Qiaozhi Wang, P.E.
(Prounouced "Chi-ao-Jhi")
Results-driven Professional Engineer specializing in mechatronics, systems integration, and autonomous systems. Demonstrated expertise leading end-to-end development of complex electro-mechanical systems — from concept design through prototype build, validation, and public debut.
Augmented NERF Blaster​
Keywords: Arduino, Finite State Machine, Circuit Design, Assembly
The aim of this project is to augment a commercial NERF blaster (Nerf N-Strike Maverick) with sensors and actuators to help the shooter compensate for projectile drop of the dart while aiming at the target which is at a distance of 4-7 m from the blaster.
Photographs of the apparatus
Background:
NERF blasters are toy plastic guns which can shoot foam darts. The NERF N-Strike Maverick features a quick-rotating barrel into which suction-cup tipped darts are loaded. To operate the Maverick, the user first pulls a primer slide at the top. This slide compresses a spring located along the axis of the barrel. A plunger connected to the spring now draws air into the chamber. The slider is locked into this position once the spring has been compressed enough. Then the user takes aim and fires the dart by depressing a trigger. This trigger unlocks the compressed spring which then pushes the plunger forward, increasing the air pressure inside the chamber. The air pressure acts on the dart and pushes it outside with a high velocity. Six darts can be loaded into the barrel and the barrel rotates after every press of the trigger. It can also be rotated manually.
The velocity of the dart ejected from the NERF blaster is only around 17 m/s. This means that the projectile drop is quite considerable even over a small range.
Justification:
Projectile drop is the effect of gravity on a body that is given an initial horizontal velocity with respect to the Earth. The dart from the NERF blaster describes a parabolic trajectory resulting in the dart hitting below the target. Therefore aiming through the line of sight of the gun is not accurate for low velocity darts over long ranges.
To compensate for the projectile drop, the shooter needs to aim at an angle that is larger than the angle of inclination of the target with respect to the gun. The required offset angle is not a fixed quantity and depends on the location of the target. As humans can see only in two dimensions, the (human) shooter cannot judge the location of the target accurately. It is also difficult for an inexperienced shooter estimate the required offset angle. Hence, it would be useful to have electronics that can tell the shooter as to how much he should tilt the gun in order for him to strike the target exactly.
Strategy:
A Laser diode is used to pinpoint the target. A range-finding sensor is required to measure the distance to the target. We use the XL-MaxsonarEZ4 sensor as it can measure distances to objects at 20 cm to 765 cm. An accelerometer (LSM303D) is used to estimate the orientation of the gun. Thus the angle of inclination of the target (along the line of sight of the gun) can be measured. The Laser diode is mounted on a servomotor. After the microprocessor calculates the required offset angle, the servomotor rotates the laser downwards by the offset angle. The laser now points to a spot below the target. Now the user needs to rotate the gun such that the laser points at the target again. This is an easy way of telling the user as to how large the offset angle should be.
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