Avinesh Prasad

Formation control of a swarm of mobile manipulators

This paper presents a new Lyapunov-based decentralized formation control planner for a swarm of 2-link mobile manipulators in an a priori known environment. To ensure a significant degree of formation stiffness along the flight-path, information on moving ghost targets, inter-robot bounds for aggregation and heading for the mobile manipulators are captured in the control planner. The final desired orientation of the formation is by observing a minimum distance between every member of the swarm and ghost walls. The nonlinear control laws extracted from the Lyapunov-based control scheme are utilized to obtain collision-free trajectories of the swarm in a low-degree formation, whilst ensuring stability of the kinodynamic system governing the swarm. The effectiveness of the controllers is demonstrated by simulating interesting situations.

A new stabilizing solution for motion planning and control of multiple robots

This paper formulates a new scalable algorithm for motion planning and control of multiple point-mass robots. These autonomous robots are designated to move safely to their goals in a priori known workspace cluttered with fixed and moving obstacles of arbitrary positions and sizes. The control laws proposed for obstacle and collision avoidance and target convergence ensure that the equilibrium point of the given system is asymptotically stable. Computer simulations with the proposed technique and applications to a team of two planar (RP) manipulators working together in a common workspace are presented. Also, the robustness of the system in the presence of noise is verified through simulations.

A -Strategy: Facilitating Dual-Formation Control of a Virtually Connected Team

This paper describes the design of new centralized acceleration-based controllers for the multitask problem of motion planning and control of a coordinated lead-carrier team fixed in a dual-formation within an obstacle-ridden environment. A -strategy, where and are Euclidean measures with respect to the lead robot, is developed to ensure virtual connectivity of the carrier robots to the lead robot. This connectivity, built into the system itself, inherently ensures globally rigid formation between each lead-carrier pair of the team. Moreover, a combination of target configuration, -strategy, orientation consensus, and avoidance of end-effector of robots results in a second, locally rigid formation (not infinitesimally rigid). Therefore, for the first time, a dual-formation control problem of a lead-carrier team of mobile manipulators is considered. This and other kinodynamic constraints have been treated simultaneously via the overarching Lyapunov-based control scheme, essentially a potential field method favored in the field of robotics. The formulation of this new scheme, demonstrated effectively via computer simulations, is timely, given that the current proposed engineering solutions, allowing autonomous vehicles on public roads, include the development of special lanes imbued with special sensors and wireless technologies.

A solution to the motion planning and control problem of a car-like robot via a single-layer perceptron

This paper tackles the problem of motion planning and control of a car-like robot in an obstacle-ridden workspace. A kinematic model of the vehicle, governed by a homogeneous system of first-order differential equations, is used. A solution to the multi-tasking problem of target convergence, obstacle avoidance, and posture control is then proposed. The approach of solving the problem is two-fold. Firstly, a novel velocity algorithm is proposed to drive the car-like robot from its initial position to the target position. Secondly, a single layer artificial neural network is trained to avoid disc-shaped obstacles and provide corresponding weights, which are then used to develop a function for the steering angles. Thus, our method does not need a priori knowledge of the environment except for the goal position. With the help of the Direct Method of Lyapunov, it is shown that the proposed forms of the velocity and steering angle ensure point stability. For posture stability, we model the two parallel boundaries of a row-structured parking bay as continua of disk-shaped obstacles. Thus, our method is extendable to ensuring posture stability, which gives the desired final orientation. Computer simulations of the generated path are presented to illustrate the effectiveness of the method.

Globally rigid formation of n-link doubly nonholonomic mobile manipulators

Abstract This paper provides a new framework for the collective motion control of a team of n -link doubly nonholonomic mobile manipulators in a constrained environment. A continuous decentralized motion planner is proposed. It guarantees the establishment and strict maintenance of a team formation using the Lyapunov-based control scheme (LbCS), which takes into account all the practical limitations, and the constraints due to fixed obstacles, nonholonomy and globally rigid formation requirements. The control scheme inherently utilizes artificial potential fields within an overarching leader–follower framework to mobilize the prescribed globally rigid formation. The designated leader of the team is modeled as a moving reference point, referred to as the virtual leader. With its protective polygonal region, it directs the motion of the team and manipulate the geometry of the formation. It is the authors’ belief that this navigation and globally rigid formation control problem of n -link doubly nonholonomic mobile manipulators is treated for the first time with the use of continuous time-invariant control laws within the framework of LbCS and a variant of the leader–follower scheme. The effectiveness of the motion planner and the resulting acceleration-based control laws are demonstrated via computer simulations.

Motion planning and control of a point-mass robot in a 3-dimensional space with application to a cylindrical manipulator

In this paper we propose a new solution to the findpath problem of a point-mass robot which is required to move safely to a designated target in a 3-dimensional workspace. We consider a priori known workspace cluttered with obstacles of arbitrary position and size. The novelty of the solution is three-fold. Firstly, a velocity algorithm is used to drive the robot from its initial position to the target position and remain there forever. Secondly, in the presence of obstacles, the control laws are generated by introducing turning angles which ensure that the robot steers safely past the obstacles. Finally, the control laws ultimately guarantee that the equilibrium point of the given system is asymptotically stable. The proposed technique is verified using computer simulations and an application consisting of a cylindrical manipulator is presented.

Landmark aided navigation of a point-mass robot via Lyapunov-based control scheme

One of the seminal attributes of mobile robots is to navigate accurately in a workspace executing tasks such as collision and obstacle avoidances and target convergence. Use of landmarks has become one of the popular methods to aid in navigation. In this paper, we present a new solution of landmark aided navigation using the Lyapunov-based Control Scheme. We assume a priori knowledge of a set of landmarks in the workspace from which it selects a subset of landmarks deploying specific metrics such as a robots field of view. This allows the robot to reach its target by maneuvering along normally the safest, smoothest and shortest path. Interesting computer simulations illustrate the effectiveness of the new control laws.

A simple approach to motion control of a three-dimensional articulated manipulator arm

In this paper, we propose a relatively simple approach to solve the motion control problem of a three dimensional articulated manipulator arm. The manipulator arm has two links connected by a revolute joint and is anchored on a rotatable base. The kinematic model is developed and a velocity based algorithm is used to move the end-effector from an initial position to a goal position taking into account the mechanical singularities of the system. For obstacle avoidance, we require every point on the two links to avoid any obstacle that it may encounter. Computer simulations are presented to illustrate the effectiveness of the proposed control laws.