This paper deals with design optimisation of hydraulic hybrid drivelines during early concept design phases. To set the design parameters of a hybrid driveline such as gear ratios, pump/motor displacements and size of energy storage, the energy management of the hybrid machine needs to be considered as well. This is problematic since a nested design and control optimisation normally requires substantial computer power and is time-consuming. Few previous studies have treated combined design and control optimisation of hydraulic hybrid vehicles using detailed, non-linear component driveline models. Furthermore, previously proposed design optimisation methods for on-road vehicles are not suitable for heavy off-road machines operating in short repetitive cycles with high transient power output. The paper demonstrates and compares different optimisation approaches for design and control optimisation combining deterministic dynamic programming and non-gradient based numerical optimisation. The results show that a simple rule-based energy management strategy can be sufficient to find the optimal hardware design even though non-optimal control laws are used.

This paper presents the development of a method for condition monitoring and online fault detection on proportional directional valves. The systems that such valves are part of might be sensitive for unexpected maintenance or long duration stops. Consequently, the implementation of a fault detection and monitoring system can reduce maintenance costs and increase safety. The method is based on monitoring both the valve supply current and spool position related to the spool positioning control signal. Therefore, it is applicable for valves with embedded electronics including spool position measurement and internal controller. The supply current and spool position behavior depends on the friction, flow forces, solenoid current, and valve closed loop controller performance. Furthermore, valve static and dynamic characteristics are influenced by the spool size, overlapping and manufacturing tolerances. The effectiveness of the method to monitor and detect faults in valves with different sizes and constructive parameters is shown experimentally using five different proportional valves. The proposed method requires reference parameters characterizing the valve operation without faults. Standard tests are proposed to determine healthy valve parameters. For the method valuation and validation, experimental results with the valve operating under healthy conditions and with induced faults were compared. Faults were added in a way to represent spool locking and increase of friction forces between the spool and sleeve. The obtained results show the capability the method for the detection of faults classified as severe even if the valve controller attempts to compensate the faulty behavior.

This paper outlines an extended analysis on how multi-chamber actuators can improve the efficiency of valve-controlled systems. Resistive control is a major source of energy losses in valve-controlled systems that share the same pump to drive multiple loads. By combining different chambers, the load on multi-chamber actuators can be transformed into different pressure and flow rate levels. This allows the adaptation of its load to the loads on other actuators. This can lead to a reduction of resistive control energy losses that occur between pump and actuators when driven simultaneously. As a case study to highlight how the system efficiency can be improved, a load sensing system with a conventional and a multi-chamber actuator is analysed. The equations that describe the system steady state behaviour are presented to evaluate the effect of the load transformations on the system efficiency. A disadvantage of such architecture is the fact that load transformations result in different actuator speeds. To reduce this effect, a compensation factor for the command signal to the proportional valve is presented. The highlight from this paper is the potential for efficiency improvement enabled by the adoption of multi-chamber actuators in a valve-controlled architecture. Further research is required for the selection of number of chambers and their areas since they directly affect the system efficiency.

This paper presents the analysis of an on-line fault detection method for proportional directional hydraulic valves applied on speed governors of hydroelectric power plants. This application area is very sensitive for unexpected maintenance or long duration stops since most of power plants are interconnected on an electrical power grid. A plant stop must be programmed previously and approved by a regulatory agency. Consequently, the implementation of a fault detection and monitoring system can reduce maintenance and operational costs as well as safety risks of equipment and operators. The developed method is based on monitoring both the valve supply current and spool position related to an input control signal. Therefore, it is applicable for so called servoproportional valves, it means, those including spool position measurement and with embedded electronics. Valve static and dynamic behaviour depends on spool friction, flow forces, solenoid force and valve closed loop controller. Such characteristics are influenced by the spool size, overlapping and manufacturing tolerances. In this paper, the effectiveness of the method to monitor and detected faults in valves with different sizes and constructive parameters is demonstrated experimentally using five proportional valves.

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