Aeroload Simulation of Interceptor Missile using Fin Load Simulator

Interceptor missiles are designed to destroy enemy targets in air. Targets can be destroyed either in atmosphere or out of atmosphere. So for Air Defence scenario, a two layer protection system is required with one taking care of exo atmosphere and another endo atmosphere. In this Air Defence scenario, irrespective of target trajectory interceptor should neutralise it. So the control, guidance are to be designed and validated thoroughly with various scenarios of interceptor and target. These interceptors sense the rates from rate gyroscopes and accelerations from accelerometers which are fitted on board the interceptor. The navigation algorithm calculates the interceptor’s position and velocity from these rates and accelerations from time to time. Using these interceptor data and target information received from ground RADAR or on board seeker, guidance calculates accelerations demand and subsequently rate demand. The control algorithm runs in on board mission computer along with guidance. The control algorithm calculates the commanded rate and eventually commanded deflections to the control fins to move towards the target. The fins have to move as per commanded deflections to meet the mission objective of hitting the target. But the load known as aeroload which comes on the control fins during mission, causes control fins not to move as per command. Due to the difference between control command and physical movement of fin, the expected path towards target deviates. This increases the miss distance and also misses the target hit. This aeroload scenario is to be simulated on ground and some feature is to be designed to take care of it during mission. By studying the control system behaviour due to load, the control autopilot is to be automatically tuned to compensate for the loss in commanded deflections. This scenario can be carried out in Hardware-in-Loop simulation (HILS) setup. Mission load conditions can be applied on hardware actuation system in HILS setup and mission performance can be seen and also with different loads and different autopilot tunings.

Design and Analysis of a Variable Inertia Spatial Robotic Tail for Dynamic Stabilization

This paper presents the design of a four degree-of-freedom (DoF) spatial tail and demonstrates the dynamic stabilization of a bipedal robotic platform through a hardware-in-loop simulation. The proposed tail design features three active revolute joints with an active prismatic joint, the latter of which provides a variable moment of inertia. Real-time experimental results validate the derived mathematical model when compared to simulated reactive moment results, both obtained while executing a pre-determined trajectory. A 4-DoF tail prototype was constructed and the tail dynamics, in terms of reactive force and moments, were validated using a 6-axis load cell. The paper also presents a case study where a zero moment point (ZMP) placement-based trajectory planner, along with a model-based controller, was developed in order for the tail to stabilize a simulated unstable biped robot. The case study also demonstrates the capability of the motion planner and controller in reducing the system’s kinetic energy during periods of instability by maintaining ZMP within the support polygon of the host biped robot. Both experimental and simulation results show an improvement in the tail-generated reactive moments for robot stabilization through the inclusion of prismatic motion while executing complex trajectories.