Mass Spring Damper

Overview

The mass spring damper digital twin (DT) has two mass spring dampers. It shows how to use a co-simulation based DT within the DTaaS.

Example Diagram

Mass Spring Damper System

Example Structure

The study includes two simulators, each representing a mass spring damper system. The first simulator calculates the displacement and speed of mass \(m_1\) for a given force \(F_k\) acting on \(m_1\). The second simulator calculates the force \(F_k\) from a given displacement and speed of mass \(m_1\). Coupling the two simulators computes how the positions of the two masses evolve.

Mass Spring Damper Structure

Digital Twin Configuration

This example uses two models and one tool:

Asset Type	Names of Assets	Visibility	Reuse in Other Examples
Models	MassSpringDamper1.fmu	Private	Yes
	MassSpringDamper2.fmu	Private	Yes
Tool	maestro-4.1.0-jar-with-dependencies.jar	Common	Yes

The DT is executed with two configuration files, cosim.json and time.json. Edit them to customise the DT.

Lifecycle Phases

Lifecycle Phase	Completed Tasks
Create	Installs Java Development Kit for Maestro tool
Execute	Produces and stores output in data/mass-spring-damper/output directory
Clean	Clears run logs and outputs

Run the example

To run the example, change to the example directory.

1	`cd /workspace/examples/digital_twins/mass-spring-damper`

If required, make the lifecycle scripts executable, for example:

1	`chmod +x lifecycle/create`

Then run the following scripts.

Create

Installs Open Java Development Kit 21 in the workspace.

1	`lifecycle/create`

Execute

Runs the digital twin. Because this is a co-simulation based digital twin, the Maestro co-simulation tool runs a co-simulation of the two FMU models.

1	`lifecycle/execute`

Examine the Results

The results are in the /workspace/examples/data/mass-spring-damper/output directory.

The run logs are in /workspace/examples/digital_twins/mass-spring-damper.

Terminate phase

Removes the debug files and co-simulation output files.

1	`lifecycle/terminate`

References

More information about co-simulation techniques and the mass spring damper case study is available in:

1 2	`Gomes, Cláudio, et al. "Co-simulation: State of the art." arXiv preprint arXiv:1702.00686 (2017).`

The source code for the models used in this DT is in the mass spring damper GitHub repository.