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.

XAircraft X650 QuadCopter QuadRotor Instruction Muanual(PDF) Release

Xaircraft release the x650 instruction muanual, chinese and english version.

 

 Download it from here

XAircraft X650 Flight Control Management(Parameter Adjustment) Software

XAircraft X650 is definitely not just a simple four-rotor aircraft toy. It has a very powerful user-defined function that player can fine-tune the various parameters to meet their flight style, such as: Joystick sensitivity, aircraft flight parameters at different load, etc.

In fact, the biaxial camera mount, in order to fit to different types of cameras, also required a powerful software to adjust different parameter, such as: different size camera, camera focus location and trigger time... all need to fine-tuning parameters.

Meanwhile XAircraft Flight Control Management(Parameter Adjustment) Software is a working status monitor that player can check the service condition of x650 to ensure safe flight. It can also help player quickly to find the problem when the aircraft broken down.

XAircraft X650 QuadCopter LED Module

All the LED that designed to indicate the circuit status are installed under the X650 body shell. And it is difficult to make out the flight attitude as the X650 are away more than 50 meters from the controler. So we designed the LED module to indicate the system status and flight attitude.

Features:

• Include 56 bright LED, 28 for overlooking, 28 for looking up, help player make out the flight attitude and dircetion of X650.

• Each one LED can be individually controlled light on or off.

• Display the any status you want via adjust the XAircraft X650 Flight Control Management(Parameter Adjustment) Software.

XAircraft X650 QuadCopter-Problem About I2C Brushless Motor Speed Ccontroller

All along along, the brushless motor speed controller (ESC) of four-rotor aircraft mostly use I2C digital communication. It put all brushless motor speed controller connection in series on the bus through two data lines (one for the clock SCL, one for data SDA), and send the control signals to brushless motor speed controller at regular time. MK products used this communication mode, as well as our early X500D X600D.


I2C communication mode looks perfect, you can save the number of communication cable, moreover does not need to modify the hardware and interface when extended the four-rotor to six or eight rotor, just directly attached to the existing communications bus. This is a economy design that easy to extend.

However, there are some problem in actual use:
1. As long as one of brushless motor speed controller broken down, will affect all the other brushless motor speed controller on I2C bus, this failure is fatal. Although we can change the software to make the all brushless motor speed controller to enter the normal working condition after broken down. But the I2C communication mode has greatly increased the probability of failure, for expensive camera equipment and x650 aircraft, this is clearly not the best choice.

2. ESC is working in Series on the I2C, the more ESC, the more time cost in communication. The maximum communication rate of the standard I2C is 400kbps, for reliability and stability, the general four-rotor will use the communication speed 100kbps, means it can only send and receive data only 10 byte per 1ms. No enough for high-speed and high-precision motor control, as 500Hz and 1000 control level with the increase in the number of motors.

3. There are many ESC in in the field of model airplane before four-rotor aircraft invention, after years of development they are become very mature and reliable and has a very rich type and power output. But I2C are incompatible with these traditional ESC interface, and nothing much in the type, inconvenient to extend.

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.

XAircraft X650 QuadCopter(QuadRotor) Flight Controller Architecture Design

XAircraft has designed several flight controllers for internal research and development and testing without sell
since 2007.

In the R&D process, in order to achieve standardization and scalability in flight control, we repeatedly modified the architecture design. The picture below shows the final design of flight control architecture which we we called "standard flight control system".

The master control chip ARM of standard flight controller provide 100MPIS processing power to meet the requirements of complex and high-speed control. Flight controllers support 7 exptend modules, two of them are built-in input signal capture module(input module) and control signal output module (output module).

Input Signal Capture Module(Input Module) Features:

• Support 12-channel remote control signal capture.

• Each capture channel has 1us pulse width identification ability.
• Compatible with any type and frequency remote control, such as Futaba, JR, Spektrum, etc.

• Support two or more remote control devices to capture the signal at the same time, on some special occasions, often requires two people to execute a remote control mission, as one person control flight, another control camera mount, requires two remote control devices to work simultaneously.

• Detect the pulse width of remote control input signal, for some advanced remote control, this feature can be used as control protection and signal stability testing.

Meanwhile, users can adjust parameters and check the working condition of input signal capture module by using
XAircraft Flight Control Management(Parameter Adjustment) Software and XAircraft USB-Link PC Connector.

Control Signal Output Module (Output Module) Features:

• 12-channel output capability.

• Each channel output control accuracy: 1us

• Support the general and high-speed digital steering engine, 12 channels are divided into 3 groups, each pulse signal can be arbitrarily adjusted.

• Support High-Speed (UltraPWM mode) Electric Speed Control Device(UltraPWM ESC), low-speed mode are also available.

Although the X650 is a quadrotor (Quadcopter) products, but it equipped with the standard flight control can support up to 12 rotor, usually retaining four output channels for the camera mount, means the X650 flight control can drive 8 rotor(8 propeller) without need to purchase a new flight controller.


Except the two built-in modules, XAircraft standard flight control module also has 5 extend ports, they are PortA to PortE, one of them used for AHRS (Attitude and Heading Reference Systems) which provides Pitch & Roll Angle and heading. As the flight control get the AHRS attitude and heading signals, like 30 degrees tilt, 18 degrees yaw, the flight control algorithms adjust the aircraft's attitude to achieve a smooth flight.

AHRS module is a standard configuration on X650.

The remaining extend port can also be used to connect other modules, such as GPS Module, Range Finder Module, LED Module(indicate aircraft status), Power Monitor Module and so on.

There is a special interface called the connector port (Link Port) in flight controller. All devices connected to the port are called connectors (Linker). Player can set the parameters of flight control Via USB-Link, or upgrade firmware for the flight control.

USB-Link is a standard configuration on X650. Users can also install the Bluetooth device (Bluetooth-Link), OSD-Link and so on. We actively cooperate with several universities in China to improve the control instruction of this interface. It will be announced to help the secondary development of flight control system.