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The cob_base_velocity_smoother package provides two implementations for a velocity smoother that both read velocity messages (geometry_msgs::Twist) and then publish messages of the same type for "smoothed" velocity to avoid jerky behavior.

The two nodes available are:

• cob_base_velocity_smoother

• velocity_smoother

Hardware Requirements

To use this package you either need a real or a simulated Care-O-Bot (see cob_bringup and cob_bringup_sim respectively).

ROS API

The following states the ROS API for the cob_base_velocity_smoother node.

cob_base_velocity_smoother

The cob_base_velocity_smoother node takes in geometry_msgs/Twist messages from the navigation or teleoperation device and publishes recalculated geometry_msgs/Twist messages to avoid jerky behavior.

Subscribed Topics

input (geometry_msgs/Twist)

• movement command published by the navigation or teleoperation device.

Published Topics

output (geometry_msgs/Twist)

• recalculated movement command

Parameters

~circular_buffer_capacity (int, default: 12 for cob3, 6 for raw3)

• Specifies the capacity of the internal circular buffer (number of saved velocity messages).

~maximal_time_delay (double, default: 4.0 [seconds])

• Specifies the maximal time delay for saved messages (older messages will be deleted).

~thresh_max_acc (double, default: 0.02 [m/s^2])

• Specifies the threshold for the maximal allowed acceleration.

~loop_rate (double, default: 30.0 [Hz])

• Specifies the ros loop rate of the velocity smoother.

~min_input_rate (double, default: 9.0 [Hz])

• Specifies the minimal input rate that is expected before filling the buffer with zeros.

~maximal_time_delay_to_stop (double, default: 0.1 [seconds])

• Specifies the maximal time-delay until stopping the robot when there are no incoming messages.

Usage

All hardware configuration is done in the cob_hardware_config package. Parameter files for both nodes have to be placed in "cob_hardware_config/$(env ROBOT)/config/" for each ROBOT.