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Yokogawa Denshikiki Co., Ltd.



Autopilot System Descriptions

Autopilot System

An autopilot controls the steering gear of a vessel to keep it on course.

There are three types of actuators: solenoid valve control, single-loop control to control torque motors, and two-loop control to control servo-cylinders.

PT500: This model is widely applicable to many types of vessels and can be easily adapted to any type of steering gears and actuators.
PT900: This model performs control to suit any type of actuator for steering gears, just like the PT500 Autopilot.

Configuration of Autopilot System

The autopilot system is configured with the following basic components.
1) Control Stand
Control stand consists of the following units, which are also adequate to the panel-mount.
- Control & Display Unit
- Annunciator unit
- Hand steering unit
- Non follow up lever
- System selector
- Mode selector
2) Control & Power Box
3) "μ"Transmitters
4) Actuators (Supplied and handled by the steering gear manufacturer)

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System Configuration


System Configuration of PT900

PT900 System Configuration
Each unit which is functionally separated is equipped with CAN-BUS network.
Thus, the system can be easily scalable and adaptable to various specifications.
CAN-BUS network allows for detection of errors each unit and cable disconnection between units.

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Steering Methods


Steering Method of Autopilot

- Follow up (FU) steering
This is servo control which drives the rudder until the command angle of the autopilot is equals to the feedback angle from the steering gear.
FU control includes automatic steering (AUTO) mode and manual steering (MAN) mode. It enables a vessel to be steered using the steering units incorporated into the system.

- Non follow up (NFU) steering
This is open loop control and it is occasionally used in emergencies. It directly drives the actuators of the steering gear. This control is well known as emergency steering and selectable when System selector is in the NFU position or Take-over unit.

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Steering Modes

  • NFU override mode (NFU lever steering)
    This mode overrides any other steering modes using NFU control. It enables the acquisition of maneuver position, with precedence over all steering locations.

  • FU override mode (FU dial steering)
    This mode overrides any other steering mode using FU control. It enables the acquisition of maneuver position, with precedence over all steering locations.

  • AUTO mode (HCS / FU Steering)
    This mode automatically keeps the ship's heading to a preset course. A heading reference signal from a gyrocompass is required.

  • CRS mode (HCS / FU Steering)
    This mode controls the ship's course by comparing a heading reference signal to the course over ground with the preset course.

  • TRACK mode (TCS / FU Steering)
    This mode enables track control. Interface with INS equipment such as ECDIS is required.

  • MANUAL mode (Control stand / FU Steering)
    This mode manually controls ship's heading from the steering wheel on the front of control stand. Number of magnetic encoder mechanized in the steering wheel can be provided in coincidence with the number of steering control system.

  • FU takeover mode (Remote control / FU Steering)
    This mode manually controls the ship's heading, and the control can be done away from the control stand. Dial steering unit or the like is required.

  • NFU takeover mode (Remote control / NFU Steering)
    This mode manually operates the ship's heading by remote control, using an Non follow up lever or similar.

  • NFU mode (NFU lever steering)
    This mode directly drives the actuators of the steering gear.
    The rudder is driven when the NFU lever is turned to port or starboard, and stops moving when the NFU lever is in neutral.

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Explanation of Units


Panel Arrangement of MPM190 Control Stand

Control & Display Unit (MPH490)
These units are used in steering mode: AUTO mode.
The AUTO mode contains following controls:
- Adaptive control, and
- PID control.
Each of the above models are customized to suite each vessel's specifications.

Hand-steering Unit (MPB390)
This unit is a steering wheel used for the manual steering. Steering angle indicators are positioned alongside the wheel.

Steering Repeater Compass (MKR056)
This unit is a ship's heading repeater for use by the helmsman, and dimming control is available. This unit is suitable for panel-mounting or wall-mounting.

Annunciator Unit (MPH690)
This unit displays the operating status of the autopilot and issues visible and audible alarms when a failure occurs. Repertoire of display is provided by accordance with the specification requirements of the autopilot.

System selector (MPH790)
This unit selects follow up control (No.1 or No.2) or non follow up (NFU) control to be used.

Non follow up lever (MPB391)
The NFU lever is functional when NFU control is selected. The rudder moves while the lever is tilted.

Mode selector (MPH791)
This unit is the steering mode selector. This unit is provided in accordance with the specifications of the autopilot.

Steering indicator (MPH590): Option unit
This unit indicates the selected steering mode and steering position.

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