Intercept

STK Premium (Air) or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

Capabilities Covered

This lesson covers the following STK Capabilities:

  • Aviator Pro

Problem Statement

The Intercept strategy is a horizontal plane strategy in which the aircraft attempts a forward quarter intercept on a moving object, guided to a constant target aspect or lateral separation.

Field Description
Target

Select a vehicle in the scenario that the aircraft will target during the maneuver.
Pos/Vel Strategies

Position and velocity strategies for the target object. The following strategies are available:

  • NoisyBrgRng - A noisy bearing and range strategy.
  • NoisySurfTgtPosVel - A strategy that periodically generates noisy position, speed, and course updates for a constant altitude target.
Tgt Pos/Vel Resolution

The frequency of sampling of the target object's position and velocity; interpolation of the object's position will be performed between sample points.

The lowest recommended value for this property is 0.1 sec, but the lowest possible value is 0.001 sec. At the lowest value, STK's Aviator capability will use the native position and velocity of the target object; this can result in dramatically slow performance when the target object is another Aviator aircraft, since STK is performing double integration calculations in such a case.
Intercept Mode

Select the guidance principle that the aircraft will use.

  • Target Aspect - maintains an approach angle relative to the target until intercept.
  • Lateral Separation - guides to a specific distance from the target; this gives the aircraft room to turn before intercepting.
Target Aspect If the Intercept Mode is Target Aspect, define the angle relative to the target that the aircraft should maintain until intercept. Valid values are from -89 to +89 degrees.
Lateral Separation If the Intercept Mode is Lateral Separation, define the distance from the target that the aircraft will guide to before intercepting.

Stop Time to Go

Select the Use Stop Constraint check box to apply a "time to go" stopping condition. If closure is required for the maneuver, then this stopping condition will end the procedure at a specified length of time before closure stops; enter the desired value in the Stop Time to Go field.

Stop Slant Range

Select the Use Stop Constraint check box to apply a range-from-target stopping condition, which will end the procedure at a specified range before the intercept occurs; enter the desired value in the Stop Slant Range field.

Maneuver Factor

The Maneuver Factor defines a dimensionless factor that influences how tightly or gently the aircraft will maneuver. At its most aggressive setting, the factor will force the strategy to achieve the specified performance values; at its most gentle setting, the factor will allow the strategy to tolerate the most deviation from those values.

Control Limits

Select a method to define the control limits (which constrain performance) of the aircraft during the maneuver.

Table - Control Limit MethodsClosed

Field Description
Use Accel Perf Model

Use the control limits specified in the current acceleration performance model.
Specify Min Turn Radius The minimum radius of a turn arc that the aircraft can perform.
Specify Max Turn Rate

The maximum rate at which the aircraft can turn.
Specify Max Horiz Accel The maximum acceleration, in the horizontal plane, that the aircraft can achieve.

Closure Mode

Select a rule that defines the closure requirement for the maneuver.

  • Not Set - the maneuver will continue whether or not the aircraft is closing with the target.
  • Closure Required - the maneuver will stop if closure stops for any reason.
  • High Off Boresight(HOBS) - the maneuver will stop if closure stops, unless the aircraft is within the HOBs Max Angle Off and HOBs Angle Tolerance values; for example, this mode allows you to perform an intercept maneuver to a target that is initially behind the aircraft.