Overview

Networked Infomechanical Systems (NIMS) actuated sensing applications have appeared immediately in terrestrial and aquatic, and Contaminant Observation and Management applications. As are described in these reports, breakthroughs in the previous year have appeared in applications ranging from the characterization of the thermal properties of alpine plants to the distribution of contaminants in a major river.

The combined rapid progress in applications combined with progress in NIMS system research has lead to the development of rapidly deployable NIMS systems, referred to as NIMS RD. This represents a new approach, guided by application demands, where investigations are directed to locations at narrowly specified times in order to capture measurements critical to understanding phenomena. Examples include terrestrial applications where a combination of terrain and climate conditions yielded an ideal location for detailed mapping of alpine plant thermal response. Another example appeared in Aquatic, and Contaminant Observation and Management research where conditions of regulated river flow created a requirement for NIMS system deployment at a specific location and time at the San Joaquin river. The combination of these needs motivated the development of the NIMS RD system.

The new requirements for multiscale actuation and NIMS characterization of complex volumes have lead to the need for devices that may operate in a large volume, not constrained to the two dimensional plane for the above NIMS RD systems. For these applications, another NIMS rapidly deployable architecture was developed that permits the NIMS node systems to be actuated and controlled in location within a large volume. This new system, NIMS 3D is also described here.

Approach

The NIMS RD architecture is an advance over previous systems. NIMS RD retains the infrastructure and mass support cableway of previous NIMS systems. This provides low energy and position-accurate transport. However, NIMS RD adds additional lightweight cable systems that provide actuation of the sensor payload. Further, NIMS RD systems relocate the electromechanical motor systems from their location within a single node, to now separate elements consisting of mobile node and actuation modules. The autonomous mobility characteristics of NIMS developed previously is fully retained. However, the new architecture, shown in Figure 1, reduces mass, increases motion speed, and offers deployment flexibility.

NIMS RD components include first an embedded node supported at the infrastructure supports show in Figure 1. This node includes required control for motor actuators that drive the NIMS cableway. Nodes also are supported on the cableway and provide interfaces to sensors. Both node systems may host algorithms for sensing and control. These further include capabilities for adaptive sampling and in situ calibration.

The NIMS RD system also includes cable systems that provide both mass support as well as position control. By partitioning the requirements for support and motion into separate cables, only one high tension, static cable is required, even for the support of large sensor systems. All other cable systems are lightweight. Power demand is therefore also small since only the work required to accelerate the node system is required for horizontal transport.

NIMS RD systems also include self-calibration methods. This includes methods that enable the node system to move between points, detect a surface, and then adjust model parameters associated with cable motion (that in this unique example where cable mass is less than suspended node mass, follows a shallow elliptical trajectory).

NIMS RD systems also include sensor calibration methods. For example, in the characterization of stream systems, important contaminant concentration measurements are or primary importance. Many of these important sensor systems display drift in their response, distorting results. As will be described below, NIMS RD systems now permit in situ calibration of the sensing system such that according to a deterministic or adaptive schedule, sensors may be removed from the medium of interest and placed in a reference medium for a calibration period. For the example below, a nitrate concentration sensor is exposed to two reference media in an autonomous and continuous cycle of operation.

NIMS RD systems operate in an unattended state in the examples below where these devices were deployed and then allowed to operate in the field without support or presence of investigators. In some cases, this occurred in remote locations.

 

Systems/Experiments

 

Accomplishments

NIMS RD has been developed and applied for a range of applications to be described below. Each of these has stimulated both fundamental research in multiscale actuated sensing as well as advancing our primary application goals. These include terrestrial, aquatic, and contaminant observation and management application examples.

A NIMS RD system was developed and successfully applied to the problem of terrestrial ecosystem research with an investigation of the thermal properties of alpine plants. This experiment required autonomous experimental systems that may combine both fixed and actuated sensing to characterize the thermal properties of plants exposed to an extreme gradient between high soil temperatures and low air temperature. Alpine plant forms have adapted to such conditions in an unknown fashion. The sustained growth of these plants is critical for global climate concerns since they represent the primary plant form at high elevations in many soil conditions.

As shown in Figure 2, a NIMS RD system was deployed at the White Mountains Research Station. The NIMS RD system was deployed quickly and was mobile between sites.

Figure 2. The NIMS RD system deployed at the White Mountains Research Station is shown at left. Here, the NIMS RD sensor node, indicated by the error in the figure, contains an imager, infrared thermometer, and laser rangefinder depth sensor. The right panel shows the time variation of temperature for each point along a transect line over a 24 hour period.

NIMS RD was also deployed in important investigations in Contaminant Observation and Management, as described in this corresponding section. Here, NIMS RD systems were deployed at Medea Creek, an urban stream in the Los Angeles area for the investigation of harmful algal blooms, and at the San Joaquin River in Central California near Merced. An example of a NIMS RD deployment at the San Joaquin River is shown in Figures 3 and 4. Note that in this example, the NIMS RD system is adaptable to a 5m to 65m span using the same structure for these two applications, respectively.

Figure 3. The NIMS RD system is shown in schematic view for river monitoring applications. The supporting structures and sensor node are shown with the sensor node shown as immersed.

Figure 4. The NIMS RD system shown deployed across a 65m span at the San Joaquin River near Merced, California. The NIMS cableway and the NIMS node are visible with the node at mid-river at the time this image was acquired.

A continuing challenge in Contaminant Observation and Management is the verification of properly calibrated operation of sensor systems. Here, the direct contact between sensor systems and media under investigation produces sensor system degradation. In addition, the many interfering signal sources associated with variability in temperature and the presence of many compounds in the sensed media also produce sensing error. A method that may calibrate sensors in situ is required. This requires that sensors be exposed properly to reference media. Figure 5 shows this system in operation. This calibration method exposed sensor devices to two reference solutions in addition to the Medea Creek stream flow.

Figure 5. NIMS RD autonomous in situ calibration is shown. Here, a nitrate sensor systems shown in the vertical (green) cylinder is alternately immersed in two reference solutions as well as into the stream shown.

 

Finally, a new NIMS system was also developed providing an extension of NIMS RD to operation with three-dimensional motion, shown in Figure 6. Here, three support structures maintain three cableway systems, each independently actuated. An embedded node system manages these cableway actuation combining motor systems and precise cable position measurement systems. A node system is suspended by the cableways and, therefore, may be positioned at any location in an accessible volume limited only by geometrical considerations and tension limitations. NIMS 3D is in use now for multiscale actuation measurements of solar radiation distribution in terrestrial ecosystems. NIMS 3D will also be combined with the new NIMS thermal mapping experimental investigations discussed above.

Figure 6. The NIMS 3D system shown in schematic view at left. This includes the support structures (1) along with actuation systems for controlling node (2) position in a three dimensional volume (3). A NIMS 3D system operating in a solar illumination mapping experiment is shown at right. Note that all embedded computing systems are contained in one module, indicated as (3) at left.

Future Directions

NIMS RD systems will be widely applied for multiscale actuation. These will also be combined with static sensor nodes and with the mobile robotic boat systems in aquatic studies. NIMS RD systems also will replace previous NIMS architectures for some permanently deployed systems in terrestrial ecosystem studies. Near term applications include lake monitoring, river monitoring, thermal mapping of plant structures and a new laser measurement system method for topographic mapping of three dimensional structures.

People

CENS Students: Henrik Borgstrom, Diane Budzik , Victor Chen, Willie Chen, A. Kansal, Richard Pon, Amarjeet Singh, Michael Stealey.

CENS Staff Members: Dr. Maxim Batalin, Dr. Eric Graham

CENS Faculty: Professor Deborah Estrin, Professor Mark Hansen, Professor William Kaiser, Professor Greg Pottie, Professor Phil Rundel, Professor Gaurav Sukhatme