Stochastic logic performs computation on data represented by random bit-streams. The representation allows complex arithmetic to be performed with very simple logic, but it suffers from high latency and poor precision. Furthermore, the results are always somewhat inaccurate due to random fluctuations. In this paper, we show that randomness is not a requirement for this computational paradigm. If properly structured, the same arithmetical constructs can operate on deterministic bit-streams, with the data represented uniformly by the fraction of 1's versus 0's. This paper presents three approaches for the computation: relatively prime stream lengths, rotation, and clock division. Unlike stochastic methods, all three of our deterministic methods produce completely accurate results. The cost of generating the deterministic streams is a small fraction of the cost of generating streams from random/pseudorandom sources. Most importantly, the latency is reduced by a factor of (1/2n), where n is the equivalent number of bits of precision. When computing in unary, the bit-stream length increases with each level of logic. This is an inevitable consequence of the representation, but it can result in unmanageable bit-stream lengths. We discuss two methods for maintaining constant bit-streams lengths via approximations, based on low-discrepancy sequences. These methods provide the best accuracy and area x delay product. They are fast-converging and therefore offer progressive precision.

Stochastic logic performs computation on data represented by random bit-streams. The representation allows complex arithmetic to be performed with very simple logic, but it suffers from high latency and poor precision. Furthermore, the results are always somewhat inaccurate due to random fluctuations. In this paper, we show that randomness is not a requirement for this computational paradigm. If properly structured, the same arithmetical constructs can operate on deterministic bit-streams, with the data represented uniformly by the fraction of 1's versus 0's. This paper presents three approaches for the computation: relatively prime stream lengths, rotation, and clock division. Unlike stochastic methods, all three of our deterministic methods produce completely accurate results. The cost of generating the deterministic streams is a small fraction of the cost of generating streams from random/pseudorandom sources. Most importantly, the latency is reduced by a factor of (1/2n), where n is the equivalent number of bits of precision. When computing in unary, the bit-stream length increases with each level of logic. This is an inevitable consequence of the representation, but it can result in unmanageable bit-stream lengths. We discuss two methods for maintaining constant bit-streams lengths via approximations, based on low-discrepancy sequences. These methods provide the best accuracy and area × delay product. They are fast-converging and therefore offer progressive precision.

Aerial robotic platforms are an increasingly sought-after solution for a variety of sensing, monitoring, and transportation challenges. However, as invaluable as unmanned aerial vehicles (UAVs) have been for these applications, fixed-wing and multi-rotor systems each have individual limitations. Fixed-wing UAVs are generally capable of high-altitude surveillance and long flight times, while quad-rotors are most effective when used for their maneuverability and close-quarters surveying. This paper improves upon the prototypes discussed in [1] by creating a series of three next-generation prototypes to isolate the aspects of solar powered fixed-wing flight, quad-rotor flight, and transformation modes of the SUAV:Q platform. Improvements to the transformation mechanism, airframe design, variable pitch propulsion system, and custom-designed power electronics are presented along with validation of the designs through empirical testing.

Given the wide variety of flight conditions typically encountered by fixed-wing aerial vehicles, the flight performance of a solar-powered unmanned aerial vehicle (SUAV) depends on many factors. Predicting the performance for a given application requires characterization of both system and environmental components. Furthermore, a SUAV with a transformable airframe increases the number of characterizable states, where each state features a unique set of capabilities. This results in significant differences with respect to power consumption, solar panel orientation, and increases the design limitations on system components. This paper characterizes the energy collection, propulsion, and power electronics subsystems of a transformable SUAV developed at the University of Minnesota. Clear-sky and solar panel models are used to predict the power available for a given location and time. Propulsion system design is validated with flight data, and a proposed model correlates propulsion limits with available energy. Power electronics are modeled and simulated to determine hardware and tracking algorithm efficiencies. Finally, a pulsed battery charging methodology is implemented in hardware and evaluated against conventional charging techniques.

Stochastic logic performs computation on data represented by random bit streams. The representation allows complex arithmetic to be performed with very simple logic, but it suffers from high latency and poor precision. Furthermore, the results are always somewhat inaccurate due to random fluctuations. The random or pseudorandom sources required to generate the representation are costly, consuming a majority of the circuit area (and diminishing the overall gains in area). In this paper, we show that randomness is not a requirement for this computational paradigm. If properly structured, the same arithmetical constructs can operate on deterministic bit streams, with the data represented uniformly by the fraction of 1's versus 0's. This paper presents three approaches for the computation: relatively prime stream lengths, rotation, and clock division. The three methods are evaluated on a collection of arithmetical functions. Unlike stochastic methods, all three of our deterministic methods produce completely accurate results. The cost of generating the deterministic streams is a small fraction of the cost of generating streams from random/pseudorandom sources. Most importantly, the latency is reduced by a factor of 1/2n, where n is the equivalent number of bits of precision.

Selecting an aerial platform for an application typically requires compromise. A choice must be made between the flight time and long-range capabilities of a fixed-wing aircraft or the maneuverability and stationary characteristics of a multi-rotor platform. Recent developments of small-scale solar-powered UAVs have leveraged the advances in solar cell, energy storage, and propulsion system technology to reach extended flight times capable of all-day and multi-day flight. This paper presents the concept of a small-scale hybrid unmanned aerial vehicle capable of augmenting the maneuverability of a quad-rotor with the energy collection and supply of a solar-powered fixed-wing aircraft. An investigation into the aircraft design, transforming mechanism, and energy management of the multi-state system is presented. A proof-of-concept prototype has been constructed to demonstrate the airframe operating in a quad-rotor configuration. Power electronics capable of simultaneous battery charging and power loading from a solar array have been validated. Additional work in optimization of the propulsion system and airframe needs to be completed to maximize the performance of the hybrid system.

Throughout the wide range of aerial robot related applications, selecting a particular airframe is often a trade-off. Fixed-wing small-scale unmanned aerial vehicles (UAVs) typically have difficulty surveying at low altitudes while quadrotor UAVs, having more maneuverability, suffer from limited flight time. Recent prior work [1] proposes a solar-powered small-scale aerial vehicle designed to transform between fixed-wing and quad-rotor configurations. Surplus energy collected and stored while in a fixed-wing configuration is utilized while in a quad-rotor configuration. This paper presents an improvement to the robot's design in [1] by pursuing a modular airframe, an optimization of the hybrid propulsion system, and solar power electronics. Two prototypes of the robot have been fabricated for independent testing of the airframe in fixed-wing and quad-rotor states. Validation of the solar power electronics and hybrid propulsion system designs were demonstrated through a combination of simulation and empirical data from prototype hardware.