This section describes the progress with the practical experimentation of the devices on one of the Scenarios.

BP Use Case: "Smart Drums"

• in-situ monitoring of a storage limit
• in-situ monitoring if incompatible chemicals, i.e. reactive chemicals, are stored together

The enabling technology in this scenario is the DigiClip platform. The DigiClip devices are attached to the drum replacements, here beverage cans, and run the previously enumerated processes. Thereby, they act collaboratively when they are in the proximity of each other and without the support of a backend system.
Within the use case, we seek to get an insight in the following technical questions:

• How is the proximity information between the drum replacements derived?
• How consistently are the different storage states monitored on each DigiClip device?

The DigiClip device decomposed

The DigiClip Platform

The DigiClip is a self-contained communication, sensing, and computation platform based on TecO's Smart-Its Particle devices.
The DigiClip device consists of

1. a single AAA battery
2. a Smart-Its Particle providing the communication interface and processing power
3. LEDs as visual indicators for presenting internal states of the processes on the item
4. a mainboard equipped with various sensors for acceleration, light, and temperature
5. plastic housing for protection against damages

The DigiClip Device on the drum replacement

Technical requirements

The use case bases on the local relation of the drums. Consequently, it heavily relies on the detection of nearby DigiClip devices. This information is gained by the field strength regulation of the wireless communication interface of the DigiClip devices. Although it gives only a rough measure, it enables the possibility to regulate the proximity of the devices to each other. The regulation enables the communication of the DigiClip devices only if they are in certain proximity. We consider the information, which is exchanged in such a situation, as proximity information. As a result, the ability to collaborate depends on the ability to exchange proximity information. Based on the Smart-Its Particle technology the DigiClip provides a bi-directional broadcast communication allowing a fast exchange of the proximity information.

In the use case the monitoring processes will result in a decision making process where the proximity information is interpreted and a conclusion is drawn. This requires the ability of local computation. The DigiClip devices bases on the Smart-Its Particle technology and therefore integrate an appropriate microcontroller for this task.

The result of the decision making process is communicated via the wireless communication interface. Although this is a feasible solution, the device integrates further local actuators like LEDs and a speaker for visual respective acoustic indication. This in-situ indication of the monitoring process and the notification of critical states support the monitoring process because it tightly couples the situation with conclusion drawn from it.

Trials and results

In the following the implementation and functionality of the collaborative monitoring processes are outlined. The processes are hard-coded in a program running on each DigiClip device.

In-Situ monitoring of storage limit

This scenario is concerned about the detection of the exceeding of a pre-defined storage limit. DigiClip devices mounted on the drum replacements communicate to each other and exchange the current amount of the chemical substance in the drum. Each of them then sums up the amount of all others received and derives whether the limit is exceeded or not. Important to note is, that the alert decision is made by each device itself.

In the trial, the limit was set on two drum replacements. As long as there are less than three drum replacements detected by the DigiClip devices, the device report the status "green" indicated by a green LED on the device. Whenever there were more than two drum replacements detected, an alert in form of a visual indication, here a red LED, and in form of an acoustic signal was raised by the DigiClip device. The following figures illustrate the process.

There are less than three drum replacements. Status "green"

DigiClips detected collaboratively more than two drum replacements. The storage limit is exceeded. Status "red"

In-Situ monitoring of compatible chemicals

In this scenario, the kind of the chemical in the drum is used to derive an alert condition. Each DigiClip device announces its identification (ID) of the chemical, which is represented through the drum. As long as the DigiClip device receives no announcements or the announcements of the same ID, it holds the status "green". In this trial, an alert is raised as soon a DigiClip device detects the presence of another one with a different ID than the one it announces. Again, the decision to raise an alert is made locally on the device.

The drum replacement is isolated. Status "green"

DigiClips detected two drum replacements representing different chemicals (note red mark on drum replacement) Those are incompatible. Status "red"

Results

The implemented use case illustrates the scenario very well. Critical situations were recognized very fast and reliable.

As we found out, consistency of the drawn conclusion depends on mainly two factors: the reliable exchange of proximity information between the DigiClip devices and the responsiveness of each device according to the situation currently monitored.

As previously stated, the proximity information enables the collaboration. However, if the communication is disturbed, then single devices may not be able to collaborate anymore. The field strength regulation and the mounting of the devices affect that behaviour strongly. The field strength might be regulated down to certain degree in order to limit the proximity information on a very small range, but then not all devices participating in the collaboration may be reachable anymore. Similar to that, the mounting of the DigiClip device on the drum replacement affects the communication of proximity information. In the real scenario, the drums are made of metal inhibiting the communication. In the use case, the replacements were also made of metal partially shielding the communication. In those situations, the not all devices concluded the same situation because the proximity information was partially lost.

This required reliability relates to the responsiveness of the devices. The responsiveness refers to the recognition speed of a state. This includes the speed to indicate the red state if it occurs as well as the green state if the red state is resolved. In a case where we demanded a fast response, the temporary lost of proximity information affects the consistency badly. The alert state fluctuated and the devices could not agree on a common state. A lower responsiveness rate on the other side affected the consistency positively. However, this situation resulted often in confusion since the devices indicated the wrong state for a relatively long period although the reason was already resolved.

Dissemination

The BP use case was demonstrated at various events for disseminaton. Please refer to the page Talks and Demos to get an overview.

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