The integration of drones, the Internet of Things (IoT), and Artificial Intelligence (AI) domains can produce exceptional solutions to today complex problems in smart cities. A drone, which essentially is a data-gathering robot, can access geographical areas that are difficult, unsafe, or even impossible for humans to reach. Besides, communicating amongst themselves, such drones need to be in constant contact with other ground-based agents such as IoT sensors, robots, and humans. In this paper, an intelligent technique is proposed to predict the signal strength from a drone to IoT devices in smart cities in order to maintain the network connectivity, provide the desired quality of service (QoS), and identify the drone coverage area. An artificial neural network (ANN) based efficient and accurate solution is proposed to predict the signal strength from a drone based on several pertinent factors such as drone altitude, path loss, distance, transmitter height, receiver height, transmitted power, and signal frequency. Furthermore, the signal strength estimates are then used to predict the drone flying path. The findings show that the proposed ANN technique has achieved a good agreement with the validation data generated via simulations, yielding determination coefficient$R^2$to be 0.96 and 0.98, for variation in drone altitude and distance from a drone, respectively. Therefore, the proposed ANN technique is reliable, useful, and fast to estimate the signal strength, determine the optimal drone flying path, and predict the next location based on received signal strength.

This paper proposes an approximate-kinetic-model-based self-adaptive (AKS) control system to rapidly generate target walking speed by an underactuated compasslike bipedal walker. First, a model of the underactuated compass-like bipedal walker is built, and an open-loop system is introduced and analysed as the prototype of AKS system. Second, the control law of AKS is described in detail. The dynamic updating of trajectory is proposed and the calculation of control parameters by an approximate linearized model is analysed. Finally, simulations are conducted, and thus the capability of disturbance rejection and versatility is tested. As a conclusion, target walking speeds with 4∼6% steady-state error can be generated rapidly and steadily. Limit cycle walker can obviously improve the capability of handling disturbance and various tasks by AKS control system.

Astronauts must go through extensive training of their tasks in a simulated microgravity or reduced-gravity environment before they can perform the same tasks in space. Scientists and engineers also need simulated reduced-gravity facilities to study human performance and factors in space. This paper presents a novel design and prototype test of a multi-DOF reduced-gravity simulator which can be used for training astronauts and studying human factors in zero or partial gravity environment. Designed based on the passive static balancing technology, the simulator can passively compensate the gravity force applied to a human to any level from 0 to 100% at all the configurations within its workspace. Therefore, a person attached to the simulator can biomechanically feel like he/she were in a real reduced-gravity environment while doing a physical activity such as walking or jumping. A prototype of the simulator was developed to study the feasibility and dynamic performance of the system. The prototype study demonstrated the reduced-gravity simulation capability of the system. It also revealed some interesting findings which motivate further research in the future.

One of the most challenging and risky missions for spacecraft is to perform Rendezvous and Docking (RvD) autonomously in space. To ensure a safe and reliable operation, such a mission must be carefully designed and thoroughly verified before a real space mission can be launched. This paper describes a new, robotics-based, hardware-in-the-loop RvD simulation facility which uses two industrial robots to simulate the 6-DOF dynamic maneuvering of the docking satellites. The facility is capable of physically simulating the final approaching within 25-meter range and the entire docking/capturing process in a satellite on-orbit servicing mission. The paper briefly discusses the difficulties of using industrial robots for HIL contact dynamics simulation and how these problems are solved.

Several solutions, based on aural and haptic feedback, have been developed to enable access to complex on-line information for people with visual impairments. Nevertheless, there are several components of widely used software applications that are still beyond the reach of screen readers and Braille displays.

This paper describes a dynamics modeling and control strategy of a chemo-electro-mechanical process for electroporation-mediated gene delivery. By extending the results in the open literature, a control-enabled dynamics model of the gene-delivery process is proposed. Based on the dynamics model, a model-based state feedback control strategy is proposed. Simulation results are provided to demonstrate the benefits and limitations of the proposed method.

This research focuses on developing a novel mapping for human visual perception from visual field to the primary visual cortex based on spatial and physiological characteristics of visual pathway. First, a spatial relationship between single visible spot in the visual field and its retinal projection on the spherical surface for a monocular vision system was established. A novel approach, called "peel-off mapping, was then formulated in dealing with flattening the spherical retina to a 2-dimensional (2-D) plane before being mapped to the visual cortex. Velocity level mapping that described how a visible moving spot was projected from visual field to the spherical retinal surface was developed and then mapped onto the visual cortex. More importantly, all the kinematical relationships established for monocular system were extended to binocular vision. Finally, a complete model was developed that allows for quantitative computation of binocular disparity as well as disparity due to stereo-motion in the primary visual cortex. Software has been written and simulation results validated the model.

This paper proposed a systematic method of verifying the force-closure condition for general 6-DOF cable manipulators with more than seven cables. Without explicitly solving the inverse dynamics problem, the method can determine, by examining the Jacobian matrix of the manipulator, whether a feasible force solution exists. The equivalence (i.e., necessity and sufficiency) of the proposed method to an existing force-closure theorem developed for the robot grasping problem is mathematically proven and hence, this work rigorously shows, for the first time, that the theory for grasping problem is also applicable to cable manipulators. Moreover, a convex-analysis based simplification of the method is discussed.

This paper proposes a mathematical model for an industrial track robot. The model is further used to analyze root cause of track robot vibration. A practical solution is proposed to suppress the vibration. Both simulation and experimental results show that the solution is effective and reliable. Comparisons of the results with existing approaches are also presented. The contributions of this paper include: a) the model abstraction and analysis, which was not reported in the open literature for such track robot system; b) a practical solution first time applied to the track robot system, which results in significant performance improvement in industrial applications

This paper describes the study of the force-closure workspace of a 6-DOF, cable-driven, parallel robot for the application in a hardware-in-the-loop dynamic simulator, which is used for simulating microgravity contact dynamics of spacecraft or robotic systems. The workspace under study is defined as the set of all end-effector poses satisfying force-closure condition. Force-closure also means that the inverse dynamics problem of the manipulator has a feasible solution. Since there is no limitation on the external wrench and the dynamic motion of the end-effector, such a workspace is the most desirable (or nonrestricted) workspace for the intended application simulating low-speed impact-contact dynamics. A systematic method of determining whether or not a given end-effector's pose is inside the workspace is proposed with mathematical proof. Based on this method, the shape, boundary, dimensions, and volume of the workspace of a 6-DOF cable robot are displayed and discussed

One of the most challenging tasks for satellite on-orbit servicing is to rendezvous and capture a non-cooperative satellite such as a tumbling satellite. This paper presents an optimal control strategy for a servicing spacecraft to rendezvous (in close range) with a tumbling satellite. The strategy is to find an optimal trajectory which will guide the servicing spacecraft to approach the tumbling satellite such that the two vehicles will eventually have no relative rotation. Therefore, a subsequent docking or capture operation can be safely performed. Pontryagin's maximum principle is applied in generation of the optimal approaching trajectory and the corresponding set of control force/torque profiles. A planar satellite chasing problem is presented as a case study, in which together with the maximum principle, the Lie algebras associated with the system are used to examine the existence of singular extremals for optimal control. Optimal trajectories for minimum fuel consumption are numerically simulated

This paper describes an R&D project aimed at experimentally validating a generic contact-dynamics toolkit in a Simulink based satellite docking simulator. The simulation software was developed to support the design and verification of the space station robotic systems and several satellite on-orbit robotic servicing systems. The hardware experiment was performed using an air-bearing supported docking testbed specially designed for testing different docking and capture mechanisms. Simulation model parameters were separately identified from the hardware. The simulation results compare favourably with the measured experimental data, which demonstrates the validity of the simulator and increases the confidence of using the simulator for design of various robotics-based satellite servicing missions such as the shuttle-return-to- flight, orbital express, and the potential hubble telescope robotic repair missions

Oligo deoxyribonucleic-acid (DNA) microarrays are fabricated through in-situ chemical synthesis. Contact and fluid dynamics contribute to this process. To produce high-quality oligo DNA microarrays, it is important to well understand the dynamics of the fabrication process. Much work has been done in understanding the chemistry principles. However, few studies have been conducted from the mechanics point of view. This paper proposes a contact dynamics model of inkjet technology-based oligo DNA microarray spotting process. The proposed dynamics model can reasonably well explain the dynamics of the oligo DNA microarray spotting process. Note to Practitioners-This research was motivated by the need to develop a dynamics model for analyzing the inkjet technology-based oligo deoxyribonucleic-acid (DNA) microarray spotting process. Modeling techniques for micro/nanoscale dynamics have not been well established in the open literature. This case study shows how this can be done for DNA spotting dynamics. Contact dynamics, electrostatic forces, viscous forces, and van der Waals forces have all been considered in this study. The method may be extended to model and analyze the dynamics of other biological particle spotting processes as well.

Dynamic simulation of manipulators doing contact tasks with stiff and complex contact interfaces is time consuming because very small integration step sizes have to be used for numerical stability. Existing model order reduction techniques cannot be readily applied due to high nonlinear nature of contact dynamics. A new method of model order reduction is proposed to deal with this problem. The method identifies the "stiffness" and "damping" terms by linearizing the contact force model and add them to those of the manipulator. Then the existing modal analysis and truncation technology is applied. An example is presented to demonstrate the significant gain in computational efficiency and unproved output results.

Determining the minimum distance between two convex objects is a problem that has been solved using many different approaches. On the other hand, computing the minimum distance between combinations of convex and concave objects is known to be a more complicated problem. Some methods propose to partition the concave object into convex sub-objects and then solve the convex problem between all possible sub-object combinations. While this method has been shown to work reliably, it adds a large computational expense when the concave objects in the scene are complicated, or when a quadratically bound object is to be linearized. An optimization approach is used to solve the concave problem without the need for partitioning the concave object into convex sub-objects. Since the optimization problem is no longer unimodal, a global optimization technique is used. Simulated annealing is used to solve the concave problem. In order to reduce the computational expense, it is proposed to replace the objects' geometry by a set of points on the surface of each body. This reduces the problem to a combinatorial problem where the combination of points that minimizes the distance will be the solution. Some examples using this method are presented.

This paper describes a general approach to the modelling and simulation of contact dynamics for robotic systems. The contact bodies under consideration are arbitrary 3-D objects as long as their bounding surfaces are linear or quadratic. Multiple-contact and body flexibility are considered. Numerical iterative procedure is used to ensure the coupling between local contact forces and system's dynamics at each simulation step. The approach has been implemented and integrated into a generic manipulator simulator currently being used to support the design of the Space Station manipulator systems.

The architecture singularity of platform manipulators is considered with reference to a class of six-DOF (degree-of-freedom) parallel manipulators. It is pointed out that an architecture singularity usually spans the whole workspace or a significant part thereof, which makes it very difficult to implement control or singularity-avoidance strategies. Several groups of singular architectures are reported, with comprehensive theoretical proofs. This work can serve as a guide for the optimum design of parallel manipulators in the sense of achieving optimum kinematic and force-transmission performances.>

The concept of dynamic isotropy, a measure of the dynamic performance of manipulators, is presented. An associated index, the dynamic conditioning index, is defined to describe this concept quantitatively. This index measures the dynamical coupling and numerical stability of the generalized inertia matrix of a manipulator in its dynamics model. Reduction of this index weakens the dynamic coupling while increasing the numerical stability of the dynamics model, which leads in turn to an improvement of the robot performance for simulation and control under dynamical conditions. The concept can be used as a criterion for manipulator performance and design optimization. The application of this concept to inverse kinematics of redundant manipulators and to the optimum trajectory planning of nonredundant manipulators is illustrated with two examples.>