Mechatronics

MRI compatibility of robot actuation techniques--a comparative study

by Gregory Fischer

Design, Fabrication and Control of a Three-Finger Robotic Gripper

by Farzad Cheraghpour Samavati

RVSP 2011-Proceeding of IEEE First International Conference on Robot, Vision and Signal Processing (RVSP), pp.280-283, 2011
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Abstract— In this article a robotic gripper with the ability of cylindrical object grasping is designed and... more Abstract— In this article a robotic gripper with the ability of cylindrical object grasping is designed and fabricated. With the increasing use of robotic arms in industry, grasping and holding, as a part of industrial processes, are of great importance. Hence, proper design of grippers plays a key role in efficient performance of robotic arms. The main feature of this design is its reliability and efficiency while maintaining simplicity. This robotic gripper is designed for installing on a mobile robot with the task of holding and moving cylindrical object. One of the aspects of an efficient robotic gripper is its ability to satisfy the “Form-gripping” feature which is utilized for the presented design. Kinematic consideration is examined by Catia. Finally, control methods through Matlab and experimental test results are presented in this paper.

Compliant mechanisms for an active cardiac stabilizer: lessons and new requirements in the design of a novel surgical tool

by Lennart Rubbert

Experimental investigations of the scanning functions of galvanometer-based scanners with applications in OCT

by Virgil-Florin Duma

Duma V. F.*, Lee K.-S., Meemon P., Rolland J. P., Experimental investigations of the scanning functions of galvanometer-based scanners with applications in OCT , Applied Optics 50(29), 5735-5749 (2011)
- also selected in Virtual Journal for Biomedical Optics 6(11), ISSN 1931-1532, 2011

We analyse three most common profiles of scanning functions for galvanometer-based scanners (GS), the sawtooth,... more We analyse three most common profiles of scanning functions for galvanometer-based scanners (GS), the sawtooth, triangular and sinusoidal functions. They are determined experimentally with regard to the scan parameters of the input signal (i.e. frequency and amplitude). We study the differences of the output function of the GS measured as the positional error of the oscillatory mirror from the ideal function given by the input signal of the device. The limits in achieving the different types of scanning functions in terms of duty cycle and linearity are determined experimentally for the possible range of scan parameters. Of particular importance are the preservation of an imposed duty cycle and profile for the sawtooth function, the quantification of the linearity for the sinusoidal function, and the effective duty cycle for the triangular, as well as for the other functions. The range of scan amplitudes for which the stability of the oscillatory regime of the galvo mirror is stable for different frequencies is also highlighted. While the use of the device in certain scanning regimes is studied, certain rules of thumb are deduced to make the best out of the galvoscanner. Finally, the three types of scanning functions are tested with a Fourier Domain Optical Coherence Tomography (FD OCT) setup and the conclusions of the study are demonstrated in an imaging application by correlating the determined limits of the scanning regimes with the requirements of OCT.

DYNAMIC FINITE ELEMENT ANALYSIS OF A HIGHLY PARALLEL ROBOTIC SURFACE

by Chris Salisbury

Published in the proceedings of the SMASIS2011 conference.

A  novel  three-dimensional  robotic  surface  is
devised  using ... more A  novel  three-dimensional  robotic  surface  is
devised  using  triangular  modules  connected  by
revolute  joints  that  mimic  the  constraints  of  a
spherical  joint  at  each  triangle  intersection.  The
finite  element  method  (FEM)  is  applied  to  the
dynamic  loading  of  this  device  using  three
dimensional    (6    degrees    of    freedom)    beam
elements  to  not  only  calculate  the  cartesian
displacement  and  force,  but  also  the  angular
displacement and torque at each joint. In this way,
the traditional methods of finding joint forces and
torques  are  completely  bypassed.  An  effiecient
algorithm  is  developed  to  linearly  combine  local
mass  and  stiffness  matrices  into  a  full  structural
stiffness  matrix  for  the  easy  application  of  loads.
An  analysis  of  optimal  dynamic  joint  forces  is
carried  out  in  Simulink®  with  the  use  of  an
algebraic Ricatti equation.

FINITE ELEMENT ANALYSIS OF A HIGHLY PARALLEL ROBOTIC SURFACE

by Chris Salisbury

Published in the proceedings of the global IMECE2011 conference.

A  novel  three-dimensional  robotic  surface  is  devised  and more A  novel  three-dimensional  robotic  surface  is  devised  and
implemented  using  triangular  modules.  Each  module  is
connected  by  a  passive  sixbar  mechanism  that  mimics  the
constraints of a spherical joint at each triangle intersection. The
finite element method (FEM) is applied to the static loading of
this  device  using  linear  three  dimensional  (6  degrees  of
freedom) beam elements to calculate the cartesian displacement
and force and the angular displacement and torque at each joint.
In this way, the traditional methods of finding joint forces and
torques  are  completely  bypassed.  An  effiecient  algorithm  is
developed  to  linearly  combine  local  stiffness  matrices  into  a
full structural stiffness matrix for the easy application of loads.
This is then decomposed back into the local matrices to easily
obtain joint variables used in the design and open-loop control
of the surface.

Electromechanical retrofit of submarine control surface actuators

by Jonathan LeSage

Modeling and Requirements Formulation for Submarine Control Surface Actuation Systems

by Jonathan LeSage

This paper examines methods that can be adopted in early stage or retro t design of actuator subsystems, and is... more This paper examines methods that can be adopted in early stage or retrot design of actuator subsystems, and is motivated by the modern trend toward retrotting legacy hydraulic actuation of submarine control surfaces with electromechanical systems. This problem highlights the familiar need designers have to relate system response requirements to selected subsystems to enable focused development of the latter. This paper shows the utility of adopting a model basis, and specically uses a bond graph approach in combination with two-port immittance relations. Bond graphs benet study of multidisciplinary systems and provide insight into system interconnection and causality. In combination with bond graphs, immittance functions enable key relations to be established based on the overall system description, and provide a way to specify response requirements. Immittance functions also enable adopting network synthesis methods, which are used in this paper to show how passive and active compensation can be integrated to benefit proposed actuation schemes. It is shown how this combination of methods provides designers with a systematic way of relating system response requirements to targeted subsystems. The methods described are demonstrated using a simplied control surface actuation problem, and simulation results of key static and dynamic requirements are presented. The derived passive and active compensation are used to augment conventional feedback controlled actuator models, and simulations demonstrate how compensation can reduce energy consumed by actuation subsystems.

Two-port synthesis for retrofit design of electric ship control surface actuation systems

by Jonathan LeSage

This paper presents an approach for using two-port circuit synthesis methods as a basis for designing actuator... more This paper presents an approach for using two-port circuit synthesis methods as a basis for designing actuator subsystems. The development of this methodology is generally motivated by problems in retrofit design, where technology reinsertion is required to replace legacy systems, or for early stage design in new mechatronic systems. The particular problem of electric ship control surface actuation is used as an example application. A procedure that integrates two-port network synthesis methods with a model-basis conveyed using bond graphs is presented and applied to the problem of synthesizing a candidate actuation system for a submarine control surface. Studying the control surface actuator problem shows that a synthesis method is capable of providing insight into balancing passive compensation with actuation (active elements). The ability to partition active and passive system elements suggests promise in developing a means for integrating passive energy storage with actuation subsystems.

Australia's telerobot on the web

by James Trevelyan

Denoising Jet Engine Gas Path Measurements Using Nonlinear Filters

by Ranjan Ganguli

A sensorless torque control for Antagonistic Driven Compliant Joints

by Tommaso Lenzi

Analytical and Experimental Comparisons of Electromechanical Vibration Response of a Piezoelectric Bimorph Beam for Power Harvesting

by Mikail Lumentut

Special Issue (In Press)

The analysis of a piezoelectric bimorph beam with two input base motions for power harvesting

by Mikail Lumentut

Duma V. F., Optical choppers with circular-shaped windows: Modulation functions, Communications in Nonlinear Science and Numerical Simulation (Elsevier) – CNSNS 16(5), 2218-2224 (2011)

by Virgil-Florin Duma

In this paper the non-linear process of light modulation performed by optical choppers is studied. The real functions... more In this paper the non-linear process of light modulation performed by optical choppers is studied. The real functions of the transmitted flux, with transition portions are derived, in contrast to approximate approaches, of flux functions considered as series of rectangular impulses. An exact mathematical model of the dynamic phenomenon is thus achieved. Top-hat light beam distributions are considered. We are developing in this paper a new type of rotating wheel with windows that have circular-shaped edges. This is the general case of the classical configuration, of choppers with wings (or, equivalent, with sector-shaped windows) that we have solved in a previous study for all its possible relationships between the geometry of the wheel and the diameter of the light beam in the plane of the chopper. This relationship is also considered in this study, while the configuration of the new device allows for more degrees of freedom in the designing process. From this discussion, the various possible geometries of choppers that may generate a required function of the transmitted flux are obtained.

Analytical Modelling of Self-Powered Electromechanical Piezoelectric Bimorph Beams with Multidirectional Excitation

by Mikail Lumentut

A mixed H2/Hinf scheduling control scheme for a two degree-of-freedom aeroelastic system under varying airspeed and gust conditions

by Benjamin Cazzolato

Zebb Prime, Ben S. Cazzolato, Con Doolan (2008)
AIAA Guidance, Navigation and Control Conference and Exhibit, AIAA Paper 2008-6787, Honolulu, Hawaii, August 18-21

This article investigates the control of a two degree-of-freedom aeroelastic system with a torsional sti ness... more This article investigates the control of a two degree-of-freedom aeroelastic system with a torsional stiness nonlinearity. The dynamics are transformed into a Linear Fractional Representation (LFR) such that the nonlinear eects of airspeed on the dynamics act as a gain feedback to the nominal system. A controller in LFR, which allows it to schedule with airspeed, is then synthesised using Linear Matrix Inequalities (LMIs). The performance objectives of the controller are the minimisation of the H2 norm from a gust input to the pitch and plunge outputs, and the minimisation of an H-infinity norm that corresponds to the systematic method of H-infinity loop-shaping. This method has a rigorous mathematical background that allows upper limits on these criteria to be established. The nonlinear system and controller are simulated under a variety of varying airspeed and gust conditions and is shown to exhibit both good robustness and rejection of gust disturbances.

An innovative digital charge amplifier to reduce hysteresis in piezoelectric actuators

by Benjamin Cazzolato

Mohsen Bazghaleh, Steven Grainger, Ben Cazzolato, Tien-fu Lu (2010)
Proceedings of the Australasian Conference on Robotics and Automation, ACRA 2010, Brisbane, Australia, 1-3 December

Nanopositioners are the key components in a variety of nanopositioning applications, such as scanning probe... more Nanopositioners are the key components in a variety of nanopositioning applications, such as scanning probe microscopes and atomic force microscopes. Piezoelectric actuators are the most common actuators among a variety of smart actuators due to their higher resolution, lower power consumption and wider operating frequency but they suffer hysteresis which affects linearity. In this paper, an innovative digital charge amplifier is presented to reduce hysteresis in stack piezoelectric actuators. Experimental results are presented.

Inverse Control of a Piezoelectric Actuator for Precise Operation of a Micro-motion Stage

by Benjamin Cazzolato

Jayesh Minase, Tien-Fu Lu, Ben S. Cazzolato, Steven Grainger (2010)
Proceedings of the Australasian Conference on Robotics and Automation, ACRA 2010, Brisbane, Australia, 1-3 December

The inverse control of a piezoelectric actuator for precise tracking operation of a three degree of freedom (DOF)... more The inverse control of a piezoelectric actuator for precise tracking operation of a three degree of freedom (DOF) micro-motion stage is presented in this paper. This stage, which provides translational motion in X and Y directions and rotation about the Z-axis, is actuated using three stack type piezoelectric actuators. Although capable of resolution in micrometres to sub-nanometres, the actuators exhibit a significant amount of hysteresis and creep, which may lead to substantial errors if the stage was used in a tracking application. Thus, for the stage to provide precise operation, it is necessary to mitigate the effects due to hysteresis and creep. To minimize these effects, an inverse, feed-forward, control strategy is presented in this paper. Experimental results are presented to display the effectiveness of this control strategy in precise operation of the stage over a wide band of amplitudes and frequencies.

Modelling, simulation and control of an electric unicycle

by Benjamin Cazzolato

A. Kadis, D. Caldecott, A. Edwards, M. Jerbic, R. Madigan, M Haynes, B. Cazzolato, Z. Prime (2010)
Proceedings of the Australasian Conference on Robotics and Automation, ACRA 2010, Brisbane, Australia, 1-3 December

In this paper the outcomes from a one year honours project to design, build and control a self-balancing electric... more In this paper the outcomes from a one year honours project to design, build and control a self-balancing electric unicycle, known as the Micycle, are presented. The design of the system along with the associated mechanical and electrical components is presented. This is followed by a derivation of the system dynamics using the Lagrangian method which are simulated using Simulink. A linear control strategy to stabilize in the pitch direction is then proposed. Finally, a comparison between the control systems results from the Simulink simulations and experimental results from the physical system is presented.