We present a new numerical optimal design for a redundant parallel manipulator, the eclipse, which has a geometrically symmetric workspace shape. We simultaneously consider the structural mass and design efficiency as objective functions to maximize the mass reduction and minimize the loss of design efficiency. The task-oriented workspace (TOW) and its partial workspace (PW) are considered in efficiently obtaining an optimal design by excluding useless orientations of the end-effector and by including just one cross-sectional area of the TOW. The proposed numerical procedure is composed of coarse and fine search steps. In the coarse search step, we find the feasible parameter regions (FPR) in which the set of parameters only satisfy the marginal constraints. In the fine search step, we consider the multiobjective function in the FPR to find the optimal set of parameters. In this step, fine search will be kept until it reaches the optimal set of parameters that minimize the proposed objective functions by continuously updating the PW in every iteration. By applying the proposed approach to an eclipse-rapid prototyping machine, the structural mass of the machine can be reduced by 8.79% while the design efficiency is increased by 6.2%. This can be physically interpreted as a mass reduction of 49 kg (the initial structural mass was 554.7 kg) and a loss of 496 mm3/mm in the workspace volume per unit length. The proposed optimal design procedure could be applied to other serial or parallel mechanism platforms that have geometrically symmetric workspace shapes.

Existing sonar rings are limited in their refresh rate to the transmit echo rate, that is, waiting for maximum range echoes to arrive before transmitting again. This paper presents a sonar ring refreshing at 60 Hz for 5.7-m range, which is twice the transmit echo rate, and this leads to lower latency, denser measurements. Two custom Field Programmable Gate Array signal processors provide real time continuous match filtering with dynamic templates. A new method is implemented to select the transmit time from a random set based on minimizing interference. Experiments demonstrate the increased refresh rate, interference rejection, and maps generated by the sonar ring.

Wireless Sensor Network (WSN) localization has shown a growing research interest, thanks to the expected proliferation of WSN applications. This work is focused on indoor localization of a mobile robot in a WSN using only inter-node range measurements, which are estimated by radio frequency signal strength attenuation. These measurements are affected by different sources of uncertainty that make them highly noisy and unreliable. The proposed approach makes use of fuzzy logic for modeling and dealing with such uncertain information. Besides, the position estimation is enhanced using a rough description of indoor environment. The experiments show that the proposed localization approach (i) is fault-tolerant, (ii) results feasible in low-density WSNs, and (iii) provides better position estimations than well-known localization methods when the position measurements are affected by high uncertainty.

Nature has always inspired engineers. This research tries to understand the contribution of snake anatomy in its locomotion from engineering point of view to be adopted in the design of snake robots. Rib design and muscular structure of snake robots will have a great impact on snake robot flexibility, weight, and actuators' torque. It will help to eliminate wheels in snake robots during serpentine locomotion. The result of this research shows that snakes can establish the required peg points on smooth surfaces by deflecting the body and ribs. The results are verified by both field observations and simulation.

Robotic-assisted surgery is a continuously developing field because robots have demonstrated clear benefits in operating rooms. Until now, vast majority of robots used in surgery had serial structures. This paper presents the kinematic modelling of a 5-degree of freedom hybrid parallel architecture in two slightly different variants. The kinematics of this structure is determined, and following the analysis of singularities, the best variant is chosen. The robot workspace is computed and finally the experimental model and some simulation results are presented.

This paper extends a recently proposed singularity analysis method to lower-mobility parallel manipulators having an articulated nacelle. Using screw theory, a twist graph is introduced in order to simplify the constraint analysis of such manipulators. Then, a wrench graph is obtained in order to represent some points at infinity on the Plücker lines of the Jacobian matrix. Using Grassmann–Cayley algebra, the rank deficiency of the Jacobian matrix amounts to the vanishing condition of the superbracket. Accordingly, the parallel singularities are expressed in three different forms involving superbrackets, meet and join operators, and vector cross and dot products, respectively. The approach is explained through the singularity analysis of the H4 robot. All the parallel singularity conditions of this robot are enumerated and the motions associated with these singularities are characterized.

This paper exploits a natural symmetry present in a 3D robot in order to achieve asymptotically stable steering. The robot under study is composed of 5-links and unactuated point feet; it has 9 DoF (degree-of-freedom) in the single-support phase and six actuators. The control design begins with a hybrid feedback controller that stabilizes a straight-line walking gait for the 3D bipedal robot. The closed-loop system (i.e., robot plus controller) is shown to be equivariant under yaw rotations, and this property is used to construct a modification of the controller that has a local, but uniform, input-to-state stability (ISS) property, where the input is the desired turning direction. The resulting controller is capable of adjusting the net yaw rotation of the robot over a step in order to steer the robot along paths with mild curvature. An interesting feature of this work is that one is able to control the robot's motion along a curved path using only a single predefined periodic motion.

This paper deals with processes of optimisation for the design of a four degree-of-freedom robot dedicated to remote ultrasound tele-echography. This robot is designed to track the medical gestures of a remote expert moving an ultrasound probe. The goal is to optimise the kinematic structure by fixing the geometric parameters; these have a significant role in robot configuration singularities, with respect to current medical gestures and mechanism compactness. After choosing a dedicated kinematic structure, several optimisations are presented. Then an optimal choice of geometrical parameters of a global function in relation with kinematic performance indices and compactness is proposed. This robot is soon to be used in the experimental medical phase of the Prosit project.

This paper introduces the design and kinematic analysis of a 5-DOF (multiple degree of freedom) hybrid-driven MR (Magnetic Resonance) compatible robot for prostate brachytherapy. It can slip the leash of template and rely on the high precise of MR imaging. After a brief introduction on design requirements of MR compatible robot, a description of our robot structure, material selection, hybrid-driven, and control architecture are presented. Secondly, the forward kinematics equations are obtained according to the equivalent diagram of this robot, and the actual workspace can be outlined. This will help the designer to determine whether this robot can be operated in the MR core without intervention with patient. And then, the inverse kinematics equations combined with trajectory planning are used to calculate the actuators movement. This will help the control system to manipulate the robotic accurately. Finally, vision based experiments on phantoms are used to verify the mechanism precision. As the results shown, the needle tip precision of mechanism is 0.9 mm in the general lab environment.

Reliability of a satellite attitude control system depends on accurate detection of failures in its sensors. This paper presents an observer for robust detection and isolation of a class of failures in satellite attitude sensors. The proposed observer uses measurement of a three-axis gyro together with only one attitude sensor, and generates a residual signal which is sensitive to faults and is simultaneously robust against disturbance and noise. A nonlinear model of satellite kinematics is considered for design of the observer. The structure of the observer is in the form of a delayed continuous-time differential equation ensuring its robustness properties. A realistic simulation is provided to illustrate the performance of the proposed observer in the face of the faults occurring in a magnetometer, as the attitude sensor, and also the faults occurring in the gyro.

This paper proposes an experimental approach for evaluating the backlash error of an ABB IRB 1600 industrial serial robot under various conditions using a laser interferometer measurement instrument. The effects of the backlash error are assessed by experiments conducted on horizontal and vertical paths. A polynomial model was used to represent the relationship between the backlash error and the robot configuration. A strategy based on statistical tests was developed to choose the degree of polynomial representing the effect of the tool center point (TCP) speed and payload. Results show that the backlash error strongly affects the repeatability of the industrial robot. Statistical analyses prove that the backlash is highly dependent on both robot configuration and TCP speed, whereas it remains nearly unaffected by changes in the payload. It was discovered that the backlash error as measured at the TCP may exceeds 100 μm, and that the positive backlash error increases and the negative backlash error decreases when there is increase in TCP speed.

This paper presents an adaptive force/position controller for a parallel robot executing constrained motions. This controller, based on an MLPNN (or Multi-Layer Perceptron Neural Network), does not require the inverse dynamic model of the robot to derive the control law. A neural identification of the dynamic model of the robot is proposed to determine the principal components of the MLPNN input vector. The latter is used to compensate the dynamic effects arising from the robot–environment interaction and its parameters are adjusted according to an adaptation law based on the Lyapunov-analysis methodology. The proposed controller is evaluated experimentally on the C5 parallel robot. This method is capable of tracking accurately the force/position trajectories and its stability robustness is proved.

Traditionally, robot motion planners use Voronoi Diagrams for generating admissible paths that connect an initial with a final configuration. When dynamic scenarios are involved, these techniques imply a heavy computational cost. The novelty of the technique presented here is that it can provide fast and particularly suitable routes without considering the full scenario if environmental changes appear. The new method is designed to work with a post-process technique in order to provide admissible paths for car-like robots coping with kinematic constraints. This new approach is capable of supplying continuous paths and also elaborate maneuvers if cluttered environments are involved.

In this paper we address the problem of stabilization and local positioning of a four-rotor rotorcraft using computer vision. Our approaches to estimate the orientation and position of the rotorcraft combine the measurements from an Inertial Measurement Unit (IMU) and a vision system composed of a single camera. In the first stage, the vision system is used to estimate the position and yaw angle of the rotorcraft, while in the second stage the vision system is used to estimate the translational velocity of the flying robot. In both cases the IMU gives the pitch and roll angles at a higher rate. The technique used to estimate the position of the rotorcraft in the first stage combines the homogeneous transformation approach for the camera calibration process with the plane-based pose method for estimating the position. In the second stage, a navigation system using the optical flow is also developed to estimate the translational velocity of the aircraft. We present real-time experiments of stabilization and location of a four-rotor rotorcraft.

The isotropy of the generalized inertia ellipsoid is an evaluation index that can measure dynamic performance of a robot. This has significance in motion planning and design of a jumping robot. The generalized inertia of a jumping robot is analyzed. The generalized inertia tensor and the generalized inertia ellipsoid (GIE) are derived from the kinetic energy of the robot mechanism. From the viewpoint of geometrical shape change of the GIE, nonlinear characteristics of a jumping robot are analyzed. With the goal of minimizing nonlinear effects during its movement, the mechanism parameters of a jumping robot are optimized by adopting isotropy of the generalized inertia ellipsoid as its objective function. Example results demonstrate the efficiency and validity of the proposed optimization method.