2015-12-29

Hybrid BLDC ESC & GX25 ECU

I have advanced my thinking about the power train. More specifically the details for the board that will handle generator stage has converged somewhat. This is the current idea:


  • Use Brushless DC (BLDC) motor as both starter and generator connected to Honda GX25 motor.
  • Build a simple DIY ESC circuit that when powered will rotate the BLDC shaft to start the GX25 (working as a starter motor).
  • Build a rectifier circuit that when engaged to BLDC will make it generate power for charging batteries and giving the robot an extra power boost in the hour of need.
  • Build an ECU circuit with inputs for tachometer, voltmeter, ammeter and outputs for throttle servo and mechanical relays that allows engaging/disengaging the ignition, ESC and rectifier circuits on demand.
GX25 BLDC generator

The basic API for the circuit should look something like this:

  • Low-level
    • Start engine
    • Stop engine
    • Set throttle
    • Set charging
  • High-level
    • Start generator only when battery is low and/or power drain is high
    • Adjust throttle to accommodate load
    • Detect, alert and manage overheating
    • Detect, alert and manage low-fuel
    • Manage motor warm-up under different ambient temperatures.

How this circuit will communicate with central command and what will happen when communication breaks down is still to be decided.

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