Stabelized Pan Tilt Positioners
MECHANICAL STABILIZATION’S ROLE IN OVERCOMING ENVIRONMENTAL FACTORS
Advanced technologies that ensure a secure physical environment are increasingly common standard features of surveillance and security systems. One long-standing issue in the surveillance and security industry is losing sight of a target due to environmental factors. While rain, snow, ice, heat, and a myriad of other forces can render a sensor or group of sensors ineffective, thereby compromising the security of the location, the focus of stabilization technologies is to mitigate the effects of undesired platform motion. Whether the disturbance is expected (such as waves in the ocean) or not (such as a gust of wind), stabilization enables users to maintain target location and identification even when conditions are less than ideal.
There are several technologies in use today to provide image stabilization ranging from mechanical stabilization to digital image processing. Each has a set of strengths and weaknesses, so choosing the correct technology for a given application is critical. Some key factors to keep in mind when selecting the correct stabilization solution include frequency and amplitude of the disturbance motion, slew rate (which relates to frequency and amplitude) and data retention/cropping.
This article specifically focuses on the use of gyroscopic feedback to an electronic positioning system to stabilize an electromechanical positioner, also referred to as a pan tilt. In addition to providing brief details regarding the system design, we present sample performance data.
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SYSTEM ARCHITECTURE
Over the years, Quickset has designed and fielded a number of systems that were configured with gyroscopic stabilization. The system featured in this paper is based on our current Mercury positioner. The architecture described below was designed such that it could be applied to a platform of products currently offered in Quickset’s portfolio.
A classic Proportional Integral Derivative (PID) control loop implemented on a microcontroller lies at the heart of this stabilization system. In this specific system, a microelectromechanical system (MEMs) based sensor is used, however the architecture allows for the use of other gyroscopic sensors by simply updating the sensor’s communication driver. The system operates as a closed loop, meaning that the MEMs device measures error and the PID loop corrects for this error.
More specifically, the gyroscopic data and position coordinates of the pan and tilt are merged to create the error signal that drives the control loop. The feedback control is user-adjustable to provide optimal functionality of the stabilization algorithm for different system designs (e.g. sensor payloads, pan and tilts) and target variation such as small watercraft, humans on foot, or unmanned aerial systems. The latency between the gyroscope’s sample acquisition and positioner’s drive electronics is minimized in order to create a high-performance system. The bandwidth of the control loop has been optimized to provide response at higher frequencies while weighing the effects of in-band noise. Drift compensation capabilities are included within the sensor board and a phase compensation filter is also available when required.
All of these features and capabilities are included to create a modular and adjustable stabilization driver that has applicability across Quickset’s high performance pan tilts.
Performance Criteria
Evaluating the performance of the stabilized Mercury system requires a special fixture that simulates the external motion inputs. This fixture creates a sinusoidal motion profile in both the azimuth and elevation axes. The amplitude and frequency of the sinusoidal motion are adjustable over a range covering many real-world mounting configurations.
In order to facilitate meaningful discussions, a straightforward calculation is used to characterize the impact of adding stabilization feedback to a standard Moog positioner.
Download the Quickset Pan Tilt White Paper to learn what the term rejection ratio is defined as.
For reference, a rejection ratio of 7.5 simply means that for a platform disturbance of 7.5°, the system will maintain the line of sight to within 1° of the target. In order to evaluate the appropriate rejection ratio for a specific application, the expected disturbance amplitude and sensor angle of view are required. For the case of a camera/lens combination, the angle of view is typically available from the manufacturer’s datasheet. If we assume a camera/lens that has an angle of view of 2.0°, then with a rejection ratio of 3.75 we should be able to maintain sight of a target with a platform disturbance of up to 7.5°. Adjustments can be made to this calculation to better serve specific system requirements.
Keep in mind that the rejection ratio varies with the frequency of the platform disturbance. For this reason, we provide performance at various frequencies to ensure that customers know what to expect from our product.
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More on rejection ratios:
In the context of testing, the term “rejection ratio” typically refers to a metric used to assess the quality of a testing process or the performance of a testing tool. It represents the proportion or percentage of test cases that are deemed unsuccessful or rejected during testing.
Where does the military utilize Quickset pan tilts?
The military utilizes pan-tilt systems in various applications to enhance situational awareness, surveillance, targeting, and reconnaissance capabilities. Pan-tilt systems are mechanisms that enable the controlled movement of cameras, sensors, or other equipment along both horizontal (pan) and vertical (tilt) axes.
Here are a few examples of how the military employs pan-tilt systems:
Surveillance and Reconnaissance
Pan-tilt systems are used to position cameras or sensors on unmanned aerial vehicles (UAVs), ground-based surveillance systems, or fixed installations. These systems allow operators to remotely control the movement of the camera or sensor to monitor an area, gather intelligence, and detect potential threats.
Remote Weapon Stations
Military vehicles, such as armored vehicles, tanks, or naval vessels, often incorporate remote weapon stations equipped with pan-tilt systems. These systems enable operators to control the movement and aiming of weapons, such as machine guns or small cannons, from a protected position inside the vehicle.
Border Security
Pan-tilt systems are employed in border surveillance systems to monitor and secure international borders. Cameras mounted on pan-tilt systems can scan large areas and provide real-time video feeds to operators, enhancing border patrol efforts and detection of unauthorized border crossings.
Target Tracking and Acquisition
Pan-tilt systems play a crucial role in target tracking and acquisition for military applications. They are used in conjunction with tracking algorithms and radar systems to keep cameras or sensors focused on a moving target, facilitating accurate tracking and improved situational awareness.
Remote Sensing and Intelligence Gathering
Pan-tilt systems equipped with specialized sensors, such as thermal imagers or multispectral cameras, are utilized for remote sensing and intelligence gathering. These systems allow military personnel to survey the environment, gather data, and identify potential threats or points of interest.
Overall, the military employs pan-tilt systems in various domains to enhance surveillance, reconnaissance, targeting, and intelligence capabilities. These systems provide flexibility, control, and precision in positioning cameras, sensors, and weapon systems, ultimately enhancing the effectiveness and efficiency of military operations.