Car-like Vehicle Research Articles

A REAL-TIME AUTONOMOUS NAVIGATION ARCHITECTURE

This paper presents a novel navigation architecture for automated carlike vehicles in urban environments. Motion safety is a critical issue in such environments given that they are partially known and highly dynamic with moving objects (other vehicles, pedestrians.). The main feature of the navigation architecture proposed is its ability to make safe motion decisions in real-time, thus taking into account the harsh constraints imposed by the type of environments considered. The architecture is based upon an efficient publish/subscribe-based middleware system that allows modularity in design and the easy integration of the key functional components required for autonomous navigation: perception, localisation, mapping, real-time motion planning and motion tracking. After an overall presentation of the architecture and its main modules, the paper focuses on the “motion” components of the architecture. Experimental results carried out on both a simulation platform and a Cycab vehicle are presented.

Intelligent mobile robot navigation, Federico Cuesta and Aníbal Ollero, Springer Tracts in Advanced Robotics, vol. 16, Springer: Berlin–Heidelberg, pages: XII + 204. Price $99.00, ISBN: 3‐540‐23956‐1 2005

Intelligent mobile robot navigation, Federico Cuesta and Aníbal Ollero, Springer Tracts in Advanced Robotics, vol. 16, Springer: Berlin–Heidelberg, pages: XII + 204. Price $99.00, ISBN: 3‐540‐23956‐1 2005

A semi-optimal path generation scheme for a frame articulated steering-type vehicle

A wheel loader is one of the main machines that is used in various applications. The present authors have been interested in autonomous control of its locomotion and navigation. An inevitable step in achieving this is path planning. The authors choose a technique of designing a steering method for car-like vehicles by proposing a semi-optimal path generation scheme using a canonical path skeleton consisting of three line segments and two clotohid pairs. Taking such a path skeleton, for any given pair of a locally desired initial configuration and a locally desired destination configuration, path planning is equivalent to finding the suitable values of parameters which characterize this skeleton. Due to the lower number of constraints than the number of parameters, ascertaining the values of parameters comes from the optimizations of the authors' formulated non-linear programmings with equality constraints. In addition, the realizable path must be subject to the upper-bounded curvature and curvature derivative. Adopting a genetic algorithm as the search tool in one of the optimizations makes it possible to allow the use of only a single canonical skeleton for the desired path planning.

Recursive Backstepping Stabilization of a Wheeled Mobile Robot

This research is aimed at the development of a dynamic control to enhance the performance of the existing dynamic controllers for mobile robots. System dynamics of the car-like robot with non-holonomic constraints were employed. A backstepping approach for the design of a discontinuous state feedback controller is used for the design of the controller. It is shown that the origin of the closed-loop system can be made stable in the sense of Lyapunov. The control design is made on the basis of a suitable Lyapunov function candidate. The effectiveness of the proposed approach is tested through simulation on a car-like vehicle mobile robot.

From Reeds and Shepp's to Continuous-Curvature Paths

This paper presents Continuous Curvature (CC) Steer, a steering method for car-like vehicles, i.e., an algorithm planning paths in the absence of obstacles. CC Steer is the first to compute paths with: 1) continuous curvature; 2) upper-bounded curvature; and 3) upper-bounded curvature derivative. CC Steer also verifies a topological property that ensures that when it is used within a general motion-planning scheme, it yields a complete collision-free path planner. The coupling of CC Steer with a general planning scheme yields a path planner that computes collision-free paths verifying the properties mentioned above. Accordingly, a car-like vehicle can follow such paths without ever having to stop in order to reorient its front wheels. Besides, such paths can be followed with a nominal speed which is proportional to the curvature derivative limit. The paths computed by CC Steer are made up of line segments, circular arcs, and clothoid arcs. They are not optimal in length. However, it is shown that they converge toward the optimal Reeds and Shepp paths when the curvature derivative upper bound tends to infinity. The capabilities of CC Steer to serve as an efficient steering method within two general planning schemes are also demonstrated.

Recursive Backstepping Stabilization of a Wheeled Mobile Robot

This research is aimed to the development of a dynamic control to enhance the performance of the existing dynamic controllers for mobile robots. System dynamics of the car-like robot with nonholonomic constraints were employed. A Backstepping approach for the design of discontinuous state feedback controller is used for the design of the controller. It is shown that the origin of the closed loop system can be made stable in the sense of Lyapunov. The control design is made on the basis of a suitable Lyapunov function candidate. The effectiveness of the proposed approach is tested through simulation on a car-like vehicle mobile robot.

Switching linear path following for bounded curvature car-like vehicles

Building on previous work of Canudas de Wit et al. a nonlinear path following controller for the kinematic model of a car-like robot with bounded curvature is designed. Given a bounded curvature reference path and an upper bound on the maximum curvature that the robot is able to drive, the proposed feedback solution guarantees asymptotic convergence to the assigned path with a Lyapunov asymptotically stable error dynamics while always satisfying the curvature constraint. Thanks to the adaptive nature of the law, the controller gain tuning is made extremely easy and convergence speed is greatly improved with respect to the original fixed gain controller. Experimental tests have been performed on a differential drive mobile robot confirming the effectiveness of the solution.

Agricultural Robotic Platform with Four Wheel Steering for Weed Detection

A robotic platform for mapping of weed populations in fields was used to demonstrate intelligent concepts for autonomous vehicles in agriculture which may eventually result in a new sustainable model for developed agriculture. The vehicle presented here is adapted to operate in 0·25 and 0·5 m row crops and equipped with cameras for row guidance and weed detection. A modular approach is taken with four identical wheel modules, allowing four wheel steering and propulsion of the platform. The result is improved mobility which allows parallel displacement of the vehicle during turns by decoupling adjustments in position from adjustments in orientation. Control of the platform is provided through a vehicle electronics and control system based on embedded controllers and standard communication protocols. The software implements a hybrid deliberate software architecture that allows a hierarchical decomposition of the operation. The lowest level implements a reactive feedback control mechanism based on an extension of simple control for car-like vehicles to the four wheel case. The controller design forces the front and rear of the vehicle to follow a pre-determined path and allows the vehicle to maintain a fixed orientation relative to the path. The controller rationale is outlined and results from experiments in the field are presented.

Path following of car-like vehicles using dynamic inversion

This paper focuses on a special path following task arising from the needs of vision-based autonomous guidance: a given front point of a car-like vehicle that is within the look-ahead range of a stereo vision system must follow a prespecified Cartesian path. A solution to this path following problem is provided by a new feedforward/feedback control strategy where the feedforward is determined by a dynamic generator based on exact dynamic inversion over the nominal vehicle model and the feedback is mainly issued by correcting terms proportional to the tangential and normal errors determined with respect to the vehicle’s ideal trajectory. A convergence analysis of the resulting dynamic inversion based controller is established versus a vehicle’s uncertain model defined via equation errors. Simulation examples highlighting the controller’s performances are included.

Quintic G/sup 2/-splines for the iterative steering of vision-based autonomous vehicles

This paper presents a new motion planning primitive to be used for the iterative steering of vision-based autonomous vehicles. This primitive is a parameterized quintic spline, denoted as /spl eta/-spline, that allows interpolating an arbitrary sequence of points with overall second-order geometric (G/sup 2/-) continuity. Issues such as completeness, minimality, regularity, symmetry, and flexibility of these G/sup 2/-splines are addressed in the exposition. The development of the new primitive is tightly connected to the inversion control of nonholonomic car-like vehicles. The paper also exposes a supervisory strategy for iterative steering that integrates feedback vision data processing with the feedforward inversion control.

A DYNAMIC INVERSION BASED CONTROLLER FOR PATH FOLLOWING OF CAR-LIKE VEHICLES

This paper focuses on a special path following task arising from the needs of vision-based autonomous guidance: a given front point of a car-like vehicle that is within the look-ahead range of a stereo vision system, must follow a prespecified Cartesian path. Solution to this path following problem is provided by a new feedforward/feedback control strategy where the feedforward is determined by a dynamic generator based on exact dynamic inversion over the nominal vehicle model and the feedback is mainly issued by correcting terms proportional to the tangential and normal errors determined with respect to the vehicle's ideal trajectory. A convergence analysis of the resulting dynamic inversion based controller is established versus a vehicle's uncertain model defined via equation errors. A simulation example highlighting the controller's performances is included.

Some Steps Towards Autonomous Cars

Developing new Intelligent Transportation Systems which take into consideration the social-economical, environmental, and safety factors of the modern human society, is one of the grand challenges of the 21th century. This paper presents the motion autonomy capabilities which have been developed for future cars in the scope of the French “Praxitele” and “Automated Road” projects. These new capabilities relies onto effective solutions that we have developed for contributing to solve three main problems: autonomous maneuvering for a car-like vehicle using the concept of Sensor-Based Maneuver, planning and controling the motions of a double-steered vehicle (the CyCab) using the concept of Differential Flatness, and obstacle avoidance in a dynamic environment using the concept of Non-Linear Velocity Obstacle. Experimental results obtained with real vehicles are also presented and discussed.

Smooth motion planning for car-like vehicles

Presents a steering method for a car-like vehicle providing smooth paths subjected to curvature constraints. We show how to integrate this steering method in a global motion planning scheme taking obstacles into account. The main idea of the paper is to consider the car as a 4-D system from a kinematic point of view and as a 3-D system from a geometric point of view of collision checking. The resulting planned motions are guaranteed to be collision-free and C/sup 2/ between two cusp points.

Fuzzy control to drive car-like vehicles

The reactive component of a motion control architecture for a car-like vehicle intended to move in dynamic and partially known environments is presented in this paper. It is called the execution monitor (EM). The purpose of EM is to generate commands for the servo-systems of the vehicle so as to follow a given nominal trajectory while reacting in real time to unexpected events. EM is designed as a fuzzy controller, i.e. a control system based upon fuzzy logic, whose main component is a set of fuzzy rules encoding the reactive behaviour of the vehicle. A behaviour-based approach is used to set up the fuzzy rule base: the overall behaviour of the vehicle results from the combination of several basic behaviours (trajectory following, obstacle avoidance, etc.), each of which is encoded by a specific set of rules. This approach permits an easy and incremental construction of the fuzzy rule base and also to develop and test the basic behaviours separately. It is the fuzzy control mechanism that straightforwardly handles the problems of behaviour arbitration and command fusion. The basic behaviour rules are simply obtained through direct encoding of the human expertise about car driving. In addition, weighing coefficients are attached to the rules thus permitting a fine tuning of the influence of each basic behaviour. EM has been implemented and tested on a real computer-controlled car, equipped with sensors of limited precision and reliability. Experimental results obtained with the prototype vehicle are presented. They demonstrate the capability of EM to actually control a real vehicle and to perform trajectory following and obstacle avoidance in real outdoor environments by using simple fuzzy behaviours relying upon low-resolution sensor data.

Sensor-based control architecture for a car-like vehicle

Presents a control architecture for a car-like vehicle moving in a dynamic and partially known environment. The key idea is to plan and carry out sensor-based manoeuvres. The paper focuses on the reactive part of the architecture that features control experts, i.e. parameterized control programs adapted to a specific manoeuvre and capable to react in real-time to unforeseen events. Experimental results obtained with an automatic car are presented for two types of manoeuvres: lane following/changing and parallel parking.

A new continuous-curvature line/path-tracking method for car-like vehicles

A new continuous-curvature line/path-tracking method for car-like vehicles

A new continuous-curvature line/path-tracking method for car-like vehicles

In this paper, we first investigate the problem of finding an algorithm for the movement of a car-like vehicle to track a given directed straight line. Car-like vehicles' motions possess 2 d.o.f., speed v and path curvature κ. We compute the 'derivative of path curvature', λ = dκ/ds, rather than the path curvature κ itself, to enforce continuous-curvature vehicle motions. Specifically, we compute λ as a linear function of the current path curvature, orientation and positional difference of the vehicle against the given line. We call this function λ the steering function. The uniform asymptotic stability of the feedback rule is proved through linearization and a Lyapunov function. Next, this basic line-tracking result is applied to the problem of path tracking where a path consists of directed straight lines. The main advantages and features of the results are summarized as follows. (i) Since the derivative dκ/ds of path curvature is obtained, the path curvature is always continuous while a vehicle converges to the line. (ii) By assuming the critical damping condition, the steering function contains one parameter σ that controls the smoothness (or equivalently, sharpness) of vehicle motions. (iii) This theory can be applied to a vehicle with any wheel architecture, i.e. this theory is vehicle independent. (iv) The theory can easily be extended to the more general problem of tracking a path consisting of any number of directed lines with a new principle of neutral switching. (v) The simplicity and machine independence of this theory makes implementation of this theory on vehicles easy. We present numerous simulation results of line/path-tracking motions. These results verify the effectiveness of this continuous-curvature motion control method. Some successful results obtained on the autonomous robot Yamabico at the Naval Postgraduate School are also included.

An architecture for motion planning and motion control of a car-like vehicle

An architecture to plan and control the motion of a car-like vehicle is presented. With this architecture, the vehicle is able to avoid stationary and moving obstacles in its local environment while obeying the highway code and its own kinematic and dynamic constraints. In our application, the model of the local environment is provided to the vehicle by an on-board perception system (cameras and internal sensors). At any time instant, the vehicle obtains information about the local structure of the roadway (number of lanes, geometrical characteristics of the lanes and road marks), the moving obstacles around, the current position of the vehicle and its internal state (velocity, acceleration and steering angle). Different kinds of obstacles are considered: other vehicles, motorcycles, pedestrians, animals, etc. The framework of this research work is the French demonstrator Pro-Lab II, part of the European programme on transport Prometheus. The purpose of Pro-Lab II is to design, integrate and demonstrate an ‘electronic copilot’ to assist the human driver in various traffic situations.