The importance of verifying safety-critical systems has been highlighted recently when the Embedded Systems Group (SEN2) and the Systems Validation Group (VASY) launched a collaboration agreement. Called SENVA, which represents System Engineering and Validation, this joint research team will add strength to this important area of endeavour.

This special issue on Micro/Nano Robotic Perception, Control and Manipulation describes several complementary research efforts from Asia, the United States, and Europe. The topic is timely and the work published in this special issue shows how traditional robotics research is contributing to the emerging micro and nano technologies that are already beginning to demonstrate a strong impact on our society. At milli to microscales, three research efforts in inspection and microassembly are presented. From the University of Minnesota, a force controlled microgripper for photonics microassembly applications is presented. Another important aspect of microassembly is the tracking and alignment of microparts using vision feedback. Work by Dr. Yesin at the Swiss Federal Institute of Technology-Zurich (ETHZ) is directed towards using CAD model-based full 3DOF tracking for closed-loop control of automated microassembly. Moving towards submicron and nano scales, work from the University of Oldenburg in Germany in developing a novel platform for nanohandling using mobile microrobots has given rise to interesting concepts in how systems that perform future nanomanipulation tasks may be configured. A paper co-authored by researchers at the University of California-Berkeley and Carnegie Mellon University considers the use of optical tweezers integrated with chemical linkages for manufacturing 2D and 3D structures at micro and nanoscales. A microbial separation system at the University of Nagoya uses a novel touch sensor and a micropipette, and demonstrates the interesting research problems that exist in the rapidly emerging field of BioMicroRobotics. It is clear that micro/nano robotics research efforts, like those presented in this special issue, represent a key component of robotics studies, and illustrate one direction where robotics must head in order to ensure that the field of robotics remains relevant to science, engineering and society as a whole.

This paper addresses a compensatory motion control algorithm of a biped robot to deal with stable dynamic walking on even or uneven terrain. This control algorithm consists of three main parts; the introduction of a virtual plane to consider ZMP (Zero Moment Point); an iteration algorithm to compute the trunk motion; and a program control to realize dynamic walking. The virtual plane is defined as a plane formed by the support points between the surface of terrain and the soles. In order to obtain the trunk motion capable of compensating for the moments produced by the motion of the lower-limbs during the walking, ZMP equation on the virtual plane is computed by using an iteration method. Also, a walking pattern is presented which is composed of the trajectories of lower-limbs, waist and trunk. The walking pattern is commanded to the joints of WL-12RIII (Waseda Leg-Twelve Refined Three) using a program control method. Through walking simulations and experiments on an uneven terrain, such as stairs and sloped terrain, the effectiveness of the control method is verified.

An analytical method is presented to obtain all surfaces enveloping the workspace of a general n degree-of-freedom mechanism with non-unilateral constraints. The method is applicable to kinematic chains that can be modeled using the Denavit-Hartenberg representation method for serial kinematic chains or its modification for closed-loop kinematic chains. The method developed is based upon analytical criteria for determining singular behavior of the mechanism. Singularities of manipulators with non-unilateral constraints have never been reported. The complete mathematical formulation is presented and illustrated using 4 & 5 DOF spatial manipulators. Four types of singularities are classified: Type I sets are position Jacobian singularities; Type II sets are instantaneous singularities that are due to a generalized joint are reaching its apex; Type III sets are domain boundary singularities, which are associated with the time initial and final values of the time interval; Type IV sets are coupled singularities, which are associated with a relative singular Jacobian, where the null space is reduced in one submatrix due to either of two occurrences: a Type II and Type III singularities.

Prosthetics presents a challenge for engineers, they must balance user needs with practicalities. In the past the compromises made have been towards simpler devices. Recently this has begun to change, new microprocessors, powerful motors and novel batteries make it possible to conceive of different solutions. These papers give an overview of what is now possible.

A real-time joint trajectory generator for planar walking bipeds is proposed. This trajectory planner generates dynamically stable motion patterns by using a set of objective locomotion parameters as its input, and by tuning and exploiting the natural upper body dynamics. The latter can be determined and manipulated by using the angular momentum equation. Basically, trajectories for hip and swing foot motion are generated, which guarantee that the objective locomotion parameters attain certain prescribed values. Additionally, the hip trajectories are slightly modified such that the upper body motion is steered naturally, meaning that it requires practically no actuation. This has the advantage that the upper body actuation hardly influences the position of the Zero Moment Point. The effectiveness of the developed strategy is demonstrated by simulation results.

Photonics is a field that straddles both the macro and micro worlds. It largely deals with macro-scale devices, but many of these require sub-micron-scale precision in assembly. This makes it a very interesting application domain. We describe a microgripper for microassembly of photonic devices and micro-exploration of the properties of sub-micron attachment means (such as solder and UV epoxy). The microgripper has multi-degree-of-freedom actuation and a unique micro/macro actuator on the gripping axis to facilitate human loading and unloading and also very precise accommodation. We demonstrate the force sensitivity and stiffness of approximately 20 mN and 70 mN/um, respectively to be sufficient for the intended tasks. Finally, we demonstrate the gripper accommodating forces of a large solder ball freezing and cooling as a prelude to our intended study of sub-millimeter solder balls in sub-second heating regimes.

This paper presents a Q-learning approach to state-based planning of behaviour-based walking robots. The learning process consists of a teaching stage and an autonomous learning stage. During the teaching stage, the robot is instructed to operate in some interesting areas of the solution space to accumulate some prior knowledge. Then, the learning is switched to the autonomous learning stage to let the robot explore the solution space based on its prior knowledge. Experiments are conducted in the RoboCup domain and results show a good performance of the proposed method.

Parallel kinematic machines (PKMs) and, in particular linapods, are being increasingly used in the industrial workplace. The complex control required for various linapod kinematics, each having different numbers and types of Degrees-of-Freedom (DOF), require corresponding transformations to be generated. This paper introduces a general form of transformation that can be adapted to a wide range of linapods. The approach is illustrated by an example and the concept of a five-DOF linapod for the milling process is proposed. Furthermore, the advantages from the two types of three-DOF Linapods are discussed, and it is shown how the position accuracy can be increased.

Several static and dynamic stability criteria have been defined in the course of walking-robot history. Nevertheless, previous work on the classification of stability criteria for statically stable walking machines (having at least four legs) reveals that there is no stability margin that accurately predicts robot stability when inertial and manipulation effects are significant. In such cases, every momentum-based stability margin fails. The use of an unsuitable stability criterion yields unavoidable errors in the control of walking robots. Moreover, inertial and manipulation effects usually appear in the motion of these robots when they are used for services or industrial applications. A new stability margin that accurately measures robot stability considering dynamic effects arising during motion is proposed in this paper. The new stability margin is proven to be the only exact stability margin when robot dynamics and manipulation forces exist. Numerical comparison has been conducted to support the margin's suitability. Stability-level curves are also presented on the basis of a suitable stability margin to control the trajectory of the center of gravity during the support phase.

Winfried Heim C.P.(c), Bloorview MacMillan Children's Centre, Prosthetic and Myoelectric Services, 350 Rumsey Road, Toronto, Ontario (Canada) M4G 1R8.

Fuzzy logic has features that are particular attractive in light of the problems posed by autonomous robot navigation. Fuzzy logic allows us to model different types of uncertainty and imprecision. In this paper, the implementation of a hexapod mobile robot with a fuzzy controller navigating in unknown environments is presented. The robot, MKIII, interprets input sensor data through the comparison of values in its fuzzy rule base and moves accordingly to avoid obstacles. Results of trial run experiments are presented.

We present simulated monopedal and bipedal robots that are capable of open-loop stable periodic running motions without any feedback even though they have no statically stable standing positions. Running as opposed to walking involves flight phases which makes stability a particularly difficult issue. The concept of open-loop stability implies that the actuators receive purely periodic torque or force inputs that are never altered by any feedback in order to prevent the robot from falling. The design of these robots and the choice of model parameter values leading to stable motions is a difficult task that has been accomplished using newly developed stability optimization methods.

We studied the pressure patterns in the residual limbs of transradial amputees during their voluntary commands for finger taps. Topographic maps of pressures exerted against the hard prosthetic socket were registered with an array of 32 pressure sensors, to produce residual kinetic images (RKIs) of the limb. Results with 2 untrained subjects demonstrated that RKIs are reliable decoders of efferent commands. Coupled with a trained filter, RKIs can provide biomimetic control over multiple degrees of freedom.

An auto-bonding robot (ABR) that consists of the mechanism of adhesive dispensing and auto-bonding, a pneumatic system and a control system, is presented in this paper. It is designed for the bonding operation of cover-glasses and space solar cells using adhesives. An adhesive dispensing method is proposed to control the thickness and position of the adhesive layer on solar cells and to provide a satisfactory bonding accuracy. The bubble-free bonding process is realized by the leaning mechanism of a pneumatic sucker. Experimental comparison of the manual and automatic bonding methods showed that there are no fragment and air bubbles between the cover-glass and the space solar cell, and no outflow adhesive on the surface by the automatic bonding process in a non-vacuum condition. The novel automatic bonding robot greatly improved the lightweight space solar cells bonding quality and production rate.

A multi-agent system based on behaviour for controlling the navigation task of a mobile robot in office-like environments is presented. The set of agents is structured into a three-layer hybrid architecture. A high level of abstraction plan is created using a topological map of the environment in the Deliberative layer. It is composed by the sequence of rooms and corridors to traverse and doors to cross in order to reach a desired room. The Execution and Monitoring layer translates the plan into a sequence of available skills in order to achieve the desired goal and monitors the execution of the plan. In the Control layer there is a set of agents that implements fuzzy and visual behaviours that run concurrently to guide the robot. Fuzzy behavior manages the vagueness and uncertainty of the range sensor information allowing to navigate safely in the environment. Visual behavior locates a required door to cross and fixate it, indicating the appropriate direction to reach it. Artificial landmarks are placed beside the doors to show its position. The system has been implemented in a Nomad 200 mobile robot and has been validated in numerous experiments in a real office-like environment.

This paper reports on the use of a particular actuator in the field of legged robots. The proposed actuator, the Pleated Pneumatic Artificial Muscle, has some interesting characteristics which makes it suitable for machines which move by means of legs. An important issue is the actuator's adaptable passive behaviour which allows the stiffness of a joint that is actuated by two antagonistically coupled muscles, to be varied online. The natural frequency of the system can thus be changed in order to reduce control efforts and energy consumption. The idea of changing this natural frequency in combination with trajectory control will be implemented on a two-dimensional leg model. It will be shown that an appropriate choice of compliance can strongly reduce the amount of needed control activity and energy consumption while tracking a given trajectory.

We present a visual feedback method for closed loop control of automated microassembly. A CAD model based multi-camera visual tracking system that is well suited for flexible automation and assembly of complex 3D geometries was developed. The system is capable of providing six degree-of-freedom pose feedback on the observed micro-components in real-time (30 Hz). Using CAD models of the observed objects, a complete description of the observed scene, including the effect of occlusions, is available and dependence on distinctive visual features such as fudicial marks is avoided.

This paper presents a strategy for generating fault-tolerant gaits of hexapod walking robots. A multi-legged robot is considered to be fault-tolerant with respect to a given failure if it is capable of continuing its walking after the occurrence of a failure, maintaining its static stability. The failure concerned in this paper is a locked joint failure for which a joint in a leg cannot move and is locked in place. The kinematic condition for the existence of fault-tolerant gaits is derived for straight-line walking of a hexapod robot on even terrain. An algorithm for generating fault-tolerant gaits is described and, especially, periodic gaits are presented for forward walking of a hexapod robot with a locked joint failure. The leg sequence and the stride length formula are analytically driven based on gait study and robot kinematics. A case study on post-failure walking of a hexapod robot with the wave gait is shown to demonstrate the applicability of the proposed method.

In this paper an inverse concept idea is presented to determine the main configuration dimensional parameters of a novel 5-DOF parallel kinematic machine tool. By the new described orientation workspace, the motion of the passive joints on the moving platform can be expressed in the fixed coordinate analytically. Some relationships between the reachable workspace and the dimensional parameters of the parallel machine tool have been obtained with graphical representation.