Mark K. Long

Kinematic analysis of 7-DOF manipulators

This article presents a kinematic analysis of seven-degree-of- freedom serial link spatial manipulators with revolute joints. To uniquely determine the joint angles for a given end-effector position and orientation, the redundancy is parameterized by a scalar variable that defines the angle between the arm plane and a reference plane. The forward kinematic mappings from joint space to end-effector coordinates and arm angle and the augmented Jacobian matrix that gives end-effector and arm angle rates as functions of joint rates are presented. Conditions under which the augmented Jacobian becomes singular are also given and are shown to correspond to the arm being either at a kinematically singular configuration or at a nonsingular configuration for which the arm angle ceases to parameterize the redundancy.

Motion control of 7-DOF arms: the configuration control approach

Graphics simulation and real-time implementation of configuration control schemes for a redundant seven-degree-of-freedom (7-DOF) Robotics Research arm are described. The arm kinematics and motion control schemes are described briefly. This is followed by a description of a graphics simulation environment for 7-DOF arm control on the Silicon Graphics IRIS Workstation. Computer simulation results are presented to demonstrate elbow control, collision avoidance, and optimal joint movement as redundancy resolution goals. The laboratory setup for experimental validation of motion control of the 7-DOF Robotics Research arm is then described. The configuration control approach is implemented on a Motorola-68020/VME-bus-based real-time controller, with elbow positioning for redundancy resolution. Experimental results demonstrate the efficacy of configuration control for real-time control. >

Kinematic analysis of 7 DOF anthropomorphic arms

A kinematic analysis of anthropomorphic 7 DOF serial link spatial manipulators with revolute joints is presented. To determine joint angles uniquely for a given end-effector position and orientation, the redundancy is parameterized by a scalar variable which corresponds to the angle between the arm plane and a reference plane. The forward kinematic mappings from joint-space to end-effector coordinates and arm angle and the augmented Jacobian matrix which gives end-effector and arm angle rates as functions of joint rates are given. Conditions under which the augmented Jacobian becomes singular are given and are shown to correspond to the arm being either at a kinematically singular configuration or at a nonsingular configuration for which the arm angle ceases to parameterize the redundancy.<<ETX>>

The modular telerobot task execution system for space telerobotics

A telerobot task execution system that has been developed for space station Freedom applications is described. The modular telerobot task execution system (MOTES) provides the remote site task execution capability in a local-remote telerobotic system. The design addresses the constraints of limited computational power available at the remote site control system while providing a large range of control capabilities. The system provides supervised autonomous control, shared control, and teleoperation for a redundant manipulator. The system is capable of nominal task execution as well as monitoring and reflex motion. A command interpreter similar to one used on robotic spacecraft is used to interpret commands received from the local site. Execution utilizes multiple control modules which execute based upon command parameterization. The system controls a seven degree-of-freedom manipulator.<<ETX>>

A PC based configuration controller for dexterous 7-DOF arms

This implementation of a configuration controller for a dexterous 7-DOF manipulator on an IBM-compatible personal computer represents a step toward high-performance robotic controllers designed with consumer electronics. The system has the capability for 3D graphical animation of the arm motion, which is performed on a separate single-board computer interfaced to the PC. Several experiments have shown the control performance comparable to that obtained with more expensive computing platforms.

Task-directed inverse kinematics for redundant manipulators

This paper presents kinematic algorithms for resolved-rate based inverse kinematics of redundant manipulators. Efficient and robust Jacobian and weighted damped least squares algorithms are given which provide a method that allows full utilization of the redundancy to best achieve task requirements. A nominal set of task space variables is suggested and procedures for modifying this specification or their relative priorities due to changing task requirements or events are discussed. Examples are shown using a simulation of the seven degree-of-freeom Robotics Research manipulator. These simulations demonstrate the singularity robustness of the algorithms and the ability to smoothly transition between task parameterizations and relative priorities.

Merging concurrent behaviors on a redundant manipulator

The control of a redundant manipulator with multiple simultaneous control sources is described. Each control source provides a different behavior type. An application is decomposed into multiple simultaneous behaviors whose resultant behavior will provide the motion necessary to execute the task. The simultaneous control inputs are merged using impedance control to compute a resultant command to the manipulator. The task space of each behavior can have the dimensionality of the mechanism being controlled. Control of a seven-degree-of-freedom manipulator is described. The available task space for each behavior has dimensionality seven.<<ETX>>

Configuration control of 7 DOF arms

Applications of the configuration control approach to motion control of redundant 7 DOF (degree-of-freedom) arms are described. This approach provides a unified framework for resolution of redundancy to accomplish a broad range of objectives. The configuration control approach is briefly described, and a graphics simulation environment for control of 7 DOF Robotics Research arms is discussed. Computer simulation results are presented to demonstrate elbow control, obstacle avoidance, and optimal joint motion as redundancy resolution goals for the 7 DOF arm.<<ETX>>

A PC-based configuration controller for dexterous 7-DOF arms

This paper describes the architecture and performance of a PC-based configuration controller for dexterous 7-DOF manipulators. The computing platform is a 486-based personal computer equipped with a bus extender to access the robot Multibus controller, together with a single-board computer as the graphical engine, and a parallel I/O board to interface with a force-torque sensor mounted on the manipulator wrist. The Windows environment is enhanced by the iRMX real-time operating system that runs the configuration control algorithms for redundancy resolution. The position control algorithm is executed every 2.5 ms; motions can be simulated and displayed in real-time by the graphical engine on a separate monitor. The results of several experiments carried out with a Robotics Research manipulator have shown motion control capabilities comparable to those obtained with more extensive computing systems, thus validating the use of PCs for dexterous manipulator control. PC-based motion controllers for RRC arms, incorporating the configuration control software, are currently produced by the Robotics Research Corporation.

A prototype ground-remote telerobot control system

A local-remote telerobot control system is described which is being developed for time-delayed groundremote control of space telerobotic systems. The system includes a local site operator interface for interactive command building and sequencing for supervised autonomy and a remote site: the Modular Telerobot Task Execution System ( MOTES ), to provide the remote site task execution capability. The local site system also provides stereo graphics overlay on video with interactive update of the remote environmental model. The operator selects objects in the environment to interact with and skill types to specify the tasks to be performed, such as grasping a module or opening a door.