Accurate Clamping Method of Multipoint Flexible Fixture for Large Complex Surface

In the field of aviation and astronautics, large complex surface parts such as aircraft cabin cover are complex, varying in model, and produced in small batch. In order to reduce fixture cost and improve production efficiency, a variable multipoint and multi-DOF supporting fixture is designed. The coordinate system of the complex structure fixture is defined, and the kinematics of the multibody structures driven by air cylinders are modeled according to the topological principle. With the help of this data structure, fast and optimal search for clamping state can be realized. With the dichotomy method, the driving amount of the electric cylinder of the suction cups and the two rotation angles of two rotation axes at the end of the linkages are solved accurately. Based on the digital twin simulation method, the precise clamping motion of flexible fixture is calculated for an aircraft cockpit cover with a software developed by the authors in C++ language on the Visual studio platform. The distance between the clamping point and the surface was verified with a laser tracker. Finally, the practical experiment of a real cockpit cover clamping proves the practicability and effectiveness of the proposed method.

PID Control Algorithm Based on Genetic Algorithm and its Application in Electric Cylinder Control

The traditional PID controller is simple in principle, easy to use, stable and reliable, and it is still widely used in the control field. However, for many nonlinear and lagging objects, the parameter tuning of PID controller is very important. Genetic algorithm provides a new way to optimize the parameters of PID. It uses simple coding techniques and propagation mechanisms to express complex phenomena, which is not restricted by the restriction of the search space. In this paper, the global optimization of genetic algorithm is used to optimize the parameters of PID, which can improve the performance and adaptive capability of PID controller. The mathematical model of the electric cylinder system is established, and the PID controller based on genetic algorithm is used to control the system. The simulation results verify the effectiveness of the proposed control algorithm.

Pre-Pressure Optimization for Ultrasonic Motors Based on Multi-Sensor Fusion

This paper investigates the pre-pressure’s influence on the key performance of a traveling wave ultrasonic motor (TRUM) using simulations and experimental tests. An analytical model accompanied with power dissipation is built, and an electric cylinder is first adopted in regulating the pre-pressure rapidly, flexibly and accurately. Both results provide several new features for exploring the function of pre-pressure. It turns out that the proportion of driving zone within the contact region declines as the pre-pressure increases, while a lower power dissipation and slower temperature rise can be achieved when the driving zones and the braking zones are in balance. Moreover, the shrinking speed fluctuations with the increasing pre-pressures are verified by the periodic-varying axial pressure. Finally, stalling torque, maximum efficiency, temperature rise and speed variance are all integrated to form a novel optimization criterion, which achieves a slower temperature rise and lower stationary error between 260 and 320 N. The practical speed control errors demonstrate that the proportion of residual error declines from 2.88% to 0.75% when the pre-pressure is changed from 150 to 300 N, which serves as one of the pieces of evidence of the criterion’s effectiveness.

Research on Performances of a Displacement Controllable Active Suspension

The suspension is one of the most important systems in a vehicle, which can decrease the vehicle body vibration and maintain good ride performance and driving stability. As for strikingly rugged roads like off-road conditions, the traditional active suspension can hardly balance the contradiction between the wheel adhesion and the vertical accelerated speed of the body. To accelerate to a higher speed while ensuring the ride performance at the same time, high-quality suspension system must be created and applied. As we all know, the active suspension can improve the driving stability and ride performance dramatically. In order to achieve the controllable adjustment of shock absorber damping and vehicle height, and realize the optimization of vehicle suspension performance, a new kind of active suspension which includes magnetorheological damper and servo electric cylinder is proposed. Then, the mathematical model of the proposed active suspension based on “Servo Electric Cylinder-Spring-Magnetorheological damper” is established after being simplified. Finally, the dynamic performances of the passive and active suspension in different modes are simulated by MATLAB based on its mathematical model and dynamic characteristic functions. The results indicate that the proposed active suspension, compared with the passive, can achieve the controlled adjustment of shock absorber damping and vehicle height, and ensure the ride performance.