Jiangbo Zhao

A case study of electro-hydraulic loading and testing technology for composite insulators based on iterative learning control

In order to simulate the vibrating condition of composite insulators in breeze, and carry out its fatigue test under loading and vibrating conditions, the electro-hydraulic loading and testing technology for the composite insulators is researched in this study. A compound electro-hydraulic loading system is first designed, including two subsystems, the static proportional loading system and the dynamic servo loading system. Then, the working principle based on this system is analyzed, and the mathematic model of electro-hydraulic servo system is also built, proved to be an inertial element with high gain. The control method based on proportional–derivative-type iterative learning control has been applied to such a dynamic servo loading system, to achieve the high-precision control for dynamic load force with repetitive regularity. Both mathematic simulation and actual experiments have been designed and carried out, and their results proved that the load principle and the control method are feasible and applicable and have the ability of achieving high-precision control effects. Based on this discussed electro-hydraulic technology, an actual electro-hydraulic loading and testing system for different kinds of composite insulators has been researched and developed, with the advanced technology indices of six loading channels, 20 kN maximum dynamic force, 0.3 kN force control precision and 100 Hz maximum vibrating frequency.

Compliance control for a hydraulic bouncing system

This paper is to reduce the contact impact, control the leg stiffness and bouncing height. Firstly, the combining position/force active compliance control was involved in the deceleration phase to decrease the impact force and improve the leg compliance capacity. Then a reasonable velocity control of cylinder was addressed to control the bouncing height to the given value in the acceleration phase. Due to the model uncertainties and disturbances in the deceleration and acceleration phase, a near inverse like controller with a proportional and differential control (PD) was added into the velocity control of acceleration phase to compensate the bouncing height control error. Finally, the effectiveness of proposed controller was validated by experiments. Experimental results showed the impact force could be reduced effectively and a significant bouncing height control performance could be achieved. The influences of initial energy, preload of spring and velocity of cylinder on the bouncing height were addressed as well.

Indirect adaptive robust dynamic surface control of electro-hydraulic fatigue testing system with huge elastic load

In this article, an electro-hydraulic-based fatigue testing system is considered. Electro-hydraulic system suffers from internal parameter uncertainties and external disturbances. Indirect adaptive robust control has been proposed to address these problems; however, since the mathematical model of this electro-hydraulic system has an order of four, the inherent “explosion of terms” problem makes the controller hard to design, and a large computational cost is needed. Thus, dynamic surface control is utilized in the design procedure of indirect adaptive robust control. The proposed indirect adaptive robust dynamic surface controller simplified the design procedure and decreased the computational cost of the controller. Furthermore, due to the fatigue of the elastic load, fast internal parameter change is encountered in this system. A fast parameter estimation scheme is proposed to adapt to the parameter change for a better estimation performance. For the mechanical system, a change in the hydraulic circuit is made to address the problem of chattering and impact caused by huge elastic load and to simplify the system model at the same time. Simulations and experiments show that the proposed controller achieves a better parameter estimation and trajectory tracking performance.