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Steam powered robots


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Steam powered robots

  1. 1. STEAM POWERED ROBOTS Presented by… Debasish Devkumar Padhy 8 th sem Mechanical Engg.
  2. 2. Contents.. <ul><li>Introduction </li></ul><ul><li>Current systems of power supply </li></ul><ul><li>A new approach (monopropellant based) </li></ul><ul><li>How does it work? </li></ul><ul><li>Description of the design </li></ul><ul><li>The prototype </li></ul><ul><li>Test results </li></ul><ul><li>Limitations </li></ul><ul><li>Future of the project </li></ul><ul><li>Conclusion </li></ul>
  3. 3. Current systems of power supply <ul><li>Parameters governing power supply design </li></ul><ul><ul><ul><li>Specific energy density of power supply (Es) the efficiency of converting energy from the power source to controlled mechanical work the efficiency of converting energy from the power source to controlled mechanical work(n) , and the maximum mass-specific power density of the energy conversion and/or actuation system(Ps) . </li></ul></ul></ul>
  4. 4. <ul><li>Actuation potential </li></ul><ul><li>A.P = Es*n*P </li></ul><ul><li>That a system with high power-source energy density, high conversion efficiency, and high actuator power density will be the lightest possible system capable of delivering a given amount of power and energy. </li></ul>
  5. 5. <ul><li>With regard to the figure of merit, batteries and dc motors capable of providing the requisite power for a human scale robot offer reasonable conversion efficiency, but provide relatively low power-source energy density and a similarly low actuator/gear head power density. A gasoline-engine-powered hydraulically-actuated human-scale robot would provide a high power-source energy density, but a relatively low conversion efficiency and actuation system power density. </li></ul>
  6. 6. Monopropellant Powered Approach <ul><li>Liquid chemical fuels can provide energy densities significantly greater than power-comparable electrochemical batteries. The energy from these fuels, however, is released as heat, and the systems required to convert heat into controlled, actuated work </li></ul><ul><li>One means of converting chemical energy into controlled, actuated work with a simple conversion process is to utilize a liquid monopropellant to generate a gas, which in turn can be utilized to power a pneumatic actuation system. </li></ul><ul><li>monopropellants are a class of fuels (technically propellants since oxidation does not occur) that rapidly decompose (or chemically react) in the presence of a catalytic material. Unlike combustion reactions, no ignition is required, and therefore the release of power can be controlled continuously and proportionally simply by controlling the flow rate of the liquid propellant. </li></ul>
  7. 7. Comparison details <ul><li>Battery powered systems </li></ul><ul><ul><ul><li>Monopropellants have better specific energy density & specific power density of conversion </li></ul></ul></ul><ul><li>Gasoline engine powered systems </li></ul><ul><ul><ul><li>Monopropellants have better conversion efficiency & specific power density of energy conversion </li></ul></ul></ul>
  8. 8. How does it work? <ul><li>Uses decomposition of hydrogen peroxide to produce steam </li></ul><ul><li>Steam pressurizes the reservoir (similar to pneumatically actuated systems-difference being absence of compressor) </li></ul><ul><li>Liquid peroxide stored at high pressure on decomposition gives high pressure gaseous products </li></ul><ul><li>Mechanical work is extracted from this as in pneumatic system </li></ul>
  9. 9. Schematic of monopropellant based actuation system
  10. 10. The Prototype
  11. 11. Data obtained from experiments <ul><li>Emphasis is on the conversion efficiency determination as the values of the other two parameters can be easily found </li></ul><ul><li>Maximum possible conversion efficiency calculated = 39% </li></ul><ul><li>Theoretical conversion efficiency = 16% </li></ul><ul><li>Actual conversion efficiency obtained = 6.6% </li></ul>
  12. 12. Reasons for lower value of n <ul><li>Heat loss from the system </li></ul><ul><li>Overshoots or deviations from the assumed trajectory of the prototype </li></ul><ul><li>Inaccuracy of controls </li></ul><ul><li>Overshooting causes intermittent exhaust of hot gas causing low n </li></ul>
  13. 13. Insulated experiments <ul><li>Prototype in the previous experiment is covered with insulation to reduce heat loss and thereby improve conversion efficiency </li></ul><ul><li>Efficiency obtained from experiment = 9% </li></ul><ul><li>Reasons for efficiency lower than theoretical value </li></ul><ul><ul><ul><li>Heat loss still exists </li></ul></ul></ul><ul><ul><ul><li>Inaccuracy of controls </li></ul></ul></ul>Fig. 8. Monopropellant actuator prototype wrapped with insulating tape and instrumented with thermocouples for measurement of surface temperature.
  14. 14. Determination of actuation potential <ul><li>Actuation system mass = 1.5Kg </li></ul><ul><li>Actuation system power density=100W/Kg </li></ul><ul><li>Considering mass of blow down tank, specific energy density = 1.7 MJ/Kg </li></ul><ul><li>For single degree of freedom system, actuation potential = 15.3 KJ KW/Kg2 </li></ul><ul><li>For six degree of freedom system A.P=26.4 KJ KW/Kg2 </li></ul><ul><li>Actuation potential of the best battery available = 4.8 KJ KW/Kg2 </li></ul>
  15. 15. Limitations <ul><li>High energy loss in the form of heat </li></ul><ul><li>At present 100% H2O2 can’t be used </li></ul><ul><li>No human scale self powered robot available at present. The study was done on a single degree of freedom manipulator </li></ul><ul><li>H2O2 is a costlier power source than electricity </li></ul><ul><li>Maintenance costs are higher </li></ul><ul><li>H2O2 is less safe compared to electricity </li></ul>
  16. 16. Future of the project <ul><li>Multiple degrees of freedom systems will give higher actuation potential </li></ul><ul><li>Better insulation can prevent heat loss </li></ul><ul><li>100% H2O2 if used would increase actuation potential </li></ul><ul><li>100 % H2O2 systems provides actuation potentials 35 & 60.4 for single and six degrees of freedom respectively </li></ul><ul><li>Better controls can contribute to improved conversion efficiency </li></ul><ul><li>Light weight components and heat resistant materials can make this technology a promising option in the future </li></ul>
  17. 17. References <ul><li>IEEE/ASME transactions on Mechatronics, vol. 8, no. 2, June 2003 </li></ul><ul><li>New Scientist, 27 April 2002 </li></ul><ul><li> vss/docs/Propulsion/3-what-is-a-monopropellant.html </li></ul><ul><li> encyclopedia/M/monopropellant.html </li></ul><ul><li> </li></ul><ul><li> </li></ul>
  18. 18. Conclusion <ul><li>A power supply and actuation system appropriate for a position or force controlled human-scale robot was proposed. </li></ul><ul><li>The proposed approach utilizes a monopropellant as a gas generant to power pneumatic-type hot gas actuators. </li></ul><ul><li>Experiments were performed that characterize the energetic behavior of the proposed system and offer the promise of an order-of-magnitude improvement in actuation potential relative to a battery-powered dc-motor-actuated approach. </li></ul>
  19. 19. <ul><li>THANK YOU </li></ul><ul><li>Debasish Devkumar Padhy </li></ul><ul><li>MECHANICAL ENGG. </li></ul>