Control-oriented modelling and development of a model-based switching algorithm for a digital hydraulic independent metering cylinder drive

Abstract

The article concerns the modelling and control of a digital hydraulic cylinder drive involving a standard differential cylinder controlled by four digital flow control units in a full bridge circuit. A special focus of the modelling lies in the compromise between the prediction accuracy of the model and the computational efficiency of the control algorithms based on the models. A physically motivated model for the static pressure-flow-characteristic of digital flow control units is derived and compared to conventional models. Based on this model, a switching algorithm is developed which finds an optimal switching combination for each DFCU, if certain dimensioning conditions are fulfilled. The algorithm forms the inner loop of a hierarchical controller for the overall system. In an outer loop, a flatness-based tracking controller is used for the independent metering control of the cylinder. The models and algorithms developed in this article are validated in experimental investigations using a laboratory test rig.

Keywords

Digital fluid power digital flow control unit flatness-based control independent metering

Get full access to this article

View all access options for this article.

References

Fischer

Laamanen

Iso-Heiko

. Digital hydraulics on rails – pilot project of improving reliability on railway rolling stock by utilizing digital valve system. In: Proc. 14th Scandinavian Int Conf Fluid Power, SICFP15, Tampere, Finland, 20–22 May 2015, Tampere University of Technology.

Linjama

Vilenius

. Improved digital hydraulic tracking control of water hydraulic cylinder drive. International Journal of Fluid Power 2005; 6(1): 29–39.

Eriksson

Palmberg

. Individual metering fluid power systems: Challenges and opportunities. Proc IME J Syst Contr Eng 2011; 225(2): 196–211.

Linjama

Huova

Boström

. Design and implementation of energy saving digital hydraulic control system. In: Proc 10th Scandinavian Int Conf Fluid Power, SICFP07, Tampere, Finland, 21–23 May 2007, pp. 341–359, Tampere University of Technology.

Linjama

Huova

Karvonen

. Modelling of flow characteristics of on/off valves. In: Proc 5th Workshop Digital Fluid Power, DFP12, Tampere, Finland, 22–24 October 2012, pp. 209–222.

Huova

Ahopelto

Ketonen

. Characteristics of digital hydraulic with commercial controllers. In: Proc. 7th Workshop Digital Fluid Power, DFP15, Linz, Austria, 26–27 February 2015, pp. 114–128. Linz Center of Mechatronics.

Linjama

Siivonen

Huova

. Numerically efficient flow model for on/off valves. In: Proc 7th Workshop Digital Fluid Power, DFP15, Linz, Austria, 26–27 February 2015, pp. 164–172.

Bindel

Nitsche

Rothfuß

. Flatness based control of a two valve hydraulic joint of a large manipulator (in German). at–Automatisierungstechnik 2000; 48(3): 124–131.

Stauch

Rudolph

Schulz

. Some aspects of modelling, dimensioning, and control of digital flow control units. In: Proc 7th Workshop Digital Fluid Power, DFP15, Linz, Austria, 26–27 February 2015, pp. 101–113.

10.

Merritt

. Hydraulic control systems. New York: John Wiley and Sons, 1967.

11.

Laamanen

Linjama

Vilenius

. On the pressure peak minimization in digital hydraulics. In: Proc 10th Scandinavian Int Conf Fluid Power, SICFP07, Tampere, Finland, 21–23 May 2007, pp. 107–121. Tampere University of Technology.

12.

Rothfuß

Rudolph

Zeitz

. Flachheit: Ein neuer Zugang zur Steuerung und Regelung nichtlinearer Systeme. at – Automatisierungstechnik 1997; 45(11): 517–525.

13.

Fliess

Rudolph

. Local tracking observers for flat systems. In: CESA’96 IMACS Multiconference: computational engineering in systems applications, Lille, France, 9–12 July 1996, pp. 213–217. Gerf EC Lille, Villeneuve d’Ascq, France.

14.

Kiltz

Rudolph

. Parametrization of algebraic numerical differentiators to achieve desired filter characteristics. In: IEEE 52nd Annual Conference on Decision and Control (CDC), Firenze, Italy, 10–13 December 2013, pp. 7010–7015. IEEE.

15.

Delaleau

Rudolph

. Control of flat systems by quasi-static feedback of generalized states. Int J Control 1998; 71(5): 745–765.