Velocity and Position Measurement for Projectile Using Double Optical Detectors and Reflectors

A novel low cost measurement method which can measure velocity and position of projectile by measuring time was proposed. The structure was double crossing Z-shaped, which was made up of two laser light sources, two optical detectors (OD) and two reflectors. The measurement principle was analyzed. A principle experiment was done on a plane table using a laser pen, two pieces of mirrors and photodiode circuit by launching a steel ball. A traditional velocity measurement device consisting of two laser pens and two sets of photodiode circuit was used for measuring velocity to compare with the velocity measured by the novel method. A high speed camera type of RedLake HG XL was used to take picture for measuring the position of the steel ball to verify the position measured by the novel method. The relative difference of velocity measurement was less than 0.2%. The difference of position measurement was less than 1 mm. The results indicated that the method proposed in this paper is feasible.