V. Pshikhopov

Homing and Docking Autopilot Design for Autonomous Underwater Vehicle

This paper presents homing and docking autopilot design for the autonomous underwater vehicle (AUV). A nonlinear interrelated dynamic model of the underwater vehicle is considered. The AUV autopilot is designed on base of a position-trajectory control method. Adaptation of the control system is based on robust disturbances estimation. Modeling and hardware results approved feasibility of the proposed methods.

Decentralized Control of a Group of Homogeneous Vehicles in Obstructed Environment

The presented solution is a decentralized control system with a minimal informational interaction between the objects in the group. During control and path planning the obstacles are transformed into repellers by the synthesized controls. The main feature distinguishing the developed approach from the potential fields method is that the vehicle moves in the fields of forces depending not only on the mutual positions of a robot and an obstacle but also on the additional variables allowing solving the problem of robot’s path planning using a distributed control system (Pshikhopov and Ali, 2011). Unlike the work by Pshikhopov and Ali, 2011, here an additional dynamic variable is used to introduce stable and unstable states depending on the state variables of the robot and the neighboring objects. The local control system of each vehicle uses only the values of its own speeds and coordinates and those of the neighboring objects. There is no centralized control algorithm. In the local control algorithms the obstacles are represented as vehicles being a part of the group which allows us to unify the control systems for heterogeneous groups. An analysis was performed that proves existence and asymptotic stability of the steady state motion modes. The preformed simulation confirms the synthesis and analysis results.

Basic algorithms of adaptive position-path control systems for mobile units

Today, mobile objects are finding increasing usage in a wide variety of applications. Robots have been put to use in the air, on the ground and under the sea. Along with this expansion in robot technology, the problem of control and autonomous decision making is an ongoing concern, especially in light of the increasing difficulty of tasks. This study is focused on the algorithms of adaptive control system for mobile objects. The authors examined the application of direct adaptive control with reference to model approaches, in particular the position-path method. Point positioning is discussed, and the authors propose a method for efficiency improvement. Parametric uncertainty and influence of immeasurable disturbances are expected. Basic algorithms for the calculation of controlling forces and moments are synthesized using the position-path control method. The authors propose a structure and algorithms of an adaptive position-path system with a reference model. The synthesis of adaptive regulator and stability analysis of closed-loop system is performed, and an example of regulator synthesis is given. Finally, the authors present simulation results for an autonomous unmanned underwater vehicle equipped with a main engine, nose and hydrodynamic rudders on the tail. Along with this, horizontal and vertical maneuvering devices are presented.

Hybrid path planner for a hexacopter in 3D uncertain environment

The article presents development and analysis of hybrid path planning systems for vehicles. Two types of planner structures were defined. In the first type of systems several basic path planning methods operate together. In the systems of the second type parameters and initial data of one basic method are modified by additional algorithms. We developed a controller that solves positioning and path-following problems with a high accuracy. A hybrid path-planning system is developed for a hexacopter based on the virtual fields method in the class of hybrid systems of the second type. In the synthesized system a special algorithm of sensor data analysis modifies the initial data to use the virtual fields method.

Path planning and control of vehicles in 3D environment using unstable modes

The article addresses the problem of controlling a vehicle in an undetermined 3D environment with mobile and stationary obstacles. We propose a two-level system performing planning and path-following. The path planning problem is split into the problem of planning and following global paths-missions and the problem of local planning in an obstructed area. The global path is built based on a priory information. A local path corrects the global one if the system detects obstacles that are not presented on the map. At first, the system is proposed that follows the global path at the controller level. Secondly, the hybrid system is introduced. It avoids obstacles using unstable modes at the lower level together with an intelligent algorithm determining the desired direction of detour at the top level. The techniques of introducing unstable modes are analyzed. Numerical modeling results are presented using the example of a hexacopter control system.

Decentralized control algorithms of a group of vehicles in 2D space

The problem of decentralized control of group of robots, described by kinematic and dynamic equations of motion in the plane, is considered. Group performs predetermined rectangular area passing at a fixed speed, keeping the line and a uniform distribution. The environment may contain a priori unknown moving or stationary obstacles. Decentralized control algorithms, based on the formation of repellers in the state space of robots, are proposed. These repellers form repulsive forces generated by dynamic subsystems that extend the state space of robots. These repulsive forces are dynamic functions of distances and velocities of robots in the area of operation of the group. The process of formation of repellers allows to take into account the dynamic properties of robots, such as the maximum speed and acceleration. The robots local control law formulas are derived based on positionally-trajectory control method, which allows to operate with non-linear models. Lyapunov function in the form of a quadratic function of the state variables is constructed to obtain a nonlinear closed-loop control system. Due to the fact that a closed system is decomposed into two independent subsystems Lyapunov function is also constructed as two independent functions. Numerical simulation of the motion of a group of five robots is presented. In this simulation obstacles are presented by the boundaries of working area and a movable object of a given radius, moving rectilinear and uniform. Obstacle speed is comparable to the speeds of the robots in a group. The advantage of the proposed method is ensuring the stability of the trajectories and consideration of the limitations on the speed and acceleration at the trajectory planning stage. Proposed approach can be used for more general robots’ models, including robots in the three-dimensional environment.