Wayne John Book

Recursive Lagrangian Dynamics of Flexible Manipulator Arms

Nonlinear equations of motion are developed for flexible manipulator arms consisting of rotary joints that connect pairs of flexible links. Kinematics of both the rotary-joint mo tion and the link deformation are described by 4 X 4 trans formation matrices. The link deflection is assumed small so that the link transformation can be composed of summations of assumed link shapes. The resulting equations are pre sented as scalar and 4 X 4 matrix operations ready for pro gramming. The efficiency of this formulation is compared to rigid-link cases reported in the literature.

Feedback Control of Two Beam, Two Joint Systems With Distributed Flexibility

The control of the flexible motion in a plane of two pinned beams is addressed with application to remote manipulators. Three types of linear feedback control schemes are considered: joint angle and velocity feedback with (GRC) and without (IJC) cross joint feedback, and feedback of flexible state variables (FFC). Two models of the distributed flexibility are presented along with some results obtained from them. The relative merit of the three control schemes is discussed.

Internet-based teleoperation using wave variables with prediction

Wave-based teleoperation has been previously attempted over the Internet, however, performance rapidly deteriorates with increasing delay. This paper focuses on the use of a modified Smith predictor, a Kalman filter and an energy regulator to improve the performance of a wave-based teleoperator. This technique is further extended for use over the Internet, where the time delay is varying and unpredictable. It is shown that the resulting system is stable even if there are large uncertainties in the model of the remote system (used in prediction). Successful experimental results using this technique for teleoperation in a master-slave arrangement over the Internet, where the control signal is streamed between Atlanta (Georgia) and Tokyo (Japan), are also given.

Controlled motion in an elastic world

The flexibility of the drives and structures of controlled motion systems are presented as an obstacle to be overcome in the design of high performance motion systems, particularly manipulator arms. The task and the measure of performance to be applied determine the technology appropriate to overcome this obstacle. Included in the technologies proposed are control algorithms (feedback and feed forward), passive damping enhancement, operational strategies, and structural design. Modeling of the distributed, nonlinear system is difficult, and alternative approaches are discussed. The author presents personal perspectives on the history, status, and future directions in this area.

Controller Design for Flexible, Distributed Parameter Mechanical Arms Via Combined State Space and Frequency Domain Techniques

The potential benefits of the ability to control more flexible mechanical arms are discussed. A justification is made in terms of speed of movement. A new controller design procedure is then developed to provide this capability. It uses both a frequency domain representation and a state variable representation of the arm model. The frequency domain model is used to update the modal state variable model to insure decoupled states. The technique is applied to a simple example with encouraging results.

A Time-Domain Inverse Dynamic Tracking Control of a Single-Link Flexible Manipulator

A manipulator system with a large workspace volume and high payload capacity has greater link flexibility than do typical industrial robots and teleoperators. If link flexibility is significant, position control of the manipulator’s end-effector exhibits nonminimum-phase, noncollocated, and flexible-structure system control problems. This paper addresses inverse dynamic trajectory planning issues of a single-link flexible manipulator. The inverse dynamic equation of a single-link flexible manipulator was solved in the time-domain. By dividing the inverse system equation into its causal part and anticausal part, the inverse dynamic method calculates the feed-forward torque and the trajectories of all state variables that do not excite structural vibrations for a given end-point trajectory. Through simulation and experiment with a single-link manipulator, the effectiveness of the inverse dynamic method in producing fast and vibration-free motion has been demonstrated.

A linear dynamic model for flexible robotic manipulators

The design of lightweight links for robotic manipulators results in flexible links. Accurate control of lightweight manipulators during the large changes in configuration common to robotic tasks requires dynamic models that describe both the rigid-body motions, as well as the flexural vibrations. This paper describes a linear state-space model for a single-link flexible manipulator and compares simulation of the model to measurements made on a 4-ft-long direct-drive arm.

Filtering micro-manipulator wrist commands to prevent flexible base motion

This paper examines control issues related to positioning a small articulating robot attached to a much larger, flexible manipulator. By shaping the joint position error with a finite impulse response filter actuation torques can be found to maneuver the small robot with minimal residual vibration of its base. This paper develops a new filter form with the advantage of shorter delay times than current input shaping methods. Experimental results show the effectiveness of the new filtering technique to prevent vibration when used as part of a feedback control system.

Verification of a linear dynamic model for flexible robotic manipulators

The design of lightweight links for robotic manipulators results in flexible links. Accurate control of lightweight manipulators during the large changes in configuration common to robotic tasks requires dynamic models that describe both the rigid-body motions, as well as the flexural vibrations. This paper describes a linear state-space model for a single-link flexible manipulator and compares simulation of the model to measurements made on a 4-ft-long direct-drive arm.This paper describes a linear state-space model for a flexible single link manipulator arm. The resultant model is compared to an experimental four foot long direct drive manipulator. The method employed to generate the model utilizes a separable formulation of assumed modes to represent the tranverse displacement due to bending. Lagrangian dynamics are applied to determine the kinetic and potential energies for the system. The resultant dynamic equations are then organized into a state space model suitable for use in linear control system design procedures. The performance of the model is considered for different model orders and assumed modes. Several important aspects of candidate mode selection, and results for different model order are discussed. The final section of the paper provides a brief summary and describes ongoing and future work.

Modeling, design, and control of flexible manipulator arms: a tutorial review

High performance manipulators with dynamic behavior in which the flexibility is an essential aspect are addressed. The mathematical representations commonly used in modeling flexible arms and arms with flexible drives are first examined. Then design considerations directly arising from the flexible nature of the arm are discussed. Finally, controls of joints for general and tip motion are discussed.<<ETX>>