Influence of counterbalance valve parameters on stability of the crane lifting system
In this paper, a model of the large crane lifting system has been developed in the AMESim environment. The comparison between the simulation results and the experimental data shows good agreement in both time and frequency domains, indicating the correctness of the model. Furthermore, the causes of pressure pulsations of the lifting system are described by means of dynamic simulation and experimental research. The analysis result indicates that the pressure pulsation of the lifting system is closely related to dynamic characteristic of the counterbalance valve, and stability of the system can be improved by means of the flow area of counterbalance valve with linear small gradient.
Experimental and modeling studies of hydrostatic systems with the counterbalance valves which are used in hydraulic lifting systems with passive and active load
The hydrostatic systems with variable load, as well as the value and the nature of action, are used in many indrustries. There may be different hydraulic solutions using the appropriate braking valves (Fig. 1.1), whose tasks include brake piston rod loaded with cargo, where it is necessary to receive power during lowering, including excavators, wheel loaders or cranes. With the correct setting, the valve also controls the movement of the piston rod with the variable load throught the work cycle (for example – eject and/or return movement of the piston rod). Thus it provides a stable work wih active force (the force vector and velocity vector are in the same sense) and passive force (the force vector and velocity vector have opposite sense). Examples of applications with braking valves are: scissor lifts, hydraulic cranes or containers lifting systems in garbage trucks. Importantly, all of the hydraulic machines operating in the EU, working as a cranes or lift loads above 1 tonne, must be secured before breaking wires. This protection is achieved thanks to braking valves. The main European document that describes the essential safety requirements for currently marketed or put into using of machinery in the European Union is directive 2006/42/EC. In the field of hydraulic systems and components of machines, the norm harmonized with the Directive 2006/42/EC is accordingly BS EN ISO 4413 (Drives and hydraulic control – General rules and safety requirements for systems and their components). One of the most important feature of the norm is to realize manufacturers and service staff of machines, etc., what are the dangers of using a hydraulic system. To the most notable include, among others, these about the typically mechanical origin, for example, associated with moving actuators, inadequate material strength of the components or accumulation of energy. Another important group are those resulting from the failure of the machine control system, for example, manifesting unusual reactions machines and systems as a result of loss of power supply or unexpected extrudes of machine parts or substances. It should be noted that the safety of these installations often depends on the reliability of the control circuit. For this purpose, in their construction it is necessary to take into account the requirements of the PN-EN ISO 13849-1 – Parts of control systems security. Research on this valve have been undertaken before those provisions came into effect and according to the data sheet of one of manufacturer [8] which gave only a small, incomplete and general information – the flow STAwińSki Ł. Experimental and modeling studies of hydrostatic systems with the counterbalance valves which are used in hydraulic lifting systems with passive and active load. Eksploatacja i Niezawodnosc – Maintenance and Reliability 2016; 18 (3): 406–412, http://dx.doi. org/10.17531/ein.2016.3.12.
Swing-Free Transport of Suspended Objects With a Path-Controlled Robot Manipulator
Objects which cannot be directly grasped by the end effector of a robot manipulator and must be carried by a hook or similar device are susceptible to swinging during transport. For a simply suspended object, it is possible to use a path-controlled manipulator to achieve a swing-free motion. The trajectory consists of an initial acceleration to an intermediate velocity, then a secondary acceleration to final velocity. An experimental demonstration of the method is presented.