Soft robot development: Air muscle for rehabilitation robotic application

2019 ◽  
pp. 256-260
Author(s):  
L F Hillesheim ◽  
V N S Ventura ◽  
Daniel A S Ponce
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Nonlinear Behavior ◽  
Parallel Robot ◽  
Ankle Injuries ◽  
Soft Robot ◽  
Locomotor System ◽  
Latex Tube ◽  
Building Purpose ◽  
Air Muscle

Physiotherapy is a science which acts in the area of biomechanical and functional disorder, establishing diagnostics and supporting the locomotor system rehabilitation. These procedures require assistance of a physiotherapist, however they are insufficient for the country´s demand. Usually such procedures use devices with the newest technology, in order to enable recovery and avoid possible permanent trauma. In order to face this reality, we have committed to develop an air muscle, based on the McKibben´s model, with the purpose of proposing a new low-cost parallel robot to physiotherapy (Soft Robot) for the rehabilitation of patients with ankle injuries. This robot is responsible for moving three degrees of freedom platform, therefore acting directly in the rehabilitation of the patient through the execution of soft and accurate therapeutic movements that stimulate the recovery of operated tissues. First, it is build an air muscle that will be used as actuator in parallel platform. Then is raised a curve of behavior to shift versus pressure on proposed muscle. In conjunction with these data to actuator behavior is modelled and simulated the new parallel robot. This air muscle was build using a latex tube covered by a braided fibred mesh and fuelled by a pneumatic tire valve, therefore obtaining a nonlinear behavior of contraction to each pressure value admitted on muscle. By means of this prototype building purpose, we obtained satisfactory results, such as a contraction of 25% of the nominal length for pressures up to six bars. Considering such a result and the low cost involved building actuator as this one, the advantage in using this model is perceptible.

Synthesizing Soft Parallel Robots Comprised of Active Constraints

2014 ◽  
Author(s):  
Jordan Rivera ◽  
Jonathan B. Hopkins ◽  
Charles Kim
Keyword(s):  
Case Studies ◽  
Degrees Of Freedom ◽  
Parallel Systems ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Soft Robot ◽  
Active Constraints ◽  
New Type ◽  
Constraint Topologies ◽  
Synthesis Approach

In this paper, we introduce a new type of spatial parallel robot that is comprised of soft inflatable constraints called Tri-Chamber Actuators (TCAs). We extend the principles of the Freedom and Constraint Topologies (FACT) synthesis approach to enable the synthesis and analysis of this new type of soft robot. The concepts of passive and active freedom spaces are introduced and applied to the design of general parallel systems that consist of active constraints (i.e., constraint that can be actuated to impart various loads onto the system’s stage) that both drive desired motions and guide the system’s desired degrees of freedom (DOFs). We provide the fabrication details of the TCA constraints introduced in this paper and experimentally validate their FACT-predicted kinematics. Examples are provided as case studies.

Synthesis and Analysis of Soft Parallel Robots Comprised of Active Constraints

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Jonathan B. Hopkins ◽  
Jordan Rivera ◽  
Charles Kim ◽  
Girish Krishnan
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Soft Robot ◽  
Element Analysis ◽  
Active Constraints ◽  
New Type ◽  
Constraint Model ◽  
Constraint Topologies ◽  
Synthesis Approach

In this paper, we introduce a new type of spatial parallel robot that is comprised of soft inflatable constraints called trichamber actuators (TCAs). We extend the principles of the freedom and constraint topologies (FACT) synthesis approach to enable the synthesis and analysis of this new type of soft robot. The concepts of passive and active freedom spaces are introduced and applied to the design of general parallel systems that consist of active constraints (i.e., constraint that can be actuated to impart various loads onto the system's stage) that both drive desired motions and guide the system's desired degrees of freedom (DOFs). We provide the fabrication details of the TCA constraints introduced in this paper and experimentally determine their appropriate FACT-based constraint model. We fabricate a soft parallel robot that consists of three TCA constraints and verify and validate its FACT-predicted performance using finite element analysis (FEA) and experimental data. Other such soft robots are synthesized using FACT as case studies.

Low-Cost PLC-Based Control of a 2-DoF Purely Translational Parallel Robot

2011 ◽  
Vol 383-390 ◽  
pp. 1542-1548
Author(s):  
Zhi Bin Li
Keyword(s):  
Control System ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Low Cost ◽  
Parallel Robot ◽  
Conveyor Belt ◽  
Workspace Analysis ◽  
Translation Motion ◽  
Control System Architecture ◽  
Pick And Place Operation

This paper describes the design and implementation of a low-cost robot control system based on a Programmable Logic Controller (PLC). The robot is a 2-DoF (Degrees of Freedom) purely translational mechanism, which has potential application in food and electronics industry for high speed pick-and-place operation. Combined with a conveyor belt, it can make 3-DoF purely translation motion. In this paper, the inverse kinematics, forward kinematics, singularity, and workspace analysis are presented. The control system architecture and software design is also introduced. The prototype is exhibited at last.

scholarly journals Parameter Sensitivity Analysis on Dynamic Coefficients of Partial Arc Annular-Thrust Aerostatic Porous Journal Bearings

2021 ◽  
Vol 11 (22) ◽  
pp. 10791
Author(s):  
Pyung Hwang ◽  
Polina Khan ◽  
Seok-Won Kang
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Air Flow ◽  
Nonlinear Behavior ◽  
Journal Bearings ◽  
Dynamic Coefficients ◽  
Spindle Shaft ◽  
Relative Eccentricity ◽  
Aerostatic Bearings ◽  
Stiffness And Damping

Aerostatic bearings are widely used in high-precision devices. Partial arc annular-thrust aerostatic porous journal bearings are a prominent type of aerostatic bearings, which carry both radial and axial loads and provide high load-carrying capacity, low air consumption, and relatively low cost. Spindle shaft tilting is a resource-demanding challenge in numerical modeling because it involves a 3D air flow. In this study, the air flow problem was solved using a COMSOL software, and the dynamic coefficients for tilting degrees of freedom were obtained using finite differences. The obtained results exhibit significant coupling between the tilting motion in the x-and y-directions: cross-coupled coefficients can achieve 20% of the direct coefficient for stiffness and 50% for damping. In addition, a nonlinear behavior can be expected, because the tilting motion within 3°, tilting velocities within 0.0012°/s, and relative eccentricity of 0.2 have effects as large as 20% for direct stiffness and 100% for cross-coupled stiffness and damping. All dynamic coefficients were fitted with a polynomial of eccentricity, tilting, and tilting velocities in two directions, with a total of six parameters. The resulting fitting coefficient tables can be employed for the fast dynamic simulation of the rotor shaft carried on the proposed bearing type.

scholarly journals Reconstruction of Relative Phase of Self-Transmitting Devices by Using Multiprobe Solutions and Non-Convex Optimization

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2459
Author(s):  
Rubén Tena Sánchez ◽  
Fernando Rodríguez Varela ◽  
Lars J. Foged ◽  
Manuel Sierra Castañer
Keyword(s):  
Iterative Algorithm ◽  
Degrees Of Freedom ◽  
Relative Phase ◽  
Low Cost ◽  
Initial Guess ◽  
Noise Model ◽  
Medium Size ◽  
Phase Reconstruction ◽  
Linear Combinations ◽  
Iterative Optimization Algorithm

Phase reconstruction is in general a non-trivial problem when it comes to devices where the reference is not accessible. A non-convex iterative optimization algorithm is proposed in this paper in order to reconstruct the phase in reference-less spherical multiprobe measurement systems based on a rotating arch of probes. The algorithm is based on the reconstruction of the phases of self-transmitting devices in multiprobe systems by taking advantage of the on-axis top probe of the arch. One of the limitations of the top probe solution is that when rotating the measurement system arch, the relative phase between probes is lost. This paper proposes a solution to this problem by developing an optimization iterative algorithm that uses partial knowledge of relative phase between probes. The iterative algorithm is based on linear combinations of signals when the relative phase is known. Phase substitution and modal filtering are implemented in order to avoid local minima and make the algorithm converge. Several noise-free examples are presented and the results of the iterative algorithm analyzed. The number of linear combinations used is far below the square of the degrees of freedom of the non-linear problem, which is compensated by a proper initial guess. With respect to noisy measurements, the top probe method will introduce uncertainties for different azimuth and elevation positions of the arch. This is modelled by considering the real noise model of a low-cost receiver and the results demonstrate the good accuracy of the method. Numerical results on antenna measurements are also presented. Due to the numerical complexity of the algorithm, it is limited to electrically small- or medium-size problems.

scholarly journals Dynamic Loads and Response of a Spar Buoy Wind Turbine with Pitch-Controlled Rotating Blades: An Experimental Study

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3598
Author(s):  
Sara Russo ◽  
Pasquale Contestabile ◽  
Andrea Bardazzi ◽  
Elisa Leone ◽  
Gregorio Iglesias ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Laboratory Data ◽  
Nonlinear Behavior ◽  
Offshore Wind ◽  
Small Scale ◽  
Wave Steepness ◽  
Design Factor

New large-scale laboratory data are presented on a physical model of a spar buoy wind turbine with angular motion of control surfaces implemented (pitch control). The peculiarity of this type of rotating blade represents an essential aspect when studying floating offshore wind structures. Experiments were designed specifically to compare different operational environmental conditions in terms of wave steepness and wind speed. Results discussed here were derived from an analysis of only a part of the whole dataset. Consistent with recent small-scale experiments, data clearly show that the waves contributed to most of the model motions and mooring loads. A significant nonlinear behavior for sway, roll and yaw has been detected, whereas an increase in the wave period makes the wind speed less influential for surge, heave and pitch. In general, as the steepness increases, the oscillations decrease. However, higher wind speed does not mean greater platform motions. Data also indicate a significant role of the blade rotation in the turbine thrust, nacelle dynamic forces and power in six degrees of freedom. Certain pairs of wind speed-wave steepness are particularly unfavorable, since the first harmonic of the rotor (coupled to the first wave harmonic) causes the thrust force to be larger than that in more energetic sea states. The experiments suggest that the inclusion of pitch-controlled, variable-speed blades in physical (and numerical) tests on such types of structures is crucial, highlighting the importance of pitch motion as an important design factor.

Analysis and Optimization of a New Differentially Driven Cable Parallel Robot

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Hamed Khakpour ◽  
Lionel Birglen ◽  
Souheil-Antoine Tahan
Keyword(s):  
Kinematic Analysis ◽  
Design Methodology ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Cable Robot ◽  
Proper Design ◽  
Two Indices ◽  
Three Degrees Of Freedom ◽  
Cable Robots

In this paper, a new three degrees of freedom (DOF) differentially actuated cable parallel robot is proposed. This mechanism is driven by a prismatic actuator and three cable differentials. Through this design, the idea of using differentials in the structure of a spatial cable robot is investigated. Considering their particular properties, the kinematic analysis of the robot is presented. Then, two indices are defined to evaluate the workspaces of the robot. Using these indices, the robot is subsequently optimized. Finally, the performance of the optimized differentially driven robot is compared with fully actuated mechanisms. The results show that through a proper design methodology, the robot can have a larger workspace and better performance using differentials than the fully driven cable robots using the same number of actuators.

scholarly journals Nonlinear Behavior of a Magnetic Bearing System

1995 ◽  
Vol 117 (3) ◽  
pp. 582-588 ◽  
Author(s):  
L. N. Virgin ◽  
T. F. Walsh ◽  
J. D. Knight
Keyword(s):  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Nonlinear Behavior ◽  
Analytical Techniques ◽  
Magnetic Bearing ◽  
Forced Response ◽  
The Mathematical Model ◽  
Two Degree Of Freedom ◽  
Sensitivity To Initial Conditions ◽  
Bearing System

This paper describes the results of a study into the dynamic behavior of a magnetic bearing system. The research focuses attention on the influence of nonlinearities on the forced response of a two-degree-of-freedom rotating mass suspended by magnetic bearings and subject to rotating unbalance and feedback control. Geometric coupling between the degrees of freedom leads to a pair of nonlinear ordinary differential equations, which are then solved using both numerical simulation and approximate analytical techniques. The system exhibits a variety of interesting and somewhat unexpected phenomena including various amplitude driven bifurcational events, sensitivity to initial conditions, and the complete loss of stability associated with the escape from the potential well in which the system can be thought to be oscillating. An approximate criterion to avoid this last possibility is developed based on concepts of limiting the response of the system. The present paper may be considered as an extension to an earlier study by the same authors, which described the practical context of the work, free vibration, control aspects, and derivation of the mathematical model.

scholarly journals Soft Spherical Tensegrity Robot Design Using Rod-Centered Actuation and Control

2016 ◽  
Author(s):  
Lee-Huang Chen ◽  
Kyunam Kim ◽  
Ellande Tang ◽  
Kevin Li ◽  
Richard House ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Space Exploration ◽  
Robot Design ◽  
The Novel ◽  
Flexible Design ◽  
Spherical Robot ◽  
Potential Benefits ◽  
And Performance ◽  
And Control

This paper presents the design, analysis and testing of a fully actuated modular spherical tensegrity robot for co-robotic and space exploration applications. Robots built from tensegrity structures (composed of pure tensile and compression elements) have many potential benefits including high robustness through redundancy, many degrees of freedom in movement and flexible design. However to fully take advantage of these properties a significant fraction of the tensile elements should be active, leading to a potential increase in complexity, messy cable and power routing systems and increased design difficulty. Here we describe an elegant solution to a fully actuated tensegrity robot: The TT-3 (version 3) tensegrity robot, developed at UC Berkeley, in collaboration with NASA Ames, is a lightweight, low cost, modular, and rapidly prototyped spherical tensegrity robot. This robot is based on a ball-shaped six-bar tensegrity structure and features a unique modular rod-centered distributed actuation and control architecture. This paper presents the novel mechanism design, architecture and simulations of TT-3, the first untethered, fully actuated cable-driven six-bar tensegrity spherical robot ever built and tested for mobility. Furthermore, this paper discusses the controls and preliminary testing performed to observe the system’s behavior and performance.

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