Hydraulic systems employed in several industrial and mobile applications present significant advantages, such as a high power-to-weight ratio and fast dynamic response. However, these systems have low efficiency due to high power dissipation. A recent concept called “digital hydraulics” comprises particularities that create opportunities for a reduction in load loss. This paper proposes a configuration and control method for actuator speed control based on the principles of digital hydraulics. In this context, several fixed displacement units and on/off valves are connected directly to the actuators without throttling valves. The system studied here presents three operation methods (pump mode, motor mode and idle mode), which allows discrete valves to replace continuous or flow control valves in order to control the actuator. Furthermore, a fixed or variable displacement pump with large displacement is replaced by several small, fixed displacement units. Simulations are performed with a co-simulation technique using AMESim and MATLAB. The actuator speed, inlet and outlet pressures on the fixed displacement units and flow rate in the circuit lines are analysed. Preliminary simulation results exhibit smooth transitions between speed levels, adequate dynamic performance, low power dissipation and high energy-storage capacity. A specific limitation of this technology is the obtained actuator discrete speed. The main contributions of this research are the development of a digital hydraulic system configuration and its control strategy, which allows speed control of hydraulic actuators and provides the capacity to store energy.

This paper presents a theoretical–experimental pressure analysis of a hydraulic press brake with synchronized cylinders. In this machine, the motion of each cylinder is controlled by independent variable-speed electrical motors. This design has many benefits over traditional solutions using hydraulic proportional valves, such as higher energetic efficiency, nonrequirement of a heat exchanger, lower oil-cleanliness requirement, and reduced audible noise. However, a critical characteristic of the press brake is the use of double acting cylinders with large rods controlled by a pump in a closed circuit. In the studied system a cap end area roughly eleven times greater than the rod end area is used. Furthermore, the synchronized hydraulic press brake operates in six stages with particular characteristics implying in different flow rate demands and pressure behaviors. Based on experimental results, the pressures in specific parts of the circuit are analyzed and critical operational conditions are identified. A simulation model using Hopsan is validated and used to propose a hydraulic circuit modification. The proposed solution eliminates the tendency for pump cavitation and pressure surges that occur during the press break operational cycle.

Hydraulic positioning control systems are widely employed in several engineering fields such as industry, aerospace, vehicles, and electrical power plants. However, their design is not a straightforward engineering task because several configurations and sizes of valves and cylinders are available, the system components exhibit nonlinear behavior, and the aspects of both fluid mechanics and control theory need to be included for achieving a suitable design. Furthermore, each application has static and dynamic requirements that need to be fulfilled under uncertain loading conditions. Dynamic simulation is an important tool for the analysis and design of hydraulic positioning systems; however, the main characteristics of the components should be known beforehand so that the parameters and model structure can be defined. To overcome these constraints, comprehensive knowledge of the design problem is necessary to ensure appropriate sizing of the hydraulic components. In this regard, this paper presents a detailed study of the influences of the natural frequency and flow coefficient of the valves. The actuator natural frequency is also analyzed, and its modification according to the system requirements is described. The influence of these parameters on the behavior of a closed-loop hydraulic control system with a proportional controller is evaluated using a detailed mathematical model implemented in MATLAB®/Simulink®. Model validation is accomplished using a workbench.

Controlling and monitoring a compressor station with more than 3,000 tags remotely can be a heavy burden for a low speed (9,600 bps) double-hop satellite link, over which an ICMP packet takes more than 2 seconds to traverse all the way across the spatial segments, forth and back. This paper presents an application named Datasync, specially developed to take full advantage of the scarce resources provided by the VSAT link. One of its main features is to enable the setting up of communication deadbands and the “hot” changing of these deadbands. Therefore, the operator is able to increase the deadband of a tag immediately after detecting that too many exceptions are reported on that tag, which would cause an undesirable increase on the traffic, ultimately resulting in unacceptable response times.

The Bolivia Brasil Gas Pipeline (GASBOL) is a pipeline extending from the gas producing fields of Rio Grande, Bolivia, to Canoas, Brazil. It distributes gas to five states in Brazil, with a total extension of 3 160 km (1,970 mi) and a rated operating pressure of 100 kgf/cm2g (1,420 psig). GASBOL is owned and operated by Transportadora Brasileira Gasoduto Bolivia-Brasil S.A., TBG, a company whose shareholders are Petrobras, AEI Ame´rica do Sul, Transredes, BBPP Holdings and Bear Ga´s. After several occurrences of flow turbine failures caused by large flow variations at some city gates, the design of new stations was modified to include a control valve upstream of the interconnection point with consumers. For operational city gates such functionality would imply delivery interruption to perform costly hot tapping procedures in order to install a flow control valve. Therefore, TBG’s engineering team was challenged to develop a cheaper and quicker solution. This paper describes TBG’s answer to that challenge, developing a low cost flow control solution at ten selected city gates along the pipeline. The stations were chosen based on several aspects such as volume capacity, line packing to the consumer, etc. The main objective is to ensure that the daily volume effectively delivered does not exceed the contracted volume, avoiding delivery failures due to imbalances caused by unplanned withdrawals, as a means to improve planning of the pipeline operational profile.