Stiffness modeling of robotic manipulator with gravity compensator

The paper focuses on the stiffness modeling of robotic manipulators with gravity compensators. The main attention is paid to the development of the stiffness model of a spring-based compensator located between sequential links of a serial structure. The derived model allows us to describe the compensator as an equivalent non-linear virtual spring integrated in the corresponding actuated joint. The obtained results have been efficiently applied to the stiffness modeling of a heavy industrial robot of the Kuka family

Identification of geometrical and elastostatic parameters of heavy industrial robots

The paper focuses on the stiffness modeling of heavy industrial robots with gravity compensators. The main attention is paid to the identification of geometrical and elastostatic parameters and calibration accuracy. To reduce impact of the measurement errors, the set of manipulator configurations for calibration experiments is optimized with respect to the proposed performance measure related to the end-effector position accuracy. Experimental results are presented that illustrate the advantages of the developed technique.Comment: arXiv admin note: substantial text overlap with arXiv:1311.667

A user oriented microcomputer facility for designing linear quadratic Gaussian feedback compensators

A laboratory design facility for digital microprocessor implementation of linear-quadratic-Gaussian feedback compensators is described. Outputs from user interactive programs for solving infinite time horizon LQ regulator and Kalman filter problems were conditioned for implementation on the laboratory microcomputer system. The software consisted of two parts: an offline high-level program for solving the LQ Ricatti equations and generating associated feedback and filter gains and a cross compiler/macro assembler which generates object code for the target microprocessor system. A PDP 11/70 with a UNIX operating system was used for all high level program and data management, and the target microprocessor system is an Intel MDS (8080-based processor). Application to the control of a two dimensional inverted pendulum is presented and issues in expanding the design/prototyping system to other target machine architectures are discussed

Precise control of flexible manipulators

The design and experimental testing of end point position controllers for a very flexible one link lightweight manipulator are summarized. The latest upgraded version of the experimental set up, and the basic differences between conventional joint angle feedback and end point position feedback are described. A general procedure for application of modern control methods to the problem is outlined. The relationship between weighting parameters and the bandwidth and control stiffness of the resulting end point position closed loop system is shown. It is found that joint rate angle feedback in addition to the primary end point position sensor is essential for adequate disturbance rejection capability of the closed loop system. The use of a low order multivariable compensator design computer code; called Sandy is documented. A solution to the problem of control mode switching between position sensor sets is outlined. The proof of concept for endpoint position feedback for a one link flexible manipulator was demonstrated. The bandwidth obtained with the experimental end point position controller is about twice as fast as the beam's first natural cantilevered frequency, and comes within a factor of four of the absolute physical speed limit imposed by the wave propagation time of the beam

Environmental test chamber for the support of learning and teaching in intelligent control

The paper describes the utility of a low cost, 1 m2 by 2 m forced ventilation, micro-climate test chamber, for the support of research and teaching in mechatronics. Initially developed for the evaluation of a new ventilation rate controller, the fully instrumented chamber now provides numerous learning opportunities and individual projects for both undergraduate and postgraduate research students

Integrated control-structure design

A new approach for the design and control of flexible space structures is described. The approach integrates the structure and controller design processes thereby providing extra opportunities for avoiding some of the disastrous effects of control-structures interaction and for discovering new, unexpected avenues of future structural design. A control formulation based on Boyd's implementation of Youla parameterization is employed. Control design parameters are coupled with structural design variables to produce a set of integrated-design variables which are selected through optimization-based methodology. A performance index reflecting spacecraft mission goals and constraints is formulated and optimized with respect to the integrated design variables. Initial studies have been concerned with achieving mission requirements with a lighter, more flexible space structure. Details of the formulation of the integrated-design approach are presented and results are given from a study involving the integrated redesign of a flexible geostationary platform

Design, Fabrication, and Validation of 3D Printed, Patient-Specific Compensators for Postmastectomy Radiation Therapy

The purpose of this study was to use 3D printed, patient-specific tissue compensators to overcome the 3D planning limitations for postmastectomy radiation therapy (PMRT). Tissue compensators can be used to reduce dose heterogeneity, hot and cold spots at field junctions, and treatment complexity, but are currently seldom used due to the difficulty in designing, fabricating, and validating them. To produce compensators using 3D printing technology, suitable materials had to be found and characterized. Several materials were found to be promising, but previously unreported material uncertainties were also discovered that must be carefully controlled for in 3D printing studies. A new algorithm was also created to optimally design the compensator shape to conform the dose to the desired region, while maintaining acceptable geometric considerations for 3D printing. Patients’ dose distributions calculated using this algorithm were superior to dose distributions calculated in those same patients using more conventional matched field plans. To validate the idealized dose distributions, a new technique was developed to 3D print patient-specific, large scale radiotherapy phantoms with dosimeters throughout that can accurately reflect patients’ anatomy better than generalized phantoms. Six of these phantoms were created for a sample of patients with a range of body vi sizes. A sample of compensators was designed and printed for these novel phantoms, and radiation doses were measured and compared to planned dose distributions. Measured doses agreed well with planned doses. This study demonstrates that 3D printed, patient-specific compensators can be used to simplify treatments, and improve dose distributions in PMRT patients relative to their conventional 3D plans. Additionally, the algorithm could be applied to calculate compensators for different treatment sites in the future, and the phantoms developed could be used to perform pseudo in vivo dosimetry measurements for a wide range of radiotherapy experiments