A General Approach to Low-Level Control of Heavy Complex Hybrid Hydromechanical Transmissions

2018 ◽  
Author(s):  
L. Viktor Larsson ◽  
Petter Krus
Keyword(s):  
Engine Speed ◽  
Dynamic Properties ◽  
Multiple Input Multiple Output ◽  
Decoupling Control ◽  
Level Control ◽  
Straightforward Manner ◽  
Low Level ◽  
Multiple Input ◽  
Input Multiple Output ◽  
Pressure Output

This paper focuses on the low-level control of heavy complex hydraulic hybrids, taking stability and the dynamic properties of the included components into account. A linear model which can describe a high number of hybrid configurations in a straightforward manner is derived and used for the development of a general multiple input multiple output (MIMO) decoupling control strategy. This strategy is tested in non-linear simulations of an example vehicle and stability requirements for the low-level actuators are derived. The results show that static decoupling may be used to simplify the control problem to three individual loops controlling pressure, output speed and engine speed. In particular, the pressure and output speed loops rely on fast displacement controllers for stability. In addition, it was found that the decoupling is facilitated if the hydrostatic units have equal response. The low-level control of heavy complex hydraulic hybrids may thus imply other demands on actuators than what is traditionally assumed.

scholarly journals Low-Level Control of Hybrid Hydromechanical Transmissions for Heavy Mobile Working Machines

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1683 ◽  
Author(s):  
L. Viktor Larsson ◽  
Liselott Ericson ◽  
Karl Uebel ◽  
Petter Krus
Keyword(s):  
Fuel Efficiency ◽  
Multiple Input Multiple Output ◽  
General Nature ◽  
Level Control ◽  
Control Approach ◽  
Low Level ◽  
Important Benefit ◽  
Input Multiple Output ◽  
High Level ◽  
Mobile Working

Fuel efficiency has become an increasingly important property of heavy mobile working machines. As a result, Hybrid Hydromechanical Transmissions (HMTs) are often considered for the propulsion of these vehicles. The introduction of hybrid HMTs does, however, come with a number of control-related challenges. To date, a great focus in the literature has been on high-level control aspects, concerning optimal utilization of the energy storage medium. In contrast, the main topic of this article is low-level control, with the focus on dynamic response and the ability to realize requested power flows accurately. A static decoupled Multiple-Input-Multiple-Output (MIMO) control strategy, based on a linear model of a general hybrid HMT, is proposed. The strategy is compared to a baseline approach in Hardware-In-the-Loop (HWIL) simulations of a reference wheel loader for two drive cycles. It was found that an important benefit of the decoupled control approach is that the static error caused by the system’s cross-couplings is minimized without introducing integrating elements. This feature, combined with the strategy’s general nature, motivates its use for multiple-mode transmissions in which the transmission configuration changes between the modes.

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