Along with the general requirement of continuously increasing efficiency of hydrostatic drivetrains, variable displacement machines are of major concern in research and development. To this effect, the whole machine performance is mainly dependent of the displacement variation system (DVS) performance. A lot of work to this topic focusses on the controller and actuator level. The aim of this paper is to offer a more fundamental view on DVS by giving a focus to the basic hydro-mechanical principles.

Current efficiency measurements of variable hydraulic axial piston pumps are performed with the displacement system locked at maximum volume, thus without the controller. Therefore, the controller’s effect on the efficiency is not quantified at state of the art measurements. Former research on control systems mainly focused on the dynamic behaviour. This paper aims to quantify the losses in the displacement and control system and to research the dependencies of those. Therefore, a test rig is built up at IFAS to measure the control power of displacement controlled pumps. Furthermore, a simulation tool is developed to increase the understanding of the loss mechanisms of the investigated control systems. In conclusion, the paper shows the potential of efficiency improvements for displacement controlled pumps.

Measures of individualization and integration offer a great potential for further development and optimization in hydraulic drive technology. Advantages are seen especially for energy efficiency and functionality. These potentials motivate current research activities for displacement controlled systems and for valve controlled structures. For the latter, the focus lies on strategies of independent metering. Furthermore, expected challenges for the future are discussed.

The floating cup principle is a general hydrostatic principle for both constant and variable displacement pumps and motors, as well as for hydraulic transformers. In this paper, the focus will be entirely on the control of the displacement of the variable 28 cc Floating Cup pump (FCVP28). The floating cup principle features two opposed swash plates, for which both angular positions need to be controlled in order to cover the entire range from zero to full displacement. The results of both extended numerical analysis as well as simplified linearized models will be compared to test results on a 28 cc FCVP. Special emphasis will be on the dynamic behaviour of the displacement control.

This paper describes a novel concept for a low cost variable delivery external gear pump (VD-EGP). The proposed VD-EGP is based on the realization of a variable timing for the connections of the internal displacement chambers with the inlet and outlet ports. With respect to a standard EGP, an additional element (slider) is used along with asymmetric gears to realize the variable timing principle. Previously performed tests confirmed the validity of the concept, for a design capable of varing the flow in the 65%-100% range. Although the VD-EGP concept is suitable for various flow control system typologies (manual, electro-actuated, hydraulically flow- or pressure- compensated), this paper particularly details the design and the test results for a prototype that includes both a manual flow control system and a pressure compensator. Flow vs pressure and volumetric efficiency curves are discussed along with transient (outlet flow fluctuation) features of the VD-EGP.

Environmental awareness, production costs and operating expenses have provided a large incentive for the investigation of novel and more efficient fluid power technologies for decades. In the earth-moving sector, hydraulic hybrids have emerged as a highly efficient and affordable choice for the next generation hydraulic systems. Displacementcontrolled (DC) actuation has demonstrated that, when coupled with hydraulic hybrids, the engine power can be downsized by up to 50% leading to substantial savings. This concept has been realized by the authors‘ group on an excavator prototype where a secondary-controlled hydraulic hybrid drive was implemented on the swing. Actuatorlevel controls have been formulated by the authors‘ group but the challenge remains to effectively manage the system on the supervisory-level. In this paper, a power management controller is proposed to minimize fuel consumption while taking into account performance. The algorithm, a feedforward and cost-function combination considers operator commands, the DC actuators‘ power consumption and the power available from the engine and hydraulic hybrid as metrics. The developed strategy brings the technology closer to the predicted savings while achieving superior operability.

Liebherr mobile harbor cranes use electrical generators to provide electrical power for load attachment devices such as container spreaders or magnets. Upcoming exhaust and noise emission standards and energy saving considerations lead to a broad diesel engine speed range. The challenging design aspect is to ensure a constant speed of the asynchronous generator by the hydraulic drive system. In addition, electrical load profiles of inductive consumers usually have DT1 system characteristics with very small time constants. They evoke fast torque variations interfacing the hydraulic transmission. Liebherr mobile harbor cranes, see Figure 1, usually have a closed hydraulic circuit containing a hydraulic pump with a high displacement volume that is adjusted electronically in accordance to the current diesel engine speed. Regarding the energy saving aspects, a further minimization of the diesel engine speed leads to a larger pump size with increasing torque losses. Depending on the pressure setting, the volume flows can be reduced in constant pressure grids. Especially in part-load operation this results in better efficiency compared to closed hydraulic circuits by minimizing the displacement volume of hydraulic components. To obtain a stable generator speed, it is essential to adjust the displacement volume of the hydraulic unit for equalizing its input torque with the Figure 1: LHM 800 Group 10 - Mobile Hydraulics | Paper 10-5 199 generator load torque. In interaction with the software-based control architecture, the stability of the electrical frequency depends on the mass inertia of the generator drive and time constants of the embedded hydraulic actuators. The system model, represented by ODEs is established and verified with a hydraulic simulation software. On that basis, the design approach of a PI-state-controller is presented. Corresponding controller gains and state feedback parameters are determined by pole placement techniques. To conclude this investigation a comparison between the hydraulically closed circuit and the constant pressure grid is shown by simulation and measurement data.

Monitoring the resistance training volume load (VL) (sets × reps × load) is essential to managing resistance training and the recovery–adaptation process. Subjects: Eight trained weightlifters, seven of which were at national level, participated in the study. Methods: VL was measured both with (VLwD) and without (VL) the inclusion of barbell displacement, across twenty weeks of training, in order to allow for comparisons to be made of these VL calculating methods. This consisted of recording the load, repetition count, and barbell displacement for every set executed. Comparisons were made between VL and VLwD for individual blocks of training, select training weeks, and select training days. Results: Strong, statistically significant correlations (r ≥ 0.78, p < 0.001) were observed between VL and VLwD between all training periods analyzed. t-tests revealed statistically significant (p ≤ 0.018) differences between VL and VLwD in four of the seven training periods analyzed. Conclusion: The very strong relationship between VL and VLwD suggest that a coach with time constraints and a large number of athletes can potentially spare the addition of displacement. However, differences in percent change indicate that coaches with ample time should include displacement in VL calculations, in an effort to acquire more precise workload totals.

This research seeks to examine the process of displacement and resettlement of residents who had been affected by regularization process within Manzese and Buguruni wards in Dar es Salaam City, Tanzania. It aimed at analyzing the issues and opportunities faced by the affected residents during regularization. The regularization which involves two processes, tenure and physical upgrading has been extensively used in solving problems associated with unplanned and informal settlements within developing countries in Africa, Asia and Latin America. It’s a process used to bring informal and unauthorized settlements into the legal, official and administrative structures of land management as well as improving the living conditions of its dwellers. In Tanzania, whereby more than 80 per cent of its urban residents live in informal settlement, the process had been practiced in order to provide basic services such as access roads, storm water drainages, street lights, water supply and public toilets within informal and unplanned settlements. Compared to previous strategies for upgrading such as slum clearance and site and services and squatter upgrading, regularization had been considered to bring positive results.  The main concern of this research is physical regularization which was implemented through Community Infrastructure Upgrading Project (CIUP) within sixteen settlements in Dar es Salaam city. During its implementation, about twenty households of tenants and house owners were displaced. This research being explorative focused on understanding the process of displacement and resettlement by using qualitative method. This was done through narrations of traced and found six tenants and four house owners within the affected settlements of Mnazi Mmoja, Mnyamani and Madenge settlements. It applied case study strategy whereby the settlements made the main case study areas and the individual displaced residents became sub cases. Experiences before, during and after displacement and resettlement were narrated by using in-depth interviews. The selected settlements were obtained through criteria sampling whereby the individual displaced residents were found by using snow balling approach. Also resettlement issues and opportunities faced by displaced tenants and house owners were analyzed and the emerging patterns of issues and opportunities were identified. The issues include loss of access to common facilities, homelessness, marginalization and social disarticulation, family disintegration and joblessness. The opportunities include improved facilities, expansion of human competence and social opportunities, enhanced capabilities and improved social services. It was also realized that the issues suffered and opportunities accrued by house owners were different from that of tenants. The research examined the process of displacement and resettlement through policy and legal frameworks which guided the regularization. It also used the justice and collaborative theories in formulating concepts for data collection, analysis and discussing the results. During the discussions it was realized that there were emerging gaps in the process as it was indicated within the experiences of individual cases. These gaps include that of lack of real participation and democracy, insufficient knowledge on compensation level, insufficient community participation especially with the affected tenants.  The research provides an indicative knowledge on regularization process which can further be used in improving the planning process. / QC 20111123

PURPOSE: Sufficient hyoid excursion plays a critical role in facilitating multiple facets of functional pharyngeal motion, phonation, and nutritional intake; however, objective quantification of hyoid displacement during modified barium swallow studies relies on variable practice protocols. This study sought to compare hyoid displacement methodological differences in the dysphagia literature to establish new clinically feasible references of normative values and measurement strategies. METHOD: The current study incorporated re-analysis of Molfenter and Steele (2011)’s meta- analysis according to measurement strategies (anterior and superior versus hypotenuse (total) displacement as well as rest-to-peak versus frame-by-frame quantification), bolus volume, and participant characteristics (sex and age). Conversion of data was completed using the Pythagorean theorem, and resulting data was then compared within the study itself and externally to Leonard et al. (2000). Two Tailed Independent t-tests and a linear regression were completed to assess the relationship between analysis factors and hyoid displacement. RESULTS: Males were found to have significantly higher hypotenuse hyoid displacement than females. No statistical significance was found between the predetermined age groups (“old” and “young”) or newly determined age groups (“old,” “young,” and “middle age”). A linear relationship between increasing bolus volume and hypotenuse hyoid displacement was established. Rest-to-peak and frame-by-frame internal measurement strategies were statistically identical, but the rest-to-peak strategy incorporates qualitative improvements regarding efficiency. The re-analysis of anterior and superior hyoid displacement norms within Molfenter and Steele (2011) resulted in slightly lower hypotenuse normative values when compared to Leonard et al (2000). CONCLUSION: The current findings suggest that measurement of hyoid hypotenuse displacement is a more efficient measurement strategy and is effective in incorporating the hyoid’s anterior and superior displacement. For clinicians, these findings suggest that normal hyoid excursion may not need to be as large as Leonard et al.’s (2000) norms proposed to be classified as within normal limits for healthy individuals. New references on normative values suggest that as bolus volumes increase, so too does the hyoid displacement, with an expected plateau due to anatomical constraints, to facilitate safe swallows. Furthermore, although rest-to-peak and frame-by-frame internal measurement strategies were statistically identical in quantifying hyoid displacement, the rest-to-peak measurement strategy stood superior when considering the qualitative improvement in a clinician’s time management. Moreover, analysis of participant characteristics identified that hyoid excursion is larger for males than females and that presbyphagia likely results in slightly reduced displacement. Further investigation is warranted and required to better understand hyoid excursion variability and refine best practices.