Trouble with rotation

Hi I have an Hquad500 and recently started getting some trouble with flying the drone. When flying the drone to rotate in a circle. Yaw control will correct for this but it makes the drone almost unflyable. I have tried using “mag” mode to lock the heading but I still get rotation. Any suggestions on how to fix this? I have tried to level the motors, but it didn’t help much.

  • The first thing would be to be sure you have all sensors calibrated (ACC & MAG).
  • Then it could be as simple as your “trim” on the transmitter. Be sure all signals are 1500 when centered in WinGUI.

Also ensure the ANGLE that the motors are installed at are the same at the hardware side of things… If after calibrations there is still rotations of a platform, there is can differences in the true angle each of the motors are mounted at. Even slight differences between them can cause aerodynamics to move the air currents in different directions then expected. One method to use is a true 90 degree triangle made from metal. The use of metal ensures the gauge does not warp over time. The gauge should show flush against the motor/shaft and the mounting point. If a craft is assembled by hand, it may appear to the human eye all the motors are mounted correctly, but there may just exist a slight variation in an angle between motors, causing the airflow to be generated in two different directions. This then causes unwanted rotations. Usually it can be corrected by trims but if the angles are beyond the end-points of the trim adjustments, the angles are only be reduced, and not fully being canceled out by the trim adjusters. So examine the angles of the mounted motors.

For example if one motor is +1 degree over 90 (at 91 degrees from the mount) and another motor is at -1 from mount (89 degrees instead of 90 degrees) then the result seen in aerodynamics would be a 2 degree rotation at all times, since air is being propelled in one direction from one motor and propelled in the other direction from the other motor. The platform will rotate, since there is nothing to resist the rotation being generated. That is the purpose of trim adjusters to trim the motor speed of one motor to spin faster or slower then then another, in order to counteract the slight angles occurring between two motors. However, if the aerodynamics are more extreme then the trims can counteract them, a platform will still rotate, minus the amount of adjusted trim. Understand?

Also, and this is something that is overlooked very often, spin opposing motors so they cancel each others shaft rotations, out. Make is a design rule. One used by Acigan here, is that starboard shafts rotate counter clockwise (CCW) and Port side shafts rotate clockwise (CW). This rule not only causes shaft rotations to self-cancel themselves out, but also ensures any rotational forces the rotating shafts generate are directed inwards towards each other, and not outwards, away from the platforms. Inward forces can be sensed more easily by onboard sensors then those that are moving away from the sensors.

So if everything has been checked out and fine based on all the previous posts, examine the mount angles and the direction of shaft rotation. You want true 90 degree angles for mounts and for shaft rotations to spin towards the body of the platforms, not away from it, so that even this very small amount of force generated by shaft rotation, is not only canceled out by the other opposing shaft, but also picked up easier by any installed sensors on the platform.

It is for this reason that quad drones (or X drones as some call them) use both CW and CCW motors and props. You want both. If all motors turn CW and only the 2 of the 4 props are CCW, there will occur rotational drift that will need some trim adjustments. Reason is, the props are canceling each other out (2 CW, 2 CCW, in the X) however if all four motors are spinning CW, there is no CCW force to counteract the shaft rotations. So always place them to cancel each other out, and you may never even need to set a trim more then a divot or so based on wind direction.

Hope this helps

Acigan International
Design Division