Measuring systems for investigation into thermal phenomena appearing in drive systems with electronic micromotors

The thermal phenomena occurring in mechatronic devices may affect the device performance characteristics in various ways. Electrical drive systems are main sources of heat emission inside the device. The paper touches upon the problems of modeling and identification of thermal models of drive systems, that are useful tool for predicting thermal behaviour of the devices analysed by means of simulation. The measuring system designed to support such works are presented.Systemy pomiarowe do badania zjawisk cieplnych w układach napędowych z mikrosilnikami elektrycznymi. Współczesne urządzenia mechatroniczne, czyli urządzenia, w których funkcje mechaniczne realizowane są w odpowiedzi na sygnały z elektronicznych układów sterujących, na ogół mikroprocesorowych, działają z wykorzystaniem różnych zjawisk fizycznych. Przebieg wielu z tych zjawisk zależy od temperatury poszczególnych zespołów urządzenia. Istotny wpływ na temperaturę urządzenia mają zjawiska cieplne zachodzące w elektrycznych układach napędowych. W artykule przedstawiono koncepcję budowania cieplnych modeli podzespołów napędowych i zasady identyfikacji ich współczynników. Omówiono problemy związane z budową systemów pomiarowych służących do wspierania tych prac

Napęd z silnikiem skokowym zamiast serwonapędu w urządzeniu technologicznym

As a result of dynamic development that takes place in the field of controlling AC motors, designers of machines and various devices usually apply servo drives with induction or synchronic motors, relying both on their remarkable operational characteristics as well as their long life. However, advanced electronic systems and sophisticated software, necessary for obtaining such characteristics, are quite expensive. The authors present in the paper an ex ample of an actuating system for a processing device powered by AC servo drive. As proved by the model studies that have been carried out, the servo drive can be replaced with a stepping motor that is few Times less expensive, and at the same time meets all the requirements related to its operation.Dynamiczny rozwój, jaki dokonuje się w dziedzinie sterowania silników prądu przemiennego powoduje, że konstruktorzy maszyn i urządzeń chętnie stosują serwonapędy z silnikami indukcyjnymi lub synchronicznymi licząc zarówno na ich znakomite charakterystyki funkcjonalne, jak i dużą trwałość. Zaawansowane układy elektroniczne i wyrafinowane oprogramowanie, które umożliwiają uzyskanie takich charakterystyk są jednak dosyć kosztowne. W artykule przedstawiono przykład układu wykonawczego urządzenia technologicznego, napędzanego przez serwonapęd prądu przemiennego. Przeprowadzono badania modelowe, które wykazały, że serwonapęd ten można zastąpić napędem z silnikiem skokowym, wielokrotnie od niego tańszym, spełniającym przy tym wszystkie wymagania funkcjonalne

Three models of hybrid stepping motor

W pracy podjęto porównanie funkcjonalnego działania trzech modeli silnika skokowego z punktu widzenia występowania i oddziaływania tłumienia elektromagnetycznego. Porównanie przeprowadzono na przykładzie silnika skokowego hybrydowego reprezentowanego kolejno przez model ruchu obrotowego o wymuszeniu dyskretnym, model elektromagnetyczny oraz model ruchu obrotowego z uwzględnieniem tłumienia elektromagnetycznego.Stepping motors are electromechanical devices which convert electrical pulses into discrete mechanical movements. The shaft of a stepping motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied. The value of the frequency of the input pulses does not depend on the shaft position, so stepping motors use open-loop control. It is very important to use correct mathematical model for computer simulation during simulation investigation of the electrical drive with stepping motor. The simplest mathematical model of the stepping motor is a model of discrete mechanical movement. But it does not take into consideration the electromagnetic damping produced by induced voltage. It is possible to use the full electromagnetic model of a stepping motor, but it is often very difficult. Particularly difficult is modelling of the winding band. Authors show that it is possible to use the simple mathematical model of discrete mechanical movement which takes into consideration the electromagnetic damping without necessity of modelling of the winding band

Measuring system for determining performance characteristics of electrical linear actuators

Elektryczne siłowniki liniowe napędzane silnikami skokowymi są chętnie stosowane w precyzyjnych układach pozycjonujących. O ich przydatności do takich zastosowań przesądza nie tylko dokładność realizacji przemieszczeń, lecz także graniczne charakterystyki mechaniczne: rozruchowa i pracy. W artykule opisano zautomatyzowane stanowisko do badania elektrycznych siłowników liniowych opracowane i wykonane w Instytucie Mikromechaniki i Fotoniki Politechniki Warszawskiej. Przedstawiono rozwiązania torów sterujących i pomiarowych. Dołączono przykładowe charakterystyki siłowników wyznaczone z użyciem stanowiska.Electrical linear actuators powered by stepping motors are commonly used for precision positioning. In some appliances not only resolution and accuracy of movement decide about their usefulness. Sometimes mechanical characteristics play an important role. These are pull-in and pull-out characteristics, which limit working areas of actuators in coordinates of developed force versus linear speed. In the paper there is a special measuring system for determining performance characteristics of actuators presented. It was designed and made in the Institute of Micromechanics and Photonics of Warsaw University of Technology. Technical solutions adopted for measuring and control channels are described. Exemplary characteristics of actuators are added

Modelling and simulation of a system for verticalization and aiding the motion of individuals suffering from paresis of the lower limbs

There has been designed a device for verticalization and aiding the gait of individuals suffering from paresis of the lower limbs. It can be counted in the category of so-called “wearable robots”, whose task is to replace or aid human limbs. Dependently on the function realized, these robots are classified into one of the following three groups: a) exoskeletons - strengthening the force of human muscles beyond their natural abilities, b) orthotic robots - restoring lost or weakened functions of human limbs, c) prosthetic robots - replacing an amputated limb. A significant feature of the device that has been designed is the fact that it has not to replace human limbs, but only restore them to their lost motor capabilities. Thus, according to the presented classification, it is an orthotic robot. Unlike in the case of the existing systems for verticalization, the gait is to be realized in a way that is automatic to the highest possible extent, keeping the user involved as little as possible, and the device is to imitate the natural movements of man with the highest fidelity. Within the works on the system for verticalization and aiding the motion, a simulation model of the device was created. It includes a structure of the robot, a model of the actuators and a model of the human body that constitutes the load for the driving units. Then, simulation studies were carried out, including evaluation of the power demand of the device as well as the influence of the gait rate and of the length of the steps on the operation of the system

Modelling of mechatronic devices supported by 3D engineering software

Modelling is considered to be an inherent part of design process of mechatronic devices and systems, in particular when solving problems of dynamics and accuracy of actuators and sensors. Mathematical software packages such as Matlab/Simulink are commonly used for this purpose. Engineers and designers who integrate mechanical components of devices under design, usually employ special computer software known as 3D CAD for creating three dimensional images. Typically it is used to generate technical drawings and layouts but its usability is more extensive. The paper presents ability of such software to support simulation where a linear stepping actuator is an example of a device under design

Simulation model of actuators of an orthotic robot

W Zakładzie Konstrukcji Urządzeń Precyzyjnych na Wydziale Mechatroniki Politechniki Warszawskiej trwają prace nad systemem do pionizacji i realizowania chodu osób z bezwładem kończyn dolnych. Projektowanie urządzenia jest wspomagane badaniami modelowymi. W artykule przedstawiono symulacyjny model elektromechanicznej części systemu opracowany w środowisku Matlab/SimMechanics. Model wykorzystano m.in. do wyznaczenia zapotrzebowania energetycznego układów wykonawczych i oceny błędów odwzorowania profili ruchu.In the Division of Design of Precision Devices at the Faculty of Mechatronics of Warsaw University of Technology works there are performed upon a system for verticalisation and substituting gait for people with paresis (Fig. 1). Works are supported with simulation software. Simulation model of the system actuators is described in the paper. The purpose of simulation was to estimate energy consumption of actuators and to assess quality of their movements. Main assumption for the model is that mechanisms activating user's legs are of a planar kind. Matlab-SimMechanics mathematical environment was used for modelling. Structure of the model is presented in Fig. 2. Parts of human body are sources of load for actuators as described by eq. (2) and (3). Their parameters are inserted into "body" blocs (Fig. 3), which represent stiff elements of mechanisms in the model. Mechanical contact between the device and a ground was modelled as reaction forces occurring in "foot" parts of the device when distance between them and the ground is less than the assumed value. The drives of actuators' employ DC motors equipped with reduction gearboxes (Fig. 4). Typical equations (4) - (9) were used for modelling DC motors and gears. Input signals are reference angular displacements of joints expressed in the form of functions approximating experimental data (Fig. 5). Simulation experiments revealed strong relation between length of gait cycle and energy consumption of actuators (Fig. 6). Reduction gear ratio also influences energy needs as well as quality of the device movements (Fig. 8). The model is being currently modified and enhanced in order to be used at the next stages of design process

Concept of the control system of an orthotic robot

Mechatronika, jako koncepcja budowy urządzeń jest obecna niemal we wszystkich działach techniki. Rozwój mikroprocesorowych układów przetwarzania danych, a także postęp w dziedzinie budowy układów wykonawczych i pomiarowych stwarzają możliwości realizowania przez urządzenia funkcji, które jeszcze do niedawna pozostawały jedynie w sferze marzeń. Postęp nie ominął również medycyny, a ściślej wyposażenia technicznego pracującego na rzecz osób chorych. Roboty ortotyczne, których szybki rozwój następuje w wielu ośrodkach naukowych na całym świecie, zastępują u ludzi utracone funkcje ruchowe. Autorzy pracują nad urządzeniem do pionizacji i wymuszania chodu osób z bezwładem nóg. W artykule przedstawiono koncepcję systemu sterowania opracowywanego urządzenia.Mechatronics seems to be nowadays the leading idea of design of machines and devices. Integration of mechanic devices with the powerful microelectronic technology forced synergy effects resulting in new applications also in medical domain. Here, wearable robots are most spectacular examples. They are person-oriented robots that may be defined as those worn by human operators, whether to support the function of a limb or to replace it completely. The authors focussed their attention on the development of an orthotic robot suited for people with paresis of lower limbs (Fig. 1). The role of the robot is to improve standard of life of handicapped people. However, for safety reasons, its usage needs additional assistance of third party persons. It leads to a conclusion, that control system of the device should be designed in such a way that movements of limbs are allowed only and only in cases when all safety conditions are fulfilled. Upon this statement, the device under design can be classified as a self optimising system. The general structure of such a system is shown in Fig. 2. This system consists of: knowledge base, multi- control subsystem, communication ports and inference machines. The block diagram of automatic control system is depicted in Fig. 3. The main purpose of knowledge base is to store and update reference data for decisions upon the device performance. This data contains records of values of selected signals, collecting information about the state of the device and a robot user, in order to detect non-safety behaviour. Tilt of the user's body and acceleration of its certain parts, as well as reaction forces between feet and crushes against ground can be considered as signals useful for decision making. A structure of the control system meeting the above considerations is presented in Fig. 4. A brief survey of data transmission protocols was carried out. A survey was focused on systems used for industrial applications taking into considerations its approved high immune against electromagnetic field transients and easiness of building redundant structures of communication networks and controllers. Finally, CAN standard was proposed as a communication protocol for the device broadly used in automotive industry (Fig. 5). In the conclusions future works are presented together with the risk analysis