16,655 research outputs found
Contact mechanics applied to the machining of thin rings
Precision machining of thin rings is of key importance in the performance of many mechanical components such as bearings, rings, turbines, etc. An important factor to take into account is to know the influence of the clamping forces values at different angular positions of the workpiece in the geometrical tolerances after machining. The lower the clamping force, better tolerances will be achieved, but with the disadvantage of reducing friction force and, therefore, increasing the risk of slipping. Therefore, achieving a minimum but safe clamping force is a key factor to control the process. This paper presents some contributions of contact mechanics to the determination of an optimum clamping force. A subsequent methodology is applied that takes into account model of bulk deformation and local contact stresses and experimental data with the object of obtain the optimum torque applied to the chuck.The authors would like to thank the Basque Government for supporting this work made under the ETORTEK Program within the MARGUNE CRC framework while the first author was a visiting professor at TECNUN
Unsupervised Contact Learning for Humanoid Estimation and Control
This work presents a method for contact state estimation using fuzzy
clustering to learn contact probability for full, six-dimensional humanoid
contacts. The data required for training is solely from proprioceptive sensors
- endeffector contact wrench sensors and inertial measurement units (IMUs) -
and the method is completely unsupervised. The resulting cluster means are used
to efficiently compute the probability of contact in each of the six
endeffector degrees of freedom (DoFs) independently. This clustering-based
contact probability estimator is validated in a kinematics-based base state
estimator in a simulation environment with realistic added sensor noise for
locomotion over rough, low-friction terrain on which the robot is subject to
foot slip and rotation. The proposed base state estimator which utilizes these
six DoF contact probability estimates is shown to perform considerably better
than that which determines kinematic contact constraints purely based on
measured normal force.Comment: Submitted to the IEEE International Conference on Robotics and
Automation (ICRA) 201
Unsupervised Contact Learning for Humanoid Estimation and Control
This work presents a method for contact state estimation using fuzzy
clustering to learn contact probability for full, six-dimensional humanoid
contacts. The data required for training is solely from proprioceptive sensors
- endeffector contact wrench sensors and inertial measurement units (IMUs) -
and the method is completely unsupervised. The resulting cluster means are used
to efficiently compute the probability of contact in each of the six
endeffector degrees of freedom (DoFs) independently. This clustering-based
contact probability estimator is validated in a kinematics-based base state
estimator in a simulation environment with realistic added sensor noise for
locomotion over rough, low-friction terrain on which the robot is subject to
foot slip and rotation. The proposed base state estimator which utilizes these
six DoF contact probability estimates is shown to perform considerably better
than that which determines kinematic contact constraints purely based on
measured normal force.Comment: Submitted to the IEEE International Conference on Robotics and
Automation (ICRA) 201
Flexible structure control laboratory development and technology demonstration
An experimental structure is described which was constructed to demonstrate and validate recent emerging technologies in the active control and identification of large flexible space structures. The configuration consists of a large, 20 foot diameter antenna-like flexible structure in the horizontal plane with a gimballed central hub, a flexible feed-boom assembly hanging from the hub, and 12 flexible ribs radiating outward. Fourteen electrodynamic force actuators mounted to the hub and to the individual ribs provide the means to excite the structure and exert control forces. Thirty permanently mounted sensors, including optical encoders and analog induction devices provide measurements of structural response at widely distributed points. An experimental remote optical sensor provides sixteen additional sensing channels. A computer samples the sensors, computes the control updates and sends commands to the actuators in real time, while simultaneously displaying selected outputs on a graphics terminal and saving them in memory. Several control experiments were conducted thus far and are documented. These include implementation of distributed parameter system control, model reference adaptive control, and static shape control. These experiments have demonstrated the successful implementation of state-of-the-art control approaches using actual hardware
Experimental investigation of an accelerometer controlled automatic braking system
An investigation was made to determine the feasibility of an automatic braking system for arresting the motion of an airplane by sensing and controlling braked wheel decelerations. The system was tested on a rotating drum dynamometer by using an automotive tire, wheel, and disk-brake assembly under conditions which included two tire loadings, wet and dry surfaces, and a range of ground speeds up to 70 knots. The controlling parameters were the rates at which brake pressure was applied and released and the Command Deceleration Level which governed the wheel deceleration by controlling the brake operation. Limited tests were also made with the automatic braking system installed on a ground vehicle in an effort to provide a more realistic proof of its feasibility. The results of this investigation indicate that a braking system which utilizes wheel decelerations as the control variable to restrict tire slip is feasible and capable of adapting to rapidly changing surface conditions
End to End Satellite Servicing and Space Debris Management
There is growing demand for satellite swarms and constellations for global
positioning, remote sensing and relay communication in higher LEO orbits. This
will result in many obsolete, damaged and abandoned satellites that will remain
on-orbit beyond 25 years. These abandoned satellites and space debris maybe
economically valuable orbital real-estate and resources that can be reused,
repaired or upgraded for future use. Space traffic management is critical to
repair damaged satellites, divert satellites into warehouse orbits and
effectively de-orbit satellites and space debris that are beyond repair and
salvage. Current methods for on-orbit capture, servicing and repair require a
large service satellite. However, by accessing abandoned satellites and space
debris, there is an inherent heightened risk of damage to a servicing
spacecraft. Sending multiple small-robots with each robot specialized in a
specific task is a credible alternative, as the system is simple and
cost-effective and where loss of one or more robots does not end the mission.
In this work, we outline an end to end multirobot system to capture damaged and
abandoned spacecraft for salvaging, repair and for de-orbiting. We analyze the
feasibility of sending multiple, decentralized robots that can work
cooperatively to perform capture of the target satellite as a first step,
followed by crawling onto damage satellites to perform detailed mapping. After
obtaining a detailed map of the satellite, the robots will proceed to either
repair and replace or dismantle components for salvage operations. Finally, the
remaining components will be packaged with a de-orbit device for accelerated
de-orbit.Comment: 13 pages, 10 figures, Space Traffic Management Conference. arXiv
admin note: text overlap with arXiv:1809.02028, arXiv:1809.04459,
arXiv:1901.0971
Evaluation of automated decisionmaking methodologies and development of an integrated robotic system simulation
A generic computer simulation for manipulator systems (ROBSIM) was implemented and the specific technologies necessary to increase the role of automation in various missions were developed. The specific items developed are: (1) capability for definition of a manipulator system consisting of multiple arms, load objects, and an environment; (2) capability for kinematic analysis, requirements analysis, and response simulation of manipulator motion; (3) postprocessing options such as graphic replay of simulated motion and manipulator parameter plotting; (4) investigation and simulation of various control methods including manual force/torque and active compliances control; (5) evaluation and implementation of three obstacle avoidance methods; (6) video simulation and edge detection; and (7) software simulation validation
Physics of windblown particles
A laboratory facility proposed for the Space Station to investigate fundamental aspects of windblown particles is described. The experiments would take advantage of the environment afforded in earth orbit and would be an extension of research currently being conducted on the geology and physics of windblown sediments on earth, Mars, and Venus. Aeolian (wind) processes are reviewed in the planetary context, the scientific rational is given for specific experiments to be conducted, the experiment apparatus (the Carousel Wind Tunnel, or CWT) is described, and a plan presented for implementing the proposed research program
Microforce sensor for microbiological applications based on a floating-magnetic principle.
International audienceIn this paper, we present the design of a new magentic nano and microforce sensor for microbiological applications. The sensing part of the sensor presents a naturally stable six degrees of freedom equilibrium state using the combination of upthrust buoyancy and magnetic force. The sensor allows force measurement without deformation of the sensing element using a feedback control loop and is able to measure the components, in the horizontal plan, of the external force applied. The measurement range varies between around ± 100 µN with a resolution of 20 nN and a linear output. The mechanical stiffness of the passive system is about 0.018 N.m−1(same order of magnitude than an AFM micro-cantilever). A complete static study and experimental validation of the used principle are presented in this paper
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