[en] This paper proposes a data-driven sliding mode control (SMC) method with tracking error constraint for a shape memory alloy (SMA) actuated system. More specifically, a new SMC method with prescribed performance is investigated by adopting the equivalent dynamic linearization technique and a novel transformed error algorithm to guarantee that the tracking error can converge into a preassigned region. Meanwhile, the proposed control method can effectively ensure the convergence rate and the steady-state error within a prescribed bound, merely depending on the input/output data without implicit or explicit information of the systems, which is more valuable for the practical application. The presented control method has been implemented on an SMA actuated system successfully and experimental results have shown that the proposed control is easily applicable and highly precise. In addition, the tracking error of the SMA actuated system can be constrained in a preassigned domain by the proposed control method. (paper)

[en] Ionic polymer metal composite (IPMC) is a novel smart material which has been widely implemented in MEMS, biomimetic mechanical and electrical integrated system and micro operation system. While the IPMC with different shapes and dimensions has been implemented in many different types of biomechanical integrated systems, one of its inherent properties called creep characteristic is difficult to be handled, which limits the further application of different IPMCs in integrated systems. A promising control method called sliding mode control (SMC) is proposed to resist the creep characteristics in this paper. The SMC controller can regulate IPMC actuators with different shapes and dimensions effectively to resist the creep characteristics without changing parameters of the control system. Experiments of four different types of IPMC actuators were conducted on the semi-physical SMC experimental platform. All the experimental results confirm the feasibility of the SMC control approach on regulating the multi-IPMCs with different shapes and dimensions based integrated system. (paper)

[en] Ionic polymer metal composites (IPMCs) are a type of electroactive polymer (EAP) that can be used as both sensors and actuators. An IPMC has enormous potential application in the field of biomimetic robotics, medical devices, and so on. However, an IPMC actuator has a great number of disadvantages, such as creep and time-variation, making it vulnerable to external disturbances. In addition, the complex actuation mechanism makes it difficult to model and the demand of the control algorithm is laborious to implement. In this paper, we obtain a creep model of the IPMC by means of model identification based on the method of creep operator linear superposition. Although the mathematical model is not approximate to the IPMC accurate model, it is accurate enough to be used in MATLAB to prove the control algorithm. A controller based on the active disturbance rejection control (ADRC) method is designed to solve the drawbacks previously given. Because the ADRC controller is separate from the mathematical model of the controlled plant, the control algorithm has the ability to complete disturbance estimation and compensation. Some factors, such as all external disturbances, uncertainty factors, the inaccuracy of the identification model and different kinds of IPMCs, have little effect on controlling the output block force of the IPMC. Furthermore, we use the particle swarm optimization algorithm to adjust ADRC parameters so that the IPMC actuator can approach the desired block force with unknown external disturbances. Simulations and experimental examples validate the effectiveness of the ADRC controller. (papers)

[en] This paper focuses on the benefits of China's Nuclear Power Plants (NPPs). By briefly analyzing and discussing the benefits in the economic, social and environmental dimensions, this paper summarizes the status quo of benefits of China's NPPs. In addition, an overview of how to guarantee the benefits of the nuclear power industry is provided in the perspective of industry regulation and technological development. Based on the overview, this paper proposes that nuclear safety is the fundamental to guarantee the benefits of nuclear power, and abiding Nuclear Security Law is the basis for securing nuclear power. Furthermore, the follow-up promotion of overall benefits of domestic nuclear power is discussed. (authors)

[en] Like most smart materials, such as piezoelectric materials and shape memory alloys, ion-exchange polymer–metal composite (IPMC), which is a kind of electroactive polymer material, exhibits the properties of hysteresis and creep. In this paper we explain the hysteresis and creep properties of IPMC, analyze the hysteresis using a discrete Prandtl–lshlinskii model, obtain a creep model of IPMC through modifying the creep model of piezoelectric material and present an inverse model of the hysteresis. For hysteresis and creep properties of IPMC changing with time at different rates, we applied the LMS (least mean square) algorithm to identify the hysteresis parameters online. An offline identification algorithm was used to obtain the creep parameters. An adaptive inverse strategy of control for IPMC actuators was set up on the basis of a superposition model of nonlinear hysteresis and linear creep, and we obtained good simulation and experiment results

[en] McKibben muscle is a kind of pneumatic artificial muscles (PAMs), and has been widely applied on robotic field as an actuator. Nevertheless, because of friction and elastic deformation, it has a strong asymmetric hysteresis which effects its actuating performance. In this paper, a novel Kriging prediction model (KPM) is proposed for describing PAM hysteresis. For improving predictive accuracy, a median filter is introduced and follows KPM, which is named Kriging-median inverse compensator (KMIC). Combining with PID controller, we present a KMIC-PID controller which consists of an open-loop KMIC and a close-loop PID controller. In order to verify the compensation control performance, some simulations and experiments are done, and the results are compared with traditional PID controller. Moreover, we introduce a Kalman filter during the experimental process, so that the effect of sensor noise can be eliminated. The Kalman filter is based on PID control parameters, so the controller used in experiment are named KMIC-Kalman PID (KPID). The simulation and experiment results show that the proposed controller has a significant compensation effect for PAM hysteresis in the condition of low frequency signal, because the hysteresis belongs to static characteristic. Furthermore, KMIC-KPID controller restricts the effect of sensor noise, which increases robustness of the system. (paper)

[en] In this paper, the basic information and operation license conditions attached to the text of Chinese nuclear power plant operation license are taken as the research object, and the current situation, content development and evolution, format change of operation license conditions are analyzed, and suggestions on the management of operation license conditions of nuclear power plant in China are put forward. (authors)

[en] IPMC is a type of electro-active polymer material, also called artificial muscle, which can generate a relatively large deformation under a relatively low input voltage (generally speaking, less than 5 V), and can be implemented in a water environment. Due to these advantages, IPMC can be used in many fields such as biomimetics, service robots, bio-manipulation, etc. Until now, most existing methods for IPMC manipulation are displacement control not directly force control, however, under most conditions, the success rate of manipulations for tiny fragile objects is limited by the contact force, such as using an IPMC gripper to fix cells. Like most EAPs, a creep phenomenon exists in IPMC, of which the generated force will change with time and the creep model will be influenced by the change of the water content or other environmental factors, so a proper force control method is urgently needed. This paper presents a novel adaptive force control method (AIPOF control—adaptive integral periodic output feedback control), based on employing a creep model of which parameters are obtained by using the FRLS on-line identification method. The AIPOF control method can achieve an arbitrary pole configuration as long as the plant is controllable and observable. This paper also designs the POF and IPOF controller to compare their test results. Simulation and experiments of micro-force-tracking tests are carried out, with results confirming that the proposed control method is viable. (paper)

[en] Fishing line can be combined with shape memory alloy (SMA) to form novel artificial muscle actuators which have low cost, are lightweight and soft. They can be applied in bionic, wearable and rehabilitation robots, and can reduce system weight and cost, increase power-to-weight ratio and offer safer physical human-robot interaction. However, these actuators possess several disadvantages, for example fishing line based actuators possess low strength and are complex to drive, and SMA possesses a low percentage contraction and has high hysteresis. This paper presents a novel artificial actuator (known as an SMA-fishing-line) made of fishing line and SMA twisted then coiled together, which can be driven directly by an electrical voltage. Its output force can reach 2.65 N at 7.4 V drive voltage, and the percentage contraction at 4 V driven voltage with a 3 N load is 7.53%. An antagonistic bionic joint driven by the novel SMA-fishing-line actuators is presented, and based on an extended unparallel Prandtl-Ishlinskii (EUPI) model, its hysteresis behavior is established, and the error ratio of the EUPI model is determined to be 6.3%. A Joule heat model of the SMA-fishing-line is also presented, and the maximum error of the established model is 0.510 mm. Based on this accurate hysteresis model, a composite PID controller consisting of PID and an integral inverse (I-I) compensator is proposed and its performance is compared with a traditional PID controller through simulations and experimentation. These results show that the composite PID controller possesses higher control precision than basic PID, and is feasible for implementation in an SMA-fishing-line driven antagonistic bionic joint. (technical note)

[en] Because of friction and elastic deformation, a pneumatic artificial muscle (PAM) has strong asymmetric hysteresis which negatively affects the driving performance. The hysteresis is generally described by a phenomenological model. However, the phenomenological hysteresis model always only depicts the hysteresis under certain conditions, so the compensator based on it has poor universality for different external conditions. In this article, we proposed a guided reinforcement learning (GRL) algorithm to online adjust the output of a Kriging-median inverse hysteresis compensator (KMIC), so that improve the compensation performance of the compensator for PAMs under different size, external load, and input signal frequency conditions. We name the novel compensator as a guided reinforcement learning Kriging- median inverse compensator (GRL-KMIC). Both simulation and experiment platform are set up to verify the effectiveness of the proposed compensator. The results show that the GRL algorithm improves the universality of KMIC obviously, so GRL-KMIC always keeps better compensation control performance than KMIC for different external conditions. (paper)