Distributed Experiment Control

Name

Distributed Experiment Control

Context

The pattern applies to a system with the following characteristics:

• An experiment plan exists that lists the predetermined actions to be performed while running the experiment.

• A remote experiment controller exists that executes the predetermined actions to be performed while running the experiment.

• Actuators may exist to allow for moving or controlling something before, during and/or after running the experiment.

• Sensors may exist to allow for measuring something before, during and/or after running the experiment.

• Instruments may exist that contain sensors and potentially actuators.

• Robots may exist that contain actuators and potentially sensors and that execute predetermined actions from the experiment plan in an automated or autonomous fashion.

• A component may exist that post-processes raw experiment data, such as to identify features.

Problem

Certain predetermined actions need to be performed while running an experiment. A remote experiment controller executes an experiment, incurring a potentially significant communication delay.

Forces

Only pre-experiment conditions are considered in performing the predetermined actions while running an experiment. Only safety-related conditions during the experiment may be considered. Other changing conditions during the experiment or post-experiment conditions are not considered.

Experiment actions are controlled with significant communication delay to remote components. Proper control capability does not need to be local, but must be able to act in time.

Solution

The is pattern implements the Experiment Control strategic pattern. A remote experiment controller executes an experiment using a predetermined experiment plan (Fig. 13). The plan’s execution is automated, performed in an open loop control and may involve human interaction. The controller may monitor the experiment for safety reasons. The plan contains a complete description of the predetermined actions to be performed for running the experiment, including any safety-related responses. Raw experiment data may be post-processed by an optional component, such as to identify features.

Fig. 13 Distributed Experiment Control architectural pattern components and control/data flow

As the experiment controller is remote, component-local storage and explicit data transfer between components may be used for sensor and controller data. Control messages between these components orchestrate the control flow.

This pattern offers an open loop control with safety-related feedback on the experiment only. Experiment plan execution is automated, i.e., its list of actions is performed without external or human intervention that can unnecessarily hold up execution. Only 1 experiment is being controlled. There is a significant communication delay to remote components in the open loop control, as the experiment controller is remote.

Resulting Context

An experiment is executed automatically using a predetermined plan executed by a remote experiment controller, i.e., with significant communication delay to remote components.

Related Patterns

This architectural pattern implements the Experiment Control strategic pattern.

In contrast to this architectural pattern, the Local Experiment Control architectural pattern executes a predetermined plan using a local experiment controller, i.e., without significant communication delay to remote components.

Examples

A robot-controlled chemistry laboratory science use case can implement the Distributed Experiment Control strategic pattern, as a robot automates experiment execution. There is only safety-related feedback, such as to stop the robot in case of an emergency. The experiment controller, a scientist’s laptop, is remote and connected to the robot-controlled chemistry laboratory over the Internet. The individual pattern components are as follows:

• The experiment plan is the sequence of predetermined steps and associated parameters necessary to run the experiment. The predetermined steps include the parameters for synthesizing the chemical compound, route navigation instructions for the robot to move the sample between the different synthesis and characterization stations, parameters for characterizing the synthesized chemical compound, and safety related feedback instructions.

• The remote experiment controller is a scientist’s laptop that is able to command and control the robot, synthesis equipment, analytical instruments, and any data and computing resources for analyzing the measurement data.

• The test performed in an experiment characterizes the synthesized chemical compound.

• The experiment result is a combination of the sample characterization results.

Known Uses

This strategic pattern is used in every experiment, where the predetermined experiment plan is automatically executed by a remote controller. This is a rather rare use case, as the communication latency between a remote controller and the test is often too long. The only feedback is related to safety, such as to perform an emergency stop of the experiment when a chemistry laboratory is on fire. This pattern is the starting point for other patterns, as any feedback implemented by the Distributed Experiment Steering or Distributed Design of Experiments patterns and any orchestration of multiple experiments by the Local Multi-Experiment Workflow and Distributed Multi-Experiment Workflow patterns require the automatic execution of a predetermined experiment plan.