Quasi-zero-stiffness (QZS) vibration isolators can achieve a considerable vibration isolation performance in the low-frequency range. However, the vibration isolation performance and stability would become worse under complex excitation environments, such as large strokes, uncertain excitation amplitudes, etc. This work proposes a hybrid time-delayed feedforward and feedback controller (HTD-FFC) to improve the broadband vibration isolation performance and stability of lever-type QZS (L-QZS) vibration isolators. The nonlinear governing equation of L-QZS vibration isolators with HTD-FFC is established and the corresponding frequency response relationship is derived by applying the harmonic balance method. The stability criterion is established. The effects of the time delay and gains of the time-delayed feedback controller (TD-FBC) and HTD-FFC are numerically and experimentally analyzed. Compared to the TD-FBC, the HTD-FFC with different time delays can efficiently suppress and even eliminate the peak transmissibility without seriously affecting the performance in the isolation region. The HTD-FFC not only improves the vibration isolation performance but also eliminates the unstable and chaotic behaviors to strengthen the robustness and stability of L-QZS vibration isolators. This article provides a time-delayed hybrid control approach to improve the vibration performance and stability of QZS vibration isolators.

High-speed and high-precision position servo system of permanent magnet synchronous motor (PMSM) is the key part of the research and development of the manipulator's joint. The active disturbance rejection control (ADRC) is one of the commonly used methods in the position servo system, which has the advantages of fast speed and easy physical realization. However, the existing ADRC mostly adopts the three-loop structure of position-speed-current, which has some problems such as slow positioning response, poor positioning accuracy, and poor load adaptability caused by difficult parameter tuning. Therefore, a new load adaptive two-loop drive system based on an improved position-speed integrated ADRC with a parameter fuzzy self-tuning method is proposed. In order to verify the effectiveness of the scheme, a test platform for a Selective Compliance Assembly Robot Arm (SCARA) is established. The results show that the drive system designed by the proposed method has high positioning accuracy, fast positioning response, and adaptability to load changes.

The effective identification of the load torque is one of the key methods to improve the positioning accuracy of the position servo system, and the sliding mode observer (SMO) is a common identification method in the speed control system because of its advantages of insensitive parameters and easy physical realisation. However, the existing SMO can not achieve high precision and high response identification of load torque in the full speed range when the motor is running at variable-speed or variable-load, which limits its application in the position servo system. Based on the analysis of the stability and the adaptive law of feedback gain coefficient, an improved SMO for adaptive identification based on adaptive control and improvement of cut-off frequency is proposed. To verify the proposed method, the dedicated simulation model and test platform are built. The results show that the proposed observer can realise the adaptive identification of the load torque under the condition of variable-speed or variable-load, and the estimation accuracy is high. The position servo system designed by the proposed observer can improve the response against load change, which is an effective method for high-precision positioning control of the position servo system with a variable-speed or variable-load.

Effective identification of the load torque is one of the key aspects in improving the performance of servo drive systems against load disturbances. Sliding mode variable structure control has become a popular method in the development of a load torque identification (LTID) algorithm due to its parameter insensitivity and easy realization features. However, existing LTID sliding mode observers with conventional structure have the disadvantages of high frequency chattering and poor estimation accuracy, which limit its application in high performance servo systems. In this paper, the mathematical model of the conventional LTID sliding mode observer is deduced and analyzed. A new LTID sliding mode observer is proposed by replacing the sign function with a saturation function and an additional feedback loop in the load torque observer. The effectiveness of the proposed observer is verified by various experiments. The results show that compared to conventional load torque observer, the proposed observer can identify the load torque with higher accuracy and faster response in different operation conditions.

Improving the positioning response is one of the key goals for permanent magnet synchronous motor position servo systems. The sliding mode variable structure controller (SMVSC) is an effective method due to the advantages of strong robustness, fast response, and easy practical implementation. However, the existing SMVSCs have difficulties in optimizing the position tracking response speed and chattering performance at the same time. This article proposes an improved position speed integrated SMVSC (ISMVSC) with a new variable exponential reaching law based on position error and a saturation function, and a speed-limiting method using speed error and trajectory planning. The general design principle is given and various tests are carried out to verify the effectiveness of the proposed method. The experimental results show that compared with traditional methods, the ISMVSC can improve the positioning response speed and reduce chattering problems at the same time; it also exhibits a stronger transient speed-limiting ability. All these advantages make the proposed controller a superior method to achieve high-response positioning control of the servo system that performs point-to-point motion.

As part of the IoT-based application, underwater wireless sensor networks (UWSN), which are typically self-organized heterogeneous wireless network, are one of the research hot-spots using various sensors in marine exploration and water environment monitoring application fields, recently. Due to the serious attenuation of radio in water, acoustic or hybrid communication is a usual way for transmitting information among nodes, which dissipates much more energy to prevent the network failure and guarantee the quality of service (QoS). To address this issue, a topology control with energy balance, namely TCEB, is proposed for UWSN to overcome time-delay and other interference, as well as make the entire network load balance. With the given underwater network model and its specialized energy consumption model, we introduce the non-cooperative-game-based scheme to select the nodes with better performance as the cluster-heads. Afterwards, the intra-cluster and inter-cluster topology construction are, respectively, to form the effective communication links of the intra-cluster and inter-cluster, which aim to build energy-efficient topology to reduce energy consumption. With the demonstration of the simulation, the results show the proposed TCEB has better performance on energy-efficiency and throughput than three other representative algorithms in complex underwater environments.