TinyOS 2.0 Support for Crossbow's IRIS Mote Platform

Earlier this month, Crossbow announced the availability of the TinyOS 2.0 Operating System for Crossbow's advanced IRIS Motes. TinyOS 2.0 is the latest major release of the popular open source embedded operating system. This release now enables developers to use the latest generation TinyOS software on the latest generation Sensor Network hardware. TinyOS is an open-source operating system designed for wireless embedded sensor networks. It features a component-based architecture which enables rapid innovation and implementation while minimizing code size as required by the severe memory constraints inherent in sensor networks. The TinyOS component library includes network protocols, distributed services, sensor drivers, and data acquisition tools. The event-driven execution model enables fine-grained power management yet allows the scheduling flexibility made necessary by the unpredictable nature of wireless communication and physical world interfaces.

The IRIS Mote platform offers users excellent RF range (over 3x improved radio range of previous generation motes), substantially lower sleep current (50% of previous generations), and double the program memory (8KB). In conjunction with TinyOS 2.0, users now have a better hardware abstraction model, improved timers, sensor interfaces, power management, arbitration and much more. The IRIS Mote is a 2.4 GHz module used for enabling low-power wireless sensor networks and is also supported by Crossbow's MoteWorks software development environment based on open-source TinyOS.

The IRIS port was created by Vanderbilt University's Institute for Software Integrated Systems. Wireless sensor network developers and researchers benefit from Vanderbilt University’s well-established, recognized expertise in TinyOS development and continued support of released code. “We are pleased to have received Crossbow’s support for the advancement of the open source TinyOS 2.0 environment and continued development of leading edge wireless sensor network platforms,” said Professor Akos Ledeczi, Research Associate Professor and principal investigator on the project.

Crossbow is the leading provider of wireless sensor nodes, or motes, and continues to offer broad operating system choice. One or more Crossbow platforms are now supported on development environments including Contiki, Linux, LiteOS, Mantis, Microsoft .NET Micro Framework, MoteWorks, SOS, and TinyOS. “Crossbow’s ability to provide software choice enables rapid development of the newest and most innovative applications of wireless sensor networks,” said Robert Robinson, Vice President of Sales & Marketing for Crossbow’s wireless division.    

Instructions for download and use of Vanderbilt’s open-source code release of TinyOS 2.0 for IRIS are available here. Crossbow’s IRIS product line includes the IRIS OEM Module, IRIS Mote, and related sensor boards. Check out the IRIS platform and other Crossbow wireless sensor networking products here.

Swarm Navigation with TelosB Motes

The concept introduced below provides a highly effective swarm navigation scheme that is of low complexity, robust, and highly scalable. Rather than using a few highly complex and expensive swarm agents to complete a mission, the group at Easysen believe in the advantages of large ultra-low complexity swarms that solve problems reliably through emergent behavior.

EasySen is a start-up company who in conjunction with the University of Notre Dame’s Mobile Sensing Systems (MOSES) Lab, has developed an autonomous sensor swarm that uses TelosB nodes for navigation of swarm agents. The principle is based on Zigbee radio beacon induced potential fields and provides an ultra low cost and complexity solution to mobile sensing for land, sea, and air vehicles. Stereo TelosB receivers and stereo sensor suites (EasySen SBT80 / SBT30-EDU) allow for rather elaborate task execution.

The group at EasySen proposed the use of radio frequency beacons to generate (switched) potential fields for navigation of large numbers of swarm agents. The idea is to use attractive beacons as waypoints and local attractors. Repelling beacons on each agent and waypoint are used to control the density of agents and avoid collisions.  If a certain sequence of waypoints defines a navigation path, then the attractive beacons need to be distinguishable and need to be visited in a certain sequence. (This is easily implemented in form of a finite state machine in each sensor swarm agent.) Repelling beacons are local and do not need to be distinguishable.  Individual sensor swarm agents are equipped with a side-looking stereo receiver with opposite directions of highest sensitivity. A simple difference between the left and the right Receive Signal Strength Intensity (RSSI) allows the agent to detect in which half space (relative to the center length axis of the vehicle) a beacon is located. One can then navigate towards a beacon by always moving towards the receiver side that has produced the stronger RSSI reading. For repelling beacons, one always moves towards the direction of the smaller RSSI signal.

The applications of this paradigm are many and range from environmental clean-up such as oil spill removal to surveillance and protection tasks. A ground vehicle swarm that performs a simple detection task is shown in the video below:

The company also produces readily usable plug-in surveillance sensor suites for the TelosB wireless 802.15.4 platform:

• The Wi-Eye, an ultra-sensitive sensor board that is capable of detecting the IR signature of moving vehicles from as far as hundreds of feet away.
• The SBT80 is an 8-modality sensing platform, ideal for sensor fusion applications.

Both sensor suites (the Wi-Eye and the SBT80) are prime candidates for perimeter security, traffic monitoring, tracking, and occupancy detection tasks, just to name a few. In addition, EasySen also offers SBT30-EDU, a low-price educational prototyping board that interfaces to external signal sources.  Click here for more information on the TelosB Mote platform.

Wireless Soil Moisture Tension Measurements for Irrigation Management

Irrigation is defined as the artificial application of water to the soil usually for assisting in growing crops. In crop production it is mainly used in dry areas and in periods of rainfall shortfalls, but also to protect plants against frost. Irrigation management in agriculture and landscaping is of growing importance as the growing global population puts more demand on finite fresh water supplies. Managing irrigation optimally improves yields and quality while reducing water user and pumping energy costs. Optimal irrigation management requires reliable knowledge of plant water stress and soil moisture status. Many different devices and techniques have been used to gather this type of information, but perhaps none as successful as one of Crossbow's beta ēKo deployments in California's Napa Valley wine country.

Mark Holler is the owner of Camalie Vineyards in Napa, Califorina. He is a viticulturist and a technology enthusiast who has been working closely with Crossbow in the development and testing of the ēKo platform over the past two years to increase the quality and quantity of his grape harvest by using and controlling his water resources. With the data he collected from the ēko platform, Mark has been able to minimize his water use and maximize his yield despite the low water season we saw this past year in 2007. This achievement was not only due to the ēko system's ability to collect data, but Mark's ability to analyze the data and apply it to his growing techniques. Mark has written a white paper on High Density, Multiple Depth, Wireless Soil Moisture Tension Measurements for Irrigation Management. Below is an extract regarding his application and findings. To read the entire article click here:

When sampled sufficiently at appropriate depths soil moisture tensions were found to correlate well with pressure chamber measurements of midday leaf water potential in Cabernet Sauvignon grape wines. Sampling 2-3 sites per acre across a 4.4 acre hillside vineyard produced a substantial correlation of midday leaf water potentials to soil moisture tensions at 24" depth. The correlations were performed on soil moisture data and pressure chamber data from the 2007 irrigation season on the Mount Veeder hillside vineyard on the western slopes of Napa Valley. The data suggests that  soil moisture tension measurements may be able to replace many leaf water potential measurements which are significantly more labor intensive. A strategy for use of soil moisture tension measurements in manging regulated deficit irrigation of grape vines and the monitoring of other irrigation system parameters using the ēko Pro Series is described in this overview.

Correlations were done between leaf water potentials and soil moisture tensions acquired at 12" depth and 24" depth. Data from all locations and times were combined for these correlations. Sample size was 43 points per depth.The soil moisture data at 12” depth does not correlate with the leaf water potential measurements but, at 24” depth there is a “substantial” correlation.  This data suggests that deeper placements of the soil moisture sensors might produce better correlations with the leaf water potentials. 

From the data gathered one could also conclude that the vines were getting their water from deeper depths and that the vines have not concentrated their root growth around the sub surface dripper which is co-located with the soil moisture sensor at 12” depth. This information was useful in deciding not to move the subsurface drippers further from the vines or deeper to encourage root growth.This type of correlation could be used to optimize locations for soil moisture sensing. In an initial deployment many sensors could be placed at different depths at a few locations for the first season. At the end of the season correlations with leaf water potentials could be done and the root zone locations with best correlations determined. The following season more sites would be added with fewer soil moisture sensors per site only at the optimal location(s) in the root zone determined. 

The general success of the 2007 growing season at this vineyard in terms of yield, ripeness and reduced water use supports the use of the modified regulated deficit irrigation though indirectly because there are many confounding factors which affect yield. In 2006 data from the soil moisture sensors was used to optimize irrigation durations and intervals. Soil moisture sensors provide good insight into how water moves within the soil – hydraulic transport, something that leaf water potentials cannot provide. The delay between wetting at 12” depth and 24” depth is a measure of how long it takes water to move downward within the soil. From this the vertical hydraulic conductivity can be inferred. The slope of the drying transient indicates how fast water is moving away from the sensors either due to diffusion or plant uptake. 

Irrigation durations and intervals were optimized to achieve desired average soil moisture at 24” depth. This soil moisture target was based on leaf water potentials as described above. Total available water supply for the season was also considered. We adopted the premise that the vines benefit from reduced variability in soil moisture over time. The best uniformity over time would be achieved by very short durations at frequent intervals. Short durations and frequent intervals, however, do not allow the water to penetrate very far between irrigations. Short intervals also result in non-uniformities across each block because the line pressures are below spec for constant drip rate during start and stop transients. The total start up and shut down transient time for this irrigation system was determined to be about 30 minutes. We set the minimum irrigation duration to 2 hours to make the transient effects less than 25% of the irrigation duration. We then checked to see that the water was reaching the 24” deep sensors consistently with an interval equal to the time it took the 24” depth to dry out to the level before the last irrigation. The interval was then varied to bring the average soil moisture level at 24” depth to the target value. We then looked at the water consumption rate of our optimized duration/interval times and forecasted total use for the season.

If this use was in excess of our water resource we lengthened the interval to the consumption rate we could afford. We then monitored the new average soil moisture and spot checked leaf water potentials to determine if we could keep the vines from becoming over stressed. If the leaf water potentials continue to drop to –15 bar and beyond as was the case in the 2007 season we purchased additional water and trucked it to the vineyard. In 2007 in light of a very dry winter rainfall we delayed irrigation until a higher stress level was achieved to reduce canopy growth and subsequent water consumption by the vines. Our yield and fruit maturity results suggest that this was a good approach. We feel strongly that high water stress transients during the growing season can damage the vines not only in the short term but over several seasons as well.

Camalie used a prototype network during the 2005 and 2006 growing seasons to guide irrigation decisions in the 4.4 acres of Camalie Vineyards. Yield per vine in 2005 was double that of the 2004 yields for same age vines yet the water consumption was kept constant.  Typically water consumption goes up with canopy size which more than doubled for these 2.5 year old vines in 2005. The grape quality was excellent. Of course, some of this success was due to generally better than average weather in 2005 but, Mark and others at Camalie believe their visibility of the soil moisture played a significant role.  Extra drippers were added to some areas of the vineyard based on the soil moisture data.   Also irrigation intervals were shortened based on sensor data to reduce the amount of water that penetrated below the root zones where it would be wasted. In 2006, the third year for their vines, the yields again doubled from 4 tons to 8 tons. In the 4th year, 2007, the network was upgraded to the latest Crossbow technology, the yield again doubled to 16 tons of fruit that was sold and another 1.5 tons that the vineyard made into wine themselves. The yield was 3.97 tons per acre which is very rare on Mt. Veeder especially with water limited due to less than half the normal rainfall in the winter of 2006/07.  Water had to be purchased but thanks to their precision irrigation the vineyard minimized water purchasing and still had great yields.  Fruit quality was excellent as before.

For more insight into the methodology used at Camalie Vineyards, be sure to read the complete white paper here.

 

ēKo series wireless crop monitoring system unveiled

On Tuesday of this week, Crossbow announced the release of ēKo™ Pro Series, a turnkey live data, wireless crop monitoring system enabling precision agriculture. The ēKo Pro Series follows Crossbow’s already popular sensor and navigation solutions for heavy agricultural equipment. See the video below for additional details.

ēKo™ represents the next generation in crop monitoring and precision agriculture techniques, employing a mesh network of wireless sensors and providing vital live data about crop health, vigor and growth progress via a simple internet browser. Among others, the ēKo Pro Series monitoring solution features the following innovations:
• Solar-powered, field-deployed wireless sensor nodes, which require no electrical power so that sensors can be placed where needed.
• Simple-to-use, web-based data viewing that allows remote access to live sensor data, critical trend charts and alarm settings - all of which are highly customizable.
• Leading-edge, reliable wireless mesh network technology that is self-configuring and self-healing, thus providing effortless setup and easy scalability, where additional wireless nodes and sensors can be added easily by non-technical users.

ēKo Pro Series drives increased profits and competitive advantage by enabling lower input costs, mitigating crop loss risks, increasing per-acre yields, and delivering higher quality crops with greater consistency.

“ēKo Pro Series enables growers to consistently improve yield and quality regardless of the variability in the terrain, soil or micro-climates,” said Robert Robinson, VP of Sales and Marketing at Crossbow. “Growers can now overcome the traditional trade off between higher yields vs. higher quality and can achieve a higher average price on larger harvests consistently by executing precision agriculture techniques with ēKo Pro Series data."

ēKo eliminates concerns about reliability and complexity in applying wireless technology to deficit irrigation and precision agriculture by delivering a more integrated solution including all the sensors, software application, sensor nodes, and network components that growers need to quickly and easily deploy a wireless monitoring system.

“ēKo takes crop monitoring using wireless technology to whole new levels in terms of reliability,  flexibility, and ease,” said Alan Broad, Director of Environmental Products at Crossbow. “Its mesh based architecture with capabilities such as data re-routing, self-organizing/self-healing network, autodetection of new nodes delivers proven reliability, effortless deployment, and easy scalability. Moreover, the unique sensor interface provides the flexibility to add any sensor from third-party vendors in the future."

The ēKo Pro Series Starter Kit provides a quick, easy way to get started with wireless monitoring. It includes an ēKo Pro Series Network Gateway, 3 ēKo Pro Series wireless nodes, 6 soil moisture/ temperature sensors, 1 ambient temperature sensor, and built-in web-based monitoring application. Additional wireless nodes and sensors are simple to add. The new ēKo Pro Series will begin shipping in volume in April 2008. Pricing and advanced sales inquiries may be directed to sales@xbow.com. Crossbow previewed the ēKo Pro Series at the Unified Wine & Grape Symposium in Sacramento, California on January 29-31 this week. To learn more about the use of ēKo for wireless crop monitoring, visit www.xbow.com/eKo.