Force Feedback Trimming

I just saw that FFB is now implemented. Unfortunately the implementation of trimming is wrong in the same way it was wrong with the MiG-21.

 

When I trim nose-up in the Viggen, two things happen simultaneously:

1. The force-center moves back. If the stick is held in place, a backwards stick force builds up. If the stick is let on its own, it will wander aft (and in the process pitches up the aircraft). This is correct.

 

2. The aircraft's controls (virtual stick, control surfaces) move aft, pitching up the aircraft. This is not correct! Even if the stick is being held centered while trimming, the aircraft still pitches up in game. That behaviour is wrong, as trimming should only affect the forces acting on the physical stick, not move the virtual stick.

 

In effect this means that while trimming with FFB you cannot apply the appropriate techniques (hold stick to get the attitude you want, then trim away stick forces). Also the amount of trim applied doubles (physical displacement of the stick due to FFB forces + virtual displacement of the stick). This is exactly the same problem that has plagued the MiG-21 for years (and that has been reported many times). As a reference for the correct implementation of FFB trimming, see Belsimtek's F-86 or F-5E for example.

Now I'm really curious which of the 2 modules gets this fixed first

 

I've been reporting this in case of the MiG-21bis like a gazillion times, practically after every single update, no matter how tiny it was

 

Meanwhile, Belsimtek sorted the very same issue out for both F-86 and MiG-15

The thing is the Viggen with the RB-75 pretty much is desperate for a trim and something to stabalize the AC so it points in the correct direction. Looking down the telescope while wobbling around and attempting to hold it steady is ridiculous. Autopiot is no help in this regard as it only faces in one direction and more often than not, not at the target way point. It needs to be fixed ASAP because it detracts from the realism a great deal.

I came here to post the same thing with pretty much the same words. I'm posting anyway as confirmation that this issue needs a fix. Same thing happened in the Mig-21 and the F-86 before.

The issue for us is that none of us have a ffb stick, so we are programming in “the blind“. We will try to fix this asap.

If that's the case, we'll be happy to report whenever the fix is out. No hurries.

The issue for us is that none of us have a ffb stick, so we are programming in “the blind“. We will try to fix this asap.

I was thinking about the difficulty of fixing this without a ffb stick and thought of something that may be useful for you. A golden rule when programming a ffb is that no matter what the trim (or autopilot for example) is doing, if the physical stick is not moving the virtual one shouldn't move. And vice-versa, if the the virtual stick moves the physical stick should.

Those differences between the virtual stick position and the real one exists to account for the limitations of the mechanical sticks (non-ffb sticks) and don't apply to ffb sticks.

Hope it helps.

And vice-versa, if the the virtual stick moves the physical stick should.

Accounting for the experience with the updated Mig-29, that part is better left out. The autopilot in the Mig-29 is unusable right now because the stick moves by itself when the autopilot is on, but it's so jerky (due to limitations of the FFB tech) that the plane doesn't stabilize.

Have you tried FFB inversion option?

 

I'm not sure what you are referring to. If you mean the axes swap/inversion at the FFB options, I have everything correctly setup. I've been using FFB since forever.

 

I'll try to explain better. When the mig-29 got its PFM update, I noticed that when the autopilot is controlling the plane the stick moves by itself, both the virtual and the real one (my ffb joystick). But I soon realized that the real joystick movements were not accurate enough to work as intended and tends to oscillate more and more.

Maybe it could be corrected with some smart control function that takes into account the physical system the FFB joystick is, but I don't think it's worth the effort. It would be more convenient that when the autopilot takes control of the aircraft the joystick input is bypassed, (like I guess it's done when the user doesn't have a FFB joystick) and ignore the position of the joystick.

Hm... What the significance to have FFB joystick in that case? Correct feedback from a game to real stick - that is the sense of FFB device

I'm referring exclusively to when the Mig-29 autopilot is on. Apparently, the autopilot controls the plane changing the position of the stick itself. The physical FFB joystick also moves. But consumer FFB technology is not smooth and accurate enough to provide stable control of the aircraft and it swings side to side more and more and out of control, rendering the autopilot useless.

So, while a cool feature and how it should be in theory, in practice, it isn't viable.

Just took the Viggen out for a spin and realised that the FFB trim on the pitch axis still is wrong (or is it again?)

It works just fine in the Tomcat but not in the Viggen.

 

edit:

Got it solved - but I had to setup the FFB different than for the F-14

Edited December 22, 2019 by golani79

Accounting for the experience with the updated Mig-29, that part is better left out. The autopilot in the Mig-29 is unusable right now because the stick moves by itself when the autopilot is on, but it's so jerky (due to limitations of the FFB tech) that the plane doesn't stabilize.

 

I think this is just a bug in DCS with the MiG-29, not any limitation of consumer FFB technology. The Su-27 autopilot works the same way (the stick physically moves) and has no issues for me in DCS with FFB (I use the Sidewinder Force Feedback 2), but I have the same issues as you with the MiG-29.

Just took the Viggen out for a spin and realised that the FFB trim on the pitch axis still is wrong (or is it again?)

It works just fine in the Tomcat but not in the Viggen.

 

edit:

Got it solved - but I had to setup the FFB different than for the F-14

Solved? How?

Solved? How?

 

 

Swap Axis and Invert Y is working for me

 

 

I appreciate the reply, but I'm afraid that the topic of the thread is different. It's about the trim acting both as non-FFB trim and FFB trim simultaneously when FFB is enabled. You can easily notice it by using the trim while keeping the joystick centered. The virtual stick in the game moves with the trim despite the physical joystick being held in the same position. Only the force should change AFAIK.

These issues are still here with us in 2023:

- Viggen is the only aircraft in DCS that requires "Invert Y" to be selected. A minor issue, as it only requires ticking that checkbox in DCS options.

- The virtual stick keeps moving when trim is applied. So we have both force trim and regular non-FFB trim acting together on top of each other. This is fixed in the Tomcat with "Use FFB Trim Implementation" option in the Special Tab, so Heatblur has the required know-how to make it work. But there is no such option for the Viggen.

On 9/2/2023 at 9:24 PM, some1 said:

These issues are still here with us in 2023:

- Viggen is the only aircraft in DCS that requires "Invert Y" to be selected. A minor issue, as it only requires ticking that checkbox in DCS options.

- The virtual stick keeps moving when trim is applied. So we have both force trim and regular non-FFB trim acting together on top of each other. This is fixed in the Tomcat with "Use FFB Trim Implementation" option in the Special Tab, so Heatblur has the required know-how to make it work. But there is no such option for the Viggen.

Hey! Thank you for the heads up. I tracked it internally for the team to look into.

Woah that may have fixed the Viggen for me and the major confusion I was having with it's AP. However the Tomcat I still cannot figure out ACLS or even the basic AP ALT Hold as it doesn't seem to care how well I trim the jet, the stick just doesn't want to let the AP keep control.

Works fine in all the FC3, A4, 21, etc but the Viggen and Tomcat have been AP nightmares with FFB Sadly even though they feel fantastic otherwise. Just doing that axis swap Seems to have fixed my issue with the Viggen, but the Tomcat is still frustrating me. 

From what I can sort of tell. Just trying to get the AP to Alt hold, If I sort of put pressure just a hair on the stick I can feel it pushing back as it maintains level flight, but if I let it go at all, or put pressure on it just a little to long, the AP just seems to let go and stops holding Alt. It's really strange like the AP has only the weakest grip on the Axis and any slight pressure over what it feels like holding it just gets overpowered. 

Have the same issue, Viggen FFB trim moves the stick virtually in game, as opposed to the tomcat, where FFB trim works great.

It seems to mess with the autopilot as well, when the autopilot needs to trim the aircraft, it appears to create inputs itself cant handle, and pushes the aircraft off course/down into the sea.