Reflexxes Motion Libraries: Description of Output Values

After calling the position-based On-Line Trajectory Generation (OTG) algorithm with ReflexxesAPI::RMLPosition(), the output values can be read from the class RMLPositionOutputParameters. The output values of the velocity-based On-Line Trajectory Generation algorithm, which is called with ReflexxesAPI::RMLVelocity() can be read from the class RMLVelocityOutputParameters. For a detailed description of these classes, please refer to the class documentation, and for a description of the input values of the Reflexxes Motion Library, please refer to the Description of Input Values.

This page contains two main sections with one example each:

Output Values of the Position-based On-Line Trajectory Generation Algorithm

Input and output values of the Reflexxes Type II Motion Library in a generic manner.

The position-based Type II On-Line Trajectory Generation algorithm called at a time instant $ T_i $ computes the following output values (cf. RMLPositionOutputParameters):

The state of motion at time instant consisting of
- the new position/pose vector $\vec{P}_{i+1} \ \Longrightarrow \$ RMLPositionOutputParameters::NewPositionVector,
- the new velocity vector $\vec{V}_{i+1} \ \Longrightarrow \$ RMLPositionOutputParameters::NewVelocityVector, and
- the new acceleration vector $\vec{A}_{i+1} \ \Longrightarrow \$ RMLPositionOutputParameters::NewAccelerationVector.
The value of the synchronization time $t_i^{\,sync}$ in seconds (RMLPositionOutputParameters::SynchronizationTime), that is, the time which is required until all selected degrees of freedom reach their desired target state of motion ${\bf M}_i^{\,trgt}$ .
A boolean flag RMLPositionOutputParameters::ANewCalculationWasPerformed, which indicates, what an entirely new computation was performed for the call of ReflexxesAPI::RMLPosition() (cf. Real-Time Behavior).
A boolean flag RMLPositionOutputParameters::TrajectoryIsPhaseSynchronized, which indicates, whether the current trajectory is phase-synchronized (cf. Synchronization Behavior).
All data about the positional extremum values that will occur if the motion trajectory is executed. This includes two vectors, which contain the positional extremum values:
- the minimum positions for each degree of freedom $\overrightarrow{\mbox{min}}\Big(\vec{p}_i\left(t\right)\Big) \ \Longrightarrow \$ RMLPositionOutputParameters::MinPosExtremaPositionVectorOnly and
- the minimum positions for each degree of freedom $\overrightarrow{\mbox{max}}\Big(\vec{p}_i\left(t\right)\Big) \ \Longrightarrow \$ RMLPositionOutputParameters::MaxPosExtremaPositionVectorOnly.
Furthermore, the times in seconds, at which the positional extremum values are reached, are stored in
- RMLPositionOutputParameters::MinExtremaTimesVector and
- RMLPositionOutputParameters::MaxExtremaTimesVector.
As a further addition, it is also possible to read the states of motion of all degrees of freedom that are reached if one degree of freedom is in its positional minimum or maximum:

See also:: RMLPositionOutputParameters; Description of Input Values

Example

The position-based On-Line Trajectory Generation algorithm of the Type II Reflexxes Motion Library is called by the method ReflexxesAPI::RMLPosition().

In this example (cf. Example 1 — Introduction to the Position-based algorithm), we assume to control a simple Cartesian robot with three translational degrees of freedom, and we apply the following input values at time instant $ T_i $ .

Sample trajectory generated by the position-based Type II On-Line Trajectory Generation algorithm of the Reflexxes Motion Libraries.

Further examples can be found on pages

Note:

The input variables

RMLPositionInputParameters::CurrentAccelerationVector (containing the the current acceleration vector $\vec{A}_i$ and
RMLPositionInputParameters::MaxJerkVector (containing the maximum jerk vector $\vec{J}_i^{\,max}$

are only used by the Type IV Reflexxes Motion Library.

Sample Source Code

For a program to set-up the corresponding input parameters please refer to the Example 1 — Introduction to the Position-based algorithm, to the Example 2 — Making Use of Output Parameters of the Position-based algorithm, and to the Screen Output of 02_RMLPositionSampleApplication.cpp.

Output Values of the Velocity-based On-Line Trajectory Generation Algorithm

Input and output values of the velocity-based Type II On-Line Trajectory Generation algorithm of the Reflexxes Motion Libraries.

The velocity-based Type II On-Line Trajectory Generation algorithm is executed by a call of ReflexxesAPI::RMLVelocity(), and its output values RMLVelocityOutputParameters are the very same as for the position-based algorithm (see above), but the values for the target position $_kP_i^{\,trgt}$ and the maximum velocity vector $\vec{V}_i^{\,max}$ are not considered, and the flag RMLPositionFlags::KeepCurrentVelocityInCaseOfFallbackStrategy is not available.

See also:: RMLVelocityOutputParameters; Description of Input Values

Note:: The velocity-based algorithm is also used in the second layer of the safety mechanism to guarantee valid output value for any given set of input values (cf. Safety: Three Layers of Error Handling).

Example

For this second example (cf. Example 4 — Introduction to the Velocity-based algorithm), we again assume a very simply Cartesian robot with three translational degrees of freedom.

Sample trajectory generated by the velocity-based Type II On-Line Trajectory Generation algorithm of the Reflexxes Motion Libraries.

Sample Source Code

For a program to set-up the corresponding input parameters please refer to the Example 4 — Introduction to the Velocity-based algorithm, to the Example 5 — Making Use of Output Parameters of the Velocity-based algorithm, and to the Screen Output of 05_RMLVelocitySampleApplication.cpp.