This paper presents a new method for solving the inverse kinematics of robot manipulators. The method defines incremental units in joint and Cartesian spaces, which represent the position resolutions in each space. Based on these units, the incremental computation of the DDA integrator is used to solve the direct kinematics. The repetitive calculation of the inverse Jacobian matrix is replaced by a simple look-up table. By using an iterative procedure with convergence rules, the inverse kinematics algorithm is established. A 3 DOF robot is considered as the combination of two types of a 2 DOF robot. Simulation and experiment are performed to test the algorithm.

We consider the problem of sensor-based motion planning for a three-dimensional robot arm manipulator operating among unknown obstacles. When every point of the robot body is subject to potential collision. The corresponding planning system must include these four basic components: sensor hardware; real-time signal/sensory data processing hardware/software; a local step planning subsystem that works at the basic sample rate of the arm; and finally, a subsystem for global planning. The arm sensor system developed at Yale University presents a proximity sensitive skin that covers the whole body of the arm and consists of an array of discrete active infrared sensors that detect obstacles by processing reflected light. The sensor data then undergoes low level processing via a step planning procedure, which converts sensor information into local normals at the contact points in the configuration space of the robot. This paper presents preliminary results on the fourth component, a real-time algorithm that realizes the upper, global level of planning. Based on the current collection of local normals, the algorithm generates preferable directions of motion around obstacles, so as to guarantee reaching the target position if it is reachable. Experimental results from testing the developed system are also discussed.

Variable geometry truss manipulators (VGTM) are static trusses where the lengths of some members can be varied, allowing one to control the position of the free end relative to the fixed one. This paper deals with a planar VGTM consisting of a n–bay triangle-triangle truss with one variable length link (i.e. one DOF) per bay. Closed-form solutions to the forward, inverse, and velocity kinematics of a 3-DOF version of this VGTM are presented, while the forward and inverse kinematics of an n–DOF (redundant) one are solved by a recursive and an iterative method, respectively. A numerical example is presented.

The description is provided for the design and implementation of a system capable of simulating the motions of a quadruped walking robot. The system aims to investigate the feasibility of the robot's walking cycle. This is achieved by considering the robot's stability and more specifically the position of its centre of gravity in relation to its supporting legs. The robot is modelled as a solid body connected to four jointed limbs which are moved through a series of gaits, their positions being calculated at a set of discrete intervals. The resulting information is displayed using a graphical module to present an image of the moving robot and indicate its centre of gravity and support pattern. The complete system indicates the stability of the robot throughout a user-defined gait cycle and is both portable and adaptable.

The system is implemented on a HLH Orion and an Atari 1040ST in the C programming language and is aimed at providing support for the Department of Mechanical Engineering at Edinburgh University where the particular robot is being built.

The problem of determining energy optimal walking motions for a bipedal walking robot is considered. A full dynamic model of a planar seven-link biped with feet is derived including the effects of impact of the feet with the ground. Motions of the hip and feet during a regular step are then modelled by 3rd order polynomials, the coefficients of which are obtained by numerically minimising an energy cost function. Results are given in the form of walking profiles and energy curves for the specific cases of motion over level ground, motion up and down an incline, and varying payload.

We have designed, built, and tested a new wheel control system for the HERMIES-III robot. HERMIES-III is a large mobile robot with omnidirectional steering that is designed for human scale experiments. During each cycle (at 20 Hz), the wheel control system moves the robot toward a goal and calculates the current position of the robot. The system has seven modes for moving to a goal and the goal may be changed during motion of the robot.

This paper presents some aspects of the behavior of hydraulically actuated heavy duty manipulators. This category of manipulators is used extensively in large resource based industries and any improvement in efficiency may result in major financial benefits. In this paper an adaptive control algorithm is used for a two rigid link manipulator driven by hydraulic actuators. The dynamic model of the manipulator is derived as well as the models of the hydraulic actuators including compliance, dead time and full dynamics of the servo valves. An adaptive control algorithm is considered since changes occur on-line in the system's parameters. The adaptive algorithm used is Generalized Predictive Control (GPC). The GPC uses a controlled autoregressive integrated moving average (CARIMA) type model and a cost function that minimizes a predicted future output error and future weighted control inputs to the plant, resulting in a sequence of future control increments. The procedure, in this work, does not separate the hydraulic actuator and the link dynamics into separate sub-systems, but controls them as one system. The changes in the system's parameters due to the hydraulics or the link dynamics can be estimated and the coefficients of the model adjusted without the necessity of identifying the exact cause of the changes.

It was found in this work that the variations of the GPC control horizon can lead to faster response during transients and significantly reduced overshoot in the nonlinear hydraulic actuation system. An on-line change of the maximum output horizon is also introduced.

This work shows the analysis and results of a two link manipulator with hydraulic actuators. It can be implemented on any hydraulically actuated manipulator with any number of links and actuators.

Numerical simulations are performed on a Vax 3200 computer and the results are presented.

A fuzzy qualitative model of a robot sensor, presented in this paper, is for locating 3-D objects, and the location information is used to guide the movements 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 held rigidly with respect to the platform. The static deflections of the column and natural frequencies of vibration of the dynamic system comprising the object, platform and column are measured and processed using a mathematical model of the system to determine the location of the object. In practice, the frequency measurements have low repeatability, which leads to inconsistent location information. Also, when the orientation is in the region 80°–90° relative to a reference axis of the sensor, the mathematical model becomes ill-conditioned. In this paper, a fuzzy qualitative model of the sensor is described. The fuzzy model is designed to yield the orientation in the region where the mathematical model is unusable. Different stages for constructing the fuzzy model are described. The on-line implementation of the model is outlined and the experimental results obtained are presented.

A manipulator regressor is an n x l matrix function in the dynamic expression τ = Y r or τ = Wr, which linearizes the robotic dynamics with respect to a properly defined inertia parameter vector ζr є R1. Many modern adaptive controllers require on-line computation of a regressor to estimate the unknown inertia parameters and ensure robustness of the closed-loop system.

While the computation of Y is studied by Atkeson, An and Hollerbach1 and Khosla and Kanade,2 the computation of W for a general n–link robot has not been reported in the literature. This paper presents an algorithm to compute W for a general n–link robotic manipulator. The variables used to construct the regressor matrix are directly available from the outward iteration of a Newton-Euler algorithm; some additional arithmetic operations and first-order, low-pass filtering are needed. The identification of unknown inertia parameters is also discussed.

The UK Advanced Robotics Research Centre's VERDEX Project (Virtual Environment demote Driving Experiment) is an experimental test bed for investigating telepresence and virtual reality technologies in the design of human-system interfaces for telerobots. The achievements of the Project to date include the transformation of scanning laser rangefinder output to stereo virtual imagery (viewed using the VPL EyePhoneTM), the Teletact® Tactile Feedback Glove (for use with the VPL DataGloveTM), a high-speed, head-slaved stereo TV system, and a T800/i860 SuperVisionTM graphics/video parallel processing system.

This paper considers the use of memory models and machine intelligence, to dynamically update a computer based representation of the occupancy of a small building. The input to the model is derived from very simple, single bit, movement sensors in each room of the premises.I It will be shown that the information derived from these sensors can provide adequate data for a building control scheme.

Short and Long Term memory models of man will be briefly reviewed. Working models for Short and Long Term memory will be discussed, which have evolved from the earlier work but which have been tuned to fit the machine level constraints of this type of application.

A review of the performance of a working pilot installation will be given. A performance measure will be derived and initial figures using this measure will be presented.

An algorithm for kinematic motion planning of redundant planar robots, having revolute joints, in an unknown dynamic environment is presented. Distance ranging sensors, mounted on the body of each manipulator link, are simulated here to estimate the proximity of an obstacle. The sensory data is analyzed through a fuzzy controller which estimates whether a collision is imminent, and if so, employs a geometric approach to compute the joint movements necessary to avoid the collision. Obstacles can sometimes move uncompromisingly in the environment attempting a deliberate collision. Strategies to deal with such cases are presented and recovery procedures to circumvent the obstacle from tight corners are suggested. Cases of link overlap have been avoided by considering each link as a body which is sensed as an obstacle by every other link of the same manipulator. Suitable examples are presented to demonstrate the algorithm.

The performance of robotic manipulators is limited by the nature of the control systems which do not satisfactorily integrate the non-linear phenomena associated with the dynamic behavior of the mechanisms. The significant variations in the axial inertias lead to control problems and require an optimization of the mechanical structures in order to improve the stability of the manipulators. This paper proposes mechanical solutions in the domain of dynamic decoupling of robots and demonstrates, using numerical simulations the value of these solutions in terms of control.

Collision-Avoidance is a key issue in planning trajectories for dual robots whose workspaces overlap. In this paper, we develop a new trajectory planning method by proposing a traffic control schemes. The traffic controller determines the next positions for each robot based on the motion priority and path direction subject to the collision-avoidance conditions and the robots' physical limits. The problem of determining the next positions is formulated and optimized. Algebraic expressions for collision avoidance between every-pair of links – one from the first robot and the other from the second robot – are derived in configuration space. These algebraic expressions are then used to solve the problem of determining “optimal” (in the sense of path direction and motion priority) robots' trajectories. A solution procedure is developed using a nonlinear programming (NLP) solver. The main advantage of our approach is that the two robots' trajectories can be determined simultaneously without requiring any a priori path information. Several numerical examples are presented to demonstrate the validity and effectiveness of the proposed approach.

This paper deals with the study of the effects of Harmonic Drives characteristics on the dynamic behaviour of industrial robots. These components are firstly analyzed on the basis of the technical literature and, as a result, a mechanical model with concentrated parameters is obtained. Finally, the influence of these parameters on the dynamic behaviour of an actual SCARA robot in our department is investigated by means of experimental tests and by a computer simulation program purposely written.

This paper illustrates means by which the techniques of compliance and electroadhesion can, using electror-heological, and other fluids, be combined to provide very effective shape adaptive robot end-effectors and similar holding surface.

Traditionally, most industrial robots are programmed by teaching. Automatic planning of robotic tasks has many potential benefits for flexible automation. It allows the user to describe a task to the robot programming system in a formal and natural manner, and reduces the time required to generate and update robot programs. Two main levels of abstraction in describing robot tasks can be identified. Robot-level programming is based on robot movements and actions, as detailed by the programmer. Object-level or task-level programming allows the user to describe assembly tasks in terms of operations performed on objects being manipulated instead of specifying the individual motions of the robot end-effector. However, commercially available robot-level programming languages still fall short of the robot user's need to programme complex tasks and consequently are not widely used in industry. There is an increasing need for integrating sensors feedback into the robot system to provide better perception and for improving the capacity of the robot to reason and make decisions intelligently in real-time. Task-level programming represents the highest level of abstraction and is the most attractive, as it uses reasoning capabilities provided by Artificial Intelligence. To date, no system of this class has been completely implemented in industry. This paper reviews the progress made in robot programming and task planning systems in the last twenty years, and discusses the current research trends.