Assessing Seaglider® Model-based Position Accuracy on an Acoustic Tracking Range

2021 ◽  
Author(s):  
James S. Bennett ◽  
Frederick R. Stahr ◽  
Charles C. Eriksen ◽  
Martin C. Renken ◽  
Wendy E. Snyder ◽  
...  
Keyword(s):  
Autonomous Underwater Vehicles ◽  
Position Error ◽  
Momentum Balance ◽  
Model Parameters ◽  
Tidal Basin ◽  
Acoustic Tracking ◽  
Position Accuracy ◽  
Dependent Flow ◽  
Tracking Range ◽  
Flight Model

AbstractSeagliders® are buoyancy-driven autonomous underwater vehicles whose sub-surface position estimates are typically derived from velocities inferred using a flight model. We present a method for computing velocities and positions during the different phases typically encountered during a dive-climb profile based on a buoyancy-driven flight model. We compare these predictions to observations gathered from a Seaglider deployment on the acoustic tracking range in Dabob Bay (200 m depth, mean vehicle speeds ~30 cm s-1), permitting us to bound the position accuracy estimates and understand sources of various errors. We improve position accuracy estimates during long vehicle accelerations by numerically integrating the flight-model's fundamental momentum-balance equations. Overall, based on an automated estimation of flight-model parameters, we confirm previous work that predicted vehicle velocities in the dominant dive and climb phases are accurate to < 1 cm s-1, which bounds the accumulated position error in time. However, in this energetic tidal basin, position error also accumulates due to unresolved depth-dependent flow superimposed upon an inferred depth-averaged current.

Dimensional Optimization for Minimally Invasive Surgery Robot Based on Double Space and Kinematic Accuracy Reliability Index

2020 ◽  
Vol 3 (2) ◽  
Author(s):  
Yang Jing ◽  
Jin Lingyan ◽  
Shi Xinge ◽  
Zhao Deming ◽  
Hu Ming
Keyword(s):  
Reliability Index ◽  
Position Error ◽  
Optimal Size ◽  
Kinematic Accuracy ◽  
Position Accuracy ◽  
Adjustment Mechanism ◽  
Error Space ◽  
Double Space ◽  
Kinematic Performance ◽  
Dimensional Optimization

Abstract To improve the kinematic performance of the remote center mechanism for surgical robot, a double space index and kinematic accuracy reliability index are proposed to optimize the dimensional sizes of mechanism. First, the influence of the angular error on the position error and the operability of the remote center in the workspace are analyzed. The position error space and operability space index are weighted to establish the double space index. Second, a kinematic accuracy reliability index is established based on the influence of joint clearance on output position accuracy. Finally, the dimensional sizes of remote center adjustment mechanism and double parallelogram mechanism are optimized based on proposed optimization indices. Multipopulation genetic algorithm is used to obtain the optimal size parameters under the corresponding index. The optimized double space index is 56.7%, which is 56.5% higher than before optimization. The optimized kinematic accuracy reliability is 0.91, which is 22.9% higher than before optimization. The kinematic performance of remote center mechanism has been significantly improved after optimization.

scholarly journals Modelling of snow entrainment and deposition in powder-snow avalanches

1998 ◽  
Vol 26 ◽  
pp. 253-258 ◽  
Author(s):  
Dieter Issler
Keyword(s):  
Kinetic Energy ◽  
Three Dimensional ◽  
Momentum Balance ◽  
Model Parameters ◽  
Momentum Exchange ◽  
Erosion And Deposition ◽  
Practical Applications ◽  
Suspension Layer ◽  
Dense Flow ◽  
Avalanche Formation

Following Norem’s description of powder-snow avalanche formation and structure, we propose a mathematical model that consists of a suspension layer and a so-called saltation layer. The latter is only a few meters deep and is modelled by depth-averaged mass and momentum balances. In the suspension layer, the mass and momentum balance equations for the mixture are supplemented by the snow mass balance and the transport equations for turbulent kinetic energy and dissipation. Mass and momentum exchange between the two layers is determined by particle settling, turbulent diffusion against the concentration gradient and aerodynamic shear forces. The net erosion or deposition rate is a function of the kinetic energy of the impacting particles. The saltation layer reacts on the suspension layer in that saltating particles extract momentum from the air flow. The preliminary estimates of the model parameters can be refined by means of saltation-trajectory simulations. Three-dimensional simulations with a simplified model have clearly shown the importance of snow erosion and deposition in practical applications. This approach is well suited for coupling to a dense-flow avalanche model.

Rheology of Semi-Solid Steel Alloys at Temperatures up to 1500°C

2006 ◽  
Vol 116-117 ◽  
pp. 606-609 ◽  
Author(s):  
Michael Modigell ◽  
Lars Pape ◽  
Horst R. Maier
Keyword(s):  
Flow Behavior ◽  
Measuring System ◽  
Model Parameters ◽  
Flow Properties ◽  
Steel Alloys ◽  
Ceramic Components ◽  
Dependent Flow ◽  
Couette Rheometer ◽  
Semi Solid ◽  
Solid Alloys

The investigation of the flow behavior of semi-solid steel alloys poses a great challenge by reason of high operation temperatures and the need of ceramic components for the measuring system. A high-temperature Couette rheometer has been developed to analyze flow properties of semi-solid alloys up to temperatures of 1500°C. In the present work the alloy under investigation is X210CrW12. Differently performed experiments clearly show its shear-thinning and time-dependent flow properties with a yield stress. This flow behavior is modeled using a Herschel-Bulkley approach where the experimental results achieved serve to identify model parameters.

scholarly journals Adaptive Machining Scheme for Multi-Hole Part with Multi-Position Accuracy Requirements

2021 ◽  
Author(s):  
Zhen Sun ◽  
Pingfa Feng ◽  
Long Zeng ◽  
Shaoqiu Zhang ◽  
Xi Cheng
Keyword(s):  
Position Error ◽  
Experimental Results ◽  
Correction Model ◽  
Topological Relationship ◽  
Position Accuracy ◽  
Compensation Process ◽  
Adaptive Machining ◽  
Hole Position ◽  
Position Correction ◽  
Relationship Of

Abstract The machining of multi-hole parts often has complex correlated position accuracy requirements. When some position accuracies do not meet the requirements, several hole axes need to be adjusted. Previous methods usually correct all deviated axes to their theoretical locations. However, the correction workload is too large and inefficient. This paper proposes an efficient and adaptive hole position correction model for multi-hole part. First, the method establishes the topological relationship of the holes and faces on the part according to the position accuracy requirements of the multi-hole part. Then, the goal is to minimize the number of holes that need to be corrected. In this model, the parallelism of holes, perpendicularity, and other constraints are considered. The simulation and experimental results show that the use of this model can effectively reduce the number of holes that need to be corrected during the compensation of the position error between holes. It improves the efficiency in the subsequent compensation process significantly.

scholarly journals Modelling of snow entrainment and deposition in powder-snow avalanches

1998 ◽  
Vol 26 ◽  
pp. 253-258 ◽  
Author(s):  
Dieter Issler
Keyword(s):  
Kinetic Energy ◽  
Three Dimensional ◽  
Momentum Balance ◽  
Model Parameters ◽  
Momentum Exchange ◽  
Erosion And Deposition ◽  
Practical Applications ◽  
Suspension Layer ◽  
Dense Flow ◽  
Avalanche Formation

Following Norem’s description of powder-snow avalanche formation and structure, we propose a mathematical model that consists of a suspension layer and a so-called saltation layer. The latter is only a few meters deep and is modelled by depth-averaged mass and momentum balances. In the suspension layer, the mass and momentum balance equations for the mixture are supplemented by the snow mass balance and the transport equations for turbulent kinetic energy and dissipation. Mass and momentum exchange between the two layers is determined by particle settling, turbulent diffusion against the concentration gradient and aerodynamic shear forces. The net erosion or deposition rate is a function of the kinetic energy of the impacting particles. The saltation layer reacts on the suspension layer in that saltating particles extract momentum from the air flow. The preliminary estimates of the model parameters can be refined by means of saltation-trajectory simulations. Three-dimensional simulations with a simplified model have clearly shown the importance of snow erosion and deposition in practical applications. This approach is well suited for coupling to a dense-flow avalanche model.

The Research of the PCB Location Based on Three Layers of MARK Point

2011 ◽  
Vol 317-319 ◽  
pp. 869-876 ◽  
Author(s):  
Hao Wu ◽  
Xian Min Zhang ◽  
Yong Cong Kuang
Keyword(s):  
Position Error ◽  
Field Of View ◽  
Uneven Surface ◽  
Position Accuracy ◽  
Loading Process ◽  
Optical Inspection ◽  
Automated Optical Inspection

In order to reduce the position error produced by single board assembly and partial uneven surface in automated optical inspection, a new position method based on three layers of MARK point is developed. the first layer is the whole board alignment which compensate the position error of the PCB loading process, the second layer is the single board alignment which compensate the position error of the single board assembly, the last layer is the partial FOV(field of view) alignment which compensate the position error of the partial uneven surface. The experiment result proved the proposed position method improved the position accuracy obviously.

scholarly journals Biology-Inspired Robust Dive Plane Control of Non-Linear AUV Using Pectoral-Like Fins

2010 ◽  
Vol 7 (2) ◽  
pp. 153-168
Author(s):  
Subramanian Ramasamy ◽  
Sahjendra N. Singh
Keyword(s):  
Control System ◽  
Internal Model ◽  
Autonomous Underwater Vehicle ◽  
Linear Time ◽  
Autonomous Underwater Vehicles ◽  
Tracking Error ◽  
Control Variable ◽  
Model Parameters ◽  
Marine Animals ◽  
Non Linear

The development of a control system for the dive plane control of non-linear biorobotic autonomous underwater vehicles, equipped with pectoral-like fins, is the subject of this paper. Marine animals use pectoral fins for swimming smoothly. The fins are assumed to be oscillating with a combined pitch and heave motion and therefore produce unsteady control forces. The objective is to control the depth of the vehicle. The mean angle of pitch motion of the fin is used as a control variable. A computational-fluid-dynamics-based parameterisation of the fin forces is used for control system design. A robust servo regulator for the control of the depth of the vehicle, based on the non-linear internal model principle, is derived. For the control law derivation, an exosystem of third order is introduced, and the non-linear time-varying biorobotic autonomous underwater vehicle model, including the fin forces, is represented as a non-linear autonomous system in an extended state space. The control system includes the internal model of ak-fold exosystem, wherekis a positive integer chosen by the designer. It is shown that in the closed-loop system, all the harmonic components of order up tokof the tracking error are suppressed. Simulation results are presented which show that the servo regulator accomplishes accurate depth control despite uncertainties in the model parameters.

A new approch for measuring ocean vertical velocities

2021 ◽  
Author(s):  
Jean-Luc Fuda ◽  
Stéphanie Barrillon ◽  
Andrea Doglioli ◽  
Anne Petrenko ◽  
Gerald Gregori ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Pressure Sensor ◽  
Sea Water ◽  
Fast Response ◽  
Hydrodynamic Drag ◽  
Model Parameters ◽  
Dead Weight ◽  
Velocity Signal ◽  
Vertical Speed ◽  
Flight Model

&lt;p&gt;Compared to horizontal components, the vertical components of ocean currents are generally very weak (a few mm/s) in all oceanic regions of the world. Due to their major role in the vertical distribution of physical and biogeochemical properties of sea water, their extended knowledge is of utmost importance for oceanographers. However, their in-situ measurement represents a real technical challenge, even using sophisticated instruments such as ADCPs.&lt;/p&gt;&lt;p&gt;&lt;span&gt;As a complement to the ADCP method presented in another session (Comby et al.), we have developed an original alternative instrument, called the VVP (Vertical Velocity Profiler). It was inspired by several published works which exploit the difference between the real vertical speed &lt;/span&gt;&lt;span&gt;&lt;em&gt;Wr&lt;/em&gt;&lt;/span&gt;&lt;span&gt; of a submarine glider (&lt;/span&gt;&lt;span&gt;&lt;em&gt;~dP/dt&lt;/em&gt;&lt;/span&gt;&lt;span&gt;, from the onboard pressure sensor) and its theoretical vertical speed &lt;/span&gt;&lt;span&gt;&lt;em&gt;Wth&lt;/em&gt;&lt;/span&gt;&lt;span&gt; extracted from a flight model. The oceanic vertical speed &lt;/span&gt;&lt;span&gt;&lt;em&gt;Woc&lt;/em&gt;&lt;/span&gt;&lt;span&gt; is thus expressed by the simple difference &lt;/span&gt;&lt;span&gt;&lt;em&gt;Woc = Wr - Wth&lt;/em&gt;&lt;/span&gt;&lt;span&gt; at any&amp;#160; point in the water column.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The very first prototype of the VVP consisted of a float and a friction disc, ballasted to sink at a very low speed (~ 0.1 m / s) and dragged down to the desired depth by a dead-weight which was automatically released after a suitable delay. The release system was developped in-house (patent filled in March 2020), based on a textured insert trapped in a volume of ice melting at controlled speed.&lt;/span&gt; &lt;span&gt;Since then, the concept of the profiler has evolved considerably. The last design uses an electric thruster that drives the profiler down to a predefined setpoint depth. Once the depth is reached, the thruster is stopped and the profiler then rises slowly (~0.1 m/s) to the surface under the sole effect of its slightly positive buoyancy. The mechanical balance between buoyancy and hydrodynamic drag results in a constant vertical speed of ascent in water at rest. Any deviation from this constant speed is then interpreted as an oceanic&amp;#160; vertical velocity signal. This new design allows a very large number of consecutive profiles to be collected, the number of descent-ascent cycles and the setpoint depth being programmed and controlled using an ARDUINO microcontroller board. The selected Li-Io battery allows for several hours of continuous profiling.&amp;#160; When on surface, the profiler is currently located by a commercial GPS tracker integrated into the electronic case. The vertical velocity of the profiler is accurately measured at&amp;#160; high frequency (2Hz) thanks to the fast-response pressure sensor of the onboard RBR-CONCERTO autonomous CTD, which also measures the sea water density involved in&amp;#160; drag and buoyancy.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;Trials both in deep pool and in the field are scheduled in spring 2021 in order to refine the prototype design and to definitely set the flight model parameters. This development benefits from CNES (Centre National d'Etudes Spatiales) financial support in the framework of the BIOSWOT international program.&lt;/p&gt;

ACOUSTIC TRACKING OF AUTONOMOUS UNDERWATER VEHICLES BY A SET-MEMBERSHIP APPROACH

2002 ◽  
Vol 35 (1) ◽  
pp. 277-282
Author(s):  
A. Caiti ◽  
A. Garulli ◽  
F. Livide ◽  
D. Prattichizzo
Keyword(s):  
Autonomous Underwater Vehicles ◽  
Underwater Vehicles ◽  
Acoustic Tracking ◽  
Set Membership
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