High speed, precision motion strategies for lightweight structures

Research on space telerobotics is summarized. Adaptive control experiments on the Robotic Arm, Large and Flexible (RALF) were preformed and are documented, along with a joint controller design for the Small Articulated Manipulator (SAM), which is mounted on the RALF. A control algorithm is described as a robust decentralized adaptive control based on a bounded uncertainty approach. Dynamic interactions between SAM and RALF are examined. Unstability of the manipulator is studied from the perspective that the inertial forces generated could actually be used to more rapidly damp out the flexible manipulator's vibration. Currently being studied is the modeling of the constrained dynamics of flexible arms

Passivity Analysis of a motion control for robots manipulators with dynamic friction

International audienceThis paper addresses the motion control in joint space of robot manipulators with friction described by the generalized LuGre friction model. The paper extends the nonadaptive version of the Slotine and Li's control system originally designed for friction--free manipulators to the case where a friction observer is incorporated to deal with friction. This observer corresponds to an adaptation of the friction compensation scheme proposed in Canudas de Wit 1995. Passivity concepts are the fundamental tools invoked in this paper to analyze the closed--loop systembehavior which lead to the conclusion of global asymptotic joint position tracking. A major advantage of this framework is that it allows to develop in a separate way the control law from the observer design provided that each part satisfies some passivity properties

Stable adaptive fuzzy control with TSK fuzzy friction estimation for linear drive systems

This paper considers the control of a linear drive system with friction and disturbance compensation. A stable adaptive controller integrated with fuzzy model-based friction estimation and switching-based disturbance compensation is proposed via Lyapunov stability theory. A TSK fuzzy model with local linear friction models is suggested for real-time estimation of its consequent local parameters. The parameters update law is derived based on linear parameterization. In order to compensate for the effects resulting from estimation error and disturbance, a robust switching law is incorporated in the overall stable adaptive control system. Extensive computer simulation results show that the proposed stable adaptive fuzzy control system has very good performances, and is potential for precision positioning and trajectory tracking control of linear drive systems

Discrete-Time Series Identification of Sliding Dynamic Friction in Industrial Robotic Joints

Abstract-In this paper, the discrete-time series identification of dynamic friction in actuated robotic joints during the sliding regime is proposed. Considering the friction lag as a firstorder time delay element behind the static friction nonlinearity a reasonable approximation of friction dynamics in sliding is proposed. The regression signal model is derived based on a discrete-time transformation of motion dynamics with nonlinear friction. A robust identification scheme is formulated in the Least-Squares (LS) sense by using an appropriate set of model-related regressors. Further, the related Recursive-LeastSquares (RLS) formulation is provided. The proposed modeling and identification are evaluated experimentally by the offline and online parameter estimation. For these purposes the first vertical rotary joint of the base of a standard industrial robotic manipulator has been used in laboratory environment

Grating Motor Control

A monochromator is a part of a spectrometer in which the grating scans the different wavelengths over the exit slit. A full spectrum is generated as the grating scans over a predefined interval. The grating must accelerate to a set speed very fast, then keep the speed constant over a predefined interval, and break to reverse the scan. On top of this come disturbances from an optical filter, causing vibrations in the housing, which can be seen in the spectra if not corrected for in the control algorithm. A model-based control system composed of Proportional-Integral (PI) control, and Iterative Learning Control (ILC), is implemented on a Field-Programmable Gate Array, using LabVIEW. The proposed controller shows promising results, with closed loop rise time within given bounds, and reduced disturbance effects

Force control and nonlinear master-slave force profile to manage an admittance type multi-fingered haptic user interface

Natural movements and force feedback are important elements in using teleoperated equipment if complex and speedy manipulation tasks are to be accomplished in remote and/or hazardous environments, such as hot cells, glove boxes, decommissioning, explosives disarmament, and space to name a few. In order to achieve this end the research presented in this paper has developed an admittance type exoskeleton like multi-fingered haptic hand user interface that secures the user’s palm and provides 3-dimensional force feedback to the user’s fingertips. Atypical to conventional haptic hand user interfaces that limit themselves to integrating the human hand’s characteristics just into the system’s mechanical design this system also perpetuates that inspiration into the designed user interface’s controller. This is achieved by manifesting the property differences of manipulation and grasping activities as they pertain to the human hand into a nonlinear master-slave force relationship. The results presented in this paper show that the admittance-type system has sufficient bandwidth that it appears nearly transparent to the user when the user is in free motion and when the system is subjected to a manipulation task, increased performance is achieved using the nonlinear force relationship compared to the traditional linear scaling techniques implemented in the vast majority of systems

Performance of modified jatropha oil in combination with hexagonal boron nitride particles as a bio-based lubricant for green machining

This study evaluates the machining performance of newly developed modified jatropha oils (MJO1, MJO3 and MJO5), both with and without hexagonal boron nitride (hBN) particles (ranging between 0.05 and 0.5 wt%) during turning of AISI 1045 using minimum quantity lubrication (MQL). The experimental results indicated that, viscosity improved with the increase in MJOs molar ratio and hBN concentration. Excellent tribological behaviours is found to correlated with a better machining performance were achieved by MJO5a with 0.05 wt%. The MJO5a sample showed the lowest values of cutting force, cutting temperature and surface roughness, with a prolonged tool life and less tool wear, qualifying itself to be a potential alternative to the synthetic ester, with regard to the environmental concern