About Evaluation Methods

Mechanism Design and Mechanism Dynamics > Mechanism Design > Creating Mechanism Models > Measures, Graphs, and Evaluation Methods > Evaluation Methods > About Evaluation Methods

When you define dynamics measures, you can choose from several evaluation methods. The graph of the measure and the quantity displayed under Value on the Measure Results dialog box are different for different evaluation methods. These options are not available for loadcell reactions or for the cam reaction measure slip component.

Evaluation Method	Value	Graph
Each Time Step	Value of the measure at the last time step	The value of the measure, calculated at each time interval of the analysis
Maximum	Maximum value over analysis	The maximum value attained so far in the analysis
Minimum	Minimum value over analysis	The minimum value attained so far in the analysis
Integral	The integrated value of the measure at the last time step	The integration of the function up to a given point in time
Average	The value of the average at the last time step	The average value of the measure up to each time step of the analysis
Root Mean Square	The root mean square value at the last time step	The root mean square of the measure up to that point at a given time step See the example for a comparison of root mean square and average graphs.
At Time	The value of the measure at a specified time	The value of the measure represented as a bar at the specified time

For Each Time Step, you can define your measure after you run the analysis. For the other methods, you must define the measure before running an analysis. If you define a measure with Maximum, Minimum, Integral, Average, Root Mean Square or At Time evaluation methods after you run an analysis, the Status column on the Measure Results dialog box reports Not computed when you select the analysis.

The values found are reported at each interval at which calculations are performed. These are not necessarily equivalent intervals. Intervals on a measure results graph are not the time intervals that are used to calculate results. The software adjusts its calculations to ensure accurate results. Consequently, your specified intervals may not be used for a dynamic analysis.

For analyses in which the quantities measured are changing quickly, the sampling rate is greater. For example, to accurately calculate an impact event, the software uses a greater sampling rate close to the time that the impact occurs. The intervals you specify when you define a dynamic analysis are used as the maximum time interval step size. The actual interval may be smaller, depending upon the demands of the calculation.

The assembly tolerance settings are used to determine the time intervals it uses for analysis calculations. The lower the tolerance, the more precise the calculations.

To verify the accuracy of a minimum or maximum value, rerun the analysis at a lower (more precise) tolerance and repeat until the reported minimum or maximum values do not change significantly from run to run.