XAircraft X650-The Difference Between UltraPWM ESC and General ESC

General ESC has been very mature after years of development, many species, current from small ampere to large ampere. But the general ESC are not designed for multi-rotor craft, there are a few common problem if it used in multi-rotor craft:

• Low control frequency: the general ESC used standard PWM pulse width which is only 50Hz(20ms cycle). In fact, most of the general ESC could work in much higher than this range without any problem. The ESC we tested they basically can work well from 200Hz to 300Hz in control frequency, but this frequency can only meet the common requirements.

• Consistency is poor: almost all general ESC have a common basic function called "the start throttle setting" that can be used to eliminate the different throttle pulse width with different remote control. That is you can set all of the ESC to start the motor at a some throttle position. Unfortunately, this feature can not solve the problem in poor consistency, for example, rocker swing 10 degrees from the start position, assuming the speed of motor is 3000 rpm at this time, and the environments are invariant, then change the setting and rocker swing 10 degrees from the start position again, you will find the motor speed may be only 2500 rpm, but also changes speed with the ESC temperature. It is caused by the general ESC have not a stable reference clock source without temperature influence. That is ok for the single rotor craft, but disaster for multi-rotor craft, because the different motor speed in four rotor is difficulty for the craft to fly Stable.

• Constant speed mode, which is the only function for senior ESC. For single rotor craft, the ESC itself is a closed loop control system, constant speed mode can eliminate the effects that output power does not vary with battery voltage drop down. This feature allows craft flight more stable. For Multi-rotor system, ESC is only responsible for driving the motor, it can not achieve and does not need self-loop, that will affect the flight stability of multi-rotor aircraft.

In order to solve these problems, we used a more stable, reliable interface solution that compatible with current brushless motor speed controller, we called it UltraPWM technology:

• All ESC are connect parallel to flight controller, any one of them brokecn down will not affect the work of the entire system, aircraft still able to landed safely via the remaining seven motor. This is essential for multi-rotor aircraft to meet high security requirement.

• Motor control frequency 500Hz, 1000 control level. The the control pulse width error between two brushless motor less than 1%.

• Compatible with the existing ESC interface, without requiring high speed and high precision control, instead, it can work with the general speed controller too.