141 research outputs found
Concept, modeling and experimental characterization of the modulated friction inertial drive (MFID) locomotion principle:application to mobile microrobots
A mobile microrobot is defined as a robot with a size ranging from 1 in3 down to 100 ”m3 and a motion range of at least several times the robot's length. Mobile microrobots have a great potential for a wide range of mid-term and long-term applications such as minimally invasive surgery, inspection, surveillance, monitoring and interaction with the microscale world. A systematic study of the state of the art of locomotion for mobile microrobots shows that there is a need for efficient locomotion solutions for mobile microrobots featuring several degrees of freedom (DOF). This thesis proposes and studies a new locomotion concept based on stepping motion considering a decoupling of the two essential functions of a locomotion principle: slip generation and slip variation. The proposed "Modulated Friction Inertial Drive" (MFID) principle is defined as a stepping locomotion principle in which slip is generated by the inertial effect of a symmetric, axial vibration, while the slip variation is obtained from an active modulation of the friction force. The decoupling of slip generation and slip variation also has lead to the introduction of the concept of a combination of on-board and off-board actuation. This concept allows for an optimal trade-off between robot simplicity and power consumption on the one hand and on-board motion control on the other hand. The stepping motion of a MFID actuator is studied in detail by means of simulation of a numeric model and experimental characterization of a linear MFID actuator. The experimental setup is driven by piezoelectric actuators that vibrate in axial direction in order to generate slip and in perpendicular direction in order to vary the contact force. After identification of the friction parameters a good match between simulation and experimental results is achieved. MFID motion velocity has shown to depend sinusoidally on the phase shift between axial and perpendicular vibration. Motion velocity also increases linearly with increasing vibration amplitudes and driving frequency. Two parameters characterizing the MFID stepping behavior have been introduced. The step efficiency ηstep expresses the efficiency with which the actuator is capable of transforming the axial vibration in net motion. The force ratio qF evaluates the ease with which slip is generated by comparing the maximum inertial force in axial direction to the minimum friction force. The suitability of the MFID principle for mobile microrobot locomotion has been demonstrated by the development and characterization of three locomotion modules with between 2 and 3 DOF. The microrobot prototypes are driven by piezoelectric and electrostatic comb drive actuators and feature a characteristic body length between 20 mm and 10 mm. Characterization results include fast locomotion velocities up to 3 mm/s for typical driving voltages of some tens of volts and driving frequencies ranging from some tens of Hz up to some kHz. Moreover, motion resolutions in the nanometer range and very low power consumption of some tens of ”W have been demonstrated. The advantage of the concept of a combination of on-board and off-board actuation has been demonstrated by the on-board simplicity of two of the three prototypes. The prototypes have also demonstrated the major advantage of the MFID principle: resonance operation has shown to reduce the power consumption, reduce the driving voltage and allow for simple driving electronics. Finally, with the fabrication of 2 à 2 mm2 locomotion modules with 2 DOF, a first step towards the development of mm-sized mobile microrobots with on-board motion control is made
Bidirectional Linear Motion by Travelling Waves on Legged Piezoelectric Microfabricated Plates
This paper reports the design, fabrication and performance of MEMS-based piezoelectric
bidirectional conveyors featuring 3D printed legs, driven by linear travelling waves (TW). The
structures consisted of an aluminiumânitride (AlN) piezoelectric film on top of millimetre-sized
rectangular thin silicon bridges and two electrode patches. The position and size of the patches were
analytically optimised for TW generation in three frequency ranges: 19, 112 and 420 kHz, by the
proper combination of two contiguous flexural modes. After fabrication, the generated TW were
characterized by means of LaserâDoppler vibrometry to obtain the relevant tables of merit, such
as the standing wave ratio and the average amplitude. The experimental results agreed with the
simulation, showing the generation of a TW with an amplitude as high as 6 nm/V and a standing
wave ratio as low as 1.46 for a device working at 19.3 kHz. The applicability of the fabricated linear
actuator device as a conveyor was investigated. Its kinetic performance was studied with sliders of
different mass, being able to carry a 35 mg silicon slider, 18 times its weight, with 6 V of continuous
sinusoidal excitation and a speed of 0.65 mm/s. A lighter slider, weighting only 3 mg, reached a mean
speed of 1.7 mm/s at 6 V. In addition, by applying a burst sinusoidal excitation comprising 10 cycles,
the TW generated in the bridge surface was able to move a 23 mg slider in discrete steps of 70 nm,
in both directions, which is a promising result for a TW piezoelectric actuator of this size
Piezoelectric MEMS Linear Motor for Nanopositioning Applications
This paper reports the design, fabrication, and performance of piezoelectric bidirectional
conveyors based on microelectromechanical systems (MEMS) and featuring 3D-printed legs in
bridge resonators. The structures consisted of aluminum-nitride (AlN) piezoelectric film on top of
millimeter-sized rectangular thin silicon bridges and two electrode patches. The position and size of
the patches were analytically optimized for travelling or standing wave generation, while the addition
of 3D-printed legs allowed for a controlled contact and amplified displacement, a further step into
the manufacturing of efficient linear motors. Such hybrid devices have recently demonstrated the
conveyance of sliders of several times the motor weight, with speeds of 1.7 mm/s by travelling waves
generated at 6 V and 19.3 kHz. In this paper both travelling and standing wave motors are compared.
By the optimization of various aspects of the device such as the vibrational modes, leg collocation
and excitation signals, speeds as high as 35 mm/s, and payloads above 10 times the motor weight
were demonstrated. The devices exhibited a promising positional resolution while actuated with
only a few sinusoidal cycles in an open-loop configuration. Discrete steps as low as 70 nm were
measured in the conveyance of 2-mg sliders
Design and Characterization of a Planar Micro-Conveyor Device Based on Cooperative Legged Piezoelectric MEMS Resonators
This paper reports the design, fabrication, and performance of a hybrid piezoelectric
planar micro-conveyor based on Micro-Electromechanical Systems (MEMS) bridge resonators and
featuring 3D-printed vertical legs. The device includes two cooperating silicon plate resonators with
an area of 5 Ă 1 mm2
, actuated by an integrated aluminum-nitride (AlN) piezoelectric thin film. An
optimally designed array of 3D-printed projection legs was attached to the plates, to convert the
standing-wave (SW) vertical vibrations into horizontal rotations or translations of the supported
slider. An open-loop control strategy based on burst-type driving signals, with different numbers of
sinusoidal cycles applied on each of the resonators, allowed the cooperation of the two bridges to set
up prescribed trajectories of small flat objects, up to 100 mg, with positional accuracy below 100 nm
and speeds up to 20 mm/s, by differential drive actuation. The effect of the leg tip and slidersâ surface
finish on the conveyor performance was investigated, suggesting that further optimizations may be
possible by modifying the tribological properties. Finally, the application of the micro-conveyor as a
reconfigurable electronic system, driven by a preprogrammed sequence of signals, was demonstrated
by delivering some surface-mount technology (SMD) parts lying on a 65 mg glass slider
Contactless acoustic micro/nano manipulation:a paradigm for next generation applications in life sciences
Acoustic actuation techniques offer a promising tool for contactless manipulation of both synthetic and biological micro/nano agents that encompass different length scales. The traditional usage of sound waves has steadily progressed from mid-air manipulation of salt grains to sophisticated techniques that employ nanoparticle flow in microfluidic networks. State-of-the-art in microfabrication and instrumentation have further expanded the outreach of these actuation techniques to autonomous propulsion of micro-agents. In this review article, we provide a universal perspective of the known acoustic micromanipulation technologies in terms of their applications and governing physics. Hereby, we survey these technologies and classify them with regards to passive and active manipulation of agents. These manipulation methods account for both intelligent devices adept at dexterous non-contact handling of micro-agents, and acoustically induced mechanisms for self-propulsion of micro-robots. Moreover, owing to the clinical compliance of ultrasound, we provide future considerations of acoustic manipulation techniques to be fruitfully employed in biological applications that range from label-free drug testing to minimally invasive clinical interventions
Micro/nanoscale magnetic robots for biomedical applications
Magnetic small-scale robots are devices of great potential for the biomedical field because of the several benefits of this method of actuation. Recent work on the development of these devices has seen tremendous innovation and refinement toward âimproved performance for potential clinical applications. This review briefly details recent advancements in small-scale robots used for biomedical applications, covering their design, fabrication, applications, and demonstration of ability, and identifies the gap in studies and the difficulties that have persisted in the optimization of the use of these devices. In addition, alternative biomedical applications are also suggested for some of the technologies that show potential for other functions. This study concludes that although the field of small-scale robot research is highly innovative âthere is need for more concerted efforts to improve functionality and reliability of these devices particularly in clinical applications. Finally, further suggestions are made toward âthe achievement of commercialization for these devices
Stepper microactuators driven by ultrasonic power transfer
Advances in miniature devices for biomedical applications are creating ever-increasing
requirements for their continuous, long lasting, and reliable energy
supply, particularly for implanted devices. As an alternative to bulky
and cost inefficient batteries that require occasional recharging and replacement,
energy harvesting and wireless power delivery are receiving increased
attention. While the former is generally only suited for low-power diagnostic
microdevices, the latter has greater potential to extend the functionality to
include more energy demanding therapeutic actuation such as drug release,
implant mechanical adjustment or microsurgery.
This thesis presents a novel approach to delivering wireless power to remote
medical microdevices with the aim of satisfying higher energy budgets
required for therapeutic functions. The method is based on ultrasonic power
delivery, the novelty being that actuation is powered by ultrasound directly
rather than via piezoelectric conversion. The thesis describes a coupled mechanical
system remotely excited by ultrasound and providing conversion
of acoustic energy into motion of a MEMS mechanism using a receiving
membrane coupled to a discrete oscillator. This motion is then converted
into useful stepwise actuation through oblique mechanical impact.
The problem of acoustic and mechanical impedance mismatch is addressed.
Several analytical and numerical models of ultrasonic power delivery
into the human body are developed. Major design challenges that have
to be solved in order to obtain acceptable performance under specified operating
conditions and with minimum wave reflections are discussed. A novel
microfabrication process is described, and the resulting proof-of-concept devices
are successfully characterized.Open Acces
Zur Mechanik vibrationsgetriebener Roboter fĂŒr terrestrische und aquatische Lokomotion
This thesis discusses the mechanics of mobile robots for terrestrial and
aquatic locomotion. Vibration-driven locomotion systems are characterised
by an internal periodic excitation, which is transformed to a directed
motion due to asymmetric properties of the system. To perform a
two-dimensional and controllable locomotion, mechanical properties of
robots are investigated dependent on the frequency of the internal
excitation. The mechanical description of the robots is done using
analytical and numerical methods and supported by experimental studies. The
applicability of the results in mobile robots is proved by prototypes.On
the basis of mechanical fundamentals, terrestrial and aquatic locomotion
principles are discussed and classified. Actuators are reviewed. The
purpose is to evaluate the performance as vibration sources for terrestrial
and aquatic systems. Piezoelectric bending elements are particular suitable
for it. An extensive overview on the state of the art shows the great
potential of vibration-driven locomotion systems for miniaturised
applications in technics.Systems with bristles can perform unidirectional
terrestrial locomotion. Different working principles of bristles are
studied based on a rigid body model and experimental investigations. A
prototype for the locomotion in tubes is presented. To perform a
controllable two-dimensional locomotion with only one actuator, it is
needed to overcome the limits of rigid body systems. The applied approach
uses the frequency-dependent vibration behaviour of elastic systems, like
beams and plates. Models of continuum mechanics and finite element methods
are used and supported by experiments. Based on the investigations, a
programmable and remote controlled prototype is developed. The locomotion
of it can be controlled on different surfaces by a change of the excitation
frequency. The velocity of the prototype is up to 100 mm/s and it can
support five times its own weight.Concluding, an innovative prototype with
a single piezoelectric actuator for a controllable locomotion on flat
ground and floating in fluids is developed. The terrestrial and aquatic
locomotion behaviour of the robot is investigated. The carrying capacity of
it is calculated using a hydrostatic model.Die Mechanik von mobilen Robotern fĂŒr terrestrische und aquatische Lokomotion ist der Gegenstand der Arbeit. In den untersuchten Systemen wird die periodische Erregung eines inneren Antriebs durch nicht symmetrische Systemeigenschaften in eine gerichtete Fortbewegung gewandelt. Durch die Nutzung des frequenzabhĂ€ngigen Schwingungsverhaltens von elastischen Systemen, wie Balken oder Platten, werden Systeme realisiert, die durch nur einen Antrieb eine steuerbare zweidimensionale Lokomotion auf festem Untergrund und an der OberflĂ€che von FlĂŒssigkeiten durchfĂŒhren können. Der Schwerpunkt der Arbeit liegt auf der mathematisch-mechanischen Beschreibung der Roboter mittels analytischer und numerischer Methoden sowie ihrer experimentellen Untersuchung. Prototypen mobiler Roboter dienen dem funktionellen Nachweis.Auch im Buchhandel erhĂ€ltlich:
Zur Mechanik vibrationsgetriebener Roboter fĂŒr terrestrische und aquatische Lokomotion / Felix Becker
Ilmenau : Univ.-Verl. Ilmenau, 2015. - XIX, 149 S.
ISBN 978-3-86360-124-9
URN urn:nbn:de:gbv:ilm1-2015000338
Preis (Druckausgabe): 21,30
Locomotion Optimization of Photoresponsive Small-scale Robot: A Deep Reinforcement Learning Approach
Soft robots comprise of elastic and flexible structures, and actuatable soft materials are often used to provide stimuli-responses, remotely controlled with different kinds of external stimuli, which is beneficial for designing small-scale devices. Among different stimuli-responsive materials, liquid crystal networks (LCNs) have gained a significant amount of attention for soft small-scale robots in the past decade being stimulated and actuated by light, which is clean energy, able to transduce energy remotely, easily available and accessible to sophisticated control.
One of the persistent challenges in photoresponsive robotics is to produce controllable autonomous locomotion behavior. In this Thesis, different types of photoresponsive soft robots were used to realize light-powered locomotion, and an artificial intelligence-based approach was developed for controlling the movement. A robot tracking system, including an automatic laser steering function, was built for efficient robotic feature detection and steering the laser beam automatically to desired locations. Another robot prototype, a swimmer robot, driven by the automatically steered laser beam, showed directional movements including some degree of uncertainty and randomness in their locomotion behavior.
A novel approach is developed to deal with the challenges related to the locomotion of photoresponsive swimmer robots. Machine learning, particularly deep reinforcement learning method, was applied to develop a control policy for autonomous locomotion behavior. This method can learn from its experiences by interacting with the robot and its environment without explicit knowledge of the robot structure, constituent material, and robotic mechanics. Due to the requirement of a large number of experiences to correlate the goodness of behavior control, a simulator was developed, which mimicked the uncertain and random movement behavior of the swimmer robots. This approach effectively adapted the random movement behaviors and developed an optimal control policy to reach different destination points autonomously within a simulated environment. This work has successfully taken a step towards the autonomous locomotion control of soft photoresponsive robots
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