The primary motivation of this study is to develop a cost-effective, safe, easily controlled, and passively adaptive robotic gripper. A novel linear series elastic actuated robotic gripper (LSEA-RG) is proposed to accomplish the aforementioned goals. The LSEA-RG has the ability to adaptively grasp objects with different shapes and sizes by grasping force control. First, the mechanical design, including the transmission scheme, the finger mechanism, and the actuating mechanism is presented. Subsequently, the kinematic analysis is performed to explore the transmission characteristic of the actuating displacement and force. Then a model-free control method based on the lookup functions of the kinematic transmission characteristics is presented to achieve the grasping range and force control. Finally, several grasping experiments are carried out based on the LSEA-RG prototype to evaluate the grasping performance. The results demonstrate that the presented grasping control method which based on the lookup functions is valid. The LSEA-RG could estimate the grasping force without the help of a fingertip force sensor and grasp objects with different shapes and hardness adaptively.

The primary motivation of this study is to develop a sensor-less, easily controlled, and passively adaptive robotic gripper. A back-drivable pneumatic underactuated robotic gripper (PURG), based on the pneumatic cylinder and underactuated finger mechanism, is presented to accomplish the above goals. A feedforward grasping force control method, based on the learned kinematics of the underactuated finger mechanism, is proposed to achieve sensor-less grasping force control. To enhance the grasping force control accuracy, a state-based actuating force modeling method is presented to compensate the hysteresis error which exists in the transmission mechanism. Actuating force control experiment is performed to validate the effectiveness of the state-based actuating pressure modeling method. Results reveal that compared with the non-state-based modeling method, the proposed state-based actuating force modeling method could reduce the modeling error and control error by about 37.0% and 77.2%, respectively. Results of grasping experiments further reveal that grasping force could be accurately controlled by the state-based feedforward control model in a sensor-less approach. Adaptive grasping experiments are performed to exhibit the effectiveness of the sensor-less grasping force control approach.

Journal provides a multidisciplinary forum for scientists, researchers and engineers involved in research and design of nonlinear processes and phenomena, including the nonlinear modelling of phenomena of the nature.

The electrocaloric effect (ECE) depends on the sudden change of the polarization field during ferroelectric phase transition near the Curie temperature. Similarly, giant ECE can be found enormously during the domain structure transition from multidomain to monodomain process in ferroelectrics. To reveal the mechanism with the effects of the electric inclusions, the ECE of PbTiO₃ (PTO) ferroelectric solids under electric loads is investigated by phase-field simulation. The giant ECEs of ferroelectric materials containing three kinds of electric inclusions, namely, air, silicone oil, and water, are discussed in detail under applied electric fields. The results suggest that an unusual ultrahigh negative ECE (−9.30 K) and a large EC strength (∆T/∆E=0.237KmMV−1 are achieved near room temperature (about 50°C) in ferroelectrics containing water inclusion. The results indicate that electric inclusions generate high electrostatic energy under electric loads to break through the energy barrier and play an importation role in the ECE. In summary, the works may provide a better way to obtain the giant ECE and large EC strength close to room temperature by effectively regulating the dielectric constant of the electric inclusion and the increment of the applied electric field.

In this paper, the existence of positive solutions for Caputo fractional differential equations boundary value problem with infnite points contained in the boundary value condition, and based on Green's function and its properties, the existence of multiple positive solutions are obtained by AveryPeterson fxed point theorem.

To evaluate the dynamic properties of a coupled structure based on the dynamic properties of its substructures, this paper investigates the dynamic substructuring issue from the perspective of response prediction. The main idea is that the connecting forces at the interface of substructures can be expressed by the unknown coupled structural responses, and the responses can be solved rather easily. Not only rigidly coupled structures but also resiliently coupled structures are investigated. In order to further comprehend and visualize the nature of coupling problems, the Neumann series expansion for a matrix describing the relation between the coupled and uncoupled substructures is also introduced in this paper. Compared with existing response prediction methods, the proposed method does not have to measure any forces, which makes it easier to apply than the others. Clearly, the frequency response function matrix of coupled structures can be derived directly based on the response prediction method. Compared with existing frequency response function synthesis methods, it is more straightforward and comprehensible. Through demonstration of two examples, it is concluded that the proposed method can deal with structural coupling problems very well.