Wednesday, October 22, 2014

Visualization of Torque Log Analyzer data with ParaView

Google Sheet charts are handy but limited in scope: there is no easy way to produce a 3D chart.
3D charts can help discover relationships with multiple variables.
We'll use ParaView, an open-source, multi-platform data analysis and visualization application.

As an example we can use the Hybrid System Indicator:

The power meter is indeed related to the accelerator pedal but, as the experience suggests, its behavior seems to be affected by the SOC level also.

We'll use with a trip of 43Km with a SOC excursion from 38 to 63.
The analysis will be limited to the 0-100 HSI range, we'll exclude the regenerative braking range.

First, here are the values, as a function of the accelerator pedal:

Values seems to be limited by a minimum and a maximum straight lines.
Some values are outside this area: they may be transition values, when the accelerator was just pressed and the HSI indicator was still settling on the target value.

We can try to filter out those values by considering only HSI values associated to accelerator pedal values that are constant for at least 2 seconds.

The resulting chart is cleaner.

To add SOC values to the chart, we must switch to 3D with ParaView.

Export the Data sheet of Torque Log Analyzer in CSV format.
Note: you can't use the Torque log file directly, as the missing values will cause the data to be marked as text instead of numbers.
Torque Log Analyzer corrects those values when running an analysis, so just export a processed log file, not a raw one.

Open the CSV file in ParaView.
Add a Table To Points filter and select which column to use as X and Y (the same from the 2D chart) and Z (SOC, that wasn't used before)
X: Accel Pedal Pos

Adjust scaling and set Coloring at Batt Pack Current Val

Here's the chart:

Points color is related to battery current: charging current in blue, discharging in red.
Most of the blue points are in the upper part of the chart, where the accelerator pressure is higher.
There are really few red points (electric contribution to the car movement), but we must remember that these point represents constant accelerator values, not spikes where the electric engine is more likely to set in.

A little animation gives a better view of the data.

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