Renwick E. Curry

Path Planning Based on Bézier Curve for Autonomous Ground Vehicles

In this paper we present two path planning algorithms based on Bezier curves for autonomous vehicles with way points and corridor constraints. Bezier curves have useful properties for the path generation problem. The paper describes how the algorithms apply these properties to generate the reference trajectory for vehicles to satisfy the path constraints. Both algorithms join cubic Bezier curve segments smoothly to generate the path. Additionally, we discuss the constrained optimization problem that optimizes the resulting path for a user-defined cost function. The simulation shows the generation of successful routes for autonomous vehicles using these algorithms as well as control results for a simple kinematic vehicle. Extensions of these algorithms towards navigating through an unstructured environment with limited sensor range are discussed.

Curvature-continuous trajectory generation with corridor constraint for autonomous ground vehicles

We present a practical path planning algorithm based on Bézier curves for autonomous vehicles operating under waypoints and corridor constraints. Bézier curves have useful properties for the trajectory generation problem. This paper describes how the algorithm apply these properties to generate the reference trajectory for vehicles to satisfy the path constraints. The algorithm generates the piecewise-Bézier-curves path such that the curves segments are joined smoothly with C2 constraint which leads to continuous curvature along the path. The degree of the curves are minimized to prevent them from being numerically unstable. Additionally, we discuss the constrained optimization problem that optimizes the resulting path for a user-defined cost function.

Real-Time Obstacle-Avoiding Path Planning for Mobile Robots

In this paper a computationally effective trajectory generation algorithm of mobile robots is proposed. The algorithm plans a reference path based on Voronoi diagram and Bcurves, that meet obstacle avoidance criteria. B´ ezier curves defining the path are created such that the circumference convex polygon of their control points miss all obstacles. To give smoothness, they are connected under C1 continuity constraint. In addition, the first B´ ezier curve is created to satisfy the initial heading constraint and to minimize the maximum curvature of the curve. For the mission, this paper analyzes the algebraic condition of control points of a quadratic Bcurve to minimize the maximum curvature. The numerical simulations demonstrate smooth trajectory generation with satisfaction of obstacle avoidance in an unknown environment by applying the proposed algorithm in a receding horizon fashion.

Obstacle avoiding real-time trajectory generation and control of omnidirectional vehicles

In this paper, a computationally effective trajectory generation algorithm of omnidirectional mobile robots is proposed. The algorithm plans a reference path based on Bézier curves, which meet obstacle avoidance criteria. Then the algorithm solves the problem of motion planning for the robot to track the path in a short travel time while satisfying dynamic constraints and robustness to noise. Accelerations of the robot are computed such that they satisfy the time optimal condition for each sample time interval. The numerical simulation demonstrates the improvement of trajectory generation in terms of travel time, satisfaction of dynamic constraints and smooth motion control compared to previous research.

L + 2 , an improved line of sight guidance law for UAVs

This paper describes a new guidance law that extends the pursuit guidance law previously developed by Park et. al. Several improvements are presented that allow operation in the real world. A stability analysis accounts for the dynamic response of the bank angle commands which leads to the definition of regions of instability. Another extension accounts for situations where the pursuit aim point is not defined by the previous work. A third extension changes the pursuit distance-to-go from a constant to a constant time-to-go so that the linearized transient response is independent of ground speed. Yet another extension defines a “homing” mode in which the UAV flies to a goal point without a defined path, commonly used as a “return-to-base,” either as a safety measure or as an end-of-mission order. Since there is no constraint that the goal point be stationary, we demonstrate that the new law can be used to follow a moving target whose location is known, such as a mobile ground control station. Simulations with a 6 degree-of-freedom aircraft model demonstrate these features.

Piecewise Bezier Curves Path Planning with Continuous Curvature Constraint for Autonomous Driving

We present two practical path planning algorithms based on Bezier curves for autonomous vehicles operating under waypoints and corridor constraints. Bezier curves have useful properties for the trajectory generation problem. This paper describes how the algorithms apply these properties to generate the reference trajectory for vehicles to satisfy the path constraints. Both algorithms generate the piecewise-Bezier-curves path such that the curves segments are joined smoothly with C 2 constraint which leads to continuous curvature along the path. The degree of the curves are minimized to prevent them from being numerically unstable. Additionally, we discuss the constrained optimization problem that optimizes the resulting path for a user-defined cost function.

Low Cost Rapidly Reconfigurable UAV Autopilot for Research and Development of Guidance, Navigation and Control Algorithms

This paper presents the development and preliminary results of a rapidly reconfigurable autopilot for small Unmanned Aerial Vehicles. The autopilot presented differs from current commercial and open source autopilots mainly as it has been designed to: (i ) be easily reprogrammable via Simulink (models are directly transferred to the autopilot through the Real-Time Workshop’s code-generation capability); (ii ) decouple the traditional tasks of attitude estimation/navigation and flight control by using two Digital Signal Controllers (one for each task) interconnected via a Serial Peripheral Interface; and, (iii ) being able to interact directly with Simulink as a Hardware-in-the-Loop simulator. This work details each of the main components of the autopilot and its ground control station software. Preliminary results for sensor calibration, Hardware-in-the-loop, ground and flight tests are presented.Copyright

Simulink Based Hardware-in-the-Loop Simulator for Rapid Prototyping of UAV Control Algorithms

This paper describes a recently developed architecture for a Hardware-in-the-Loop simulator for Unmanned Aerial Vehicles. The principal idea is to use the advanced modeling capabilities of Simulink rather than hard-coded software as the flight dynamics simulating engine. By harnessing Simulink’s ability to precisely model virtually any dynamical system or phenomena this newly developed simulator facilitates the development, validation and verification steps of flight control algorithms. Although the presented architecture is used in conjunction with a particular commercial autopilot, the same approach can be easily implemented on a flight platform with a different autopilot. The paper shows the implementation of the flight modeling simulation component in Simulink supported with an interfacing software to a commercial autopilot. This offers the academic community numerous advantages for hardware-in-the-loop simulation of flight dynamics and control tasks. The developed setup has been rigorously tested under a wide variety of conditions. Results from hardware-in-the-loop and real flight tests are presented and compared to validate its adequacy and assess its usefulness as a rapid prototyping tool.

SLUGS UAV: A flexible and versatile hardware/software platform for guidance navigation and control research

This paper presents the Santa Cruz Low-Cost UAV GNC Subsystem (SLUGS) developed at the University of California Santa Cruz. It is a versatile and flexible autopilot capable of controlling a small unmanned system. It is tightly integrated with MATLAB/Simulink, and allows for a simple and easy transition from pure simulation to HIL simulation to flight code. The hardwares main processing units are two low-cost dsPIC33F DSCs, one handling sensor input and the other managing the navigation and control loops. The sensor DSC implements a complementary attitude and position filter. An interprocessor communication protocol delivers fused attitude and position estimates to the control DSC. The control DSC implements low-level platform stabilization using PID loops, and higher level waypoint following based on a line-of-sight guidance law. Data is logged and available for replay post flight on both the ground station software, and also within MATLAB/Simulink. The hardware was installed on a low-cost single engine electric RC aircraft, and has been demonstrated to be capable of sustained autonomous flight. Several estimation topologies have been tested and developed using the system. The SLUGS is general, and can be adapted to multiple autonomous platforms such as helicopters, quadrotors, twin engine aircraft, ground, and marine surface vehicles.

The Design of Rapidly Recongurable Filters for Attitude and Position Determination

Attitude and position estimation are essential components of any Unmanned Aerial Vehicle. Linear and Extended Kalman Filters as well as complementary lters have traditionally played a major role in these calculations. In order to successfully eld these estimators, a design process requiring many iterations is required. We describe the design process using a new and exible platform developed for rapid prototyping of UAV Guidance, Navigation, and Control algorithms. The evolution of the design begins with a hybrid model consisting of combined Extended Kalman and complementary lters and ends with complementary lters alone. The resulting complementary lters compare favorably with traditional fteen-state Extended Kalman Filters previously reported in the literature and are thus attractive candidates where computational resources are limited. The lter results are shown for actual ight test data.