Feasible Reference Trajectories Research Articles

Formation control of multiple elliptical agents with limited sensing ranges

This paper presents a design of cooperative controllers that force a group of N mobile agents with an elliptical shape and with limited sensing ranges to perform a desired formation. The controllers guarantee no collisions between any agents in the group. The desired formation can be stabilized at feasible reference trajectories with bounded time derivatives. The formation control design is based on an algebraic separation condition between ellipses, Lyapunov’s method, and smooth or p -times differentiable step functions. These functions are introduced and incorporated into novel potential functions to solve the collision avoidance problem without the need for switchings under the agents’ limited sensing ranges.

Rigid Formation Keeping and Formation Reconfiguration of Multi-Agent Systems

A motion planning algorithm is presented for formation control of coordinating multi agents engaged in rigid formation keeping and formation reconfiguration. The multi agent system is separated into geometrically equivalent subsystems for distributed control. The proposed motion planning algorithm generates reference trajectories for each of these subsystems in real-time for online, distributed and autonomous control. Deriving the constrained kinematics eliminates the need for nonlinear programming to account for the system constraints, making the approach amenable to real-time control. A control strategy accounts for actuator/operating constraints to give dynamically feasible reference trajectories. Explicit consideration of actuator and operating limitations and nonholonomic constraints in the design of the reference trajectories, thereby addressing the important issue of dynamic feasibility, is one of the main contributions of the proposed approach. The motion planning algorithm is verified through simulations for a team of multi-agents moving in and switching between formations in a scouting scenario.

Walking Primitive Databases for Perception-Based Guidance Control of Biped Robots

This paper presents a systematic approach to the generation of walking primitive (WP) databases for perception-based guidance control of humanoid 3D bipeds. Individual WPs are computed off-line by optimal control techniques such that they can be concatenated into a physically feasible reference trajectory for walking with step length adaptation, direction changing and stepping over or upon obstacles. Zero moment point and friction conditions ensuring stability of the foot contacts, as well as bounds on joint angles and control torques are considered as constraints. Numerical results are presented for ‘optimal’ WPs generated for the human-size 3D walker JOHNNIE taking into account typical energy based performance indexes. Resulting reference trajectories applied to locomotion control are validated by dynamic simulations of the 3D biped walker. An approach to predictive step sequence planning based on the WP database concept is proposed.

FLATNESS BASED CONTROL OF A DUAL COIL SOLENOID VALVE

This paper presents first results in the attempt to control a dual coil solenoid valve by means of a flatness based approach. First the modeling effort is described, then the differential flatness of the system is shown. The modeling results revealed that the system lacks controllability, when considering one coil only for actuating the valve. Therefore a suitable strategy for energizing both coils has been developed. The flatness property then is used to design feasible reference trajectories for the spool motion with the following properties: soft-landing of the spool, minimal driving current, feasible subject to voltage constraints. Simulation results demonstrate the usefulness and robustness of the approach.

A unified dynamics-based motion planning algorithm for autonomous underwater vehicle-manipulator systems (UVMS)

A new unified motion planning algorithm for autonomous Underwater Vehicle-Manipulator Systems (UVMS) has been presented in this paper. Commonly, a UVMS consists of two sub-systems, a vehicle and a manipulator, having vastly different dynamic responses. The proposed algorithm considers the variability in dynamic bandwidth of the complex UVMS system and generates not only kinematically admissible but also dynamically feasible reference trajectories. Additionally, this motion planning algorithm exploits the inherent kinematic redundancy of the whole system and provides reference trajectories that accommodates other important criteria such as thruster/actuator faults and saturations, and also minimizes hydrodynamic drag. Effectiveness of the proposed unified motion planning algorithm has been verified by extensive computer simulation. The results are quite promising.

Autonomous fuzzy parking control of a car-like mobile robot

This paper is devoted to design and implement a car-like mobile robot (CLMR) that possesses autonomous garage-parking and parallel-parking capability by using real-time image processing. For fuzzy garage-parking control (FGPC) and fuzzy parallel-parking control (FPPC), feasible reference trajectories are provided for the fuzzy logic controller to maneuver the steering angle of the CLMR. We propose two FGPC methods and two FPPC methods to back-drive or head-in the CLMR to the garage and the parking lot, respectively. Simulation results illustrate the effectiveness of the developed schemes. The overall experimental setup of the parking system developed in this paper is composed of a host computer, a communication module, a CLMR, and a vision system. Finally, the image-based real-time implementation experiments of the CLMR demonstrate the feasibility and effectiveness of the proposed schemes.