SIMULATE
Usage
simulate (type="DYNAMICS", start=0.0, end=None, duration=None, dtout=None, steps=None, dsa="", start=None, print_increment=None, constraint_tol=None, implicit_diff_tol=None, onOutputStep =None, returnResults=False, output=”on")
Description
Argument
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Description
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type
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String
Defines the type of analysis to be performed. You must select one from:
type is optional. When not specified, type is set to "DYNAMICS"
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start
|
Double
Defines the starting time value for a simulation.
This attribute is optional. start defaults to 0.0 when not specified.
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end
|
Double
Defines the end time for a simulation.
duration and end are mutually exclusive. Only one of these must always be specified.
0 ≤ start < end
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duration
|
Double
Specifies the duration of the analysis. Thus end = start + duration
duration and end are mutually exclusive. Only one of these must always be specified.
duration > 0
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dtout
|
Double
Defines the time interval between consecutive output steps for plotting and animation output.
dtout is optional. Defaults to 0.01 when not specified.
When specified, dtout > 0
Note that the maximum integrator step size (HMAX) is set to the dtout if dtout is smaller than HMAX.
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steps
|
Integer
Defines the number of output steps to take between start and end.
steps and dtout are mutually exclusive. Only one of these must always be specified.
When specified, steps > 0.
dtout will be determined as (end-start)/steps.
Note that the maximum integrator step size (HMAX) is set to the dtout if dtout is smaller than HMAX.
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dsa
|
String
Defines the type of design sensitivity analysis to perform in conjunction with the analysis. When specified you must select one of:
| • | “Auto”: MotionSolve will determine the best algorithm to use for computing design sensitivities |
| • | “Adjoint”: MotionSolve will use the Adjoint method for computing design sensitivities. This method is recommended when there a lot of design variables and only a few responses. |
| • | “Direct”: MotionSolve will use the Direct Differentiation method for computing design sensitivities. This method is recommended when there a few design variables and but many responses. |
dsa is optional. When it is not specified, no design sensitivity analysis is done. Design sensitivity analysis can be expensive. So you should specify dsa only when you need it.
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start
|
Double
Currently unsupported.
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print_increment
|
Double
Specifies the frequency of output in terms of the integrator steps that have been taken. An output is performed when the function:
mod (integration_step_number, print_increment) = 0.
print_increment is optional.
| • | When specified, print_increment > 0 |
| • | print_increment = 1 generates outputs at every integration step |
| • | print_increment = n generates outputs at every nth integration step |
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constraint_tol
|
Double
Specifies the accuracy to which the simulation is required to satisfy the constraints (Joints, Jprims, Motions, etc.) in the model.
constraint_tol is optional.
| • | When specified, constraint_tol > 0 |
| • | When not specified, constraint_tol = 1.0e-4 |
Be careful when using constraint_tol.
| • | If the value is too small, simulations may take a significantly longer time. Simulations may even fail because they cannot satisfy the value you provided |
| • | If the value is too large, results will become noisy and inaccurate. |
| • | Change the default value only when you see that the results are noisy with the default value. Decrease it by successive factors between 2-5, see the effect of the change and then finalize a value. Do not decrease it by a large factor such as 100. |
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implicit_diff_tol
|
Double
Specifies the accuracy to which the implicit differential equations in your model are satisfied. These are the DIFFs in your model that have implicit = True.
The argument implicit_diff_tol is optional. When not specified, implicit_diff_tol = 1.0E-5.
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onOutputstep
|
Python function
This is a callback function that will be invoked when the solver hits an output step. It can be used for animation, live plots etc..
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returnResults
|
bool
returnResults is a boolean that, if True, causes the simulate command to return a data structure filled with results.
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Examples
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# Create a model
m = CreateStewartPlatform (output=”Stewart-Platform”)
# Do a static analysis first
m.simulate (type="Statics", returnResults=True)
# Then do a dynamic analysis
run=m.simulate (type="DYNAMICS", end=1.77, dtout=0.01, returnResults=True)
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