Tuning closed loop speed mode I was looking through the Vector forums and there seems to be a lot of confusion around Closed Loop throttle modes. It isn’t broken! It just has limitations that we have to abide by. The Vectors closed loop speed system may not be perfect as some think it should be. There just has to be some form of compromise, so that all the Vectors functions can interact without losing any of them. But if we work within the parameters Eagle Tree have given us. It can be made work with no issues that I, or the guys I fly with have found. Short of an Air speed sensor failure. Go to the stick menus under – Safety/RTH/NAV/Configuration > Close Loop Speed control menu *Auto Navigation Speed *Min Speed for 2D+Speed Modes *Max Speed for 2D+Speed Modes *Speed Ctrl Throt Gain Proportional *Speed Ctrl Throt Gain Integral *Minimum Closed Loop Throttle *Loiter Speed (0=Not used_Auto Spd) There are 5 settings that have to be set and tuned correctly for the Closed Loop Speed mode to function correctly. If any of these are omitted, it will be unreliable. 1) *Min Speed for 2D+Speed Modes *Max Speed for 2D+Speed Modes These settings dictate the Min and Max Speed at which 2D Closed Loop Speed modes will operate between. While in the Cruise Control Flight Modes. (2D+S – 2DH+S) 2) *Speed Ctrl Throt Gain Proportional *Speed Ctrl Throt Gain Integral These settings control the P & I loop gain between the throttle and Speed sensor. *Proportional Gain : It dictates how aggressively the throttle will Increase or Decrease to changes in the Air or Ground Speed. *Integral Gain : It dictates how Tight or loose; Closed Loop Speed mode will act upon the speed setting that the user has selected. Higher gain = less speed drift, above or below the selected speed. 3) *Minimum Closed Loop Throttle : (Zero by default) This function sets the Minimum throttle set point that Closed Loop Speed control will reduce the throttle too; while attempting to reduce the planes flying speed. 4) *Disable Altitude Hold when Amps are lower than: 5) *Minimum Ground Speed : This function is an essential requirement for use in conjunction with the use of an Air Speed sensor, when using the Closed Loop Speed function. The reason being. The Closed Loop Speed function will set the planes speed according to air speed. So if the plane is encountering a strong headwind, the throttle will be reduced to maintain the users air speed setting. The drawback to this is that the ground speed will drop off. And the plane may take a long time to return. By setting the minimum ground speed value to a comfortable speed for your planes airframe. You will ensure that the planes Ground Speed will not drop below that value; even in a strong head wind. Start of tuning A) All tuning of Close Loop Speed control should be done in 2DH+S Cruise flight mode. With Auto Navigation Speed left at Zero - Disabled B) In the Configurator or Stick menus. Select the Min and Max Speed that you wish Closed loop Cruise throttle to maintain your planes speed between. e.g. Min. 50km – Max. 55km C) Choose a Minimum Close Loop Throttle value. To start with I would set it to around 1300uS (30%) This value may have to be changed later after flight information is gathered. D) On your OSD. Be sure to have the Throttle OUTPUT value displayed as a reference. You will also require - Altitude, Air Speed, Ground Speed and Main Pack Current. E) The default P & I gains are far too low for reliable use with any model; small or large that I have tuned. (P=100 and I=30) Smaller planes with less drag will generally require the Integral gain to be set higher, due to the models lower inertia. While larger planes with more drag will generally require the Integral gain to be set lower, due to their higher inertia. The Proportional gain is more a combination of the models thrust verse weight. The less thrust your motor prop combo produces; the more Proportional gain you will generally require. I would start with a base of – P = 120 and I = 45 for a model of 1.8KG and up. P = 130 and I = 70 for a model under 1KG. F) It is ideal to have an in built microphone on board your plane for this setup. So you can hear the responsiveness of the throttle increasing and decreasing. Or if not; then do the setup within ear shot of your location. ************************************************** ************************************************** ************************************************** ********* The tuning is done with the Integral gain first. Based upon the above mentioned Proportional gain being good enough for a start point. 1) Choose a day that has less wind. Take off and get some altitude. Then flick your Mode or Submode switch to select 2DH+S. Let the plane fly level until it gets towards the Maximum Speed that you set earlier under the Close Loop Speed Cruise mode. Then apply a small amount of elevator UP; so that the nose will pitch up and start to climb. Watch you’re Air Speed and Throttle Output values as the plane starts to climb. If the Air Speed decreases noticeably, below the Minimum Speed set point; before the throttle value starts to rise from the value it was cruising at. Then the - Speed Ctrl Throttle Integral Gain needs to be increased. In the same way; if the Speed control is loose at the bottom end, it will also be loose at the Top end of the speed range. 2) Enter the Close Loop Speed stick menu and start increasing the Integral gain value by 10 at a time. Then go through procedure #1) again until the throttle starts to increase at the instant that the speed decreases below the Min. set value. Or the throttle decreases as the speed increases above the Max, set Value. This will ensure that it holds the set speed tightly and reacts as soon as any elevator is applied by the Auto Navigation system later on. e.g. Higher I gain = less speed drift from your setting point If the gain set too high. It will possible cause ESC and motor hunting; while trying to maintain the correct speed setting. This may be acceptable in some applications when precise speed control is needed. But it maybe to the detriment of your ESC over time. 3) Once the Integral is tuned. You can then run through the same tuning procedure with the Proportional gain this time. When tuning the Proportional gain. You want to listen to how aggressive or sluggish the throttle is responding to the speed changes, when they move outside of the speed range that you chose. e.g. Higher P gain = faster throttle response. If this gain is set too high. The throttle will Max. out at the Climb throttle value or reduce the throttle to the Minimum close loop throttle value; every time a speed change is implemented. So watch that you don’t take the P gain too high. So that you get smooth variations on Closed loop speed control. 4) The next step requires the current drain setting for, Disable Altitude Hold when Amps are lower than – to be set at a value that is LOWER than the amount of current your motor is drawing; at the value you give to Minimum Closed Loop Throttle. This is an important step. Otherwise, when the Closed Loop throttle mode reduces its throttle back to slow the plane. The motors current drain will drop below the Minimum Amps value that maintains altitude hold. This will cause the Closed Loop throttle to fight its altitude hold set point. And it can end up losing altitude; all the way to the ground. If, Disable Altitude Hold when Amps are lower than – is set to 3amps. Make sure that your Minimum Closed Loop Throttle, percentage value. Draws more current than 3amps. e.g. Minimum Closed Loop Throttle @ 35% = 3.5amp Then set Disable Altitude Hold when Amps are lower than @ 3amps. 5) Once these settings are complete. You can now turn on Auto Navigation Speed to your desired speed set point and use it. The tuning above was predominantly for use with an Air Speed sensor. But The GPS ground speed sensing can be tuned in the same way. The main difference between the two is – Air Speed sensing will reduce the motor speed into a head wind, to maintain a constant air speed. And will increase the throttle while going down wind. To stay ahead of the wind speed and maintain good airflow over the wing. So the plane will have adequate lift; when a climb out is required. While GPS ground speed will Increase the throttle into a head wind to maintain ground speed. And will reduce the throttle while going down wind. This is not ideal. But if the user knows their airframe well enough; and sets the Minimum Closed Loop Throttle at a value that will produce adequate thrust. So that the plane will still produce enough lift to climb out when required. Then GPS Ground speed sensing is safe enough to use in mildly windy condition. I would only use it with 2DH+S cruise modes when using GPS speed sensing. And not use it with Auto navigation Speed, especially at any distance. When wind may have picked up and could cause a problem. One thing you can do to help figure out what the throttle values should be is this. Go into the advanced OSD setup and put Altitude, Speed and Climbrate - Climbrate and Servo/Motor Outputs - Throttle onto the OSD. Then go fly the plane with stabilization turned off and trim it for level flight. Incorporate trims. Then: Slowly reduce the throttle until it stalls. Note the airspeed and throttle value just above stall. Adjust the throttle to your comfortable cruise speed. Note the airspeed and throttle value. Climb at your desired climb rate. Note the throttle value. Descend at your desired rate, with throttle set just at or above where it was when it stalled during level flight. Note the throttle value and current draw. Now you can translate those throttle values (I think it shows %) into the 1000-2000uS scale. Set your Auto Navigation Speed to your cruise airspeed. Set your Min speed for 2D+ to just above your stall speed. Set your Minimum Closed Loop throttle to a little above what it was when it stalled (it should only be used while descending so this should be safe. It exists mainly to keep it from cutting the throttle completely and triggering Disable Alt when amps below X). Set your Disable Alt when amps below X value to 1-2A below the minimum you saw while descending. That should mostly cover it. Having the info on the OSD means you won't have to keep guessing whether minimum throttle value is too low or too high.