I. AUTOMATION REPORTS

I.1. UK Manufacturers Buy Largest Number of Robots Since Records Began in 1978

Latest research figures from the University of Warwick (UK) show that UK manufacturers installed a record breaking 1,941 robots in 2001 – the largest number of new robots ever installed in the UK in any one year since records began in 1978.

A multifunctional 4 legged walking machine that is being developed in the Robotics Research Centre (NTU) is described. The major factors influencing the design requirements include minimisation of the weight of the machine and maximisation of workspace of the legs. The designed walking machine can adopt a variety of configurations, such as insect, mammalian, reptile or human. The device is invertable (i.e. can turn over). It can use its legs as manipulators, hence it can perform basic pick-and-place functions. A control system was built using the QNX real-time operating system platform. The software was designed using the client-server approach.

Several static and dynamic stability criteria have been defined in the course of walking robot history. Nevertheless, different applications may require different stability criteria and, to the authors' best knowledge, there is no qualitative classification of such stability measurements. Using the wrong stability criterion to control a robot gait may prevent the task from succeeding. Furthermore, if the optimum criterion is found, the robot gait can also be optimized. In this paper, the stability criteria that have been applied to walking robots with at least four legs are examined in terms of their stability margins in different static and dynamic situations. As a result, a qualitative classification of stability criteria for walking machines is proposed so that the proper criterion can be chosen for every desired application.

This paper extends the model developed previously by the authors,1 for studying dynamic stability of mobile manipulators. The extended model not only takes into account the dynamics of the base that can potentially rock back-and-forth, but also accounts for the flexibility of the contact between the base and the ground. A novel method of virtual links is used to reformulate the problem of modeling the non-fixed base manipulator in terms of a fixed-base manipulator with one degree of freedom joints. The resulting model is then used to simulate planar movements of a Caterpillar excavator-based log-loader. The results clearly demonstrate the relationship between movement of the implement and the stability of the machine. The flexible contact between the base and the ground is also shown to influence the stability. The results are also compared with those obtained by the previous model, which assumed rigid contact between the base and the ground. It is demonstrated that the assumption of rigid contact tends to overestimate the stability. Consequently, flexibility in the contact bet- ween the base and the ground must be considered to more accurately predict the stability of mobile manipulators.

This paper presents an attractive position-based visual servoing approach for camera-in-hand robotic systerns. The major contribution of this work is in devising an elegant and pragmatic approach for 3D visual tracking, which yielded good target tracking performance. It differs from the other known techniques, in its approach for image interpretation and the introduction of a Smith-like predictor control structure to overcome the inherent multi-rate time delayed nature of the visual servoing system. A complete description is made of the proposed MSP-DH visual servoing system. Experiments on the target tracking performance on XY planar motion using an AdeptOne robotic system are presented to illustrate the controller performance. In addition, experimental results have clearly shown the capability of the MSP-DH visual servoing system in performing 3D-dynamic visual servoing.

The manipulator with a large degree of redundancy is useful for realizing multiple tasks such as maneuvering the robotic arms in the constrained workspace, e.g. the task of maneuvering the end-effector of the manipulator along a pre-specified path into a window. This paper presents an on-line technique based on a posture generation rule to compute a null-space joint velocity vector in a singularity-robust redundancy resolution method. This rule suggests that the end of each link has to track an implicit trajectory that is indirectly resulted from the constraint imposed on tracking motion of the end-effector. A proper posture can be determined by sequentially optimizing an objective function integrating multiple criteria of the orientation of each link from the end-effector toward the base link as the secondary task for redundancy resolution, by assuming one end of the link is clamped. The criteria flexibly incorporate obstacle avoidance, joint limits, preference of posture in tracking, and connection of posture to realize a compromise between the primary and secondary tasks. Furthermore, computational demanding of the posture is reduced due to the sequential link-by-link computation feature. Simulations show the effectiveness and flexibility of the proposed method in generating proper postures for the collision avoidance and the joint limits as a singularity-robust null-space projection vector in maneuvering redundant robots within constrained workspaces.

This paper focuses on using a singularly perturbed approach to derive a vibration damping control law in which a pole assignment feedback method is utilized. The composite control system is characterized by two components which can be computed separately. The one is Cartesian-based PI control which drives the end-effector of a flexible manipulator to track the desired time-based trajectory. The other is pole assignment feedback control which damps out vibrations during and at the end of trajectory tracking. An advantage of this composite control method in real implementation is that it does not require a derivative of the end-effector's position, and the derivatives of signals from the strain gauges. From the characteristics and implementation points of view, it appears to be simple to use. Laboratory experiments were conducted to evaluate the performance of the proposed control method.

In this paper a new robust adaptive control law for n-link robot manipulators with parametic uncertainties is derived using the Lyapunov theory thus guaranteed the stability of an uncertain system. The novelty of the adaptive robust control algorithm is that manipulator parameters and adaptive upper bounding functions are estimated to control the system properly, and the adaptive robust control law is also updated as an exponential function of manipulator kinematics, inertia parameters and tracking errors. The proposed adaptive control input includes a parameter estimation law as an adaptive controller and an additional control input vector as a robust controller. The developed approach has the advantages of both adaptive and robust control laws, without their discolour tags.

In this paper we consider thc problem of optimal control design for off-line programming in educational assembly robotics. After introducing some key features for mechanical, electrical design systems and computer-control and programming of a prototype robot, we discuss the control system and the off-line programming for a case study of educational robotics. We propose a new Dynamic Optimal Time-Energy Trajectography (DOTET) controller based on the complete dynamic model of the robot and which takes into account intrinsic and extrinsic constraints, robot singularities and requirements of the task and the environment. Numerical results are given to demonstrate the efficiency of our design.

Robots are expected to be pervasive in the society in a not too distant future where they will work extensively as assistants of humans in various activities. With this in view, a novel affect-sensitive architecture for human-robot cooperation is presented in this paper where the robot is expected to recognize human psychological states. As a demonstration, an online heart rate variability analysis to infer the mental stress of a human engaged in a task is presented. This technique involves real-time heart rate monitoring, signal processing using both Fourier Transforrn and Wavelet Transform, and inferring the stress condition based on the level of activation of the sympathetic and parasympathetic nervous systems using fuzzy logic. Results from human subject trials are presented to validate the presented methodology. This stress detection technique is expected to be useful in the future human-robot cooperation activities, where the robot will recognize human stress and respond appropriately.

The use of Clifford or geometric algebra for dealing with three dimensional geometry is discussed. One issue is the representation of the rigid body motions of rotations and translations as elements within the algebra. The approach used is to work with projective geometry and choose the square of an additional basis element to be large (infinite). This allows Euclidean points to be represented as vectors in the algebra and transforms on these to be handled using bivectors. This paper looks at the use of Clifford algebra for handling the types of transforms required in robotic applications. A number of example applications are given.

15th TRIENNIAL WORLD CONGRESS OF THE INTERNATIONAL FEDERATION OF AUTOMATIC CONTROL (IFAC), BARCELONA, SPAIN, 21st–26th JULY, 2002

The World Congress under the Spanish presidency (Prof. P. Albertos) brought together about 2000 researchers and practitioners of control theory, technology and applications. The famous Gran Teatro del Liceo of Barcelona was the right location for the opening ceremony, whereas the congress sessions were held at the campus of the Universidad Politecnica de Catalunia.

INTERKAMA AUTOMATION FAIR

Düsseldorf (Germany); February 16–20, 2003.

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