Robot has trouble to complete trajectory at medium to high speeds

[JonaRo4]

Hello everyone,
im using a Yaskawa HC10 robot with YRC1000 controller and Motoros2 and Moveit2. Im using follow joint trajectory mode to implement a PnP application off a moving conveyor belt.
Using
setMaxVelocityScalingFactor();
setMaxAccelerationScalingFactor();
i can set the speed and acceleration from 0.1 to 1.0. For the scaling factor, Moveit2 is referencing this joint_limits.yaml.

joint_limits.yaml

default_velocity_scaling_factor: 1.0
default_acceleration_scaling_factor: 1.0

joint_limits:
  joint_1_s:
    has_velocity_limits: true
    max_velocity: 2.2689280275926285
    has_acceleration_limits: true
    max_acceleration: 3.75
  joint_2_l:
    has_velocity_limits: true
    max_velocity: 2.2689280275926285
    has_acceleration_limits: true
    max_acceleration: 1.875
  joint_3_u:
    has_velocity_limits: true
    max_velocity: 3.1415926535897931
    has_acceleration_limits: true
    max_acceleration: 2.5
  joint_4_r:
    has_velocity_limits: true
    max_velocity: 3.1415926535897931
    has_acceleration_limits: true
    max_acceleration: 3.125
  joint_5_b:
    has_velocity_limits: true
    max_velocity: 4.3633231299858242
    has_acceleration_limits: true
    max_acceleration: 3.75
  joint_6_t:
    has_velocity_limits: true
    max_velocity: 4.3633231299858242
    has_acceleration_limits: true
    max_acceleration: 5.0

At speed and acceleration of 0.1 (10% of maximum speed) the robot completes the trajectory in a very smooth manner. However, when i try to use full speed or even just 50 %, it keeps interrupting the trajectory without an error message in Moveit2.

But the YRC1000 pendant shows me the Alarm 4315 with:

Alarm content: A collision was detected because of the interference between the manipulator and a peripheral device. The external force applied to the robot exceeded the threshold.

Cause: Setting error

However, there is no visible collision.

Furthermore the movement of the robot is generally very stuttery and jerky at medium to high speeds, which also leads to trajectory interruptions.
Is this a hardware issue or a software issue?

Regarding the FSU of the robot, there are no speed limits or joint limits set on the YRC1000 Pendant, just robot range limits.

I would appreciate any ideas as to what could prevent the robot of completing the trajectory at higher speeds.

Thank you very much in advance.

[ted-miller]

Hello @JonaRo4

The collision-detect alarm can occur if the acceleration is too high. The inertia of the arm can trip the torque limits.

Please ensure that the mass properties of your tooling are correct. This is under Robot > Tool.

Then go to Robot > Shock Sense Level. From here, you can verify that the DETECT LEVEL is set appropriately. (The default is 100.) Plus, you can see which axis is exceeding the limit.

Furthermore the movement of the robot is generally very stuttery and jerky at medium to high speeds, which also leads to trajectory interruptions. Is this a hardware issue or a software issue?

I suggest programming a basic job on the teach pendant. This will allow you to see the robot's "optimal" motion profile.

[ted-miller]

It seems that I was wrong. I'm sorry for giving you incorrect information. The specs above (+-290) are for the newer models, HC-10DTP.

The older HC-10 models have a different range of -5 to +355. Your picture above represents the 0 position.

[JonaRo4]

Ah I see, it seems i have looked at the wrong robot model aswell. That explains the Alarm but makes the whole thing more troublesome for me.

[JonaRo4]

Regarding the earlier problem of stuttery and jerky robot movement:
I have implemented a simple teaching job on my robot to see the robots optimal motion profile. What does this value VJ = ... represent? It increases the joint speed but what is it`s unit? deg/s? m/s? cm/s?
Furthermore what acceleration value does it use as standard if i don´t manually set a joint acceleration value?

The reason for my questions is that I´m trying to replicate the "smooth" motion of the robot, while executing the teaching job, using values of acceleration and velocity in MoveIt2. To find the equivalent, so to speak, and set them as limits, so that the robot moves in a smooth manner in my MoveIt2+MotoROS2 application.

I would greatly appreciate it, if you could help me out here.

[ted-miller]

What does this value VJ = ... represent? It increases the joint speed but what is it`s unit?

Percentage. 100.00 = 100.00%.
In the case of using an I variable, such as I000, the unit is 0.01%. So, if I000 = 1234, then it would be VJ=12.34%.

The VJ tag is only used for the Joint motion profile.

Furthermore what acceleration value does it use as standard if i don´t manually set a joint acceleration value?

There are multiple factors that affect the acceleration. This includes posture/reach of the arm and the mass properties of the tooling.

Unfortunately, Yaskawa does not publish acceleration limits of the arm. But the acceleration should not cause the torque to exceed these published values.

[JonaRo4]

Hello, i have one more follow up question, I hope this is okay. Otherwise I can open another issue.

What is the maximum TCP velocity of the HC10 (m/s) ? Are there any values i can look up or are just the maximum joint velocities (rad/s) known?

I have seen this table:

here: https://knowledge.motoman.com/hc/en-us/articles/5749953905431-Changing-Speed

But for what robot are those values ? And is this just in teach mode or a general maximum TCP velocity?

[ted-miller]

That table represents the general maximum TCP velocity for all robot models.

Please note that with an HC10, the practical limit is much lower. When operating in a collaborative environment without an enclosure, it is very likely the FSU will limit the max speed for the sake of safety.

[JonaRo4]

The robot is being used in an enclosure in a non-collaborative way. I have not set any speed limitations in the FSU myself. Are there any more speed restrictions, that i have no control over, if yes, is there a way to override them, to reach the TCP-velocity of 1,5 m/s?

[ted-miller]

By default, in the US, you can disable PFL by NOT'ing the first line of the Safety Logic Circuit. I don't know whether that is applicable in other regions though.

Beyond that, you'll want to make sure that the mass properties of your tooling are accurate. Additionally, to reach max velocity, you'll want to use larger motions to accommodate the accel and decel rates.