Discrete modular serpentine robotic tail: design, analysis and experimentation

Robotica ◽  
2018 ◽  
Vol 36 (7) ◽  
pp. 994-1018 ◽  
Author(s):  
Wael Saab ◽  
William S. Rone ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Dynamic Models ◽  
Design Analysis ◽  
Degree Of Freedom ◽  
Legged Robots ◽  
Design Parameters ◽  
Inertial Loading ◽  
Forward Kinematic ◽  
The Impact ◽  
Accuracy And Repeatability ◽  
Two Degree Of Freedom

SUMMARYThis paper presents the design, analysis and experimentation of a Discrete Modular Serpentine Tail (DMST). The mechanism is envisioned for use as a robotic tail integrated onto mobile legged robots to provide a means, separate from the legs, to aid stabilization and maneuvering for both static and dynamic applications. The DMST is a modular two-degree-of-freedom (DOF) articulated, under-actuated mechanism, inspired by continuum and serpentine robotic structures. It is constructed from rigid links with cylindrical contoured grooves that act as pulleys to route and maintain equal displacements in antagonistic cable pairs that are connected to a multi-diameter pulley. Spatial tail curvatures are produced by adding a roll-DOF to rotate the bending plane of the planar tail curvatures. Kinematic and dynamic models of the cable-driven mechanism are developed to analyze the impact of trajectory and design parameters on the loading profiles transferred through the tail base. Experiments using a prototype are performed to validate the forward kinematic and dynamic models, determine the mechanism's accuracy and repeatability, and measure the mechanism's ability to generate inertial loading.

Dynamic Behavior of Piezoelectric Recurve Actuation Architectures

2004 ◽  
Vol 126 (1) ◽  
pp. 37-46 ◽  
Author(s):  
James D. Ervin ◽  
Diann E. Brei
Keyword(s):  
Dynamic Behavior ◽  
Architectural Design ◽  
Dynamic Models ◽  
Dynamic Performance ◽  
Design Parameters ◽  
New Family ◽  
State Frequency ◽  
Actuation Scheme ◽  
The Impact ◽  
High Work

A new family of piezoelectric actuators, called Recurves, exhibits high work per volume and have the extra benefit of performance and packaging tailorability. The focus of this paper is the dynamic performance of this novel actuation scheme. Two dynamic models, a detailed transfer matrix model and a simpler rod approximation model, are presented to predict the steady state frequency response of a general Recurve actuator driving a mass and spring load. Results from a 23 design of experiments are given that validate these models and demonstrate the impact of the architectural design parameters on the dynamic behavior of a generic Recurve actuator.

Controller Design, Analysis, and Experimental Validation of a Robotic Serpentine Tail to Maneuver and Stabilize a Quadrupedal Robot

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
William S. Rone ◽  
Wael Saab ◽  
Anil Kumar ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Experimental Validation ◽  
Dynamic Models ◽  
Controller Design ◽  
External Disturbance ◽  
Legged Robots ◽  
Legged Robot ◽  
Outer Loop ◽  
Inertial Loading ◽  
Yaw Angle ◽  
System Designs

This paper analyzes how a multisegment, articulated serpentine tail can enhance the maneuvering and stability of a quadrupedal robot. A persistent challenge in legged robots is the need to account for propulsion, maneuvering, and stabilization considerations when generating control inputs for multidegree-of-freedom spatial legs. Looking to nature, many animals offset some of this required functionality to their tails to reduce the required action by their legs. By including a robotic tail on-board a legged robot, the gravitational and inertial loading of the tail can be utilized to provide for the robot's maneuverability and stability, while the legs primarily provide the robot's propulsion. System designs for the articulated serpentine tail and quadrupedal platform are presented, along with the dynamic models used to represent these systems. Outer-loop controllers that implement the desired maneuvering and stabilizing behaviors are discussed, along with an inner-loop controller that maps the desired tail trajectory into motor torque commands for the tail. Case studies showing the tail's ability to modify yaw-angle heading during locomotion (maneuvering) and to reject a destabilizing external disturbance in the roll direction (stabilization) are considered. Simulation results utilizing the tail's dynamic model and experimental results utilizing the tail prototype, in conjunction with the simulated quadrupedal platform, are generated. Successful maneuvering and stabilization are demonstrated by the simulated results and validated through experimentation.

Modeling and Experimental Characterization of the Dynamic Behavior of Piezoelectric Recurve Actuation Architectures

1999 ◽  
Author(s):  
James D. Ervin ◽  
Diann E. Brei
Keyword(s):  
Dynamic Behavior ◽  
Architectural Design ◽  
Dynamic Models ◽  
Dynamic Performance ◽  
Design Parameters ◽  
New Family ◽  
State Frequency ◽  
Actuation Scheme ◽  
The Impact

Abstract There are numerous applications that require fast actuators to deliver specific force and displacement output while fitting into confined spaces. A new family of piezoelectric actuators called Recurves exhibit high work per volume and have the extra benefit of having both the force-deflection performance and packaging tailorable to fit the requirements of a given application. The focus of this paper is the dynamic performance of this novel actuation scheme. Two dynamic models, a detailed transfer matrix model and a simpler rod approximation model, are presented to predict the steady state frequency response of a general Recurve actuator driving a mass and spring load. Results from a 23 design of experiments are given that validate these models and demonstrate the impact of the architectural design parameters on the dynamic behavior of the general Recurve actuator.

Modeling and Experimental Evaluation of Asymmetric Pantograph Dynamics

1988 ◽  
Vol 110 (2) ◽  
pp. 168-174 ◽  
Author(s):  
S. D. Eppinger ◽  
D. N. O’Connor ◽  
W. P. Seering ◽  
D. N. Wormley
Keyword(s):  
High Performance ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Dynamic Testing ◽  
Dynamic Performance ◽  
Performance Model ◽  
Degree Of Freedom ◽  
Additional Degree ◽  
Three Degree Of Freedom ◽  
Two Degree Of Freedom

High-performance pantograph design requires control of pantograph dynamic performance. Many pantograph dynamic models developed to aid in the design process have employed two degrees of freedom, one for the head mass and one for the frame. In this paper, the applicability of these models to symmetric and asymmetric pantograph designs is reviewed. Two degree-of-freedom models have been shown to be appropriate to represent a number of symmetric pantograph designs. To represent the asymmetric designs considered in this paper, an additional degree of freedom representing frame dynamics has been introduced to yield a three degree-of-freedom nonlinear dynamic performance model. The model has been evaluated with experimental data obtained from laboratory dynamic testing of an asymmetric pantograph.

THE IMPACT OF THE DIMENSION OF A MATHEMATICAL MODEL OF INTERNAL BALLISTICS ON DESIGN PARAMETERS OF A SHOT FOR GRAIN GUNPOWDER CHARGES

2021 ◽  
pp. 95-110
Author(s):  
I.G. Rusyak ◽  
◽  
V.A. Tenenev ◽  
Keyword(s):  
Mathematical Model ◽  
Powder Mixture ◽  
Thermodynamic Model ◽  
Dynamic Models ◽  
Design Parameters ◽  
Variable Cross ◽  
One Dimensional ◽  
Gas Dynamic ◽  
Wide Range ◽  
The Impact

The problem of the impact of the mathematical model dimension on the calculated intraballistic characteristics of a shot for the charges made of granulated powder is considered. Mathematical models of the shot are studied using the spatial (axisymmetric), one-dimensional, and zero-dimensional (thermodynamic) formulations. The thermodynamic model takes into account the distribution of the pressure and velocity of a gas-powder mixture behind the shot for a channel of variable cross-section. Comparison of simulation results is carried out in a wide range of loading parameters. It is shown that there is a range of the loading parameters for a thermodynamic approach to give satisfactory approximation to the parameters obtained using the gas-dynamic approach, which describes the flow of a heterogeneous reacting mixture with a separate consideration of phases and intergranular interactions between them. Notably that in the entire range of the charging parameters studied in this work, the one-dimensional and twodimensional gas-dynamic models only slightly differ from each other. Therefore, in the main pyrodynamic period, the actuation of the charge, made of granulated powder, can be simulated using a one-dimensional gas-dynamic model or a zero-dimensional thermodynamic model with allowance for spatial distribution of the pressure and velocity of the gas-powder mixture.

scholarly journals DYNAMICS OF A TWO DEGREE OF FREEDOM VIBRO-IMPACT SYSTEM WITH MULTIPLE MOTION LIMITING CONSTRAINTS

2004 ◽  
Vol 14 (01) ◽  
pp. 119-140 ◽  
Author(s):  
D. J. WAGG ◽  
S. R. BISHOP
Keyword(s):  
Degrees Of Freedom ◽  
Dynamical Behavior ◽  
Mathematical Formulation ◽  
Constrained Systems ◽  
Degree Of Freedom ◽  
Dimensional Parameter ◽  
Impact Oscillators ◽  
Single Mass ◽  
The Impact ◽  
Two Degree Of Freedom

We consider the dynamics of impact oscillators with multiple degrees of freedom subject to more than one motion limiting constraint or stop. A mathematical formulation for modeling such systems is developed using a modal approach including a modal form of the coefficient of restitution rule. The possible impact configurations for an N degree of freedom system are considered, along with definitions of the impact map for multiply constrained systems. We consider sticking motions that occur when a single mass in the system becomes stuck to an impact stop, and discuss the computational issues related to computing such solutions. Then using the example of a two degree of freedom system with two constraints we describe exact modal solutions for the free flight and sticking motions which occur in this system. Numerical examples of sticking orbits for this system are shown and we discuss identifying the region, S in phase space where these orbits exist. We use bifurcation diagrams to indicate differing regimes of vibro-impacting motion for two different cases; firstly when the stops are both equal and on the same side (i.e. the same sign) and secondly when the stops are unequal and of opposing sign. For these two different constraint configurations we observe qualitatively different dynamical behavior, which is interpreted using impact mappings and two-dimensional parameter space.

scholarly journals Robotic Modular Leg: Design, Analysis, and Experimentation

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Wael Saab ◽  
William S. Rone ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Dynamic Models ◽  
Degree Of Freedom ◽  
Experimental Results ◽  
Maximum Deviation ◽  
Parallel Orientation ◽  
Mechanical Constraints ◽  
Straight Line ◽  
Accuracy And Repeatability ◽  
Leg Design ◽  
Support Phase

This paper presents the design and analysis of a reduced degree-of-freedom (DOF) robotic modular leg (RML) mechanism. The RML is composed of a two serially connected four-bar mechanisms that utilize mechanical constraints between articulations to maintain a parallel orientation between the foot and body without the use of an actuated ankle. Kinematic and dynamic models are developed for the leg mechanism and used to analyze actuation requirements and aid motor selection. Experimental results of an integrated prototype tracking a desired foot trajectory are analyzed to improve the accuracy and repeatability of the mechanism. The prototype weighs 4.7 kg and measures 368 mm in a fully extended configuration and exhibits a maximum deviation from the straight line support phase equivalent to 5.2 mm.

Characterisation of anti-resonance in two-degree-of-freedom electromagnetic kinetic energy harvester, with modified electromagnetic model

2018 ◽  
Vol 29 (10) ◽  
pp. 2295-2306
Author(s):  
Eoghan O’Riordan ◽  
Ronan Frizzell ◽  
Diarmuid O’Connell ◽  
Elena Blokhina
Keyword(s):  
Kinetic Energy ◽  
Energy Harvester ◽  
Degree Of Freedom ◽  
Design Parameters ◽  
Nonlinear Behaviour ◽  
Nonlinear Phenomenon ◽  
Efficient Energy Transfer ◽  
The Masses ◽  
Two Degree Of Freedom ◽  
Modelling Approach

This article presents a detailed approach to the analysis of a two-degree-of-freedom electromagnetic kinetic energy harvester. These systems use multiple disconnected masses that can impact each other and the harvester housing. This causes complex dynamics in the system as significant momentum is transferred between the masses and, ultimately, results in strongly nonlinear behaviour. One particular nonlinear phenomenon of interest, which has not been previously characterised, is anti-resonance. Observing this phenomenon is important as it highlights efficient energy transfer between the masses, and maximising its effect can be used to enhance the harvesters’ overall performance. A range of mathematical techniques are used to better explain the concept of anti-resonance and how it can be used to improve the understanding of the system dynamics. In addition, the widely used model for electromagnetic transduction is amended to give a more precise representation of the transducer force for this embodiment of the kinetic energy harvester. This unique analysis yields a rich modelling approach that can be used to inform future kinetic energy harvester designs by identifying and optimising key design parameters. Comparisons are made with experimental measurements of a two-mass electromagnetic kinetic energy harvester, validating the modelling approach.

scholarly journals A Configurable Architecture for Two Degree-of-Freedom Variable Stiffness Actuators to Match the Compliant Behavior of Human Joints

2021 ◽  
Vol 8 ◽  
Author(s):  
Simon Lemerle ◽  
Manuel G. Catalano ◽  
Antonio Bicchi ◽  
Giorgio Grioli
Keyword(s):  
Variable Stiffness ◽  
Degree Of Freedom ◽  
Design Parameters ◽  
Dimensional Parameter ◽  
Passive Behavior ◽  
Compliant Behavior ◽  
Wide Range ◽  
Articulated Robots ◽  
Variable Stiffness Actuators ◽  
Two Degree Of Freedom

Living beings modulate the impedance of their joints to interact proficiently, robustly, and safely with the environment. These observations inspired the design of soft articulated robots with the development of Variable Impedance and Variable Stiffness Actuators. However, designing them remains a challenging task due to their mechanical complexity, encumbrance, and weight, but also due to the different specifications that the wide range of applications requires. For instance, as prostheses or parts of humanoid systems, there is currently a need for multi-degree-of-freedom joints that have abilities similar to those of human articulations. Toward this goal, we propose a new compact and configurable design for a two-degree-of-freedom variable stiffness joint that can match the passive behavior of a human wrist and ankle. Using only three motors, this joint can control its equilibrium orientation around two perpendicular axes and its overall stiffness as a one-dimensional parameter, like the co-contraction of human muscles. The kinematic architecture builds upon a state-of-the-art rigid parallel mechanism with the addition of nonlinear elastic elements to allow the control of the stiffness. The mechanical parameters of the proposed system can be optimized to match desired passive compliant behaviors and to fit various applications (e.g., prosthetic wrists or ankles, artificial wrists, etc.). After describing the joint structure, we detail the kinetostatic analysis to derive the compliant behavior as a function of the design parameters and to prove the variable stiffness ability of the system. Besides, we provide sets of design parameters to match the passive compliance of either a human wrist or ankle. Moreover, to show the versatility of the proposed joint architecture and as guidelines for the future designer, we describe the influence of the main design parameters on the system stiffness characteristic and show the potential of the design for more complex applications.

Neimark-Sacker Bifurcations Near Degenerate Grazing Point in a Two Degree-of-Freedom Impact Oscillator

2018 ◽  
Vol 13 (11) ◽  
Author(s):  
Shan Yin ◽  
Jinchen Ji ◽  
Shuning Deng ◽  
Guilin Wen
Keyword(s):  
Periodic Motion ◽  
Small Neighborhood ◽  
Period Doubling ◽  
Degree Of Freedom ◽  
Grazing Impact ◽  
Mapping Technique ◽  
Impact Oscillator ◽  
Parameter Continuation ◽  
The Impact ◽  
Two Degree Of Freedom

Saddle-node or period-doubling bifurcations of the near-grazing impact periodic motions have been extensively studied in the impact oscillators, but the near-grazing Neimark-Sacker bifurcations have not been discussed yet. For the first time, this paper uncovers the novel dynamic behavior of Neimark-Sacker bifurcations, which can appear in a small neighborhood of the degenerate grazing point in a two degree-of-freedom impact oscillator. The higher order discontinuity mapping technique is used to determine the degenerate grazing point. Then, shooting method is applied to obtain the one-parameter continuation of the elementary impact periodic motion near degenerate grazing point and the peculiar phenomena of Neimark-Sacker bifurcations are revealed consequently. A two-parameter continuation is presented to illustrate the relationship between the observed Neimark-Sacker bifurcations and degenerate grazing point. New features that differ from the reported situations in literature can be found. Finally, the observed Neimark-Sacker bifurcation is verified by checking the existence and stability conditions in line with the generic theory of Neimark-Sacker bifurcation. The unstable bifurcating quasi-periodic motion is numerically demonstrated on the Poincaré section.

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