Georgia Institute of Technology | Marquette University | Milwaukee School of Engineering | North Carolina A&T State University | Purdue University | University of California, Merced | University of Illinois, Urbana-Champaign | University of Minnesota | Vanderbilt University Design of a Lightweight, Portable Hydraulic Power Supply Jonathan Nath, M.S. Student William Durfee, PhD University of Minnesota Fluid Power Innovation & Research Conference Minneapolis, MN | October 10 - 12, 2016
Project Objectives • Develop an analytical model to aid in the system level design of a minimal-weight portable hydraulic power supply • Develop design guidelines for optimal component integration techniques FPIRC16 2
Motivation • October 2015 CCEFP Strategic Research Plan (SRP) identifies excessive weight and size as a barrier for new portable applications, and particularly for new human-scale applications http://www.jawsoflife.com/en/product/edraulic-s700e2-cutter FPIRC16 3
Methods for Minimizing Weight • Optimal Component Selection Using Computer Modeling – Battery, motor, pump parameter selection • Component Integration – Packaging techniques – 3D Printing https://www.asme.org/engineering-topics/articles/manufacturing-processing/spotlight-tim-simpson-penn-state-cimp3d FPIRC16 4
3D Printing Child Hydraulic Ankle-Foot Orthosis: Boston Dynamic: Atlas 3D Printed Titanium Version http://3dprint.com/89974/googles-atlas-3d-print-robot/ FPIRC16 5
Hydraulic Ankle-Foot Orthosis Axial piston pump Brushless DC Motor Untethered, hydraulic power supply Hydraulic Gearbox actuators Lithium polymer battery FPIRC16 6
Power Supply Configuration http://www.maxonmotorusa.com/ FPIRC16 7
Circuit Selection Electro-hydraulic actuator (EHA) Throttling valve configuration FPIRC16 8
Motor and Pump Selection Procedure Basic Procedure -Does not consider operation efficiency Pressure Electric Pump Flowrate Motor Optimized Procedure -Considers operation efficiency Pressure Electric Flowrate Pump Battery Motor Run Time Size Size Swashplate Angle FPIRC16 9
Motor Modeling No-load Losses - Core losses (magnetic losses/iron losses): alternating magnetic flux produces hysteresis losses and eddy current losses in the stator and rotor cores, magnets, and other motor components - Mechanical losses: including bearing friction Load Losses - Resistive losses (copper losses) : losses in the windings 𝑑 = 𝐽 2 𝑆 𝑄 Mechanical Design of Electric Motors: Wei Tong FPIRC16 10
Motor Modeling: Maximum Power At Steady-State: 𝑄 𝑗𝑜 = 𝑄 𝑝𝑣𝑢 + 𝑅 𝑝𝑣𝑢 𝑅 𝑝𝑣𝑢 = 𝑄 𝑗𝑜 (1 − 𝜃) 𝜃 = 𝑄 𝑝𝑣𝑢 𝑄 𝑗𝑜 1 − 𝜃 ∗ 𝑆 𝑢𝑝𝑢𝑏𝑚 ] + 𝑈 𝑈 𝑥𝑗𝑜𝑒𝑗𝑜 = [𝑄 𝑗𝑜 ∗ 𝑡𝑣𝑠𝑠𝑝𝑣𝑜𝑒𝑗𝑜 FPIRC16 11
Motor Model: Validation http://www.maxonmotorusa.com/ FPIRC16 12
Battery + Motor Configuration Case Study 70W 100W vs. 0.390 kg 0.140 kg R = 1.01 Ohm R = 0.608 Ohm Kt = 0.091 Nm/A Kt = 0.036 Nm/A -3600 run time -Picked 4 steady-state operating points -Calculated overall system weight, battery + motor http://www.maxonmotorusa.com/ FPIRC16 13
Motor Case Study: Results 0.05 Nm, 0.28 Nm, 0.39 Nm, 0.5 Nm, 300 rad/sec 200 rad/sec 150 rad/sec 100 rad/sec Increasing torque FPIRC16 14
Large vs. Small Motor 𝑑 = 𝐽 2 𝑆 • Copper Losses: 𝑄 𝜍𝑀 • Resistivity: 𝑆 = 𝐵 If L is doubled, Pc is cut in half http://www.maxonmotorusa.com/ FPIRC16 15
Axial-Piston Pump Modeling Required torque w/o friction Viscous friction loss, pistons and cylinder block Coulomb friction, pistons and cylinder block Viscous friction, slippers and swash plate Viscous friction, valve plate and cylinder block Jeong , H., 2007. “A novel performance model given by the physical dimensions of hydraulic axial piston motors: model derivation”. Journal of Mechanical Science and Technology, 21(1), pp. 83 – 97. FPIRC16 16
Axial-Piston Pump Modeling Flowrate w/o leakage Leakage between pistons and cylinder block Leakage between valve plate and cylinder block Jeong , H., 2007. “A novel performance model given by the physical dimensions of hydraulic axial piston motors: model derivation”. Journal of Mechanical Science and Technology, 21(1), pp. 83 – 97. FPIRC16 17
Axial-Piston Pump Model: Validation -Model compared to Takako miniature axial-piston pump line performance 0.4 cc/rev Pump Comparison, 200 rad/sec FPIRC16 18
Combined System Model Desired Run Time Inputs Desired Flowrate Desired Output Pressure Motor Sizing Iterative Pump Sizing Component Swashplate Angle Variables Motor size, pump size, Output swashplate angle to achieve minimum system weight FPIRC16 19
Fixed Pump, Variable Motor Size >155 W required, 155 W >155 W required, 245 W for minimum system weight for minimum system weight FPIRC16 20
Fixed Motor Size, Variable Pump Parameters FPIRC16 21
0.5 hour run time, 10 Mpa, 10 cc/sec 285W Motor, 1.48 kg 193W Motor, 1.16 kg 124W Motor, 1.24 kg 95W Motor, 0.84 kg FPIRC16 22
8 hour run time, 10 Mpa, 10 cc/sec 285W Motor, 8.11 kg 193W Motor, 7.23 kg 124W Motor, 7.97 kg 95W Motor, 8.04 kg FPIRC16 23
Uses for the Program • Can be used to provide an exact custom solution for a minimum-weight power supply • Could be used to help guide selection of off- the-shelf components – Fix pump and select optimal motor size – Fix motor to select optimal pump size FPIRC16 24
Next Steps • Expand from steady-state to a quasi-static analysis • Eventually consider dynamic operation • Create test stand to validate system modeling and explore optimized integration techniques FPIRC16 25
Conclusions • Required system pressure, flowrate, and runtime are what drive an optimized design • A system that is optimized for one set of desired outputs will likely not be a minimum- weight solution for another set of outputs FPIRC16 26
Questions? FPIRC16 27
Recommend
More recommend
