Shoukun Wang

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.

The control of the electro-hydraulic shaking table based on dynamic surface adaptive robust control

The electro-hydraulic shaking table is investigated, in the present paper, to simulate the vibrational working environment of industrial components and equipment. Adaptive robust control can be applied to the shaking table system because electro-hydraulic systems suffer from internal parameter uncertainties and external disturbances. However, the adaptive robust controller design is complicated and has a large computational cost owing to the ‘explosion of terms’ problem. Thus dynamic surface control is applied in the design procedure of adaptive robust controllers to overcome the ‘explosion of terms’ problem. In this work, dynamic surface adaptive robust control is proposed. It simplifies the designed procedure of the controller and decreases its computational cost. Firstly, the structure of a shaking table is formulated and the operation principles of the shaking table, including the hydraulic and control principles, are analysed. A change is made in the mechanical-hydraulic system of the fluid circuit to address the problem of changing the vibration direction. Secondly, a dynamic model of a shaking table is proposed. Based on analysis of this model, the design of a dynamic surface adaptive robust controller for a shaking table is presented so as to improve its performance. Finally, comparative simulations and experiments are carried out. The comparison of performance results with proportional-integral-derivative control verify the correctness of the hydraulic scheme and control principle, as well as the high-performance of the dynamic surface adaptive robust controller. The shaking table achieves a guaranteed dynamical performance and tracking accuracy for the output in the presence of parameter and load uncertainties.

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.

Dynamic image stabilization precision test system based on the Hessian matrix

Dynamic image stabilization precision of an optical image-stable device is a key technical indicator. Therefore, a fast dynamic image stabilization precision test system for an optical image-stable device is developed. A large-aperture collimator with a designed cross divisional board is used to simulate the infinity goal. The image-stable device is installed on the motion simulator with six degrees of freedom which is used to simulate the moving state of the device. The CCD camera installed behind the eyepiece lens of the image-stable device acquires images rapidly and in real time. The local energy maxima center of the cross light spot can be acquired accurately through the proposed algorithm using the Hessian matrix. In addition, to deal with the CCD non-uniformity, an adaptive non-uniformity correction algorithm based on bi-dimensional empirical mode decomposition is provided. The actual test results for the proposed method show that the test error of dynamic image stabilization is less than 0.7″, and the time for the frame image acquisition and processing is less than 10 ms, which demonstrates the effectiveness of the test system.

A novel parameter adaptive nonlinear model of proportional valve

This paper aims at controlling the nonlinear coupled variables force and velocity precisely in the electro-hydraulic proportional system. An open-loop control method based on a certain nonlinear model of force (F), voltage (U) and velocity (V), which is established from formula derivation and experimental data analysis, is presented. The experimental results and applications show that the proposed model achieves high precision in velocity and force control. Depending on realtime online parameters identification and amendment, it can adapt the parameters change caused by unknown factors such as oil temperature variation.