This research focuses on soft robotic bladders that are used to monitor and control the interaction between a user's head and the shell of a Smart Helmet. Compression of these bladders determines impact dissipation; hence the focus of this paper is sensing and estimation of bladder compression. An IR rangefinder-based solution is evaluated using regression techniques as well as a Neural Network to estimate bladder compression. A Hall-Effect (HE) magnetic sensing system is also examined where HE sensors embedded in the base of the bladder sense the position of a magnet in the top of the bladder. The paper presents the HE sensor array, signal processing of HE voltage data, and then a Neural Network (NN) for predicting bladder compression. Efficacy of different training data sets on NN performance is studied. Different NN configurations are examined to determine a configuration that provides accurate estimates with as few nodes as possible. Different bladder compression profiles are evaluated to characterize IR range finding and HE based techniques in application scenarios.

Maintaining lateral and longitudinal trajectory tracking accuracy is challenging for autonomous ground vehicles (AGVs). This paper considers kinematics and dynamics of longitudinal and lateral motion to form a novel composite structure considering the cross-impacts of acceleration and steering commands on tracking errors in the lateral and longitudinal directions, respectively. The multi-tiered structure uses backstepping with smooth robust control to iteratively map kinematics-based velocity and yaw rate commands to slip-yaw dynamics-based acceleration and steering commands. In kinematics, longitudinal tracking error is stabilized by sliding mode control (SMC) while variable structure control (VSC) stabilizes lateral tracking error and balances tracking accuracy and steering gracefulness. Backstepping extends these commands through vehicle dynamics to provide robust steering and acceleration commands. Cross impacts between lateral and longitudinal motion is addressed by vehicle modeling and controller designs. A robust observer is applied for sideslip estimation to reject uncertainties. Peaking from the high gain observer and robust control is addressed. Stability analysis is provided and field experiments on an open road demonstrate and validate effectiveness of the controllers.

Path following accuracy and error convergence with graceful motion in vehicle steering control is challenging due to the competing nature of these requirements, especially across a range of operating speeds. This work is founded upon slip-based kinematic and dynamic models, which allow derivation of controllers considering error due to sideslip and the mapping between steering commands and graceful lateral motion. A novel recursive backstepping steering controller is proposed that better couples yaw-rate based path following commands to steering angle and rate. Observer based sideslip estimates are combined with heading error in the kinematic controller to provide feedforward slip compensation. Path following error is compensated by a Variable Structure Controller (VSC) to balance graceful motion, path following error, and robustness. Yaw rate commands are used by a backstepping dynamic controller to generate robust steering commands. A High Gain Observer (HGO) estimates sideslip and yaw rate for output feedback control. Stability analysis is provided and peaking is addressed. Field experimental results evaluate the work and provide comparisons to MPC.

We design and test a 3 DoF parallel cable system capable of applying precise and accurate impulses to walking and running subjects for the University of Utah's Treadport Active Wind Tunnel (TPAWT). Using Nexus VICON motion capture and gait algorithms, perturbations can be applied at different points in the subject's gait. The use of a PID force controller allow the system to create omnidirectional perturbations with walking and running subjects while having the capability to vary amplitude and direction of perturbations. Analysis is presented of the workspace of the large treadmill to test whether the workspace available to activate these perturbations is safe. This paper reports the efficacy of the system and evaluates how warning a runner before impact may affect their displacement. Participants experienced 48 perturbations while running applied with a random combination of a front/back/left/right impact at either toe-off or mid-stance with or without warning. A two sample T-test reveals that warning a runner before impact significantly reduced the magnitude they were displaced for both toe-off (t(46) = 4.98 p<; .001) and mid-stance (t(46) = 3.44, p = .001).

With a growing number of applications in the world for UAVs, there is a clear limitation regarding the need for extended battery life. With the current flight times, many users would benefit greatly with an innovative option of field charging these devices. The objective of this project is to investigate feasibility of inductively harvesting energy from a power line cable for applications such as charging a UAV drone. Research investigates a dual hook perching device that securely attaches to a power cable and aligns an inductive core with the cable for harvesting energy from its electro-magnetic field. Modeling and analysis of the core highlights critical design parameters, leading to evaluation of circular, semi-cylindrical, and u-shaped prototypes designed to interface with a 1" power cable. Underactuated two jaw manipulators at each end of the coil are proposed for grasping the cable and aligning it with the charging coil, ultimately providing a firm grasp and perch. An open source hexacopter drone was used in this study to integrate with the charging novelty. The results provided can be used as a starting point to study the reliability of this method of charging and to further investigate perching abilities of UAVs.

The exploration of an “intelligent” orthotic shoe sole to negate, or minimize, longitudinal slip by momentarily increasing friction force is presented. The conceptual device takes the form of a rubberized shoe sole containing pockets of air that can be released via valves controlled by a microprocessor. During a slip event, the valves would be opened and the bladders would be collapsed by the weight of the user, which modulates contact and friction forces. The goal is to increase friction forces in this process, by creating an impact force between the user and ground surface, with the potential to increase friction and mitigate slip. Simulations of bladder walls, air flow through valves, contact forces, and friction forces are modeled and combined into a lumped parameter model to predict device behavior. Prototypes of the device are created and evaluated to validate models and slip-mitigating potential.

In this paper, a curvature-based control method capable of both forward and backward path following is developed for off-axle hitching trailers. Compared with earlier methods, this controller handles varying path curvature better while also being easy to implement and tune. The controller also addresses two major issues that deteriorate tracking accuracy: limited steering actuation and sideslip. An active speed limiter brakes the vehicle when the steering angle error is too high and therefore allows the same set of control gains to work across a relatively large range of reference speeds without significantly increasing lateral error or losing stability, which further simplifies controller tuning. An extended Kalman filter (EKF) sideslip estimator is designed to allow sideslip compensation, which considers the varying noise magnitude in GPS measurements caused by varying vehicle speeds so that the braking maneuver will not significantly deteriorate the estimations. To our knowledge, this paper presents the first publication of these two algorithms with trailer control. This method is compared with results from two earlier hitch-angle-based control methods in simulation and experiment. The active speed limiter and the EKF are also implemented on these control methods for fair comparison, during which it is found that the two algorithms can directly work with other control methods and benefit their performance. The results show the curvature-based controller provides better maneuverability and reduced tracking error.

Much research has been done recently on getting various UAVs to perch on various surfaces, however very little research has looked at how to detect when this perch has failed, especially when the surface the UAV is perched on is moving. This paper proposes a method to detect these types of falls using the Instantaneous Center of Rotation (ICR) of the UAV. Two methods are proposed to calculate this ICR, one based on integrating accelerometers to get velocities at various points on the UAV, the other based on using the magnitude of the acceleration at these points to estimate the distance to the ICR from that point. These methods provide a way to detect a fall from a moving perch that should work with different types of perching mechanisms and perches, while requiring minimal additional hardware on the UAV.

This paper presents the Treadport Active Wind Tunnel (TPAWT)-a full-body immersive virtual environment for the Treadport locomotion interface designed for generating wind on a user from any frontal direction at speeds up to 20 kph. The goal is to simulate the experience of realistic wind while walking in an outdoor virtual environment. A recirculating-type wind tunnel was created around the pre-existing Treadport installation by adding a large fan, ducting, and enclosure walls. Two sheets of air in a non-intrusive design flow along the side screens of the back-projection CAVE-like visual display, where they impinge and mix at the front screen to redirect towards the user in a full-body cross-section. By varying the flow conditions of the air sheets, the direction and speed of wind at the user are controlled. Design challenges to fit the wind tunnel in the pre-existing facility, and to manage turbulence to achieve stable and steerable flow, were overcome. The controller performance for wind speed and direction is demonstrated experimentally.

Tracking accuracy in ground vehicle path following is an important topic addressed by vehicle steering control. While several controllers exist, this controller aims to provide improved path following while cornering on sloped terrain. Towards this goal, this work develops a new kinematic controller that considers the effect of slip and a new dynamic controller that better compensates modelling error and actuator disturbances. The kinematic controller uses a new kinematic model and applies backstepping architecture with variable structure control manifolds to assure smooth and graceful yaw rate commands. The dynamic controller is also based upon backstepping, but introduces integrator states to the architecture and derives a new controller to improve yaw rate tracking. Simulations and field experiments demonstrate resulting performance improvements, which are compared to prior work to highlight contributions of this work.

Haptic terrain display in Virtual Environments is important for increasing realism and immersion. While several terrain display devices exist, the Smart Shoe aims to render subtle terrain features while still being able to accommodate gross features, like sloped terrain. The compactness and portability of this haptic wearable device allows it to not only display terrain features on flat treadmill surface, but also potentially be able to compensate terrain unevenness to maintain level ankle posture for rehabilitation purposes. A novel elastomer based bladder system is designed to provide elasticity and support of the Smart Shoe. A mechatronic top plate is made by molding electronics and miniature solenoid valves into rubber material, providing sensing and control of pressure and height of the shoe. Evaluations of the Smart Shoe indicate promises to improve the haptic perception of different terrain features in a virtual environment.

Graceful motion in vehicle steering is an important issue. Generally, this problem can be solved by controller design or planning a path in a real time. However, it may need the system to carry on more computing effort or make a compromise between the tracking accuracy and motion smoothness. In this paper, a multi-tiered model based steering control strategy is proposed for considering vehicle kinematics and dynamics simultaneously. In this strategy, the kinematic controller applies motion trajectory generation as basis to produce a set of hierarchal manifolds that gradually converge tracking errors by providing softer yaw rate commands. To minimize steady-state error caused by path curvature discontinuity, an integrator is embedded to these manifolds. A robust output feedback dynamic controller is designed to reject modeling errors and disturbances caused by side slip estimation from a robust observer. Steering rate is applied as the control input by considering steering actuator capabilities to replace traditional steering angle commands. Simulations and experiments validate control performance with a full-size passenger vehicle.

One of the concerns in vehicle steering controls regards how to manipulate a vehicle to follow a designated path accurately. Generally, this issue is usually solved by linear or nonlinear control techniques based exclusively on vehicle kinematics or on a solution that partially combines dynamics. In this paper, an integral robust multi-tiered model-based vehicle steering control strategy is proposed in order to consider both kinematics and dynamics simultaneously. In this strategy, the kinematic controller provides yaw rate commands to converge the vehicle to a designated path by tuning an embedded sliding surface based on vehicle capability. To minimize steady-state errors caused by path curvature discontinuity, integral control is also applied. A robust dynamic controller is designed to reject modeling errors and disturbances caused by side slip angle from robust observer estimations. Steering rate is implemented to consider steering actuator capabilities and to smooth steering commands. Simulations and experiments validate control performance with a full-size passenger vehicle.

Backing of a tractor-trailer system is a problem addressed in many literatures. It is usually solved using various nonlinear-based control methods, which are often not easy to implement or tune and do not consider the influence of side-slope. We propose a two-tier controller that is simple and intuitive, which directly controls the curvature of the trailer's trajectory. It allows the control input to be more directly related to path specification and handles path curvature discontinuity better. A side-slope compensator is designed upon the simple controller to prevent side-slope from deteriorating tracking performance. Experimental results are provided to illustrate the capability of this new algorithm applied to a full scale autonomous vehicle and trailer system in a real field environment using minimal sensing capability. Performance comparison between the compensated and uncompensated systems is also presented. Results demonstrate good performance on modest side-slope.

Flying robots capable of perch-and-stare are desirable for reconnaissance missions. Current solutions for perch-and-stare applications utilize various methods to create an aircraft that can land on a limited set of surfaces that are typically horizontal or vertical planes. This paper presents a bio-inspired concept that allows for passive perching on cylindrical-type surfaces. The prototype provides compliant gripping through the use of an underactuated foot. A mechanism inspired by songbird anatomy is integrated that utilizes rotorcraft weight as a way to passively actuate the foot. Successful perching trials on two rods of differing diameters were performed and are discussed. The purpose of this initial design is to act as a proof of concept for the mechanical action of the mechanism; our results demonstrate that passive perching can be achieved through the integration of underactuated gripping with mechanism-generated mechanical advantage.

In this paper we propose a multi-tiered full-size road vehicle steering controller that simultaneously considers kinematics and dynamics. The kinematic controller embeds a surface for converging to the desired path that is tuned based upon vehicle capability in order to provide robust yaw rate references commands. The dynamic controller then establishes a sliding surface for yaw rate error convergence that allows the controller to be tuned based upon vehicle speed. The dynamic controller is designed to be robust to lateral disturbances characterized by side-slip angle, which is estimated by a robust observer. Simulations verify capabilities of this system with various speeds and road friction coefficients. Experiments using a full scale road vehicle with lateral disturbances demonstrate this approach at low speeds.

Backing of tractor-trailer systems is a problem addressed in many literatures. It is usually solved using various nonlinear-based control methods, which are often not easy to implement or tune. Similar to other work focused on backing a single axle trailer with a car like vehicle, we propose a two-tier controller that is simple and intuitive. However, ours is based upon curvature as opposed to hitch angle, which allows the control input to be more directly related to path specification and to handle path curvature discontinuity better. Experimental results are provided to illustrate the capability of this new algorithm applied to a full scale autonomous vehicle and trailer system in a real field environment using minimal sensing capability. Results demonstrate good performance on sloped grounds with various grades.

Traction estimation and control, common in the automotive industry, have yet to be extended to human bipedal motion. This paper presents a novel metric for slip and traction optimization using the partial derivative of a traction force estimate to slip velocity. The metric is verified computationally using an existing dynamic mode and experimentally using a multi-camera motion capture system.

This paper presents coordinated kinematic control of compliantly coupled multirobot systems for payload transportation. In the robot, unicycle-type axles are connected to a moving platform in an array format using compliant frames. A coordinate system is attached to an ideal center point on the platform to establish robot kinematics. In order to drive the system along a reference trajectory, we coordinate axle velocity commands, while considering frame compliance, nonholonomic constraints, and rigid body kinematics, respectively. These commands are further coordinated to consider configuration stability and physical limitations. Simulation and experimental results evaluate the coordination algorithms for various trajectories.

This paper presents a data fusion structure based on comparing geometric configurations of serial connected multi-axle compliant framed robots. Data sources include global odometry derived sources and a novel strain-measurement based relative posture sensor (RPS). Geometric methods are used because stochastic data fusion, developed from prior research, was erroneous when applied to more generalized multi-axle configurations. Our results show an excellent response predicting expected configurations and a reasonable response with un-expected configurations.

A state estimation algorithm for rejecting noise and tracking bias in both real-time and post-processing applications of inertial measurement for intermittent motion is presented with experimental results for one-dimensional motion. The algorithm uses characteristics of the sensor noise to automatically recognize motionless periods and update the sensor's bias level without any dependency on application-specific parameters, frequency separation between the signal of interest and the sensor noise, or a high-level system model. Accumulated error in the velocity estimate is eliminated during periods of rest allowing useful velocity estimates to be obtained for arbitrarily long periods given reasonably frequent pauses in the motion. This significantly extends the length of time over which useful position estimates are obtained, especially for postprocessing applications. While derived and demonstrated in the context of inertial measurement, the algorithm can be used to reject noise and/or track bias drift for any signal where zero-level inputs occur intermittently and limits can be set on the noise amplitude, frequency, and bias drift rate.

This paper presents a time invariant kinematic motion controller for wheeled mobile robots. A path manifold that considers curvature limitations is used to provide a desired path shape and convergence to the reference posture or trajectory. Lyapunov based techniques are then used to derive a control law that asymptotically converges the robot to the path manifold. Posture regulation, path following, and trajectory tracking capability are provided. Allowable initial conditions are estimated based upon curvature constraints of the robot. Curvature boundaries and asymptotic convergence naturally limit allowable initial conditions and are resolved by driving the robot to intermediate goal points within regions of allowable initial conditions. The proposed controller is evaluated in simulation.

This research creates a steady headwind at a user position in the scaled Treadport Active Wind Tunnel (TPAWT). The TPAWT adds a wind display system to the previously developed Treadport virtual environment, and this research builds upon prior work to provide improved control of headwind angle at the user position. Key to this research is the addition of a negative pressure plenum at the rear of the treadport to improve nominal flow stability. The previous controller based upon the small gain theorem with a dynamic extension is then modified to provide wind angle feedback control. A conditional angular rate-switching controller is added to reduce wind angle oscillations at the user. A vorticity-meter is developed to assure that the wind flow is centered at the user position. As a result, this research reduces wind angle error by 75% compared to previous work.

Motivated by the need for greater speed, adaptability and efficiency in legged robots, a class of hybrid robots have been developed which hybridize rolling locomotion with legged locomotion. Herein we present a quasi-static rolling control law for the hybrid climbing/rolling robot the rolling disk biped. We provide experimental results comparing speed and energy consumption data for quasi-static rolling versus walking. We show that rolling can significantly improve energy efficiency over walking-by as much as a factor of 3.9.

This paper presents coordinated kinematic motion control of a compliant framed wheeled modular mobile robot (CFMMR). Two coordination algorithms are demonstrated here based upon front and rear axles. An error coordinate system is applied to an ideal point on the robot that will be driven to a reference posture or target for motion control. Posture regulation, path following, and trajectory tracking capability is provided by a kinematic motion controller. Axle motion of the robot is then coordinated using a steering ratio and compliant constraints. The allowable steering ratios are established considering path curvature, steering angle limitations, and steering stability. Coordination algorithms are finally evaluated in simulation and experiment on the CFMMR.

This paper develops a static observer for estimating wind speed in order to control wind speed and angle control at a user position in a submersive virtual environment. Addition of wind display evolves the Treadport Virtual environment into a highly immersive virtual environment called Treadport Active Wind Tunnel (TPAWT). Experiments on a scaled model of the TPAWT show that headwind flow stream diverges at the user. Pitot tube sensors placed at a particular region of converged flow in the scaled TPAWT provide measurements with lower noise. Open loop experiments on a scaled model of TPAWT show that there exists a relationship between speed measured at this region of converged flow and the wind speed at the user position. Using this relationship, the wind speed at the user can be estimated. We use this relation and combine previously used speed and angle controllers based upon the small gain theorem with a dynamic extension and conditional angular rate-switching control. Finally, we simultaneously control wind speed and headwind angle.

Motivated toward dynamic rolling control of hybrid walking-climbing-rolling robots, this paper presents a greedy graph search method using two different metrics for purposes of joint path planning for a planar three degree of freedom hybrid mobility robot. Given an initial configuration and a desired net center of gravity location for the robot, the graph search finds joint paths that relocate the robotpsilas center of gravity to the desired position without causing its links to collide. An emphasis is placed on fast search times such that the planners may be used as part of real-time control loops for rolling mobile robots.

Mobile robots are used to venture through types of environments, at low wheel speeds, where wheel slip is a threat. We present a unique traction estimation algorithm for low speed applications that estimates traction loss by measuring the wheel slip velocity. We also propose a modified Kalman Filter that fuses a system model of a DC motor with an estimate of the disturbances acting on the system model. Using the wheel slip velocity we propose a traction control law for low speed applications that provides the ability of tracking a desired reference while mitigating traction loss.

Motivated by the need for greater speed, efficiency, and adaptability in climbing and walking robots, we have developed a bipedal planar robot that complements its walking and climbing capabilities with rolling. Rolling capabilities are provided by an innovative morphology, without the need for additional resources beyond those required by walking and climbing. Herein, we present the design of this robot, the development of a quasi-static rolling controller, and a comparison of experimentally obtained speed and energy data for walking versus rolling locomotion. We show that rolling can significantly improve energy efficiency over walking-as much as a factor of 5.5. We also demonstrate the ability to roll up slopes and roll over obstacles.

Teleoperated robots generally receive high level commands from a remote system, while accomplishing motion control through conventional means. We present a teleoperated system that removes the entire motion control structure from the robot, in order to preserve the availability of crucial onboard resources. The operation of state feedback control is performed by a system remote from the robot. We have designed a computerized motion planning and control system for Mobile Emulab, and in this article, discuss the implementation of trajectory tracking control. A component of the Emulab network testbed, Mobile Emulab is used for wireless network experiments requiring mobility; and is publicly available to remote researchers via the Internet. Medium scale wheeled mobile robot couriers are used to move wireless antennas within a semi-controlled environment. Experimenters use a Web-based GUI to specify desired paths and configurations for multiple robots. State feedback is provided by an overhead camera based visual localization system. Kinematic control is used to generate velocity commands, which are sent to robots over a computer network. Data availability is restricted to a low sampling frequency. There is significant noise, loss, and phase lag present in the robot localization data, which our research overcomes to provide an autonomous trajectory tracking mobile robot control system.

This research focuses on development of a haptic system to create controlled air flow acting on a user in the Treadport virtual environment. The Treadport active wind tunnel (TPAWT) is thus created in order to produce air flow patterns that allow a variety of wind angles and speeds to be felt by the user. In order to control this system in real-time, the small gain theorem is used in conjunction with a dynamic extension to formulate an output feedback control law. Examples of controller formulations are derived and discrete time simulations in FLUENT demonstrate their effectiveness. The controller is then validated experimentally using a scale model of the TPAWT.

A novel motion control and sensing architecture for a two-axle compliant framed wheeled modular mobile robot (CFMMR) is proposed in this paper. The CFMMR is essentially a cooperative mobile robotic system with complex physical constraints and highly nonlinear interaction forces. The architecture combines a kinematic controller for coordinating motion and providing reference commands, robust dynamic controllers for following these commands and rejecting disturbances, and a sensor fusion system designed to provide accurate relative posture estimates. Requirements for each of these subsystems and their respective interconnections are defined in this paper in order to optimize system performance. Experimental results compare performance of the proposed architecture to sub-optimal configurations. Results derived from seven groups of experiments based upon 35 individual tests validate superiority of the architecture.

A novel motion control and sensing strategy for a two-axle compliant framed wheeled modular mobile robot (CFMMR) is studied in this paper. This type of wheeled mobile robot uses rigid axles coupled by compliant frame modules to provide both full suspension and enhanced steering capability without additional hardware. The proposed control and sensing system is developed by combining a curvature-based kinematic controller, a robust dynamic motion controller and a sensor fusion algorithm incorporating relative position sensors. Experimental results verify improved motion control of posture regulation

This paper presents a kinematic motion control strategy for a multiple-axle compliant framed modular wheeled mobile robot. A decentralized master-slave type control scheme is proposed here to solve motion control problems (posture regulation, path following, and trajectory tracking) of the n-axle robot. The controller considers physical constraints on the path curvature, wheel velocity, and traction forces as well as compliance between nonholonomic axle modules of the robot. The target application is an n-axle compliant framed modular mobile robot. This robot utilizes compliant frames to couple the unicycle type axles, which facilitates a simple modular design with full suspension and advanced steering capability. Simulation results are presented and the proposed control scheme is evaluated

Kinematic models and motion control algorithms for a two-axle compliant frame mobile robot are examined. General kinematics describing the compliantly coupled nonholonomic kinematics are derived using velocity constraints that minimize traction forces and consider foreshortening of the frame. Given the complexity of these equations, the steering ratio a is defined to describe the relative heading angles of the front and rear axles. Simplified kinematic models are developed based upon a (Types I, II, and III) and the reference point used to guide the robot. Physical limitations and performance metrics (lateral mobility and maneuverability per unit of traction force) are derived to evaluate the models. Six groups of simulations and 24 experimental tests consisting of 120 trials evaluate the performance of the algorithms on carpet, sand, and sand with rocks. Results indicate that Type I (curvature-based steering) provides superior maneuverability and regulation accuracy, whereas Type II provides excellent lateral mobility at the cost of high traction forces, reduced accuracy, and potential singularities. Both models offer significant reductions in complexity for simplified control using standard curvature-based unicycle control algorithms. These results support expectations derived from performance metrics and physical limitations. Experimental results also demonstrate the efficacy of the robot to adapt to and maneuver over extremely rugged rocky terrain.

This paper presents a new curvature based smooth time invariant control law for posture regulation and path following control of unicycle type kinematic models. The control law is developed in polar coordinates for posture regulation using nonlinear Lyapunov techniques and extended for path following via waypoint navigation techniques. The algorithm is then applied to a two-axle compliant framed modular mobile robot. To this goal the complex robot kinematics are reduced to an equivalent unicycle kinematic model where we must consider physical constraints on wheel velocity and frame curvature. Bounded curvature and velocity expressions are thus derived as control inputs. The controller is then extended to compensate for non-ideal initial conditions and drift. Simulation and experimental results evaluate algorithm performance.

A new bipedal mobile robot design that combines the benefits of rolling, walking, and climbing locomotion is discussed. The design provides these locomotion primitives without the addition of actuators beyond those required for climbing through the use of a disk-like exoskeleton that provides a rolling surface. Small joint oscillations control the center of gravity of the robot in order to initiate and perpetuate quasi-static rolling motion. Simulation results are also included to validate this algorithm.

No abstract available.

No abstract available.

To ensure safety during extravehicular activity (EVA), crewmembers must use tethers that constrain them and their tools to the spacecraft. A prototype automated tether system has been designed to increase the efficiency of such tether use. The system consists of a remotely releasable robotic gripper that serves to anchor the system, and a retractor that contains and controls the length of the tether in the workspace. In this paper, dynamic simulations of the system are derived and analyzed to predict retraction behavior in an orbital environment. The system was also tested using air bearing facilities to simulate a microgravity environment. Functional tests of the system are also discussed in order to characterize and quantify its performance.

Dynamic models and controllers for compliant framed wheeled modular mobile robots are studied in this paper. This is a new type of wheeled mobile robot using axle and frame modules that can provide both full suspension and enhanced steering capability without additional hardware. In this research modular kinematic and dynamic models of the modules are developed and assembled into a scalable dynamic system model such that a wide variety of configurations could be described. Dynamic control is then achieved by coordinated control of the individual wheel torques as specified by a backstepping controller scaled to the dimension of the system configuration. These results are applied to a two-axle scout case study in order to demonstrate their implementation and performance. Simulation and experimental results illustrate dynamic control of trajectory tracking while path following.

Posture stabilization of a compliant framed modular mobile robot is the subject of this paper. This is a new type of wheeled mobile robot that has advantages of a simple modular design that provides full suspension and steering capability without any additional components. Steering is achieved by coordinated control of the individual wheels to realize a desired trajectory. Due to the flexible nature of the robot, the kinematics is simplified by using an equivalent curvature based model, which increases mobility and decreases required traction forces for improved towing capacity. A time invariant control law is developed and extended to compensate for non-ideal initial conditions and drift. Simulation and experimental results are presented and show the proposed control law performs as expected.

The subject of this paper is a hybrid hip biped climbing robot. The hybrid hip provides both prismatic and revolute motion, discretely, to the robot, using a single actuator. This is intended to improve its adaptability in confined environments and its capability to maneuver over and around obstacles. Optimization of the hybrid hip relative to the robot size, weight, and actuation limits is considered while maximizing range of motion. The mechanical structure of the robot is discussed, as well as forward and inverse kinematics for motion planning. Workplace analysis indicates the hip provides an appreciable improvement in foot placement capability when compared to a purely prismatic or revolute hip movement.

Abstract- A sensor fusion algorithm for flexible framed modular mobile robots is presented in this paper. This algorithm uses traditional Kalman filters and rigid axle kinematic models to predict the global posture of each axle. A Covariance Intersection filter is then proposed for fusing these axle modules using data provided by the compliant frame module. Modeling and instrumentation of the compliant frame module is the remaining focus. The instrumented frame is required to estimate the relative posture of the axles as well as the force components and moment that the beam exerts on each axle. These estimates must also be valid for large deflections in order to accommodate a reasonable turning radius. To accomplish these goals the beam equations are derived. A linear interpolation of the strain gauge data is used to calculate posture, force, and moment estimates. Experimental results show that the frame module can yield accurate relative posture estimates for large deflection. 1.

An automated tether system has been developed for the purpose of improving the efficiency of micro-gravity activities of fully suited astronauts. System features include gripping of multiple anchor types, remote release of the tether from an anchor, and controlled retraction of the tether. Two main mechanisms make up the system. First, a remotely releasable, self-locking robotic gripper with opposing jaws that grasps a variety of anchors such as handrails, tether loops, and guide wires. Second, an automated tether retractor that is capable of active or passive operation. Passive retractor operation saves power by emulating existing safety tether systems and active operation expedites tether retraction and allows towing.

Design, control and performance of a ball-throwing robot are examined in this paper. The objective of this project is to provide an interactive ball-throwing robotic arm for illustrating the roles of engineers and computer scientists in the design and usage of such a system to high school or pre-engineering students. Activities in particle dynamics and trajectory calculation will provide basic hands on engineering experience and the opportunity to interact with the robot. In order to effectively provide this activity, the robot must consistently throw the ball from a known point with a desired velocity. This requires a minimum of a two-link manipulator with control strategies sufficient to converge two joint positions and velocities simultaneously. Due to limited microcontroller computational resources, feedforward torques are calculated off-line based on 3/sup rd/ order cubic spline trajectories. Feedback compensation for position and velocity error is then examined and compared for ball throwing accuracy and precision to a technique supplementing the previous controller with acceleration error compensation. Experimental results are presented that illustrate the improved accuracy and reduced repeatability of the later technique. Gripper design providing consistent hold on the ball and rapid release is also examined.

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.