[jordan]

       
Hi,

I'm currently working on generating a list of joint angles for a UR5e robot using RoboDK, and I've noticed that the output joint angles' acceleration ramps up very quickly. Is there any way to control or adjust the rate at which the acceleration ramps up (i.e., control the jerk)? Additionally, how accurate is the timing when using the InstructionListJoints() command with the flag set to 4, so the outputted joint angles are split based on timing increments compared to a running it on a real UR5e?

I'm using RoboDK to generate a sequence of joint angles at 2ms intervals from a program using the InstructionListJoints() command. Here is an example of the code I'm using to find the list of joint angles for a path:

Code:

def create_joint_angle_path(robot_file_path="C:/RoboDK/Library/UR5e.robot") -> bool:
    RDK = robolink.Robolink()
    robot = RDK.AddFile(robot_file_path)
    robot.MoveJ(robot.JointsHome())
    if not robot.Valid():
        print("Failed to load robot.")
        return False
    robot.MoveJ([0.000000, -90.000000, -90.000000, 0.000000, 90.000000, 0.000000])
    program = RDK.AddProgram("UR5e_path", robot)
    program.MoveJ([0.000000, -90.000000, -90.000000, 0.000000, 90.000000, 0.000000])
    program.MoveJ([18.314638, -92.959960, -80.024722, 14.043931, 72.834395, -6.483384])
    output_file_path = os.path.join("..", "output_files", "path.txt")
    message, joint_list, status = program.InstructionListJoints(
        save_to_file=output_file_path, flags=4, time_step=0.002
    )
    if status < 0:
        print("status ", status)
        print("message ", message)
        return False
    print("Joint angles exported to", output_file_path)
    return True

Here is what the output of the joint q and qdd looks like when it's plotted out. I'm concerned with how quickly the acceleration ramps up to the maximum and whether the actual UR5e will be able to handle this. Is there any way to make the acceleration ramp-up more gradual? There might also be a better way of getting the joint lists.

Cheers for any help or advice.

[Albert]

It is currently not possible to set how fast the acceleration changes. RoboDK simulates robot programs and timings assuming the robot can maintain a constant acceleration until reaching the desired speed (or maximum robot speed).

You can find more information about timings and cycle time here:
https://robodk.com/doc/en/General.html#CycleTime

[jordan]

It is currently not possible to set how fast the acceleration changes. RoboDK simulates robot programs and timings assuming the robot can maintain a constant acceleration until reaching the desired speed (or maximum robot speed).
You can find more information about timings and cycle time here:
https://robodk.com/doc/en/General.html#CycleTime

Thanks!

It mentions that RoboDK simulates 5 times faster than real time by default. Is this true for the 2ms time increments I'm splitting the joint angles into with the InstructionListJoint function? If I adjust the simulation speed, it doesn't seem to affect the outputted joint list (with RDK.setSimulationSpeed(1)).

[Albert]

RoboDK simulates 5 times faster than real time by default if you don't alter the simulation speed. You can change the simulation speed here:

1. Select Tools-Options
   
2. Select the Motion tab
   
3. Update the Simulation time ratio
   

You can also switch between normal and fast simulation by using the spacebar. And using the dropdown in the corresponding menu allows you to change the simulation ratio as well.

This ratio does not apply to API functions that perform calculations such as the InstructionListJoints function.