Mechatronics Laboratory: Technological Background Objective: This document illustrates the main research areas currently active in the Mechatronics Laboratory of Politecnico di Torino – Verrès campus. The Mechatronics Laboratory (Laboratorio Interdisciplinare di Meccatronica, LIM) at the Politecnico di Torino is an interdepartmental structure founded in 1993 as a “joint-­‐venture” by a number of people of the Departments of Control and Computer Sciences (DAUIN), Electronics and Telecomunications (DET) and Department of Mechanical and Aerospace Engineering (DIMEAS) of Politecnico di Torino. From 2008 the main facilities of LIM are located in the Verrès campus of Politecnico di Torino. LIM activities are organized in terms of projects where different disciplinary expertise is integrated to optimise the overall performance. Most of the projects are in cooperation with companies and start from their needs of innovative solutions. These solutions are not only studied but also tested through the development of working prototypes and demonstrators. The technological and scientific relevance of LIM activities is documented by the number of industrial partners and by a number of papers in international conference proceedings, journals and patents. The instrumentation of the Laboratory is also available for different type of tests ranging from modal tests, vibration tests, electrical/electronic characterization. The main technological areas currently active in the Mechatronics Laboratory of Politecnico di Torino – Verrès campus are the following: 1. Control Units for Mechatronics Applications 2. Energy Scavenging 3. Energy Storage 4. Active Magnetic Suspensions 5. Passive Magnetic Suspensions 6. Mechatronic Systems for Automotive 7. Mobile robotics / Unmanned Vehicles 8. Power Actuations 9. Vibration Control Systems 1. Control Units for Mechatronics Applications a. Description The combination of algorithmic and logic processing power by means of digital signal processors (DSP) and Field Programmable Gate Arrays (FPGA) can result in a powerful and modular Electronic Control Unit (ECU) to be used in many different and demanding mechatronic applications. This approach allows a really fast and modular control solution to all those mechatronic (automotive, industrial, space, etc...) applications where the flexibility and the performance of the control system is mandatory for a reliable and robust solution. This is the real "heart beat" of all mechatronic systems. b. Innovation In this field the most important innovation is based on the system integration of state-­‐of-­‐the-­‐art electronic components in order to develop new generation embedded computing units for real-­‐time model-­‐based control systems. This type of embedded ECU can be used in different fields of application (automotive, industry, aerospace, energy) directly connected with the sensor/actuator system in such a way to optimize performances and possibly costs. RTOS (real-­‐time operating systems) is the other key factor for this technology: flexible, configurable and possibly automatically generated code (starting from high-­‐level design and simulation tools) is essential for both the prototyping and industrial phase. c. Future Applications Reconfigurable ECU can be used for fast prototyping of ASIC (Application Specific Integrated Circuit) and SiP (System in Package) industrial components where many different devices (die) can be integrated together in a single component for a specific application. Design process for such devices in the different application fields can take months and several skills to finish: the fast prototyping approach can lead to the final result (in terms of hardware and software) trough experimental and validation steps that help to understand the behaviour of the application and the critical aspects. Moreover the interface between control ECU and actuation ECU (power electronics) can be developed during the prototyping phase with considerable savings in terms of time and non-­‐recurrent initial costs. d. Advantages The major advantages are based on the fast development of the final application and related critical components with the possibility to “scale” the computational power of the ECU and the “size” of the power electronics in the very early phase of the design process. Each prototype ECU and related power electronics became a kind of “instrument” that can be used to precisely size the final product in terms of performances, control hardware (DSP, FPGA, FPAA, etc…), control software and power electronics (topology, strategies, modulations, fault detection, fault tolerance, etc….). e. State of Development The Mechatronics Lab has developed in the last ten years a numbers of platforms based on FPGA and DSP state-­‐of-­‐the-­‐art components and related actuation power stages based on MOSFET/IGBT very high frequency switching components and is always looking at new applications to develop next generation reconfigurable control platforms. f. Keywords Real-­‐time control, fast prototyping, DSP, FPGA, Real-­‐time operating systems, ASIC/SiP prototyping g. Images 2. Energy Scavenging a. Description Energy scavenging, or energy harvesting, is a process that captures, converts and store small amounts of wasted energy. The energy source for energy harvesters is present as ambient background and is free for example: kinetic energy, thermal energy, temperature gradients, etc ...Vibration, movement and sound can be captured and transformed into electrical power using piezoelectric materials. Heat can be captured and transformed into electrical power using thermoelectric materials. These systems will be capable of monitoring the environment, communicating with people and among each other, actuating and supplying themselves independently. This concept is now possible thanks to the low power consumption of electronic devices and accurate design of energy scavengers to harvest energy from the surrounding environment. Self powered wireless sensor networks for household application In principle, an autonomous device comprises three main subsystems: an energy scavenger, an energy storage unit and an operational stage. The energy scavenger is capable of harvesting very small amounts of energy from the surroundings and converting it into electrical energy. This energy can be stored in a small storage unit like a small battery or capacitor, thus being available as a power supply. The operational stage can perform a variety of tasks depending on the application TEG - Thermoelectric Generator
The thermoelectric modules are solid-­‐state devices commonly used in cooling/heating applications, but in the last years they have been largely studied and utilized as energy converters since they are able to produce electricity from heat absorption. Piezoelectric Energy Harvesting
The piezoelectric effect converts mechanical strain into electric current or voltage. This strain can come from many different sources. Human motion, low-­‐frequency seismic vibrations, and acoustic noise are everyday examples. Except in rare instances the piezoelectric effect operates in AC requiring time-­‐varying inputs at mechanical resonance to be efficient. b. Innovation Self powered wireless sensor networks for household application. An hydraulic energy harvesting system used to supply a control valve of a heating system for a typical residential application was studied and realized. The system converts the kinetic energy from the water flow inside the pipes of the heating system to power the energy scavenger. TEG -­‐ Thermoelectric Generator Within this research, we extend the area of interest for the employment of thermoelectric generators to the environmental monitoring, in particular to supply energy to autonomous sensors, placed in remote locations with hard environmental conditions (very low temperature, difficult access, etc...), where the usual renewable energy sources, like solar and wind energy, are not regularly available. The novelty of our prototype with respect to the previous devices is found in its smallness, both for dimensions and power requirements, and in the heat source employed since in our case it is supplied by a flameless catalytic burner. Piezoelectric Energy Harvesting We are developing an energy harvester based on piezoelectric materials. Such device is able to capture the energy from vibrations generated in various applications (aerospace, automotive, industrial, etc...) and to convert it into electrical power used to supply autonomous sensors. c. Future Applications Efficiency optimization for energy harvester, self powered wireless sensors network systems, extension to renewable heat sources (geothermal, ocean thermal energy, waste heat), environmentally friendly piezo transducers. d. Advantages Remote monitoring, self powered systems, competitive and reliable for applications with low power and small dimensions. e. State of Development Specific and custom application design; modelling, prototype building and testing (laboratory and real conditions). f. Keywords Energy harvesting, energy scavenging, scavenger, efficiency optimization, scavenger, microgenerator, wireless sensor network, thermoelectric generator, thermal energy harvesting system, piezoelectric transducers, g. Images Vibration Energy Scavenger
Thermoelectric Generator, environmental testing.
3. Energy Storage a. Description The "energy issue" is becoming increasingly important. The cost of conventional energy is growing exponentially with no control and the effects of pollution due to the use of oil and other fossil fuels are simply obvious. The growing energy demand, not just from industry but also by common civil loads, requires a gradual increase of the power generated by power plants, which however, is not sufficient to cover the entire national need, forcing the power distributor to buy energy from foreign countries with a high price and then provide consumers with significant increases on the cost per kWh. LIM has been active for several years with projects aimed at improving local and distributed energy management using different kind of storage systems: •
Predetermination of produced energy: This application is one of the most required from the energy market in Italy due to the predetermination of the energy production profile offers the possibility to access to national incentive for each kWh produced. •
Systems to support local self-­‐consumption: The self-­‐consumption of auto produced energy is becoming more and more important to increase the energy efficiency on the whole distribution system and is one of the main goal of new Smart Grids systems. •
Peak shaving and UPS: Another important activity is the reduction of peak absorption of civil and industrial loads. Local system able to manage this discontinuous absorption can prevent the grid oversizing and overloading. b. Innovation Predetermination of produced energy from non-­‐programmable renewable sources LIM’s systems use energy storage as complement to traditional discontinuous power source; as reserve of energy is possible to compensate any underproduction from renewable sources and respect the predetermined profile; the storage is then recharged when is available an overproduction or simply with part of the energy that is not necessary to inject in the national grid. In this way is possible to guarantee a specific energy production along the day/week also using traditional renewable sources that are characterized by a natural unpredictability of their production. Systems to support local self-­‐consumption of produced energy Starting from the V Italian Energy Directive, for each kWh produced by PV plants, is applied an all-­‐inclusive incentive and in addition a further incentive for all the energy self-­‐consumed on-­‐site. Actually the only way to increase the self-­‐energy consumption is to implement a storage system to the standard PV plants in order to store the energy that is not instantly consumed for future use and inject in the grid only that amount of energy that is not required from the whole load. For this reason is necessary not only a storage composed by accumulator and their BMS, but also a system able to manage the flux of energy according to a combination of absorption profile, historical data and instantaneous request. Beside accumulators, inertial storage can be an alternative; for large scale storage the feasibility need to be better investigated, while for small sized systems promising performances can be achieved especially for application with high ratio between instantaneous power versus stored energy. Peak shaving An important use of the storage is the peak shaving of impulsive absorption in civil and industrial loads. For example typical behavior of civil load is characterized by a very discontinuous absorption of energy from the distribution grid only in some time slot along the day; normally is required a high power contract respect to the average power consumption of the whole appliances, reaching some times 6-­‐8 times the average power that is really necessary. Applying these systems to civil loads is possible to define the absorption profile independently from the real power requested according to the user behaviour; the profile become substantially constant along all the day, allowing to optimize the power purchase contract with a substantial reduction of the necessary power peak. Also in case of industrial loads, usually characterized by high impulsive absorptions for short periods, the system make possible to size the entire power supply system on the average power rather than the peak power. The usage of inertial accumulators, i.e. flywheels, for peak shaving is a promising solution due their high power density, reliability and lower power consumption (especially if the flywheel is supported with magnetic bearings: see “Active and Passive Magnetic Suspension” in the following). Even from the environment point of views, flywheels solution have a better sustainability compared to chemical storage based solutions. c. Future Applications Local energy storage for peak shaving, reduction of reverse energy conversion in substation, grid frequency stabilization, reactive power corrector, predictable power sources for RES, local blackout prevention. d. Advantages Reduction of energy flow in substation and in high voltage distribution lines, local uninterruptible power supply, automatic compensation of reactive power, increase of power production from RES. e. State of Development First prototype for peak shaving and ups already realized and implemented in real condition. New systems based on LiPo accumulators under realization. Inertial accumulators (flywheels) under research for future high power management in substation. Flywheel on magnetic bearings available as prototype in laboratory, ready for engineering and production. f. Keywords Energy Storage, UPS, Peak Shaving, Smart Grids, Virtual Power Systems, Renewable Energy Sources (RES), Lithium accumulators (LiPo), Inertial Accumulators (Flywheel) g. Images ESS 1.0: Energy Storage System: first prototype developed and installed in residential buildings for peak
shaving and ups
Flywheel: Schematic layout of Flywheel Energy Storage system with magnetic bearings
(picture from paper: Filatov, A., McMullen, P., Davey, K., Thompson, R., Flywheel energy storage system with homopolar electrodynamic
magnetic bearing, Proceedings of the tenth international symposium on magnetic bearings, Martigny, Switzerland, 2006)
4. Active Magnetic Suspensions a. Description Active magnetic Suspensions exploit electromagnets working principles to perform contactless control of rotating machines. They are created by combining electromagnets, power amplifiers, non-­‐contact position sensors and an electrical control system. The control unit uses signals from the position sensors to determine commands to be sent to the power actuation (amplifiers) unit. The amplifiers, in turn, drive current through the electromagnet coils to produce forces which act on the suspended rotor. Typically three actuation stages are used to control rotors (2 radial + 1 axial), but a conical bearing configuration can be used to reduce the number of electromagnets and hence costs, weight and size. Each actuation stage is realized with at least 3 actuation poles even if the most frequent solution counts on 4 electromagnets per stage. The power actuation can be performed by linear amplifiers (less noisy but able to provide low control power) or switching amplifiers (more noise and higher control power). Position sensors can be optical, inductive or capacitive depending on application, precision and size requirements. Sensorless controls have been developed in the last years to get rid of position sensors and to overcome non-­‐collocation issue. b. Innovation Innovation is focused mostly on following aspects: a) driving techniques in switching power actuators, b) sensors technology, c) control strategies and d) actuators morphology. In all these fields the aim is the reduction of size, costs and weight. c. Future Applications This technologies can now be installed in server fields regardless the size of the machine application. Some application fields can be: High Vacuum and cryogenic, Turbomolecular pumps, medical devices (artificial heart), nuclear power plant, tooling machines, flywheel for energy storage, aerospace application (high speed compressor/reaction wheel, gyroscopes), Oil&Gas (subsea compressor, pump stations), high speed rotating machine. d. Advantages Absence of contact (no wearing, longer MTBM); absence of lubrication, tunable control loop during operation; online functional and operational monitoring; lower losses (power consumption); scalable design. e. State of Development Reedy for specific/custom application design; prototype build and tested in real environment. Industrial application developed built and operating (Turbomolecular pumps). f. Keywords Magnetic Suspension, Active Magnetic Bearing, AMB, Contactless, Active Control of Vibration, No lubricant, Vacuum Application, High MTBM, Online/continuous Monitoring and Diagnostics, Tuning in Operation g. Images Test Rig: spindle on Active Magnetic Bearings
Turbomolecular Pump: rotor on Active Magnetic Bearings.
Magnetic Levitated Turbo Compressor : CAD Mock Up and conical shaped active magnetic bearing set-­‐up. 5. Passive Magnetic Suspensions a. Description Electrodynamic bearings (EDBs) are passive magnetic bearings that exploit the interaction between eddy currents developed in a rotating conductor and a static magnetic field to generate forces. Similar to other types of magnetic suspensions, EDBs provide contactless support, thus avoiding problems with lubrication, friction and wear. The most interesting aspect of EDBs is that levitation can be obtained by passive means, hence, no electronic equipment, such as power electronics or sensors, are necessary. The radial electrodynamic bearing in the axial flux configuration is composed by a rotating conductor, for example, a copper disc, immersed in a constant magnetic field. The magnetic circuit is composed by two concentric, axially polarized, permanent magnet rings oriented in attraction and a toroidal shaped iron yoke for enclosing the magnetic flux. The conductor disc is located between the permanent magnets and is free to move radially while its motion along the axial direction is constrained. If the rotor spins around the symmetry axis of the magnetic field (centered position), an electric field takes place in the conductor, but due to the axial symmetry of the distribution, no eddy currents are induced and, consequently, no force is generated by the bearing. If the rotation occurs at an off centered position, the nonsymmetrical electric field in the conductor induces eddy currents with the consequent force generation. b. Innovation Electrodynamic bearings allow obtaining levitation by passive means; thus, no electronic equipment, such as power electronics or sensors, are necessary for them to be functional. Electrodynamic suspensions represent an alternative to active magnetic suspensions, as they are less complex, less subject to failure, and possibly far lower in cost. c. Future Applications Electrodynamic bearings are a promising system for supporting high rotational speed machines in absence of contact and with relatively low costs. The main application fields are: flywheels, small compressors, ultracentrifuges, turbomolecular pumps and vacuum cleaners. d. Advantages The electrodynamic bearings, due to their passive nature, do not need electronic equipment such as power electronics, control electronics and sensors. As no electrical connections are required, an electrodynamic bearing system has less complex layout in comparison with active magnetic bearing. Electrodynamic bearings are highly reliable since they are not subject to failure. Electrodynamic bearing allows obtaining a contact free and lubrication free suspension. e. State of Development Analytical and numerical models of electrodynamic bearings have been developed in the last years. The developed models are able to describe the quasi-­‐static and the dynamic behaviour of a rotor on electrodynamic bearings. A design procedure based on non-­‐dimensional maps has been developed. Three test rig have been designed and built to validate the developed models and characterize axial and radial electrodynamic bearings. An innovative stabilization system has been patented. f. Keywords Electrodynamic, eddy current, rotor levitation, magnetic suspension, rotor stability. g. Images Radial EDB – Axial Flux Configuration.
EDB test rig for quasi-static characterization a) picture; b) cross-sectional view; c) EDB cross-sectional view.
Horizontal axis EDB test rig 2: a) drawing; b) picture
6. Mechatronic Systems for Automotive a. Description Automotive systems are at the base of world’s mobility. At present, the energetic issues related to internal combustion engines require special attention to reduce fuel consumption and contemporary increase the vehicle’s performance. To achieve these goals it is necessary to introduce smart systems in the internal combustion engine powertrain that allow controlling and improving its performance both in terms of energetic efficiency and mass reduction. The apexes of this type of system are the hybrid and full electric powertrains. The development of hybrid powertrains has become a primary target for many automotive industries but the optimal solution is still far from commercial applications. Another key aspect in automotive mobility is the compromise between handling and comfort. The vehicle’s suspension plays an important role in this sense, and commercial oil dampers are designed to match an specification that is not optimal for a large range of manoeuvring conditions. In this context, LIM has been active for many years with projects aimed at improving the efficiency of the powertrain of internal combustion engines, studying alternative types of powertrains, and improving both handling and comfort of vehicles. •
•
Efficiency improvement of Internal combustion engine powertrain: This application is one of the most important in the European market. LIM has been working in this field with the following research topics: o
Smart belt tensioner: A mechatronic belt tensioner has been studied and developed to improve the performance of the belt transmission between the engine’s output shaft and the accessories aiming specially at the optimization of the start & stop working condition. o
Magnetic couplers: The research in this field is addressed to develop hysteresis couplers for driving the water pump of internal combustion engines. For this application such a coupler seems to be the most appropriate solution also in comparison to eddy current devices. o
Torsional dampers: Torsional eddy current dampers allow reducing the vibration motion in the crankshaft of internal combustion engines. The research is motivated by the need of developing contactless devices which are not affected by wear, friction, fatigue and sensitivity to the operating conditions that are the typical drawbacks of the conventional fluid and rubber damping devices currently used in this field. An eddy current damper exploits damping effects due to eddy currents that take place in a conductor rotating in a constant magnetic field. No contact between the moving parts occurs, no additional devices as sensors, control units, power electronics that are typical of active systems are requested. Mechatronic shock absorbers: Electromechanical vehicle suspension systems represent a promising substitute to conventional hydraulic solutions. Electromechanical dampers present important advantages with respect to hydraulic ones, for instance, lower sensitivity to ageing and environmental conditions and larger bandwidth. When used within active configurations, they can be easily controlled and offer a high degree of versatility to improve both handling and comfort of the vehicle. Additionally, the reversible nature of the electrical machine inside the device allows part of the energy exchanged during damping to be recovered, thus contributing for the energetic efficiency of whole system. For the afore-­‐mentioned reasons mechatronic shock absorbers are so important as a strategic research topic for LIM. b. Innovation The improvement of energetic efficiency, comfort and handling of automotive systems is the most attracting issue on our research. LIM also focuses on developing innovative mechanical layouts to allow reduction of packaging and complete interchangeability. The developed systems reduce the need of oil and lubricants by means of magnetic interactions, this being an innovation in the automotive field. c. Future Applications The mechatronic systems for automotive applications we develop will be especially interesting for hybrid and full electric cars that are gaining the market and will represent the standard in the next few years. d. Advantages The possibility of control and the use of magnetic interaction to generate the forces represent two important advantages with respect to the equivalent systems used nowadays. The control allows improving performance while the magnetic systems eliminate the use of oil, reducing the system’s sensitivity to environmental parameters and ageing, thus reducing problems related to maintenance. e. State of Development The present state of development allows these systems to be ready for industrial application after a customized design phase. f. Keywords Belt tensioner, magnetic coupling, magnetic damping, shock absorber. g. Images Testing of a Belt Drive System equipped with active tensioners to control the belt tension according to the operating conditions (Courtesy of Dayco). Hysteresis coupler a) stator, b) rotor Torsional dampers. a) Laboratory test rig for the experimental characterization the eddy current torsional dampers, b) Testing of a torsional damper for the crankshaft of a 6 cylinders Diesel engine(Courtesy of Dayco). Electromagnetic shock absorber. a) Electromagnetic shock absorber system, b) test rig for experimental testing of shock absorbers. 7. Mobile Robotics/ Unmanned Vehicle a. Description Unmanned Vehicles (ground, sea or air) are capable to move in an unknown environment to perform specific tasks, as exploration, surveillance, assistance, logistic services, demining, environmental monitoring, and others. These tasks can be performed alone or with other devices in collaborating teams, with a various degree of autonomy, from the simple human supervisors remote-­‐operated systems, to a truly autonomous systems capable to high level planning and decision making. Unmanned Vehicles are a truly mechatronic research area since, to design and build innovative rovers, it is necessary to study and integrate several scientific and technical aspects, as mechanical structures, powertrain design, electrical and electronic on-­‐board systems, control and supervision architectures, information and telecommunication technologies, and artificial intelligence (AI) approaches. Legged Robots Walking machines are a specific field of mobile robotics, aimed to the study and design of legged systems. In the past most work was based on zoomorphic configurations, which require complex electromechanical layouts and complex control strategies. This complexity has prevented this type of machines from finding wide acceptance in the applications for which they are potentially suited Wheeled Robots Mobility on wheels allows a simpler approach. The study was concentrated on the mobile platform considered as a vehicle, applying the basic concepts of wheel longitudinal and side slip to the design of the control strategies. In particular, trajectory control through slip steering was studied in detail and implemented in a ten wheels demonstrator. Elastic wheels for planetary exploration application were studied and designed. UAV -­‐ Unmanned Aerial Vehicles This topic is gaining more and more interest in scientific community mainly due to the number of potential applications (defence, search and rescue missions, inspections and diagnosis of hazardous places, entertainment, virtual and augmented reality... ). b. Innovation Legged Robots The research performed in this area was mainly aimed to identify simplified configurations, allowing to simplify both the mechanical and control layout, without penalizing too much performances, particularly in specific application areas like planetary exploration or surveillance and survey. A line of hexapod walking machines based on the twin rigid frames configuration was developed, showing that this approach allows to obtain good performance with a limited complication. Tests showed in particular the good reliability of this design. The possibility of combining wheels and legs to obtain hybrid configurations was thoroughly studied. Wheeled Robots Wheeled rover research has developed in the following areas: •
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•
•
•
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mechanical structures and powertrain architectures (full electrical electro-­‐hydraulics motors) to allow true all-­‐terrain efficient mobility; light articulated arm design for heavy weight manipulation; efficient control of coordinated motion between the wheeled platform and the articulated arm; human machine interface (HMI) design for efficient and effective supervision in fully and partially remote-­‐operated activities; sensors integration: mainly vision, in future also IMU (inertial measurement unit) assisted motion; path planning and exploration algorithms. UAV -­‐ Unmanned Aerial Vehicles The research performed in this area is mainly related to the architecture design in order to accomplish the mission specific task or, in a general view, to develop a versatile system that can be easily customized to the application. Visual technologies (stereo-­‐cameras and point cloud sensors) has been developed, meanwhile it is planned to provide the UAV platforms with some high-­‐level on-­‐board electronics, to manage the heavy workload typical of autonomous navigation tasks. c. Future Applications Search and Rescue; Contaminated/Hazard environment operation; Remote Operation; Pipeline and Oil Wells patrolling; Aerial surveillance and Construction site inspection; Leakage detection (already used in garbage dumps analysis); Plant diagnosis and analysis. d. Advantages Remote operation; Autonomous operation; Low skilled operator needed; Lower risk in operation; Automatic execution of complex or repetitive tasks. e. State of Development Reedy for specific/custom application design; prototype build and tested in real environment. f. Keywords Unmanned; UAV; UAG; UAS; Robots, Walking Robots, Wheeled Robots, Autonomously; Remote Operation; Survelliance; Search & Rescue; Monitoring; Homeland Security; Defense. g. Images Walkie 6: Legged Robot during test on volcano Etna.
10-wheels rover: It is an all-terrain rover with the capability to climb short stair ramps, designed for surveillance
and exploration tasks. Endowed with an articulated arm to grasp and carry heavy loads, it carries cameras and
can be wireless tele-operated from a supervisor staying within short distance.
UAV-­‐Quadrotor : Prototype testing in a Mars simulator for vision based descend loop design and tuning. 8. Power Actuations a. Description Electro Hydraulic with Servo-­‐valves (EHS) actuators are typically composed by a motor, working at constant speed, coupled with a pump. The load is regulated by the action of a swash plate of a variable displacement pump or servo-­‐valves. This kind of circuit requires a significant number of components (tank, servo-­‐valves), involving considerable sizes and costs. From the energy point of view the efficiency of such systems is rather low because the pump continuously runs, irrespective of the control action. The Electro Hydrostatic Actuator (EHA) is characterized by an electromagnetic actuator (rotational or linear) that drives a hydraulic pump or piston connected to a hydraulic transmission line. The hydraulic line is then connected to a linear or rotational actuator. It is worth to underline the load control is demanded to the control of the electromagnetic actuator, and the hydraulic system has only the rule of power transmission without any control function. b. Innovation The configuration is the same as a hydrostatic transmission exploiting fixed displacement hydraulic machines to realize a fixed transmission ratio. The load can be controlled in this case by controlling the speed or the torque of the electric motor in a closed loop, based on the measurement of the load. c. Future Applications Power actuations in industrial machines. Mobile robotic arm actuation and power transmission. Construction machines and diggers. Aeronautics and aerospace applications. Compact machines. d. Advantages The advantages of using a fixed displacement gear pump are the little size and the very high speed range of operation, as well as the high transmission ratio achievable. Shakers. e. State of Development Custom design procedure for stationary and dynamic applications. Industrial application developed for a bending and punching machine for materials characterizations. Development of a test bench for comparing EHA with electro mechanical actuators (EMA). Development of a EHA power transmission for mobile robotic. f. Keywords EHA, power actuation, electrohydrostatic industrial applications, load control, dynamic applications. g. Images Typical EHA System: a) linear application, b) rotative application Test Bench Picture – Rotational to rotational EHA 9. Vibration Control Systems a. Description The presence of vibrations in mechanical equipment limits the accuracy of high-­‐precision applications, so the use of a vibration control system is mandatory. The control can be achieved with various technologies using passive or active solutions. Different passive solutions have been implemented to solve the vibration problem in heavy structures or systems, looking for either dissipate the energy produced by the vibrations. It is possible to control the vibration using electromagnetic systems operating in active or semiactive mode. The main principle of an active vibration system is the generation of a force equal and in opposite direction to the forces generated by the mechanical system. A generic composition of an active control system can be divided into two parts: •
•
A control algorithm with an electrical amplifier, which commands the actuation system. An actuation system, where an active driver applies the force(s) in charge to reduce or cancel the vibrations. The active driver employed will depend on the specific characteristics of the system to be controlled (voice coils, piezoelectric stacks, pneumatic or hydraulic systems, electromagnetic actuators) In the case of semiactive solutions, the performance of the actuator are controlled acting the parameters that characterize the system. The Mechatronic Laboratory has developed active and semiactive vibration control systems for several application: rotating machines in the field of aerospace, milling machines, high precision machines for the production of electronic components, torsional vibration of crankshafts. Different technologies have been employed for the purpose: eddy-­‐currents, piezoelectric transducers, Maxwell type actuators (the same technology of active magnetic bearings). b. Innovation Eddy current dampers: high level of damping, compact size, vacuum applications, contactless damping devices. Electro-­‐hydrostatic dampers: compact sizes for high power applications. Piezo-­‐stack dampers: high frequency range, compact size. c. Future Applications Vibration control systems, in the field of aerospace,industry robotics. d. Advantages Eddy current dampers: Eddy-­‐current dampers characteristics are, over the others, the reliable stiffness of the support (granted by a mechanical support), the considerable level of damping achievable with lower added mass, the small sensitivity to the operating conditions, the wide possibility of tuning even during operation and the predictability of the behavior. Electro-­‐hydrostatic dampers: electro-­‐hydrostatic dampers offer a high power/weight ratio, small overall sizes, high efficiency. Piezo-­‐stack dampers: Piezoelectric devices are widely employed in the vibration control of systems due to their excellent actuation at high frequencies and sensing abilities. e. State of Development Rotating machines application have been developed using real aero engines. Electro-­‐hydrostatic damper for aerospace application is under study. Piezo-­‐stack damper for industrial machinery has been developed as prototype. f. Keywords Vibration control systems, eddy-­‐current damper, piezo-­‐stack damper, electro-­‐hydrostatic damper. g. Images Active Magnetic Damper for Rotating Systems – Section Layout Prototype of a precision micro machining actively controlled.