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How to get a smooth motion of a JACO-Arm following trajectory points

asked 2015-10-26 12:31:39 -0600

kural gravatar image

updated 2015-10-29 03:03:12 -0600

gvdhoorn gravatar image

The jaco arm follows a trajectory points but stops briefly in those points, is there a package or suggestion to eliminate this stops and make the arm move smoothly over the trajectories?


using namespace std;
void letswait(int);
int main(int argc, char **argv)
    char filename[100];
    float temp;
    int row=0;
    stringstream rosrun;
    //find out number of rows
    ifstream myfile (filename);
    //refresh the file read

    //create dynamic table
    float **table; 
    table = new float* [row];
    for(int i=0;i<row;i++)
    table[i] = new float [6];

    //read the file into table
    for (int j=0;j<4;j++)
                for(int i=0;i<row;i++)
                    for(int j=0;j<6;j++)

        for(int i=0;i<row;i++)

            //create string stream for rosrun
            rosrun<<"rosrun jaco_demo jaco "<<table[i][0]<<" "<<table[i][1]<<" "<<table[i][2]<<" "<<table[i][3]<<" "<<table[i][4]<<" "<<table[i][5];
            //call rosrun jaco_demo with one set of angles
            //clear stream

            if (j == 0 && i == 0)
                    rosrun<<"rosrun jaco_demo jaco 60 60 60";
    return 0; 
void letswait(int secs){
    clock_t end;
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Can you add information about how you are currently commanding the trajectories?

Airuno2L gravatar image Airuno2L  ( 2015-10-26 13:11:17 -0600 )edit

i have attached the code bellow. I am taking a set of points (joint angles) from a text file and giving as an input. But the arm pauses at each point and then moves to the next. I want it not to stop and move smoothly. Please suggest

kural gravatar image kural  ( 2015-10-28 10:24:41 -0600 )edit

@kural: please do not post answers that are not actually answers. If you need to provide more information, edit your original question. Use the edit link/button below your question for that.

gvdhoorn gravatar image gvdhoorn  ( 2015-10-29 03:04:04 -0600 )edit

sorry @gvdhoorn . New here. :-)

kural gravatar image kural  ( 2015-10-30 12:29:34 -0600 )edit

1 Answer

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answered 2015-10-29 08:48:26 -0600

Airuno2L gravatar image

What you're seeing happen is the intended behavior given the inputs you're providing. You're telling the arm to go to one point, then another, and that is what it is doing. If you want to tell it to go through a smooth trajectory without stopping you need a way to tell it that you don't want zero velocity at those points. That is what the trajectory_msgs is for.

I don't think the jaco package has support for receiving trajectory_msgs so you'll need someway of implementing it external to the robot or jaco package. I believe the moveit! package might be able to help with this.

Also, you might want to peek inside the Kinova Jaco API and see if it is possible to command trajectories through it and it just wasn't implemented in the ROS package.

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Thanks. I have found the wpi wrapper package from github which supports my needs, but sadly i dont know how to use it now. Can you please help me about how to provide my input in to this package.

kural gravatar image kural  ( 2015-10-30 12:02:33 -0600 )edit

It looks like they have pretty good documentation here: link. Have you looked through that yet?

Airuno2L gravatar image Airuno2L  ( 2015-10-30 12:14:46 -0600 )edit

yes, but in vain. I am new to ros. can you please tell me the command line in ros i should type to give in 3 points trajectory for the smooth motion function in this package. Please.

kural gravatar image kural  ( 2015-10-30 12:21:04 -0600 )edit

e.g., rosrun jaco_demo jaco -0.314 -0.339 0.600 -0.591 -0.519 0.324 0.525 . This is a example line given in the ros-jaco package, which takes the arm to the specified position. Can you tell me similarly the line to execute the smooth arm motion for the wpi wrapper package?.Pleas

kural gravatar image kural  ( 2015-10-30 12:23:53 -0600 )edit

Those command line tools are really just examples to demo. You'll need to write your own code to interface with their nodes. If you haven't done them yet I suggest doing the beginner tutorials here then here.

Airuno2L gravatar image Airuno2L  ( 2015-10-30 15:28:25 -0600 )edit

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Asked: 2015-10-26 12:31:39 -0600

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Last updated: Oct 29 '15