Randal W. Beard

Brigham Young University - Provo Main Campus | BYU · Department of Electrical and Computer Engineering

This work presents a multiplicative extended Kalman filter (MEKF) for estimating the relative state of a multirotor vehicle operating in a GPS-denied environment. The filter fuses data from an inertial measurement unit and altimeter with relative-pose updates from a keyframe-based visual odometry or laser scan-matching algorithm. Because the global...

Unlike many current navigation approaches for micro air vehicles, the relative navigation (RN) framework presented in this paper ensures that the filter state remains observable in GPS-denied environments by working with respect to a local reference frame. By subtly restructuring the problem, RN ensures that the filter uncertainty remains bounded,...

As relevant technologies become smaller and less expensive, micro air vehicles (MAVs) are transitioning from predominantly military and hobbyist applications to mainstream use. Exciting new applications include the delivery of medical supplies to remote areas, infrastructure inspection, environmental change detection, precision agriculture, survell...

In this Paper, we present a complete, proof-of-concept sense-and-avoid solution for small unmanned aircraft systems, including a small low-cost ground-based radar system, multitarget tracking and estimation, collision detection, and an avoidance planner. We describe the development of a small frequency-modulated continuous-wave phased-array radar s...

In this chapter, we propose a 3D path planning algorithm for small unmanned aircraft systems (UASs). We develop the path planning logic using a body fixed relative coordinate system which is the unrolled, unpitched body frame. In this relative coordinate system, the ownship is fixed at the center of the coordinate system, and the detected intruder...

For unmanned aircraft systems to gain full access to the National Airspace System, they must have the capability to detect and avoid other aircraft. To safely avoid another aircraft, an unmanned aircraft must detect the intruder aircraft with ample time and distance to allow the ownship to track the intruder, perform risk assessment, plan an avoida...

This paper proposes a system architecture for tracking multiple ground-based objects using a team of unmanned air systems (UAS). In the architecture pipeline, video data is processed by each UAS to detect motion in the image frame. The ground-based location of the detected motion is estimated using a geolocation algorithm. The subsequent data point...

In both simulated and real experiments, the recursive-RANSAC (R-RANSAC) algorithm has shown promise as an efficient multiple target tracking (MTT) filter. In this paper we introduce a generalized and modular framework for the RRANSAC algorithm, analyze the sensitivity of the R-RANSAC tuning parameters, and compare R-RANSAC to five well-known MTT al...

This paper explores the use of radar odometry for Global Positioning System–denied navigation. The range progression from arbitrary ground-based point scatterers is used to estimate an unmanned aerial vehicle’s relative motion. In high clutter environments, the recursive-RANSAC algorithm provides robust and efficient feature identification, data as...

This paper addresses the problem of navigating an Unmanned Aerial Vehicle in an environment where GPS quality is degraded or lost. A method is described to return the aircraft from the GPS-degraded region to its launch point by means of visual navigation techniques. We record a string of overlapping images, or keyframes, on the outbound flight. On...

A method for cooperative estimation is proposed for use in multi-vehicle unmanned air systems with vision-based target tracking capabilities. The method first seeks to estimate the relative rotational and translational biases that exist between tracks from different vehicles. It then accounts for the biases and performs the track-to-track associati...

A two step path planning algorithm with collision detection logic for small UAS is proposed. The path planning approach taken in this work is carried out in two steps. In the first step, an initial suboptimal path is generated using A∗ search. In the second step, a chain of unit masses connected by springs and dampers evolves in a simulated force f...

Aerial robotic vehicles are becoming a core field in mobile robotics. This chapter considers some of the fundamental modelling and control architectures in the most common aerial robotic platforms; small-scale rotor vehicles such as the quadrotor, hexacopter, or helicopter, and fixed wing vehicles. In order to control such vehicles one must begin w...

With the increasing demand to integrate unmanned aircraft systems (UAS) into the National Airspace System (NAS), new procedures and technologies are necessary to ensure safe airspace operations and minimize the impact of UAS on current airspace users. Currently, small UAS face limitations on their use in civil airspace because they lack the ability...

The airborne collision detection is a challenging problem due to inherent noise in onboard sensor(s), limited computational resources available for unmanned aircraft system and variability in intruder dynamics resulting in uncertainty in predicting intruder future trajectories. In this paper, we develop an innovative approach to quantify likely int...

This paper presents a vision-based three-tiered path planning and collision avoidance scheme for small and miniature air vehicles (MAVs), which consists of global, local, and reactive path planners. The global path planner generates inertial paths to the goal configuration based on a known world map that may not necessarily be up-to-date. The local...

This paper considers the problem of fixed wing unmanned air vehicles following straight lines and orbits. To account for ambient winds, we use a path following approach as opposed to trajectory tracking. The unique feature of this paper is that we explicitly account for roll and flight path angle constraints. The guidance laws are derived using the...

A method for aerial rendezvous of small unmanned aircraft systems is proposed. The system includes placing a passively towed drogue into an orbit that is suitable for a small unmanned aircraft systems to follow, and a seeker guidance method for use with a monocular camera mounted on the centerline of the unmanned aircraft systems. The principle con...

The tailsitter is a promising airframe that can take off and land on its tail and transition to level flight. While this ability provides vertical takeoff and landing capabilities with no additional moving parts, it introduces interesting control challenges. In this paper, we look at the attitude control system of a tailsitter in hover flight and s...

This paper presents a strategy of designing a trajectory-tracking control law for unmanned aerial vehicles where an unmodifiable autopilot is incorporated in the closed-loop system. The main contributions of this paper include a novel control structure that enables an explicit design of tracking methods for a system with an unmodifiable autopilot i...

Estimating the states of multiple dynamic targets is difficult due to noisy and spurious measurements, missed detections, and the interaction between multiple maneuvering targets. In this paper a novel algorithm, which we call the recursive random sample consensus (R-RANSAC) algorithm, is presented to robustly estimate the states of an unknown numb...

We introduce an intelligent cooperative control system for ground target tracking in a cluttered urban environment with a team of autonomous Unmanned Air Vehicles (UAVs). We extend the work of Yu et al. to use observations of target position to learn a model of target motion. Simulated cooperative control of a team of 9 UAVs in a 100-block city fil...

Quadrotors are ideal platforms for autonomous flight in unknown and complex environments. Their small size and maneuverability are conducive to operating in confined spaces and avoiding obstacles. Equipped with appropriate sensors and algorithms, quadrotors could enable several applications currently infeasible for ground robots.

In cooperative localization a group of robots exchange relative position measurements from their exteroceptive sensors and their motion information from interoceptive sensors to collectively estimate their position and heading. For the localization errors to be bounded, it is required that the system be observable, independent of the estimation tec...

In this paper we present an observability-based local path planning and obstacle avoidance technique that utilizes an extended Kalman Filter (EKF) to estimate the time-to-collision (TTC) and bearing to obstacles using bearing-only measurements. To ensure that the error covariance matrix computed by an EKF is bounded, the system should be observable...

This paper studies the trajectory-tracking strategy for unmanned aerial vehicles where the autopilot is involved in the feedback control. The trajectory-tracking controller is derived based on a generalized design model using Lyapunov based backstepping. The augmentations of the design model and trajectory-tracking controller are conducted to invol...

We introduce an intelligent cooperative control system for ground target tracking in a cluttered urban environment with a team of Unmanned Air Vehicles (UAVs). We extend the work of Yu et. al. [1] to add a machine learning component that uses observations of target position to learn a model of target motion. Our learner is the Sequence Memoizer [2]...

GPS-denied aerial flight is a popular research topic. The problem is challenging and requires knowledge of complex elements from many distinct disciplines. Additionally, aerial vehicles can present challenging constraints such as stringent payload limitations and fast vehicle dynamics. In this paper we propose a new architecture to simplify some of...

GPS-denied aerial flight is a challenging research problem and requires knowledge of complex elements from several distinct disciplines. Additionally, aerial vehicles can present challenging constraints such as stringent payload limits and fast vehicle dynamics. In this paper we propose a new architecture to simplify some of the challenges that con...

This paper studies trajectory generation for an aircraft that tows an aerial body using a flexible cable. The major contributions of this paper include model validation for a lumped mass extensible cable using flight test data, and optimal trajectory generation for the towed cable system with tension constraints using model predictive control. The...

A new method for motion estimation using RGB-D cameras has been developed. This new method proposes that a RGB-D sensor provides three distinct modalities that can be used to compute motion estimation solutions: a monocular camera, a range camera, and the combination of the two sensors providing depth at every pixel. By utilizing a novel approach t...

In this paper, we present a cooperative approach to geo-localize a ground target using bearing-only localization of Unmanned Aerial Vehicles (UAVs). We design a distributed path planning algorithm using receding horizon control, which improves the localization accuracy of the target and of all of the air vehicles simultaneously while satisfying the...

In this paper, we investigate the nonlinear observability properties of bearing-only cooperative localization. We establish a link between observability and a graph that represents measurements and communication between the robots. It is shown that graph theoretic properties like the connectivity and the existence of a path between two nodes can be...

Autonomous unmanned air vehicles (UAVs) are critical to current and future military, civil, and commercial operations. Despite their importance, no previous textbook has accessibly introduced UAVs to students in the engineering, computer, and science disciplines--until now. Small Unmanned Aircraftprovides a concise but comprehensive description of...

Autonomous path planning of Micro Air Vehicles (MAVs) in an urban environment is a challenging task because urban environments are dynamic and have variety of obstacles, and the locations of these obstacles may not be available a priori. In this paper we develop a reactive guidance strategy for collision avoidance using bearing-only measurements. T...

We develop aerobatic maneuvering for obstacle avoidance by autonomous miniature air vehicles (MAVs) using a path following control law. A method for developing maneuver paths that accounts for maneuver boundary conditions is presented along with a method for determining the orthogonal distance (position error) from the vehicle to the path. The cont...

This paper presents a vision-based collision avoidance technique for Miniature Air Vehicles (MAVs) using local-level frame mapping and planning in spherical coordinates. To explicitly address the obstacle initialization problem, the maps are parameterized using the inverse time-to-collision (TTC), which is independent of the ground speed of the MAV...

Multirotor aircraft have become a popular platform for indoor flight. To navigate these vehicles indoors through an unknown environment requires the use of a SLAM algorithm, which can be processing intensive. However, their size, weight, and power capacity limit the processing capabilities available onboard. In this paper, we describe an approach t...

In this paper, we present a probabilistic path planning algorithm for tracking a moving ground target in urban environments using UAVs in cooperation with UGVs. The algorithm takes into account vision occlusions due to obstacles in the environments. The target state is modeled using the dynamic occupancy grid and the probability of the target locat...

This paper considers the problem of fixed wing unmanned air vehicles following straight lines and orbits. To account for ambient winds, we use a path following approach as opposed to trajectory tracking. The unique feature of this paper is that we explicitly account for roll angle constraints and flight path angle constraints. The guidance laws are...

This paper presents a method for recovering Micro Air Vehicles (MAVs) in flight using a mothership and towed drogue, in which the mothership executes an orbit that places the drogue in a stable, slower orbit that can be tracked by a MAV. This paper is particularly challenging in the presence of wind. The equations of motion of the cable using an el...

The consensus or agreement problem enables a team of agents to agree on certain information variables using a low-bandwidth, dynamic, and sparsely-connected graph. How ever, most prior work on agreement protocols has focused on converging to a single, static variable. In this paper, we propose a consensus filter that accepts dynamically changing in...

In this paper we detail an observability based path planning algorithm for Small and Miniature Air Vehicles (MAVs) navigating among multiple static obstacles. Bearing only measurements are utilized to estimate the time-to-collision (TTC) and bearing to obstacles using the extended Kalman filter (EKF). For the error covariance matrix computed by the...

The Consensus-Based Bundle Algorithm (CBBA) is incorporated into a hierarchical concept of operation. In the Team CBBA each team of unmanned vehicles plans for all agents in the team to service a set of tasks. This team planning is carried out separately using the traditional CBBA. An "outer-loop" Team CBBA strategy is presented that coordinates pl...

This paper addresses the problem of autonomously maneuvering a miniature air vehicle (MAV) to follow a road using computer vision as the primary guidance sensor. We focus on low-altitude flight with the objective of maximizing the pixel density of the road in the image. The airframe is assumed to be a bank-to-turn fixed-wing MAV with a downward-loo...

Unmanned aerial vehicles (UAVs) have the potential to carry resources in support of search and prosecute operations. Often to completely prosecute a target, UAVs may have to simultaneously attack the target with various resources with different capacities. However, the UAVs are capable of carrying only limited resources in small quantities, hence,...

This paper presents a method for recovering Micro Air Vehicles (MAVs) in flight using a mothership and towed drogue. A method for modelling the dynamics of the mothership-cable-drogue system, based on Gauss’s principle, is presented. The differential flatness property of the system is exploited to calculate mothership trajectories from desired drog...

The objective of this chapter is to give an overview of autopilot software design for small and miniature unmanned air systems. An architecture that is typical of commercially available autopilots is described. A detailed explanation of the inner-loop control structure is described, including the lateral directional feedback loops and the longitudi...

Aerial recovery of micro air vehicles (MAVs) presents a challenging problem in multi-vehicle dynamics and control. This paper presents a method for recovering MAVs in flight using a mothership and towed drogue, in which the mothership executes an orbit that places the drogue in a stable, slower orbit that can be tracked by a MAV. The differential f...

This paper explores the feasibility of improving unmanned air vehicle (UAV) mission effectiveness by extracting energy from the atmosphere. Specifically, we consider an aerial surveillance mission in the vicinity of a geographic ridge. Cross winds flowing over the ridge produce regions of lift on the windward side that can be exploited to increase...

Path planning and obstacle avoidance involve planning a feasible path from the initial to goal configurations while avoiding obstacles. This paper presents a vision-based three dimensional navigation frame mapping and path planning technique for collision avoidance for Micro Air Vehicles (MAVs) using a forward-looking onboard camera. Using computer...

This paper describes a new approach for autonomous road following for an unmanned air vehicle (UAV) using a visual sensor. A road is defined as any continuous, extended, curvilinear feature, which can include city streets, highways, and dirt roads, as well as forest-fire perimeters, shorelines, and fenced borders. To achieve autonomous road-followi...

In this paper, we present two strategies to stabilize the altitude of the towed body (drogue) in the presence of the steady wind. The ight test results are presented to verify the concept of aerial recovery and the mathematical model of the system. By using the parameter conguration and the data collected in the ight test, a matching work is conduc...

UAS flight simulation for research and development is a difficult problem because each airframe requires accurate physical models, control systems, an organized method of testing new control systems, virtual cameras for vision-based control, and methods of testing new control in the transition from simulation to flight tests. In an environment wher...

Miniature air vehicles (MAVs) are often used for low altitude flights where unknown obstacles might be encountered. Path planning and obstacle avoidance for MAVs involve planning a feasible path from an initial state to a goal state while avoiding obstacles in the environment. This paper presents a vision-based local multi-resolution mapping and pa...

We address the problem of generating feasible paths from a given start location to a goal configuration for multiple unmanned aerial vehicles (UAVs) operating in an obstacle rich environment that consist of static, pop-up and moving obstacles. The UAVs have limited sensor and communication ranges, when they detect a pop-up or a moving obstacle that...

This paper presents a new concept for aerial recovery of micro air vehicles (ARMAVs) using a large mothership and a recovery drogue. The mothership drags a drogue attached to a cable and the drogue is controlled to match the flight patten of the MAV. This paper uses Gauss's principle to derive the dynamic model of the cable-drogue systems. A contro...

In this paper we present a new information consensus filter for distributed dynamic-state estimation. Estimation is handled by the traditional information filter, while communication of measurements is handled by a consensus filter. First and second-order statistics of local estimates are discussed. It is shown that local information consensus filt...

A distributed double integrator discrete time consensus protocol is presented along with stability analysis. The protocol will achieve consensus when the communication topology contains at least a directed spanning tree. Average consensus is achieved when the communication topology is strongly connected and balanced, where average consensus for dou...

This paper poses the cooperative perimeter-surveillance problem and offers a decentralized solution that accounts for perimeter growth (expanding or contracting) and insertion/deletion of team members. By identifying and sharing the critical coordination information and by exploiting the known communication topology, only a small communication rang...

Miniature Air Vehicles (MAVs) equipped with lightweight, inexpensive cameras have recently been employed in a great variety of missions due to their increased capability and continued affordability. Unfortunately, MAVs often experience unintended motions due to atmospheric turbulence. As a result, MAV video streams are often characterized by high-f...

Unmanned aerial vehicles (UAVs) have the potential to carry munitions in support of battlefield operations, however they have limited sensor range and can carry only small quantities of resources. Often, to fully prosecute a target, a variety of assets may be required, and it may be necessary to deliver these assets simultaneously. Therefore, a tea...

This paper addresses the problem of using a team of UAVs to cooperatively monitor multiple forest fires (called hotspots) in a region. We deploy two types of agents: service agents that locally monitor the state of the hotspots and detector agents that search for hotspots and assign service agents to those that are detected. We develop an assignmen...

The focus of this talk will be cooperative control techniques for small and micro air vehicles. There are numerous potential applications of this technology including aerial reconnaissance, border patrol, monitoring forest fires, oil fields, and pipelines, and tracking wildlife. This talk will present a general approach to cooperative control probl...

Most of the applications envisioned for micro air vehicles require an on-board E(MR camera. It is only natural to investigate using the on-board camera as a sensor for navigation, guidance, and control. This paper investigates the use of an EO/IR sensor as a seeker in a proportional navigation guidance law for micro air vehicles. Proportional navig...

Allocating tasks efficiently to multiple UAVs with limited sensor and communication ranges is a difficult problem. In this paper, we present a distributed sequential auction scheme that takes the UAV limitations into account and provides a systematic procedure for the auction process. The task allocation scheme first validates the targets using nei...

Miniature air vehicles (MAVs) are particularly well suited for short distance, over the horizon, low altitude surveillance and reconnaissance tasks. In this paper we focus on aerial surveillance of borders and roads, where a strap- down EO camera is used in-the-loop to track a border or road pathway. We assume that quality tracking requires that th...

In this paper, we propose a cooperative path planning technique for multiple UAVs that need to cover an unknown region in the presence of obstacles. The UAVs are subjected to limited sensor range, limited communication range and minimum turn radius constraints. A world map of the unknown region is dynamically created based on the information obtain...

This paper presents experimental results for two cooperative timing missions carried out using a team of three miniature air vehicles (MAVs). Using a cooperative timing algorithm based on coordination functions and coordination variables, the MAV team executed a series of simultaneous arrival and cooperative fly-by missions. In the presence of sign...

Autopilots for small UAVs are generally equipped with low fidelity sensors that make state estimation challenging. In addition, the sensor suite does not include units that measure angle-of-attack and side-slip angles. The achievable flight performance is directly related to the quality of the state estimates. Unfortunately, the computational resou...

In this paper, a method for accurate path following for miniature air vehicles is developed. The method is based on the notion of vector fields, which are used to generate desired course inputs to inner-loop attitude control laws. Vector-field path-following control laws are developed for straight-line paths and circular arcs and orbits. Lyapunov s...

This report describes research in the area of cooperative control of unmanned air vehicles carried out at Brigham Young University with the support of AFOSR during the period from April 2004 to March 2007. Our research focused on cooperative control of unmanned air vehicles (UAVs). Under this AFOSR supported effort, we have sought to accomplish thr...

This paper outlines a simple algorithm for automated landing of miniature aerial vehicles (MAVs). Utilizing estimates of height above ground from barometric pressure and optic flow measurements, repeated landings were performed with a 1.5 m wingspan MAV. With height above ground estimated from barometric pressure measurements alone, landing errors...

The career and contributions of George Nikolaos Saridis, the founding president of the IEEE Robotics and Automation Council/Society, are recounted.

The abundance of embedded computational resources in autonomous vehicles enables enhanced operational effectiveness through cooperative teamwork in civilian and military applications. Unlike with autonomous vehicles, greater efficiency and operational capability are realized from teams of autonomous vehicles operating in a coordinated way. This pap...

This paper presents a method for determining the GPS location of a ground-based object when imaged from a fixed-wing miniature air vehicle (MAV). Using the pixel lo- cation of the target in an image, with measurements of MAV position and attitude, and camera pose angles, the target is localized in world coordinates. The main contribution of this pa...

One of the challenges in designing low level control loops for Micro Air Vehicles (MAVs) is that the manufacturing process for airframes is not consistent enough to ensure uniform aerodynamic properties. Therefore, there is a significant need for robust adaptive control techniques that are computationally simple. Conventional Model Reference Adapti...

This paper describes a multi-static radar network composed of multiple unmanned air vehicles (UAVs). Time-delay and Doppler measurements taken by the UAV team are passed to a centralized processor to determine optimal heading commands for the UAV team to reduce tracking error. However, due to power and communication constraints on the UAVs, the opt...

Numerous applications require aerial surveillance. Civilian applications include monitoring forest fires, oil fields, and pipelines and tracking wildlife. Applications to homeland security include border patrol and monitoring the perimeter of nuclear power plants. Military applications are numerous. The current approach to these applications is to...

This paper presents a method for localizing a ground-based object when imaged from a small fixed-wing unmanned aerial vehicle (UAV). Using the pixel location of the target in an image, with measurements of UAV position and attitude, and camera pose angles, the target is localized in world coordinates. This paper presents a study of possible error s...

This paper develops a distributed algorithm for average-consensus in a discrete-time framework based on a formal matrix limit definition of average-consensus. Using this algorithm, the average-consensus problem is solved under switching network topologies provided that the network switch between instantaneously balanced, connected-over-time network...