A Complete Model of a Two Degree of Freedom Platform Actuated by Three Pneumatic Muscles Elaborated for Control Synthesis

2016 ◽  
Author(s):  
David Bou Saba ◽  
Eric Bideaux ◽  
Xavier Brun ◽  
Paolo Massioni
Keyword(s):  
Volume Ratio ◽  
Degree Of Freedom ◽  
Control Synthesis ◽  
Complete Model ◽  
Pneumatic Muscles ◽  
Wide Range ◽  
Mechanical Study ◽  
Industrial Use ◽  
Two Degree Of Freedom ◽  
Nonlinear Control Synthesis

Pneumatic muscles have a high potential in industrial use, as they provide safety, high power over volume ratio, low price and wide range of pulling effort. Nevertheless, their control is quite hard to achieve due to the non linearity and hysteresis phenomena, plus the uncertainties in their behavior. This paper presents the modeling of a two degree of freedom platform actuated by three pneumatic muscles for control purposes. Three servovalves are used to supply airflow inside the muscles. The innovative concept is the modeling of each component including the static and dynamic muscle behavior. The model of the servovalve consists of a look-up table gathering the three variables: airflow, pressure and voltage applied to the servovalve. In addition, a thermodynamic and a mechanical study of the system complete the model. The result is a complete model design having as input the voltage applied to the three servovalves, and as outputs, the two angles of rotation. Simulated and experimental results permit to validate the complete model for high variation in static and dynamic conditions. These results will be helpful for nonlinear control synthesis.

scholarly journals A Two-Degree-of-Freedom Cantilever-Based Vibration Triboelectric Nanogenerator for Low-Frequency and Broadband Operation

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1526 ◽  
Author(s):  
Gang Tang ◽  
Fang Cheng ◽  
Xin Hu ◽  
Bo Huang ◽  
Bin Xu ◽  
...  
Keyword(s):  
Output Voltage ◽  
Low Frequency ◽  
Degree Of Freedom ◽  
Triboelectric Nanogenerator ◽  
Energy Harvesters ◽  
Harvesting Technique ◽  
Wide Range ◽  
Operating Bandwidth ◽  
Self Powered ◽  
Two Degree Of Freedom

With the continual increasing application requirements of broadband vibration energy harvesters (VEHs), many attempts have been made to broaden the bandwidth. As compared to adopted only a single approach, integration of multi-approaches can further widen the operating bandwidth. Here, a novel two-degree-of-freedom cantilever-based vibration triboelectric nanogenerator is proposed to obtain high operating bandwidth by integrating multimodal harvesting technique and inherent nonlinearity broadening behavior due to vibration contact between triboelectric surfaces. A wide operating bandwidth of 32.9 Hz is observed even at a low acceleration of 0.6 g. Meanwhile, the peak output voltage is 18.8 V at the primary resonant frequency of 23 Hz and 1 g, while the output voltage is 14.9 V at the secondary frequency of 75 Hz and 2.5 g. Under the frequencies of these two modes at 1 g, maximum peak power of 43.08 μW and 12.5 μW are achieved, respectively. Additionally, the fabricated device shows good stability, reaching and maintaining its voltage at 8 V when tested on a vacuum compression pump. The experimental results demonstrate the device has the ability to harvest energy from a wide range of low-frequency (<100 Hz) vibrations and has broad application prospects in self-powered electronic devices and systems.

Hydrodynamics Loads on Two Degree-of-Freedom Cylinder With Uncertain Natural Frequencies Subject to VIV

2009 ◽  
Author(s):  
Didier Lucor
Keyword(s):  
Natural Frequencies ◽  
Numerical Study ◽  
Spectral Element ◽  
Numerical Approach ◽  
Response Surfaces ◽  
Degree Of Freedom ◽  
Two Dimensional ◽  
Wide Range ◽  
Two Dimensional Flow ◽  
Two Degree Of Freedom

In this numerical study, we build response surfaces of two degree-of-freedom vortex-induced vibrations (VIV) of flexibly mounted cylinders for a wide range of transverse and in-line natural frequencies. We consider both the structure and the flow to be two-dimensional and the structure has a low mass damping. The emphasis is put on the representation of the hydrodynamic loads acting on the cylinder in response to the change in the natural frequencies of the structure. The system is sampled for a wide range of natural frequencies within the synchronization region, totaling 149 two-dimensional flow-structure simulations. The parametric range of the in-line frequency is chosen to be larger than the one of the transverse frequency in order to favor multi-modal responses. No preferred frequencies are emphasized within the intervals of study. The fully spectral numerical approach relies on a stochastic collocation method coupled to a spectral element-based deterministic solver.

The Design of Modeled Cam Systems—Part I: Dynamic Synthesis and Chart Design For the Two-Degree-of-Freedom Model

1975 ◽  
Vol 97 (4) ◽  
pp. 1175-1180 ◽  
Author(s):  
G. K. Matthew ◽  
D. Tesar
Keyword(s):  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Dynamic Synthesis ◽  
Wide Range ◽  
Cam Follower ◽  
Chart Design ◽  
Mass Spring ◽  
Two Degree Of Freedom ◽  
Cam Systems ◽  
Made In

An extension of the dynamic synthesis philosophy given earlier [1] for cam follower systems is made in terms of a two-degree-of-freedom model. Three additional dimensionless parameters η, λ, γ for the distribution of mass, spring, and dashpot content are sufficient to describe this more complex system relative to the single degree-of-freedom coefficients. Charts in terms of η, λ, γ are presented to assist in choosing the best set of these values. Finally, “rules of thumb” are given which are applicable to a wide range of mechanical systems.

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.

Two Degree of Freedom Control Synthesis With Applications to Agricultural Systems

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Yangmin Xie ◽  
Andrew Alleyne
Keyword(s):  
Disturbance Rejection ◽  
Feedforward Control ◽  
Mechanical Design ◽  
System Modeling ◽  
Degree Of Freedom ◽  
Control Synthesis ◽  
Height Control ◽  
Performance Improvements ◽  
Elevation Changes ◽  
Two Degree Of Freedom

This paper presents a two degree of freedom (DOF) controller for combine harvester header height control (HHC). Fundamental limitations to the tracking and disturbance rejection bandwidth for feedback control designs exist in the HHC system due to the considerable actuator delay and underactuated and noncollocated mechanical design. In this work, we utilize H∞ optimal control design to ensure closed-loop stability and robust performance, and augment the feedback loop with a feedforward control structure based on readily available global positioning system (GPS) information. The GPS provides anticipatory information of the field map elevation; albeit with noise, resolution limits, and latency. The elevation changes result in disturbances to the header height control problem and the feedforward controller uses the knowledge of the field to increase the overall disturbance rejection bandwidth. Simulation and experimental results illustrate the performance improvements resulting from the 2-DOF design over the stand alone feedback controller, which removes a long standing obstacle in increasing the harvesting productivity. Additionally, an error analysis examines the effect of uncertainties from system modeling and field map measurements on the system performance.

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