljne jednadžbe za uređenje mehaničkih i hidrauličnih sustava. Izvršena provjera i simulacija tipičnog kopanja pokazuju primjenjivost sustava za proučavanje simulacije kretanja bagera. Daju se simulacijski rezultati reakcije stroja. Pokazano je da postupak kopanja znatno utječe na parametre mehaničkog i hidrauličkog sustava. Takvi se modeli mogu koristiti za obučavanje simulatora, dimenzioniranje sastavnih dijelova i dizajniranje sustava.This paper considers the development of a plane multibody mechanical model of a hydraulic excavator simultaneously containing an open kinematic chain and closed loops. The Lagrange multiplier technique is used for modelling of the constrained mechanical systems. This approach is used for working out the dynamic equations of excavator motion in the case of performing transportation and digging operations. The excavator is considered as a rigid body system and detailed governing equations of the mechanical and hydraulic systems are presented. The performed verification and a typical digging task simulation show the applicability of the model for study of the excavator motion simulation. Simulation results of the machine’s response are provided. It is shown that the digging process considerably influences the mechanical and hydraulic system parameters. Such models can be used for training simulators, sizing components and system design

Theoretical and Experimental Study of a Thermo-Mechanical Model of a Shape Memory Alloy Actuator Considering Minor Hystereses

The paper presents a theoretical and experimental investigation of a thermo-mechanical model of an actuator composed of a shape memory alloy wire arranged in series with a bias spring. The developed mathematical model considers the dynamics of the actuator in the thermal and mechanical domains. The modelling accuracy is increased through the developed algorithm for modelling the minor and sub minor hystereses, thus removing the disadvantages of the classical model. The algorithm improves the accuracy, especially when using pulse-width modulation control, for which minor and sub minor hystereses are likely to occur. Experimental studies show that the system is very sensitive, and there are physical factors whose presence cannot be considered in the mathematical model. The experimental research has shown that setting constant values of the duty cycle is impossible to obtain a stable value of displacement and force. The comparison between the developed mathematical model results and the experimental results shows that the differences are acceptable. The improved modelling serves as a basis for designing such actuators and creating an improved automatic feedback control system to maintain a given displacement (force) or trajectory tracking