Abstract:
A 3DOF crane is a lifting machine that mostly works with the use of pulleys and cables. For the construction and many other industries, cranes are valuable assets because they make working with heavy machinery and construction materials easy. These are widely used for moving, lifting and placing payloads from one location to another location. During the movement of payload, there is often an undesirable vibration or swing in the payload, and this payload vibration causes uneven trolley motion. So, for a smooth trajectory of a crane; a control technique, which gives a suitable input to the plant that causes a smooth trolley motion, is desirable.
In this research work, three control techniques namely PID tuned by LQR, PID tuned by pole placement and a dual loop control scheme has been investigated. The performance of three schemes has been analysed on controlling the trolley position and payload vibrational motion of the jib system of Quanser made three degrees of freedom (3DOF) crane. The classical PID techniques often face tuning issues. Issues such as overshoot, affect the smooth operation of crane if gains are not properly tuned. Many times large integral and derivative gains are required for smooth and safe operation of crane. That in practice is not feasible due to limitation of energy resources. In this research work, a dual-loop control scheme (DLCS) has been investigated to handle such type of issues. The DLCS, is a combination of classical PID and advanced state feedback control techniques. Extensive simulations have been carried out using MATLAB / Simulink and practically validated on a Quanser 3DOF crane prototype. The simulations and experimental results indicate that the proposed DLCS control scheme provides better results as compared to classical PID in context of overshoot and steady state error of the trolley position along with improvement of payload vibration.
