Nikolaos I. Vitzilaios

Experimental Validation of a Helicopter Autopilot Design using Model-Based PID Control

Autonomous helicopter flight provides a challenging control problem. In order to evaluate control designs, an experimental platform must be developed in order to conduct flight tests. However, the literature describing existing platforms focuses on the hardware details, while little information is given regarding software design and control algorithm implementation. This paper presents the design, implementation, and validation of an experimental helicopter platform with a primary focus on a software framework optimized for controller development. In order to validate the operation of this platform and provide a basis for comparison with more sophisticated nonlinear designs, a PID controller with feedforward gravity compensation is derived using the generally accepted small helicopter model and tested experimentally.

Survey of Unmanned Helicopter Model-Based Navigation and Control Techniques

Unmanned Aircraft Systems(UAS) have seen unprecedented levels of growth during the last two decades. Although many challenges still exist, one of the main UAS focus research areas is in navigation and control. This paper provides a comprehensive overview of helicopter navigation and control, focusing specifically on small-scale traditional main/tail rotor configuration helicopters. Unique to this paper, is the emphasis placed on navigation/control methods, modeling techniques, loop architectures and structures, and implementations. A ‘reference template’ is presented and used to provide a basis for comparative studies and determine the capabilities and limitations of algorithms for unmanned/autonomous flight, as well as for navigation, and control. A detailed listing of related research is provided, which includes model structure, helicopter platform, control method and loop architecture, flight maneuvers and results for each. The results of this study was driven by and has led to the development of a ‘one-fits-all’ comprehensive and modular navigation controller and timing architecture applicable to any rotorcraft platform.

A mobile self-leveling landing platform for VTOL UAVs

A semi-autonomous mobile self-leveling landing platform designed to launch, recover and re-launch VTOL UAVs without the need for human intervention is described. The landing platform is rugged, lightweight and inexpensive, making it ideal for civilian applications that require a base station from which a rotorcraft UAV can be launched and/or recovered on terrain that is normally unsuitable for UAV take-off and landing. This landing platform is capable of autonomously self-leveling on rough terrain and inclines up to 25°, and can operate in isolated remote locations for extended periods of time using large onboard lithium batteries and wireless communication. The unique design aspects of this landing platform are that it is mobile, self-leveling, and man-portable. A fully-operational prototype has been designed, constructed and evaluated. Design details and experimental results are presented to demonstrate the landing platforms functionality, and that all primary design requirements have been met.

Design and development of an Air Supply Unit for Circulation Control Wing-based UAVs

The main contribution of this paper is the design, development and evaluation of a light-weight Air Supply Unit (ASU) and its associated speed controller, suitable for use in Circulation Control Wings (CCW) of small-scale Unmanned Aerial Vehicles (UAVs). An iterative process, presented here, is used to optimize the design of the centrifugal compressor for the ASU through extensive simulation. The implemented speed controller provides the necessary mass flow rate on-demand by maintaining a fixed velocity ratio (Vjet=V∞) thereby reducing the power penalties associated with operating the ASU continuously. The ASU/controller system is evaluated by integrating with a CCW plenum design capable of distributing air evenly across the span and measuring the Vjet at the slot exit in a laboratory environment. Results obtained demonstrate a close match between experimental tests and simulation in all cases considered. In particular, the velocity at the slot (Vjet) is measured to be 24.5 m/s, which provides sufficient velocity to accomplish Circulation Control during both take off and cruise flight for the purposes of this research.

Experimental Study of Circulation Control Wings at Low Reynolds Numbers

The objective of this research is to design, develop and compare the effectiveness of upper slot blowing on three Circulation Control Wings (CCWs) and to find the configuration that gives the best lift augmentation. A low-speed wind-tunnel experimental study is undertaken to evaluate the effect of upper slot blowing along the span over four different Trailing-Edge (TE) Coanda surfaces on three 3-D CCWs for the purpose of lift augmentation. Wind tunnel tests are conducted at Mach numbers of 0.022, 0.024, 0.029 and 0.04, at Reynolds numbers of 0.67 × 10 to 1.26 × 10 with moment coefficients of blowing from 0.0 to 0.011. It is found that the (2:1) Coanda surface configuration is the most effective in all three CCWs. At Ma = 0.022 and α = 18, the (2:1) Coanda surface on the symmetrical NACA0015 CCW gives the maximum ∆CL = 0.2 at Cμ = 0.011. The maximum lift augmentation ratio of 61 is observed with the (2:1) Coanda surface on the S8036 CCW at α = 2.

Experimental validation of a helicopter autopilot: Time-varying trajectory tracking

Research in helicopter UAV control is inherently based on testing flight performance in the field. This paper extends preliminary flight test results previously published by the authors and provides a more thorough experimental validation of the helicopters motion control. A new input model, which includes velocity dependence in the main rotor thrust, is incorporated in the control. Experimental results for translational position control are presented using a number of reference trajectories.

An integrated framework for cooperative ground and aerial vehicle missions utilizing Matlab and X-Plane

This paper presents an integrated control framework for the simulation and visualization of cooperative missions for unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs). The X-Plane simulator is utilized to simulate vehicle dynamics and visualize experiments in realistic environments, whereas the control algorithms are executed and validated in Matlab/Simulink. A novel approach to integrate ground vehicles in X-Plane is presented and an overall open source framework is developed to facilitate the interaction and usability of the two software programs used. The framework facilitates research in cooperative vehicle control, path planning, formation control, and centralized control topologies through straightforward and cost effective system simulation, visualization and evaluation.

Scaled control performance benchmarks and maneuvers for small-scale unmanned helicopters

The paper proposes a methodology for designing trajectories to form a basis for evaluating and comparing performance of navigation controllers on any small-scale helicopter platforms, as there currently exist no benchmarks for small-scale helicopters. Consideration is given to maneuvers designed to evaluate full-scale helicopter/pilot combinations adapting them to the dynamics of small-scale helicopters. Two helicopter models are used as experimental testbeds: the DU2SRI Bergen Industrial Turbine and Raptor SE90 helicopters. Three different controllers, ℋ∞, LQR, and PID, are tested against the scaled maneuvers in order to evaluate and compare the performance of each controller. Trajectories are designed according to the proposed scaling laws and they are chosen to be outside and well within the capabilities of the helicopter dynamics to demonstrate the importance of selecting trajectories that both exploit the controller weaknesses while remaining within the flight capabilities of the helicopter.

Kinematic Analysis of the Human Thumb with Foldable Palm

There have been numerous attempts to develop anthropomorphic robotic hands with varying levels of dexterous capabilities. However, these robotic hands often suffer from a lack of comprehensive understanding of the musculoskeletal behavior of the human thumb with integrated foldable palm. This paper proposes a novel kinematic model to analyze the importance of thumb-palm embodiment in grasping objects. The model is validated using human demonstrations for five precision grasp types across five human subjects. The model is used to find whether there are any co-activations among the thumb joint angles and muskuloskeletal parameters of the palm. In this paper we show that there are certain pairs of joints that show stronger linear relationships in the torque space than in joint angle space. These observations provide useful design guidelines to reduce control complexity in anthropomorphic robotic thumbs.

The Role of Morphology of the Thumb in Anthropomorphic Grasping: A Review

The unique musculoskeletal structure of the human hand brings in wider dexterous capabilities to grasp and manipulate a repertoire of objects than the non-human primates. It has been widely accepted that the orientation and the position of the thumb plays an important role in this characteristic behavior. There have been numerous attempts to develop anthropomorphic robotic hands with varying levels of success. Nevertheless, manipulation ability in those hands is to be ameliorated even though they can grasp objects successfully. An appropriate model of the thumb is important to manipulate the objects against the fingers and to maintain the stability. Modeling these complex interactions about the mechanical axes of the joints and how to incorporate these joints in robotic thumbs is a challenging task. This paper presents a review of the biomechanics of the human thumb and the robotic thumb designs to identify opportunities for future anthropomorphic robotic hands.