An analysis of underactuated manipulators from both the dynamic and control points of view is presented. While the unactuated joints dynamic equation is recognized to be a nonholonomic constraint in the general case, necessary and su#cient conditions are given to identify special cases in which such a constraint is integrable. In contrast to most examples in the literature, the unactuated joints dynamics are an instance of second-order nonholonomic constraint. It is shown that smooth feedback stabilization to a single equilibrium point is not possible, and a feedback scheme providing stabilization to a manifold of equilibrium positions is proposed. 1. Introduction The control of nonholonomic mechanical systems, i.e. systems with non-integrable di#erential constraints on generalized coordinates, has attracted growing attention in recent years. Even if the existence of non-integrable constraints in a system is strictly a mechanical property, the control problem for nonholonomic systems...

. This paper explores a method of manipulating a planar rigid part on a conveyor belt using a robot with just one joint. This approach has the potential of offering a simple and flexible method for feeding parts in industrial automation applications. In this paper we develop a model of this system and of a variation which requires no sensing. We have been able to characterize these systems and to prove that they can serve as parts feeding devices for planar polygonal parts. We present the planners for these systems and describe our implementations. Key Words. Robotics, Manipulation, Mechanics, Planning, Minimalism, Automation, Manufacturing, Parts feeding. 1. Introduction. The most straightforward approach to planar manipulation is to use a rigid grasp and a robot with at least three joints, corresponding to the three motion freedoms of a planar rigid part, but three joints are not really necessary to manipulate a part in the plane. In this paper we achieve effective control of all t...

We are interested in using low degree-of-freedom robots to perform complex tasks by nonprehensile manipulation (manipulation without a form- or force-closure grasp). By not grasping, the robot can use gravitational, centrifugal, and Coriolis forces as virtual motors to control more degreesof -freedom of the part. The extra motion freedoms of the part are exhibited as rolling, slipping, and free flight.

The possibility of controlling humanoid robots in free-space opens new fields of application involving freefloating behaviors. Recently, we presented a prioritized taskoriented control framework for the control of multiple motion primitives while complying with physical constraints imposed by the robot's body and environment. We adapt here this framework to the control of free-floating robots.

Pairs of bodies with regular rigid surfaces rolling onto each other in space form a nonholonomic system of a rather general type, posing several interesting control problems of which not much is known. The nonholonomy of such systems can be exploited in practical devices, which is very useful in robotic applications. In order to achieve all potential benefits, a deeper understanding of these types of systems and more practical algorithms for planning and controlling their motions are necessary. In this paper, we study the controllability aspect of this problem, giving a complete description of the reachable manifold for general pairs of bodies, and a constructive controllability algorithm for planning rolling motions for dexterous robot hands. Index Terms---Nonholonomic systems, nonlinear controllability theory, robotic manipulation. I. INTRODUCTION N ON-HOLONOMIC systems have been attracting much attention in control literature recently, due to both their relevance to practical ap...

In this paper we study underactuated manipulator systems, which are composed of both active and passive joints. The study of underactuated systems is interesting for a variety of applications including space robots, hyperredundant robots, and mobile robots. When one or more joints in a normal manipulator system fail, control techniques for the resulting underactuated system can make use of dynamic coupling within the system for position control. In this paper, we define a performance measure for the motion of these underactuated manipulator systems. We call this performance measure actuability. Actuability is a measure of the ability of the actuators in a robot manipulator to cause acceleration of the end-effector. Based on this concept, we develop sensitivity analysis of the system's performance with respect to geometric and dynamics parameters of the robot. This investigation is significant for the design and control of an underactuated robot system. Contents 1 Introduction 1 2 Ac...

Underactuated manipulators are robot manipulators composed of both active and passive joints in serial chain mechanisms. The study of underactuation is significant for the control of a variety of rigid-body systems, such as free-floating robots in space and gymnasts, whose structure include passive joints. For mechanisms with large degrees of freedom, such as hyper-redundant snake-like robots and multi-legged machines, the underactuated structure allows a more compact design, weight decrease and energy saving. Furthermore, when one or more joints of a standard manipulator fail, it becomes an underactuated mechanism; a control technique for such system will increase the reliability and fault-tolerance of current and future robots. The goal of this study is to present a robust control method for the control of underactuated manipulators subject to modelling errors and disturbances. Because an accurate modelling of the underactuated system is more critical for control issues than it is fo...

The nonlinear motion of underactuated mechanisms has drawn recent interests of researchers. Underactuated mechanical systems are often subject to so-called nonholonomic constraints which are related to many both theoretical and practical issues. In this paper, we first analyze the nonlinear behavior of a twojoint planar manipulator with the second joint free, from nonlinear dynamics point of view. We then discuss the simultaneous positioning of both joints. We use a time-periodic input and propose an amplitude modulation of the feedback error. The analysis via the Poincar'e map shows that the behavior becomes chaotic with large amplitude. The effectiveness of the proposed positioning control are verified by experiments. I. Introduction Study of the nonlinearity of motion is a major common problem in many fields of robotics. In particular, the nonlinear motion of underactuated mechanisms has drawn recent interests of researchers. Underactuated mechanical systems are often subject to s...

iv The class of underactuated systems is composed of a variety of mechanical as well as biological systems. The term underactuation refers to the fact that not all joints or degreesof -freedom (DOFs) of the system are equipped with actuators, or are directly controllable. The DOFs of an underactuated system are dynamically coupled, and their dynamic equations are nonlinear and are constrained by nonholonomic differential equations. In this dissertation, it is our goal to study these fundamental characteristics toward the aim of developing modeling and control methods for underactuated systems, with focus on the class of serial chain underactuated manipulators with joints connected by rigid links.

In this paper we consider some new avenues that the design and control of versatile robotic end-effectors, or "hands", are taking to tackle the stringent requirements of both industrial and servicing applications. A point is made in favour of the so--called minimalist approach to design, consisting in the reduction of the hardware complexity to the bare minimum necessary to fulfill the specifications. It will be shown that to serve this purpose best, more advanced understanding of the mechanics and control of the hand--object system is necessary. Some advancements in this direction are reported, while few of the many problems still open are pointed out.