Safety Module

This package interacts with the hardware safety system of Robotnik Robots. It is used to:

• publish the status of the safety system,
• set the working mode for the current operation,

It interacts with the hardware safety system via a set of digital input/outpus, accessed via the robotnik_io_msgs messages definition. The package was designed originally to work through a modbus interface, but it should work with any other.

Main features

Feature	Description
Laser mode switching	Selects the safety zones of the front/rear lasers.
Watchdog	Sends a toggling signal so the PLC knows that PC↔PLC communication is alive.
State aggregation	Publishes a single “global state” derived from multiple PLC inputs (E-Stop, key switch, selector, etc.).
Speed feedback	Writes the robot's internally computed speed as a 12-bit word to the PLC.

ROS Integration

Topics

Output topics

• ~/status (robotnik_safety_msgs/msg/SafetyModeStatus)

Current status of the safety system

• ~/emergency_stop (std_msgs/msg/Bool)

Wether the emergency stop is active (emergency stop requires manual reset)

Input topics

• io (robotnik_io_msgs/msg/InputsOutputs)

Used to read the current inputs/outputs values

• odom (nav_msgs/msg/Odometry)

Used to read the current odometry value

Services

Services provided

• ~/set_laser_mode (robotnik_common_msgs/srv/SetString)

Sets the current laser mode.

Services called

• set_digital_output_array (robotnik_io_msgs/srv/SetDigitalOutputArray)

Used to write the digital outputs

Configuration file

The node reads a YAML file organised in four sections. Each section defines a set of high-level tags that are mapped to the input/output bits accessed via the robotnik_io_msgs interface.

2.1 Global tags

Aggregates high-level safety signals, used to publish a general status.

global:
  emergency_stop: emergency_stop
  safety_stop: safety_stop

  selector_mode_auto: selector_mode_auto
  selector_mode_manual: selector_mode_manual
  selector_mode_maintenance: selector_mode_maintenance

  laser_mute: laser_mute

Left-hand keys are fixed and must be filled right-hand values are the bit-names provided by robotnik_io_msgs.

---

2.2 Watchdog

This feature sends a toggling signal to the PLC to indicate that the PC is still alive and communicating.

watchdog:
  enabled: true
  period_ms: 1400
  signal_a: watchdog_signal_a
  signal_b: watchdog_signal_b

• When enabled is false no watchdog is transmitted.
• period_ms is the full square-wave period.
• signal_b is the logic-negated copy of signal_a.

---

2.3 Speed controller

This feature writes the robot's speed as a 12-bit word to the PLC.

speed:
  enabled: true
  period_ms: 100
  prefix: speed_bit_

• Writes 12 bits (<prefix>11...<prefix>0) at the specified period.
• Speed is written in cm/s, with <prefix0> being the LSB.

---

2.4 Laser controller

This feature allows switching between different laser modes, which can be used to adapt the robot's behavior based on the current task or environment.

laser:
  default_mode: standard        # Mode used at node start-up or when PLC comms are lost
  modes:
    standard:                   # --- Mode definition ---------------------------
      input:
        laser_mode_standard: true
      output:
        laser_mode_standard_legacy_1: false
        laser_mode_standard_legacy_2: false
        laser_mode_standard_legacy_3: false
        laser_mode_standard_legacy_4: false

    charging_station:
      input:
        laser_mode_charging_station: true
      output:
        laser_mode_standard_legacy_1: true
        laser_mode_standard_legacy_2: true
        laser_mode_standard_legacy_3: true
        laser_mode_standard_legacy_4: true

  attributes:                   # --- Laser diagnostic bits ---------------------
    front_laser:
      detecting_obstacles: front_laser_detecting_obstacles
      contamination: front_laser_contamination_led
      free_warning: front_laser_free_warning

    rear_laser:
      detecting_obstacles: rear_laser_detecting_obstacles
      contamination: rear_laser_contamination_led
      free_warning: rear_laser_free_warning

• laser.default_mode If empty, no mode is forced on start-up.

• laser.modes.<name> Each mode describes

  • input - which bit(s) confirm that the PLC has applied the mode.
  • output - which bit(s) must be written to request the mode.

• Add as many modes as needed; simply copy an existing block and adjust the bit-names.

• laser.attributes Diagnostics for each laser (obstacle detection, contamination LED, etc.). The field names (detecting_obstacles, contamination, free_warning) are fixed; change only the bit-names on the right.

---

License

Distributed under the BSD-3-Clause license. See LICENSE for details.