This paper focuses on the application of adjustable speed induction motor drives for gantry cranes. Modern solution considers application of frequency converters for all drives. Multi-motor drives are standard solutions in crane application and requirements of load sharing are present. Presented algorithm provides load sharing proportional to the rated motor power on the simple and practically applicable method on the basis of estimated torques by frequency converters, and controller realized in PLC. Special attention is devoted to wide span gantry drive and algorithm for skew elimination. Solutions for load distribution in multi-motor drive, as well as mode of gantry drive skew elimination, are described. Suggested solution concept is confirmed by the experimental results

This paper analyses symmetrical and unsymmetrical voltage sag effects on the torque and speed deviation in direct torque controlled (DTC) induction motors (IMs) for adjustable speed drives (ASDs). The capability of an ASD for continuous normal operation in case of short supply disturbances is essential for high performance drives. In this paper, an updated scheme is proposed for boosting ASD performances during supply disturbances with voltage reduction. Flux weakening is an effective method to overcome the torque-decreasing problem in case of DC-link voltage diminishing. It is also shown that speed reduction is an efficient procedure to obtain the voltage sag insensitivity of an ASD, which is appropriate for the existing industrial applications. Extensive laboratory testing has been conducted to verify the performances and effectiveness of the proposed control algorithm. The suggested method requires only a modification of converter control software or operating speed change without any additional hardware components. Extended tests under various voltage sags events were carried out on a 1.5 kW laboratory drive, and the obtained results have been compared with an industrial DTC drive.

The paper proposes a discrete-time sliding mode controller for single input linear dynamical systems, under requirements of the fast response without overshoot...

This work presents a comparative study of two approaches for design of high performance discrete‐time velocity servo systems with induction motors (IMs). The first approach uses the conventional proportional–integral controller with one‐step delayed disturbance compensator (OSDC). The OSDC is based on measurements of the control input and plant states. The second approach uses the discrete‐time integral sliding mode (DISM) controller with a first‐order disturbance compensator, which is based on switching function signal measurement only. The controlled plant, consisting of IM in the commonly used indirect field‐oriented control (IFOC) scheme, is approximated by first‐order dynamic model for control design purpose. Comparisons are conducted through simulations considering an ideal case (without unmodelled dynamics) and a regular one, using MATLAB/Simulink models of real IFOC structure elements. The experimental investigation is conducted as well. The performed tests show that both controllers enhanced with the corresponding disturbance compensators are suitable for high‐performance control systems design if speed measurement is near noise‐free case, with better performance from DISM. If Euler backward difference is applied for speed detection, both control systems need some retuning in order to make a compromise between chattering and tracking accuracy.