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 consider the problem of the stabilization in single support of the vertical posture for a two-link, a three-link, and a five-link planar biped without feet. The control torques are applied in the inter-link joints only. Thus, our objects are under-actuated systems. The control laws are designed, using the biped linear models and their associated Jordan forms. The feedback is synthesized to suppress the unstable modes. The limits imposed on the torques are taken into account explicitly. Thus, the feedback laws with saturation are designed. The numerical investigations of the nonlinear models with the designed control laws are presented.

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.

In this paper, we propose a model-based control system design for autonomous flight and guidance control of a small-scale unmanned helicopter. Small-scale unmanned helicopters have been studied by way of fuzzy and neural network theory, but control that is not based on a model fails to yield good stabilization performance. For this reason, we design a mathematical model and a model-based controller for a small-scale unmanned helicopter system. In order to realize a fully autonomous small-scale unmanned helicopter, we have designed a MIMO attitude controller and a trajectory controller equipped with a Kalman filter-based LQI for a small-scale unmanned helicopter. The design of the trajectory controller takes into consideration the characteristics of attitude closed-loop dynamics. Simulations and experiments have shown that the proposed scheme for attitude control and position control is very useful.

In this paper, the design and control of an omni-directional mobile microrobot are described for micro-assembling in a micro-factory. A unique locomotion mechanism composed of three special castors units is proposed. The castor consists of two coaxial conventional wheels, connected to the chassis and connected with each other by a set micro-gears. The microrobot is approximately 8 mm in length, 6 mm in width and 6 mm in height. Its kinematics and characteristics are analyzed. Experimental results from a prototype of a microrobot are presented, which demonstrates the feasibility of building an omni-directional microrobot with micromotor and special castors.

This paper presents a simplified kinematics propulsive model for carangiform propulsion. The carangiform motion is modeled as a serial $N$-joint oscillating mechanism that is composed of two basic components: the streamlined fish body represented by a planar spline curve and its lunate caudal tail by an oscillating foil. The speed of fish's straight swimming is adjusted by modulating the joint's oscillatory frequency, and its orientation is tuned by different joint's deflections. The experimental results showed that the proposed simplified propulsive model could be a viable candidate for application in aquatic swimming vehicles.

For conventional designs of robots, manipulator motions result in forces and moments on the base. These forces and moments may cause undesirable translation and rotation of the base. The objective of this paper is to systematically analyze the fundamentals of reactionless robots. Based on this analysis, a design of one distinct class of spatial robot is proposed. The design is achieved through appropriate choices of geometric and inertial parameters. Due to the underlying conservation laws, the trajectory must satisfy additional constraints. We illustrate the reactionless feature of this robot through computer simulations. We are also fabricating reactionless robots to illustrate the underlying concepts.

In this study, a new approach of adaptive control law for controlling robot manipulators using the Lyapunov based theory is derived, thus the stability of an uncertain system is guaranteed. The control law includes a PD feed forward part and a full dynamics feed forward compensation part with the unknown manipulator and payload parameters. The novelty of the obtained result is that an adaptive control algorithm is developed using trigonometric functions depending on manipulator kinematics, inertia parameters and tracking error, and both system parameters and adaptation gain matrix are updated in time.

For robotic manipulators that are redundant or with high degrees of freedom (dof), an analytical solution to the inverse kinematics is very difficult or impossible. Pioneer 2 robotic arm (P2Arm) is a recently developed and widely used 5-dof manipulator. There is no effective solution to its inverse kinematics to date. This paper presents a first complete analytical solution to the inverse kinematics of the P2Arm, which makes it possible to control the arm to any reachable position in an unstructured environment. The strategies developed in this paper could also be useful for solving the inverse kinematics problem of other types of robotic arms.

In this paper, jamming analyses of the three dimensional dual peg-in-hole are presented. First, for a three dimensional dual peg-in-hole, possible contact states are enumerated and geometric analyses are presented. Second, the contact forces are described by the screw theory in three dimensions. The force/moment equations for static equilibrium states of three dimensional dual-peg insertions are derived. Third, jamming diagrams are obtained. Eleven kinds of possible jamming diagrams are analyzed. Finally, an experiment of a dual peg-in-hole assembly is presented to show the effectiveness of the above analyses.

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.

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.

In part I of this paper (previous issue of Robotica) a dual stage system with the coarse and fine actuators is adopted to achieve sub-micron accuracy with a large working space for the proposed new three degree-of-freedom (DOF) miniaturized micro parallel mechanism with high mobility and one type of the architecture with vertical actuator locations in all three legs (C-VV type) among six possible coarse actuator architectures is selected for the coarse actuator architecture.

In this part of the paper, an optimal kinematic parameter set is determined for the selected coarse actuator architecture. To determine this set, the design tool of the physical model of the solution space (PMSS) and the evaluation of the conditioning index (CI) and global mobility conditioning index (GMCI) are used. The basic size of the micro parallel mechanism is 45.0 mm×22.5 mm×22.9 mm with 100° mobility, the workspace 5.0 mm (y-axis)×5.0 mm (z-axis), and sub-micron resolution. After finishing the design of the main coarse actuator architecture, one architecture among six possible fine actuator architectures is selected to achieve sub-micron positioning accuracy based on the requirements of the continuous fine motion and smaller platform resolution. The selected coarse-and-fine actuator combination is used for the micro positioning platform for laser-machining application.