This paper describes the robotics facilities and associated research program of the Jet Propulsion Laboratory, lead center in telerobotics for the United States National Aeronautics and Space Administration. Emphasis is placed on evolution from teleoperation to remote System automation. Research is described in manipulator modelling and control, real-time planning and monitoring, navigation in outdoor terrain, real-time sensing and perception, human-machine interface, and overall System architectures. Applications to NASA missions emphasize robotic spacecraft for solar System exploration, satellite servicing and retrieval, assembly of structures, and surveillance. Applications to military missions include battlefield navigation, surveillance, logistics, command and control.

This study develops a novel image-guided robotic system that can be used to position biopsy needles or drill fixation holes. After the patient has received a CT-scan, the registration of the image, localizer (patient), and robot frames will be done by finding the optimum transformation matrix among the image and localizer coordinates of the fiducial markers and the DRFs mounted on the robot. Then, surgical paths planned on the computer displayed images can be transformed to the robot frame, and the robot is thus capable to move surgical tools to the preplanned location. The positioning error is about 2 mm and the orientation error is about 0.23°.

This paper deals with the design of the control structure of a lower-limbs rehabilitation device in closed muscular chain called Sys-Reeduc. This control structure aims at providing a safe behavior to the user when performing rehabilitation exercises. It is based on two levels. The first level is concerned with the robust trajectory tracking of robotic device and has been the subject of previous studies. Nevertheless, it does not allow, by itself, the user to voluntarily drive the device. Therefore, a trajectory generator constituting the second level is presented in this paper to complete the whole control structure. This high-level control layer is described by a set of dedicated discrete state machines that provide the appropriate sequencing of elementary rehabilitation movements. These elementary movements are dynamically characterized so that clinician may choose the required trajectory parameters to adapt rehabilitation protocols and training to each individual. To realize a complete rehabilitation exercise, the sequence of elementary movements is triggered by thresholds relative to the measurement of the efforts applied by the user on the device. This allows the user to play an active role in its rehabilitation exercises and safely drive the machine at his/her own initiative. The design of the main exercises (isokinetic, isometric, and isotonic) used in the context of lower limbs rehabilitation is described, and simulation results illustrate the effectiveness of the proposed trajectory generator-based control approach.

In this study, some geometric, kinematic, and dynamic aspects of the design of a Stewart-Gough platform are examined. The focus of the analyses is on a particular Stewart-Gough platform that we have constructed. The analysis begins with workspace simulations for different moving platform orientations. The computations extend to a parametric study of some geometric and kinematic constraints: Joint angle, rotation angle, and limb length. Actuator force is another parameter considered; and the triple relationship between workspace, joint angle, and actuator force is discussed. Parametric analyses are culminated with a brief discussion of the real design parameters.

This paper introduces a solution to the problem of steering an aerodynamical system, with non-holonomic constraints superimposed on dynamic equations of motion. The proposed approach is a dimensionality reduction of the Optimal Control Problem (OCP) with heavy path constraints to be solved by Rapidly-Exploring Random Tree (RRT) algorithm. In this research, we formulated and solved the OCP with Euler–Lagrange formula in order to find the optimal-time trajectory. The RRT constructs a non-collision path in static, high-dense obstacle environment (i.e. heavy path constraint). Based on a real-world aircraft model, our simulation results found the collision-free path and gave improvements of time and fuel consumption of the optimized Hamiltonian-based model over the original non-optimized model.

This paper presents a novel method for generating three-dimensional optimal trajectories for a vehicle or body that moves forward at a constant speed and steers in both horizontal and vertical directions. The vehicle's dynamics limit the body-frame pitch and yaw rates; additionally, the climb and decent angles of the vehicle are also bounded. Given the above constraints, the path planning problem is solved geometrically by building upon the two-dimensional Dubins curves and then Pontryagin's Maximum Principle is used to validate that the proposed solution lies within the family of candidate time-optimal trajectories. Finally, given the severe boundedness constraints on the vertical motion of the system, the robustness of the proposed path planning method is validated by naturally extending it to remain applicable to high-altitude final configurations.

This paper deals with the kinematic calibration of the Argos mechanism which is a novel, spherical parallel structure having 3 rotational degrees of freedom. Its design is based on 3 actuators carrying a pantograph each which are connected to the end-effector by means of 3 spherical joints. Two different calibration models are introduced. The first one models mechanical deviations in all parts except for the spherical joints and the assumption that they are moving on a perfect circle (“model 27”). The second model considers only deviations which affects the orientation of the end-effector but not its position assuming that the mechanism remains spherical (“model 9”). A measurement set-up allows to measure the full pose (position and orientation) of the end-effector with respect to its base. These measurement data are used to identify the parameters of the two calibration models resulting in an accuracy improvement of RMS (root mean squares errors) of a factor of 5.3 for the orientation and a factor of 3.4 for the prediction of the position.

Endowing robots with the ability of skill learning enables them to be versatile and skillful in performing various tasks. This paper proposes a neuro-fuzzy-based, self-organizing skill-learning framework, which differs from previous work in its capability of decomposing a skill by self-categorizing it into significant stimulus-response units (SRU, a fundamental unit of our skill representation), and self-organizing learned skills into a new skill. The proposed neuro-fuzzy-based, self-organizing skill-learning framework can be realized by skill decomposition and skill synthesis. Skill decomposition aims at representing a skill and acquiring it by SRUs, and is implemented by stages with a five-layer neuro-fuzzy network with supervised learning, resolution control, and reinforcement learning to enable robots to identify a sufficient number of significant SRUs for accomplishing a given task without extraneous actions. Skill synthesis aims at organizing a new skill by sequentially planning learned skills composed of SRUs, and is realized by stages, which establish common SRUs between two similar skills and self-organize a new skill from these common SRUs and additional new SRUs by reinforcement learning. Computer simulations and experiments with a Pioneer 3-DX mobile robot were conducted to validate the self-organizing capability of the proposed skill-learning framework in identifying significant SRUs from task examples and in common SRUs between similar skills and learning new skills from learned skills.

This paper presents a computational method for obtaining an optimal control trajectory for point-to-point motion of a cooperating robot carrying a flexible object. To increase the overall productivity and its efficiency, it is required to move the object as fast as possible using the maximum capacity of actuators of robots. If the carrying object is very sensitive to vibration, the robots should be operated so as not to cause excessive vibration of that object. This work deals with optimal input design for cooperative robots to reduce vibration of flexible objects that are handled at speed, under firm constraints on control torques.

The 3-PS structure features one rigid body (platform) connected to another rigid body (base) by means of three kinematic chains (limbs) of type PS (P and S stand for prismatic pair and spherical pair, respectively). All the 3-degree-of-freedom parallel manipulators with three connectivity-5 limbs, each one constituted of one passive (i.e. not actuated) prismatic pair, one passive spherical pair and one actuated kinematic pair of any type, become 3-PS structures when the actuated pairs are locked. Direct kinematics of this class of manipulators is tied to the properties of the 3-PS structure. In particular, the direct position analysis is tied to the assembly modes of the 3-PS structure; whereas the determination of the singularities of the direct instantaneous problem is tied to the determination of the singular geometries of the 3-PS structure, where instantaneous relative motions between platform and base are possible. The solution of these two problems is necessary both for designing the manipulators and for controlling them during motion. This paper deal with the determination of the singular geometries of the 3-PS structure.

The balance control problem of planar bipedal robots during disturbed standing is investigated. Virtual holonomic constraints which specify the angles of actuated joints as a function of the rotation angle between the sole of the stance foot and the ground are recalled. These constraints enable the robot to avoid turnover during external disturbances similar to how a human being would react. Moreover, for a disturbance beyond the balance conditions for single-leg support, the robot changes to a double support posture to avoid turnover by the virtual holonomic constraints. Further, for a special kind of balance: standing on toe which leads to underactuation, we also give the design conditions of the virtual holonomic constraints.

Vision-aided flexible link robot positoning using the Camera Space Manipulation (CSM) method is developed. The primary motivation for this work is to use an autonomous vision-aided robotic system to pick-up and accurately move a flexible object that it encounters. The work consists of analytical and experimental investigation of the performance of CSM for a kinematic model of the PUMA manipulator with a flexible structure at the wrist which accounts for the gravitation. Trade-offs between camera view parameters and axial deflection model parameters were investigated. View parameter reestimation and maneuvering resulted a very accurate placement of the end-effector at the target.

Nature has always inspired engineers. This research tries to understand the contribution of snake anatomy in its locomotion from engineering point of view to be adopted in the design of snake robots. Rib design and muscular structure of snake robots will have a great impact on snake robot flexibility, weight, and actuators' torque. It will help to eliminate wheels in snake robots during serpentine locomotion. The result of this research shows that snakes can establish the required peg points on smooth surfaces by deflecting the body and ribs. The results are verified by both field observations and simulation.

This paper presents a Chebyshev Pseudospectral (PS) method for solving the motion planning problem of nonholonomic mobile robots with kinematic and dynamic constraints. The state and control variables are expanded in the Chebyshev polynomial of order N, and Chebyshev–Gauss–Lobatto (CGL) nodes are provided for approximating the system dynamics, boundary conditions, and performance index. For the lack of enough nodes nearby the obstacles, the interpolation of trajectory may violate the obstacles and the multiple-interval strategy is proposed to deal with the violation. Numerical examples demonstrate that multiple-interval strategy yields more accurate results than the single-interval Chebyshev PS method.

In order to allow people to explore potential fire environments without risk of danger, a new fire scout mobile robot used in urban environments is introduced in this paper. It adapts itself to stair climbing by using articulated-chain-wheeled mobile style with differential wheels. The positive pressure with continuous flow of protected gas inside the body endows the robot with explosion protection capability. When the wireless control signal is interrupted, it could automatically return to safe place along previous path based on sensorial data. Since position estimation only using encoders reading has serious limitations as mobile robot movement proceeds, a novel method integrating data of encoders and ultrasonic sensors is built, which uses iterative closest point algorithm to do data matching so as to adjust position and orientation of the mobile robot. This path retracing method realizes high accuracy and fast speed of automatic returning when the mobile robot is working in static urban environment even if the environment is unknown.

This paper describes a software tool to automate a design method for robotic fuzzy force control. The original method was developed to ensure robust and stable force control in situations where environmental stiffness at the robot/task interface is unknown, obviating the use of fixed-gain controllers. It did, however, involve a manual design process requiring significant knowledge of control theory and fuzzy logic. This process has been automated in the form of a Windows-based application, requiring minimal user inputs and incorporating an automatic tuning technique for improved performance in the final controller application. Results obtained from an experimental robot are presented.

Multibody dynamics methodologies have been fundamental tools utilized to model and simulate robotic systems that experience contact conditions with the surrounding environment, such as in the case of feet and ground interactions. In addressing such problems, it is of paramount importance to accurately and efficiently handle the large body displacement associated with locomotion of robots, as well as the dynamic response related to contact-impact events. Thus, a generic computational approach, based on the Newton–Euler formulation, to represent the gross motion of robotic systems, is revisited in this work. The main kinematic and dynamic features, necessary to obtain the equations of motion, are discussed. A numerical procedure suitable to solve the equations of motion is also presented. The problem of modeling contacts in dynamical systems involves two main tasks, namely, the contact detection and the contact resolution, which take into account for the kinematics and dynamics of the contacting bodies, constituting the general framework for the process of modeling and simulating complex contact scenarios. In order to properly model the contact interactions, the contact kinematic properties are established based on the geometry of contacting bodies, which allow to perform the contact detection task. The contact dynamics is represented by continuous contact force models, both in terms of normal and tangential contact directions. Finally, the presented formulations are demonstrated by the application to several robotics systems that involve contact and impact events with surrounding environment. Special emphasis is put on the systems’ dynamic behavior, in terms of performance and stability.

The Flight Telerobotic Servicer (FTS) is a robotic device which will be used to build and maintain Space Station Freedom. The FTS is expected to evolve from its initial capability of teleoperation toward greater autonomy by taking advantage of advances in technology as they become available. In order to support this evolution, NASA has chosen the NASA/NIST Standard Reference model for Telerobot Control System Architecture (NASREM) as the FTS functional architecture. As a result of the definition of generic interfaces in NASREM, the system can be modified without major impact. Consequently, different approaches to solve a problem can be tested easily. This paper describes the implementation of NASREM in the NIST laboratory. The approach is to build a flexible testbed to enhance research in robot control, computer vision, and related areas. To illustrate the real-time aspects of the implementation, a sensory interactive motion control experiment will be described.

It is standard now in undergraduate and graduate courses in robotics to teach the basic concepts of position control design strategies. Due to the geared motors inherent in most educational and industrial manipulators, sophisticated control design strategies such as the inverse dynamics technique cannot be easily demonstrated in a laboratory setting. A direct drive 5-bar-linkage manipulator with reduced motor torque requirements is proposed in this paper for such a purpose. The manipulator dynamics are easily understood by undergraduates and an inverse dynamics control strategy is suggested which can be easily designed by students at the undergraduate level.