Energy savings through displacement control - an opportunity and challenge for Fluid Power Dr. Monika IVANTYSYNOVA MAHA Fluid Power Research Center Purdue University, West Lafayette, USA
Content 1. Introduction & state of the art 2. Displacement controlled actuation 3. Prototype machines 4. Energy & fuel savings demonstrated 5. Hybrid DC systems 2
State of the Art in Fluid Power Hydraulic resistances used for motion control 15% energy wasted Low efficiency of pumps & motors HumanWaste Control 33% energy wasted of energy No power management Too many different components Only few standardized interfaces 3
Major question being answered How much can efficiency of these mul3 actuator machines be improved with new system architectures, more advanced or new components, and new control algorithms? How are these concepts transformational? 4
Our System Approach Energy Savings by Throttle-less Actuator Technology Machine Control Controller Each actuator requires itsmobile own Robots variable displacement pump Controller energy recovery no throttling losses Pump controlled actuator 5
Displacement Control - new circuit for linear actuators Circuit 1st published @ 1st Bratislavian Fluid Power Symposium in 1998 in Casta Pila Q A no throttling losses! Pumping CE F load v Operation in Pumping Mode Q B 1
Displacement Control Operation in Motoring Mode Q A CE Motoring v F load Q B energy recovery! 2
Advantages of DC circuits No Resistance control Better use of primary energy & energy recovery Less components, easy interface Less fuel consumption Less heat generation Machine function via SW Improved operator feeling System simplification Lower operating costs Reduction of cooler Easy to control Higher productivity
History of Displacement Control Rahmfeld, R. and Ivantysynova, M. 1998. Energy Saving Hydraulic Actuators for Mobile Machines. Proceedings of 1st Bratislavian Fluid Power Symposium, pp. 47-57. Častá-Píla, Slovakia. 2001 DC wheel loader prototype @ TUHH with O&K 15% less fuel measured in comparison test 2003 2nd wheel loader prototype @ TUHH with CNH DC + New transmission+active damping 2010 Mini excavator @ Purdue 40% less fuel measured by CAT 2007 Skid steer loader @ Purdue 15-20% less fuel and active damping 9
DC Controlled Excavator 435H Bobcat Mini Excavator Engine: Kubota 2.0 liter diesel, 37 kw Machine weight: 5 000 kg 10
Analyze LS - System Matlab Co-Simulation Hydraulic Model Matlab/SimMechanics Multi-body mechanics Mechanical Model Matlab/Simulink Pressure, flow, power 11
Simulation Results Define typical machine operations Trench Digging cycle Chicago 20 Nov 29, 2012
Simulation Results LS Excavator System Trench digging cycle Actuator Work 14% 25% Cooler/Charge Pump Valve losses 44% 6% other 11% Pump losses 18
Baseline Instrumentation temperature sensors pressure sensors position sensors engine speed Model validation & benchmark new system Chicago19 Nov 29, 2012
DC Controlled Excavator Offset Bucket Stick Boom Swing 15
Simulation Results Displacement Controlled Excavator System 39% less energy consumed for same cycle Trench digging cycle by eliminating throttling losses and energy recovery 16
Simulation Results Displacement Controlled Excavator System Charge pump Cylinder 23% 25% 13% 0% 39% Trench digging cycle Actuator DC work Pump loss Actuator Work Pumps Valve Losses are the main Pump Losses source of losses in DC controlled machine Fric=on, Other Charge & Cooler Drive 17
Side by side machine test 90 truck loading cycle @ CAT test facility 18
Side by side machine test Machine Results Raw data, average of selected cycles Soil loaded (ton) Fuel consumed (kg) Cycle time (s) Standard 7.55 0.533 12.1 LS Prototype 7.66 0.321 10.4 DC Difference +1.5% -39.7% -14.1% 40% less fuel 19
Side by side machine test Results Calculated results for selected cycles Machine Fuel Consumption (l/h) Productivity (t/h) Efficiency (t/l) Standard 9.36 101.7 10.9 LS Prototype 6.57 120.9 18.4 DC Difference -29.8% +18.9% +69.4% 70% productivity increases 20
Energy use comparison based on simulation models for same digging cycle 50#%#energy# savings## Reduced&hydraulic&losses& Reduced&engine&loads& Reduced&cooling&demands& LS DC 21
8 Mul2- actuator machines 7 6 5 4 H Pump Sharing US Patent 8,191,290 B2 issued June 5, 2012 G Advantages Fewer pumps than actuators F Lower parasitic losses Combined E pumps flows Limitation Simultaneous D operations limited to # pumps C 11 pump 1 E N G I N E 22 33 pump 2 22
Hybrid DC Systems allow engine downsizing and further fuel savings DC hydraulic system power Hydraulic shaft power [kw] 50 Rated engine power 37 kw Peng,max 40 30 Target rated engine power 18.5 kw Ptarget 20 10 0-10 40 42 44 46 48 50 52 Time [sec] 54 56 58 23 60
Hybrid DC Systems series- parallel arrangement Boom Stick Bucket Benefits energy storage without adding a pump load leveling Belt drive Swing all rotary actuator can share one pump Engine HP Swing high pressure rail can be used for pump controls valves can be added for on/off functions US#Provisional#Patent#Applica2on# Serial#No.#61/453.368# 24
Pump & Motor Requirements highly efficient electro-hydraulically controllable variable pumps & motors Increase of Efficiency Simulation Results why so important? 25
Example - efficiency ηt max=0.88 ηtmax=0.91 only 3% Difference Willimanson, C. and Ivantysysnova, M. 2007. The effect of pump efficiency on displacement controlled actuator systems. Proceedings. 10th SICFP 07, Tampere, Finland, Vol. 2, pp. 301-326. MAHA Fluid Power Research Center
Example - efficiency Skid steer loader - Truck loading Cycle 16.2% less power consumption MAHA Fluid Power Research Center
Pump & Motor Requirements highly efficient electro-hydraulically controllable variable pumps & motors Increase of Efficiency Smart Pumps Advanced Pump Control Increase of Power Density Low Noise Emission 28
Thank You! 29