6 research outputs found
Climbing and Walking Robots
Nowadays robotics is one of the most dynamic fields of scientific researches. The shift of robotics researches from manufacturing to services applications is clear. During the last decades interest in studying climbing and walking robots has been increased. This increasing interest has been in many areas that most important ones of them are: mechanics, electronics, medical engineering, cybernetics, controls, and computers. Today’s climbing and walking robots are a combination of manipulative, perceptive, communicative, and cognitive abilities and they are capable of performing many tasks in industrial and non- industrial environments. Surveillance, planetary exploration, emergence rescue operations, reconnaissance, petrochemical applications, construction, entertainment, personal services, intervention in severe environments, transportation, medical and etc are some applications from a very diverse application fields of climbing and walking robots. By great progress in this area of robotics it is anticipated that next generation climbing and walking robots will enhance lives and will change the way the human works, thinks and makes decisions. This book presents the state of the art achievments, recent developments, applications and future challenges of climbing and walking robots. These are presented in 24 chapters by authors throughtot the world The book serves as a reference especially for the researchers who are interested in mobile robots. It also is useful for industrial engineers and graduate students in advanced study
Generating Trajectories for Wide Ditch Crossing of Biped Robots
Ditch crossing is one of the essential capabilities required for a biped robot in disaster management
and search and rescue operations. This thesis presents di�erent approaches for trajectory generation
of a planar biped robot crossing a wide ditch, which is de�ned as a ditch for which the ankle to
ankle stretch required to cross the ditch is equal to or more than the leg length of the biped robot.
Crossing a wide ditch can be considered as an application of long step walking. It is an extreme
case walking demanding more attention than normal walking. In crossing a wide ditch the di�culty
lies in generating trajectories considering friction and impact. With the proposed approaches in this
work trajectories are generated for crossing wide ditch considering a least friction coe�cient of 0.15
also. With the analysis carried out in this work, some of the key issues to be considered in crossing
a wide ditch are identi�ed.
The thesis starts with proposing an o�ine approach for �nding feasible trajectories for dynamically
crossing a wide ditch in ideal conditions. Later an online approach for the same task is
proposed using the concept control constraints. The e�orts have been extended further to propose
a real time approach for �nding joint trajectories crossing a wide ditch with uncertainties and also
to �nd optimal solutions with Genetic Algorithm (GA).
In generating feasible trajectories o�ine for a biped robot to dynamically cross a wide ditch,
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 are considered. 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 �nd 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 signi�cance 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. From the results obtained it is felt that an approach for �nding faster solutions (trajectories)
is essential for studying the behavior of the biped robot with various initial postures.
Ful�lling the above requirement this work also proposes a multibody dynamics approach to
generate online trajectories. 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 �nd 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 coe�cients 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 su�ciently low for online implementation.
The work has been extended for generating trajectories for wide ditch crossing with uncertainties.\ud
viii
Wide ditch crossing with landing uncertainties by a planar biped robot demands real-time solutions,
at the same time it has to ful�ll the necessary criteria mentioned before. Besides using the timeindependent
control constraints, considering the impact, dynamic balance and friction, to generate
real time solutions, a novel concept called the point of feasibility is introduced, for bringing the
biped robot to complete rest at the end of ditch crossing. With the proposed approach real-time
solutions are found for various initial postures of the biped robot at di�erent friction coe�cients
to give the feasible regions for crossing a wide ditch with landing uncertainties. A study on the
in
uence of initial posture on landing impact and net energy consumption is presented. Through
simulations, the best initial postures to e�ciently cross a wide ditch of width 1.05 m, with less
impact and without singularities are found. Finally, the advantage of the proposed approach to
cross a wide ditch when the surface friction is not same on both sides of the ditch is demonstrated.
Using the model with control constraints an approach is proposed for �nding optimal solutions
for wide ditch crossing with GA multiobjective optimization. With the proposed approach optimal
solutions with GA can be obtained without any additional constraints. Finally optimal initial
postures for the biped robot to cross a wide ditch are given along with the peak torque, peak
rotational speed and the peak power rating of the actuators required at various joints of the biped
robot
Generating real-time trajectories for a planar biped robot crossing a wide ditch with landing uncertainties
Ditch crossing is one of the essential capabilities required for a biped robot in disaster management and search and rescue operations. Present work focuses on crossing a wide ditch with landing uncertainties by an under-actuated planar biped robot with five degrees of freedom. We consider a ditch as wide for a robot when the ankle to ankle stretch required to cross it is at least equal to the leg length of the robot. Since locomotion in uncertain environments requires real-time planning, in this paper, we present a new approach for generating real-time joint trajectories using control constraints not explicitly dependent on time, considering impact, dynamic balance, and friction. As part of the approach, we introduce a novel concept called the point of feasibility for bringing the biped robot to complete rest at the end of ditch crossing. We present a study on the influence of initial posture on landing impact and net energy consumption. Through simulations, we found the best initial postures to efficiently cross a wide ditch of width 1.05 m, with less impact and without singularities. Finally, we demonstrate the advantage of the proposed approach to cross a wide ditch when the surface friction is not same on both sides of the ditch
Robotics 2010
Without a doubt, robotics has made an incredible progress over the last decades. The vision of developing, designing and creating technical systems that help humans to achieve hard and complex tasks, has intelligently led to an incredible variety of solutions. There are barely technical fields that could exhibit more interdisciplinary interconnections like robotics. This fact is generated by highly complex challenges imposed by robotic systems, especially the requirement on intelligent and autonomous operation. This book tries to give an insight into the evolutionary process that takes place in robotics. It provides articles covering a wide range of this exciting area. The progress of technical challenges and concepts may illuminate the relationship between developments that seem to be completely different at first sight. The robotics remains an exciting scientific and engineering field. The community looks optimistically ahead and also looks forward for the future challenges and new development
Reports to the President
A compilation of annual reports for the 1990-1991 academic year, including a report from the President of the Massachusetts Institute of Technology, as well as reports from the academic and administrative units of the Institute. The reports outline the year's goals, accomplishments, honors and awards, and future plans