Tuning up

Motor update

Since yesterday, Sibille and I have worked on reducing the voltage threshold for motor acceleration we’ve mentioned here

After a meeting with Alexis yesterday and with the school mechanic this morning, we have two main leads.

Reflashing BLHeli ESC

The first lead is to take a look and the programmable  parameters of the ESC. We previously hadn’t given this much thought, but ESCs usually allow for the tweaking of several parameters in how they control the motor. Usually there’s a way to access these settings by playing with the PWM throttle input and using the feedback bips to identify various menus. That is meant to allow easy programmation using a remote control throttle for modelism applications. But since we use DShot instead of PWM control, that wasn’t an easy option for us.

Instead, I put my previous research on how to reflash an ESC to good use : there’s an ESC programmation method called “FC Passthrough” where the ESC can be reprogrammed directly through the normal connection to a Flight Controller – in our case, an appropriately flashed Arduino. This method also allows us to just access the ESC settings. We used a Windows app called BLHeliSuite, which offers a clunky but workable interface to first flash the Arduino, and then access the ESC through it.

After playing around with various parameters for a bit and managed to lower the voltage threshold with the PVC plate load from 16.5 V to around 13 V.

We’ll soon do a test with a fuller load (3D-printed shell and structures on the PVC plate).

While we were at it, we also noticed there’s a parameter for the volume of the ESC. This means we’ll be able to turn the ESC’s annoying startup ringtone off in our final prototype.

Flexible coupling

Our second lead is to reduce the friction due to concentricity deviation of the motor shaft. To do so, Alexis suggested yesterday to use a flexible coupling between the motor shaft and the axis. We would like it to be as small as possible to avoid increasing the height of the base too much. Our best find so far is a 21mm long flexible coupling, but we have some doubts about its other dimensions. Actually, while the datasheet says (page 13) that it can be used with axis of 8mm in diameter, the description on the supplier website claims that it can only be used with axis of 6mm in diameter. 

We talked to the school mechanic who think that it isn’t a bad idea and who agreed to help us try it, so we have ordered one. We will keep you updated !

LED-driving code

Simultaneously, we have continued to work on the software of the LED-driving processors and we received this afternoon the devboard with the right CPU (STM32F207). The code is now compiling, we will test it tomorrow and keep you posted 🙂

Stay tuned !

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