Real-Time Simulation Of Parachute-Payload System For Virtual Parachute Jumps Training Simulator

The virtual parachute jumps training simulator can shorten the parachute training time,and reduce the training costs and risks as well.Therefore its practical need is becoming more and more urgent.As its critical module,the parachute-payload system simulation is very important for standardized training of the parachute maneuvering techniques and malfunctions handling abilities of the trainees.There are technical difficulties in the realtime simulation of the parachute-payload system with dynamic motion responses and parachute cable-membrane structural deformation function.Therefore,a relevant research is necessary.Based on the multi-body system dynamics theory,this thesis establishes the kinematic equations of the parachute-payload system.The parachute cable-membrane structural deformation is simulated by the Position-Based Dynamics method.The compute shader technology is used for parallel acceleration to construct a real-time parafoil simulation system with practicality and stability.The main work is summarized as follows:Based on the multi-body system dynamics theory,this thesis establishes a nine-degreeof-freedom dynamics model of the parachute-payload system.Besides,the effect of apparent mass on system motion is taken into consideration.Furthermore,a rotational spring-damper model is used to characterize the torsional coupling moment between the payload and the parachute.The simulation results show that the parachute-payload system has correct dynamic motion characteristics such as gliding,turning,deceleration and landing.The torsional moment keeps the relative yaw angle between the payload and the parachute within a small range of 6 degrees.A dynamic response of the system deflecting to the upwind direction is observed as encountering a lateral wind.Based on the Position-Based Dynamics method,this thesis simulates the cablemembrane structural dynamic deformation and proposes an improved algorithm on the basis of spatial hashing collision detection to advance the efficiency of the program.The improved algorithm takes advantage of the fine-grained feature bounding boxes to improve the efficiency of culling.The time-stamp and bit-marks array are used to eliminate the duplicate detections completely.In addition,the unnecessary testings between adjacent features are avoided by adjacency information.Compared with the original inefficient spatial hashing collision detection method,the improved algorithm obtains 12-fold increase in efficiency.Based on the nine-degree-of-freedom dynamics model of the parachute-payload system and the cable-membrane structural simulation,this thesis builds a framework for parafoil system simulation and proposes the CPU/GPU heterogeneous computing flow.Based on the compute shader technology,the GPU multi-core parallel computing power is fully utilized to parallelize and accelerate the program of the cable-membrane structural simulation.Finally,the parafoil system with about 4k particles is taken as a test case,and its simulation frame rate reaches 82.6 fps,which meets the real-time requirement.