Reflashing a quad ESC to BLHELI firmware in an attempt to solve pancake motor cogging issues

Ever since I've switched motors and ESC's on my "primary" quadcopter, I have been running on problems keeping it reliable. Every now and then it would crash, once because of a motor connection that got broken, and other times in a unpredictable manner without  a cause that I could identify.

Gimbal finally onboard

After a long wait and a hassle with a chinese seller, finally I could but together the gimbal, flash the board with Brugi (Martinez) and do some tuning and testing.

While a first flight have not yet been done, manual handling with rough attitude change movements shows that the gimbal seems to respond pretty well and no vibration could be perceived in the video at 1080p.

Custom made BEC

BEC's, which is short for Battery Eliminator Circuit is a fancy RC hobby term for a DC-DC converter that steps down the voltage to a given value used for example by servos and control electronics such as radio gear and flight controllers.

In the market there are two main types, most of which convert from a higher voltage to 5-6 Volts DC. These can either be of the linear type, or switching mode. The first is the simplest, where a simple linear regulator is used to drop the voltage to a constant value at the output. These tend to be very low noise steady sources of voltage, but have the disadvantage of being quite inefficient, getting worse the higher the input-output voltage differential. A considerable amount of energy is wasted in the form of heat.

2nd quadcopter practically RTF...

Other than having the recently ordered flight control board (Multiwii SE) mounted and configured, everything else was completed today with the addition of the custom made landing gear:

Brushless gimbal almost complete

With the arrival of the Mobius action camera, which is a Full HD (1920x1080 @ 30 Hz) little animal (very nice video quality for the price), my aerial filming addition to my #1 quadcopter is almost complete. The only missing element is the gimbal controller board, which I have ordered through ebay, but my mistake (or not) the seller have sent the MPU6050 instead (which I had at the same time ordered from a different seller). Result: I have two MPU6050 gimbal sensors and no gimbal controller. As such a dispute is being solved, and the seller decided to (supposedly) ship me the controller board. Otherwise I will escalate to ebay, get refunded, and the seller downgraded (or banned, who knows..).

Improved quadcopter - more "avionics" and increased run time

In the several weeks that followed a crash caused by an ESC failure, plenty of work have taken place (some of which documented here). Several things have been done since:

• Replacement of the ESCs with a 30 Amp quad ESC;
• Upgrade of the flight controller firmware;
• Building and programming the PPM Sum encoder;
• Building a BEC/filter with 12 V and 5 V outputs;
• Adding landing gear;
• Adding voltage and current sensor;
• OSD firmware upgrade;
• Change of LiPO battery from 11.1 V (3S) to 14.8 V (4S);

Smoke test after a lot of changes

It's always a stressful moment when after many changes something is put to the test. This was the case, taking into account that since the last flight there was a replacement of all ESCs, upgrade to Arducopter MPNG 3.0.1 R4, installation of PPM Sum module, addition of voltage and current measurement, and use of a higher system voltage (4S instead of 3S LiPo).

Busy quadcopter setup weekend

With the arrival of some of the parts I have been waiting for, more work accumulated with the finishing of my 2nd quadcopter. The parts were the landing gear and the quadruple ESC: The landing gear arrived with all the necessary parts as expected, including the lower crossing bar and the foam rods. The bar and other rods are all made of carbon fiber. The 4 support rings (for attaching to the frame) all had a rubber ring which helps to further dampen the vibration to additional items such as a camera:

Reflash the ESCs

Multicopters require a tight control loop for all the motors as part of their ability to perform stable flight. A basic requirement for an efficient closed loop PID system is that it has a high enough sample rate and fast response to error input when the knowledge about the system is minimal. Until recently most ESCs were designed for airplane and helicopter applications, where gradual response to input is desirable for saving the gears against abrupt torque variations. In quadcopters, direct driving of the propeller is normally the case (and as such mechanical wear is not much of an issue), and as explained, quick response to throttle input is required for good PID response.

One step closer...

A tray for the battery was added. Keeping simplicity and light weight in mind, I have built this tray based on an aluminium foil and four threaded rods. Four plastic straws (from kids balloons) served as spacers between the tray and the quadcopter chassis. The height of the tray was set based on the Turnigy 5000 mAh 3S battery I will be using:

New quadcopter taking shape

One evening at a time and this new drone begins to get closer to completion. Motors installed and thread locked. Power distribution board and flight controller also installed. The next step will be to install the reprogrammed ESCs (I will check for SimonK updates), wire things together, and make a support for the battery (I'm thinking about using some folded threaded rods as a kind of cage for holding it, or something similar).

New drone, old parts

With all the changes and upgrades I performed on my current quadcopter, I realized  I had about enough spare parts to build another one. The only missing thing was the frame, but this is where the fun part goes. With this I had the opportunity to build a frame from scratch after buying 1m of aluminum rod, and a 1.5 mm sheet of the same material. This resulted in a 177 gr frame, which is not too bad.

Ground Control Station

With the model aircraft hobby scaling beyond line of sight, control equipment also grows more complex and sophisticated these days. To the point where we no longer designate it of transmitter, but refer to it as "Ground Control Station".

Gathering with fellow pilots and Multicopter improvements

Most of the time I have been a lone rider in this hobby, having started from scratch on my own, since the traditional helicopters back in 2009. I would occasionally go to local air fields and try to mix in with seasoned RC airplane and helicopter pilots. But the environment would not always be too friendly, with the fixed wing guys not enjoying much the flying grass cutters.

Going higher with the flyer

After very conservative steps with this model aviation hobby, I decided to get closer to the trends, and do some updates/improvements on my quadcopter while still being careful with the budget.

Powerwheels RC conversion

I soon noticed my 20 month daughter affinity to vehicles. I wanted to give her one where she could sit and enjoy the ride, but currently most powered vehicles for infants require they are able to reach the throttle pedal and properly handle the steering wheel. So I figured out the best way would be to go remote controlled. As I already had done previous projects involving RC gear, it would be piece of cake to turn a regular electric car into a large scale RC car where a small kid could sit inside.

Power Supply Refactoring - finishing the details

In spite of already being a working device, there were aspects that like I explained in the previous post, required some attention. One of the major fixes was the voltage drift. This was caused by the 5 K potentiometer used to set the voltage end point. It was too large (the sweet spot of my setup was around 500 Ohms), which besides making it difficult to adjust, caused temperature induced resistance drift to be too large, causing an increase of around 200 mV from the initial voltage once the temperature settled.

Power Supply Refactoring - closing the hood

After many hours of work I finally can say it's done. Even though I don't consider it the perfect work, I can definitively consider it a major improvement in respect to the previous version of the PSU:

Before:

Power Supply Refactoring - part 5

Prior to assembling the definitive power supply circuit board (i.e. the main electronics featuring the LM723) I took the time to set it up on a breadboard. Before that I finished the board containing only the large components such as the filter capacitors and the high wattage resistors (current shunt used by the regulator chip to sense the current across the power rail, and a bleed resistor for the output capacitor):

Power Supply Refactoring - part 4

Another weekend have passed, and along with it a few more results as I slowly but steadily walk towards completion of the project. The digital voltmeter/ammeter displays have still not arrived from China. This is the last piece of hardware missing. Adding time to the equation and all the elements necessary to complete the project are available.