In this paper we present an approach to robot arm control based on exploiting the dynamical properties of a simple neural network oscillator circuit coupled to the joints of an arm. The entrainment and input/output properties of the oscillators are used to perform a variety of tasks with the same architecture, without any modeling of the arm or its environment. The approach is implemented on two real robot arms, and has been used to tune into the resonant frequency of pendulums, perform multi-joint coordinated motion by turning cranks, and exploit the dynamics of a `Slinky' toy to coordinate the motion of two arms. By exploiting the coupling between the physical arm and the neural oscillator, a range of complex behaviors can be achieved with a very simple system. Keywords: Oscillator, Neural control, Neural network, Robot Manipulator, Rhythmic movement. Neural Control of Rhythmic Arm Movements 2 1 Introduction This paper describes the properties of a set of simple neural network os...

Our previous work has demonstrated how biologicallyinspired behaviors can serve as an effective substrate for control, representation, and learning in mobile robots and multi-robot systems, in order to generate adaptive individual and group behavior. In this paper, we expand the behavior-based approach to the domain of manipulator control, and demonstrate first results in applying biological inspiration to a 20 degree-offreedom humanoid dynamical torso simulation. 1. Introduction Behavior-based systems take inspiration from biology, ethology, and neuroscience, in order to construct controllers for agents situated in noisy and dynamic environments (Matari'c 1997). Behaviors impose a distributed, bottom-up approach to control, which eliminates bottlenecks and enables emergent functionality (Steels 1994). Aside from its pragmatic role in achieving distributed, real-time control in robotics, the behaviorbased framework has also been used to model and implement simulations of biol...

In this thesis, we investigate modeling, control, and coordination of mobile manipulators. A mobile manipulator in this study consists of a robotic manipulator and a mobile platform, with the manipulator being mounted atop the mobile platform. A mobile manipulator combines the dextrous manipulation capability offered by fixed-base manipulators and the mobility offered by mobile platforms. While mobile manipulators offer a tremendous potential for flexible material handling and other tasks, at the same time they bring about a number of challenging issues rather than simply increase the structural complexity. First, combining a manipulator and a platform creates redundancy. Second, a wheeled mobile platform is subject to nonholonomic constraints. Third, there exists dynamic interaction between the manipulator and the mobile platform. Fourth, manipulators and mobile platforms have different bandwidths. Mobile platforms typically have slower dynamic response than manipulators. The objectiv...

This paper presents an approach to robot arm control based on exploiting the dynamical properties of an adaptive oscillator circuit coupled to the joints of an arm. The approach is implemented on a real robot arm, and swings pendulums at their natural frequencies, turns cranks and manipulates slinky toys. These actions are all achieved using the same architecture, without any modeling of the arm or its environment. The simple nature of the oscillators, and the lack of modeling results in a robust and very simple system. 1 Introduction This paper presents an approach to the control of robot arms which exploits the physical coupling of the arm and its environment. Dynamical characteristics of the arm are exploited rather than modeled, allowing a very simple control scheme to exhibit a variety of interesting rhythmic behaviors. The system is implemented on the arms of the humanoid robot Cog [ Brooks and Stein, 1994 ] , which is illustrated in Figure 1. Robot arms are complex systems, wit...

An internal force-based impedance control scheme for cooperating manipulators is introduced which controls the motion of the objects being manipulated and the internal force on the objects. The controller enforces a relationship between the velocity of each manipulator and the internal force on the manipulated objects. Each manipulator is directly given the properties of an impedance by the controller, thus, eliminating the gain limitation inherent in the structure of previously proposed schemes. The controller uses the forces sensed at the robot end effectors to compensate for the effects of the objects' dynamics and to compute the internal force using only kinematic relationships. Thus, knowledge of the objects' dynamics is not required. Stability of the system is proven using Lyapunov theory and simulation results are presented validating the proposed concepts. The effect of computational delays in digital control implementations is analyzed vis-a-vis stability and a lower bound der...

This paper presents a complete overview of basic strategies that have been proposed for force control of robot manipulators. First, the model of the plant to be controlled is reviewed. Next, the strategies are divided into force-based and position-based categories, according to previously reported implementations. Each of the controller types within these categories are analyzed, and predictions of stability and efficacy are made. Then it is shown that these two categories are actually the same, and this recognition leads to the concept of a novel second order low pass filter controller. Finally, all of the controllers are experimentally tested on the CMU DD Arm II , confirming the theoretical predictions. Among the important results presented is the conclusive demonstration for the first time that integral gain control is the best basic strategy for force control of manipulators. 1 Introduction Many automation tasks require manipulators to interact with their environments. Necessary ...

This paper discusses computational and experimental details necessary for successfully implementing and evaluating a wide variety of force control strategies. First, a review of both explicit force and impedance control strategies is provided. Second, the basic computational requirements of these schemes are discussed, and the hardware and timing information for our implementation is provided. Third, computational problems such as noise filtering and sampling rates are explained and discussed in detail. Finally, a review of the experimental results obtained is provided. These results support the previous discussions by demonstrating the importance of fully considering the implementational details required for successful force control of robotic manipulators.

This paper presents an approach to robot arm control based on exploiting the dynamical properties of a simple oscillator circuit coupled to the joints of an arm. Using the same architecture, a wide variety of tasks can be achieved without any explicit modeling of the arm or its environment. The inherent properties of the oscillators give robustness to perturbations and changes in frequency. The approach is implemented on two compliant arms, and is demonstrated to swing pendulums at their natural frequencies, turn cranks and manipulate 'Slinky' toys.

In multimodal tele-cooperation as considered in this paper two humans in distant locations jointly perform a task requiring multimodal including haptic feedback. One human operator teleoperates a remotely placed humanoid robot which is collocated with the human cooperator. Time delay in the communication channel as destabilizing factor is one of the multiple challenges associated with such a tele-cooperation setup. In this paper we employ a control architecture with forceposition exchange accounting for the admittance type of the haptic input device and the telerobot, which both are positionbased admittance controlled. Llewellyn’s stability criteria are employed for the parameter tuning of the virtual impedances in the presence of time delay. The control strategy is successfully validated in an intercontinental tele-cooperation experiment with the humanoid telerobot HRP-2 located in Japan/Tsukuba and a multimodal human-system-interface located in Germany/Munich, see also the corresponding video submission. The proposed setup gives rise to a large number of exciting new research questions to be addressed in the future.

. In robotic tasks where the manipulator has to make transition from free space motion to constrained one, there always exists a inevitable phase transition. A number of controllers have been proposed in the literature with various discussions on their practical implications. In this paper for the first time a novel framework for studying design of controllers for robotic contact tasks problem is proposed. This framework presents a natural set-up to study the performance of controller. The method of this paper combines the embedded passive compliant properties of the interacting system (i.e. manipulator and the contacting environment) with the basic controller to achieve the hybrid bounce-less property. Here the interacting environment is used as a natural switching surface for the discontinuous controller. The application of the proposed framework is demonstrated through experimental results. Key Words. Robotic, contact tasks, discontinuous controller, differential inclusions, stabil...