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Electro-hydraulic systems are extensively utilized to generate desired acceleration waveforms to provide a vibration environment for testing the performance and reliability of objects in various industrial applications. However, as electro-hydraulic systems are often affected by some inevitable drawbacks resulted from hydraulic nonlinearities, unwanted dynamic variations and disturbances, the generated acceleration waveform is generally far behind the expectation. In this paper, a convex combined adaptive controller with input shaping technique is proposed for enhancing the transient acceleration waveform replication accuracy of electro-hydraulic systems. The proposed controller is comprised of a three variable controller at the bottom level, an input shaping technique controller at the middle level, and a convex combined adaptive controller at the upper level. The three variable controller is firstly utilized for the establishment of a fundamental closed-loop acceleration control system, and then the input shaping technique controller is constructed by introducing an offline designed inverse prefilter utilizing the multi-innovation recursive least squares algorithm and the zero magnitude error tracking algorithm. The convex combined adaptive controller at the upper level is comprised of two individual adaptive filters with high and low step sizes, which provides the merits of fast convergence rate and high tracking accuracy, and it is further exploited to address for system's dynamic variations, model uncertainties and unexpected perturbations. Comparative experiments of the proposed controller with a manually generated random waveform and a recorded earthquake waveform as the testing inputs are conducted on a typical electro-hydraulic test bench, and the corresponding results demonstrate the feasibility and superiority of the proposed controller in improving the transient acceleration waveform replication performance of electro-hydraulic systems. • A new transient acceleration waveform replication strategy using convex combined adaptive controller with input shaping technique is proposed. • Input shaping technique controller acting as a prefilter is adopted to enhance tracking frequency bandwidth and reduce phase delay error. • Convex combined adaptive controller is exploited to address for system's dynamic variations, model uncertainties and unexpected disturbances. • Experimental results validate feasibility and superiority of the proposed controller than the other comparative methods. [ABSTRACT FROM AUTHOR]

Abstract This paper focuses on the design of a novel path following control concept for fixed-wing aircraft, which systematically incorporates the nonlinearities of the flight dynamics. By introducing an acceleration based inner loop control, feedforward acceleration demands of nonlinear 3D paths can be directly taken into account. Furthermore, the nonlinear effects of airspeed, orientation, and gravity are considered separately by implementing a cascaded design and feedback linearization. As a result, robust performance of the path following control is achieved even for wind speeds in the order of the aircraft's airspeed and path accelerations significantly higher than the gravitational acceleration. By further including direct lift control, a high-bandwidth vertical acceleration control is developed. Results of flight experiments show that the designed control concept is particularly beneficial in terms of the tracking performance for 3D paths, the incorporation of input constraints, the robustness against wind and turbulence effects, and the ease of implementation as well as the low computational complexity. [ABSTRACT FROM AUTHOR]

Abstract Electro-hydraulic shake table (EHST), also known as earthquake simulator, is of considerable significance in civil engineering for evaluating structures or infrastructures subjected to earthquake ground motions. However, reproduction of prescribed accelerations at table for EHST systems remains to be imperfect as the whole systems are confronted with hydraulic nonlinearity, varying dynamics, unexpected disturbance, etc. For enhancing the acceleration tracking performance of EHST systems, an acceleration waveform reproduction strategy using offline designed parametric feedforward compensator (PFC) and online functional link adaptive controller (FLAC) is proposed in this paper. The PFC controller is established on the basis of classical three variable controller (TVC) as an inner compensation loop, in which multi-innovation forgetting gradient (MIFG) algorithm together with zero magnitude error tracking (ZMET) technique are utilized during the design process. The FLAC controller is combined to the PFC controller as an outer loop for further acceleration enhancement purpose, and the controller's nonlinear mapping ability is achieved with trigonometric expansion implementation. Following theoretical analysis of the proposed controller, comparative experiments are performed on an established unidirectional EHST test bench with both random and real-time recorded earthquake input waveforms. The experimental results validate the feasibility and superiority of the proposed acceleration reproduction strategy. Highlights • A new compound acceleration control strategy using parametric feedforward compensator and functional link adaptive controller is proposed. • An inner-loop parametric feedforward compensator is designed with MIFG algorithm and ZMET technique. • An outer-loop functional link adaptive controller with nonlinear mapping ability is developed to address the system's nonlinearity and varying dynamics. • Experimental results validate the superiority of the proposed controller than the other comparative methods. [ABSTRACT FROM AUTHOR]

A novel controller for three-dimensional contouring control of three-degrees-of-freedom (3-DOF) robotic manipulators is presented in this paper. The proposed controller comprises of an independent joint controller, designed in the configuration space, and a sliding mode controller that enforces desired dynamics for the tracking error projections to the Frenet-Serret frame. Therefore, the presented controller has a hybrid structure and it is named as hybrid contouring controller. In this paper, contour tracking with constant magnitude tangential velocity is discussed. Reference trajectory is generated using the time based spline approximation in order to provide a smooth reference path. The proposed hybrid contouring controller was experimentally compared with the independent joint controller that is designed in the acceleration control framework with disturbance observer. Experimental results, undertaken on a delta robot, showed that hybrid contouring controller outperforms independent joint control architecture. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of path following for unmaned cars using only GNSS positionning. Several papers have already addressed the lane keeping, usually restricting the focus to the computation of the optimal steering wheel angle, therefore usually offering a good solution in either straight lines or curves, but rarely both. Moreover the GNSS receiver have a sampling time higher than the required one for the proposed strategies in the literature. In this paper, a control algorithm is proposed for the steering wheel angle, with adaptation of the speed of the car, in order to provide a solution working both for straight lines and curves by using only GNSS. The presented solution has been used in real conditions to realize the demonstration “speed synchronization at intersections using intervehicular communication, x.icars” shown at the Intelligent Transportation System World Congress in Bordeaux, 2015 1 1 https://www.youtube.com/watch?v=KBx6qks8kCI . [ABSTRACT FROM AUTHOR]

Abstract: Advances in manufacturing technologies and in machine tools allow for unprecedented quality and efficiency in production lines, but also ask for new and increasing requirements on the motion planning and control systems. The increase of CPU processing power has permitted, in traditional CNC systems, the introduction of NURBS interpolation capabilities, thus determining a further increase in machining quality and efficiency. This has posed new and still unsolved issues, such as the need to satisfy multiple opposite constraints like limiting chord error, acceleration and jerk and offering real-time guarantees. In addition, the ability of privileging the production throughput by relaxing one or more of the previous constraints in a simple way, has emerged as another requirement of modern manufacturing plants. Nevertheless, none of the existing NURBS interpolators have these characteristics. In this work, we propose a NURBS interpolator that is able to satisfy all the manufacturing technology requirements and is able to respect, thanks to its bounded computational complexity, the position control real-time constraints. Such an interpolator is easily reconfigurable, i.e., it can relax some of the constraints while maintaining performances better than previously proposed solutions, and can be adapted in order to include constraints that were not originally considered. Performances of the proposed algorithm have been evaluated both by simulations and by real milling experiments. [Copyright &y& Elsevier]

Abstract: A fuzzy logic based digital time domain sinusoidal acceleration waveform amplitude controller for an electrodynamic shaker is presented. The purpose of Fuzzy Logic Control (FLC) is to reproduce a pre-defined sinusoidal acceleration amplitude profile (in amplitude, frequency and time) at the shaker table. Sinusoidal vibration profiles (sine and logarithmic sine sweep) are considered for a controlled vibration generation in typical automotive and aerospace testing. The difficulty in sine sweep testing is that the non-rigid load dynamics are unknown and it can severely modify the shaker’s performance during sweep test. Since a logarithmic frequency sweep is normally used, a controller needs to be robust to un-modeled dynamics and also fast enough to hold the desired acceleration amplitude within predefined limits throughout the sweep test. The controller structure is developed based on the usual power amplifier technology. The control action is implemented on a waveform-by-waveform basis and a FLC is developed in the LabVIEW environment on a PXI platform for real time control of the shaker. To attenuate the shaker suspension mode resonance a compensator based on electromechanical model of the shaker is designed and cascaded to FLC. The shaker model, suspension mode compensator design, FLC synthesis and experimental implementation results are presented in this paper. [Copyright &y& Elsevier]

Abstract: The purpose of earthquake simulators is to reproduce reference accelerations on a shake table. However, acceleration control is extremely difficult in earthquake simulators due to an inability to directly control acceleration with feedback, inherent nonlinearities in servo hydraulic systems, control-structure interactions, etc. This study presents a control method called acceleration trajectory tracking control (ATTC) that improves the acceleration control performance of earthquake simulators. The ATTC method consists of an acceleration feed-forward controller, a system dynamics command shaping, an intentional time-delay, a Kalman filter for displacement measurement, and an actuator displacement feedback controller. The ATTC method not only provides acceleration tracking capability, but also ensures stability of the system. Following the theoretical description of the ATTC method, an experimental investigation is presented. The ATTC method is successfully implemented in the control system for the uniaxial earthquake simulator at Johns Hopkins University, and the experimental results show the superior performance of the ATTC method over the conventional displacement feedback with command shaping. Furthermore, repeatability of the ATTC method is experimentally verified. [Copyright &y& Elsevier]

Abstract: Human-friendly robots have begun to spread in society. In the future such robots and intelligent machines should be autonomous in open situations. To give dexterity to a robot, teaching motion is a good candidate. However, there are some problems from the operational point of view due to gravity and friction effects. In this paper, a shadow robot is proposed for teaching motion instead of force sensors. The shadow robot is a novel disturbance compensation method that consists of a twin robot system. Two of the same type of robot are required and they are controlled with the same position, velocity, and acceleration by bilateral acceleration control based on a disturbance observer. One robot is in the teaching motion controlled by a human and the other is unconstrained. Thus the purity of the human force is extracted by subtracting the disturbance torque in the unconstrained robot from the constrained one. As a result, the shadow robot observes the human force with gravity and friction compensation. Since it is possible to apply this concept to a multi-degree-of-freedom system, the human operationality in teaching motion are improved. The experimental results show the viability of the proposed method. [Copyright &y& Elsevier]

Abstract: This paper describes a precise position synchronous control of multi-axis rotating system. The control strategies to achieve precise servo system are summarized in two main points: an acceleration control is adopted in an inner loop to ensure robustness of speed of each axis against disturbances, and then a maximum error comparison method has been introduced to minimize not only position synchronous errors but also speed errors of all motor axes. At first, the system dynamics including dc motor drive are rigorously presented by using motor circuit equations and Newton’s formulation. Next, the acceleration and speed controllers are readily designed via proportional-integral (PI) control law. Also, to reduce position synchronous errors caused by different motor dynamics, each axis is coupled by the maximum error comparison scheme. The control system presented is investigated through extensive simulations under step- and sinusoidal-type disturbances. Finally, it has been shown that experimental results successfully demonstrate the effectiveness of the proposed control system for four-axis position synchronous control. [Copyright &y& Elsevier]