This paper presents a novel systematic approach to identify the dynamic parameters of robotic manipulators. A sequential identification procedure is first proposed to deal with the difficulties usually encountered with standard approaches. An all-accelerometer inertial measurement unit (IMU) is also suggested to estimate the joint velocities and accelerations, which are traditionally obtained by differentiating the joint positions. The IMU kinematics and the computation method for estimation joint motion from IMUs are provided. The proposed method yields promising results in improving the identification precision compared to conventional methods. Finally, practical experiments are conducted to validate the theoretical results.

The technologies of autonomous rendezvous and robotic capturing of non-cooperative targets are very crucial for the future on-orbital service. In this paper, we proposed a method to achieve this aim. Three problems were addressed: the target recognition and pose (position and attitude) measurement based on the stereo vision, the guidance, navigation and control (GNC) of the chaser, and the coordinated plan and control of space robot (CP&C). The pose measurement algorithm includes image filtering, edge detection, line extraction, stereo match and pose computing, et al. Based on the measured values, a certain GNC algorithm was designed for the chaser to approach and rendezvous with the target. Then the CP&C algorithm, which is proved to be advantageous over the traditional separated method, was used to plan and track the trajectories of the base pose and the joint angle. At last, a 3D simulation system was developed to evaluate the proposed method. Simulation results verified the corresponding algorithms.

Reliability of any model-based failure detection and isolation (FDI) method depends on the amount of uncertainty in a system model. Recently, it has been shown that the use of joint torque sensing results in a simplified manipulator model that excludes hardly identifiable link dynamics and other nonlinearities such as friction, backlash, and flexibilities. In this paper, we show that the application of the simplified model in a fault detection algorithm increases reliability of fault monitoring system against modeling uncertainty. The proposed FDI filter is based on a smooth velocity observer of degree 2n where n stands for the number of manipulator joints. No velocity measurement and assumptions on smoothness of faults are used in the fault detection process. The paper focuses on actuator faults and investigates the effect of torque sensor noise on threshold selection. The FDI filter is further improved to become robust against an unknown bias in torque sensor reading. The effect of position sensor noise together with position sensor faults are also investigated. Simulation example on a 6-degrees of freedom manipulator is carried out to illustrate the performance of the proposed FDI method.

In this paper we are concerned with control of rigid robots equipped with brushless DC-motors (BLDC) when the electric dynamics of these actuators is taken into account. We show for the first time that a saturated PD controller suffices to achieve global asymptotic stability. Our controller is the simplest controller proposed until now to solve this problem: it only requires position measurements and linear feedback of electric current.

This paper presents a control algorithm for biped walking by extension of previous work in the fields of central pattern generator (CPG) and passive walking. The algorithm takes advantage of the passive dynamics of walking, assisting only when necessary with an intermittent sinusoidal oscillator. The parameterized oscillator is used to drive the hip joint; the triggering and ceasing of the oscillator during a walking cycle can be modulated by the sensory feedback. The results from simulation indicate a stable, efficient gait, and robustness against model inaccuracy and environmental variation. We also examine the effects of oscillator parameters and link parameters on the gait, and design a controller to suppress the bifurcation phenomenon based on the error of prior step periods.

This paper reports on recent progress made toward the development of a new magnetic resonance imaging (MRI)-compatible robot-assisted surgical system for closed-bore image-guided prostatic interventions: thermal ablation, radioactive seed implants (brachytherapy), and biopsy. Each type of intervention will be performed with a different image-guided, robot-based surgical tool mounted on the same MRI-guided robot through a modular trocar. The first stage of this development addresses only laser-based focal ablation. The robot mechanical structure, modular surgical trocar, control architecture, and current stage of performance evaluation in the MRI environment are presented. The robot actuators are ultrasonic motors. A methodology of using such motors in the MRI environment is presented. The robot prototype with surgical ablation tool is undergoing tests on phantoms in the MRI bore. The tests cover MRI compatibility, image visualization, robot accuracy, and thermal mapping. To date, (i) the images are artifact- and noise-free for certain scanning pulse sequences; (ii) the robot tip positioning error is less than 1.2 mm even at positions closer than 0.3 m from the MRI isocenter; (iii) penetration toward the target is image-monitored in near-real time; and (iv) thermal ablation and temperature mapping are achieved using a laser delivered on an optical fiber and MRI, respectively.

In this paper, we propose an approach for computing suboptimal grasps of polyhedral objects. Assuming n hard-finger contact with Coulomb friction model and based on central axes of the grasp wrench, we develop a new necessary and sufficient condition for n-finger grasps to achieve force-closure property. Accordingly, we reformulate the proposed force-closure test as a new linear programming problem, which we solve using an interior point method. Furthermore, we present an approach for finding appropriate stable grasps for a robotic hand on arbitrary objects. We use the simulated annealing technique for synthesizing suboptimal grasps of 3D objects. Through numerical simulations on arbitrary shaped objects, we show that the proposed approach is able to compute good grasps for multifingered hands within a reasonable computational time.

In this paper a general methodology for obtaining static stiffness maps in lower mobility parallel manipulators is proposed. The main objective is to define a set of guidelines, which allow the experimental work to be optimized and computational time to be reduced. First, a two-degree-of-freedom (DOF) mechanism will be used for methodology validation, since it is the stiffness of the basic kinematic chain of the manipulator that is to be analysed. Two mathematical models of this mechanism and an experimental prototype will be considered for the validation. After that, the methodology will be applied to a lower mobility (4-DOF) parallel manipulator. In this paper, the experimental prototype and its set-up is highly important because some particular features of the experimental analysis will be defined. This paper introduces a key experimental tool: the preload, which allows the clearances and possible assembling errors to be considered. The added value from the application of this procedure is the obtaining of graphs that describe, in an intuitive and useful way, the behaviour of the manipulator's stiffness inside its workspace as a function of the mobile platform position and orientation.

This paper describes a project that aims to demonstrate two-way communication between robots using chemical signals. The project is part of a wider investigation examining the potential advantages and drawbacks of implementing pheromone signalling between robots. It is well known that all kinds of biological creatures use chemicals as a means of attracting, repelling, controlling, guiding and informing their fellow creatures. This very wide range of effective biological forms of chemical communication is the inspiration to look at potential robotic applications. In previous work involving the use of physical chemical signals in robotics the case of one robot releasing or depositing a chemical for other robots (or the same robot) to detect and act upon has been addressed. This project moves a step forward to investigate a group of robots where each group member emits and detects pheromone chemicals. The example task addressed in the project is to use chemical signalling to help a collection of robots to assess group size. Bacteria provide a model for this kind of chemical communication. By monitoring chemical concentration bacteria can assess group size and hence modify their behaviour as appropriate. Although not intending to model bacterial quorum sensing in detail this behaviour provides inspiration for our demonstration of bi-directional communication. This paper provides details of the implementation of quorum sensing in a group of robots. The robots used in the project, their control algorithms and experimental results are presented. Both beneficial aspects and the pitfalls of pheromone communication in robotic systems are also discussed.

This paper presents a bipedal locomotion model for passive dynamic walking with flat feet and compliant ankles. The two-dimensional seven-link model extends the simplest walking model with the addition of hip actuation, knee joints, flat feet and torsional springs based compliance on ankle joints, concerning heel-strike and toe-strike transitions, to achieve adaptive bipedal locomotion on level ground with controllable walking speed. We investigate the effects of foot geometric parameters and ankles stiffness on bipedal walking. The model achieves satisfactory walking results not only on even ground but also on uneven terrain with no active control and on different walking velocities. In addition, from the view of stability, there is an optimal foot-ankle ratio of the passivity-based walker. The results can be used to explore further understanding of bipedal walking, and help the design of future intelligent ankle-foot prosthesis and passivity-based robot prototypes towards more practical uses.

It is difficult to design controllers for the complicated dynamics of omnidirectional vehicles steered by multiple wheels with distributed traction force. In this paper, the dynamic model of a three-wheel omnidirectional vehicle, which is linearized to simplify controller design, is developed. The conditions of making its dynamics linear are derived first. Then, a strategy of planning wheel velocities to satisfy these conditions is proposed. Consequently, three-wheel omnidirectional vehicle can be easily treated by classical linear control theories. Finally, a linear optimal tracker is designed to control the omnidirectional vehicle for desired movement trajectories. In particular, the dynamic model includes the motors installed in the three-wheel omnidirectional vehicle, making it a practical model. Three kinds of vehicle trajectories illustrate the planning of wheel trajectories for linearizing the vehicle dynamics, and simulations demonstrate the performance of the linear optimal tracker. In addition, experimental results of a practical three-wheel omnidirectional vehicle are also included.

This paper presents a task-priority motion planning algorithm for underactuated robotic systems. The motion planning algorithm combines two features: the idea of the task-priority control of redundant manipulators and the endogenous configuration space approach. This combination results in the algorithm which solves the primary motion planning task simultaneously with one or more secondary tasks ordered in accordance with decreasing priorities. The performance of the task-priority motion planning algorithm has been illustrated with computer simulations of the motion planning problem for a container ship.

Robotic technology has been used in urological surgery since the late 1980's with the invention of robotic endoscopic prostate surgery. The major technological landmark has been the widespread introduction of the da Vinci master-slave manipulator which is now used in up to 60% of radical prostatectomy operations in the USA. These machines offer a number of tools to facilitate laparoscopic surgery though they require both a human console operator and a surgical team to connect the device to laparoscopic ports in the patient's abdomen. We outline the improved outcomes and future development of prostatectomy, cystectomy and pyeloplasty associated with robotic technology.

This paper studies the parameters contained in the truncated Fourier series (TFS) formulation for bipedal walking balance control. Using the TFS generated lateral motion reference, 3D bipedal walking can be directly achieved without any parameter adjustment. Furthermore, the potential of this TFS formulation for motion balance control has also been investigated. One more motion balance strategy is developed through the reinforcement learning, which adjusts the motion's reference trajectory according to the selected dynamic feedback in real time. Dynamic simulation results of the presented balance control method show that the resulting motion can be constrained periodical and long-distance 3D bipedal walking motions are achievable.

This paper describes a dynamic synthesis method for generating optimal walking patterns of biped robots having a human-like locomotion system. The generating principle of gait is based on the minimisation of driving torques. A parametric optimisation technique is used to solve the underlying optimal control problem. Special attention is devoted to foot-ground interactions in order to ensure a steady dynamic balance of the biped. Transition states between step sub-phases are fully optimised together with step length and sub-phase lengths with respect to a given walking velocity. The data needed to generate purely cyclic steps can be reduced to the forward velocity.

This paper explores the design of humanoid complicated dynamic motion based on human motion capture. Captured human data must be adapted for the humanoid robot because its kinematics and dynamics mechanisms differ from those of the human actor. It is expected that humanoid movements are highly similar to those of the human actor. First, the kinematics constraints, including ground contact conditions, are formulated. Second, the similarity evaluation on the humanoid motion based on both the spatial and temporal factors compared with the human motion is proposed. Third, the method to obtain humanoid motion with high similarity is presented. Finally, the effectiveness of the proposed method is confirmed by simulations and experiments of our developed humanoid robot “sword” motion performance.

A Jacobian-based algorithm that is useful for planning the motion of a floating rigid body operated using two input torques is addressed in this paper. The rigid body undergoes a four-rotation fully reversed (FR) sequence of rotations which consists of two initial rotations about the axes of a coordinate frame attached to the body and two subsequent rotations that undo the preceding rotations. Although a Jacobian-based algorithm has been useful in exploring the inverse kinematics of conventional robot manipulators, it is not apparent how a correct FR sequence for a desired orientation could be found because the Jacobian of FR sequences is singular as well as being a null matrix at the identity. To discover the FR sequences that can synthesize the desired orientation circumventing these difficulties, the Jacobian algorithm is reformulated and implemented from arbitrary orientations where the Jacobian is not singular. Due to the insufficient degrees-of-freedom of four-rotation FR sequences required to achieve all possible orientations, the rigid body cannot achieve certain orientations in the configuration space. To best approximate these infeasible orientations, the Jacobian-based algorithm is implemented in the sense of least squares. As some orientations can never be attained by a single four-rotation FR sequence, two different four-rotation FR sequences are exploited alternately to ensure the convergence of the proposed algorithm. Assuming the orientation is supposed to be manipulated using three input torques, the switching Jacobian algorithm proposed in this paper has significant practical importance in planning paths for aerospace and underwater vehicles which are maneuvered using only two input torques due to the failure of one of the torque-generation mechanisms.

A hydraulic flexible joint inspired by the actuation system of spiders is investigated in this paper. Its design and characteristics are discussed and a mathematical model is developed to describe its static behaviour. Results of experimental tests are presented to validate its performance. A comparison to other hydraulic actuation systems is performed. The use of the proposed hydraulic flexible joint in adaptive robotic structures is addressed and discussed.

This paper proposes a new approach for solving a generalization of the task scheduling problem for articulated robots (either redundant or non-redundant), where the robot's 2D environment is cluttered with obstacles of arbitrary size, shape and location, while a set of task-points are located in the robot's free-space. The objective is to determine the optimum collision-free robot's tip tour through all task-points passing from each one exactly once and returning to the initial task-point. This scheduling problem combines two computationally NP-hard problems: the optimal scheduling of robot tasks and the collision-free motion planning between the task-points.

The proposed approach employs the bump-surface (B-Surface) concept for the representation of the 2D robot's environment by a B-Spline surface embedded in 3D Euclidean space. The time-optimal task scheduling is being searched on the generated B-Surface using a genetic algorithm (GA) with a special encoding in order to take into consideration the infinite configurations corresponding to each task-point. The result of the GA's searching constitutes the solution to the task scheduling problem and satisfies optimally the task scheduling criteria and objectives. Extensive experimental results show the efficiency and the effectiveness of the proposed method to determine the collision-free motion among obstacles.

In recent years hexagonal hexapod robots gained the interest of international research community. The aim of this paper is twofold. First, after summarizing all known gaits of such robots, we introduce some improvements both for normal conditions and for fault tolerance. Then we show the advantages of hexagonal hexapod robots over rectangular ones by comparing different gaits from theoretical and experimental points of view. Stability, fault tolerance, turning ability, and terrain adaptability are analyzed. For reaching these aims we also introduce a robot kinematics that considers at the same time supporting and transferring legs. The trajectories of feet are described as well. Finally, single leg stride selection is studied for side wave and for kick-off gaits to optimize walking ability and energy management.

The theoretical results presented herein have been validated with experiments conducted on a prototype of the Novel Robotics System for Planetary Exploration (Rovetta et al., “New Robot Concepts for Mars Soil Exploration: Mechanics and Functionality,” ASTRA 2004, Eighth ESA Workshop on Advanced Space Technologies for Robotics and Automatian, Nordwijk, The Netherlands Nov. 2–4, 2004) (NOROS), developed by Politecnico di Milano and Beijing University of Astronautics and Aeronautics, and the results are summarized in this paper.