Document Type : Original Article
Ass. Prof., Radar and Guidance Dpt., Military Technical College, Cairo, Egypt.
Ass. Lecturer, Radar and Guidance Dpt. , Military Technical College, Cairo, Egypt.
Smart or homing guided bombs are used to destroy difficult-to-hit targets with minimum number of strikes and high accuracy. There are two basic types of smart bombs, laser or TV guided bombs. The guided bomb is formed by adding a seeker and a control section to the traditional unguided bombs. The seeker searches for and tracks the target. It provides the line-of-sight rate to the guidance module that generates and provides guidance commands to the control fins. The autopilot of the guided bomb is mainly used to improve the accuracy, maintain a near constant steady-state aerodynamic gain, and help in steering the bomb to the target with a very high accuracy. Undesirable behavior characteristics of the guidance and control may originate due to several sources of disturbances such as flight vibrations and oscillations due to external environmental effects and/or the airframe coupling mechanisms flutter or the propulsion system motor chamber pressure oscillations. The latter will produce phase-coherent quasi-sinusoidal vibration while the former is random and unpredicted and can only be evaluated using statistical methods of analysis. In this paper, the external noise presented by the atmospheric turbulence during the bomb flight is investigated through computer simulation. The noise process is modeled and generated to enable evaluation of the system performance. The zero-mean white Gaussian noise is generated and provided as a superimposed input with the acceleration input command of the bomb autopilot. The system performance is measured for different signal-to-noise ratios (SNR) of the input noise. The performance evaluation is made via a six-degrees-of-freedom (6-D0F) flight model of the bomb. The measured parameters are the trajectory, the final missdistance, and the autopilot acceleration response.