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Flight Control

MK- Flight Control and Sensors

Contents

Contents

  1. 1 Overview
  2. 2 Terms
  3. 3 Sensor Description
    1. 3.1 Gyroscopes (Gyros)
    2. 3.2 Acceleration Sensor  (Accelerometer-ACC)
    3. 3.3 Atmospheric Pressure Sensor

Overview

The purpose of this review is to examine the Mikrokopter Flight Control board (FC-Ctrl) and the various flight control sensors used on the board to maintain smooth level and controllable flight. This review does not cover the navigation systems such as the Navi Board, GPS, and Compass.


Flight Control Computer 

 

The Flight-Control (Flight-Ctrl) is the main board of the MikroKopter. It contains the primary processor and all the sensors that are necessary for a stable flight.

 

The primary sensors on the FC are the rotation speed sensors (Gyros). The FC software uses them to determine the position in the air and to compensate for external influences. A gyro is needed for every axis (x,y and z) so three sensors all together. These gyroscopes/gyros measure rotation speed changes in degrees per second.

 

Another important sensor is the acceleration sensor. It senses the acceleration in all of the three axis. The vertical acceleration sensor is also able to measure the angle of the mikrokopter towards the earth. Usually they are referred to as Accellerometers or ACC. You can fly without them, but with these sensors you are able to automatically get the MK back to level flight. This way you can let go of the joysticks and the MikroKopter will stay at its position. Without these sensors, the Mikrokopter will keep on flying in a prescribed angle.

 

There are several other functions that the Flight Control (FC) performs, including altitude calculation, servo control output, and transistor voltage output. The FC also manages the additional boards navi, gps, and mag compass when they are attached.

 

In the lower photo, you can see the Flight Control Board (circled in red) mounted onto the MK. 


If the flight controller software is properly programmed and the sensors correctly calibrated, the MK will remain steady in the air and respond smoothly to flight commands from the pilot.  While there are other systems on the MK that also need to be correctly set and operated, the proper understanding and setup of the flight control sensors is critical to quality flight characteristics.

Terms

    Gyroscope/Gyro - electromechanical devices that measure the angular velocity of an object in degrees per second.
    Accelerometer (ACC) - A special gyro that determines the acceleration by measuring the force on a known sample mass.
    Center of Gravity (CG) - the average location of the weight of an object.The point at which the MK would balance if it were possible to suspend it at that point.
    MK -  Abbreviation for Mikrokopter
    MK Flight Control  Circuit board that contains all of the electronics needed for MK flight.
    Nick - MK pitch controlled by the right control stick on the radio transmitter in a forward/reverse direction.
    Roll - MK roll controlled by the right control stick on the radion transmitter in a right/left direction.
    YAW - MK rotation in a horizontal plane controlled by the left stick on the radio transmitter in a right/left direction.
    MEMS - Microelectromechanical systems is the technology of very small mechanical devices driven by electricity.
    EEPROM -  Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration tables or device configuration.
    Weight and Balance - The science of properly distributing load to operate the MK within proper weight limits and center of gravity location. Flight performance is greatly affected by weight and balance.

Sensor Description

The MK-Flight Control Board has five separate sensors that work together to maintain stable and controlled flight. Three Gyroscopes are installed on the board to sense angular movement in the three different geometric axis planes, an accelerometer capable of detecting movement speed in all three directions, and an atmospheric pressure sensor used for altitude control.
The following description will further define the purpose of each device.

Gyroscopes (Gyros)

The Mikrokopter uses three MEMS ADXRS610 gyros. Of all the sensors, the gyroscopes are most important. The Flight Control software uses inputs from the gyros to determine the position in the air and to compen
sate for external influences. A gyro is needed for each geometric axis (x,y and z) of the Mikrokopter. Gyros measure the angular velocity in degrees per second. The Mikrokopter uses three MEMS Gyroscopes, each placed on a different X, Y, Z axis.

The invention of the Microelectromechanal (MEMS) gyro was a breakthrough in gyro technology and allows gyro installation in everything from cameras to cell phones. The MEMS Gyro does not use a rotating mass as in older version rather it has an electostatically suspended membrane that accomplishes the same task only in a much smaller and less costly method. This new type of gyro is simpler and cheaper than conventional rotating gyroscopes of similar accuracy.



Acceleration Sensor  (Accelerometer-ACC)

The main function of the acceleration sensor is to measure the actual tilt of the MikroKopter and to support the attitude adjustments from the gyros.
The sensor measures static (gravitational acceleration) and dynamic acceleration using the LIS344ALH which is an ultra compact consumer low-power three-axis linear accelerometer. The sensor is a special MEMS Gyro that senses acceleration in all of three axis. Usually referred to as Accellerometers or ACC, you can fly without them, but with this sensor you are able to automatically get the MikroKopter back to level flight. When properly configured, you can let go of the joysticks and the MikroKopter will stay at its position. Without these sensors, the Mikrokopter will keep on flying in a prescribed angle.

The ACC Sensor converts acceleration values into proportional voltage levels, which are than evaluated, along with other gyro information by the microcontroller on board the Flight Control.

The sensor is also used in conjunction with the gyroscopes to determine attitude.

Atmospheric Pressure Sensor

A height sensor can be placed on the Flight-Ctrl as an option. This precise barometric pressure instrument enables  the ability to optionally flying at the same height all the time. This optional sensor also serves to stabilize the flight altitude.

Note: It is important to be aware that this is a standard "off the shelf" part and needs to be retrofitted for the MK by covering the small pressure port with open cell foam held in place by shrink wrap. 





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