In a variety of machinery, working members are driven by hydraulic cylinders. Such hydraulic systems are used to control multiple functions, such as raising and lowering the member, tilting and rotating the member about an axis, and sliding the member fore and aft. Flow-control valves are used in these hydraulic systems to control rate of flow from one part of the system to another. A proportional-priority-pressure compensating type of flow-control valve is used to proportionally divide the pump flow between the branches of the circuit based on their requirement. The valve uses a pressure compensator for accurate flow rate control. The pressure compensator maintains a constant pressure drop across the main spool valve. The pressure compensator is an integral part of the flow-control valve. In this thesis, a model and stability analysis for the pressure compensator is presented.

Drives and Control for Industrial Automation presents the material necessary for an understanding of servo control in automation. Beginning with a macroscopic view of its subject, treating drives and control as parts of a single system, the book then pursues a detailed discussion of the major components of servo control: sensors, controllers and actuators. Throughout, the mechatronic approach – a synergistic integration of the components – is maintained, in keeping with current practice. The authors’ holistic approach does not preclude the reader from learning in a step-by-step fashion – each chapter contains material that can be studied separately without compromising understanding. Drives are described in several chapters according to the way they are usually classified in industry, each comprised of its actuators and sensors. The controller is discussed alongside. Topics of recent and current interest – piezoelectricity, digital communications and future trends – are detailed in their own chapters.