Many robotic tasks require the end-effector to come into contact with the external environment. In such complex tasks, the manipulator is constrained by the environment, and certain DOFs are lost for motion. The contact forces must be controlled in constraint directions, while the tip position is simultaneously controlled in the free directions.

In this study, highly practical and reliable methods are proposed to determine arm solutions for a six-link robot manipulator. Based on a typical mathematical structure of minimizing an objective function, the optimization theory is applied to solve a reduced system of kinematic equations. The performance tests show that three different approaches are superior to a conventional method and of sufficiently practical use. Especially, the use of an algorithm presented in a linear search is promising.

The need to meet demanding control requirements in increasingly complex dynamical control systems under significant uncertainties makes neural networks very attractive, because of their ability to learn, to approximate functions, to classify patterns and because of their potential for massively parallel hardware implementation. This paper proposes the use of artificial neural networks (ANN) as a novel approach to the control of robot manipulators. These are part of the general class of non-linear dynamic systems where non-linear compensators are required in the controller.

The consideration of part motion instability is crucial to the determination of assembly sequence since this affects the complexity of fixtures and dexterity of robots. This paper presents a new approach to the inference of robotic assembly sequences, taking into consideration the instability of base assembly motions. Based upon the evaluation of motion instability, the method generates stable assembly sequences by use of the precedence constraint inference method previously developed by the authors. An example assembly of a 10-part electrical relay is given to illustrate the concepts and procedure of the proposed scheme. The results show that the proposed method can be effectively utilized to generate stable assembly sequences, thus providing crucial information on the fixture design and selection of types of assembly robots.

A method is presented for generating the path which significantly reduces residual vibration. The desired path is optimally designed so that the system completes the required move with minimum residual vibration. The dynamic model and optimal path are effectively formulated and computed by using special moving coordinates, called virtual rigid link coordinates, to represent the link flexibilities. Also joint compliances are included in the model. Characteristics of residual vibration are identified from the linearized equations of motion. From these results, the performance index is selected to reduce residual vibration effectively. The path to be designed is developed by a combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems. The concept of correlation coefficients is used to select the minimum number of design variables, i.e. Fourier coefficients, the only ones which have a considerable effect on the reduction of residual vibration. A two-link manipulator is used to evaluate this method. Results show that residual vibration can be drastically reduced by selecting an appropriate manipulator path.

For a kinematically redundant manipulator, some performance indices can be optimized while carrying out a given task. So far, the redundancy resolution has been solved at the joint angle level, the joint velocity level, or joint acceleration level depending on the performance indices. According to the resolution level, the solution is represented by high-order differential equations or superfluous number of equations. We propose a unified approach to the inverse kinematic solution which optimizes it at the joint velocity level regardless of the types of the performance indices. A unified approach to obtain an optimal joint velocity is derived by using the necessary condition for optimality so that the proposed method provides an optimal solution for any performance indices and tasks. The optimal solution becomes a set of the minimum number of first-order differential equations which requires a minimum search dimension.To show the validity of the approach, it is applied to a three-link planar manipulator for various types of performance indices.

The combination of robotics and medical imaging may soon provide orthopaedic surgeons with a tool that significantly increases the precision of cementless total hip replacement operations and directly links preoperative planning with surgical execution. Twenty-six successful robot-assisted operations have been performed on dogs and the first clinical trials on human patients have recently taken place.

This paper present a nonlinear, model-based control of flexible link robots. The control task is formulated requiring rigid joints variables to track reference time-varying trajectory and elastic deflection to be damped. The stability and robustness properties of the control scheme are analyzed from a passive energy consideration. A direct adaptive version is also proposed. Extensive evaluation of this approach is performed using experimental validations involving a single-flexible-link and a two-flexible-link horizontal robot. Experimental results show significant performances of the controller under relatively severe working conditions: 700% payload to arm ratio and 20% elastic deflection ratio at highest acceleration stages.

In this paper a control law, which consists of a fuzzy logic controller plus a nonlinear effects negotiator for a flexible robot manipulator, is presented. The nonlinear effects negotiator is used to enhence the control system's ability in dealing with the uncertainty of the mathematical model. The control algorithm is simple and easy to tune as opposed to conventional control law which requires time consuming gains selections. To obtain fuzzy control rules, an error response plane method is proposed.

Fluid power is one of the vast fields and its applications in manufacturing are not used for many real-time problems though its capabilities are known. One such application is fluid power for robotic systems. More specifically, in this study, a new hydraulic system is developed for use in actuating a robotic gripper. Electric motors were found unsatisfactory due to their poor power to weight ratio. Hydraulics were attempted using a master slave hydraulic system. Powering and positioning was done on the master cylinder, while the remote slave cylinder followed the motion. The control of the master cylinder was done with a ground based stepping motor and lead screw mechanism. Small hoses ran to the gripper based slave cylinder, which copied the motions.

Present study on industrial manipulator control either completely neglects structural flexibility or only considers manipulator link flexibility. Ignoring joint flexibility may cause significant errors in gross motion control if the joint elastic effect is predominant. This paper presents an effective control scheme which can compensate for the motion errors generated by simultaneous existence of both link and joint flexibility. The manipulator dynamics is formulated comprehensively by a superposition of two models, namely, an assumed modes of vibration model for links and a torsional spring model.for joints. Then, a nonlinear feedback rate servo control system is developed that compensates for the gross motion errors introduced by both joint elasticity and link flexibility. Motion simulation results show that the proposed formulation can effectively describe the dynamic behavior of a flexible-link, elastic-joint robot. They also verify that the proposed controller is robust in that it can satisfactorily suppress the manipulator end oscillations and yield an accurate gross motion.

A special-purpose robot for prostatectomies has been developed. Details of the robot mechanism, control system and human/computer interface (HCI) are discussed with special emphasis on software methods to ensure system safety. The clinical application of the system is described and software requirements for operating-theatre use are indicated. These requirements include safe error recovery, facilitation of reliable surgical procedures, and an effective HCI.

In this paper the role that shear deformation effect plays in flexible manipulator dynamics is investigated and reported. The shear deformation effect of manipulators with three typical cross-sectional geometries, namely, hollow round, hollow square, and hollow rectangle, is studied. In addition, one important issue for manipulator design considerations regarding the influence of the link dimension variations on flexible dynamics is also investigated. The dynamic simulation results show that the shear deformation effect is approximately inverse proportional to the thickness of manipulator link regardless of cross-sectional shapes, if the link length is fixed. It can also be observed that the longer the manipulator link the less shear effect will influence the manipulator deflection, although the frequency of deflection variances becomes less. Based on the simulation results, it is suggested that hollow circular cross-sectional link should be adopted to reduce shear effect for short and thin manipulator links as far as the flexible linkage manipulator design is concerned. For hollow square and hollow rectangular link cross-sections, the manipulator link must be long and thick to avoid significant influences of shear effects.

This paper deals with the synthesis of a robot mechanism, which has an open kinematic chain structure. The aim of the synthesis is to find optimal mechanism link lengths and the elevation of the robot mechanism base, with respect to the arbitrary chosen task which is described in a task space.

A mathematical model, which describes the problem and enables one to use a nonlinear optimization algorithm, was developed. The usefulness of the approach is demonstrated by the example of the Manutec r3 mechanism with a prescribed task for the robot's end-effector.

We describe a robot capable of performing all procedures necessary to carry out a complete stereotactic neurosurgical operation under the control and supervision of a surgeon. The operation consists of the introduction of a small probe with diameter 2–3 mm through a hole without trepanation. The robot has been built and is now being tested and evaluated. The accompanying control software as well as various medical probes are either in development or partially tested. The installation will be able to carry out a complete intervention under the surveillance of a computed tomography scanner. In this article we emphasize the design choices required to eliminate gearing backlash in a crucial degree of freedom.

This paper describes a new approach to the automatic generation of assembly precedence constraints for robotic assembly, using a part contact level graph. Since inference of precedence constraints is a prerequisite to generate assembly sequences of a product, much work has been done in this field. However, most of it has some limitations in that they use a cumbersome user query or time-consuming geometric reasoning. To cope with these problems, this paper utilizes three directional part contact level graphs which, in three orthogonal directions, contain the information on directional connections for each pair of mating parts. By using these graphs, an assembly precedence constraint is inferred in two steps: The first step infers a precedence constraint for each directional connection by applying the path-finding algorithm. Utilizing the precedence constraints thus obtained, the next step infers the precedence constraint for each part to be assembled with its base assembly. Examples are given to illustrate the concepts and procedure of the proposed scheme.

Control laws are described for solving the task of stabilization of motion and force of interaction of a robot with its environment with a prescribed quality of transient processes with respect to position and in the presence of control, motion, and interaction force constraints. The robustness of these laws to parametric perturbations and their stability with respect to initial and external perturbations and measuring sensor errors have been proven.