Off-road RumiCar - Investigating the Cause and Countermeasures for the Resetting of the Microcontroller #4

[Annami1213]

English ver. https://github.com/RumiCar-group/RumiCar/issues/4#issue-1729464821

10/25/2022 (Posted by Mr. Oe)
It appears that when the front wheel motor stalls, the voltage drops, causing the Arduino microcontroller to reset.

Investigation:

When the front wheels are vigorously turned without the vehicle in motion, noise occurs, but the microcontroller does not reset. It is believed that the lack of driving resistance is the reason for this. The voltage of the dry cell battery has dropped to a minimum of 1.4468V. At this level, the microcontroller may become unresponsive. It is possible that the DCDC converter is no longer outputting due to the decrease in voltage on the battery side. there is an unexplained factor or issue preventing the voltage from being recorded accurately as the minimum value, despite dropping to around 1V.

The sudden power consumption in the front wheel motor occurs only at the moment of stalling. This period is very short, around 50ns. It happens when switching the front or rear wheel motor between forward and reverse. To prevent this, it is advisable to introduce a delay in the software settings when switching between forward and reverse to allow for a smoother transition.

The waveform images on the oscilloscope:

• The yellow waveform represents the input of the DCDC converter.
• The blue waveform represents the output.
• The faintly visible parts show the overlaid display of waveforms from the past 10 seconds.

5/15/2023 (Posted by Mr. Kataoka)

The voltage required to start the front wheel motor = 3.0V.
The voltage required to start the rear wheel motor = 1.5V.
The voltage supplied from the motor driver to the motor = 4.5V, which is considered overvoltage for the rear wheel motor.

5/25/2023 (Posted by Mr. Kataoka)
The internal resistance of the motor = approximately 3Ω.