Fluid Power systems Zonal hydraulics - industrial case 10 October 2017

Content Goal of the research Case: wood material handling Test rig Frame and load compensation DDH components Cabinet for electric installations Hydraulic circuits Initial measurements and position control Research tasks References

Goal Goal: Testing suitability of electro- hydraulic actuators (EHA), or direct driven hydraulics (DDH) for industrial applications. Typically, actuators in industrial fluid power systems are valve operated (Fig. 1a) However, directional valves or servo valves cause high pressure losses. By using displacement controlled actuators (i.e., DDH), a more energy efficient system can be built (Fig. 1b). (a) (b) Figure 1. (a) Valve controlled actuator [1]. (b) Displacement controlled actuator [2].

Case Wood material handling Material is being lifted and lowered in rapid motion in a continuous process. A mockup of the actual machine has been built in the Fluid Power Lab. The frame has been designed and manufactured by a company delivering wood handling machinery. The other components have been delivered by a large fluid power company. Figure 2. Test rig with 700 kg load.

Test rig – frame and load compensation Steel frame with vertical rails Carriage for load (barrel of concrete or stack of weights) Load compensating circuit Accumulator Differential cylinder Figure 3. (a) Side view: Concrete barrel load on carriage (b) Load compensating circuit (b) (a)

Test rig – DDH and I/O DDH (variable-speed pump drive) Drive (motor controller) PLC (programmable logic control); Small real time computer to handle motion control. Bus-connected I/O (Sercos Automation Bus) Sensors: position, pressure, temperature Servo motor: three-phase synchronous permanent magnet motor (MSK101E) Axial piston variable displacement pump for closed circuits (A10VZG) Figure 4. Back view of test rig: I/O modules, servo motor, pump

Test rig – cabinet for electric installations 1 3 2 4 5 Power electronics High voltage installations HSC03 drive (1) and its filter (2) Brake resistor (3) PLC/Controller (4) (XM21) 24 V supply (5) The cabinet is equipped with cooling fans Figure 5. Contents of electric cabinet

Hydraulic circuits Two actuator circuit variants will be tested Mass Two actuator circuit variants will be tested Two cylinder system with symmetrical actuation cylinder and load compensating circuit (variant 1) Differential actuation cylinder with valve operated, accumulator fed volume compensation (variant 2) Figure 6. Variant 1 (symm & LC) Mass Figure 7. Variant 2 (diff & brute force)

Test rig – initial measurements – x, v, w (mm) 75 225 Figure 8. Three liftings (manual control), 150 mm,  0,9 s. - (75 mm – 225 mm) Figure 9. - Three liftings 150 mm - Speed up to max  350 mm/s 300 (mm/s) 200 1000 (rpm) Figure 10. - Three liftings 150 mm - Rpm max  1000 rpm Screen shots from trending tool

Position control Accuracy of the position control is ok for the application Figure 11. Five liftings of 700 kg load. Command value and actual value Figure 12. Close-up of 1st step in Fig. 11. Command value and actual value

Research tasks Demonstrate performance characteristics (and compare to simulation) The fast lifting motion specified by the partner companies should be reached Measure motor speed and torque, cylinder chamber pressures, speed of lifting motion etc. Calculate power consumptions (electric, hydraulic, mechanical) and overall efficiency Monitor development of oil temperature and motor temperature in longer test runs Two test setups (variants, slide 8): First (‘running-in’) with the symmetric actuator cylinder and load compensation Next with differential cylinder and without load compensation Comparison with conventional valve controlled hydraulics solution (utilizing a pressure accumulator) Figure 13. Examples of simulation results [1] that should be validated with the test rig.

References [1] Hänninen H, Minav T, Pietola M (2016), Replacing a Constant Pressure Valve controlled System with a Pump Controlled System. Proc Bath/ASME Symp Fluid Power and Motion Control FPMC2016, Sep 7-9, Bath, UK. [2] Lee S-R, Hong Y-S (2017), A dual EHA System for the Improvement of Position Control Performance via Active Load Compensation. IJ Precision Engineering and Manufacturing, Vol 18, No 7, pp. 937-944.

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