High Performance Adaptive Robust Control Research Articles

Advanced Valves and Pump Coordinated Hydraulic Control Design to Simultaneously Achieve High Accuracy and High Efficiency

The rapid industrial development in the fields, such as robotics and high-tech manufacturing, has put forward much higher requirements for the application of high-performance electrohydraulic system, which should not only achieve high control accuracy but also work in a highly energy-efficient way. As we know, a valve control method could achieve good accuracy, but the low energy efficiency is its essential drawback. Conversely, a pump control method could achieve good energy efficiency, but the achievable accuracy is the drawback. Since neither individual valve control nor individual pump control method can meet the dual requirements, a novel idea of advanced valves and pump coordinated hydraulic control design is developed in this article. Within the control details, the high-performance adaptive robust control law is synthesized to handle the nonlinearities and uncertainties of the electrohydraulic system, and the optimized command generation approach for the valves and the pump is developed to attain the high level of energy efficiency while considering the control performance. Essentially, the control command of the pump is based on the desired model compensation to provide the majority amount of flow in an energy-efficient way, and control commands of the valves are generated directly by tracking errors to guarantee the control accuracy. The theoretical performance of the overall system control design is analyzed. Comparative experiments are conducted, and impressive results are obtained, showing that the proposed system could achieve even better tracking accuracy than the typical valve-controlled system, while the energy efficiency reached a high level. The advantages of the advanced system control design can be verified both in theory and experiments.

Energy Saving Motion Control of Independent Metering Valves and Pump Combined Hydraulic System

The independent meter-in and meter-out valves control approach makes the two chamber pressures of the hydraulic actuator completely controllable, and offers possibilities for energy conservation. However, the entire flow rate is throttling controlled by the metering valves, which leads to the essential difficulty to realize the high level of energy efficiency further. On the other hand, although the direct pump controlled system might be an option with high energy efficiency, the poor dynamic response, and complicated controller design restrict its applications in precise motion occasions. To further improve the energy efficiency as well as guarantee the high precision position tracking performance, a novel hardware configuration that combines the independent metering valves and the direct pump control method is proposed in this paper, which is essentially different from our previous works and other independent metering research works. The motion control of the single-DOF cylinder actuator is studied to verify the effectiveness and advantages of the proposed system. During the tracking process, the pump is controlled by the reference velocity feedforward method and provides the majority amount of the flow rate without throttling losses, while the rest amount is accurately controlled by the independent metering valves in the closed loop for high precision tracking. Since the hydraulic system is highly nonlinear with uncertainties and disturbances, the high-performance adaptive robust control approach is applied in the closed-loop controller. Besides, the mode selection method and the flow distribution law are involved to deal with the enhanced flexibilities brought by the proposed configuration.Comparative experiments are carried out and the results show the proposed combined hydraulic system achieves the same level of position tracking precision as the independent metering system with less than a half of total energy consumption.

High-performance adaptive robust control with balanced torque allocation for the over-actuated cutter-head driving system in tunnel boring machine

The tunnel boring machine(TBM) is a kind of large-scale underground equipment for the tunnel and subway excavations. The cutter-head driving system is one of the key components in hard rock TBM, which is driven by multiple motors to provide enough torque during the excavation. Synchronizing motions of the multiple driving motors and balancing the driving torques are two essential control issues to be addressed of cutter-head driving system. However, the existing synchronization control approaches usually focus on the pure motion synchronization of the multiple driving motors only. These methods will lead to the phenomena of uneven driving torques even when their motions are quite well synchronized, and may result in the shaft broken accident. Instead in this paper, an adaptive robust control law integrated with torque allocation technique scheme is proposed that achieves not only better motion synchronization of the driving motors but also simultaneous regulation of driving torques. Namely, the adaptive robust control (ARC) is introduced to deal with the negative effects from uncertainties and variable load acting on the cutter-head. And a torque allocation algorithm is proposed to distribute the driving torque of each motor evenly. Comparative simulations are carried out to verify the excellent performance of the proposed scheme.

High dynamic adaptive robust control of load emulator with output feedback signal

This paper is concerned with the high performance adaptive robust control problem for an aircraft load emulator (LE). High dynamic capability is a key performance index of load emulator. However, physical load emulators exist a lot of nonlinearities and modeling uncertainties, which are the main obstacles for achieving high performance of load emulator. To handle the modeling uncertainty and achieve adjustable model-based compensation, firstly, the mathematical model of the load emulator is built, and then a nonlinear adaptive robust controller only with output feedback signal is proposed to improve the tracking accuracy and dynamic response capability. The controller is constructed based on the adaptive robust control framework with necessary design modifications required to accommodate uncertainties and nonlinearities of hydraulic load emulator. In this approach, nonlinearities are canceled by output feedback signal; and modeling errors, including parametric uncertainties and uncertain nonlinearities, are dealt with adaptive control and robust control respectively. The resulting controller guarantees a prescribed disturbance attenuation capability in general while achieving asymptotic output tracking in the absence of time-varying uncertainties. Experimental results are obtained to verify the high performance nature of the proposed control strategy, especially the high dynamic capability.

A Globally Stable High-Performance Adaptive Robust Control Algorithm With Input Saturation for Precision Motion Control of Linear Motor Drive Systems

This paper focuses on the synthesis of nonlinear adaptive robust controller with saturated actuator authority for a linear motor drive system, which is subject to parametric uncertainties and uncertain nonlinearities such as input disturbances as well. Global stability with limited control efforts is achieved by breaking down the overall uncertainties to state-linearly-dependent uncertainties (such as viscous friction) and bounded nonlinearities (such as Coulomb friction, cogging force, etc.), and dealing with them via different strategies. Furthermore, a guaranteed transient performance and final tracking accuracy can be obtained by incorporating the well-developed adaptive robust control strategy and effective parameter identifier. Asymptotic output tracking is also achieved in the presence of parametric uncertainties only. Meanwhile, in contrast to the existing saturated control structures that are designed based on a set of transformed coordinates, the proposed saturated controller is carried out in the actual system states, which have clear physical meanings. This makes it much easier and less conservative to select the design parameters to meet the dual objective of achieving global stability with limited control efforts for rare emergency cases and the local high-bandwidth control for high performance under normal running conditions. Real-time experimental results are obtained to illustrate the effectiveness of the proposed saturated adaptive robust control strategy