Operational PAP Simulator (OPPAS)
A PAP (Poisson Auto Propulsé) is a small, remotely controlled, submarine in use with several naval forces. A PAP is used for identifying possible mine-like objects underwater with a camera. Upon positive identification, the PAP releases an explosive charge near the mine that will be detonated after the PAP has been recovered. However, training PAP operators is a costly and time-consuming activity. Generally, it involves the deployment of a minehunter equipped with a PAP on the high seas, the placement of a dummy mine, and suitable weather conditions. The PAP is controlled aboard the minehunter through a cable link, operating in this way the engines and relaying the video signal from the camera back to a monitor screen aboard the minehunter.
At the end of 1986, TNO-FEL was approached by the Royal Dutch Navy with the question of developing a system to roll up the cable that connects the PAP to the mine-hunter for reuse. After some discussions, TNO convinced the Navy that there was a better solution to save money: the use of a simulator so that PAPs do not need to be launched for training personnel.
A feasibility study by TNO followed regarding the Operational PAP Simulator or OPPAS. OPPAS could not only cut the training costs but also could reduce the skill acquisition period of the PAP operator, whilst, at the same time, the training capacity could be increased. Mid of 1987, the development of OPPAS was commissioned by the Royal Netherlands Navy to TNO. Mid-1990, the first OPPAS system was officially demonstrated and put to the test. In June 1991, the Navy commissioned ten OPPAS systems.
The developed OPPAS system is versatile and can simulate all of the PAP’s functions. OPPAS is installed in the combat information centre of the minehunter and eliminates the need for a real PAP and a dummy mine during training sessions. OPPAS can be used without having to leave the harbour and even can be installed on land in a mock-up of the combat information centre of a minehunter.
The simulator calculates the PAP’s reaction to the steering commands and gives a relevant response by realistically positioning a simulated echo on the sonar display. During a simulated training run, OPPAS can generate a dummy mine; a computer-generated image of this object appears on the screen of the PAP operating console as soon as it is picked up by the simulated camera. Of course, OPPAS not only simulates PAP behaviour but also simulates the interaction of a complex of other systems that are routinely used during a mine-hunting sortie, such as two different sonar systems, a DoppIer-log, the compass and a navigation system. All this has been accomplished within the limits of a necessarily small-sized system.
OPPAS can be deployed in four operation modes.
- Mode 1
Simulation of a PAP run, including the complete scenario of PAP testing, and launching a recovery from a stable platform (usually a minehunter in a harbour). Ship movement and a mine-like object are simulated.
- Mode 2
Simulation of a PAP run, including the complete scenario of PAP testing, launching and recovery, from a sailing ship at sea. Current ship position information is used in the simulation. A mine-like object may be simulated but also a real mine, detected by the ship’s sonar can be used.
- Mode 3
Target approach exercise. This mode is similar to mode 1 or mode 2, except for PAP testing, launching and recovery procedures.
- Mode 4
PAP steering exercise. This mode is used for training operators in just controlling and manoeuvring the PAP.
The OPPAS system
OPPAS meets the following specifications:
- The system simulates the launching procedure of the PAP, including setting the gyro compass and testing the engines and battery voltage.
- Simulation of the procedures for the target approach is provided by representing a simulated mine-shaped target on both the detection sonar display and the classification sonar display. This representation is linked to the sonar systems’ settings. The image is sufficiently realistic to make target classification possible.
- The PAP’s response to steering commands is simulated, taking into account both its mass and water current. Minehunter movement too must be processed.
- Battery discharge is calculated, as must the length of cable dispensed as well as a possible collision course of the PAP with the target.
- Images of a simulated target are generated for display on a monitor screen, together with compass and gyroscope information. Target image generation yields a three-dimensional picture, allowing for realistic movement of the simulated PAP around this target.
An operational OPPAS system is linked to the PAP console, the ship’s log and compass and the two sonar systems used. OPPAS can be linked to the navigation system. The OPPAS system consists of a main processor unit and an instructor console. The main processor unit lies at the heart of the system, and fulfils three major tasks:
- Data processing.
The processor unit extracts real, operational data from the ship’s systems and injects the simulated echoes into the sonar system. These simulated echoes of both the target and the PAP are fused with the real sonar video signal. The sonar systems require only a minor modification to benefit from the advantages of simulated sonar echo fusion and the extraction of actual data. Compass and log data, sonar control signals, and, most important of all, steering data directing the PAP are collected to be processed for successful and accurate simulation.
- Target generation.
The processor unit is capable of generating realistic echoes of the PAP and mine-shaped objects that are displayed on both sonar displays. It also synchronises the simulator with the actual sonar video signal. Moreover, this unit takes care of generating a synthetic image of the mine and translates it into an image that is interpreted by the PAP’s camera which is then passed on to the monitor of the PAP operator console.
- Running the simulation.
This is the processor unit’s first and foremost task. The simulator calculates the position and direction of the PAP using a mathematical model of the PAP. The steering commands that have been processed function as model input. The model is subject to evaluation four times every second to provide a regularly updated position and direction of the PAP. The PAP’s movement affects both the sonar picture as well as the target image on the monitor screen.
The instructor console
The simulator is controlled with the help of the instructor console. Menu-driven programs guide the user through the various system settings. The instructor can control, for instance, such parameters as:
- position and type of the simulated mine,
- the starting position of the ship and the PAP,
- environmental conditions such as current and sea bottom characteristics.
The system even incorporates the possibility to simulate certain malfunctions that sometimes occur with the PAP or the ship’s systems.
At the instructor console PAP information, such as elapsed time, battery condition, wire length used etc. is presented on the monitor screen. Data concerning the operators’ performance like PAP-track, steering commands and location of the dropped explosive charge is presented to the instructor. Simulated PAP operation sessions may be recorded for subsequent evaluation, replay or analysis.