Remove the four round standoffs by hand and set them aside. Note that the PCBA is now free to move and care should be taken to ensure it is not damaged.
Use alternative standoffs (e.g. from Mcmaster Carr) or other mounting options. The threaded inserts of the robot are M4x0.7mm. The mounting pattern can be taken from 3D CAD available on Github or it can be transferred from the integration plate itself.
When reassembling the robot with new hardware, ensure that all fasteners are torqued according to the fastener and mating threads and that a threadlocker is used.
For the TurtleBot4 Lite, the Create 3 plate can be used to secure payloads. Tips for mounting directly to this plate can be found on the Create 3 Github.
The minimum clearance to accommodate the OAK-D-Pro is 108mm. For the OAK-D-Lite it is 102mm.
The pictures below show a Clearpath Robotics Hackday project where a NED2 Robot manipulator (8.9kg) mounted on top of a TurtleBot4 Lite using 4X2 M4 standoffs (Mcmaster Carr P/N 98952A450) and an integration plate from a TurtleBot4 Standard.The manipulator was mounted such that the COG was further forward and supported by the front caster wheel. An external NEC ALM 12V7 Battery (0.9kg) was also attached to power the device. In this particular case the battery was installed on a hinge that would allow the battery to sit closer to the robot or to be laid out and supported on its own omni-wheel. This was a design choice to allow the demonstration of either a larger weight mounted to the unit or a payload hitched to the robot as an alternative payload mounting design method.
Velocity and acceleration limits should be set appropriately to maintain stability when driving the robot. Otherwise you may find that the robot will shake, stall, or not drive as commanded.
The acceleration limit on the Create® 3 can be changed using the
wheel_accel_limit parameter of the
ros2 param set /motion_control wheel_accel_limit 300
The acceleration value can be between 1 and 900.
wheel_accel_limit is applied to both acceleration and deceleration. If you set it too low, the robot will stop very slowly.
The Create® 3 has linear velocity limits of 0.31 m/s with safety enabled, and 0.46 m/s with safety overridden. The angular velocity is limited to 1.9 rad/s. For heavy payloads you may want to limit this further. The method to do this will vary based on how you are driving the robot.
If you are using the
teleop_twist_keyboard ROS2 node, you can follow the CLI instructions to reduce linear and angular velocities.
To limit the
teleop_twist_joy velocities you will need create a modified version the TurtleBot4 controller config file. The
scale_linear.x value limits the linear velocity, and the
scale_angular.yaw value limits the angular velocity.
Once you have created the config file, you can launch
joy_teleop and set the
controller_config parameter to the full path of your new config file.
ros2 launch turtlebot4_bringup joy_teleop.launch.py controller_config:=/path/to/config.yaml
If you are manually sending the velocity through the
/cmd_vel topic, simply reduce the velocity values to an appropriate level.
If you are driving the robot through one of the Create® 3 actions, you can set velocity limits in the action goal.
To limit velocity during navigation, you can create a modified nav2.yaml configuration file. Changing parameters such as
controller_server.FollowPath.max_vel_x will limit the velocity commands sent by the Nav2 stack.
Launch Nav2 with your modified parameter file:
ros2 launch turtlebot4_navigation nav_bringup.launch.py params_file:=/path/to/your/nav2.yaml