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BRUIN FORMULA RACING · CASE STUDY 02

Motor Torque Response & Operating Behaviour

Bruin Formula Racing — Inverter torque tracking and motor operating-region analysis

This study examines how accurately the inverter delivered requested motor torque and where the motor operated during the dynamic portion of the logged run. The analysis focuses on torque-command tracking, RPM usage, and the distribution of positive motor torque.

Measured results

Key metrics

Torque correlation
0.9999
Mean absolute torque error
0.17 Nm
Torque RMSE
0.32 Nm
Maximum delivered torque
95.5 Nm
Maximum motor speed
3,967 RPM

Project question

What was investigated?

The analysis was designed to answer two questions: how closely did delivered motor torque follow the inverter’s commanded value, and which RPM and torque regions were used most often during dynamic running?

Analysis workflow

Method

  1. Select the motor channels

    Use:

    • time_s
    • inv.rpm
    • inv.tq_cmd
    • inv.tq_fb

  2. Prepare the signals

    The selected channels were converted to numeric values, sorted by elapsed time, and checked for duplicate timestamps.

  3. Align the torque convention

    The torque-feedback signal used the opposite sign convention from the commanded-torque signal. Its sign was corrected after confirming that the inverted signal produced the stronger command–feedback correlation.

  4. Resample the data

    The data was resampled to 10 Hz so repeated held CAN values would not receive excessive weighting in the analysis.

  5. Isolate representative running

    The dynamic-running section began at approximately 65 seconds, after the initial steady operating period. This produced a 93.6-second segment for the operating-distribution analysis.

  6. Calculate the results

    Torque tracking was evaluated using correlation, mean absolute error, and root-mean-square error. RPM and delivered torque were then grouped into operating bands to calculate their time shares.

Scatter plot of commanded torque against delivered torque, with nearly all points following the perfect-tracking line.
Torque command–feedback accuracy after aligning the feedback sign convention; the dashed line represents perfect tracking.

Result 01 · Torque tracking

Delivered torque closely followed the command

The command–feedback relationship remained almost perfectly linear across the recorded torque range. Delivered torque followed commanded torque with a correlation of 0.9999, a mean absolute error of 0.17 Nm, and an RMSE of 0.32 Nm.

The points remain close to the perfect-tracking line from low torque through the approximately 95 Nm maximum-torque region.

Bar chart showing the percentage of dynamic-running time spent in each motor RPM range.
Dynamic-running time share across the recorded motor-speed bands.

Result 02 · RPM operating distribution

Most dynamic operation occurred between 1,500 and 3,000 RPM

During the 93.6-second dynamic-running segment, 81.3% of recorded operation occurred between 1,500 and 3,000 RPM. The most common individual range was 2,000–2,500 RPM, accounting for 37.7% of the segment.

Below 1,500 RPM
7.4%
1,500–2,000 RPM
19.3%
2,000–2,500 RPM
37.7%
2,500–3,000 RPM
24.3%
3,000–3,500 RPM
8.2%
Above 3,500 RPM
3.1%

Only 11.3% of dynamic operation occurred above 3,000 RPM.

Bar chart showing the percentage of positive-torque operation spent in each delivered torque range.
Positive-torque time share across delivered-torque bands during motoring.

Result 03 · Torque operating distribution

Positive torque demand was split between moderate and high-load operation

Positive-torque operation showed two prominent behaviours: moderate demand in the 20–40 Nm range and strong acceleration above 60 Nm. In total, 52.2% of positive-torque operation occurred between 60 and 100 Nm.

5–20 Nm
5.1%
20–40 Nm
26.4%
40–60 Nm
16.2%
60–80 Nm
25.8%
80–100 Nm
26.4%

The 80–100 Nm band accounted for 26.4% of positive-torque operation, showing repeated use of the approximately 95 Nm maximum-torque region.

What the results show

Engineering interpretation

Torque response

The inverter delivered the requested motor torque with extremely small tracking error across the measured range.

Operating speed

The motor spent most of the dynamic segment in the 2,000–3,000 RPM region rather than continuously operating near its recorded maximum speed.

Driver demand

The torque distribution suggests repeated switching between moderate demand and high-load acceleration, with relatively little operation in the 5–20 Nm range.

Summary

Key takeaway

The inverter’s torque response was highly consistent: commanded and delivered torque remained almost perfectly aligned despite repeated transitions between moderate and maximum demand. During dynamic running, the motor operated primarily between 1,500 and 3,000 RPM, while more than half of positive-torque operation occurred above 60 Nm.