When defining a guidance system, we refer to a set of commands sent to the platform controller in order to make it carry out a certain task. This task could be follow a line, climb, land, hold one of its states at a certain value and so on.
In Veronte Pipe, it is possible to combine a series of guidances to create custom flight phases that will make the aircraft perform in a given way. For example, to create a Take Off phase, the guidances to be included could be a “Runway”, which defines a line over the runway to make the aircraft follow it, and a “Hold” that will keep the roll and pitch angle at zero to keep the aircraft level when it is accelerating on the runway.
Each Guidance contains a different set of parameters to be configured. All of them are presented as follows and its parameters are explained in detail.
The Hold guidance is used to introduce in the control system a desired variable with a certain value especified by the user. It is different than the other guidances, where for example the user determines a path to follow and the desired heading that makes the aircraft follow that path is not determined by the user, is determined by the path.
There are 4 ways in Pipe to determine how the variable is introduced in the controller in a Hold Guidance.
- None: a simple value is specified. As soon as the aircraft enters in the phase that has this hold guidance, the desired variable will take the value specified in this option. It is possible to define a constant value for the desired variable, or take the value that another variable has at the instant when the aircraft enters in that phase. Example: to make the aircraft keep the heading that it has when changing to a phase, select Desired Heading as the hold variable, and choosing heading.
- Time (Ramp Time): in this case, the desired variable introduced in the controller will take first the value (or the variable) introduced. After a certain time established, the variable reached the value (or variable) indicated.
- Slope (Ramp Rate): the same case as before, but know instead of the time between the two values of the ramp, the slope of that ramp can be indicated.
- Ewma (TAU): the variation between the start and final points is exponential.
The climbing guidance is used to make the aircraft climb from the start of the phase to another altitude. Commonly, this guidance is used after the take off to climb from the ground to the cruise altitude, but can be used for the proposit desired by the user.
All the parameters that appear in the previous figure (and can be modified) are the ones that rule the climb of the aircraft. They are detailed as follows:
- Line attraction: is a parameter that determines how the platform is attracted to the line that determines the path that has to follow. The value is the distance perpendicular to the path at which the vehicle will try to go back to the line with a heading of 45 degrees with respect to it. When it is closer than this distance the heading angle is lower, and bigger when the distance is higher. So a small value will make the aircraft go to the line at high angles during more time (because the distance of 45 degrees is now small), and a big value implies less attraction because the platform will go to the line at smaller angles than 45 degrees from a bigger distance.In the climbing phase the path is not directly indicated by the user as in the cruise (which is defined in the Mission menu) but there is still a trajectory whose parameters are detalied later in this section, so this value is as important as it is for the Waypoint following route. The common values of the line attraction are between 20 and 40 for airplanes, and 15 for multicopters. This parameter only has to be changed by advanced users.
- Acceleration proportional gain: this parameters is releated with a new control system that Embention is developing in which elevator and thurst work side by side in both the pitching and thrusting.
- Set limit acceleration: here are set the limits for deceleration and acceleration of the platform when it is climbing. Normally the limits set here are due to structural stability and to avoid extreme movements of the vehicle.
- Set Speed: this option sets the speed that the vehicle will have during the climb. It could be IAS (indicated airspeed) or Speed (Ground Speed). Normally, the IAS is used for airplanes and the Speed for multicopters. The option waypoint reach is used to indicate the speed at which the platform will reach the waypoints, so it will travel along the path with the speed indicated in the option “Cruise”, then it will decelerate or accelerate to the speed indicated in”Waypoint Reach” and then it will go back to the cruise speed.
- Hover Gain: those gains are used by the multicopters when it is hovering over a certain location. When the vehicle is moved from that hover point because of a wind gust, it will try to go back to that location using the gains specified here.
- Route: here are set the parameters that define the route followed by the aircraft when is climbing until a certain altitude.
- Flight Path Angle: angle at which the aircraft will climb.
- Radius: the climb is done in two segments. First a straight flight and then a circular route that allows the climb to be done in a reduced area. This parameter indicates the radius of that circular route.
- Distance: is the distance from the point where the aircraft enters in the phase which contains the climbing guidance, to the start of the circular climbing path.
- Sense of arcs: here is defined the sense of rotation of the aircraft in the circular route.
The yaw guidance is used in multicopters to indicate the behaviour of the platform in the yaw axis. This option is normally used during the cruise phase of the multicopters, because the route can be carried out with the aircraft without rotating in the yaw axis, or rotate it to point its longitudinal axis parelel to the path.
The modes available in the yaw guidance are:
- Current: the multicopter will keep the yaw angle that has when enters in the phase that contains this guidance.
- Fixed: the yaw is kept at a constant value indicated by the user.
- Heading: the yaw takes the value of the heading when the aircraft enters in this phase.
- Position: the yaw of the multicopter will be rotated so its longitudinal axis is always focusing a point defined by the user in the menu shown in the previous figure (absolute or relative).
The landing guidance is used to create the route that the airplane will follow to land in a certain runway (defined by the user).
- Line attraction: as in the case of the climbing, is a parameter that determines how the aircraft is attracted to the line that it has to follow. A higher value produces a lower attraction.
- Acceleration proportional gain: the same as in the climbing.
- Set limit acceleration: establish a limit for acceleration and deceleration.
- Set speed: determine the speed of the airplane during the landing phase. In some cases, if the aircraft does not have flaps or airbrakes it will be impossible for it to decelerate and achieve the established velocity, so that is something to be considered during the operation.
- Route: the route section of the landing guidance defines the route that the aircraft takes to go from the point when this phase is commanded, to the point where it touches the ground. The landing route has two parts: the first one consists on a descending loiter used to descend from the cruise altitude to an altitude where the manoeuvre of heading the airplane towards the runway direction and make it touch ground can be performed, the second part is the path that takes the aircraft to ground (to the runway). If the airplane starts the landing phase at an altitude at which it can perform the landing manoeuvre without the descending loiter, this one will not be performed, so the descending circular route will automatically be done when the aircraft is at a great height. The parameters that define the landing route are presented as follows:
- Loiter descending: center point of the loiter descending route. It is indicated just by clicking on the map.
- Margin: percentage of the runway distance at which the airplane will try to touch the ground.
- Flight path angle: angle of the descent during all the landing phase.
- Horizontal distance for descending: distance between the head of the runway and the center of the turn made to head the airplane towards the runway direction.
- Radius of head turn: radius of the turn made to head the airplane towards the runway direction.
- Radius of helix: radius of the loiter descending made by the aircraft to reach an altitude suitable to perform the landing manoeuvre.
The following figure details schematically all the parameters detailed previously.
Finally, in the landing the user has to define the runway. There are two different ways to indicate which will be the runway for the landing phase. The first one is to define directly on the map the 2 points. With (1) the user clicks over the map to indicate the start of the runway (2 in this case). The end point is created as the start but selecting now (3). The direction of the landing is indicated with the arrows shown in the figure. The Auto option takes a direction according to the position of the aircraft when entering in the landing phase (it chooses automatically the shortest landing path).
Landing Guidance Panel
The other way of indicating a runway is to select the desired one from the Veronte Pipe database.
The cruise phase is used to make the aircraft follow a determined route created by the user in the Mission menu. This is the principal use of this guidance mode, but it can also be used to make the aircraft go to a certain location (waypoint) without indicating the full route, so in general is a guidance used to command a movement to be done by the platform. Some examples will be detailed later, by firstly all the parameters that define the cruise guidance are detailed.
- Line attraction: is the same parameter as the one explained in the climbing guidance.
- Patch: in Pipe, a path is defined as the line between two waypoints. This option is used to force the aircraft to go to a certain patch when entering in the cruise phase. For example, it the Mission created by the used has 4 lines (a square), this option could be used to force the aircraft to take one of the lines (patch) as the first line to cover during its operation. In the previous figure, if the line that starts at the yellow waypoint wants to be taken as the first one of the route, clicking on 1 will allow the user to select that patch (a patch is selected by choosing its first waypoint, taking into account the direction). The numeration of the patchs is related with the order in which they were created. If the waypoint selected in the “Patch” option is alone (is not in a line), the aircraft will go to this point continuosly, so it will loiter around it. To sum up, if the path selected is part of a route with more than one line, the platform will first go to this line and the it will continue with the route. On the other hand, if the path selected is a single point, the vehicle will loiter around it (or hover in the case of a multicopter).
- Acceleration proportional gain: explained in the climbing guidance.
- Set height mode: the height mode indicates how the aircraft will perform the route. If the 2D mode is selected, the platform will follow the predifined route without taking into account the altitutde of the waypoints, it will keep the altitude that it has at the moment it enters in the cruise guidance. The 2.5D mode is used in multicopters only, in this case the vehicle will climb vertically to the altitude of the first point of the route and then it will begin it. Finally, in the 3D mode the vehicle goes from the altitude at which it enters in cruise mode, to the beginning of the route in a diagonal trajectory (it follows a 3D trajectory that connects the two points).
- Set limit acceleration: the acceleration and deceleration can be limited to increase the safety of the operation.
- Set speed: here is set the velocity that the aircraft will have during the cruise phase. The speed can be defined as IAS or ground speed.
- Hover Gain: explained in the climbing phase.
The VTOL guidance (vertical take-off and landing) is used in multicopters for the take-off and landing operations. This guidance consists on the creation of a vertical line that starts at the point where the platform enters in this guidance.
- Line Attraction: parameter defined in the climbing guidance.
- Acceleration proportional gain: parameter defined in the climbing guidance.
- Set limit acceleration: limit the values of the acceleration and deceleration during this guidance.
- Set Speed: here is set the speed that the multicopter will have while it is going up or down.
- Hover Gain: explained in the climbing guidance.
- Route: this parameters are used to indicate the route followed by the multicoter during the take-off and landing. The path consists on a vertical line from the point where the vehicle enters in this phase. In the case of a take-off, the line goes from the ground to an altitude indicated by the user. This altitude can be relative (starting from the initial point of the route) or an absolute altitude (MSL,AGL or WGS84). As an example, in a take-off operation, an altitude of 10000 meters can be indicated as the final point of the route, so it is sure that the multicopter will keep climbing until another phase is commended (via automation or manually). The same procedure is done in the landing, indicating a big relative distance (for example 100 meters from the starting point) so it is sure that the vehicle reaches the ground, and an automation is set to stop the platform when it touches the surface.
The runway guidance is used to create a linear path along the runway that is followed by the aircraft. This command is normally used in the take-off phase, where the airplane is wanted to keep the direction of the runway while is accelerating until the lift-off point.
The runway is created as in the Landing guidance. Just clicking over the map to select the start and end points will create the path over the runway. Besided there are three more values to configure:
- Line attraction: value that indicates how the vehicle is attracted to the line. A bigger value implies a lower attraction.
- Speed: ground speed that the aircraft will have while travelling along the path that defines the runway.
- Acceleration proportional gain: parameter defined in the climbing guidance.
The guidances contained within Veronte generate a series of variables that are later used in the control system as the input of the PIDs. In the Hold guidance is the user the one that selects the desired variables to be generated. The guidances which create a route that is followed by the aircraft generate the following variables:
- Desired Heading
- Desired Flight Path Angle
- Desired Front GS
- Desired Ground Speed Down
- Desired Lateral GS
- Desired Vertical Error
- Desired Along-Track Position Error
The yaw guidance produces the Desired Yaw only, and finally the runway guidance generates the Desired Heading and Desired Yaw angles.