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.

This paper discusses the problem of stable grasping and object manipulation by a pair of robot fingers when fingertips are covered with soft compressible material and fingers are allowed to incline their last link against the object surface. The area contact between the fingertips and the rigid object surface leads to nonholonomic constraints even for the planar case; however, the variational principle can be applied and the equation of motion is derived as a set of nonlinear differential equations with extra terms of Langrange multipliers incorporating the constraints. The proposed feedback controller is a linear combination of simple feedback control signals each designed for realizing grasp stabilization, regulation of object rotation and regulation of object position respectively. The controller is shown to achieve asymptotic convergence to the desired state at a stable grasping configuration. Simulation results are presented confirming the theoretical findings.

AUTONOMOUS LEGGED ROBOT

1. Developing the RS-01 RoboDog

What is claimed to be the world's most advanced, autonomous legged robot to be developed and marketed is called the RS-01 RoboDog. Produced with the aid of collaborative design software it is being marketed after less than a year's development and was available from April 2001 after its launch by its British developers, RoboScience.

This paper analyses lumped-parameter dynamics of a pair of robot fingers with soft and deformable tips pinching a rigid object under the effect of a gravity force. The dynamics of the system in which area contacts between the finger-tips and the surfaces of the object arise are compared with those of a pair of rigid robot fingers with rigid contacts with an object, with or without effect of the gravity. It is then shown that there exists a sensory feedback from measurement of finger joint angles and the rotational angle of the object to command inputs to joint actuators, and this feedback connection from sensing to action realizes secure grasping of the object in a dynamic sense and regulation of the object posture. It is further shown that there are various types of other feedback connections from sensing to action, which can be used in combination of feedback signals for stable grasping and posture control of the object for realizing sophisticated object manipulation.

In the literature, 3-RRPRR architectures were proposed to obtain pure translation manipulators. Moreover, the geometric conditions, which 3-RRPRR architectures must match, in order to make the end-effector (platform) perform infinitesimal (elementary) spherical motion were enunciated. The ability to perform elementary spherical motion is a necessary but not sufficient condition to conclude that the platform is bound to accomplish finite spherical motion, i.e. that the mechanism is a spherical parallel manipulator (parallel wrist). This paper demonstrates that the 3-RRPRR architectures matching the geometric conditions for elementary spherical motion make the platform accomplish finite spherical motion, i.e. they are parallel wrists (3-RRPRR wrist), provided that some singular configurations, named translation singularities, are not reached. Moreover, it shows that 3-RRPRR wrists belong to a family of parallel wrists which share the same analytic expression of the constraints which the legs impose on the platform. Finally, the condition that identifies all the translation singularities of the mechanisms of this family is found and geometrically interpreted. The result of this analysis is that the translation singularity locus can be represented by a surface (singularity surface) in the configuration space of the mechanism. Singularity surfaces drawn by exploiting the given condition are useful tools in designing these wrists.

This paper presents a general control architecture for bipedal walking which is based on a divide-and-conquer approach. Based on the architecture, the sagittal-plane motion-control algorithm is formulated using a control approach known as Virtual Model Control. A reinforcment learning algorithm is used to learn the key parameter of the swing leg control task so that speed control can be achieved. The control algorithm is applied to two simulated bipedal robots. The simulation analyses demonstrate that the local speed control mechanism based on the stance ankle is effective in reducing the learning time. The algorithm is also demonstrated to be general in that it is applicable across bipedal robots that have different length and mass parameters.

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.

In this paper two explicit force control schemes for underwater vehicle-manipulator systems are presented. The schemes take into account several factors such as uncertainty in the model knowledge, presence of hydrodynamic effects, kinematic redundancy of the system, and poor performance of vehicle's actuation system. The possible occurrence of loss of contact due to vehicle's movement during the task is also considered, and the adoption of an adaptive motion control scheme is investigated to take advantage of dynamic compensation. The proposed control schemes have extensively been tested in numerical simulation runs; the results obtained in a case study are reported to illustrate their performance.

In this paper we propose an analytical formulation for simulation and design of a one d.o.f. articulated finger mechanism with three phalanges. The formulation is based on a study of the design and operation of an index human finger. In particular, we have proposed a suitable mechanical design for an anthropomorphic finger as both an approximation of human architecture and an easy practical design. Kinematic characteristics are illustrated with numerical examples.

Robotic technology can be used in several ways to benefit people with disabilities. This paper describes the mounting of a robotic arm to a powered wheelchair to assist disabled users in daily activities. Although there are many potential benefits for the disabled user, there are also very strong requirements and compromises, which must be considered in integrating the robotic arm with the wheelchair. This paper focuses on how these integration issues have been addressed.

In multi-robot assembly of parts, for successful mating, the grasped parts must be located with sufficiently small position and orientation errors so that assembly can be achieved. This paper describes a new approach for determining the absolute three-dimensional spatial location of parts grasped by robots during assembly. Through a combination of robot pose calibration and part-sensor calibration, the robot, used to grasp the part, is calibrated to accurately position and orient parts to a designated mating location. First, by employing a robot pose measurement system, the 6 DOF robot pose errors relative to a reference coordinate frame are compensated. Second, with the implementation of a part pose measurement, the 6 DOF part pose errors, relative to the robot tool frame, are estimated in real time. An experimental verification of the proposed methodology using a single FANUC S–110 robot manipulating an automotive sheet metal part is described.

In this paper, we focus on the base and tool calibration of a self-calibrated parallel robot. After the self-calibration of a parellel robot by using the built-in sensors in the passive joints, its kinematic transformation from the robot base to the mobile platform frame can be computed with sufficient accuracy. The base and tool calibration, hence, is to identify the kinematic errors in the fixed transformations from the world frame to the robot base frame and from the mobile platform frame to the tool (end-effector) frame in order to improve the absolute positioning accuracy of the robot. Using the mathematical tools from group theory and differential geometry, a simultaneous base and tool calibration model is formulated. Since the kinematic errors in a kinematic transformation can be represented by a twist, i.e. an element of se(3), the resultant calibration model is simple, explicit and geometrically meaningful. A least-square algorithm is employed to iteratively identify the error parameters. The simulation example shows that all the preset kinematic errors can be fully recovered within three to four iterations.

Parametric formulation is a systematic method that ties the constraint functions to the resulting joint profiles for bipedal robots. Acceptable joint profiles for continuous and steady walking must satisfy the additional condition of being repeatable. This extra condition imposes restrictions on the selection of constraint functions, gait parameters and the initial posture of each step, and can make the synthesis of joint profiles extremely challenging. This paper presents a correlation between the gait parameters used in a class of specific constraint functions and the initial posture that will create repeatable gait. Furthermore, a general necessary and sufficient condition for repeatable gait is proposed. This condition provides a guideline for selecting constraint functions and their associated gait parameters in the context of producing repeatable gait. This research can not only provide valuable insights into bipedal walking, but also serve as a stepping stone for employing parametric formulation with various constraint functions.

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.

Robotic laser welding places extreme demands on the spatial accuracy with which the robot must position the focal point of the laser with respect to the joint to be welded. The required level of accuracy is difficult to achieve in a production environment without the use of end-point sensor based control of the robot. This requires that the end-point sensor frame and welding laser frame be accurately calibrated with respect to each other, as well as with respect to the robot wrist frame. This calibration can be difficult to perform since the sensor and laser frames are virtual in the sense that these are located in space with respect to the physical hardware, and the wrist frame of the robot is often not physically accessible. This paper presents the design of a calibration system with which these frames may be precisely defined with respect to each other.

This paper presents a neural model to solve the visual-tactile-motor coordination problem in robotic applications. The proposed neural controller is based on the VAMC (Vector Associative Map) model. This algorithm is based on the human biological system and has the ability of learning the mapping that establishes the relationship between the spatial and the motor coordinates. These spatial inputs are composed of visual and force parameters. The LINCE stereohead carries out a visual detection process, detecting the positions of the object and of the manipulator. The artificial tactile skins placed over the two fingers of the gripper measure the force distribution when an object is touched. The neural controller has been implemented for robotic operations of reaching and object grasping. The reaching process is fed back in order to minimize the Difference Vector (DV) between the visual projections of the object and the manipulator. The stable grasping task processes the force distribution maps detected in the contact with the two surfaces of the gripper, in order to direct the object into the robotic fingers. Experimental results have demonstrated the robustness of the model and the accuracy of the final pick-and-place process.

This paper addresses an optimal study of workspace for spherical parallel mechanism for laparoscopic surgery. The spherical parallel manipulator has been selected because of its characteristics. Two designs have been studied for maximizing their workspaces; a haptic device, as part of training system, and a laparoscope holding mechanism. The laparoscope holding mechanism has to satisfy additional constraints by minimizing the occupied space above the patient. The objective is to solve design problem to offer the maximal workspace for such mechanisms. The design of a haptic interface and the laparoscope holding mechanism based on the optimal parameters are presented. This paper presents a Genetic Algorithm (GA) approach for selecting optimal design parameters for maximizing workspace of spherical parallel mechanism.

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 rechecks the relative degree of the end-point tracking control system of a flexible manipulator. New added insights into the ill-defined behavior of the relative degree are presented by constructing a perturbed truncation model. The implications for the inverse dynamics motivate us to reformulate the inverse dynamics based on the perturbed truncation model in the extreme case of truncating all of the flexible modes. New potential advantages arising from this novel formulation are investigated for the inverse dynamics control design as well.