The Control of Hexapod Parallel Mechanism

2012 ◽  
Vol 195-196 ◽  
pp. 1030-1034
Author(s):  
Chun Ping Pan ◽  
Hsin Guan
Keyword(s):  
Tracking Error ◽  
Joint Space ◽  
Variable Load ◽  
Phase Lag ◽  
Parallel Mechanisms ◽  
Nonlinear Controller ◽  
Cartesian Space ◽  
Motion System ◽  
Wide Range ◽  
System Output

In order to enhance the innervations fidelity of simulators, an adaptive nonlinear controller is developed, which guarantees parallel mechanisms closed loop system global asymptotical stability and the convergence of posture tracking error in Cartesian space. The problem of rapid tracking under the condition of the wide range, nonlinear and variable load is solved. After the adaptive nonlinear controller is actually applied to the hexapod parallel mechanisms of simulator, the dynamic-static capabilities of motion system is tested by amplitude-frequency response and posture precision. The experimental results show that the static precision improves ten times and system output amplitude increase and the phase lag reduce with respect to the same input signal in Cartesian space in comparison with the traditional proportional and derivative controlling method in joint space. Therefore the adaptive nonlinear controller can effectively improve the dynamic-static response performance of the hexapod parallel mechanisms of simulators in Cartesian space.

A 3-ṞPR Parallel Mechanism With Singularities That are Self-Motions

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Novona Rakotomanga ◽  
Ilian A. Bonev
Keyword(s):  
Parallel Mechanism ◽  
Control Strategies ◽  
Joint Space ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Active Joint ◽  
Cartesian Space ◽  
Three Degree Of Freedom

The Cartesian workspace of most three-degree-of-freedom parallel mechanisms is divided by Type 2 (also called parallel) singularity surfaces into several regions. Accessing more than one such region requires crossing a Type 2 singularity, which is risky and calls for sophisticated control strategies. Some mechanisms can still cross these Type 2 singularity surfaces through “holes” that represent Type 1 (also called serial) singularities only. However, what is even more desirable is if these Type 2 singularity surfaces were curves instead. Indeed, there exists at least one such parallel mechanism (the agile eye) and all of its singularities are self-motions. This paper presents another parallel mechanism, a planar one, whose singularities are self-motions. The singularities of this novel mechanism are studied in detail. While the Type 2 singularities in the Cartesian space still constitute a surface, they degenerate into lines in the active-joint space, which is the main result of this paper.

Research on the dynamic characteristics of a 3-DOF parallel tool head

2017 ◽  
Vol 44 (1) ◽  
pp. 28-37 ◽  
Author(s):  
Dong Wang ◽  
Jun Wu ◽  
Liping Wang ◽  
Yuzhe Liu ◽  
Guang Yu
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Dynamic Performance ◽  
Tracking Error ◽  
Joint Space ◽  
Time Varying ◽  
Parallel Mechanisms ◽  
Content Type ◽  
Dynamic Index ◽  
Coupling Dynamic

Purpose The purpose of this paper is to describe and evaluate the time-varying and coupling dynamic characteristics of a 3-DOF parallel tool head. Design/methodology/approach From the view of control, a new dynamic index of a 3-DOF parallel tool head is proposed based on the dynamic model in the joint space. This index can reflect the time-varying and coupling dynamic characteristics which are the main characteristics of the parallel mechanisms, and its distribution in the whole workspace is also given. Through comparison of the dynamic load (driving current) of each driving shaft, a series of experiments is designed and carried out on a prototype to validate the effectiveness of the dynamic analysis. The tracking error of each driving shaft has also been taken into consideration. Findings The simulations of the index have the same variation law with the experimental results. The dynamic load of the driving shaft becomes larger with the increase of the dynamic index, and the dynamic performance becomes worse at the same time. Originality/value The main dynamic characteristics of the 3-DOF parallel tool head can be described and evaluated through this work.

Feedback controller designs for an electromagnetic micromanipulator

2019 ◽  
Vol 234 (6) ◽  
pp. 759-772
Author(s):  
Mustafa Böyük ◽  
Yakup Eroğlu ◽  
Günyaz Ablay ◽  
Kutay İçöz
Keyword(s):  
Tracking Error ◽  
Control Unit ◽  
Maximum Output ◽  
Nonlinear Controller ◽  
Magnetic Forces ◽  
Nonlinear Controllers ◽  
Wide Range ◽  
Fully Automatic ◽  
Magnetic Microparticle ◽  
And Control

Magnetic micromanipulators are capable of generating wide range of magnetic forces to manipulate magnetic microparticles for biomedical applications. In this study, a multipole magnetic micromanipulator system including electromagnets, driver circuitry and control unit is designed, modeled and implemented. The micromanipulator can produce a broad range of magnetic forces up to 25 pN on a single magnetic microparticle (1–10 µm diameter) that is 5 mm away from the electromagnet core tip. Both linear and nonlinear controllers are designed and implemented, and the proposed nonlinear controller produces smooth control currents to assure closed-loop stability of the system with 1 s non-overshoot transient response and zero steady-state tracking error. The maximum output current of the driver circuitry is set to 1 A. The single particle at the center is moved at a speed of 5 mm/s. The fully automatic system can be utilized in applications related to single cell or microparticle manipulations.

scholarly journals Continuum modeling perspectives of non-Fourier heat conduction in biological systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ákos Sudár ◽  
Gergely Futaki ◽  
Róbert Kovács
Keyword(s):  
Biological Systems ◽  
Phase Lag ◽  
Dual Phase ◽  
Continuum Modeling ◽  
Biological Origin ◽  
Ultrasound Surgery ◽  
Thermal Models ◽  
Wide Range ◽  
Fourier Heat Conduction ◽  
The Continuum

Abstract The thermal modeling of biological systems is increasingly important in the development of more advanced and more precise techniques such as ultrasound surgery. One of the primary barriers is the complexity of biological materials: the geometrical, structural, and material properties vary in a wide range. In the present paper, we focus on the continuum modeling of heterogeneous materials of biological origin. There are numerous examples in the literature for non-Fourier thermal models. However, as we realized, they are associated with a few common misconceptions. Therefore, we first aim to clarify the basic concepts of non-Fourier thermal models. These concepts are demonstrated by revisiting two experiments from the literature in which the Cattaneo–Vernotte and the dual phase lag models are utilized. Our investigation revealed that these non-Fourier models are based on misinterpretations of the measured data, and the seeming deviation from Fourier’s law originates from the source terms and boundary conditions.

scholarly journals SHEETFLOW SEDIMENT TRANSPORT UNDER SKEWED - ASYMMETRIC WAVES AND CURRENTS

2012 ◽  
Vol 1 (33) ◽  
pp. 50 ◽  
Author(s):  
Le Phuong Dong ◽  
Shinji Sato
Keyword(s):  
Sediment Transport ◽  
Laboratory Experiments ◽  
Fine Sand ◽  
Sand Transport ◽  
Phase Lag ◽  
Half Cycle ◽  
Experimental Conditions ◽  
Wide Range ◽  
Waves And Currents ◽  
Asymmetric Flows

Prototype scale laboratory experiments have been conducted to investigate the sheetflow sediment transport of uniform sands under different skewed-asymmetric oscillatory flows. Experimental results reveal that in most of the case with fine sand, the “cancelling effect”, which balances the on-/off-shore net transport under pure asymmetric/skewed flows and results a moderate net transport, was developed for combined skewed-asymmetric flow. However, under some certain conditions (T > 5s) with coarse sands, the onshore sediment transport was enhanced by 50% under combined skewed-asymmetric flows. Sand transport mechanism under oscillatory sheetflow conditions is also studied by comparing the maximum bed shear stress and the phase lag parameter at each half cycle. A comparison of measurements including the new experimental data with a number of practical sand transport formulations shows that the Dong et al. (2013) formulation performs the best in predicting the measured net transport rates over a wide range of experimental conditions

scholarly journals Regions of Feasible Point-to-Point Trajectories in the Cartesian Workspace of Fully-Parallel Manipulators

1999 ◽  
Author(s):  
Damien Chablat ◽  
Philippe Wenger
Keyword(s):  
Parallel Manipulator ◽  
Cartesian Product ◽  
Parallel Manipulators ◽  
Joint Space ◽  
Inverse Kinematic ◽  
Connected Components ◽  
Feasible Point ◽  
Cartesian Space ◽  
Point Trajectories ◽  
Point To Point

Abstract The goal of this paper is to define the n-connected regions in the Cartesian workspace of fully-parallel manipulators, i.e. the maximal regions where it is possible to execute point-to-point motions. The manipulators considered in this study may have multiple direct and inverse kinematic solutions. The N-connected regions are characterized by projection, onto the Cartesian workspace, of the connected components of the reachable configuration space defined in the Cartesian product of the Cartesian space by the joint space. Generalized octree models are used for the construction of all spaces. This study is illustrated with a simple planar fully-parallel manipulator.

Position Domain PD Control for Contour Tracking

2010 ◽  
Author(s):  
P. R. Ouyang ◽  
Truong Dam
Keyword(s):  
Motion Tracking ◽  
Control Method ◽  
Tracking Error ◽  
Original System ◽  
Contour Tracking ◽  
Pd Control ◽  
Tracking Errors ◽  
Motion System ◽  
Common Control ◽  
The Time Domain

For multi-axis motion control applications, contour tracking is one of the most common control problems encountered by industrial manipulators and robots. In this paper, a position domain PD control method is proposed for the purpose of improving the contour tracking performance. To develop the new control method, the multi-axis motion system is viewed as a master-slave motion system where the master motion is sampled equidistantly and used as an independent variable, while the slave motions are described as functions of the master motion according to the contour tracking requirements. The dynamic model of the multi-axis motion system is developed in the position domain based on the master motion by transforming the original system dynamic equations from the time domain to the position domain. In this control methodology, the master motion will yield zero tracking error for the position as it is used as reference, and only the slave motion tracking errors will affect the final contour tracking errors. The proposed position domain PD controller is successfully examined in a Cartesian robotic system for linear motion tracking and circular contour tracking.

Mechanical Contact Frequency Response Measurements

2000 ◽  
Vol 122 (4) ◽  
pp. 828-833 ◽  
Author(s):  
S. S. Kupchenko ◽  
D. P. Hess
Keyword(s):  
Frequency Response ◽  
Phase Lag ◽  
Lithium Grease ◽  
Mineral Oils ◽  
Vibration Data ◽  
Response Data ◽  
Lubricated Contacts ◽  
Wide Range ◽  
Contact Frequency ◽  
Dry Conditions

This paper presents friction frequency response measurements taken from a planar steel contact subjected to controlled random broadband normal vibration. Data are included from both dry and various lubricated contact conditions under different vibration input levels and different sliding velocities. Frequency response data for dry contacts are found to have nearly steady magnitude and negligible phase lag over a relatively wide range of frequencies. This suggests a coefficient of friction, independent of frequency but dependent on levels of normal acceleration and sliding velocity, may adequately define the dry contact frequency response. The frequency response data for lubricated contacts are mixed. For example, with MoS2 grease the frequency response may adequately be defined by a constant, as with dry conditions. However, frequency response data for contacts with pure mineral oils, mineral oils with additives, and lithium grease are found to be dependent on frequency. [S0742-4787(11)00101-9]

Experimental Study on H∞ Control for United Brake of Electric Vehicle

2011 ◽  
Vol 204-210 ◽  
pp. 498-501
Author(s):  
Chuan Wei Zhang
Keyword(s):  
Robust Control ◽  
Electric Vehicle ◽  
Pid Control ◽  
Control Strategies ◽  
Tracking Error ◽  
Research Work ◽  
Response Speed ◽  
Rotational Inertia ◽  
Variable Load ◽  
Braking Distance

This paper discusses different united brake control strategies of electric vehicle (EV), presents a novel H∞ robust united brake control strategy for EV. Research work is done under different conditions namely variable battery voltage and variable load rotational inertia, separately. A comparison between conventional PID control and H∞ robust control is done when they are applied to the above mentioned conditions. Under the united brake condition, the experimental results show that the braking distance is shortened by the united brake system in the emergent brake; the braking ability of the EV is improved. H∞ robust control has better performance than the traditional PID control both in steady-state tracking error and response speed.

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