chrono::ChFunctionPosition_setpoint Class Reference

Description

A motion function p=f(s) where p(t) is an externally-provided sample, as a ZOH (zero order hold) of FOH (first order).

You must keep the setpoint p updated via multiple calls to SetSetpoint(), for example calling SetSetpoint() at each timestep in the simulation loop. It is assumed that one will later evaluate Get_p(), Get_p_ds() etc. in close vicinity of the setpoint (old setpoints are not saved), preferably ecactly at the same s, but in vicinity of s there will be extrapolation (after last s) and interpolation (before last s) according to: If in ZOH mode: value p will persist indefinitely until next call, derivative p_ds and p_dsds will be zero. If in FOH mode: value p will interpolate linearly from the previous value, derivative p_ds will be constant, p_dsds will be zero. If in SOH mode: value p will interpolate quadratically, derivative p_ds will be linear, p_dsds will be constant. Default: uses FOH mode. Use SetMode() to change it.

#include <ChFunctionPosition_setpoint.h>

Inheritance diagram for chrono::ChFunctionPosition_setpoint:
Collaboration diagram for chrono::ChFunctionPosition_setpoint:

Public Types

enum  eChSetpointMode { ZOH, FOH, SOH, OVERRIDE }
 Type of setpoint interpolation/extrapolation - zero order hold, first order hold, etc. More...
 

Public Member Functions

 ChFunctionPosition_setpoint (const ChFunctionPosition_setpoint &other)
 
virtual ChFunctionPosition_setpointClone () const override
 "Virtual" copy constructor.
 
void SetMode (eChSetpointMode mmode)
 Sets the extrapolation/interpolation mode.
 
eChSetpointMode GetMode ()
 Gets the extrapolation/interpolation mode.
 
void Reset (double ms=0)
 Use this to go back to s=0 (the SetSetpoint() function works only if called at increasing s values)
 
virtual void SetSetpoint (ChVector<> p_setpoint, double s)
 Set the setpoint, and compute its derivatives (speed, acceleration) automatically by backward differentiation (only if s is called at increasing small steps, most often s is time). More...
 
virtual void SetSetpointAndDerivatives (ChVector<> p_setpoint, ChVector<> p_setpoint_ds, ChVector<> p_setpoint_dsds)
 Set the setpoint, and also its derivatives. More...
 
virtual ChVector Get_p (double s) const override
 Return the p value of the function, at s, as p=f(s).
 
virtual ChVector Get_p_ds (double s) const override
 Return the dp/ds derivative of the function, at s.
 
virtual ChVector Get_p_dsds (double s) const override
 Return the ddp/dsds double derivative of the function, at s.
 
virtual void ArchiveOUT (ChArchiveOut &marchive) override
 Method to allow serialization of transient data to archives.
 
virtual void ArchiveIN (ChArchiveIn &marchive) override
 Method to allow de-serialization of transient data from archives.
 
- Public Member Functions inherited from chrono::ChFunctionPosition
 ChFunctionPosition (const ChFunctionPosition &other)
 
virtual void Estimate_s_domain (double &smin, double &smax) const
 Return an estimate of the domain of the function argument. More...
 
virtual void Estimate_boundingbox (ChVector<> &pmin, ChVector<> &pmax) const
 Return an estimate of the range of the function value. More...
 
virtual void Update (const double t)
 Update could be implemented by children classes, ex. to launch callbacks.
 

Member Enumeration Documentation

◆ eChSetpointMode

Type of setpoint interpolation/extrapolation - zero order hold, first order hold, etc.

Enumerator
ZOH 

Zero Order Hold: p constant, p_ds = p_dsds = 0 in neighbour of setpoint s.

FOH 

First Order Hold: p linear, p_ds constant, p_dsds = 0 in neighbour of setpoint s.

SOH 

First Order Hold: p parabolic, p_ds linear, p_dsds constant in neighbour of setpoint s.

OVERRIDE 

p, p_ds, p_dsds are set via SetSetpointAndDerivatives() and will be considered constant in Get_p(s) regardless of s until next SetSetpointAndDerivatives()

Member Function Documentation

◆ SetSetpoint()

void chrono::ChFunctionPosition_setpoint::SetSetpoint ( ChVector<>  p_setpoint,
double  s 
)
virtual

Set the setpoint, and compute its derivatives (speed, acceleration) automatically by backward differentiation (only if s is called at increasing small steps, most often s is time).

Note: each time must be called with increasing s so that internally it add sthe 'new' setpoint and scrolls the previous samples for computing extrapolation/interpolation, but if called multiple times with exactly the same s value, the buffer of past samples is not scrolled: it just recompute setpoint and derivatives according to the 'updated' setpoint. If in ZOH mode: value p will persist indefinitely until next call, derivative p_ds and p_dsds will be zero. If in FOH mode: value p will interpolate linearly from the previous value, derivative p_ds will be constant, p_dsds will be zero. If in SOH mode: value p will interpolate quadratically, derivative p_ds will be linear, p_dsds will be constant.

◆ SetSetpointAndDerivatives()

virtual void chrono::ChFunctionPosition_setpoint::SetSetpointAndDerivatives ( ChVector<>  p_setpoint,
ChVector<>  p_setpoint_ds,
ChVector<>  p_setpoint_dsds 
)
inlinevirtual

Set the setpoint, and also its derivatives.

Moreover, changes the mode to eChSetpointMode::OVERRIDE, so all values will persist indefinitely until next call, that is multiple calls to Get_p(s) Get_p_ds() etc. will give same results (non interpolated) regardless of s.


The documentation for this class was generated from the following files:
  • /builds/uwsbel/chrono/src/chrono/motion_functions/ChFunctionPosition_setpoint.h
  • /builds/uwsbel/chrono/src/chrono/motion_functions/ChFunctionPosition_setpoint.cpp