3,557 research outputs found
Effective Viscous Damping Enables Morphological Computation in Legged Locomotion
Muscle models and animal observations suggest that physical damping is
beneficial for stabilization. Still, only a few implementations of mechanical
damping exist in compliant robotic legged locomotion. It remains unclear how
physical damping can be exploited for locomotion tasks, while its advantages as
sensor-free, adaptive force- and negative work-producing actuators are
promising. In a simplified numerical leg model, we studied the energy
dissipation from viscous and Coulomb damping during vertical drops with
ground-level perturbations. A parallel spring-damper is engaged between
touch-down and mid-stance, and its damper auto-disengages during mid-stance and
takeoff. Our simulations indicate that an adjustable and viscous damper is
desired. In hardware we explored effective viscous damping and adjustability
and quantified the dissipated energy. We tested two mechanical, leg-mounted
damping mechanisms; a commercial hydraulic damper, and a custom-made pneumatic
damper. The pneumatic damper exploits a rolling diaphragm with an adjustable
orifice, minimizing Coulomb damping effects while permitting adjustable
resistance. Experimental results show that the leg-mounted, hydraulic damper
exhibits the most effective viscous damping. Adjusting the orifice setting did
not result in substantial changes of dissipated energy per drop, unlike
adjusting damping parameters in the numerical model. Consequently, we also
emphasize the importance of characterizing physical dampers during real legged
impacts to evaluate their effectiveness for compliant legged locomotion
Development of novel micropneumatic grippers for biomanipulation
Microbjects with dimensions from 1 μm to 1 mm have been developed
recently for different aspects and purposes. Consequently, the development of
handling and manipulation tools to fulfil this need is urgently required.
Micromanipulation techniques could be generally categorized according to
their actuation method such as electrostatic, thermal, shape memory alloy,
piezoelectric, magnetic, and fluidic actuation. Each of which has its advantage
and disadvantage. The fluidic actuation has been overlooked in MEMS despite
its satisfactory output in the micro-scale.
This thesis presents different families of pneumatically driven, low cost,
compatible with biological environment, scalable, and controllable
microgrippers. The first family demonstrated a polymeric microgripper that
was laser cut and actuated pneumatically. It was tested to manipulate microparticles
down to 200 microns. To overcome the assembly challenges that
arise in this family, the second family was proposed.
The second family was a micro-cantilever based microgripper, where the
device was assembled layer by layer to form a 3D structure. The microcantilevers
were fabricated using photo-etching technique, and demonstrated
the applicability to manipulate micro-particles down to 200 microns using
automated pick-and-place procedure. In addition, this family was used as a
tactile-detector as well. Due to the angular gripping scheme followed by the
above mentioned families, gripping smaller objects becomes a challenging
task. A third family following a parallel gripping scheme was proposed
allowing the gripping of smaller objects to be visible. It comprises a compliant
structure microgripper actuated pneumatically and fabricated using picosecond
laser technology, and demonstrated the capability of gripping microobject
as small as 100 μm microbeads. An FEA modelling was employed to
validate the experimental and analytical results, and excellent matching was
achieved
Experimental Evaluation of A Cylinder Actuator Control Using McKibben Muscle
There has been an increased interest in applying pneumatic muscle actuator (PMA) in robotic systems because of its low weight and high compliant characteristics. On the other hand, pneumatic muscle actuator (PMA) is gaining attention in robotic applications because of its low weight and high compliant characteristics. It is known that the McKibben muscle is different from the fluidic cylinder actuator in that the cylinder was unstable in its position and in its velocity in an open-loop system unlike the McKibben that is stable in its position. The modeling and control of McKibben muscle as the actuator for the cylinder are crucial because it is known to have non-linear response, hysteresis and small stroke. In this project, a single acting cylinder model which would have uncontrolled extension to push direction by compressed air, is actuated and controlled using a PMA. The system is designed with two 1.3mm-diameter McKibben muscles attached to the cylinder. Open loop control was used and the result shows that the PMA is able to control the cylinder with good performance
DEVELOPMENT OF A SOFT PNEUMATIC ACTUATOR FOR MODULAR ROBOTIC MECHANISMS
Soft robotics is a widely and rapidly growing field of research today. Soft
pneumatic actuators, as a fundamental element in soft robotics, have gained
huge popularity and are being employed for the development of soft robots.
During the last decade, a variety of hyper-elastic robotic systems have been
realized. As the name suggests, such robots are made up of soft materials,
and do not have any underlying rigid mechanical structure. These robots are
actuated employing various methods like pneumatic, electroactive, jamming
etc. Generally, in order to achieve a desired mechanical response to produce
required actuation or manipulation, two or more materials having different
stiffness are utilized to develop a soft robot. However, this method introduces
complications in the fabrication process as well as in further design
flexibility and modifications. The current work presents a design scheme of
a soft robotic actuator adapting an easier fabrication approach, which is economical
and environment friendly as well.
The purpose is the realization of a soft pneumatic actuator having functional
ability to produce effective actuation, and which is further employable
to develop modular and scalable mechanisms. That infers to scrutinize the
profile and orientation of the internal actuation cavity and the outer shape of
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the actuator. Utilization of a single material for this actuator has been considered
to make this design scheme convenient. A commercial silicone rubber
was selected which served for an economical process both in terms of the
cost as well as its accommodating fabrication process through molding. In
order to obtain the material behavior, \u2018Ansys Workbench 17.1 R
\u2019 has been
used. Cubic outline for the actuator aided towards the realization of a body
shape which can easily be engaged for the development of modular mechanisms
employing multiple units. This outer body shape further facilitates
to achieve the stability and portability of the actuator. The soft actuator has
been named \u2018Soft Cubic Module\u2019 based on its external cubic shape. For the
internal actuation cavity design, various shapes, such as spherical, elliptical
and cylindrical, were examined considering their different sizes and orientations
within the cubic module. These internal cavities were simulated in order
to achieve single degree of freedom actuation. That means, only one face
of the cube is principally required to produce effective deformation. \u2018Creo
Perametric 3.0 M 130\u2019 has been used to design the model and to evaluate the
performance of actuation cavities in terms of effective deformation and the
resulting von-mises stress. Out of the simulated profiles, cylindrical cavity
with desired outcomes has been further considered to design the soft actuator.
\u2018Ansys Workbench 17.1 R
\u2019 environment was further used to assess the
performance of cylindrical actuation cavity. Evaluation in two different simulation
environments helped to validate the initially achieved results. The
developed soft cubic actuator was then employed to develop different mechanisms
in a single unit configuration as well as multi-unit robotic system
developments.
This design scheme is considered as the first tool to investigate its capacity
to perform certain given tasks in various configurations. Alongside
its application as a single unit gripper and a two unit bio-mimetic crawling
mechanism, this soft actuator has been employed to realize a four degree
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of freedom robotic mechanism. The formation of this primitive soft robotic
four axis mechanism is being further considered to develop an equivalent
mechanism similar to the well known Stewart platform, with advantages of
compactness, simpler kinematics design, easier control, and lesser cost.
Overall, the accomplished results indicate that the design scheme of Soft
Cubic Module is helpful in realizing a simple and cost-effective soft pneumatic
actuator which is modular and scalable. Another favourable point of
this scheme is the use of a single material with convenient fabrication and
handling
Hubungan di antara pengaturan kerja fleksibel dan prestasi pekerja dalam kalangan ejen insurans wanita
Ejen insurans merupakan jurujual pertengahan bagi syarikat insurans di mana mereka memainkan peranan penting dalam memberi khidmat nasihat kewangan (Hannah, 2011). Ejen insurans bekerja berdasarkan persekitaran pengaturan kerja yang fleksibel di mana mereka boleh menyediakan jadual waktu bekerja sendiri. Sebahagian daripada mereka bertemu dengan pelanggan pada waktu perniagaan siang hari, sementara yang lain pula membuat kertas kerja dan menyediakan konsultasi untuk pelanggan pada waktu petang. Kebanyakan mereka bekerja selama 40 jam seminggu dan ada juga beberapa ejen yang bekerja lebih lama daripada 40 jam (Hannah, 2011). Prestasi ejen insurans sangat penting untuk mengekalkan jenama produk insurans. Penilaian terhadap prestasi di kalangan ejen insurans biasanya bergantung kepada kejayaan atau kegagalan mencapai sasaran penjualan (Insurance Agent Job Overview, 2019). Proses menjual produk insurans memerlukan masa kerana mereka perlu mendekati pelanggan sebanyak mungkin dan ketersediaan waktu bekerja yang tidak tetap
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