3,093 research outputs found
Rotary Microspine Rough Surface Mobility
No full textRotary microspine rough surface climbing extends previous successful linear implementations of bio inspired robots. Arrays of independently compliant rotary microspines are used to build wheels that enable the robots to seamlessly transition from horizontal to vertical surfaces, rapidly mount curbs, and climb stairs and rough walls. Building off of a basic first implementation of a rotary microspine robot, this work presents many improvements to the rotary microspine wheels and several new configurations of robotic platforms including miniaturized insect sized robots weighing less than 10 g. Rapid iteration of microspine designs was accomplished using shape deposition manufacturing allowing new wheel concepts to go from design to testing in one to three days. New configurations of robots with a powered wheel in the tail have improved reliability and demonstrated new capabilities like climbing heavily painted curbs and overhanging face angle stairs. Another platform climbed a six story building. These results are presented in the following thesis and in video documentation
Scaling hard vertical surfaces with compliant microspine arrays
No full textA new approach for climbing hard vertical surfaces has been developed that allows a robot to scale concrete, stucco, brick and masonry walls without using suction or adhesives. The approach is inspired by the mechanisms observed in some climbing insects and spiders and involves arrays of microspines that catch on surface asperities. The arrays are located on the toes of the robot and consist of a tuned, multi-link compliant suspension. In this paper we discuss the fundamental issues of spine allometric scaling versus surface roughness and the suspension needed to maximize the probability that each spine will find a useable surface irregularity and to distribute climbing tensile and shear loads among many spines. The principles are demonstrated with a new climbing robot that can scale a wide range of exterior walls
Design of a Robotic Ankle Joint for a Microspine-Based Robot
No full textSuccessful robotic exploration of near-Earth asteroids necessitates a method of securely anchoring to the surface of these bodies without gravitational assistance. Microspine grip- per arrays that can grasp rock faces are a potential solution to this problem. A key component of a future microspine-based rover will be the ankle used to attach each microspine gripper to the robot. The ankle's purpose is twofold: 1) to allow the gripper to conform to the rock so a higher percentage of microspines attach to the surface, and 2) to neutralize torques that may dislodge the grippers from the wall. Parts were developed using computer aided design and manufactured using a variety of methods including selective laser sintering, CNC milling, and traditional manual machining techniques. Upon completion of the final prototype, the gripper and ankle system was tested to demonstrate robotic engagement and disengagement of the gripper and to determine load bearing ability. The immediate application of this project is to out t the Lemur IIb robot so it can climb and hang from rock walls
Synthesis of Multiple Beam Linear Arrays with Uniform Amplitudes
No full textA convex iterative algorithm for the synthesis of uniform amplitude, space-tapered linear phased arrays with simultaneous multiple beam optimization for 5G applications is presented. The performance of the algorithm is demonstrated by the synthesis of two arrays having 16 and 24 elements with 60 and 90 degree scan range, respectively. The effect of phase shifter quantization is also addressed. The results indicate that the space-tapered arrays with multiple beam optimization have improved radiation performance in terms of the side lobe level when compared to both single, broadside, beam optimized space-tapered arrays and uniformly distributed arrays with half wavelength spacing.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Microwave Sensing, Signals & System
Mapping a class of run-time dependencies onto regular arrays
No full textThe production of regular computations using algorithmic engineering techniques is beginning to play an important role in the synthesis of massively parallel and VLSI processor arrays. The author widens the class of algorithms that can be formally synthesized by introducing a mapping theorem for a class of algorithms with run-time dependencies. The technique is illustrated by deriving uniform recurrences for the so-called knapsack problem, the resulting systolic array is known to be optimal
Near-field focusing using phased arrays with dynamic polarization control
No full textPhased arrays in near-field communication allow the transmitter to focus wireless signals in a small region around the receiver. Proper focusing is achieved by carefully tuning the phase shifts and the polarization of the signals transmitted from the phased array. In this paper, we study the impact of polarization on near-field focusing and investigate the use of dynamic polar-ization control (DPC) phased arrays in this context. Our studies indicate that the optimal polarization configuration for near-field focusing varies spatially across the antenna array. Such a spatial variation motivates the need for DPC phased arrays which allow independent polarization control across different antennas. We show using simulations that DPC phased arrays in the near-field achieve a higher received signal-to-noise ratio than conventional switched- or dual-polarization phased arrays.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Nitin MyersMicrowave Sensing, Signals & SystemsSignal Processing System
Robotic Ankle for Omnidirectional Rock Anchors
No full textFuture robotic exploration of near-Earth asteroids and the vertical and inverted rock walls of lava caves and cliff faces on Mars and other planetary bodies would require a method of gripping their rocky surfaces to allow mobility without gravitational assistance. In order to successfully navigate this terrain and drill for samples, the grippers must be able to produce anchoring forces in excess of 100 N. Additionally, the grippers must be able to support the inertial forces of a moving robot, as well gravitational forces for demonstrations on Earth. One possible solution would be to use microspine arrays to anchor to rock surfaces and provide the necessary load-bearing abilities for robotic exploration of asteroids. Microspine arrays comprise dozens of small steel hooks supported on individual suspensions. When these arrays are dragged along a rock surface, the steel hooks engage with asperities and holes on the surface. The suspensions allow for individual hooks to engage with asperities while the remaining hooks continue to drag along the surface. This ensures that the maximum possible number of hooks engage with the surface, thereby increasing the load-bearing abilities of the gripper. Using the microspine array grippers described above as the end-effectors of a robot would allow it to traverse terrain previously unreachable by traditional wheeled robots. Furthermore, microspine-gripping robots that can perch on cliffs or rocky walls could enable a new class of persistent surveillance devices for military applications. In order to interface these microspine grippers with a legged robot, an ankle is needed that can robotically actuate the gripper, as well as allow it to conform to the large-scale irregularities in the rock. The anchor serves three main purposes: deploy and release the anchor, conform to roughness or misalignment with the surface, and cancel out any moments about the anchor that could cause unintentional detachment. The ankle design contains a rotary DC motor that can drag the microspine arrays across the surface to engage them with asperities, as well as a linear actuator to disengage the hooks from the surface. Additionally, the ankle allows the gripper to rotate freely about all three axes so that when the robot takes a step, the gripper may optimally orient itself with respect to the wall or ground. Finally, the ankle contains some minimal elasticity, so that between steps, the gripper returns to a default position that is roughly parallel to the wall
Semi-active multiple beam arrays
No full textThe low power efficiency (5-15%) of solid state power amplifiers, working in back-off to guarantee a good linearity, could become the show stopper for some future space and terrestrial communication ventures at Ka-band and above. Semi-active reflector and conformal antennas, using Butler-like matrices between the power amplifiers and the feed elements, were first introduced to directly generate flexible multiple beams most efficiently.For linear and planar arrays, such phase-only control at power amplifier inputs can provide beam zooming or amplitude tapering, but no proper beam steering. The paper discusses and analyses the extension of the semi-active principle to linear and planar arrays, by use of multiport amplifiers with amplitude and phase input control to power the elements most efficiently.Performances and limitations of such systems are analyzed and demonstrated for a few examples.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Microwave Sensing, Signals & System
Load assessment of optimally-arranged point absorbers arrays in front of a vertical wall
No full textIn this paper, we assess numerically the loads applied on PAs of optimally-arranged linear arrays in front of a bottom-mounted vertical wall of finite length under normal operating conditions. The arrays, maximizing the yearly absorbed energy, consist of five, identical, oblate spheroidal heaving PAs and are deployed at three near-shore sites in the Aegean Sea, Greece. The PAs are assumed to be attached on the wall via connection configurations restraining all rigid-body modes except heave. A spectral analysis is performed to quantify loads. The corresponding transfer functions are obtained from a frequency-based hydrodynamic model that solves the diffraction/radiation problem of the multi-body arrangement in the presence of the wall. Results, focusing on surge and sway restraining loads, are, initially, presented for regular waves and, then, for normal operating conditions (irregular waves), highlighting the effect of the arrays’ layouts and of the local wave conditions on the restraining loads. Comparison is also made with equally-spaced arrays to reveal potential positive effects of optimum layouts on structural integrity related issues.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Offshore Engineerin
Self-Calibration of Acoustic Scalar and Vector Sensor Arrays
No full textIn this work, we consider the self-calibration problem of joint calibration and direction-of-Arrival (DOA) estimation using acoustic sensor arrays. Unlike many previous iterative approaches, we propose solvers that can be readily used for both linear and non-linear arrays for jointly estimating the sensor gain, phase errors, and the source DOAs. We derive these algorithms for both the conventional element-space and covariance data models. We focus on sparse and regular arrays formed using scalar sensors as well as vector sensors. The developed algorithms are obtained by transforming the underlying non-linear calibration model into a linear model, and subsequently by using convex relaxation techniques to estimate the unknown parameters. We also derive identifiability conditions for the existence of a unique solution to the self-calibration problem. To demonstrate the effectiveness of the developed techniques, numerical experiments, and comparisons to the state-of-The-Art methods are provided. Finally, the results from an experiment that was performed in an anechoic chamber using an acoustic vector sensor array are presented to demonstrate the usefulness of the proposed self-calibration techniques.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
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