Whisking with robots

This article summarizes some of the key features of the rat vibrissal system, including the actively controlled sweeping movements of the vibrissae known as whisking, and reviews the past and ongoing research aimed at replicating some of this functionality in biomimetic robots.     

Meaningful conversation with mobile robots

We describe an implementation integrating a complete spoken dialogue system with a mobile robot, which a human can direct to specific locations, ask for information about its status and supply information about its environment. The robot uses an internal map for navigation, and communicates its current orientation and accessible locations to the dialogue system using a topological map as interface. We focus on linguistic and inferential aspects of the human–robot communication process. The result is a novel approach using a principled semantic theory combined with techniques from automated deduction applied to a mobile robot platform. Due to the abstract level of the dialogue system, it is easily portable to other environments or applications.     

On controlling robots with redundancy

Recently there has been considerable interest in increasing the applicability and utility of robots by developing manipulators which possess kinematic and/or actuator redundancy. This paper presents a unified approach to controlling these redundant robots. The proposed control system consists of two subsystems: an adaptive position controller which generates the Cartesian-space control force FR^m required to track the desired end-effector position trajectory, and an algorithm that maps this control input to a robot joint torque vector TRⁿ. The F → T map is constructed so that the robot redundancy (kinematic and/or actuator) is utilized to improve the performance of the robot. The control scheme does not require knowledge of the complex robot dynamic model or parameter values for the robot or the payload. As a result, the controller is very general and is computationally efficient for on-line implementation. Computer simulation results are given for a kinematically redundant robot, for a robot with actuator redundancy, and for a robot which possesses both kinematic and actuator redundancy. In each case the results demonstrate that accurate end-effector trajectory tracking and effective redundancy utilization can be achieved simultaneously with the proposed scheme.     

Force control of robots with nonlinearities

This paper explores two practical issues related to the force control of manipulators. The first issue examined is how system stability is effected by commonly occurring manipulator nonlinearities, such as sampled-data, control signal saturation and slip-stick friction. It is shown that discretely implemented force control algorithms can drive the feedback force controlled manipulator into a limit cycle, even for a very small sampling period that by far satisfies Shannon's sampling theorem. The bounds of stability are enhanced by the presence of control signal saturation and slip stick friction. The second issue investigated is the inclusion of a high gain inner position loop as a means to minimize the unpredictability in the steady state error due to slip-stick friction. In order to support the theoretical conclusions, experiments were performed with the PUMP 560 industrial robot testbed facility developed at Colorado State University.     

Studying laughter in combination with two humanoid robots

To let humanoid robots behave socially adequate in a future society, we started to explore laughter as an important para-verbal signal known to influence relationships among humans rather easily. We investigated how the naturalness of various types of laughter in combination with different humanoid robots was judged, first, within a situational context that is suitable for laughter and, second, without describing the situational context. Given the variety of human laughter, do people prefer a certain style for a robot??s laughter? And if yes, how does a robot??s outer appearance affect this preference, if at all? Is this preference independent of the observer??s cultural background? Those participants, who took part in two separate online surveys and were told that the robots would laugh in response to a joke, preferred one type of laughter regardless of the robot type. This result is contrasted by a detailed analysis of two more surveys, which took place during presentations at a Japanese and a German high school, respectively. From the results of these two surveys, interesting intercultural differences in the perceived naturalness of our laughing humanoids can be derived and challenging questions arise that are to be addressed in future research.     

Forming tile shapes with simple robots

Natural Computing - Motivated by the problem of manipulating nanoscale materials, we investigate the problem of reconfiguring a set of tiles into certain shapes by robots with limited computational...     

Stepping over obstacles with humanoid robots

The wide potential applications of humanoid robots require that the robots can walk in complex environments and overcome various obstacles. To this end, we address the problem of humanoid robots stepping over obstacles in this paper. We focus on two aspects, which are feasibility analysis and motion planning. The former determines whether a robot can step over a given obstacle, and the latter discusses how to step over, if feasible, by planning appropriate motions for the robot. We systematically examine both of these aspects. In the feasibility analysis, using an optimization technique, we cast the problem into global optimization models with nonlinear constraints, including collision-free and balance constraints. The solutions to the optimization models yield answers to the possibility of stepping over obstacles under some assumptions. The presented approach for feasibility provides not only a priori knowledge and a database to implement stepping over obstacles, but also a tool to evaluate and compare the mobility of humanoid robots. In motion planning, we present an algorithm to generate suitable trajectories of the feet and the waist of the robot using heuristic methodology, based on the results of the feasibility analysis. We decompose the body motion of the robot into two parts, corresponding to the lower body and upper body of the robot, to meet the collision-free and balance constraints. This novel planning method is adaptive to obstacle sizes, and is, hence, oriented to autonomous stepping over by humanoid robots guided by vision or other range finders. Its effectiveness is verified by simulations and experiments on our humanoid platform HRP-2.     

Motion planning of walking robots in environments with uncertainty

We present a general approach for coordinating the legs of a multi-legged statically stable walking machine on an uneven terrain. We are interested in an optimized motion plan for several “body-lengths” that specifies the footholds and the gait of the walking machine. We assume that a terrain map is available but that this map may be characterized by uncertainty. We also assume that the optimality of the motion plan can be measured by a suitable metric. The method of ordinal optimization is used to find a motion plan that is guaranteed to be in a desired percentile with a given confidence level. Depending on the available computational resources we can improve our confidence level and/or get closer to the optimal plan. Finally, our approach allows us to trade off speed with safety and speed with optimality. ©1999 John Wiley & Sons, Inc.     

Holonomy in mobile robots

The search for a simple and accurate odometry is a main concern when working with mobile robots. This article presents a general analysis of the problem and proposes a particular solution to improve the odometry. The three crucial kinematical aspects of mobile robots (mobility, control, and positioning) are reviewed in detail for vehicles based both in conventional and in omnidirectional wheels. The latter case is more suitable from a maneuvering point of view as it provides the robot frame with the three Degrees Of Freedom (DOF) of plane motion without singular configurations. Moreover, a suitable design of the omnidirectional wheels leads to a strictly invariant Jacobian matrix and thus to a linear control equation with constant coefficients. It is shown that such vehicles may have a holonomic behavior when moving under suitable kinematical restrictions without constraining their trajectory. In that case, the odometry is algebraic (instead of integrative) and thus more accurate. An application case is presented.     

Social interaction with robots: three questions

Robots are coming into different spheres of our daily lives, and therefore it is important that we now reflect systematically and in a comprehensive and inclusive way on the effects this may have on human interactions with other people and with machines. In Delmenhorst we held the conference “Going beyond the Laboratory.” Reflecting on the discussions of the conference, the editorial team realized a conceptual gap between the engineering sciences on the one hand and the social sciences and philosophy on the other hand. In order to initiate first steps in the direction of overcoming this divide, the editorial team decided to put forth three questions crucial for the issue of social interaction with robots and collected answers by experts in different robotics research projects. The questions are: How are we to understand the term robot autonomy in robotics and in social life? How is the idea of robot autonomy related to the limits of mathematization? I.e. is it possible, to fully express mathematically processes of social interaction? And finally, how are interactions between humans and robots in everyday life related to social institutions on a micro- and macro-level?     

Autonomous stair-climbing with miniature jumping robots.

The problem of vision-guided control of miniature mobile robots is investigated. Untethered mobile robots with small physical dimensions of around 10 cm or less do not permit powerful onboard computers because of size and power constraints. These challenges have, in the past, reduced the functionality of such devices to that of a complex remote control vehicle with fancy sensors. With the help of a computationally more powerful entity such as a larger companion robot, the control loop can be closed. Using the miniature robot's video transmission or that of an observer to localize it in the world, control commands can be computed and relayed to the inept robot. The result is a system that exhibits autonomous capabilities. The framework presented here solves the problem of climbing stairs with the miniature Scout robot. The robot's unique locomotion mode, the jump, is employed to hop one step at a time. Methods for externally tracking the Scout are developed. A large number of real-world experiments are conducted and the results discussed.     

Cricket-based robots

This article describes the development of an autonomous hybrid microrobot that uses legs for propulsion and support of the rear half of the body and a pair of wheels for support of the front half. McKibben artificial muscles actuate the legs, and compressed air is generated by an onboard power plant. Control is also onboard in the form of a PIC microcontroller, from Microchip Technology Inc., that controls the actuators through four three-way valves that are each made up of a pair of microelectromechanical system devices. Its motion resembles that of a cricket.     

Self-reconfigurable robots

In this article, the concept of a cellular robot that is capable of reconfiguring itself is reviewed. This "self-reconfigurable (SR) robot" exemplifies a new trend in robotics, indeed, we can now build various kinds of SR robots with off-the-shelf technologies of processors, actuators, and sensors. These SR robots, based on modern mechatronics, are still not as adaptable as the liquid metal robot in The Terminator 2 but are just as flexible as any conventional robots     

Scalable and practical pursuit-evasion with networked robots

In this paper, we consider the design and implementation of practical pursuit-evasion games with networked robots, where a communication network provides sensing-at-a-distance as well as a communication backbone that enables tighter coordination between pursuers. We first develop, using the theory of zero-sum games, an algorithm that computes the minimal completion time strategy for pursuit-evasion when pursuers and evaders have same speed, and when all players make optimal decisions based on complete knowledge. Then, we extend this algorithm to when evader are significantly faster than pursuers. Unfortunately, these algorithms do not scale beyond a small number of robots. To overcome this problem, we design and implement a partition algorithm where pursuers capture evaders by decomposing the game into multiple multi-pursuer single-evader games. We show that the partition algorithm terminates, has bounded capture time, is robust, and is scalable in the number of robots. We then describe the design of a real-world mobile robot-based pursuit evasion game. We validate our algorithms by experiments in a moderate-scale testbed in a challenging office environment. Overall, our work illustrates an innovative interplay between robotics and communication.     

Exponential stabilization of mobile robots with nonholonomicconstraints

An exponentially stable controller for a two-degree-of-freedom robot with nonholonomic constraints is presented. Although this type of system is open-loop controllable, this system has been shown to be nonstabilizable via pure smooth feedback. A particular class of piecewise continuous controllers is shown to exponentially stabilize the mobile robot about the origin. This controller has the characteristic of not requiring infinite switching like other approaches, such as the sliding controller. Simulation results are presented     

Cooperative manipulation and transportation with aerial robots

In this paper we consider the problem of controlling multiple robots manipulating and transporting a payload in three dimensions via cables. We develop robot configurations that ensure static equilibrium of the payload at a desired pose while respecting constraints on the tension and provide analysis of payload stability for these configurations. We demonstrate our methods on a team of aerial robots via simulation and experimentation.