An analytic solution approach to the time-varying obstacle avoidance problem is adopted. The problem considers the collision between any link of the robotic manipulator and the time-varying obstacle. The information on the motion and shape change of the obstacle is given prior to robot motion planning. To facilitate the problem, we analyze and formulate it mathematically in a robot joint space. We then introduce the view-time concept and analyze its properties. Using the properties of the view-time, a view-time based motion planning method is proposed. The view-time based method plans the robot motion by units of the view-time. In every view-time, it uses a stationary obstacle avoidance scheme. The proposed method is applied to the motion planning of a 2 DOF robotic manipulator in an environment with a polyhedral moving obstacle.

More than 50 ‘Handy 1’ robotic aids are now in use that enable some handicapped people to feed themselveswithout assistance from a carer. The benefits of thisdevice include much greater control of the eating process by the user as well as the development of eating skills. The article describes the genesis of this device and its subsequent development and early evaluation.

In standard classical kinematic and dynamic considerations the equations of motion for an n-link manipulator can be obtained as recursive Newton-Euler equations. Another approach to finding the inverse dynamics equations is to formulate the system dynamics and kinematics as a two-point boundary-value problem. The equivalence between these two approaches has been proved in this paper. Solution to the two-point boundary-value problem leads to the forward dynamics equations which are similar to the equations of Kalman filtering and Bryson-Frazier fixed time-interval smoothing. The extensive numerical studies conducted by the author on the new inverse and forward dynamics algorithms derived from the two-point boundary-value problem establish the same level of confidence as exists for current methods. In order to obtain the algorithms with the smallest coefficients of the polynomial of order O(n), the categorization procedure has been implemented in this work.

A modular hierarchical model for controlling robots is presented. This model is targeted mainly for research and development; it enables researchers to concentrate on a certain specific task of robotics, while using existing building blocks for the rest of their applications. The presentation begins by discussing the problems with which researchers and engineers of robotics are faced whenever trying to use existing commercial robots. Based on this discussion we propose a new general model for robot control to be referred as TERM (TEchnion Robotic Model). The viability of the new model is demonstrated by implementing a general purpose robot controller.

Increased speed of inverse dynamics computation is essential for improving the characteristics of robot control systems. This is achieved by reducing the numerical complexity of the models and by introducing parallelism in model computation. In this paper customized symbolic models with a near minimum numerical complexity will be used as a basis for the examination of parallelism in inverse dynamic robot models. A scheduling algorithm for the distribution of computational load onto an arbitrary linear array of pipelined processors will be developed. The proposed algorithm is experimentally evaluated on a transputer network.

An analysis is presented in this paper for the equilibrium of a class of parallel manipulators resembling the Stewart platform in a general form. General coordinates and 4 x 4 homogeneous transformations are employed to arrive at exact expressions for the force distribution in all six legs given the general 6-dimensional wrench (generalized force) at the upper platform of a parallel manipulator. Numerical examples are carried out to examine the validity of the approach and the accuracy of the numerical technique employed.

This paper presents a sensory gripper, consisting of two tactile sensing matrices which acquire three dimensional images of objects of interest. The image processing algorithm uses elastostatic contact information to discriminate among a host of parts made of different materials. The algorithm also enables the assessment of orientation of parts without the pre-requisite of having to recognise them. The positions of stable holdsites and a safe gripping force are also evaluated.

It is expected that an appropriate robotic appliance can play a major role in providing long periods of independence, which in turn will lead to improved quality of life, for people who are severely physically limited. As part of its research programme over the past several years the Neil Squire Foundation has been developing a workstation-based robotic assistive appliance (RAA) for use by such persons. We feel that robotic aids initially will have their most profound impact when applied in a vocational environment. Although other rehabilitation researchers have similar interests there is a great need for the utility of robots in these environments to be more fully substantiated and assessed. A formal evaluation process currently is under way in an attempt to quantify and to understand the cost/benefit results of using the RAA in office situations.

In this paper, we investigate the crab gaits of a quadruped. Some important characteristics that simplify the analysis of crab gaits are presented, and several formulas for optimizing the longitudinal gait stability margin of a quadruped crab gait are derived by incorporating the time weighting factor. The analysis and implementation of the gait have been simplified by employing a pseudo-world coordinate frame as a reference frame for describing footholds and vehicle's motion. We also suggest a unique gait which optimizes gait stability margin according to the range of crab angle. Finally, we consider the effects of variations of footholds on stability and maximum permissible stroke in terms of support boundary angle. The results derived in this paper contain previous works on the forward walking gait as a special case of the crab gait.

This paper presents a Kalman filtering technique for reducing errors in locating 3-D objects using a sensor system. The location information is employed to control the motion of an industrial robot to pick up the objects. The sensor consists of a rigid platform mounted on a flexible column. Each object to be located is placed on the sensor. The static deflections and natural frequencies of vibrations of the sensor are measured and processed to determine the position and orientation of the object. In practice, the sensor signals obtained are corrupted with noise leading to errors in location determination. A Kalman filter is used to reduce the noise present in the sensor system.

In this paper, we suggest an optimal force distribution scheme by weak point force minimization and we also present an efficient method to solve the problem. The concept of a weak point is a generalized one which is applicable to any points of interest, as well as joints or contact points between end-effectors and an object. The problem is formulated by a quadratic objective function of the forces exerted at weak points subject to the linear equality and inequality constraints, and its optimal solution is obtained by an efficient method. As regards the solution of the problem, the original problem is reformulated to a reduced order dual problem after the equality constraints are eliminated by force decomposition.

A method is presented to perform path planning in the Cartesian space. The motion velocity and acceleration are continuous. This is the first polynomial path planning algorithm in the Cartesian space working in real-time; it does not need an advanced knowledge of the trajectory and can be used when knot points are provided on-line by a sensor. The Bézier representation is used to compute a fifth degree polynomial path. It has been tested on an industrial robot controller.

Human posture is the co-operation of parts of the body to perform a task. This organization is self optimised by the operator to minimize strain and pain and maximize efficiency. This problem is formulated as a problem of inverse kinematic of a redundant robot. Constraints are imposed by the visual and manual task, and criteria may be modified in relation to operator motivation and tiredness. An interactive graphical software is designed to teach the postural problem and as an ergonomic aid.

This paper discusses the problem of impact with robotic systems. The original method for the solution of impact is presented. The main idea is the replacement of impact with a singularity and hence the approach is called the IVSA (Impact-Via-Singularity-Analysis) Method. This goal is achieved by considering the obstacle as a unilateral constraint and introducing the new set of generalized coordinates so as to incorporate the constraint in the dynamic model. Using the IVSA Method the impact is not described by algebraic equations but by a reduced set of differential equations resulting directly from the initial dynamic model. The integration of dynamic equations over the impact points is thus possible. A numerical example is presented.

This paper describes the first prototype of the robot system ‘MASTER’ for helping disabled people. The results of evaluations after one year of experiments in French rehabilitation centres are reported. Following comments and criticisms by staff and users, many improvements were made to the first version and have been taken into account in the design of a new version which will be evaluated in 1992–93 in French and European projects.

This paper presents a new approach for simplifying dynamic equations of motion of robot manipulators by using a nondimensionalization scheme. With this approach the dynamic analysis is done in a nondimensional space. That is, it is required to establish a dimensionless coordinate system in which the dynamic equations of motion of manipulators are formulated. The characteristic parameters of the manipulators are then defined by choosing proper physical quantities as basic units for nondimensionalization. Within the nondimensional space the Lagrange method is applied to the manipulator to obtain a set of general dimensionless equations of motion. This dimensionless dynamic formulation of manipulators leads to an easier way to simplify the dynamic formulation by neglecting insignificant terms using the order of magnitude comparison. The dimensionless dynamic model and its simplified version of PUMA 560 robot are implemented using the proposed approach. It is found that the simplified dynamic model greatly reduces the computation burden of the inverse dynamics. Simulation results also show that the simplified model is extremely accurate. This implies that the proposed nondimensional simplification emethod is reliable.

Recent hardware advances for robot accessories include self changing grippers. A universal wrist has the capability of accessing and pneumatically attaching itself to a limited number of grippers that can be stored in a magazine. This paper addresses the determination of self changing gripper characteristics to permit the grasping of a wide variety of geometric shapes with a limited number of different gripper types.

The concept of the force ellipsoid and the manipulability ellipsoid of robotic mechanism is extended to two cooperating robot arms, and the equations of the dual arm force and manipulability ellipsoids are derived. The load distribution problem for two cooperating robots is studied using the concept of the force ellipsoid. The problem is usually underspecified mathematically and a variety of optimal solutions may exist. A new solution approach utilizing the force ellipsoid is proposed in this paper. The load distribution problem is formulated as a nonlinear optimization problem with a quadratic cost function and inequality constraints. The optimality criterion is the minimum energy, and two different cases are considered depending on the presence of the constraints on joint torques.

The application of the joint force sensory feedback in both the gross and fine motion control of manipulation robots is considered in the paper. One of the objectives of the paper is to give a historical overview how the idea of the joint force sensory feedback has appeared and developed in the past two decades. The control schemes, which include joint torque sensory feedback, are surveyed in the paper. The main advantages of this approach are discussed: the joint torque feedback offers an elegant way to compensate for the effects of the robot dynamics without real time computation of the robot dynamics, the control schemes are robust in respect of parameter variations. Various problems regarding design and implementation of joint torque sensor are also considered. Special emphasis is given to the application of this approach in hybrid position/force control schemes.

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.