Human Oriented Sustainable Transport
The HOST vehicle (Human Oriented Sustainable Transport) is a prototype with all-electric drive and hybrid-series energy system , coordinator of a European project with plug-in function for electric charging from external. It is driven by electric wheel-motors (independent steering wheels up to 90 °), which make it able to move horizontally and rotate on itself. HOST has a completely DBW guidance system (Drive by wire) and has been developed by GEA-GRA Energy Environment Group and Automotive Research Group CIRPS – Interuniversity Research Center for Sustainable Development of the Sapienza University of Rome with a partnership also made up of KTH – Royal Institute of Technology in Stockholm – Sweden, IST – Instituto Superior Técnico – Portugal, Cargo Technologies – Austria, Stile Bertone SpA – Italy Jelley Limited – United Kingdom, Volvo – Sweden, Robosoft-France, KVD – The Netherlands. HOST is known as the vehicle that never sleeps because it is equipped with an automatic system of transhipment that allows it to change the body and intended use during the same day and to perform in the 24 hours different tasks in the city service.
The sixth framework program
The HOST project was initiated under the Sixth Framework Program of the European Union with the aim of rethinking the technology of means of transport, placing itself as a starting point not the existing technology but the users’ needs. The objective was the design of a vehicle suitable for the transport of goods and people that was not very polluting and versatile .
HOST 2.0
HOST 2.0 was developed by SEM – Systems for Energy and Mobility of CIRPS Sapienza University of Rome – Automotive laboratory of the Lazio Region, whose head is Prof. Fabio Orecchini. HOST 2.0 is a new version of the HOST vehicle with: lithium batteries equipped with BMS (Battery Management System) for the control of voltage, current and temperature of all 70 cells implemented; Inverter controllable via CAN and wireless with the possibility of working up to voltages of 800 V; steering system with 4 steering wheels at 90 ° moves with 1/500 mm precision electric actuators with single encoder on the motor as position sensor (against 6 for the wheel of the previous version); central logic of real time command that governs the 4 inverters of the 4 wheel motors, the 3 inverter of the batteries, the ultracapacitors, .
Description of the architecture and operation of the HOST vehicle
The acronym HOST means “Human Oriented Sustainable Transport” and with it we set ourselves the goal of realizing a series electric hybrid vehicle that allows you to find alternative solutions to traditional internal combustion vehicles. The main aims and the innovative aspects of this project concern its flexibility of use which leads to a drastic lowering of the polluting emissions typical of conventional vehicles.
The concept of the vehicle is based on transhipment, in fact on the hybrid thermal-electric power train can be grafted several bodies that perform the function of transforming the vehicle in such a way that it can be changed the intended use of the same during the same day and so that can perform various tasks in the city during the 24 hours. The services that HOST can perform are as follows:
Daytime car sharing services (car for the day);
Nocturne collective taxi (collective taxi for the night hours);
Nocturne garbage collection;
Daytime freight collection and distribution.
HOST is equipped with four independent steering wheels and steering wheels (each has its own permanent magnet synchronous electric motor and inverter) which also allows it to carry out special maneuvers such as horizontal and rotary movements around itself.
By virtue of its maneuverability, HOST guarantees a great ease in the loading / unloading of both goods and people and is therefore designed to carry out continuously various tasks ranging from urban transport, night-time taxis, waste collection to goods transport. The idea of having a vehicle available that works 24 hours a day and can be used for all city needs, both as a car and as a small truck. In fact it can be assembled according to the type of task required, being able to go from a basic module of 3.5 m up to 6 m in length. This vehicle could be exploited by the municipal administrations in order to be able to obtain goods, people and waste collection with a single means with less environmental impact thanks to hybrid technology.
Power train
HOST is a series electric hybrid vehicle in which the internal combustion engine (ICE) is coupled directly to a permanent magnet synchronous generator (GU) which converts the mechanical power available to the shaft into electrical power. The alternating current, supplied by the generator, is converted into continuous by a boost rectifier so it can be sent to the continuous link which is fixed at 300 V. The combined storage system consists of two battery packs (B), specifically use Lithium-Ion batteries in HOST 2.0 while in the previous version of HOST there were NiMH batteries, which are made to work with not too high dynamics to ensure durability and efficiency. This is possible through the use of Supercapacitor(C) that intervene in the fast transients linked to the traction drive, given their excellent dynamic behavior. Both the batteries and the supercapacitors are connected to the continuous link by means of bidirectional boost that allow the passage of current in both directions depending on the strategy that at that time the “power controller” (manager of energy flows or System Manager) is implementing for satisfy loading requests from the pilot. The energy flow manager is identified with the BU node on whose DSP (Digital Signal Processing) a current control is implemented.
To do this, the power controller acquires all the necessary data such as the battery charge status, the supercapacitors, the torque to which the thermal works and the pilot inputs (therefore the required load torque to the wheels) and through their knowledge determines the sorting of the available power among the various sources in order to satisfy the pilot’s requests compatibly with the availability of instantaneous energy sources or to recharge the storage systems in times of low power demand to the wheels. The logic of the energy management algorithm consists, in the last analysis, in the monitoring of the difference between the power input on the continuous link, by the GU node through the generator, and that required by the traction motors to the wheels.. The microprocessors that control the node converters communicate with each other through a channel better known as a bus. The communication must be as free as possible from external disturbances and be managed according to a protocol that has a high internal diagnostics for any errors that may occur. This task optimally fulfills the CAN bus (Controller Area Network) and has been chosen as a bus for the power electronics of the HOST vehicle.
Finally, there are the four traction drives, related to the four permanent magnet synchronous motors connected to the vehicle wheels, which have their own bus where they pass information on wheel traction control and those concerning the percentage of regenerative braking to be performed.. The wheel traction motor control bus is 24 V with a mass separate from the CAN to avoid the propagation of any disturbance between the two communication systems. The information that these buses must share are also inherent to procedures that must be implemented in extraordinary situations, in fact, if the System Manager detects that the combined storage system is fully charged, it will have to warn the circuit of the bus level bus communication so as not to practice regenerative braking, thus avoiding serious damage. It is noted that this is a safety procedure because the storage system is designed with a control algorithm that works so as to remain below the maximum storage capacity in order to always recover part of the energy with regenerative braking. The choice of permanent magnet motors is currently widely used in hybrid and purely electric car traction as these engines provide pairs per volume unit higher than other machines. So at the same volume of the engine we have pairs (or power since the thermal works at “fixed point”) at the higher output and for a given current (therefore the torque is fixed) lower losses due to joule effect given the absence of the rotor circuit. It is also known that the behavior of these machines is analogous to DC machines in terms of torque characteristics and speed regulation with the great advantage of not having the brushes and making the switching by means of static converters: The permanent magnet electric machine is connected to the internal combustion engine without gearboxes, the latter is the 3 cylinder of the 800cc diesel SMART. In order to increase the efficiency of the propulsion system it is necessary to have an energy storage system which, together with the GU generation unit, can meet drive requests. Obviously, the main requirement of an accumulation system must be its reliability in terms of durability when it is subjected to continuous charge and discharge cycles. In HOST there is a combined storage system, therefore, besides a battery pack, there is a capacitor pack that takes on energy demands with fast dynamics. The batteries and the supercapacitors differ for some characteristics and for the precision they are the complementary of the others, in fact the former have a high capacity to store energy (kWh) while the latter have a high power density (kW / dm3) and they therefore have an excellent ability to provide fast responses in fast transients such as acceleration and braking. Since the. Going into more detail with the power electronics of HOST, we have already mentioned the three fundamental units present in the hybrid vehicle in question:
Generation Unit GU
BU Battery Unit
Ultracapacitors Unit UC
The components of the power train
Internal Combustion Engine
The internal combustion engine is the 3 cylinder of the 800cc SMART diesel, which in the speed range between 1700-1800 rpm is able to provide the full range of powers required by the vehicle that have been estimated to be between 4.5 kW (25% of P) and 13.5 kW (75% of P) with high efficiency both in terms of consumption and emissions.
Lithium Ion batteries
The type of batteries used in the HOST 2.0 vehicle is that of Lithium-Ion. Among the advantages of this type of batteries are: the high energy density with the same volume and weight installed on board the vehicle and the high charge / discharge cycles. The energy density for these batteries is approximately 150 Wh / kg and 400 Wh / lt.
Supercapacitors
The Supercapacitors accumulate electric energy in two capacitors in series of double electric layer EDL (Electrochemical Double Layer) by placing the electrical charges at the electrode / electrolyte interface in a “physical” and not chemical way, therefore there are no chemical oxidation-reduction processes, as in the accumulators (rechargeable batteries) and have the advantage of being able to be loaded or unloaded instantly, thus ensuring a very high specific power. They are energy conversion and accumulation devices characterized by high specific powers and energies far higher than conventional condensers. The most important disadvantage, always with respect to chemical accumulators, is the low energy stored.
NiMH battery technology combined with the use of Supercapacitors
The use of NiMH battery technology, used in the first version of HOST, combined with the use of Supercapacitors allows to improve the reliability of the storage system in terms of durability when it is subjected to continuous charging and discharging cycles. Remember that the batteries and the supercapacitors differ for some features that make them complementary, in fact the former have a high capacity to store energy (kWh) while the latter have a high power density (kW / dm3) and therefore have a excellent ability to provide fast responses in fast transients such as acceleration and braking. THE’ use of supercapacitors combined with that of batteries (NiMH) is optimal as it appears to support the operation of the batteries that, not being “stressed”, have better functioning and greater autonomy. It is good to underline that the combined use of the two previously described technologies can be applied to the different series hybrid connections, parallel hybrid and series-parallel hybrid.
The Drive By Wire system
The “drive by wire” (DBW) finds its first automotive application in the control of the power supplied by the engine, which is no longer controlled directly (a simple steel cable that opens or closes the injection system’s laminating valves), but through an indirect system that, connected to the accelerator, operates a potentiometer; this instrument in turn transmits to an electronic control unit the information related to the power demand transmitted by the accelerator, thanks to a calculation of how much the pedal has been pressed. This information is processed together with a series of other data (such as the relative speed of the wheels, the transverse and axial acceleration to which the vehicle is subjected, the steering angle, the outside temperature, the loads on the shock absorbers, the yaw and roll angle as well as numerous other parameters) and transmitted back to a servomotor which rotates the injection system’s rolling valves in such a way as to avoid loss of adhesion due to excessive applied torque on the driving wheels. Basically, the electronic control unit responds to the need for an optimal power supply, trying to satisfy the user’s request through the accelerator and the physical limits of the vehicle in the conditions that occur at a given instant. In HOST, the driver’s interface has been revisited by a system for adjusting the steering of the wheels by means of pedals. The driving interface is described as an MMI (Man Machine Interface) and has two main functions: the yaw and roll angle as well as numerous other parameters) and transmitted to a servomotor which rotates the injection system’s rolling valves in such a way as to avoid loss of adhesion due to excessive torque applied to the drive wheels. Basically, the electronic control unit responds to the need for an optimal power supply, trying to satisfy the user’s request through the accelerator and the physical limits of the vehicle in the conditions that occur at a given instant. In HOST, the driver’s interface has been revisited by a system for adjusting the steering of the wheels by means of pedals. The driving interface is described as an MMI (Man Machine Interface) and has two main functions: the yaw and roll angle as well as numerous other parameters) and transmitted to a servomotor which rotates the injection system’s rolling valves in such a way as to avoid loss of adhesion due to excessive torque applied to the drive wheels. Basically, the electronic control unit responds to the need for an optimal power supply, trying to satisfy the user’s request through the accelerator and the physical limits of the vehicle in the conditions that occur at a given instant. In HOST, the driver’s interface has been revisited by a system for adjusting the steering of the wheels by means of pedals. The driving interface is described as an MMI (Man Machine Interface) and has two main functions: yaw and roll angle as well as numerous other parameters) and retransmitted to a servomotor which rotates the injection system’s rolling valves in such a way as to avoid loss of adhesion due to excessive torque applied to the drive wheels. Basically, the electronic control unit responds to the need for an optimal power supply, trying to satisfy the user’s request through the accelerator and the physical limits of the vehicle in the conditions that occur at a given instant. In HOST, the driver’s interface has been revisited by a system for adjusting the steering of the wheels by means of pedals. The driving interface is described as an MMI (Man Machine Interface) and has two main functions: yaw and roll angle as well as numerous other parameters) and retransmitted to a servomotor which rotates the injection system’s rolling valves in such a way as to avoid loss of adhesion due to excessive torque applied to the drive wheels. Basically, the electronic control unit responds to the need for an optimal power supply, trying to satisfy the user’s request through the accelerator and the physical limits of the vehicle in the conditions that occur at a given instant. In HOST, the driver’s interface has been revisited by a system for adjusting the steering of the wheels by means of pedals. The driving interface is described as an MMI (Man Machine Interface) and has two main functions: optimal power delivery, trying to satisfy the user’s request through the accelerator and the physical limits of the vehicle in the conditions that occur at a given instant. In HOST, the driver’s interface has been revisited by a system for adjusting the steering of the wheels by means of pedals. The driving interface is described as an MMI (Man Machine Interface) and has two main functions: optimal power delivery, trying to satisfy the user’s request through the accelerator and the physical limits of the vehicle in the conditions that occur at a given instant. In HOST, the driver’s interface has been revisited by a system for adjusting the steering of the wheels by means of pedals. The driving interface is described as an MMI (Man Machine Interface) and has two main functions:
Wheel Speed – wheel speed (traction);
Wheel Steering – wheel steering.
Transhipment
The use of a single chassis involves the creation of a basic platform which can be used for different types of vehicles. In the last few years in the automotive market there has been a tendency to produce parts such as mechanical gearboxes, which could be used for different vehicle models and car brands. The advantage of using a single frame is that it does not require an “adaptation” process of the piece to the vehicle in which it is chosen to install it, since the vehicle’s base is the same for vehicles suitable for satisfying different purposes. a standardization is assumed also in the production process of the frame itself which would lead to a lowering of the price. A concept of “modularity” of vehicle power is applicable to HOST: thanks, in fact, to the wheel motors it is possible to add a “power rear axle”, which includes two wheel motors, to the basic power train thus obtaining a vehicle characterized by a greater power. In this way HOST can fulfill different services that require higher powers.
Engines Wheel
The wheel motors are one of the most interesting solutions for vehicles with electric drive as they completely free the car body from the rest and therefore reduces the overall dimensions of the engine / transmission unit. These are discoidal motors housed in the rim and integrated with the braking system. In fact it is the entire engine to rotate, while the crankshaft is fixed to the car body.
Inverter
The data plate of the converter, an element of power electronics, follows directly from the dimensioning of the electric motor and of the connection to the dc-link. The structure of this element is as follows: three phases with voltage source of the IGBT inverter (3 phone IGBT inverter VSI), this structure is standard for the supply of the axial flow in a permanent magnet motor. The IGBT (Insulated Gate Bipolar Transistor) is a device driven by a gate on one side and on the other has a collector and an emitter. It is used to switch high voltages and high currents; the larger models are capable of switching 1200A on voltages of 6000V. The only warning that must be taken into consideration is the fact that the converter does not allow any type of overload; the inverters need to be sized for the maximum voltage and current required. Furthermore, in order to save space and weight inside the vehicle, a further requirement is that the inverter must be liquid-cooled. At present, there is no commercial inverter available on the market that meets the aforementioned requirements and is therefore suitable for installation on a vehicle. In reality, there are several prototypes of inverters available for use on hybrid vehicles, but none of these are, of course, for sale. In fact, an adaptation process was carried out to obtain the required characteristics inverter must be liquid-cooled. At present, there is no commercial inverter available on the market that meets the aforementioned requirements and is therefore suitable for installation on a vehicle. In reality, there are several prototypes of inverters available for use on hybrid vehicles, but none of these are, of course, for sale. In fact, an adaptation process was carried out to obtain the required characteristics inverter must be liquid-cooled. At present, there is no commercial inverter available on the market that meets the aforementioned requirements and is therefore suitable for installation on a vehicle. In reality, there are several prototypes of inverters available for use on hybrid vehicles, but none of these are, of course, for sale. In fact, an adaptation process was carried out to obtain the required characteristics.
Suspensions
The suspensions are of the double arm type with second MacPherson arm. The inner arm is anchored fixed and has the possibility to rotate on itself, the exterior works like a classic MacPherson and is dragged in rotation by the internal arm (90 °). The 90 ° rotation is made by two actuators. The result of this activity is a modular “wheel-corner” conceived with minimal impact on the frame design and with the possibility of being fixed in every position of the vehicle.
Source from Wikipedia