Fluid Power Innovation & Research Conference Minneapolis, MN October 10 12, 2016 ing and Optimization of a Linear Electromagnetic Piston Pump Paul Hogan, MS Student Mechanical Engineering, University of Minnesota Advisor: Dr. James D. Van de Ven October 12, 2016
Agenda Guiding question: What is the most direct means of converting stored electrical energy to hydraulic energy? 2
Motivation Hydraulic actuation for human-scale power applications (< 1 kw) Mobile applications, robotics, prostheses Electrical storage has superior energy density, hydraulic actuators have superior power density Applications require efficient and compact energy conversion 3
Issue: Multiple Energy Conversions Typical electric-to-hydraulic energy conversion at humanscale power requires modularization: Electric motor Shaft coupling Hydraulic pump Simplify by converting electric energy directly to linear piston motion Concentric hydraulic power unit Image: Northern Tool 4
Direct Energy Conversion Electrical Energy Linear Mechanical Energy Hydraulic Energy Linear electromagnetic actuators convert stored electrical energy directly into linear mechanical energy 5
Piezoelectric Piston Pumps High forces (70 kn) High frequencies (400 Hz) due to short stroke Challenges with friction, inertia, and valve resonances Image: Henderson et al. (2013) 6
Linear Diaphragm Pumps Low noise High reliability Low power output (0.3 lpm, 12.8 psi) Image: GD-Thomas LMF Series 7
Objectives Reduce complexity of electrical-to-hydraulic energy conversion Fewer energy conversions: increased efficiency Fewer moving parts: increased reliability Fewer components: decreased package volume 8
Linear Electromagnetic Piston Pump HP Manifold X N S S N Piston S N N S X LP Manifold 9
Coupled Construction Goal: computationally inexpensive with reasonable accuracy Assumptions: Square-wave electrical current input Quasi-steady state linear actuator performance Instantaneous check valve transitions Constant tank and rail pressure Evaluate Magnetic Equivalent Circuit Calculate Actuator Force vs Displacement Solve Pump to Steady State Calculate Power Density and Efficiency 10
Actuator Magnetic Equivalent Circuit (MEC) actuator as reluctance network for flow of magnetic flux Calculate the force and inductance vs actuator displacement Significantly less computationally expensive than FEA 11
Coupled Construction P rail N S X F act P 1 F m x press F spring P 2 S N F drag S N N S X P tank 12
MEC Actuator Validation Parameter Error Force @ dx = 0 mm -2.0% Force @ dx = 5 mm -5.7% Inductance @ dx = 0 mm 3.4% Cycle Power Density 1.8% Cycle Efficiency 0.3% 13
Genetic Optimization Multiple objectives: Power density: Efficiency: cycle output power package volume Multiple constraints: P out P out + P drag + P leak + P loss,act Maximum flux density in linear actuator Peak voltage supplied during current ramp-up 14
Genetic Optimization 10 stator poles 6 stator poles 4 stator poles 15
Genetic Optimization Large diameter, low driving frequency Small diameter, high driving frequency 16
Genetic Optimization Comparison: Concentric power pack supplies 0.15 W/cc 17
Conclusions More stator poles, larger piston diameters, lower frequencies are associated with higher efficiencies Fewer poles, smaller diameters, higher frequencies give higher power densities Higher power densities and efficiencies than stateof-art are achievable 18
validation and proof of concept with experimental linear electromagnetic actuator coupled to piston heads Looking for: Expertise in manufacturing of linear actuators Off-the-shelf linear actuator of similar design Check valves capable of operation at 60-100 Hz 19
Acknowledgments Dr. Eric Severson, post-doctoral researcher in Electrical Engineering at University of Minnesota Minnesota Supercomputing Institute (MSI) at the University of Minnesota 20
References Henderson et al. The Influence of Passive Valve Characteristics on the Performance of a Piezo Pump. (2013). 21