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Version: 8

Real-time Performance and Trajectory Jitter Troubleshooting

Arm movements have noticeable hitches and jitter in real-time setup​

Problem: When running MoveIt Pro drivers container in real-time on x86/Intel or ARM/Nvidia Jetson platforms, arm motions show noticeable hitches and jitter that can be seen and felt during movement, even with real-time kernel and priority settings configured.

Solution: This issue typically manifests in two different ways that require different solutions:

For Large Jerky Motions (Real-time Performance Issues)​

If you see large, irregular jerky motions, this indicates real-time performance problems. Try these Docker container CPU optimization settings in your docker-compose.yaml:

services:
  drivers:
    # ... existing configuration ...
    # Ensures the drivers container has RT priority
    ulimits:
      rtprio: 99
    # CPU optimization options
    cpuset-cpus: "0-3"  # Pin to specific CPUs for isolation
    cpu-shares: 2048    # Increase CPU priority (>1024)

For advanced real-time optimization, consider CPU isolation using boot parameters:

# Add to boot parameters
isolcpus=0,1 nohz_full=0,1 rcu_nocbs=0,1

Then pin the drivers container to those isolated CPUs:

services:
  drivers:
    cpuset-cpus: "0,1"  # Use isolated CPUs

For Small Regular "Staccato" Jitter (Trajectory Configuration Issues)​

If you see small, regular jitter where the arm appears to go to zero velocity at each trajectory step (creating a staccato effect), this is likely a trajectory configuration issue, not a real-time performance problem.

This can be caused by using both position and velocity command interfaces simultaneously. To fix this:

  1. Remove the velocity command_interface from your ros_controllers.yaml file
  2. Remove the velocity command_interface from your robot's ros2_control xacro file
  3. Ensure only the position command interface is used for joints

You can also try increasing the collision_check_rate parameter in your MoveIt Servo YAML configuration to match your robot's duty cycle:

collision_check_rate: 100.0  # [Hz] Match your robot's expected duty cycle
tip

If real-time optimization eliminates large jerky motions but small regular jitter persists, you've likely resolved the real-time issues and should focus on trajectory configuration instead.