Performance analysis of an electro-hydrostatic actuator with high-pressure load sensing based on fuzzy PID

Electro-hydrostatic actuator (EHA) is an important form of power-by-wire (PBW) technology, which is widely used in aircraft because of the characteristics of small size, high power and light weight. However, the current traditional EHA with fixed pump displacement and variable motor speed (FPVM-EHA) has the problems of high energy consumption and heating of the motor under heavy load. An improved EHA with high-pressure load sensing (HPLS-EHA) is proposed in this paper, which can reduce the pump displacement under heavy load, so as to achieve reducing the torque and heating of the motor, solving the problem of high energy consumption of EHA system and improving the efficiency. The co-simulation model of the FPVM-EHA and the HPLS-EHA was established using the software programs AMESim and MATLAB, and then the simulation results are analysed. The simulation results show that the HPLS-EHA can reduce the torque and heat flow rate of the motor by 23.20 % and 41.02 % under the load of 20.2 MPa, and the fluctuation times and amplitude of output position are also reduced under varying loads at 5 s, but it will slightly reduce the position accuracy of the EHA system. In order to solve this problem, the fuzzy PID control strategy is adopted for the HPLS-EHA. The simulation results show that the position accuracy and response speed of the HPLS-EHA based on fuzzy PID are improved, the output position is improved from 8.93 to 9.25 mm, better than 9.19 mm of the FPVM-EHA, and it also maintains the advantages of low motor torque, heating and output position fluctuation.

Beam on beam control: Beyond the particle approximation

The all-optical control of the trajectory of a nonlinear optical beam propagating in a nematic liquid crystal cell is studied using a combination of modulation theory and full numerical solutions of the governing nematic equations. In detail, the output position of a signal beam is controlled via its interaction with a second, co-propagating control beam. The input positions of both the signal and control beams are fixed, with the output position of the signal beam determined by the input angle of the control beam. A simple modulation theory based on treating the optical beams as mechanical particles in a potential well is found to give only adequate agreement with numerical solutions. However, extending this modulation theory to include the detailed profiles of the beams, so that the beams are treated as rigid bodies moving in a potential well, leads to simple, extended equations which determine the input angle of the control beam required for a given output position of the signal beam. The predictions of this extended particle theory, or rigid body theory, are compared with full numerical solutions of the nematic equations and excellent agreement is found.

Sliding-Bar MACCEPA for a Powered Ankle Prosthesis

This paper describes a new design that improves several aspects of the mechanically adjustable compliance and controllable equilibrium position actuator (MACCEPA). The proposed design avoids premature wear and attachment issues found in the cable transmission used in previous MACCEPA designs and allows the use of high-performance compact compression springs. The mechanical configuration of the actuator provides an adjustable stiffness with a nonlinear stiffening output torque. The output position of the actuator and its global stiffness are independent from each other. In this work, we provide a mathematical description of the actuation principle along with an experimental verification of its performance in a powered ankle–foot prosthesis. This work is part of the CYBERLEGs project funded by the European Commissions 7th Framework Programme.

Ore Types and Characteristics of Melt (Fluid) Inclusions on the Maoniuping REE Deposit Mianning, Sichuan, China

The Maoniuping REE deposit located in the northern section of the Panxi (Panzhihua and Xichang) rift zone of western margin of the Yangtze plate. It is by far the world's youngest discovered endogenous LREE deposit, and is also the world's third largest endogenous LREE deposit. Yanshanian alkaline granites are widely developed in Mianxi region, and the Maoniuping REE deposit hosts in the middle of Mianqi granite body. Surrounding rocks of REE ore body are nordmarkite and carbonatite. According to the output position, mineralization types, structure and other features, ore types of the Maoniuping REE deposit are designated as carbonatite type, pegmatite type, breccia type, and fine stockwork type. According to phase characteristics at room temperature and change of heating process, inclusions can be divided into three kinds: melt inclusions (M), melt fluid inclusions (ML) and fluid inclusions (L).