Arto Laamanen

Energy Efficiency of Three-Chamber Cylinder with Digital Valve System

ABSTRACT Commonly used hydraulic cylinders have a piston and a piston rod. The piston divides the inside of the cylinder in two chambers and pressures which affect how the piston generates the linear motion. Use of distributed valve system enables several control modes in a system of this type because different control edges can be controlled independently. These control modes can be used for decreasing energy consumption and improving controllability. The traditional hydraulic cylinder has only a limited number of control modes, but by utilizing a multi-chamber cylinder the number of control modes can be increased. In this paper, a three-chamber cylinder is studied using measurements and simulations. The control of the cylinder is presented and measurements are done in a 1-DOF boom mock-up to show the operation of the system in practice. A simulation model is built to investigate further the energy saving capability of the system. The studies show that losses can be significantly reduced by replacing traditional cylinder drives with multi-chamber cylinders.

Parallel Pump-Controlled Multi-Chamber Cylinder

This study focused on the use of fixed displacement pumps in parallel connection to control the velocity of a multi-chamber cylinder piston. The system’s basic principle was to combine the discrete flow supply control of parallel pumps with the discrete effective area control of a multi-chamber cylinder to produce a speed control resolution high enough for accurate velocity tracking and positioning. Some throttling was used in the return line to control the system with overrunning loads.The properties of the system were tested with a 1-DOF boom mockup mimicking a medium-sized mobile machine boom. The test system revealed a feature that caused load acceleration to drop when the effective cylinder area was reduced during movement. Additionally, some delay was observed in accelerating the piston against the load force. These two system properties along with the discrete control method resulted in mediocre speed and position tracking in the system when movement was directed against the load force. The system was able to control restricting and overrunning loads as well as a large inertia mass with a low load force. The system’s energy losses were low considering that no pressure accumulators were used, but the throttling losses in the return line and the lack of energy recuperation leave room for improvement.Copyright