In this paper, we have reported a trajectory planning for a 1-degree-of-freedom clutched robotic arm. This novel robotic arm has only one actuator, but it can work in a spatial space by using a proper clutch system and a suitable trajectory planning. An algorithm has been proposed for generating a prescribed trajectory by means of seven operation modes, which are generated by different states of clutches.

This paper proposes a novel dynamic walker capable of walking with heel, ankle, and toe rocker motions. The heel and toe rocker motions are obtained by using inelastic stoppers between leg and foot, which limit the range of rotation of the foot about the ankle joint. A generalized set of equations of motion and associated transition equations applicable for multiple foot segments is derived. Passive dynamic walking is studied with equal heel and toe strike angles for the case of symmetric foot walking. It is shown that by including the ankle joint, low-speed walking is made possible. The energy efficiency of the proposed walker is studied theoretically and through numerical simulations. Finally, three different underactuated modes of active walking that do not require toe and heel actuation are presented. In order to implement these modes of walking, the proposed walker can be constructed with little modification from an existing flat-foot walker that uses ankle rocker motion alone. Results show that substantial benefits can be obtained in efficiency and stability compared to point/flat-foot walker of the same leg length and mass distribution.

This paper is devoted to the study of systems of entities that are capable of generating other entities of the same kind and, possibly, self-reproducing. The main technical issue addressed is to quantify the requirements that such entities must meet to be able to produce a progeny that is not degenerative, i.e., that has the same reproductive capability as the progenitor. A novel theory that allows an explicit quantification of these requirements is presented. The notion of generation rank of an entity is introduced, and it is proved that the generation process, in most cases, is degenerative in that it strictly and irreversibly decreases the generation rank from parent to descendent. It is also proved that there exists a threshold of rank such that this degeneracy can be avoided if and only if the entity has a generation rank that meets that threshold – this is the von Neumann rank threshold. On the basis of this threshold, an information threshold is derived, which quantifies the minimum amount of information that must be provided to specify an entity such that its descendents are not degenerative. Furthermore, a complexity threshold is obtained, which quantifies the minimum length of the description of that entity in a given language. As an application, self-assembly for a 2 Degrees of Freedom planar robot is considered, and simulation results are presented. A robot arm capable of picking up and placing the components of another arm, in the presence of errors, is considered to have successfully reproduced if these are placed within an allowable tolerance. The example shows that, due to the kinematics of the robot, errors can grow from one generation to the next, until the reproduction process fails eventually. However, error correction (via error sensing and feedback control) can then be used to prevent such degeneracy. The von Neumann generation rank and information thresholds are computed for this example, and are consistent with the simulation results in predicting degeneracy in the case without error correction, and predicting successful self-reproduction in the case with error correction.

A new localization algorithm is proposed for a fast moving mobile robot, which utilizes only one beacon and the global features of the differential-driving mobile robot. It takes a relatively long time to localize a mobile robot with active beacon sensors, since the distance to the beacon is measured based on the traveling time of the ultrasonic signal. When the mobile robot is moving slowly, the measurement time does not yield a high error. At a higher speed, however, the localization error becomes too large for the mobile robot to be located accurately. Therefore, in high-speed mobile robot operations, instead of using two or more active beacons, only one active beacon and the global features of the mobile robot are used to localize the mobile robot. The two global features are the radius and center of the rotational motion for the differential-driving mobile robot, which generally describe the motion of, and are used for the trace prediction of, a mobile robot. In high-speed operations, the localizer finds the intersection point of this predicted trace and the circle, which is centered at the beacon whose radius is the distance between the mobile robot and the beacon. This new approach overcomes the large localization error caused by the high speed of the mobile robot. The performance of the new localization algorithm is verified through experiments with a high-speed mobile robot.

This paper presents the development of a self-replicating mobile robot that functions by undergoing stochastic motions. The robot functions hierarchically. There are three stages in this hierarchy: (1) An initial pool of feed modules/parts together with one functional basic robot; (2) a collection of basic robots that are spontaneously formed out of these parts as a result of a chain reaction induced by stochastic motion of the initial seed robot at stage 1; (3) complex formations of joined basic robots from stage 2. In the first part of this paper we demonstrate basic stochastic self-replication in unstructured environments. A single functional robot moves around at random in a sea of stock modules and catalyzes the conversion of these modules into replicas. In the second part of the paper, the robots are upgraded with a layer that enables mechanical connections between robots. The replicas can then connect to each other and aggregate. Finally, self-reconfigurability is presented for two robotic aggregations.

A method is presented for the type synthesis of a class of parallel mechanisms having one-dimensional (1D) rotation based on the theory of Generalized Function sets (GF sets for short), which contain two classes. The type synthesis of parallel mechanisms having the first class GF sets and 1D rotation is investigated. The Law of one-dimensional rotation is given, which lays the theoretical foundation for the intersection operations of GF sets. Then the kinematic limbs with specific characteristics are designed according to the 2D and 3D axis movement theorems. Finally, several synthesized parallel mechanisms have been sketched to show the effectiveness of the proposed methodology.

Hybrid actuation systems consist of two types of motors: constant velocity (CV) motor and servo (SV) motor. The CV motor can produce a large power but with a poor task flexibility. On the other hand, the SV motor has an excellent task flexibility but with a small power capacity. Combination of these two types of motors into a coherent driver architecture for machine systems is extremely promising, because they complement each other. Existing studies on the hybrid actuation or machine system usually employ two servo motors, one of which substitutes the CV motor. This treatment compromises the control accuracy for the trajectory tracking at the end-effector. This paper presents a study on a new controller for the hybrid machine that considers one SV motor and one CV motor and for trajectory tracking at the end-effector level. A comparison of this new controller with the controller we developed previously is provided. A five-bar mechanism with two degrees of freedom is employed for the illustration purpose.

The generalized Jacobian matrix was introduced for dealing with end-effector control in space robots. One of the applications of this Jacobian is to be used in Jacobian transpose control to generate joint torques given end-effector position error. It would be misleading, however, to consider the transpose of this Jacobian as a mapping from end-effector force/moment to controlled joint torques for underactuated systems or floating base robots. This paper explains why it does not represent the mapping and provides a simple example. Later, the correct mapping is provided using the dynamically consistent Jacobian inverse and then a method to compute the actuated-joint torques is explained given the desired end-effector force. Finally, the effect of using the generalized Jacobian in the Jacobian transpose control is analyzed.

This work presents biologically inspired method of gait generation. It uses the reference to the periodic signals generated by biological central pattern generator. The coupled oscillators with correction functions are used to produce leg joint trajectories. The human gait is the reference pattern. The features of generated gait are compared to the human walk. The spring-loaded foot design is presented together with experimental results.

In this study, modelling and control of a two-link robot manipulator whose first link is rigid and the second one is flexible is considered for both land and underwater conditions. Governing equations of the systems are derived from Hamilton's Principle and differential eigenvalue problem. A computer program is developed to solve non-linear ordinary differential equations defining the system dynamics by using Runge–Kutta algorithm. The response of the system is evaluated and compared by applying classical control methods; proportional control and proportional + derivative (PD) control and an intelligent technique; integral augmented fuzzy control method. Modelling of drag torques applied to the manipulators moving horizontally under the water is presented. The study confirmed the success of the proposed integral augmented fuzzy control laws as well as classical control methods to drive flexible robots in a wide range of working envelope without overshoot compared to the classical controls.

The Secondary Adjustable System (SAS) addressed here is a central component of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). It is a 6-degree-of-freedom rigid Stewart manipulator, in which one platform (the end-effector) should be controlled to track-desired trajectory when another platform (denoted as the base) is moving. Driving force analysis of the SAS is the basis for selecting rational servomotors and guaranteeing the dynamic performance, which will affect the terminal pose accuracy of the FAST. In order to determine the driving forces of the SAS, using the Newton–Euler method, the inverse dynamics of the Stewart manipulator is modeled by considering the motion of the base. Compared with the traditional dynamic models, the inverse dynamic model introduced here possesses an inherent wider application range. By adopting the kinematic and dynamic parameters of the FAST prototype, the driving force analysis of the SAS is carried out, and the driving force optimization strategies are proposed. Calculation and analysis presented in the paper reveal that there are three main factors affecting the driving forces of the SAS. In addition, the driving force analysis of this paper lays out guidelines for the design and control of the FAST prototype, as well as the structure and trajectory optimization.

This paper presents a method to generate humanoid gaits from a human locomotion pattern recorded by a motion capture system. Thirty seven reflective markers were fixed on the human subject skin in order to get the subject whole body motion. To reproduce the human gait, especially the toes and heel contacts, the front and back edges of the robot's feet are used as support at the start and the end of the double support phase. The balance of the robot is respected using the zero moment point (ZMP) criterion and confirmed by the simulation software OPENHRP (General Robotics, Inc®). First, the feet trajectory as well as the ZMP reference trajectory are defined from the motion of the robot controlled as a marionette with the measured human joint angles. Then a specific inverse kinematic (IK) algorithm is proposed to find the humanoid robot's joint trajectories respecting the constraints of balance, floor contacts, and joint limits. The studied motion presented in this paper is a human walking trajectory containing a start, a movement in a straight line, a stop, and a quarter turn. The method was developed to be easily used for human-like robots of different sizes, masses, and structures and has been tested on the robot HRP-2 (AIST, Kawada Industries, Inc®) and on the small-sized humanoid robot HOAP-3 (Fujitsu Automation Ltd®).

In parametric excitation walking, up-and-down motion of the center of mass restores mechanical energy and sustainable gait is generated. Not only walking performance but also walking ability strongly depends on the reference trajectory of the center of mass. In this paper, we propose an optimization method for the reference trajectory, in which the reference trajectory is confined to the quartic spline curves and the parameters of spline curves are optimized by a local search method usually used in combinatorial optimization. We apply the proposed method to a kneed biped robot and find some remarkably interesting results by numerical simulations.

This paper presents closed-form analytic solutions for collision detection among multiagents traveling along specified paths. Previous solutions for centralized multiagent systems have mainly used iterative computational approaches for collision detection, which impose a heavy computational burden on the systems. In this paper, we formalize a new mathematical approach to overcoming the difficulty on the basis of simple continuous curvature (SCC) path modeling and a collision representation tool, extended collision map (ECM) method. The formulation permits all the potential collisions to be detected, represented, and parameterized with physical and geometric variables. The proposed parameterized collision region (PCR) method is a simple but precise, computationally efficient tool for describing complicated potential collisions with time traveled. Several simulations are presented to validate the proposed approach for use in centralized collision detectors and to compare the results with those of the iterative computational method and the proximity query package (PQP) method that are available.

This paper presents a new algorithm for the control of a snake-like robot with passive joints and active wheels. Each segment has four autonomously driven and steered wheels. The algorithm approximates the ideal solution in which all wheels on a segment have the same centre of curvature with wheel speeds, providing cooperative redundancy. Each hitch point joining segments traverses the same path, which is determined by an operator, prescribing the path curvature and front hitch speed. The numerical algorithm developed in this paper is simulation tested against a previously derived analytical solution for a predetermined path. Further simulations are carried out to show the effects of changing curvature and front hitch speed on hitch path, wheel angles and wheel speeds for a one, two and three segment robot.

Independent mobility is one of the major challenges for elderly. Assistive robots must guarantee user's safety. Existing methods to quantitatively express user's safety are not applicable to mobility assistance robots due to physical attachment. This paper proposes a danger index to estimate user's safety during mobility assistance. The formulation and validation of the index is achieved through extensive subjective and objective experimentation. A motion control method is also introduced that uses the proposed danger index for monitoring user's safety and initiating proper safety actions in case of danger. As an example, experimental results with SpiderBot-II are reported in this paper.

Cellular automata can model the information processing aspects of a self-replicating programmable constructing system (SRPC), but these models do not contain any notion of material parts and are poor at modelling features of a system that depend upon the motion and connectivity of its components. Physical systems with thousands of parts have the disadvantage that they are time consuming to develop. To overcome these limitations, a simulation environment is presented at a level of abstraction that models motion and connectivity. An SRPC which takes a disorganised collection of parts as its input has been implemented in this environment.

This paper presents the results to date of the RepRap project – an ongoing project that has made and distributed freely a replicating rapid prototyper. We give the background reasoning that led to the invention of the machine, the selection of the processes that we and others have used to implement it, the designs of key parts of the machine and how these have evolved from their initial concepts and experiments, and estimates of the machine's reproductive success out in the world up to the time of writing (about 4500 machines in two and a half years).

From the viewpoint of the system's mechanical energy, the passive inverted pendulum model (PIPM) is proposed for the generation of more energy-efficient biped gait pattern. The generated walking pattern, based on the PIPM, enables the fully actuated biped robots to closely mimic the behavior of stable passive walking, so that it can have good energy-efficiency, which is the inherent advantage of the passive system. Furthermore, the pattern generation method is extended to any desired terrain as well. As for SHR-1, the first-generation biped robot of Shanghai Jiao Tong University, gait synthesis is clarified in detail. Finally, the walking experiments are carried out on SHR-1, and the effectiveness of the proposed pattern generation method is confirmed.

This paper presents a new planar passive dynamic model with contact between the feet and the ground. The Hertz contact law and the approximate Coulomb friction law were introduced into this human-like model. In contrast to McGeer's passive dynamic models, contact stiffness, contact damping, and coefficients of friction were added to characterize the walking model. Through numerical simulation, stable period-one gait and period-two gait cycles were found, and the contact forces were derived from the results. After investigating the effects of the contact parameters on walking gaits, we found that changes in contact stiffness led to changes in the global characteristics of the walking gait, but not in contact damping. The coefficients of friction related to whether the model could walk or not. For the simulation of the routes to chaos, we found that a small contact stiffness value will lead to a delayed point of bifurcation, meaning that a less rigid surface is easier for a passive model to walk on. The effects of contact damping and friction coefficients on routes to chaos were quite small.