Example 6 — Different Synchronization Behaviors of the Velocity-based algorithm

Below, you can find the source code of a further sample application that makes use of the velocity-based Reflexxes algorithm, and that generates a time-synchronized motion trajectory. The source file can be found in the folder

/src/RMLVelocitySampleApplications/06_RMLVelocitySampleApplication.cpp

The resulting trajectory of this sample program is displayed below the source code.

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#include <stdio.h>
#include <stdlib.h>

#include <ReflexxesAPI.h>
#include <RMLVelocityFlags.h>
#include <RMLVelocityInputParameters.h>
#include <RMLVelocityOutputParameters.h>


//*************************************************************************
// defines

#define CYCLE_TIME_IN_SECONDS                   0.001
#define NUMBER_OF_DOFS                          3


//*************************************************************************
// Main function to run the process that contains the test application
//
// This function contains source code to get started with the Type II
// Reflexxes Motion Library. Only a minimum amount of functionality is
// contained in this program: a simple trajectory for a
// three-degree-of-freedom system is executed. This code snippet
// directly corresponds to the example trajectories shown in the
// documentation.
//*************************************************************************
int main()
{
    // ********************************************************************
    // Variable declarations and definitions

    int                         ResultValue                 =   0       ;

    ReflexxesAPI                *RML                        =   NULL    ;

    RMLVelocityInputParameters  *IP                         =   NULL    ;

    RMLVelocityOutputParameters *OP                         =   NULL    ;

    RMLVelocityFlags            Flags                                   ;

    // ********************************************************************
    // Creating all relevant objects of the Type II Reflexxes Motion Library

    RML =   new ReflexxesAPI(                   NUMBER_OF_DOFS
                                            ,   CYCLE_TIME_IN_SECONDS   );

    IP  =   new RMLVelocityInputParameters(     NUMBER_OF_DOFS          );

    OP  =   new RMLVelocityOutputParameters(    NUMBER_OF_DOFS          );

    // ********************************************************************
    // Set-up a timer with a period of one millisecond
    // (not implemented in this example in order to keep it simple)
    // ********************************************************************

    printf("-------------------------------------------------------\n"  );
    printf("Reflexxes Motion Libraries                             \n"  );
    printf("Example: 06_RMLVelocitySampleApplication.cpp           \n\n");
    printf("This example demonstrates the most basic use of the    \n"  );
    printf("Reflexxes API (class ReflexxesAPI) using the velocity- \n"  );
    printf("based Type II Online Trajectory Generation algorithm.  \n\n");
    printf("Copyright (C) 2014 Reflexxes GmbH                      \n"  );
    printf("-------------------------------------------------------\n"  );

    // ********************************************************************
    // Set-up the input parameters

    // In this test program, arbitrary values are chosen. If executed on a
    // real robot or mechanical system, the position is read and stored in
    // an RMLVelocityInputParameters::CurrentPositionVector vector object.
    // For the very first motion after starting the controller, velocities
    // and acceleration are commonly set to zero. The desired target state
    // of motion and the motion constraints depend on the robot and the
    // current task/application.
    // The internal data structures make use of native C data types
    // (e.g., IP->CurrentPositionVector->VecData is a pointer to
    // an array of NUMBER_OF_DOFS double values), such that the Reflexxes
    // Library can be used in a universal way.

    IP->CurrentPositionVector->VecData      [0] =    100.0      ;
    IP->CurrentPositionVector->VecData      [1] =     50.0      ;
    IP->CurrentPositionVector->VecData      [2] =   -100.0      ;

    IP->CurrentVelocityVector->VecData      [0] =     80.0      ;
    IP->CurrentVelocityVector->VecData      [1] =     25.0      ;
    IP->CurrentVelocityVector->VecData      [2] =    -50.0      ;

    IP->CurrentAccelerationVector->VecData  [0] =    -50.0      ;
    IP->CurrentAccelerationVector->VecData  [1] =   -150.0      ;
    IP->CurrentAccelerationVector->VecData  [2] =     80.0      ;

    IP->MaxAccelerationVector->VecData      [0] =    400.0      ;
    IP->MaxAccelerationVector->VecData      [1] =    300.0      ;
    IP->MaxAccelerationVector->VecData      [2] =    500.0      ;

    IP->MaxJerkVector->VecData              [0] =    500.0      ;
    IP->MaxJerkVector->VecData              [1] =    400.0      ;
    IP->MaxJerkVector->VecData              [2] =    300.0      ;

    IP->TargetVelocityVector->VecData       [0] =    200.0      ;
    IP->TargetVelocityVector->VecData       [1] =   -150.0      ;
    IP->TargetVelocityVector->VecData       [2] =    -20.0      ;

    IP->SelectionVector->VecData            [0] =    true       ;
    IP->SelectionVector->VecData            [1] =    true       ;
    IP->SelectionVector->VecData            [2] =    true       ;

    Flags.SynchronizationBehavior   =   RMLFlags::ONLY_TIME_SYNCHRONIZATION;

    // ********************************************************************
    // Starting the control loop

    while (ResultValue != ReflexxesAPI::RML_FINAL_STATE_REACHED)
    {

        // ****************************************************************
        // Wait for the next timer tick
        // (not implemented in this example in order to keep it simple)
        // ****************************************************************

        // Calling the Reflexxes OTG algorithm
        ResultValue =   RML->RMLVelocity(       *IP
                                            ,   OP
                                            ,   Flags       );

        if (ResultValue < 0)
        {
            printf("An error occurred (%d).\n", ResultValue );
            break;
        }

        // ****************************************************************
        // Here, the new state of motion, that is
        //
        // - OP->NewPositionVector
        // - OP->NewVelocityVector
        // - OP->NewAccelerationVector
        //
        // can be used as input values for lower level controllers. In the
        // most simple case, a position controller in actuator space is
        // used, but the computed state can be applied to many other
        // controllers (e.g., Cartesian impedance controllers,
        // operational space controllers).
        // ****************************************************************

        // ****************************************************************
        // Feed the output values of the current control cycle back to
        // input values of the next control cycle

        *IP->CurrentPositionVector      =   *OP->NewPositionVector      ;
        *IP->CurrentVelocityVector      =   *OP->NewVelocityVector      ;
        *IP->CurrentAccelerationVector  =   *OP->NewAccelerationVector  ;
    }

    // ********************************************************************
    // Deleting the objects of the Reflexxes Motion Library end terminating
    // the process

    delete  RML         ;
    delete  IP          ;
    delete  OP          ;

    exit(EXIT_SUCCESS)  ;
}

Resulting trajectory of example 6 for velocity-based trajectory generation (06_RMLVelocitySampleApplication.cpp).

Note:

The variables

• RMLPositionInputParameters::CurrentAccelerationVector (containing the the current acceleration vector and
  
  
• RMLPositionInputParameters::MaxJerkVector (containing the maximum jerk vector
  
  

are only used by the Type IV Reflexxes Motion Library.

See also:

Synchronization Behavior

Example 4 — Introduction to the Velocity-based algorithm