We have an Myxa with v3 firmware and we’re trying to maximize thrust of the propulsion system. Motor has 500-550kv and is supplied with 25V. This should give 12500-13750rpm with no-load. We get around 11500 rpm without propeller.
Problem is that the motor with propeller can’t get over 9980rpm in rpm control mode. Different values on m.max_eangvel doesn’t change anything here, there is no difference between 10000, 12000, 15000.
We tested this motor with other ESCs. With Jeti Spin we was able to achieve around 10800 rpm with propeller, so we trying to achieve this with Myxa.
The no load motor speed is proportional to Kv and the voltage indeed. But you forgot about the voltage utilization factor, which is described in the section 3.1 of the Myxa datasheet. The voltage utilization factor depends on the motor control principle. The common BLDC control principle has the maximum value of the factor equal to 1 because it doesn’t require to measure the motor current and the PWM itself at the max speed. The FOC principle requires the PWM at the max speed too. The utilization factor is always < 1 therefore. We have increased its value in v0.3 firmware, but it’s still around 0.95-0.99.
The motor is loaded with propeller. The max speed depends on the motor current value. The best way to understand this phenomenon is to study the DC Motor characteristics. The PMSM and BLDC motors behave the same way. At maximum speed, the controller can no longer compensate for the decrease in speed by increasing the voltage, since the voltage has already reached the maximum.