Haptic feedback is proposed in sewing machine operations with the objective of reducing errors in seam allowance. Similar to the lane departure warning system in modern cars, such modality of feedback is expected to alert the operator in real-time and improve the performance of the human control system. A traditional sewing machine was outfitted with a camera, a single board computer, and an eccentric motor. Experimental results demonstrate the potential for deployment of such systems in apparel manufacturing industries and provide opportunities for greater inclusion of people with disabilities in the workforce.

This paper explores a novel approach to model strategies for flattening wrinkled cloth learning from humans. A human participant study was conducted where the participants were presented with various wrinkle types and tasked with flattening the cloth using the fewest actions possible. A camera and Aruco marker were used to capture images of the cloth and finger movements, respectively. The human strategies for flattening the cloth were modeled using a supervised regression neural network, where the cloth images served as input and the human actions as output. Before training the neural network, a series of image processing techniques were applied, followed by Principal Component Analysis (PCA) to extract relevant features from each image and reduce the input dimensionality. This reduction decreased the model's complexity and computational cost. The actions predicted by the neural network closely matched the actual human actions on an independent data set, demonstrating the effectiveness of neural networks in modeling human actions for flattening wrinkled cloth.

Stabilization of an equilibrium point is an important control problem for underactuated systems. For a given control design, the ability of the system to remain stable in the presence of disturbances depends on the size of the region of attraction of the stabilized equilibrium. The sum of squares and trajectory reversing methods are combined together to generate a large estimate of the region of attraction. Then, this estimate is effectively enlarged by applying the impulse manifold method, which can stabilize equilibria from points lying outside the estimated region of attraction. In this paper, the generality of the approach is demonstrated using simulations of a three-link underactuated system. Experimental validation using the pendubot is provided to demonstrate the feasibility of practical implementation.

Children with severe motor impairments require the use of assistive devices to perform activities of daily living. Brain-machine interfaces are not suited for children due to various factors such as surgical risks. In this paper, we present a non-invasive body-machine interface where upper body movements are recorded by wireless inertial measurement units (IMUs) and used to control a robot arm. We develop a novel approach, called the virtual body model (VBM), which allows for control of high number of degrees-of-freedom (DOF). Our results show that participants could use the VBM to control up to five DOFs of a robot arm, and perform a pick-and-place task. Even with minimal training, trajectories of the end effector were smooth and positioning was accurate. These results show the potential of this safe, non-invasive approach to control high DOFs in children.

The spring loaded inverted pendulum (SLIP) model is commonly used to describe the dynamics of hopping robots. Based on this model, the control of hopping robots has been widely investigated. A fundamental limitation of the model is that it fails to account for impact with the ground, and this is due to its single degree-of-freedom in the vertical direction. A more accurate representation of the hopping robot is proposed using a two mass model and inelastic impact with the ground. A control scheme is developed to converge the maximum jumping height of the robot to a desired value. The control scheme utilizes feedback linearization in continuous time and updates a control parameter in discrete time to achieve the control objective. Simulation results are presented to show the efficacy of the control scheme.

Bipedal robots have the potential to provide robust locomotion over uneven terrain and its dynamic stability has been shown to be analogous to that of a spring loaded inverted pendulum (SLIP). The SLIP model is fundamentally limited in its ability to accurately represent legged locomotion since it does not take into account the impulsive dynamics of foot ground interaction. In this paper we investigate the control of a four-link hopping robot based on the complete dynamics of the system. Using partial feedback linearization to control the configuration in continuous time, and discrete parameter variations the control object of apex height control of the robot is achieved. Simulation results are presented to show the efficacy of the control scheme.

We have developed a novel type of submersible called a Synergistically Propelled Ichthyoid [SPI] which is propelled by the combined jet action and oscillatory motion of a fluttering fluid-conveying tail. Two dynamic models for an SPI are presented and solved. An analytically tractable model presented in a previous work which assumes a submersible at constant velocity has been included as a reference point. A more complex model in a general planar reference frame is also presented and is solved numerically. These simulations show a benefit to using a fluttering tail relative to a dimensionally identical rigid tail. Results which show that the SPI can be turned by an appropriate choice of time-variable fluid velocity are also presented. Construction details of an experimental realization are provided. Preliminary measurements taken using that platform are also provided; these measurements qualitatively confirm the simulation's conclusion that a fluttering flexible tail is capable of higher speed than a dimensionally identical rigid tail.

We present the design and control of a simple three-link underactuated synthetic wheel biped composed of a torso and two legs with arc-shaped feet. The equations of motion are derived and a controller based on feedback linearization is used to constrain the controllable degrees of freedom and develop a simple gait. Experimental results show successful gait generation and relatively good trajectory tracking. The data on energy consumption indicates a reasonably low cost of transport, even without design or trajectory optimization.

Impedance and Admittance Control are two distinct implementations of the same control goal. It is well known that their stability and performance properties are complementary. In this paper, we present a hybrid system approach, which incorporates Impedance and Admittance Control as two extreme cases of one family of controllers. This approach allows to continuously switch and interpolate between Impedance and Admittance Control. We compare the basic stability and performance properties of the resulting controllers by means of an extensive case study of a one-dimensional system and present an experimental evaluation using the KUKA-DLR-lightweight arm.

The design of a new biped robot is proposed. Based on the concept of a self-propelled wheel, the design eliminates vertical impact forces from the ground during walking. The biped comprises a torso and two legs. With arc-shaped feet, each leg is constrained to move in a manner that allows the robot to walk by rolling alternately on its two feet. The purpose of the torso is to generate motion through unbalance. The mathematical model of the robot is developed, and constraints are imposed to generate simple walking gaits. A hardware prototype of the biped was fabricated, and a controller was designed to generate one specific gait. This gait results in horizontal impulsive forces at the time of touchdown of the swing leg and the effect of these forces is studied through experiments. The experimental results of the biped successfully walking down a hallway are presented.

The standard control problem of the pendubot refers to the task of stabilizing its equilibrium configuration with the highest potential energy. Linearization of the dynamics of the pendubot about this equilibrium results in a completely controllable system and allows a linear controller to be designed for local asymptotic stability. For the underactuated pendubot, the important task is, therefore, to design a controller that will swing up both links and bring the configuration variables of the system within the region of attraction of the desired equilibrium. This paper provides a new method for swing-up control based on a series of rest-to-rest maneuvers of the first link about its vertically upright configuration. The rest-to-rest maneuvers are designed such that each maneuver results in a net gain in energy of the second link. This results in swing-up of the second link and the pendubot configuration reaching the region of attraction of the desired equilibrium. A four-step algorithm is provided for swing-up control followed by stabilization. Simulation results are presented to demonstrate the efficacy of the approach.

The standard control problem of the pendubot refers to the task of stabilizing its equilibrium configuration with the highest potential energy. Linearization of the dynamics of the pendubot about this equilibrium results in a completely controllable system and allows a linear controller to be designed for local asymptotic stability. For the under-actuated system, the important task is therefore to design a controller that will swing up both links and bring the configuration variables of the system within the region of attraction of the desired equilibrium. This paper provides a method for swing-up control based on a series of rest-to-rest maneuvers of the first link about its vertically upright configuration. The rest-to-rest maneuvers are designed such that each maneuver results in a net gain in energy of the second link. This results in swing-up of the second link and the pendubot configuration reaching the region of attraction of the desired equilibrium. A four-step algorithm is provided for swing-up control followed by stabilization. Simulation results are presented to demonstrate the efficacy of the approach.

This paper presents our development of a network-enabled human/robot cooperative interface for tele- diagnostics of breast pathology. To enhance telepresence capabilities, our human/robot interface is comprised of an anthropomorphic arm/hand equipped with haptic and tactile sensing, ultrasound imaging capabilities, a physician interface capable of rendering both haptic and tactile information, and two-way audio and video. This cooperative and multimedia interface was tested via the Internet and enables tele-diagnostics. Preliminary experiments had demonstrated the effectiveness of the developed human/robot tele-diagnostic interface. That is, it will greatly enhance and improve the diagnostic performance as well as promote the tele-diagnostics of breast pathology in remote areas a reality.

A robotic device with haptic, tactile, and ultrasound capabilities, which can acquire and render information of breast pathology was developed. A physician interface that can examine the human breast remotely and accurately, using such a robotic device was also developed. Such a robotic device can be used to do screening or focused breast exams for patients in remote areas without convenient access to physicians. Because of in-situ ultrasound imaging, examination by the robotic device may prove to be more accurate than examination by the physicians own hand. In addition, the robotic device can also be used to train healthcare professionals in breast pathology

As robots become more human-centric it is envisioned that they will provide greater assistance to the elderly in long term care facilities. With the objective of transporting the elderly within the bounds of long term care facilities, a single arm is designed for a holonomic mobile robot such that the robot can push and steer wheel chairs along predefined trajectories. The associated control problem of pushing and steering wheelchairs is also addressed where it is assumed that the mass of the wheelchair and its friction characteristics are not known. Simulation results demonstrate the feasibility of the design and the control strategy

This paper presents a fuzzy control system that incorporates sensing, control and planning to improve the performance of the wall-climbing microrobots in unstructured environments. After introduction of the robot system, a task reference method is proposed which is based on a fuzzy multisensor data fusion scheme. The method provides a novel mechanism to efficiently integrate task scheduling, action planning and motion control in a unified framework. A robot gait generation method is described which switches the robot locomotion between different motion modes with the help of a finite state machine driven by sensory information. A fuzzy motion controller is designed to improve control performance and reduce power consumption by the suitable selection of fuzzy sets and inference methods, as well as the definition of corresponding membership functions and control rule bases. A fuzzy logic compensator is developed to compensate the gravitational effects according to different robot configurations and task situations. Experimental results prove the validity of the proposed methods.

In this paper we discuss the problem of reconfiguring a sphere, rolling without slipping on a flat surface, from an arbitrary initial configuration to a desired final configuration. We propose a control algorithm that utilizes two control actions that are applied alternately. The individual control actions cause trajectories that are circular arcs and straight line segments. Through judicious choice of the sequence of individual control actions based on state feedback, we construct a control strategy that stabilizes the sphere to its desired configuration. Simulation results are presented to demonstrate the efficacy of the strategy.

This paper presents the modeling and control of our second generation prototype miniature crawler robot which was targeted to applications in constrained environments. The mechanical design and the drive mechanism of the robot are first discussed A kinematic model is then derived and the motion planning is analyzed. A description of the Texas Instrument DSP-based embedded controller is presented. Finally, experimental results are presented for evaluation of the robot performance.

The design, implementation, and evaluation of a miniature biped robot for urban reconnaissance are presented. Design specifications for mobility, space requirement weight, sensing, and control are defined. A revolute hip joint is selected based on its enhanced mobility and capability to function in reasonably confined spaces. Small size dictates minimal weight, which is achieved by an under actuated joint structure, providing steering at only one foot, minimizing sensors, and structural optimization. The smart robotic foot supports the robot on a variety of smooth surfaces and provides feedback when a firm grip is established. Adaptable control strategies and dithering are implemented in lieu of minimal sensors and uncertainty created by backlash, gravity, and compliance in the suction feet. The robot is evaluated while performing tasks on surfaces with a variety of inclinations.

The dynamic workspace and the motion plans for a micro biped walking robot are studied in the paper. The dynamic model and controller of an under-actuated walking robot system are developed. Two optimal navigation algorithms for the motion of the robot in the same plane without obstacles are developed, and optimality is proved. The motion of the robot is divided into normal motion status and transition status. The complete scheme to perform the two status and this real time implementation are presented. The dynamic simulation results and 2D-rendering of the robot navigation is given.

Presented here is the design of a mechanism for dexterous placement of an end-effector (forceps, scissors, dissectors) during minimally invasive surgery. The mechanism is best suited to function as a manipulator for a surgical robotics system where motion scaling and filtering of surgeon hand movements could be realized in a fashion to improve ergonomics. End-effector degrees of freedom in the form of actuation, bidirectional 180/spl deg/ articulation, and rotation are provided by a compact multilink structure comprised of gears and gear-links. This structure has been optimized to provide a large dexterous workspace, low backlash, small force magnification, excellent stiffness, load capacity and infinite life durability. These conditions are achieved through selection of link configuration, forceps design, optimal link thicknesses, gear profile design, and high strength steels.

A team of interdisciplinary researchers are involved in the development of a miniature biped robot that can traverse flat inclined surfaces such as walls and ceilings (R.L. Tummala et al., 1999). Unlike conventional biped robots, only limited degrees-of-freedom are available in the design. Thus the kinematics and workspace analyses become important for motion planning and control. The paper briefly discusses the mechanical structure and drive mechanism of the miniature robot. The kinematic model of the robot is then developed, and its workspace is analyzed in detail. Simulation results of the robot motion are also presented.

We address the configuration control problem in free-flying planar space robots. Such multibody systems are nonholonomic in nature due to conservation of angular momentum. We develop an almost smooth and time-invariant control strategy that guarantees Lyapunov stability and convergence of the states to the desired configuration. The controller suffers from a slow rate of convergence when the desired configuration is close to the locus of dynamic singularities. This problem can be remedied by modifying the controller, and two modified controllers are proposed in this paper. The stability of the desired configuration and convergence of closed loop system trajectories are mathematically established for the original controller. Simulations of the closed loop system have been carried out with the original controller and the modified controllers.

Redundant manipulators under pseudoinverse control are nonholonomic systems in general. The nonholonomy manifests itself when closed paths in the workspace of the manipulator fail to produce closed paths in the joint space. Previous research indicates that repeatability may be guaranteed if the initial manipulator configuration lies on a stable surface. In such cases repeatability is achieved due to the integrability of the nonholonomic constraints. Since stable surfaces are rare, we look into the design of holonomic loops that will guarantee repeatability in the absence of integrability. We present a necessary condition for the existence of holonomic loops and we design holonomic loops for redundant manipulators in three dimensions. The extension of our results to higher dimensional systems lies in the scope of our future research.

The angular momentum of a free-flying space robot is a conserved quantity. This conservation law acts as a nonholonomic constraint and manifests itself when cyclic motion of the joints of the space robot produces a change in the orientation of the whole system. Consequently closed trajectories in the joint space of the robot usually fail to produce closed trajectories in the workspace. In this paper the authors first show that there exist some closed paths that are "holonomic loops" in the sense that the nonholonomic space robot exhibits holonomic behavior globally on these trajectories. When the joints of the space robot move along these trajectories, the end-effector traces a closed curve in the workspace. In this paper, the authors present a simple method to plan such trajectories that produce repeatable motion of the space robot.>

Proposes to control the attitude of space structures using a serial three-link PUMA-type manipulator that can be mounted on the space structure. This unconventional method of attitude control exploits the nonholonomic nature of the constraints that arise due to the conservation of angular momentum. The author adopts a surface integral approach for manipulator motion planning that will reorient the space structure in any desired way. The salient features of the algorithm are (a) it is possible to mathematically prove the controllability of the system, (b) the motion of the manipulator can be planned amidst additional constraints like joint limits of the manipulator, and (c) the algorithm can be easily extended to flexible space structures.

Underactuated mechanisms will provide low-cost automation, easily overcome actuator failures, and be particularly useful for space applications because of their reduced mass and lower power consumption. In space underactuation can be effectively introduced in robot manipulators. Such mechanisms will however be difficult to control because of the fewer number of actuators in the system. It is shown that when the actuated joints do not have brakes, it is possible to bring the system to a complete rest and converge the actuated joints to their desired values, provided the system maintains zero momentum and none of the unactuated joints are cyclic coordinates. To converge both the actuated and the unactuated joints to their desired set of values, it is assumed that the number of actuated joints is more than the number of unactuated joints, and the unactuated joints have brakes. It is shown that if there exists sufficient dynamical coupling between the set of actuated and unactuated joints it is possible to converge all the manipulator joints to their desired values.>

Nonholonomic redundancy is an intrinsic property of nonholonomic mechanical systems. A free-flying space robot is a nonholonomic mechanical system, and exhibits the presence of nonholonomic redundancy even in the absence of ordinary kinematic redundancy. Like ordinary kinematic redundancy, nonholonomic redundancy can also be utilized while planning trajectories for the system. In the paper, a trajectory planning scheme for a 6-DOF space robot is developed in which nonholonomic redundancy for avoiding joint limits and obstacles is utilized.>

A free-flying space robot has kinematic and dynamic features different from those fixed on the Earth because of the momentum constraints that govern its motion. The authors present the solution to the inverse dynamics problem of a space robotic system in the presence of external generalized forces. While solving for the inverse dynamics, the computations for the inverse kinematics are considered simultaneously, and both computations are developed on the basis of momentum constraints. An efficient computational scheme for the inverse dynamics problem is then established. Space robotic systems have an intrinsic feature that can be utilized to reduce the computational time by parallel recursion. Finally, the scope of parallel recursion is discussed.>

A free-flying space robot for the construction and maintenance of space structures is considered. Such a robotic system has kinematic and dynamic features that differ from those fixed on the earth mainly because of the momentum constraints that govern its motion. The solution to the inverse dynamics problem of a space robotic system in the presence of external generalized forces is presented. The computations for the inverse kinematics are considered simultaneously, and both computations are developed on the basis of momentum constraints. An efficient computational scheme for the inverse dynamics problem is then established. An intrinsic feature of space robotic systems that can be utilized to reduce the computational time by parallel recursion is discussed, as is the importance of the role of momentum constraints in the solution of inverse dynamics.>

The path planning of nonholonomic motion of space robot systems is discussed. A space vehicle with a 6-DOF (degrees of freedom) manipulator is described as a nine-variable system with six inputs. It is shown that, by carefully utilizing the nonholonomic mechanical structure, the vehicle orientation in addition to the joint variables of the manipulator can be controlled by actuating only the joint variables. The nonholonomic mechanical structure of space robot systems is shown. A rigorous mathematical proof of the nonholonomic nature of the free-flying space robot systems is provided using Frobenius's theorem. A method for nonholonomic motion planning for space robot systems is established by using a Lyapunov function.>

The nonholonomic path planning of space robot systems is discussed. A space vehicle with a 6-DOF (degree of freedom) manipulator is described as a nine-variable system with six inputs. Utilizing the nonholonomic nature, the vehicle orientation can be controlled in addition to the joint variables of the manipulator by actuating only the joint variables, if the trajectory is carefully planned. A path-planning method of nonholonomic motion is developed using a Lyapunov function.>

The authors discuss the nonholonomic mechanical structure of a space robot and its path planning. The conservation of angular momentum works as a nonholonomic constraint, whereas the conservation of linear momentum is a holonomic one. In this framework a vehicle with a 6-DOF (six-degree-of-freedom) manipulator is described as a nine-variable system with six inputs. This implies the possibility of controlling the vehicle orientation as well as the joint variables of the manipulator by actuating the joint variables only if the trajectory is carefully planned, although both the variables and the trajectory cannot be controlled independently. In planning a feasible path, a system than consists of a vehicle and a 6-DOF manipulator can be treated as a 9-DOF kinematically redundant system. The nonholonomic mechanical structure of the space vehicle/manipulator system is shown, and a path planning scheme for nonholonomic systems using Lyapunov functions is proposed.>