GATLING GUN FIRE MECHANISM SECTION 6 GATLING GUN FIRE MECHANISM

GATLING GUN FIRE MECHANISM Model one cycle of a Gatling gun firing sequence, ensuring proper barrel and firing synchronization. What’s in this section: Spline Creation and Manipulation Sensors IF Function Workshop 6: Gatling Gun Fire Mechanism

SPLINE CREATION AND MANIPULATION The SPLINE data element can be used to store x-y data in an MSC.ADAMS model. This data can then be referenced by MSC.ADAMS functions in other modeling elements. You can create and populate spline elements manually in ADAMS/View, or by importing data from an external file. Importing SPLINE data From the File menu, point to Import, and then select Test Data. Select Create Splines. Browse for an existing comma delimited file (*.csv).

SPLINE CREATION AND MANIPULATION (CONT.) Referencing 2DSPLINE data AKISPL(x,0,id,[iord]); [iord] is optional – it specifies the order of derivative returned by the function. CUBSPL(x,0,id,[iord]) Example use in a custom spring force function Potential Applications Nonlinear springs and dampers Driving motions from test data Nonlinear bushings Impulse force from test data Variable-pressure air spring (3D)

SPLINE CREATION AND MANIPULATION (CONT.) Referencing SPLINE Data (3D)

SPLINE CREATION AND MANIPULATION (CONT.) Referencing SPLINE Data (3D) (Cont.) The SPLINE reference functions will interpolate along both the x- and z-axes when a three-dimensional SPLINE is referenced (x is interpolated cubic; z, linear). Tip Use the SPLINE modification functionality in ADAMS/View to view the interpolation that each function will apply to your SPLINE. From the Build menu, point to Data Elements, point to Modify, and then select Spline. View as Plot.

SENSORS Overview A SENSOR statement senses a user-defined event and affects a set of simulation controls when the event occurs. Evaluate (and store) a user-defined expression (use SENVAL function) Generate additional output step at event Set output step size Terminate current simulation and stop/continue Set integration step size Restart integrator Refactorize Jacobian Dump state-variable vector

SENSORS (CONT.) EVALUATE keyword for SENSOR Statement The SENSOR element has an additional keyword, EVALUATE, which takes a function expression or user-subroutine values (for SEVSUB) as its argument. There is an associated measure, SENVAL(senid), in the expression language. The purpose of this statement pair is to evaluate the EVALUATE expression whenever the sensor triggers. The resulting value is the value of SENVAL(senid) until the next time the sensor triggers. Example 1 This is an example of how you could store a computed value into a variable at time sensed during solution. With this sensor, when TIME equals 5, ADAMS/Solver uses the DY function to measure the distance between MAR/3 and MAR/2 and stores that distance value in VARIABLE/4.

SENSORS (CONT.) EVALUATE keyword for SENSOR Statement (Cont.) Cautions Example 2 This SENSOR statement counts the number of times function AZ(22,11) passes through pi/2. The VARIABLE statement defines a variable equal to the count. Cautions If the SENSOR/id does not have the EVALUATE argument, SENVAL(id) returns zero

SENVAL() Example: SENSOR compares value of itself via SENVAL(); able to capture ‘MAX (or MIN) ever seen’.

IF FUNCTION Overview The arithmetic IF function allows you to conditionally define a function expression. IF (expression 1: expression 2, expression 3, expression 4) ADAMS/Solver (FORTRAN) evaluates expression 1. If the value of expression 1 is less than zero, the arithmetic IF is evaluated using expression 2. If the value of expression 1 is zero, the arithmetic IF is evaluated using expression 3. If the value of expression 1 is greater than zero, the arithmetic IF is evaluated using expression 4.

IF FUNCTION (CONT.) Cautions When using an arithmetic IF function, ensure that the resulting function is continuous. If the function is discontinuous, ADAMS/Solver (FORTRAN) may fail to find a solution when it encounters the discontinuity. Even the greater reliability can be achieved if continuity of the first derivative can be ensured. Much greater care is required when using an arithmetic IF function to define a MOTION element. In this case, a continuous second derivative is also required. The use of arithmetic IF functions to define MOTION is best avoided.

IF FUNCTION (CONT.) Examples This function is interpreted as follows: If the radial velocity between Markers 20 and 31 is less than or equal to zero, the value of SFORCE/1 is zero. If the radial velocity between Markers 10 and 31 is greater than zero, the value of SFORCE/1 is -6*VR(10,31)**3.

WORKSHOP Complete Workshop 06: Gatling Gun Fire Mechanism