Development and Testing of a Steerable Cruciform Parachute System
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This thesis focuses on the development of a parachute payload system which is capable of precision aerial delivery yet only represents a modest cost increase over ballistic unguided systems. In order to develop such a system, ﬁrst a canopy is selected. The canopy should be simple and inexpensive to make; in this case a cruciform canopy was selected because this design is material efﬁcient and requires far less labor to manufacture compared to parafoil parachutes. Next some method of stabilizing that canopy during ﬂight must be proposed. In this case, the system heading is to be stabilized via a single actuator by asymmetric deﬂection of the leading edge of one canopy panel. At this stage in the development, a controller must be designed and implemented which stabilizes the system in the proposed way. Outdoor ﬂight testing is the gold standard of parachute testing methodology since it offers the most realistic ﬂight conditions. However, the unmeasured wind disturbances encountered in outdoor ﬂight testing can confound results and interfere with repeatability of experiments. The ﬁrst experiment explained in this thesis revolves around the testing of a steer able cruciform parachute system using a vertical wind tunnel. The primary goal of the experiment was to develop a heading stabilizing controller. Additionally, a closed-loop system model was identiﬁed and a technique was developed for estimating canopy glide ratio (GR). The vertical wind tunnel testing methodology is far faster and less expensive than the outdoor ﬂight testing which would be needed to accomplish the same goals. After proving that a system can be steered via the proposed methodology, the next stage in the developing of a precision guided vehicle is to demonstrate that the stabilization technique is viable. This is accomplished in both outdoor ﬂight testing and a simulation based on the closed-loop model identiﬁed earlier. Furthermore, the precision navigation potential of the system must be demonstrated; speciﬁcally, the system must be capable of arriving closer to the desired impact point on the ground than an unguided system dropped under the same conditions. The work described in this thesis has advanced the development of the steerable cruciform parachute system beyond the point of simply being a feasibility demonstrator. The vertical wind tunnel experiments demonstrated that the system heading could be stabilized and subsequent navigation experiments demonstrated that the system outperforms an unguided system during real drops. The work done to compare the effectiveness of different navigation strategies in a simulated environment represents the beginning of the next stage in the development of the parachute system. This next stage involves reﬁnement and performance improvements of the existing platform through engineering design in order to advance the technical readiness level of the project.
Table of Contents
Introduction -- Literature review -- Vertical wind tunnel experiment -- Investigation of navigation strategies -- Conclusions -- Appendix A. Unmanned aerial systems and parachute release mechanisms -- Appendix B. Aerial guidance unit redesign