ubiquity_motor

Introduction

This is a Package that provides a ROS interface for the motors in UbiquityRobotics robots. It communicates with the motor controller via a serial port.

Installation

This package may be installed from binaries for both x86 and ARM architectures.

The package may be installed with:

sudo apt-get install ros-kinetic-ubiquity-motor

Configuration launch files for the Magni robot are in the package magni_robot.

ROS API

Subscribed topics

cmd_vel geometry_msgs/Twist The command input.

system_control std_msgs/String A channel to command the motor node to change mode of operation. A text string with a commnad followed by parameter such as enable or disable are used.

motor_control disable      Stops the MCB control over serial (used for firmware load)
motor_control enable       Re-attaches the MCB control over serial for normal operation


speed_control disable      Stops the robot so no speed control is used for collision avoiance
speed_control enable       Re-enables the motor node to respond to cmd_vel speed messages

Published topics

odom nav_msgs/Odometry Odometry computed from motor controller messages.

/tf tf/tfMessage The transform from odom to base_link

firmware_version std_msgs/String Version of motor control board (MCB) firmware formatted as “vXX YYYYMMDD” or just “vXX” if there’s no daycode found.

battery_state sensor_msgs/BatteryState Charge state of the robot’s batteries.

publish_cmd geometry_msgs/TwistStamped The value of cmd_vel after limits were applied. Available if the publish_cmd paramater is set.

motor_power_active std_msgs/Bool The state of motor power being active is published. This follows the ESTOP switch within about a half second.

motor_state ubiquity_motor::MotorState The combined motor state for both wheels with positions, rotate rates, currents, pwm drive values

left_error std_msgs/Int32 The error in expected left wheel position relative to current left wheel position is published for diagnostics purposes.

right_error std_msgs/Int32 The error in expected right wheel position relative to current right wheel position is published for diagnostics purposes.

left_current std_msgs/Int32 The motor current in amps that the left motor is running at at this time

right_current std_msgs/Int32 The motor current in amps that the right motor is running at at this time

left_tick_interval std_msgs/Int32 A value that is proportional to the time between left wheel encoder ticks for usage in diagnostics. This unsigned value is only published when velocity is non zero.

right_tick_interval std_msgs/Int32 A value that is proportional to the time between right wheel encoder ticks for usage in diagnostics. This unsigned value is only published when velocity is non zero.

Parameters

Comms paramaters

serial_port (string, default: “/dev/ttyS0”) Name of device with which to communicate with motor controller hardware.

baud_rate (int, default: 9600) Baud rate for serial communication with motor controller hardware.

Firmware parameters

pid_proportional (int, default: 5000) The P paramater for the motor controller’s PID controller.

pid_integral (int, default: 10) The I paramater for the motor controller’s PID controller.

pid_derivative (int, default: 1) The D paramater for the motor controller’s PID controller.

pid_denominator (int, default: 1000) Divisor for the above PID paramaters.

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