This paper offers a new approach for specifying the waveforms of driving voltages for a Piezo LEGS motor. A novel idea of coordinate transformation to define the waveforms of driving voltages, based ...on the motor static model, is presented. This transformation defines driving voltages according to the desired motion of the motor legs in the x- and y-directions. The approach allows a user to first define force acting on the motor rod in the y-direction and define the rod's x-direction trajectory profile. Waveforms of the driving voltages are subsequently defined to meet these requirements. The proposed approach also enables the possibility of defining the desired step shape for the motor and, according to that definition, producing driving voltages. Based on the given coordinate transformation, a simple method for Piezo LEGS motor control, identified as virtual time control, is presented. This method results in overshoot-free high precision positioning.
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.
Sub-millimeter scale devices are developing rapidly taking smaller, smarter, and more precise forms. This is achieved thanks to advancements in micro-manufacturing tools and techniques. For ...micro-production, a miniaturization of the machinery is a prominent idea that has numerous benefits in terms of material usage, precision, transportation, modularity, and reconfigurability. In this paper, a modular and reconfigurable desktop microfactory for high precision machining and assembly of sub-millimeter scale mechanical parts is presented and experimentally validated. The proposed system is built based on important functional and performance requirements, including miniaturization, high precision operation, modular and reconfigurable design, parallel processing capability, ease of installation, and transportation. The miniature factory consists of five mini processing units; two parallel kinematic robots for manipulation, the laser micro-machining system, the camera system for detection and inspection, and the rotational conveyor system for micro-part delivery. Different configurations of the system layout are proposed taking advantage of their modular design. Experiments are conducted to evaluate the system performance within a single process, like pick-place of a metallic ball with 3 mm diameter, laser machining of a half-millimeter size contour on the surface of the ball, and inspection and verification of the machined contour by means of microscopic camera. The results presented in this work demonstrate micrometer precision operation of the microfactory, showing high potential for manufacturing electro-mechanical devices with ease of readjustment of the microfactory layout.
In shared human-robot environments, control systems operate based on the information about both human and robot activities to facilitate the successful collaboration between the two. This paper ...contributes to the emerging field of human-robot collaboration (HRC) by unifying human action recognition (HAR) and high-level robot control technique into single control system. Approach in this paper includes artificial neural network based classifier for recognition of human activity and task-based control as an example of high-level control technique. Classifier is developed based on the data from wearable sensors attached on the human arms. Recognized human activity is used as the input for the selection of functions that describe robot's activity (task). This papers combines both the theoretical approach to the task-based control and it's synergy with HAR while the developed artificial neural network classifier is experimentally validated.
This article presents a kinematic model and control of a galvanometric laser beam steering system for high precision marking, welding or soldering applications as a microfactory module. Galvo systems ...are capable of scanning laser beam with relatively high frequencies that makes them suitable for fast processing applications. For the sake of flexibility and ease of use 2D reference shapes to be processed are provided as CAD drawings. Drawings are parsed and interpolated to x - y reference data points on MATLAB then stored as arrays in C code. C header file is further included as reference data points to be used by the system. Theoretical kinematic model of the system is derived and model parameters are tuned for practical implementation and validated with respect to measured positions on rotation space with optical position sensor and image field with position sensitive device. Machining with material removal requires high power laser to be employed that makes position measurement on image field unfeasible. Therefore for closed loop applications optical position sensor embedded in galvo motors is used for position feedback. Since the model approved to be approximately linear in the range of interest by simulations, a PI controller is used for precise positioning of the galvo motors. Experimental results for tracking circular and rectangular shape references are proved to be precise with errors of less than 2%.
U radu je predložen funkcijski obzerver za sustave upravljanja gibanjem koji ostvaruje veću preciznost i manji šum estimacije u usporedbi s postojećim obzerverima. Obzerver estimira brzinu, ...akceleraciju i poremećaj korištenjem mjerenja ulazne struje, položaja te poznatih nominalnih parametara sustava. Znanstveni doprinos predloženog obzervera je funkcijska struktura koja omogućava intrinzičnu estimaciju i kompenzaciju nemjerljivih ulaznih veličina (kao što je poremećaj koji djeluje na sustav) korištenjem mjerenja ulazne struje. Eksperimentalni rezultati potvrđuju kako predloženi obzerver ostvaruje točniju estimaciju brzine, akceleracije i poremećaja u usporedbi s ostalim obzerverima drugog reda.
U članku se raspravlja o algoritmu za generiranje trajektorija, metodi za konstrukciju pogreške konture te o sintezi konturnog regulatora. U algoritum za generiranje trajektorija, korištena je ...kombinacija eliptičnih Fourierovih odrednika (EFD) i vremenske aproksimacije splajnovima (TBSA) za odre.ivanje referentnih vrijednosti položaja, brzine i ubrzanja. Pogreška konture je konstruirana korištenjem transformirane pogreške slije.enja trajektorije. Transformacija je računski efikasna i potrebna joj je samo informacija o referentnoj brzini. Konturni regulator je projektiran koristeći upravljanje u kliznim režimima. Provedeni su eksperimenti na linearnom slijednom sustavu i primijećena su znatna smanjenja pogreške konture.
This paper presents a novel functional observer for motion control systems to provide higher accuracy and less noise in comparison to existing observers. The observer uses the input current and ...position information along with the nominal parameters of the plant and can observe the velocity, acceleration and disturbance information of the system. The novelty of the observer is based on its functional structure that can intrinsically estimate and compensate the un-measured inputs (like disturbance acting on the system) using the measured input current. The experimental results of the proposed estimator verifies its success in estimating the velocity, acceleration and disturbance with better precision than other second order observers.
This paper discusses the trajectory generation algorithm, contour error construction method and finally the contour controller design. In the trajectory generation algorithm combination of elliptical ...Fourier descriptors (EFD) and time based spline approximation (TBSA) is used to generate position, velocity and acceleration references. Contour error is constructed using transformation of trajectory tracking errors. Transformation is computationally efficient and requires only reference velocity information. Contour controller is designed using sliding mode control. Experiments are performed on planar linear motion stage and significant contour error reduction is observed.
PDF
