Limb/Ground Impacts and Unexpected Impacts Control Strategy for a Model of a Walking Robot Limb

2010 ◽  
Vol 164 ◽  
pp. 377-382
Author(s):  
Krzysztof Lipiński
Keyword(s):  
Control System ◽  
Normal Component ◽  
Contact Forces ◽  
Walking Robots ◽  
Unilateral Constraints ◽  
Multibody Model ◽  
Dc Motors ◽  
Tangent Direction ◽  
Analysis Of Dynamics ◽  
The Impact

The paper deals with numerical analysis of dynamics of walking robots. The focus is on limb/ground contact. Normal and tangent direction are considered separately. In the normal one, the contacts are modeled as unilateral constraints. In the tangent one, slip and friction are considered. As the contacts are unilateral, nonzero velocities could be present before the contact. These velocities diminish rapidly, and significant contact forces are present. The forces have destructive influence on the robot structure, and the impulsive changes of the arms velocities can disorient the control system. In the paper, the impact consequences are discussed, as well as consequences of installation of a 0/1 contact sensor. A 3D mechatronic multibody model of a quote of a robot is considered. Its limb is driven by DC motors and controlled by a dedicated control system. With the zero signals from the sensor, the control prevents a constant velocity of the limb end. The normal component of the velocity has to be stopped at the positive signals, and the motor current has to be reduced. Exemplary calculations are presented in the paper.

Dynamics of High Speed Roller Chain Drives

1995 ◽  
Author(s):  
Peter Fritz ◽  
Friedrich Pfeiffer
Keyword(s):  
High Speed ◽  
Contact Forces ◽  
System Structure ◽  
Unilateral Constraints ◽  
Roller Chain ◽  
Contact Configuration ◽  
Nonlinear Force ◽  
A Chain ◽  
The Impact ◽  
Chain Drives

Abstract This paper deals with roller chain drives applied in combustion engines. In order to find characteristics for an optimal design, all components of a chain drive are taken into account. For a detailed analysis of the chain strand vibrations and the contact configurations each chain link, sprocket and guide is treated as a separate body. A nonlinear force element describes the joint forces, including elasticity, damping, backlash and oil-displacement. To determine real contact forces between a link and a sprocket or a guide, the exact contour and the mutual dependence of the contacts are considered. The impact of one link may influence the other links in such a manner that their contact configuration may change. In the mechanical model these contacts are represented by unilateral constraints. Applying the formulation of the linear complementarities including additional inequality conditions, the determination of a valid contact configuration after a change in the system structure is simplified.

scholarly journals State observer design for a walking in-pipe robot

2018 ◽  
Vol 161 ◽  
pp. 03012 ◽  
Author(s):  
Sergei Savin ◽  
Sergey Jatsun ◽  
Ludmila Vorochaeva
Keyword(s):  
Control System ◽  
State Observer ◽  
Contact Forces ◽  
Observer Design ◽  
Walking Robots ◽  
Accurate Information ◽  
Precise Control ◽  
Mechanical Constraints ◽  
Wide Range ◽  
Reaction Forces

In this paper, a state observer design for a walking in-pipe robot is studied. The necessity of using a state observer is related to the fact that sensors have limited accuracy and are prone to producing noise. This is especially problematic for in-pipe walking robots, since they use model-based control and require accurate information of their current state. The paper shows that an iterative state observer based on solving Riccati equation provides significant improvements in the behaviour of the control system. It allows to smooth out the spikes in the control actions requested by controller and to minimize tremor of the robot links. In order to study the behaviour of the observer when different sensors are used, a performance function was introduced. It was shown that the observer allows to improve the performance of the control system for a wide range of sensor parameters. Additionally, it was shown that the introduction of the observer allows to choose higher feedback controller gains, enabling more precise control. Simulations on the full robot model, taking into account mechanical constraints and contact forces showed that the linear observer is capable of improving the behaviour of the control system of the walking robot, if measurements of the reaction forces are provided. The effects that the noise and quantization in the reaction forces measurements have on the behaviour of the state observer is studied.

scholarly journals OPTIMAL CONTROL OF AN ACTUATOR OF A ROBOTIC GEARBOX

2021 ◽  
Vol 1 (92) ◽  
pp. 72
Author(s):  
Alexander Gurko ◽  
Mykola Mykhalevych
Keyword(s):  
Optimal Control ◽  
Control System ◽  
High Speed ◽  
Performance Criterion ◽  
Optimal Controller ◽  
Mechanical Transmission ◽  
Linear Quadratic ◽  
Weighting Factors ◽  
Dc Motors ◽  
The Impact

Problem. Despite the vigorous development of electric vehicles, the task of facilitating the driver to handle with elements of mechanical transmission remains relevant. For this purpose, the automation of mechanical transmission units is performed. For instance, so-called robotic gearboxes are widespread. The principle of operation of such gearboxes is similar to mechanical ones, but special separate actuators carry out the selection and shifting into the desired gear. The design of a robotic gearbox was proposed at the Automobile Department of Kharkiv National Automobile and Highway University. At this gearbox, two DC motors are used as actuators. The efficiency of this gearbox largely depends on the efficiency of the DC motors control system, which should provide smooth but at the same time fast and accurate positioning of their shafts. In previous works, PID controllers were used to controlling the actuator of the gearbox. However, although the PID controller provides satisfactory quality of the control system, it is not an optimal controller. Goal. The goal of this paper is to develop an optimal controller for the actuators of the robotic gearbox mentioned above. Methodology. To meet this goal, it was proposed to use a linear-quadratic controller (LQR). The analysis of the impact on transient processes in the control system of the values of the weighting factors in the quadratic performance criterion is performed. Results. The LQR synthesized provides high speed of response (within of 0.5 s) at the desired gear selecting and more than two times less overshoot compared to the PID regulator. Originality. The regularities in the gearbox drive performance when changing the values of the weighting factors in the performance criterion have been established. An optimal control system for the robotic gearbox actuator has been developed. Practical value. The implementation of the designed controller will increase the efficiency of the gearbox under consideration.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

scholarly journals Simulation Verification of the Contact Parameter Influence on the Forces’ Course of Cereal Grain Impact against a Stiff Surface

2021 ◽  
Vol 11 (2) ◽  
pp. 466
Author(s):  
Włodzimierz Kęska ◽  
Jacek Marcinkiewicz ◽  
Łukasz Gierz ◽  
Żaneta Staszak ◽  
Jarosław Selech ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Decisive Role ◽  
Force Sensor ◽  
Contact Forces ◽  
Correct Selection ◽  
Contact Parameter ◽  
Cereal Grain ◽  
Wide Range ◽  
The Impact ◽  
Selection Of

The continuous development of computer technology has made it applicable in many scientific fields, including research into a wide range of processes in agricultural machines. It allows the simulation of very complex physical phenomena, including grain motion. A recently discovered discrete element method (DEM) is used for this purpose. It involves direct integration of equations of grain system motion under the action of various forces, the most important of which are contact forces. The method’s accuracy depends mainly on precisely developed mathematical models of contacts. The creation of such models requires empirical validation, an experiment that investigates the course of contact forces at the moment of the impact of the grains. To achieve this, specialised test stations equipped with force and speed sensors were developed. The correct selection of testing equipment and interpretation of results play a decisive role in this type of research. This paper focuses on the evaluation of the force sensor dynamic properties’ influence on the measurement accuracy of the course of the plant grain impact forces against a stiff surface. The issue was examined using the computer simulation method. A proprietary computer software with the main calculation module and data input procedures, which presents results in a graphic form, was used for calculations. From the simulation, graphs of the contact force and force signal from the sensor were obtained. This helped to clearly indicate the essence of the correct selection of parameters used in the tests of sensors, which should be characterised by high resonance frequency.

scholarly journals Dynamics of Multibody Systems With Spherical Clearance Joints

2005 ◽  
Author(s):  
P. Flores ◽  
J. Ambro´sio ◽  
J. C. P. Claro ◽  
H. M. Lankarani
Keyword(s):  
Contact Force ◽  
Multibody Systems ◽  
Contact Forces ◽  
Force Model ◽  
Clearance Joints ◽  
Continuous Contact ◽  
Clearance Joint ◽  
Contact Force Model ◽  
Dynamics Of Multibody Systems ◽  
The Impact

This work deals with a methodology to assess the influence of the spherical clearance joints in spatial multibody systems. The methodology is based on the Cartesian coordinates, being the dynamics of the joint elements modeled as impacting bodies and controlled by contact forces. The impacts and contacts are described by a continuous contact force model that accounts for geometric and mechanical characteristics of the contacting surfaces. The contact force is evaluated as function of the elastic pseudo-penetration between the impacting bodies, coupled with a nonlinear viscous-elastic factor representing the energy dissipation during the impact process. A spatial four bar mechanism is used as an illustrative example and some numerical results are presented, being the efficiency of the developed methodology discussed in the process of their presentation. The results obtained show that the inclusion of clearance joints in the modelization of spatial multibody systems significantly influences the prediction of components’ position and drastically increases the peaks in acceleration and reaction moments at the joints. Moreover, the system’s response clearly tends to be nonperiodic when a clearance joint is included in the simulation.

Development of an End-Effector for Mitigation of Collisions

2021 ◽  
Author(s):  
Domenico Tommasino ◽  
Matteo Bottin ◽  
Giulio Cipriani ◽  
Alberto Doria ◽  
Giulio Rosati
Keyword(s):  
Numerical Simulations ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Contact Forces ◽  
Design Parameters ◽  
End Effector ◽  
Linear Behavior ◽  
Stable Mechanism ◽  
Robot Tasks ◽  
The Impact

Abstract In robotics the risk of collisions is present both in industrial applications and in remote handling. If a collision occurs, the impact may damage both the robot and external equipment, which may result in successive imprecise robot tasks or line stops, reducing robot efficiency. As a result, appropriate collision avoidance algorithms should be used or, if it is not possible, the robot must be able to react to impacts reducing the contact forces. For this purpose, this paper focuses on the development of a special end-effector that can withstand impacts and is able to protect the robot from impulsive forces. The novel end-effector is based on a bi-stable mechanism that decouples the dynamics of the end-effector from the dynamics of the robot. The intrinsically non-linear behavior of the end-effector is investigated with the aid of numerical simulations. The effect of design parameters and the operating conditions are analyzed and the interaction between the functioning of the bi-stable mechanism and the control system is studied. In particular, the effect of the mechanism in different scenarios characterized by different robot velocities is shown. Results of numerical simulations assess the validity of the proposed end-effector, which can lead to large reductions in impact forces.

scholarly journals Estimating Contact Forces and Moments for Walking Robots and Exoskeletons Using Complementary Energy Methods

2018 ◽  
Vol 3 (4) ◽  
pp. 3410-3417 ◽  
Author(s):  
Jonas Vantilt ◽  
Chetan Giraddi ◽  
Erwin Aertbelien ◽  
Friedl De Groote ◽  
Joris De Schutter
Keyword(s):  
Contact Forces ◽  
Walking Robots ◽  
Energy Methods ◽  
Complementary Energy

scholarly journals ТНЕ WORLD OIL MARKET: THE SEARCH FOR BALANCE IN THE NEW "OIL" REALITY

2016 ◽  
pp. 115-124
Author(s):  
T. A. Malova ◽  
V. I. Sisoeva
Keyword(s):  
Price Volatility ◽  
Future Market ◽  
Oil Market ◽  
The World ◽  
Competitive Relations ◽  
The Face ◽  
The Usa ◽  
Analysis Of Dynamics ◽  
State Of Research ◽  
The Impact

The article provides an analysis of change of the world oil market in the face of new "oil" reality. Factors of formation of new "oil" reality in the global world defined. Scientific background and current state of research of the problem are described. It is shownthat in the Russian and foreign literature the considerable attention is paid to the analysis of dynamics of the quantitative variables characterizing fluctuations and shocks in the oil market. At the same time the search for balance in the new "oil" reality are not considerably investigated yet. The proposed approach allows toreveal the substance of the transformation of the world oil market, to assess the changes in the oil market with the development of rhenium in terms of efficiency and functioning of the mechanism, the prospects of price volatility in the oil market. The main directions of transformation of the oil market are follows. Development of a subject basis of the oil market due to changes of a role of the main market players whose structure includes the USA, Saudi Arabia, Russia now. The impact of regulatory factors complex in the oil market towards equilibrium, which include activity of OPEC, supply of shale oil, future market,activity of the uniform regulator and national regulators. Transformation of the oil market in the direction of perfection of the competitive relations, achievement of optimum market balance as a result of coordination and interaction of interests of participants of the global oil market.

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