CSIR Opto-mechanical engineer, Mark Holloway
The CSIR has been working on a novel camera-based surveillance system for the South African Navy (SAN) to provide a real-time, 360° video view of a ship's surrounds. To augment the 360° video, the Stand Alone Tracker (SAT) has been developed to carry a multi-spectral high resolution digital sensor suite to aid with the recognition of potential threats. One of the challenges in designing a system such as SAT is image stabilisation, considering the constant rocking motion of a vessel at sea. This is not a testing scenario one finds in Pretoria where the CSIR’s Optronic sensor systems team is based.
The solution? A modified platform using pneumatics and mechanical design to give the surveillance system a simulated ship motion. This means that the team could continue work on the system, without needing to be out on the ocean.
Challenges at sea
Surveillance is arguably one of the most critical components of any nation's approach to coastal defence and security strategy – even viewed by some as the very first component of protection. Challenges to surveillance include establishing the perfect ‘all seeing eye’ able to detect clearly what is happening in the full spectrum of your surrounds.
The CSIR designed a camera-based surveillance system for the SAN comprising five high-resolution cameras, each capturing a section of the surrounds. Footage is then ‘stitched together’ to create a real-time, 360° video-based view of the entire area surrounding a vessel. If and when a potential threat is detected, the SAT sensor suite is designated from the 360° video image. Using the combination of a high magnification zoom, High Defintion and Infrared cameras, the target can be observed for a decision to be made on the appropriate action. For example, a commander needing to dock safely in a harbour or unknown area has the benefit of a 360° video view, all around his vessel, surveyed in real-time.
Anti-piracy operations are currently the most important operational role of the SAN. This implies that the ships of the SAN are expected to detect very small targets (even small wooden boats) with a very low profile against a highly-cluttered background of waves and white caps. Optronic sensors offer an important complimentary choice of surveillance to the radar systems on the ships – especially for these scenarios.
The navy’s duty to protect the sovereignty of the state includes involvement in search and rescue missions, harbour-based criminal activity and the scourge of poaching and smuggling of South Africa’s wildlife such as abalone.
Ongoing work deals with challenges such as the glare of changing light, and processing extensive volumes of incoming data from the hi-resolution cameras. But over time, the outcome was a system that could pick up a specific object, follow it, zoom in on it, fully identify it – in real-time, to allow for immediate action. Used on a navy vessel, the system had to allow for the ship motion that would result in footage with shifting horizons, changing clouds and water swells obscuring objects.
The ship motion simulator is a modified version of the 3 DOF (Degrees of Freedom) Stewart platform. It operates on a roll and pitch axis at different frequencies and amplitudes using a combination of pneumatic actuators and position feedback into a custom control system.
The CSIR is in discussion with the University of Pretoria’s Department of Mechanical Engineering. The ship motion simulator will be made available for postgraduate research on mathematical modelling and control systems studies.
With the challenges of ship movement now better understood, the team will be working on other platforms for the surveillance systems – such as land-based patrol or response vehicles.