228 research outputs found
Accounting for Resilience in the Selection of R Factors for a RC Unsymmetrical Building
No full textSeveral design codes consider the non-linear response of a building by using one of the most important seismic parameters, called the response reduction factor (R). The lack of a detailed description of the R factor selection creates the need for a deeper study. This paper emphasises a methodology for the selection of a proper R factor based on resilience aspects. Unsymmetrical/irregular buildings have become the most common in recent times due to aesthetic purposes. However, because of the complexity due to the torsional effect, the selection of the R factor is even more difficult for this type of building. Therefore, a high-rise G+10-storey L-shaped building is herein considered. The building has re-entrant corners based on the structural/plan arrangement. Different R factors were used in the building design, considering buildings subjected to both unidirectional and bidirectional seismic loading scenarios. The building response with respect to various R factors (R equal to 3, 4, 5 and 6) in terms of its performance level, functionality, damage ratio and resilience was assessed at two design levels, i.e., design basic earthquake (DBE) and maximum considered earthquake (MCE). The study concludes that, considering the above criteria along with the resilience aspect, a maximum R factor up to 4 can be recommended for unidirectional loading, whereas for bidirectional loading, the maximum recommended R factor is 3
Indian Scientists Making Snake Robot for Search and Rescue Missions
No full text"When deployed in a search and rescue operation or a surveillance mission (defence-related), snake robots communicate with each other and with a central station from a cyber-physical system through various sensors such as video camera, GPS, Infrared and ultrasonic range finders," Kumar said
Optimal energy consumption of a biped robotfor crossing a wide ditch
No full textOptimization is the making
best out of available resources. Fo
r a biped,
cross
ing
a wide ditch is a
difficult task.
Wide ditch means the width of the ditch should be equal to or greater than the leg
length. In our case the length of the leg of the biped is 1.05 meter.
The biped possesses
five
degree of freedom.
Equation
s
of motion for
a biped has been derived in body coordinate
formulation.
For optimization genetic algorithm optimization is used.
Genetic algorithm
optimization is a search method which gives optimum input value and optimum output value
based on some guess value if requir
ed so. The result
s
desired are
based on
variables obtained
from control constraints
responsible for crossing the ditch. More the number of variable
s
more
expensive
the problem will become. In order to reduce the number of variable
s
, the body
coordinate for
mulation has been converted into joint coordinate formulation.
The center
of mass
(COM) is exactly above the ankle of the biped making. There is no variation of COM in y
direction
(one of the control constraint)
while crossing the ditch.
The motor torque a
nd rpm
required to cross t
he wide ditch have been
observed to be minimum and
thus are optimal values.
The biped is able to cross
9
out of
16
cases taken
in four equal intervals
in each knee and torso
angle
s
. The results are found
to be
better and reaso
nable than conventional
method
s
of
optimization
Online trajectory generation for wide ditch crossing of biped robots using control constraints
No full textThis work proposes a multibody dynamics approach to generate joint trajectories for a five degrees of freedom biped robot crossing a wide ditch whose width is greater than or equal to the robot’s leg length. Trajectories are generated using control constraints that depend on the horizontal distance traveled by the center of mass and are not explicitly dependent on time. Behavior of the biped robot for various initial postures is studied considering dynamic balance, friction, and impact in order to find the preferred initial postures considering the net energy consumption and peak power requirements at various joints. Several cases of friction, zero moment point location, and the center of mass height variation are considered in the study. Using the proposed approach, feasible trajectories for an adult sized biped robot could be generated for a wide ditch of 1.05 m width at coefficients of friction as low as 0.2. The results obtained are useful for designing reference trajectories and actuation systems for biped robots that need to cross wide ditches or take large steps. Time needed for trajectory generation is found to be sufficiently low for online implementation
Generating Feasible Solutions for Dynamically Crossing a Wide Ditch by a Biped Robot
No full textThe aim of this research work is to generate feasible motion for a biped robot to dynamically cross a wide ditch which is defined as a ditch with width more than or equal to the leg length. We propose an approach to obtain feasible solutions for dynamically crossing the wide ditch considering the dynamic balance of the biped robot, friction between the robot foot and ground, impact on the foot, limitations on the joint actuator torques and angular velocities. The biped robot is modeled as a seven link planar robot with the ditch crossing task consisting of two single support phases and a double support phase. An algorithm is developed to find the joint trajectories and the joint torques in each phase of ditch crossing by formulating the ditch crossing task as a constrained nonlinear optimization problem. In order to make the algorithm converge fast and to give feasible solutions, additional constraints called Adopted Constraints (ACs) are incorporated into the system of constraints. With time being one of the parameters, the developed algorithm adaptively adjusts the time for crossing a wide ditch. The significance of ground reaction force constraints in obtaining feasible solutions for crossing the wide ditch is shown through simulations. Feasible solutions obtained from simulation results provide not only the feasible joint angle trajectories, but also the joint torques required for the selection of actuators for a biped robot crossing the wide ditch
Biped dynamic walker modeling and control for underactuated gait cycle
No full textA biped dynamic walker with two legs and two feet capable of walking in double support phase and allowing starting the gait cycle from rest position is proposed. The walker is actuated at the ankle joints alone with no hip actuator, fully actuated in double support phase, and unactuated in single support phase. Assuming a static configuration at the start of each single support phase, fixed point information for the gait cycle at various step lengths is extracted and represented with four parameters of a cubic polynomial. This is used as the end configuration for the position controller’s reference target in the double support phase. Actuation at the ankles considers the unilateral constraints at the front and rear feet. Even with trajectory tracking controller, low cost of transport is achieved by ensuring no negative power inputs during actuation. A proportional feedback controller is employed for cycle convergence, and the stability of gait cycles, disturbance handling, and energetic efficiency for various step lengths is shown through simulations. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature
Working and Limitations of Cable Stiffening in Flexible Link Manipulators
No full textRigid link manipulators (RLMs) are used in industry to move and manipulate objects in their workspaces. Flexible link manipulators (FLMs), which are much lighter and hence highly flexible compared to RLMs, have been proposed in the past as means to reduce energy consumption and increase the speed of operation. Unlike RLM, an FLM has infinite degrees of freedom actuated by finite number of actuators. Due to high flexibility affecting the precision of operation, special control algorithms are required to make them usable. Recently, a method to stiffen FLMs using cables, without adding significant inertia or adversely affecting the advantages of FLMs, has been proposed as a possible solution in a preliminary work by the authors. An FLM stiffened using cables can use existing control algorithms designed for RLMs. In this paper we discuss in detail the working principle and limitations of cable stiffening for flexible link manipulators through simulations and experiments. A systematic way of deciding the location of cable attachments to the FLM is also presented. The main result of this paper is to show the advantage of adding a second pair of cables in reducing overall link deflections
Cable stiffened flexible link manipulator
No full textFlexible link manipulators (FLMs) have several advantages over rigid link manipulators (RLMs) in aspects such as mass and moment of inertia, energy consumption, and speed. However, they suffer from a major limitation of flexibility that affects precision of operation. Control algorithms that are currently used for RLMs cannot be directly applied to FLMs. Majority of research on FLMs has focused on how to eliminate or reduce the undesirable effects of flexibility by specially developed control algorithms. In this paper, we introduce a new design change that stiffens the flexible link manipulator using cables and minimizes the effect of flexibility while retaining the advantages of FLMs. Such cable stiffened flexible link manipulators have the advantage of allowing the use of existing control techniques designed for RLMs. Effectiveness of this new approach is shown through simulations and experiments
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