Overview

There are three states: raw, follow and twist. The output torque and speed of each motor of the chassis can be calculated according to the current state of the control, the received speed and pose of the pan/tilt, and the speed and acceleration commands, and the data is returned by the motor to calculate The speed and posture of the chassis are released. The control algorithm involved in the chassis controller is PID algorithm.

Keywords: mecanum, swerve, balance, chassis, ROS, RoboMaster

Hardware interface type

JointStateInterface Used to get the position and speed of chassis wheel joint.
EffortJointInterface Used to send the torque command of chassis wheel joint.
RoboSateInterface Used for high-frequency maintenance of the transformation relationship of changing odom to base_link.

Installation

Installation from Packages

To install all packages from the this repository as Debian packages use

sudo apt-get install ros-noetic-rm-chassis-controllers

Or better, use rosdep:

sudo rosdep install --from-paths src

Dependencies

Robot Operating System (ROS) (middleware for robotics),
roscpp
rm_common
controller_interface
effort_controllers
tf2_geometry_msgs
angles
robot_localization

ROS API

Subscribed Topics

base_imu (sensor_msgs/Imu)

The inertial measurement unit data of base command.
command (rm_msgs::ChassisCmd)

Set the mode, acceleration, and maximum power of the chassis.
cmd_vel (geometry_msgs/Twist)

Set the speed of the chassis.

Published Topics

odom(nav_msgs/Odometry)

Chassis odometer information (speed, position, covariance).
state(rm_msgs::BalanceState)

Contains quantities of state and control about the Balance.

Parameters

common

wheel_radius (double)

Radius of the wheels.
wheel_track (double)

The distance between the center of the left and right wheels on the same side.
wheel_base (double)

The distance between the center of the front and rear wheels on the same side.
twist_angle (double)

Amplitude of twist at twist state.
enable_odom_tf (bool, default: true)

Option.If it is set to true, it will store Transform in tf_buffer.
publish_odom_tf_ (bool, default: false)

Option.If it is set to true, enable_odom_tf is also true, it will send Transform from odom to base.
twist_covariance_diagonal (double[6])

The diagonal covariance matrix of twist.
publish_rate (double, default: 50)

Frequency (in Hz) of publishing Transform.
coeff (double)

A coefficient. Adjust this coefficient to reduce the impact of power loss.
min_vel (double)

The minimum velocity of chassis joint which is used to calculate the max torque.
timeout (double)

Allowed period (in s) between two commands. If the time is exceed this period, the speed of chassis will be set 0.
power_offset (double)

Fix the difference between theoretical power and actual power.

Balance

imu_name (string, default: "base_imu")

Chassis imu name.
left/wheel_joint (string, default: "left_wheel_joint")

left wheel joint name.
left/block_joint (string, default: "left_momentum_block_joint")

left momentum block joint name.
right/wheel_joint (string, default: "right_wheel_joint")

right wheel joint name.
right/block_joint (string, default: "right_momentum_block_joint")

right momentum block joint name.
m_w (double, default: 0.72)

mass of single wheel.
m (double, default: 11.48)

mass of the robot except wheels and momentum_blocks.
m_b (double, default: 1.13)

mass of single momentum_block.
i_w (double, default: 0.01683)

The moment of inertia of the wheel around the rotational axis of the motor.
l (double, default: 0.0587)

The vertical component of the distance between the wheel center and the center of mass of robot.
y_b (double, default: 0.16)

The y-axis component of the coordinates of the momentum block in the base_link coordinate system.
z_b (double[4], default: 0.0468)

The vertical component of the distance between the momentum block and the center of mass of robot.
g (double, default: 9.8)

Gravity constant.
i_m (double, default: 0.1982)

The moment of inertia of the robot around the y-axis of base_link coordinate.
q (double[16])

Weight matrix.
r (double[4])

Weight matrix.

Swerve

/modules/<module_name>/position (double[2])

The position of module.
/modules/<module_name>/pivot/joint (string)

Joint between chassis and privot.
/modules/<module_name>/pivot/offset (double)

Angle between the wheel rotation axis and the chassis's Y axis.
/modules/<module_name>/wheel/joint (string)

Joint between privot and wheel.
/modules/<module_name>/wheel/radius (double)

The radius of wheel.

Omni

/wheels/<wheels_name>/pose (double[3])

The pose of wheel.
/wheels/<wheels_name>/joint (string)

wheel joint name.
/wheels/left_front/roller_angle (double)

The roller angle of wheel.
/wheels/left_front/radius (double)

The radius of wheel.

Controller configuration examples

Complete description

chassis_controller:
  type: rm_chassis_controllers/OmniController
  publish_rate: 100
  enable_odom_tf: true
  publish_odom_tf: false
  power:
    effort_coeff: 10.0
    vel_coeff: 0.003
    power_offset: -8.41
  twist_angular: 0.5233
  timeout: 0.1
  pid_follow: { p: 5.0, i: 0, d: 0.3, i_max: 0.0, i_min: 0.0, antiwindup: true, publish_state: true }
  twist_covariance_diagonal: [ 0.001, 0.001, 0.001, 0.001, 0.001, 0.001 ]
 
  wheels:
    left_front:
      pose: [ 0.147, 0.147, 2.356 ]
      joint: left_front_wheel_joint
      <<: &wheel_setting
        roller_angle: 0.
        radius: 0.07625
        pid: { p: 0.41, i: 0, d: 0.0, i_max: 0.0, i_min: 0.0, antiwindup: true, publish_state: true }
    right_front:
      pose: [ 0.147, -0.147, 0.785 ]
      joint: right_front_wheel_joint
      <<: *wheel_setting
    left_back:
      pose: [ -0.147, 0.147, -2.356 ]
      joint: left_back_wheel_joint
      <<: *wheel_setting
    right_back:
      pose: [ -0.147, -0.147, -0.785 ]
      joint: right_back_wheel_joint
      <<: *wheel_setting

Bugs & Feature Requests

Please report bugs and request features using the Issue Tracker.