Mixed signal approach for rapid prototyping of a compact smart pebble for sediment transport monitoring in river beds

Low-cost accelerometers and gyro ICs were used to develop a smart sediment particle to study the sediment transport in rivers. With strap-down MEMS, battery, a processing subsystem and memory, this self contained unit captures semiprocessed data for durations up to 15 minutes. In a mixed-mode design, analog multiplier ICs with limited digital circuits transform the body frame data to a reference frame using Euler angles, with adequate accuracy despite cumulative errors. For 3D motion, up to nine sensor inputs from three orthogonal modules are coupled to a multiplexed analog processing module, and processed by a digital module for data conversion and storage. Despite the simplified mathematics used, experimental data from the proof-of-concept system provided adequate accuracy. Subsequent processing of the raw sensor data using an external PC program with smart algorithms allowed the comparison of accuracy of the mixed mode approach. The adopted mixed signal design approach helps the packaging requirements due to the specific nature of the problem with short recording durations

Implementation aspects and offline digital signal processing of a smart pebble for river bed sediment transport monitoring

Conceptualization aspects of a smart sediment particle (smart pebble) for monitoring of sediment transport in riverbeds have been documented previously [1]. However, this mixed signal approach was done only at a conceptual level and lacks complete implementation aspects such as limited PCB real estate, a miniaturized power source and adequately addressing the offset errors. A fully digital version with multiple strap-down MEMs, signal conditioning blocks, an 8-bit processor and a memory subsystem was designed and assembled within a less than 4 cm diameter sphere to allow data capture for up to 15 minutes. This compact subsystem allows exporting of output data, stored within the memory from nine sampled MEM sensors, into an offline-processing environment for further processing to generate essential motion information. Complex mathematical algorithms for axis conversion, etc, are housed within the offline-processing environment reducing the burden on the smart pebble. The total electronic subsystem embedded within the pebble together with the external processing algorithms tackle cumulative errors, gravitational compensation requirements and offset errors, while being powered by a specially designed power stage, based on a single alkaline cell

Testing and calibration of smart pebble for river bed sediment transport monitoring

The Smart Pebble (smart particle), SP, has been developed for the past two years to monitor sediment transport in riverbeds. The implementation is based on use of small size and low cost acceleration and angular motion sensors. In this stage, the project is focused on calibrating and testing the final version of the SP as well as its packaging in a 4-cm diameter spherical package. The calibration was done in two stages; individual sensor calibration and complete system calibration. The complete SP unit was tested under linear motions generated by a shake table, and 2D rotational motions using two manually controlled servomotors. Offline digital signal conditioning was done in MATLAB. The preliminary results show that the system has relatively large amplitude error due to low sampling frequency. Experiments conducted by sampling a 1-Hz sinusoidal signal at different rates show that to keep the amplitude error of the system under 5% the sampling rate has to be at least 10 times the maximum bandwidth of the signals acquired from sensors

Sustainability of the Western Rock Lobster Fishery: A review of past progress and future challenges

The Western Rock (spiny) Lobster Fishery has 594 boats operating about 57,000 pots. The average annual catch of 11,000 tonnes is valued at around US$150 million. In addition to the commercial catch, recreational fishers take about 600 tonnes a year. Sustainability in this fishery is maintained by analysis of a comprehensive fisheries database, some of which dates back to the 1960s (e.g. catch, effort, length-frequencies, fishery-independent breeding-stock surveys, puerulus settlement monitoring, recreational catch monitoring); an extensive set of management controls (including a limited fishing season and legal minimum and maximum sizes); and an effective compliance program. Effort in the fishery is controlled by input restrictions on the number of pots allowed and number of days fishing, which are implemented after considerable consultation with industry. The principal method of ensuring the sustainability of the fishery is by monitoring the size of the breeding stock, using data from both a commercial at-sea monitoring program and an annual fishery-independent breeding-stock survey. When the breeding stock fell to low levels in the early 1990s, management initiatives succeeded in returning it to what are considered to be safe levels. Catches are currently high, but fishers have acquired sufficient scientific knowledge to understand that catches will fluctuate for environmental reasons and to take this into account in their fishing operations. Environmental effects have been shown to drive the level of settlement in a particular season. These settlement levels are in turn highly correlated with catches three to four years later, which provides a means of predicting future catches and managing the fishery accordingly. There are issues to be considered in assessing the sustainability of this fishery in the future. The fishery may be overly reliant on egg production from the Abrolhos Islands; catching power of the commercial fleet is increasing due to improvements in gear and technological equipment; growth in catches made by the recreational sector are currently unconstrained; pueruli may be harvested for aquaculture in the near future; and regulations protecting the female brood stock more than the male population could lead to reproductive issues. These potential threats are considered to be low, but will need to be monitored. The fishery was awarded Marine Stewardship Council certification in March 2000, the first in the world to receive this imprimatur

Topography Changes during Bedform Development

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Low-cost autonomous 3-D monitoring systems for hydraulic engineering environments and applications with limited accuracy requirements

The details of developing autonomous 3-D motion monitoring systems based on commercial off-the-shelf (COTS) motion sensors for hydraulic environments are discussed. Possible areas of application, are river bed sediment transport monitoring and monitoring the agitation and other physical parameters inside milk vats with a mechanized agitator. Simplified calculations of inertial navigation systems (INSs) such as Euler angle method, MATLAB programs for further processing, power management systems for autonomous operation including the possibility of inductive power transfer (IPT) and use of microelectromechanical systems (MEMS) technology are discussed. Experimental results for proof of concept systems are highlighted