Optimal path crossing the orientation exclusion zone of a robot with offset wrist

An unexpected path reversal is discovered for a serial robot with an offset-axis wrist over a finite range of proximity to the wrist singularity. This is replicated by a kinematic model. A prior spherical-wrist method transits the singularity with limited joint rate and acceleration under a constant rate of tool traversal. Accurate position is maintained by controlling a small deviation in orientation. Extensions to the method for an offset wrist (1) find the least-maximum deviation, (2) identify and locate where a path reversal occurs, and (3) use this point to control step size in a high-order predictor-correction path following procedure.

A COMPUTATIONAL INTELLIGENT APPROACH TO KINEMATICS PROBLEMS IN ROBOTICS AND COMPUTER ANIMATION

The paper presents a novel method for solving the kinematics problems in real time for fast-moving robot manipulators, animation characters, and hexapod robots. The method uses certain properties of the kinematics map and is based on spatial decomposition, classification with fuzzy logic, and neural network representation of data that are performed during an off-line process. As a result of the preprocessing, the online time for computing the kinematics is extremely small making it possible to perform real-time operations. Examples are provided to demonstrate the performance of the method.

Multiobjective trajectory planner for industrial robots with payload constraints

A general new methodology using evolutionary algorithms viz., Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi-objective Differential Evolution (MODE), for obtaining optimal trajectory planning of an industrial robot manipulator (PUMA 560 robot) in the presence of fixed and moving obstacles with payload constraint is presented. The problem has a multi-criterion character in which six objective functions, 32 constraints and 288 variables are considered. A cubic NURBS curve is used to define the trajectory. The average fuzzy membership function method is used to select the best optimal solution from Pareto optimal fronts. Two multi-objective performance measures namely solution spread measure and ratio of non-dominated individuals are used to evaluate the strength of Pareto optimal fronts. Two more multi-objective performance measures namely optimiser overhead and algorithm effort are used to find computational effort of the NSGA-II and MODE algorithms. The Pareto optimal fronts and results obtained from various techniques are compared and analysed. Both NSGA-II and MODE are best for this problem.

A new geometric approach to characterize the singularity of wheeled mobile robots

This research presents a new and genericgeometric approachthat characterizes the kinematic singularity of wheeled mobile robots. First, the kinematic models of all the common wheels are obtained:fixed,centered orientable,castor, andSwedish. Then, a procedure for generating robot kinematic models is presented based on the set of wheel equations and thenull spaceconcept. Next,two examplesare developed to illustrate the nongeneric singularity characterization. In order to improve that approach, agenericandpracticalgeometric approach is established to characterize the singularity of any kinematic model of a wheeled mobile robot (WMR). Finally, thesingular configurationsfor many types of mobile robots are depicted employing the proposed approach.

A tele-operated mobile ultrasound scanner using a light-weight robot

This paper presents a new tele-operated robotic chain for real-time ultrasound image acquisition and medical diagnosis. This system has been developed in the frame of the Mobile Tele-Echography Using an Ultralight Robot European Project. A light-weight six degrees-of-freedom serial robot, with a remote center of motion, has been specially designed for this application. It holds and moves a real probe on a distant patient according to the expert gesture and permits an image acquisition using a standard ultrasound device. The combination of mechanical structure choice for the robot and dedicated control law, particularly nearby the singular configuration allows a good path following and a robotized gesture accuracy. The choice of compression techniques for image transmission enables a compromise between flow and quality. These combined approaches, for robotics and image processing, enable the medical specialist to better control the remote ultrasound probe holder system and to receive stable and good quality ultrasound images to make a diagnosis via any type of communication link from terrestrial to satellite. Clinical tests have been performed since April 2003. They used both satellite or Integrated Services Digital Network lines with a theoretical bandwidth of 384 Kb/s. They showed the tele-echography system helped to identify 66% of lesions and 83% of symptomatic pathologies.