The DIRECTA steering system can work in three distinct operating modes:

• MAIN mode
• OVERRIDE mode (Emergency level I)
• BACKUP mode (Emergency level II)

MAIN mode is the principal operation mode and allows to control the rudders through the main control system (PLC), either by autopilot or manually using the rudder wheel or joysticks in the desired control stations (Wheelhouse, SGC, Fly bridge, Wing stations). OVERRIDE mode and BACKUP mode are two Emergency modes, and allow the user to override the main controls and directly command the actuators through an EMERGENCY STEERING CONTROL panel. The selection of Operating Modes can be controlled by Selector Switch presented on EMERGENCY STEERING CONTROL. Further details about these functions are described in the chapters below.

1. MAIN MODE

In MAIN mode the user can control the rudders by autopilot or manually, using the touchscreens on the control stations and the rudder wheel or joysticks. In this operating mode the actuators’ brushless motors are controlled by the inverters and managed by the PLCs in order to follow the rudder angle set point.

The user can select the operating mode and how the rudder angle set point is set by selecting on the touchscreen either in

1. AUTOPILOT
2. MANUAL

A section of the HMI is reported below for better clarity.

HMI view from touch screen panel with indication of Manual and Autopilot (selected) modes

        1. AUTOPILOT

In Autopilot mode the rudders are automatically controlled by the autopilot device which provides reference set point. This mode is disabled if manual mode is selected from touch screen, if there is an abrupt motion of the wheel (safety measure), or if the EMERGENCY switch is not in “main” position. The Autopilot mode can only be enabled from Wheel House or Optional Flybridge.

Autopilot selection – summary scheme

        2. MANUAL

In Manual control mode the rudders can be controlled by manual devices (wheel or joysticks). From the wheelhouse, SGC, flybridge or Wings stations, the User can control the rudders synchronously with wheel, while on the wings stations the User can control the rudders with joysticks, either in synchronous or asynchronous mode (according to the selection on HMI. See Figure 5), based on the configuration chosen.

Manual mode is disabled if Autopilot mode is selected from touch screen or if the EMERGENCY switch is not in “main” position.

HMI view from touch screen panel with indication of Manual mode selected from wheelhouse station

HMI view from touch screen panel with indication of Manual mode selected from wing station.

Manual selection – summary scheme

EMERGENCY MODES

The EMERGENCY modes can be activated by selecting the relative position of the emergency switch on the Emergency steering control panel.

The EMERGENCY modes are classified in two levels, namely the Level I (EMERGENCY switch in the “override” position), and the Level II (EMERGENCY switch in the “backup” position), described in the following sub-sections. The EMERGENCY modes are disabled if the EMERGENCY switch is in the “main” position.

2. OVERRIDE mode (Emergency level I)

In this operating mode, the Emergency steering control panel overrides the main controls, allowing to actuate directly the inverter drives which command the actuators.

Emergency mode Level I (Override) – summary scheme

3. BACKUP mode (Emergency level II)

In this operating mode, the Emergency steering control panel override the main controls, the inverter drives, and the main on-board supply, allowing to control the actuators directly with the joysticks through the installed 24V DC motor.

Emergency mode Level II (Backup) – summary scheme

EMERGENCY SCENARIOs

The EMERGENCY mode can be activated in case of fault of any of the main steering system components. Examples of possible scenario are provided below:

• Emergency scenario 1: in case main control components are in fault (e.g., both the PLCs are in fault, or the ethernet communication is down), then both the actuators can be operated independently in EMERGENCY mode Level I (Override).

• Emergency scenario 2: in case both inverters are in fault, or in case of power blackout (no 230V supply to the inverters), then both the actuators can be operated independently in EMERGENCY mode Level II (Backup).

• Emergency scenario 3: if one of the two rudder actuation system (inverter or motor) is in fault condition or not able to operate, by enabling EMERGENCY mode Level II (Backup) the user can move the faulty rudder to 0° and then switch back to MAIN mode, in order to control the system with the functioning rudder.

 

In any configuration of the system, in emergency condition the rudder angle can be visualized by means of graduated crown mounted on the tiller, or by rudder indicators installed on the Emergency steering control panel.

SYSTEM COMPONENTS

1. ELECTRIC LINEAR ACTUATOR

The electric linear actuator used in the DIRECTA steering system acts on the tiller to reach rudder angles range of at least -35° to +35°. The maximum rudder angles are also dependant on the tiller dimensions. The electrical linear actuator is equipped with the following components:

• Two inductive limit switches to limit the actuator stroke through an electrical signal N.C. 24VDC.
• Main Brushless Motor.
• Auxiliary Motor 24V DC to move the actuator in Emergency mode Level II (Backup).
• Absolute encoder installed on the motor for rudder angle feedback.
• Potentiometer installed on the tiller for rudder angle feedback redundancy.

2. MAIN BRUSHLESS MOTOR AND AUXILIARY MOTOR

The motor is a three-phase synchronous motor with permanent magnets, equipped with thermal protection (PTO). The thermal protection is of bimetallic type, calibrated to signal temperatures at the stator windings for temperature above 130 °C (motor overheat).

In the event of overtemperature (overload) of the motor, the visual and buzzer signals in all control stations are activated (cumulative alarm). The error is also displayed on the touchscreen panel in the Wheelhouse and other optional control stations.

Note: steering control remains active even in the event of motor overheat alarm.

3. ABSOLUTE ENCODER AND POTENTIOMETER

A potentiometer is installed on each actuator’s tiller for redundancy visualization of rudder angle. These encoders are isolated from control circuit. The potentiometer is powered by stabilised 24V DC.

Two rudder angle displays for Port and Stbd rudder are installed in the Wheelhouse Control Station and directly connected to the potentiometers to monitor the actual angle of the rudders.

Motor encoder is installed on actuator brushless motor shaft. This signal is read by the inverter and sent to the PLC controller, that converts it into rudder angle. This information is transmitted to all control stations’ touchscreen displays.

4. AUXILIARY JUNCTION BOX

The auxiliary junction box (JB_2 PORT / STBD as indicated in the Cable Layout) houses the connections for the auxiliary control circuit (limit switches, potentiometer) and acts as disconnector system between 230V motor and the Inverter when the EMERGENCY switch is in the “Backup” position. It also contains the soft starter that, when the Emergency switch is in the “Backup” position, opens the circuit between Inverter and motor and activates the Clutch to engage the actuator with the 24V DC motor.

AUXILIARY JB FOR DIRECTA WITH AUXILIARY 24V MOTOR

Example of auxiliary junction box for Directa R4 with 24V motor.

This junction box includes a soft starter, used to enable the 24VDC motor in case of EMERGENCY mode Level II (Backup). It also includes two push buttons to control the 24VDC motor in the same conditions and a Rudder Angle display directly connected to the potentiometer installed on the tiller.

The feeder of the circuit breaker for this circuit (24V) is set to trip instantaneously at no less than 200% of the rated full-load current of the auxiliary steering gear motor. The rated power of the DC motor is 150W (for Directa 100/120), 300W (for Directa 140/150).

The function of the disconnector within the JB is to isolate the power supply of the motor from the inverter. Once the AC motor has been disconnected, the actuator can be moved by actuating the auxiliary 24VDC motor as previously described.

5. INVERTER

STANDARD OPTIONS BUILT IN EACH INVERTER

Standard features of the inverter:

• MODBUS TCP Communication with PLC
• ENCODER reading through SSI protocol
• Integrated Motion Control Board
• 24Vdc BACKUP Connection Possibility (to keep active the inverter control circuitry in case of 220V supply failure)

INVERTER INPUT/OUTPUT LIST

The following is the I/O list provided in each Inverter:

• Move actuator FWD
• Move actuator reverse
• Enable Override mode
• Enable Start FWD (Limit Switch)
• Enable Start Reverse (Limit Switch)
• Motor PTO Alarm
• General Alarm
• Power failure Alarm
• Motor Overload Alarm (cumulative to OverTemp, Overcurrent, Over Torque)

In case of normal operation (MAIN mode), the inverter is controlled by the PLC via Modbus TCP/IP.

The inverter LCP display also allows to visualise the operating status, descriptive variables like alarms and warnings, e.g., main phase loss, inverter overload, current limit, torque limit, overcurrent, ground fault, earth fault, short circuit, motor phase missing, feedback error (loop failure). Alarms are displayed also in the touchscreen panels in the control stations.

Example of LCP Display on Inverter

6. WHEELHOUSE JUNCTION BOX_1

The wheelhouse junction box houses all the connections related to the manual control devices signal cables (wheels, joysticks) as well as the ethernet switch that connects all the components in the ethernet network (PLCs, touchscreen panels, inverters).

Example of wheel house junction box

The Wheelhouse JB_1 contains the following inputs:

• EMERGENCY switch
• AP_Consense
• AP_Port_Cmnd
• AP_Stbd_Cmnd
• SGC_Joy_Port_cmd
• SGC_Joy_Stbd_cmd
• WingP_Port_Joy_Port_cmd
• WingP _Port_Joy_Stbd_cmd
• WingP _Stbd_Joy_Port_cmd
• WingP _Stbd_Joy_Stbd_cmd
• WingS_Port_Joy_Port_cmd
• WingS _Port_Joy_Stbd_cmd
• WingS _Stbd_Joy_Port_cmd
• WingS _Stbd_Joy_Stbd_cmd
• JB_2_Port Power supply OK
• JB_2_Stbd Power supply OK
• WHEEL HOUSE Analog Input 0-10V
• FLY Wheel Input 0-10V
• Autopilot_Reference Input 0-10V
• Autopilot_Reference Input 4-20mA
• PORT Angle positioning Analog Output 0-10V
• STBD Angle positioning Analog Output 0-10V

7. EMERGENCY STEERING CONTROL PANEL

The emergency steering control panel, used for emergency maneuvers, is equipped with the following components:

Emergency steering control panel

1. 1. 1. EMERGENCY SWITCH

The emergency switch has three positions, MAIN (O), OVERRIDE (I), and BACKUP (II).

• When in MAIN position, EMERGENCY mode is disabled and the system works with the main controls (PLC).

• When in OVERRIDE position it isolates actuators from main control and allows joysticks (P, S) on the Emergency steering control panel to directly actuate the inverter drives.

• When in BACKUP position, it isolates actuators from inverter drives and from main on-board 230V supply, allowing to directly actuate rudders with the Emergency steering control panel’s joysticks.

The components in the Emergency steering control panel are powered from respective JB_2. (Means Port Joystick, Display, alarms powered from JB_2 Port).

1. 1. 2. JOYSTICKS FOR DIRECT RUDDER ACTUATION (PORT/STBD)

The joysticks for direct actuation of rudders in EMERGENCY mode are directly connected to the inverter drives/ to the auxiliary 24V motors based on the EMERGENCY switch position (Override or Backup respectively).

1. 1. 3. RUDDER ANGLE INDICATORS (PORT/STBD)

The rudder angle indicators visualise the rudder angle independently from the touch screen panel. They are isolated from main control circuit and directly connected to the potentiometers installed on the rudders’ tiller. These angle indicators serve as redundancy display of the actual rudder angle and for visual feedback in EMERGENCY mode.

1. 1. 4. VISUAL AND ACOUSTIC ALARMS INDICATORS

The Emergency steering control panel is equipped with visual and acoustic indicators for both cumulative and dedicated alarms. These include 2 buzzers (PORT/STB), and 7 LEDs, namely 2 LEDs for inverter general alarms (PORT/STB), 2 LEDs for power failure alarms (PORT/STB), 2 LEDs for motor overload alarms (PORT/STB), 1 LED for PLC failure alarm. These components are independent from the ethernet network and therefore are operational also in EMERGENCY mode. Each steering system (PORT/STBD) can be independently monitored by its specific visual alarms (LED) and buzzers.

 

8. WHEELHOUSE CONTROL STATION

The main control station is the Wheelhouse Control Station and has the following components:

wheelhouse control station

1. 1. 1. CONTROL DEVICES (POTENTIOMETRIC WHEEL, JOYSTICKS)

From the Wheelhouse control station, it is possible to control the rudders in manual mode, using the wheel (rudders are controlled synchronously).

1. 1. 2. TOUCH SCREEN PANEL

The touchscreen panel on the wheelhouse station is the main user interface.

It displays the data from the PLC, the inverters and the motors encoders.

• The status bar displaying the current station in command
• The selected operating mode
• The rudders set point
• Actual rudders angle
• All the alarms for both PORT and STARBOARD inverters on the alarm page.

Furthermore, the touchscreen panel allows to:

• Take command from the wheelhouse station (and override command from other stations with the command changeover procedure).
• Select operating modes (autopilot or manual).
• Configure the user parameters (actuation speed, wheel sensitivity, etc.) from general setting page.
• Configure the system parameters (actuation speed, wheel sensitivity, etc.) from service menu.

 

Example of touchscreen home page.

General Settings Page

The General Settings Page is accessible to the user from the touchscreen home page. It allows to configure high-level steering system parameters (actuation speed, wheel sensitivity, etc.) and to perform systems control actions such as Inverters reset, Communication Network restart, and touchscreen restart.

Example of touchscreen general settings page.

Alarms Page

The Alarms Page is accessible to the user from the touchscreen home page. It reports a detailed status of the steering system, allows to monitor all alarms occurrence time and resolution times, and to acknowledge such alarms muting the buzzer.

Example of touchscreen alarm page.

Service Menu

The Service Menu pages are only accessible from the Wheelhouse touch screen home page and protected by password. These pages allow CMC Marine Service technicians to configure, monitor and debug the steering system hardware and software functionalities.

Example of service menu page.

The service menu pages allow to:

• Configure low-level steering system parameters.
• Perform set-up of rudder actuators.
• Monitor characteristic software and hardware signals.
• Initiate rudder motion tests routines.
• Perform system control actions (e.g., resetting drives, communication network, touchscreens)

9. FLYBRIDGE CONTROL STATION

Example of flybridge control station layout

Optional Flybridge Control Station is equipped with:

• Touch screen panel for control and display.
• Analog Potentiometric wheel for manual command (synchronous) of the rudders.
• Visual and audible alarm These alarms are independent from the ethernet network and therefore are operational also in EMERGENCY mode.

The touch screen panel has the following functions:

• Take command from the flybridge station (and override command from other stations with the command changeover procedure).
• Select operating mode (autopilot or manual).
• Rudder angle visualization (set point and actual angle).
• Monitor all the alarms for both PORT and STARBOARD inverters.

10. WING CONTROL STATION

Example of wings control station layout

Optional Wing Control Stations equipped with:

• Touch screen panel for control and display.
• Joysticks for manual command (synchronous / asynchronous) of the rudder.
• Visual and audible alarm These alarms are independent from the ethernet network and therefore are operational also in EMERGENCY mode.

The touch screen panel has the following main functions:

• Take command from the wings station (and override command from other stations with the command changeover procedure).
• Select operating mode (Synchronous / Asynchronous).
• Rudder angle visualization (set point and actual angle).
• Monitor all the alarms for both PORT and STARBOARD inverters.

 

Example of wing station touchscreen home page.

11. STEERING GEAR COMPARTMENT CONTROL STATION

The Steering Gear Compartment (SGC) has the following components:

SGC control station

1. 1. 1.  TOUCH SCREEN PANEL

The touchscreen panel on the SGC control station is the main user interface.

It displays the data from the PLC, the inverters and the motors encoders, and it allows to operate rudders.

• The status bar displaying the current station in command
• The selected operating mode
• The rudders set point
• Actual rudders angle
• All the alarms for both PORT and STARBOARD inverters

Furthermore, the touchscreen panel allows to:

• Take command from the steering gear compartment station (and override command from other stations with the command changeover procedure).
• Select operating modes (autopilot or manual).
• Configure the system parameters (actuation speed, wheel sensitivity, etc.).

 

Example of SGC touchscreen home page.

12. MAIN PLC CONTROL PANEL

The PLC acts as master of the ethernet network; thus, it manages the communication between the control stations and other devices connected in the same network (autopilot, inverters, wheelhouse junction box, and Optional Control stations). The system is controlled by a MITSUBISHI PLC in the main control switchboard.

13. BACKUP PLC CONTROL PANEL

The BACKUP PLC has a redundancy purpose, to guarantee the DIRECTA system functionalities in case of faults in the MAIN PLC.

The backup PLC operates in a state of “silent monitoring” where all the control functionalities are disabled, and the state of the main PLC is monitored via ethernet communication.

In case a fault of the main PLC is detected (PLC in error, failure in the main PLC supply), the backup PLC is automatically activated in all the control functionalities to fully replace the main PLC and restore the system functionalities. After clearance of Fault in Main PLC, it is required for a power cycle to bring back MAIN PLC in action.

14. AUTOPILOT CONTROL

In the DIRECTA systems the rudders can be controlled by the autopilot when the AUTOPILOT mode is selected from the touchscreen panel. Autopilot signals can be exchanged between the autopilot device and the PLC for automatic control of the rudders.

The signals sent from the PLC to the autopilot device are the following:

• autopilot request (digital, 24V relay)
• autopilot in command (digital, 24V relay)
• rudder angle (analog, 0-10V DC)

The signals sent from the autopilot device to the PLC are the following:

• autopilot consensus (digital, 24V relay)
• setpoints port/starboard (analog, 0-10V DC)

Depending on the type of autopilot device, the 2 rudders can be controlled both with

• Proportional control (analog signals)
• ON/OFF logic (digital signals)

15. ALARMS SYSTEM

The alarms system is managed by the PLC and the inverters, as detailed below.

• PLC ALARMS MANAGEMENT

The PLC collects status and alarms from the Inverters (Port/Stbd) and displays them on the touchscreen panels installed on control stations. The PLC management cover the alarms related to the MAIN operating mode. The following table reports the alarms displayed on the touchscreens.

ID	CONDITION (FAILURE OR ALARM DESCRIPTION)	DESCRIPTION
1	Manual Override	The emergency switch is activated, and the system is switched onto EMERGENCY mode.
2	Port/Stbd Inverter Fault	Inverter in fault.
3	Port/Stbd AC Supply Fault	Lack of power supply to respective Inverter.
4	Port/Stbd Motor excessive load	The actuator motor exceeds the max current power, but the system keeps working.
5	Port/Stbd Motor Overheat	The system exceeded the maximum temperature on the motor, but the system keeps working to guarantee emergency manoeuvres.
6	Port/Stbd FC OFF	The inverter display is set on HAND-ON mode, or the Inverter turned off
7	Limit Switch IN/OUT	The rudder has reached the maximum angle on Port/Stbd side, or the Limit switch is faulty.
8	Port/Stbd Encoder Error	The feedback transducer is Faulty.
9	Wheel 1 Fault	The rotary encoder of the wheelhouse control station wheel has no power supply, or it is faulty.
10	Wheel 2 Fault	The rotary encoder of the fly-bridge control station wheel has no power supply, or it is faulty.
11	Communication Fault (Port/Stbd side)	The communication between PLC & Inverter is interrupted.
12	Rudder Reference Deviation	The rudder actual position does not reach the set point within acceptable time limits.
13	Autopilot Disengaged	Unexpected autopilot disengage (*distinct-beep alarm).

Those alarms activate a buzzer and visual alarm on each touchscreen. The alarm can be acknowledged only by the station in command (or from any station if no station is in command). When the alarm is acknowledged, the buzzer is muted.

• INVERTER ALARMS MANAGEMENT

A Cumulative secondary alarm management system is available on each control station, to indicate a fault in the inverters. In case of inverter fault, the Alarm activates a LED and buzzer on all control stations. These alarms remain active until the fault is cleared. Furthermore, each inverter has a local control panel (LCP) to display its alarms or (see INVERTER section).

16. SOFTWARE SPECIFICATIONS

The DIRECTA Software is developed in compliance with the following requirements:

• Maintain an independent control and safety. For this purpose, the failure of one rudder system does not degrade the performance of the other rudder.
• Manual operation: any failure in the system does not prevent the use of the manual override (EMERGENCY).
• The software maintains constant system performances.
• Control and monitoring are independent.
• An audible and visible alarm is generated in case of failure.
• In case of failure the rudder remains in the position it was when the failure occurred.
• Manual operation: each rudder can be operated manually and independently.
• Only one control station at a time is active.
• The transfer of control is to be acknowledged by the receiving control station within a limited time frame.
• An automatic software routine monitors and manages the backup PLC intervention in case of failure in the main PLC.
• Alarms remain active and displayed if they are acknowledged and visual indications are on until the faults disappear.

1. 1. SOFTWARE FUNCTIONALITIES DESCRIPTION

This section describes the software functionalities of the DIRECTA steering system. The following table shows the buttons used in the user interface, to describe the available actions:

 

BUTTON	ACTION	DESCRIPTION
	TAKE COMMAND	Take or release the command. From any station: Press “TAKE COMMAND” once and then once again for 2s to perform the command changeover maneuver and acquire command from previous station.
	MANUAL	Switch to manual control mode
	AUTOPILOT	ONLY AVAILABLE FROM WHEELHOUSE/FLYBRIDGE STATIONS Switch to autopilot control mode.
	ALARM ACK	Acknowledge the alarm. Mute the buzzer.
	SYNC ASYNC	ONLY AVAILABLE FROM WINGS STATIONS To control both rudders at same angles with (Main Joystick, Stbd side) To control the Rudders at different angles with both the Jotsticks.
	RUDDERS AT CENTER	When the button is held for 2s, the command will be issued to bring both rudders top 0° angle position. The RUDDER AT CENTER function in available only in MANUAL mode (will not be displayed in other control modes).

 

1. 2. TAKE COMMAND

In MAIN mode, the user can take command from different control stations (Wheelhouse, SGC, Flybridge, and the Wings control stations). Each control station can take command but only one control station can be enabled at any time. If no station is in command, the “TAKE COMMAND” button on each touchscreen allows to request authority to control Rudder from that position. If any station is in command, the “command changeover maneuver” can be performed from any other station to acquire command from the previous station by pressing “TAKE COMMAND” once and then holding it once again for 2s. During the changeover maneuver, the last station in command remains in command until the changeover is completed and the final station successfully acquires command.

During the transfer of the command the status of TAKE COMMAND button (Blink/Fixed on/Turned off) indicates the status of the control station:

• BLINK GREEN – No station is in command, ready to take command by any control station.
• FIXED ON GREEN – the control station is in command.
• TURNED OFF BLUE – the control station is not in command.
• BLINK RED – command changeover maneuver in action

 

If the TAKE COMMAND is released, and not activated in any other station within a time frame of 100s, the last station from which the command was released returns in command.

1. 3.  AUTOPILOT MANAGEMENT

The autopilot control can be selected by pushing the AUTOPILOT button, only from the Wheelhouse and Flybridge control stations. The Autopilot rudder reference is synchronously sent to both the Inverters.

The user can disengage the autopilot and engage the manual control mode swiftly, by operating the rudder wheel with a sufficient acceleration and angle. As an example, if the Autopilot is in control and the user moves the rudder wheel over a certain angle and acceleration, the PLC detects the request, release the autopilot control mode, enables the manual control mode, and generates a specific alarm.

Alternatively, the user can press the MANUAL button to disengage the autopilot and engage manual control.

An alarm is activated if there is a significant deviation between rudders set point from the autopilot and the actual rudders position for more than 30 sec.

In every control mode the software controls the maximum reachable rudder angles. The default limit is ±35°. In any case, the limit switches on the actuator act as end-stop. If the actuator reaches the limit switch sensor, the Inverter stops the motor.

1. 4. MANUAL CONTROL

In MANUAL control mode, the software allows to control the rudders either with a wheel (when available in the control station) or with joysticks (when available).

The software allows to operate the Rudders (Port/Stbd) synchronously (with wheel or main joystick) or asynchronously (with two joysticks). To support the asynchronous control, the control station must include two joysticks (e.g., wing stations).

From the wings control stations, by pressing SYNC, the joystick on STBD Side acts as the master command for Port/Stbd Rudders, and the rudders are controlled synchronously.

By pressing ASYNC the joysticks control the two rudders asynchronously.

1. 5.  RUDDERS AT CENTER

When the RUDDERS AT CENTER button is pressed (held for 2s), both port and stbd setpoints are set to 0° position. Consequently, the control will bring both rudders to the center position. This functionality is only available in MANUAL mode. In all other control modes, the RUDDER AT CENTER button will not be visualized.

1. 6.  BRIGHT/DARK GRAPHIC INTERCHANGE

To accommodate both needs of high visibility during day navigation and low illumination during night navigation, the software graphic theme can be easily interchanged between BRIGTH and DARK respectively, by pressing the home screen page button from the home screen page, or by pressing the alarm page button from the alarm page.

Example of Bright/Dark graphic swap.