scholarly journals Hovering Stability of Helicopters With Elastic Constraints

2010 ◽  
Author(s):  
Paul E. I. Pounds ◽  
Aaron Dollar
Keyword(s):  
Proof Of Concept ◽  
Free Flight ◽  
Contact Constraint ◽  
Grasping And Manipulation ◽  
Reaction Forces ◽  
Manipulation Task ◽  
The Stability ◽  
External Forces ◽  
Elastic Constraints ◽  
Constraint Model

Aerial vehicles are difficult to stabilize, especially when acted upon by external forces. A hovering vehicle in contact with objects and surfaces must maintain flight stability while subject to forces imparted to the airframe through the point of contact. These forces couple with the motion of the aircraft to produce distinctly different dynamics from free flight. While external contact is generally avoided, extending aerial robot functionality to include contact with the environment during flight opens up new and useful areas such as perching, object grasping and manipulation. In this paper, we present a general elastic contact constraint model and analyze helicopter stability in the presence of those contacts. As an example, we evaluate the stability of a proof-of-concept helicopter system for manipulating objects using a compliant gripper that can be modeled as an elastic linkage with angular reaction forces. An off-the-shelf PID flight controller is used to stabilize the helicopter in free flight, as well as during the aerial manipulation task. We show that the planar dynamics of the object-helicopter system in vertical, horizontal and pitch motion around equilibrium are shown to remain stable, within a range of contact stiffnesses, under unmodified PID control.

scholarly journals A Bio-Inspired Compliance Planning and Implementation Method for Hydraulically Actuated Quadruped Robots with Consideration of Ground Stiffness

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2838
Author(s):  
Xiaoxing Zhang ◽  
Haoyuan Yi ◽  
Junjun Liu ◽  
Qi Li ◽  
Xin Luo
Keyword(s):  
Harmonic Oscillation ◽  
Ground Surface ◽  
Legged Locomotion ◽  
Soft Ground ◽  
Quadruped Robots ◽  
In Series ◽  
Reaction Forces ◽  
Implementation Method ◽  
The Stability ◽  
Natural Dynamics

There has been a rising interest in compliant legged locomotion to improve the adaptability and energy efficiency of robots. However, few approaches can be generalized to soft ground due to the lack of consideration of the ground surface. When a robot locomotes on soft ground, the elastic robot legs and compressible ground surface are connected in series. The combined compliance of the leg and surface determines the natural dynamics of the whole system and affects the stability and efficiency of the robot. This paper proposes a bio-inspired leg compliance planning and implementation method with consideration of the ground surface. The ground stiffness is estimated based on analysis of ground reaction forces in the frequency domain, and the leg compliance is actively regulated during locomotion, adapting them to achieve harmonic oscillation. The leg compliance is planned on the condition of resonant movement which agrees with natural dynamics and facilitates rhythmicity and efficiency. The proposed method has been implemented on a hydraulic quadruped robot. The simulations and experimental results verified the effectiveness of our method.

Controlling Origami Stability Profile Using Magnets

2018 ◽  
Author(s):  
Hongbin Fang ◽  
Tse-Shao Chang ◽  
K. W. Wang
Keyword(s):  
Potential Energy ◽  
Wide Spectrum ◽  
Concept Design ◽  
Proof Of Concept ◽  
Potential Energy Landscape ◽  
Mechanical Metamaterials ◽  
Elastic Potential Energy ◽  
The Stability ◽  
Novel Applications ◽  
Stable Structures

Multi-stable structures and materials have attracted extensive research interests because they can provide a wide spectrum of adaptive properties and functionalities. Recently, origami has been identified as an important source for achieving multi-stability and has been exploited for developing unconventional mechanical metamaterials and metastructures. Once the crease pattern and the constituent materials have been specified for an origami structure, its multi-stability profile becomes unchangeable. On the other hand, a controllable profile would be desirable to endow the origami structures and origami metamaterials with further adaptability and versatility. This research investigates how to integrate magnets with origami to fundamentally alter the stability profiles. By embedding magnets into the origami facets or vertices, the magnetic potential energy would modify the original elastic potential energy landscape both quantitatively and qualitatively. Taking the stacked Miura-ori structures as examples, we show that different magnet assignments could either enrich the original bistable profile into a tri-stable or quad-stable profile, or simplify it into a mono-stable profile. Simultaneously, such magnet-induced evolutions of stability profile would trigger essential changes of the structure’s mechanical properties, which are promising to be used for developing multi-functional devices or metamaterials/metastructures. In this paper, in addition to the analyses, proof-of-concept design and prototype are presented. The results of this research would open up a new path for designing origami structures and metamaterials with controllable stability profiles that can be harnessed for many novel applications.

Added Fluid Mass and the Equations of Motion of a Parachute

1983 ◽  
Vol 34 (3) ◽  
pp. 226-242 ◽  
Author(s):  
John A. Eaton
Keyword(s):  
Equations Of Motion ◽  
Added Mass ◽  
Unsteady Forces ◽  
Fluid Mass ◽  
Mass Tensor ◽  
Body Shapes ◽  
The Stability ◽  
External Forces ◽  
Six Degree Of Freedom ◽  
Nonlinear Solutions

SummaryWhile it has long been known that added fluid mass may be important in the dynamics of parachutes, due to inadequate or incorrect derivation and/or implementation of the added mass tensor its full significance in the stability of parachutes has yet to be appreciated. The concept of added mass is outlined and some general conditions for its significance are presented. Its implementation in the parachute equations of motion is reviewed, and the equations used in previous treatments are shown to be erroneous. A general method for finding the equivalent external forces and moments due to added mass is given, and the correct, anisotropic forms of the added mass tensor are derived for the six degree-of-freedom motion in an ideal fluid of rigid body shapes with planar-, twofold- and axisymmetry, These derivations may also be useful in dynamic stability studies of other low relative density bodies such as airships, balloons, submarines and torpedoes. Full nonlinear solutions of the equations of motion for the axisymmetric parachute have been obtained, and results indicate that added mass effects are more significant than previously predicted. In particular, the component of added mass along the axis of symmetry has a strong influence on stability. Better data on unsteady forces and moments on parachutes are needed.

Lyapunov-stable control of mechatronic systems

2005 ◽  
Vol 219 (2) ◽  
pp. 173-185 ◽  
Author(s):  
O Enge ◽  
P Maißer
Keyword(s):  
Inverse Dynamics ◽  
Dynamic Control ◽  
Linear Feedback ◽  
Mechatronic Systems ◽  
Electromechanical Systems ◽  
Starting Point ◽  
Reaction Forces ◽  
The Stability ◽  
Lagrange Formalism ◽  
Stable Control

In this paper, a method for controlling mechatronic systems using inverse dynamics is proposed. The starting point is a unified mathematical approach to modelling electromechanical systems based on Lagrange formalism. This mathematical theory is used to represent such systems taking into account all interactions between their substructures. The concept of Lagrange formalism for electromechanical systems is given and the complete governing equations are presented. The Voronetz equations of a partially kinematically controlled electromechanical system (EMS) are derived. The corresponding reaction forces and voltages following from the Voronetz equations are determined. Using these reactions with small modifications, a so-called ‘augmented proportional-derivative (PD) dynamic control law’ is generated. This controller consists of a non-linear feedforward - based on inverse dynamics - and a linear feedback. The stability of the controller is proved using a Lyapunov function. The controller can also be applied to pure multibody systems or a sheer electrical system, both of which are borderline cases of mechatronic systems.

Object Manipulation Using Compliant Fingerpads: Modeling and Control

1993 ◽  
Vol 115 (4) ◽  
pp. 638-648 ◽  
Author(s):  
A. M. Annaswamy ◽  
D. Seto
Keyword(s):  
Adaptive Control ◽  
Feedback Linearization ◽  
Industrial Robots ◽  
Dynamic Interactions ◽  
Modeling And Control ◽  
Grasp Stability ◽  
Grasping And Manipulation ◽  
End Effectors ◽  
Geometric Techniques ◽  
The Stability

Current industrial robots are often required to perform tasks requiring mechanical interactions with their environment. For tasks that require grasping and manipulation of unknown objects, it is crucial for the robot end-effector to be compliant to increase grasp stability and manipulability. The dynamic interactions that occur between such compliant end-effectors and deformable objects that are being manipulated can be described by a class of nonlinear systems. In this paper, we determine algorithms for grasping and manipulation of these objects by using adaptive feedback techniques. Methods for control and adaptive control of the underlying nonlinear system are described. It is shown that although standard geometric techniques for exact feedback linearization techniques are inadequate, yet globally stable adaptive control algorithms can be determined by making use of the stability characteristics of the underlying nonlinear dynamics.

Determining the Static Joint Torques of a Digital Human Model Considering Balance

2009 ◽  
Author(s):  
Jingzhou James Yang ◽  
Yujiang Xiang ◽  
Joo Kim
Keyword(s):  
Human Model ◽  
Joint Torques ◽  
Digital Human Model ◽  
Human Models ◽  
Support Reaction ◽  
Reaction Forces ◽  
Zero Moment ◽  
The Stability ◽  
Physics Based Simulation ◽  
Digital Human

This paper presents a methodology for determining the static joint torques of a digital human model considering balance for both standing and seating tasks. An alternative and efficient formulation of the Zero-Moment Point (ZMP) for static balance and the approximated (ground/seat) support reaction forces/moments are derived from the resultant reaction loads, which includes the gravity and externally applied loads. The proposed method can be used for both standing and seating tasks for assessing the stability/balance of the posture. The proposed formulation can be beneficial to physics-based simulation of humanoids and human models. Also, the calculated joint torques can be considered as an indicator to assess the risks of injuries when human models perform various tasks.

Defect Interactions and Polytype Transitions

2011 ◽  
Vol 324 ◽  
pp. 217-220 ◽  
Author(s):  
Jörg Pezoldt ◽  
Andrei Alexandrovich Kalnin
Keyword(s):  
Stacking Faults ◽  
Stability Loss ◽  
Original Structure ◽  
Initial Structure ◽  
Nonequilibrium Phase Transition ◽  
Partial Dislocations ◽  
The Stability ◽  
Defect Interactions ◽  
External Forces ◽  
Selective Interactions

The polytype transitions are caused by disorder generation in the initial structure due to energy dissipation. The disorder is strongly related to the formation and propagation of stacking faults and partial dislocations. Collective and selective interactions between these defects result in a stability loss of the original structure leading to nonequilibrium phase transition occur if the critical point is reached. The stability of the defect subsystem was investigated in the stationary state for three types of stacking faults. The combination of the stability analysis with the defect generation processes during the different technological and devices operation processes allows predicting the critical values for the external forces and fluxes leading to phase transitions.

Analytical Method for Determining the Static Equilibrium Position of the Rear Axles Guiding Mechanisms of the Motor Vehicles

2016 ◽  
Vol 841 ◽  
pp. 59-64 ◽  
Author(s):  
Cătălin Alexandru
Keyword(s):  
Equilibrium Position ◽  
Original Method ◽  
Static Equilibrium ◽  
Motor Vehicles ◽  
Car Body ◽  
Mathematical Algorithm ◽  
Positional Analysis ◽  
Reaction Forces ◽  
External Forces ◽  
Elastic Elements

The work deals with an analytical algorithm for determining the static equilibrium position of the multi-link guiding mechanisms used for the rear axles of the motor vehicles. The method is based on the virtual mechanical work principle, considering the external forces applied to the wheels, as well the reaction forces in the elastic elements of the suspension. The equilibrium position of the guiding mechanism is established relative to the car body, considering the static model of the suspension system, in which the car body is fixed connected to ground (in other words, the car body is the reference part of the system). For determining the reaction forces in the elastic elements of the suspension (springs, bumpers and rebound elements, bushings, anti-roll bar), an original method for the positional analysis of the axle guiding mechanisms was developed and integrated in the mathematical algorithm for establishing the equilibrium position.

scholarly journals STABILITY ASSESSMENT OF ADJACENT ROCK MASS IN THE DEVELOPMENT OF COALBED OUTLETS

2018 ◽  
pp. 51-59
Author(s):  
Olga G. Bessimbaeva ◽  
Elena N. Khmyrova ◽  
Farit K. Nizametdinov ◽  
Elena A. Oleinikova
Keyword(s):  
Rock Mass ◽  
Coal Seam ◽  
Active Phase ◽  
Geological Structure ◽  
Stability Assessment ◽  
South Side ◽  
Southern Side ◽  
The Stability ◽  
External Forces ◽  
Adjacent Rock

The problems of stability assessment of the quarry’s southern side during the development of the coal seam D6 are considered. To  assess the stability of the quarry’s southern side in the development  of coalbed outlets, modern research methods are applied: study of  the geological structure and analysis of the adjacent rock mass  state, the creation of an observation station and the production of observations, calculation of stability of adjacent rock mass of the  quarry’s south side and the research results analysis. Quarry’s south  side consists of clayey sediments up to 5 m, then siltstones and  mudstones up to 10-20 m and a coal seam with a capacity of up to  5 m. The substantiation of the calculated strength characteristics of  rocks composing the slopes of the quarry ledges, which determine the stress state of the slopes arising under the influence  of internal and external forces, is done. Instrumental observations of the laid station and the survey of cracks on the quarry’s side allowed  to determine the contours of the deformation zone and the  landslide prism size. A geomechanical model of adjacent rock mass  was created and the stability assessment was carried out for the  geological section along the line of the maximum development  depth. After additional loading on the quarry’s southern side slopes,  the safety factor of stability is nу = 1.69−173, which means active  phase termination of quarry’s side deformation and sustainable condition.

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