1. Hydraulic and Electrical Power Design Decision Cynthia Perreira IMDL and SRL Dr. Book and Dr. Paredis February 21, 2003

2. Introduction Two major power sources for mechanical devices Two major power sources for mechanical devices  Electrical  Hydraulic Decision not always made in best, most informed manner Decision not always made in best, most informed manner Decision is often made too early in the design process Decision is often made too early in the design process Develop method of dealing with this type of decision Develop method of dealing with this type of decision

3. Introduction Research into Electrical, Hydraulic power as separate power sources Research into Electrical, Hydraulic power as separate power sources Little specifically comparing their advantages/disadvantages Little specifically comparing their advantages/disadvantages Doesn’t appear to be any formalized method for making the choice between them Doesn’t appear to be any formalized method for making the choice between them

4. Approach 1. Develop a method for choosing between two families Multiple Levels of choices/modeling Multiple Levels of choices/modeling Performance Measurements Performance Measurements Develop systematic method Develop systematic method 2. Examine an example and apply the method Understand current technology choices Understand current technology choices Add to proposed method Add to proposed method Apply proposed method Apply proposed method Examine results Examine results

5. Power Tree Inside each family of power there are many difference options Inside each family of power there are many difference options Composition Selection ElectricHydraulicPneumatic Drive System OR linkagecylinder ValvesActuatorPump RotationalTranslational Rotational Translational OR AND

6. Multiple Levels of Modeling Selection between two families of solutions Selection between two families of solutions Best family = family containing the best instance Best family = family containing the best instance Requires design knowledge Requires design knowledge Models at different levels of abstraction Models at different levels of abstraction Hydraulic Electrical Performance H E

7. Levels of Modeling Simple models Simple models  F=ma  P=Tv Rules of thumb Rules of thumb Known values for groups of components Known values for groups of components Simulation Simulation  Matlab  Modelica

8. Performance Measurements Power output Power output Velocity, Torque Velocity, Torque Geometry, space required Geometry, space required Weight Weight Efficiency Efficiency Cost Cost Noise Noise Other application specific factors Other application specific factors

9. Applications of Fluid Power Automotive Automotive  Drive  Brakes  Power Steering Manufacturing machinery Manufacturing machinery Construction equipment Construction equipment  Loaders  Cranes  Bulldozers Robots Robots Elevators Elevators

10. Power Steering Example Technology that lends itself well to the use of either hydraulic or electrical power Technology that lends itself well to the use of either hydraulic or electrical power Currently dominated by hydraulics Currently dominated by hydraulics Electro-hydraulic systems Electro-hydraulic systems Electrical recently implemented in some new small cars Electrical recently implemented in some new small cars ***Contacts with NSK, Ford, Siemens

11. Hydraulic Power Steering

12. Electro-hydraulic Systems Electric motor to power steering pump Electric motor to power steering pump Speed of motor can be varied or turned off Speed of motor can be varied or turned off Can be used for large and small vehicles Can be used for large and small vehicles Advantages Advantages  Better fuel efficiency  Motor can turn off when not in use  Less energy consumption

13. Electrical Power Steering

14. Advantages Advantages  Environment  Off when not turning  Lower weight and size  Energy consumption as little as 1/20 of hydraulic  Can reduce fuel consumption by 3-5%  Contains no oil  Better feel when driving  Reduced rattling noise Disadvantages Disadvantages  Cost  Low force output – only currently suitable for small cars 42V may allow the system to be used in heavier vehicles with larger tire contact patches 42V may allow the system to be used in heavier vehicles with larger tire contact patches Now present in 2002 Saturn Vue, Honda Civic SI, Honda Insight Now present in 2002 Saturn Vue, Honda Civic SI, Honda Insight

15. Future Work Further develop systematic method Further develop systematic method Determine levels of modeling and information needed at each Determine levels of modeling and information needed at each Relate measures of performance to customer’s wishes Relate measures of performance to customer’s wishes Continue with power steering example Continue with power steering example Continue contacts with Ford, NSK Continue contacts with Ford, NSK

16. Questions?