Remote Touchscreen-Controlled Defense Turret Senior Design Documentation Courtney Mann, Brad Clymer, Szu-yu Huang Group 11

Targeting acquisition involves the visual processing of the images obtained from the camera to determine the existence and the location of a target. The software must be capable of tracking up to three individual moving targets at one time. First it must recognize that a new subject has entered its field of view, at least within the turret’s 30m range, such as a person walking by. Then it has to find the location of the target, so the motors can be directed where to aim.

Object detection can be implemented with the use of a background subtraction technique. This will require that the system capture and store background frames to be the reference against which new frames will be compared. Due to inevitable sporadic background movement, for example a car being parked or a trashcan being moved from one side of the frame to the other, the reference image will have to be periodically updated so that the newly positioned objects are not read as targets. Current frames must be acquired and stored at a relatively high rate, so that new targets can be detected quickly.

After the current frames are compared with the reference, the target will be identified. The center of the target can be found using a centroid calculation. By looping through this process, an object can be tracked by the changes in their centroid locations. This will inform the microcontroller how much it needs to move the servos to maintain its aim with the target. If the gun is in its reset position facing straight ahead, the program must compare the target’s position with this default location in order to orient the gun correctly.

Another feature of the system is the ability to select stationary targets. When a user has selected an object that is contained in the background layer, the system must recognize the specified point as the new target. As with the moving targets, the location must be calculated, however since the object does not move, the ‘tracking’ is unnecessary, so this calculation only needs to be done once.

6. Wireless Communication

Data rate in the communication module between microcontroller and the user interface does not need to be as high as it is for the camera system. In the project, only small packets of data will be transmitted from the user interface to microcontroller. That is, only simple pulse signals that have been converted from analog to digital in the image processing module on the tablet will be sent through the protocol. Data rate anywhere between hundred bits per second to kilo bits per second will be sufficient. Network acquisition time is still important in this module, since the whole project is operated in real time, so 2 milliseconds will be adequate. The requirements are summarized in Table 2, below.

7. Range Calculation

Rangefinder Hardware

In the scenario where a paintball gun is used as the firing mechanism, a rangefinder will be necessary to properly orient the gun to counteract gravitational forces. The range of the turret system was determined to be an approximately 30 meter arc spanning an 85 degree angle. This sets the requirement for the maximum distance from the turret that the rangefinder must be able to read at 30 meters, as illustrated in Figure 4 given below. Because the rangefinder will most likely operate at a single point at any given time, it must also have the capability to change position, so that it can effectively mirror the target movement. This can be easily accomplished by securing the rangefinder to the gun.

Paintball Gun/ Turret

Shooting Range: 30m
Shooting Range: 30m

Software