SECTION 4 WASHING MACHINE

WASHING MACHINE Create a simple controller to drive the washing machine spinner at a given speed. What’s in this section: Tracking System Velocities Implementing Simple Controllers Computing the Derivative of a Run-Time Function Batch-Mode, Stand-Alone ADAMS/Solver FILE Command Workshop: Washing Machine

TRACKING SYSTEM VELOCITIES As with tracking system loads, there are several functions available in MSC.ADAMS that allow you to track system velocities throughout a simulation.

TRACKING SYSTEM VELOCITIES (CONT.) Where: I - The marker whose velocity is being measured. J - The marker with respect to which the velocity is being measured. Set J = 0, while still specifying l, if you want J to default to the global coordinate system. K - The marker in whose coordinate system the velocity vector is being expressed. Set K = 0, while still specifying L, if you want the results to be calculated along the x-axis of the global coordinate system. L - The reference frame in which the first time derivative of the displacement vector is taken. Set L = 0 or omit the argument if you want the time derivatives to be taken in the ground coordinate system (GCS). Note: Rotational velocities are reported from ADAMS/Solver (and, therefore, into your functions) in units of radians/[unit_time].

TRACKING SYSTEM VELOCITIES (CONT.) Make use of the Adams/Solver constants RTOD and DTOR for handy conversions. Example of VM vs. VR Functions

IMPLEMENTING SIMPLE CONTROLLERS With the use of differential equations and state variables, simple control systems can be modeled easily in MSC.ADAMS. Proportional-Only Controller Proportional and Integral Controller

IMPLEMENTING SIMPLE CONTROLLERS (CONT.) Example MSC.ADAMS Elements (PI Controller) ADAMS/View variables: ADAMS/Solver variables: Differential Equation: Force Function:

COMPUTING THE DERIVATIVE OF A RUN-TIME FUNCTION You can use an implicit DIFF to get the time derivative of just about anything. Because it references itself, it requires a two-step definition in ADAMS/View. For example, you need dataset language something like: VARIABLE/2, FUNCTION = WZ(2) DIFF/1, IMPLICIT, FUNCTION=DIF(1)-VARVAL(2) You can then access the derivative as DIF1(1).

COMPUTING THE DERIVATIVE OF A RUN-TIME FUNCTION (CONT.) Caveats Since this method writes a DIFF for MSC.ADAMS to differentiate, it will not work during a static or quasi-static analysis, as MSC.ADAMS forces the derivative of the DIFF to zero during these analyses. This method does not work when using a coordinate partitioning method for dynamics solution. The DIF1 function will always be zero if you're using an integrator such as ABAM. This will not work for kinematics (SIM/KIN). You have no error control in the differentiated signal, so the accuracy of the answer can never be ascertained. The only way to control the error is by controlling the step size. If you feed the differentiated signal back into the system it can cause integration difficulties.

BATCH-MODE, STAND-ALONE ADAMS/SOLVER What? String several simulations together and run them at once, serially, on one ADAMS/Solver license. Why? Large models can take a long time to simulate. Simulations run faster in stand-alone mode. Maximize your software investment using ADAMS/View, while running simulations in ADAMS/Solver externally.

BATCH-MODE, STAND-ALONE ADAMS/SOLVER (CONT.) How? General acf file syntax Line 1: Model name Line 2: Output name (same as model name if none entered) Line 3 through last line: ADAMS/Solver commands Last line: stop

BATCH-MODE, STAND-ALONE ADAMS/SOLVER (CONT.) Example master .acf: Example sim_01.acf:

BATCH-MODE, STAND-ALONE ADAMS/SOLVER (CONT.) Notes: It is important to delete or comment out stop to keep the simulation running. dummy.adm must be a valid MSC.ADAMS model. For more information, see the guides, Running MSC.ADAMS on Windows and Running and Configuring MSC.ADAMS on UNIX.

FILE COMMAND The FILE command either restarts ADAMS/Solver with a new model (MODEL) or executes a set of commands from a file (COMMAND). MODEL - Specifies a new dataset (.adm) file. ADAMS/Solver closes any output files from a previous simulation, and then completely restarts by setting the simulation time to zero and reading the new model. Next, ADAMS/Solver prompts you for a new command, as if ADAMS/Solver had read the model when first started. By default, the output files use the same base name as the model file. The optional OUTPUT_PREFIX argument specifies a different base name, if needed. COMMAND - Specifies a file containing ADAMS/Solver commands. ADAMS/Solver reads and executes the commands in the file. If the FILE command was interactive, ADAMS/Solver returns to interactive input when the command file is done. If the FILE command was in a command file itself, ADAMS/Solver returns to reading commands from that file. Command files can contain other FILE commands, nested up to 10 files deep. For more information, see the ADAMS/Solver online help.

WORKSHOP Complete Workshop 04: Washing Machine