1、1The Design of Sustainable Energy Supply for Mechanical Exoskeleton based on the Fuel CellAbstract. In this article, it takes the small power mechanical exoskeleton with fuel cells as the main application target. Based on different two hydrogen supply methods, high-pressure hydrogen cylinders and po
2、rtable metal hydride hydrogen cylinders, the box structure and shape design of small power PEMFC is made. It cannot only provide power as a independent component using high-pressure hydrogen cylinders supply gas equipment, but also as transportation power or portable equipment by installing rapidly
3、metal hydride hydrogen storage cylinders, which realized the use of reliability, flexibility and convenience for mechanical exoskeleton. Key words: PEMFC；mechanical exoskeleton；mobile power 1. Introduction Fuel cells are highly efficient, environmentally friendly, renewable energy, and is widely use
4、d in various fields. Proton exchange membrane fuel cell (ProtonExchange Membrane Fuel Cell, hereinafter referred to as PEMFC) due to a high rate of energy conversion, fast startup, long life, specific power and 2specific energy advantages, is a very attractive energy. Small power (1 kW) proton excha
5、nge membrane fuel cell system is its use of high energy density and longer time to get a lot of development in the field of low-power mobile power, digital cameras and laptop computers, with a wide range application prospects. Currently, low-power proton exchange membrane fuel cell system developed
6、countries in the field of proton exchange membrane fuel cell and a new research focus. Countries small power fuel cell design of mobile power companies, such as the Asia-Pacific fuel cell technology company, Manhattan Scientifics, Materflex AG company, Horizon fuel cell technology companies. In this
7、 study, low-power mechanical exoskeleton fuel cell prototype, small power fuel cell functions and works to achieve the different fuel supply (such as high pressure bottle gaseous hydrogen storage and metal hydride hydrogen storage) box structure and shape of the design to achieve low power fuel cell
8、 box structure is flexible, reliable and portable design purposes. Today there are more than a dozen well-known laboratories and research structure exoskeleton robot. In recent years, the relevant domestic colleges and universities to accelerate the study of the human lower limb exoskeleton China HK
9、UST, Naval 3Aeronautical Engineering Institute, Harbin Engineering University, the outer bone research has made significant progress. Funded by the National Natural Science Foundation of China, East China University of intelligent sensing Measurement and Control Laboratory developed shown in Figure
10、1, lower limb bones the the robot experimental prototype ELEBOT-2008. Lower limb exoskeleton robot is essentially a wearable robot design the main purpose is to extend the human lower limb exercise capacity, reduce physical exertion during weight-bearing and walking. Article exoskeleton robot develo
11、ped mainly used in outdoor harsh road conditions weight and long-distance walking, to study the entire power supply system. 2.Working principle of proton exchange membrane fuel cell The working principle of the proton exchange membrane fuel cell is actually the inverse process of the electrolysis of
12、 water, i.e. through an electrochemical reaction of hydrogen and oxygen to produce water and release energy process. A typical PEMFC fuel cell is provided by the current collecting plate, flow field plate, the gas diffusion layer, the catalyst further layer and a proton exchange membrane composed of
13、 4. When the hydrogen and oxygen is supplied to the anode and the cathode, respectively, the hydrogen in the anodic oxidation, the oxygen 4reduced at the cathode, the protons pass through the electrolyte membrane is transferred from the anode to the cathode, the electrons pass through the external e
14、lectric power load. On the cathode catalyst layer, hydrogen ions and oxygen atoms combine to form water molecules, to produce water and heat. 3.The principle of circuit The circuit shown in Figure 2. Wherein the DC / DC converter to the instability of the fuel cell terminal voltage becomes the capac
15、itor C3, the stable DC voltage on C4. Inverter to the capacitor C3, C4 stable DC voltage is converted into a desired AC voltage. Switch tube in a working cycle, the duty cycle of VS7, and VS8 are entirely complementary to the dead time is removed, the switching control of the drive voltage waveform,
16、 to switch tube the VS7 withstand voltage waveform, the current waveform and the current waveform in the inductor L1, such as Figure 2. The output capacitor C3, C4 on the amplitude of the voltage can be changed by changing the duty cycle of the switching tube VS7, but also can change the size of the
17、 energy transfer from the fuel cell to the output terminal. AC voltage three-phase four-wire power supply mode, the voltage between each phase can be done independently of 5each other, there is no coupling between. Thus the output of the inverter can be regarded as three output voltage phase of the
18、single-phase inverters each difference 120 combined. Therefore, the control methods and measures used in single-phase inverter system can be used directly. DC / DC converter in a complete switching cycle 5 process. Take advantage of the state average method can be drawn between the input voltage, ou
19、tput voltage, and the switch duty cycle average small signal state space mathematical model: Where： ；Ra is DC resistance of Boost inductor L1；n is Transformer ratio；D1 is Duty cycle of VS7 and VS8。Set ，Draw the output voltage and inductor current transfer function in the small signal input voltage p
20、erturbation alone: Inverter link is the bridge supply three-phase four-wire mode, the voltage between each phase independently of each other, there is no coupling between. Its control method can be used to the control mode of the individual half-bridge circuit. Bipolar SPWM modulation state average
21、method the transfer function between the input voltage and the output voltage of the inverter can be drawn: Wherein: L is the filter inductance of the output of the inverter; C for the inverter output of the filter capacitor; R 6is the load resistor; tube conduction duty ratio D2 for the inverter sw
22、itches. 4. Power supply system simulation and experimental results Simulation software to establish requirements for the control system, the control scheme has been designed and calculated parameters of the components, including the main circuit of the DC / DC converter current feedback loop, voltag
23、e feedback loop and the inverter voltage feedback the ring closed loop simulation system. Figure 4 is showing the relationship between the terminal voltage and the DC / DC converter output voltage of the fuel cell. When the fuel cell can be seen from the figure due to the reduction of the output pow
24、er, the terminal voltage will rise, but the converter output voltage after a brief adjustment remains stable at 300 V, so the output terminal of the converter can be obtained a stable output voltage. Figure 5 is the output voltage of the inverter whose output voltage frequency can be based on the ne
25、eds of the network and to set the switching frequency of the switching tube. From the figure can be seen that the waveform of the three-phase voltage is equal in magnitude and phase is symmetrical, to meet the requirements of the power supply system. 7Fig 4 Output voltage of fuel cell and converter
26、Fig 5 Output waves of inverter 5. Conclusion For the mechanical exoskeleton supply system, the use of fuel cells to proceed from the basic principles of the analysis system, the establishment of the system of control model. The last principle is verified through simulation waveforms and experimental
27、 waveforms to control the correctness of the choice of methods and parameters selection. Reference 1 DYER C K.Fuel Cells for Portable ApplicationsJ.Journal of Power Sources，2002，106 : 3134. 2GOU Bei，WOON Ki Na， DIONG Ill. Fuel Cells：Modeling，Control and ApplicationM.Taylor & Group，2010. 3 HAYRE Ryan O，CHA Suk-won，COLELLA Whitney G.Fuel Cell FundamentalsM. John Wiley & Sons Publication，2005. 4LARMINIE J，DICKS A. Fuel Cell System ExplainedM.John Wiley & Sons Publication，2003. 5 MATTHEW M Mench.Fuel Cell EnginesM.John Wiley &Sons Publication，2008.
