Jiang Hongzhou

PC Based High Quality and Low Cost Flight Simulator

The development of a flight simulator is a challenging work because of its complexity and tremendous cost. We have accomplished a flight simulator composed of PC cluster and non-flight-certified COTS components and have proved its fidelity and coordination characters as a flight training device. The main purpose of this project is to find a low cost solution to man-in-the-loop flight simulation while still accomplishing a competitive high level of quality. This paper describes the architecture of the flight simulator, the software development tools and hardware platform. These software and hardware constituted a PC based simulation environment and made the expense of the simulation application affordable. We also present the simulation modeling process. And for the integrity of the cueing system, we established a virtual prototype of the motion system which should support the cockpit of the simulator. The integrated system gave us a chance to testify the fidelity and coordination of the simulator. The validation method and simulation results are presented finally to show the feasible design based on PC to carry out flight simulation application with high quality and low cost.

Object-oriented landing gear model in a PC-based flight simulator

Abstract Training pilots the skill of maneuvering an aircraft on ground is important for flight safety. This demands a detailed landing gear model running in real-time. We developed the model and verified its validity by contrast with flight test data. It is accurate sufficiently and very suitable for real-time flight simulation to represent complex ground reaction behavior under various conditions and occasions. Based on this model, we realized a landing gear class in a unified flight simulation framework written in C++ and successfully applied the whole simulation codes through S-function in a PC-based experimental flight simulator. Because of the unique features of object-oriented design principles, the software framework presented here is structural, transplantable and convenient to maintain. The constitution and the quality of the simulator reveal that it would have cause to decrease the cost for developing a flight simulator with higher fidelity in future.

A Study of the Planar Serial-Parallel Mechanism With Various Stiffness for a Biotic Compliant Fish

Previous biological experiments show that the fish use their muscles to stiffen their bodies for improving the swimming performance. Inspired by that, we propose a planar model of oscillatory propulsor with variable stiffness using hyper redundant serial-parallel mechanisms to mimic a fish. Our goal in the paper is to identify the swimming characteristics with respect to the body stiffness. Moreover, a simulation model is presented and its results show that the swimming performance is largely dependent on the body stiffness and the driven frequency. Our primary conclusions include: 1) when the driven frequency is closed to the design frequency, the robotic fish with the calculated body stiffness has a super swimming performance. 2) Driven at the design frequency, the forward speed of robotic fish is linearly proportional to the driving frequency and the Strouhal number is consistent with the experiment results 0.25

Variable step euler method for real-time simulation

Many systems have stiff characteristics. To simulate such system in real-time demands solver of differential equation having small fixed step size to guarantee stability and accuracy even if it may cost large number of computing resource. An adaptive variable minor step size Euler method is developed for real-time simulation. It alternately uses forward Euler and backward Euler method based on morbid degree. And then it divides fixed major step equally into multiple minor steps in according to local truncation error. Because of this, it is more precise and more robust than classic Euler method. While simulating large scale system, it realizes computing resource dynamic allocation in different sub-systems. The advantageous abilities are verified by typical real-time simulation problems and the usage in a flight simulator. These shows the method is very suitable for a long real-time simulation.

Analysis of Coupling Effects on Hydraulic Controlled 6 Degrees of Freedom Parallel Manipulator Using Joint Space Inverse Mass Matrix

This paper presents an analysis of the coupling effects between degrees of freedom of a hydraulic controlled six DOF parallel manipulator. Based on the singular value decomposition to the properties of its joint space inverse mass matrix, the method is put forward to analyze coupling effects between degrees of freedom using a transformation matrix, the product of transposed Jabobian matrix and an orthogonal unitary matrix, of which each element represents decoupled modal space coordinates with respect to physical task space frame. The simulation results in frequency domain prove the theoretical analysis right. The analysis will provide useful information to mechanism and controller designer, to asses from concept the coupling effects between DOF in respect of the requirement for a particular application and also for the study on decoupling control strategies.

Modal space decoupled optimal design for a class of symmetric spatial parallel mechanisms with consideration of passive joint damping

In this study, we analyze the influence of passive joint viscous friction (PJVF) on modal space decoupling for a class of symmetric spatial parallel mechanisms (SSPM). The Jacobian matrix relating the platform movements to each passive joint velocity is first gained by vector analysis and the passive joint damping matrix is then derived by applying the Kane method. Next, an analytic formula index measuring the degree of coupling effects between the damping terms in the modal coordinates is proposed using classical modal analysis of dynamic equations in task space. Based on the index, a new optimal design method is found which establishes the kinematics parameters for minimizing the coupling degree of damping and achieves optimal fault tolerance for modal space decoupling when all struts have identical damping and stiffness coefficients in their axial directions. To illustrate the effectiveness of the theory, the new method was used to redesign two configurations of a specific manipulator.

Modal space decoupled controller for hydraulically driven six degree of freedom parallel robot

This paper proposes a modal space decoupling controller for the highly coupled six degrees of freedom parallel robot. It is based on singular value decomposition to the properties of the joint space inverse mass matrix, using an orthogonal unitary matrix. The method moreover, maps the control and feedback variables from the joint space to the decoupled modal space. Using this method, the highly coupled six-input-six-output dynamics of the parallel robot was transformed into six independent single inputs, single output one degree of freedom hydraulically driven mechanical system. The simulation result shows that the controller improved the trajectory performance more than the conventional PID controller in all DOF and eliminated the dynamic coupling effects.

Kinematics Analysis of a 3-dof Rotational Parallel Mechanism

A 3-dof rotational parallel mechanism is presented which has three struts and three actuators and is a plasmodium of the Stewart platforms. The kinematics of this robot is derived, and the kinematics analysis is investigated based on analytical solution of the inverse kinematics and numerical solution of the forward kinematics. This mechanism is popular in the fields of simulators and parallel kinematics machines.

Variable-stiffness decoupling of redundant planar rotational parallel mechanisms with crossed legs:

For redundant planar rotational parallel mechanisms (RPRPM), stiffness consists of active stiffness resulting from internal forces and passive stiffness caused by compliances of flexible elements, and the active stiffness is coupled with the passive stiffness. The stiffness variations with stretching internal force and compressing internal force of flexible elements are analyzed. By combining the leg-crossed RPRPM and leg-uncrossed RPRPM of different leg arrangements, the active stiffness is decoupled from the passive stiffness. The stiffness is modulated by changing the internal force and hence the spring stretching length independently to avoid being influenced by the passive stiffness. The stiffness variation multiple with given spring stretching length is maximized by decoupling the active stiffness from the passive stiffness. The variation of natural frequency of RPRPM is maximized by maximizing the stiffness variation, and the RPRPM can employ vibration of resonance to improve the working performance in a large range of driving frequency.

Solving the Steady Flight State of Aircraft Based on Hybrid Genetic Algorithm

Steady flat flight is widely used in the flight simulator training as an ideal initial state. To ensure the accurate solving of the steady flat flight state a hybrid genetic algorithm is put forward. The algorithm based on the new concept of “individual learning potentiality” make the Lamarckian learning and Baldwinina learning genetic algorithm combination together organically according to the particularity of the solving in the steady flat flight state. The algorithm could make the advantage of the learning into full play and make the disadvantage into inhibitory. The algorithm has generality which just use the state variable to calculate and can be independent of the airplane dynamic. Simulation result shows that the new algorithm combined the tow learning mechanism has made a good effect.