Logging Data

The purpose of SADYCOS simulations is to generate data that can be analyzed to understand the behavior of the system. This page describes how data can be logged during a simulation and how to access it.

Page Contents

• Logging in SADYCOS
• Add Data to Logging Signals
  • Add Data to Logging Output
  • Adjust Bus Definition

Logging in SADYCOS

Data logging in SADYCOS is done with Simulink’s logging functionality for signals which means that all data of a signal that was marked for logging will be made available as a timeseries object. When the simulation has finished, the property simulation_outputs of the configuration class instantiation will be a Simulink.SimulationOutput object that contains all corresponding timeseries objects.

SADYCOS does not log any of the signals that are used for data transfer between the subsystems. Instead, every subsystem has a dedicated output (e.g. LogEnvironment for the Environment subsystem) that is piped through Goto and From blocks to the top-level Periphery subsystem where they are marked for logging. This gives the user the ability to decide which data should be logged and to make the trade-off between memory usage and data availability.

Add Data to Logging Signals

Adding new data to the logging signals requires two steps:

1. Add the data to the subsystem’s logging output
2. Adjust the corresponding bus definition

Add Data to Logging Output

Each subsystem function has a dedicated output that is mapped to the corresponding block’s logging port. Adding data to it is done by assigning values to the structure’s fields.

E.g., the following code block shows an excerpt from the subsystem function gncAlgorithms of the configuration class DefaultConfiguration within the ExampleMission namespace.

LogGncAlgorithms.ActuatorsCommands = ActuatorsCommands;
LogGncAlgorithms.GncAlgorithmsStates = GncAlgorithmsStates;
LogGncAlgorithms.GncAlgorithmsStatesUpdateInput = GncAlgorithmsStatesUpdateInput;
LogGncAlgorithms.reference_frame_attitude_quaternion_RI = reference_frame_attitude_quaternion_RI;
LogGncAlgorithms.reference_angular_velocity_RI_B__rad_per_s = reference_angular_velocity_RI_B__rad_per_s;
LogGncAlgorithms.error_quaternion_RB = error_quaternion_RB;
LogGncAlgorithms.angular_velocity_error_RB_B = angular_velocity_error_RB_B;

In this example, the logging output contains the inputs to the subsystem function (GncAlgorithmsStates), outputs of the subsystem function (ActuatorsCommands, GncAlgorithmsStatesUpdateInput) and intermediate variables that were used during the computation and aid in debugging (reference_frame_attitude_quaternion_RI, reference_angular_velocity_RI_B__rad_per_s, error_quaternion_RB, angular_velocity_error_RB_B).

Adjust Bus Definition

As described in Buses Configuration, there must be a bus object containing the format definition for every Simulink bus signal. The log signals are no exception. After adding new data to the logging output, the new elements must be added to the corresponding bus object in the configuration class’ static method configureBuses.m. The section of the above example for the LogGncAlgorithms bus object in the configureBuses.m file would look like this:

%% LogGncAlgorithms

% Top-Level Bus

elems = [simpleBusElement('ActuatorsCommands', 1, 'Bus: ActuatorsCommands'), ...
            simpleBusElement('GncAlgorithmsStates', 1, 'Bus: GncAlgorithmsStates'), ...
            simpleBusElement('GncAlgorithmsStatesUpdateInput', 1, 'Bus: GncAlgorithmsStates'), ...
            simpleBusElement('reference_frame_attitude_quaternion_RI', 4, 'double'), ...
            simpleBusElement('reference_angular_velocity_RI_B__rad_per_s', 3, 'double'), ...
            simpleBusElement('error_quaternion_RB', 4, 'double'), ...
            simpleBusElement('angular_velocity_error_RB_B', 3, 'double')];

busesInfoCreator.setBusByElements('LogGncAlgorithms', elems);

First, an array of bus elements is created using the utility method simpleBusElement by providing the name, dimension, and data type of the element. Then, the bus object is created by calling the setBusByElements method of the busesInfoCreator object with the name of the bus object and the array of bus elements.