5,665 research outputs found
Evaluation of servo, geometric and dynamic error sources on five axis high-speed machine tool
Many sources of errors exist in the manufacturing process of complex shapes.
Some approximations occur at each step from the design geometry to the machined
part. The aim of the paper is to present a method to evaluate the effect of
high speed and high dynamic load on volumetric errors at the tool center point.
The interpolator output signals and the machine encoder signals are recorded
and compared to evaluate the contouring errors resulting from each axis
follow-up error. The machine encoder signals are also compared to the actual
tool center point position as recorded with a non-contact measuring instrument
called CapBall to evaluate the total geometric errors. The novelty of the work
lies in the method that is proposed to decompose the geometric errors in two
categories: the quasi-static geometric errors independent from the speed of the
trajectory and the dynamic geometric errors, dependent on the programmed feed
rate and resulting from the machine structure deflection during the
acceleration of its axes. The evolution of the respective contributions for
contouring errors, quasi-static geometric errors and dynamic geomet- ric errors
is experimentally evaluated and a relation between programmed feed rate and
dynamic errors is highlighted.Comment: 13 pages; International Journal of Machine Tools and Manufacture
(2011) pp XX-X
The use of an automated flight test management system in the development of a rapid-prototyping flight research facility
An automated flight test management system (ATMS) and its use to develop a rapid-prototyping flight research facility for artificial intelligence (AI) based flight systems concepts are described. The ATMS provides a flight test engineer with a set of tools that assist in flight planning and simulation. This system will be capable of controlling an aircraft during the flight test by performing closed-loop guidance functions, range management, and maneuver-quality monitoring. The rapid-prototyping flight research facility is being developed at the Dryden Flight Research Facility of the NASA Ames Research Center (Ames-Dryden) to provide early flight assessment of emerging AI technology. The facility is being developed as one element of the aircraft automation program which focuses on the qualification and validation of embedded real-time AI-based systems
The application of NASREM to remote robot control
The implementation of a remote robot controller, wherein the distance to the remote robot causes significant communication time delays is described. The NASREM telrobot control architecture is used as a basis for the implementation of the system. Levels 1 through 4 of the hierarchy were implemented. The solution to the problems encounterd during the implementation and those which are unique to remote robot control are described
SAI: safety application identifier algorithm at MAC layer for vehicular safety message dissemination over LTE VANET networks
Vehicular safety applications have much significance in preventing road accidents and fatalities. Among others, cellular networks have been under investigation for the procurement of these applications subject to stringent requirements for latency, transmission parameters, and successful delivery of messages. Earlier contributions have studied utilization of Long-Term Evolution (LTE) under single cell, Friis radio, or simplified higher layer. In this paper, we study the utilization of LTE under multicell and multipath fading environment and introduce the use of adaptive awareness range. Then, we propose an algorithm that uses the concept of quality of service (QoS) class identifiers (QCIs) along with dynamic adaptive awareness range. Furthermore, we investigate the impact of background traffic on the proposed algorithm. Finally, we utilize medium access control (MAC) layer elements in order to fulfill vehicular application requirements through extensive system-level simulations. The results show that, by using an awareness range of up to 250 m, the LTE system is capable of fulfilling the safety application requirements for up to 10 beacons/s with 150 vehicles in an area of 2 × 2 km2. The urban vehicular radio environment has a significant impact and decreases the probability for end-to-end delay to be ≤100 ms from 93%–97% to 76%–78% compared to the Friis radio environment. The proposed algorithm reduces the amount of vehicular application traffic from 21 Mbps to 13 Mbps, while improving the probability of end-to-end delay being ≤100 ms by 20%. Lastly, use of MAC layer control elements brings the processing of messages towards the edge of network increasing capacity of the system by about 50%
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