by "Dr. Ben" Minor
revised December 8, 2010
Over the past few years, integrated electronic speed control (ESC) integrated governors have evolved to be quite functional. Be that as it may, no system out there as yet allows the pilot to set, from the transmitter, a known head speed by programming the desired value into the transmitter’s governor menu. By virtue of its ability to integrate with an ESC, the GY701’s governor functionality offers great possibilities for electric helicopter enthusiasts.
In consideration of the use of the GY701’s governor with an ESC, the user must always understand that there is a tremendous variability across the marketplace when it comes to ESC, brushless motor, and model design and function. Thus a set up, even one of the choices described here that is known to work well for one combination may not work as well for another. Various parameters may need to be tweaked in some situations to allow for these variations. Be patient and adjust as needed; the result is worth the effort.
When investigation of the use of the GY701 in electric models began, I started with a known, well-flying model, motor, and ESC combination. For the purposes of this discussion, I used a popular ESC, the Castle Creations ICE80HV, and a Scorpion 500 kV motor. As mentioned before, specific parameter recommendations for this combination may not apply directly to other brands, so be willing to adjust as needed for an ideal result.
As for the ESC itself, the controller should be calibrated to the transmitter as usual and per the manufacturer’s instructions. For Castle Creations products, the controller should be calibrated in HELI FIXED ENDPOINT mode and left there for use with the GY701. Do NOT use the ESC’s native SET RPM or Governor High functions. The Castle Creation native autorotation recovery mode is not lost when the controller is in FIXED ENDPOINT mode and used with the GY701.
The ESC should be treated as an ANALOG “servo” in the GY701. Set it as such.
The parameter recommendations that appear below were suggested by Futaba Japan. It would be reasonable to try these settings as-is and assess how they work in the user’s particular application. Should problems arise, the set up can be modified as I will describe later based on my own model.
Servo type: Analog
Throttle mode: Optimize
Up delay: 10
Down delay: 10
Start delay: 5
Low limit hovering: 15%
Low limit idle up: 75%
* Others parameter are default
The first parameter of interest is the OPERATION RESPONSE. The suggested setting is QUICK. On my model, QUICK resulted in rpm hunting, regardless of gain setting. If you experience such hunting, try the MIDDLE setting.
GAIN is the next setting in the GY701’s menu. The settings from Japan suggested 30% gain. I personally found that gain to be too low to adequately hold the head speed. If you are NOT experiencing any hunting, run the GAIN as high as possible without creating hunting while in your aerobatics (idle up) flight condition.
In the manual, THROTTLE DATA MODE for electric models is suggested to be set to FIXED. In reality, neither Futaba Japan nor I could make that work. Use OPTIMIZE.
The LIMITS and delays (all of them) suggested in the Futaba Japan suggested parameters should be followed. ESPECIALLY the LOW LIMIT at IDLE UP should be raised as noted from default setting to keep the governor from markedly UNDER speeding the head in certain aerobatic maneuvers.
The SERVO LIMIT POINT which defines the overall “throttle” range for the governor should be set using a default, linear, 0-100% throttle curve. Set these limits AFTER you have calibrated your ESC. More information on calibration of the ESC appears below.
Set the gear ratio in the GY701 as indicated by your model. You have several choices for magnet placement in the model. The first choice is to place the magnets at perfect spacing either in the outer diameter of the main gear or in the autorotation hub or second gear assembly. If you choose this option, the pockets for the magnets MUST be precision machined. Hand measurement and placement are not sufficient. Obviously, many users do not have access to the machine tools required for this operation, but there are other options. Some model helicopters employ a second gear shaft to drive the tail rotor. It is permissible to mount a single magnet either in a small aluminum collar on that shaft or in the tail rotor drive pulley or driveshaft. Finally, if sufficient motor shaft length is available, an aluminum collar with magnet could be mounted directly to the motor shaft. It is fine to be creative, but follow a few rules:
- If you put the magnets anywhere on the autorotation hub or main gear, their placement must be done with perfection that comes only with machine tooling. Failure to do so may result in hunting or the governor misregulating head speed.
- If you put magnets in the autorotation hub or main gear, use SIX and set the gear ratio to 6:1. ALL MAGNET POLARITY GOES THE SAME WAY.
- If you put a magnet in the counter gear shaft or assembly, set the gear ratio equal to the model’s main:tail drive ratio. In most models, this ratio is between 4.3 and 5.0:1. Count the main gear teeth and the counter gear/tail drive teeth, divide the latter into the former, and you will get exact ratio ratio for your model.
- If you are able to mount the magnet in a collar directly on the motor shaft (really, this is the best way), then the ratio set in the GY701 is the same as the number obtained by dividing the number of teeth in the main gear by the number of teeth on the gear on the motor.
- Sensor placement is exactly like it is with a fuel powered model; position it for the highest possible reading percentage.
Actual head speed in GOVERNOR mode is set in the transmitter’s governor menu as usual.
Due to the aforementioned variances in model, ESC , and motor type, it is possible that you will not achieve acceptable performance in GOVERNOR mode. The most common problems will be a failure to hold head speed because the gain cannot be raised to an effective level without hunting or head under speeding in certain maneuvers and in spite of raising the LOW LIMIT for IDLE UP to its highest value. Should you experience these problems, we have another very effective option………
REVOLUTION LIMITER (Rev.Lmt) MODE!
The use of rev limiter mode requires no change in the ESC programming. The GOVERNOR WORKING MODE should be changed from GOVERNOR to Rev.LMT. Set the GAIN to 40% to start. Set the THROTTLE DATA MODE to Tx.CURVE.
The transmitter throttle curves are especially important in Rev.LMT mode. For hover, make sure your throttle curve is set WELL ABOVE what is needed to maintain hover rpm over the entire charge. A curve which starts at 0 percent (to allow the controller to arm) and then rises to and becomes a straight line at 75% all the way to maximum collective position works fine. For idle ups, run the curves as straight lines, 100% from full low to maximum collective. The goal of this set up is to have the system always limiting the head speed from over speed. You must set up in this manner to build sufficient so-called headroom into the system to allow for maintenance of programmed head speed over the entire charge. Actual head speed is set as usual in the transmitter’s governor software menu. My experience found the use of LIMITER MODE to be superior to GOVERNOR MODE, but please use whichever method works best for your application.