Unless youve been living under a rock, you know that flybarless helicopters using 3-axis stabilization have exploded in popularity. In the past, flybarless controller choices were very limited and costly, but technology has advanced bringing prices down and features up. The Microbeast, manufactured by BeastX in Germany, is a 3-axis gyro system, utilizing MEMS technology that allows RC helicopters to enjoy fully stabilized flybarless flight. At about $200, the Microbeast is a bargain, costing about as much as a high end tail gyro, but with much more functionality and capability.
The Microbeast itself is a single unit, about the size of a small 7- or 8-channel receiver. The base of the case is constructed out of machined aluminum, while the top is plastic. The aluminum case adds some extra mass to the unit, enhancing its ability to work optimally in vibration-prone environments. The overall fit and finish of the case is top notch and screams quality.
The Microbeast is very flexible in terms of the types of receivers it can interface with. Of course, it can be hooked up via multiple wires to any standard receiver, but it can also be configured to work with a single Spektrum satellite receiver or Futabas S-BUS, forgoing a lot of extra wiring and weight. This can be important in smaller setups, where space can be at a premium. In terms of mounting, the Microbeast can be mounted in almost any orientation. The only requirement is that the connector side of the unit must face towards the front or the back of the helicopter.
GAUI X5 TEST BED
I chose to test out the Microbeast on my Gaui X5 helicopter, which I reviewed in flybarred form in a past issue of Heli Pilot. Empire RC was nice enough to provide a flybarless conversion for this helicopter, which consists of a new rotor head block and swash follower, control arms for the main blade grips, a shorter main shaft, and some hardware. Converting over the X5 was easy, taking less than an hour to remove the flybarred rotor head and install the flybarless components. Total weight of parts removed, including the original tail gyro was 7.5 ounces. The weight of the new parts, including the Microbeast was 5.0 ounces, for a nice weight savings of 2.5 ounces.
Rather than mount the Microbeast up on the X5s gyro platform, I chose to attach it to the side of the frames, next to the receiver to keep the wiring runs short. I used the included double-sided foam tape to affix it, after cleaning both mounting surfaces adequately with rubbing alcohol.
Programming is accomplished with a single button and multiple LEDs on the unit itself along with stick movements from the connected transmitter. The steps are clearly laid out in the well written manual. Rather than going through all the programming steps here, you can download the manual by visiting Find.helipilotonline. com/061128. I left all the parameters as recommend, and set the tail gain in the transmitter to 50 percent.
Next, I took the heli outside for its first test flight as a flybarless helicopter. I spooled up normally, and since everything felt fine, I brought it into a 3-foot hover. The entire time, everything felt well controlled and positive, without any bobbles or sluggishness. I was really impressed at the fact that I didnt have to make any adjustments outside of the normal initial setup to get a heli that was totally stable within seconds of spooling it up for the first time.
Prior to performing any of the flybarless modifications, I used my Eagle Tree flight recorder to measure hover power required. At 2200 rpm, in the original flybarred configuration, it took 478 watts to hover out of ground effect. With the Microbeast and the flybarless head, it took only 448 watts to hover, over a 6 percent gain in efficiency. The gain is probably more significant once the helicopter is pushed harder, as the flybar is no longer fighting the actions of the main rotor blades. This improvement translates into more flight time and more reserve power for 3D flight.
After performing my controlled tests, it was time to let the Microbeast stretch its legs. In fast forward flight, the Microbeast made the X5 feel even better than it already was, with the X5 holding a perfect line across the horizon, without any pitch up or pitch down. Loops and rolls also tracked perfectly. For 3D pilots, the default sport settings, limits the flip rate to about 1 every 2 seconds, which is a tad slow for my tastes. I later switched it to the extreme settings, which greatly sped up the cyclic controls. I dialed in a little exponential on my transmitter to soften up the control around center while still maintaining a fast flip rate.
The Microbeast also excelled at keeping the tail rotor in check, holding a very consistent pirouette rate from hover though moderate speed forward flight. During hard punchouts from a hover, the tail rotor barely moves and in backwards flight holds the tail like a vise. This was all at the default gain settings that I had originally programmed into my radio during initial setup. I havent had a reason to change it yet from this initial setting.
MICROBEAST TECHNICAL DESIGN DETAILS
The Microbeast is a 3-axis electronic stability augmentation system (SAS) recently introduced by Beastx and that is distributed by Horizon Hobby. I had a unique opportunity to discuss its development with Markus, the president and owner of Freakware, www.freakware. de, the German company that produces the Microbeast, and I also had the chance to chat with Hans, the original designer of the Microbeast. This unit (a flybarless œblack box) is an all-German design and it is manufactured in Germany.
The introductory price, around $200 US, is an incredible value considering each Microbeast comes with three built-in MEMS gyros jammed into a tiny orange colored aluminum case. The three gyros in it stabilize the heli in its yaw, pitch and roll axes. MEMS is the latest œrate-sensor technology that is also used by most top name yaw rate gyros. Gyros made with MEMS are more sensitive and have less temperature drift than gyros made with the piezoelectric crystals (lead tech 10 years ago). In simplest terms, the yaw gyro replaces the standard tail gyro; two gyros for stabilizing pitch and roll replace the flybar. The original Microbeast was introduced in 2009; here we look at Version 2 with enhanced software.
We used to pay $200 just for a standard single-axis tail rotor headinglock gyro. The price has dropped owing to economies of scale for these chips in other industries building automobiles, smart phones and e-reader tablets. Interestingly, Hans also designed the original Mikado V-Stab system. The original V-Stab had a pitot tube to sense velocity and its input helped improve forward flight stability. That was Hanss idea, but he later found that by adding an additional integration of the signal he could eliminate the pitot tube. The Microbeast is designed solely as an SAS for a flybarless RC helicopters only. It can hold the helicopter almost stationary in a hover if you do not touch the sticks. But it is not an autopilot nor a training device for beginners. It is easy to program. There are 14 setup menus and four parameters that can be set directly from the Microbeast unit by simply pushing one button and then using the transmitter rudder stick to make selections. This allows fine tuning at the flying field. You dont need to use a personal computer with a USB cable although an optional USB cord is available from Beastx for downloading new software. Hans also shared a œsecret. The Microbeast is very good at doing a slow pirouette while holding the heli level, and it does not care about the location of the helis CG. His earlier flybarless controller designs were more sensitive to the CG position, especially in a cross wind.
Hans also notes that he worked with test pilots to optimize the gain between angular rate feedback and mathematically- integrated angular attitude feedback to give a nice balance. That is, the unit does not stop any motion so soft as to be mushy, nor too hard so as to cause a bounce. Some flybarless controllers use just P (proportional) and I (integration) feedback, but he uses a full P, I, D (differential) feedback system. The result is astounding: a flybarless helicopter that is even more stable than a flybarred helicopter.
Before first flight, try setting all the parameters on the Microbeast in accordance with the recommendations in the instruction manual. In order to fine tune the unit, the pilot should be proficient at hovering and flying a model helicopter so that it is easy to tweak the parameters to get the desired handling characteristics (another reason this is not for beginners). You can make your heli as sporty and agile as a race car, or as docile and lazy as a trainer. The parameter called œControlled Behavior controls the helicopter rotation rate and how sensitive it is to control inputs. Another parameter called œSwashplate Pitch Up Behavior determines helicopter responsiveness. Getting this dialed in can involve a few trial and error flight tests.
Amazingly, I found that once the system is set up, the Microbeast can keep the cyclic control response nearly constant regardless of rotor rpm. Testing an electric helicopter, even as rotor speed dropped as the battery was depleted, the model could still flip, tumble and roll at nearly the same rate. I have varied rpm from 1200 to 2000 rpm by changing the throttle curve and battery cell count, and the flybarless helicopter equipped with the Microbeast flipped, tumbled and rolled at nearly the same rate! Astounding.
Since flybarless helicopters do not have Bell-Hiller mixing arms and a flybar to relieve the steady and vibratory aerodynamic loads feeding back from the rotor blades to the servos, it is critical to employ the highest quality and most rugged servos you can find to get the best performance. The servos should have metal gears and output shafts supported by two radial bearings. The torque rating should be greater than 100 oz.-in. for 50 to 90 size helicopters.
The instruction manual explains how to make the Microbeast work with different brands and types of digital and analog servos. It is very important to consult the appendix of the Microbeast instruction manual to ensure you set the pulse width and frame rate on the Microbeast to match your particular servos. To get the best performance, it is necessary to invest in top notch servos. For best performance with the heading lock tail gyro, use a high speed digital servo that can handle a high signal frame rate of 270 to 330 Hz.
SIZE: 1.34 x 1 x .5 in. (34 x 25 x 13.5mm)
WEIGHT WITHOUT CABLE: .7 oz. (20g)
OPERATING VOLTAGE: 3.5V to 8.5V DC (possible to use 2S Li-Po)
PROCESSOR: 32Bit ARM
ANALOG PROCESSING: 17Bit
SENSOR TECHNOLOGY: 3 MEMS angular rate sensors
ADJUSTABLE SERVO CENTER PULSE WIDTH: TAIL: 760us / 960us / 1520us
ADJUSTABLE SERVO PULSE RATE: TAIL: 50 Hz / 165 Hz / 270 Hz / 330 Hz
SWASHPLATE: 50 Hz / 65 Hz / 120 Hz / 200 Hz
SWASHPLATE MIXER: for 90, 120, and 140 degree eCCPM
1 USB-Interface for installing software update
2 Spektrum satellite receiver
3 Connection cable for using Microbeast as a tail gyro only
The flybarless revolution is in full swing, and if youre looking to get onto the bandwagon, the BeastX Microbeast deserves serious consideration. Its easy to setup, takes very little room on your helicopter, and is priced comparable to a good tail gyro. Highly recommended!
BeastX Manual, www.helipilotonline.com/061128
Horizon Hobby Distributors, www.horizonhobby.com , (800) 338-4639