Re: [Flightgear-devel] control surface normalization
Hi, Pilots are taught to think in terms of pressure on stick not displacement. That is part of the reason that the F-16 is built the way it is. Thats OK, I agree, with one small change: pilots are not *taught* to think in terms in terms of pressure on stick. It is the natural way of sensing the aircraft. cheers, Gordan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] control surface normalization
Hi Jon, output laterally, on the pedals, and front/back on the stick. I think that's why the control law diagrams I have seen use pilot stick force as the input unit. One hundred percent of the control law diagrams I have seen that include pilot inputs use force. Once more, do not make general statements, based on a few examples. There are _many_ FCS's out there, not using input you just described. Fore examples, take a look at the Flight control and simulation, the book with examples that are completely based on F16 dynamics. cheers, Gordan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] control surface normalization
Hi, I agree with Norman. As long as control system is of concern, it is much better to use normalized units. surface deflections in degrees, and for good reason: it's natural, it's physical. From the point of view of JSBSim, normalized aerosurface Degrees are not natural, nor physical. We may argude that *radians* might be natural, but *not* degrees. This would lead us to another class of problems, what system of measurements is used? (I'm used to SI system) or what about input (I mean stick, pedals positions...)? Should the input be expressed in natural or normalized units? And about FDM itself, aerodata to be used are not unified... I have seen some using degrees as a control surface deflections units, and others using radians. What would you choose as a natural? I think normalized deflections *are* the best solution. just my 2$ :) cheers, Gordan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] control surface normalization
Hi, Control law block diagrams I have seen take stick input in pounds force (pilot inputs) and output in degrees to actuators. I've never seen one that output control commands to an aerosurface actuator in a range from 0 to 1. Have you? I have seen (and I've seen more than few) control law diagrams taking some generalized input (0-1 range), taking target speed, or attitude, or something,... but havent seen any, taking as a input force that pilot has to produce. Could you pls give some pointers? I'd like to take a look; it's never to late to learn something new :) As far as the force in the stick is of concern, I've seen exactly oposite situation: one has position of the stick, speed of the stick, dynamic properties of the linkage, and all data from FDM. Using those as input, force to be produced on the stick is calculated, and generated. By natural I mean that it's: the most commonly seen angular command unit for aerosurfaces, that it's what is used by the rendering routines to rotate 3D objects, that it completely specifies the commanded angular position without the need for a range (a range of 0 to 1 by itself specifies nothing without the definition of what the maximum is - there is no standard here for that), and much aero data is non-dimensionalised using degrees (or radians, see below). So, sorry, but based on the above description, for this application, yes, degrees are natural. Ok, I see your point as: natural -- most common. But IMO, degrees are wrong choice; in that case I would use radians. After all, isn't the standard that RAD-ians are used deep in CPU math unit, meaning the need for yet another conversion? best regards, Gordan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] control surface normalization
Hi Jon, I see you are really mad :) Look here at the X-15 data and FCS diagram: http://jsbsim.sourceforge.net/X-15Aero.html The USAF F-16 (Block 40) FCS diagram is the same way: stick force is the input. Same with Space Shuttle control Law diagrams. The JSBSim X-15 model simulates the X-15 control laws as shown in the link above. We take the -1 to +1 joystick input from FlightGear and turn it into a stick force, mapping to the force range described in Etkin's book as a sort of standard. These are 3 particular examples only. (about F16) AFAIK, it has nonmoving joystick, and force transducers, and it is normal for that plane to ise output from the transduced as a input. (about X15) AFAIK, it had 2 completely different (unconnected?) sticks, one for lower speeds (usual stick), and the other one (joystick actually) used for control in higer speeds regimes. Does it apply for both sticks? As I mentioned, these are 3 particular examples only, not a general rule . cheers, :) Gordan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] New autopilot
Hi, That has nothing at all to do with what I said. We are controlling individual control surfaces. Period. I don't think we should have subclasses for each desired action/process. Only each control surface type. Roll control ends up being intrinsically part of aileron control is it not? Pitch control is intrinsically part of elevator control, regardless of whether you are targeting speed or pitch (maybe you are confusing control targets with outputs?). The variable input sources and targets and how those are handled are all that needs to be configured per instance. Keeping it to that will make the configuration process much simpler. That's not entirely true. For example (AFAIK) B-727 uses ailerons as a means of roll control on lower speeds, and speed brakes on higher speeds. The other example might be MU-2, AC that relies entirely on speedbrakes for roll control (i.e no ailerons at all). ciao, Gordan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
